[Federal Register Volume 89, Number 82 (Friday, April 26, 2024)]
[Rules and Regulations]
[Pages 32532-32757]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-07773]
[[Page 32531]]
Vol. 89
Friday,
No. 82
April 26, 2024
Part II
Environmental Protection Agency
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40 CFR Parts 141 and 142
PFAS National Primary Drinking Water Regulation; Final Rule
Federal Register / Vol. 89 , No. 82 / Friday, April 26, 2024 / Rules
and Regulations
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 141 and 142
[EPA-HQ-OW-2022-0114; FRL 8543-02-OW]
RIN 2040-AG18
PFAS National Primary Drinking Water Regulation
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
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SUMMARY: In March 2023, the U.S. Environmental Protection Agency (EPA)
proposed and requested comment on the National Primary Drinking Water
Regulation (NPDWR) and health-based Maximum Contaminant Level Goals
(MCLGs) for six per- and polyfluoroalkyl substances (PFAS):
perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS),
perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA),
hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX
Chemicals), and perfluorobutane sulfonic acid (PFBS). After
consideration of public comment and consistent with the provisions set
forth under the Safe Drinking Water Act (SDWA), the EPA is finalizing
NPDWRs for these six PFAS. Through this action, the EPA is finalizing
MCLGs for PFOA and PFOS at zero. Considering feasibility, the EPA is
promulgating individual Maximum Contaminant Levels (MCLs) for PFOA and
PFOS at 4.0 nanograms per liter (ng/L) or parts per trillion (ppt). The
EPA is also finalizing individual MCLGs and is promulgating individual
MCLs for PFHxS, PFNA, and HFPO-DA at 10 ng/L. In addition to the
individual MCLs for PFHxS, PFNA, and HFPO-DA, in consideration of the
known toxic effects, dose additive health concerns and occurrence and
likely co-occurrence in drinking water of these three PFAS, as well as
PFBS, the EPA is finalizing a Hazard Index (HI) of 1 (unitless) as the
MCLG and MCL for any mixture containing two or more of PFHxS, PFNA,
HFPO-DA, and PFBS. Once fully implemented, the EPA estimates that the
rule will prevent thousands of deaths and reduce tens of thousands of
serious PFAS-attributable illnesses.
DATES: This final rule is effective on June 25, 2024. The incorporation
by reference of certain publications listed in the rule is approved by
the Director of the Federal Register as of June 25, 2024.
ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-HQ-OW-2022-0114. All documents in the docket are
listed on the http://www.regulations.gov website. Although listed in
the index, some information is not publicly available, e.g.,
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Certain other material, such as
copyrighted material, is not placed on the internet and will be
publicly available only in hard copy form. Publicly available docket
materials are available electronically through https://www.regulations.gov.
FOR FURTHER INFORMATION CONTACT: Alexis Lan, Office of Ground Water and
Drinking Water, Standards and Risk Management Division (Mail Code
4607M), Environmental Protection Agency, 1200 Pennsylvania Avenue NW,
Washington, DC 20460; telephone number 202-564-0841; email address:
[email protected].
SUPPLEMENTARY INFORMATION:
Executive Summary
The Environmental Protection Agency (EPA) is issuing an adaptive
and flexible National Primary Drinking Water Regulation (NPDWR) under
the Safe Drinking Water Act (SDWA) to manage risks of per- and
polyfluoroalkyl substances (PFAS) in drinking water. The EPA is
establishing drinking water standards for six PFAS in this NPDWR to
provide health protection against these individual and co-occurring
PFAS in public water systems. The EPA's final rule represents data-
driven drinking water standards that are based on the best available
science and meet the requirements of SDWA. For the six PFAS, the EPA
considered PFAS health effects information, evidence supporting dose-
additive health concerns from co-occurring PFAS, as well as national
and state data for the levels of multiple PFAS in finished drinking
water. SDWA provides a framework for the EPA to regulate emerging
contaminants of concern in drinking water. Under the statute, the EPA
must act based on the ``best available'' science and information. Thus,
the statute recognizes that the EPA may act in the face of imperfect
information. It also provides a mechanism for the EPA to update
standards as more science becomes available. For the PFAS covered by
this rule, the EPA concluded that the state of the science and
information has sufficiently advanced to the point to satisfy the
statutory requirements and fulfill SDWA's purpose to protect public
health by addressing contaminants in the nation's public water systems.
PFAS are a large class of thousands of organic chemicals that have
unique physical and chemical properties. These compounds are designed
to be stable and non-reactive because of the applications in which they
are used: certain industrial and manufacturing processes; stain and
water repellants in clothing, carpets, and other consumer products, as
well as certain types of fire-fighting foams. PFAS tend to break down
slowly and persist in the environment, and consequently, they can
accumulate in the environment and the human body over time. Current
scientific research and available evidence have shown the potential for
harmful human health effects after being exposed to some PFAS. Although
some PFAS have been phased out of use in the United States, they are
still found in the environment and in humans based on biomonitoring
data.
Drinking water is one of several ways people can be exposed to
PFAS. The EPA's examination of drinking water data shows that different
PFAS can often be found together and in varying combinations as
mixtures. Additionally, decades of research demonstrates that exposure
to mixtures of different chemicals can elicit dose-additive health
effects: even if the individual chemicals are each present at levels
considered ``safe,'' the mixture may cause significant adverse health
effects. The high likelihood for different PFAS to co-occur in drinking
water; the additive health concerns when present in mixtures; the
diversity and sheer number of PFAS; and their general presence and
persistence in the environment and the human body are reflective of the
environmental and public health challenges the American public faces
with PFAS, which poses a particular threat for overburdened communities
that experience disproportionate environmental impacts. The final NPDWR
includes:
1. Individual Maximum Contaminant Levels (MCLs)
a. Perfluorooctanoic acid (PFOA) MCL = 4.0 nanograms per liter or
parts per trillion (ng/L or ppt)
b. Perfluorooctane sulfonic acid (PFOS) MCL = 4.0 ng/L
c. Perfluorohexane sulfonic acid (PFHxS) MCL = 10 ng/L
d. Perfluorononanoic acid (PFNA) MCL = 10 ng/L
e. Hexafluoropropylene oxide dimer acid (HFPO-DA) MCL = 10 ng/L
2. A Hazard Index MCL to account for dose-additive health effects
for mixtures that could include two or more of four
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PFAS (PFHxS, PFNA, HFPO-DA, and perfluorobutane sulfonic acid (PFBS)).
The Hazard Index MCL defines when the combined levels of two or more of
these four PFAS requires action. A PFAS mixture Hazard Index less than
or equal to 1 (unitless) indicates a level at which no known or
anticipated adverse effects on the health of persons occur and allows
for an adequate margin of safety with respect to health risk associated
with a mixture of PFAS in finished drinking water. A PFAS mixture
Hazard Index greater than 1 (unitless) indicates an exceedance of the
health protective level. To calculate the Hazard Index, a ratio is
developed for each PFAS by dividing the measured level of the PFAS in
drinking water by the level (in ng/L or ppt) below which adverse health
effects are not likely to occur (i.e., the Health Based Water
Concentration or HBWC). The HBWCs for each PFAS in the Hazard Index
are:
a. PFHxS = 10 ng/L or ppt
b. PFNA = 10 ng/L
c. HFPO-DA = 10 ng/L
d. PFBS = 2,000 ng/L
The individual PFAS ratios are then summed across the mixture to
yield the Hazard Index MCL as follows:
[GRAPHIC] [TIFF OMITTED] TR26AP24.000
Based on the administrative record for the final PFAS NPDWR and as
discussed above, certain PFAS (including PFHxS, PFNA, HFPO-DA, and
PFBS) have been shown to be toxicologically similar; i.e., elicit the
same or similar profile of adverse effects in several biological organs
and systems (see USEPA, 2000a; USEPA, 2007; USEPA, 2024a; USEPA, USEPA,
2024c; and section IV.B of this preamble). Studies with PFAS and other
classes of chemicals support the health-protective conclusion that
chemicals that have similar observed adverse effects following
individual exposure should be assumed to act in a dose-additive manner
when in a mixture unless data demonstrate otherwise (USEPA, 2024a).
Additionally, the record further supports that there is a substantial
likelihood that PFBS, PFHxS, PFNA, and HFPO-DA co-occur as mixtures in
drinking water at levels of public health concern (see USEPA, 2024b and
sections VI.C and D of this preamble). Though the EPA is not
promulgating an individual MCL or Maximum Contaminant Level Goal (MCLG)
for PFBS at this time as it is for PFHxS, PFNA, and HFPO-DA (see
section III.A of this preamble for specific discussion), based on these
evaluations, the agency is establishing a Hazard Index MCL that
addresses PFBS as part of mixtures where its co-occurrence with other
PFAS (PFHxS, HFPO-DA, and/or PFNA) can affect health endpoints when
present in these mixtures.
The individual and Hazard Index MCLs are independently applicable
for compliance purposes.
Additionally, the EPA is finalizing important public ``right to
know'' provisions of the EPA's SDWA regulations, specifically, public
notification (PN) and Consumer Confidence Report (CCR) requirements.
The changes under this rule will strengthen risk communication and
education for the public when elevated levels of these PFAS are found.
Finally, the EPA is finalizing monitoring and reporting requirements
that enable public water systems (PWSs) and primacy agencies to
implement and comply with the NPDWR.
Consistent with the timelines set out under SDWA, PWSs are required
to conduct their initial monitoring by April 26, 2027, and to conduct
PN and include PFAS information in the CCR. After carefully considering
public comment, the EPA is extending the compliance deadline for all
systems nationwide to meet the MCL to allow additional time for capital
improvements. As such, PWSs are required to make any necessary capital
improvements and comply with the PFAS MCLs by April 26, 2029.
As part of its Health Risk Reduction and Cost Analysis (HRRCA), the
EPA evaluated quantifiable and nonquantifiable health risk reduction
benefits and costs associated with the final NPDWR. At a two percent
discount rate, the EPA estimates the quantifiable annual benefits of
the final rule will be $1,549.40 million per year and the quantifiable
costs of the rule will be $1,548.64 million per year. The EPA's
quantified benefits are based on the agency's estimates that that there
will be 29,858 fewer illnesses and 9,614 fewer deaths in the
communities in the decades following actions to reduce PFAS levels in
drinking water. While the modeled quantified net benefits are nearly at
parity, under SDWA, the EPA must consider whether the costs of the rule
are justified by the benefits based on all statutorily prescribed costs
and benefits, not just the quantified costs and benefits (see SDWA
1412(b)(3)(c)(i)).
The EPA expects that the final rule will result in additional
nonquantifiable costs, including costs with generally greater
uncertainty, which the EPA has examined in quantified sensitivity
analyses in the Economic Analysis for the final rule. First, the EPA
had insufficient nationally representative data to precisely
characterize occurrence of HFPO-DA, PFNA, and PFBS. In an effort to
better consider and understand the costs associated with treatment of
these regulated compounds at systems both with and without PFOA, PFOS
and PFHxS occurrence in exceedance of the MCLs, the EPA performed a
quantitative sensitivity analysis of the costs associated with Hazard
Index and/or MCL exceedances resulting from HFPO-DA, PFNA, and PFBS.
The EPA expects that the quantified national costs, which do not
include HFPO-DA, PFNA, and PFBS treatment costs are marginally
underestimated (on the order of 5 percent). Second, stakeholders have
expressed concern to the EPA that a hazardous substance designation for
certain PFAS may limit their disposal options for drinking water
treatment residuals (e.g., spent media, concentrated waste streams)
and/or potentially increase costs. The EPA has conducted a sensitivity
analysis and found that should all water systems use hazardous waste
disposal options national costs would increase by 7 percent.
The EPA anticipates significant additional benefits that cannot be
quantified, will result from avoided negative developmental,
cardiovascular, liver, immune, endocrine, metabolic, reproductive,
musculoskeletal, and carcinogenic effects as a result of reductions in
the levels of the regulated PFAS and other co-removed contaminants. For
example, elevated
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concentrations of both PFOA and PFOS negatively impact the immune and
endocrine systems, impacts which the agency is unable to quantify at
this time. As another example, the EPA assessed the developmental
benefits associated with PFNA exposure reductions semi-quantitively in
sensitivity analysis, and the analysis demonstrates significant
additional benefits associated with reductions in PFNA. There are other
nonquantifiable benefits for other PFNA health endpoints, and numerous
endpoints for PFHxS, HFPO-DA, PFBS, and other PFAS that are anticipated
to be removed as a result of the final NPDWR. Additionally, as a result
of the ability for available treatment technologies to remove co-
occurring contaminants, there are benefits not quantified for removal
of co-occurring contaminants for this regulation (e.g., certain
pesticides, volatile organic compounds). Considering both quantifiable
and nonquantifiable costs and benefits of the rule, the EPA is
reaffirming the Administrator's determination at the time of proposal,
that the quantifiable and nonquantifiable benefits of the final rule
justify the quantifiable and nonquantifiable costs.
To help communities on the frontlines of PFAS contamination, the
passage of the Infrastructure Investment and Jobs Act (IIJA), also
referred to as the Bipartisan Infrastructure Law (BIL), invests
billions of dollars over a 5-year period. BIL appropriates over $11.7
billion in the Drinking Water State Revolving Fund (DWSRF) General
Supplemental; $4 billion to the DWSRF for Emerging Contaminants; and $5
billion in grants to the Emerging Contaminants in Small or
Disadvantaged Communities. These funds will assist many disadvantaged
communities, small systems, and others with the costs of installation
of treatment when it might otherwise be cost-challenging.
Table of Contents
I. General Information
A. What are the EPA's final rule requirements?
B. Does this action apply to me?
II. Background
A. What are PFAS?
B. Human Health Effects
C. Statutory Authority
D. Statutory Framework and PFAS Regulatory History
E. Bipartisan Infrastructure Law
F. EPA PFAS Strategic Roadmap
III. Final Regulatory Determinations for Additional PFAS
A. Agency Findings
B. Statutory Criterion 1--Adverse Health Effects
C. Statutory Criterion 2--Occurrence
D. Statutory Criterion 3--Meaningful Opportunity
E. The EPA's Final Determination Summary
IV. MCLG Derivation
A. MCLG Derivation for PFOA and PFOS
B. MCLG Derivation for Additional PFAS
V. Maximum Contaminant Levels
A. PFOA and PFOS
B. PFAS Hazard Index: PFHxS, PFNA, HFPO-DA, and PFBS
C. Individual MCLs: PFHxS, PFNA and HFPO-DA
VI. Occurrence
A. UCMR 3
B. State Drinking Water Data
C. PFAS Co-Occurrence
D. Occurrence Relative to the Hazard Index
E. Occurrence Model
F. Combining State Data With Model Output To Estimate National
Exceedance of Either MCLs or Hazard Index
G. UCMR 5 Partial Dataset Analysis
VII. Analytical Methods
A. Analytical Methods and Practical Quantitation Levels (PQLs)
for Regulated PFAS
VIII. Monitoring and Compliance Requirements
A. What are the Monitoring Requirements?
B. How are PWS Compliance and Violations Determined?
C. Can Systems Use Previously Collected Data To Satisfy the
Initial Monitoring Requirement?
D. Can systems composite samples?
E. Can primacy agencies grant monitoring waivers?
F. When must systems complete initial monitoring?
G. What are the laboratory certification requirements?
H. Laboratory Quality Assurance/Quality Control
IX. Safe Drinking Water Act (SDWA) Right To Know Requirements
A. What are the Consumer Confidence Report requirements?
B. What are the Public Notification (PN) requirements?
X. Treatment Technologies
A. What are the best available technologies?
B. PFAS Co-Removal
C. Management of Treatment Residuals
D. What are Small System Compliance Technologies (SSCTs)?
XI. Rule Implementation and Enforcement
A. What are the requirements for primacy?
B. What are the record keeping requirements?
C. What are the reporting requirements?
D. Exemptions and Extensions
XII. Health Risk Reduction and Cost Analysis
A. Public Comment on the Economic Analysis for the Proposed Rule
and EPA Response
B. Affected Entities and Major Data Sources Used To Develop the
Baseline Water System Characterization
C. Overview of the Cost-Benefit Model
D. Method for Estimating Costs
E. Nonquantifiable Costs of the Final Rule
F. Method for Estimating Benefits
G. Nonquantifiable Benefits of PFOA and PFOS Exposure Reduction
H. Nonquantifiable Benefits of Removal of PFAS Included in the
Final Regulation and Co-Removed PFAS
I. Benefits Resulting From Disinfection By-Product Co-Removal
J. Comparison of Costs and Benefits
K. Quantified Uncertainties in the Economic Analysis
XIII. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 14094 Modernizing Regulatory Review
B. Paperwork Reduction Act (PRA)
C. Regulatory Flexibility Act (RFA)
D. Unfunded Mandates Reform Act (UMRA)
E. Executive Order 13132: Federalism
F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
G. Executive Order 13045: Protection of Children From
Environmental Health and Safety Risks
H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution, or Use
I. National Technology Transfer and Advancement Act of 1995
J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations and Executive Order 14096: Revitalizing Our Nation's
Commitment to Environmental Justice for All
K. Consultations With the Science Advisory Board, National
Drinking Water Advisory Council, and the Secretary of Health and
Human Services
L. Congressional Review Act (CRA)
XIV. Severability
XV. Incorporation by Reference
XVI. References
I. General Information
A. What are the EPA's final rule requirements?
The Safe Drinking Water Act (SDWA) provides a framework for the
Environmental Protection Agency (EPA) to regulate emerging contaminants
of concern in drinking water. Under the statute, the EPA may act based
on the ``best available'' science and information. Thus, the statute
recognizes that the EPA may act in the face of imperfect information
and provides a mechanism for the EPA to update standards as more
science becomes available. For the per- and polyfluoroalkyl substances
(PFAS) covered by this rule, the EPA concluded that the state of the
science and information has sufficiently advanced to the point to
satisfy the statutory requirements and fulfill SDWA's purpose to
protect public health by addressing contaminants in the nation's public
water systems. In this final action, the EPA is finalizing the PFAS
National Primary Drinking Water Regulation (NPDWR) that is based upon
the best available peer-reviewed
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science. The final NPDWR for PFAS establishes Maximum Contaminant Level
Goals (MCLGs) and enforceable Maximum Contaminant Levels (MCLs) for six
PFAS compounds: perfluorooctanoic acid (PFOA), perfluorooctane sulfonic
acid (PFOS), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic
acid (PFNA), hexafluoropropylene oxide dimer acid (HFPO-DA, commonly
known as GenX Chemicals), and perfluorobutane sulfonic acid (PFBS). The
final rule requirements and references to where additional discussion
can be found on these topics are summarized here:
The EPA is finalizing MCLGs for PFOA and PFOS at zero (0) and
enforceable MCLs for PFOA and PFOS at 4.0 ng/L (ng/L or ppt). Please
see section IV of this preamble on the MCLG derivation for PFOA and
PFOS. Additionally, please see section V of this preamble for
discussion on the MCL for PFOA and PFOS.
The EPA is finalizing individual regulatory determinations to
regulate PFHxS, PFNA, and HFPO-DA (commonly known as ``GenX
Chemicals''). The EPA is deferring the individual regulatory
determination to regulate PFBS in drinking water. Concurrent with the
final determinations, the EPA is promulgating individual MCLGs and MCLs
for PFHxS, PFNA, and HFPO-DA at 10 ng/L each.
Additionally, the EPA is finalizing a regulatory determination for
mixtures of PFHxS, PFNA, HFPO-DA, and PFBS due to their substantial
likelihood for co-occurrence and dose-additive health concerns when
present as a mixture in drinking water. Concurrent with this final
determination, the EPA is finalizing a Hazard Index (HI) of 1 as the
MCLG and enforceable MCL to address mixtures of PFHxS, PFNA, HFPO-DA,
and PFBS where they co-occur in drinking water. Please see section III
of this preamble for discussion on the EPA's final regulatory
determinations; section IV of this preamble for discussion on the MCLG
derivation for these additional compounds; and section V of this
preamble for a discussion on the final MCLs.
This action also lists feasible technologies for public water
systems (PWSs) that can be used to comply with the MCLs. The EPA notes
that systems are not required to use the listed technologies to meet
the MCL; rather, the MCL is a numeric regulatory limit systems must
meet that is developed while considering treatment feasibility and
cost. Please see section X for additional discussion on feasible
treatment technologies.
The EPA is finalizing SDWA Right-to-Know requirements for the final
rule, including Consumer Confidence Report (CCR) and Public
Notification (PN) requirements. Community water systems (CWSs) must
prepare and deliver to its customers an annual CCR in accordance with
40 CFR part 141, subpart O. Under this rule, CWSs will be required to
report detected PFAS in their CCRs and provide health effects language
in the case of MCL violations. Additionally, under the final rule, MCL
violations require Tier 2 public notification, or notification provided
as soon as practicable but no later than 30 days after a system learns
of the violation, as per 40 CFR 141.203. Additionally, monitoring and
testing procedure violations require Tier 3 notification, or notice no
later than one year after the system learns of the violation. Please
see section IX of this preamble for additional discussion on SDWA
Right-to-Know requirements.
Additionally, the EPA is finalizing monitoring and reporting
requirements for PWSs to comply with the NPDWR. PWSs are required to
sample each EP using a monitoring regime generally based on the EPA's
Standard Monitoring Framework (SMF) for Synthetic Organic Contaminants
(SOCs). As a part of these requirements, to establish baseline levels
of regulated PFAS, water systems must complete initial monitoring
within three years following rule promulgation and/or use results of
recent, previously acquired monitoring to satisfy the initial
monitoring requirements. Following initial monitoring, beginning three
years following rule promulgation, to demonstrate that finished
drinking water does not exceed the MCLs for regulated PFAS, PWSs will
be required to conduct compliance monitoring for all regulated PFAS at
a frequency specifically based on sample results. Compliance with the
NPDWRs will be based on analytical results obtained at each sampling
point. PWSs are required to report to primacy agencies the results of
all initial and compliance monitoring to ensure compliance with the
NPDWRs. Please see section VIII of this preamble for additional
discussion on these requirements.
Finally, the EPA is exercising its authority under SDWA section
1412(b)(10) to implement a nationwide capital improvement extension to
comply with the MCL. All systems must comply with the MCLs by April 26,
2029. All systems must comply with all other requirements of the NPDWR,
including initial monitoring, by April 26, 2027. For additional
discussion on extensions and exemptions, please see section XI.
B. Does this action apply to me?
Entities regulated by this action are CWSs and non-transient non-
community water systems (NTNCWSs). A PWS, as defined in 40 CFR 141.2,
provides water to the public for human consumption through pipes or
``other constructed conveyances, if such system has at least fifteen
service connections or regularly serves an average of at least twenty-
five individuals daily at least 60 days out of the year.'' A PWS is
either a CWS or a non-community water system (NCWS). A CWS, as defined
in Sec. 141.2, is ``a public water system which serves at least
fifteen service connections used by year-round residents or regularly
serves at least twenty-five year-round residents.'' The definition in
Sec. 141.2 for a NTNCWS is ``a public water system that is not a [CWS]
and that regularly serves at least 25 of the same persons over 6 months
per year.'' The following table provides examples of the regulated
entities under this rule:
------------------------------------------------------------------------
Examples of potentially affected
Category entities
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Public water systems.............. CWSs; NTNCWSs.
State and Tribal agencies......... Agencies responsible for drinking
water regulatory development and
enforcement.
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This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be regulated by this
action. This table includes the types of entities that the EPA is now
aware could potentially be regulated by this action. To determine
whether your entity is regulated by this action, this final rule should
be carefully examined. If you have questions regarding the
applicability of this action to a particular entity, consult the person
listed in the FOR FURTHER INFORMATION CONTACT section.
All new systems that begin operation after, or systems that use a
new source of water after, April 26, 2024, must demonstrate compliance
with the MCLs
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within a period of time specified by the Primacy Agency. The EPA has
defined in 40 CFR chapter I, subchapter D, part 141, Sec. 141.2, a
wholesale system as a PWS that supplies finished PWSs and a consecutive
system as a PWS that buys or otherwise receives some or all its
finished water from a wholesale system. In this action, the EPA
reiterates that all CWS and NTNCWS must comply with this regulation.
This includes consecutive CWS and NTNCWS systems; however, the
requirements these consecutive systems must implement to comply with
the regulation may be, and often are, much less extensive. For finished
water that is provided through a system interconnection, the wholesale
systems will be responsible for conducting the monitoring requirements
at the entry point (EP) to the distribution system. The final
regulation does not require that any monitoring be conducted at a
system interconnection point. Where a violation does occur, the
wholesale system must notify any consecutive systems of this violation
and it is the responsibility of the consecutive system to provide PN to
their customers pursuant to Sec. 141.201(c)(1). In addition, wholesale
systems must also provide information in Subpart O to consecutive
systems for developing CCRs (Sec. 141.201(c)(1)). Consecutive systems
are responsible for providing their customers with the reports (Sec.
141.153(a)).
II. Background
A. What are PFAS?
Per- and polyfluoroalkyl substances (PFAS) are a large class of
thousands of synthetic chemicals that have been in use in the United
States and around the world since the 1940s (USEPA, 2018a). The ability
for PFAS to withstand heat and repel water and stains makes them useful
in a wide variety of consumer, commercial, and industrial products, and
in the manufacturing of other products and chemicals. This rule applies
directly to six specific PFAS: perfluorooctanoic acid (PFOA),
perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA),
hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX
Chemicals), perfluorohexane sulfonic acid (PFHxS), and perfluorobutane
sulfonic acid (PFBS). Due to their widespread use, physicochemical
properties, and prolonged persistence, many PFAS co-occur in air,
water, ice, and soil, and in organisms, such as humans and wildlife.
Exposure to some PFAS can lead to bioaccumulation in tissues and blood
of aquatic as well as terrestrial organisms, including humans (Domingo
and Nadal, 2019; Fromme et al., 2009). Pregnant and lactating women, as
well as infants and children, may be more sensitive to the harmful
effects of certain PFAS, such as PFOA, PFOS, PFNA, and PFBS. For
example, studies indicate that PFOA and PFOS exposure above certain
levels may result in adverse health effects, including developmental
effects to fetuses during pregnancy or to breast- or formula-fed
infants, increased risk for certain cancers, and negative immunological
effects, among others (USEPA, 2024c; USEPA, 2024d). It has been
documented that exposure to other PFAS are associated with a range of
adverse health effects (USEPA, 2021a; USEPA, 2021b; ATSDR, 2021; NASEM,
2022).
The Environmental Protection Agency (EPA) is aware that PFAS still
enter the environment and there are viable pathways for human exposure.
Most United States production of PFOA, PFOS, and PFNA, along with other
long-chain PFAS, was phased out and then generally replaced by
production of PFHxS, HFPO-DA, PFBS, and other PFAS. The EPA is also
aware of ongoing use of PFOA, PFOS, PFNA, and other long-chain PFAS
(USEPA, 2000b; ATSDR, 2021). Long-chain PFAS are typically defined as
including perfluoroalkyl sulfonic acids containing >= 6 carbons, and
perfluoroalkyl carboxylic acids with >=7 carbons. While domestic
production and import of PFOA has been phased out in the United States
by the companies participating in the 2010/2015 PFOA Stewardship
Program, small quantities of PFOA may be produced, imported, and used
by companies not participating in the PFOA Stewardship Program (USEPA,
2021c). The EPA is also aware of ongoing use of PFAS available from
existing stocks or newly introduced via imports (see USEPA, 2022a).
Additionally, the environmental persistence of these chemicals and
formation as degradation products from other compounds may contribute
to their ongoing release in the environment (ATSDR, 2021).
The six PFAS in this rule and their relevant Chemical Abstract
Service registry numbers (CASRNs) are:
PFOA (C8F15O2-;
CASRN: 45285-51-6)
PFOS (C8F17SO3-;
CASRN: 45298-90-6)
PFHxS (C6F13SO3-;
CASRN: 108427-53-8)
PFNA (C9F17O2-;
CASRN: 72007-68-2)
HFPO-DA (C6F11O3-;
CASRN: 122499-17-6)
PFBS (C4F9SO3-;
CASRN: 45187-15-3)
These PFAS may exist in multiple forms, such as isomers or
associated salts, and each form may have a separate CAS registry number
or no CASRN at all. Additionally, these compounds have various names
under different classification systems. However, at environmentally
relevant pHs, these PFAS are expected to dissociate in water to their
anionic (negatively charged) forms. For instance, International Union
of Pure and Applied Chemistry substance 2,3,3,3-tetrafluoro-2-
(heptafluoropropoxy) propanoate (CASRN: 122499-17-6), also known as
HFPO-DA, is an anionic molecule which has an ammonium salt (CASRN:
62037-80-3), a conjugate acid (CASRN: 13252-13-6), a potassium salt
(CASRN: 67118-55-2), and an acyl fluoride precursor (CASRN: 2062-98-8),
among other variations. At environmentally relevant pHs these all
dissociate into the propanoate/anion form (CASRN: 122499-17-6). Each
PFAS listed has multiple variants with differing chemical connectivity,
but the same molecular composition (known as isomers). Commonly, the
isomeric composition of PFAS is categorized as `linear,' consisting of
an unbranched alkyl chain, or `branched,' encompassing a potentially
diverse group of molecules including at least one, but potentially
more, offshoots from the linear molecule. While broadly similar,
isomeric molecules may have differences in chemical properties. This
rule covers all salts, isomers and derivatives of the chemicals listed,
including derivatives other than the anionic form which might be
created or identified.
B. Human Health Effects
The publicly available landscape of human epidemiological and
experimental animal-based exposure-effect data from repeat-dose studies
across PFAS derive primarily from carboxylic and sulfonic acid species
such as PFOA, PFOS, PFHxS, PFNA, HFPO-DA, and PFBS (ATSDR, 2021; USEPA,
2021a; USEPA, 2021b; USEPA, 2024c; USEPA, 2024d). Many other PFAS have
some human health effects data available (Mahoney et al., 2022) and
some PFAS, such as PFBS, HFPO-DA, PFNA, and PFHxS, have sufficient data
that has allowed Federal agencies to publish toxicity assessments
(USEPA, 2021a; USEPA, 2021b; USEPA, 2024c; USEPA, 2024d; ATSDR, 2021)
and derive toxicity values (e.g., a reference dose), which is an
estimate of daily exposure to the human population
[[Page 32537]]
(including sensitive populations) that is likely to be without an
appreciable risk of deleterious effects during a lifetime). The adverse
health effects associated with exposure to such PFAS include (but are
not limited to): effects on the liver (e.g., liver cell death), growth
and development (e.g., low birth weight), hormone levels, kidney, the
immune system (reduced response to vaccines), lipid levels (e.g., high
cholesterol), the nervous system, and reproduction, as well as
increased risk of certain types of cancer.
Exposure to PFAS may have disproportionate health effects on
children. Adverse health effects relevant to children associated with
exposure to some PFAS include developmental effects to fetuses during
pregnancy or to breast-fed infants, cardiovascular effects, immune
effects, endocrine effects, and reproductive effects. Additionally,
PFAS are known to be transmitted to the fetus via the placenta and to
the newborn, infant, and child via breast milk (USEPA, 2021a; USEPA,
2021b; USEPA, 2024c; USEPA, 2024d; ATSDR, 2021).
Please see sections III.B and IV of this rule for additional
discussion on health considerations for the six PFAS the EPA is
regulating in this document.
C. Statutory Authority
Section 1412(b)(1)(A) of SDWA requires the EPA to establish
National Primary Drinking Water Regulations (NPDWRs) for a contaminant
where the Administrator determines that the contaminant: (1) may have
an adverse effect on the health of persons; (2) is known to occur or
there is a substantial likelihood that the contaminant will occur in
PWSs (public water systems) with a frequency and at levels of public
health concern; and (3) in the sole judgment of the Administrator,
regulation of such contaminant presents a meaningful opportunity for
health risk reduction for persons served by PWSs.
D. Statutory Framework and PFAS Regulatory History
Section 1412(b)(1)(B)(i) of the Safe Drinking Water Act (SDWA)
requires the EPA to publish a Contaminant Candidate List (CCL) every
five years. The CCL is a list of contaminants that are known or
anticipated to occur in PWSs, are not currently subject to any proposed
or promulgated NPDWRs and may require regulation under the drinking
water program. In some cases, developing the CCL may be the first step
in evaluating drinking water contaminants. The EPA uses the CCL to
identify priority contaminants for regulatory decision-making (i.e.,
regulatory determinations), and for data collection. Publishing a CCL
does not impose any requirements on PWSs. The EPA included PFOA and
PFOS on the third and fourth CCLs published in 2009 (USEPA, 2009a) and
2016 (USEPA, 2016a). The EPA then included PFAS as a chemical group in
its most recent list, the fifth CCL (CCL 5) (USEPA, 2022b). This group
is inclusive of the PFAS the EPA is regulating through this action;
however, the fifth CCL did not include PFOA and PFOS as they had
already had final positive regulatory determinations completed for them
in March 2021 (USEPA, 2021d).
The EPA collects data on the CCL contaminants to better understand
their potential health effects and to determine the levels at which
they occur in PWSs. SDWA 1412(b)(1)(B)(ii) requires that, every five
years and after considering public comments on a ``preliminary''
regulatory determination, the EPA issues a determination to regulate or
not regulate at least five contaminants on each CCL. In addition,
section 1412(b)(1)(B)(ii)(III) authorizes the EPA to make a
determination to regulate a contaminant not listed on the CCL at any
time so long as the contaminant meets the three statutory criteria
based on available public health information. SDWA 1412(b)(1)(B)(iii)
requires that ``each document setting forth the determination for a
contaminant under clause (ii) shall be available for public comment at
such time as the determination is published.'' To implement these
requirements, the EPA issues preliminary regulatory determinations
subject to public comment and then issues a final regulatory
determination after consideration of public comment. Section
1412(b)(1)(E) requires that the EPA propose an NPDWR no later than 24
months after a final determination to regulate. The statute also
authorizes the EPA to issue a proposed rule concurrent with a
preliminary determination to regulate. The EPA must then promulgate a
final regulation within 18 months of the proposal (which may be
extended by 9 additional months).
The EPA also implements a monitoring program for unregulated
contaminants under SDWA 1445(a)(2) that requires the EPA to issue a
list once every five years of priority unregulated contaminants to be
monitored by PWSs. This monitoring is implemented through the
Unregulated Contaminant Monitoring Rule (UCMR), which collects data
from community water systems (CWSs) and non-transient community water
systems (NTNCWSs) to better improve the EPA's understanding of the
frequency of unregulated contaminants of concern occurring in the
nation's drinking water systems and at what levels. The first four
UCMRs collected data from a census of large water systems (serving more
than 10,000 people) and from a statistically representative sample of
small water systems (serving 10,000 or fewer people).
Between 2013-2015, water systems collected monitoring data for six
PFAS (PFOA, PFOS, PFHxS, PFNA, PFBS, and perfluoroheptanoic acid
(PFHpA)) as part of the third UCMR (UCMR 3) monitoring program. The
fifth UCMR (UCMR 5), published December 2021, requires sample
collection and analysis for 29 PFAS, including PFOA, PFOS, PFHxS, PFNA,
HFPO-DA, and PFBS, to occur between January 2023 and December 2025
using drinking water analytical methods developed by the EPA. Section
2021 of America's Water Infrastructure Act of 2018 (AWIA) (Pub. L. 115-
270) amended SDWA and specifies that, subject to the availability of
the EPA appropriations for such purpose and sufficient laboratory
capacity, the EPA must require all public water systems (PWSs) serving
between 3,300 and 10,000 people to monitor and ensure that a nationally
representative sample of systems serving fewer than 3,300 people
monitor for the contaminants in UCMR 5 and future UCMR cycles. All
large water systems continue to be required to participate in the UCMR
program. Section VI of this preamble provides additional discussion on
PFAS occurrence. While the complete UCMR 5 dataset was not available to
inform this rule and thus not a basis for informing the agency's
decisions for the final rule, the EPA acknowledges that the small
subset of data released (7 percent of the total results that the EPA
expects to receive) as of July 2023 confirms the EPA's conclusions
supported by the extensive amount of data utilized in its UCMR 3, state
data, and modelling analyses. This final rule allows utilities and
primacy agencies to use the UCMR 5 data to support implementation of
monitoring requirements. Sections VI and VIII of this preamble further
discusses these occurrence analyses as well as monitoring and
compliance requirements, respectively.
After careful consideration of public comments, the EPA issued
final regulatory determinations for contaminants on the fourth CCL (CCL
4) in March of 2021 (USEPA, 2021d) which included determinations to
regulate two contaminants, PFOA and PFOS, in drinking water. The EPA
found that PFOA and PFOS may have
[[Page 32538]]
an adverse effect on the health of persons; that these contaminants are
known to occur, or that there is a substantial likelihood that they
will occur, in PWSs with a frequency and at levels that present a
public health concern; and that regulation of PFOA and PFOS presents a
meaningful opportunity for health risk reduction for persons served by
PWSs. As discussed in the final Regulatory Determinations 4 Notice for
CCL 4 contaminants (USEPA, 2021d) and the EPA's PFAS Strategic Roadmap
(USEPA, 2022c), the agency has also evaluated additional PFAS chemicals
for regulatory consideration as supported by the best available
science. The agency finds that additional PFAS compounds also meet SDWA
criteria for regulation. The EPA's regulatory determination for these
additional PFAS is discussed in section III of this preamble.
Section 1412(b)(1)(E) provides that the Administrator ``may publish
such proposed regulation concurrent with the determination to
regulate.'' The EPA interprets this provision as allowing concurrent
processing of a preliminary determination with a proposed rule, not a
final determination (as urged by some commenters--see responses in
section III of this preamble). Under this interpretation, section
1412(b)(1)(E) authorizes the EPA to issue a preliminary determination
to regulate a contaminant and a proposed NPDWR addressing that
contaminant concurrently and request public comment at the same time.
This represents the only interpretation that accounts for the statutory
language in context and is the only one that fulfills Congress's
purpose of permitting the agency to adjust its stepwise processes where
appropriate to avoid any unnecessary delay in regulating contaminants
that meet the statutory criteria. To the extent the statute is
ambiguous, the EPA's interpretation is the best interpretation of this
provision for these same reasons. As a result, this rule contains both
a final determination to regulate four PFAS contaminants (individually
and/or as part of a PFAS mixture), and regulations for those
contaminants as well as the two PFAS contaminants (PFOA and PFOS) for
which the EPA had already issued a final Regulatory Determination. The
EPA developed an MCLG and an NPDWR for six PFAS compounds pursuant to
the requirements under section 1412(b)(1)(B) of SDWA. The final Maximum
Contaminant Level Goals (MCLGs) and NPDWR are discussed in more detail
in the following section.
E. Bipartisan Infrastructure Law
The passage of the Infrastructure Investment and Jobs Act (IIJA),
often referred to as the Bipartisan Infrastructure Law or BIL, invests
over $50 billion to improve drinking water, wastewater, and stormwater
infrastructure--the single largest investment in water by the Federal
Government. This historic investment specific to safe drinking water
includes $11.7 billion in the Drinking Water State Revolving Fund
(DWSRF) General Supplemental (referred to as BIL DWSRF General
Supplemental); $4 billion to the Drinking Water SRF for Emerging
Contaminants (referred to as BIL DWSRF EC); and $5 billion in grants
for Emerging Contaminants in Small or Disadvantaged Communities
(referred to as EC-SDC) from Federal fiscal years 2022 through 2026
(USEPA, 2023a). For the BIL DWSRF General Supplemental and BIL DWSRF
EC, states must provide 49% and 100%, respectively, as additional
subsidization in the form of principal forgiveness and/or grants. The
EC-SDC grant has no cost-share requirement. Together, these funds will
assist many disadvantaged communities, small systems, and others with
the costs of addressing emerging contaminants, like PFAS, when it might
otherwise be cost-challenging. This financial assistance can be used to
address emerging contaminants in drinking water through actions such as
technical assistance, certain water quality testing, operator and
contractor training and equipment, and treatment upgrades and
expansion. Investments in these areas which will allow communities
additional funding to meet their obligations under this regulation and
help ensure protection from PFAS contamination of drinking water. The
Drinking Water SRF can be used by water systems to reduce the public
health concerns around PFAS in their drinking water and is already
being successfully utilized. Additionally, to support BIL
implementation, the EPA is offering water technical assistance
(WaterTA) to help communities identify water challenges and solutions,
build capacity, and develop application materials to access water
infrastructure funding (USEPA, 2023b). The EPA collaborates with
states, Tribes, territories, community partners, and other stakeholders
with the goal of more communities with applications for Federal
funding, quality water infrastructure, and reliable water services.
F. EPA PFAS Strategic Roadmap
In October 2021, the EPA published the PFAS Strategic Roadmap (or
Roadmap) that outlined the whole-of-agency approach to ``further the
science and research, to restrict these dangerous chemicals from
getting into the environment, and to immediately move to remediate the
problem in communities across the country'' (USEPA, 2022c). The Roadmap
offers timelines by which the EPA acts on key commitments the agency
made toward addressing these contaminants in the environment, while
continuing to safeguard public health. These include the EPA proposing
to designate certain PFAS as Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) hazardous substances; issuing
advance notice of proposed rulemakings on various PFAS under CERCLA;
and issuing updated guidance on destroying and disposing of certain
PFAS and PFAS-containing materials. Additionally, the EPA is issued a
memorandum to states in December 2022 that provides direction on how to
use the National Pollutant Discharge Elimination System (NPDES) program
to protect against PFAS (USEPA, 2022d; USEPA, 2022e). The EPA also
announced revisions to several Effluent Limitation Guidelines (ELGs)
including, Organic Chemical, Plastic, Synthetic Fibers manufacturing,
Metal Finishing & Electroplating, and Landfills to address PFAS
discharge from these point source categories. These ELGs collectively
will, if finalized, restrict and reduce PFAS discharges to waterways
used as sources for drinking water. The EPA is taking numerous other
actions to advance our ability to understand and effectively protect
people from PFAS, such as the October 11, 2023, rule finalized under
the Toxic Substances Control Act (TSCA) that will provide the EPA, its
partners, and the public with a dataset of PFAS manufactured and used
in the United States. The rule requires all manufacturers (including
importers) of PFAS and PFAS-containing articles in any year since 2011
to report information to the extent known or reasonably ascertainable:
chemical identity, uses, volumes made and processed, byproducts,
environmental and health effects, worker exposure, and disposal to the
EPA. With this final NPDWR, the EPA is delivering on another key goal
in the Roadmap to ``establish a National Primary Drinking Water
Regulation'' for PFAS. This rule will protect the American people
directly from everyday PFAS exposures that might otherwise occur from
PFAS-contaminated drinking water,
[[Page 32539]]
complementing the many other actions in the Roadmap to protect public
health and the environment from PFAS.
III. Final Regulatory Determinations for Additional PFAS
A. Agency Findings
As noted earlier, in 2021, the EPA made a determination to regulate
two per- and polyfluoroalkyl substances--perfluorooctanoic acid (PFOA)
and perfluorooctane sulfonic acid (PFOS)--in drinking water under the
Safe Drinking Water Act. This section describes the EPA's regulatory
determination findings with respect to three additional PFAS and
mixtures of four PFAS.
Pursuant to sections 1412(b)(1)(A) and 1412(b)(1)(B)(ii)(II) of
SDWA, the EPA is making a final determination to individually regulate
as contaminants PFHxS, PFNA, and HFPO-DA and is publishing Maximum
Contaminant Level Goals (MCLGs) and promulgating National Primary
Drinking Water Regulations (NPDWRs) for these compounds individually.
Under this authority, the EPA is also making a final determination to
regulate as a contaminant a mixture of two or more of the following:
perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid
(HFPO-DA, commonly known as GenX Chemicals), perfluorohexane sulfonic
acid (PFHxS), and perfluorobutane sulfonic acid (PFBS), and is
publishing an MCLG and promulgating an NPDWR for mixtures of these
compounds. The agency has determined that PFHxS, PFNA, and HFPO-DA may
have individual adverse health effects, and any mixture of these three
PFAS and PFBS may also have dose-additive adverse effects on the health
of persons; that there is a substantial likelihood that PFHxS, PFNA,
and HFPO-DA occur individually with a frequency and at levels of public
health concern and that mixtures of these three PFAS and PFBS occur and
co-occur in public water systems (PWSs) with a frequency and at levels
of public health concern; and that, in the sole judgment of the
Administrator, individual regulation of PFHxS, PFNA, and HFPO-DA, and
regulation of mixtures of these three PFAS and PFBS, presents a
meaningful opportunity for health risk reduction for persons served by
PWSs. The EPA refers to ``mixtures'' in its regulatory determinations
to make clear that its determinations cover all the combinations of
PFHxS, PFNA, HFPO-DA, and PFBS that could co-occur in a mixture but
that each regulated mixture is itself a contaminant.
While the final determination includes mixtures of PFBS in
combinations with PFHxS, HFPO-DA, and PFNA, the EPA is deferring the
final individual regulatory determination for PFBS to further evaluate
it individually under the three SDWA regulatory determination criteria;
consequently, the agency is not promulgating an individual MCLG or
NPDWR for PFBS in this action. The EPA is deferring its final
individual regulatory determination because after considering the
public comments, the EPA has decided to further consider whether
occurrence information supports a finding that there is a substantial
likelihood that PFBS will individually occur in public water systems
and at levels of health concern. However, as stated previously, when
evaluating PFBS in mixtures combinations with PFHxS, PFNA, and/or HFPO-
DA, the EPA has determined that based on the best available information
it does meet all three statutory criteria for regulation when a part of
these mixtures, including that it is anticipated to have dose-additive
adverse health effects (see sections III.B and IV.B.1), there is a
substantial likelihood of its co-occurrence in combinations with PFHxS,
PFNA, and/or HFPO-DA with a frequency and at levels of public health
concern (see sections III.C, VI.C, VI.D, and USEPA 2024b), and there is
a meaningful opportunity for health risk reduction by regulating
mixture combinations of these four PFAS (see section III.D of this
preamble). Hence, although the agency is deferring the individual final
regulatory determination for PFBS, it is included in the final
determination to regulate mixture combinations containing two or more
of PFHxS, PFNA, HFPO-DA, and PFBS.
This section describes the best available science and public health
information used by the agency to support the regulatory
determinations. The MCLGs and NPDWR, including the MCLs, are discussed
further in sections IV and V of this preamble.
1. Proposal
The agency proposed preliminary determinations to regulate PFHxS,
PFNA, HFPO-DA, and PFBS individually, and to regulate mixtures of these
four PFAS contaminants, in drinking water. In the proposal, the agency
concluded that PFHxS, PFNA, HFPO-DA, and PFBS, and mixtures of these
PFAS, may cause adverse effects on the health of persons; there is a
substantial likelihood that they will occur and co-occur in PWSs with a
frequency and at levels of public health concern, particularly when
considering them in a mixture; and in the sole judgment of the
Administrator, regulation of PFHxS, PFNA, HFPO-DA, PFBS, and mixtures
of these PFAS, presents a meaningful opportunity for health risk
reductions for people served by PWSs.
Within the proposal, the agency described section 1412(b)(1)(E)
which provides that the Administrator may publish a proposed drinking
water regulation concurrent ``with the determination to regulate.''
This provision authorizes a more expedited process by allowing the EPA
to make concurrent the regulatory determination and rulemaking
processes. As a result, for the proposal, the EPA interpreted the
relevant reference to ``determination to regulate'' in section
1412(b)(1)(E) as referring to the regulatory process in
1412(b)(1)(B)(ii) that begins with a preliminary determination. Under
this interpretation, section 1412(b)(1)(E) authorizes the EPA to issue
a preliminary determination to regulate a contaminant and a proposed
NPDWR addressing that contaminant concurrently and request public
comment at the same time. This allows the EPA to act expeditiously
where appropriate to issue a final determination to regulate
concurrently with a final NPDWR to avoid delays to address contaminants
that meet the statutory criteria.
Additionally, as part of the proposal, the EPA explained why
mixtures of PFAS qualify as a ``contaminant'' for purposes of section
1412. SDWA section 1401(6) defines the term ``contaminant'' to mean
``any physical, chemical or biological or radiological substance or
matter in water.'' A mixture of two or more of the regulated PFAS
qualifies as a ``contaminant'' because the mixture itself is ``any
physical, chemical or biological or radiological substance or matter in
water'' (emphasis added). Therefore, pursuant to the provisions
outlined in section 1412(b)(1)(A) and 1412(b)(1)(B) of SDWA, the agency
made a preliminary determination to regulate PFHxS, PFNA, HFPO-DA,
PFBS, and any mixtures of these PFAS as a contaminant in drinking
water. In the past and in this instance, the EPA's approach to
regulating contaminant groups or mixtures under SDWA considers several
factors, including health effects, similarities in physical and
chemical properties, contaminant co-occurrence, ability for treatment
technology co-removal, or where such a regulatory structure presents a
meaningful opportunity to improve public health protection.
[[Page 32540]]
2. Summary of Major Public Comments and EPA Responses
The EPA requested comments on its preliminary regulatory
determinations for PFHxS, PFNA, HFPO-DA, and PFBS, and mixtures of
these PFAS, including the agency's evaluation of the statutory criteria
and any additional data or studies the EPA should consider that inform
the preliminary regulatory determinations for these contaminants and
their mixtures. The EPA also requested comment on its preliminary
determination that regulation of PFHxS, PFNA, HFPO-DA, PFBS, and their
mixtures, in addition to regulation of PFOA and PFOS, will also provide
protection from PFAS (e.g., PFDA, PFDoA, PfHpA, PFHxA, PFHpS, PFPeS)
that will not be regulated because the treatment technologies that
would be used to ensure compliance for these PFAS are also effective in
reducing concentrations of other unregulated PFAS.
Many commenters expressed support for the EPA's preliminary
regulatory determinations, including that the EPA has appropriately
determined that the three statutory criteria for regulation have been
met for all four contaminants and their mixtures using the best
available information. Many other commenters did not agree that the
agency presented sufficient information to make a preliminary
determination to regulate PFHxS, PFNA, HFPO-DA, PFBS, and their
mixtures, with some commenters recommending that that the agency
withdraw the portion of the proposed rule associated with these four
PFAS because in their view there is insufficient health effects and/or
occurrence data at this time to support the EPA's action. For some of
the four contaminants and their mixtures, a few commenters stated that
the EPA had not met the statutory criteria for regulation or that data
suggests a determination not to regulate is more appropriate. The EPA
disagrees with these commenters because there is information to support
individual regulation of PFHxS, PFNA, and HFPO-DA, as well as mixtures
of these three PFAS and PFBS, based on the three statutory criteria
(these findings are discussed in this section).
As discussed earlier in this section, after consideration of all
the public comments on this issue, the agency is deferring the
determination to individually regulate PFBS for further evaluation
under the statutory criteria. This determination is informed by public
comment suggesting that the three statutory criteria for individual
regulation of PFBS, particularly related to the occurrence criterion
have not been met. The EPA will continue to consider other available
occurrence information, including from UCMR 5, to determine whether the
information supports a finding that there is a substantial likelihood
that PFBS will individually occur in PWSs and at a level of public
health concern. The record demonstrates that exposure to a mixture with
PFBS may cause adverse health effects; that there is a substantial
likelihood that PFBS co-occurs in mixtures with PFHxS, PFNA, and/or
HFPO-DA in PWSs with a frequency and at levels of public health
concern; and that, in the sole judgment of the Administrator,
regulation of PFBS in mixtures with PFHxS, PFNA, and/or HFPO-DA
presents a meaningful opportunity for health risk reduction for persons
served by PWSs.
Furthermore, the EPA is making a final determination to regulate
PFHxS, PFNA, and HFPO-DA individually. While the EPA recognizes there
will be additional health, occurrence, or other relevant information
for these PFAS and others in the future, the EPA has determined that
there is sufficient information to make a positive regulatory
determination and the agency concludes that these three PFAS currently
meet all of the statutory criteria for individual regulatory
determination. Therefore, the agency is proceeding with making final
determinations to regulate these contaminants both individually and as
part of mixtures with PFBS and is concurrently promulgating individual
MCLs for PFHxS, PFNA, and HFPO-DA (see section V of this preamble). For
detailed information on the EPA's evaluation of the three regulatory
determination statutory criteria for PFHxS, PFNA, and HFPO-DA
individually and mixtures of these three PFAS and PFBS, as well as more
specific comments and the EPA responses related to each of the three
statutory criteria, see subsections III.B, C, and D.
Several commenters requested that the EPA evaluate additional
occurrence data to further inform its analysis for the regulatory
determinations. In response to public comments on the proposal, the EPA
evaluated updated and new occurrence data and the updates are presented
within subsection III.C. and section VI of this preamble. These
additional occurrence data further confirm that the SDWA criteria for
regulation have been met for PFHxS, PFNA, and HFPO-DA as individual
contaminants and for mixtures of PFHxS, PFNA, HFPO-DA, and/or PFBS.
A couple of commenters questioned the EPA's rationale for selecting
PFHxS, PFNA, HFPO-DA, and PFBS for regulation. The agency's process is
allowable under SDWA and, as described within this section of the
preamble, there is available health, occurrence, and other meaningful
opportunity information for three PFAS (PFHxS, PFNA, and HFPO-DA) to
meet the SDWA statutory criteria for regulation individually and four
PFAS (PFHxS, PFNA, HFPO-DA, and PFBS) as a mixture. The EPA disagrees
with commenters who suggested that the agency should not develop
national regulations that differ from state-led actions. While states
may establish drinking water standards for systems in their
jurisdiction prior to regulation under SDWA, once an NPDWR is in place,
SDWA 1413(a)(1) requires that states or Tribes adopt standards that are
no less stringent than the NPDWR to maintain primacy. Moreover, the
agency further notes that all four PFAS the EPA is regulating
individually or as a mixture are currently regulated by multiple states
as shown in table 4-17 of USEPA, 2024e.
The EPA received several comments related to the EPA's
interpretation in the proposal that the agency may, as it did here,
issue a preliminary regulatory determination concurrent with a proposed
NPDWR. Many stated that the EPA is authorized under SDWA to process
these actions concurrently and agreed with the EPA's interpretation of
the statute, noting that the EPA has followed all requirements under
SDWA including notice and opportunity for public comment on both the
preliminary regulatory determination and proposed NPDWR, and that
simultaneous public comment periods are not precluded by SDWA. Several
other commenters expressed disagreement with the EPA's interpretation.
These dissenting commenters contend that the statute only allows the
EPA to ``publish such proposed regulation concurrent with the
determination to regulate'' (i.e., in their view, the final
determination), not the ``preliminary determination to regulate.''
Moreover, some of these commenters further indicated that they believe
the EPA's final determination to regulate must precede the EPA's
proposed regulation. The EPA disagrees with commenters who stated that
the EPA cannot issue a preliminary determination concurrent with a
proposed NPDWR. Section 1412(b)(1)(e) states that ``[t]he Administrator
shall propose the maximum contaminant level goals and national primary
drinking water regulation for a contaminant not later than 24 months
[[Page 32541]]
after the determination to regulate under subparagraph (B), and may
publish such proposed regulation concurrent with the determination to
regulate'' (emphasis added). The EPA maintains its interpretation that
``determination to regulate'' in the second phrase of 1412(b)(1)(E)
allows for concurrent processing of a preliminary determination and
proposed rule, not a final determination and proposed rule.
The first clause of the provision provides an enforceable 24-month
deadline for the EPA to issue a proposed rule once it has decided to
regulate. Contrary to the suggestion of some commenters, the statutory
language providing that the EPA ``shall'' propose an NPDWR ``not later
than 24 months after the determination to regulate'' states when the 24
months to issue a proposed rule begins, i.e., the deadline is 24 months
after making a final determination to issue a proposed regulation. The
phrase ``after the determination to regulate'' here simply identifies
when SDWA's deadline begins to run; there is no textual or other
indication in the language that Congress meant it to constitute the
beginning of an exclusive 24-month window in which the EPA is permitted
to propose an NPDWR. Further, though the EPA's reading is clear on the
face of the provision, it is also supported by language elsewhere in
SDWA illustrating that when Congress intends to provide a window for
action (as opposed to a deadline for action) it knows how to do so
clearly. In fact, Congress did so in this very provision when it
required the EPA to ``publish a maximum contaminant level goal and
promulgate a national primary drinking water regulation within 18
months after the proposal thereof.'' See also, 42 U.S.C. 1448
(providing, among other things, that petitions for review of the EPA
regulations under SDWA ``shall be filed within the 45-day period
beginning on the date of the promulgation of the regulation . . .'')
(emphasis added). In addition, the phrase ``not later than,'' expressly
acknowledges that the EPA may issue a proposed rule concurrent with a
final determination. And because this language only provides a deadline
without a beginning trigger, the language in the first clause of this
provision would also not preclude the EPA from issuing a proposed rule
at any time prior to the expiration of the 24 months after a final
regulatory determination, including issuing the proposed rule on the
same day as the preliminary regulatory determination.
The second clause, which states that the Administrator ``may
publish such proposed regulation concurrent with the determination to
regulate'' should not be read to limit when the EPA can issue a
proposed rule prior to a final determination. First, Congress's use of
the phrase ``determination to regulate'' elsewhere in SDWA is not
consistent, requiring the agency to discern its meaning based on
statutory context. Second, reading ``determination to regulate'' to
refer to a final determination would, without good reason, hinder
Congress' goal in enacting this provision, to accelerate the EPA action
under SDWA. Finally, the EPA's interpretation to allow for concurrent
processes is fully consistent with, and indeed enhances, the
deliberative stepwise process provided in the statute for regulating
new contaminants.
Language throughout the statute demonstrates that Congress did not
use the term ``determination to regulate'' consistently. In fact,
``preliminary determination'' only appears once in the entire
provision, ``final determination'' is never used, and the remainder of
the references simply refer to ``determination.'' Specifically, section
1412(b)(1)(B)(ii)(I) expressly requires public comment on a
``preliminary'' regulatory determination made as part of the
contaminant candidate listing process. The rest of section
1412(b)(1)(B)(ii) and (iii) as well as the title of the provision only
refer to a ``determination to regulate'' or ``determination.'' For
example, 1412(b)(1)(B)(iii) states that ``[e]ach document setting forth
the determination for a contaminant under clause (ii) shall be
available for public comment at such time as the determination is
published.'' \1\ Although this provision only refers to a
``determination for a contaminant under clause (ii),'' this language
clearly refers to public comment on a preliminary determination and not
a final determination to regulate. The EPA has interpretated
``determination'' in this paragraph to refer to ``preliminary
determination'' because that is the best interpretation to effectuate
Congressional intent to provide public comment prior to issuing a final
determination. The EPA has done the same with section 1412(b)(1)(E)
here, as only a reading that allows for, in appropriate cases,
concurrent processing of a preliminary determination to regulate and
proposed NPDWR allows for rulemaking acceleration by the EPA as
Congress envisioned. To the extent there is ambiguity, the EPA's
reading of section 1412(b)(1)(E) is the best one to effectuate these
purposes.
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\1\ Even the first clause of section 1412(b)(1)(E) setting the
24-month deadlines use ``regulatory determination'' without further
clarifying whether it is preliminary or final. Again, it is clear
when viewed in context that the term refers to a final
determination, as triggering a deadline to propose regulations on a
preliminary decision to regulate would not be reasonable, as the
agency may change its mind after reviewing publicv comment,
obviating the need for a proposed NPDWR.
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The EPA could issue a proposed rule concurrent with a final
determination; there is nothing in the statute or the APA that requires
the EPA to wait. The SDWA gives the EPA 24 months to act after a final
determination but does not require the agency to wait 24 months. The
``no later than'' language in the first clause of section
1412(b)(1)(E), expressly acknowledges that the EPA may issue a proposed
rule concurrent with a final determination. Therefore, construing the
second phrase of section 1412(b)(1)(E) simply to authorize the EPA to
issue a proposed rule concurrent with a final determination renders
that provision of the statute authorizing the EPA to publish such
proposed regulation concurrent with the determination to regulate a
nullity. The well-known tools of statutory construction direct the
agencies and courts not to construe statutes so as to render Congress's
language mere surplusage, yet that it is what commenters'
interpretation would do. The EPA's construction is the one which gives
meaning to that language.
Moreover, the EPA's interpretation of ``determination to regulate''
in the phrase ``may publish such proposed regulation concurrent with
the determination to regulation'' in section 1412(b)(1)(E) to be a
preliminary determination best effectuates Congress' goal in enacting
this provision, to accelerate the EPA action under SDWA when the EPA
determines such a step is necessary and the EPA has, as it does here, a
sufficient record to proceed with both regulatory determination and
regulation actions concurrently. In addition to authorizing concurrent
processes, Congress' intent to expedite regulatory determinations when
necessary is evidenced more generally by the text and structure of
section 1412(b)(1)(B)(ii). The statute contemplates regulatory
determinations could be made as part of the 5-year cycle for the
contaminant candidate list under section 1412(b)(1)(B)(ii)(I) but may
also be made at any time under section 1412(b)(1)(B)(ii)(III). The fact
that Congress provided the EPA with express authority to make a
regulatory determination at any time is a recognition that the EPA may
need to act expeditiously to address public
[[Page 32542]]
health concerns between the statutory periodic 5-year cycle. The EPA's
interpretation of the relevant language in section 1412(b)(1)(E) best
effectuates all provisions of the statute because simultaneous public
processes for off-cycle regulatory determinations and NPDWRs allow for
administrative efficiency that may be needed to address pressing public
health concerns.
Finally, the EPA's interpretation of the statute allowing for
concurrent processes is fully consistent with the stepwise process for
issuing an NPDWR set out by the statute. Here, the EPA provided for
public comment on an extensive record for both the regulatory
determinations and the proposed regulatory levels and it is not clear
what further benefit would be provided by two separate public comment
periods. This is especially true given the D.C. Circuit's ruling in
NRDC v. Regan, 67 F.4th 397 (D.C. Cir 2023), which held that the EPA
cannot withdraw a final determination to regulate a contaminant. Thus,
even if the EPA were to provide two separate comment periods, the
information provided on a proposed rule cannot be used to undo a final
regulatory determination. Indeed, although not required by the statute,
the EPA in proposing actions concurrently provides commenters with much
more information to evaluate the preliminary regulatory determinations.
This is because the EPA has provided not just the information to
support the preliminary determinations to regulate but also the full
rulemaking record and supporting risk, cost, occurrence, and benefit
analysis that supports the proposed Maximum Contaminant Levels (MCLs).
Further, the EPA has a much more comprehensive record for the
regulatory determinations to ensure that the final determination, which
cannot be withdrawn, is based on the comprehensive record provided by
the rulemaking and Health Risk Reduction and Cost Analysis (HRRCA)
development processes.
The EPA received comments on its statutory authority to regulate
mixtures of PFHxS, PFNA, HFPO-DA, and/or PFBS, specifically the
agency's interpretation under section 1401(6) that a mixture of two or
more contaminants also qualifies as the definition of a contaminant
under SDWA since a mixture itself meets the same definition. A few
commenters disagreed and contended that a mixture does not meet the
definition of being a single contaminant under SDWA. The EPA disagrees
with these commenters, as the SDWA definition of a contaminant does not
specify that a contaminant is only a singular chemical. The SDWA
definition is very broad, specifically stating that a contaminant is
``any physical, chemical or biological or radiological substance or
matter'' (emphasis added), with no specific description or requirement
for how it is formed. Matter for example, by definition, is comprised
of either pure substances or mixtures of pure substances. A pure
substance is either an element or compound, which would include any
PFAS chemical. The statute encompasses ``matter'' which is a broad term
that includes mixtures and therefore definitionally includes PFAS
mixtures, comprised of a combination of PFAS (chemical substances), as
itself qualifying as a ``contaminant'' under SDWA. Moreover, other
provisions of the statute, would be restricted in a manner inconsistent
with Congressional intent if the EPA were to adopt the cabined approach
to ``contaminant'' suggested by some commenters. For example, section
1431 of SDWA provides important authority to the EPA to address
imminent and substantial endangerment to drinking water supplies posed
by ``a contaminant'' that is present in or threatened those supplies.
Congress clearly intended this authority to be broad and remedial, but
it would be significantly hampered if the EPA would be restricted to
only addressing individual chemicals and not mixtures threatening a
water supply. For these reasons, the EPA's interpretation of the
definition of contaminant is the only reading that is consistent with
the statutory definition and use of the term in context and at to the
extent the definition of contaminant is ambiguous, the EPA's
interpretation represents the best interpretation of that term.
Finally, even if a mixture is considered a group, as some commenters
suggest, Congress clearly contemplated that the EPA could regulate
contaminants as groups. See H.R. Rep. No 93-1185 (1974), reprinted in
1974 U.S.C.C.A.N. 6454, 6463-64) (noting the tens of thousands of
chemical compounds in use commercially, with many more added each year,
of which many will end up in the nation's drinking water and finding
that ``[i]t is, of course, impossible for EPA to regulate each of these
contaminants which may be harmful to health on a contaminant-by-
contaminant basis. Therefore, the Committee anticipates that the
Administrator will establish primary drinking water regulations for
some groups of contaminants, such as organic and asbestos.'') Thus, the
EPA has the authority to regulate a mixture as a contaminant under
SDWA.
The commenters also suggested that the EPA has not followed its
Supplementary Guidance for Conducting Health Risk Assessment of
Chemical Mixtures (USEPA, 2000a), specifically that the agency did not
use a ``sufficiently similar mixture'' where ``components and
respective portions exist in approximately the same pattern'' and
suggested that there has to be consistent co-occurrence of the mixture
components. The EPA disagrees with these comments. It is not possible
or necessary to use a whole-mixture approach for PFHxS, PFNA, HFPO-DA,
and PFBS or a ``sufficiently similar mixture.'' Instead, the EPA is
using a longstanding component-based mixture approach called the Hazard
Index, which was endorsed in the context of assessing potential risk
associated with PFAS mixtures by the Science Advisory Board (SAB)
during its 2021 review of the EPA's Draft Framework for Estimating
Noncancer Health Risks Associated with Mixtures of Per- and
Polyfluoroalkyl Substances (PFAS) (USEPA, 2021e) (see section IV of
this preamble). The goal of this component-based approach is to
approximate what the whole-mixture toxicity would be if the whole
mixture could be tested and relies on toxicity information for each
individual component in a mixture (USEPA, 2000a). A whole-mixture
approach for regulating these four PFAS in drinking water is not
possible because it would entail developing a single toxicity value
(e.g., a reference dose (RfD)) for one specific mixture of PFHxS, PFNA,
HFPO-DA, and PFBS with defined proportions of each PFAS. Toxicity
studies are typically conducted with only one test substance to isolate
that particular substance's effects on the test organism, and whole-
mixture data are exceedingly rare. There are no known whole-mixture
studies for PFHxS, PFNA, HFPO-DA, and PFBS, and even if they were
available, the corresponding toxicity value (i.e., a single RfD for a
specific mixture of these four PFAS) would only be directly applicable
to that specific mixture. Thus, a more flexible approach that takes
into account the four component PFAS in different combinations and at
different concentrations (i.e., the Hazard Index approach) is
necessary. The Hazard Index indicates risk from exposure to a mixture
and is useful in this situation to ensure a health-protective MCLG in
cases where the mixture is spatially and/or temporally variable. For a
more detailed discussion on whole-mixture and component-based
approaches for PFAS health assessment, please see the EPA's Framework
for
[[Page 32543]]
Estimating Noncancer Health Risks Associated with Mixtures of Per- and
Polyfluoroalkyl Substances (PFAS) (USEPA, 2024a).
Many other commenters supported the EPA's interpretation of
regulating a mixture as a ``contaminant'' that consists of a
combination of certain PFAS, citing the EPA's broad authority under
SDWA to set regulatory standards for groups of related contaminants and
the EPA precedent for doing so under other NPDWRs including
disinfection byproducts (DBPs; for total trihalomethanes [TTHMs] and
the sum of five haloacetic acids [HAA5] (USEPA, 1979; USEPA, 2006a)),
as well as radionuclides (USEPA, 2000c) and polychlorinated biphenyls
(PCBs). The EPA also noted some of these examples within the proposed
rule. One commenter disagreed that these previous EPA grouping
approaches are applicable to the mixture of the four PFAS, noting that
TTHMs and HAA5 are byproducts of the disinfection process and are the
result of naturally occurring compounds reacting with the disinfectants
used in drinking water treatment; thus, their formation cannot be
controlled and is dependent on the presence and amount of disinfectant.
As a result of these factors, measuring them as a class is required;
however, the four PFAS are not byproducts, and the presence of one PFAS
does not change the presence of the other PFAS. Moreover, the commenter
provided that related to radionuclides, alpha particles are identical
regardless of their origination and using this example for PFAS is not
supported since the four PFAS are fundamentally different. The EPA
disagrees with this commenter. As noted above, the SDWA definition of
contaminant is very broad (``any physical, chemical or biological or
radiological substance or matter'' (emphasis added)) with no
limitations, specific description or requirement for how it is formed.
The statute therefore easily encompasses a mixture, comprised of a
combination of PFAS (chemical substances), as itself qualifying as a
``contaminant'' under SDWA. Moreover, as also noted above, to the
extent the mixture is considered a ``group,'' Congress clearly
anticipated that the EPA would regulate contaminants by group. As a
result, even if the PFAS ``group'' is different than other SDWA
regulatory groupings, such a regulation is clearly authorized under the
statute. Furthermore, it makes sense to treat these mixtures as a
``contaminant'' because the four PFAS share similar characteristics: it
is substantially likely that they co-occur; the same treatment
technologies can be used for their removal; they are measured
simultaneously using the same analytical methods; they have shared
adverse health effects; and they have similar physical and chemical
properties resulting in their environmental persistence.
3. The EPA's Final Determination
The EPA is making determinations to regulate PFHxS, PFNA, and HFPO-
DA individually and to regulate mixtures of PFHxS, PFNA, HFPO-DA, and/
or PFBS. A mixture of PFHxS, PFNA, HFPO-DA, and PFBS can contain any
two or more of these PFAS. The EPA refers to ``mixtures'' in its final
regulatory determinations to make clear that its determinations cover
all of the combinations of PFHxS, PFNA, HFPO-DA, and PFBS that could
co-occur in a mixture but that any combination itself qualifies as a
contaminant.
In this preamble, as discussed earlier, the EPA is deferring the
final determination to regulate PFBS individually to further evaluate
the three criteria specified under SDWA 1412(b)(1)(A), particularly
related to its individual known or likely occurrence, but is making a
final determination to regulate PFBS as part of a mixture with PFHxS,
PFNA, and/or HFPO-DA.
To support the agency's regulatory determinations, the EPA
carefully considered the public comments and examined health effects
information from available final peer-reviewed human health assessments
and studies, as well as drinking water monitoring data collected as
part of the UCMR 3 and state-led monitoring efforts. The EPA finds that
oral exposure to PFHxS, PFNA, and HFPO-DA individually, and
combinations of these three PFAS and PFBS in mixtures, may result in a
variety of adverse health effects, including similar or shared adverse
effects on several biological systems including the endocrine,
cardiovascular, developmental, immune, and hepatic systems (USEPA,
2024f). Based on the shared toxicity types, exposure to PFHxS, PFNA, or
HFPO-DA individually, or combinations of these three PFAS and PFBS in a
mixture, is anticipated to affect common target organs, tissues, or
systems to produce dose-additive effects from co-exposures.
Additionally, based on the agency's evaluation of the best available
science, including a review of updated data from state-led drinking
water monitoring efforts discussed in subsection III.C of this
preamble, the EPA finds that PFHxS, PFNA, and HFPO-DA each have a
substantial likelihood to occur in finished drinking water and that
these three PFAS and PFBS are also likely to co-occur in mixtures and
result in increased total PFAS exposure above levels of public health
concern. Therefore, as discussed further in this section, the agency is
determining that:
exposure to PFHxS, PFNA, or HFPO-DA individually, and any
mixture of these three PFAS and PFBS, may have adverse effects on the
health of persons;
there is a substantial likelihood that PFHxS, PFNA, and
HFPO-DA will occur and there is a substantial likelihood that
combinations of these three PFAS plus PFBS will co-occur in mixtures in
PWSs with a frequency and at levels of public health concern; and
in the sole judgment of the Administrator, individual
regulation of PFHxS, PFNA, and HFPO-DA, and mixtures of the three PFAS
plus PFBS, presents a meaningful opportunity for health risk reductions
for persons served by PWSs.
The EPA is making a final individual regulatory determination for
PFHxS, HFPO-DA, and PFNA and promulgating individual MCLGs and NPDWRs
for PFHxS, HFPO-DA, and PFNA. These NPDWRs ensure public health
protection when one of these PFAS occurs in isolation above their MCLs
and also support risk communication efforts for utilities (see section
V of this preamble for more information). The EPA is also making a
final mixture regulatory determination and promulgating a Hazard Index
MCLG and NPDWR for mixtures containing two or more of PFHxS, PFNA,
HFPO-DA, and PFBS. The Hazard Index is a risk indicator and has been
shown to be useful in chemical mixtures decision contexts (USEPA,
2023c).\2\ Individual NPDWRs do not address dose additive risks from
co-occurring PFAS. However, the Hazard Index NPDWR accounts for PFAS
co-occurring in mixtures where the individual concentrations of one or
more PFAS may not exceed their individual levels of public health
concern, but the combined levels of these co-occurring PFAS result in
an overall exceedance of the health-protective level. In this way, the
Hazard Index NPDWR protects against dose-additive effects. This
approach also recognizes that exposure to the PFAS included in the
Hazard Index is associated with adverse health effects at differing
potencies (e.g., the toxicity reference value for PFHxS is lower than
[[Page 32544]]
the one for PFBS) and that, regardless of these potency differences,
all co-occurring PFAS are included in the hazard calculation (i.e., the
health effects and presence of lower toxicity PFAS are neither ignored
nor are they over-represented). Furthermore, the approach accounts for
all the different potential combinations of these PFAS that represent a
potential public health concern that would not be addressed if the EPA
only finalized individual NPDWRs and considered individual PFAS in
isolation.
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\2\ Some describe the Hazard Index as an indicator of potential
hazard because it does not estimate the probability of an effect;
others characterize the Hazard Index as an indicator of potential
risk because the measure integrates both exposure and toxicity
(USEPA 2000c; USEPA, 2023c).
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B. Statutory Criterion 1--Adverse Health Effects
The agency finds that exposure to PFHxS, PFNA, and HFPO-DA
individually, and any mixture of these three PFAS and PFBS, may have an
adverse effect on the health of persons. Following is a discussion of
health effects information for each of these four individual PFAS and
the levels at which those health effects may be adverse. The agency
developed health reference levels (HRLs) for PFHxS, PFNA, HFPO-DA, and
PFBS as part of its effort to identify the adverse effects each
contaminant may have on the health of persons. In this instance, the
EPA identified the HRL as the level below which adverse health effects
over a lifetime of exposure are not expected to occur, including for
sensitive populations and life stages, and allows for an adequate
margin of safety. The HRLs are also used as health-based water
concentrations (HBWCs) in the calculation of the Hazard Index MCLG (see
section IV).
1. PFHxS
Studies have reported adverse health effects, including on the
liver, thyroid, and development, after oral exposure to PFHxS (ATSDR,
2021). For a detailed discussion on adverse effects associated with
oral exposure to PFHxS, please see ATSDR (2021) and USEPA (2024f).
The EPA derived the individual HRL/HBWC for PFHxS using a chronic
reference value of 0.000002 (2E-06) mg/kg/day based on adverse thyroid
effects (follicular epithelial hypertrophy/hyperplasia), a sensitive
noncancer effect determined to be adverse and relevant to humans,
observed in male rats after oral PFHxS exposure during adulthood
(ATSDR, 2021; USEPA, 2024f). The EPA applied a bodyweight-adjusted
drinking water intake (DWI-BW) exposure factor for adults within the
general population (0.034 L/kg/day; 90th percentile direct and indirect
consumption of community water, consumer-only two-day average, adults
21 years and older) and a relative source contribution (RSC) of 0.20 to
calculate the HRL/HBWC (USEPA, 2024f). The HRL/HBWC for PFHxS is 10 ng/
L which was used to evaluate individual occurrence of PFHxS for the
final regulatory determination as discussed in section III.C of this
preamble.
2. PFNA
Studies have reported adverse health effects, including on
development, reproduction, immune function, and the liver, after oral
exposure to PFNA (ATSDR, 2021). For a detailed discussion of adverse
effects associated with oral exposure to PFNA, please see ATSDR (2021)
and USEPA (2024f).
The EPA derived the HRL/HBWC for PFNA using a chronic reference
value of 0.000003 (3E-06) mg/kg/day based on decreased body weight gain
and impaired development (i.e., delayed eye opening, delayed sexual
maturation) in mice born to mothers that were orally exposed to PFNA
during gestation (with presumed continued indirect exposure of
offspring via lactation) (ATSDR, 2021; USEPA, 2024f). These sensitive
noncancer effects were determined to be adverse and relevant to humans
(ATSDR, 2021; USEPA, 2024f). The EPA applied a DWI-BW exposure factor
for lactating women (0.0469 L/kg/day; 90th percentile direct and
indirect consumption of community water, consumer-only two-day average)
and an RSC of 0.20 to calculate the HRL/HBWC (USEPA, 2024f). The HRL/
HBWC for PFNA is 10 ng/L which was used to evaluate individual
occurrence of PFNA for the final regulatory determination as discussed
in section III.C of this preamble.
3. HFPO-DA
Animal toxicity studies have reported adverse health effects after
oral HFPO-DA exposure, including liver and kidney toxicity and immune,
hematological, reproductive, and developmental effects (USEPA, 2021b).
The EPA determined that there is Suggestive Evidence of Carcinogenic
Potential after oral exposure to HFPO-DA in humans, but the available
data are insufficient to derive a cancer risk concentration for oral
exposure to HFPO-DA. For a detailed discussion of adverse effects of
oral exposure to HFPO-DA, please see USEPA (2021b).
The most sensitive noncancer effects observed among the available
data were the adverse effects on liver (e.g., increased relative liver
weight, hepatocellular hypertrophy, apoptosis, and single-cell/focal
necrosis), which were observed in both male and female mice and rats
across a range of exposure durations and dose levels, including the
lowest tested dose levels and shortest exposure durations. The EPA
derived the HRL/HBWC for HFPO-DA from a chronic oral RfD of 0.000003
(3E-06) mg/kg/day that is based on adverse liver effects, specifically
a constellation of liver lesions including cytoplasmic alteration,
single-cell and focal necrosis, and apoptosis, observed in parental
female mice following oral exposure to HFPO-DA from pre-mating through
day 20 of lactation (USEPA, 2021b). The EPA applied a DWI-BW exposure
factor for lactating women (0.0469 L/kg/day; 90th percentile direct and
indirect consumption of community water, consumer-only two-day average)
and an RSC of 0.20 to calculate the HRL/HBWC (USEPA, 2024f). The HRL/
HBWC for HFPO-DA is 10 ng/L which was used to evaluate individual
occurrence of HFPO-DA for the final regulatory determination as
discussed in section III.C of this preamble.
4. PFBS
Toxicity studies of oral PFBS exposure in animals have reported
adverse health effects on development, as well as on the thyroid and
kidneys (USEPA, 2021a). Human and animal studies evaluated other health
effects following PFBS exposure including effects on the immune,
reproductive, and hepatic systems and lipid and lipoprotein
homeostasis, but the evidence was determined to be equivocal (USEPA,
2021a). No studies evaluating the carcinogenicity of PFBS in humans or
animals were identified. The EPA concluded that there is Inadequate
Information to Assess Carcinogenic Potential for PFBS and its potassium
salt (K + PFBS) by any route of exposure based on the EPA's Guidelines
for Carcinogen Risk Assessment (USEPA, 2005a). For a detailed
discussion on adverse effects after oral exposure to PFBS, please see
USEPA (2021a).
As noted previously, the agency is deferring the final individual
regulatory determination for PFBS. For the purposes of evaluating PFBS
in mixture combinations with PFHxS, PFNA, and HFPO-DA (see section
III.B.5 of this preamble), the EPA derived the HRL/HBWC for PFBS from a
chronic RfD of 0.0003 (3E-04) mg/kg/day that is based on adverse
thyroid effects (decreased serum total thyroxine) observed in newborn
mice following gestational exposure to the potassium salt of PFBS
(USEPA, 2021a). The EPA applied a DWI-BW exposure factor for women of
child-bearing age (0.0354 L/kg/day; 90th percentile direct and indirect
consumption of community water, consumer-only two-day average) and an
[[Page 32545]]
RSC (relative score contribution) of 0.20 to calculate the HRL/HBWC
(USEPA, 2024f). The HRL/HBWC for PFBS is 2000 ng/L.
5. Mixtures of PFHxS, PFNA, HFPO-DA, and PFBS
Exposure to per- and polyfluoroalkyl acids (PFAAs), a subclass of
PFAS that includes PFHxS, PFNA, HFPO-DA, and PFBS, can disrupt
signaling of multiple biological pathways, resulting in a shared set of
adverse effects, including effects on thyroid hormone levels, lipid
synthesis and metabolism, development, and immune and liver function
(ATSDR, 2021; EFSA et al., 2018; EFSA et al., 2020; USEPA, 2021a;
USEPA, 2021b; USEPA, 2024f; see further discussion in section III.B.6.e
of this preamble).
Studies with PFAS and other classes of chemicals support the
health-protective conclusion that chemicals that have similar observed
adverse effects following individual exposure should be assumed to act
in a dose-additive manner when in a mixture unless data demonstrate
otherwise (USEPA, 2024a). Dose additivity means that the combined
effect of the component chemicals in the mixture (in this case, PFHxS,
PFNA, HFPO-DA, and/or PFBS) is equal to the sum of their individual
doses or concentrations scaled for potency (USEPA, 2000a). In other
words, exposure to these PFAS, at doses that individually would not
likely result in adverse health effects, when combined in a mixture may
result in adverse health effects. See additional discussion of PFAS
dose additivity in section IV of this preamble.
The EPA used a Hazard Index (HI) HRL of 1 (unitless) to evaluate
co-occurrence of combinations PFHxS, PFNA, HFPO-DA, and PFBS in
mixtures for the final regulatory determination as discussed in section
III.C of this preamble. For technical details on the Hazard Index
approach, please see section IV of this preamble, USEPA (2024a), and
USEPA (2024f).
6. Summary of Major Public Comments and EPA Responses
Commenters referred to the HRLs and HBWCs interchangeably, so
comments related to those topics are addressed in this section. (Other
comments related to the MCLGs are addressed in section IV of this
preamble.)
Many commenters expressed support for the EPA's derivation of HRLs/
HBWCs and use of best available peer-reviewed science, specifically the
use of the final, most recently published Agency for Toxic Substances
and Disease Registry (ATSDR) minimal risk levels for PFHxS and PFNA as
chronic reference values. Other commenters criticized the EPA for using
ATSDR minimal risk levels and stated that they are inappropriate for
SDWA rulemaking.
The EPA finds that the ATSDR minimal risk levels for PFHxS and PFNA
currently represent the best available, peer-reviewed science for these
chemicals. SDWA specifies that agency actions must rely on ``the best
available, peer-reviewed science and supporting studies conducted in
accordance with sound and objective scientific practices.'' At this
time, the 2021 ATSDR Toxicological Profile for Perfluoroalkyls, which
covers 10 PFAS including PFHxS and PFNA, represents the best available
peer-reviewed scientific information on the human health effects of
PFHxS and PFNA. ATSDR minimal risk levels for PFHxS and PFNA are
appropriate for use under SDWA because ATSDR uses scientifically
credible approaches, its work is internally and externally peer-
reviewed and undergoes public comment, and its work represents the
current best available science for these two chemicals. The 2021 ATSDR
Toxicological Profile for Perfluoroalkyls underwent intra- and
interagency review and subsequent external peer review by seven experts
with knowledge of toxicology, chemistry, and/or health effects.
The agency acknowledges that ATSDR minimal risk levels and EPA RfDs
are not identical. The two agencies sometimes develop toxicity values
for different exposure durations (e.g., intermediate, chronic) and/or
apply different uncertainty/modifying factors to reflect data
limitations. Additionally, ATSDR minimal risk levels and EPA RfDs are
developed for different purposes: ATSDR minimal risk levels are
intended to serve as screening levels and are used to identify
contaminants and potential health effects that may be of concern at
contaminated sites, whereas EPA RfDs are used to support regulatory and
nonregulatory actions, limits, and recommendations in various
environmental media. However, from a practical standpoint, an oral
minimal risk level and an oral RfD both represent the level of daily
oral human exposure to a hazardous substance for a specified duration
of exposure below which adverse health effects are not anticipated to
occur. The EPA has routinely used and continues to use ATSDR minimal
risk levels in human health assessments when they represent the best
available science--for example, in the context of Clean Air Act section
112(f)(2) risk assessments in support of setting national emission
standards for Hazardous Air Pollutants (HAPs), developing Clean Water
Act ambient water quality criteria, evaluating contaminants for the
CCL, and site evaluations under the Resource Conservation and Recovery
Act (RCRA) and the Comprehensive Environmental Response, Compensation,
and Liability Act (CERCLA).
Some commenters questioned the EPA's external peer-review process
for the four underlying final toxicity assessments used to calculate
the HRLs/HBWCs. Some commenters noted that the EPA does not yet have
completed Integrated Risk Information System (IRIS) assessments for
PFHxS and PFNA, questioning the EPA's use of non-EPA assessments (see
above). The EPA notes that all four toxicity assessments containing the
toxicity values (RfD or minimal risk level) used to calculate the HRLs/
HBWCs (i.e., the EPA human health toxicity assessments for HFPO-DA and
PFBS (USEPA, 2021a; USEPA, 2021b) and the ATSDR toxicity assessments of
PFNA and PFHxS (ATSDR, 2021)) underwent rigorous, external peer review
(ATSDR, 2021; USEPA, 2021a; USEPA, 2021b). The EPA is not required
under SDWA to exclusively use EPA assessments to support an NPDWR, and
in fact, SDWA's clear direction in section 1412(b)(3)(A)(i) is to use
the best available, peer-reviewed science when developing NPDWRs
(emphasis added). Final EPA assessments for PFHxS and PFNA are under
development but are not currently available; final, peer reviewed ATSDR
assessments are available.
Other commenters offered critical comments on the HRLs/HBWCs for
PFHxS, PFNA, HFPO-DA, and PFBS and raised technical and process
concerns with the underlying human health assessments. Some commenters
asserted that the human health toxicity values (EPA RfDs, ATSDR minimal
risk levels) upon which the HRLs/HBWCs are based have too much
uncertainty (e.g., inappropriately apply a composite uncertainty factor
(UF) of 3,000) and are therefore inadequate to support a SDWA
regulatory determination. The EPA disagrees with these comments. The
HRLs/HBWCs are data-driven values that incorporate UFs based on the EPA
guidance and guidelines thus, represent the levels below which adverse
health effects are not expected to occur over a lifetime. According to
the EPA guidelines and longstanding practices (USEPA, 2002a; USEPA,
2022f), UFs reflect the limitations of the data across the five areas
used in the current EPA human health risk assessment development: (1)
human interindividual
[[Page 32546]]
variability (UFH); (2) extrapolation from animal to human
(UFA); (3) subchronic-to-chronic duration extrapolation
(UFS); (4) lowest-observed-adverse-effect level-to-no-
observed-adverse-effect level (LOAEL-to-NOAEL) extrapolation
(UFL); and (5) database uncertainty (UFD). In
minimal risk level development, ATSDR also applies uncertainty factors
as appropriate to address areas of uncertainty, with the exception of
subchronic-to-chronic duration extrapolation (ATSDR, 2021). For the
ATSDR minimal risk levels on which the HRLs/HBWCs for PFNA and PFHxS
are based, ATSDR utilized UFHs, UFAs, and what
ATSDR calls a modifying factor to address database deficiencies
(equivalent to the EPA's UFD) (ATSDR, 2021). The EPA
carefully reviewed ATSDR's application of uncertainty and modifying
factors for PFNA and PFHxS and applied additional uncertainty factors
as warranted. Specifically, the EPA applied an additional UF
(UFS) for PFHxS to extrapolate from subchronic to chronic
duration per agency guidelines (USEPA, 2002a) and standard practice
because the critical effect was not observed during a developmental
lifestage (i.e., the effect was in parental male rats). A chronic
toxicity value (i.e., RfD, MRL) represents the daily exposure to the
human population (including sensitive subgroups) that is likely to be
without an appreciable risk of deleterious effects during a lifetime;
the EPA is using a chronic toxicity value to derive the MCLG to ensure
that it is set at a level at or below which no known or anticipated
adverse effects on human health occur and allowing an adequate margin
of safety. The EPA guidelines indicate that the composite (total) UF
may be equal to or below 3,000; composite UFs greater than that
represent ``excessive uncertainty'' (USEPA, 2002a; USEPA, 2022f). In
the case of this final NPDWR, a composite UF of 3,000 was appropriately
applied to derive toxicity values used to develop HRLs/HBWCs for two of
the four PFAS (HFPO-DA and PFHxS) following peer-reviewed agency
guidance and longstanding practice (see USEPA (2024f) for complete
discussion of UF application for all four PFAS). The EPA has previously
developed an MCLG for a chemical that had a composite UF of 3,000
applied to derive a toxicity value (e.g., thallium [USEPA, 1992]).
Further, a composite uncertainty factor of 3,000 has been applied in
the derivation of oral RfDs for several chemicals that have been
evaluated within the EPA's IRIS (Integrated Risk Information System)
program (e.g., fluorene, cis- and trans-1,2-dichloroethylene, 2,4-
dimethylphenol; please see the EPA's IRIS program website [https://www.epa.gov/iris] for further information).
Some commenters opposed the EPA's application of a 20 percent RSC
(relative source contribution) in the HRL/HBWC calculations and stated
that it was a ``conservative default'' approach not supported by
available information and that adequate exposure data exist to justify
an RSC other than 20 percent (although commenters did not offer a
suggested alternative RSC). The EPA disagrees with these comments. The
EPA applies an RSC to account for potential aggregate risk from
exposure routes and exposure pathways other than oral ingestion of
drinking water to ensure that an individual's total exposure to a
contaminant does not exceed the daily exposure associated with toxicity
(i.e., threshold level or reference dose). Application of the RSC in
this context is consistent with EPA methods (USEPA, 2000d) and long-
standing EPA practice for establishing drinking water MCLGs and NPDWRs
(e.g., see USEPA, 1989; USEPA, 2004; USEPA, 2010). The RSC represents
the proportion of an individual's total exposure to a contaminant that
is attributed to drinking water ingestion (directly or indirectly in
beverages like coffee, tea, or soup, as well as from dietary items
prepared with drinking water) relative to other exposure pathways. The
remainder of the exposure equal to the RfD (or minimal risk level) is
allocated to other potential exposure sources (USEPA, 2000d). The
purpose of the RSC is to ensure that the level of a contaminant (e.g.,
MCLG) in drinking water, when combined with other identified potential
sources of exposure for the population of concern, will not result in
total exposures that exceed the RfD (or minimal risk level) (USEPA,
2000d). This ensures that the MCLG under SDWA meets the statutory
requirement that it be a level of a contaminant in drinking water at or
below which no known or anticipated adverse effects on human health
occur and allowing an adequate margin of safety.
To determine the RSCs for the four HRLs/HBWCs, the agency assessed
the available scientific literature on potential sources of human
exposure other than drinking water. The EPA conducted literature
searches and reviews for each of the four HRLs/HBWCs to identify
potential sources of exposure and physicochemical properties that may
influence occurrence in environmental media (Deluca et al., 2022;
USEPA, 2024f). Considering this exposure information, the EPA followed
its longstanding, peer-reviewed Exposure Decision Tree Approach in the
EPA's Methodology for Deriving Ambient Water Quality Criteria for the
Protection of Human Health (USEPA, 2000d) to determine the RSC for each
PFAS. As discussed by the EPA in the Hazard Index MCLG document (USEPA,
2024f), the EPA carefully evaluated studies that included information
on potential exposure to these four PFAS (PFHxS, PFNA, HFPO-DA, and
PFBS) via sources other than drinking water, such as food, soil,
sediment, and air. For each of the four PFAS, the findings indicated
that there are significant known or potential uses/sources of exposure
beyond drinking water ingestion (e.g., food, indoor dust) (Box 6 in the
EPA Exposure Tree; USEPA, 2000d), but that data are insufficient to
allow for quantitative characterization of the different exposure
sources (Box 8A in USEPA, 2000d). The EPA's Exposure Decision Tree
approach states that when there are insufficient environmental and/or
exposure data to permit quantitative derivation of the RSC, the
recommended RSC for the general population is 20 percent (Box 8B in
USEPA, 2000d). This means that 20 percent of the exposure equal to the
RfD is allocated to drinking water, and the remaining 80 percent is
attributed to all other potential exposure sources.
Some commenters disagreed with the bodyweight-adjusted drinking
water intake (DWI-BWs) that the EPA used to calculate the HRLs/HBWCs
and thought the selected DWI-BWs were too high (overly health
protective). One commenter stated that the DWI-BW used in the
calculation of the HRL/HBWC for HFPO-DA is inappropriate and that the
EPA should have used a DWI-BW for general population adults instead of
for lactating women. The EPA disagrees with this comment. To select an
appropriate DWI-BW for use in derivation of the HRL/HBWC for HFPO-DA,
the EPA considered the HFPO-DA exposure interval used in the oral
reproductive/developmental toxicity study in mice that served as the
basis for chronic RfD derivation (the critical study). In this study,
parental female mice were dosed from pre-mating through lactation,
corresponding to three potentially sensitive human adult life stages
that may represent critical windows of HFPO-DA exposure: women of
childbearing age, pregnant women, and lactating women (Table 3-63 in
USEPA, 2019a). Of these three, the highest DWI-BW, for lactating women
(0.0469 L/kg/day), is anticipated to be protective of the other two
sensitive life
[[Page 32547]]
stages and was used to calculate the HRL/HBWC for HFPO-DA (USEPA,
2024f).
Other commenters urged the EPA to consider infants as a sensitive
life stage for PFHxS, PFNA, and PFBS and use the DWI-BW for infants to
calculate the HRLs/HBWCs. The EPA disagrees with this comment. The
EPA's approach to DWI-BW selection includes a step to identify the
sensitive population(s) or life stage(s) (i.e., those that may be more
susceptible or sensitive to a chemical exposure) by considering the
available data for the contaminant, including the adverse health
effects observed in the toxicity study on which the RfD/minimal risk
level was based (known as the critical effect within the critical or
principal study). Although data gaps can complicate identification of
the most sensitive population (e.g., not all windows or life stages of
exposure and/or health outcomes may have been assessed in available
studies), the critical effect and point of departure (POD) that form
the basis for the RfD (or minimal risk level) can provide some
information about sensitive populations because the critical effect is
typically observed at the lowest tested dose among the available data.
Evaluation of the critical study, including the exposure window, may
identify a sensitive population or life stage (e.g., pregnant women,
formula-fed infants, lactating women). In such cases, the EPA can
select the corresponding DWI-BW for that sensitive population or life
stage from the Exposure Factors Handbook (USEPA, 2019a). DWI-BWs in the
Exposure Factors Handbook are based on information from publicly
available, peer-reviewed studies, and were updated in 2019. In the
absence of information indicating a sensitive population or life stage,
the DWI-BW corresponding to the general population may be selected.
Following this approach, the EPA selected appropriate DWI-BWs for each
of the four PFAS included in the Hazard Index MCLG (see USEPA, 2024f).
The EPA did consider infants as a sensitive life stage for all four
PFAS; however, the agency did not select the infant DWI-BW because the
exposure intervals of the critical studies supporting the chronic
toxicity values did not correspond to infants. Instead, the exposure
intervals were relevant to other sensitive target populations (i.e.,
lactating women or women of childbearing age) or the general
population. (See also comments related to DWI-BW selection under PFBS
section III.B.6.d. of this preamble).
a. PFHxS
Some commenters noted a typographical error in the HRL/HBWC
calculation for PFHxS which was reported as 9.0 ng/L in the proposal.
The agency has corrected the value in this NPDWR and within the
requirements under 40 CFR part 141, subpart Z. The correct HRL/HBWC for
PFHxS is 10 ng/L.
Two commenters questioned the human relevance of thyroid effects
(i.e., changes in tissue structure (e.g., enlarged cells; increased
numbers of cells) in the thyroids of adult male rats) observed in the
critical study used to derive the ATSDR minimal risk level and the
EPA's PFHxS HRL/HBWC because, as noted in the ATSDR Toxicological
Profile for Perfluoroalkyls, this observed effect may have been
secondary to liver toxicity and, therefore, the commenters state that
its significance is unclear. The EPA disagrees with this comment. SDWA
requires that the EPA use ``the best available, peer reviewed science''
to inform decision making on drinking water regulations. Although there
is some uncertainty regarding the selection of thyroid alterations as
the critical effect (as the ATSDR toxicological profile notes), at this
time, the 2021 ATSDR toxicological profile represents the best
available peer reviewed scientific information regarding the human
health effects of PFHxS. As the most sensitive known effect as
supported by the weight of the evidence, the thyroid effect was
appropriately selected by ATSDR as the critical effect. Additionally,
published studies in rats have shown that PFHxS exposure results in
other thyroid effects, including decreases in thyroid hormone
(primarily T4) levels in serum (NTP, 2018a; Ramh[oslash]j et al.,
2018). Similarly, peer-reviewed final EPA assessments of other PFAS,
including PFBS (USEPA, 2021a) and perfluorobutanoic acid (PFBA) (USEPA,
2022g), have concluded that these changes in rodents are adverse and
human-relevant, and appropriate for RfD derivation. Furthermore, it is
appropriate to use other health protective (toxicity) values developed
by other authoritative governmental agencies, including ATSDR minimal
risk levels, if available, as these agencies use scientifically
credible approaches and their work is peer-reviewed (the ATSDR
toxicological profile underwent intra- and interagency review and
external peer review by seven experts with knowledge of toxicology,
chemistry, and/or health effects). The ATSDR minimal risk levels
reflect the best available, peer-reviewed science.
Furthermore, the EPA's draft IRIS Toxicological Review of
Perfluorohexanesulfonic Acid (PFHxS) and Related Salts (Public Comment
and External Review Draft) (USEPA, 2023d), which is in the public
domain, preliminarily provides confirmatory evidence that PFHxS
significantly affects human development (emphasis added): ``Overall,
the available evidence indicates that PFHxS exposure is likely to cause
thyroid and developmental immune effects in humans, given sufficient
exposure conditions. For thyroid effects, the primary supporting
evidence for this hazard conclusion included evidence of decreased
thyroid hormone levels, abnormal histopathology results, and changes in
organ weight in experimental animals. For immune effects, the primary
supporting evidence included decreased antibody responses to
vaccination against tetanus or diphtheria in children.'' Although the
EPA did not rely on this draft IRIS toxicological review for PFHxS in
this rule, the draft is available to the public and offers confirmation
that PFHxS elicits developmental effects in humans.
b. PFNA
Some commenters questioned the human relevance of developmental
effects observed in PFNA animal studies (i.e., decreased body weight
gain, delayed eye opening, delayed sexual maturation) used to derive
the ATSDR minimal risk level and the EPA's PFNA HRL/HBWC. The EPA
disagrees with this comment. At this time, the 2021 ATSDR Toxicological
Profile for Perfluoroalkyls represents the best available peer-reviewed
scientific information regarding the human health effects of PFNA. In
addition, according to the March 2023 Interagency PFAS Report to
Congress, PFNA is documented to affect the developmental health domain
(United States OSTP, 2023), and a recently published meta-analysis
(Wright et al., 2023) specifically supports decreases in birth weight
as an effect of PFNA exposure in humans. Published studies have shown
that PFNA exposure results in statistically significant, dose-
responsive developmental effects, including reduced fetal/pup
bodyweight, reduced fetal/pup survival, changes in fetal/pup liver gene
expression, increased fetal/pup liver weight, and delayed onset of
puberty. Also, the EPA's 1991 Guidelines for Developmental Toxicity
Risk Assessment (USEPA, 1991a; pp. vii-ix and pp. 1-2) cites evidence
that, in the absence of clear evidence to the
[[Page 32548]]
contrary, developmental effects observed in experimental animals are
interpreted as relevant to humans.
c. HFPO-DA
A few commenters submitted critical comments related to the adverse
health effects associated with exposure to HFPO-DA and how these health
effects are quantified to derive the RfD in the human health toxicity
assessment for HFPO-DA (USEPA, 2021b). Commenters claimed that the RfD
for HFPO-DA is not scientifically sound, and cited one or more of the
following reasons why: (1) the selected critical effect from the study
(constellation of liver lesions) includes different liver effects that
were not consistently observed across male and female mice and were not
necessarily all adverse; (2) the hepatic effects in mice (the selected
critical effect) are mediated by a rodent specific MOA, peroxisome
proliferator-activated receptor alpha (PPAR[alpha]), and therefore not
relevant to humans; (3) the EPA incorporated results of a pathology
working group which misapplied diagnostic criteria classifying
apoptotic and necrotic lesions; and (4) the EPA misapplied uncertainty
factors (UFs) (i.e., the subchronic to chronic UF and database UF)
according to agency guidance resulting in the maximum possible UF of
3,000 (USEPA, 2002a; USEPA, 2022f). Another commenter thought that the
interspecies UF should be further increased. Also, some commenters
stated that the EPA did not properly consider all available
epidemiological data. These comments are addressed in this preamble.
Overall, the EPA disagrees with the commenters and maintains that
the final published peer-reviewed human health toxicity assessment that
derived the RfD for HFPO-DA is appropriate and sound, reflects the best
available peer-reviewed science, and is consistent with agency
guidance, guidelines, and best practices for human health risk
assessment. Notably, the EPA sought external peer review of the
toxicity assessment twice (USEPA, 2018b; USEPA, 2021f), released the
draft toxicity assessment for public comment and provided responses to
public comment (USEPA, 2021g), and engaged a seven-member pathology
working group at the National Institutes of Health--an entirely
separate and independent organization--to re-analyze pathology slides
from two critical studies (USEPA, 2021b, appendix D), all of which
supported the EPA's conclusions in the toxicity assessment, including
the RfD derivation.
Regarding critical effect selection: the EPA's approach to critical
effect selection for the RfD derivation considers a range of factors,
including dose at which effects are observed, biological variability
(which can produce differences in effects observed between sexes), and
relevance of the effect(s) seen in animals to human health. The EPA
maintains that selection of the constellation of liver lesions as the
critical effect for HFPO-DA RfD derivation is appropriate and
scientifically justified, and that the constellation of liver lesions
represents an adverse effect. The EPA engaged a pathology working group
within the National Toxicology Program (NTP) at the National Institutes
of Health to perform an independent analysis of the liver tissue
slides. The pathology working group determined that the tissue slides
demonstrated a range of adverse effects and that the constellation of
liver effects caused by HFPO-DA exposure, which included cytoplasmic
alteration, apoptosis, single cell necrosis, and focal necrosis,
constitutes an adverse liver effect in these studies (USEPA, 2021b,
appendix D). The EPA evaluated the results of the pathology working
group and determined that the effects were relevant to humans according
to the best available science (e.g., Hall et al., 2012). Additionally,
the EPA convened a second independent peer-review panel of human health
risk assessment experts to review the EPA's work on HFPO-DA, including
critical effect selection. The panel unanimously agreed with the
selection of the constellation of liver lesions as the critical effect,
the adversity of this effect and its relevance to humans (USEPA,
2021f).
The commenters' assertion that the hepatic effects observed in mice
are not relevant to humans because they are PPAR[alpha]-mediated is
unsupported. The commenter claims that one specific effect--apoptosis--
can be PPAR[alpha]-mediated in rodents (a pathway that some data
suggest may be of limited or no relevance to humans). However, in
supporting studies cited by commenters, a decrease in apoptosis is
associated with a PPAR[alpha] MOA, with Corton et al. (2018) stating,
``[t]he data indicate that a physiological function of PPAR[alpha]
activation is to increase hepatocyte growth through an increase in
hepatocyte proliferation or a decrease in apoptosis or a combination of
both effects'' while HFPO-DA is associated with increased apoptosis
(USEPA, 2021b). Therefore, the commenter's claim that apoptosis is
associated with the known PPAR[alpha] MOA is unsupported. the critical
study selected by the EPA, and indeed other studies as well, reported
not only apoptosis but also other liver effects such as necrosis that
are not associated with a PPAR[alpha] MOA and therefore are relevant
for human health (Hall et al., 2012). Further, according to the
available criteria, effects such as cytoplasmic alteration in the
presence of liver cell necrosis are considered relevant to humans (Hall
et al., 2012). Additionally, commenters asserted that a 2020 study by
Chappell et al. reported evidence demonstrating that the rodent liver
effects are not relevant to humans, and that the EPA failed to consider
this study. It is important to note that while Chappell et al. (2020)
was published after the assessment's literature search cut-off date
(USEPA, 2021b, appendix A; USEPA, 2022h), the EPA considered this paper
initially through the Request for Correction process (USEPA, 2022h) and
noted that this study specifically assessed evidence for PPAR[alpha]-
driven apoptosis and did not investigate other potential modes of
action or types of cell death, specifically necrosis. The authors state
that they could ``not eliminate the possibility that necrotic cells
were also present.'' The EPA again considered Chappell et al., (2020),
in addition to other studies submitted through public comment (Heintz
et al., 2022; Heintz et al., 2023; Thompson et al., 2023), and
determined that these studies do not fully explore a necrotic/cytotoxic
MOA with Thompson et al., 2023 stating that ``there are no gene sets
for assessing necrosis in transcriptomic databases.'' Critically, the
commenter and these cited studies fail to recognize that increased
apoptosis is a key criterion to establish a cytotoxic MOA. As outlined
in the toxicity assessment (USEPA, 2021b), Felter et al., (2018)
``identified criteria for establishing a cytotoxicity MOA, which
includes: . . . (2) clear evidence of cytotoxicity by histopathology,
such as presence of necrosis and/or increased apoptosis.'' Overall, the
EPA has determined that these studies support the mechanistic
conclusions of the toxicity assessment ``that multiple MOAs could be
involved in the liver effects observed after GenX chemical exposure''
including PPAR[alpha] and cytotoxicity (USEPA, 2021b).
With respect to claims that the EPA misapplied diagnostic criteria
classifying apoptotic and necrotic lesions: as mentioned above, the EPA
engaged a pathology working group within the NTP at the National
Institutes of Health to perform an independent analysis of the liver
tissue slides. Seven pathologists--headed by Dr. Elmore, who was the
lead author of the pathology criteria that the
[[Page 32549]]
commenter cites (Elmore et al., 2016)--concluded that exposure to HFPO-
DA caused a ``constellation of liver effects'' that included
cytoplasmic alteration, apoptosis, single cell necrosis, and focal
necrosis, and that this full ``constellation of lesions'' should be
considered the adverse liver effect within these studies. The EPA then
used the established Hall criteria (Hall et al., 2012) to determine
that since liver cell death was observed, all effects, including
cytoplasmic alteration, were considered adverse and relevant to humans.
The EPA disagrees with the commenters' assertion about UF
application. As noted above, agency guidance (USEPA, 2002a; USEPA,
2022f) have established the appropriateness of the use of UFs to
address uncertainty and account for data limitations. UFs reflect the
limitations of the data across the five areas used in the current EPA
human health risk assessment development (referenced above); all
individual UFs that are applied are multiplied together to yield the
composite or total UF. The EPA guidance dictates that although a
composite UF greater than 3,000 represents ``excessive uncertainty''
(USEPA, 2002a; USEPA, 2022f), a composite UF can be equal to 3,000. For
HFPO-DA, a composite UF of 3,000 was appropriately applied to account
for uncertainties, including variability in the human population,
database uncertainties, and possible differences in the ways in which
humans and rodents respond to HFPO-DA that reaches their tissues.
Furthermore, the composite UF of 3,000 and specifically the database UF
and subchronic-to-chronic UF used for HFPO-DA was peer-reviewed by a
panel of human health risk assessment experts, and the panel supported
the application of the database UF of 10 and the subchronic-to-chronic
UF of 10 (USEPA, 2021f). Additionally, a UFA of 3 was
appropriately applied, consistent with peer-reviewed EPA methodology
(USEPA, 2002a), to account for uncertainty in characterizing the
toxicokinetic and toxicodynamic differences between rodents and humans.
As noted in the toxicity assessment for HFPO-DA (USEPA, 2021b), in the
absence of chemical-specific data to quantify residual uncertainty
related to toxicokinetics and toxicodynamic processes, the EPA's
guidelines recommend use of a UFA of 3.
Finally, some commenters claimed that the EPA did not consider
available epidemiological evidence showing no increased risk of cancers
or liver disease attributable to exposure to HFPO-DA. The EPA disagrees
with this comment because the agency considered all available
scientific evidence, including epidemiological studies (USEPA, 2021b).
The exhibit submitted by the commenter presents an observational
analysis comparing cancer and liver disease rates in North Carolina to
rates in other states. It does not present the results of a new
epidemiological study that included HFPO-DA exposure measures, health
outcome measures, or an assessment of association between exposure and
health outcome. The exhibit submitted by the commenter consists of a
secondary analysis of disease rate information that was collected from
various sources and does not provide new, high-quality scientific
information that can be used to assess the impact of exposure to
concentrations of HFPO-DA on human health.
d. PFBS
A few commenters suggested that the EPA lower the HRL/HBWC for PFBS
to account for thyroid hormone disruption during early development and
cited the Washington State Action Level for PFBS, which is 345 ng/L.
Washington State used the same RfD (3E-04 mg/kg-d) but a higher DWI-BW
to develop their Action Level as compared to the EPA's HRL/HBWC
(Washington State used the 95th percentile DWI-BW of 0.174 L/kg/day for
infants, whereas the EPA selected the 90th percentile DWI-BW of 0.0354
L/kg/day for women of child-bearing age). The EPA disagrees that the
infant DWI-BW is more appropriate for HRL/HBWC calculation. The EPA
selected the thyroid hormone outcome (decreased serum total thyroxine
in newborn mice seen in a developmental toxicity study) as the critical
effect in its PFBS human health toxicity assessment (USEPA, 2021a).
Notably, the RfD derived from this critical effect included application
of a 10X UF to account for life-stage-specific susceptibility
(UFH). To select a DWI-BW for use in deriving the HRL/HBWC
for PFBS, the EPA followed its established approach of considering the
PFBS exposure interval used in the developmental toxicity study in mice
that was the basis for chronic RfD derivation. In this study, pregnant
mice were exposed throughout gestation, which is relevant to two human
adult life stages: women of child-bearing age who may be or become
pregnant, and pregnant women and their developing embryos or fetuses
(Table 3-63 in USEPA, 2019a). To be clear, the critical study exposed
mice to PFBS only during pregnancy and not during postnatal
development; newborn mice in early postnatal development, which would
correspond to the human infancy life stage, were not exposed to PFBS.
Of the two relevant adult stages, the EPA selected the 90th percentile
DWI-BW for women of child-bearing age (0.0354 L/kg/day) to derive the
HRL/HBWC for PFBS because it is the higher of the two, and therefore
more health-protective. Please see additional information related to
DWI-BW selection above.
Other commenters stated that the EPA's human health toxicity
assessment for PFBS is overly conservative, uncertain, and that the
confidence in the chronic RfD is low. The EPA disagrees with these
comments. Confidence in the critical study (Feng et al., 2017) and
corresponding thyroid hormone critical effect in newborn mice was rated
by the EPA as `High;' this rating was a result of systematic study
evaluation and risk of bias analysis by a team of EPA experts. The Feng
et al. (2017) study, the critical effect of thyroid hormone disruption
in offspring, dose-response assessment, and corresponding RfD were
subjected to extensive internal EPA, interagency, and public/external
peer review. While confidence in the critical study was rated `High,'
the `Low' confidence rating for the PFBS chronic RfD was in part a
result of the lack of a chronic exposure duration study in any
mammalian species; this lack of a chronic duration study was one of the
considerations that resulted in the EPA applying a UF of 10 to account
for database limitations (UFD). Based on the EPA's human
health assessment practices, the lowest confidence rating across the
areas of consideration (e.g., existent hazard/dose-response database)
is assigned to the corresponding derived reference value (e.g., RfD).
Thus, the EPA has high confidence in the critical study (Feng et al.,
2017) and critical effect/thyroid endpoint, but the database is
relatively limited. Although the PFBS RfD was based on best available
peer-reviewed science, there is uncertainty as to the hazard profile
associated with PFBS after prolonged (e.g., lifetime) oral exposure. In
the toxicity assessment for PFBS (USEPA, 2021a), the EPA noted data
gaps in specific health effects domains, as is standard practice.
Toxicity assessments for most chemicals identify data gaps; the issue
of uncertainty due to toxicological study data gaps is not unique to
PFBS. Data gaps are considered when selecting the UFD
because they indicate the potential for exposure to lead to adverse
health effects at doses lower than the POD derived from the
assessment's critical
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study. There is a potential that effects with greater dose-response
sensitivity (i.e., occurring at lower daily oral exposures) might be
discovered from a chronic duration exposure study. Due to this
uncertainty, the EPA applied a UFD of 10.
One commenter questioned the EPA's approach to estimating the human
equivalent dose (HED) from the animal data using toxicokinetic (TK)
data rather than using default body-weight scaling and suggested that
the default allometric approach is more appropriate for estimating an
HED. The EPA disagrees with this comment. In human health risk
assessment practice, the EPA considers a hierarchical approach to
cross-species dosimetric scaling consistent with technical guidance to
calculate HEDs (USEPA, 2011; see pp. X-XI of the Executive Summary in
`Recommended Use of Body Weight3/4 as the Default Method in Derivation
of the Oral Reference Dose'). The preferred approach is physiologically
based toxicokinetic (PBTK) modeling; however, there are rarely
sufficient chemical-specific data to properly parameterize such a
model. In the absence of a PBTK model, the EPA considers an
intermediate approach in which chemical-specific data across species,
such as clearance or plasma half-life, are used to calculate a
dosimetric adjustment factor (DAF) (USEPA, 2011). If chemical-specific
TK data are not available, only then is a default approach used wherein
allometric scaling, based on body weight raised to the \3/4\ power, is
used to calculate a DAF. The human health toxicity assessment for PFBS
invoked the intermediate approach, consistent with guidance, as TK data
were available for humans and rodents.
e. Mixtures of PFHxS, PFNA, HFPO-DA, and PFBS
Comments on the EPA's preliminary regulatory determination on the
mixtures of PFHxS, PFNA, HFPO-DA, and/or PFBS were varied. Many
commenters supported the EPA's proposal to regulate a mixture of these
PFAS and agreed with the EPA's scientific conclusions about PFAS dose
additivity. Many commenters urged the EPA to consider making a
determination to regulate for additional PFAS (in a mixture) or all
PFAS as a class. As described throughout section III of this preamble,
the agency is required to demonstrate a contaminant meets the SDWA
statutory criteria to make a regulatory determination. In this
preamble, in addition to PFOA and PFOS which the EPA has already made a
final determination to regulate, the agency is making final
determinations for all PFAS with sufficiently available information to
meet these statutory criteria either individually and/or as part of
mixture combinations. As information becomes available, the agency will
continue to evaluate other PFAS for potential future preliminary
regulatory determinations.
Many commenters opposed the EPA's conclusion about PFAS dose
additivity and use of the Hazard Index approach to regulate co-
occurring PFAS. A few commenters agreed with the EPA's decision to
regulate mixtures of certain PFAS and the EPA's conclusion about dose
additivity but questioned the EPA's use of the general Hazard Index,
and instead, suggested alternative approaches. Please see section IV of
this preamble for a summary of comments and the EPA responses on the
Hazard Index MCLG and related topics.
There is substantial evidence that PFHxS, PFNA, HFPO-DA, and PFBS
act in a dose additive manner, that these four PFAS elicit similar
health effects, and that exposure to mixtures of these PFAS may have
adverse health effects. Following is a discussion of dose additivity
and similarity of adverse effects of PFHxS, PFNA, HFPO-DA, and PFBS.
As noted in this section, the available data indicate that PFHxS,
PFNA, HFPO-DA, and PFBS, while not necessarily toxicologically
identical, elicit many of the same or similar adverse health effects
across different levels of biological organization, tissues/organs,
lifestages, and species (ATSDR, 2021; EFSA et al., 2018; EFSA et al.,
2020; USEPA, 2021d; USEPA, 2021f; USEPA, 2024f). Each of these PFAS
disrupts signaling of multiple biological pathways, resulting in a
shared set of adverse effects including effects on thyroid hormone
levels, lipid synthesis and metabolism, development, and immune and
liver function (ATSDR, 2021; EFSA et al., 2018; EFSA et al., 2020;
USEPA, 2021d; USEPA, 2021f; USEPA, 2024f). Please also see USEPA
(2024a) for an overview of recent studies that provide supportive
evidence of similar effects of PFAS.
Available health effects studies indicate that PFAS mixtures act in
a dose-additive manner when the individual components share some health
endpoints/outcomes. Individual PFAS, each at doses that are not
anticipated to result in adverse health effects, when combined in a
mixture may result in adverse health effects. Dose additivity means
that when two or more of the component chemicals (in this case, PFHxS,
PFNA, HFPO-DA, and/or PFBS) exist in one mixture, the risk of adverse
health effects following exposure to the mixture is equal to the sum of
the individual doses or concentrations scaled for potency (USEPA,
2000a). Thus, exposure to these PFAS, at doses that individually would
not likely result in adverse health effects, when combined in a mixture
may pose health risks.
Many commenters supported the EPA's scientific conclusions about
PFAS dose additivity and agreed that considering dose-additive effects
is a health-protective approach. Many other commenters disagreed with
the EPA's scientific conclusions regarding PFAS dose additivity and a
few commenters questioned the agency's external peer-review process and
whether the agency sufficiently responded to SAB (Science Advisory
Board) comments. For example, these commenters stated that the evidence
base of PFAS mixture studies is too limited to support dose additivity
for these four PFAS and recommended that the EPA re-evaluate its
conclusion about dose additivity as new data become available. A few
commenters stated that the EPA failed to adequately follow the SAB
recommendation that ``discussion of studies of toxicological
interactions in PFAS mixtures in the EPA mixtures document be expanded
to also include studies that do not indicate dose additivity and/or a
common MOA [mode of action] for PFAS.'' The EPA's responses to these
comments are summarized in this section.
The EPA continues to support its conclusion that PFAS that elicit
similar adverse health effects following individual exposure should be
assumed to act in a dose-additive manner when in a mixture unless data
demonstrate otherwise. Numerous published studies across multiple
chemical classes, biological effects, and study designs support a dose-
additive mixture assessment approach for PFAS because they demonstrate
that experimentally observed responses to exposure to PFAS and other
chemical mixtures are consistent with modeled predictions of dose
additivity (see the EPA's Framework for Estimating Noncancer Health
Risks Associated with Mixtures of Per- and Polyfluoroalkyl Substances
(PFAS) (USEPA, 2024a)). Since the EPA's draft PFAS Mixtures Framework
underwent SAB review in 2021, new studies from the EPA and others have
published robust evidence of combined toxicity of PFAS in mixtures,
corroborating and confirming earlier findings (e.g., Conley et al.,
2022a; Conley et al., 2022b; USEPA, 2023c; see USEPA, 2024a for
additional examples). Additionally, the National Academies of
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Sciences, Engineering, and Medicine (NASEM, 2022) recently recommended
that clinicians apply an additive approach for evaluating patient
levels of PFAS currently measured in the National Health and Nutrition
Examination Survey (NHANES) in order to protect human health from
additive effects from PFAS co-exposure.
The EPA directly asked the SAB for feedback on PFAS dose additivity
in the charge for the 2021 review of the EPA's draft PFAS Mixtures
Framework. Specifically, the EPA asked the SAB to, ``[p]lease comment
on the appropriateness of this approach for a component-based mixture
evaluation of PFAS under an assumption of dose additivity'' (USEPA,
2022i). The SAB strongly supported the scientific soundness of this
approach when evaluating PFAS and concurred that it was a health
protective conclusion. For example, the SAB said:
. . . The information included in the draft framework supports the
conclusion that toxicological interactions of chemical mixtures are
frequently additive or close to additive. It also supports the
conclusion that dose additivity is a public health protective
assumption that typically does not underestimate the toxicity of a
mixture . . . (USEPA, 2022i)
The SAB Panel agrees with use of the default assumption of dose
additivity when evaluating PFAS mixtures that have similar effects
and concludes that this assumption is health protective. (USEPA,
2022i)
Regarding the commenters' assertion that the agency did not
adequately follow the SAB recommendation to expand its discussion of
PFAS mixtures study results that did not show evidence of dose
additivity and/or a common MOA, the EPA disagrees. The EPA reviewed all
studies provided by the SAB and in response, included a discussion of
relevant additional studies in its public review draft PFAS Mixtures
Framework (see section 3 in USEPA, 2023w). Since then, the EPA has
included additional published studies and those findings further
confirm dose additive health concerns associated with PFAS mixtures
(see section 3 in USEPA, 2024a). Data from in vivo studies that
rigorously tested accuracy of Dose Additivity (DA), Integrated Addition
(IA), and Response Additivity (RA) model predictions of mixtures with
components that disrupted common pathways demonstrated that DA models
provided predictions that were better than or equal to IA and RA
predictions of the observed mixture effects (section 3.2 in USEPA,
2024a). The National Academy of Sciences (NAS) conclusions on
phthalates (and related chemicals) (NRC, 2008) and systematic reviews
of the published literature (Boobis et al., 2011 and Martin et al.,
2021; see also section 3.2 in USEPA, 2024a) support DA as the default
model for estimating mixture effects in some circumstances, even when
the mixtures included chemicals with diverse MOAs (but common target
organs/effects) (Boobis et al., 2011; Martin et al., 2021; USEPA,
2024a). Recent efforts to investigate in vitro and in vivo PFAS mixture
effects have provided robust evidence that PFAS behave in a dose-
additive manner (see section 3 in USEPA, 2024a).
As supported by the best available science, the SAB, the agency's
chemical mixtures guidance (USEPA, 1991b; USEPA, 2000a), and the EPA
Risk Assessment Forum's Advances in Dose Addition for Chemical
Mixtures: A White Paper (USEPA, 2023c), the EPA proposed a Hazard Index
MCLG for a mixture of up to four PFAS (PFHxS, PFNA, HFPO-DA, and PFBS)
based on dose additivity because published studies show that exposure
to each of these individual four PFAS elicits some of the same or
similar adverse health effects/outcomes. As noted above, many
commenters, as well as the SAB (USEPA, 2022i), supported this
conclusion of dose additivity based on similarity of adverse effects.
While the SAB also noted that there remain some questions about
PFAS interaction in mixtures (USEPA, 2022i), the available data justify
an approach that accounts for PFAS dose additivity. Studies that have
assessed PFAS mixture-based effects do not offer evidence for
synergistic/antagonistic effects (USEPA, 2024a). For example, Martin et
al. (2021), following a review of more than 1,200 mixture studies
(selected from > 10,000 reports), concluded that there was little
evidence for synergy or antagonism among chemicals in mixtures and that
dose additivity should be considered as the default. Experimental data
demonstrate that PFAS disrupt signaling in multiple biological pathways
resulting in common adverse effects on several of the same biological
systems and functions including thyroid hormone signaling, lipid
synthesis and metabolism, developmental toxicity, and immune and liver
function (USEPA 2024a). Additionally, several EPA Office of Research
and Development (ORD) studies provide robust evidence that PFAS behave
in a dose-additive manner (Conley et al., 2022a; Conley et al., 2022b;
Conley et al., 2023; Gray et al., 2023).
Several commenters opposed the conclusion of dose additivity based
on similarity of adverse effects and stated that the EPA failed to
establish that the four PFAS included in the Hazard Index (PFHxS, PFNA,
HFPO-DA, and PFBS) elicit similar adverse health effects. The EPA
disagrees with these comments because the available epidemiology and
animal toxicology studies demonstrate that these four PFAS (PFHxS,
PFNA, HFPO-DA, and PFBS) have multiple health endpoints and outcomes in
common (USEPA, 2024f). Further, these four PFAS are well-studied PFAS
for which the EPA or ATSDR have developed human health assessments and
toxicity values (i.e., RfDs, minimal risk levels). As shown in Table 1,
available animal toxicological data and/or epidemiological studies
demonstrate that PFHxS, PFNA, HFPO-DA, and PFBS are documented to
affect at least five (5) of the same health outcomes for this
evaluation: lipids, developmental, immune, endocrine, and hematologic
(USEPA, 2024g). Similarly, according to the 2023 Interagency PFAS
Report to Congress (United States OSTP, 2023), available animal
toxicological data show that PFHxS, PFNA, HFPO-DA, and PFBS are
documented to significantly affect at least eight (8) of the same major
health effect domains: body weight, respiratory, hepatic, renal,
endocrine, immunological, reproductive, and developmental. In short,
multiple evaluation efforts have clearly demonstrated that each of the
PFAS regulated by this NPDWR impact numerous of the same or similar
health outcomes or domains.
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In summary, there is substantial evidence that mixtures of PFHxS,
PFNA, HFPO-DA, and PFBS act in a dose-additive manner and elicit
multiple similar toxicological effects. Studies by the EPA and others
provide evidence that corroborates the dose-additive toxicity of PFAS
mixtures, and data on different chemical classes and research also
provide support for dose additivity. Additionally, numerous in vivo and
in vitro studies demonstrate that these four PFAS share many common
health effects across diverse health outcome categories (e.g.,
developmental, immunological, and endocrine effects), and that they
induce some of the same effects at the molecular level along biological
pathways (USEPA, 2024f).
C. Statutory Criterion 2--Occurrence
The EPA has determined that there is a substantial likelihood that
PFHxS, PFNA, and HFPO-DA will individually occur and combinations of
these three PFAS and PFBS will co-occur in mixtures in PWSs with a
frequency and at levels of public health concern based on the EPA's
evaluation of the best available occurrence information. In this
preamble, while the EPA is making a final determination to regulate
PFBS in mixtures with PFHxS, PFNA, and/or HFPO-DA, the agency is
deferring the final individual regulatory determination for PFBS so
that the agency can continue to evaluate this contaminant relative to
the SDWA criteria for regulation, particularly related to its
individual known or likely occurrence. For the other three PFAS, the
EPA is making a final determination to regulate them individually in
this preamble (i.e., PFHxS, PFNA, and HFPO-DA). The EPA recognizes
there will be additional occurrence or other relevant information for
these and other PFAS in the future. The EPA has, however, determined
that there is more than sufficient occurrence information to satisfy
the statutory criterion to regulate PFNA, PFHxS, and HFPO-DA.
The EPA's evaluation of the second statutory criterion for
regulation of PFHxS, PFNA, and HFPO-DA individually and regulation of
combinations of these PFAS and PFBS in mixtures follows a similar
process to previous rounds of regulatory determinations including the
written Protocol developed under Regulatory Determination 3 (USEPA,
2014a) and also described in detail in the Preliminary Regulatory
Determination 4 (USEPA, 2020a). Using the Protocol, and as conducted
for the regulatory determinations in this action, the agency compares
available occurrence data relative to the contaminant HRL, a health-
based concentration against which the agency evaluates occurrence data
when making regulatory determinations, as a preliminary factor in
informing the level of public health concern. For both this regulatory
determination and previous regulatory determinations, this is the first
screening factor in informing if there is a substantial likelihood the
contaminant will occur at a frequency and level of public health
concern. Consistent with the Protocol and similar to all past
regulatory determinations, these regulatory determinations are also
based on other factors, not just the direct comparison to the HRL. As
described clearly in the proposal, the EPA has not been able to
determine a simple threshold of public health concern for all
contaminants the agency considers for regulation under SDWA; rather, it
is a contaminant-specific decision which ``involves consideration of a
number of factors, some of which include the level at which the
contaminant is found in drinking water, the frequency at which the
contaminant is found and at which it co-occurs with other contaminants,
whether there is an sustained upward trend that these contaminant will
occur at a frequency and at levels of public health concern, the
geographic distribution (national, regional, or local occurrence), the
impacted population, health effect(s), the potency of the contaminant,
other possible sources of exposure, and potential impacts on sensitive
populations or lifestages.'' (USEPA, 2023f). It also includes
consideration of production and use trends and environmental fate and
transport parameters which may indicate that the contaminant would
persist and/or be mobile in water. Appropriately, the EPA has
considered these relevant factors in its evaluation
[[Page 32553]]
that there is a substantial likelihood that PFHxS, PFNA, and HFPO-DA
will individually occur and combinations of these three PFAS and PFBS
will co-occur in mixtures in PWSs with a frequency and at levels of
public health concern.
The EPA's evaluation of the second statutory criterion is based on
the best available health information, which includes UCMR 3 data and
more recent PFAS drinking water data collected by several states. Based
on suggestions in public comments to update state occurrence data, the
EPA supplemented the data used to inform the rule proposal with new
data from states included in the original proposal and additional
states that have made monitoring data publicly available since the rule
proposal (USEPA, 2024b). Consistent with section 1412(b)(1)(B)(II),
this information combined represents best available occurrence data. It
includes results from tens of thousands of samples and the assembled
data represent one of the most robust occurrence datasets ever used to
inform development of a drinking water regulation of a previously
unregulated contaminant. The state data were primarily gathered after
the UCMR 3 using improved analytical methods that could measure more
PFAS at lower concentrations. These additional data demonstrate greater
occurrence and co-occurrence of the PFAS monitored under UCMR 3 (PFHxS,
PFNA, and PFBS) at significantly greater frequencies than UCMR 3 and
the data initially included in the analysis. Furthermore, the state
data show the co-occurrence of PFAS at levels of public health concern,
as well as the demonstrated occurrence and co-occurrence of HFPO-DA
which was not included within UCMR 3. As discussed subsequently, these
data demonstrate that there is a substantial likelihood PFHxS, PFNA,
and HFPO-DA will occur and combinations of PFHxS, PFNA, HFPO-DA, and
PFBS will co-occur in mixtures with a frequency and at levels of public
health concern. When determining that there is a substantial likelihood
PFHxS, PFNA, and HFPO-DA will occur and PFHxS, PFNA, HFPO-DA, and/or
PFBS will co-occur at levels of public health concern, the EPA
considered both the occurrence concentration levels for PFHxS, PFNA,
and HFPO-DA individually, as well as their collective co-occurrence and
corresponding dose additive health concerns from co-exposures with PFBS
for purposes of considering a regulatory determination for mixtures of
these four PFAS. The EPA also considered other factors in evaluating
the second criterion and informing level of public health concern for
PFHxS, PFNA, and HFPO-DA individually and combinations of these three
PFAS and PFBS in mixtures, including the frequency at which the
contaminant is found, the geographic representation of the
contaminant's occurrence, and the environmental fate and transport
characteristics of the contaminant. As the EPA noted previously, while
the agency is not making an individual regulatory determination for
PFBS at this time, PFBS is an important component in mixtures with
PFHxS, PFNA, and HFPO-DA and the EPA presents occurrence information
for PFBS as part of section III.C.5 and its co-occurrence analyses in
sections VI.C and D of this preamble.
The EPA focused the evaluation of the state data on the non-
targeted or non-site specific (i.e., monitoring not conducted
specifically in areas of known or potential contamination) monitoring
efforts from 19 states. Non-targeted or non-site-specific monitoring is
likely to be more representative of general occurrence because its
framework and monitoring results will be less likely to potentially
over-represent concentrations at locations of known or suspected
contamination. Sixteen (16) of 19 states reported detections of at
least three of PFHxS, PFNA, HFPO-DA, or PFBS.
The EPA considered the targeted state monitoring data separately
since a higher rate of detections may occur as a result of specifically
looking in areas of suspected or known contamination. For the targeted
state data nearly all these states also reported detections at systems
serving millions of additional people, as well as at levels of public
health concern, both individually for PFHxS, PFNA, and HFPO-DA, and as
mixtures of these three PFAS and PFBS. State data detection frequency
and concentration results vary for PFHxS, PFNA, HFPO-DA, and PFBS, both
between these four different PFAS and across different states, with
some states showing much higher reported detections and concentrations
of these PFAS than others. The overall results demonstrate the
substantial likelihood that individually PFHxS, PFNA, and HFPO-DA and
mixtures of these three PFAS with PFBS will occur and co-occur at
frequencies and levels of public health concern. Tables 2 and 3 show
the percent of samples with state reported detections of PFHxS, PFNA,
HFPO-DA, and PFBS, and the percentage of monitored systems with
detections of PFHxS, PFNA, HFPO-DA, and PFBS, respectively, across the
non-targeted state finished water monitoring data. The EPA notes that
Alabama is not included in Tables 2 and 3 as only detections were
reported and there was no information on the total number of samples
collected to determine percent detection.
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As shown in Tables 2 and 3, all states except three report sample
and system detections for at least three of the four PFAS. For those
states that reported detections, the percentage of samples and systems
where these PFAS were found ranged from 1 to 39.8 percent and 0.1 to
38.1 percent, respectively. While these percentages show occurrence
variability across states, several of these states demonstrate that a
significant number of samples (e.g., detections of PFHxS in 26.2
percent of New Jersey samples) and systems (e.g., detections of HFPO-DA
in 12.2 percent of monitored systems in Kentucky) contain some or all
four PFAS. This occurrence information, as well as the specific
discussion related to individual occurrence for PFHxS, PFNA, and HFPO-
DA and co-occurrence of these three PFAS and PFBS, supports the
agency's determination that there is a substantial likelihood that
PFHxS, PFNA, HFPO-DA occur and PFHxS, PFNA, HFPO-DA, and PFBS co-occur
in combinations of mixtures with a frequency of public health concern.
Additionally, the agency emphasizes that occurrence and co-occurrence
of these PFAS is not only at a regional or local level, rather it
covers many states throughout the country; therefore, a national level
regulation is necessary to ensure all Americans served by PWSs are
equally protected.
1. PFHxS
The occurrence data presented above, throughout section VI of this
preamble and discussed in the USEPA (2024b) support the agency's final
determination that there is a substantial likelihood PFHxS occurs with
a frequency and at levels of public health concern in drinking water
systems across the United States. PFHxS was found under UCMR 3 in
approximately 1.1 percent of systems, serving 5.7 million people across
25 states, Tribes, and U.S. territories. However, under UCMR 3, the
minimum reporting level for PFHxS was 30 ng/L. As this reporting level
is three times greater than the health-based HRL for PFHxS (10 ng/L),
it is extremely likely there is significantly greater occurrence and
associated population exposed in the range between the HRL of 10 ng/L
and the UCMR 3 minimum reporting level of 30 ng/L (as demonstrated by
both the more recent state data and the EPA's occurrence model
discussed in this section and in section VI of this preamble showing
many results in this concentration range). Through analysis of
available state data, which consisted of approximately 48,000 samples
within 12,600 systems, 18 out of the 19 states that conducted non-
targeted monitoring had reported detections of PFHxS in 1.3 to 32.9
percent of their systems (Tables 2 and 3). These same systems reported
concentrations ranging from 0.2 to 856
[[Page 32556]]
ng/L with median sample concentrations ranging from 1.17 to 12.1 ng/L,
demonstrating concentrations above the HRL of 10 ng/L.
Targeted state monitoring data of PFHxS show similar results. For
example, in its targeted monitoring efforts, California reported 38.5
percent of monitored systems found PFHxS, where concentrations ranged
from 1.1 to 160 ng/L, also demonstrating concentrations above the HRL.
In total, considering both the non-targeted and targeted state data,
PFHxS was found above the HRL in at least 184 PWSs in 21 states serving
a population of approximately 4.3 million people.
The EPA also evaluated PFHxS in a national occurrence model that
has been developed and utilized to estimate national-scale PFAS
occurrence for four PFAS that were included in UCMR 3 (Cadwallader et
al., 2022). The model has been peer reviewed and is described
extensively in Cadwallader et al. (2022). The model and results are
described in section VI.E of this preamble; briefly, both the UCMR 3
and some state data were incorporated into a Bayesian hierarchical
model which supported exposure estimates for select PFAS at lower
levels than were measured under UCMR 3. Hundreds of systems serving
millions of people were estimated to have mean concentrations exceeding
the PFHxS HRL (10 ng/L). Therefore, the UCMR 3 results, the national
occurrence model results, and the substantial state data demonstrate
the substantial likelihood PFHxS occurs at a frequency and level of
public health concern. Finally, UCMR 5 data are being reported to the
EPA while this final rule is being prepared. See section VI of this
preamble for more information on the preliminary results. While these
UCMR 5 PFHxS data are too preliminary to provide the basis for the
regulatory determination, these preliminary UCMR 5 results appear to
confirm state data and model results.
Further supporting this final determination, PFHxS is very stable
and persistent in the environment. While PFHxS was phased out in the
U.S. in the early 2000's there are still detections as previously
demonstrated. In addition, legacy stocks may also still be used,
production continues in other countries, and products containing PFHxS
may be imported into the U.S. (USEPA, 2000b). Since PFHxS is
environmentally persistent and products containing PFHxS are still in
use and may be imported into the United States, the EPA anticipates
environmental contamination to sources of drinking water will continue.
To illustrate this point further, PFOA and PFOS, two of the most
extensively sampled PFAS, are also very environmentally persistent and
have similarly been phased out in the U.S. for many years, though these
two contaminants continue to often be found at levels of public health
concern as discussed in section VI of this preamble. Currently, this
also appears to be a similar trend for PFHxS occurrence, where the
drinking water sample data demonstrates it continues to occur at levels
of public health concern. Therefore, in consideration of factors
relating to the environmental persistence of PFHxS, its presence in
consumer products and possible continued use, and the observed
occurrence trend of PFOA and PFOS, the EPA finds that there is a
substantial likelihood PFHxS occurs or will occur at a frequency and
level of public health concern.
2. PFNA
The occurrence data presented above, throughout section VI of this
preamble, and discussed in USEPA (2024b) support the agency's final
determination that there is a substantial likelihood PFNA occurs with a
frequency and at levels of public health concern in drinking water
systems across the U.S.
PFNA was found under UCMR 3 in approximately 0.28 percent of
systems, serving 526,000 people in 7 states, Tribes, and U.S.
territories, using a minimum reporting level of 20 ng/L. As this
reporting level is two times greater than the health-based HRL of 10
ng/L, the EPA expects there is even greater occurrence and exposed
population in the range between 10 and 20 ng/L. Additionally, through
analysis of the extensive amount of available state data, which
consisted of approximately 57,000 samples within approximately 12,400
systems, 16 of 19 non-targeted monitoring states reported detections of
PFNA within 0.3 to 16.5 percent of their systems (Tables 2 and 3).
These same states reported sample results ranging from 0.23 to 330 ng/
L, demonstrating levels above the HRL of 10 ng/L, with median sample
results ranging from 0.35 to 7.5 ng/L.
Targeted state monitoring data of PFNA are also consistent with
non-targeted state data; for example, Pennsylvania reported 5.8 percent
of monitored systems found PFNA, where concentrations ranged from 1.8
to 18.1 ng/L, also showing concentrations above the HRL. When
considering all available state data, there are at least 480 systems in
19 states serving more than 8.4 million people that reported any
concentration of PFNA, and at least 52 systems in 12 states within
different geographic regions serving a population of 177,000 people
with reported concentrations above the HRL of 10 ng/L. Furthermore,
when evaluating only a subset of the available state data representing
non-targeted monitoring, PFNA was reported in approximately 3.6 percent
of monitored systems; if these results were extrapolated to the nation
and those system subject to the final rule requirements, the agency
estimates that PFNA would be detectable in over 2,300 PWSs serving 24.9
million people. If those results were further compared to the HRL for
PFNA (10 ng/L), PFNA would be detected above the HRL in 228 systems
with 830,000 people exposed. Thus, in addition to the UCMR 3 results,
these extensive state data also reflect there is a substantial
likelihood PFNA occurs at a frequency and level of public health
concern because it is observed or likely to be observed within numerous
water systems above levels of public health concern across a range of
geographic locations. Finally, UCMR 5 data are being reported to the
EPA while this final rule is being prepared. See section VI of this
preamble for more information on the preliminary results. While these
PFNA UCMR 5 data are too preliminary to provide the basis for the
regulatory determination, these preliminary UCMR 5 results appear to
confirm state data discussed above.
Further supporting this final determination, PFNA is very stable
and persistent in the environment. While it has generally been phased
out in the U.S. there are still detections as demonstrated previously.
Additionally, legacy stocks may still be used and products containing
PFNA may still be produced internationally and imported to the U.S.
(ATSDR, 2021). Since PFNA is environmentally persistent and products
containing PFNA are still in use and may be imported into the U.S.,
there is a substantial likelihood that environmental contamination of
sources of drinking water will continue. To illustrate this point
further, PFOA and PFOS, two of the most extensively sampled PFAS, are
also very environmentally persistent and have similarly been phased out
in the U.S. for many years, though these two contaminants continue to
often be found at levels of public health concern as discussed in
section VI of this preamble. Currently, this also appears to be a
similar trend for PFNA occurrence, where the drinking water sample data
demonstrates it continues to occur at levels of public health concern.
Therefore, in consideration of factors relating to the environmental
persistence of PFNA, its presence in
[[Page 32557]]
consumer products and possible continued use, and the observed
occurrence trend of PFOA and PFOS, the EPA finds that there is a
substantial likelihood PFNA occurs or will co-occur at a frequency and
level of public health concern.
3. HFPO-DA
The occurrence data presented above, throughout section VI of this
preamble, and discussed in the USEPA (2024b) support the agency's final
determination that there is a substantial likelihood HFPO-DA occur with
a frequency and at levels of public health concern in drinking water
systems across the U.S. HFPO-DA was not included as a part of the UCMR
3; however, through analysis of available state data, which consisted
of approximately 36,000 samples within approximately 10,100 systems, 10
of the 16 states that conducted non-targeted monitoring had state
reported detections of HFPO-DA within 0.1 to 12.2 percent of their
systems (Tables 2 and 3). These same states reported sample results
ranging from 0.7 to 100 ng/L and median sample results ranging from 1.7
to 29.6 ng/L, demonstrating concentrations above the HRL of 10 ng/L.
Additionally, targeted state monitoring in North Carolina included
sampling across six finished drinking water sites and 438 samples with
HFPO-DA. Concentrations ranged from 9.52 to 1100 ng/L, a median
concentration of 40 ng/L, and 433 (99 percent) samples exceeding the
HRL (10 ng/L). When considering all available state data, there are at
least 75 systems in 13 states serving more than 2.5 million people that
reported any concentration of HFPO-DA, and at least 13 systems in 5
states within different geographic regions of the country serving a
population of 227,000 people with reported concentrations above the HRL
of 10 ng/L. Additionally, when evaluating only a subset of the
available state data representing non-targeted monitoring to ensure
that the data were not potentially over-represented by sampling
completed in areas of known or suspected contamination, HFPO-DA was
reported in approximately 0.48 percent of monitored systems; if these
results were extrapolated to the nation and those system subject to the
final rule requirements, the agency estimates that HFPO-DA would be
detectable in over 320 PWSs serving 9.9 million people. If those
results were further compared to the HRL for HFPO-DA (10 ng/L), HFPO-DA
would be detected above the HRL in 42 systems with at least 495,000
people exposed. Finally, UCMR 5 data are being reported to the EPA
while this final rule is being prepared. See section VI of this
preamble for more information on the preliminary results. While these
HFPO-DA UCMR 5 data are too preliminary to provide the basis for the
regulatory determination, these preliminary UCMR 5 results appear to
confirm the state data discussed above.
Further supporting this final determination, HFPO-DA is very stable
and persistent in the environment. Additionally, unlike PFOA, PFOS,
PFHxS, and PFNA which have been phased out in the U.S, HFPO-DA
continues to be actively produced and used within the country and is
generally considered to have replaced the production of PFOA. Since
HFPO-DA is environmentally persistent and products containing HFPO-DA
are still being actively produced and used, the EPA anticipates that
contamination will continue, if not increase, due to disposal and
breakdown in the environment. To illustrate this point further, PFOA
and PFOS, two of the most extensively sampled PFAS, are also very
environmentally persistent and have been phased out in the United
States for many years, though these two PFAS continue to often be found
at levels of public health concern as discussed in section VI of this
preamble. Therefore, in consideration of factors relating to the
environmental persistence of HFPO-DA, its continued and possibly
increasing presence in consumer products and use, and the observed
occurrence trend of PFOA and PFOS, the EPA anticipates that occurrence
levels of HFPO-DA will similarly continue to be found at least to the
levels described in this preamble demonstrating that there is a
substantial likelihood HFPO-DA will occur at a frequency and level of
public health concern.
As discussed, HFPO-DA continues to be actively produced and used
throughout the U.S., it currently occurs at levels above its HRL, and
it occurs within geographically diverse areas of the country
demonstrating it is not a local or regional issue only. While the
current individual occurrence profile of HFPO-DA is not as pervasive
and is found at somewhat lower frequency as the currently observed
levels of PFOA, PFOS, or PFHxS, based upon the available substantial
amount of state occurrence data and given factors previously described,
the EPA has determined that there is a substantial likelihood HFPO-DA
occurs or will occur at a frequency and level of public health concern.
4. PFBS
The agency is deferring the final individual regulatory
determination for PFBS to further consider whether occurrence
information supports a finding that there is substantial likelihood
that PFBS will individually occur in PWSs and at a level of public
health concern. While current information demonstrates that PFBS
frequently occurs, it has not been observed to exceed its HRL of 2,000
ng/L in isolation. However, when considered in mixture combinations
with other PFAS, including PFHxS, PFNA, and HFPO-DA, PFBS is
anticipated to have dose-additive adverse health effects (based on
available data on PFAS and dose additivity) and there is a substantial
likelihood of its co-occurrence in combinations of mixtures with PFHxS,
PFNA, and HFPO-DA with a frequency and at levels of public health
concern. This is described further in sections III.C.5 and VI.C. and
VI.D of this preamble.
5. Mixtures of PFHxS, PFNA, HFPO-DA, and PFBS
Through the information presented within this section and in USEPA
(2024b), along with the co-occurrence information presented in sections
VI.C and VI.D of this preamble, the EPA's evaluation of all available
UCMR 3 and state occurrence data demonstrates that there is a
substantial likelihood that combinations of PFHxS, PFNA, HFPO-DA, and
PFBS (collectively referred to as ``Hazard Index PFAS'') co-occur or
will co-occur in mixtures at a frequency and level of public health
concern.
As discussed throughout section III.C of this preamble, the EPA has
determined that PFHxS, PFNA, and HFPO-DA each meet the second statutory
criterion for individual regulation. Additionally, as demonstrated in
sections VI.C. and D. of this preamble, the EPA has determined that
these three PFAS also meet the second statutory criterion when present
in mixture combinations. PFBS has not been observed to exceed its HRL
of 2,000 ng/L in isolation; therefore, the EPA is deferring the
individual regulatory determination for this PFAS to further consider
future occurrence information. However, the agency has determined that
PFBS frequently occurs (as shown in Table 2 and Table 3), and that when
considering dose additivity there is a substantial likelihood of its
co-occurrence in mixtures of PFHxS, PFNA, and/or HFPO-DA with a
frequency and at a level of public health concern. Therefore, the
agency has
[[Page 32558]]
determined that PFBS also meets the criterion when present in mixture
combinations with PFHxS, PFNA, and/or HFPO-DA.
In sections VI.C and D of this preamble, the EPA has presented its
evaluation and findings related to the likelihood and frequency of co-
occurrence of the four Hazard Index PFAS, including both through
groupwise and pairwise analyses for the Hazard Index PFAS, in non-
targeted state monitoring datasets. The groupwise co-occurrence
analysis established the broad occurrence frequency of Hazard Index
PFAS through a linkage to the presence of PFOA and PFOS. Because not as
many states have monitored for the Hazard Index PFAS as compared to
PFOA and PFOS, their occurrence information is less extensive than the
occurrence information for PFOA and PFOS. Therefore, though the agency
has previously made a final regulatory determination for PFOA and PFOS,
establishing co-occurrence of Hazard Index PFAS with PFOA and PFOS is
important to better understand the likelihood of Hazard Index PFAS
occurrence. In this analysis, the six PFAS were separated into two
groups--one consisted of PFOS and PFOA and the other group included the
four Hazard Index PFAS. The analysis broke down the systems and samples
according to whether chemicals from the two respective groups were
detected. Given that the groupwise co-occurrence analysis established
that there is a substantial likelihood that the Hazard Index PFAS
frequently occur, particularly alongside PFOA or PFOS, the pairwise co-
occurrence was relevant for understanding how the Hazard Index PFAS co-
occur with each other instead of occurring independently. Pairwise co-
occurrence analysis explored the odds ratios for each unique pair of
PFAS included in the regulation. For every pair of PFAS chemicals
included in the final regulation, the odds ratio, a statistic that, in
this context, quantifies the strength of association between two PFAS
being present, was found to be statistically significantly greater than
1. This means there was a statistically significant increase in the
odds of reporting a chemical as present after knowing that the other
chemical was detected. In most instances the odds appeared to increase
in excess of a factor of ten. Thus, based on the large amount of
available data, the chemicals are clearly demonstrated to frequently
co-occur rather than occur independently of one another, supporting the
agency's determination for mixtures of the four PFAS.
For the groupwise analysis, results generally indicated that when
PFOA and PFOS were found, Hazard Index PFAS were considerably more
likely to also be present. Additionally, for systems that only measured
PFOA and/or PFOS and did not measure the Hazard Index PFAS, it can be
assumed that the Hazard Index PFAS are more likely to be present in
those systems, and that Hazard Index occurrence may be underestimated.
Moreover, while PFOA and PFOS are not included within the Hazard Index
PFAS or the determination to regulate mixtures of these PFAS, the
pervasive occurrence of PFOA and PFOS shown in section VI of this
preamble is a strong indicator that these other Hazard Index PFAS are
also more likely to be found than what has been reported in state
monitoring data to date. In this analysis, comparisons were also made
between the number of Hazard Index PFAS analyzed and the number of
Hazard Index PFAS reported present. As more Hazard Index PFAS were
analyzed, more Hazard Index PFAS were reported present. Systems and
samples where Hazard Index PFAS were found were more likely to find
multiple Hazard Index PFAS than a single Hazard Index PFAS (when
monitoring for three or four Hazard Index PFAS), demonstrating an
increased likelihood of their co-occurrence. Additionally, for both
system-level and sample-level analyses where PFOA and/or PFOS were
reported present and all four Hazard Index PFAS were monitored, two or
more Hazard Index PFAS were reported present more than half of the
time, exhibiting they are more likely to occur together than in
isolation. Furthermore, the EPA notes that when evaluating only a
subset of the available state data representing non-targeted monitoring
where either three or four Hazard Index PFAS were monitored, regardless
of whether PFOA or PFOS were reported present, two or more of the
Hazard Index PFAS were reported in approximately 12.1 percent of
monitored systems; if these results were extrapolated to the nation,
two or more of these four PFAS would co-occur in about 8,000 PWSs (see
section VI.C.1 of this preamble for additional information).
The EPA uses a Hazard Index of 1 as the HRL to further evaluate the
substantial likelihood of the Hazard Index PFAS co-occurring at a
frequency and level of public health concern. As discussed in greater
detail in section VI.D, of this preamble based on available state data
the EPA finds that across 21 states there are at least 211 PWSs serving
approximately 4.7 million people with results above a Hazard Index of 1
for mixtures including two or more of the Hazard Index PFAS.
Specifically evaluating the presence of PFBS, in these same 211 systems
where the Hazard Index was found to be greater than 1, PFBS was
observed at or above its PQL in mixtures with one or more of the other
three Hazard Index PFAS in at least 72 percent (152) of these systems
serving approximately 4.5 million people. Additionally, as described
previously in sections III.C.1-3, PFHxS, PFNA, HFPO-DA, and PFBS are
all very stable and persistent in the environment. All are either still
being actively used or legacy stocks may be used and imported into the
U.S. Consequently, there is a substantial likelihood that environmental
contamination of sources of drinking water from these PFAS will
continue to co-occur to at least the levels described in this preamble.
Therefore, in consideration of the environmental persistence of
these PFAS, their presence in consumer products and continued use, the
findings of both the pairwise and groupwise co-occurrence analyses, and
demonstration of combinations of Hazard Index PFAS mixtures exceeding
the Hazard Index of 1, the EPA has determined there is sufficient
occurrence information available to support the second criterion that
there is a substantial likelihood that combinations of the four Hazard
Index PFAS in mixtures co-occur at frequencies and levels of public
health concern.
6. Summary of Major Public Comments and EPA Responses
The EPA requested comment on its preliminary regulatory
determination for all four PFAS and their mixtures and its evaluation
of the statutory criteria that supports the finding. The EPA also
requested comment on additional occurrence data the agency should
consider regarding its decision that PFHxS, PFNA, HFPO-DA, and PFBS and
their mixtures occur or are substantially likely to occur in PWSs with
a frequency and at levels of public health concern. The EPA received
many comments on the agency's evaluation of the second statutory
criterion under section 1412(b)(1)(A) of SDWA. Many commenters
supported the EPA's preliminary determination that PFHxS, PFNA, HFPO-
DA, and PFBS and mixtures of these four contaminants meet the second
statutory occurrence criterion under SDWA.
[[Page 32559]]
A couple of commenters claimed that the EPA does not have a robust
understanding of available occurrence data that supports any of the
regulatory determinations for the four PFAS in this rule. Additionally,
some commenters suggested that the preliminary determinations were
``rushed'' and ``non-scientific,'' and that the agency should wait
until some or all of the UCMR 5 data is available and considered. The
EPA disagrees. Sufficient occurrence data are available to establish a
substantial likelihood of occurrence at frequencies and levels of
health concern. Per the intent of the statute, the agency used the best
available data in an expeditious manner, which, as the agency described
earlier, was also a very large dataset consisting of tens of thousands
of samples and representing one of the most robust occurrence datasets
ever used to inform development of a drinking water regulation of a
previously unregulated contaminant. The agency also disagrees that the
occurrence analyses undertaken and available in the preamble as well as
the technical support document for occurrence were non-scientific.
Based on publicly available information within the state data, the EPA
verified that the very large majority of samples (at least 97 percent)
were collected using EPA-approved methods; the slight percentage the
agency was unable to verify would not result in different agency
conclusions. Additionally, the EPA notes that the aggregated data were
assessed using precedented statistical metrics and analyses. In
addition, the Cadwallader et al. (2022) model uses a robust, widely
accepted Bayesian statistical approach for modeling contaminant
occurrence. Based on these analyses, the EPA has a clear understanding
of the occurrence of the modeled contaminants. As discussed in section
III.C of this preamble and USEPA, 2024b, the EPA also has sufficient
state data which consist of a greater number of total systems and
samples than that included within the monitoring under UCMR 3, to
confidently establish that there is a substantial likelihood of
occurrence at frequencies and levels of public health concern.
As discussed above, the agency believes that the best currently
available occurrence data demonstrate substantial likelihood of
occurrence for the chemicals included in the final rule as they are
demonstrated at frequencies and levels of public health concern. UCMR 5
data are being reported to the EPA while this final rule is being
prepared. See section VI of this preamble for more information on the
EPA's evaluation of the preliminary results. While these data are too
preliminary to provide the basis for a regulatory determination, these
preliminary UCMR 5 results appear to support the data discussed
previously.
Several commenters disagreed that the available occurrence
information supports a preliminary determination for HFPO-DA, with a
few citing a lack of nationally representative data and suggesting a
delay until UCMR 5 data is collected. The EPA disagrees with these
comments, as the state monitoring data for the proposed rule
demonstrates HFPO-DA occurrence in 13 geographically diverse states,
including at 75 systems serving at least 2.5 million people. Moreover,
non-national datasets may serve to demonstrate occurrence of a
contaminant to warrant a positive determination and subsequent
development of an NPDWR. For example, the best available HFPO-DA state
data consists of approximately 36,000 samples within 10,000 systems and
is representative of multiple geographic locations.
One commenter stated that a regulatory determination for PFNA was
unnecessary as they do not believe it occurred with frequency under
UCMR 3 monitoring, and a couple of other commenters suggested that a
negative determination was appropriate for PFNA citing occurrence
levels. The EPA disagrees that a negative determination is appropriate
for PFNA as it has been demonstrated to occur at levels of public
health concern in at least 52 water systems across 12 states.
Furthermore, as described previously, when evaluating only a subset of
the available state data representing non-targeted monitoring, PFNA was
reported in approximately 3.6 percent of monitored systems and if those
results were extrapolated across the country, PFNA would be detectable
at any concentration in over 2,300 PWSs serving 21.2 million people and
detectable above 10 ng/L in 227 systems serving 711,000 people.
Additionally, PFNA frequently co-occurs with other PFAS, and as
previously discussed in this section, presents dose additive health
concerns with other PFAS demonstrating it is also an important
component of the determination to regulate it in mixtures with PFHxS,
HFPO-DA, and/or PFBS.
Commenters both agreed and disagreed with the EPA's individual
preliminary determination for PFBS. With respect to commenters who
suggested that the EPA has not met the occurrence criterion, while PFBS
occurs at significant frequency, the agency is deferring the individual
determination to regulate PFBS when it occurs individually until it
conducts further evaluation under the statutory criteria. The EPA
further finds that PFBS exposure may cause dose additive adverse health
effects in mixtures with PFHxS, PFNA, and/or HFPO-DA; that there is a
substantial likelihood that PFBS co-occurs in mixtures with PFHxS,
PFNA, and/or HFPO-DA in PWSs with a frequency and at levels of public
health concern; and that, in the sole judgment of the Administrator,
regulation of PFBS in mixtures with PFHxS, PFNA, and/or HFPO-DA
presents a meaningful opportunity for health risk reduction for persons
served by PWSs. Therefore, PFBS will be regulated as part of a mixture
with PFHxS, PFNA, and HFPO-DA.
A few commenters provided feedback on occurrence thresholds the
agency should consider when evaluating the second statutory criterion
for regulatory determinations. Particularly, these commenters
recommended that the EPA should define a threshold for frequency and
level of public health concern that warrants a specific regulatory
determination. A few commenters cited other previous regulatory
determinations where the agency made a determination not to regulate
contaminants with similar or lower levels of occurrence suggesting that
this should be the same for some or all of these four PFAS.
Furthermore, some of these commenters stated that it would be arbitrary
and capricious and conflict with the SDWA if the EPA did not use the
level of adverse health effect (i.e., the HRL) to represent the level
at which a contaminant is considered a public health concern.
The EPA disagrees with these commenters and as demonstrated in the
proposal and noted earlier in section III of this preamble, for this
regulatory determination, as well as past determinations, the agency
did compare available occurrence data relative to the contaminant HRL
as a factor in informing the occurrence level of public health concern.
However, the level of public health concern for purposes of the second
criterion is a contaminant-specific analysis that include consideration
of the HRL, as well as other factors and not solely based on the direct
comparison to the HRL. There is not just one simple threshold used for
public health concern for all contaminants. In the case of PFAS, this
is particularly relevant given the dose-additivity of mixtures.
The EPA also disagrees with these commenters as SDWA does not
define the occurrence level of public health
[[Page 32560]]
concern for contaminants, nor does it prescribe the level of adverse
health effects that must be used for a regulatory determination.
Ultimately, the overall decision to regulate a contaminant considers
all three statutory criteria, including the comprehensive assessment of
meaningful opportunity which is in the Administrator's sole discretion.
In previous EPA regulatory determinations, the agency has considered
the occurrence criteria unique to the contaminant it is evaluating and
has made decisions not to regulate contaminants both where there was
substantial likelihood of occurrence at frequency and/or at levels of
public health concern and where there was limited or no substantial
likelihood of occurrence at frequency and/or at levels of public health
concern. Consistent with this past regulatory history and the
Administrator's authority under the terms of the statute, the decision
considers all three criteria and cannot be determined in the exact same
manner for different contaminants. While the EPA may have made negative
determinations for other contaminants demonstrating occurrence at
different frequencies and levels of public health concern, the basis
for those decisions was specific to those contaminants and does not
apply to these PFAS or any other future contaminants for which the EPA
would make regulatory determinations. Therefore, the statute does not
require, and the EPA does not use a minimum or one-size-fits-all
occurrence thresholds (for either frequency or precise level) for
regulatory determinations.
As described in section VI of this preamble, many commenters
supported the EPA's proposal to regulate mixtures of PFAS. Specific to
occurrence, some of these commenters particularly expressed support for
the EPA's preliminary determination that mixtures of these four PFAS
meet the second statutory occurrence criterion under SDWA, citing that
the agency has used the best available information to determine that
there is a substantial likelihood that combinations of these PFAS will
co-occur in mixtures at a frequency and level of public health concern.
One commenter stated that the additional occurrence data presented by
the EPA in the proposal for the Hazard Index PFAS supports the EPA's
proposed determination that these PFAS should be regulated under the
SDWA. Conversely, several other commenters stated that there was not
supporting evidence for the co-occurrence of the four Hazard Index
PFAS. The EPA disagrees; the extent to which Hazard Index PFAS
chemicals co-occur in the non-targeted state dataset is discussed
extensively in the record for this rule and made evident through the
system level analysis in section VI.C. of this preamble. As also
discussed elsewhere in the record for this rule, in both system level
and sample level analyses where PFOA and/or PFOS were reported present
and all four Hazard Index PFAS were monitored, two or more Hazard Index
PFAS were reported present more than half of the time. Further, the
odds ratios tables in Exhibit 11 provide a statistical examination of
pairwise co-occurrence. The odds ratio is a statistic that quantifies
the strength of association between two events. In the context
described here, an ``event'' is the reported presence of a specific
PFAS contaminant. The odds ratio between PFOA and PFHxS, for example,
reflects the strength of association between PFHxS being reported
present and PFOA being reported present. If an odds ratio is greater
than 1, the two events are associated. The higher the odds ratio, the
stronger the association. For every pair of PFAS chemicals included in
the proposed regulation, the odds ratio was found to be statistically
significantly greater than 1. This means there was a statistically
significant increase in the odds of a PFAS being present if the other
PFAS compound was detected (e.g., if PFOA is detected, PFHxS is more
likely to also be found). In most instances the odds appeared to
increase in excess of a factor of ten. Thus, based on the large amount
of available data, the chemicals are clearly demonstrated to co-occur
rather than occur independently of one another, further supporting the
agency's determination for combinations of mixtures of the four PFAS.
After considering the public comments and additional occurrence
data evaluated as requested by public commenters, the EPA finds that
PFHxS, PFNA, and HFPO-DA individually and mixtures of these three PFAS
and PFBS, meet the second statutory criterion for regulatory
determinations under section 1412(b)(1)(A) of SDWA that the contaminant
is known to occur or co-occur or there is a substantial likelihood that
the contaminant will occur or co-occur in PWSs with a frequency and at
levels of public health concern (USEPA, 2024b).
D. Statutory Criterion 3--Meaningful Opportunity
The agency has determined that individual regulation of PFHxS,
PFNA, and HFPO-DA and regulation of combinations of PFHxS, PFNA, HFPO-
DA, and PFBS in mixtures presents a meaningful opportunity for health
risk reduction for persons served by PWSs. As discussed in section
III.C. of this preamble, the EPA evaluated this third statutory
criterion similarly to previous regulatory determinations using the
Protocol developed under Regulatory Determination 3 (USEPA, 2014b) and
also used in the Regulatory Determination 4. This evaluation includes a
comprehensive assessment of meaningful opportunity for each unique
contaminant including the nature of the health effects, sensitive
populations affected, including infants, children and pregnant and
nursing women, number of systems potentially affected, and populations
exposed at levels of public health concern, geographic distribution of
occurrence, technologies to treat and measure the contaminant, among
other factors. The agency further reiterates that, per the statute,
this determination of meaningful opportunity is in the Administrator's
sole discretion.
Accordingly, the EPA is making this determination of meaningful
opportunity after evaluating health, occurrence, treatment, and other
related information and factors including consideration of the
following:
PFHxS, PFNA, and HFPO-DA and combinations of these three
PFAS and PFBS in mixtures may cause multiple adverse human health
effects, often at very low concentrations, on several biological
systems including the endocrine, cardiovascular, developmental, renal,
hematological, reproductive, immune, and hepatic systems as well as are
likely to produce dose-additive effects from co-exposures.
The substantial likelihood that PFHxS, PFNA, and HFPO-DA
individually occur or will occur and that mixtures of PFHxS, PFNA,
HFPO-DA, and/or PFBS co-occur or will co-occur together at frequencies
and levels of public health concern in PWSs as discussed in section III
of this preamble above and in section VI of this preamble, and the
corresponding significant populations served by these water systems
which potentially include sensitive populations and lifestages, such as
pregnant and lactating women, as well as children.
PFHxS, PFNA, HFPO-DA and combinations of these three PFAS
and PFBS in mixtures are expected to be persistent in the environment,
with some (e.g., PFHxS, PFNA) also demonstrated to be very persistent
in the human body.
Validated EPA-approved measurement methods are available
to measure PFHxS, PFNA, HFPO-DA, and
[[Page 32561]]
PFBS. See section VII of this preamble for further discussion.
Treatment technologies are available to remove PFHxS,
PFNA, and HFPO-DA and combinations of these three PFAS and PFBS from
drinking water. See section X of this preamble for further discussion.
Even though PFBS is very likely to be below its
corresponding individual HRL when it occurs in a mixture, the record
indicates that there is a substantial likelihood that it co-occurs with
the regulated PFAS throughout public water systems nationwide. See
sections III.C.5 and VI.C. of this preamble for further discussion.
According to the 2023 Interagency PFAS Report to Congress (United
States OSTP, 2023), PFBS has been shown to affect the following health
endpoints: body weight, respiratory, cardiovascular, gastrointestinal,
hematological, musculoskeletal, hepatic, renal, ocular, endocrine,
immunological, neurological, reproductive, and developmental. Thus,
including PFBS as a mixture component represents a meaningful
opportunity to reduce PFBS' contributions to the overall hazard of the
mixture and resulting dose additive health concerns. This is
particularly relevant where the exposures of the other three PFAS in
the mixture are also below their respective HRLs but when the hazard
contributions of each mixture component are summed, the total exceeds
the mixture HRL. In this scenario, the inclusion of PFBS allows for a
more accurate picture of the overall hazard of the mixture so that PFBS
can be reduced along with associated dose additive health concerns. In
short, hazard would be underestimated if PFBS was not included in the
regulated mixture. The EPA also considered the situation where PFHxS,
PFNA, or HFPO-DA exceed one or more of their corresponding HRLs and co-
occur with PFBS below its corresponding HRL. Although the exceedance of
the mixture HRL is driven by a PFAS other than PFBS, PFBS is
contributing to the overall hazard of the mixture and resulting dose
additive health concerns. Including PFBS in the regulated mixture
offers a meaningful opportunity to reduce dose additive health concerns
because, when PFBS and other Hazard Index PFAS are present, public
water systems will be able to better design and optimize their
treatment systems to remove PFBS and any other co-occurring Hazard
Index PFAS. This optimization will be even more effective knowing both
that PFBS is present in source waters and its measured concentrations.
Regulating PFHxS, PFNA, and HFPO-DA and combinations of
these three PFAS and PFBS in mixtures is anticipated to reduce the
overall public health risk from other PFAS, including PFOA and PFOS,
that co-occur and are co-removed. Their regulation is anticipated to
provide public health protection at the majority of known PWSs with
PFAS-impacted drinking water.
There are achievable steps to manage drinking water that
can be taken to reduce risk.
As described in sections III.C, VI.C, VI.D, and USEPA (2024b), data
from both the UCMR 3 and state monitoring efforts demonstrates the
substantial likelihood of individual occurrence of PFHxS, PFNA, and
HFPO-DA and co-occurrence of mixture combinations of PFHxS, PFNA, HFPO-
DA, and PFBS at frequencies and levels of public health concern. Under
UCMR 3, 5.7 million and 526,000 people had reported detections (greater
than or equal to their minimum reporting levels which were two to three
times their HRLs of 10 ng/L), of PFHxS and PFNA, respectively.
Additionally, based on the more recent available state monitoring data
presented earlier in this section, a range of geographically diverse
states monitored systems that reported individual detections of PFHxS,
PFNA, and HFPO-DA and serve approximate populations of 26.5 million,
2.5 million, and 8.4 million, respectively. Of these same systems,
detections above the EPA's HRLs for PFHxS, PFNA, and HFPO-DA were seen
in systems that serve approximate populations of 4.3 million, 227,000,
and 177,000 people, respectively. As discussed previously, if these
monitored systems were extrapolated to the nation, the EPA estimates
that thousands of additional systems serving millions of people could
have detectable levels of these three PFAS and hundreds of these
systems may show values above the EPA's HRLs. Lastly, in evaluating the
available state data, the EPA has found that mixtures of PFHxS, PFNA,
HFPO-DA, and/or PFBS occur with a Hazard Index greater than 1 in
systems serving approximately 4.7 million people. The agency further
notes that while it has demonstrated through sufficient data that these
four PFAS co-occur in mixtures at a frequency and level of public
health concern in PWSs, throughout the nation it is extremely likely
that additional systems and associated populations served would also
demonstrate a Hazard Index greater than 1 if data for all PWSs were
evaluated.
Analytical methods are available to measure PFHxS, PFNA, HFPO-DA,
and PFBS in drinking water. The EPA has published two multi-laboratory
validated drinking water methods for individually measuring PFHxS,
PFNA, HFPO-DA, and PFBS. Additional discussion on analytical methods
can be found in section VII of this preamble.
The EPA's analysis, summarized in section X of this preamble, found
there are available treatment technologies capable of reducing PFHxS,
PFNA, HFPO-DA, and PFBS. These technologies include granular activated
carbon (GAC), anion exchange (AIX) resins, reverse osmosis (RO), and
nanofiltration (NF). These treatment technologies remove PFHxS, PFNA,
HFPO-DA, and PFBS and their mixtures. They also have been documented to
co-remove other PFAS (S[ouml]reng[aring]rd et al., 2020; McCleaf et
al., 2017; Mastropietro et al., 2021). Furthermore, as described in
section VI of this preamble, PFHxS, PFNA, HFPO-DA, and PFBS also co-
occur with PFAS for which the agency is not currently making a
regulatory determination. Many of these other emergent co-occurring
PFAS are likely to also pose hazards to public health and the
environment (Mahoney et al., 2022). Therefore, based on the EPA's
findings that PFHxS, PFNA, HFPO-DA, and PFBS have a substantial
likelihood to co-occur in drinking water with other PFAS and treating
for PFHxS, PFNA, HFPO-DA, and PFBS is anticipated to result in removing
these and other PFAS, individual regulation of PFHxS, PFNA, and HFPO-DA
and regulation of mixtures of these three PFAS and PFBS also presents a
meaningful opportunity to reduce the overall public health risk from
all other PFAS that co-occur and are co-removed with PFHxS, PFNA, HFPO-
DA, and PFBS.
With the ability to monitor for PFAS, identify contaminated
drinking water sources and contaminated finished drinking water, and
reduce PFAS exposure through management of drinking water, the EPA has
identified meaningful and achievable actions that can be taken to
reduce the human health risk of PFAS.
1. Proposal
The EPA made a preliminary determination that regulation of PFHxS,
PFNA, HFPO-DA, and PFBS, both individually and in a mixture, presents a
meaningful opportunity for health risk reduction for persons served by
PWSs. The EPA made this preliminary determination after evaluating
health, occurrence, treatment, and other related information against
the three SDWA statutory criteria including consideration of the
factors previously
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described in section III.D of this preamble above.
2. Summary of Major Public Comments and EPA Responses
The EPA received many comments on the agency's evaluation of the
third statutory criterion under section 1412(b)(1)(A) of SDWA. Most
commenters supported the EPA's evaluation under the preliminary
determination that regulation of PFHxS, PFNA, HFPO-DA, PFBS and
mixtures of these four contaminants presents a meaningful opportunity
for health risk reduction and that the EPA had sufficiently justified
this statutory criterion as well as the health and occurrence
criterion. This included comments highlighting the extensive amount of
work done by several states developing regulatory and non-regulatory
levels for several PFAS compounds, including the PFAS for which the EPA
is making regulatory determinations either individually or as a
mixture. These commenters also noted the need for a consistent national
standard for use in states where a state-specific standard has not yet
been developed. Several commenters have also noted that although some
states have developed or are in the process of developing their own
state-level PFAS drinking water standards, regulatory standards
currently vary across states. These commenters expressed concern that
absence of a national drinking water standard has resulted in risk
communication challenges with the public and disparities with PFAS
exposure. Some commenters noted there are populations particularly
sensitive or vulnerable to the health effects of these PFAS, including
newborns, infants, and children. The EPA agrees with commenters that
there is a need for a national PFAS drinking water regulation and that
moving forward with a national-level regulation for PFHxS, PFNA, HFPO-
DA, mixtures of these three PFAS and PFBS, as well as PFOA and PFOS,
will provide improved national consistency in protecting public health
and may reduce regulatory uncertainty for stakeholders across the
country.
A few commenters expressed support for the EPA's evaluation of
meaningful opportunity based on the treatment technologies which can
remove the six PFAS for which the EPA is finalizing regulation.
Furthermore, these commenters noted the meaningful opportunity to not
only provide protection from the six regulated PFAS, but also other
PFAS that will not be regulated as a part of this action.
Several commenters did not support the EPA's evaluation of the
third statutory criterion, offering that in their opinion the EPA
failed to justify that there is a meaningful opportunity for health
risk reduction for the PFAS both individually and for their mixtures
and stating that the EPA should consider other factors such as costs. A
few of these commenters wrote that the EPA provided limited rationale
and factors for its meaningful opportunity determination. The EPA
disagrees with these commenters that the agency failed to justify that
there is meaningful opportunity for health risk reduction or that the
EPA provided limited rationale and factors in its meaningful
opportunity evaluation for these contaminants individually and as
mixtures. As described in the EPA's March 2023 proposal (USEPA, 2023f)
and summarized previously, the EPA fully considered many factors both
individually and within mixtures including individual contaminant and
dose additive toxicity and health concerns, individual contaminant
occurrence and co-occurrence of mixtures at frequencies and levels of
public health concern, availability of similar treatment technologies
to remove these four PFAS and analytical methods to measure them, and
their individual and collective chemical and physical properties
leading to their environmental persistence. Additionally, the EPA notes
in this preamble, and as demonstrated through representative occurrence
data, for the three contaminants individually and mixtures of the four,
occurrence and co-occurrence is not only at a regional or local level,
rather it covers multiple states throughout the country; therefore, a
national level regulation is necessary to ensure all Americans served
by PWSs are equally protected.
Some comments indicate that the health and occurrence information
do not support that establishing drinking water standards presents a
meaningful opportunity for health risk reduction. The agency disagrees
with the commenters' assertion that the health and occurrence
information are insufficient to justify a drinking water standard as
supported in sections III.B. and III.C. of this preamble, and the
agency finds that there is a meaningful opportunity for health risk
reduction potential based upon multiple considerations including the
population exposed to PFHxS, PFNA, HFPO-DA, and mixtures of these three
PFAS and PFBS including sensitive populations and lifestages, such as
newborns, infants and children.
Other comments assert that the EPA must evaluate the potential
implementation challenges and cost considerations of regulation as part
of the meaningful opportunity evaluation. The EPA disagrees with these
commenters. The SDWA states that that the meaningful opportunity for
overall health risk reduction for persons served by PWSs is in the sole
judgement of the Administrator and does not require that the EPA
consider costs for a regulatory determination. The SDWA does require
that costs and benefits are presented and considered in the proposed
rule's Health Risk Reduction Cost Analysis which the EPA did for the
proposal and has updated as a part of the final rule within section
XII.
A few other commenters provided that due to all of the additional
human health exposure pathways other than drinking water for these
PFAS, that regulation of drinking water would not represent a
meaningful opportunity for overall health risk reduction. While the EPA
recognizes that drinking water is one of several exposure routes, the
EPA disagrees with these commenters. Removing the PFAS that have been
found to occur or are substantially likely to occur from drinking water
systems will result in a significant improvement in public health
protection. The EPA also notes that through its PFAS Strategic Roadmap
and associated actions, the agency is working expeditiously to address
PFAS contamination in the environment and reduce human health PFAS
exposure through all pathways. While beyond the scope of this rule, the
EPA is making progress implementing many of the commitments in the
Roadmap, including those that may significantly reduce PFAS source
water concentrations.
E. The EPA's Final Determination Summary
The SDWA provides the EPA significant discretion when making a
regulatory determination under section 1412(b)(1)(A). This decision to
make a regulatory determination to individually regulate PFHxS, PFNA,
and HFPO-DA and to regulate combinations of these three PFAS and PFBS
in mixtures is based on consideration of the evidence supporting the
factors individually and collectively.
The EPA's determination that PFHxS, PFNA, and HFPO-DA individually
and mixtures of these three PFAS and PFBS ``may have an adverse effect
on the health of persons'' is strongly supported by numerous studies.
These studies demonstrate several adverse health effects, such as
immune, thyroid, liver,
[[Page 32563]]
kidney and developmental effects, and increased cholesterol levels, may
occur following exposure to individual PFAS, and dose-additive health
effects can occur following exposure to multiple PFAS at doses that
likely would not individually result in these adverse health effects,
but may pose health risks when combined in mixtures. Importantly, the
best available peer reviewed science documents that these PFAS may have
multiple adverse human health effects even at relatively low levels
individually and when combined in mixtures (see section III.B.6.e f of
this preamble or further information on studies supporting the
conclusion of dose additivity).
The EPA's determination there is a substantial likelihood that the
contaminant will occur in PWS with a frequency and at levels of public
health concern is supported by evidence documenting the measured
occurrence of PFHxS, PFNA, and HFPO-DA, and co-occurrence of these
three PFAS and PFBS above the HRL, the stability and persistence of the
contaminant in humans and/or the environment, and the current or legacy
production and use in commerce.
Finally, the EPA's determination that individual regulation of
PFHxS, PFNA, and HFPO-DA and regulation of these three PFAS and PFBS in
mixtures presents a meaningful opportunity for health risks reductions
is strongly supported by numerous factors, including the potential
adverse human health effects at low levels and potential for exposure
and co-exposure of these PFAS on sensitive populations and lifestages
such as lactating and pregnant women and children, their persistence,
and the availability of both analytical methods and treatment
technologies to remove these contaminants in drinking water.
After considering these factors individually and together, the EPA
has determined that PFHxS, PFNA, and HFPO-DA individually and mixtures
of these three PFAS and PFBS meet the statutory criteria for regulation
under SDWA. The EPA has an extensive record of information to make this
determination now and recognizes the public health burden of these PFAS
as well as PFOA and PFOS. The EPA notes the public urgency to reduce
PFAS concentrations in drinking water described in the public comments.
A PFAS NPDWR provides a mechanism to reduce these PFAS expeditiously
for these impacted communities. In addition to making this final
regulatory determination, the EPA is exercising its discretion to
concurrently finalize MCLGs and NPDWRs for these PFAS as individual
contaminants and for the specified PFAS mixtures in part to allow
utilities to consider these PFAS specifically as they design systems to
remove PFAS and to ensure that they are reducing these PFAS in their
drinking water to the extent feasible and as quickly as practicable.
IV. MCLG Derivation
Section 1412(a)(3) of the Safe Drinking Water Act (SDWA) requires
the Administrator of the Environmental Protection Agency (EPA) to
publish a final MCLG simultaneously with the NPDWR. The MCLG is set, as
defined in section 1412(b)(4)(A), at ``the level at which no known or
anticipated adverse effects on the health of persons occur and which
allows an adequate margin of safety.'' Consistent with SDWA section
1412(b)(3)(C)(i)(V), in developing the MCLG, the EPA considers ``the
effects of the contaminant on the general population and on groups
within the general population such as infants, children, pregnant
women, the elderly, individuals with a history of serious illness, or
other subpopulations that are identified as likely to be at greater
risk of adverse health effects due to exposure to contaminants in
drinking water than the general population.'' Other factors considered
in determining MCLGs can include health effects data on drinking water
contaminants and potential sources of exposure other than drinking
water. MCLGs are not regulatory levels and are not enforceable. The
statute does not dictate that the MCLG take a particular form; however,
it must represent a ``level'' that meets the MCLG statutory definition.
Given that the MCL must be ``as close as feasible'' to the MCLG, and
that the MCL is defined as the ``maximum permissible level of a
contaminant in water which is delivered to any user of a public water
system,'' the MCLG can take any form so long as it is a maximum level
of a contaminant in water.
Due to their widespread use and persistence, many PFAS are known to
co-occur in drinking water and the environment--meaning that these
contaminants are often together and in different combinations as
mixtures (see sections III.C and VI of this preamble for additional
discussion on occurrence). PFAS exposure can disrupt signaling of
multiple biological pathways resulting in common adverse effects on
several biological systems and functions, including thyroid hormone
levels, lipid synthesis and metabolism, development, immune function,
and liver function. Additionally, the EPA's examination of health
effects information found that exposure through drinking water to a
mixture of PFAS can act in a dose-additive manner (see sections III.B
and IV.B of this preamble for additional discussion on mixture
toxicity). Dose additivity means that exposure to multiple PFAS, at
doses that individually would not be anticipated to result in adverse
health effects, may pose health risks when combined in a mixture.
A. MCLG Derivation for PFOA and PFOS
To establish an MCLG for individual contaminants, the EPA assesses
the peer-reviewed science examining cancer and noncancer health effects
associated with oral exposure to the contaminant. For known or likely
linear carcinogenic contaminants, where there is a proportional
relationship between dose and carcinogenicity at low concentrations or
where there is insufficient information to determine that a carcinogen
has a threshold dose below which no carcinogenic effects have been
observed, the EPA has a long-standing practice of establishing the MCLG
at zero (see USEPA, 1998a; USEPA, 2000c; USEPA, 2001; See S. Rep. No.
169, 104th Cong., 1st Sess. (1995) at 3). For nonlinear carcinogenic
contaminants, contaminants that are designated as Suggestive Human
Carcinogens (USEPA, 2005a), and non-carcinogenic contaminants, the EPA
typically establishes the MCLG based on a noncancer RfD. An RfD is an
estimate of a daily oral exposure to the human population (including
sensitive populations) that is likely to be without an appreciable risk
of deleterious effects during a lifetime. A nonlinear carcinogen is a
chemical agent for which the associated cancer response does not
increase in direct proportion to the exposure level and for which there
is scientific evidence demonstrating a threshold level of exposure
below which there is no appreciable cancer risk.
1. Proposal
To support the proposed rule, the EPA published PFOA and PFOS draft
toxicity assessments and the proposed MCLGs for public comment (USEPA,
2023g; USEPA, 2023h). Prior to conducting the systematic review for the
PFOA and PFOS draft toxicity assessments, the EPA established the
internal protocols for the systematic review steps of literature
search, Population, Exposure, Comparator, and Outcomes (PECO)
development, literature screen, and study quality evaluation. The EPA
incorporated detailed, transparent, and complete protocols for all
steps of the systematic
[[Page 32564]]
review process (USEPA, 2023g; USEPA, 2023h; USEPA, 2023i; USEPA,
2023j). Additionally, the EPA updated and expanded the protocols and
methods based on SAB recommendations to improve the transparency of the
process the EPA used to derive the MCLGs for PFOA and PFOS and to
improve consistency with the ORD Staff Handbook for Developing IRIS
Assessments (USEPA, 2022f). The EPA followed this transparent
systematic review process to evaluate the best available peer-reviewed
science and to determine the weight of evidence for carcinogenicity and
the cancer classifications for PFOA and PFOS according to agency
guidance (USEPA, 2005a).
Based on the EPA's analysis of the best available data and
following agency guidance, the EPA determined that both PFOA and PFOS
are Likely to be Carcinogenic to Humans based on sufficient evidence of
carcinogenicity in humans and animals (USEPA, 2005a; USEPA, 2023g;
USEPA, 2023h). The EPA also determined that a linear default
extrapolation approach is appropriate for PFOA and PFOS as there is no
evidence demonstrating a threshold level of exposure below which there
is no appreciable cancer risk for either compound (USEPA, 2005a).
Therefore, the EPA concluded that there is no known threshold for
carcinogenicity. Based upon a consideration of the best available peer-
reviewed science and the statute's directive that the MCLG be ``set at
the level at which no known or anticipated adverse effects on the
health of persons occur and which allow an adequate margin of safety,''
the EPA proposed MCLGs of zero for both PFOA and PFOS in drinking
water. Setting the MCLG at zero under these conditions is also
supported by long standing practice at the EPA's Office of Water for
Likely or Known Human Carcinogens (see USEPA, 1998a; USEPA, 2000c;
USEPA, 2001; USEPA, 2016b; See S. Rep. No. 169, 104th Cong., 1st Sess.
(1995) at 3).
2. Summary of Major Public Comments and EPA Responses
The EPA requested comment on both the toxicity assessment
conclusions and the proposed MCLG derivation for PFOA and PFOS. In this
section the EPA focuses the summary of public comments and responses on
comments related to the cancer classification determinations for PFOA
and PFOS because that was the basis for the proposed MCLG derivations
(USEPA, 2023g; USEPA, 2023h). The noncancer health effects that the EPA
identified as hazards in the draft toxicity assessments (i.e.,
decreased immune response in children, increased alanine
aminotransferase (ALT), decreased birth weight and increased
cholesterol) were not the basis for the proposed MCLG derivation.
Importantly, an MCLG of zero is also protective of noncancer endpoints
which were evaluated in the EPA's HRRCA (Health Risk Reduction and Cost
Analysis). Comments related to the benefits the EPA quantified that are
associated with noncancer health effects are described in section XII.
A few commenters agreed with the systematic review protocol the EPA
used to evaluate the studies that supported the PFOA and PFOS cancer
classification determinations in the draft toxicity assessments (USEPA,
2023g; USEPA, 2023h; USEPA, 2023i; USEPA, 2023j), with one commenter
stating that the approach was ``thorough and well-reasoned.''
Commenters stated that the systematic review protocol was clear because
the EPA had addressed all concerns highlighted during the peer review
process.
One commenter stated that the EPA did not conduct a systematic
review of the literature and did not follow the ORD Staff Handbook for
Developing IRIS Assessments (USEPA, 2022f) to develop the toxicity
assessments for PFOA and PFOS. This commenter stated the EPA lacked ``a
predefined protocol'' and that the ``systematic review methods lack[ed]
transparency and consistency.'' The commenter took particular issue
with the EPA's protocols for study quality evaluations, stating that
they were inconsistent and not aligned with the ORD Staff Handbook for
Developing IRIS Assessments (USEPA, 2022f). The EPA disagrees with this
commenter's claims. The EPA adopted the overall approach and steps in
the ORD Staff Handbook for Developing IRIS Assessments (USEPA, 2022f)
and the Systematic Review Protocol for the PFAS IRIS Assessments
(USEPA, 2021h) to develop PFOA- and PFOS-specific protocols that then
formed the basis for performing study quality evaluations, evidence
integration, and critical study selection (see appendix A in USEPA,
2023g; USEPA, 2023h; USEPA, 2023i; USEPA, 2023j). This predefined
protocol was made available for public comment as appendix A of the
toxicity assessments (USEPA, 2023i; USEPA, 2023j). Importantly, the
EPA's Office of Water collaborated with the EPA's Office of Research
and Development in conducting study quality evaluations, evidence
integration, and selection of critical studies to ensure consistency
with the ORD Staff Handbook for Developing IRIS Assessments (USEPA,
2022f) and the Systematic Review Protocol for the PFAS IRIS Assessments
(USEPA, 2021h).
A few commenters claimed that the EPA did not use the best
available science when developing the toxicity assessments for PFOA and
PFOS, asserting that the EPA did not follow its own guidance or data
quality standards and that the EPA's systematic review process was
flawed (see discussion above). The EPA disagrees with these commenters'
claims. The EPA has followed statutory requirements to use the best
available peer-reviewed science in two respects: by (1) considering
relevant peer-reviewed literature identified by performing systematic
searches of the scientific literature or identified through public
comment and (2) relying on peer-reviewed, published EPA human health
risk assessment methodology as well as systematic review best practices
(USEPA, 2021h; USEPA, 2022f). The risk assessment guidance and best
practices serve as the basis for the PFOA and PFOS health effects
systematic review methods used to identify, evaluate, and quantify the
available data. Not only did the EPA incorporate literature identified
in previous assessments, as recommended by the SAB (USEPA, 2022i), but
the EPA also conducted several updated systematic literature searches,
the most recent of which was completed in February 2023. This approach
ensured that the literature under review encompassed studies included
in the 2016 Health Effects Support Documents (HESDs) (USEPA, 2016c;
USEPA, 2016d) and recently available studies. The results of the most
recent literature search provide further support for the conclusions
made in the draft toxicity assessments for PFOA and PFOS (USEPA, 2023g;
USEPA, 2023h) and are described in appendix A of the final toxicity
assessments (USEPA, 2024h; USEPA, 2024i).
As described above, the PFOA and PFOS systematic review protocol is
consistent with the ORD Staff Handbook for Developing IRIS Assessments
(USEPA, 2022f) and also considers PFOA- and PFOS-specific protocol
updates outlined in the Systematic Review Protocol for the PFBA, PFHxA,
PFHxS, PFNA, and PFDA (anionic and acid forms) IRIS Assessments (USEPA,
2021h). The EPA additionally followed human health risk assessment
methods for developing toxicity values (e.g., USEPA, 2002a), conducting
benchmark dose (BMD) modeling (USEPA, 2012), and other analyses. In the
PFOA and PFOS toxicity assessments and the appendices, the EPA clearly
describes
[[Page 32565]]
the methods used and how those methods and decisions are consistent
with the EPA practices and recommendations (i.e., through quotes and
citations) described in various guidance documents.
One commenter stated that the EPA did not use the best available
peer-reviewed science because the assessments did not follow
methodological or statistical guidance. Specifically, this commenter
stated the EPA did not follow A Review of the Reference Dose and
Reference Concentration Processes (USEPA, 2002a) when selecting
uncertainty factors and claimed the EPA did not follow guidance on data
quality (USEPA, 2003; USEPA, 2006b; USEPA, 2014b). The commenter stated
they believed the assessments contained flaws including exclusion of
covariates in modeling, reliance on peer-reviewed studies published by
non-EPA employees, and an inability to replicate results. The EPA
disagrees with these comments. Regarding data quality control, data
quality objectives are an integral part of the ORD Staff Handbook for
Developing IRIS Assessments (USEPA, 2022f) and many of the concepts
outlined in data quality guidance recommended by the commenter (USEPA,
2003; USEPA, 2006b; USEPA, 2014b) are addressed through the EPA's use
of the ORD Handbook (USEPA, 2022f). Furthermore, this work was
conducted under a programmatic quality assurance project plan (QAPP)
which ensures that all EPA data quality guidance is followed, including
those cited by the commenter. Additionally, by developing and
implementing a systematic review protocol consistent with the ORD
Handbook (USEPA, 2022f), the EPA reduced potential confirmation bias, a
concern raised by another commenter, by conducting multiple independent
evaluations of studies, relying on a data-driven, weight of evidence
approach, and by incorporating expertise from across the agency.
In many cases the commenters have misinterpreted the methods and
decisions the EPA used to analyze the data or misinterpreted the
guidance itself. For example, one commenter mistakenly suggested that
the EPA did not consider covariates in its analyses of epidemiological
studies; the EPA described which covariates were considered in each
analysis in several sections of the draft toxicity assessments and
appendices (USEPA, 2023g; USEPA, 2023h; USEPA, 2023i; USEPA, 2023j),
including in descriptions of the studies in section 3 and modeling of
the studies in appendix E. The EPA also notes that the primary studies
that provide the data describe covariate adjustments in their published
analyses.
A couple of commenters suggested that the toxicity assessments for
PFOA and PFOS were not adequately peer-reviewed because changes were
made post peer review (i.e., after publication of the final report by
the SAB PFAS Review Panel (USEPA, 2022i)), the most significant of
which was the updated cancer classification for PFOS, but also included
the addition of figures and mechanistic syntheses. The EPA disagrees
with this assertion. The toxicity assessments, including the
conclusions that are material to the derivation of the MCLGs, were
peer-reviewed by the SAB PFAS review panel (USEPA, 2022i). Notably,
this panel ``agreed with many of the conclusions presented in the
assessments, framework and analysis'' (USEPA, 2022i). The only
assessment conclusion that changed and impacted MCLG derivation between
SAB review and rule proposal was that the cancer classification for
PFOS of Suggestive Evidence of Carcinogenicity was updated to Likely to
be Carcinogenic to Humans according to the Guidelines for Carcinogen
Risk Assessment (USEPA, 2005a). This conclusion for PFOS was based on a
reevaluation of the available data in response to multiple comments
from the SAB PFAS review panel stating that ``[s]everal new studies
have been published that warrant further evaluation to determine
whether the `likely' designation is appropriate'' for PFOS and that the
EPA's ``interpretation of the hepatocellular carcinoma data from the
Butenhoff et al. (2012) study in the 2016 HESD is overly conservative
in dismissing the appearance of a dose-response relationship for this
endpoint, particularly in females'' (USEPA, 2022i). In responding to
the SAB's recommendation that the EPA provide an ``explicit description
of why the available data for PFOS do not meet the EPA Guidelines for
Carcinogen Risk Assessment (2005) criterion for the higher designation
as `likely carcinogenic,' '' and taking into consideration recently
published peer-reviewed epidemiological studies demonstrating
concordance in humans identified through the final updated literature
search recommended by the SAB, the EPA determined that PFOS meets the
criterion for the higher designation of Likely to Be Carcinogenic to
Humans (USEPA, 2005a). This decision was described in sections 3.5.5
and 6.4 of the draft assessment (USEPA, 2023h). Additional discussion
regarding the PFOS cancer descriptor decision is provided here.
One commenter stated that the EPA addressed the SAB's concerns
regarding the systematic review protocol in the documents supporting
the proposed rulemaking. A few commenters reiterated the importance of
the SAB's recommendations, including to more thoroughly describe
systematic review methods used in the assessment (e.g., study inclusion
and exclusion criteria), incorporate additional epidemiological
studies, provide rationale for critical study selection, and derive
candidate toxicity values from both human and animal data. In contrast,
a few commenters claimed that the EPA did not adequately consider
several recommendations made by the SAB PFAS Review Panel in their
final report (USEPA, 2022i), including that the EPA did not incorporate
studies from the 2016 HESDs (USEPA, 2016c; USEPA, 2016d) or develop
multiple cancer slope factors (CSFs). One commenter requested
clarification on whether the EPA had implemented the feedback from the
SAB.
The EPA disagrees with the comments that the agency did not
``meaningfully implement'' SAB feedback. The EPA agrees with commenters
that highlighted the importance of the SAB's suggestions, and notes
that the EPA addressed the SAB's recommendations to more thoroughly
explain the systematic review protocol and expand the systematic review
protocol beyond study quality evaluation and data extraction in the
draft toxicity assessments published at the time of rule proposal
(USEPA, 2023g; USEPA, 2023h; USEPA, 2023i; USEPA, 2023j). As outlined
in the EPA Response to Final Science Advisory Board Recommendations
(August 2022) on Four Draft Support Documents for the EPA's Proposed
PFAS National Primary Drinking Water Regulation (USEPA, 2023k), the EPA
considered all of the comments and recommendations from the SAB and
made substantial improvements to address the reported concerns prior to
publishing the public comment draft assessments (USEPA, 2023g; USEPA,
2023h). The EPA published a response to SAB comments document that
detailed how the agency considered and responded to the SAB PFAS Review
Panel's comments at the time of rule proposal (USEPA, 2023k). The
resulting draft toxicity assessments and protocol released for public
comment along with the proposed rule reflect improvements including
thorough and detailed descriptions of the methods used during
assessment development, inclusion of
[[Page 32566]]
epidemiological studies from the 2016 HESDs for PFOA and PFOS in the
systematic review (USEPA, 2016c; USEPA, 2016d), updates to the
literature, implementation of an evidence integration framework,
expansion of rationale for critical study and model selections,
development of toxicity values from both animal toxicological and
epidemiological data, when warranted, and many other actions. The EPA
appreciated the SAB's engagement, extensive review, and comments on the
Proposed Approaches documents (USEPA, 2021i; USEPA, 2021j).
Furthermore, the EPA provided its consideration of every recommendation
the SAB provided when updating and finalizing the assessments for PFOA
and PFOS at the time of rule proposal (USEPA, 2023k).
Many commenters agreed that that available data indicate that
exposure to either PFOA or PFOS is associated with cancer in humans and
supported the EPA's determination that PFOA and PFOS are Likely to be
Carcinogenic to Humans according to the Guidelines for Carcinogen Risk
Assessment (USEPA, 2005a). Multiple commenters agreed that studies
published since the 2016 HESDs (USEPA, 2016c; USEPA, 2016d) have
strengthened this conclusion. In particular, one commenter supported
the EPA's conclusions regarding the human relevance of hepatic and
pancreatic tumors observed in rats administered PFOS, citing their own
independent health assessment conclusion that ``several lines of
evidence do not support a conclusion that liver effects due to PFOS
exposure are PPAR[alpha]-dependent'' and therefore, may be relevant to
humans (NJDWQI, 2018).
Several commenters disagreed with the EPA's determinations that
PFOA and PFOS are each Likely to be Carcinogenic to Humans. Two
commenters claimed that the tumor types observed in rats (e.g., hepatic
tumors) after PFOA or PFOS administration are not relevant to humans.
Some commenters also stated that the human data do not support an
association between PFOS exposure and cancer. One commenter
specifically claimed that Shearer et al. (2021) does not provide
sufficient evidence for changing PFOS's cancer classification from
Suggestive Evidence of Carcinogenicity to Likely to be Carcinogenic to
Humans because it did not report associations between PFOS exposure and
risk of renal cell carcinoma (RCC). Two commenters stated that the
EPA's discussion using structural similarities between PFOA and PFOS to
support evidence of the carcinogenicity of PFOS was inconsistent with
the Guidelines for Carcinogen Risk Assessment (USEPA, 2005a). A few
commenters additionally questioned or disagreed with the determination
that PFOA is Likely to be Carcinogenic to Humans because of
uncertainties in the epidemiological database and a lack of evidence
indicating that PFOA is genotoxic.
The EPA disagrees with these comments. With respect to the human
relevance of the animal tumors observed in rats after chronic oral
exposure to either PFOA or PFOS, the EPA considered all hypothesized
modes of action (MOAs) and underlying carcinogenic mechanisms in its
cancer assessments, including those that some commenters have argued
are irrelevant to humans (e.g., peroxisome proliferator-activated
receptor [alpha] (PPAR[alpha]) activation), the discussion for which is
available in section 3.5.4.2 of the toxicity assessments for PFOA and
PFOS (USEPA, 2024c; USEPA, 2024d). After review of the available
mechanistic literature for PFOA and PFOS, the EPA concluded that there
are multiple plausible mechanisms, including some that are independent
of PPAR[alpha], that may contribute to the observed carcinogenicity of
either PFOA or PFOS in rats. Further confirmatory support for the EPA's
conclusions regarding multiple plausible mechanisms of carcinogenicity
comes from literature reviews published by state and global health
agencies which concluded that the liver tumors associated with PFOA
and/or PFOS exposure may not entirely depend on PPAR[alpha] activation
and therefore may be relevant to humans (CalEPA, 2021; IARC, 2016;
NJDWQI, 2017; NJDWQI, 2018).
Additionally, the EPA did not rely on results reported by Shearer
et al. (2021) as a rationale for updating the cancer classification for
PFOS to Likely to be Carcinogenic to Humans (USEPA, 2005a) and
acknowledges uncertainties in the results from this study, including
that the effect in the third PFOS exposure quartile was null, the
effects were attenuated (i.e., reduced in magnitude) when adjusted for
exposure to other PFAS, and there was no association when exposure to
PFOS was considered as a continuous variable, rather than when PFOS
exposure levels were stratified by quartiles (USEPA, 2023h). As
described in sections 3.5.5 and 6.4 of the draft PFOS toxicity
assessment, the available information exceeds the characteristics for
the classification of Suggestive Evidence of Carcinogenic Potential
(USEPA, 2005a) because there is statistically significant evidence of
multi-sex and multi-site tumorigenesis from a high confidence animal
toxicological study, as well as mixed but plausible evidence of
carcinogenicity in humans and mechanistic data showing potential human
relevance of the observed tumor data in animals (USEPA, 2023h). The EPA
notes that the recently published studies reporting associations
between PFOS exposure and hepatocellular carcinoma in humans (Goodrich
et al., 2022; Cao et al., 2022) further strengthen the epidemiological
database and support the cancer classification of Likely to be
Carcinogenic to Humans for PFOS.
Regarding commenters' claims that the EPA used the structural
similarities between PFOA and PFOS as supporting evidence of the
carcinogenic potential of PFOS, the EPA did not rely on structural
similarities to draw conclusions about the cancer classification (see
rationale listed above) but instead used this information as
supplemental support for the Likely classification. The EPA originally
included this supplemental line of evidence because the Guidelines for
Carcinogen Risk Assessment (USEPA, 2005a) explicitly states that
``[a]nalogue effects are instructive in investigating carcinogenic
potential of an agent as well as in identifying potential target
organs, exposures associated with effects, and potential functional
class effects or modes of action.'' PFOA and PFOS differ in their
chemical structure by a single functional group; nevertheless, since a
full structure-activity relationship analysis was not conducted, the
EPA removed discussion on this supplemental line of evidence from the
final toxicity assessment for PFOS (USEPA, 2024d).
Further, the EPA disagrees with comments stating that the
epidemiological database for PFOA is too uncertain to support a
classification of Likely to be Carcinogenic to Humans (USEPA, 2005a).
As described in both the draft (USEPA, 2023g) and final toxicity
assessments for PFOA (USEPA, 2024c), as well as the Maximum Contaminant
Level Goals for Perfluorooctanoic Acid (PFOA) and Perfluorooctane
Sulfonic Acid (PFOS) document (USEPA, 2024j) the available data support
an increased risk of both kidney and testicular cancers associated with
PFOA exposure. There is also evidence that PFOA exposure may be
associated with an increased breast cancer risk, based on studies in
populations with specific polymorphisms and for specific types of
breast tumors. Taken together, these results provide consistent and
plausible
[[Page 32567]]
evidence of PFOA carcinogenicity in humans. Additionally, the EPA notes
that while genotoxicity is one potential MOA leading to
carcinogenicity, there is no requirement that a chemical be genotoxic
for the EPA to classify it as either Carcinogenic to Humans, Likely to
be Carcinogenic to Humans, or Suggestive Evidence of Carcinogenic
Potential according to the Guidelines for Carcinogen Risk Assessment
(USEPA, 2005a). Importantly, the SAB PFAS Review Panel supported the
Likely to be Carcinogenic to Humans designation for PFOA in its final
report (USEPA, 2022i).
Many commenters supported the EPA's proposed MCLGs of zero for both
PFOA and PFOS, citing well-documented health effects, including cancer,
resulting from exposure to either PFOA or PFOS as rationale for their
support of the proposed rulemaking. Several commenters also agreed with
the EPA's long-standing practice of establishing the MCLG at zero (see
USEPA, 1998a; USEPA, 2000c; USEPA, 2001; See S. Rep. No. 169, 104th
Cong., 1st Sess. (1995) at 3) for known or likely linear carcinogenic
contaminants, with one commenter stating that it is ``appropriate based
on the weight of evidence for carcinogenicity and other adverse health
impacts of PFOA and PFOS at very low exposures.''
Two commenters disagreed with MCLGs of zero for PFOA and PFOS, with
one commenter claiming that the EPA's determinations were ``not
consistent with the evidence the EPA presents nor with its own
guidance'' (i.e., the EPA's cancer assessment was not consistent with
assessment approaches recommended in the Guidelines for Carcinogen Risk
Assessment (USEPA, 2005a)). The EPA disagrees with these commenters'
assertions because there is sufficient weight of evidence for
carcinogenic risk of both PFOA and PFOS exposures supporting a
classification of Likely to be Carcinogenic to Humans according to the
Guidelines for Carcinogen Risk Assessment (USEPA, 2005a) from the
available epidemiological and animal toxicological studies. Consistent
with the guidelines, the EPA provided a narrative to ``explain the case
for choosing one descriptor and discuss the arguments for considering
but not choosing another'' (USEPA, 2005a) in the draft and final
toxicity assessments (USEPA, 2024c; USEPA, 2024d; USEPA, 2023g; USEPA,
2023h).
3. Final Rule
Based on the best available peer-reviewed science and consistent
with agency guidance (USEPA, 2005a), the EPA has determined that both
PFOA and PFOS are Likely to be Carcinogenic to Humans. Therefore,
following established agency practice regarding contaminants with this
classification and consistent with the statutory directive to set an
MCLG ``at the level at which no known or anticipated adverse effects on
the health of persons occur and which allows for an adequate margin of
safety,'' the EPA set individual MCLGs for both PFOA and PFOS at zero.
As described above, the EPA used the best available peer-reviewed
science, followed agency guidance and current human health risk
assessment methodology, including the ORD Staff Handbook for Developing
IRIS Assessments (USEPA, 2022f) and the Guidelines for Carcinogen Risk
Assessment (USEPA, 2005a), and adequately peer-reviewed (USEPA, 2022i)
the science underlying the MCLG derivation for both PFOA and PFOS
(USEPA, 2024c; USEPA, 2024d; USEPA, 2024j).
Consistent with the Guidelines for Carcinogen Risk Assessment
(USEPA, 2005a), the EPA reviewed the weight of evidence and determined
that PFOA and PFOS are each designated as Likely to Be Carcinogenic to
Humans, because ``the evidence is adequate to demonstrate carcinogenic
potential to humans but does not reach the weight of evidence for the
descriptor Carcinogenic to Humans.'' For PFOA, this determination was
based on the evidence of kidney and testicular cancer in humans and
Leydig cell tumors, pancreatic acinar cell tumors, and hepatocellular
tumors in rats as described in USEPA (2024c). For PFOS, this
determination was based on the evidence of hepatocellular tumors in
male and female rats, which is further supported by recent evidence of
hepatocellular carcinoma in humans (Goodrich et al., 2022; Cao et al.,
2022), pancreatic islet cell carcinomas in male rats, and mixed but
plausible evidence of bladder, prostate, kidney, and breast cancers in
humans (USEPA, 2024d). The EPA has updated and finalized the toxicity
assessment for PFOS to reflect the new epidemiological evidence (USEPA,
2024d; USEPA, 2024i).
Consistent with the statutory definition of MCLG, the EPA
establishes MCLGs of zero for carcinogens classified as either
Carcinogenic to Humans or Likely to be Carcinogenic to Humans where
there is a proportional relationship between dose and carcinogenicity
at low concentrations or where there is insufficient information to
determine that a carcinogen has a threshold dose below which no
carcinogenic effects have been observed. In these situations, the EPA
takes the health protective approach of assuming that carcinogenic
effects should therefore be extrapolated linearly to zero. This is
called the linear default extrapolation approach. This approach ensures
that the MCLG is set at a level where there are no known or anticipated
adverse health effects, allowing for an adequate margin of safety.
Here, the EPA has determined that PFOA and PFOS are Likely to be
Carcinogenic to Humans based on sufficient evidence of carcinogenicity
in humans and animals (USEPA, 2024c; USEPA, 2024d). The EPA has also
determined that a linear default extrapolation approach is appropriate
as there is no evidence demonstrating a threshold level of exposure
below which there is no appreciable cancer risk (USEPA, 2005a). Based
on this lack of evidence, the EPA concluded that there is no known
threshold for carcinogenicity. Based upon a consideration of the best
available peer-reviewed science and statutory directive to set the MCLG
``at the level at which no known or anticipated adverse effects on the
health of persons occur and which allows an adequate margin of
safety,'' the EPA has finalized MCLGs of zero for PFOA and PFOS in
drinking water.
While not a basis for the EPA's MCLG, the EPA notes that its
toxicity assessments indicate either PFOA or PFOS exposure are also
associated with multiple non-cancer adverse health effects. The PFOA
and PFOS candidate non-cancer RfDs based on human epidemiology studies
for various health outcomes (i.e., developmental, cardiovascular,
immune, and hepatic) range from 2 x 10-7 to 3 x
10-8 mg/kg/day (USEPA, 2024c; USEPA, 2024d; USEPA, 2024h;
USEPA, 2024i).
B. MCLG Derivation for Additional PFAS
Section 1412(b)(4)(A) requires the EPA to set the MCLG at a ``level
at which no known or anticipated adverse effects on the health of
persons occur and which allows an adequate margin of safety.'' In this
action, the EPA is setting MCLGs (and MCLs) for five individual PFAS
(section IV.C of this preamble) as well as for mixtures of three of
these PFAS plus PFBS. In the context of this NPDWR, the Hazard Index is
a method which determines when a mixture of two or more of four PFAS--
PFHxS, PFNA, HFPO-DA, and PFBS--exceeds the level of health concern
with a margin of safety and thus the Hazard Index (equal to 1) is the
MCLG for any mixture of those four PFAS. Based on the scientific
record, each PFAS within the mixture has a HBWC, which is set at the
level below which adverse effects
[[Page 32568]]
are not likely to occur and allows for an adequate a margin of safety.
See USEPA, 2024f and section IV.B. of this preamble. The scientific
record also shows that PFHxS, PFNA, HFPO-DA, and PFBS elicit the same
or similar profiles of adverse health effects in several biological
organs and systems, but with differing potencies for effect(s) (see
USEPA, 2022i and 2024a; and section IV.B of this preamble). As a
result, as discussed elsewhere in the preamble, PFAS that elicit
similar observed adverse health effects following individual exposure
should be assumed to act in a dose-additive manner when in a mixture
unless data demonstrate otherwise (USEPA, 2024a). See USEPA, 2024a and
section II and IV.B of this preamble. This means that where drinking
water contains any combination of two or more of these PFAS, the hazard
associated with each PFAS in the mixture must be added up to determine
whether the mixture exceeds a level of public health concern.
The Hazard Index is the method for calculating this level (i.e.,
the mixture MCLG) and reflects both the measured amount of each of the
four PFAS in the mixture and the toxicity (represented by the HBWC) of
each of the four PFAS. The PFAS mixture Hazard Index is an approach to
determine whether any mixture of two or more of these four PFAS in
drinking water exceeds a level of health concern by first calculating
the ratio of the measured concentration of each of the four PFAS
divided by its toxicity (the HBWC). This results in the ``hazard
quotient'' (HQ) for each of the four PFAS. Because the health effects
of these PFAS present dose additive concerns (USEPA, 2024a), the four
HQs are added together, and if the result exceeds 1, then the hazard
from the combined amounts of the four PFAS in drinking water exceeds a
level of public health concern.
1. MCLG Derivation for a PFAS Mixture
a. Proposal
The EPA proposed a Hazard Index MCLG to protect public health from
exposure to mixtures of any combination of PFHxS, PFNA, HFPO-DA, and/or
PFBS, four PFAS that elicit a shared set of adverse effects and co-
occur in drinking water. The Hazard Index is an approach based on dose
additivity that has been validated and used by the EPA to assess
chemical mixtures in several contexts (USEPA, 1986; USEPA, 2000a;
USEPA, 2022i). The EPA's proposal was based on the agency's finding
that the Hazard Index approach is the most practical approach for
establishing an MCLG for PFAS mixtures that meets the statutory
requirements outlined in section 1412(b)(1)(A) of SDWA. This is because
the Hazard Index assesses the exposure level of each component PFAS
relative to its HBWC, which is based on the most sensitive known
adverse health effect (based on the weight of evidence) and considers
sensitive population(s) and life stage(s) as well as potential exposure
sources beyond drinking water. Furthermore, the Hazard Index accounts
for dose additive health concerns by summing the hazard contribution
from each mixture component to ensure that the mixture is not exceeding
the level below which there are no known or anticipated adverse health
effects and allows for an adequate margin of safety.
The proposal defined a mixture as containing one or more of the
four PFAS and therefore covered each contaminant individually if only
one of the four PFAS occurred. Thus, the Hazard Index as proposed
ensures that the level of exposure to an individual PFAS remains below
that which could impact human health because the exposure for that
measured PFAS is divided by its corresponding HBWC. For example, if the
mixture only included PFNA, then under the Hazard Index approach as
proposed any measured concentrations over 10.0 ng/L divided over the
10.0 ng/L HBWC would be greater than the 1.0 Hazard Index MCLG. The
proposed Hazard Index MCLG was 1.0 and the HBWCs of each mixture
component were as follows: 9.0 ng/L \3\ for PFHxS; 10.0 ng/L for HFPO-
DA; 10.0 ng/L for PFNA; and 2000.0 ng/L for PFBS (USEPA, 2023e).
---------------------------------------------------------------------------
\3\ Some commenters noted an error in the HBWC calculation for
PFHxS which was reported as 9.0 ng/L in the proposal. The agency has
corrected the value in this NPDWR and within the requirements under
40 CFR part 141 subpart Z. The correct HRL/HBWC for PFHxS is 10 ng/
L.
---------------------------------------------------------------------------
b. Summary of Major Public Comments and EPA Responses
Many commenters supported the EPA's proposal to regulate a mixture
of PFAS and agreed with the EPA's scientific conclusions about PFAS
dose additivity and the agency's use of the Hazard Index approach to
develop an MCLG for a mixture of PFHxS, PFNA, HFPO-DA, and/or PFBS.
Many commenters opposed the EPA's conclusion about dose additivity and
the use of the Hazard Index approach to regulate co-occurring PFAS. A
few commenters opposed the EPA's use of shared or similar health
endpoints/outcomes rather than a shared MOA as a basis for assessing
risks of PFAS mixtures. A few commenters agreed with the EPA's decision
to regulate these PFAS as a mixture (that some commenters referred to
as a ``group'') and supported the EPA's conclusion about dose
additivity but questioned the EPA's use of the Hazard Index and
suggested alternative approaches such as development of individual
MCLGs or a target organ-specific Hazard Index (TOSHI). Some commenters
claimed that the EPA did not appropriately seek review from the SAB,
particularly on the application of the Hazard Index as an approach to
regulate PFAS under SDWA. Comments on the number of significant digits
applied in the HBWCs and the Hazard Index were varied. For a discussion
of comments and the EPA responses on dose additivity and similarity of
toxic effects, see section III.B of this preamble. Commenters referred
to the HRLs and the HBWCs interchangeably; see section III of this
preamble for comments on HBWCs and the EPA's responses. Responses to
the other topics raised are discussed in the following paragraphs.
The EPA disagrees with commenters that the agency did not seek
adequate consultation from the EPA SAB in the development of the NPDWR.
SDWA section 1412(e) requires that the EPA ``request comments'' from
the SAB ``prior to proposal'' of the MCLG and NPDWR. Consistent with
this statutory provision, the EPA consulted with the SAB from 2021-
2022. As discussed in the proposed rule, the SAB PFAS Review Panel met
virtually via a video meeting platform on December 16, 2021, and then
had three (3) subsequent meetings on January 4, 6 and 7, 2022 to
deliberate on the agency's charge questions, which included a question
specifically focused on the utility and scientific defensibility of the
Hazard Index approach in the context of mixtures risk assessment in
drinking water. Another virtual meeting was held on May 3, 2022, to
discuss the SAB PFAS Review Panel's draft report. Oral and written
public comments were considered throughout the advisory process. The
SAB provided numerous recommendations to the EPA which can be found in
the SAB's final report (USEPA, 2022i). The EPA addressed the SAB's
recommendations and described the EPA's responses to SAB
recommendations in its EPA Response to Final Science Advisory Board
Recommendations (August 2022) on Four Draft Support Documents for the
EPA's Proposed PFAS National Primary Drinking Water Regulation (USEPA,
2023k) and also in the EPA's Response to Comments document in response
to public comments on the proposed PFAS
[[Page 32569]]
NPDWR (USEPA, 2024k). Further discussion on the EPA consultations and
stakeholder engagement activities can be found in section XIII of this
preamble.
The agency also disagrees with commenters who contend that the EPA
must seek advice from the SAB on all aspects of the NPDWR. The statute
does not dictate on which scientific issues the EPA must request
comment from the SAB. In this case, the EPA sought comments on four
documents: Proposed Approaches to the Derivation of a Draft Maximum
Contaminant Level Goal for Perfluorooctanoic Acid (PFOA) in Drinking
Water (USEPA, 2021i); Proposed Approaches to the Derivation of a Draft
Maximum Contaminant Level Goal for Perfluorooctanesulfonic Acid (PFOS)
in Drinking Water (USEPA, 2021j); Analysis of Cardiovascular Disease
Risk Reduction as a Result of Reduced PFOA and PFOS Exposure in
Drinking Water (USEPA, 2021k); and Draft Framework for Estimating
Noncancer Health Risks Associated with Mixtures of PFAS (USEPA, 2021e).
The approach of the EPA's Framework for Estimating Noncancer Health
Risks Associated with Mixtures of PFAS (USEPA, 2024a) and this rule is
to evaluate risks from exposure to mixtures of PFAS that elicit the
same or similar adverse health effects (but with differing potencies
for effect(s)) rather than similarity in MOA. This is consistent with
the EPA's Supplementary Guidance for Conducting Health Risk Assessment
of Chemical Mixtures (USEPA, 2000a) and expert opinion from the NAS
National Research Council (NRC, 2008). MOA, which describes key changes
in cellular or molecular events that may cause functional or structural
changes that lead to adverse health effects, can be a useful metric by
which risk can be assessed. It is considered a key determinant of
chemical toxicity, and chemicals can often be classified by their type
of toxicity pathway(s) or MOAs. However, because PFAS are an emerging
chemical class, MOA data can be limited or entirely lacking for many
PFAS. Therefore, the EPA's approach for assessing risks of PFAS
mixtures is based on the conclusion that PFAS that share one or more
adverse outcomes produce dose-additive effects from co-exposures. This
evidence-based determination supports a health-protective approach that
meets the statute's directive to set the MCLG at a level at which there
are no known or anticipated adverse health effects and which allows for
an adequate margin of safety (1412(b)(4)(A)). The EPA's evidence-based
determination regarding dose additivity, based on similarity of adverse
health effects rather than MOA, and use of the Hazard Index approach to
assess risks of exposure to PFAS mixtures were supported by the SAB in
its review of the Draft Framework for Estimating Noncancer Health Risks
Associated with Mixtures of PFAS (USEPA, 2022i). For a detailed
description of the evidence supporting dose additivity as the default
approach for assessing mixtures of PFAS, see the final Framework for
Estimating Noncancer Health Risks Associated with Mixtures of PFAS
(USEPA, 2024a).
A few commenters supported the EPA's approach to assessing risks of
PFAS mixtures based on similarity of toxicity effect rather than
similarity in MOA. A few commenters opposed the EPA's use of same or
similar adverse health effects/outcomes rather than MOA as a basis for
the approach to assessing risks of PFAS mixtures and suggested that the
agency is not following its own chemical mixtures guidance (USEPA,
2000a). The EPA disagrees with these commenters' assertions. The EPA's
approach, to evaluate health risks of exposure to mixtures of these
four PFAS based on shared or similar adverse health effects of the
mixture components rather than a common MOA, is consistent with the
EPA's Supplementary Guidance for Conducting Health Risk Assessment of
Chemical Mixtures (USEPA, 2000a). Although a conclusion about dose
additivity can be based on mixture components sharing a common MOA,
dose additivity can also be based on ``toxicological similarity, but
for specific conditions (endpoint, route, duration)'' (see the EPA's
Supplementary Guidance for Conducting Health Risk Assessment of
Chemical Mixtures, USEPA, 2000a). The EPA's Supplementary Guidance for
Conducting Health Risk Assessment of Chemical Mixtures indicates that
although basing a conclusion about dose additivity on a common MOA
across mixture components is optimal, there is flexibility in the level
of biological organization at which similarity among mixture components
can be determined.
The EPA directly asked the SAB for feedback on this issue during
its 2021 review of the EPA's draft Framework for Estimating Noncancer
Health Risks Associated with Mixtures of PFAS. Specifically, the EPA
asked the SAB, ``If common toxicity endpoint/health effect is not
considered an optimal similarity domain for those PFAS with limited or
no available MOA-type data, please provide specific alternative
methodologies for integrating such chemicals into a component-based
mixture evaluation(s)'' (USEPA, 2022i). The SAB strongly supported the
EPA's approach of using a similar toxicity endpoint/health effect
instead of a common MOA as a default approach for evaluating mixtures
of PFAS using dose additivity and did not offer an alternative
methodology. For example, the SAB panel stated that:
The Panel agreed with use of a similar toxicity endpoint/health
effect instead of a common MOA as a default approach for evaluating
mixtures of PFAS. This approach makes sense because multiple
physiological systems and multiple MOAs can contribute to a common
health outcome. Human function is based on an integrated system of
systems and not on single molecular changes as the sole drivers of
any health outcome. The Panel concluded that rather than the common
MOA, as presented in the EPA draft mixtures document, common
physiological outcomes should be the defining position (USEPA,
2022i).
The SAB panel also stated:
Furthermore, many PFAS, including the four used in the examples
in the draft EPA mixtures document and others, elicit effects on
multiple biological pathways that have common adverse outcomes in
several biological systems (e.g., hepatic, thyroid, lipid synthesis
and metabolism, developmental and immune toxicities) (USEPA, 2022i).
Some commenters expressed support for the EPA's proposed Hazard
Index approach to regulating a mixture of one or more of the four PFAS
in drinking water. The commenters also stated that occurrence and co-
occurrence of these four PFAS in PWSs, as well as individual and dose-
additive effects of these PFAS, justify the general Hazard Index
approach. The EPA agrees that the general Hazard Index approach is the
most scientifically sound and health-protective approach to deriving a
PFAS mixtures MCLG which considers both their dose additive health
concerns and co-occurrence in drinking water (see additional discussion
in the following paragraphs).
Some commenters opposed the EPA's use of a general Hazard Index as
opposed to a target organ-specific Hazard Index (TOSHI) and suggested
the use of a TOSHI instead. As discussed in this section, the EPA
disagrees with these comments because the use of the general Hazard
Index approach to develop an MCLG for a mixture of PFHxS, PFNA, HFPO-
DA, and/or PFBS is scientifically sound, supported by external peer
review (SAB), and consistent with the EPA's Supplementary Guidance for
Conducting Health Risk Assessment of Chemical Mixtures (USEPA, 2000a).
The EPA considered the two main types of Hazard Index approaches:
(1)
[[Page 32570]]
the general Hazard Index, which allows for component chemicals in the
mixture to have different health effects or endpoints as the basis for
their toxicity reference values (e.g., RfDs, minimal risk levels), and
(2) the TOSHI, which relies on toxicity reference values based on the
same specific target organ or system effects (e.g., effects on the
liver or thyroid; effects on developmental or reproductive systems)
(USEPA, 2000a). The general Hazard Index approach uses the most health-
protective RfD (or minimal risk levels) available for each mixture
component, irrespective of whether the RfDs for all mixture components
are based on effects in the same target organs or systems. These
``overall'' RfDs (as they are sometimes called) are protective of all
other adverse health effects because they are based on the most
sensitive known endpoints as supported by the weight of the evidence.
As a result, this approach is protective of all types of toxicity/
adverse effects, and thus ensures that the MCLG is the level at and
below which there are no known or anticipated adverse human health
effects with an adequate margin of safety with respect to certain PFAS
mixtures in drinking water. The TOSHI produces a less health protective
indicator of risk than the general Hazard Index because the basis for
the component chemical toxicity reference values has been limited to a
specific target organ or system effect, which may occur at higher
exposure levels than other effects (i.e., be a less sensitive
endpoint). Additionally, since a TOSHI relies on toxicity reference
values aggregated for the same specific target organ or system
endpoint/effect, an absence or lack of data on the specific target
organ or system endpoint/effect for a mixture component may result in
that component not being adequately accounted for in this approach
(thus, underestimating health risk of the mixture). A TOSHI can only be
derived for those PFAS for which the same target organ or system
endpoint/effect-specific RfDs have been calculated. Many PFAS have data
gaps in epidemiological or animal toxicological dose-response
information for multiple types of health effects, thus limiting
derivation of target organ-specific toxicity reference values; target
organ-specific toxicity reference values are not currently available
for PFHxS, PFNA, HFPO-DA, and PFBS. The EPA's Supplementary Guidance
for Conducting Health Risk Assessment of Chemical Mixtures recognizes
the potential for organ- or system-specific data gaps and supports use
of overall RfDs in a general Hazard Index approach, stating, ``The
target organ toxicity dose (TTD) is not a commonly evaluated measure
and currently there is no official EPA activity deriving these values,
as there is for the RfD and RfC'' . . . ``Because of their much wider
availability than TTDs, standardized development process including peer
review, and official stature, the RfD and RfC are recommended for use
in the default procedure for the HI'' (USEPA, 2000a). The EPA
determined that the general Hazard Index approach is the most
scientifically defensible and health protective approach for
considering PFAS mixtures in this rule because it is protective of all
adverse health effects rather than just those associated with a
specific organ or system, consistent with the statutory definition of
MCLG.
The EPA directly asked the SAB about the utility and scientific
defensibility of the general Hazard Index approach (in addition to
other methods, including TOSHI) during the 2021 review of the EPA's
draft Framework for Estimating Noncancer Health Risks Associated with
Mixtures of PFAS. Specifically, the EPA asked the SAB to ``Please
provide specific feedback on whether the HI approach is a reasonable
methodology for indicating potential risk associated with mixtures of
PFAS. If not, please provide an alternative;'' and ``Please provide
specific feedback on whether the proposed HI methodologies in the
framework are scientifically supported for PFAS mixture risk
assessment'' (USEPA, 2022i). In its report (USEPA, 2022i), the SAB
stated its support for the general Hazard Index approach:
In general, the screening level Hazard Index (HI) approach, in
which Reference Values (RfVs) for the mixture components are used
regardless of the effect on which the RfVs are based, is appropriate
for initial screening of whether exposure to a mixture of PFAS poses
a potential risk that should be further evaluated. Toxicological
studies to inform human health risk assessment are lacking for most
members of the large class of PFAS, and mixtures of PFAS that
commonly occur in environmental media, overall. For these reasons,
the HI methodology is a reasonable approach for estimating the
potential aggregate health hazards associated with the occurrence of
chemical mixtures in environmental media. The HI is an approach
based on dose additivity (DA) that has been validated and used by
the EPA. The HI does not provide quantitative risk estimates (i.e.,
probabilities) for mixtures, nor does it provide an estimate of the
magnitude of a specific toxicity. This approach is mathematically
straightforward and may readily identify mixtures of potential
toxicological concern, as well as identify chemicals that drive the
toxicity within a given mixture.
A few commenters stated that it is inappropriate to use the general
Hazard Index in the context of a drinking water rule because it is a
screening tool. The EPA guidance (e.g., Risk Assessment Guidance for
Superfund [RAGS], USEPA, 1991b) and the SAB does characterize the
general Hazard Index as appropriate for screening, but the SAB did not
say that the methodology's use was limited to screening, nor that the
agency would or should be prohibited from considering its use in any
regulatory or nonregulatory application. The general Hazard Index is a
well-established methodology that has been used for several decades in
at least one other regulatory context to account for dose additivity in
mixtures. The EPA routinely uses the Hazard Index approach to consider
the risks from multiple contaminants of concern in the Remedial
Investigations and Feasibility Studies for cleanup sites on the
Superfund National Priorities List under the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA).
Noncarcinogenic effects are summed to provide a Hazard Index that is
compared to an acceptable index, generally 1. This procedure assumes
dose additivity in the absence of information on a specific mixture.
These assessments of hazards from multiple chemical exposures are
important factors to help inform the selection of remedies that are
ultimately captured in the Superfund Records of Decision. Moreover, the
EPA has determined that in the context of SDWA, the Hazard Index is
also an appropriate methodology for determining the level at and below
which there are no known or anticipated adverse human health effects
with an adequate margin of safety with respect to certain PFAS mixtures
in drinking water. The Hazard Index approach is the most practical
approach for establishing an MCLG for PFAS mixtures that meets the
statutory requirements outlined in section 1412(b)(1)(A) of SDWA. This
is because the Hazard Index assesses the exposure level of each
component PFAS relative to its HBWC, which is based on the most
sensitive known adverse health effect (based on the weight of evidence)
and considers sensitive population(s) and life stage(s) as well as
potential exposure sources beyond drinking water. Furthermore, the
Hazard Index accounts for dose additive health concerns by summing the
hazard contribution from each mixture component to ensure that the
mixture is not exceeding the level below which there are no known or
anticipated adverse health effects and allows for an
[[Page 32571]]
adequate margin of safety. In addition, given the temporal and spatial
variability of PFAS occurrence in drinking water across the nation
(USEPA, 2024b), this methodology allows the EPA to regulate these
chemicals in drinking water by taking into account site-specific data
at each PWS. Component PFAS HQs (hazard quotients) are expected to
differ across time and space depending on the actual measured
concentrations of each of the four PFAS at each PWS. This approach thus
allows for flexibility beyond a one-size-fits-all approach and is
tailored to address risk at each PWS. The EPA has made a final
regulatory determination for mixtures of two or more of these PFAS. The
EPA's application of the Hazard Index approach to regulate such
mixtures accounts for the dose additivity that was the basis for the
EPA's final determination to regulate such mixtures.
A Hazard Index greater than 1 is generally regarded as an indicator
of adverse health risks associated with a specific level of exposure to
the mixture; a Hazard Index less than or equal to 1 is generally
regarded as not being associated with any appreciable risk (USEPA,
1986; USEPA,1991b; USEPA, 2000a). Thus, in the case of this drinking
water rule, a Hazard Index greater than 1 indicates that occurrence of
two or more of these four component PFAS in a mixture in drinking water
exceeds the health protective level(s) (i.e., HBWC(s)), indicating
health risks.
The EPA proposed a Hazard Index MCLG of 1.0, expressed with two
significant digits. The EPA's proposal expressed the HBWCs to the
tenths place, as follows: 9.0 ng/L for PFHxS, 10.0 ng/L for HFPO-DA;
10.0 ng/L for PFNA; and 2000.0 ng/L for PFBS. The EPA's draft Hazard
Index MCLG document expressed all of the HBWCs with one significant
digit (9, 10, 10, 2000 ng/L, respectively) (USEPA, 2023e). A few
commenters supported the use of two significant digits for the HBWCs,
individual HQs, and the Hazard Index MCLG and stated that the use of
two significant digits would not be expected to result in issues
related to analytical methods precision. One commenter supported using
all digits of precision in calculations but rounding to two significant
digits for the final reported value of the Hazard Index, noting that
the number of significant digits used only affects rounding during
steps prior to the point at which a Hazard Index MCL is reached.
Commenters noted the importance of clearly communicating the number of
significant digits to be used in the documents, and that the choice of
the number of significant digits could impact implementation of an MCL
based on the Hazard Index. For example, a Hazard Index of 1 (i.e.,
using one significant digit) would not be exceeded unless the value is
calculated to be at 1.5 or above. Alternatively, a Hazard Index of 1.0
(reporting with more than one significant digit) would be exceeded when
the Hazard Index is calculated to be 1.05 or above. For additional
discussion on significant digit usage, please see sections V and VIII.
A few commenters did not support more than a single significant
digit for the HBWCs and Hazard Index MCLG, with some stating that using
two or more significant digits for the Hazard Index contradicts the EPA
chemical mixtures guidance (USEPA, 2000a) and the RAGS (USEPA, 1991b).
The EPA agrees that one (1) significant digit is appropriate for the
HBWCs and the Hazard Index MCLG (i.e., 1 rather than 1.0, as in the
proposal) because although there is sufficient analytical precision for
two significant digits at these concentrations, the RfVs (RfDs and
minimal risk levels) used to derive the HBWCs have one significant
digit. According to the EPA chemical mixtures guidance (USEPA, 2000a),
``Because the RfDs (and by inference the TTDs) are described as having
precision no better than an order of magnitude, the HI should be
rounded to no more than one significant digit.'' This approach of using
a Hazard Index of 1 is consistent with agency chemical mixtures
guidance (USEPA, 1986; USEPA, 2000a) and RAGS (USEPA, 1991b; USEPA,
2018c). The EPA's Risk Assessment Guidance for Superfund Volume 1 Human
Health Evaluation Manual states, ``For noncarcinogenic effects, a
concentration is calculated that corresponds to an HI of 1, which is
the level of exposure to a chemical from all significant exposure
pathways in a given medium below which it is unlikely for even
sensitive populations to experience adverse health effects,'' and ``The
total risk for noncarcinogenic effects is set at an HI of 1 for each
chemical in a particular medium'' (USEPA, 1991b). Finally, ``Cancer
risk values and hazard index (HI) values may express more than one
significant figure, but for decision-making purposes one significant
figure should be used'' (USEPA, 2018c).
c. Final Rule
The EPA has made a final determination to regulate mixtures
containing two or more of PFHxS, PFNA, HFPO-DA, and/or PFBS. For the
final determination, the EPA's evaluation utilized an HRL as part of a
general Hazard Index approach (for additional discussion on the EPA's
Final Regulatory Determinations, please see section III of this
preamble). The EPA's proposal included individual preliminary
regulatory determinations for PFHxS, PFNA, HFPO-DA, and PFBS and a
mixture regulatory determination for mixtures of those PFAS. The EPA's
proposal addressed these regulatory determinations through the Hazard
Index MCLG and MCL that would apply to a mixture containing one or more
of PFHxS, PFNA, HFPO-DA, and PFBS. If two or more of these PFAS were
present then the MCLG and MCL would account for dose additivity of all
of the contaminants present, but if only one of the contaminants were
present then the Hazard Index would operate as an individual MCLG and
MCL. In this final rule, the EPA is promulgating individual MCLGs and
MCLs to address the individual final regulatory determinations (PFHxS,
PFNA, and HFPO-DA) and is promulgating a Hazard Index MCLG and MCL to
address the final mixtures regulatory determination for two or more
Hazard Index PFAS (PFHxS, PFNA, HFPO-DA, and PFBS) present.
The EPA used the same general Hazard Index approach for the mixture
MCLG. In the general Hazard Index approach, individual PFAS HQs are
calculated by dividing the measured concentration of each component
PFAS in water (e.g., expressed as ng/L) by the corresponding HBWC for
each component PFAS (e.g., expressed as ng/L), as shown in the
following equation (and described in USEPA, 2024f). For purposes of
this NPDWR, the EPA is using the term ``health-based water
concentration'' or ``HBWC'' given its role in calculating the Hazard
Index (see the Executive Summary of this preamble). The EPA notes that
the Hazard Index MCLG applies to the entire mixture but the EPA's
technical justification for the HBWCs for the mixture components is the
same as for the individual MCLGs provided in this rule. In this final
rule, component PFAS HQs are summed across the PFAS mixture to yield
the Hazard Index MCLG. The final PFAS mixture Hazard Index MCLG is set
at 1 (one significant digit). A Hazard Index greater than 1 (rounded to
one significant digit) indicates that exposure (i.e., PFAS occurrence
in drinking water) exceeds the health protective level (i.e., HBWC) for
two or more of the individual PFAS mixture components, and thus
indicates health risks. The Hazard Index MCLG ensures that even when
the individual
[[Page 32572]]
components are below a level of concern, the components when added
together in the mixture do not result in a mixture that itself exceeds
a level of concern. A Hazard Index less than or equal to 1 indicates
that occurrence of these four PFAS in drinking water does not exceed
the health protective level and is therefore generally regarded as
unlikely to result in any appreciable risk (USEPA, 1986; USEPA, 1991b;
USEPA, 2000a). For more details, please see USEPA (2024a; USEPA,
2024f). The final Hazard Index MCLG for a mixture of PFHxS, PFNA, HFPO-
DA, and/or PFBS is derived as follows:
[GRAPHIC] [TIFF OMITTED] TR26AP24.004
Where
[PFASwater] = the measured component PFAS concentration
in water and
[PFASHBWC] = the HBWC of a component PFAS.
2. MCLG Derivation for PFHxS, PFNA, and HFPO-DA
a. Proposal
As described in section IV.B.1.a of this preamble, in March 2023,
the EPA proposed a Hazard Index MCLG to protect public health from
exposure to mixtures of PFHxS, PFNA, HFPO-DA, and PFBS, four PFAS that
affect many similar health endpoints/outcomes and that occur and co-
occur in drinking water. At that time, the EPA also considered setting
individual MCLGs for these PFAS either instead of or in addition to
using a mixtures-based approach for PFHxS, PFNA, HFPO-DA, and PFBS. The
EPA ultimately proposed the Hazard Index approach for establishing an
MCLG for a mixture of these four PFAS.
b. Summary of Major Public Comments and EPA Responses
Several commenters favored finalization of individual MCLGs (and
MCLs) for some or all of the PFAS included in the proposed Hazard
Index, with or without a Hazard Index approach to address mixtures of
these PFAS. Specifically, commenters supported establishing individual
MCLGs for PFHxS, PFNA, HFPO-DA, and PFBS because they questioned the
EPA's scientific conclusions regarding PFAS dose additivity and raised
concerns about potential risk communication issues and confusion about
the EPA's use of the Hazard Index to establish drinking water standards
(for additional discussion on MCLs, please see section V of this
preamble). The EPA agrees with commenters who favored finalization of
individual MCLGs for some of the PFAS included in the Hazard Index, and
to do so in addition to the Hazard Index MCLG being finalized for the
mixture of the four PFAS. The EPA believes this provides clarity for
purposes of implementation of the rule. The EPA is finalizing
individual MCLGs for PFHxS, PFNA, and HFPO-DA (for additional
discussion on the final regulatory determinations, please see section
III of this preamble). Regarding risk communication and potential
confusion about the use of the Hazard Index, the EPA acknowledges that
effective risk communication is important, and the agency will develop
communication materials to facilitate understanding of all aspects of
this NPDWR, including the Hazard Index MCL (for additional discussion
on MCLs, please see section V of this preamble). The EPA has provided
language for consumer notifications as part of CCR (see section IX of
this preamble).
One commenter stated that developing individual MCLGs (and MCLs) in
addition to the Hazard Index mixture MCLG (and MCL) would have no
practical impact, since an exceedance of an HBWC for an individual PFAS
within a mixture would result in an exceedance of the Hazard Index even
if none of the other PFAS included in the Hazard Index are detected.
The EPA clarifies the final rule promulgates individual MCLs for PFHxS,
PFNA and HFPO-DA as well as a mixture Hazard Index MCL for two or more
of these PFAS and PFBS. There may be a practical impact of these
individual MCLs (for PFHxS, PFNA and HFPO-DA) where one of these three
PFAS occur in isolation (i.e., without one of the other four Hazard
Index PFAS present) above their individual MCLs. The EPA notes that
this regulatory structure is consistent with the intended effect of the
proposed regulation, where as proposed, a single PFAS above its HBWC
would have caused an exceedance of the MCL. Based on public comment,
the EPA has restructured the rule such that two or more of these
regulated PFAS would be necessary to cause an exceedance of the Hazard
Index and instead will regulate individual exceedances of PFNA, PFHxS,
and HFPO-DA as individual MCLs to improve risk communication. Risk
communication is an important focus for water systems and the EPA
believes that finalizing individual MCLs for PFHxS, PFNA, and HFPO-DA
can support risk communication as utilities and the public may be more
familiar with this regulatory framework. Additionally, the final
individual MCLs for PFHxS, PFNA and HFPO-DA will address and
communicate health concerns for these compounds where they occur in
isolation. At the same time, since those individual MCLs do not address
additional risks from co-occurring PFAS, the EPA is finalizing a Hazard
Index MCL that provides a framework to address and communicate dose
additive health concerns associated with mixtures of PFHxS, PFNA, HFPO-
DA, and PFBS that co-occur in drinking water. For the EPA's discussion
on the practical impact of the establishment of stand-alone standards
in lieu of or in addition to the Hazard Index MCL, please see sections
V and IX.A of this preamble. The EPA's discussion on the practical
impact of the establishment of stand-alone standards in lieu of or in
addition to the Hazard Index MCL, please see sections V and IX.A of
this preamble.
A few commenters questioned why the EPA is developing an NPDWR for
contaminants that do not have EPA Drinking Water Health Advisories
(PFHxS, PFNA), and stated that the EPA should wait to propose an NPDWR
for PFHxS and PFNA until after Health Advisories are finalized for
these PFAS. The EPA disagrees with this comment. Health Advisories are
not a pre-requisite for an NPDWR under SDWA and there is nothing in the
statute or the EPA's historical regulatory practice that suggests that
the agency must or should
[[Page 32573]]
delay regulation of a contaminant in order to develop a health advisory
first.
c. Final Rule
As described in section III of this preamble, the EPA has made a
final determination to individually regulate PFHxS, PFNA, and HFPO-DA.
The EPA is finalizing individual MCLGs for PFHxS, PFNA, and HFPO-DA
as follows: PFHxS MCLG = 10 ng/L; HFPO-DA MCLG = 10 ng/L; and PFNA MCLG
= 10 ng/L. The technical basis for why each of these levels satisfies
the statutory definition for MCLG is described in section III of this
preamble (and is the same technical basis the EPA used to explain the
levels identified as the HBWCs). These MCLGs are expressed with one
significant digit and are based on an analysis of each chemical's
toxicity (i.e., RfD/minimal risk level) and appropriate exposure
factors (i.e., DWI-BW, RSC) (USEPA, 2024f).
The EPA is deferring its individual regulatory determination for
PFBS and not finalizing an individual MCLG for PFBS at this time
(please see section III of this preamble, Final Regulatory
Determinations for Additional PFAS, for further information).
V. Maximum Contaminant Levels
Under current law and as described in the proposed rule (USEPA,
2023f), the Environmental Protection Agency (EPA) establishes drinking
water standards through a multi-step process. See S. Rep. No. 169,
104th Cong., 1st Sess. (1995) at 3. First, the agency establishes a
non-enforceable Maximum Contaminant Level Goals (MCLG) for the
contaminant in drinking water at a level which no known or anticipated
adverse effects to the health of persons will occur and which allow for
an adequate margin of safety. Second, the agency generally sets an
enforceable Maximum Contaminant Level (MCL) as close to that public
health goal as feasible, taking costs into consideration.
In this second step, consistent with the definition of ``feasible''
in section 1412(b)(4)(D), the EPA evaluates the availability and
performance of Best Available Technologies (BATs) for treating water to
minimize the presence of the contaminant consistent with the MCLG (see
section X for additional discussion on BATs) as well as the costs of
applying those BATs to large metropolitan water systems when treating
to that level (1412(b)(4)(E) and (5)).\4\ The definition of
``feasible'' means feasible with the use of the best technology . . .
``which includes consideration of the analytical limits of best
available treatment and testing technology.'' see S. Rep. No. 169,
104th Cong., 1st Sess. (1995) at 3; see also section 1401(1)(C)(i)
stating that a NPDWR includes an MCL only ``if, in the judgment of the
Administrator, it is economically and technologically feasible to
ascertain the level of such contaminant in water in public water
systems.'' In addition, the MCL represents ``the maximum permissible
level of a contaminant in water which is delivered to any user of a
public water system,'' section 1401(3). Thus, in setting the MCL level,
the EPA also identifies the level at which it is technologically
feasible to measure the contaminant in the public water system. To
identify this level, the EPA considers (1) the availability of
analytical methods to reliably quantify levels of the contaminants in
drinking water and (2) the lowest levels at which contaminants can be
reliably quantified within specific limits of precision and accuracy
during routine laboratory operating conditions using the approved
methods (known as the practical quantitation levels (PQLs)). The
ability of laboratories to measure the level of the contaminant with
sufficient precision and accuracy using approved methods is essential
to ensure that any public water system nationwide can monitor,
determine compliance, and deliver water that does not exceed the
maximum permissible level of a contaminant in water to any of its
consumers. (See section VII of this preamble for additional discussion
on analytical methods and PQLs for the per- and polyfluoroalkyl
substances (PFAS) regulated in this rule.)
---------------------------------------------------------------------------
\4\ Based on legislative history, the EPA interprets ``taking
cost into consideration'' in section 1412(b)(4)(D) to be limited to
``what may be reasonably be afforded by large metropolitan or
regional public water systems.'' H.R. Rep. No 93-1185 (1974),
reprinted in 1974 U.S.C.C.A.N. 6454, 6470-71.
---------------------------------------------------------------------------
In practice this means that where the MCLG is zero, the EPA
typically sets MCLs at the PQLs when treatment is otherwise feasible,
based on cost and treatment availability, because the PQL is the
limiting factor. Conversely, for contaminants where the MCLG is higher
than the PQL, the EPA generally sets the MCL at the MCLG when treatment
is otherwise feasible, based on costs and treatment availability,
because the PQL is not a limiting factor.
The Safe Drinking Water Act (SDWA) defines an MCL as ``the maximum
permissible level of a contaminant in water which is delivered to any
user of a public water system.'' Like the MCLG, SDWA does not dictate
that the MCL take a particular form; however, given this definition, an
MCL establishes a ``maximum permissible level of a contaminant in
water'' and as a practical matter the identified ``level'' must be
capable of being validated so that it can be determined whether that
public water systems are delivering water to any user meeting or
exceeding that ``level.''
A. PFOA and PFOS
1. Proposal
In the March 2023 proposal, the EPA proposed individually
enforceable MCLs for PFOA and PFOS at the PQL which is 4.0 ng/L (USEPA,
2023f). Section 1412(b)(4)(E) of SDWA requires that the agency ``list
the technology, treatment techniques, and other means which the
Administrator finds to be feasible for purposes of meeting [the MCL],''
which are referred to as Best Available Technologies (BATs). The EPA
found multiple treatment technologies to be effective and available to
treat PFOA and PFOS to at or below the proposed standards (please see
and section X (10) of this preamble and USEPA, 2024l for additional
discussion on feasible treatment technologies including BAT/SSCT
identification and evaluation). In addition, the EPA found that there
are analytical methods available to reliably quantify PFOA and PFOS at
the PQL. The EPA requested comment on regulatory alternatives for both
compounds at 5.0 ng/L and 10.0 ng/L. The EPA also requested comment on
whether setting the MCL at the PQL for PFOA and PFOS is implementable
and feasible.
2. Summary of Major Public Comments and EPA Responses
The EPA received many comments that strongly support the proposed
MCLs of 4.0 ng/L and the agency's determination that the standards are
as close as feasible to the MCLG. These commenters request the agency
to finalize the standards as expeditiously as possible. Consistent with
these comments, through this action, the agency is establishing
drinking water standards for PFOA and PFOS (and four other PFAS) to
provide health protection against these contaminants found in drinking
water.
Many commenters assert that implementation of the PFOA and PFOS
standards would be challenging because the MCLs are set at the PQLs for
each compound, and some commenters recommended alternative standards
(e.g., 5.0 ng/L or 10.0 ng/L). These commenters contend that by setting
the
[[Page 32574]]
MCLs at the PQLs, utilities would not be able to reliably measure when
the concentration of contaminants in their drinking water is
approaching the MCLs. Some of these commenters suggest that having a
buffer between the PQLs and the MCLs may allow utilities to manage
treatment technology performance more efficiently because utilities
generally aim to achieve lower than the MCLs to avoid a violation and
that this buffer would provide some level of operational certainty for
systems treating for PFAS. The EPA disagrees that the PFOA and PFOS
standards are not implementable because the MCLs are set at their
respective PQLs.
As the agency noted in the proposed rule preamble, the EPA has
promulgated, and both the EPA and water systems have successfully
implemented, several NPDWRs with MCLs equal to the contaminant PQLs. As
examples, in 1987, the EPA finalized the Phase I Volatile Organic
Compounds (VOC) rule (USEPA, 1987), where the agency set the MCL at the
PQL for benzene, carbon tetrachloride, trichloroethylene, vinyl
chloride, and 1,2-dichloroethane (52 FR 25690). Other examples where
MCLs were set at the PQL include benzo(a)pyrene, di(2-ethylhexyl)
phthalate, dioxin, dichloromethane, hexachlorobenzene, and PCBs (see
USEPA, 1991c and USEPA, 1992). Some commenters at the time stated they
believed implementation would be challenging because the MCLs were set
at the PQL in these examples; however, the EPA notes that those rules
have been implemented successfully despite commenters initial concerns.
The agency does not agree with commenters that operational flexibility
(i.e., the inclusion of a `buffer' between the PQL and MCL) is relevant
for purposes of setting an MCL. That is because the PQL is the lowest
level that can be reliably achieved within specified limits of
precision and accuracy and is therefore the metric by which the agency
uses to evaluate the most feasible MCL pursuant to SDWA requirements.
Considerations for operational flexibility may be relevant to other
parts of the rule, such as determining monitoring and compliance with
the rule. First, for purposes of determining compliance with the MCL,
water systems must calculate the running annual average (RAA) of
results, which could allow some results to exceed 4.0 ng/L for single
measurements if the overall annual average is below the MCL. In other
words, there is a buffer built into determining compliance with the
MCL. Second, when calculating the RAA, zero will be used for results
less than the PQL which provides an additional analytic buffer for
utilities in their compliance calculations. This monitoring and
compliance framework allows for temporal fluctuations in concentrations
that may occur because of unexpected events such as premature PFOA and
PFOS breakthrough or temporary elevated source water concentrations.
Thus, periodic occurrences of PFOA or PFOS that are slightly above the
PQLs do not necessarily result in a violation of the MCL if other
quarterly samples are below the PQL. The agency notes that in general,
PQLs are set above the limit of detection; for PFAS specifically, all
the PQLs are well above their limits of detection. The PQL is also
different than detection limits because the PQL is set considering a
level of precision, accuracy, and quantitation. Systems may be able to
use sample results below the PQL to understand whether PFOA and PFOS
are present. While the EPA has determined that results below the PQL
are insufficiently precise for determining compliance with the MCL,
results below the PQL can be used to determine analyte presence or
absence in managing a system's treatment operations and to determine
monitoring frequency. See discussion in section VII of this preamble
for further discussion of the PQL, results below the PQL, and how those
results provide useful information.
Some commenters contend that the PQLs for PFOA and PFOS are not set
at an appropriate level (e.g., the PQLs are either too high or too low
for laboratories to meet). Specifically, these commenters question
whether enough laboratories have the ability to analyze samples at 4.0
ng/L and, as a result, contend it is not a ``reasonable quantitation
level.'' The EPA disagrees with commenters who suggest the PQLs for
PFOA and PFOS are not set at an appropriate level or that they should
be either higher or lower levels than that proposed. As discussed above
and in the March 2023 proposal, the EPA derives PQLs that reflect the
level of contaminants that laboratories can reliably quantify within
specific limits of precision and accuracy during routine laboratory
operating conditions. The ability to reliably measure is an important
consideration for feasibility to ensure that water systems nationwide
can monitor and dependably comply with the MCLs and deliver drinking
water that does not exceed the maximum permissible level. In the rule
proposal (USEPA, 2023f), the EPA explained that the minimum reporting
levels under UCMR 5 reflect ``a minimum quantitation level that, with
95 percent confidence, can be achieved by capable lab analysts at 75
percent or more of the laboratories using a specified analytical
method'' (USEPA, 2022k). The PQLs for the regulated PFAS are based on
the UCMR 5 minimum reporting levels. The EPA calculated the UCMR 5
minimum reporting levels using quantitation-limit data from multiple
laboratories participating in multi-lab method validation studies
conducted in the 2017-2019 timeframe, prior to the UCMR 5 Laboratory
Approval Program (see appendix B of USEPA, 2020b). The calculations
account for differences in the capability of laboratories across the
country. Laboratories approved to analyze UCMR samples must demonstrate
that they can consistently make precise measurements of PFOA and PFOS
at or below the established minimum reporting levels. Therefore, the
EPA finds that the UCMR 5 minimum reporting levels are appropriate for
using as PQLs for this rule: the EPA estimates that laboratories across
the nation can precisely and accurately measure PFOA and PFOS at this
quantitation level. After reviewing data from laboratories that
participated in the minimum reporting level setting study under UCMR 5
and in consideration of public comment, the EPA finds that the minimum
reporting levels set in UCMR 5 of 4.0 ng/L for PFOA and PFOS, that are
also the PQLs, are as close as feasible to the MCLG. While lower
quantitation levels may be achievable for some laboratories, it has not
been demonstrated that these lower quantitation levels can be achieved
for ``at 75 percent or more of the laboratories using a specified
analytical method'' across laboratories nationwide. Moreover, though
the EPA is confident of sufficient laboratory capacity to implement
this PFAS National Primary Drinking Water Regulation (NPDWR) as
finalized, a lower PQL could potentially limit the number of
laboratories available to support analytical monitoring that would be
otherwise available to support analytical monitoring with PFOA and PFOS
PQLs of 4.0 ng/L.
In the proposal, the EPA discussed how utilities may be able to use
sample results below the PQL to determine analyte presence or absence
in managing their treatment operations; however, a few commenters
contend that this is not practical to determine compliance with the MCL
as these values are less precise and violations may result in expensive
capital
[[Page 32575]]
improvements. Commenters are conflating two different issues. While
commenters are referring to quantitation of a sampling result for
compliance with the rule, the EPA's discussion on results below the PQL
refers to determining simple presence or absence of a contaminant for
other purposes. Sampling results below the PQL may not have the same
precision as a sampling result at or above the PQL but they are useful
for operational purposes such as understanding that PFOA and PFOS may
be present, which can inform treatment decisions and monitoring
frequency. For example, a utility may use sampling results below 4.0
ng/L as a warning that they are nearing the PFOA and PFOS MCLs of 4.0
ng/L prior to an exceedance. Then, the utility can make informed
treatment decisions about managing their system (e.g., replacing GAC).
Additionally, the EPA evaluated data submitted as part of the UCMR 5
Laboratory Approval Program (LAP) and found that 47 of 53 laboratories
(89 percent) that applied for UCMR 5 approval generated a minimum
reporting level confirmation at 2 ng/L (one-half the proposed MCL) or
less for Method 533 (USEPA, 2022j). This suggests that the majority of
laboratories with the necessary instrumentation to support PFAS
monitoring have the capability to provide useful screening measurement
results below the PQL. Further, as discussed in section VII of this
preamble, all labs are required per the approved methods to demonstrate
whether laboratory reagent blank (LRB) quality control (QC) samples
have background concentrations of less than one-third the minimum
reporting level (i.e., the minimum concentration that can be reported
as a quantitated value for a method analyte in a sample following
analysis). Therefore, for a laboratory to be compliant with the
methods, they must be able to detect, not necessarily quantify,
analytes at or above \1/3\ the minimum reporting level.
The EPA agrees with commenters that it is inappropriate to make
potentially costly compliance decisions based on measurements below the
PQL because they do not have the same level of precision and accuracy
as results at or above the PQL. As previously discussed, for MCL
compliance purposes, results less than the PQL will be recorded as
zero. For additional details on monitoring and compliance requirements,
please see section VIII of this preamble.
Some commenters argue that the EPA did not sufficiently consider
cost in the agency's feasibility analysis of the proposed MCLs and
therefore disagreed with the EPA that the standards are feasible. In
particular, these commenters suggest that the agency did not adequately
consider costs associated with implementation (e.g., costs for labor,
materials, and construction of capital improvements) and compliance
(e.g., costs to monitor) with the proposed MCLs. Based on these
factors, many of these commenters suggest either raising the MCLs or
re-proposing the standard in its entirety. The EPA did consider these
costs and therefore disagrees with commenters' assertions that the
agency did not consider these issues in establishing the proposed MCLs
for PFOA and PFOS (USEPA, 2024g; USEPA, 2024l; USEPA, 2024m). The EPA
considers whether these costs are reasonable based on large
metropolitan drinking water systems. H.R. Rep. No 93-1185 (1978),
reprinted in 1974 U.S.C.C.A.N. 6454, 6470-71. The EPA considered costs
of treatment technologies that have been demonstrated under field
conditions to be effective at removing PFOA and PFOS and determined
that the costs of complying with an MCL at the PQL of 4.0 are
reasonable for large metropolitan water systems at a system and
national level (USEPA, 2024e; USEPA, 2024g). To designate technologies
as BATs, the EPA evaluated each technology against six BAT criteria,
including whether there is a reasonable cost basis for large and medium
water systems. The EPA evaluated whether the technologies are currently
being used by systems, whether there were treatment studies available
with sufficient information on design assumptions to allow cost
modeling, and whether additional research was needed (USEPA, 2024l). In
considering the results of this information, the EPA determined that
these costs are reasonable to large metropolitan water systems.
Pursuant to SDWA section 1412(b)(4)(E)(ii), the agency also
evaluated ``technolog[ies], treatment technique[s], or other means that
is affordable'' for small public water systems. In this evaluation, the
agency determined that the costs of small system compliance
technologies (SSCTs) to reach 4.0 ng/L are affordable for households
served by small drinking water systems. Additionally, the EPA notes
that SDWA section 1412(b)(4)(D) states that ``granular activated carbon
is feasible for the control of synthetic organic chemicals'' which the
agency lists as a BAT for this rule (section X). All PFAS, including
PFOA and PFOS, are SOCs, and therefore, GAC is BAT as defined by the
statute. For additional discussion on BATs and SSCTs, please see
section X of this preamble.
Some commenters disagreed with the EPA's determination that the
rule is feasible under SDWA asserting that there is insufficient
laboratory capacity and other analytic challenges to measure samples at
these thresholds. As described above in the agency's approach toward
evaluating feasibility, the EPA assesses (1) the availability of
analytical methods to reliably quantify levels of the contaminants in
drinking water and (2) the lowest levels at which contaminants can be
reliably quantified within specific limits of precision and accuracy
during routine laboratory operating conditions using the approved
methods (i.e., the PQLs). This framework inherently considers both the
capacity and capability of labs available to meet the requirements of
the NPDWR. Based on the EPA's analysis of these factors, the EPA
disagrees with commenter assertions that there is insufficient
laboratory capacity at this time to support implementation of the
NPDWR. Currently, there are 53 laboratories for PFAS methods (Method
533 or 537.1) in the EPA's Unregulated Contaminant Monitoring Rule
(UCMR) 5 Laboratory Approval Program, more than double the
participation in UCMR 3 (21 laboratories), with several laboratory
requests to participate after the lab approval closing date. At a
minimum, these 53 labs alone have already demonstrated sufficient
capacity for current UCMR 5 monitoring, which requires monitoring for
all systems serving above 3,300 or more persons and 800 systems serving
less than 3,300 persons over a three-year period. The 21 laboratories
participating in UCMR 3 provided more than sufficient capacity for that
monitoring effort, which required monitoring for all systems serving
greater than 10,000 persons and 800 systems serving less than 10,000.
Further, a recent review of state certification and third-party
accreditation of laboratories for PFAS methods found an additional 25
laboratories outside the UCMR 5 LAP with a certification or
accreditation for EPA Method 533 or 537.1. Additionally, as has
happened with previous drinking water regulations, the EPA anticipates
laboratory capacity to grow once the rule is finalized to include an
even larger laboratory community, as the opportunity for increased
revenue by laboratories would be realized by filling the analytical
needs of the utilities (USEPA, 1987; USEPA, 1991c; USEPA, 1991d; USEPA,
1992; USEPA, 2001). Finally, with the use of a reduced monitoring
schedule to once every three years for eligible systems, and the
[[Page 32576]]
ability for systems that are reliably and consistently below the MCLs
of 4.0 ng/L to only monitor once per year, the EPA anticipates that the
vast majority of utilities may be able to take advantage of reduced or
annual monitoring, and will not require a more frequent monitoring
schedule, thus easing the burden of laboratory capacity as well.
The EPA also disagrees with commenter assertions that there is
insufficient laboratory capability at this time. As discussed above and
in the proposed rule preamble, the EPA proposed a PQL of 4.0 ng/L for
both PFOA and PFOS based on current analytical capability and from the
minimum reporting levels generated for the UCMR 5 program. The EPA
evaluated data submitted as part of the UCMR 5 LAP and found that 47 of
53 laboratories (89 percent) that applied for UCMR 5 approval generated
a minimum reporting level confirmation at 2 ng/L (one-half the proposed
MCL) or less for Method 533. The MCLs for PFOA and PFOS were also set
at 4.0 ng/L as a result of the analytical capability assessment under
the minimum reporting level setting study for UCMR 5, as well as
consideration of other factors (e.g., treatment, costs) as required
under SDWA. For UCMR 5, all UCMR-approved laboratories were able to
meet or exceed the PFOS and PFOA UCMR minimum reporting levels, set at
4 ng/L, the proposed MCL for both. The UCMR 5 minimum reporting levels
of 4 ng/L for PFOS and PFOA are based on a multi-laboratory minimum
reporting level calculation using lowest concentration minimum
reporting level (LCMRL) data. The LCMRL and minimum reporting level
have a level of confidence associated with analytical results. More
specifically, the LCMRL calculation is a statistical procedure for
determining the lowest true concentration for which future analyte
recovery is predicted with 99% confidence to fall between 50 and 150%
recovery (Martin et al., 2007). The multi-laboratory minimum reporting
level is a statistical calculation based on the incorporation of LCMRL
data collected from multiple laboratories into a 95% one-sided
confidence interval on the 75th percentile of the predicted
distribution referred to as the 95-75 upper tolerance limit. This means
that 75% of participating laboratories will be able to set a minimum
reporting level with a 95% confidence interval. The quantitation level
of 4 ng/L has been demonstrated to be achieved with precision and
accuracy across laboratories nationwide, which is important to ensure
that systems can dependably comply with the MCL and deliver drinking
water that does not exceed the maximum permissible level. The agency
anticipates that these quantitation levels for labs will continue to
improve over time, as technology advances and as laboratories gain
experience with the PFAS Methods. The EPA's expectation is supported by
the record borne out by the significant improvements in analytical
capabilities for measuring certain PFAS, including PFOA and PFOS,
between UCMR 3 and UCMR 5. For example, the minimum reporting levels
calculated for UCMR 3 (2012-2016) were 40 ng/L and 20 ng/L for PFOS and
PFOA, respectively, the minimum reporting levels calculated for UCMR 5
(2022-2025) were 4 ng/L each for PFOA and PFOS.
Some commenters recommend a different regulatory framework than
what the EPA proposed to alleviate perceived implementation concerns
(e.g., reduce the potential of inundating laboratories or providing
more time to plan and identify opportunities for source water
reduction). For example, a few commenters suggest a phased-in MCL,
where systems demonstrating higher concentrations are addressed first
in the NPDWR, or MCL approaches where interim targets are set for
compliance. Upon consideration of information submitted by commenters,
particularly issues related to supply chain complications that are
directly or indirectly related to the COVID-19 pandemic residual
challenges, the EPA has determined that a significant number of systems
subject to the rule will require an additional 2 years to complete the
capital improvements necessary to comply with the MCLs for PFAS
regulated under this action. Thus, the EPA also disagrees with
recommendations to create a phased schedule for rule implementation
based on the concentrations of PFAS detected because the EPA has
granted a two-year extension for MCL compliance to all systems. For
additional discussion on this extension and the EPA responses to public
comment on this issue, please see section XI.D.
Some commenters argue for a lower PFOA and PFOS MCL due to the
underlying health effects of these contaminants. These commenters
suggest the EPA establish MCLs lower than the agency's proposed
standard of 4.0 ng/L due to the capability of some laboratories to
quantitate lower concentrations. Some of these commenters also argue
that since PFOA and PFOS are likely human carcinogens, the EPA should
consider an MCL at zero. While the EPA agrees with the health concerns
posed by PFAS that are the basis for the proposed health based MCLGs
for these contaminants, the agency disagrees with commenters on these
alternative MCL thresholds given the EPA's consideration of feasibility
as required by SDWA. These commenters did not provide evidence
demonstrating the feasibility of achieving lower MCL thresholds
(including an MCL at zero) consistent with SDWA requirements in
establishing an MCL. For example, commenters did not provide evidence
to support a lower PQL that can be consistently achieved by
laboratories across the country. They also did not provide arguments
supporting why the EPA should accept less than 75% of participating
laboratories will be able to set a minimum reporting level with a 95%
confidence interval. Thus, the agency is finalizing the MCLs for PFOA
and PFOS at 4.0 ng/L (at the PQL) as this is the closest level to the
MCLG that is feasible due to the ability of labs using approved
analytical methods to determine with sufficient precision and accuracy
whether such a level is actually being achieved. The record supports
the EPA's determination that the lowest feasible MCL for PFOA and PFOS
at this time is 4.0 ng/L.
A few commenters suggest the EPA did not appropriately consider
disposal concerns for spent treatment media as part of the agency's
feasibility determination. These commenters state that they believe
disposal options are currently limited for liquid brine, reject waters
resulting from RO, or solid waste from GAC treatment and that disposal
capacity will be further limited should the EPA designate PFAS waste as
hazardous. These commenters contend that these limitations increase
operating expenses for utilities and should be factored in the
establishment of the PFOA and PFOS MCLs. The EPA disagrees with these
commenters that the agency did not adequately consider disposal of
spent treatment media in the rule. First, disposal options for PFAS are
currently available. These destruction and disposal options include
landfills, thermal treatment, and underground injection. Systems are
currently disposing of spent media, such as activated carbon, through
thermal treatment, to include reactivation, and at landfills. While
precautions should be taken to minimize PFAS release to the environment
from spent media, guidance exists that explains the many disposal
options with relevant precautions. See section X for further
discussion. Furthermore, the EPA has provided guidance for pretreatment
and wastewater disposal to manage PFAS
[[Page 32577]]
that enters the sanitary sewer system and must be managed by publicly
owned treatment works (POTWs) (USEPA, 2022d; USEPA, 2022e). As
discussed in the proposed rule (USEPA, 2023f), the EPA assessed the
availability of studies of full-scale treatment of residuals that fully
characterize residual waste streams and disposal options. Although the
EPA anticipates that designating chemicals as hazardous substances
under CERCLA generally should not result in limits on the disposal of
PFAS drinking water treatment residuals, the EPA has estimated the
treatment costs for systems both with the use of hazardous waste
disposal and non-hazardous disposal options to assess the effects of
potentially increased disposal costs. Specifically, the EPA assessed
the potential impact on public water system (PWS) treatment costs
associated with hazardous residual management requirements in a
sensitivity analysis. The EPA's sensitivity analysis demonstrates that
potential hazardous waste disposal requirements may increase PWS
treatment costs marginally; however, the increase in PWS costs is not
significant enough to change the agency's feasibility determination nor
the determination made at proposal that benefits of the rulemaking
justify the costs. These estimates are discussed in greater detail in
the HRRCA section of this final rule and in appendix N of the Economic
Analysis (EA) (USEPA, 2024e). For the discussion on management of
treatment residuals and additional responses to stakeholder concerns on
this topic, please see section X of this preamble. While beyond the
scope of this rule, the EPA further notes that the agency is proposing
to amend its regulations under the Resource Conservation and Recovery
Act (RCRA) by adding nine specific per-and polyfluoroalkyl substances
(PFAS), their salts, and their structural isomers, to the list of
hazardous constituents at 40 CFR part 261, appendix VIII (89 FR 8606).
The scope of the proposal is limited and does not contain any
requirements that would impact disposal of spent drinking water
treatment residuals. This is because listing these PFAS as RCRA
hazardous constituents does not make them, or the wastes containing
them, RCRA hazardous wastes. The principal impact of the proposed rule,
if finalized, will be on the RCRA Corrective Action Program.
Specifically, when corrective action requirements are imposed at a RCRA
treatment, storage, and disposal facility (TSDF), these specific PFAS
would be among the hazardous constituents expressly identified for
consideration in RCRA facility assessments and, where necessary,
further investigation and cleanup through the RCRA corrective action
process.
Some commenters suggest that the EPA failed to consider the costs
and impacts of the proposed MCLs in non-drinking water contexts, such
as its potential uses as CERCLA clean-up standards. As required by
SDWA, this rule and analyses supporting the rulemaking only includes
costs that ``are likely to occur solely as a result of compliance with
the [MCL].'' (SDWA section 1412(b)(3)(C)(i)(III)) Thus, the EPA's cost
analyses focused on the compliance costs of meeting the MCL to public
water systems that are directly subject to this regulation. The same
provision expressly directs the EPA to exclude ``costs resulting from
compliance with other proposed or promulgated regulations.'' Thus, the
EPA cannot consider the costs of use of the MCLs under other EPA
statutes (such as CERCLA) as part of its EA because SDWA specifically
excludes such consideration (42 U.S.C. 300g-1(b)(3)(C)(i)(III)). See
also City of Waukesha v. EPA, 320 F.3d 228, 243-244 (D.C. Cir. 2003)
(finding that SDWA excludes consideration of the costs of, for example,
CERCLA compliance, as part of the required cost/benefit analysis). In
addition, whether and how MCLs might be used in any particular clean-up
is very site-specific and as a practical matter cannot be evaluated in
this rule.
Many commenters compared the proposed MCLs to existing state and
international standards, regulations, and guidelines. In particular,
these commenters acknowledge the fact that several states have
conducted their own rulemakings to promulgate MCLs and suggest that the
EPA's analysis in support of the proposed MCLs are inconsistent with
these state approaches. Further, these commenters ask the EPA to
explain why certain states' cost-benefit analyses supported their
respective levels and why the EPA's analysis is different. Regarding
state PFAS regulations, the EPA disagrees with commenters who suggested
that the agency should develop regulations consistent with current
state-led actions in setting a national standard in accordance with
SDWA. While some states have promulgated drinking water standards for
various PFAS prior to promulgation of this NPDWR, this rule provides a
nationwide, health protective level for PFOA and PFOS (as well as four
other PFAS) in drinking water and reflects regulatory development
requirements under SDWA, including the EPA's analysis of the best
available and most recent peer-reviewed science; available drinking
water occurrence, treatment, and analytical feasibility information
relevant to the PQL; and consideration of costs and benefits. After the
NPDWR takes effect, SDWA requires primacy states to have a standard
that is no less stringent than the NPDWR. Additionally, analyses
conducted by the agency in support of an NPDWR undergo a significant
public engagement and peer review process. The EPA notes that the EA
for this rule accounts for existing state standards at the time of
analysis. Specifically, to estimate the costs and benefits of the final
rule, the EPA assumed that occurrence estimates exceeding state limits
are equivalent to the state-enacted limit. For these states, the EPA
assumed that the state MCL is the maximum baseline PFAS occurrence
value for all EP in the state. Additionally, while states may establish
drinking water regulations or guidance values absent Federal regulation
as they deem appropriate, the presence of state regulations does not
preclude the EPA from setting Federal regulations under the authority
of SDWA that meets that statute's requirements. For additional
information on the EPA's EA, please see section XII.
3. Final Rule
After considering public comments, the EPA is finalizing
enforceable MCLs for PFOA and PFOS at 4.0 ng/L as the closest feasible
level to the MCLG. First, the agency is establishing non-enforceable
MCLGs at zero for contaminants where no known or anticipated adverse
effects to the health of persons will occur, allowing for an adequate
margin of safety. The EPA then examined the treatment capability of
BATs and the accuracy of analytical techniques as reflected in the PQL
in establishing the closest feasible level. In evaluating feasibility,
the agency has determined that multiple treatment technologies (e.g.,
GAC, AIX) ``examined for efficacy under field conditions and not solely
under laboratory conditions'' are found to be both effective and
available to treat PFOA and PFOS to the standards and below. The EPA
also determined that there are available analytical methods to measure
PFOA and PFOS in drinking water and that the PQLs for both compounds
reflect a level that can be achieved with sufficient precision and
accuracy across laboratories nationwide using such methods. Since
limits of analytical measurement for PFOA and PFOS require the MCL to
be set at some
[[Page 32578]]
level greater than the MCLG, the agency has determined that 4.0 ng/L
(the PQL for each contaminant) represents the closest feasible level to
the MCLG and the level at which laboratories using these methods can
ensure, with sufficient accuracy and precision, that water systems
nationwide can monitor and determine compliance so that they are
ultimately delivering water that does not exceed the maximum
permissible level of PFOA and PFOS to any user of their public water
system. The EPA evaluates the availability and performance of BATs for
treating water to minimize the presence of the contaminant consistent
with the MCLG as well as the costs of applying those BATs to large
metropolitan water systems when treating to that level. In
consideration of these factors, the EPA is therefore establishing the
MCL of 4.0 ng/L for both PFOA and PFOS. The EPA further notes that the
agency has determined that the costs of SSCTs to reach 4.0 ng/L are
affordable for households served by small drinking water systems. For
additional discussion on the EPA's EA, please see section XII of this
preamble. For additional discussion on the PQLs for the PFAS regulated
as part of this NPDWR, please see section VII of this preamble. The EPA
notes that upon consideration of information submitted by commenters
regarding the implementation timeline for the rule, the agency is also
exercising its authority under SDWA section 1412(b)(10) to allow two
additional years for systems to comply with the MCL. For additional
discussion on this extension, please see section XI.
The EPA clarifies that the MCLs for PFOA and PFOS are set using two
significant digits in this final rule. In the proposed rule, the EPA
proposed MCLGs for PFOA and PFOS at zero (0) and an enforceable MCL for
PFOA and PFOS in drinking water with two significant digits at 4.0 ng/
L. As previously discussed in section IV of this preamble, the MCLG for
PFOA and PFOS is zero because these two PFAS are likely human
carcinogens. Because the MCLGs are zero, the number of significant
digits in the MCLGs are not the appropriate driver for considering the
number of significant digits in the MCLs. This approach is consistent
with other MCLs the EPA has set with carcinogenic contaminants,
including for arsenic and bromate.
By setting the MCLs at 4.0, the EPA is setting the MCLs as close as
feasible to the MCLGs. The EPA guidance states that all MCLs should be
expressed in the number of significant digits permitted by the
precision and accuracy of the specified analytical procedure(s) and
that data reported should contain the same number of significant digits
as the MCL (USEPA, 2000h). The EPA determined that two significant
digits were appropriate for PFOA and PFOS considering existing
analytical feasibility and methods. The EPA drinking water methods
typically use two or three significant digits to determine
concentrations. The EPA methods 533 and 537.1, those authorized for use
in determining compliance with the MCLs, state that ``[c]alculations
must use all available digits of precision, but final reported
concentrations should be rounded to an appropriate number of
significant digits (one digit of uncertainty), typically two, and not
more than three significant digits.'' The EPA has determined that both
methods 533 and 537.1 provide sufficient analytical precision to allow
for at least two significant digits.
B. PFAS Hazard Index: PFHxS, PFNA, HFPO-DA, and PFBS
1. Proposal
The EPA proposed an MCL for mixtures of PFHxS, PFNA, HFPO-DA, and
PFBS expressed as a Hazard Index to protect against additive health
concerns when present in mixtures in drinking water. As discussed in
the March 2023 proposal (USEPA, 2023f), a Hazard Index is the sum of
hazard quotients (HQs) from multiple substances. An HQ is the ratio of
exposure to a substance and the level at which adverse effects are not
anticipated to occur. The EPA proposed the MCL for mixtures of PFHxS,
PFNA, HFPO-DA, and PFBS as the same as the MCLG: as proposed, the
Hazard Index must be equal to or less than 1.0. This approach would set
a permissible level for the contaminant mixture (i.e., a resulting PFAS
mixture Hazard Index greater than 1.0 is an exceedance of the health
protective level and has potential human health risk for noncancer
effects from the PFAS mixture in water). The proposal defined a mixture
as containing one or more of the four PFAS and therefore covered each
contaminant individually if only one of the four PFAS occurred. Thus,
the Hazard Index as proposed ensures that the level of exposure to an
individual PFAS remains below that which could impact human health
because the exposure for that measured PFAS is divided by its
corresponding HBWC. The EPA proposed HBWCs of 9.0 ng/L \5\ for PFHxS;
10.0 ng/L for HFPO-DA; 10.0 ng/L for PFNA; and 2000.0 ng/L for PFBS
(USEPA, 2023e).
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\5\ Some commenters noted an error in the HBWC calculation for
PFHxS which was reported as 9.0 ng/L in the proposal. The agency has
corrected the value in this NPDWR and within the requirements under
40 CFR part 141 subpart Z. The correct HRL/HBWC for PFHxS is 10 ng/
L.
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The EPA requested comment on the feasibility of the proposed Hazard
Index MCL, including analytical measurement and treatment capability,
as well as reasonable costs, as defined by SDWA.
2. Summary of Major Public Comments and EPA Responses
The EPA received many comments supporting the use of the Hazard
Index approach and regulation of additional PFAS. Consistent with these
comments, through this action, the agency is establishing drinking
water standards for PFHxS, PFNA, HFPO-DA, and PFBS (as well as PFOA and
PFOS) to provide health protection against these contaminants found in
drinking water. The EPA considered PFAS health effects information,
evidence supporting dose additive health concerns from co-occurring
PFAS, as well as national and state data for the levels of multiple
PFAS in finished drinking water.
A few commenters disagreed with the EPA's feasibility evaluation in
setting the MCL at the MCLG (i.e., Hazard Index value of 1.0). Some of
these commenters assert that technologies to remove the Hazard Index
PFAS are not the same as those that effectively remove PFOA and PFOS. A
couple of commenters were concerned that meeting the Hazard Index MCL
may require more frequent media change-outs (e.g., GAC), thereby
increasing operating costs such that the Hazard Index MCL of 1.0 is not
feasible. The agency disagrees with these commenters. As described
above in part A of this section for PFOA and PFOS, the agency similarly
considered feasibility as defined by SDWA for PFHxS, PFNA, HFPO-DA, and
PFBS. First, the EPA established a Hazard Index MCLG as a Hazard Index
of 1 for mixtures of PFHxS, PFNA, HFPO-DA, and PFBS. As part of setting
the Hazard Index MCLG, the agency defined an HBWC for PFHxS, PFNA,
HFPO-DA, and PFBS used in the calculation (see discussion in section IV
of this preamble for further information).\6\
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\6\ The EPA notes that the HBWC are akin to an MCLG in that they
reflect a level below which there are no known or anticipated
adverse effects over a lifetime of exposure, including for sensitive
populations and life stages, and allows for an adequate margin of
safety.
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In considering the feasibility of setting the MCLs as close as
feasible to the MCLG, the EPA first evaluated the (1) the availability
of analytical methods to reliably quantify levels of the contaminants
in drinking water and (2)
[[Page 32579]]
the lowest levels at which contaminants can be reliably quantified
within specific limits of precision and accuracy during routine
laboratory operating conditions using the approved methods (i.e., the
PQLs). The EPA determined that there are available analytical methods
approved (i.e., Methods 533 and 537.1, version 2.0) to quantify levels
below these HBWC levels. In addition, the PQLs for PFHxS, PFNA, HFPO-
DA, and PFBS (between 3.0 to 5.0 ng/L) are all lower than the
respective HBWCs used in setting the Hazard Index MCLG for each of
these PFAS (10 ng/L for PFHxS, PFNA, and PFHxS, and 2000 ng/L for
PFBS). Thus, the PQLs are not a limiting factor in determining the MCL.
Second, the EPA evaluated the availability and performance of Best
Available Technologies (BATs) for treating water to minimize the
presence of these contaminants consistent with the MCLGs (see section X
for additional discussion on BATs) as well as the costs of applying
those BATs to large metropolitan water systems when treating to that
level. The EPA has found the same technologies identified for PFOA and
PFOS are also both available and have reliably demonstrated PFAS
removal efficiencies that may exceed >99 percent and can achieve
concentrations less than the proposed Hazard Index MCL for PFHxS, PFNA,
HFPO-DA, and PFBS, and that the cost of applying those technologies is
reasonable for large metropolitan water systems. As discussed above,
for contaminants where the MCLG is higher than the PQL, the EPA sets
the MCL at the MCLG if treatment is otherwise feasible because the PQL
is not a limiting factor. In consideration of the availability of
feasible treatment technologies, approved analytical methods to
reliably quantify levels of the contaminants in drinking water, the
EPA's cost analysis, and the fact that the PQLs are below the HBWCs
used in setting the Hazard Index MCLG, the agency determines that
setting the MCL at the same level as the MCLG for mixtures of PFHxS,
PFNA, HFPO-DA and PFBS is feasible. Thus, the EPA is setting the Hazard
Index MCL of 1 for mixtures of PFHxS, PFNA, HFPO-DA, and/or PFBS. For
additional discussion and considerations surrounding BATs, please see
section X.A of this preamble. For more information about the EPA's cost
estimates, please see section XII of this preamble.
Many commenters support excluding PFOA and PFOS from the Hazard
Index MCL. The EPA agrees with these commenters as there are analytical
limitations that would complicate including PFOA and PFOS in the Hazard
Index. As discussed in section IV of this preamble of the Hazard Index
approach, individual PFAS hazard quotients (HQs) are calculated by
dividing the measured concentration of each component PFAS in water
(e.g., expressed as ng/L) by the corresponding health-based water
concentration (HBWC) for each component PFAS (e.g., expressed as ng/L).
The HBWC is akin to an MCLG in that they reflect a level below which
there are no known or anticipated adverse effects over a lifetime of
exposure, including for sensitive populations and life stages, and
allows for an adequate margin of safety. Since PFOA and PFOS are likely
human carcinogens, the MCLG (and if included in the Hazard Index, the
HBWC) for each contaminant is zero. The only feasible way to represent
PFOA and PFOS in the Hazard Index approach would be to only consider
values for PFOA and PFOS at or above the PQL of 4.0 ng/L, however the
level at which no known or anticipated adverse effects on the health of
persons would occur is well below the PQL. As a result, any measured
concentration above 4.0 ng/L for PFOA and PFOS would result in an
exceedance of the Hazard Index MCL. The Hazard Index is intended to
capture the aggregate risks of the Hazard Index PFAS when the monitored
concentration is above the PQL but below the HBWC. These risks are not
relevant to PFOA and PFOS given their PQLs. Because of the PQL
considerations discussed in the preceding section V.A of this preamble,
the EPA is not including PFOA and PFOS in the final rule Hazard Index.
Therefore, the EPA is finalizing individual MCLs for PFOA and PFOS but
not including these contaminants in the Hazard Index.
A few commenters provided feedback on the EPA's request for comment
regarding the usage of significant figures to express the MCLs. See
discussion on this issue in section IV of this preamble above. In
summary, after considering public comment, the EPA agrees that one (1)
significant digit is appropriate for the individual PFAS for PFHxS,
PFNA and HFPO-DA (i.e., 10 ng/L rather than 10.0 ng/L), and Hazard
Index MCL (i.e., 1 rather than 1.0).
Some commenters asked about inclusion of other PFAS in the Hazard
Index in future revisions. The agency believes the Hazard Index
approach can be an adaptive and flexible framework for considering
additional PFAS. The EPA is required to review NPDWRs every six years
and determine which, if any, need to be revised (i.e., the Six-Year
Review Process). The purpose of the review is to evaluate current
information for regulated contaminants and to determine if there is any
new information on health effects, treatment technologies, analytical
methods, occurrence and exposure, implementation and/or other factors
that provides a health or technical basis to support a regulatory
revision that will improve or strengthen public health protection. This
process allows the agency to consider these and other information as
appropriate in deciding whether existing NPDWRs should be identified as
candidates for revision as required by SDWA.
Many commenters compared the proposed MCLs to existing state and
international standards, regulations, and guidelines. In particular,
these commenters acknowledge that several states have conducted their
own rulemakings to promulgate MCLs and suggest that the EPA's analysis
in support of the proposed MCLs is inconsistent with these state
approaches. Further, these commenters ask the EPA to explain why
certain states' cost-benefit analyses supported their respective levels
and why the EPA's analysis is different. Regarding state PFAS
regulations, the EPA disagrees with commenters who suggested that the
agency should not develop regulations different from state-led actions.
SDWA mandates Federal regulation where the EPA determines that a
contaminant meets the criteria for regulation under the statute.
Moreover, the EPA's rule sets a national standard in accordance with
SDWA for certain PFAS in drinking water that provides important
protections for all Americans served by PWSs. Please see discussion
above in part A under this section for consideration for existing state
and international standards.
A few commenters suggest a need for effective data management
systems to implement the Hazard Index. These commenters indicated that
it will be challenging to implement the Hazard Index as proposed due to
the tracking of multiple contaminants and automating these data into
existing data management systems. For discussion on rule implementation
issues, including primacy agency record keeping and reporting
requirements, please see section XI of this preamble.
Some commenters raised concerns that the EPA did not consider a
sufficient range of regulatory alternatives. For example, a few
commenters contend that the EPA violated 1412(b)(3)(C)(i) of SDWA and
the Unfunded Mandates Reform Act (UMRA) because the agency did not
identify and consider what they deem a
[[Page 32580]]
reasonable number of regulatory alternatives for PFHxS, PFNA, HFPO-DA
and its ammonium salts, and PFBS. Specifically, these commenters cite
that the EPA only considered a single HBWC and did not consider any
alternatives to the Hazard Index MCL of 1 itself. The EPA disagrees
with these commenters.
SDWA does not require the agency to consider any certain number of
alternative MCLs or a range of alternatives. SDWA 1412(b)(3)(C)(i)(IV)
only requires that in developing the HRRCA, the agency must consider
the ``incremental costs and benefits associated with each alternative
maximum contaminant level considered.'' Thus, the agency must conduct a
cost-benefit analysis with each alternative MCL that is considered, if
any. The EPA maintains that the proposed rule and regulatory
alternatives considered at proposal met all requirements to consider
alternatives. In the proposed rule, the EPA did not separately present
changes in quantified costs and benefits for these approaches because
the agency described that including individual MCLs in addition to the
Hazard Index approach will be not change costs and benefits relative to
the proposal (i.e., the same number of systems will incur identical
costs to the proposed option and the same benefits will be realized).
For the final rule, the EPA has also estimated the marginal costs for
the individual PFHxS, PFNA, and HFPO-DA MCLs in the absence of the
Hazard Index (See chapter 5.1.3 and appendix N.4 of the EA for
details). The EPA notes that the costs for the individual PFHxS, PFNA,
and HFPO-DA MCLs have been considered in this final rule. For further
discussion of how the EPA considered the costs of the five individual
MCLs and the HI MCL, see section XII.A.4 of this preamble.
The EPA identified and analyzed a reasonable number of regulatory
alternatives to determine the MCL requirement in the proposed rule as
required by UMRA. UMRA's requirement to identify and consider a
reasonable number of regulatory alternatives builds on the assessment
of feasible alternatives required in E.O. 12866.\7\ Specifically, as
described in the proposed rule, the EPA considered an alternative
approach to the one proposed that only used the Hazard Index MCL. The
proposal took comment on establishing individual MCLs instead of and in
addition to using a mixture-based approach for PFHxS, PFNA, HFPO-DA,
and/or PFBS in mixtures. In that proposal, the EPA described how a
traditional approach may be warranted should the EPA not finalize a
regulatory determination for mixtures of these PFAS. Under this
alternative, ``the proposed MCLG and MCL for PFHxS would be 9.0 ng/L;
for HFPO-DA the MCLG and MCL would be 10.0 ng/L; for PFNA the MCLG and
MCL would be 10.0 ng/L; and for PFBS the MCLG and MCL would be 2000.0
ng/L.'' The agency requested comment on these alternatives for PFHxS,
PFNA, HFPO-DA, and PFBS and whether these individual MCLs instead of or
in addition to the Hazard Index approach would change public health
protection, improve clarity of the rule, or change costs. Additionally,
the EPA considered alternative mixture-based approaches such as a
target organ-specific Hazard Index (TOSHI) or relative potency factor
(RPF) approach. The agency requested comment on these approaches. Based
on the EPA's technical expertise, the agency determined that the Hazard
Index is the most cost-effective and least burdensome alternative for
purposes of UMRA because this approach for mixtures that achieves the
objectives of the rule because of the level of protection afforded for
the evaluation of chemicals with diverse (but in many cases shared)
health endpoints. The EPA followed agency chemical mixture guidance
(USEPA, 1986; USEPA, 1991b; USEPA, 2000a, which explain that when the
Hazard Index value is greater than one (1) then risk is indicated
(because exposure exceeds toxicity). The agency did not propose
alternative Hazard Index values (i.e., higher Hazard Index values)
because the EPA determined that a Hazard Index MCL of 1 is feasible:
multiple treatment technologies are available and are found effective
to treat to or below the MCL; the costs of applying these technologies
to large metropolitan water systems are reasonable; and there are
analytical methods available to reliably quantify the four PFAS
captured in the Hazard Index MCL. In addition, these alternative Hazard
Index or mixture-based approaches would not provide sufficient
protection against dose-additive health concerns from co-occurring
PFAS. For example, a higher Hazard Index value (e.g., Hazard Index
equal to 2) allows for exposure to be greater than the toxicity and
will not result in a sufficient health-protective standard that is
close as feasible to the MCLG, which is a level at which there are no
known or anticipated adverse effects on human health and allows for an
adequate margin of safety. The EPA notes that commenters have not
provided support justifying an alternative MCL standard for the Hazard
Index. For additional discussion on UMRA, please see chapter 9 of USEPA
(2024g).
---------------------------------------------------------------------------
\7\ See OMB Memorandum M-95-09, Guidance for Implementing Title
II of S.1.
---------------------------------------------------------------------------
3. Final Rule
Through this action, the EPA is promulgating the Hazard Index MCL
for mixtures of two or more of PFHxS, PFNA, HFPO-DA and PFBS. The
following equation provides the calculation of the PFHxS, PFNA, HFPO-
DA, and PFBS Hazard Index MCL as finalized:
[GRAPHIC] [TIFF OMITTED] TR26AP24.005
Where:
HFPO-DAwater = monitored concentration of HFPO-DA in ng/
L;
PFBSwater = monitored concentration of PFBS;
PFNAwater = monitored concentration of PFNA and
PFHxSwater = monitored concentration of PFHxS
The presence of PFBS can only trigger an MCL violation if it is
present as part of a mixture with at least one of the other three PFAS
(PFHxS, PFNA and
[[Page 32581]]
HFPO-DA). As such, elevated PFBS concentrations that would normally
cause a Hazard Index exceedance in isolation will not cause a violation
if none of the other three PFAS are present in the mixture. The EPA is
promulgating individual MCLs for PFHxS, PFNA, and HFPO-DA as well the
Hazard Index MCL for mixtures of PFHxS, PFNA, HFPO-DA and PFBS
concurrent with final regulatory determinations for these contaminants
(please see section III of this preamble for additional discussion on
the EPA's regulatory determinations).
The EPA has determined that it is feasible to set the MCL at the
same level as the MCLG for mixtures of PFHxS, PFNA, HFPO-DA and PFBS as
current BATs can remove each contaminant to a level equal to or below
their respective HBWC. In addition, there are analytical methods
available for these contaminants and the PQL for each contaminant is
below the level established by the MCLG. The EPA also considered costs
and determined that establishing a Hazard Index MCL of 1 is reasonable
based on consideration of the costs to large metropolitan water
systems. These considerations support a determination that a Hazard
Index MCL of 1 for mixtures of two or more of PFHxS, PFNA, HFPO-DA and
PFBS is feasible and therefore the EPA is setting the MCL at the same
level as the MCLG. The EPA's MCL of 1 establish a ``maximum permissible
level of contaminant in water'' because it is a limit for a mixture
with PFAS components that must be met before the water enters the
distribution system. Public water systems use their monitoring results
as inputs into the Hazard Index equation to determine whether they are
delivering water to any user that meets the MCL. For additional
discussion regarding the derivation of the individual HBWCs and MCLGs,
please see discussion in section III and IV of this preamble above.
C. Individual MCLs: PFHxS, PFNA and HFPO-DA
1. Proposal
As described in section V.B of this preamble above, the EPA
proposed an MCL for mixtures of PFHxS, PFNA, HFPO-DA and PFBS based on
a Hazard Index. The EPA proposed to address its preliminary regulatory
determinations for PFHxS, PFNA, HFPO-DA, and/or PFBS and mixtures of
these PFAS together through the Hazard Index approach. The proposal
defined a mixture as containing one or more of the four PFAS and
therefore covered each contaminant individually if only one of the four
PFAS occurred. The EPA considered and took comment on establishing
individual MCLGs and MCLs in lieu of or in addition to the Hazard Index
approach for mixtures of PFHxS, PFNA, HFPO-DA, and/or PFBS.
2. Summary of Major Public Comments and EPA Responses
Commenters were mixed on the EPA's request for public comment on
the establishment of stand-alone MCLs in lieu of or in addition to the
Hazard Index MCL. Many of the comments were related to risk
communications and messaging to consumers. While several commenters
favored stand-alone MCLs in lieu of the Hazard Index to improve
communications to their customers, several other commenters recommended
stand-alone MCLs in addition to the Hazard Index MCL to achieve this
purpose. Several commenters opposed individual MCLs for some or all of
the PFAS because they believe it may complicate risk communication.
After consideration of public comments, the EPA is addressing the final
individual regulatory determination for PFHxS, HFPO-DA, and PFNA by
promulgating individual MCLGs and NPDWRs for PFHxS, HFPO-DA, and PFNA.
The EPA is addressing the final mixture regulatory determination by
promulgating a Hazard Index MCLG and NPDWR for mixtures containing two
or more of PFHxS, PFNA, HFPO-DA, and PFBS. This approach avoids
confusion caused by the EPA's proposal that covered all the preliminary
regulatory determinations in one Hazard Index standard. The EPA agrees
that proper risk communication is an important focus for water systems
and believes that finalizing individual MCLs for PFHxS, PFNA and HFPO-
DA may help support risk communication as utilities and the public may
be more familiar with this regulatory framework. At the same time,
since those individual MCLs do not address additional risks from co-
occurring PFAS, the EPA is finalizing a Hazard Index MCL to address
dose additive health concerns associated with mixtures of two or more
of PFHxS, PFNA, HFPO-DA, and PFBS that co-occur in drinking water. For
additional discussion on the Hazard Index approach and other mixture-
based approaches (e.g., TOSHI), please see section IV of this preamble
above.
3. Final Rule
The EPA is promulgating individual MCLs for PFHxS, PFNA and HFPO-DA
at the same level as their respective MCLGs (which are equivalent to
the HBWCs). The EPA is finalizing individual MCLs as follows: HFPO-DA
MCL = 10 ng/L; PFHxS MCL = 10 ng/L; and PFNA MCL = 10 ng/L. The EPA is
promulgating individual MCLs for PFHxS, PFNA, and HFPO-DA as well the
Hazard Index MCL for mixtures of PFHxS, PFNA, HFPO-DA and PFBS
concurrent with final determinations for these contaminants (please see
section III of this preamble for additional discussion on the EPA's
regulatory determinations).
The agency considered feasibility as defined by SDWA and the EPA's
feasibility justification for these individual PFHxS, PFNA and HFPO-DA
MCLs are the same and based on the same information as the Hazard Index
MCL discussed in V.B above. The EPA further notes that the Hazard Index
MCLG applies to the entire mixture but the EPA's technical
justification for the underlying values (i.e., HBWCs) are the same as
the individual MCLGs in this rule. In summary, the EPA has determined
that it is feasible to set the individual MCLs at the MCLGs for PFHxS,
PFNA and HFPO-DA because current BATs can remove each contaminant to a
level equal to or below their respective MCLGs. In addition, there are
analytical methods available for these contaminants and the practical
quantitation level (PQL) for each contaminant is below the level
established by the MCLG. The EPA also considered costs and determined
that establishing individual MCLs of 10 ng/L for PFHxS, PFNA, and HFPO-
DA is reasonable based on consideration of the costs to large
metropolitan water systems. These considerations support a
determination that individual MCLs of 10 ng/L for PFHxS, PFNA, and
HFPO-DA are feasible and therefore the EPA is setting the MCL at the
same level as the MCLG. For additional discussion regarding the
derivation of the individual HBWCs and MCLGs, please see section III
and IV of this preamble above.
VI. Occurrence
The EPA relied on multiple data sources, including Unregulated
Contaminant Monitoring Rule (UCMR) 3 and state finished water data, to
evaluate the occurrence of PFOA, PFOS, PFHxS, PFNA, and HFPO-DA and
probability of co-occurrence of these PFAS and PFBS. The EPA also
incorporated both the UCMR 3 and some state data into a Bayesian
hierarchical model which supported exposure estimates for select PFAS
at lower levels than were measured under UCMR 3. The EPA has utilized
similar statistical approaches in past regulatory actions to inform its
decision making, particularly where a contaminant's occurrence is at
low concentrations
[[Page 32582]]
(USEPA, 2006c). The specific modeling framework used to inform this
regulatory action is based on the peer-reviewed model published in
Cadwallader et al. (2022). Collectively, these data and the occurrence
model informed estimates of the number of water systems (and associated
population) expected to be exposed to levels of the final and proposed
alternative MCLs for PFOA and PFOS, the final MCLs for PFHxS, PFNA, and
HFPO-DA, and the final Hazard Index MCL for PFHxS, PFNA, HFPO-DA, and
PFBS.
The EPA notes that, as described in sections III and V of this
preamble, the EPA is finalizing individual Maximum Contaminant Levels
(MCLs) for three of the four Hazard Index PFAS (PFHxS, PFNA, and HFPO-
DA) at 10 ng/L each. An analysis of occurrence relative to HRLs for
PFHxS, PFNA, and HFPO-DA (which are the same as the final individual
MCLs for these compounds at 10 ng/L) using UCMR 3 data and updated
state datasets is presented in section III.C of this preamble and
further described in the Occurrence Technical Support Document (USEPA,
2024b). The information in the following sections supports the agency's
finding that PFHxS, PFNA, and HFPO-DA occur at a frequency and level of
public health concern as discussed in section III.C of this preamble.
A. UCMR 3
1. Proposal
UCMR 3 monitoring occurred between 2013 and 2015 and is currently
the best nationally representative finished water dataset for any PFAS,
including PFOA, PFOS, PFHxS, PFNA, and PFBS. Under UCMR 3, 36,972
samples from 4,920 public water systems (PWSs) were analyzed for these
five PFAS. PFOA was found above the UCMR 3 minimum reporting level (20
ng/L) in 379 samples at 117 systems serving a population of
approximately 7.6 million people located in 28 states, Tribes, or U.S.
territories. PFOS was found in 292 samples at 95 systems above the UCMR
3 minimum reporting level (40 ng/L). These systems serve a population
of approximately 10.4 million people located in 28 states, Tribes, or
U.S. territories. PFHxS was found above the UCMR 3 minimum reporting
level (30 ng/L) in 207 samples at 55 systems that serve a population of
approximately 5.7 million located in 25 states, Tribes, and U.S.
territories. PFBS was found in 19 samples at 8 systems above the UCMR 3
minimum reporting level (90 ng/L). These systems serve a population of
approximately 350,000 people located in 5 states, Tribes, and U.S.
territories. Lastly, PFNA was found above the UCMR 3 minimum reporting
level (20 ng/L) in 19 samples at 14 systems serving a population of
approximately 526,000 people located in 7 states, Tribes, and U.S.
territories.
2. Summary of Major Public Comments and EPA Responses
Some commenters supported the EPA's use of the best available
public health information including data from UCMR 3 and state
occurrence data. A few commenters criticized the use of UCMR 3 data,
stating that the data suffer from limitations. These commenters
expressed concern over the high minimum reporting levels, the exclusion
of many small systems, and the lack of national monitoring of HFPO-DA.
Some of these commenters assert that UCMR 3 does not represent best
available occurrence data for this rule. The EPA disagrees with these
commenters. While UCMR 3 does have higher reporting limits than those
available through current analytical methods, the data still provides
the best available nationwide occurrence data to inform the occurrence
and co-occurrence profile for the regulated PFAS for which monitoring
was conducted. These data are also a critical component of the EPA's
model to estimate national level occurrence for certain PFAS and ensure
it is nationally representative (see subsection E of this section). The
EPA also disagrees that the UCMR 3 excludes small water systems as it
included a statistically selected, nationally representative sample of
800 small drinking water systems. Regarding commenter concerns for lack
of UCMR monitoring data on HFPO-DA, the agency notes that the EPA
examined recent data collected by states who have made their data
publicly available. A discussion of these data and public comments on
this information is presented in sections III.C and VI.B of this
preamble.
3. Final Rule
After considering public comment, the EPA maintains that UCMR 3
data are the best available, complete nationally representative dataset
and they play an important role in supporting the EPA's national
occurrence analyses, demonstrating occurrence and co-occurrence of the
monitored PFAS in drinking water systems across the country that serve
millions of people.
B. State Drinking Water Data
1. Proposal
The agency has supplemented the UCMR 3 data with more recent data
collected by states who have made their data publicly available. In
general, the large majority of these more recent state data were
collected using newer EPA-approved analytical methods and state results
reflect lower reporting limits than those in the UCMR 3. State results
show continued occurrence of PFOA, PFOS, PFHxS, PFNA, and PFBS in
multiple geographic locations. These data also show these PFAS occur at
lower concentrations and significantly greater frequencies than were
measured under the UCMR 3 (likely because the more recent monitoring
was able to rely on more sensitive analytical methods). Furthermore,
these state data include results for more PFAS than were included in
the UCMR 3, including HFPO-DA.
At the time of proposal, the EPA evaluated publicly available state
monitoring data from 23 states, representing sampling conducted on or
before May 2021. The EPA acknowledged that the available data were
collected under varying circumstances; for example, targeted vs. non-
targeted monitoring (i.e., monitoring not conducted specifically in
areas of known or potential contamination). Due to the variability in
data quality, the EPA further refined this dataset based on
representativeness and reporting limitations, resulting in detailed
technical analyses using a subset of the available state data. A
comprehensive discussion of all the available state PFAS drinking water
occurrence data was included in the Occurrence Technical Support
Document (USEPA, 2023l).
2. Summary of Major Public Comments and EPA Responses
Commenters generally supported the use of state datasets. A few
commenters discussed their own PFAS occurrence data, some of which were
provided to the EPA, relative to the EPA's proposed regulatory levels
and/or provided summaries of other monitoring efforts. Where possible,
the EPA presents this information within its occurrence analysis--see
the Other Data sections of USEPA (2024b). A few commenters recommended
that the EPA expand the datasets used for the final rule to include
additional and updated state sampling information. The EPA agrees with
these suggestions to rely on additional and updated sampling
information in order to evaluate PFAS occurrence in drinking water.
Therefore,
[[Page 32583]]
the agency has included updated information in its occurrence analyses
as described in section VI.B.3 of this preamble. The EPA notes that
this information is consistent with the analyses contained in the
proposal for this action.
A few commenters criticized the use of state datasets in occurrence
analyses. These commenters claimed that the state datasets were
insufficient for national extrapolation and not dependable due to being
collected under variable circumstances. These commenters expressed the
need for enhanced quality control (QC) by the EPA to exclude data below
reasonable reporting thresholds. The agency disagrees with commenters
who contend that state datasets are insufficient for national
extrapolation. For both the rule proposal and this final action, the
EPA took QC measures to ensure the EPA used the best available data for
national extrapolation. For example, the EPA acknowledged in the
proposal that states used various reporting thresholds when presenting
their data, and for some states there were no clearly defined reporting
limits. The EPA identified state reporting thresholds where possible
and, when appropriate, incorporated individual state-specific
thresholds when conducting data analyses. For other states, the EPA
presented the data as provided by the state. Due to the reporting
limitations of some of the available state data (e.g., reporting
combined analyte results rather than individual analyte results), the
EPA did not utilize all of these data in the subsequent occurrence
analyses/co-occurrence analyses. Specific data analysis criteria (e.g.,
separation of non-targeted and targeted monitoring results) were also
applied. Additionally, the agency also verified that the vast majority
of the data were collected using EPA-approved methods. Further, the EPA
reviewed all available data thoroughly to ensure that only finished
drinking water data were presented. A description of the scope and
representativeness of the state data was provided in the proposal of
this action in the PFAS Occurrence and Contaminant Background Support
Document (USEPA, 2023l). These include describing the states the EPA
found to have publicly available data, identifying the reporting
thresholds where possible, and distinguishing whether monitoring was
non-targeted or targeted (i.e., monitoring in areas of known or
potential PFAS contamination). These QC measures ensured that the EPA
utilized the best available data for national extrapolation.
3. Final Rule
In the proposed rule preamble, the EPA discussed how states may
have updated data available and that additional states have or intend
to conduct monitoring of finished drinking water and that the agency
would consider these additional data to inform this final regulatory
action. After consideration of all the public comments on this issue,
the EPA has updated its analysis of state monitoring data by including
results that were available as of May 2023. This updated state dataset
includes publicly available data from 32 states: Alabama, Arizona,
California, Colorado, Delaware, Georgia, Idaho, Illinois, Indiana,
Iowa, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota,
Missouri, New Hampshire, New Jersey, New Mexico, New York, North
Carolina, North Dakota, Ohio, Oregon, Pennsylvania, South Carolina,
Tennessee, Vermont, Virginia, West Virginia, and Wisconsin. The dataset
includes data from 9 states that were not available at the time of
proposal.
Tables 4 and 5 in this section demonstrate the number and percent
of samples with PFOA and PFOS based on state-reported detections, and
the number and percent of systems with PFOA and PFOS based on state-
reported detections, respectively, for the non-targeted state finished
water monitoring data. Section III.B. of this preamble describes the
state reported finished water occurrence data for PFHxS, PFNA, HFPO-DA,
and PFBS data.
BILLING CODE 6560-50-P
[[Page 32584]]
[GRAPHIC] [TIFF OMITTED] TR26AP24.006
[[Page 32585]]
[GRAPHIC] [TIFF OMITTED] TR26AP24.007
As illustrated in Tables 4 and 5, there is a wide range in PFOA and
PFOS results between states. Nonetheless, more than one-third of states
that conducted non-targeted monitoring observed PFOA and/or PFOS at
more than 25 percent of systems. Among the detections, PFOA
concentrations ranged from 0.21 to 650 ng/L with a range of median
concentrations from 1.27 to 5.61 ng/L, and PFOS concentrations ranged
from 0.24 to 650 ng/L with a range of median concentrations from 1.21
to 12.1 ng/L.
Monitoring data for PFOA and PFOS from states that conducted
targeted monitoring efforts, including 15 states, demonstrate results
consistent with the non-targeted state monitoring. For example, in
Pennsylvania, 26.3 and 24.9 percent of monitored systems found PFOA and
PFOS, respectively, with reported concentrations of PFOA ranging from
1.7 to 59.6 ng/L and PFOS ranging from 1.8 to 94 ng/L. California
reported 35.8 and 39.0 percent of monitored systems found PFOA and
PFOS, respectively, including reported concentrations of PFOA ranging
from 0.9 to 190 ng/L and reported concentrations of PFOS from 0.4 to
250 ng/L. In Maryland, PFOA and PFOS were found in 57.6 and 39.4
percent of systems monitored, respectively, with reported
concentrations of PFOA ranging from 1.02 to 23.98 ng/L and reported
concentrations of PFOS ranging from 2.05 to 235 ng/L. In Iowa,
[[Page 32586]]
PFOA and PFOS were found in 11.2 and 12.1 percent of systems monitored,
respectively, with reported concentrations of PFOA ranging from 2 to 32
ng/L and reported concentrations of PFOS ranging from 2 to 59 ng/L.
As discussed above in section V of this preamble, the EPA is
finalizing individual MCLs of 4.0 ng/L for PFOA and PFOS, individual
MCLs for PFHxS, PFNA, and HFPO-DA, and a Hazard Index level of 1 for
PFHxS, PFNA, HFPO-DA, and PFBS. The EPA also evaluated occurrence for
the regulatory alternatives discussed in section V of this preamble,
including alternative MCLs for PFOA and PFOS of 5.0 ng/L and 10.0 ng/L.
Table 6, Table 7, and Table 8 demonstrate, based on available state
data, the total reported number and percentages of monitored systems
that exceed these proposed and alternative MCL values across the non-
targeted state finished water monitoring data.
[GRAPHIC] [TIFF OMITTED] TR26AP24.008
[[Page 32587]]
[GRAPHIC] [TIFF OMITTED] TR26AP24.009
[[Page 32588]]
[GRAPHIC] [TIFF OMITTED] TR26AP24.010
BILLING CODE 6560-50-C
Based on the available state data presented in Table 6, Table 7,
and Table 8, within 20 states that conducted non-targeted monitoring
there are 1,260 systems with results above the PFOS MCL of 4.0 ng/L and
1,577 systems with results above the PFOA MCL of 4.0 ng/L. These
systems serve populations of 12.5 and 14.4 million people,
respectively. As expected, the number of systems exceeding either of
the proposed alternative MCLs decreases as the values are higher;
however, even at the highest alternative PFOS and PFOA MCL values of
10.0 ng/L, there are still 491 and 612 systems with exceedances,
serving populations of approximately 5.3 and 6.0 million people,
respectively.
Monitoring data for PFOA and PFOS from states that conducted
targeted sampling efforts shows additional systems that would exceed
the final and alternative MCLs. For example, in California, Maine,
Maryland, and Pennsylvania, 30.9 percent (38 PWSs), 27.8 percent (5
PWSs), 25 percent (18 PWSs), and 19.3 percent (66 PWSs) of monitored
systems reported results above the proposed PFOS MCL of 4.0 ng/L,
respectively, and 29.3 percent (36 PWSs), 27.8 percent (5 PWSs), 25
percent (18 PWSs), and 21.1 percent (72 PWSs) of monitored systems
reported results above the proposed PFOA MCL of 4.0 ng/L, respectively.
While these frequencies may be anticipated given the sampling
locations, within only these four states that conducted limited,
targeted monitoring, the monitored
[[Page 32589]]
systems with results above the proposed PFOS MCL and proposed PFOA MCL
serve significant populations of approximately 5.7 million people and
approximately 5.6 million people, respectively.
C. PFAS Co-Occurrence
While the discussions in sections III.B, VI.A. and VI.B of this
preamble describe how PFOA, PFOS, PFHxS, PFNA, and HFPO-DA occur
individually, numerous studies and analyses have documented that PFAS
co-occur in finished drinking water (Adamson et al., 2017; Cadwallader
et al., 2022; Guelfo and Adamson, 2018). As discussed in section V of
this preamble, the EPA is finalizing regulation of mixtures that
include at least two of PFHxS, PFNA, HFPO-DA, and PFBS (collectively
referred to as ``Hazard Index PFAS'') as part of a Hazard Index
approach.
1. Proposal
In the March 2023 proposal preamble, the EPA presented occurrence
data that illustrated the extent to which PFOA, PFOS, PFHxS, PFNA,
HFPO-DA, and PFBS co-occur in drinking water. Co-occurrence analyses
primarily utilized available non-targeted state PFAS finished drinking
water data, though UCMR 3 data analysis is presented in the PFAS
Occurrence and Contaminant Background Support Document (USEPA, 2024b).
The EPA also conducted two separate analyses using state datasets to
determine the extent to which these six PFAS co-occur: a groupwise
analysis and a pairwise analysis.
When analyzing PFAS co-occurrence, groupwise analysis is important
for determining whether the presence of PFOA and PFOS provides insight
regarding the likelihood of Hazard Index PFAS being present as well,
which has broad implications for public health. This is because
occurrence information for the Hazard Index PFAS is less extensive than
the occurrence information for PFOA and PFOS due to fewer states
monitoring the Hazard Index PFAS; therefore, establishing co-occurrence
with PFOA and PFOS helps with understanding the extent of general
Hazard Index PFAS occurrence. For the groupwise analysis, the six PFAS
were separated into two groups--one consisted of PFOS and PFOA and the
other group included the four Hazard Index PFAS. The analysis broke
down the systems and samples according to whether chemicals from the
respective groups were detected. Results were also shown separated by
state. Results generally indicated that when PFOA or PFOS were found,
Hazard Index PFAS were considerably more likely to also be found. This
implies that, for systems that only measured PFOA and/or PFOS, detected
those PFAS, and did not measure the Hazard Index PFAS, the Hazard Index
PFAS are more likely to also be present than if PFOA and/or PFOS were
not detected. At a national level, since many systems monitored for
PFOA and PFOS only and detected these PFAS, this means that estimates
of Hazard Index PFAS occurrence based on state Hazard Index PFAS data
alone are likely to be underestimated. Given that the state datasets
varied in the specific PFAS that were monitored, the analysis also
compared the number of Hazard Index PFAS analyzed with the number of
Hazard Index PFAS reported present. As more Hazard Index PFAS were
analyzed, more Hazard Index PFAS were found. Further, systems and
samples where Hazard Index PFAS were found were more likely to find
multiple Hazard Index PFAS than a single Hazard Index PFAS (when
monitoring for 3 or 4 Hazard Index PFAS).
Given that the groupwise co-occurrence analysis established that
the Hazard Index PFAS, as a group, occur with a substantial level of
frequency, particularly alongside PFOA or PFOS, the pairwise co-
occurrence is relevant for understanding how the individual PFAS
included in the rule co-occur with each other. The pairwise co-
occurrence analysis explored the odds ratios for each unique pair of
PFAS included in the regulation. Pairwise co-occurrence through odds
ratios showed statistically significant relationships between nearly
all unique pairs of PFAS included in the proposed rule. Odds ratios
reflect the change in the odds of finding one chemical (e.g., Chemical
A) given that the second chemical (e.g., Chemical B) is known to be
present compared to the odds of finding it if the second chemical is
not present. For example, an odds ratio of 2 would indicate that the
presence of the second chemical would be expected to double the odds of
the first chemical being reported present. An odds ratio of 1 indicates
that there is no association between the two chemicals. At the system
level, point odds ratios estimates ranged from 1.7-142.7, indicating
that in some instances the odds of finding one PFAS increased by more
than two orders of magnitude if the other PFAS was reported present (in
other words, for some PFAS combinations, if one PFAS is present, there
is more than 100 times the odds of certain other PFAS being present).
HFPO-DA and PFHxS was the only pair of PFAS chemicals included in the
proposed regulation that did not have a statistically significant
relationship; 1 fell within the 95 percent confidence interval,
indicating that the odds ratio was not determined to be statistically
significantly different from 1.
In the proposed rule, the agency determined that, both as a group
and as individual chemicals, the Hazard Index PFAS had a higher
likelihood of being reported if PFOS or PFOA were present, First, the
groupwise analysis established that the Hazard Index PFAS, in addition
to PFOA and PFOS, occur at a significant frequency in drinking water.
Then, the pairwise analysis demonstrated that PFOA, PFOS, PFHxS, PFNA,
HFPO-DA, and PFBS (the individual PFAS) generally co-occur with each
other, as opposed to occurring independently. These data further
support the EPA's finding that these PFAS are likely to occur, and that
there is a substantial likelihood that combinations of PFHxS, PFNA,
HFPO-DA, and PFBS co-occur in mixtures with a frequency of public
health concern in drinking water systems.
2. Summary of Major Public Comments and EPA Responses
Some commenters agreed with the agency's conclusion in the March
2023 proposal that the PFAS included in the regulation appeared to
meaningfully co-occur. However, some other commenters stated that they
believed the data used to assess PFAS co-occurrence were too limited to
make substantive conclusions. The EPA disagrees that the data were too
limited or that the co-occurrence analysis was inconclusive. Based on
the non-targeted state monitoring data used in the co-occurrence
analysis (from 11 states), findings of the pairwise and groupwise
analyses established a strong likelihood that these chemicals
meaningfully co-occur in drinking water. This was observed through odds
ratios statistically significantly greater than 1 in the pairwise
analysis as well as frequency at which multiple chemicals were detected
in the groupwise analysis. Based on public comment, the agency has
updated its analysis to include more recent non-targeted state data
that became publicly available after the proposal analyses were
finalized. This ensures that findings are up to date; as discussed
further in the following subsection, the more recent data confirms the
proposal analysis.
3. Final Rule
After considering public comment and updating analyses, the EPA
concluded that the co-occurrence analyses continue to support the
[[Page 32590]]
premise in the proposed rule that PFAS are likely to co-occur and
support the EPA's final rule approach. Following is a discussion and
presentation of information related to the EPA's co-occurrence analysis
for this final rule effort. These data include all data from the rule
proposal, in addition to the updated data the EPA incorporated based on
public comment. As discussed elsewhere in this preamble, the newer data
confirm the EPA's conclusions from proposal.
a. Groupwise Chemical Co-Occurrence
Table 9 shows the distribution of systems and samples according to
whether states reported detections for any Hazard Index PFAS (PFHxS,
PFNA, HFPO-DA, and PFBS) and whether they also reported detections of
PFOS or PFOA. USEPA (2024b) provides additional information for this
analysis.
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Considering eligible samples and systems within the aggregated
state dataset, states reported either PFOA, PFOS, or one or more Hazard
Index PFAS in 42.2 percent (20,640 of 48,889) of samples and 29.4
percent (3,569 of 12,145) of systems. When any PFAS (among PFOA, PFOS,
and the Hazard Index PFAS) were reported, at least one Hazard Index
PFAS was also reported in 64.3 percent (13,275 of 20,640) of samples
and at 69.8 percent (2,490 of 3,569) of systems. Further, among samples
and systems that reported PFOS or PFOA, at least one Hazard Index PFAS
was reported in 61.9 percent (11,954 of 19,319) of samples and at 65.9
percent (2,089 of 3,168) of systems. This demonstrated strong co-
occurrence of Hazard Index PFAS with PFOA and PFOS and a substantial
likelihood (over 60 percent) of at least one Hazard Index PFAS being
present at systems reporting the presence of PFOS or PFOA. Overall, one
or more Hazard Index PFAS were reported at about 20.5 percent (2,490 of
12,145) of systems included in the aggregated state dataset of non-
targeted monitoring. If this percentage were extrapolated to the
nation, one or more Hazard Index PFAS would be found in over 13,000
systems. Table 10 shows the distribution of systems in a similar manner
but provides a breakdown by state and includes only systems that
monitored for either three or four of the Hazard Index PFAS.
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Tennessee only had data from one system which did not report the
presence of any of the six PFAS. Otherwise, the percentage of systems
included in Table 10 that reported any Hazard Index PFAS ranged from
3.9 to 52.4 percent of systems when broken down by state, with eight
states exceeding 20 percent of systems. The percentage of systems that
reported any PFAS ranged from 5.5 to 73.0 percent. Many systems and/or
samples that were included in the aggregated state dataset did not
monitor for all four Hazard Index PFAS. It is possible that more
systems would have reported the presence of Hazard Index PFAS if they
had monitored for all four Hazard Index PFAS. Additionally, as
demonstrated in Table 10, when PFOA and/or PFOS were reported, at least
one of the Hazard Index PFAS chemicals were also frequently reported.
For systems that did not measure Hazard Index PFAS but measured and
detected PFOA and/or PFOS, the groupwise analysis demonstrates that the
Hazard Index PFAS were more likely to have been present in those
systems as well. Table 11 presents system counts for systems where PFOS
or PFOA were reported according to a) how many Hazard Index PFAS were
monitored and b) how many Hazard Index PFAS were reported present.
[[Page 32592]]
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Among systems that reported the presence of PFOS and/or PFOA, the
fraction of systems that also reported any Hazard Index PFAS tended to
increase as systems monitored for more of the Hazard Index PFAS. At
systems monitoring for a single Hazard Index PFAS, 34.5 percent
reported a positive result at some point during sampling. This
increased to 73.5 percent of systems reporting the presence of at least
one Hazard Index PFAS when monitoring for all four Hazard Index PFAS.
Not only did the fraction of systems reporting the presence of any
Hazard Index PFAS increase as the number of Hazard Index PFAS monitored
increased, so did the number of Hazard Index PFAS that were reported as
present. When four Hazard Index PFAS were monitored, nearly 50 percent
of systems reported the presence of two to three of the Hazard Index
PFAS. Thus, if PFOS or PFOA are reported, there is a reasonable
likelihood that multiple Hazard Index PFAS would be present as well.
b. Pairwise Chemical Co-Occurrence
In addition to considering the co-occurrence of six PFAS as two
groups, the EPA conducted a pairwise analysis to further explore co-
occurrence relationships. Table 12 shows the calculated system-level
odds ratios for every unique pair of PFAS chemicals evaluated. The
equation for calculating odds ratios is symmetrical. Because of this,
in a given row it does not matter which chemical is ``Chemical A'' and
which is ``Chemical B.'' Additional information on odds ratios may be
found in USEPA (2024b) and a brief explanation is described following
Table 12 as well as in section III.C of this preamble.
[[Page 32593]]
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Odds ratios reflect the change in the odds of finding one chemical
(e.g., Chemical A) given that the second chemical (e.g., Chemical B) is
known to be present compared to the odds of finding it if the second
chemical is not present. For example, as shown in Table 12, the point
estimate of 92.4 for the odds ratio between PFOA and PFOS indicates
that the odds of finding PFOA after knowing that PFOS has been observed
are 92.4 times what the odds would have been if PFOS was not observed,
and vice versa. For every pair of chemicals, both the point estimate
and 95 percent confidence interval (CI) were above 1, indicating
significant increases in the likelihood of detecting one chemical if
the other is present.
Both as a group and as individual chemicals, the Hazard Index PFAS
had a higher likelihood of being reported if PFOS or PFOA were present.
PFHxS, PFNA, HFPO-DA, and PFBS (the individual Hazard Index PFAS) are
demonstrated to generally co-occur with each other, as well. These data
support that there is a substantial likelihood that PFHxS, PFNA, HFPO-
DA, and PFBS co-occur in mixtures with a frequency of public health
concern in drinking water systems as discussed in section III.C of this
preamble.
[[Page 32594]]
D. Occurrence Relative to the Hazard Index
1. Proposal
In the proposed rule, the EPA analyzed the available state data in
comparison to the proposed Hazard Index MCL of 1.0 to evaluate the co-
occurrence of PFHxS, PFNA, HFPO-DA, and PFBS. The EPA requested comment
on the number of systems estimated to solely exceed the Hazard Index
(but not the PFOA or PFOS MCLs) according to the approach outlined in
USEPA (2024b).
2. Summary of Major Public Comments and EPA Responses
The EPA received comments on the analyses presented in the proposal
of occurrence relative to the Hazard Index. Many commenters agreed that
the Hazard Index PFAS co-occurred in mixtures at levels of health
concern. Two of these comments came from states that conducted
monitoring of Hazard Index PFAS post-UCMR 3 and stated that those
occurrence data supported the EPA's findings. Several state agencies
provided a summarized analysis of the number of systems expected to
exceed the proposed Hazard Index of 1.0 in their state. The EPA notes
that these estimates were based on the proposed Hazard Index, which
included two significant figures. Since the EPA has determined to
finalize the Hazard Index with one significant figure, these
estimations are likely high. Nonetheless, these state data and the
analyses provided by commenters provide illustrative confirmatory
insight of the EPA's Hazard Index analyses (please see section IV of
this preamble for additional discussion on the usage of significant
figures).
One commenter suggested that a national dataset and model complete
with all four Hazard Index PFAS are necessary to accurately estimate
the number of systems that may exceed the Hazard Index. The EPA
disagrees with the commenter; as described in section F, state data and
model outputs were appropriately combined to estimate exceedance of the
Hazard Index on a national level. Several commenters stated that there
was a limited amount of available data to determine the prevalence of
co-exposure of the Hazard Index compounds, and that further review
would be needed prior to establishing the Hazard Index. The EPA
disagrees with these commenters and believes that sufficient data were
available to reasonably assess the occurrence of Hazard Index PFAS. An
analysis of co-occurrence of Hazard Index compounds using a substantial
amount of data encompassing tens of thousands of samples across over
10,000 systems is provided in section VI.C. of this preamble above and
demonstrates that the four Hazard Index PFAS co-occur with each other
as well as with PFOA and PFOS. One commenter suggested that more
systems may exceed the Hazard Index than the PFOA and PFOS MCLs, since
current treatment technologies have been optimized for PFOA and PFOS
and not for other PFAS. The EPA's analysis of state datasets clearly
contradicts this claim; using the best available data and
scientifically robust analytical approaches, the EPA estimates more
systems will exceed the PFOA and PFOS MCLs than the Hazard Index MCL.
The use of a single significant figure for the Hazard Index MCL in this
final rule will further increase the likelihood of this being the case.
3. Final Rule
The EPA used its updated state dataset to update analyses related
to Hazard Index occurrence and found the analyses generally consistent
with the proposal analyses. In the final rule, the EPA is reducing the
number of significant figures used to determine Hazard Index exceedance
following all calculations and rounding from two to one; this change
had the effect of reducing system counts expected to exceed the Hazard
Index. For purposes of the final analyses, only systems with an
unrounded Hazard Index of 1.5 or greater were counted as an exceedance.
Table 13 presents the total number and percentage of monitored systems
with results above the proposed Hazard Index MCL based on state
reported Hazard Index PFAS data for the states that conducted non-
targeted monitoring and that sampled all four Hazard Index PFAS as a
part of their overall monitoring efforts. The EPA notes that for
equivalent comparison purposes Table 13 only accounts for samples that
included reported values (including non-detects) of all four Hazard
Index PFAS. As shown within the table, the majority of states evaluated
had monitored systems with results above the proposed Hazard Index MCL,
ranging from 0.35 to 3.17 percent of total monitored systems. For
additional discussion on the usage of significant figures in this rule,
please see section IV of this preamble.
[[Page 32595]]
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Further evaluating the available state data related to the proposed
Hazard Index MCL of 1, Table 14 presents the total number of systems
that exceed the final Hazard Index of 1 based on state reported Hazard
Index PFAS results for the same states shown in Table 13. However, in
this case, the EPA also analyzed the same non-targeted state data,
including additional samples even if those samples did not contain
reported values (including non-detects) for all four Hazard Index PFAS
(i.e., exceeding the Hazard Index based on two or three Hazard Index
PFAS with reported values included within a sample). Moreover, while
these states did monitor for all four Hazard Index PFAS as a part of
their overall monitoring, in a subset of those states some samples did
not include reported data on all four Hazard Index PFAS (i.e., values
of one or more of the Hazard Index PFAS were not reported as non-
detect, rather no value was reported). This analysis, presented in
Table 14, shows an increase in the number of monitored systems
exceeding the proposed Hazard Index of 1 and demonstrates prevalence of
these PFAS at levels of concern, even when all four PFAS may not be
included within a sample.
[[Page 32596]]
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Combining the non-targeted monitoring results shown previously with
targeted state monitoring conducted for all four Hazard Index PFAS
showed at least 864 samples from 211 PWSs in 21 states had results
above the final Hazard Index of 1. These systems serve approximately
4.7 million people. More information on occurrence in state monitoring
is available in section III.C of this preamble and in USEPA (2024b).
In summary, the finished water data collected under both non-
targeted and targeted state monitoring efforts from 32 states showed
there are at least 1,772 PWSs serving a total population of
approximately 24.3 million people that have at least one result
exceeding the final PFOA MCL of 4.0 ng/L. In those same 32 states,
there are also at least 1,432 PWSs serving a total population of
approximately 21.0 million people that have at least one result
exceeding the final PFOS MCL of 4.0 ng/L. Finished water data showed
that there are at least 187 systems in 23 states serving a total
population of approximately 4.4 million people with at least one result
exceeding the final PFHxS MCL of 10 ng/L. Finished water data from 12
states showed there are at least 52 systems serving a total population
of approximately 176,000 people that have at least one result exceeding
the final PFNA MCL of 10 ng/L. Finished water data showed 13 systems
from 5 states serving over 226,000 people have at least one result
exceeding the final HFPO-DA MCL of 10 ng/L. Related to the Hazard
Index, finished water data collected under both non-targeted and
targeted state monitoring efforts in 21 states showed there are at
least 211 systems serving a total population of approximately 4.7
million people with results above the final Hazard Index value of 1 for
PFHxS, PFNA, HFPO-DA, and PFBS. Samples that only had monitoring
results for one Hazard Index PFAS were not included. USEPA (2024b)
presents a detailed discussion on state PFAS monitoring information.
E. Occurrence Model
A Bayesian hierarchical occurrence model was developed to
characterize national occurrence of the four PFAS that were most
frequently detected in the UCMR 3: PFOA, PFOS, PFHxS, and PFHpA.\8\
This model was used to generate the baseline national occurrence
estimates for PFOA, PFOS, and PFHxS, which were used in the subsequent
economic analysis in USEPA (2024g). Bayesian hierarchical models are a
widely used statistical approach in which subsets of data may be
recognized as more related than others (such as samples from the same
PWS are more related than samples between different PWSs) to capture
complex relationships between levels of data and can aid in
understanding the factors that influence outcomes. The objective of
this model was to use both UCMR 3 data and supplemental state data to
develop national estimates of
[[Page 32597]]
PFAS occurrence that inform occurrence distributions both within and
across PWSs. Supplemental state data were incorporated to improve the
model's ability to estimate PFAS occurrence at levels below the UCMR 3
minimum reporting levels (20 ng/L for PFOA, 40 ng/L for PFOS, and 30
ng/L for PFHxS). The state data incorporated to supplement the model
came from publicly available datasets. In order to maintain the
statistically robust UCMR 3 sampling framework, thereby enabling the
agency to make conclusions about national representativeness of the
model results, incorporation of state data into the model was limited
only to data from systems that took part in the UCMR 3. The model does
not include PFNA and PFBS due to data limitations; PFNA and PFBS lacked
sufficient reported values above the UCMR 3 minimum reporting levels to
be incorporated into the model. The model has been peer reviewed and is
described extensively in Cadwallader et al. (2022).
---------------------------------------------------------------------------
\8\ PFHpA was included in the model because of its UCMR 3
occurrence data availability.
---------------------------------------------------------------------------
The model uses Markov chain Monte Carlo (MCMC) simulation and the
assumption of lognormality in PFAS chemical occurrence. Markov chain
Monte Carlo is a powerful statistical tool used to understand
uncertainty and making informed decisions when analyzing data. The EPA
has used similar hierarchical models to inform regulatory decision
making in the past, such as for development of the NPDWR for Arsenic
and Cryptosporidium parvum (USEPA, 2006c; USEPA, 2000e).
After log-transformation of data informing the model, system-level
means (where each system has a mean concentration for each chemical)
were assumed to be distributed multivariate normally. Further, within-
system occurrence was assumed to be distributed normally for each
chemical. Since system-level means were modeled multivariate normally,
correlation between estimated system-level means across chemicals could
also be assessed. The assumption of lognormality as well as the
incorporation of state data with lower reporting limits allowed the
model to generate reasonable estimates for PFAS occurrence at levels
below the UCMR 3 minimum reporting levels.
After the model was fit with available data from PWSs that were
included in the UCMR 3, it was used to simulate occurrence at an
inventory of active community water systems (CWS) and non-transient
non-community water systems (NTNCWS) extracted from the Safe Drinking
Water Information System (SDWIS). System-level means for non-UCMR 3
systems were simulated by sampling from the multivariate normal
distribution of system-level means that was produced during the model
fitting process. For systems that were included in the UCMR 3, the
fitted system-level mean was used directly. This approach allowed
national occurrence distributions to be estimated alongside the
associated populations when combined with population data from SDWIS.
1. Proposal
In the March 2023 proposal preamble, model estimates of contaminant
occurrence were presented. For the analysis presented in the proposal,
UCMR 3 data were supplemented with 23,130 analytical results from 771
systems across 17 states that were available from public state websites
through August 2021. Key model results that were presented directly
included correlation coefficients across pairs of chemicals included in
the model, extrapolated estimates of the number of system level means
anticipated to exceed various threshold, and the estimated population
associated with systems that had mean concentrations exceeding the
various thresholds. The results indicated that system-level mean
concentrations were moderately to strongly correlated across the
modeled PFAS and that thousands of systems were estimated to have mean
PFAS concentrations in the range of single digit ng/L.
2. Summary of Major Public Comments and EPA Responses
A few commenters stated that they believed the model was an overly
complicated approach to characterizing chemical occurrence and found it
difficult to understand. Further, a few commenters stated that they
believed the model was not transparent. The EPA disagrees; the
occurrence approach used by the agency in this rule is based on a
widely utilized and accepted statistical approach which is used in a
variety of fields from education to health care and from business to
the environment. These models allow exploration of the relationships
among groups of data and the EPA used this model to better inform the
agency's understanding of probable PFAS occurrence. For more
information about Bayesian statistics and the wide variety of potential
applications, see, for example, Hoff (2009); van de Schoot et al.
(2021); Aguilera et al. (2011); and Messner et al. (2001). While the
model uses an advanced statistical method and requires some statistical
background to fully understand, Bayesian hierarchical models have
previously been employed to assess occurrence for drinking water
contaminants, as was discussed in the March 2023 proposal preamble as
well as Cadwallader et al. (2022). Cadwallader et al. (2022) describes
the model structure while the annotated model code and inputs were
provided directly as supporting information alongside the manuscript.
This information was incorporated into the docket for this rule's
proposal. Sufficient information to replicate the model run was
provided. Thus, the agency disagrees with the assertion that the model
was not transparent.
Regarding the model complexity, the core structure of this specific
model is comparatively simple among Bayesian hierarchical models. The
model uses a multivariate normal distribution of system-level means (of
log transformed data) for the four modeled PFAS. It also includes a
parameter for small systems to assess whether they appear to have
systematically different (higher or lower) concentrations than large
systems. As stated in Cadwallader et al. (2022), the model extrapolates
to the nation by sampling from the multivariate normal distribution and
accounting for whether the system being simulated was small. The
multivariate normal distribution and the parameter to distinguish small
systems from large systems are two simple but important pieces of the
model structure.
Many commenters stated that the model relied on insufficient data
and produced substantial underestimates of the number of systems that
would fail to meet MCL requirements. The agency disagrees both that the
approach taken would systematically underestimate PFAS occurrence and
that the data were insufficient inform the model. The Bayesian approach
used here makes a precedented assumption about drinking water
contaminant occurrence distributions (lognormality) and uses the
available data to generate iterative estimates of distribution
parameters that capture uncertainty through MCMC simulation. Across
these iterations, the density of the posterior distribution for model
parameters is proportionate to the likelihood that a given value would
have produced the observed data. The subsequent national extrapolations
also reflect this uncertainty.
For the results presented in the March 2023 proposal preamble, the
model was fit using 171,017 analytical results across the 4,920 UCMR 3
systems. This was a nationally representative set of systems. 147,887
of the analytical results were collected as part of UCMR 3 while 23,130
were aggregated from 17 subsequently collected state datasets. The
model was designed to utilize both results reported as observed
concentrations (8,209 results) and
[[Page 32598]]
results reported as less than a reporting limit (162,808 results).
While the UCMR 3 used higher reporting limits than are currently
available, both reported concentrations and values reported as below
the minimum reporting level cumulatively make substantial contributions
to informing the model's estimates of the PFAS occurrence distribution
because of this statistically robust framework. Due to this efficient
use of data, and the steps taken to maintain a nationally
representative set of systems, the agency believes that the over
170,000 analytical results were sufficient to generate reasonable
estimates of occurrence for the modeled contaminants.
Several commenters expressed concern with model bias resulting from
the supplemental state data that was incorporated when fitting the
model. The hierarchical structure of the model minimizes the bias
impact of introducing additional state data for only some UCMR 3
systems (those with additional data available) because the data are
explicitly linked to their parent systems rather than being pooled with
all other data informing the model. The primary impact that these data
have is on the model's estimate of specific system means for those
systems that had additional data and informing the within-system
variability parameters in the model. Refinement of a single system's
mean estimate has a much smaller impact on the high-level distribution
of system-level means and such shifts are proportionate to the added
evidence derived from the supplemental data.
The addition of data from systems not included in the UCMR 3 would
pose a much greater concern for bias, since not all states have
publicly available data. States with additional data would become
disproportionately represented in the fit of the high-level
distribution, since each system acts as a data point in fitting the
distribution. The resulting high-level distribution would shift to
resemble the states more closely with higher system representation in
the source dataset. This would also be reflected in the subsequent
national extrapolation. This same bias concern applies to national
extrapolation approaches where some fraction of systems in a subset are
identified as exceeding a given threshold and the national inventory of
systems is multiplied by that fraction to generate a national estimate
of systems that would exceed the threshold. If certain states have a
disproportionate number of systems included in the subset compared to
in the nation as a whole, the national estimate will be biased towards
the tendencies of those states. In addition to this bias, the simple
example approach discussed above would not naturally reflect
uncertainty. Thus, for the purpose of national extrapolation, a
nationally representative set of systems is more appropriate, even if
data from other systems are available.
While the EPA believes the model design and data selected for the
analysis presented in the March 2023 proposal remain appropriate given
the data availability at the time, the EPA has also continued to
collect newly available data from publicly available state datasets, as
the agency committed to in the proposed rulemaking (USEPA, 2023f). The
Bayesian hierarchical model has been refit using the updated dataset
with the same methods and criteria for data selection that were used
for the analysis presented in the March 2023 proposal.
3. Final Rule
After considering public comment, the agency has used the Bayesian
statistical model described in Cadwallader et al. (2022) to support the
economic analysis for this final regulation by combining the available
occurrence information from UCMR 3 and state data subsequently
collected at UCMR 3 systems to maintain the nationally representative
nature of the set of drinking water systems informing the model,
utilizing those data to compute estimates of national occurrence for
PFAS contaminants, and providing estimates on the number of systems
impacted by this final rule. These estimates directly informed the
economic analysis in USEPA (2024g). For the final rule, the model was
updated with additional state data collected through May 2023. In
total, based on public comment, the EPA supplemented the state dataset
with 65,537 analytical results from 1,156 systems across 28 states. Of
these supplemental data, 24,950 analytical results were observed
concentrations while 40,587 results were reported as below some
reporting limit. The previously presented results have been updated and
are presented in Table 15. The EPA notes that results from the updated
dataset and model were confirmatory of its proposal analyses and did
not result in changes to the EPA's final decisions. Median estimates
and 90 percent credible intervals are shown for counts of systems with
system-level means at or above various PFAS concentrations in Table 15
and the population served by those systems in Table 16.
[GRAPHIC] [TIFF OMITTED] TR26AP24.017
[[Page 32599]]
[GRAPHIC] [TIFF OMITTED] TR26AP24.018
For PFOA, PFOS, and PFHxS, thousands of systems were estimated to
have mean concentrations over the lowest thresholds (i.e., 4.0 and 5.0
ng/L) presented in Tables 15 and 16 with the total population served
estimated to be in the tens of millions. The populations shown here
represent the entire populations served by systems estimated to have
system-level means over the various thresholds. It is likely that
different subpopulations would be exposed to different mean PFAS
concentrations if multiple source waters are used.
In addition to the estimates of individual chemical occurrence, the
multivariate normal distribution of system-level means allowed the
model to provide insight on estimated co-occurrence. The model results
support the co-occurrence of PFOA, PFOS and Hazard Index PFAS. The
model evaluated whether untransformed (i.e., expressed in the original
units of measurement) estimates of system-level means were correlated
across each unique pair of the four modeled chemicals included in the
model. Estimates of the Pearson correlation coefficient are shown in
Table 17. The Pearson correlation coefficient serves as an indicator of
the strength of the linear relationship between two variables and may
range from -1 to 1. Positive values indicate a positive relationship
(i.e., as one variable increases, so does the other). shown in Table
17. The Pearson correlation coefficient serves as an indicator of the
strength of the linear relationship between two variables and may range
from -1 to 1. Positive values indicate a positive relationship (i.e.,
as one variable increases, so does the other).
[GRAPHIC] [TIFF OMITTED] TR26AP24.019
The EPA considered a moderate strength correlation as greater than
0.5 and a strong correlation as greater than 0.7. Each point estimate
of correlation coefficients between two chemicals was above the
threshold for a moderate strength correlation. The carboxylic acids
(PFOA-PFHpA) and sulfonic acids (PFOS-PFHxS) had the highest estimated
correlation strengths, with both the point estimate and the 90 percent
credible interval above the threshold for a strong correlation. PFOS-
PFOA and PFOS-PFHpA had similar point estimates and 90 percent credible
interval ranges, spanning the moderate-to-strong correlation range.
Both PFOA-PFHxS and PFHpA-PFHxS had the bulk of their posterior
distributions fall in the range of a moderate strength correlation.
Thus, the
[[Page 32600]]
model predicted significant positive relationships among system-level
means of all four chemicals that were included. These results support
the co-occurrence discussion presented in section VI.C of this preamble
that indicated extensive co-occurrence of PFOA, PFOS, and the Hazard
Index PFAS observed in state datasets from both groupwise and pairwise
chemical perspectives.
F. Combining State Data With Model Output To Estimate National
Exceedance of Either MCLs or Hazard Index
In order to broadly estimate the number of systems that would be
impacted by the regulation, including MCLs of 4.0 ng/L for PFOA and
PFOS alongside a Hazard Index of 1 for PFHxS, PFNA, HFPO-DA, and PFBS,
findings from non-targeted monitoring in state datasets were combined
with model estimates. Specific details on the methodology can be found
in USEPA (2024b). Briefly, information collected from non-targeted
state datasets included the fractions of systems that reported a
measurement at or above the UCMR 5 minimum reporting level for a given
analyte and an empirical cumulative distribution function (eCDF)
consisting of system-level maximum observed concentrations of that
chemical at these systems. The UCMR 5 minimum reporting levels for
PFNA, HFPO-DA, and PFBS are equivalent to 4 ng/L, 5 ng/L, and 3 ng/L,
respectively (USEPA, 2022j). This applies the assumption that the
fraction of systems that observed PFNA, HFPO-DA, and PFBS at or above
UCMR 5 minimum reporting levels and the maximum concentrations observed
at those systems are reasonably representative of the nation.
1. Proposal
The model was used to simulate EP-level concentrations of the four
modeled PFAS (PFOA, PFOS, PFHpA, and PFHxS) under the assumption that
within-system concentrations are lognormally distributed (a common
assumption for drinking water contaminants, see (Cadwallader et al.
(2022)) and that variability in concentrations is entirely across EP
(thus a given EP is assumed to have a constant concentration). For each
system, the maximum estimated EP PFOA or PFOS concentration was
selected to determine whether the system exceeded either of the
proposed MCLs of 4.0 ng/L. The EP with the maximum concentration is the
point that determines whether a system has an EP that is above an MCL.
Estimates of the system-level maximum for PFHxS were also selected for
the Hazard Index calculation. The maximum value of the sum of the four
modeled PFAS at each system was selected and used as a basis for
determining which systems would receive superimposed concentrations of
the three remaining Hazard Index chemicals (PFNA, HFPO-DA, and PFBS).
This approach was selected due to the extensive observed co-occurrence
of PFAS in the UCMR 3, state data, and modeled estimates.
Multiple methods of system selection were used that reflected
different degrees of co-occurrence. The chemical concentration that was
applied to selected systems were randomly sampled from the eCDF for
each chemical. Based on the model output, this assumes that system-
level maximums for PFNA, HFPO-DA, and PFBS would occur at the same
location within a system. Given the substantial co-occurrence among
PFAS observed and estimated across various analyses, combination of
system-level maximums independently pulled from chemical eCDFs is a
reasonable simplifying assumption. This is particularly true since
systems selected for each chemical are not necessarily the same and in
most cases were probability weighted. Estimates of the range of systems
impacted were developed by taking Q5 and Q95 estimates for each method.
The low end of the range was taken as the lowest Q5 estimate across
methods, rounded down, while the high end of the range was taken as the
highest Q95 estimate across methods, rounded up. This was also done for
the total population served by these systems.
The analysis to support the March 2023 proposal estimated that 100-
500 systems that were not already exceeding an MCL for PFOA or PFOS
would exceed the Hazard Index. This resulted in a total of 3,400-6,300
systems estimated to be exceeding either the Hazard Index, the MCL for
PFOA, or the MCL for PFOS.
2. Summary of Major Public Comments and EPA Responses
One commenter stated that they believed it is difficult to
determine whether the estimated number of systems exceeding the Hazard
Index is a reasonable estimate until a complete national dataset is
available. The EPA disagrees with this commenter. The agency believes
that it has taken steps to produce reasonable estimates using a robust
set of available data, and that the data and analyses are sufficient to
inform the EPA's regulatory decisions. Namely, this includes the use of
non-targeted state datasets and multiple scenarios reflecting varying
degrees of co-occurrence as described in USEPA (2024b). Among other
important uses for these data, the EPA considered them to inform the
regulatory determination for the mixture of the Hazard Index PFAS and
the EA. The EPA has used these data to clearly demonstrate that there
is a substantial likelihood that combinations of the Hazard Index PFAS
co-occur as mixtures in public water systems with a frequency and at
levels of public health concern. See section III of this preamble for
additional discussion. Additionally, these data support the EPA's EA,
and considerations of costs and benefits consistent with SDWA's
requirements. See section XII of this preamble for further discussion.
3. Final Rule
The method to combine state data for non-modeled Hazard Index PFAS
with model estimates has largely remained the same for this final rule
as it was for the March 2023 proposal. One key change, based on public
comments, was to use an updated set of non-targeted state data to
inform Hazard Index contaminant prevalence above UCMR 5 minimum
reporting levels and eCDFs. Another key alteration, also based on
public comments, was accounting for significant figures when counting
systems exceeding the MCL for PFOA, the MCL for PFOS or the Hazard
Index. For a system to be exceeding the Hazard Index, it must be
greater than or equal to 2 (i.e., greater than 1) after rounding (for
additional discussion on significant figure usage in the final rule,
please see section IV of this preamble). To exceed the MCLs for PFOA or
PFOS, the concentration must be greater than or equal to 4.1 ng/L after
rounding. Finally, model estimates of PFHxS were converted to zero for
the purposes of calculating the Hazard Index if they fell below the PQL
of 3 ng/L.
The total number of systems estimated to be exceeding one or more
MCLs in the rule was 4,100-6,700 (compared to 3,400-6,300 in the
proposal) serving a total population of 83-105 million people. Among
these systems, 100-300 are estimated to be exceeding the Hazard Index
without exceeding the PFOA or PFOS MCLs. The EPA used these modeled
estimates to inform the costs and benefits determination as described
in section XII of this preamble. Additional details regarding the
approach used here can be found in USEPA (2024b).
[[Page 32601]]
G. UCMR 5 Partial Dataset Analysis
1. Summary of Major Public Comments and EPA Responses
UCMR 5 occurrence data were not available to inform the proposal,
but the agency discussed that additional nationwide monitoring data
would be available for systems participating in the monitoring program.
Some commenters called for the EPA to delay issuance of the final PFAS
rule until the complete UCMR 5 occurrence dataset can be analyzed, and
some commenters stated that rule promulgation should be delayed until
at least a portion of the UCMR 5 data is obtained. The EPA disagrees
with these commenters. The EPA is not required under the statute to
wait for another round of UCMR data to be collected before proposing or
finalizing a regulation; in this case, the completion of UCMR 5 data
reporting is expected at the end of 2025, with the final dataset not
being available until 2026. Rather, SDWA section 1412(b)(1)(B)(ii)(II)
expressly provides that the EPA must use the ``best available public
health information'' in making a regulatory determination (emphasis
added). The EPA has sufficiently robust occurrence information to make
regulatory determinations and promulgate a regulation for the six PFAS
in this regulation. In addition to serving as a significant way for
helping many utilities reduce initial monitoring costs, the final full
UCMR 5 dataset will also be valuable for informing future regulatory
decisions for the 23 PFAS included in UCMR 5 that are not directly
addressed by this rulemaking. The agency believes that the best
currently available occurrence data demonstrate sufficient occurrence
or substantial likelihood of occurrence for the contaminants included
in the final rule.
2. Final Rule
While the EPA is under no legal obligation to consider the
preliminary, partial UCMR 5 dataset prior to rule promulgation, based
on public comment and interest, the agency examined UCMR 5 data
released as of February 2024 (USEPA, 2024n). While these data were not
available for this rule's proposal, are not complete, and are not a
basis for informing the agency's decisions for the final rule, the EPA
notes that they generally confirm the extensive occurrence analyses the
agency has conducted: namely, that all six regulated PFAS occur in
finished drinking water and that the six regulated PFAS co-occur with
one another. The EPA notes some important caveats when considering
these data. First, as of February 2024, the partial UCMR 5 dataset is a
subset of data that will be collected, representing approximately 24
percent of the total data that might be collected under that effort.
Additionally, under UCMR 5, systems must collect either 2 or 4 samples,
depending on their source water characteristics. In this preliminary
dataset, systems have varying degrees of completeness in their sample
collection and results may shift at the system level as additional
samples are collected. Analyses included examination of sample-level
results as well as EP mean-level results.
The UCMR 5 data publicly available as of February 2024 included a
combined total of 100,629 analytical results for PFOA, PFOS, PFHxS,
PFNA, HFPO-DA, and PFBS ranging from 16,766 to 16,778 analytical
results for each chemical. 16,743 complete sample sets where an
analytical result was reported for each chemical were available. 9,528
EPs and 3,719 PWS had at least one analytical result for each of the
six PFAS and one sample for which the Hazard Index could be calculated.
As mentioned previously, this partial dataset is estimated to contain
approximately 24 percent of the data that will be available once the
dataset is completed and finalized.
The preliminary dataset was assessed for sample-level threshold
exceedances of PFOA (4.0 ng/L), PFOS (4.0 ng/L), PFHxS (10 ng/L), PFNA
(10 ng/L), HFPO-DA (10 ng/L), and the Hazard Index (1). Note that for
PFOA and PFOS, two significant figures were considered (i.e.,
analytical results had to meet or exceed 4.05 to be considered
exceedances) while for PFHxS, PFNA, HFPO-DA, and the Hazard Index one
significant figure was considered (i.e., an analytical result had to
meet or exceed 15 to be considered an exceedance for PFHxS, PFNA, and
HFPO-DA and 1.5 to be considered an exceedance for the Hazard Index).
Sample-level analysis only included complete sample sets while EP and
system-level analysis included only systems that provided sufficient
data to determine maximum PFOA, PFOS, PFHxS, PFNA, and HFPO-DA, and
Hazard Index (which required at least one sample set where the Hazard
Index could be calculated). The EPA notes that this analysis does not
represent an estimate for the number of systems that will be in
compliance with the MCL; as discussed in section V of this preamble,
MCL compliance is determined based on an RAA. Additionally, samples
below the PQL would be treated as zero in the compliance calculation.
In the preliminary UCMR 5 dataset, PFOA exceeded 4.0 ng/L in 6.1
percent of samples (1,024 samples), at 7.5 percent of EPs (719 EPs),
and at 11.2 percent of systems (415 systems). PFOS exceeded 4.0 ng/L in
6.6 percent of samples (1,100 samples), at 8.0 percent of EPs (766
EPs), and at 12.4 percent of systems (462 systems). PFHxS exceeded 10
ng/L in 0.4 percent of samples (66 samples), at 0.6 percent of EPs (53
EPs), and at 1.1 percent of systems (42 systems). PFNA exceeded 10 ng/L
in <0.1 percent of samples (5 samples), at <0.1 percent of EPs (5 EPs),
and at 0.1 percent of systems (5 systems). HFPO-DA exceeded 10 ng/L in
<0.1 percent of samples (2 samples), at <0.1 percent of EPs (1 EP), and
at <0.1 percent of systems (1 system). The Hazard Index exceeded 1 in
0.5 percent of samples (76 samples), at 0.6 percent of EPs (60 EPs),
and at 1.3 percent of systems (48 systems). When the thresholds were
considered simultaneously, 9.0 percent of samples (1,504 samples), 10.9
percent of EPs (1,043 EPs), and 15.8 percent of systems (589 systems)
exceeded a threshold. Note that single sample exceedances of thresholds
do not necessarily reflect the averages that might be observed in the
completed dataset. Specifically, the EPA notes that it is likely that
many of the 15.8 percent of systems with an exceedance would not exceed
the MCLs because additional samples used to determine an RAA may
produce lower results.
To further illustrate this point, though there is insufficient data
to fully evaluate RAAs,\9\ EP-level means and systems with EP-level
means exceeding an MCL threshold were also assessed with the
preliminary dataset. For this analysis, only complete sample sets and
EPs with multiple complete sample sets were included. 5,269 EPs and
2,498 systems had data that met these criteria. When calculating EP
means, results reported as less than the minimum reporting limit were
treated as zero. Note that for PFOA and PFOS, two significant figures
were considered (i.e., calculated means had to meet or exceed 4.05 to
be considered exceedances) while for PFHxS, PFNA, HFPO-DA, and the
Hazard Index one significant figure was considered (i.e., calculated
mean had to meet or exceed 15 to be considered an exceedance for PFHxS,
PFNA, and HFPO-DA and 1.5 to be considered an exceedance for the Hazard
Index). Mean PFOA concentration exceeded 4.0 ng/L at 4.8
[[Page 32602]]
percent of EPs (253 EPs) and at 6.0 percent of systems (149 systems).
Mean PFOS concentration exceeded 4.0 ng/L at 5.3 percent of EPs (278
EPs) and at 7.2 percent of systems (179 systems). Mean PFHxS
concentration exceeded 10 ng/L at 0.3 percent of EPs (15 EPs) and at
0.4 percent of systems (11 systems). Mean PFNA concentration exceeded
10 ng/L at <0.1 percent of EPs (1 EP) and at <0.1 percent of systems (1
system). Mean HFPO-DA concentration exceeded 10 ng/L at <0.1 percent of
EPs (1 EP) and at <0.1 percent of systems (1 system). Mean Hazard Index
exceeded 1 at 0.3% of EPs (18 EPs) and at 0.6% of systems (14 systems).
Considered simultaneously, an MCL was exceeded at 7.2 percent of EPs
(381 EPs) and 9.4 percent of systems (235 systems). While the EP means
described above include multiple sample sets, observed mean
concentrations are likely to change as systems complete UCMR 5
sampling.
---------------------------------------------------------------------------
\9\ An RAA is calculated using results for samples taken at a
particular monitoring location during the previous four consecutive
quarters (see section XIII.B for more information).
---------------------------------------------------------------------------
Among 16,743 completed sample sets and 9,529 EPs and 3,719 systems
which had at least one result for each analyte, 13.9 percent of samples
(2,335 samples), 16.5 percent of EPs, and 22.6 percent of systems (842
systems) had an observed concentration at or above the minimum
reporting level for at least one of the 6 PFAS. Table 18 shows counts
of samples, EPs, and systems according to how many of the 6 PFAS
included in this final rule were present at or above the minimum
reporting level. As shown in Table 18, about 7.5 percent of samples,
9.4 percent of EPs, and 14.2 percent of systems observed multiple PFAS
at or above the minimum reporting level.
[GRAPHIC] [TIFF OMITTED] TR26AP24.020
Groupwise co-occurrence was also examined in the preliminary UCMR 5
dataset. Table 19 provides the counts and percentages of systems, EPs,
and samples where PFOA and/or PFOS were reported as well as whether any
of the Hazard Index PFAS were reported. Sample-level results only
included completed sample sets while system-level results only included
systems which provided one analytical result for each of the 6 PFAS.
[[Page 32603]]
[GRAPHIC] [TIFF OMITTED] TR26AP24.021
In samples, at EPs, and at systems where PFOA and/or PFOS were
reported present, one or more Hazard Index contaminant was reported at
or above the minimum reporting level about 68, 70, and 76 percent of
the time, respectively. As UCMR 5 monitoring continues, it is possible
that additional systems from this subset will report the presence of
PFOA, PFOS or a Hazard Index PFAS. The percentage of systems detecting
neither PFOA, PFOS, nor a Hazard Index PFAS would then decrease. Table
20 shows the number of Hazard Index PFAS that were observed in samples,
at EPs, and at systems where PFOA and/or PFOS were reported.
[GRAPHIC] [TIFF OMITTED] TR26AP24.022
[[Page 32604]]
At systems where Hazard Index PFAS were reported in addition to
PFOA/PFOS, about 51.0 percent of systems reported multiple Hazard Index
PFAS. As described above, it is possible that systems may detect
additional PFAS as sample collection continues under UCMR 5. System-
level pairwise odds ratios based on the first release of UCMR 5 data
are shown in Table 21.
[GRAPHIC] [TIFF OMITTED] TR26AP24.023
[[Page 32605]]
Except for two chemical pairings with HFPO-DA, each pairwise odds
ratio estimate between PFAS is statistically significantly greater than
one. As previously described, this indicates an increased likelihood of
reporting one chemical given that the other chemical is known to be
present. HFPO-DA odds ratios with PFBS, PFOS, and PFOA were also
statistically significantly above 1. Given that the UCMR 5 dataset is
not complete, it is important to note that, for chemical pairs where
very few systems have fallen into one or more of the categories of
chemical pairings, subsequent sampling may result in substantial shifts
in the odds ratio estimate and the associated CI. For example, if one
more system reported both HFPO-DA and PFHxS, the odds ratio estimate
would increase by 33 percent. On the other hand, if one more system
detected both PFOA and PFOS, the odds ratio estimate would shift by
less than 1 percent. As the count of systems in each category
increases, the odds ratio estimate becomes more stable with subsequent
sampling. This may be particularly relevant for relationships with
HFPO-DA and other Hazard Index PFAS, given the relatively low number of
systems (17 systems) that reported HFPO-DA at or above the minimum
reporting level in the preliminary UCMR 5 dataset as of February 2024.
After the release of approximately 24 percent of the data that will
be available in the full UCMR 5 dataset, there appears to be
considerable PFAS occurrence and co-occurrence demonstrated (USEPA,
2024n). Over 15 percent of systems with appropriate data described
above have observed a sample-level exceedance of any of the MCLs while
over 9 percent of systems have had an EP with a mean concentration
exceeding an MCL. Approximately 75 percent of systems that reported the
presence of PFOA or PFOS also observed at least one Hazard Index
contaminant. Over half of these systems reported the presence of
multiple Hazard Index contaminants. The national PFAS occurrence model
estimated between about 6.2 percent and 10.1 percent of all CWS and
NTNCWS would have an exceedance of an MCL. The 9.4 percent of UCMR 5
systems that had an EP mean concentration over an MCL is not a direct
comparison to this because not all EPs have sampled a year worth of
quarterly data and because large systems make up a larger fraction of
UCMR systems than systems in the national inventory (the model
estimated generally higher concentrations at larger systems). However,
separating these UCMR 5 results by system size and weighting according
to system counts in the national inventory of systems would result in
an estimation of 7.8 percent of all systems having an EP with a mean
concentration exceeding an MCL threshold. These estimates are likely to
shift as UCMR 5 sampling continues and system sampling regimes are
completed.
VII. Analytical Methods
A. Analytical Methods and Practical Quantitation Levels (PQLs) for
Regulated PFAS
1. Proposal
The agency proposed two EPA methods to support the monitoring
requirements of this regulation. The EPA developed the two liquid
chromatography/tandem mass spectrometry (LC/MS/MS) analytical methods
to quantitatively monitor drinking water for targeted PFAS: EPA Method
533 (USEPA, 2019b) and EPA Method 537.1, Version 2.0 (USEPA, 2020c).
The agency found that all six PFAS proposed for regulation can be
measured by both EPA Methods 533 and 537.1, ver. 2.0 and both methods
are acceptable for meeting the monitoring requirements of this
regulation.
Additionally, the EPA proposed PQLs for the six PFAS proposed for
regulation, as outlined in Table 22.
[GRAPHIC] [TIFF OMITTED] TR26AP24.024
In the proposed rule preamble (USEPA, 2023f), the EPA discussed
laboratory performance in the EPA's Unregulated Contaminant Monitoring
Rule (UCMR) 5 Laboratory Approval Program (LAP) and found that the UCMR
5 minimum reporting levels are appropriate as the basis for the
practical quantitation level (PQL) in this rule. These quantitation
levels account for the measurement precision and accuracy that the EPA
estimates can be achieved across laboratories nationwide.
2. Summary of Major Public Comments and EPA Responses
Several commenters note analytical differences between EPA Methods
533 and 537.1 such as differences in the quality control (QC)
acceptance levels between the methods, sample preservation and holding
times, as well as variability in sample and spike duplicates. In some
instances, these commenters request specific modification to the
methods, revisions to the EPA laboratory certification manual, or for
the agency to develop guidance that laboratories and state
accreditation/certification bodies could use. These commenters note
that while both methods are valid under the proposed rule, variability
between the two may lead to differences in sampling results and may
impact a water system's compliance status. The EPA agrees that Methods
533 and 537.1 have some differences that allow for analysis of varying
chain lengths and molecular structures of PFAS. Method 533 generally
captures ``short chain'' PFAS (i.e., those with carbon chain lengths of
4 to 12) and fluorotelomer sulfonic acids. Method 537.1 includes some
overlap with Method 533's analyte list while including some longer-
chain PFAS. However, the agency notes that
[[Page 32606]]
all six PFAS proposed for regulation can be analyzed by either Method
533 or 537.1 and neither method has inherent QC issues that lead to
significant variation in sampling results when followed. While there
are differences between the methods and how they measure their
respective target analytes, both EPA Methods 533 and 537.1 perform
comparably. The methods are clear and outline specific instructions
regarding requirements that are needed for compliance monitoring
measurements.
Some public commenters suggested that the EPA allow alternate
analytical procedures or modifications to the two published EPA methods
for meeting the monitoring requirements in the final rule. The EPA
continues to specify the use of Methods 533 and 537.1 because
consistent, reliable compliance data are necessary for implementation
of the regulation at the maximum contaminant level (MCL) However, the
EPA recognizes that improvements in analytical technology and
methodology occur. The EPA's Drinking Water Alternate Test Procedure
(ATP) Program provides a mechanism for submission and review of
alternative methods to measure a contaminant for nationwide use under
40 CFR 141.27. A method developer may apply for the EPA review of a
method modification or a new method through the ATP Program. In the
meantime, the agency has concluded that Methods 533 and 537.1 are
reliable for use in compliance monitoring with respect to accuracy and
recovery (lack of bias) and precision (good reproducibility) at the MCL
levels.
Several commenters requested that all laboratories be required to
identify their quantitation limits (i.e., the smallest detectable
concentration of an analyte greater than the detection limit where the
accuracy (precision and bias) achieves the objectives of the intended
purpose) and/or method detection limits (i.e., the minimum result which
can be reliably discriminated from a blank). Specifically, some
commenters note if labs have to demonstrate they can get below the PQL,
the EPA should establish reporting or detection limits demonstrating
they can get to these levels. The EPA is finalizing rule trigger levels
below the PQL to support the monitoring provisions discussed in section
VIII of this preamble. The EPA disagrees with these commenters that
such reporting is needed to support compliance monitoring for the rule
and that such reporting would be a cost burden on laboratories. All
labs are required per the approved methods to demonstrate whether
laboratory reagent blank (LRB) QC samples have background
concentrations of less than one-third the minimum reporting level
(i.e., the minimum concentration that can be reported as a quantitated
value for a method analyte in a sample following analysis). Therefore,
for a laboratory to be compliant with the methods, they must be able to
detect, not necessarily quantify, analytes at or above \1/3\ the
minimum reporting level.
Some commenters sought clarity on which methods are approved for
use in compliance monitoring for the final PFAS National Primary
Drinking Water Regulation (NPDWR). Some of these commenters requested
that only Method 533 be approved for monitoring under the final NPDWR,
noting that it may be more suitable should additional PFAS analytes
within its scope be targeted for regulation at the future date. Others
requested that they be permitted to use Method 537, version 1.1. The
EPA disagrees and reaffirms that Methods 537.1, version 2.0 and Method
533 are both applicable and suitable for use in compliance monitoring
in the final rule. The EPA notes that HFPO-DA is one of the PFAS
regulated under this action and only Method 537.1, version 1.0 and
version 2.0, and Method 533 support the collection of data for HFPO-DA.
The agency notes that the primary difference between Method 537.1,
version 1.0 and Method 537.1, version 2.0 is the field reagent blank
(FRB) preparation: version 2.0 exposes the FRB to the preservative
(Trizma) at the time of field sample collection. Version 1.0 combines
the lab reagent water and the preservative together in the FRB prior to
field sampling. Version 2.0 was created to more-closely mimic the FRB
process used in Method 533. Additionally, Version 2.0 explicitly states
that the solid phase extraction (SPE) cartridge sorbents may not be
modified with monomers other than styrene divinylbenzene (SDVB).
A few commenters critiqued how the proposed PQLs were established
for the rule. Some of these commenters provided feedback on the
feasibility of the proposed PQL and suggested that it may be too low,
resulting in recurring QC failures that will necessitate repeat sample
analysis, increased cost, and reduced laboratory capacity. Other
commenters suggest that lower PQLs can be attainable by larger labs
with advanced analytical instruments. The agency disagrees that PQLs
should be established at either a higher or lower level than that
proposed. As discussed in the proposed rule preamble, the PQLs are
based on a multi-laboratory assessment of analytical capacity. The EPA
derives PQLs which reflect the level that can be reliably quantified
within specific limits of precision and accuracy during routine
laboratory operating conditions. Based on the multi-laboratory data
acquired for the UCMR 5 rule, the EPA has defined the PQL for the PFAS
regulated in this rule (Table 22). This quantitation level considers
the precision and accuracy that the EPA estimates can be achieved
across laboratories nationwide. The EPA anticipates that over time, as
technology advances and as laboratories gain experience with the PFAS
Methods, laboratories will generally improve their capability to
measure at lower levels.
3. Final Rule
The EPA is establishing the following approved methods for use in
compliance monitoring in the final PFAS NPDWR: EPA Method 533 (USEPA,
2019b) and EPA Method 537.1, Version 2.0 (USEPA, 2009b; USEPA, 2020c).
The PFAS addressed by this regulation can be measured by both EPA
Methods 533 and 537.1 and either method is acceptable for meeting the
monitoring requirements of this regulation. Table 1 to paragraph
(f)(1)(iv) of Sec. 141.903 of subpart Z lists the PQLs for the PFAS
regulated under this action.
VIII. Monitoring and Compliance Requirements
A. What are the Monitoring Requirements?
1. Proposal
The EPA proposed requirements for community water systems (CWS) and
non-transient non-community water systems (NTNCWSs) to monitor for six
PFAS. The agency proposed to amend 40 CFR part 141 by adding a new
subpart to incorporate the regulated PFAS discussed in this preamble.
Under this new subpart, public water systems (PWSs) would be required
to sample EP using a monitoring regime based on the EPA's Standard
Monitoring Framework (SMF) for Synthetic Organic Contaminants (SOCs).
The EPA proposed the following requirements for initial monitoring,
which systems would be required to complete by the date three years
after the date of rule promulgation (see section VIII.F of this
preamble for more information). The EPA proposed that, consistent with
the SMF for SOCs, groundwater systems serving greater than 10,000
persons and all surface water systems would be initially required to
monitor quarterly within a 12-month period for regulated PFAS. To
provide additional flexibilities for small groundwater systems, the EPA
proposed to modify the SMF for SOCs such that
[[Page 32607]]
groundwater systems serving 10,000 or fewer persons would be initially
required to monitor only twice for regulated PFAS within a 12-month
period, each sample at least 90 days apart. In the proposal, all
systems would be allowed to use previously acquired monitoring data to
satisfy the initial monitoring requirements (see section VIII.C of this
preamble for additional details about using previously acquired
monitoring data to satisfy initial monitoring requirements). Based on
the SMF, the EPA also proposed that primacy agencies be able to use
initial monitoring results to reduce compliance monitoring frequency
for a system to once or twice every three years (depending on system
size) if the monitoring results are below the proposed rule trigger
level (defined in the following paragraphs).
The EPA proposed that, after initial monitoring, water systems
would conduct compliance monitoring to demonstrate that finished
drinking water does not exceed the maximum contaminant levels (MCLs)
for regulated PFAS. The EPA proposed that systems with multiple EP may
establish different compliance monitoring schedules for those EP
depending on their monitoring results.
The EPA proposed to base compliance monitoring requirements on
initial monitoring results and on system size. Then subsequent
monitoring requirements would be based on results from compliance
monitoring and, for systems on triennial monitoring, also on system
size. To determine compliance monitoring frequency only, the EPA
proposed a rule trigger level of one-third the MCLs (1.3 ng/L for PFOA
and PFOS and 0.33 for Hazard Index PFAS (PFHxS, PFNA, HFPO-DA, and
PFBS)). If results for an EP are below the trigger level, systems would
be eligible for reduced monitoring. To implement this provision, the
EPA proposed to include the ``trigger level'' concept in the new
subpart.
As proposed, each water system would be eligible for reduced
compliance monitoring at each EP for which all PFAS results are below
the rule trigger level, according to the following schedule:
A water system that serves 3,300 or fewer customers would
be required to analyze one sample for all regulated PFAS per three-year
compliance period at each EP where the water system does not have
results for any regulated PFAS at or above the rule trigger level (1.3
ng/L for PFOA and PFOS and 0.33 for the Hazard Index PFAS (PFHxS, PFNA,
HFPO-DA, and PFBS)),
A water system that serves more than 3,300 persons would
be required to analyze two samples for all regulated PFAS at least 90
days apart in one calendar year per three-year compliance period at
each EP where the water system does not have results for any regulated
PFAS at or above the rule trigger level (1.3 ng/L for PFOA and PFOS and
0.33 for the Hazard Index PFAS (PFHxS, PFNA, HFPO-DA, and PFBS).
In the proposal, if any result for an EP is at or above the rule
trigger level for regulated PFAS, the water system would be required to
monitor at that EP for all regulated PFAS quarterly. For compliance
monitoring collection schedules, the EPA did not specify the required
number of days between sampling events and only required collection
during a quarter. Systems monitoring an EP less frequently than
quarterly whose sample result is at or above the rule trigger level
would also be required to begin quarterly sampling at the EP where
regulated PFAS were observed at or above the trigger level. In either
case, the primacy agency would be able to allow a system to move an
individual EP to a reduced monitoring frequency when the primacy agency
determines that the EP is below the rule trigger level and reliably and
consistently below the MCL. However, primacy agencies would not be
permitted to determine that the EP is below the rule trigger level and
reliably and consistently below the MCL until at least four consecutive
quarters of quarterly compliance monitoring have occurred with all
sample results below the rule trigger level.
Additionally, related to laboratory capacity considerations, the
EPA described in the proposal that it anticipates that laboratories
will be able to adjust to demand and that the demand will be
distributed across the three-year implementation period.
2. Summary of Major Public Comments and EPA Responses
The following discussion details numerous comments the EPA received
on the proposed monitoring requirements, both for initial monitoring
and long-term compliance monitoring.
The majority of comments the EPA received on the initial monitoring
requirements related to the number of initial samples systems would be
required to collect and the intervals between required samples. Most
commenters were generally supportive of the EPA's proposed initial
monitoring requirements, including the flexibilities to use previously
acquired monitoring data to satisfy some or all the initial monitoring
requirements and, for those groundwater systems serving 10,000 or fewer
that do not have this data, that they be required to only collect two
samples at each EP to satisfy initial monitoring requirements. For a
discussion of comments and final rule requirements specific to the use
of previously acquired monitoring data to satisfy the initial
monitoring requirements see section VIII.C of this preamble.
While most commenters were supportive of the number of initial
monitoring samples the EPA proposed, a few commenters indicated they
thought the EPA should not allow the flexibility for groundwater
systems serving 10,000 or fewer to collect only two samples and instead
require quarterly samples be collected by all systems to meet initial
monitoring requirements, which would be fully consistent with the SMF
framework for other SOCs. A couple of these commenters suggested that
there are no data demonstrating that smaller systems are less likely to
have elevated levels of PFAS than large systems or that groundwater
systems are less likely to have elevated levels of PFAS than surface
water systems. Additionally, other commenters generally suggested that
two samples may not generate enough data to accurately capture the
level of PFAS in drinking water and any potential seasonal variability.
Related to potential seasonal changes in measured PFAS concentrations,
some commenters from state agencies indicated that they have not
observed seasonal variations in concentrations of PFAS measured by
groundwater systems, whereas other commenters suggested the opposite
and that they have seen changes seasonally based on their state's
monitoring data.
The EPA disagrees with commenters that suggest two samples for
small groundwater systems would not accurately capture the baseline
level of regulated PFAS in drinking water. The EPA determined the
initial monitoring requirements based on both source water type and
system size considerations. First, from a national-level perspective,
the EPA's model for estimating national PFAS drinking water occurrence
(see section VI.E of this preamble) indicates that, regardless of
source water type, small systems generally have lower mean PFAS
concentrations and lower within-system variability than large systems.
Further accounting for source water type, as compared to all
groundwater systems, all surface water systems potentially have a
larger number of sources of contamination and greater hydrology
variability so more monitoring data is
[[Page 32608]]
necessary to ensure an appropriately protective monitoring schedule.
Both the differences in the occurrence estimations for large and small
sized systems as well as the general source water characteristics of
groundwater systems were collectively considered as part of
establishing the proposed initial monitoring requirements for small
groundwater systems. Consequently, the agency expects that small
groundwater systems would be less likely to experience variations
throughout a year and, where there may be seasonal variations,
requiring the samples to be collected in different parts of a year
would provide sufficient information to determine the appropriate
compliance monitoring schedule. Furthermore, given the different
experiences cited by commenters, possible seasonal variation is likely
based on the specific geographic location and other localized factors.
If there are regional factors that suggest more frequent sampling is
warranted, the rule provides that primacy agencies may increase the
required monitoring frequency, where necessary, to detect variations
within the system (e.g., fluctuations in concentrations due to seasonal
use or changes in water source).
In response to comments about the alignment of Unregulated
Contaminant Monitoring Rule (UCMR) 5 sampling with initial monitoring
requirements, a couple of commenters indicated that requiring larger
groundwater systems to collect four samples would translate into these
systems needing to collect two additional samples beyond those
collected for the UCMR 5 monitoring effort. The EPA acknowledges that
while the initial monitoring requirements generally align with the UCMR
5 sampling requirements, groundwater systems serving greater than
10,000 would need to collect two additional samples and notes that they
have the three years following rule promulgation to complete this
monitoring. As described previously, the model for estimating national
PFAS drinking water occurrence indicates that larger systems have
greater within-system variability than smaller systems, therefore it is
appropriate that these larger groundwater systems collect four initial
monitoring samples; this is consistent with initial monitoring
requirements for groundwater systems under existing SOC National
Primary Drinking Water Regulations (NPDWRs).
In addition, a couple of commenters recommended that the number of
required samples for initial monitoring be based on the results of the
first two samples, with subsequent monitoring only required if
regulated PFAS are detected in those earlier samples. The EPA
recognizes there is some logic to this approach; however, there would
be challenges implementing it. Specifically, it could be challenging
for primacy agencies to track and implement the proposed approach,
particularly for groundwater systems serving 10,000 or fewer which
would require the additional samples to occur in quarters not
represented by the first two samples. Furthermore, tracking this
varying monitoring would result in additional administrative burden and
oversight challenges for primacy agencies, rather than having a
consistently defined schedule for monitoring requirements as is used
for other SOCs.
The EPA also received several comments from state agencies about
the required intervals associated with initial quarterly and semiannual
sample collection. In its proposal, the EPA specified that samples be
collected at least 90 days apart, whether the samples were required of
a system monitoring on a quarterly basis or a system monitoring semi-
annually. A couple of commenters noted that they believed that
semiannual samples should be separated by more than 90 days to better
capture seasonal variations (e.g., seasonal changes in the percent
contributions of water blended from different sources, other
fluctuations in concentrations). One commenter suggested semiannual
samples should be collected at least 180 days apart, which would also
be in better alignment with the required schedule for UCMR 5 semiannual
sampling. The EPA agrees with these comments. In the final rule, the
EPA is requiring that the samples be collected 5 to 7 months apart for
semiannual initial monitoring (see table 2 to paragraph (a)(4)(i)(B) of
the regulations governing the UCMR program in 40 CFR 141.40).
With respect to the sample collection timing requirements for
quarterly initial monitoring (for all surface water systems and
groundwater systems serving greater than 10,000), a few commenters
indicated that they were opposed to the proposed requirement for
samples to be spaced at least 90 days apart. These commenters indicated
that such a requirement was unnecessarily prescriptive and would make
sample collection logistically challenging for public water systems.
These commenters suggested the EPA change the required spacing in a way
that still satisfies the EPA's intent to not have samples collected
only a few days apart, but in different quarters, so that quarterly
samples are more representative of fluctuations in concentrations over
time. The EPA agrees with these comments and sees the value of systems
being able to use four existing samples collected in separate quarters
but also allow flexibility that they are not all spaced at least 90
days apart. In the final rule, the EPA is modifying the required
spacing of quarterly initial monitoring samples to be 2 to 4 months
apart if samples are collected in a 12-month period. For systems that
would need to supplement previously acquired data to satisfy all the
initial monitoring requirements, the final rule requires that they must
also be 2 to 4 months apart from the months of available pre-existing
data. This will also better parallel the language outlining the
required spacing of quarterly samples collected for the UCMR 5
monitoring effort.
Some commenters asked the EPA to clarify which systems would be
subject to the initial monitoring requirements for surface water
systems and which systems would be subject to the requirements for
groundwater systems, in some cases presenting examples of specific
scenarios. One example is when a system relies on surface water at some
EP and groundwater at other EP. The EPA has modified the language of
the final rule in Sec. 141.902(b)(1)(ii) to clarify that initial
monitoring requirements are to be determined based on the type(s) of
water serving as the source for a given EP; thus, one system may have
different initial monitoring requirements that apply to different EP.
In response to questions, the EPA is clarifying in Sec.
141.902(b)(1)(iv) that, if an EP uses water blended from multiple
sources (some groundwater and some surface water), or if it uses
different types of sources throughout the year, the system must follow
the monitoring frequency for a surface water system (since water from
surface water sources is used at least in part, for at least a portion
of the year). This approach is more protective of public health
because, as described earlier, generally surface water systems have
more variable hydrology and potentially more sources of contamination
so more monitoring data is necessary to ensure an appropriately
protective monitoring schedule.
A couple of commenters asked for clarification about whether EP
supplying groundwater under the direct influence of surface water
(GWUDI) would qualify for semiannual initial monitoring. As noted in
Sec. 141.902(b)(1)(iii), GWUDI systems follow the requirements for
surface water systems. GWUDI systems may be as susceptible to
contamination as surface water systems; thus, these systems must use
the sampling
[[Page 32609]]
requirements for surface water during the initial sampling phase to
establish baseline levels of regulated PFAS.
Regarding the requirements for longer-term compliance monitoring,
the comments the EPA received related primarily to the frequency with
which sampling would occur under different circumstances, whether each
EP would be allowed to be on a different compliance monitoring
schedule, and the trigger levels that would support decisions about
reduced triennial monitoring. Regarding the latter point, commenters
also addressed laboratory capabilities to measure levels below
practical quantitation levels (PQLs).
The EPA's proposal would allow systems eligible for reduced
monitoring, and serving 3,300 or fewer, to collect one sample
triennially and would allow eligible larger systems to collect two
samples during a three-year compliance period. The EPA specifically
requested comment on whether all water systems, regardless of system
size, should be allowed to collect and analyze one sample per three-
year compliance period if the system does not measure any regulated
PFAS in their system at or above the rule trigger level. A few
commenters stated that they did not agree with a different number of
triennial samples eligible systems must collect based on the size of
the population a system serves. These commenters indicated that they
believe that one sample collected every three years is sufficient for
systems of any size on reduced monitoring. The EPA agrees with these
commenters that systems eligible for triennial monitoring should be
allowed to collect one sample every three years, regardless of system
size, especially considering other changes to the compliance monitoring
framework, as described subsequently.
Several commenters recommended that an annual sampling frequency
tier be added to the required monitoring framework for various reasons
including the mobility and persistence of PFAS in the environment, to
ensure that systems that have demonstrated elevated levels of regulated
PFAS are not allowed to move directly from quarterly to triennial
monitoring, and based on their concerns that some laboratories may not
be able to produce results at or below the rule trigger levels
(resulting in some systems remaining on quarterly monitoring
indefinitely even if they can consistently demonstrate they are below
the MCLs). A few commenters supported offering three possible
monitoring frequencies: quarterly, annually, and triennially, whereas
many other commenters recommended against allowing triennial sampling
at all and recommended that sampling be required no less than annually,
to best protect public health. Those commenters supportive of allowing
both annual and triennial monitoring, depending on prior sample
results, suggested that annual monitoring should be an option for
systems with regulated PFAS concentrations that are reliably and
consistently below the MCLs. This modification would parallel the three
tiers of monitoring allowed for other organic chemicals under the SMF.
The EPA does not agree with the comments suggesting that no systems
should be allowed to sample triennially and that the longest sampling
interval at any location should be one year. Based on the EPA's
national occurrence estimates, most water systems subject to the rule's
requirements will not have results for regulated PFAS that exceed the
MCLs, and many will not identify PFAS at or above the triggers for
reduced monitoring. These systems, after demonstrating results below
the trigger level and therefore no or very little presence of regulated
PFAS during the initial monitoring period or through ongoing compliance
monitoring, should be able to reduce their monitoring burden and
conduct triennial sampling. These monitoring requirements will
sufficiently maintain public health protection. If a system monitoring
triennially did have a sample result with elevated levels of a
regulated PFAS (at or above the trigger level), it would be required to
immediately initiate quarterly monitoring. Additionally, the rule
specifically provides that primacy agencies may increase the required
monitoring frequency for compliance sampling for a variety of reasons,
including to detect variations within specific systems (e.g.,
fluctuations in concentrations due to seasonal use patterns or changes
in water sources).
For any system that has regulated PFAS concentrations at or above
the trigger level, but reliably and consistently below the applicable
MCL, the EPA is introducing in the final rule an annual monitoring
frequency within the compliance monitoring framework, consistent with
the SMF for SOCs. A demonstration of reliably and consistently below
the MCL would include consideration of at least four quarterly samples
below the MCL. Annual samples would be collected during the quarter
with the highest concentration measured during the prior round of
quarterly sampling. The EPA expects this modification in the final rule
to reduce the number of systems that are required to be on quarterly
monitoring for extended periods of time, compared to the EPA's
proposal.
In adopting a three-tiered monitoring framework, the EPA is
modifying the required sampling frequency from triennial to annual for
systems determined by states to be reliably and consistently below the
MCL and changing the threshold for this determination from the trigger
level to the MCL. To further reduce monitoring, any system that
transitions into annual sampling will be required to collect three
years of annual samples each of which show concentrations of regulated
PFAS below trigger levels (i.e., not an average of the three annual
sample results) before then being eligible for triennial monitoring.
Moreover, no system required to collect quarterly samples during
compliance monitoring would be allowed to transition to triennial
monitoring without first conducting three years of annual monitoring,
with all results below the trigger level. If eligible for triennial
monitoring, the sample collected triennially would need to be collected
in the same quarter during which prior results were highest.
This additional tier is intended to create a gradual step-down
schedule for affected EP to confirm levels of regulated PFAS are
remaining consistently low or decreasing. The modifications to the
requirements for a reliable and consistent determination and the
creation of the new annual sampling tier in the final rule make the
requirements for regulated PFAS more consistent with the NPDWR
requirements for SOCs. They also represent flexibilities that address
concerns about laboratory capability concerns. The EPA believes this
three-tier approach, including the eligibility criteria for each
outlined above, provides the best approach to protect public health and
moderate the total cost of sampling borne by a system.
The EPA also received a few comments about the practice by systems
that have installed treatment for PFAS to regularly sample finished
water to ensure the efficacy of their treatment media (e.g., filters),
above and beyond what they would do for compliance monitoring. A few
commenters suggested systems that have installed treatment would
conduct this additional sampling voluntarily, typically for process
control purposes. A few state agency commenters suggested that any
system that is treating its water for PFAS should be required to sample
more frequently than triennially (e.g., annually) no matter the levels
of previous PFAS detections, since the effectiveness of treatment media
may decline over time, if not replaced. The EPA disagrees with the
commenters
[[Page 32610]]
recommending a greater sampling frequency for systems that treat their
water for PFAS and does not see a compelling reason to depart from the
three-tier compliance monitoring program for a system that has
installed treatment. In the final rule, the EPA is adding an annual
tier of sampling for any system with concentrations reliably and
consistently below the MCL but not consistently below the trigger
level. The EPA believes this tier will likely apply to most systems
treating their water for regulated PFAS, at least for the first three
years of treatment, as the EPA estimates as part of its rule costs that
systems needing to install treatment will assume a treatment target of
80 percent of the MCLs. The majority of systems with elevated levels of
regulated PFAS contamination are likely to sample quarterly, at least
initially (unless they have treatment for PFAS in place prior to the
collection of initial monitoring samples). In practice, the result is
that most systems with PFAS contamination will likely not be eligible
for triennial sampling unless their PFAS treatment is consistently
optimized and maintained. However, the rule provides that primacy
agencies may increase the required monitoring frequency, where
necessary to detect variations within the system, and this approach
could be applied to those systems that have installed treatment. In
addition, the EPA notes that, when systems are treating for other
regulated chemicals pursuant to NPDWRs, no distinctions are made
between the monitoring frequency required of a system that is treating
for a chemical and a system that has not installed treatment. Thus, not
establishing a different monitoring frequency specifically for systems
that are treating their water for PFAS is consistent with existing
NPDWRs.
The EPA requested comment on the proposed allowance of a water
system to potentially have each EP on a different compliance monitoring
schedule based on specific EP sampling results (i.e., some EP being
sampled quarterly and other EP sampled only once or twice during each
three-year compliance period), or if compliance monitoring frequency
should be consistent across all of a system's sampling points. A few
commenters recommended that all EP used by a system monitor at the same
frequency, or that doing so be optional, to reduce the complexity of
monitoring requirements or the potential for mistakes to be made with
respect to sampling windows. However, the overwhelming majority of
those who commented on this topic indicated they supported allowing
different sampling frequencies for different EP. The EPA agrees that it
would be beneficial to allow different sampling frequencies for
different EP because it would allow utilities to realize cost savings
if only the EP with elevated levels of PFAS are required to sample most
frequently. In addition, the EPA notes it allows systems to use
different sampling frequencies for different EP for compliance with
other NPDWRs.
The EPA requested comment on monitoring-related flexibilities that
should be considered to further reduce burden while also maintaining
public health protection, including setting a rule trigger level at
different values than the proposed values of 1.3 ng/L for PFOA and PFOS
and 0.33 for the Hazard Index PFAS (PFHxS, PFNA, HFPO-DA, and PFBS).
Alternative values of 2.0 ng/L for PFOA and PFOS and 0.50 for the
Hazard Index PFAS were identified as possibilities. The EPA received
numerous comments on the proposed rule trigger levels. Comments
addressed the proposed values, specifically for PFOA and PFOS, and
their intended purpose for determination of compliance monitoring
frequency. Several commenters suggested that the proposed values (i.e.,
1.3 ng/L for PFOA and PFOS and 0.33 for the Hazard Index) are too high
and the EPA should instead set lower trigger level to ensure greater
public health protection. Many other commenters suggested the opposite,
stating that the proposed levels are too low, that laboratories will
not be able to achieve these levels, and that it may exacerbate any
laboratory capacity issues. Consequently, some of these commenters were
concerned that water systems would be ineligible for reduced monitoring
based on their laboratory's analytical limitations. Several commenters
suggested that the proposed values are inconsistent with the SMF for
SOCs.
Many who commented on the subject were fully supportive of the
EPA's proposed alternative trigger level values of 2.0 ng/L for PFOA
and PFOS and 0.50 for the Hazard Index, while others expressed support
for the inclusion of trigger levels only if these higher levels were
incorporated. Some noted that these higher trigger levels would better
align with current laboratory capabilities and allow greater use of
previously collected drinking water data (to demonstrate systems are
eligible for reduced triennial monitoring under the rule's initial
monitoring requirements). A few commenters recommended alternative
values of 70-80 percent of the MCLs be used as the trigger levels.
The EPA agrees with commenters that the trigger levels should be
finalized as one-half of the MCLs (i.e., PFOA and PFOS at 2.0 ng/L
each, PFHxS, PFNA, and HFPO-DA at 5 ng/L each, and Hazard Index at
0.5). Using data submitted as part of the UCMR 5 LAP as a reference
point, the EPA notes that 47 of 53 laboratories (89 percent) that
applied for UCMR 5 approval generated a minimum reporting level
confirmation at 2 ng/L (one-half the proposed MCL) or less for Method
533. This suggests that most laboratories with the necessary
instrumentation to support PFAS monitoring have the capability to
provide screening measurement results at the revised trigger level of
one-half of the MCL. This corresponds with other comments described in
section VIII.C of this preamble that provided their experience that
laboratories are capable of reliably quantifying values below the PQLs,
particularly to 2.0 ng/L for PFOA and PFOS.
Additionally, based on the EPA's evaluation of state drinking water
data, updating the final rule trigger levels (to one-half of the MCL)
will result in a considerable number of additional water systems
significantly reducing their ongoing monitoring frequency from
quarterly or annual monitoring to triennial monitoring. Although this
modification from one-third of the MCL to one-half of the MCLs may
provide slightly less information on a water system's measured PFAS
levels as a result of their less frequent monitoring, the trigger
levels for the final rule (i.e., one-half of the MCLs) will ensure
sufficient public health protection while reducing burden for water
systems.
Many other commenters stated that either trigger levels should be
removed from the rule entirely or that trigger levels should not be set
to any levels below PQLs since these represent the level that can be
reliably measured with a high degree of precision and accuracy across
all laboratories. Several of these commenters suggested that data below
the PQL are unreliable, would result in higher costs, and should not be
used as the basis for any regulatory decisions. Thus, they suggested
that if trigger levels are incorporated, they should be the same as the
PQLs. These commenters also cited laboratory challenges in achieving
measurement below the PQLs and suggested that water systems would not
be eligible for reduced triennial monitoring as a result of these
limitations. Additionally, some of these commenters suggested that
decision making based on any values below the PQLs may exacerbate
laboratory capacity issues, claiming that such trigger levels would
result in
[[Page 32611]]
errors, such as false positives, which would lead to increased
monitoring where samples need to be re-tested.
The EPA emphasizes that the use of trigger levels set at values
below the MCLs is consistent with other SOCs under the SMF and not
novel for drinking water regulations (as described in the subsequent
paragraph). Their use allows water systems the opportunity to reduce
their monitoring schedule and burden where it can be demonstrated
through sampling results that they are at low risk of PFAS
contamination. In the absence of trigger levels, or some other
threshold, all water systems would be deprived of the opportunity for
reduced monitoring. At a national level, were the EPA to eliminate
reduced monitoring options, this would result in a significant increase
in costs to utilities. Consequently, the EPA is choosing to incorporate
these levels to allow flexibility and reduce burden for water systems
while maintaining health protection.
For commenters that suggest the trigger levels should be identical
to the PQLs, particularly for PFOA and PFOS, the EPA disagrees as the
agency must have greater assurance that the levels are below the
regulatory standard, the systems are actually lower risk, and a reduced
monitoring schedule is appropriate. Specifically, in the case of PFOA
and PFOS, the EPA believes it would represent an unacceptable public
health risk to set trigger levels at the PQLs because the EPA is
setting the MCL at the PQL which means that it represents the ``maximum
permissible level.'' Moreover, the approach of considering measured
levels lower than PQLs for determining monitoring frequency is not
novel but has been part of the drinking water standards for many years.
Many drinking water standards even use a method detection limit, which
by definition is lower than the PQL. Under the SMF for SOCs, for
example, results both at or below detection limits and between
detection limits and the MCL are utilized for monitoring frequency
determination. Additionally, 40 CFR 141.24(h)(7) prescribes the
monitoring frequency for organic contaminants based on sample results
relative to detection limits (as defined in in paragraph (h)(18) of the
same section). In each of these cases, detection limits are below their
PQLs (often by a factor of 10). The approach in this rule--using levels
lower than the PQL to determine monitoring frequency--is consistent
with the EPA's approach for other NPDWRs (see section V of this
preamble).
As described earlier, some commenters raised concerns about
potential laboratory analytical and capacity issues. Some suggested
that laboratories cannot achieve levels below the PQLs, which would
result in water systems not being eligible for reduced monitoring based
on not demonstrating results below trigger levels. The EPA recognizes
that some laboratories may not be able to produce results at these
lower levels with the same degree of accuracy and precision as results
at or above the PQLs, and notes that there is not a requirement that
they do so for these purposes. The EPA uses the PQL to inform the MCL
feasibility determination and the same level of precision and accuracy
is not required to determine monitoring frequency. Along these lines,
several commenters questioned if the sample results must be quantified
to be used for the determination of monitoring frequency, given the
proposed trigger level values were set below the PQLs, requesting
further clarity from the EPA on how to interpret and utilize quantified
and non-quantified data. Furthermore, some commenters suggested that if
values below the PQLs are used, only quantified results should be used
for determining monitoring frequency. Other commenters stated there
should not be a numerical value associated with results below the PQL
(e.g., results between the trigger levels and the PQLs) and instead
such results should only be reported on an absence/presence basis.
The EPA agrees that results below the PQL may not have the same
precision and accuracy as higher-level measurements; however, results
below the PQL can be sufficiently determined for these purposes. Data
below the PQL will be critical to ensuring that systems are monitoring
at the correct frequency and whether a contaminant is present within a
certain range. Moreover, while results near the trigger level may be
less definitive than results at or above the PQL, such results are
appropriate for establishing monitoring frequency, as well as for
reporting as part of the annual Consumer Confidence Report (CCR). CCR
reporting is based on detected contaminants and for the purposes of the
PFAS NPDWR, Sec. 141.151(d) defines ``detections'' as results at or
above the rule trigger levels (see section IX of this preamble for more
information on CCR requirements).
Under this final rule, for monitoring frequency determination
purposes, systems are required to use all compliance sample results,
including those below the PQLs and not quantified with the same
precision and accuracy as is associated with the MCL compliance
calculation determination. Additionally, the determination of
monitoring frequency is not based on a running annual average result,
but each individual sampling result. As an illustration of the
approach, if a water system has quarterly sampling results at an EP
from initial monitoring for PFOA that are 2.0, 1.5, 5.0, and 1.5 ng/L,
there are two results (i.e., 2.0 and 5.0 ng/L) at or above the EPA's
final trigger level for PFOA (i.e., 2.0 ng/L). Thus, the water system
would not be eligible for triennial monitoring at this EP for all
regulated PFAS when compliance monitoring begins. Providing a different
example, if a water system that is currently required to conduct
quarterly compliance monitoring has quarterly sampling results at an EP
for PFOA that are 2.0, 3.5, 2.5, and 1.5 ng/L, all results are below
the MCL for PFOA (i.e., 4.0 ng/L), however three results are above the
PFOA trigger level. In this case, because four quarters of data have
been collected and assuming all other regulated PFAS sampling results
are below their MCLs as well, the water system could be deemed
reliability and consistently below the MCL by the primacy agency and be
eligible to monitor annually at this EP. For all frequencies of ongoing
compliance monitoring, including quarterly, annual and triennial, this
determination would be done the same where all sample results are used,
even those below the PQLs.
Many commenters requested that the EPA provide clarification on how
laboratories and PWSs should report levels below the PQLs for
monitoring frequency purposes. All results at or above the trigger
level are to be reported as numeric values and used for determining
monitoring frequency. Under the EPA approved analytical methods
discussed in section XII, numeric values as low as the rule trigger
levels will be available because of the need to meet ongoing QC
requirements of the methods for blanks, demonstrating no background
contamination. Within each analytical batch of samples, the laboratory
must document passing blank QC criteria by attaining qualitative
measurements of the regulated PFAS that are no higher than one-third of
the laboratories reporting limit, which must be at or below the PQL.
The EPA intends to provide guidance materials with details and examples
on this to support successful implementation of the final rule.
Some commenters suggested the potential for confusion related to
the differences in how results less than PQLs are used in monitoring
frequency determination and the MCL compliance determination. Several
commenters
[[Page 32612]]
suggested that there should be a consistent approach. Most commenters
suggested that the approach should follow that of the MCL compliance
determination, where zero is used in the calculation of annual averages
when measured values are below PQLs. The EPA reiterates that the
trigger levels are used for establishing appropriate monitoring
frequency. For certain regulated PFAS, they are set at a defined
threshold that shows if these PFAS are present or absent. The PQLs,
which are used for the MCL compliance determination, are set at
specific concentrations that laboratories nationwide can measure with
high certainty. To alleviate possible confusion, the EPA intends to
provide communication materials on these monitoring requirements to
support successful implementation of the final rule. Nevertheless, the
difference in approach (between data used for compliance monitoring
determinations and data used to determine monitoring frequency)
reflects the most appropriate application of the data for each of the
intended purposes and assures that adequate monitoring is occurring in
systems where the regulated PFAS have been shown to be present at the
trigger level or higher. The EPA's rationale is described in detail in
section VIII.B of this preamble.
Several other issues related to monitoring flexibilities were
raised in public comments. One commenter asked, if one EP has a result
for a single regulated PFAS at a concentration above the trigger level,
but other regulated PFAS are below trigger levels, must the system
initiate quarterly sampling for all regulated PFAS at the EP or are
they only required to initiate quarterly sampling for PFAS observed at
or above the trigger level. As described in the rule proposal, if a
regulated PFAS is detected at or above a trigger level, the system must
monitor quarterly at that sampling point for all regulated PFAS. This
is appropriate as the same analytical methods are used for the analysis
of all regulated PFAS (no extra analyses need to be performed to
measure the other PFAS) and the regulated PFAS have been shown to
significantly co-occur.
In addition, commenters questioned whether quarterly sampling would
be triggered when a result is equal to but does not exceed the trigger
level for systems monitoring triennially. One commenter pointed out
that the language proposed for inclusion in Sec. 141.905(b)(2) stated
that systems monitoring triennially whose sample result is at or
exceeds the trigger level must begin quarterly sampling, whereas Sec.
141.902(b)(2)(ii) stated the trigger level must be exceeded before
quarterly monitoring is required. The EPA is clarifying this point in
the final rule to reflect the EPA's intent that quarterly sampling
would be triggered when a result is at or above the trigger level as
prescribed in Sec. 141.905(b)(2). This same approach has been used in
other NPDWRs (e.g., for SOC trigger levels).
3. Final Rule
This final rule establishes initial monitoring requirements and
reflects minor modifications to the proposed approach. Groundwater CWS
and NTNCWS serving 10,000 or fewer must collect two (semiannual)
samples in a consecutive 12-month period and must collect the samples 5
to 7 months apart, to better capture seasonal variation. Groundwater
CWS and NTNCWS serving greater than 10,000 and all surface water CWS
and NTNCWS must collect four (quarterly) samples 2 to 4 months apart in
a consecutive 12-month period. The EPA is maintaining the provision
described in the proposed rule that allows PWSs to use previously
collected data to satisfy initial monitoring requirements; see Sec.
141.902(b)(1)(vi). Systems that need to collect additional quarterly
samples to meet the initial monitoring requirements may sample outside
of a 12-month period, if all quarters are represented with sample
months 2 to 4 months apart. This 2-to-4-month interval also aligns with
UCMR 5 sampling requirements for surface water systems subject to this
rule and better captures possible seasonal variability establishing a
well-informed baseline. In addition, the EPA is modifying the proposed
initial monitoring requirements to now specify that if the water source
for the EP is surface water, a blend of surface water and groundwater,
or GWUDI, the initial monitoring requirements for surface water source
(4 quarterly samples) apply. If the EP source is only groundwater,
initial semiannual monitoring is required.
The EPA is modifying the number of samples required for some
systems with sampling locations eligible for triennial monitoring.
Regardless of the population served, all systems with sampling
locations eligible for triennial sampling will collect one sample every
three years. The sample is to be collected during the quarter with the
highest prior concentration identified in the most recent year when
samples were collected.
In the final rule the EPA is establishing a third tier for
monitoring frequencies and updating the proposed requirements for each
tier. The new monitoring frequency tier provides for annual monitoring
at sampling locations that have collected at least four consecutive
quarterly samples following initial monitoring if the primacy agency
determines the results at that EP are reliably and consistently below
the MCL. In establishing this tier, the EPA is removing the proposed
rule requirement for a state to determine that the running annual
average (RAA) concentration is below the trigger levels to reach this
reliably and consistently below the MCL determination. Instead, in the
final rule, reliably and consistently below the MCL means that each of
the sample results for the regulated PFAS are below the applicable
MCLs. In this new annual monitoring tier, if EP receive the reliably
and consistently below the MCL determination and remain below the MCLs
in subsequent sampling, even if above a trigger level, they may
continue on an annual monitoring schedule.
The criteria eligibility for triennial monitoring have been changed
accordingly. EP with all results below the trigger levels during
initial monitoring are eligible for triennial monitoring, as described
in the proposed rule. But, under the final rule, if an EP is required
to conduct quarterly sampling during the compliance monitoring period,
then triennial monitoring is only available after the EP has three
consecutive annual samples that each contain concentrations below the
trigger level. For EP that consistently have results between the
trigger levels and the MCLs, as described previously most would remain
on annual monitoring, rather than quarterly monitoring, which provides
a sufficient indication of contaminant level while reducing the total
sampling costs.
With respect to whether different EP for a particular water system
may be sampled at different compliance monitoring frequencies, based on
specific EP sampling results, the final NPDWR affirms this flexibility,
as proposed. In addition, there is no change to the language in the
final rule discussing the timing for taking quarterly samples during
the long-term compliance monitoring period. The EPA does not specify a
required interval between samples; the requirement is quarterly.
The EPA is finalizing rule trigger levels for compliance monitoring
frequency purposes only at one-half of the MCLs for regulated PFAS
(i.e., 2.0 ng/L for PFOA and PFOS, 5 ng/L for PFHxS, PFNA, and HFPO-DA,
and 0.5 for Hazard Index). If all PFAS results for an EP are below
these levels, the EP
[[Page 32613]]
would be eligible for triennial monitoring, with the following
exception. If sampling location is under an annual monitoring schedule,
it would be eligible for triennial monitoring following three
consecutive annual samples with all sample results below the trigger
levels.
The EPA's proposed rule included monitoring requirements specific
to PFAS. To avoid possible confusion, the EPA is amending 40 CFR
141.24(h) to clarify that the applicable monitoring requirements for
PFAS are in 40 CFR 141.902 and that the monitoring requirements for
non-PFAS SOCs in 40 CFR 141.24(h) do not apply to PFAS.
B. How are PWS compliance and violations determined?
1. Proposal
Consistent with existing rules for determining compliance with
NPDWRs, the EPA proposed that compliance would be determined based on
the analytical results obtained at each sampling point. For systems
monitoring quarterly, compliance with the proposed MCLs would be
determined by calculating RAAs for each sampling point. As proposed,
eligibility for reduced monitoring would be determined by the sample
result(s) at the sampling point. If the sample result(s) are at or
exceed the rule trigger level, the system would be required to revert
to quarterly sampling, for all regulated PFAS, at each EP where a
result is at or above the trigger level. In such case, the sample event
that included a result(s) at or above the trigger level would be
considered the first quarter of monitoring in calculating the RAA.
An RAA is calculated using results for samples taken at a
particular monitoring location during the previous four consecutive
quarters. As proposed, if a system takes more than one compliance
sample during each quarter at a particular monitoring location, the
system must average all samples taken in the quarter at that location
to determine the quarterly average, which would then be used in
calculating the RAAs. Conversely, if a system does not collect required
samples for a quarter, the RAA would be based on the total number of
samples collected for the quarters in which sampling was conducted. As
proposed, MCL compliance determinations would not be made until a
system has completed one year of quarterly sampling, except in the case
where a quarterly sampling result is high enough that it will clearly
cause the RAA to exceed an MCL (i.e., the analytical result is greater
than four times the MCL). In that case, the system would be in
violation with the MCL immediately.
In the proposal, when calculating the RAAs, if a sample result is
less than the PQL for the monitored PFAS, the EPA proposed to use zero
to calculate the average for compliance purposes.
2. Summary of Major Public Comments and EPA Responses
The agency received a few different types of comments on how the
compliance determination and violations were proposed to be assessed.
Many commenters supported the EPA's approach to assess violations,
including that violations are only assessed through an RAA for systems
conducting quarterly monitoring. A couple of commenters suggested that
in a scenario where a particular high quarterly sample (i.e., result
greater than four times the MCL) would cause the RAA to exceed an MCL,
the system should not be deemed out of compliance until the end of the
quarter (to allow utilities to conduct additional monitoring during
that quarter and average the results from the multiple samples). The
EPA disagrees with commenters that suggest additional voluntary
sampling be used in calculating the quarterly average. The final rule
requires that a compliance sample be taken during each quarter for
those systems conducting quarterly monitoring. Further, as prescribed
under 141.902(b)(2)(v), the state may require a confirmation sample for
any sampling results and, if this sample is required, the result must
be averaged with the first sampling results and used for the compliance
determination. Therefore, any samples other than a state-required
confirmation sample should not be averaged within the quarterly
compliance result which will be assessed at the end of the quarter.
A couple of other commenters suggested changing the time periods
for determining compliance (for both systems conducting quarterly
monitoring and those conducting triennial monitoring). These
recommendations included assessing compliance based on the results from
eight consecutive quarterly samples (rather than four). For those
systems conducting triennial monitoring, some commenters proposed that
the compliance determination be based on one triennial sample result.
For systems determining compliance through an RAA calculation, the EPA
believes four consecutive quarterly samples is an adequate
representation of the regulated PFAS levels while also assessing
compliance in a timely manner. For systems conducting triennial
monitoring, if a water system has a sample result at or above the EPA's
trigger levels, the system will immediately be required to begin
quarterly monitoring. This is consistent with other monitoring
requirements for other SOCs and, given the change in measured
concentration, will provide additional information over a consistent
and longer period of time to better assess the average level of
regulated PFAS within the water supply and ensure the water system is
reliably and consistently below the MCL.
In the proposed rule, the EPA requested comment on whether the
agency should consider an alternative to the approach of using zero
when calculating the RAAs if a sample result is less than the PQL.
Specifically, in the case where a regulated PFAS is detected but the
result is below its proposed PQL, the proposed rule invited comment on
whether the trigger level (proposed as one third of the PQL) should be
used as the value in calculating the RAA for compliance purposes.
The EPA received numerous comments related to the proposed approach
for calculating the RAA for compliance with the NPDWRs, particularly on
the incorporation of sample results below the PQLs for the regulated
PFAS (see sections V and VII for more information on PQLs.) Many
commenters, including some states, supported the EPA's proposed
approach to utilize zero for results below PQL to calculate the average
for compliance purposes. These commenters cited the definition of the
PQL as the lowest concentration of an analyte that can be reliably
measured within specified limits of precision and accuracy during
routine laboratory conditions and noted that this is a level that all
laboratories should be able to achieve. Consequently, they suggested
that values below these PQLs should not be used for the compliance
calculation. Several of these commenters expressed concern that using
estimated or other values with less precision in the compliance
calculation could result in utilities needing to take actions to
address levels of regulated PFAS that are not well-quantified and may
not be representative of regulated PFAS levels. Many commenters
suggested that since all laboratories cannot achieve values less than
the PQLs, this would result in equity issues with respect to disparate
laboratories capabilities. Some also suggested that the approach could
exacerbate any potential laboratory capacity issues.
The EPA agrees with these commenters that values below the PQLs
[[Page 32614]]
for the regulated PFAS should not be used in the compliance
calculation. As cited previously by commenters and the EPA in sections
V and VII, PQLs are the lowest concentration that can be reliably
measured within specified limits of precision and accuracy during
routine laboratory operations. As noted in the rule proposal, ``the
agency must have a high degree of confidence in the quantified result
as it may compel utilities to make potentially costly compliance
decisions in order to comply with the MCL.'' Moreover, because
compliance with the MCL is determined by analysis with approved
analytical techniques, the ability to analyze consistently and
accurately for a contaminant is important to enforce a regulatory
standard. The EPA recognizes the potential for minor analytical
variabilities within sampling procedures and laboratory analyses below
the PQL and this approach offers operational certainty to utilities,
provides assurances of precision and accuracy in the concentrations at
or above the PQL that are achievable for all laboratories, ensures
equitable access to all laboratories with comparable analytical
capabilities for the purposes of compliance sample results, and reduces
the potential for laboratory capacity issues.
Many other commenters did not support the EPA's proposed approach
and offered that all sample results between method detection limits and
PQLs, even if estimated, should be used. Alternatively, some suggested
that any results that laboratories are able to quantify should be used
in calculating the RAA for compliance. A subset of these commenters
suggested that using zero (instead of an estimated or semi-quantitative
value) biases the RAA compliance calculation, is even less precise and
accurate than using the values below the PQLs, is contrary to the RAA
compliance calculation for other SOC NPDWRs and demonstrates a
reduction in public health protection. Some commenters also suggested
that this could result in public communication challenges if
laboratories are able to estimate or quantify values below the PQLs and
zero is instead used in the calculation. Further, several commenters
submitted that, in their experiences, some laboratories are capable of
reliably and accurately reporting below the PQLs.
While the EPA recognizes that using zero for values below the PQL
would result in a differing RAA compliance calculation result than if
the values below the PQL were instead used, on a national scale, these
values below the PQL do not consistently represent values with the
precision, accuracy, and reliability the EPA believes are necessary for
compliance determination purposes. Therefore, the EPA's national
approach to achieve consistency (recognizing that laboratories have
varying analytical capabilities) is to judge compliance based on
results at or above the PQL. Using inconsistent values below the PQL
may result in MCL compliance determination inequities across systems.
The EPA agrees that some laboratories are capable of reliably
measuring the regulated PFAS below the EPA's PQLs. This is supported by
a subset of state PFAS monitoring data that represents some sampling
with quantified values below the EPA's PQLs. Further, in the March 2023
proposal, the EPA recognized that ``quantitation of the contaminants
can be achieved between the method detection limit and the PQL'' though
the EPA also noted in the proposal that this is ``not necessarily with
the same precision and accuracy that is possible at and above the
PQL.'' The EPA must set requirements evaluating the circumstances of
all PWSs and laboratory capabilities throughout the country. The agency
notes that states must establish requirements at least as stringent as
the EPA to maintain primacy; however, under the Safe Drinking Water Act
(SDWA), states with primacy may establish more stringent requirements.
In instances where a laboratory can demonstrate it is capable of
precisely and accurately quantifying values below the PQLs, some states
may choose to establish their own requirements that are more stringent
and use these values for the compliance calculation.
The agency also received a few comments on the possible alternative
approach of using the proposed trigger level as the value in
calculating the RAA for compliance purposes when the result is
estimated as between the trigger level and PQL. Most commenters did not
agree with using the trigger levels as an estimate instead of zero when
values are below the PQL and noted that these values could result in
inequitable implementation of the rule based on laboratory analytical
capabilities.
After consideration of all these comments and for the reasons
described previously, the EPA does not believe it is appropriate to use
trigger level values or any other values above defined detection limits
but below the PQL as part of the RAA compliance calculation based on
the information available to the agency today. Trigger levels are
appropriate to determine if the contaminant is present (i.e., detected)
and for the determination of reduced monitoring frequency, however the
EPA concludes that values below the PQL would not consistently and
reliably demonstrate the accuracy and reliability necessary for
compliance determination purposes that can result in make potentially
costly expenditures for PWSs.
3. Final Rule
For the final rule, the EPA is maintaining the proposed compliance
calculation determination approach. For systems with sampling locations
monitoring quarterly, compliance with the MCLs for regulated PFAS is
determined by calculating RAAs using compliance results for particular
sampling points. Based on final rule changes to the compliance
monitoring requirements previously described in section VIII.A of this
preamble above, systems with sampling locations monitoring less
frequently than quarterly are required to revert to quarterly sampling
for all regulated PFAS in the next quarter at each EP with the
exceedance where either the sample result(s) are at or above the rule
trigger level (for those on triennial monitoring) or the sample
result(s) are at or exceed the MCL (for those on annual monitoring). In
both cases, the triggered sample result is required to be used for the
first quarter of monitoring in calculating the RAA. If a system takes
more than one compliance sample during each quarter at a particular
monitoring location, the system must average all samples taken in the
quarter at that location to determine the quarterly average and this
will be used in calculating the RAAs. Conversely, if a system does not
collect the required compliance samples for a quarter, the RAA will be
based on only those quarters where samples were collected during the
past four quarters. A system will generally not be considered in
violation of an MCL until it has completed one year of quarterly
sampling (i.e., a system on an annual or triennial monitoring schedule
with an exceedance of the MCL is not in violation until it completes
one year of quarterly sampling with the sample exceeding the MCL used
as the sample result for the first quarter of the RAA). However,
regardless of the result of subsequent monitoring, if a quarterly
sample result will cause the RAA to exceed an MCL at any sampling point
(e.g., the first quarter sample result is greater than twice the MCL
and the second quarter sample result is also greater than twice the
MCL) or if an annual or triennial sample result causes the RAA to
exceed an MCL at any sampling point (i.e., the analytical result
[[Page 32615]]
is greater than four times the MCL), then the system is out of
compliance with the MCL immediately.
The EPA is also retaining the proposed approach for the MCL
compliance calculation where, if a sample result is less than the PQL
for the monitored PFAS, zero will be used to calculate the RAA (if
monitoring quarterly). To clarify how to implement approach, the EPA is
providing a few different examples related to calculating the RAA for
the PFOA/PFOS MCLs, the individual MCLs for PFHxS, PFNA, and HFPO-DA,
and the Hazard Index MCL for the mixtures of PFHxS, PFNA, HFPO-DA, and
PFBS.
If a system conducting quarterly monitoring has sample results for
PFOA that are 2.0, 1.5, 5.0, and 1.5 ng/L for their last four quarters
at a sample location, the values used to calculate the RAA for that
sample location would be 0, 0, 5.0, and 0 ng/L with a resulting PFOA
RAA of 1.3 ng/L (i.e., (0 + 0 + 5.0 + 0)/4 = 1.3 ng/L). For PFOA and
PFOS, as described in section V of this preamble, the MCLs of 4.0 ng/L
are promulgated with two significant figures and must be expressed as
such in the calculation with any rounding not occurring until the end
of the calculation. Data reported to the primacy agency must contain
the same number of significant digits as the MCL. In calculating data
for compliance purposes, the number must be rounded to two significant
digits. The last significant digit should be increased by one unit if
the digit dropped is 5, 6, 7, 8, or 9, and if the digit is 0, 1, 2, 3,
or 4, the preceding number does not change (e.g., 1.37 is reported as
1.4).
As described in section V of this preamble, the EPA is finalizing
individual MCLs and Health Based Water Concentrations (HBWCs) for PFHxS
(10 ng/L), HFPO-DA (10 ng/L), and PFNA (10 ng/L), the HBWC for PFBS
(2000 ng/L), and the Hazard Index MCL (1 unitless) with one significant
figure. Similar to PFOA and PFOS, if a sample result is less than the
respective PQLs for these PFAS (i.e., 3.0 ng/L for PFHxS, 5.0 ng/L for
HFPO-DA, and 4.0 ng/L for PFNA), zero will be used to calculate
compliance both for the PFHxS, PFNA, and HFPO-DA MCLs and the Hazard
Index MCL for mixtures of PFHxS, PFNA, HFPO-DA, and PFBS. As an
example, for the HFPO-DA MCL compliance calculation (which would be the
same for the PFHxS and PFNA MCLs using their respective PQLs), if a
system conducting quarterly monitoring has HFPO-DA sample results that
are 3.2, 6.1, 5.5, and 2.7 ng/L for the last four quarters at a sample
location, the values used to calculate the RAA for that sample location
would be 0, 6.1, 5.5, and 0 ng/L with a resulting HFPO-DA RAA of 3 ng/L
after rounding to one significant figure at the end of the calculation
(i.e., (0 + 6.1 + 5.5 + 0)/4 = 2.9 ng/L). Therefore, this system has
not violated the MCL for HFPO-DA. The EPA notes that for all MCL RAA
calculations, water systems are required to retain the unrounded RAA
value (2.9 ng/L in this example) for use in the next RAA calculation as
no rounding should occur until the end of the overall compliance
calculation (i.e., 2.9 ng/L, not 3 ng/L, should be used).
To provide an example calculation for determining compliance with
the Hazard Index MCL for mixtures of PFHxS, PFNA, HFPO-DA, and PFBS, if
the quarterly sample results at a sample location are 2.1 ng/L for
PFHxS, 3.4 for HFPO-DA, 4.1 for PFNA, and 20.0 for PFBS, the water
system would first determine the Hazard Index value for that quarter,
which is 0.42 (i.e., ((0/10) + (0/10) + (4.1/10) + (20.0/2000) = 0.42).
To then calculate the RAA Hazard Index MCL, if the preceding three
quarters had unrounded Hazard Index values of 0.76, 1.10, and 0.53 at
the same sample location, the resulting RAA Hazard Index MCL would be
0.7 after rounding to one significant figure at the end of the
calculation (i.e., (0.76 + 1.10 + 0.53 + 0.42)/4 = 0.70). Consequently,
this system has not violated the Hazard Index MCL.
C. Can systems use previously collected data to satisfy the initial
monitoring requirement?
1. Proposal
The EPA proposed that systems be allowed to use previously
collected monitoring data to satisfy the initial monitoring
requirements. In general, a system with appropriate historical
monitoring data for each EP, collected using EPA Methods 533 or 537.1
as part of UCMR 5 or a state-level or other appropriate monitoring
campaign, could use that monitoring data to satisfy initial monitoring
requirements. The EPA notes that for systems monitoring under UCMR 5,
all surface water systems are required to collect four quarterly
samples and all groundwater systems are required to collect two
quarterly samples over a period of 12 months.
While the EPA expects most systems serving 3,300 or greater will
have some UCMR 5 data, the EPA also proposed that systems with
previously acquired monitoring data from outside UCMR 5, including
state-led or other appropriate occurrence monitoring using EPA Methods
533 or 537.1 would also be permitted to use these other monitoring data
in lieu of separate initial monitoring for regulated PFAS. The proposed
approach may have allowed systems serving fewer than 3,300 (many of
whom do not participate in UCMR 5) to otherwise satisfy the initial
monitoring requirements. The EPA proposed that data collected after
January 1, 2023, be accepted for EP samples, and data collected between
January 1, 2019, and December 31, 2022, also be accepted if it is below
the proposed rule trigger level of 1.3 ng/L for PFOA and PFOS and a
Hazard Index of 0.33 for PFHxS, PFNA, HFPO-DA, and PFBS. Additionally,
the EPA proposed that if systems have multiple years of data, the most
recent data were to be used.
In the proposal, the EPA stated that if a system had conducted
prior monitoring involving fewer than the number of samples required
for initial monitoring under this PFAS NPDWR, then all surface water
systems, GWUDI systems, and groundwater systems serving greater than
10,000 would be required to collect at least one sample in each quarter
of a calendar year that was not acquired and groundwater systems
serving 10,000 or fewer would be required to collect one sample in a
different quarter of the calendar year than the one in which the
previous sample was acquired.
2. Summary of Major Public Comments and EPA Responses
The EPA requested comment on the proposal to allow the use of
previously acquired monitoring data to satisfy the initial monitoring
requirements. This included a request for feedback on the data
collection timeframe requirements and on whether particular QA
requirements should be established for such data. Of commenters that
provided input on the proposed allowance, nearly all supported the use
of previously collected data to support the initial monitoring
requirements. The EPA agrees with these commenters that appropriate,
previously collected data should be allowed and notes that there will
be significant data available from UCMR 5 monitoring and from the many
states that have been proactively conducting PFAS drinking water
monitoring. This will allow for a significant opportunity to reduce
burden for numerous water systems, as well as decrease the potential
for laboratory capacity issues. One commenter suggested that the use of
this data may not be sufficiently representative of current PFAS
concentrations in drinking water systems as the laboratory analyses
previously used may not have been
[[Page 32616]]
sufficiently sensitive to detect the analytes, relative to the proposed
PFAS regulatory standards. The EPA disagrees with this commenter as the
analytical methods proposed for PFAS analysis were available for the
majority of the time period (i.e., 2019 and after) in which data are
allowed to be used to satisfy the initial monitoring requirements.
Furthermore, the rule provides that a primacy agency may choose to not
allow these data to satisfy initial monitoring requirements and may
require more frequent monitoring on a system-specific basis.
Additionally, the EPA clarifies that previous monitoring does not
automatically qualify water systems for reduced compliance monitoring;
rather it is the results from that monitoring that determine the
eligibility for a reduced compliance monitoring schedule.
Many commenters suggested that the use of these data should be at
the state's discretion and requested that the EPA provide additional
flexibility to the primacy agencies in the determination of which data
are allowed, including the number of samples and the QA requirements.
Moreover, several commenters asked that the EPA clarify how much
additional data would be needed to satisfy the initial monitoring
requirements if a previous monitoring campaign included less sampling
than required under the rule initial monitoring requirements.
Specifically, a few commenters noted that, under the requirements of
UCMR 5 monitoring, groundwater systems serving greater than 10,000
would have results from two sampling events, not the four needed to
satisfy the initial monitoring requirements of this rule. Commenters
requested that the EPA explain if these UCMR 5 systems would need to
collect additional (supplemental) samples. A few commenters suggested
UCMR 5 monitoring should sufficiently meet the requirements for all
systems, even though the proposed rule requires quarterly sampling for
all groundwater systems serving greater than 10,000.
Having considered the public comments, the EPA is establishing in
the final rule that water systems that have collected fewer samples
(under UCMR or other programs) than required in this rule for initial
monitoring must conduct supplemental monitoring that allows them to
meet the minimum requirements. Additional details on this requirement
are in section VIII.C.3 of this preamble. In the case of UCMR 5, for
example, groundwater systems serving greater than 10,000 will be
required to collect two additional samples beyond the two collected for
UCMR 5. For more information on the initial monitoring requirements,
please see section VIII.A of this preamble.
Several commenters requested that the EPA clarify whether only
samples collected under UCMR 5 would be allowed to fulfill initial
monitoring requirements, or if data under other monitoring efforts,
such as state monitoring, would also be acceptable. As provided in the
proposal and final rule, a state may accept results from all
appropriate monitoring efforts, as determined by the state, including,
but not limited to, UCMR 5 and other state-led efforts.
Several commenters provided various comments related to QA
requirements for previously collected data, including data analysis
methods, minimum reporting levels, and data collection timeframe. A few
commenters expressed that the EPA should allow the use of results from
modified EPA methods and/or other state-developed analytical methods.
The EPA disagrees with these commenters. While there are other methods
that have been used for data collection and analysis, the EPA is
requiring that any data used for this rule be collected and analyzed
using Methods 533 and 537.1 to ensure consistency across analytical
results, as well as to align with the final rule analytical method
requirements described in Sec. 141.901. A few commenters requested
that the EPA provide additional information on reporting level
requirements of the data, with one commenter suggesting that the EPA
should not allow this data to be used for initial monitoring purposes
if the reporting limits of the laboratory are higher than the EPA's
proposed PQLs. The rule provides that the available data can be used
regardless of reporting or detection limits to satisfy the initial
monitoring requirements; however, given these factors, the results may
not support determinations for reduced compliance monitoring. Regarding
data collection timeframes, a few commenters questioned why data
collected prior to 2023 would not be accepted where the results are
higher than the proposed rule trigger levels. In response, the EPA has
modified the rule to allow data from January 1, 2019, and later to
satisfy initial monitoring requirements, even if it is not below the
final rule trigger levels if it meets all other requirements (including
being analyzed using Methods 533 and 537.1). Data collected prior to
2019 may not be representative of water quality conditions and likely
would not have been analyzed using these methods (given when they were
published). The EPA notes if the results exceed the final rule trigger
levels the system will not be eligible for a reduced monitoring
schedule at that EP.
3. Final Rule
The EPA is retaining the proposed allowance of using previously
collected monitoring data to satisfy some or all of the initial
monitoring requirements. The agency notes that while use of this data
is allowed, water systems may choose to conduct additional monitoring
to satisfy their initial monitoring requirement in lieu of using pre-
existing data. As described previously in section VIII.A of this
preamble, the final rule initial monitoring requirements specify that
all system sizes with surface water or GWUDI sources and groundwater
systems serving greater than 10,000 are required to collect four
quarterly samples, and groundwater systems serving 10,000 or fewer are
required to collect two samples. The EPA is clarifying that the number
of samples required is based at the EP; therefore, if a system serving
10,000 or fewer has EP with different source water types, the required
monitoring is based on the source water type of that EP (i.e., a system
serving 10,000 or fewer that has surface water, groundwater, and/or
GWUDI sources during the initial monitoring period must collect two
samples at the EP sourced by groundwater and four samples at the EP
sourced by surface water or GWUDI). For systems serving 10,000 or fewer
that change the source water type at EP throughout the initial
monitoring period (i.e., one part of the year is surface water, and the
remaining part of the year is groundwater and/or GWUDI), the EP must
follow the sampling requirements of surface water systems.
In the final rule under Sec. 141.902(b)(1)(viii), the EPA is
maintaining that if a system has some previously collected results, but
fewer than the number required to satisfy the initial monitoring
requirements, they must conduct additional monitoring such that it,
coupled with the previous monitoring, meets the requirements of this
rule. All surface water and GWUDI systems, and groundwater systems
serving greater than 10,000, must collect the required additional
samples 2-4 months apart from the months with available data, without
regard to year, such that all quarters are represented (see section
VIII.A of this preamble for more information).
In Sec. 141.902(b)(1)(vi), the final rule maintains the
requirement that the data must have been collected and analyzed using
EPA Methods 533 or 537.1, and eliminates the requirement that data
collected between January 1, 2019, and December 31, 2022, must reflect
the
[[Page 32617]]
laboratory's ability to measure at or below the rule trigger level to
satisfy initial monitoring requirements. Data collected before January
1, 2019, cannot be used to satisfy these requirements. Additionally,
any results above the final rule trigger levels of 2.0 ng/L each for
PFOA and PFOS, 5 ng/L each for PFHxS, PFNA, and HFPO-DA, and a Hazard
Index of 0.5 for PFHxS, PFNA, HFPO-DA, and PFBS would not allow the
associated EP to be eligible for reduced monitoring.
D. Can systems composite samples?
1. Proposal
Subpart C of 40 CFR 141.24 describes instances where primacy
agencies may reduce the samples a system must analyze by allowing
samples to be composited. Composite sampling can potentially reduce
analytical costs because the number of required analyses is reduced by
combining multiple samples into one and analyzing the composited
sample. However, in the proposal, the EPA noted that based on input the
agency received from consulting with state regulators and small
business entities (operators of small PWSs), PFAS are ubiquitous in the
environment at low concentrations, which necessitates robust laboratory
analytical precision at these low concentrations. Based on these
potential implementation issues, the EPA proposed that compositing of
samples would not be allowed.
2. Summary of Major Public Comments and EPA Responses
The EPA received comments related to composite sampling. The
majority of these commenters agreed with the EPA's proposal to not
allow samples to be composited due to analytical limitations and the
increased potential for background contamination, along with the
physical and chemical characteristics of PFAS. A few commenters
suggested that they believed composite sampling could be implemented
and would reduce the cost of analyses. Further, some of these
commenters suggested that with proper guidelines and procedures for
analyzing samples, possible contamination issues could be mitigated and
asserted that issues with false negative and positive samples also
impact discrete samples (i.e., that they are not unique to composite
sampling).
The EPA received other comments regarding the specifics of
composite monitoring. One commenter noted grab samples as more
appropriate and suggested that individual systems be permitted to
request alternative sampling methodologies if needed. One other
commenter suggested that compositing samples from varying EP should not
be allowed. In addition, one commenter requested that the EPA provide
information as to the increased risk of compositing samples, along with
discussion of the proposed departure from the SMF for SOC ahead of rule
finalization.
For commenters who offered that composite sampling could be
implemented, the EPA agrees it would potentially decrease sampling
analysis costs and that sampling errors can occur when handling and
analyzing discrete samples. However, the compositing of samples
necessarily involves additional handling, opening, and transfer steps
than are required for the collection and analysis of individual
samples. Therefore, the combining of samples that must be done for
composite sample analysis represents an increased risk of sampling
error, which could result in decreased public health protection and
additional sampling costs. The agency also does not agree that
alternative sampling methodologies should be permitted and requires the
use of EPA Methods 533 and 537.1 for monitoring per the requirements of
the rule. Please see section VII of this preamble for more information
on methods.
As discussed previously, PFAS are pervasive in the environment and
require robust laboratory analytical precision, particularly at low
concentrations. Accordingly, the EPA agrees with commenters that do not
support the allowance of composite sampling and maintains that discrete
sampling is the most appropriate type of sampling for regulated PFAS.
3. Final Rule
Based on consideration of public comments (many of which supported
the EPA's concerns about the ubiquitous nature of PFAS at low
concentrations in the environment, the necessary robust laboratory
analytical precision required, and potential implications for
implementation), the final rule does not allow composite samples.
E. Can primacy agencies grant monitoring waivers?
1. Proposal
Subpart C of 40 CFR 141.24 describes instances where the primacy
agency may grant waivers predicated on proximity of the system to
contaminant sources (i.e., susceptibility to contamination) and
previous uses of the contaminant within the watershed (including
transport, storage, or disposal). The EPA did not include a provision
to allow primacy agencies to grant monitoring waivers as a regulatory
flexibility in the proposed rule. The EPA did, however, request public
comment on whether to allow systems to apply to the primacy agency for
a monitoring waiver of up to nine years (one full compliance cycle) if,
after at least one year of quarterly sampling, the results are below
the rule trigger level, or for systems that may be approved for reduced
monitoring, if at least two consecutive results are below the rule
trigger level. The EPA also requested comment on allowing similar
monitoring waivers to be granted based on previously acquired
monitoring data as described in section VIII.C of the preamble for the
proposed rulemaking. The EPA additionally sought comment on possible
alternatives to traditional vulnerability assessments that should be
considered in order to identify systems as low risk and potentially
eligible for monitoring waivers.
2. Summary of Major Public Comments and EPA Responses
Several commenters suggested that monitoring waivers should not be
allowed for this rule. Several additional commenters cited the
persistence and mobility of PFAS in the environment and advised that
reduced monitoring frequencies should be no less than every three years
on the basis that drinking water consumers in unmonitored areas may
unknowingly be exposed to these PFAS. Furthermore, many other
commenters suggested that PFAS contamination can migrate significantly
over a three-year period.
Many other commenters were supportive of monitoring waivers for
this rule under certain circumstances. Several commenters indicated
that waivers would be appropriate if they were based on monitoring
results. A few commenters recommended that if monitoring waivers were
to be allowed, that they should not be based solely on a traditional
vulnerability assessment. A couple of commenters stated that waivers
based on vulnerability alone should not be allowed during the initial
monitoring period. One commenter recommended waiting until UCMR 5
monitoring is complete before allowing monitoring waivers to be granted
through vulnerability assessments. A couple of commenters suggested
that waivers be considered if they are based on a combination of
vulnerability and monitoring results, while one other commenter
suggested that assessing watershed characteristics to demonstrate
eligibility for monitoring waivers would be protective of chronic
health risks. One commenter noted that
[[Page 32618]]
merely allowing waivers to be granted would not necessarily reduce
public health protection under the rule, as primacy agencies will
retain the ability to deny waiver applications.
After consideration of these comments, and due to the mobility and
persistence characteristics of the regulated PFAS, the final rule does
not allow monitoring waivers. These specific properties of the
regulated PFAS and their observed ubiquity in both drinking water and
within many other sources make waivers impractical and complicate the
ability to maintain public health protection if such a provision were
included as part of this rule. Moreover, the EPA is not confident that
allowing monitoring any less frequently than every three years or
conducting vulnerability assessments will accurately capture potential
concentration variations over the long term or protect against risks
from new contamination sources.
3. Final Rule
Consistent with the proposal, the final rule does not include a
provision that would allow primacy agencies to issue monitoring
waivers. These waivers would increase the potential for public health
risks and the EPA does not consider them necessary to reduce burdens on
primacy agencies, water systems and communities given the other
flexibilities provided in the rule.
F. When must systems complete initial monitoring?
1. Proposal
Pursuant to section 1412(b)(10), the proposed rule required
compliance with all aspects of the NPDWR three years after
promulgation. This included satisfying initial monitoring requirements
as described in sections VIII.A and VIII.C within the three years
following rule promulgation.
2. Summary of Major Public Comments and EPA Responses
In the proposal, the EPA requested public comment on the proposed
initial monitoring timeframe, particularly for NTNCWS or all systems
serving 3,300 or fewer. Many commenters expressed support for the EPA
requiring initial monitoring as soon as possible with a few commenters
explicitly supporting the EPA's proposed initial monitoring timeframe
noting it allows sufficient time for water systems to comply with the
initial monitoring requirements. However, other commenters suggested
that water systems would not be able to utilize the full three years
following rule promulgation to perform initial monitoring and take
actions to ensure compliance with the MCL if monitoring results showed
elevated levels of PFAS. While the agency agrees that it may be
difficult to conduct initial monitoring and take necessary remedial
actions (e.g., treatment installation) within three years, the EPA
finds that it is practicable for all systems to complete their initial
monitoring within three years. This is particularly the case since the
large majority of systems serving greater than 3,300 will have
sufficient monitoring data from UCMR 5 and many other systems will have
at least some data to satisfy the rule's initial monitoring
requirements. Moreover, as described in section XI.D. of this preamble,
the EPA is exercising its authority under SDWA section 1412(b)(10) to
implement a nationwide two-year capital improvement extension to comply
with MCL. Consequently, water systems will have up to the full three
years following rule promulgation to plan and conduct monitoring and
still have two additional years to complete any actions needed to
comply with the MCLs.
Several commenters suggested that the EPA consider a staggered
initial monitoring timeframe by system size, such as those used in
other previous NPDWRs, where, for example, larger sized systems conduct
monitoring first followed by smaller systems. In the examples provided
by commenters, this staggered monitoring could also allow systems to
achieve compliance on a staggered schedule. A few commenters suggested
that this is necessary to address potential laboratory capacity issues
and to allow smaller systems additional time to plan and obtain
resources to conduct the monitoring. The EPA disagrees that staggering
the monitoring requirements to allow different compliance dates is
necessary. SDWA 1412(b)(10) specifies that all systems must demonstrate
compliance three years following rule promulgation except where a state
or the EPA may grant an extension of up to two additional years to
comply with MCL(s) if the EPA or the state (for an individual system)
needs additional time for capital improvements. Therefore, the intent
of the statute is to allow extensions to complete the capital
improvements necessary to comply with the MCL. The EPA considers the
three years sufficient for completing the rule's initial monitoring
requirement. The EPA's allowance of previously collected monitoring
data will also significantly reduce the potential for laboratory
capacity challenges. As previously noted in section VIII.A of this
preamble, the EPA has revised the required intervals between samples
collected for initial monitoring under this rule to closely parallel
the intervals required for UCMR 5, to promote the useability of
existing data.
The EPA is not prescribing any staggering of monitoring (e.g.,
based on system size) but encourages primacy agencies to work with the
systems they oversee to ensure their initial monitoring occurs and
adjust schedules (within the three years following rule promulgation)
as appropriate.
3. Final Rule
The EPA is finalizing the requirement that initial monitoring, or
demonstration of previously collected data to satisfy initial
monitoring requirements, must be completed within the three years
following rule promulgation (i.e., April 26, 2027) to ensure that water
systems have the information needed to inform decisions to meet the MCL
compliance date. As described previously and in section XI.D, the EPA
is providing a two-year capital improvement extension under SDWA
1412(b)(10), allowing additional time for those systems to comply with
the MCL. Requiring water systems to conduct initial monitoring within
the three years following rule promulgation will ensure public health
protection as soon as practicable and allow these water systems to
maximize utilization of the capital-improvement extension time.
Additionally, the flexibility in the final rule for systems to use
previously acquired monitoring data to satisfy some or all of their
initial monitoring will reduce the potential for laboratory capacity
challenges. The EPA encourages systems that may not have available data
and/or choose to conduct additional monitoring to conduct their initial
monitoring as soon as practicable following rule promulgation to allow
for remedial actions that may needed, based on monitoring results, and
to comply with the MCL by the compliance date.
G. What are the laboratory certification requirements?
1. Proposal
The EPA proposed that laboratories demonstrate their capability to
meet the objectives of this regulation. The proposal would require
laboratories to analyze performance evaluation (PE) samples every year
for each method and contaminant in order to achieve and maintain
certification from their primacy agency.
2. Summary of Major Public Comments and EPA Responses
A few commenters requested that the EPA develop guidance and
training for
[[Page 32619]]
drinking water laboratory certification programs to evaluate
laboratories seeking certification. The EPA agrees that training for
laboratory certification officers is appropriate. The EPA will develop
training materials and guidance for drinking water certification
programs to evaluate laboratories to ensure adherence to the
requirements of EPA Methods 533 and 537.1 (USEPA, 2005b).
One commenter requested that the EPA establish reciprocity between
laboratory certification programs to utilize all potential laboratory
capacity available. As described in the EPA's Manual for the
Certification of Laboratories Analyzing Drinking Water, laboratory
certification programs may recognize drinking water laboratory
certifications (or comparable ``accreditation'') from other laboratory
certification programs, by reciprocity (USEPA, 2005b). Most laboratory
certification programs do utilize the practice of reciprocal
certification. Reciprocal certification can only be granted to
laboratories utilizing EPA Methods 533 and 537.1.
3. Final Rule
Under the final rule, certified laboratories must demonstrate their
capability to meet the objectives of this regulation. Laboratories are
required to analyze PE samples every year for each method and
contaminant in order to achieve and maintain certification from their
primacy agency.
H. Laboratory Quality Assurance/Quality Control
In the proposal, the EPA requested comment on other monitoring-
related considerations including quality assurance/quality control (QA/
QC) associated with drinking water sampling and analysis.
Many commenters suggested the potential for false positives to
misrepresent actual levels of the regulated PFAS within the drinking
water sample due to the ubiquity of PFAS and the possible background
interference. The EPA is aware of the potential for background
contamination due to the ubiquitous nature of PFAS in the environment.
The EPA agrees that PFAS sampling is highly sensitive and there is
potential for sample contamination. However, with proper training tools
and communications, that potential can be mitigated, though not
sufficiently enough to allow for composite sampling as discussed in
section VIII.D of this preamble. For example, the UCMR program has
released several sampling guidance documents and a small-systems
sampling video to assist small and medium utilities with the PFAS
sampling. These products have also been distributed to the UCMR
laboratory community, which has been encouraged to share them with
their PWS clients.
Also, Method 533 and Method 537.1 require the analysis of an LRB
with each extraction batch. If method analytes are detected at or above
\1/3\ the minimum reporting level, suggestive of background
contamination, all positive field sample results associated with that
extraction batch are invalid for the impacted analytes. Both methods
also require the analysis of an FRB (a blank that is prepared at the
sampling location) when any PFAS are detected above the minimum
reporting level in field samples. The use of laboratory and field
blanks were incorporated into the methods as QC to reduce the potential
for false positives due to background contamination.
IX. Safe Drinking Water Act (SDWA) Right To Know Requirements
A. What are the Consumer Confidence Report requirements?
1. Proposal
A community water system (CWS) must prepare and deliver to its
customers an annual Consumer Confidence Report (CCR) in accordance with
requirements in 40 CFR part 141, subpart O. A CCR provides customers
with information about their local drinking water quality as well as
information regarding the water system's compliance with drinking water
regulations. The EPA proposed that CWSs be required to report detected
PFAS in their CCRs, specifically, PFOA, PFOS, PFHxS, PFNA, HFPO-DA, and
PFBS, and the Hazard Index for mixtures of PFHxS, PFNA, HFPO-DA, and
PFBS. The EPA also proposed adding paragraph (g) to 40 CFR 141.154 that
would require health effects language be provided when any regulated
PFAS is measured above the maximum contaminant level (MCL), in addition
to those with an MCL violation.
2. Summary of Major Public Comments and EPA Responses
A few commenters requested clarification of the health effects
language included in the CCR. Specifically, a couple of commenters said
the proposed standard health effects language included in the CCR for a
Hazard Index MCL exceedance was not clear. Commenters found some of the
language regarding the Hazard Index MCL to be confusing and offered
suggestions for clarification. The EPA has considered this input and
revised the health effects language associated with PFAS exposure,
including the Hazard Index.
A few of commentors raised concerns about requiring reporting of
results below the practical quantitation level (PQL) in the CCR as
these data may not be quantified with what they deem is appropriate
precision. One commentor requested that any detected PFAS, not just the
six regulated contaminants, be reported in the CCR. The EPA disagrees
with commenters who voice concern over reporting measurements below the
PQLs for PFOA and PFOS as ``detected'' contaminants in the CCR.
Reporting these measurements in the CCR will allow customers to
understand that the contaminant was detected in the water supply. While
measurements below the PQL will not be used to calculate compliance
with MCLs for the final rule, measurements lower than the PQL are
achievable by individual laboratories, and therefore these measurements
can be used for screening, to determine compliance monitoring
frequency, and to educate consumers about the existence of PFAS (for
further discussion of PQLs for regulated PFAS, please see section VII
of this preamble). As such, the EPA believes that measurements below
the PQL can reasonably be reported as ``detected'' for purposes of the
CCR. This requirement is consistent with the CCR Rule in 40 CFR
141.153(d) which requires CWSs to report information on detected
contaminants for which monitoring was required by the EPA or the state.
The CCR reporting requirement includes unregulated contaminants for
which monitoring is required pursuant to the Unregulated Contaminant
Monitoring Rule (UCMR) as well as regulated contaminants in accordance
with SDWA (Safe Drinking Water Act) 1414(c)(4). If the system has
performed additional monitoring, the EPA strongly encourages them to
include the results in the CCR, consistent with 40 CFR 141.153(e)(3).
3. Final Rule
As part of this action, the EPA has modified the trigger level
value for quarterly monitoring from one-third of the MCL to one-half of
the MCL in response to concerns that laboratories would not have the
capacity to consistently measure as low as the threshold of one-third
of the MCL (for further discussion of the EPA's trigger levels for the
final rule, please see section VIII of this preamble). To reflect this
change in the trigger level, the EPA has modified 40 CFR 141.151(d),
which identifies what is considered detected
[[Page 32620]]
for purposes of reporting in CCRs consistent with SDWA 1414(c)(4). The
EPA had also proposed adding a provision to require CWSs that detect
any PFAS above the MCL to include health effects language for PFAS and
stated in the preamble for the rule proposal that CWSs would be
required to report detected PFAS as part of their CCRs. Because SDWA
1414(c)(4)(B) specifies that the Administrator may only require health
effects language be reported in the CCR for situations other than an
MCL violation for not more than three regulated contaminants, the EPA
has removed the amendment to paragraph (g) of 40 CFR 141.154 included
in the proposed rule from the final rule and has instead updated
appendix O to part 141 for the final rule to only require CWSs that
have violations of the PFAS MCLs to include health effects language for
PFAS. Since systems must complete initial monitoring within three years
of rule promulgation, systems will be required to report results and
other required information in CCRs beginning with 2027 reports. As the
MCL compliance date is set at five years following rule promulgation,
systems will be required to report MCL violations in the CCR,
accompanied by the required health effects language and information
about violations, starting in 2029.
The EPA acknowledges the need to protect public health with clear
and concise language that outlines the risks associated with exposures
exceeding the MCLs and Hazard Index. The EPA's broad review of the most
current research provides a comprehensive understanding of how exposure
to PFAS may result in adverse impacts on the health of individuals. In
response to commenter requests for plain language explanations of the
Hazard Index, the EPA is adding the following definition of the Hazard
Index in 40 CFR 141.153(c)(3)(v) of the CCR Rule to improve clarity and
understandability for consumers (for more information on how the Hazard
Index is calculated for this rule, please see table to paragraph (b)
under 40 CFR 141.50):
Hazard Index or HI: The Hazard Index is an approach that determines
the health concerns associated with mixtures of certain PFAS in
finished drinking water. Low levels of multiple PFAS that individually
would not likely result in adverse health effects may pose health
concerns when combined in a mixture. The Hazard Index MCL represents
the maximum level for mixtures of PFHxS, PFNA, HFPO-DA, and/or PFBS
allowed in water delivered by a public water system. A Hazard Index
greater than one (1) requires a system to take action.
Additionally, in response to commenters' request for clearer
mandatory health effects language, the final rule includes revised
mandatory health effects language required as part of CCRs, in cases
when MCL violations have occurred.\10\ Identical mandatory health
effects language is also required for public notification (PN) under
the final rule (PN requirements are described further in section IX.B
of this preamble). The mandatory health effects language in the final
rule reads as follows:
---------------------------------------------------------------------------
\10\ The EPA has developed the existing mandatory health effects
language to communicate accurate, clear health information to a non-
technical audience. Although the EPA believes additional detail is
not necessary to include in the mandatory health effects language
which is required only where MCL violations have occurred, the EPA
also recognizes that, in general, a single exposure at a critical
time in development may produce an adverse developmental effect (see
USEPA, 1991a).
---------------------------------------------------------------------------
Health effects language for PFOA: Some people who drink water
containing PFOA in excess of the MCL over many years may have increased
health risks such as cardiovascular, immune, and liver effects, as well
as increased incidence of certain types of cancers including kidney and
testicular cancer. In addition, there may be increased risks of
developmental and immune effects for people who drink water containing
PFOA in excess of the MCL following repeated exposure during pregnancy
and/or childhood.
Health effects language for PFOS: Some people who drink water
containing PFOS in excess of the MCL over many years may have increased
health risks such as cardiovascular, immune, and liver effects, as well
as increased incidence of certain types of cancers including liver
cancer. In addition, there may be increased risks of developmental and
immune effects for people who drink water containing PFOS in excess of
the MCL following repeated exposure during pregnancy and/or childhood.
Health effects language for PFHxS: Some people who drink water
containing PFHxS in excess of the MCL over many years may have
increased health risks such as immune, thyroid, and liver effects. In
addition, there may be increased risks of developmental effects for
people who drink water containing PFHxS in excess of the MCL following
repeated exposure during pregnancy and/or childhood.
Health effects language for PFNA: Some people who drink water
containing PFNA in excess of the MCL over many years may have increased
health risks such as elevated cholesterol levels, immune effects, and
liver effects. In addition, there may be increased risks of
developmental effects for people who drink water containing PFNA in
excess of the MCL following repeated exposure during pregnancy and/or
childhood.
Health effects language for HFPO-DA: Some people who drink water
containing HFPO-DA in excess of the MCL over many years may have
increased health risks such as immune, liver, and kidney effects. There
is also a potential concern for cancer associated with HFPO-DA
exposure. In addition, there may be increased risks of developmental
effects for people who drink water containing HFPO-DA in excess of the
MCL following repeated exposure during pregnancy and/or childhood.
Health effects language for Hazard Index PFAS: Per- and
polyfluoroalkyl substances (PFAS) can persist in the human body and
exposure may lead to increased risk of adverse health effects. Low
levels of multiple PFAS that individually would not likely result in
increased risk of adverse health effects may result in adverse health
effects when combined in a mixture. Some people who consume drinking
water containing mixtures of PFAS in excess of the Hazard Index (HI)
MCL may have increased health risks such as liver, immune, and thyroid
effects following exposure over many years and developmental and
thyroid effects following repeated exposure during pregnancy and/or
childhood.
B. What are the Public Notification (PN) requirements?
1. Proposal
As part of SDWA, the PN Rule ensures that consumers will know if
there is a problem with their drinking water. Notices alert consumers
if there is risk to public health. They also notify customers: if the
water does not meet drinking water standards; if the water system fails
to test its water; if the system has been granted a variance; or if the
system has been granted an exemption (that is, more time to comply with
a new regulation).
All public water systems (PWSs) must give the public notice for all
violations of National Primary Drinking Water Regulations (NPDWRs) and
for other situations. Under the EPA's PN Rule, the public notice
requirements for each violation or situation are determined by the tier
to which it is assigned. The EPA specifies three categories, or tiers,
of PN requirements, to take into account the seriousness of the
violation or situation and any potential adverse health effects that
may occur (USEPA, 2000f). The
[[Page 32621]]
EPA proposed that violations of the three MCLs in the proposal be
designated as Tier 2 and as such, PWSs would be required to comply with
40 CFR 141.203. Per 40 CFR 141.203(b)(1), notification of an MCL
violation should be provided as soon as practicable but no later than
30 days after the system learns of the violation. The proposed rule
also designated monitoring and testing procedure violations as Tier 3,
which would require systems to provide notice no later than one year
after the system learns of the violation. The system would then be
required to repeat the notice annually for as long as the violation
persists.
2. Summary of Major Public Comments and EPA Responses
Many commenters support the Tier 2 PN requirement for MCL
violations. Commenters assert that Tier 2 notification is appropriate
and consistent with other MCLs for chemicals with chronic effects.
Conversely, many commenters suggest that the PN tiering be raised from
Tier 2 to Tier 1 or that the EPA consider other PN approaches given
concerns about health impacts resulting from exposure on timescales
shorter than chronic exposure. Commenters assert that raising PN for
MCL violations from Tier 2 to Tier 1 would ensure that consumers are
informed of potential harm associated with elevated PFAS levels in a
timelier manner so they can make informed risk management decisions.
Additionally, a few commenters request the EPA re-categorize repeat MCL
violations to Tier 3 due to the expected length of time needed for a
PWS to design and construct treatment. Commenters argue that quarterly
PN would not offer added value and could possibly result in confusion
for consumers.
The EPA agrees with commenters that Tier 2 PN is appropriate for
MCL violations based on analysis of a wide range of scientific studies
that shows that long-term exposure may have adverse health effects. The
EPA disagrees with commenters who recommend issuing Tier 1 notification
for MCL violations. Tier 1 notices must ``be distributed as soon as
practicable, but no later than 24 hours, after the public water system
learns of the violation'' pursuant to section 1414(c)(2)(C)(i) of SDWA.
The PN Rule preamble characterizes contaminants with violations
routinely requiring a Tier 1 notice as those with ``a significant
potential for serious adverse health effects from short-term
exposure'', stating that other violations do not require Tier 1 notice
because elevated levels of these contaminants are not ``strongly or
consistently linked to the occurrence of the possible acute health
effects'' (USEPA, 2000f). The EPA has not characterized health risks
resulting from acute exposure (i.e., < or = 24 hours) to PFAS and the
EPA believes that issuing Tier 2 PN for MCL violations constitutes a
health protective approach given that the MCLG values are based on
health effects that occur after chronic exposure to PFAS (i.e.,
cancer). Based on the available health effects information, the EPA has
characterized developmental effects, including immune impacts,
associated with developmental PFAS exposure in addition to health
effects that occur after chronic exposure. The agency considers it
reasonable to notify consumers within 30 days of a PWS learning of an
MCL violation because it generally provides protection of the adverse
health effects that may occur from exposure to PFAS during sensitive
lifestages such as gestation. The EPA typically reserves Tier 1
notifications for acutely toxic contaminants. For example, nitrate,
nitrite, or total nitrate and nitrite require Tier 1 notice because
exceedances can result in immediate life-threatening health impacts for
infants (i.e., methemoglobinemia). Based on the currently available
information, the developmental and chronic effects associated with
exposure to these PFAS are not known to represent immediate acute
health effects. For more information on the EPA's characterization of
health effects resulting from PFAS exposure, please see (USEPA, 2024c;
USEPA, 2024d). This approach is also consistent with the PN
requirements for other synthetic organic contaminants regulated under
SDWA. The EPA acknowledges that there may be instances in which it is
appropriate to elevate the tiering of PN on a case-by-case basis. Under
the existing PN Rule in 40 CFR 141.202(a), a violation that routinely
requires a Tier 2 notice but poses elevated risk from short-term
exposure may be elevated to Tier 1 at the discretion of the primacy
agency (USEPA, 2000f). Additionally, the EPA will develop appropriate
implementation guidance to assist in the understanding of PN
requirements among other final rule requirements.
The EPA disagrees with commenters that recommended reclassifying
ongoing MCL violations to Tier 3 for repeat notices. The EPA believes
there is sufficient flexibility in the existing PN Rule 40 CFR
141.203(b)(2) that allows primacy agencies to allow a less frequent
repeat notice on a case-by-case basis for unresolved violations, but no
less than once per year, and the determination must be in writing. The
EPA believes repeat notices are valuable to consumers that may not
receive the initial notice and allow water systems to provide any
updates to consumers, such as actions being taken to resolve the
situation and estimated timelines.
A few commenters recommended that the EPA update the proposed PN
health effects language. Commenters stated that the proposed health
effects language was confusing and needed to be clarified as it did not
sufficiently explain the health effects resulting from PFAS exposure.
Additionally, commenters stated that further clarifying the health
effects language would mitigate confusion from customers when receiving
PN from their water system.
The EPA agrees with commenters that additional explanation of the
health effects of PFAS exposure will more effectively communicate risk
to consumers when they receive PN from their water system. The EPA has
considered this input and has revised health effects language for the
final rule to further clarify the health effects associated with PFAS
exposure.
3. Final Rule
The final rule requires the PN of violations of all MCLs
promulgated under this final rule to be designated as Tier 2 and as
such, PWSs would be required to comply with 40 CFR 141.203. The final
rule also designates monitoring and testing procedure violations as
Tier 3, requiring systems to provide notice no later than one year
after the system learns of the violation. Systems are also required to
repeat the notice annually for as long as the violation persists. As
systems must comply with initial monitoring requirements within three
years of rule promulgation, systems will be required to provide Tier 3
notification for monitoring and testing procedure violations starting
in 2027. As the MCL compliance date is set at five years following rule
promulgation, systems will be required to provide Tier 2 notification
for MCL violations starting in 2029. However, the EPA acknowledges that
primacy agencies have the authority in the existing PN Rule (table 1 to
Sec. 141.201) to require systems to provide notices to consumers prior
to the MCL compliance date. The EPA encourages primacy agencies to use
this flexibility to require systems to provide notices to consumers for
PFAS detections that precede the date that MCL compliance will take
effect, as they deem appropriate. By encouraging systems to provide
timely notification, it
[[Page 32622]]
allows customers to take actions to protect their health, such as using
a filter, while systems take necessary steps to apply treatment.
With respect to violations and reporting associated with the
individual MCLs and Hazard Index MCL, the EPA recognizes that a utility
may have two or more of these PFAS present that, over the course of
four quarterly samples, may result in violation of multiple MCLs. For
example, if, following four quarterly samples, a utility has PFHxS and
HFPO-DA present and the RAA is above their respective MCLs and HBWCs of
10 ng/L, the system would be in violation of both the individual MCLs
for PFHxS and HFPO-DA, as well as the Hazard Index MCL. Issuing
multiple notifications (three in this example) for these violations may
cause public confusion as the adverse health effects and exposure
concern in this instance is not meaningfully different from either a
Hazard Index or individual MCL perspective. To simplify implementation
of PN in this scenario, the EPA is finalizing requirements in appendix
A to subpart Q of part 141 such that utilities who violate the Hazard
Index MCL and one or more individual MCLs because of the same compounds
can issue one notification to satisfy the PN requirements for the
multiple violations.
The EPA has also made edits to clarify the mandatory health effects
language required in the PN of an MCL violation, as well as the CCR.
The mandatory health effects language required for both PN and CCRs is
summarized in section IX.A.3 of this preamble above.
X. Treatment Technologies
Section 1412(b)(4)(E) of the Safe Drinking Water Act (SDWA)
requires that the agency ``list the technology, treatment techniques,
and other means which the Administrator finds to be feasible for
purposes of meeting [the MCL],'' which are referred to as best
available technologies (BATs). The EPA generally uses the following
criteria for identifying ``feasible'' BATs: (1) The capability of a
high removal efficiency; (2) a history of full-scale operation; (3)
general geographic applicability; (4) reasonable cost based on large
metropolitan water systems; (5) reasonable service life; (6)
compatibility with other water treatment processes; and (7) the ability
to bring all the water in a system into compliance. Section
1412(b)(4)(E)(ii) of SDWA requires that the agency identify small
system compliance technologies (SSCTs), which are affordable treatment
technologies, or other means that can achieve compliance with the
maximum contaminant level (MCL).
In the proposed rule, the EPA requested comments on: technologies
designated as BATs, costs associated with nontreatment options; whether
employing these treatment technologies are sound strategies to address
PFAS as well as whether the BATs could feasibly treat to below the
proposed MCLs; the type of assistance that would help public water
systems (PWSs); potential benefits from co-removal; treatment residual
disposal estimates; the capacity to address the increased demand for
BATs as well as residuals disposal or reuse; impacts that PFAS
residuals disposal may have in communities adjacent to the disposal
facilities; the most appropriate disposal means for PFAS contaminated
residuals and waste the systems may be generating; and SSCT selection
as well as national affordability analysis, specifically on the
methodologies.
A. What are the best available technologies?
1. Proposal
The agency proposed GAC, AIX, NF, and RO as BATs for the six PFAS
under consideration in the proposed rule. The EPA also acknowledged
that there are nontreatment options which may be used for compliance
such as replacing a PFAS-contaminated drinking water source with a new
uncontaminated source. The EPA also stated that conventional and most
advanced water treatment methods are ineffective at removing PFAS.
2. Summary of Major Public Comments and EPA Responses
The vast majority of comments germane to the BAT designations
support the EPA's designation of granular activated carbon (GAC), anion
exchange resins (AIX), and high-pressure membranes (nanofiltration (NF)
and reverse osmosis (RO)) as BATs that are technologically feasible for
treating drinking water to the proposed standards or below. Many
commenters shared practical experience with installed treatment
including successes, costs, implementation considerations, challenges,
and other areas. The EPA agrees that GAC, AIX, RO, and NF are BATs and
consistent with the criteria outlined in the BAT/SSCT document for
identifying ``feasible'' treatment for PFAS in this rule, and the
comments providing information on practical full-scale experience with
these technologies further support for this finding.
A few commenters suggested either that the designated BATs could
not treat to or below the MCL or that not enough data was available to
support the conclusion that the BATs could treat to at or below the
proposed MCL. The EPA disagrees with these commenters based on the
history of full-scale use as documented in the Best Available
Technologies and Small System Compliance for Per- and Polyfluoroalkyl
Substances (PFAS) in Drinking Water document (USEPA, 2024l), the
information in the rule preamble, and in the comments that provided
full-scale data as well as case studies. For example, commenters
highlighted more than 45 military installations that have treated PFAS,
including those in this rule, successfully for more than 15 years, a
major water treatment company provided information on over 150
successful installations they had performed, and comments supported
that there are significant numbers of industrial users successfully
treating PFAS, including those in this rule. One commenter noted the
example of the Chemours Fayetteville facility which used GAC to
eliminate PFAS, including those in this rule, as high as 345,000 ng/L
and has reduced PFAS in effluent to non-detect levels for several PFAS.
Finally, the Water Quality Association reviewed proprietary performance
data from its accredited laboratory demonstrating that this standard is
feasible for the BATs selected to effectively remove the PFAS regulated
in this rule from drinking water.
Many commenters pointed out site-specific issues with particular
BATs. The EPA acknowledges that not every BAT represents the best
treatment option for an individual system and site-specific
considerations can limit BAT selection. For instance, residuals
management considerations can limit the choice of RO/NF; particularly
in states with limited water resources. While many commenters agreed
that high pressure membranes such as RO and NF can remove the six PFAS
included in the proposal, many commenters also suggested that high
pressure membranes may not be the most feasible treatment option for
some systems because of residual management considerations, which are
discussed in the residuals management section. There are, however,
documented RO/NF facilities for treating PFAS in California, Illinois,
North Carolina, and Alabama (USEPA, 2024l). In response to public
comment and residual management concerns surrounding high pressure
membrane technologies, the EPA has adjusted RO/NF's technology
projection compliance forecast to 0% in the EA. While the EPA
[[Page 32623]]
does not estimate any water systems will elect to install RO/NF to
comply with the PFAS rule, it remains a BAT for water systems to
consider. For additional details on the EPA's EA, please see section
XII.
The EPA also acknowledges that due to technical site-specific
considerations, some BATs may not be the best choice for particular
water types. PFAS treatment option selection should consider conditions
for a given utility including water quality, available space, disposal
options, and currently installed unit operations. AIX may be the
preferred technology for some utilities based on expected treatment
needs, while others may select GAC or other technologies. However, as
many commenters indicated, the BAT designations are appropriate for
water systems across the country.
Several commenters pointed out that GAC may release arsenic at
levels exceeding arsenic's MCL temporarily when installed and upon
changing media, deleteriously impacting finished water quality. While
the EPA has documented challenges surrounding GAC and arsenic (USEPA,
2024l), the EPA disagrees that the arsenic release poses an exposure
concern so long as appropriate procedures are followed. Those
procedures include discarding the initial bed volumes (BVs) after
installation or replacement of media. A bed volume is the volume of
liquid contained within a GAC contactor, it is the container volume
minus the solids volume and void space. The quantity of treated water
discarded can be significant (e.g., as high as 350 BVs as one commenter
noted). However, this amount of discarded water is low in comparison to
the normal service life between GAC replacement, which is approximately
84,000 BVs or approximately about 0.5% of the total treated volume. The
total water volume discarded is also low in comparison to water loss
through leaks across the United States, which account for about 15% of
treated water or what would be approximately 12,600 BV equivalents for
this system. While conserving water is a significant issue, the water
discarded due to GAC applications is relatively low. Systems can reduce
water discard associated with BAT implementation by using acid washed
and/or prerinsed GAC or using buffered/pre-flushed resins for AIX. Any
treatment technology can create problems if improperly maintained and
operated. Finally, GAC has been statutorily designated as ``feasible
for the control of synthetic organic chemicals,'' such as PFAS, in SDWA
section 1412(b)(5).
The EPA received many suggestions for additional BATs including
powdered activated carbon (PAC), alternative sorbents, and new
destructive technologies. However, these alternative BATs proposed,
except for PAC, currently lack demonstrated full-scale removal of the
six PFAS under consideration. The EPA notes that there are some reports
of PAC use on a temporary basis and that it can reduce PFAS
concentrations in drinking water. PAC may be an appropriate choice of
technology in certain circumstances, however, its efficacy for trace
removal tends to be variable due to factors such as carbon particle
size, background organics, and plant efficiency. Therefore, PAC is not
as effective as GAC overall, and the agency has not designated it as a
BAT. The EPA periodically reevaluates treatment technologies and may
add additional technologies based on updated information. It is
important to note that water systems may use any technology or practice
to meet the PFAS MCLs and are not limited to the BATs in this rule.
Other technologies may be chosen in lieu of BAT because they may be
more cost effective or better suited to the specific operating
conditions of the particular site to meet the MCL. Electing not to use
a BAT, however, means that a system will not be eligible for a variance
under SDWA section 1415(a)(1)(A). For example, if a facility does not
install GAC where it is the designated BAT, but uses PAC instead, and
fails to meet the MCL, the facility would not be eligible for a
variance under SDWA section 1415(a)(1)(A). On the other hand, the same
facility may be eligible for an exemption under SDWA section 1416 if,
for example, GAC could not be installed due to an inability to obtain
financing and PAC was used instead, and the facility failed to meet the
MCL.
Many commenters pointed out the need for increased research,
technological innovation, and guidance in treating drinking water for
PFAS. The available information is sufficient to finalize the BATs as
proposed but the EPA agrees that more research may be beneficial
(USEPA, 2022c). With respect to the EPA's request for public comment on
additional guidance materials that would be helpful to support
successful technical implementation of the rule, the EPA received many
comments related to the need for technical materials to support rule
implementation. The agency plans to collaborate with states, technical
assistance providers, industry associations and interested
stakeholders, including small systems, following the rule promulgation
to provide technical materials that can assist water systems in
complying with the regulations. The EPA is currently funding many
technical assistance efforts associated with PFAS, including supporting
treatment infrastructure projects through the Drinking Water State
Revolving Fund (DWSRF) and the Emerging Contaminant grant program as
designated and funded through the Bipartisan Infrastructure Law (BIL).
Many commenters supplied information related to capital as well as
operations and maintenance costs. Many commenters expressed concerns
over potential costs and capacity while some commenters expressed the
opposite opinion. These issues are further addressed in the EPA cost
analysis in section XII and within the EPA's Response to Public
Comments on the Proposed PFAS NPDWR (USEPA, 2024k). For additional
discussion regarding the feasibility of the final MCLs, please see
section V of this preamble above.
Many comments pointed to potential supply chain issues in both
material and technical capacity such as qualified personnel, including
certified operators. While there may be some supply chain issues in the
short-term, comments from BAT suppliers indicate excess capacity as
well as investment in production. Furthermore, while there may be
temporary difficulties in supply chain and technical capacity, the
structural demand increase is expected to lead to supply increases as
well as innovation such as proposed technologies which were not
designated as BATs. This has been historically demonstrated multiple
times in prior drinking water rules. For example, activated alumina was
listed as one of the BATs and a SSCT for arsenic removal in the Arsenic
Rule (USEPA, 2001), and acknowledgement was given to granular ferric
hydroxide media as a developing technology. While the granular ferric
hydroxide media was not selected as a BAT/SSCT at the time due to lack
of full-scale demonstration, these media became the predominant
approach to addressing arsenic: Rubel (2003) stated that new iron-based
materials could be ``employed economically on a spent media basis
without the incorporation of pH adjustment chemicals and equipment.''
McCullough et al. (2005) cited over a dozen demonstration sites across
the US implementing granular iron media treatment technologies,
providing further supporting evidence that new technologies evolved in
the wake of the Arsenic rule to provide more efficient and economical
treatment
[[Page 32624]]
systems. Additionally, the present statutory standard for ``best
available technology'' under 1412(b)(4)(D) represents a change from the
provision prior to 1986, which required the EPA to judge feasibility on
the basis of ``best technologies generally available'' (BTGA). The 1986
Amendments to the SDWA changed BTGA to BAT and added the requirement
that BAT must be tested for efficacy under field conditions, not just
under laboratory conditions. The legislative history explains that
Congress removed the term ``generally'' to assure that MCLs ``reflect
the full extent of current technology capability'' [S. Rep. No. 56,
99th Cong., 1st Sess. at 6 (1985)]. Read together with the legislative
history, the EPA has concluded that the statutory term ``best available
technology'' is a broader standard than ``best technology generally
available,'' and that this standard allows the EPA to select a
technology that is not necessarily in widespread use, as long as its
performance has been validated in a reliable manner. Indeed, the 1991
Lead and Copper Rule stated, ``as long as it has been tested beyond the
laboratory under full-scale conditions for other contaminants, and the
performance of the technology for lead and copper may reasonably be
projected based upon other available treatment data (i.e., laboratory
or pilot scale), the EPA believes the technology can be established as
BAT.''
With respect to the challenges raised by commenters surrounding
capital improvement, the EPA has provided compliance flexibility by
providing a two-year capital improvements extension of the MCL
compliance deadline allowed by section 1412(b)(10) of SDWA.
Additionally, the EPA will continue its research as well as outreach
efforts to help develop technical and operator capacities. For comments
and additional information regarding the implementation timeframe for
this rule, please see section XI.D.
Many commenters stated that permitting needs to be streamlined and
that more assistance should be proffered to primacy agencies,
utilities, and other interested stakeholders. While SDWA does not
require permits, state and local authorities often require permits for
the installation of treatment facilities at water systems. The EPA has
developed supporting rule documents such as the Best Available
Technologies and Small System Compliance for Per- and Polyfluoroalkyl
Substances (PFAS) in Drinking Water document (USEPA, 2024l) that can be
used to help permitting authorities develop more familiarity with these
technologies over time. After finalization of the PFAS National Primary
Drinking Water Rule (NPDWR), the EPA also intends to work with
stakeholders to provide support to utilities, primacy agencies, and
other interested parties to ensure successful rule implementation.
3. Final Rule
In the final rule, the EPA is codifying GAC, AIX, NF, and RO as
BATs. The record does not support including additional BATs at this
time. A BAT designation is informational, and while installation of the
BAT is a condition of a variance under section 1415(a)(1)(A), systems
without a variance are not required to use a BAT for MCL compliance.
The owner/operator of a PWS will need to consider site specific
circumstances as well as technical, economic, and local regulatory
considerations when choosing a compliance technology for this rule. To
address the challenges raised by commenters surrounding capital
improvement, the EPA has provided a two-year compliance extension for
capital improvements which is discussed in greater detail in section XI
(Rule Implementation and Enforcement) and will continue its research
efforts. The two-year capital improvement extension should also provide
time for development of technical capacities and qualified personnel
including certified operators. In response to public comment and in
acknowledgement of residuals management concerns surrounding high
pressure membrane separation technologies, the EPA is lowering RO/NF's
technology projection compliance forecast in the EA. For comments and
additional information related to the EPA's cost analysis, please see
section XII. For comments and additional information regarding the
implementation timeframe for this rule, please see section XI.D.
B. PFAS Co-Removal
1. Proposal
The EPA stated that AIX and GAC are effective at removing PFAS and
there is generally a linear relationship between PFAS chain length and
removal efficiency shifted by functional group. The EPA also notes that
perfluoroalkyl sulfonates (PFSA), such as PFOS, are removed with
greater efficiency than the corresponding perfluoroalkyl carboxylic
acid (PFCA), such as PFOA, of the same carbon backbone length.
Additionally, the compounds with longer carbon chains display a smaller
percentage decrease in average removal efficiency over time (McCleaf et
al., 2017). These same technologies also remove other long-chain and
higher carbon/higher molecular weight PFAS as well as total organic
carbon (TOC, DBP precursors). RO and NF may also remove other
contaminants including arsenic, TOC, and chromium-VI. In short, the EPA
noted that this regulation, if finalized, would result in a reduction
of the six PFAS proposed for regulation, other co-occurring PFAS, and
other co-occurring contaminants.
2. Summary of Major Public Comments and EPA Responses
A significant majority of commenters supported the EPA's position
that treatment technologies which remove PFAS provide ancillary
benefits by removing other known or potential contaminants. One
commenter disputed the ability of these technologies to provide
ancillary benefits, and others suggested that the EPA's proposed
regulation would provide only limited protection against the many PFAS
not under consideration in the rule. The EPA disagrees with the
commenters who state that the proposed regulation would not result in a
reduction in co-occurring PFAS and other contaminants. Burkhardt et al.
(2023) used a theoretical approach \11\ to estimate that all but one of
the PFAS that are quantified by EPA Methods 533 and 537.1 could be
economically removed by GAC in typical water qualities and that of 428
PFAS evaluated, 76-87 percent could be cost-effectively treatable. The
co-removal benefits are well documented in the scientific literature
and in the evidence submitted by public comment. The Best Available
Technologies and Technologies and Cost support documents summarize
literature demonstrating the co-removal capabilities of treatment
technologies.
---------------------------------------------------------------------------
\11\ While PFAS are often discussed as a group, the individual
PFAS species can have a range of different removal efficacies using
GAC. A theoretical approach for PFAS fills information gaps where
analytical methods do not exist for all PFAS and testing is
expensive and time consuming
---------------------------------------------------------------------------
Some commenters stated that treatment for one PFAS does not
inherently imply removal of other PFAS. The EPA agrees, as discussed in
the proposed rule preamble. In general, there is an inverse
relationship between treatability and toxicity which is tied to the
carbon backbone (Bellia et al., 2023). Generally, the longer the carbon
backbone length, the more easily the PFAS is removed by a given
treatment technology. For example, if PFOA (C8) is targeted for removal
by the water system, perfluorodecanoic acid (PFDA, C10) would most
likely be removed as well. However, the converse would not
[[Page 32625]]
be true (i.e., a system targeting PFNA (C9) removal would reduce PFHxA
(C6) to a lesser extent).
Some commenters suggested that co-removal would decrease the
removal efficiency of GAC or AIX and that removal efficiency of non-
target contaminants is lower than it could otherwise be. The EPA agrees
that the removal of non-targeted contaminants by GAC or AIX can lower
the PFAS removal efficiency; the agency has accounted for this
uncertainty in appendix N of the EA (USEPA, 2024e). The EPA also agrees
that targeting contaminants for removal will be more effective than
relying on other non-targeted removal. For example, a GAC facility
designed to remove PFAS will not be as effective at removing DBP
precursors as a facility designed for that; however, there will still
be co-removal of DBP precursors which may lead to a reduction in DBPs.
Ultimately, treatment facilities operate best when tailored to specific
contaminants or mixture of contaminants unique to that location. For
additional information on the EPA's co-benefit analysis, please see
section XII.
Some commenters expressed concern about co-removal taking
beneficial ions from water, specifically fluoride ions, and suggested
that would be an added cost to the rule. The EPA notes that fluoride
has a legally enforceable MCL of 4.0 mg/L, and a non-enforceable
secondary standard of 2.0 mg/L to prevent mild or moderate dental
fluorosis. The EPA also notes that while some PFAS do contain organic
fluorine bound to carbon, fluorine and fluoride are not the same. The
BATs identified for the removal of PFAS for drinking water are not
optimized for the removal of fluoride and do not necessarily provide
effective removal of naturally occurring fluoride. For example, GAC is
ineffective for fluoride removal at environmentally relevant pHs
(USEPA, 2024o).
Some commenters suggested that co-removal may make it more
difficult to dispose of materials left over from the drinking water
treatment processes, known as treatment residuals. For example, GAC may
remove and concentrate radon or other contaminants to such an extent
that the spent media is considered hazardous. The EPA believes that
removing hazardous constituents from drinking water is generally
beneficial even though it could complicate residual management. More
details on treatment residuals, are discussed in part C of this
section.
Some commenters also suggest more research may be beneficial to
understanding co-removal. The EPA agrees (USEPA, 2022c).
3. Final Rule
GAC, AIX, NF, and RO are codified in the final rule as BATs. As
discussed elsewhere in the record for this final rule, because of PFAS
co-occurrence and the ability for treatment technologies to co-remove
co-occurring PFAS and other contaminants, the EPA anticipates the final
rule will result in significant co-removal public health benefits in
addition to those benefits from removing the six PFAS being directly
regulated by this action.
C. Management of Treatment Residuals
1. Proposal
As part of the BAT evaluation, the EPA reviews full-scale studies
that fully characterize residual waste streams and disposal options.
The EPA found that the most likely management options for spent
material containing PFAS is reactivation for GAC, incineration for
spent IX resin, and for disposal of RO/NF retentate, treatment and
discharge via a NPDES compliant facility to surface water or, sanitary
sewer, or in limited circumstances, underground injection. Large
volumes of spent GAC and AIX containing PFAS are periodically generated
and must be removed which does not lend itself to on-site storage over
time. The EPA stated that the disposal options identified in the 2020
Interim PFAS Destruction and Disposal Guidance (USEPA, 2020d) are
landfill disposal, thermal treatment, and in limited circumstances,
underground injection.
The EPA recognizes that future actions through statutory
authorities other than SDWA may have direct or indirect implications
for the residuals from drinking water treatment. Future hazardous waste
listings for certain PFAS may limit disposal options for spent drinking
water treatment residuals containing PFAS and/or potentially increase
costs. A CERCLA designation as a hazardous substance does not restrict,
change, or recommend any specific activity or type of waste (USEPA,
2022l). The EPA evaluated the potential impact on PWS treatment costs
to PWSs associated with hazardous residual management should PFAS be
listed as a hazardous waste in the future. For comments and additional
information related to the EPA's cost analysis, please see section XII.
2. Summary of Major Public Comments and EPA Responses
While some commenters stated that more research can be beneficial
to further our understanding of managing PFAS treatment residuals,
others urged the EPA to proceed with this rulemaking as expeditiously
as possible in the interest of public health. Others argued that the
EPA should delay this action until the PFAS Destruction and Disposal
Guidance is updated. The National Defense Authorization Act for Fiscal
Year 2020, Public Law 116-92, section 7361, directs the EPA to revise
the PFAS Destruction and Disposal Guidance triennially; the new
destruction and disposal guidance is anticipated to be released
approximately concurrently with this rule and further revisions may be
expected before the effective dates for this rule. The EPA disagrees
that the projected significant and direct public health protections for
drinking water consumers in this rule should be delayed for the
revision of guidance on management of PFAS waste streams.
Many commenters expressed concern that not enough was being done to
manage spent drinking water treatment residuals containing PFAS at the
end of their useful working life and that residual management amounted
to media shifting (i.e., taking PFAS from water via sorption media then
landfilling that media does nothing to reduce the overall amount of
PFAS). Many commenters stated that landfills and thermal treatment
facilities can potentially be PFAS sources as the BATs in this rule are
separative as opposed to destructive technologies.
The EPA notes that from a mass balance perspective, PFAS removal
from drinking water is generally anticipated to result in lower
concentrations of PFAS in the environment. With appropriate controls,
landfills, and thermal treatment of PFAS contaminated media can
minimize PFAS releases to the environment (USEPA, 2020d). Sorptive
media can be incinerated or reactivated. There is also ongoing research
into destructive and sequestration technologies that may help quantify
the extent to which PFAS may be destroyed some of which is funded by
the EPA (USEPA, 2022c).
Furthermore, it is also important to distinguish between a
potential environmental release and a direct exposure. A PFAS release
does not inherently imply human exposure and a release is not
inherently risky to specific populations. From a risk management
perspective, while the EPA acknowledges that while each destruction and
disposal technology has limitations, a potential environmental release
under point source management is anticipated to be a more health
[[Page 32626]]
protective alternative than human exposure through drinking water.
Some commenters recommended the EPA consider additional destruction
and disposal technologies. The EPA notes that disposal and destruction
technologies are currently available to manage drinking water
residuals. The EPA appreciates the example destructive technologies,
and while beyond the scope of finalizing this NPDWR, the agency intends
to consider additional destruction and disposal technologies in future
destruction and disposal guidance.
Many commenters, including destruction and disposal trade
associations, stated there would be difficulties managing spent
residuals containing PFAS generated from drinking water treatment. In
contrast, other commenters stated that there was existing national
capacity and at least one company stated they were actively evaluating
investment for additional capacity to handle residuals. The record
demonstrates that there is existing national capacity to handle spent
drinking water residuals containing PFAS in a manner that minimizes
risk to human health. Destruction and disposal of PFAS-containing
materials is currently not subject to certain hazardous waste
regulation and therefore the materials may be managed in non-hazardous
and hazardous waste treatment and disposal systems (USEPA, 2020d).
Hazardous waste is regulated pursuant to RCRA authority 42 U.S.C. 6921-
6939 (also known as RCRA ``Subtitle C''). The regulatory definition of
hazardous waste is found in 40 CFR 261.3. PFAS are currently not a
listed hazardous waste or characterized as a hazardous waste, but a
PFAS-containing waste may meet the regulatory definition of hazardous
waste if PFAS is mixed with a listed hazardous waste or if a PFAS-
containing mixture exhibits a hazardous characteristic (e.g.,
corrosivity or another characteristic stemming from the material that
is mixed with PFAS). PFAS which are commingled with hazardous
substances and/or hazardous wastes will be subject to the appropriate
rules and regulations and may be included as Applicable or Relevant and
Appropriate Requirements on a site-specific basis. Not all disposal
sites may be appropriate for spent drinking water treatment residuals
containing PFAS and the EPA strongly encourages owners and operators of
treatment facilities to refer to appropriate and up-to-date guidance on
treatment residual management such as the 2020 Interim Guidance on the
Destruction and Disposal of Perfluoroalkyl and Polyfluoroalkyl
Substances and Materials Containing Perfluoroalkyl and Polyfluoroalkyl
Substances (USEPA, 2020d) and subsequent updates.
The EPA anticipates approximately 226,500 short tons of spent
drinking water media such as activated carbon and AIX resin to be
generated annually as a result of this rule; in calendar year 2018
alone, the U.S. generated about 290 million short tons of waste (USEPA,
2022m). The increase in total waste caused by this action is
approximately 0.08% of the total U.S. waste produced. This is a minor
change in aggregate waste produced; the same amount as a pound
contributes to a ton. Even if PFAS were to be designated in the future
as regulatory hazardous waste, there is existing capacity to handle
these waste streams through existing hazardous waste facilities in
every state. Some water systems may have to ship hazardous wastes
significant distances; however, the main cost driver is disposal fees
not transportation. The EPA rejects the assertion that it has not
evaluated if sufficient capacity exists for disposal and storage of
PFOA and PFOS contaminated materials. The EPA also acknowledges that
CERCLA section 104(c)(9) does not allow the agency to initiate a
remedial action, unless the state first enters into a state Superfund
State Contract or Cooperative Agreement (CA) that assures the
availability of adequate capacity to manage hazardous wastes generated
in the state for 20 years following the date of the response agreement.
The EPA's rulemaking designating PFOA and PFOS as CERCLA hazardous
substances, if finalized, does not impose any capacity concerns that
require further action under section 104(c)(9). In that action, the EPA
is designating PFOA and PFOS as CERCLA hazardous substances. No PFAS
are currently listed, or being proposed to be listed, as hazardous
wastes under RCRA. The 2021 Biennial Report Summary Results indicate
about 18 million tons of hazardous wastes are normally generated
annually. Drinking water treatment materials then would constitute
about a 1.26% increase in hazardous wastes generated annually. Since
there is over twenty years' capacity, the relatively small magnitude of
the increase indicates that waste management capacity is sufficient in
the short term should PFAS be designated as regulatory hazardous
wastes.
Many commenters conveyed concern over the cost of drinking water
residuals management resulting from finalizing this rule. The EPA
conducted an EA to help address these concerns. For comments and
additional information related to the EPA's cost analysis, please see
section XII.
While no PFAS are currently listed as regulatory hazardous wastes
under RCRA, in response to stakeholder feedback, the EPA included a
sensitivity analysis to determine the impact on water systems should
they be required to handle and dispose of PFAS treatment materials as
hazardous waste in the future. The results of this analysis can be
found in the EA for this rule (USEPA, 2024g). Some commenters suggested
that accounting for future potential regulations is uncommon, and
trying to account for all potential future contingencies would make
economic analyses impossible. The EPA strongly agrees and has not
attempted to do so here; this analysis was limited to looking at a
hypothetical future hazardous waste listing situation because that has
been of particular concern in this rule. Some commenters stated that
the EPA should account for the public health benefits of treating PFAS
as hazardous wastes, not just additional costs incurred. The EPA agrees
and has modified the analysis to include a qualitative statement about
the public health benefits which could potentially arise from treating
PFAS as hazardous wastes. Many commenters stated that the EPA hazardous
waste cost would drive the total cost higher than the 3-5% estimated by
the EPA. After considering public comment, the EPA has revised the
final cost estimates in this rule. The EPA estimated increased cost
would be approximately $99M at the 2% discount rate. The increased cost
was driven by updating the dollar year of cost curves from 2021 to 2022
which increased waste management unit costs by approximately 12%;
implementing a cap on media life even if not indicated; changing the
technology compliance forecast by eliminating RO/NF while increasing
GAC and AIX (thereby increasing spent media volume); and increasing
occurrence estimates for the final rule compared to the proposed rule,
triggering more systems into treatment. The increased costs were not
driven by changes to unit cost estimates for hazardous waste
management. The EPA believes its assessment is accurate; the total cost
encompasses capital costs, maintenance, design, and operations,
including waste management. Waste management costs are thus a subset of
operational cost which in turn is a subset of total costs; generally,
changes in the cost of one subcomponent would not significantly
influence total costs, and the record does not reflect that a change in
waste disposal costs would
[[Page 32627]]
have a significant impact on total costs under this rule. These
estimates are discussed in greater detail in the HRRCA section of this
rule and in appendix N of the EA (USEPA, 2024e).
Many commenters suggested that regulations under other statutes,
particularly a potential CERCLA hazardous substance designation, will
increase disposal costs. The EPA disagrees that, if finalized, the
CERCLA hazardous substance designation for PFOA and PFOS will increase
disposal costs for water treatment facilities. The designation of PFOA
and PFOS as CERCLA hazardous substances would not require waste (e.g.,
biosolids, treatment residuals, etc.) to be treated in any particular
fashion, nor disposed of at any specific particular type of landfill.
The designation also does not restrict, change, or recommend any
specific activity or type of waste at landfills. Along with other
release notification requirements, CERCLA designation would require
that any person in charge of a vessel or facility report a release of
PFOA and/or PFOS of one pound or more within a 24-hour period. The EPA
does not expect spent drinking water treatment residuals containing
PFAS to be released into the environment at or above the reportable
quantity as a part of standard residuals management practices used by
water systems. This is because the PFAS loading onto sorptive media is
very small. The weight percent of PFAS onto GAC under normal treating
scenarios will vary widely; however, a reasonable order of magnitude
estimate is 1 x 10-5 grams PFAS per gram of sorbent in full-
scale applications. High pressure membranes split water into a treated
stream and concentrated waste stream. The concentrated waste stream
will contain about 5-12 times more PFAS than the influent which is
likely to still be in the ng/L scale. A drinking water facility which
takes reasonable precautions is unlikely to release enough low
concentration residuals to release one pound of PFOA and/or PFOS within
a 24-hour period. At the concentrations discussed above, to exceed a
one-pound threshold, a facility using sorptive techniques would have to
release approximately 50 tons of sorbent, within a 24-hour period. A
one-pound uncontrolled release from RO or NF facilities, assuming 500
ng/L of PFAS in the reject water, would require approximately 240
million gallons of high-pressure membrane concentrate to be released
within 24 hours. Additionally, neither a release nor a report of a
release automatically requires any response action under CERCLA. The
EPA makes CERCLA response decisions based on site-specific information,
which includes evaluating the nature, extent, and risk to human health
and/or the environment from the release. Hazardous substance
designations do not automatically result in CERCLA liability for any
specific release. Whether an entity may be subject to litigation or
held liable under CERCLA are site-specific and fact-dependent
inquiries. Likewise, CERCLA affords the Federal Government broad
discretion as to whether or how to respond to a release. For those
reasons, the EPA cannot assess with reasonable certainty what
litigation or liability outcomes may indirectly result from this
designation since those outcomes are often linked to the EPA's
discretionary decisions with respect to CERCLA response actions as well
as site-specific and fact-dependent court rulings.
Many commenters suggested that high pressure membranes, which
separate PFAS from one stream and concentrate it in another stream, may
not be feasible as a BAT because utilities treating and discharging
reject water from high pressure membranes typically require a NPDES
permit. The EPA disagrees because there are currently full-scale
facilities which use this technology to treat PFAS and high-pressure
membranes may be the best viable option in a multi-contaminant setting.
The brine may undergo further pre-treatment as part of a process train
to enable discharge, such as GAC or AIX treatment. Some RO/NF
applications discharge directly to surface water or through an
interconnection to a wastewater treatment plant. The EPA, however, does
agree that brine treatment or disposal may be challenging and in 2022,
the EPA issued memorandum that recommended NPDES and POTW pretreatment
program permitting conditions for PFAS discharges (USEPA, 2022d; USEPA,
2022e). In conclusion, in limited applications, high pressure membranes
may still serve as a viable treatment strategy, such as for facilities
with access to brine treatment or disposal.
Some commenters suggested that reactivation was not permissible
under the 2020 Interim PFAS Destruction and Disposal Guidance or that
interim storage was required. Commenters are incorrect in their
interpretation of the plain language in that guidance. The guidance
does not state that reactivation or thermal treatment are prohibited.
The guidance does acknowledge a need for further refinement and
research and that interim storage may be an option if the immediate
dispensation of PFAS-containing materials is not imperative. However,
nowhere does that guidance mandate interim storage or prohibit other
forms of PFAS destruction and disposal.
3. Final Rule
The final rule does not specifically require any specific
destruction or disposal practices for spent media containing PFAS. The
EPA has considered residual waste streams and disposal options and
found that management options exist for treatment residuals containing
PFAS.
D. What are Small System Compliance Technologies (SSCTs)?
1. Proposal
Section 1412(b)(4)(E)(ii) requires that the agency identify SSCTs,
which are affordable treatment technologies, or other means that can
achieve compliance with the MCL. The EPA identified SSCTs using the
affordability criteria methodology developed for drinking water rules
(USEPA, 1998b) and proposed the following table which shows which of
the BATs listed above are also affordable for each small system size
category listed in section 1412(b)(4)(E)(ii) of SDWA.
[[Page 32628]]
[GRAPHIC] [TIFF OMITTED] TR26AP24.025
Point-of-use (POU) and point-of-entry (POE) were not listed as
compliance options because the regulatory options under consideration
require treatment to concentrations below the current NSF
International/American National Standards Institute (NSF/ANSI)
certification standard for POU device removal of PFAS. As the EPA has
determined that affordable SSCTs are available, the agency is not
proposing any variance technologies.
2. Summary of Major Public Comments and EPA Responses
Many commenters stated that the POU/POE water treatment industry
may already have multiple products that can reduce PFAS chemicals to
below the proposed MCL. Additionally, some commenters stated that the
influent used (i.e., the challenge water) to test these POU/POE
products often contains much higher concentrations of PFAS than would
normally be found in most source waters. Commenters also pointed out
that under NSF/ANSI, 53 and 58 certifications exist for total PFAS
(PFOA, PFOS, PFHxS, PFHxA, and PFDA), as well as PFHpA, PFHxS, and PFNA
individually. However, SDWA section 1412(b)(4)(E)(ii) requires that
SSCTs achieve compliance with the MCL or treatment technique. While
devices certified to the NSF/ANSI standards must be demonstrated to
significantly reduce PFAS concentrations and, in many cases, can
reasonably be expected to treat below this rule's MCLs, the current
standards and certification procedures do not assure compliance with
this rule. In particular, PFBS and HFPO-DA, have no certification
standards at this time and the certification standards for PFOA, PFOS,
and PFHxS are above this rule's MCL. The certification standards for
PFOA, PFOS, and PFHxS are 20 ng/L, compared to the MCLs of 4.0 ng/L for
PFOA and PFOS, as well as 10 ng/L for PFHxS; the total PFAS
certification standard is 20 ng/L effluent comprised of PFOA, PFOS,
PFHxS, PFHxA, and PFDA compared to a Hazard Index of 1 for mixtures of
PFHxS, PFNA, HFPO-DA and PFBS. Since the NPDWR has standards that NSF/
ANSI are currently unable to verify, POE/POU technologies could
potentially not achieve compliance contrary to SDWA section
1412(b)(4)(E)(ii) which requires that SSCTs achieve compliance with the
MCL. While POU/POE technologies may provide significant levels of
protection, and the EPA anticipates they will eventually comply with
the NPDWR, there is not yet a systematic verification process in place
for the level of protection provided by these devices. As mentioned in
the proposal, the EPA is aware that the NSF/ANSI Drinking Water
Treatment Unit Joint Committee Task Group is in the process of updating
their standards; should these future standards meet the NPDWR, the EPA
could revise the SSCT list to include POE/POU.
Many commenters also correctly pointed out numerous challenges
surrounding POU/POE as a compliance option for some PWSs such as
resident cooperation, operation and maintenance, monitoring, and
implementation of distributed treatment approaches. The EPA agrees
implementation of POU/POE as a compliance option for any NPDWR can be
challenging for some PWSs but also agrees with commenters who noted
that POU/POE can provide flexibility and compliance options to very
small water systems or certain NTNCWS such as schools, factories,
office buildings, and hospitals that provide their own water.
The EPA received many comments that other POU devices other than
RO/NF should be acceptable ways to meet the MCLs for small systems. For
instance, commenters noted that a combination GAC/AIX device with
filters could reduce PFAS concentrations to below the MCL values. The
EPA agrees and has changed wording in the final rule preamble and
related supporting documents that implied that only RO/NF POU devices
would be able to meet a future certification standard. The EPA notes
that for small systems, as long as the proposed POU/POE devices are
certified by an appropriate third-party certifier (e.g., ANSI/NSF) to
meet the regulatory MCL, they would meet the requirements of this
regulation. The EPA also received many requests to change the way data
was displayed in tables 20 and 22 of the proposed rule which summarized
proposed SSCTs for PFAS removal and total annual cost per household for
candidate technologies. In the proposal, the EPA wrote that this data
was ``Not Applicable'' because of the economies of scale for
centralized treatment. While the EPA still believes that a POU program
that large is likely to be impractical, the EPA has changed the way
this is displayed by replacing the term ``Not Applicable'' with ``Data
Unavailable.'' The EPA notes that neither of these changes imposes nor
relieves any rule requirements and only serve to recharacterize the way
the EPA reports available technologies.
The EPA asked for comment on the national level analysis of
affordability of SSCTs and specifically on the potential methodologies
presented in the EA for the proposed rule section 9.12. A couple of
commenters recommended the EPA not use median household income (MHI) in
the affordability analysis. The EPA decided to retain the MHI measure
of income in its primary national level SSCT affordability methodology,
and specifically use 2.5% of the MHI as the affordability threshold,
given the value is easily understandable and available, providing a
central tendency for income which is representative of a whole
community's ability to pay and is not unduly influenced by outlier
values. However, in this rule, the EPA
[[Page 32629]]
recognizes the value in examining alternative measures of a community's
ability to afford an SSCT, so the agency chose to include supplemental
analyses that use alternative metrics, specifically 1% of MHI, 2.5% of
lowest quintile income (LQI), and an analysis accounting for financial
assistance. See chapter 9.13.2 of the EA for more details. These
supplemental analyses help to characterize affordability when
considering the marginal impact, disadvantaged community groups, and
subsidization.
Some commenters stated that the data the EPA used to inform current
water rates from the 2006 Community Water System Survey (CWSS) is
outdated. While dated, the data from the 2006 CWSS remains the best
available dataset for this national level analysis and affordability
determination for the following reasons: (1) the CWSS survey used a
stratified random sample design to ensure the sample was representative
and (2) these responses can be extrapolated to national estimates since
the survey has a known sampling framework; and the data can be
organized by system size, source, and ownership (USEPA, 2020e).
Some commenters recommended the EPA extend the affordability
analysis to medium and large systems. The EPA disagrees with this
recommendation, as the purpose of this analysis is to determine if
available SSCTs are affordable, per SDWA section 1412(b)(4)C(ii).
Therefore, the EPA chose to continue to analyze small system
technologies rather than include medium and large systems.
Some commenters specifically disagreed with one of the EPA's
supplemental affordability analyses that examined the impact of the
rule when accounting for the financial assistance through BIL and other
sources that are generally available to small systems. These commenters
stated that the EPA should not assume that this funding will be
available or enough to cover the small system capital costs associated
with the rule. The EPA conducted this supplemental analysis in response
to the recommendations of the SAB, which stated, ``[i]f this funding is
readily available to many or most systems facing affordability
problems, it seems appropriate to take the availability of this funding
into account in determining national level affordability.'' (USEPA,
2002b) The EPA disagrees with these commenters as this significant
funding will be generally available, and the EPA continues its efforts
to help PWSs access it. It is therefore reasonable to consider the
burden reduction in the supplemental affordability analysis.
Some commenters disagreed with the EPA's affordability
determination because they stated it was based on inaccurate treatment
cost information. A couple of commenters presented their own estimates
for small system household costs and compared these estimates to the
EPA's affordability threshold and concluded the rule is unaffordable.
The EPA disagrees with many of the underlying assumptions in the
commenters' cost estimates which, on whole, result in overestimated
household costs, see section XII.A. These commenters cited cost
information that is not representative of the range of treatment costs
nationally, and the EPA disagrees with the commenter's cost model that
systematically overestimates capital operation and treatment costs. The
EPA updated the affordability analysis for the national affordability
determination using the updated treatment cost curves (discussed in
section XII.D) and found for systems serving between 25 and 500 people,
that the upper bound estimated annual household treatment costs for GAC
exceed the expenditure margin. Lower bound estimated annual household
treatment costs for GAC do not exceed the expenditure margin; for more
information see section XII. These exceedances are primarily driven by
capital costs and attributable to the use of high-cost materials (e.g.,
stainless steel) in the upper bound estimates. Systems using low-cost
materials, but with source water characteristics otherwise set to the
upper bound (e.g., influent PFAS at approximately 7,000 ng/L, influent
TOC at 2 mg/L), would fall below the expenditure margin. Although costs
increase in some scenarios, the increases are not significant enough to
change the conclusions about affordability. The small system compliance
technologies available to meet the requirements of the final rule are
affordable for all small systems when the technologies do not use the
high-end materials. Technologies that do not use high end materials may
be less durable but nonetheless are available for small systems and can
meet the requirements of the final rule. For more information on the
EPA's response to comments on treatment costs see section XII. The EPA
also disagrees that there are no affordable compliance technologies for
small systems as the EPA has demonstrated that SCCTs are available
below the affordability threshold using the best available peer
reviewed information to support the agency's cost estimates.
3. Final Rule
The final rule includes sorptive devices as well as combination
devices, should they meet third party verification standards and the
MCL. In USEPA, 2024l, the EPA also changed the way data are presented
by replacing the term ``Not Applicable'' with ``Data Unavailable'' in
response to public comment. Finally, the final affordability analysis
reflects updates made to the unit cost curves after considering public
comments. The EPA has determined that affordable SSCTs are available
that meet the requirements of the final rule (see table 6 to paragraph
(e) of 40 CFR 141.61).
The EPA's affordability determination for the final rule, using
long standing EPA methodology and supplemental affordability analyses
can be found in the EA chapter 9.12.
The EPA notes that POU RO devices are not currently listed as a
SSCT because the NPDWR requires treatment to concentrations below the
current NSF International/American National Standards Institute (NSF/
ANSI) certification standard for POU device removal of PFAS. However,
POU treatments are reasonably anticipated to become a compliance option
for small systems in the future if NSF/ANSI develop a new certification
standard that mirrors or is more stringent than the final regulatory
standards. Other third-party entities including NSF can independently
certify drinking water treatment units (DWTUs) that meet these
standards. NSF/ANSI is considering lowering its current standard to
levels closer to final standards in this NPDWR. Based on efficacy of
reverse osmosis technology, RO POU devices can reasonably be
anticipated to remove the majority of PFAS when they are properly
designed and maintained. Other POU devices (e.g., activated carbon) may
also meet future EPA PFAS regulatory limits. These devices would also
need third-party testing and certified against the regulatory
standards. Further, the EPA notes that water systems may use any
technology or practice to meet the MCLs promulgated in this NPDWR and
are not limited to the BATs nor SSCTs discussed in this section. Other
technologies or nontreatment options may be chosen in lieu of a BAT or
SSCT because they may be more cost effective or better suited to the
specific operating conditions of the particular site to meet any MCL.
[[Page 32630]]
XI. Rule Implementation and Enforcement
A. What are the requirements for primacy?
1. Proposal
SDWA section 1413 establishes requirements that primacy agencies
(states, Tribes and territories) must meet to have primary enforcement
responsibility (primacy) for its PWSs. These include: (1) adopting
drinking water regulations that are no less stringent than Federal
NPDWRs in effect under sections 1412(a) and 1412(b) of SDWA; (2)
adopting and implementing adequate procedures for enforcement; (3)
keeping records and making reports available on activities that the EPA
requires by regulation; (4) issuing variances and exemptions (if
allowed by the state) under conditions no less stringent than allowed
by SDWA sections 1415 and 1416; and (5) adopting and being capable of
implementing an adequate plan for the provision of safe drinking water
under emergency situations. The regulations in 40 CFR part 142 set out
the specific program implementation requirements for states to obtain
primacy for the Public Water System Supervision (PWSS) Program, as
authorized under section 1413 of the Act.
Under 40 CFR 142.12(b), all primacy agencies are required to submit
a revised program to the EPA for approval within two years of
promulgation of any final PFAS NPDWR or request an extension of up to
two years in certain circumstances. To be approved for a program
revision, primacy agencies are required to adopt revisions at least as
stringent as the revised PFAS-related provisions. To obtain primacy for
this rule, primacy applications must address the general requirements
specified in subpart B of part 142. The EPA proposed special primacy
requirements for the PFAS NPDWR (Sec. 142.16(r)), to outline
additional requirements for a primacy agency related to identifying its
plan for implementing the initial monitoring requirements.
2. Summary of Major Public Comments and EPA Responses
The EPA received one comment that most of the initial monitoring
may occur before primacy applications will be submitted, which are not
due until two years after final rule promulgation. A couple of
commenters assert that it is unclear why states are required to include
an initial monitoring plan in their primacy application and that states
will not be able to implement and demonstrate that this monitoring plan
is enforceable under state law until state regulations have been
promulgated. The EPA recognizes that some initial monitoring by water
systems may occur prior to a state, territory, or Tribe receiving the
EPA approval for primacy and agrees with the commentor that for states
to develop a monitoring plan that addresses when systems will be
scheduled to conduct initial monitoring is not a necessary requirement
for a primacy application. However, where states are approved for
primacy before the compliance date for the water systems, primacy
agencies should have procedures for evaluating whether data that a CWS
or NTNCWS submits to satisfy the initial monitoring requirements are
acceptable. It is therefore appropriate to require primacy agencies to
include in their primacy application a description of their procedures
for reviewing water system's use of pre-existing data to meet initial
monitoring requirements, including the criteria that will be used to
determine if the data are acceptable and the primacy agency's
procedures for ensuring water system compliance within the required
timeframes. The compliance deadline for this initial monitoring by
systems is three-years from promulgation, by which time primacy
agencies should have primacy or interim primacy. To address the
possibility that a state, Tribe, or territory may get an extension to
apply for primacy, the final rule provides that these special primacy
requirements are not applicable after the initial monitoring deadline
(i.e., three years after publication of the rule in the Federal
Register). When a primacy agency does not yet have primacy for a new
drinking water rule, an NPDWR is nonetheless applicable to water
systems and may be enforced by the EPA following the compliance dates
specified in Sec. 141.900(b).
3. Final Rule
The EPA is revising the requirements for primacy as proposed in 40
CFR 142.16(r) by removing the requirements to develop an initial
monitoring plan, although the EPA is finalizing the proposed
requirement for primacy agency procedures for ensuring all systems
complete the initial monitoring period requirements, including for
determining whether pre-existing data are acceptable, but clarifying
that these requirements would not apply after the deadline for initial
monitoring has passed (i.e., three years after publication of the rule
in the Federal Register). The EPA also corrected two grammatical
errors. In the final rule, the EPA requires that a PWS complete the
initial monitoring by three years following date of promulgation (for
additional discussion on monitoring and compliance requirements, please
see section VIII of this preamble). It is the EPA's expectation that
primacy agencies will have completed the requirements for primacy
within the two years (i.e., without an extension) and in that case,
they will have the authority in place to ensure that systems comply
with the initial monitoring requirements. If a primacy agency is
applying for primacy after the deadline for initial monitoring has
passed, then the requirement is no longer applicable. In that case, an
NPDWR is nonetheless applicable to water systems and implementation
would be overseen and enforced by the EPA consistent with any
agreements with the state pursuant to the primacy application extension
approval.
B. What are the record keeping requirements?
1. Proposal
The current regulations in 40 CFR 142.14 require primacy agencies
to keep records of analytical results to determine compliance, system
inventories, sanitary surveys, state approvals, vulnerability and
waiver determinations, monitoring requirements, monitoring frequency
decisions, enforcement actions, and the issuance of variances and
exemptions. The primacy agency record keeping requirements remain
unchanged and would apply to PFAS as with any other regulated
contaminant.
2. Summary of Major Public Comments and EPA Responses
The EPA received a few comments about the record keeping that
primacy agencies must maintain for compliance determinations and
reporting, storing PWS facility data, tracking monitoring schedules,
and keeping the public informed of the quality of their drinking water.
As noted in the comments, most primacy agencies rely on SDWIS,
developed by the EPA, to support this record keeping requirement. It
was recommended that the EPA develop a data system, either SDWIS or a
replacement, that is capable of fully managing the data associated with
the proposed rule. Further, it was recommended that the EPA develop
data management solutions such as a mechanism for migrating UCMR data
into SDWIS State to reduce or eliminate the burden of ensuring
compliance with the initial monitoring. The EPA agrees that appropriate
data management solutions are needed to effectively comply with SDWA
requirements; however, the agency does not believe
[[Page 32631]]
these systems must be available at the time of rule promulgation.
Additionally, while beyond the scope of this rulemaking itself, the EPA
is actively working on PFAS data management solutions, including DW-
SFTIES support and potentially updating the SDWIS suite of applications
to manage data reported from this rule.
3. Final Rule
The primacy agency record keeping requirements in 40 CFR 142.14
remain unchanged and would apply to PFAS as with any other regulated
contaminants. Water system recordkeeping requirements are referenced
within subpart Z in Sec. 141.904. In the final rule, the EPA updated
this regulatory text to cross-reference the record retention provisions
in Sec. 141.33. The EPA is developing the Drinking Water State-
Federal-Tribal Information Exchange System (DW-SFTIES) that will
support all SDWA drinking water rules. The EPA plans to continue to
provide support for necessary updates to SDWIS State, including for
reporting requirements for new rules, until the DW-SFTIES is in
production and in use by primacy agencies. SDWIS State support and
updates will continue until the DW-SFTIES Board recommends a sunset
date after DW-SFTIES is in production and in use by primacy agencies.
The EPA will evaluate the migration of UCMR data into the suite of
SDWIS applications.
C. What are the reporting requirements?
1. Proposal
Under 40 CFR 142.15, primacy agencies must report to the EPA
information regarding violations, variances and exemptions, enforcement
actions, and general operations of state PWS programs. The primacy
agency reporting requirements remain unchanged and would apply to PFAS
as with any other regulated contaminant. The water system reporting
requirements are mentioned in Sec. 141.904 and cross-reference the
reporting timeframes and provisions in Sec. 141.31.
2. Summary of Major Public Comments and EPA Responses
A few commenters recommended that the EPA provide Data Entry
Instructions within six months of the promulgation of the rule to allow
primacy agencies, particularly those that do not use SDWIS State, to
implement their data systems for reporting to the EPA, prepare their
PWS, and train staff. The EPA acknowledges this comment and will work
to develop Data Entry Instructions as soon as possible. One commentor
recommended that the EPA provide separate tracking of reporting and
monitoring violations. The EPA acknowledges this comment and will
consider this as data reporting tools are developed. A couple of
commentors recommended that the reporting and recordkeeping
requirements for compliance within the rule should provide an option
for not requiring the RAA to be reported by the laboratories if the
primacy agency performs the RAA calculations for the water system. In
addition, one commenter requested that the primacy agency calculate the
RAA, and another commentor inquired whether the EPA intended to allow
the water systems not to perform the RAA calculations if the primacy
agency performs the RAA calculations. The EPA disagrees with these
comments. To ensure that the water system has immediate knowledge of
their compliance status, the final rule requires that water systems
calculate the RAA and report this to the primacy agency. Primacy
agencies or laboratories may also calculate the RAA, to confirm the
results of the water system, but it is not a required reporting element
under this regulation. Lastly another commentor suggested that
utilities be required to report the occurrence and concentration of
other PFAS listed in the method (preferably 533) to facilitate data
collection and to better inform water treatment objectives. The EPA
notes that many water systems are currently collecting samples and
reporting monitoring data for 29 PFAS that can be measured with EPA
Methods 533 and 537.1 under UCMR 5 where EPA has the regulatory
authority.
3. Final Rule
The reporting requirements for primacy agencies under 40 CFR 142.15
remain unchanged and apply to PFAS as with any other regulated
contaminant. The EPA intends to develop and provide access to Data
Entry Instructions within one year after rule publication. The EPA will
follow the usual protocol of engaging with a State-EPA workgroup for
drafting the Data Entry Instructions. In this process, the EPA will
consider the use of separate monitoring and reporting violation codes,
like is used for the Revised Total Coliform Rule (RTCR). In this final
regulation, the cross-reference to the water system reporting
timeframes and provisions in Sec. 141.31 at the start of Sec. 141.904
is retained, and, at 40 CFR 141.904(b), table 2, the EPA requires water
systems to report PFAS RAAs to their primacy agency. As a general
process, the laboratory will conduct the analysis of the sample and the
system will use the result to calculate their RAA; the RAA calculation
may subsequently be completed by the primacy agency as a compliance
check. The EPA does recognize that state laboratories often directly
report results to the state as allowed in 40 CFR 141.31(c) and that
electronic reporting tools, such as the Compliance Monitoring Data
Portal (CMDP), may be used by systems to comply with this reporting
requirement.
D. Exemptions and Extensions
1. Proposal
Pursuant to SDWA section 1412(b)(10), the EPA proposed that all
systems must comply with the NPDWR three years after rule promulgation.
The EPA's proposal acknowledged that a primacy agency or the EPA may
grant an extension of up to two additional years to comply with an
NPDWR's MCL(s) if the primacy agency or the EPA determines an
individual system needs additional time for capital improvements. The
EPA stated that ``[a]t this time, the EPA does not intend to provide a
two-year extension nationwide.'' 88 FR 18689. The proposal also
discussed how a state which has primary enforcement responsibility may
exempt any individual system facing compelling factors, such as
economic factors, additional time to comply with any requirement
respecting an MCL of any applicable NPDWR under SDWA section 1416
(USEPA, 2023f).
2. Summary of Major Public Comments and EPA Responses
SDWA section 1412(b)(10) requires that a ``NPDWR shall take effect
``3 years after the date on which the regulation is promulgated unless
the administrator determines that an earlier date is practicable.''
Section 1412(b)(2) also authorizes ``the Administrator, or a State (in
the case of an individual system), may allow up 2 additional years to
comply with a maximum contaminant level . . . if the Administrator or
the State . . . determines that additional time is necessary for
capital improvements'' (emphasis added). Congress intended the
extension under this provision to allow for a total of five years to
comply with the MCL. Thus, if the EPA provides a two-year extension of
the MCL compliance deadline for all systems based on the need for
capital improvements, a state cannot provide an additional two-year
extension under section 1412(b)(10) for capital improvements but may
grant exemptions under section 1416
[[Page 32632]]
consistent with applicable requirements.
Many commenters, including utilities and state primacy agencies,
expressed difficulty in meeting the three-year compliance deadline.
Commenters expressed that it will be very challenging to both conduct
initial monitoring and take actions (e.g., installing treatment) to
comply with the MCL within three years. Many of these commenters shared
their on-the-ground experience in managing facilities that required
capital improvements and provided evidence that additional time is
needed to procure, design, pilot, permit, and ultimately construct
treatment systems. Additionally, several commenters provided evidence
of on-going labor and workforce challenges as well as recent experience
with supply chain difficulties to obtain materials necessary to design
and construct treatment facilities, which many attributed as a direct
or indirect result of the COVID-pandemic residual impacts (AWWA, 2023).
The agency has evaluated the data and information shared by
commenters regarding their experience with the time it takes to
implement capital improvement projects. The EPA estimates that
approximately 4,100-6,700 systems will be impacted by the MCLs in this
final rule. Based on the EPA's initial compliance forecast, the agency
anticipates that many of these systems will be installing advanced
treatment technologies to meet the final PFAS standards (for additional
discussion on the compliance forecast, please see section XII). The
treatment technologies listed as BAT for the final rule include GAC,
ion exchange resins, and centralized RO/NF (please see section X for
more information). To ensure cost effective compliance with the PFAS
MCLs, systems often need to evaluate their treatment technology options
as a first step. Several commenters have noted that this planning step
may include pilot studies with potential treatment systems, or it may
be limited to an evaluation of the raw water characteristics. Further,
some commenters have submitted data and project management plans for
systems choosing to conduct pilot testing, indicating that it may take
a year or more to contract with vendors and to perform pilot testing.
Once the planning step is completed, systems must design and construct
the treatment systems. Several commenters submitted information to the
EPA indicating that the design and permitting of the treatment systems
can take an additional year or longer, and construction of the
treatment system can take another year or longer. Because systems will
also need time to obtain funding, obtain local government approval of
the project, or acquire the land necessary to construct these
technologies, many commenters contend that systems will need additional
time beyond the three-year effective date to comply with the MCLs.
While the EPA stated in the proposed rule that the agency did not
intend to provide a two-year extension nationwide necessary for capital
improvements, the EPA finds that the evidence submitted by commenters
strongly supports that a significant number of systems covered by this
rule will need two additional years to make capital improvements to
meet the MCL. Specifically, the EPA reviewed data from applicants
seeking DWSRF funding for capital improvement projects (e.g.,
installation of advanced treatment technologies such as GAC or IX) and
confirmed that these projects, on average, take about three or more
years to complete (which excludes the time and activities that may
occur to ensure these capital improvement projects are implemented
successfully, such as the time it may take to secure funding or to
conduct pilot testing). This evidence along with the breadth of
practicable experience shared by utilities and primacy agencies
demonstrate that additional time is necessary for a significant number
of system sizes and types located throughout the country to make
capital improvements. Additionally, the EPA notes that the number of
systems estimated to be impacted by the MCLs are greater than what the
agency anticipated in the proposal (i.e., an increase from 3,400-6,300
systems to 4,100-6,700 systems nationally). This increase provides
further evidence that a capital improvement extension is warranted as
the agency expects that many of these systems will be installing
advanced treatment technologies to meet the final PFAS standards. The
agency also agrees with commenters that on-going labor and workforce
challenges exist and can limit the ability to design, construct and
operate treatment facilities. These workforce challenges facing water
utilities and other sector organizations support the need for a capital
improvement extension as a sufficient availability of qualified
personnel is necessary to implement and sustain capital improvement
projects. These issues may be attributed as a direct or indirect result
of the recent COVID-19 pandemic and are clearly documented in data
submitted to the agency as part of the public comment process (AWWA,
2023). Based upon these considerations, the EPA determined, in
accordance with section 1412(b)(10) of SDWA, that the compliance date
for the PFAS MCLs, regardless of system size, will be 5 years from the
date of promulgation of the standard.
Some commenters recommend the EPA to follow a staggered
implementation timeframe similar to what was done in some previous
NPDWRs where compliance deadlines were staggered based on system size
(USEPA, 2001; USEPA, 2006a). In these prior examples, larger systems
typically conducted their monitoring and implemented the MCL first,
followed by smaller systems. Upon consideration of information
submitted by commenters, particularly issues related to supply chain
complications that are directly or indirectly related to the COVID-19
pandemic residual challenges, the EPA has determined that a significant
number of systems subject to the rule, including large systems, will
require two additional years to complete the capital improvements
necessary to comply with the MCLs for PFAS regulated under this action.
For this reason, the EPA disagrees with commenters that staggered
implementation based on system size is warranted for this rule. While
large systems may have greater resources to implement capital
improvements (e.g., engineering and construction management staff to
manage the projects), they still require time to design, pilot, permit,
and construct treatment facilities.
Some commenters note that it will be challenging for systems to
conduct their initial monitoring and install treatment within three
years, particularly for those systems not conducting UCMR 5 monitoring
that is ongoing until 2026. The EPA notes that the agency is finalizing
a flexibility for systems to use previously acquired monitoring data
from UCMR 5 or an equivalent state-led monitoring program for their
initial monitoring which is intended to alleviate the burden placed on
water systems in collecting additional data (see section VIII of this
preamble for additional information on monitoring). While the agency
agrees that systems need an additional two years to make capital
improvements, the EPA finds that it is practicable for most systems to
complete their initial monitoring within three years because all
systems serving greater than 3,300 people will have appropriate
monitoring data from UCMR 5. Many systems smaller than 3,300 people
will also have appropriate monitoring data from state-led
[[Page 32633]]
monitoring programs that may be eligible to meet the rule's initial
monitoring requirements, and some will have UCMR 5 or other data. If
systems find elevated levels of PFAS, these systems have an additional
two years to comply with the MCL. If a system does not have eligible
previously collected monitoring data and are concerned about
insufficient time to install capital improvements, the EPA encourages
these facilities to collect monitoring data as soon as possible after
rule promulgation, allowing them the bulk of the five-year period to
plan for and install any capital improvements if necessary.
Some commenters point to concerns regarding laboratory capability
and capacity in supporting the proposed three-year compliance timeline.
Additionally, a couple of commenters noted that if additional time were
allowed, water systems that are close to the MCL may have time to
identify and address sources of PFAS in their watersheds rather than
investing resources on treatment initially. Finally, a couple of
commenters recommend the EPA consider implementation flexibilities for
small and rural water systems and suggest that these types of utilities
may not have staff capacity nor expertise to compete for funding to
implement the rule. The EPA notes that these issues are not directly
related to capital improvements and thus were not the basis for the
EPA's decision to extend the compliance date for the PFAS MCLs.
Although the EPA disagrees with assertions about insufficient
laboratory capacity and capability at this time to support
implementation of the NPDWR, to the extent there are initial
implementation issues just after promulgation, extending the compliance
date will also provide ancillary benefits toward addressing any such
laboratory capability and capacity issues and may provide opportunities
for systems who are close to exceeding the MCLs to investigate sources
of contamination. Additionally, the extended compliance deadline may
give smaller and rural water utilities more time to apply for funding
under BIL (please see section II of this preamble above for a
discussion on BIL). Further, other assistance programs such as the
Environmental Justice Thriving Communities Technical Assistance Centers
may provide additional fundamental training and capacity building
activities for underserved and overburdened communities toward
navigating Federal grant applications and managing funding
opportunities.
The EPA requested comment as to whether there are specific
conditions, in addition to the statutory conditions, that should be
mandated for systems to be eligible for exemptions from the PFAS NPDWR
under SDWA section 1416. Several commenters requested the EPA provide
additional guidance to primacy Agencies on when exemptions are
appropriate under SDWA section 1416 similar to what was done for the
final Arsenic NPDWR (USEPA, 2002c). The EPA is not issuing additional
guidance around implementation of SDWA section 1416 at this time but
may consider it in the future. The EPA notes primacy agencies who have
adopted the 1998 Variance and Exemptions Regulation (USEPA, 1998c) may
choose to grant exemptions consistent with the requirements under this
regulation to encourage systems facing compelling circumstances to come
into compliance with the MCLs in an appropriate period of time.
3. Final Rule
Pursuant to SDWA section 1412(b)(10), the final PFAS NPDWR is
effective June 25, 2024. The compliance date for the PFAS NPDWR, other
than the MCLs, is April 26, 2027. As discussed above and upon
consideration of information submitted by commenters, the EPA is
exercising its authority under SDWA section 1412(b)(10) to implement a
nationwide capital improvement extension to comply with the MCLs. All
systems must comply with the MCLs by April 26, 2029. All systems must
comply with other requirements of the NPDWR, including initial
monitoring, by April 26, 2027.
Systems must comply with initial monitoring requirements within
three years of rule promulgation and will be required to summarize PFAS
monitoring results and applicable information beginning with CCRs
delivered in 2027. As the MCL compliance date is set at five years from
rule promulgation, systems must report MCL violations in the CCR,
accompanied by the required health effects language and information
about violations, starting in 2029. Monitoring and testing procedure
violations require Tier 3 notification: systems must provide notice no
later than one year after the system learns of the violation. Systems
must repeat the notice annually for as long as the violation persists.
Systems must comply with initial monitoring requirements within three
years of rule promulgation and systems must provide Tier 3 notification
for monitoring and testing procedure violations starting in 2027. As
the MCL compliance date is set at five years from rule promulgation,
systems must provide Tier 2 notification for MCL violations, starting
in 2029. For more information on SDWA Right-to-Know requirements,
please see section IX of this preamble above.
The agency notes that SDWA section 1416(a) and (b)(2)(C) describe
how the EPA or states may also grant an exemption for systems meeting
specified criteria that provides an additional period for compliance.
PWSs that meet the minimum criteria outlined in the SDWA may be
eligible for an exemption from the MCLs for up to three years. For
smaller water systems (<=3,300 population), exemptions can provide up
to six additional years to achieve compliance with the MCLs. States
exercising primacy enforcement responsibility must have adopted the
1998 Variance and Exemption Regulation (USEPA, 1998c) for water systems
in those jurisdictions to be eligible for an exemption.
XII. Health Risk Reduction and Cost Analysis
This section summarizes the final rule Health Risk Reduction and
Cost Analysis (HRRCA) supporting document (USEPA, 2024g) for the per-
and polyfluoroalkyl substances (PFAS) National Primary Drinking Water
Regulation (NPDWR), which is prepared in compliance with section
1412(b)(3)(C) of the Safe Drinking Water Act (SDWA) and under Executive
Order (E.O.) 12866. Section 1412(b)(3)(C)(i) lists the analytical
elements required in a HRRCA applicable to an NPDWR that includes a
Maximum Contaminant Level (MCL). The prescribed HRRCA elements include:
(1) Quantifiable and nonquantifiable health risk reduction
benefits;
(2) quantifiable and nonquantifiable health risk reduction benefits
from reductions in co-occurring contaminants;
(3) quantifiable and nonquantifiable costs that are likely to occur
solely as a result of compliance;
(4) incremental costs and benefits of each alternative MCL
considered;
(5) effects of the contaminant on the general population and
sensitive subpopulations including infants, children, pregnant women,
the elderly, and individuals with a history of serious illness;
(6) any increased health risks that may occur as a result of
compliance, including risks associated with co-occurring contaminants;
and
(7) other relevant factors such as uncertainties in the analysis
and factors with respect to the degree and nature of the risk.
Based on this analysis, the Administrator confirms the finding
[[Page 32634]]
made at proposal under section 1412(b)(4)(C) of SDWA that the
quantified and nonquantifiable benefits of the MCLs justify the costs.
The complete HRRCA for the final NPDWR is commonly referred to as the
``Economic Analysis'' (or EA) in this final rule and can be found in
the docket at USEPA (2024g).
Because this NPDWR is promulgated in 2024 and provides a 2-year
nationwide extension of the date for MCL compliance, the EA assumes
that capital improvements (i.e., installation of treatment
technologies) for systems taking action under the rule will be
completed by five years from the date promulgated, or in 2029. All
other requirements, including initial monitoring, are assumed to be
completed within three years of rule promulgation, or by 2027. Based on
an assumed mean human lifespan of 80 years, the Environmental
Protection Agency (EPA) evaluates costs and benefits under the final
rule through the year 2105.
The EPA selected this period of analysis to capture health effects
from chronic illnesses that are typically experienced later in life
(i.e., cardiovascular disease [CVD] and cancer). Capital costs for
installation of treatment technologies are spread over the useful life
of the technologies. The EPA does not capture effects of compliance
with the final rule after the end of the period of analysis. Costs and
benefits discussed in this section are presented as annualized present
values in 2022 dollars. The EPA determined the present value of these
costs and benefits using a discount rate of 2 percent, which is the
discount rate prescribed by the Office of Management and Budget (OMB;
OMB, 2023). All future cost and benefit values are discounted back to
the initial year of the analysis, 2024, providing the present value of
the cost or benefit.
Estimates of PFAS occurrence used for cost-benefit modeling rely on
a Bayesian hierarchical estimation model of national PFAS occurrence in
drinking water (Cadwallader et al., 2022) discussed in section VI.E. of
this preamble. The model was fitted using sample data from systems
participating in PFAS sampling under the third Unregulated Contaminant
Monitoring Rule (UCMR 3) and included all systems serving over 10,000
customers and a subset of 800 smaller systems. A best-fit model was
selected using sample data to define occurrence and co-occurrence of
perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS),
and perfluorohexane sulfonic acid (PFHxS \12\) in water systems
stratified by system size and incorporating variations within and among
systems. Sample data were derived from state-level datasets as well as
from UCMR 3. For more information on the EPA's occurrence model, please
see section VI.E. of this preamble.
---------------------------------------------------------------------------
\12\ The EPA notes that perfluoroheptanoic acid (PFHpA) is not
included in the proposed or final PFAS NPDWR; however, it was
included in the occurrence model because of its UCMR 3 occurrence
data availability; please see Cadwallader et al., 2022 for
additional details.
---------------------------------------------------------------------------
In the EA, the EPA analyzes the costs and benefits of the final
rule, which includes MCLs for PFOA and PFOS at 4.0 ng/L each and MCLs
for PFHxS, perfluorononanoic acid (PFNA), and hexafluoropropylene oxide
dimer acid (HFPO-DA) at 10 ng/L each and a unitless Hazard Index (HI)
of 1 for any mixtures of PFHxS, PFNA, HFPO-DA, and PFBS. The EPA also
analyzed the costs and benefits for several regulatory alternatives.
The EPA analyzed the costs and benefits of setting individual MCLs for
PFOA and PFOS at 4.0 ng/L, 5.0 ng/L, and 10.0 ng/L, referred to as
regulatory alternative MCLs under option 1a, option 1b, and option 1c,
respectively. The EPA assessed these regulatory alternative MCLs in the
EA to understand the impact of less stringent PFOA and PFOS MCLs.
Additionally, the EPA has separately estimated national level marginal
costs associated with the individual MCL for PFHxS if this MCL were to
be promulgated in the absence of the Hazard Index; see chapter 5.1.3 of
the EA for details. The EPA has also estimated the marginal costs for
the individual PFNA and HFPO-DA MCLs if there were no Hazard Index in
the sensitivity analysis found in appendix N.4. The EPA notes that the
costs for the individual PFHxS, PFNA, and HFPO-DA MCLs have been
considered in this final rule.
Section A summarizes public comments received on the EA for the
proposed rule and the EPA's responses to comments. Section B summarizes
the entities which would be affected by the final rule and provides a
list of key data sources used to develop the EPA's baseline water
system characterization. Section C provides an overview of the cost-
benefit model used to estimate the national costs and benefits of the
final rule. Section D summarizes the methods the EPA used to estimate
costs associated with the final rule. Section E summarizes the
nonquantifiable costs of the final rule.\13\ Section F summarizes the
methods the EPA used to estimate quantified benefits associated with
the final rule. Section G provides a summary of the nonquantifiable
benefits associated with reductions in exposure to both PFOA and PFOS
expected to result from the final rule. Section H provides a
qualitative summary of benefits expected to result from the removal of
PFAS included in the Hazard Index component of the final rule and
additional co-removed PFAS contaminants. Section I of this preamble
summarizes benefits expected to result from the co-removal of
disinfection byproducts (DBPs). Section J provides a comparison of cost
and benefit estimates. Section K summarizes and discusses key
uncertainties in the cost and benefit analyses. Quantified costs and
benefits for the final rule and regulatory alternative MCLs under
options 1a-1c are summarized in section XII.J, specifically Tables 68-
71. Tables 72-73 summarize the non-quantified costs and benefits and
assess the potential impact of nonquantifiable costs and benefits on
the overall cost and benefit estimates for the final rule.
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\13\ This section includes costs with generally greater
uncertainty that the EPA assesses in quantified sensitivity
analyses.
---------------------------------------------------------------------------
A. Public Comment on the Economic Analysis for the Proposed Rule and
EPA Response
1. Methods for Estimating Benefits
a. Methods for Estimating Benefits in the Proposed Rule
In the EA for the proposed rule, the EPA presented quantified and
nonquantifiable health benefits expected from reductions in PFAS
exposures. Quantified benefits are assessed as avoided cases of illness
and deaths (or morbidity and mortality, respectively) associated with
exposure to some of the regulated PFAS contaminants. The EPA provided a
quantitative estimate of CVD, birth weight, and renal cell carcinoma
(RCC) avoided morbidity and mortality associated with reductions in
PFOA and PFOS consistent with the proposed rule. The EPA also developed
a quantitative analysis for reductions in bladder cancer morbidity and
mortality that stem from removal of DBP precursors as a function of
PFAS treatment. Adverse human health outcomes associated with PFAS
exposure that cannot be quantified and valued are assessed as
nonquantifiable benefits.
The EPA qualitatively summarized potential health benefits
associated with reduced exposure to PFAS other than PFOA and PFOS in
drinking water. In the proposal, the EPA discussed non quantified
benefits associated with health endpoints including developmental
effects, cardiovascular effects, hepatic effects, immune effects,
[[Page 32635]]
endocrine effects, metabolic effects, renal effects, reproductive
effects, musculoskeletal effects, hematological effects, other non-
cancer effects, and COVID-19.
b. Summary of Major Public Comments on Method for Estimating Benefits
and EPA Responses
Overestimation of Quantified Benefits
The EPA received comments from industry groups and organizations
representing water utilities about the EPA's methodology for estimating
quantitative benefits associated with the NPDWR. While some commenters
supported the EPA's analysis, a few commenters stated that the agency
overestimated quantified benefits. These commenters asserted that the
EPA overstated the benefits of the rule and that the HRRCA is flawed
because the existing health evidence does not support the quantified
benefits. The EPA disagrees with commenters that the existing evidence
does not support the EPA's estimate of quantified benefits from avoided
adverse health effects likely to occur as a result of treatment and
that these benefits are overstated. Among other things, the EPA has
used the best available science in three key respects: by (1)
considering relevant peer-reviewed literature identified by performing
systematic searches of the scientific literature or identified through
public comment, (2) relying on peer-reviewed, published EPA human
health risk assessment methodology (USEPA, 2022f), and (3) utilizing
peer-reviewed methodologies to valuing and quantifying avoided adverse
health outcomes. Specifically, the EPA identified the full range of
expected human health outcomes, including quantified benefits
associated with co-removal of co-occurring contaminants (i.e., DBPs).
This process was built upon multidisciplinary research, including
hazard identification and dose-response analysis, exposure assessment,
and economic valuation methods recommended by the EPA's Guidelines for
Preparing Economic Analyses (USEPA, 2016e) and updated Circular A-4
Guidance (OMB, 2023) to enumerate all beneficial outcomes, identify
beneficiaries, and determine human health endpoints that can be valued.
The EPA notes that the benefits analysis contains uncertainties
associated with the modeling inputs in each of the steps listed above.
In accordance with OMB Circular A-4 guidance (OMB, 2023), the EPA
characterizes sources of uncertainty in its quantitative benefits
analysis and reports uncertainty bounds for benefits estimated for each
health endpoint category modeled in the final rule. See Table 75 and
also section 6.1 of the EA for the final rule (USEPA, 2024g) for the
list of quantified sources of uncertainty in benefits estimates. The
reported uncertainty bounds reflect the best available data on health
effect-serum slope factors, baseline PFAS occurrence, population size
and demographic composition, and the magnitude of PFAS concentration
reductions. In addition, some model inputs did not have sufficient
distributional data to be included in the quantitative uncertainty
analysis, and there are also uncertainties that could not be assessed
quantitatively. These sources of uncertainty are described in Table 62
and also in section 6.8 of the EA for the final rule (USEPA, 2024g).
Although some imprecision in the estimated benefits may be expected due
to the lack of perfect information, the EPA has demonstrated, using the
best science and data available, that there is sufficient health
evidence to support the estimation of quantified benefit values and
that these values are not systematic overestimates of the welfare
improvements derived from implementation of the NPDWR.
Another commenter claimed that ``for the large majority of health
endpoints discussed, the EPA has not provided a factual basis by which
to conclude that such benefits are likely to occur when the EPA
decreases the levels of PFAS in drinking water.'' The EPA disagrees
with the commenter's assertion that the agency has not provided a
factual basis for the benefits that are likely to occur as a result of
the rule, which is amply supported in the HRRCA by the best available
peer-reviewed science, consistent with SDWA section 1412(b)(3).
Moreover, the commenter did not provide any additional or contrary
factual information for the EPA to consider.
One commenter stated that the EPA did not provide data to support
the analysis of benefits predicted from the implementation of the
Hazard Index MCL. The EPA disagrees with commenter that the EPA did not
provide evidence to support Hazard Index MCL benefits. In section XII
of the preamble and in section 6.2 of the EA (USEPA, 2024g), the EPA
qualitatively summarized and considered the potential health benefits
resulting from reduced exposure to PFAS other than PFOA and PFOS in
drinking water. These qualitative potential health benefits are based
on summaries of a significant body of peer reviewed science. As
summarized in the EA, the qualitatively discussed health effects of the
Hazard Index PFAS are considerable; reducing human exposure to the
Hazard Index PFAS is expected to reduce the incidence of multiple
adverse health impacts. The qualitative benefits discussion of the
impacts of the four PFAS which are regulated through the Hazard Index,
as well as their co-occurrence in source waters containing PFOA and/or
PFOS and additive health concerns, supports the EPA's decision to
regulate them through the Hazard Index in this rulemaking.
Additionally, the EPA evaluated the impacts of PFNA (one of the
Hazard Index PFAS) on birthweight in quantitative sensitivity analyses
(USEPA, 2024e). The EPA notes that new evidence since the release of
the current, best available peer reviewed scientific assessment for
PFNA (ATSDR, 2021) provides further justification for the EPA's
analysis of potential economic benefits of PFNA exposure reduction and
avoided birthweight effects. Specifically, this new evidence confirms
that in instances where PFNA is present, the national quantified
benefits may be underestimated; however, birth weight benefits are
considered quantitatively as part of this EA in the sensitivity
analysis and support the EPA's decision to regulate PFNA.
The EPA received a number of comments on the quantitative analysis
for CVD risk reduction. These commenters disagree with the EPA's
assessment that cardiovascular benefits are likely to occur as a result
of PFOA and PFOS exposure reduction. One commenter stated that the
associations with total cholesterol (TC) are not biologically
significant and criticized the EPA's use of linear models in the CVD
meta-analysis, stating that this approach biases the analysis by
excluding higher-quality studies. The EPA disagrees with the
commenter's statement that associations between PFOA/PFOS and TC are
not biologically significant. Such serum lipid changes may or may not
result in a concentration considered clinically elevated in a
particular individual; however, given the distribution of individual
concentrations within the population, small changes in average serum
lipid concentrations can result in substantial adverse health effects
at the population level (Gilbert and Weiss, 2006). The EPA disagrees
with the commenter's suggestions that linear assumptions are
inappropriate for use in this context. The EPA presents the exposure-
response estimates evaluated considering all studies, studies with
linear models only, and a variety of sensitivity analyses in appendix F
of the
[[Page 32636]]
EA (Tables F-2 and F-3, USEPA, 2024e). Meta-analyses of studies
reporting linear associations had statistically significant
relationships. These relationships are supported by the EPA's review of
epidemiological studies showing positive associations between PFOA/PFOS
and TC. The EPA used data from peer-reviewed studies, and the
assumption of linear exposure-response function to explain associations
between PFAS and serum lipids such as TC which are supported by data
from numerous studies, including those used in the meta-analysis. Other
studies have explored log-linear or linear-log relationships between
PFAS and serum lipids, while acknowledging only ``slight improvements''
in model fit, especially for serum lipids with least skewed
distributions (Steenland et al., 2009).
A couple of commenters stated that the downward trend in decreasing
total and low-density lipid cholesterol since the 1970s coupled with
the decreasing PFOA and PFOS serum levels suggests that there is a
substantial likelihood that the proposed MCLs for PFOA and PFOS are
unlikely to result in benefits as great as those reported in the
proposal. The EPA disagrees with these comments asserting that
decreasing trends in cholesterol levels over time indicate that PFAS
exposure is unlikely to contribute to a measurable increase in CVD
risk. The EPA relied on recent National Health and Nutrition
Examination Study (NHANES) data (2011-2016) to inform baseline
cholesterol and blood pressure conditions in the population evaluated
under the proposed rule. These data reflect the current population and
do not reflect cholesterol conditions in the population between 1970
and 2010. Therefore, the CVD benefits analysis examines how the
probability of the current population might benefit from reduced
incidence of hard CVD events.\14\
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\14\ Hard CVD events include fatal and non-fatal myocardial
infarction (i.e., heart attack), fatal and non-fatal stroke, and
other coronary heart disease mortality.
---------------------------------------------------------------------------
The EPA received a comment stating that the benefits associated
with high-density lipoprotein cholesterol (HDLC, often referred to as
the `good cholesterol') changes are not likely to accrue because the
evidence of the relationship between PFAS and the health outcome is not
conclusive, and that this endpoint should not have been quantified. The
EPA disagrees; although the evidence of a relationship between PFAS
exposure and HDLC is not conclusive, the SAB recommended that the EPA
evaluate how the inclusion of HDLC effects would influence results.
Thus, the EPA evaluated how benefits results are affected by the
inclusion of HDLC effects in a sensitivity analysis presented in
appendix K of the EA for the proposed (USEPA, 2023f) and final rule
(USEPA, 2024e). Additionally, the same commenter and one other
commenter challenged the EPA's quantification of PFOS and blood
pressure, stating that the EPA's finding that PFOS might have ``the
potential'' to affect blood pressure does not meet the SDWA standard
for inclusion in a benefits analysis and that the ``rationale for
including changes in BP in relation to PFOS is not clear.'' Another
comment identified a study that utilized NHANES data and ``did not
observe an association'' between PFOA and blood pressure. Finally,
another commenter mentioned that ``neither the ATSDR nor the National
Academy of Sciences (NAS) have found an association between PFOA/PFAS
and increased blood pressure.'' While the EPA is aware of this previous
work, in the EPA's own, more recent assessment, the strength of the
evidence is determined both by the number but also the quality of
studies investigating the relationship. One high confidence study
conducted using U.S. general population data from NHANES showed a
relationship between PFOS exposure and systolic blood pressure in
humans (Liao et al., 2020). In addition, several medium and low
confidence studies provided evidence for an association between PFOS
and blood pressure and/or hypertension (Mitro et al., 2020; Bao et al.,
2017; Mi et al., 2020; Liu et al., 2018). Because blood pressure is an
important component of the Atherosclerotic Cardiovascular Disease
(ASCVD) model used to estimate hard CVD event risk, and because
epidemiology reports show consistent evidence of an association between
PFOS and blood pressure in general adult populations (i.e., the
populations evaluated using the ASCVD model), the EPA included the
relationship between PFOS exposure and blood pressure in the analysis.
The EPA further notes that the Science Advisory Board recommended
modeling the impacts of changes in all ASCVD model predictors
(including blood pressure and HDLC) for which there is evidence of a
likely causal relationship (USEPA, 2022i).
A few commenters questioned the evidence or stated that the
evidence supporting an association between exposure to PFOA and PFOS
and CVD is insufficient. The EPA disagrees with these comments. The
agency's approach to estimating reductions in CVD risk was reviewed and
supported by SAB panelists (USEPA, 2022i). Numerous studies have shown
consistent associations between PFOA/PFOS exposure and changes in TC
and blood pressure which are biomarkers for CVD risk. TC and blood
pressure are well-established CVD risk biomarkers, are clearly
associated with CVD events, and are important inputs to the ASCVD model
that the EPA used to estimate CVD outcomes.
The EPA received public comments on the benefits analysis for
developmental effects. A few commenters claimed that the studies used
for developmental modeling did not provide sufficient evidence of an
association between PFOA and PFOS exposure and stated that the studies
which the EPA used to model the developmental effects relationship did
not consider confounders including pregnancy hemodynamics and other
chemical and non-chemical stressors, including other PFAS. One
commenter stated that the EPA's findings are inconsistent with other
regulatory agency findings that small decreases in birth weight are
associated with maternal exposure to PFOA and PFOS but not increased
risk of low birth weight. Other commenters stated that the EPA did not
address these concerns and inappropriately used these studies to
support quantitative analysis, and one commenter stated that because of
the shortcomings of the studies used and the modeling uncertainties,
peer review of the developmental effects modeling should be completed.
Although there are some uncertainties in the developmental
epidemiological effects data (e.g., differences seen across biomarker
sample timing), the EPA disagrees with these comments: the
developmental benefits analysis is supported by a wide body of peer
reviewed science (Verner et al., 2015; Negri et al., 2017; ATSDR, 2021;
Waterfield et al., 2020; USEPA, 2016c; USEPA, 2016d; USEPA, 2024c;
USEPA, 2024d). Specifically, birth weight was determined to be a
critical effect based on findings in the EPA's health assessments (see
USEPA, 2024c; USEPA, 2024d), and low birth weight is linked to a number
of health effects that may be a source of economic burden to society in
the form of medical costs, infant mortality, parental and caregiver
costs, labor market productivity loss, and education costs.
Discussion regarding the selection of decreased birth weight as a
critical effect, including the selection of specific studies for
candidate RfD derivation and the evidence supporting associations
between PFOA or PFOS and
[[Page 32637]]
developmental effects, is available in sections 3.4.4 and 4.1 of the
final toxicity assessments for PFOA and PFOS (USEPA, 2024c; USEPA,
2024d). In estimating benefits of reducing PFOA and PFOS in drinking
water, the agency selected results from Steenland et al. (2018) as the
birth weight exposure-response function for PFOA and results from
Dzierlenga et al. (2020) as the birth weight exposure-response function
for PFOS. The agency chose the results from these studies because they
include the most recent meta-analyses on PFOA- and PFOS-birth weight
relationships, and they included a large number of studies, including
multiple studies with first trimester samples (seven studies in
Steenland et al., 2018 and eight studies in Dzierlenga et al., 2020).
To provide insights into the potential effects of sample timing and
pregnancy hemodynamics, the EPA also performed a sensitivity analysis
considering only first trimester estimates from Steenland et al (2018)
for PFOA and Dzierlenga et al. (2020) for PFOS in section K.4 of the EA
appendices (USEPA, 2024e). While reports prior to 2019 found
``plausible'' or ``suggestive'' (USEPA, 2016d; ATSDR, 2018) evidence of
relationships between PFOA and PFOS and developmental outcomes, the
EPA's assessment found clear evidence of an association for PFOA and
PFOS in both toxicological and epidemiological studies (USEPA, 2024h;
USEPA, 2024i). The agency further disagrees with the commenter's
statement that further peer review is needed, as the EPA relies
extensively on peer-reviewed studies in its developmental benefits
model. Furthermore, the EPA characterizes the uncertainty in the PFOA
and PFOS exposure-response functions as described in appendix L of the
EA (USEPA, 2024e). In short, the benefits analysis for developmental
effects relies on a wide body of the best available, peer-reviewed
science, and the epidemiological evidence provides a reliable basis for
quantifying the risks of low birth weight.
A different commenter claimed that the EPA relied on equivocal
epidemiological evidence to estimate developmental benefits, stating
that the RfDs calculated from animal studies in the EPA's health
assessment documents for PFOA and PFOS are significantly higher than
those based on human studies used for benefits analysis and that the
animal studies represent a more appropriate estimate of the risk of
PFOA and PFOS exposure. The EPA disagrees with the commenter that the
analysis relies on equivocal epidemiological evidence to estimate
benefits. The systematic literature review and assessment conducted by
the EPA, the most comprehensive evaluation of the current literature to
date, concluded that there is moderate evidence for developmental
effects based on consistent adverse effects for fetal growth
restriction including birthweight measures which are the most accurate
endpoint (USEPA, 2024c; USEPA, 2024d). One commenter raised concerns
about the EPA's reliance on the study (Steenland et al., 2018) that the
EPA uses to model PFOA dose response for benefits analysis, stating
that the EPA's benefits analysis for PFOA and developmental effects is
not supported by the underlying publication. The same commenter
questioned the EPA's reliance on the study that is used to model PFOS
dose response for benefits analysis (Dzierlenga et al., 2020), stating
that the study found that there was no evidence of a relationship at
the beginning of pregnancy. The commenter contended that the meta-
analysis was not peer reviewed and thus the validity of the EPA's
methods should be questioned. The EPA disagrees with the commenter's
criticism of the studies used to assess dose response in developmental
benefits analysis. The selected meta-analyses on the relationship
between PFOA/PFOS exposure and birth weight produced statistically
significant results, are based on recent data, and include a large
number of studies in each meta-analysis.
One commenter stated that given the discussion about changes over
time in infant mortality, a dataset containing only two years of data
is insufficient to build infant mortality regression models. The EPA
disagrees that two years of data is insufficient to build regression
models relating infant birth weight to infant mortality. The EPA's
regression analysis improves upon earlier analyses relating birth
weight to infant mortality (Almond et al., 2005; Ma and Finch, 2010) by
evaluating two years of recent data. Sample sizes among the Centers for
Disease Control and Prevention (CDC) National Center for Health
Statistics (NCHS) linked birth/infant death data per year are large (n
= approximately 3.8 million infants) and contribute to the overall
statistical significance of regression results. As described in
appendix E of the EA (section E.2, USEPA, 2024e), there has been a
notable decline in U.S. infant mortality rates since the analyses
reported in Ma and Finch (2010) and Almond et al. (2005). Using recent
data from two CDC NCHS linked birth/infant death data cohorts results
is a more accurate and conservative characterization of recent infant
mortality trends than if the EPA had included older CDC NCHS data.
The EPA received comments on the benefits analysis for RCC. Two
commenters expressed concerns with the EPA's use of Shearer et al.
(2021) to estimate RCC risk in benefits analysis and claimed flaws in
the study related to outliers in the RCC group and inconsistent
evidence of an association across epidemiological studies. One
commenter stated that given what they perceive as SAB concerns and
uncertainties in the modeling, further peer review is warranted. The
EPA disagrees with the comments critical of the agency's use of
information from the Shearer et al (2021) study for purposes of PFOA
health assessment and benefits analysis. As noted in section 3.5.1 of
the Final Toxicity Assessment for PFOA (USEPA, 2024c), the EPA
determined that Shearer et al. (2021) is a medium confidence study
after conducting study quality evaluation consistent with the ORD Staff
Handbook for Developing IRIS Assessments (USEPA, 2022f). The
biomonitoring measures of PFOA levels in Shearer et al. (2021) were
reliable measures of PFOA exposure due to the chemical's well-
established long half-life. The commenters failed to acknowledge
multiple studies further supporting a positive association between PFOA
exposure and RCC risk (Bartell and Vieira, 2021; Vieira et al., 2013;
Steenland et al., 2022). Critically, the SAB PFAS Review Panel
supported the Likely to be Carcinogenic to Humans designation for PFOA
in its final report (USEPA, 2022i). Shearer et al (2021) has been
sufficiently peer reviewed and it represents the best available science
for purposes of health and benefits assessment in the PFAS NPDWR.
The EPA received comments on uncertainties associated with bladder
cancer reductions. One commenter incorrectly stated that the ``EPA does
not recognize the uncertainty that there is not always direct
correlation between THM4 levels and TOC in all public water systems''.
In response, the EPA notes that the THM concentrations in this co-
removal analysis were not calculated based on TOC reduction. TOC was
used to bin systems in the universe of PWSs using the fourth Six-Year
Review (SYR4) database and PFAS occurrence model with the THM4
reduction calculated from the formation potential experiments before
and after GAC treatment in the DBP Information Collection Rule
Treatment Study Database. This dataset reflects the current best
available data to determine THM4 reduction based on TOC removal
[[Page 32638]]
using GAC treatment. Another commenter stated that the causal link of
DBPs and bladder cancer has not been established. The EPA notes that an
extensive body of epidemiological studies have shown that increased
exposure to chlorinated DBPs is associated with higher risk of bladder
cancer and other adverse health outcomes (Cantor et al., 1998; Freeman
et al., 2017). Weisman et al. (2022) found that approximately 8,000 of
the 79,000 annual bladder cancer cases in the U.S. were potentially
attributable to chlorinated DBPs in drinking water systems. While
research has not established a causal link between THM4 and bladder
cancer, there is strong evidence that there is a correlation between
THM4 and bladder cancer.
One commenter stated that the DBP co-removal benefit analysis did
not meet the standards required by SDWA for estimating benefits since
it was not reviewed by the SAB. The commenter is incorrect. SDWA
1412(e) directs the EPA to request comments from the SAB prior to
proposing an MCLG and NPDWR. The EPA sought and received comment from
the SAB prior to proposing this NPDWR (see USEPA, 2022i). The statute
does not dictate the precise level of scientific questions for which
the EPA must seek comments from the SAB. The EPA sought SAB comment on
the four most significant areas that informed derivation of the MCLGs
for all six PFAS regulated by this action and for other parts of the
benefits analysis that informed the overall development of the NPDWR.
The EPA did seek additional peer review of its DBP co-removal benefit
analysis prior to its inclusion in the EA for which it received
overwhelmingly favorable comments from reviewers (see USEPA, 2023m).
Furthermore, this rule is based on the EPA's consideration of a wide
body of existing peer-reviewed science on this subject (e.g., Regli et
al., 2015; Weisman et al., 2022). In short, the EPA has used peer
reviewed science and sought further peer review to support its DBP co-
removal analysis, and as part of the supporting material for the rule
proposal, the EPA included the comments from the expert peer reviewers
as well as how each comment was addressed or the rationale for why it
was not changed. Please see Response to Letter of Peer Review for DBP
Co-benefits (USEPA, 2023m) for discussion of that peer review and the
EPA's responses to peer reviewed comments.
Another commenter claimed that the EPA improperly quantified
benefits of co-removed substances rather than co-occurring substances.
The EPA disagrees with these assertions since the analysis of DBP co-
removal is focused on co-occurring contaminants. As demonstrated
elsewhere in the record for this action, PFAS commonly co-occur with
each other. Additionally, in waters where disinfection is required, TOC
(i.e., a DBP precursor) and PFAS may co-occur. The DBP co-removal
benefits analysis relied on DBP formation potential experiments that
highlighted the changes to TOC with and without GAC treatment.
Furthermore, as discussed above, the methodology to estimate THM4
reductions was externally peer reviewed by three experts in GAC
treatment for PFAS removal and DBP formation potential.
A few commenters stated that the EPA already had initiatives to
reduce THMs in drinking water and suggested that reduction of bladder
cancer cases is better addressed through existing DBP rules. While the
EPA agrees that there are existing DBP regulations to reduce DBP
exposure and risks, this rule will provide additional health risk
reduction benefits associated with enhanced DBP reduction. The EPA has
considered those co-removal benefits as part of the EA. The EPA notes
that it is required under the SDWA 1412(b)(3)(C)(i)(II) to assess
quantifiable and nonquantifiable health risk reduction benefits for
which there is a factual basis in the rulemaking record to conclude
that such benefits are likely to occur from reductions in co-occurring
contaminants that may be attributed solely to compliance with the MCL,
excluding benefits resulting from compliance with other proposed or
promulgated regulations. DBP reductions presented in the EPA's HRRCA
are those that are anticipated to result solely from compliance with
the PFAS MCLs. As required under the SDWA, any quantifiable and
nonquantifiable benefits from future actions concerning DBPs in
drinking water will be addressed at the time of those actions and are
independent from benefits stemming as a result of the PFAS rulemaking.
A couple of commenters supported the EPA's analysis of DBP benefits but
recommended that the EPA also consider other co-removed contaminants.
The EPA agrees with the commenters that multiple co-occurring
contaminants will be removed as a result of this rule. Furthermore, the
EPA acknowledges in the EA that additional co-removal benefits would be
realized due to treatment for PFAS. With the exception of DBPs co-
removed, the EPA has not quantified other co-removal benefits at this
time because of data limitations, the agency included discussion of
nonquantifiable benefits for multiple other PFAS and for other
contaminants.
Nonquantifiable Benefits of PFAS Exposure Reduction
One commenter expressed that the EPA's characterization of benefits
is inadequate and not supported by science. The commenter specifically
discussed hepatic effects, endocrine effects, and musculoskeletal
effects and asserted that the EPA's characterization is based on mixed
findings and inconsistent evidence regarding PFAS exposures and
specific health outcomes. The EPA disagrees with this comment, as the
EPA has evaluated the best available peer reviewed science, as required
under SDWA. The EPA did not quantify or monetize benefits where there
are inadequate data. For hepatic effects, the EPA's toxicity
assessments determined that there is moderate evidence supporting the
association between exposure to PFOA/PFOS and hepatic toxicity in
humans. However, the EPA did not quantify benefits for hepatic effects
because although there will be benefits delivered by reducing PFOA and
PFOS in drinking water, there is a lack of adequate data available to
accurately quantify those benefits. Further information on health
effects related to PFAS exposures is provided in the health assessments
within the MCLG documents (USEPA, 2024c; USEPA, 2024d).
Conversely, some commenters expressed support for the
quantification that the EPA has already performed, stated that the
benefits of the rule are underestimated, and urged the EPA to quantify
and monetize additional health endpoints, particularly mammary gland
and lactational effects, immunotoxicity, and liver disease. These
commenters also provided additional resources and information with the
intention of the EPA using that information to update analyses
regarding lactational effects, expand analyses to include immune
effects, and adjust analyses to characterize hepatotoxicity as a
quantifiable benefit, as opposed to a non-quantifiable one. Commenters
also urged the EPA to quantify some of the benefit categories, even if
monetization is not possible, and to highlight the magnitude of some of
the qualitatively discussed benefits. The EPA agrees with these
commenters that the quantified benefits of the rule are underestimated.
Where appropriate, the EPA used medical cost information provided by
the commenters to supplement qualitative discussion of adverse effects.
Additionally, and based on these comments, the EPA considered
[[Page 32639]]
information in the record and added additional quantified benefits
analysis in the sensitivity analysis evaluating the reductions in liver
cancer cases expected by reducing concentrations of PFAS. This
additional analysis was confirmatory of the EPA's previous analysis and
did not result in changes to the NPDWR's requirements.
Some commenters also provided recommendations regarding the
inclusion of additional costs and benefits beyond health endpoints.
These included the opportunity cost of time, environmental benefits,
and psychosocial benefits that are expected to result from the rule.
The opportunity cost of time was suggested to be incorporated into
morbidity estimates, while the other benefits were suggested to be
encapsulated in a qualitative summary.
In the EA document, the EPA describes that the cost of illness
(COI)-based approach does not account for the pain and suffering
associated with non-fatal CVD events. Based on the above comments, for
quantified cancer endpoints (i.e., RCC and bladder cancers), the EPA
has included a new sensitivity analysis using willingness to pay values
for risk reductions which can inform the direction of benefits when
opportunity cost is included. This additional analysis was confirmatory
of the EPA's previous analysis and did not result in changes to the
NPDWR's requirements.
c. Final Rule Analysis
For the final rule, the EPA retained the quantitative benefits
analyses from the proposal for developmental, CVD, and cancer endpoints
as well as the bladder cancer benefits from DBP exposure reduction as a
result of the rule. In response to comments described above, the agency
identified new information on willingness to pay values for non-fatal
cancer risk reductions and added additional sensitivity analyses for
RCC and bladder cancer in appendix K to the final rule EA (USEPA,
2024e). In light of new epidemiological studies on PFOS exposure and
liver cancer that strengthened the weight of evidence and supported the
toxicological information that was identified in the proposed rule, and
comments received requesting that the EPA monetize additional health
endpoints, the EPA developed a sensitivity analysis assessing the liver
cancer impacts in appendix O of the final rule EA (USEPA, 2024e). The
EPA estimates that PFOS liver cancer benefits would add $4.79 million
annually to the national benefits estimates. The EPA retained
discussion of nonquantifiable benefits associated with PFAS exposure
reduction from the proposed rule for the final rule EA.
2. Treatment Costs
a. Treatment Cost Estimates in the Proposal
The EPA estimated costs associated with engineering, installing,
operating, and maintaining PFAS removal treatment technologies,
including treatment media replacement, and spent media destruction or
disposal, as well as nontreatment actions that some PWSs may take in
lieu of treatment, such as constructing new wells in an uncontaminated
aquifer or interconnecting with and purchasing water from a neighboring
PWS. To evaluate the treatment costs to comply with the proposed PFAS
NPDWR, the EPA used the agency's Work Breakdown Structure (WBS) models,
a spreadsheet-based engineering models for individual treatment
technologies, linked to a central database of component unit costs. The
WBS models are extensively peer-reviewed engineering models for
individual treatment technologies and discussed in section XII.D of
this preamble. The EPA used PFAS occurrence outputs from a Bayesian
hierarchical estimation model of national PFAS occurrence in drinking
water (Cadwallader et al., 2022), to estimate the number of water
systems exceeding the proposed MCLs, and therefore triggered into
action to comply with the proposed MCLs.
b. Summary of Major Public Comments on Treatment Costs and EPA
Responses
Many commenters state that the EPA has underestimated the treatment
costs required to comply with the proposed MCLs. One commenter
suggested that the EPA has not complied ``with its statutory
requirements by conducting an analysis that fully captures these
costs.'' The EPA disagrees with the few commenters that suggested the
EPA has not met its requirements under SDWA, and the EPA emphasizes the
agency has used the best available peer reviewed science to inform it
cost estimates, including treatment costs, of the MCLs. Specific
aspects of comments related to treatment costs and the EPA's response
are discussed further in this section.
Many commenters cited rising costs in the drinking water sector and
discussed the effects of inflation and the COVID-19 pandemic on the
costs of labor, construction, and capital, among other materials
related to compliance with the MCLs. These commenters emphasized the
significant impacts felt from supply chain and workforce issues. The
EPA recognizes these impacts, and as recommended by commenters,
adjusted the cost estimates by escalating unit costs using indices
including the Bureau of Labor Statistics producer price indices (USBLS,
2010). The EPA updated each unit cost using the change in the relevant
price index from year 2020 to 2022. For example, the EPA applied the
percent increase of the price of metal tanks and vessels (50 percent
increase from 2020 to 2022) to the price of metal tanks and vessels in
the WBS cost models. The EPA also collected new vendor price quotes for
cost driver equipment components (e.g., pressure vessels, treatment
media) and made several other adjustments to WBS model assumptions,
described further in this section. Taken together, these adjustments
increased the system level capital cost estimates in the EPA's cost
assessment by a percentage that varied depending on the system size and
treatment technology. For small systems using GAC and IX, the increase
ranged from approximately 40 percent to 110 percent. For medium
systems, the increase was approximately 20 to 60 percent; for large
systems, 10 to 40 percent. Additionally, while revising the SafeWater
model to incorporate new information from public comments, the EPA
identified and corrected a coding error related to the discounting of
future operation and maintenance costs resulting in increased estimated
annualized treatment costs. The result of these changes are increased
cost estimates for the final rule.
Some commenters state that while BIL funding is available, it is
not enough to cover the compliance costs of the rule. For example, one
commenter noted that, ``[t]his amount of funding support, while
crucial, will come nowhere near the cost to ratepayers that must be
borne to implement necessary compliance actions for these MCLs.'' The
EPA disagrees with the commenter that BIL funding will be nowhere near
the cost'' necessary to implement compliance actions. The EPA estimates
that the initial capital costs of the rule in undiscounted dollars is
approximately $14.4 billion (see appendix P of the EA for more
information). Given the BIL appropriations of $11.7 billion in DWSRF
and an additional $5 billion for emerging contaminants, the EPA
reasonably anticipates BIL funding is likely to be able support a
substantial portion of the initial capital costs of the final rule. BIL
funding appropriations began in the Federal Fiscal Year (FFY) 2022 and
appropriations are anticipated to continue through FFY 2026.
Many commenters shared some information about the costs that they
[[Page 32640]]
have incurred or estimated they would incur at a system level to
install, operate, and maintain treatment to remove PFAS. Some system
level cost information provided by commenters fell within the ranges of
costs presented in the EPA's supporting documentation for the proposal
and other information provided by commenters exceeded the EPA's system
level cost ranges. The EPA does not dispute the commenters stated
experience of costs to install, operate and maintain treatment to
remove PFAS; however, many of these comments lacked supporting details.
Many of the comments cited preliminary or conceptual estimates and did
not specify the methods and assumptions used to develop the estimate.
Furthermore, most comments did not include information to confirm that
all of the reported or estimated costs were or would be directly
associated with PFAS treatment, as opposed to other infrastructure
improvements (e.g., capacity expansion, administrative facilities,
distribution system improvements) that happened to be completed as part
of the same project. Most commenters also did not include information
to confirm that key design and operating parameters (e.g., empty bed
contact time, media replacement frequency) would be similar to the
typical values assumed in the EPA's estimates. To fully evaluate the
commenters' reported or estimated costs in comparison to WBS model
results, the EPA would need itemized line-item cost details and
engineering design parameters. To inform the cost estimates of the
proposed and final PFAS NPDWR, the EPA conducted an extensive review of
the literature. The EPA has further validated the unit costs in the
PFAS rule with equipment cost information from 2023 from a major
supplier of treatment media. While the EPA recognizes there are likely
site-specific instances where costs exceed the EPA's cost ranges, there
are also likely site-specific instances where costs are less than the
EPA's cost ranges, and this level of accuracy is appropriate for a
national level analysis.
Other commenters compared state-level costs to the EPA's national
level cost estimates, noting that the EPA's estimates appeared too low.
Utilizing this permit data and project cost data submitted by water
systems in applications to the DWSRF, one state estimated that total
capital costs for installation of PFAS treatment to meet the EPA's
proposed standards across the state could be as high as $1.065 billion.
The EPA's EA analysis, however, presents national level cost estimates
that are annualized over the period of analysis and are therefore not
directly comparable to a single year estimate of capital costs.
A few commenters stated that the EPA incorrectly omitted the costs
associated with performance monitoring, which commenters believe will
be necessary because a water system needs to know how often it needs to
replace its media. The EPA disagrees that large amounts of additional
samples in performance monitoring will be required, and the commenter
provided no data to support their assertion that this would be
necessary. The EPA anticipates that many water systems will conduct a
pilot test before implementing a full-scale treatment installation and
that the operational results from the pilot test will be a sufficient
indicator of performance; therefore, water systems should not have to
collect large amounts of performance samples indefinitely during the
full-scale operation of treatment technologies. The EPA includes the
costs of pilot testing, and sampling during that time, in the treatment
capital cost estimates. In response to public comments, the EPA
increased the estimated length of the pilot study and the frequency of
sampling during the pilot study. Additionally, the EPA added a full
year of confirmation sampling after full-scale installation to the
estimated pilot study costs. Taken together, these changes doubled to
more than tripled the pilot study costs included in the EPA's
estimates.
In response to public comments about residual management concerns
for high pressure membrane technologies, the EPA has adjusted RO/NF's
technology projection compliance forecast to zero percent in the EA for
the final rule. Therefore, the EPA assumes that RO/NF will not
generally be used solely for the purpose of complying with the final
rule. For more information on public comments on residuals management
and the EPA's response please see section X.
A few commenters stated that the EPA underestimated or
insufficiently incorporated contingency in its cost estimates. For
example, one commenter stated that the EPA's contingency assumptions in
the proposal were ``. . . inconsistent with recommended best practices
for cost estimators and [are] expected to be a major contributor to the
EPA WBS' failure to accurately capture costs for PFAS treatment
facility implementation.'' In response to these comments, the EPA
changed its approach and incorporated contingency for all systems, not
just high-cost systems. The EPA also increased the complexity factor
applied to estimate contingency for systems using GAC. Taken together,
these changes result in a contingency factor of 5 to 10 percent
depending on total project cost at all cost levels for systems
installing treatment. Additionally, the EPA includes a miscellaneous
allowance of 10 percent. This allowance can be viewed as either as a
form of contingency or a method to increase the level of project
definition (thus reducing the amount of contingency required).
One commenter stated that the EPA underestimated the costs
associated with interconnection.\15\ This commenter stated that it was
``unrealistic to assume that booster pumps are unlikely to be
necessary. Pressure loss associated with friction could be significant,
especially for an interconnection that may span 10,000 feet or more,''
and recommended that the EPA include booster pumps in the cost
estimate. Commenters also pointed out that ``. . . systems considering
interconnections will need to thoroughly investigate this option and
determine if it is both cost effective and appropriate given the water
quality impacts.'' In response to these comments, the EPA made several
changes to the assumptions used to estimate costs for interconnection
in the WBS model for nontreatment options. The EPA agrees that booster
pumps may be needed and added the costs of booster pumps designed to
account for friction loss in interconnecting piping. The EPA also
agreed that there are many considerations for water systems pursuing
interconnections including elevated water age, nitrification, and DBPs,
as pointed out by commenters, and therefore the EPA increased the
complexity factor applied to estimate contingency for systems using
nontreatment options. Taken together with the escalation to 2022
dollars, these changes increased the system level capital costs for
interconnection by approximately 60 to 100 percent.
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\15\ Interconnection is when a system replaces their
contaminated water source by purchasing water from another nearby
system that is in compliance. Booster pumps can be needed when the
pressure from the supplying system is lower than required at the
purchasing system and also to overcome pressure losses due to
friction in interconnecting piping.
---------------------------------------------------------------------------
Many commenters cited and expressed agreement with the conclusions
of a study conducted by Black & Veatch on behalf of the American Water
Works Association (AWWA) (hereafter referred to as AWWA's B&V report)
(AWWA, 2023). The EPA disagrees with many of the assumptions in AWWA's
B&V report and the report's overall conclusions
[[Page 32641]]
about the estimated national costs of the PFAS NPDWR. Tables 24-26
detail some of the key assumptions related to (1) PWSs that exceed the
MCL, (2) capital costs and (3) operation and maintenance costs that
overestimate national treatment costs in AWWA's B&V report and the
EPA's response to those assumptions and resulting estimates. In
combination, all these factors result in an overestimate of treatment
costs. For example, AWWA's B&V report Table 6-1 reports an average
capital cost per EP for the smallest size category of $900,000. Using
AWWA's B&V report's (overestimated) design flow calculations, the
treatment system design flow at each EP would be approximately 0.062
million gallons per day (mgd). For comparison, Forrester (2019) reports
capital equipment costs of approximately $300,000 for a 1 mgd GAC PFAS
treatment system. Even after adding indirect capital and building
costs, the $900,000 estimate appears substantially overestimated, given
that it is for a treatment system designed for approximately 1/16th of
the flow of the system in the Calgon Carbon estimate (Forrester, 2019).
When AWWA's B&V report's EP level results are aggregated nationally to
an overestimated number of systems treating for PFAS, the overestimates
are compounded at the national level.
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c. Treatment Costs in the Final Rule Analysis
The cost estimates in the EA for the final PFAS NPDWR reflects the
adjustments made to the WBS curves and decision tree based on public
comments discussed above as well as the additional occurrence
information available since the publication of the proposed PFAS NPDWR.
For detailed information on the EPA's occurrence analysis, see section
VI of this preamble. For detailed information on the EPA's cost
analysis and the EPA's estimates of the national annualized costs of
the final MCLs, see section XII.D.
3. Primacy Agency Costs
a. Primacy Agency Cost Estimates in the Proposal
In the EA for the proposed rule, the EPA estimated the costs
incurred by primacy agencies associated with the rule, including up
front implementation costs as well as costs associated with system
actions related to sampling and treatment.
b. Summary of Major Public Comments on Primacy Agency Costs and EPA
Responses
Many commenters state that the EPA has underestimated the costs to
primacy agencies required to comply with the rule. One commenter
stated, ``EPA's analysis of primacy agency costs does not accurately
capture all the activities that primacy agencies will undergo for PFAS
implementation and underestimates the number of hours for the primacy
tasks.'' Commenters recommend that the EPA use findings from ASDWA's
PFAS Cost of State Transactions Study (PCoSTS) to reevaluate the
primacy agency costs estimated in the EA. The EPA's response to
specific recommendations is discussed here.
The EPA agrees with commenters on the burdens associated with
regulatory start up; primacy package adoption; technical, managerial,
and financial (TMF) assistance to water systems; and reviewing and
approving treatment. Commenters pointed out activities not explicitly
accounted for in the regulatory start up estimate in the EA for
proposal including accreditation of laboratories for PFAS testing;
SDWIS updates; monitoring schedule updates; time spent responding to
questions from members of the public; inquiries from public officials;
and media requests immediately following the final publication of the
NPDWR. Commenters also pointed out that adopting primacy packages is a
significant undertaking with ``specific and very detailed
administrative procedures that must be adhered to in order to adopt
water quality regulations'' and that ``some primacy agencies have
requirements for robust public comment periods as a component of new
rule adoption.'' As recommended by commenters, the EPA created a new
cost item for primacy package adoption. Commenters stated the EPA's
assumption in the proposal that the amount of time a primacy agency
will need to review treatment plans directly correlates with the size
of the water system was inaccurate. Commenters noted that ``. . . small
systems often take the most time as they need significant assistance to
navigate the process for the design and construction of new treatment
and get into compliance.'' After considering these comments, the EPA
agrees that reviewing and approving treatment for small systems is
likely to take more time given the assistance needed for these systems.
Because small systems often lack the technical, managerial, and
financial capacity, it is likely that primacy agencies will spend more
time assisting these systems in navigating compliance with the PFAS
NPDWR. As such, the EPA adjusted burden estimates in the final rule to
reflect the largest primacy agency burden per EP at the smallest
systems and decreased burden hours with increasing system size, as
commenters suggested.
Several commenters disagreed with the EPA's exclusion of additional
costs to primacy agencies associated with reporting regarding
violations, variances and exemptions, enforcement actions, and other
compliance related primacy agency activities in the national cost
analysis. One commenter estimated the PFAS NPDWR will likely result in
hundreds of violations once in effect. The EPA recognizes that these
activities do have an associated burden for primacy agencies but
disagrees that these costs should be included in the EA. The EPA
assumed 100 percent compliance for its national level analysis in the
EA for the final rule because the EPA has determined that the final
rule is feasible given known occurrence concentrations and efficacy of
the technologies available. Further, this is consistent with the
approach taken in EAs for other NPDWRs (USEPA, 2005c; USEPA, 2019c;
USEPA, 2020f). Commenters recommended that the EPA include hours for
additional annual reporting. The EPA disagrees and expects that adding
PFAS results to already-required reports will have no discernable
incremental burden for quarterly or annual reports to SDWIS Fed.
Commenters recommended that the EPA include the costs associated
with various compliance activities. Given the EPA's assumption of 100
percent compliance for its national level analysis in the EA discussed
above, the EPA disagrees and did not take commenters' recommendations
to include the costs associated with assisting out of compliance
systems and assisting systems to remain in compliance, pursuing
enforcement actions, staff time checking in with system violations and
reviewing system variances and exemptions. The EPA did include the
costs associated with compliance activities for systems in compliance,
including updating inspection SOPs and additional sanitary survey
burden at water systems that have installed treatment to comply with
the PFAS NPDWR.
c. Primacy Agency Costs in the Final Rule Analysis
After considering public comments on the burden hours associated
with primacy agency activities, the EPA made the following changes. The
EPA increased the estimate from 416 hours to ``read and understand the
rule as well as adopt reg requirements'' to 4,000 hours per primacy
agency to conduct a suite of regulatory start up activities. Per
commenters' recommendation, the EPA included a new line item for
primacy package adoption and estimated 300 hours per primacy agency.
The EPA lowered the water system operator TMF training from 2,080 hours
to 1,500 hours per primacy agency based on commenter recommendations.
The EPA added a one-time burden estimate of 20 hours to inspection SOPs
and an additional 2-5 burden hours for the primacy agency, by water
system size, per sanitary survey per system installing treatment to
comply with the rule. For more information see section XII.D.
4. Costs of the Hazard Index
a. Hazard Index Cost Estimates in the Proposal
In the EA for the proposed rule, the EPA estimated national costs
associated with PFOA, PFOS, and PFHxS. Given available occurrence data
for the other compounds in the proposed rule (PFNA, HFPO-DA, and PFBS)
and the regulatory thresholds under consideration, the EPA did not use
SafeWater to model national costs associated with potential Hazard
Index (HI) exceedances as a direct result of these contaminants. To
assess the potential impact of these compounds in the proposed rule,
the EPA conducted an analysis of the additional, or
[[Page 32649]]
incremental, system level impact that occurrence of these contaminants
would have on treatment costs. The EPA estimated that the Hazard Index
would increase costs by 0-77 percent at the system level, with costs
varying due to PFAS occurrence scenario and treatment technology used.
b. Summary of Major Public Comments on Hazard Index Costs and EPA
Responses
A few commenters recommended that the EPA further consider the
costs associated with compliance with the Hazard Index (HI) MCL.
Specifically, commenters stated that the EPA's analysis of system level
costs associated with the Hazard Index does not adequately characterize
the overall costs that will be incurred due to the Hazard Index
standard. One commenter stated that ``EPA should not move forward with
the Hazard Index until it has satisfied its statutory and policy
obligation to conduct a cost-benefit analysis.'' Some commenters voiced
concern regarding the EPA's assumption that costs associated with
compliance with the Hazard Index MCL are insignificant and asserted
that these costs must be reexamined, stating that this assessment
``requires more knowledge on the nationwide occurrence of these
compounds'' and that the EPA ``cannot assume that addressing the costs
of PFOA and PFOS is sufficient when the additional four PFAS will be
driving treatment decisions at some PWSs.'' Conversely, one commenter
asserted that available occurrence data demonstrate that few systems
will be required to install treatment to comply with the Hazard Index
MCL that would not already be treating to comply with the PFOA and PFOS
MCLs.
The EPA disagrees with commenters who state that the agency did not
meet its requirements under SDWA, which requires the agency to analyze
``quantifiable and nonquantifiable costs . . . that are likely to occur
solely as a result of compliance with the maximum contaminant level.''
In the proposal, the EPA analyzed the quantifiable costs of the Hazard
Index at the system level, using the best available information at the
time of publication, and analyzed the nonquantifiable costs of the
Hazard Index by including a qualitative discussion of the national
level impacts and therefore met the statutory requirements under SDWA
1412(b)(3)(C). After considering recommendations from the public
comments to further analyze the costs of the Hazard Index and the data
available to support a quantitative analysis of the costs of the Hazard
Index, the EPA decided to conduct a sensitivity analysis of the costs
of the Hazard Index at the national level. The results of the
sensitivity analysis supported the EPA's assumption in the proposal
that quantified national costs are marginally underestimated as a
result of this lack of sufficient nationally representative occurrence
data. The EPA's consideration of Hazard Index costs in the final rule
analysis are discussed in the following subsection.
c. Hazard Index and PFHxS, PFNA, and HFPO-DA MCL Costs in the Final
Rule Analysis
To estimate quantified costs of the final rule presented in the
national-level summary tables, the EPA first estimated baseline PFAS
occurrence using a Bayesian hierarchical model fitted with sampling
data collected from systems participating in UCMR 3. The model included
three of the six PFAS compounds regulated through this NPDWR: PFOA,
PFOS, and PFHxS (see section VI of this preamble). This permitted the
agency to quantify costs at a national level with a higher degree of
confidence and precision for these three PFAS than if simple
extrapolations had been used. Since there are some limitations with
nationally representative occurrence information for the other
compounds that were either not included in UCMR 3 (HFPO-DA) or did not
have a sufficient number of observed values above the UCMR 3 reporting
limits (PFNA, PFBS), the EPA has a lesser degree of confidence and
precision for its quantified estimates of these three PFAS, which are
informed by a significant amount of available state-level data.
Therefore, the EPA presented the cost estimates for PFNA, HFPO-DA, and
PFBS in a sensitivity analysis in the EA (i.e., national-level
sensitivity analysis, see appendix N.3) instead of including these
costs in the summary tables of quantified national level costs.\16\
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\16\ When available, nationally representative occurrence
information is preferable for an economic analysis of national level
costs and benefits. In the case of PFOA, PFOS, and PFHxS, the EPA
has a sufficiently robust nationally representative dataset from
UCMR 3. The EPA used additional state data that were available at
systems that were part of this UCMR 3 set of systems to fit the
national occurrence model that informed cost estimates for PFOA,
PFOS, and PFHxS (see Cadwallader et al., 2022). In the case of PFNA,
HFPO-DA, and PFBS, the EPA lacks the same level of precision as
described above for PFOA, PFOS, and PFHxS. State-led data collection
efforts provided valuable information about occurrence for PFNA,
HFPO-DA, and PFBS, however they did not provide the nationally
representative foundation provided by UCMR3 for PFOA, PFOS, and
PFHxS to be incorporated into the MCMC national occurrence model.
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In the EA for the proposed PFAS NPDWR, the EPA used a model system
approach \17\ to illustrate the potential incremental costs for
removing PFAS not included in the national economic model (i.e., PFNA,
HFPO-DA, and PFBS). After considering public comments on the
incremental cost analysis, many of which encouraged the EPA to further
evaluate and consider quantified costs of the Hazard Index MCL where
feasible, the EPA updated and combined existing analyses contained in
the rule proposal to evaluate the incremental costs associated with the
Hazard Index MCL and individual MCLs for PFNA and HFPO-DA with a
quantified national level sensitivity analysis in the final rule. The
updated analysis for the final rule builds on the proposal analysis by
combining information that was presented separately at proposal. The
analysis in appendix N of the final EA utilizes the system level
treatment cost information presented at proposal (See appendix N of
USEPA, 2023n, 2023o) with updates to the cost models for the final rule
detailed in section XII.A.2. These treatment costs were applied to the
number of systems expected to exceed the standards based on PFNA, PFBS,
and HFPFO-DA occurrence using the approaches for estimating occurrence
of these compounds presented at proposal (see section 10.3 of USEPA,
2023l). This modified analysis was primarily conducted to ensure that
the EPA has not, as some commenters claim, substantially underestimated
the potential magnitude of these costs. The EPA notes the approach
presented in appendix N for the final rule and summarized here, by
connecting analyses for proposed rule, allows the agency to consider
and compare the relative degree of the potential overall costs of these
otherwise nonquantifiable costs of the Hazard Index and PFNA and HFPO-
DA MCLs relative to overall national rule costs. This analysis confirms
the EPA's findings at proposal that the Hazard Index costs (and those
costs for regulating PFNA and HFPO-DA individually) make up a small
portion of
[[Page 32650]]
the overall rule costs. Likewise, the EPA notes that while these costs
are presented in appendix N because of the lesser degree of confidence
and precision in the estimates, the EPA has considered these costs as
part of this final regulation. It has done so by evaluating
nonquantifiable costs and accounting for uncertainty, characterizing
these otherwise nonquantifiable costs in appendix N to generate cost
estimates that, while useful, are not as statistically robust as the
national cost estimates presented in chapter 5 of the EA. Using this
analysis, the agency has confirmed the Hazard Index and PFNA and HFPO-
DA MCLs drive a relatively low percentage of the overall rule costs.
The EPA has also considered these costs in the context that the Hazard
Index and PFHxS, PFNA, and HFPO-DA MCLs are expected to deliver
important nonquantifiable health benefits, including PFNA birth weight
benefits \18\ and other nonquantifiable benefits associated with the
reduction of the Hazard Index PFAS (PFNA, PFHxS, HFPO-DA, and PFBS)
\19\ described in chapter 6.2 of the EA.
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\17\ At proposal, the EPA used a model system approach for
estimating potential incremental treatment costs associated with co-
occuring PFAS at systems already required to treat in the national
model framework and the potential per system costs for the set of
systems triggered into treatment as a result of Hazard Index MCL
exceedances not already captured in the national analysis. For
further detail on the assumptions and findings of the EPA's analysis
of incremental costs of other PFAS at rule proposal, please see
appendix N.3 in the Economic Analysis for the Proposed Per- and
Polyfluoroalkyl Substances National Primary Drinking Water
Regulation (USEPA, 2023n, 2023o).
\18\ As discussed in appendix K.4, a 1 ppt reduction in both
PFOA and PFOS for a system serving a population of 100,000 would
result in $0.101 million in annualized birth weight benefits. If
including a 1 ppt PFNA reduction, in addition to a 1 ppt reduction
in both PFOA and PFOS, for a system serving a population of 100,000,
the resulting annualized birth weight benefits would increase by
$0.464 to $0.689 million, depending on the slope factor used for
PFNA. The EPA estimates that 208 water systems may exceed the PFNA
MCL.
\19\ The EPA also anticipates additional substantial benefits to
PWS customers associated with reduced exposure to Hazard Index
compounds (PFHxS, HFPO-DA, PFNA, and PFBS) not included in the
primary analysis. The nonquantifiable benefits impact categories
include developmental, cardiovascular, immune, hepatic, endocrine,
metabolic, reproductive, musculoskeletal, and carcinogenic effects.
See chapter 6.2 of the EA for more information.
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The proposed rule included a Hazard Index MCLG and MCL for any
mixture of one or more of PFHxS, HFPO-DA, PFNA, and PFBS. The final
rule includes a Hazard Index MCLG and MCL for any mixture of two or
more of PFHxS, HFPO-DA, PFNA, and PFBS. The final rule also includes
individual MCLGs and MCLs for PFHxS, PFNA, and HFPO-DA. The EPA's cost
analysis at proposal considered the costs associated with the
individual MCLs for PFHxS, PFNA, and HFPO-DA because the proposed
Hazard Index MCL would function as individual MCLs when these
contaminants occur in isolation. While the rule structure has changed
in the final NPDWR, the costing framework used at proposal is still
applicable in the final rule: what was considered a Hazard Index MCL
exceedance at proposal would be an individual MCL exceedance under the
final rule should those contaminants occur in isolation. Further, a
Hazard Index exceedance in the final rule (defined as two or more of
PFHxS, PFNA, HFPO-DA, and PFBS) is unchanged from a costing perspective
to what the EPA proposed. Whether a system exceeds a Hazard Index MCL
or individual MCL in the final rule, these costs are captured in the
cost estimates the EPA considered and presented in appendix N.3 of the
EA and summarized in this section. Specifically, if a system exceeds
only one of the individual MCLs for PFHxS, PFNA, or HFPO-DA that
exceedance is costed by estimating the removal needed to achieve
compliance with a given individual MCL. If a system exceeds the Hazard
Index MCL, that exceedance is costed by estimating the removal of the
combination of contaminants needed to achieve compliance with the
Hazard Index MCL. Therefore, the national level cost estimate for PFHxS
is reflective of both the total national cost of the PFHxS individual
MCL and instances of Hazard Index MCL exceedances where PFHxS is
present above its HBWC while other Hazard Index PFAS are present.
To understand the totality of national-level cost impacts for the
Hazard Index MCL, the EPA considered both the contribution of PFHxS
(estimated as part of the national level cost analysis), as well as the
costs for PFNA, HFPO-DA, and PFBS (estimated in the appendix N
sensitivity analysis). Together, these provide information on the costs
for the Hazard Index MCL and the individual MCLs for PFHxS, PFNA, and
HFPO-DA, as a whole. Due to available data informing the Bayesian
hierarchical occurrence model, the EPA was only able to quantify the
portion of total costs for the Hazard Index MCL attributable to PFHxS
\20\ in the national level analysis. The EPA notes that this estimate
also represents the national level quantified costs for the individual
PFHxS MCL. The EPA acknowledges that this $11.6 million estimate is
only a portion of the costs imposed by the Hazard Index MCL and also
does not account for the costs imposed by the individual PFNA and HFPO-
DA MCLs. The EPA accounted for those potential additional costs through
the sensitivity analysis described in appendix N, in which the EPA
found that costs of treating for PFNA, HFPO-DA, and PFBS to meet the
Hazard Index MCL and individual MCLs for PFNA and HFPO-DA increased
national costs by approximately 5 percent, from $1,549 million to
$1,631 million. These costs represent the total costs of the final
rule; in other words, this includes the costs associated with
individual MCLs for PFOA, PFOS, PFHxS, HFPO-DA, and PFNA, as well as
the Hazard Index MCL. Due to data limitations, the EPA has not
separately estimated the costs of the Hazard Index in the absence of
the individual MCLs. The sensitivity analysis demonstrates that the
quantified national analysis cost estimate that includes only PFOA,
PFOS, and PFHxS (where PFHxS represents only a portion of the Hazard
Index costs) marginally underestimates total rule costs when also
considering the potential cost impacts attributable to HFPO-DA, PFNA,
and PFBS. The cost estimates stemming from both the quantified national
estimate for PFOA, PFOS, and PFHxS, and from the sensitivity analysis
conducted for PFNA, HFPO-DA, and PFBS together inform the impact of the
Hazard Index MCL as required by the HRRCA under SDWA.
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\20\ The EPA notes that there are anticipated to be
circumstances where PFHxS exceeds its individual MCL and HBWC where
PFNA, PFBS, and HFPO-DA do not co-occur. While resulting in an
exceedance of the PFHxS MCL, if PFHxS exceeds its HBWC without other
Hazard Index PFAS present, this would not result in an exceedance of
the Hazard Index MCL. At rule proposal, a single exceedance of any
of the four Hazard Index PFAS would have resulted in an exceedance
of the Hazard Index MCL. However, to improve rule implementation and
to support effective risk communication, the EPA has structured the
final rule such that a Hazard Index exceedance only occurs when
there are two or more of the Hazard Index PFAS present. Therefore,
while for purposes of informing its quantified cost analysis the EPA
is assuming that every PFHxS exceedance of the MCL also causes an
exceedance of the Hazard Index MCL, this approach results in the EPA
overestimating PFHxS-attributable Hazard Index costs in its national
cost analysis.
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To fully weigh the costs and benefits of the action, the agency
considered the totality of the monetized values, the potential impacts
of the nonquantifiable uncertainties, the nonquantifiable costs and
benefits, and public comments received by the agency related to the
quantified and qualitative assessment of the costs and benefits. For
the final rule, the EPA is reaffirming the Administrator's
determination made at proposal that the quantified and nonquantifiable
benefits of the rule justify its quantified and nonquantifiable costs.
In light of the individual MCLs, the EPA has separately presented
national level marginal costs associated with the individual MCLs for
PFHxS, PFNA and HFPO-DA in the absence of the Hazard Index MCL; see
chapter 5.1.3 and appendix N.4 of the EA for details. Therefore, the
costs for the individual PFHxS, PFNA, and HFPO-DA MCLs have been
considered both in the
[[Page 32651]]
proposed and final rule. For more information on the agency's
methodology, findings, and limitations of the EPA's updated analysis of
costs associated with compliance with the Hazard Index, please see
appendix N.3 of the EA (USEPA, 2024e).
5. Benefit-Cost Determination
a. Benefit-Cost Determination in the Proposal
When proposing an NPDWR, the Administrator shall publish a
determination as to whether the benefits of the MCL justify, or do not
justify, the costs based on the analysis conducted under section
1412(b)(3)(C). For the proposed rule, the Administrator determined that
the quantified and nonquantifiable benefits of the proposed PFAS NPDWR
justified the costs.
b. Summary of Major Public Comments on Benefit-Cost Determination and
EPA Responses
Many commenters agreed with the Administrator's determination that
the benefits of the rule justify its costs. Specifically, commenters
asserted that the EPA's estimation of the net benefits of enacting the
MCLs is reasonable, stating that ``even if the costs are very
substantial, the benefits associated with the anticipated drinking
water improvements justify such expenditures.'' Commenters also stated
that it is likely that ``the analysis understates the benefits'' of the
rule, particularly given the ``significant unquantified risk reduction
benefits and co-benefits'' that are anticipated to result from the
rule.
In response to these comments, the EPA agrees that its quantified
benefits likely significantly understate the benefits of the rule due
to the large share of nonquantifiable benefits that are expected to be
realized as avoided adverse health effects, in addition to the benefits
that the EPA has quantified. The EPA anticipates additional benefits
associated with developmental, cardiovascular, liver, immune,
endocrine, metabolic, reproductive, musculoskeletal, and carcinogenic
effects beyond those benefits associated with decreased PFOA and PFOS
that the EPA has quantified. In response to commenters urging the EPA
to quantify additional health endpoints associated with PFAS exposure,
the EPA has developed a quantitative sensitivity analysis of PFOS
effects and liver cancer, further strengthening the justification for
this determination. Due to occurrence, health effects, and/or economic
data limitations, the EPA is unable to quantitatively assess additional
benefits of the rule.
Conversely, several commenters stated that the EPA has failed to
demonstrate that the benefits of the rule justify its costs.
Specifically, commenters disagreed with this determination because the
EPA's analysis ``significantly underestimates the costs of the proposed
MCLs. . .and overestimates its benefits.'' Commenters asserted that the
EPA needs to update its EA to more accurately reflect the true costs of
compliance of the rule to make the determination that the rule's costs
are justified by its benefits. A few commenters urged the EPA to
consider whether the benefits of finalizing the rule at regulatory
alternative MCLs (e.g., 5.0 or 10.0 ng/L) would better justify the
costs of the rule.
After considering public comments, the EPA has made a number of
adjustments to the cost model and collectively these changes have
increased the agency's estimated annualized costs. The EPA has used the
best available peer reviewed science to inform the cost estimates,
including treatment costs, of the final PFAS NPDWR. For more
information on the EPA's responses to comments on the rule costs, see
sections XII.A.2-XII.A.4 of this preamble. The EPA disagrees with
commenters that the EPA has overstated the benefits. As discussed in
section XII.A.1, the EPA has used the best available peer reviewed
science to quantify the benefits of the rule. The EPA also disagrees
with commenters that suggested the benefits ``better justify'' the
costs of PFOA and PFOS standards at 5.0 or 10.0 ng/L. These commenters
pointed to the quantified net benefits of the regulatory alternatives
and noted that net benefits are positive at 3 and 7 percent discount
rates for a standard of 10.0 ng/L for PFOA and PFOS. The commenters'
sole reliance on the quantified costs and benefits of the rule to
support their argument is incorrect, as SDWA requires the agency to
consider both the quantifiable and nonquantifiable impacts of the rule
in the determination. Under SDWA 1412(b)(4)(B), the EPA is required to
set an MCL as close as feasible to the MCLG, taking costs into
consideration. In other words, SDWA does not mandate that the EPA
establish MCLs at levels where the quantified benefits exceed the
quantified costs. This was many commenters' justification for the
recommendation to promulgate a standard of 10.0 ppt each for PFOA and
PFOS in lieu of the proposed rule, and the EPA therefore disagrees that
quantified costs and benefits can or should be the sole determinant of
an MCL value. The Administrator's assessment that the benefits of the
proposed rule justified its costs was based on the totality of the
evidence, specifically the quantified and nonquantifiable benefits,
which are anticipated to be substantial, as well as the quantified and
nonquantifiable costs. Other commenters incorrectly stated that SDWA
requires the EPA to set an MCL at a level `` . . . that maximizes
health risk reduction benefits at a cost that is justified by the
benefits.'' This test is found in section 1412(b)(6)(A) of SDWA and
applies only when the Administrator determines based on the HRRCA that
the benefits of a proposed MCL developed in accordance with paragraph
(4) would not justify the costs of complying with the level. In the
case of the proposed PFAS NPDWR, the Administrator determined that the
benefits justify the costs for MCLs set as close as feasible to the
MCLGs. For more information on the EPA's response to comments on the
regulatory alternative MCLs considered in this rule, see section V of
this preamble.
c. Benefit-Cost Determination in the Final Rule Analysis
For the final rule, considering both quantifiable and
nonquantifiable costs and benefits of the rule as discussed in the EA
and EA Appendices, the EPA is reaffirming the Administrator's
determination made at proposal that the quantified and nonquantifiable
benefits of the MCLs justify their costs.
B. Affected Entities and Major Data Sources Used To Develop the
Baseline Water System Characterization
The entities potentially affected by the final rule are primacy
agencies and PWSs. PWSs subject to final rule requirements are either
CWSs or NTNCWSs. These water systems can be publicly or privately
owned. PWSs subject to the rule would be required to meet the MCL and
comply with monitoring and reporting requirements. Primacy agencies
would be required to adopt and enforce the drinking water standard as
well as the monitoring and reporting requirements.
Both PWSs and primacy agencies are expected to incur costs,
including administrative costs, monitoring, and reporting costs, and in
some cases, anticipated costs to reduce PFAS levels in drinking water
to meet the final rule using treatment or nontreatment options. Section
D of this preamble summarizes the method the EPA used to estimate these
costs.
The systems that reduce PFAS concentrations will reduce associated
[[Page 32652]]
health risks. The EPA developed methods to estimate the potential
benefits of reduced PFAS exposure among the service populations of
systems with PFAS levels exceeding the final drinking water standard.
Section E summarizes the method used to estimate these benefits.
In its Guidelines for Preparing Economic Analyses, the EPA
characterizes the ``baseline'' as a reference point that reflects the
world without the final regulation (USEPA, 2016e). It is the starting
point for estimating the potential benefits and costs of the final
NPDWR. The EPA used a variety of data sources to develop the baseline
drinking water system characterization for the regulatory analysis.
Table 27 lists the major data sources and the baseline data derived
from them. Additional detailed descriptions of these data sources and
how they were used in the characterization of baseline conditions can
be found in chapter 4 of USEPA (2024g).
[GRAPHIC] [TIFF OMITTED] TR26AP24.032
C. Overview of the Cost-Benefit Model
The EPA's existing SafeWater Cost Benefit Model (CBX) was designed
to calculate the costs and benefits associated with setting a new or
revised MCL. Since the final rule simultaneously regulates multiple
PFAS contaminants, the EPA developed a new model version called the
SafeWater Multi-Contaminant Benefit Cost Model (MCBC) to efficiently
handle more than one contaminant. SafeWater MCBC allows for inputs that
include differing mixtures of contaminants based on available
occurrence data as well as multiple regulatory thresholds. The model
structure allows for assignment of compliance technology or
technologies that achieve all regulatory requirements and estimates
costs and benefits associated with multiple PFAS contaminant
reductions. SafeWater MCBC is designed to model co-occurrence,
sampling, treatment, and administrative costs, and simultaneous
contaminant reductions and resultant benefits. The modifications to the
SafeWater model are consistent with the methodology that was developed
in the single MCL SafeWater CBX Beta version that was peer reviewed.
More detail on the modifications to the SafeWater model can be found in
section 5.2 of the EPA's EA.
The costs incurred by a PWS depend on water system characteristics;
SDWIS
[[Page 32653]]
Fed provides information on PWS characteristics that typically define
PWS categories, or strata, for which the EPA developed cost estimates
in rulemakings, including system type (CWS, NTNCWS), number of people
served by the PWS, the PWS's primary raw water source (ground water or
surface water), the PWS's ownership type (public or private), and the
state in which the PWS is located.
Because the EPA does not have complete PWS-specific data across the
approximately 49,000 CWSs and 17,000 NTNCWSs in SDWIS Fed for many of
the baseline and compliance characteristics necessary to estimate costs
and benefits, such as design and average daily flow rates, water
quality characteristics, treatment in-place, and labor rates, the EPA
adopted a ``model PWS'' approach. SafeWater MCBC creates model PWSs by
combining the PWS-specific data available in SDWIS Fed with data on
baseline and compliance characteristics available at the PWS category
level. In some cases, the categorical data are simple point estimates.
In this case, every model PWS in a category is assigned the same value.
In other cases, where more robust data representing system variability
are available, the category-level data include a distribution of
potential values. In the case of distributional information, SafeWater
MCBC assigns each model PWS a value sampled from the distribution.
These distributions are assumed to be independent.
For a list of PWS characteristics that impact model PWS compliance
costs, please see chapter 5 of USEPA (2024g). These data include
inventory data specific to each system and categorical data for which
randomly assigned values are based on distributions that vary by
category (e.g., ground water and surface water TOC distributions or
compliance forecast distributions that vary by system size category).
Once model PWSs are created and assigned baseline and compliance
characteristics, SafeWater MCBC estimates the quantified costs and
benefits of compliance for each model PWS under the final rule. Because
of this model PWS approach, SafeWater MCBC does not output any results
at the PWS level. Instead, the outputs are cost and benefit estimates
for 36 PWS categories, or strata. Each PWS category is defined by
system type (CWS and NTNCWS), primary water source (ground or surface),
and size category. Note the EPA does not report state-specific strata
although state location is utilized in the SafeWater MCBC model (e.g.,
current state-level regulatory limits on PFAS in drinking water). The
detailed output across these strata can be found in the chapter 5 of
USEPA (2024g).
For each PWS category, the model then calculates summary statistics
that describe the costs and benefits associated with final rule
compliance. These summary statistics include total quantified costs of
the final rule, total quantified benefits of the final rule, the
variability in PWS-level costs (e.g., 5th and 95th percentile system
costs), and the variability in household-level costs.
D. Method for Estimating Costs
This section summarizes the cost elements and estimates total cost
of compliance for the PFAS NPDWR discounted at 2 percent. The EPA
estimated the costs associated with monitoring, administrative
requirements, and both treatment and nontreatment compliance actions
associated with the final rule (USEPA, 2024g).
1. Public Water System (PWS) Costs
a. PWS Treatment and Nontreatment Compliance Costs
The EPA estimated costs associated with engineering, installing,
operating, and maintaining PFAS removal treatment technologies,
including treatment media replacement and spent media destruction or
disposal, as well as nontreatment actions that some PWSs may take in
lieu of treatment, such as constructing new wells in an uncontaminated
aquifer or interconnecting with and purchasing water from a neighboring
PWS. The EPA used SafeWater MCBC to apply costs for one of the
treatment technologies or nontreatment alternatives at each EP in a PWS
estimated to be out of compliance with the final rule. For each
affected EP, SafeWater MCBC selected from among the compliance
alternatives using a decision tree procedure, described in more detail
in USEPA (2024j). Next, the model estimated the cost of the chosen
compliance alternative using outputs from the EPA's WBS cost estimating
models. The WBS models are spreadsheet-based engineering models for
individual treatment technologies, linked to a central database of
component unit costs.
Specifically, the EPA used cost equations generated from the
following models (USEPA, 2024m):
the GAC WBS model (USEPA, 2024p);
the PFAS-selective IX WBS model (USEPA, 2024q); and
the nontreatment WBS model (USEPA, 2024r).
The Technologies and Costs (T&C) document (USEPA, 2024m) provides a
comprehensive discussion of each of the treatment technologies, their
effectiveness, and the WBS cost models as well as the equations used to
calculate treatment costs. In total, there are more than 2,600
individual cost equations across the categories of capital and
operation and maintenance (O&M) cost, water source, component level,
flow, bed life (for GAC and IX), residuals management scenarios (for
GAC and IX), and design type (for GAC). These models are available on
the EPA's website at https://www.epa.gov/sdwa/drinking-water-treatment-technology-unit-cost-models as well as in the docket for this rule.
b. Decision Tree for Technology Selection
For EP at which baseline PFAS concentrations exceed regulatory
thresholds, SafeWater MCBC selects a treatment technology or
nontreatment alternative using a two-step process that both:
Determines whether to include or exclude each alternative
from consideration given the EP's characteristics and the regulatory
option selected, and
Selects from among the alternatives that remain viable
based on percentage distributions derived, in part, from data on recent
PWS actions in response to PFAS contamination.
Inputs to SafeWater MCBC used in Step 1 include the following:
Influent concentrations of individual PFAS contaminants in
ng/L (ppt)
EP design flow in MGD
TOC influent to the new treatment process in mg/L.
The EPA relied on information from the national PFAS occurrence
model to inform influent PFAS concentrations. The EPA relied on
Geometries and Characteristics of Public Water Supplies (USEPA, 2000g)
and SDWIS inventory information to derive EP design flow. SafeWater
MCBC selects influent TOC using the distribution shown in Table 28.
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In Step 1, SafeWater MCBC uses these inputs to determine whether to
include or exclude each treatment alternative from consideration in the
compliance forecast. For the treatment technologies (GAC and IX), this
determination is based on estimates of each technology's performance
given available data about influent water quality and the regulatory
option under consideration.
The EPA assumes a small number of PWSs may be able to take
nontreatment actions in lieu of treatment. The viability of
nontreatment actions is likely to depend on the quantity of water being
replaced because the ability to purchase from another water system is
limited by the seller water system's capacity and the ability to drill
another well is limited by the ability to find an accessible,
sufficiently large source. Therefore, SafeWater MCBC considers
nontreatment only for EP with design flows less than or equal to 3.536
MGD. The EPA estimates approximately 2 percent of systems of this size
will develop new wells and approximately 6-7 percent of systems will
elect to interconnect with another system to achieve compliance.
In Step 2, SafeWater MCBC selects a compliance alternative for each
EP from among the alternatives that remain in consideration after Step
1. Table 29 shows the initial compliance forecast that is the starting
point for this step. The percentages in Table 29 consider data
presented in the T&C document (USEPA, 2024m) on actions PWSs have taken
in response to PFAS contamination.
To date, the majority of PWSs for which data are available have
installed GAC (USEPA, 2024m). USEPA (2024m) includes data for 52
systems, 34 of which (65%) have installed GAC. The data in USEPA
(2024m) also suggest that an increasing share of PWSs have selected IX
in response to PFAS since the first full-scale system treated with
PFAS-selective IX in 2017. Specifically, for systems installed prior to
2017, 78% used GAC. The EPA expects this trend to continue, so the
initial percentages include adjustments to account for this
expectation. In addition, the performance of GAC is affected by the
presence of TOC, as further described in the cost chapter of the EA
(USEPA, 2024g). Accordingly, the table includes adjusted distributions
for systems with higher influent TOC. Finally, while central RO/NF
remains a BAT for the final rule, the EPA does not anticipate water
systems will select this technology to comply with the rule, largely
due to the challenges presented by managing the treatment residuals
from this process.
The list of compliance alternatives in Table 29 does not include
POU devices for small systems. At this time, the EPA is not including
POU devices in the national cost estimates because the final rule
require treatment to concentrations below the current NSF/ANSI
certification standard for POU devices. However, POU treatment is
reasonably anticipated to become a compliance option for small systems
in the future if independent third-party certification organizations,
such as NSF or ANSI develop a new certification standard that mirrors
the EPA's final regulatory standard. Therefore, the decision tree
excludes POU devices from consideration.
[[Page 32655]]
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If all the compliance alternatives remain in consideration after
Step 1, the decision tree uses the forecast shown in Table 29 above. If
Step 1 eliminated one or more of the alternatives, SafeWater MCBC
proportionally redistributes the percentages among the remaining
alternatives and uses the redistributed percentages.
The EPA's approach to estimating GAC and IX performance for the
final rule and all alternatives considered is discussed in detail
within the cost chapter of the EA (USEPA, 2024g).
c. Work Breakdown Structure Models
The WBS models are spreadsheet-based engineering models for
individual treatment technologies, linked to a central database of
component unit costs. The EPA developed the WBS model approach as part
of an effort to address recommendations made by the Technology Design
Panel (TDP), which convened by the EPA in 1997 to review the agency's
methods for estimating drinking water compliance costs (USEPA, 1997).
The TDP consisted of nationally recognized drinking water experts from
the EPA, water treatment consulting companies, public as well as
private water utilities along with suppliers, equipment vendors, and
Federal along with state regulators in addition to cost estimating
professionals.
In general, the WBS approach involves breaking a process down into
discrete components for the purpose of estimating unit costs. The WBS
models represent improvements over past cost estimating methods by
increasing comprehensiveness, flexibility, and transparency. By
adopting a WBS-based approach to identify the components that should be
included in a cost analysis, the models produce a more comprehensive,
flexible, and transparent assessment of the capital and operating
requirements for a treatment system.
Each WBS model contains the work breakdown for a particular
treatment process and preprogrammed engineering criteria and equations
that estimate equipment requirements for user-specified design
requirements (e.g., system size and influent water quality). Each model
also provides unit and total cost information by component (e.g.,
individual items of capital equipment) and totals the individual
component costs to obtain a direct capital cost. Additionally, the
models estimate add-on costs (e.g., permits and land acquisition),
indirect capital costs, and annual O&M costs, thereby producing the
EPA's best estimates of complete compliance costs.
Primary inputs common to all the WBS models include design flow and
average daily flow in MGD. Each WBS model has default designs (input
sets) that correspond to specified categories of flow, but the models
can generate designs for many other combinations of flows. To estimate
costs for PFAS compliance, the EPA fit cost curves to the WBS estimates
across a range of flow rates, which is described in chapter 5 of the EA
(USEPA, 2024g).
Another input common to all the WBS models is ``component level''
or ``cost level.'' This input drives the selection of materials for
items of equipment that can be constructed of different materials. For
example, a low-cost system might include fiberglass pressure vessels
and polyvinyl chloride (PVC) piping. A high-cost system might include
stainless steel pressure vessels and stainless-steel piping. The
component level input also drives other model assumptions that can
affect the total cost of the system, such as building quality and
heating and cooling. The component level input has three possible
values: low cost, mid cost, and high cost. The components used in each
of the estimated component/cost levels provide the treatment efficacy
needed to meet the regulatory requirements. Note that the level of
component (e.g., plastic versus resin or stainless-steel piping and
vessels) may impact the capital replacement rate but does not interfere
with treatment efficacy. The EPA estimates the three levels of cost
because it has found that the choice of materials associated with the
installation of new treatment equipment often varies across drinking
water systems. These systems may, for example, choose to balance
capital cost with staff familiarity with certain materials and existing
treatment infrastructure. Given this experience, the EPA models the
potential variability in treatment cost based on the three component/
cost levels. To estimate costs for PFAS treatment, the EPA generated
separate cost equations for each of the three component levels, thus
creating a range of cost estimates for use in national compliance cost
estimates.
The third input common to all the WBS models is system automation,
which allows the design of treatment systems that are operated manually
or with varying degrees of automation (i.e., with control systems that
reduce the need for operator intervention). Cost
[[Page 32656]]
equations for system automation are described in chapter 5 of the EA
(USEPA, 2024g).
The WBS models generate cost estimates that include a consistent
set of capital, add-on, indirect, and O&M costs. Table 30 identified
these cost elements, which are common to all the WBS models and
included in the cost estimates. As described and summarized in Tables
31-34 the WBS models also include technology-specific cost elements.
The documentation for the WBS models provides more information on the
methods and assumptions in the WBS models to estimate the costs for
both the technology-specific and common cost elements (USEPA, 2024p;
USEPA, 2024q; USEPA, 2024r). WBS model accuracy as well as limitations
and uncertainty are described in chapter 5 of the EA (USEPA, 2024g).
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[[Page 32657]]
The GAC model can generate costs for two types of design:
Pressure designs where the GAC bed is contained in
stainless steel, carbon steel, or fiberglass pressure vessel.
Gravity designs where the GAC bed is contained in open
concrete basins.
Table 31 shows the technology-specific capital equipment and O&M
requirements included in the GAC model. These items are in addition to
the common WBS cost elements listed in the Table 30 above.
[GRAPHIC] [TIFF OMITTED] TR26AP24.036
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For small systems (less than 1 MGD) using pressure designs, the GAC
model assumes the use of package treatment systems that are pre-
assembled in a factory, mounted on a skid, and transported to the site.
These assumptions are based on common vendor practice for these
technologies, for example, see Khera et al. (2013) which says ``. . .
small systems are often built as packaged, pre-engineered, or skid-
mounted systems.'' The model estimates costs for package systems by
costing all individual equipment line items (e.g., vessels,
interconnecting piping and valves, instrumentation, and system
controls) in the same manner as custom-engineered systems. This
approach is based on vendor practices of partially engineering these
types of package plants for specific systems (e.g., selecting vessel
size to meet flow and treatment criteria). The model applies a variant
set of design inputs and assumptions that are intended to simulate the
use of a package plant and that reduce the size and cost of the
treatment system. USEPA (2024p) provides complete details on the
variant design assumptions used for package plants.
To generate the GAC cost equations, the EPA used the following key
inputs in the GAC model:
For pressure designs, two vessels in series with a minimum
total empty bed contact time (EBCT) of 20 minutes;
For gravity designs, contactors in parallel with a minimum
total EBCT of 20 minutes; and
Bed life varying over a range from 5,000 to 75,000 BV.
The EPA generated separate cost equations for two spent GAC
management scenarios:
Off-site reactivation under current RCRA non-hazardous
waste regulations;
Off-site disposal as a hazardous waste in a RCRA Subtitle
C landfill and replacement with virgin GAC (i.e., single use
operation).
The T&C document (USEPA, 2024m) provides a comprehensive discussion
of
[[Page 32658]]
these and other key inputs and assumptions.
Table 32 shows the technology-specific capital equipment and O&M
requirements included in the PFAS selective IX model. These items are
in addition to the common WBS cost elements listed in the Table 30
above.
[GRAPHIC] [TIFF OMITTED] TR26AP24.037
For small systems (less than 1 MGD), the PFAS-selective IX model
assumes the use of package treatment systems that are pre-assembled in
a factory, mounted on a skid, and transported to the site. The IX model
estimates costs for package systems using an approach similar to that
described for the GAC model, applying a variant set of inputs and
assumptions that reduce the size and cost of the treatment system.
USEPA (2024q) provides complete details on the variant design
assumptions used for IX package plants.
To generate the IX cost equations, the EPA used the following key
inputs in the PFAS-selective IX model:
Two vessels in series with a minimum total EBCT of 6 minutes
Bed life varying over a range from 20,000 to 260,000 BV
The EPA generated separate cost equations for two spent resin
management scenarios:
Spent resin managed as non-hazardous and sent off-site for
incineration.
Spent resin managed as hazardous and sent off-site for
incineration.
The T&C document (USEPA, 2024m) provides a comprehensive discussion
of these and other key inputs and assumptions.
USEPA (2024r) provides a complete description of the engineering
design process used by the WBS model for nontreatment actions. The
model can estimate costs for two nontreatment alternatives:
interconnection with another system and drilling new wells to replace a
contaminated source. Table 33 shows the technology-specific capital
equipment and O&M requirements included in the model for each
alternative.
[[Page 32659]]
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To generate the cost equations, the EPA used the following key
inputs in the nontreatment model for interconnection:
An interconnection distance of 10,000 feet
Includes booster pumps designed to account for friction loss
in interconnecting piping
An average cost of purchased water of $3.35 per thousand
gallons in 2022 dollars.
For new wells, the EPA used the following key inputs:
A maximum well capacity of 500 gallons per minute (GPM), such
that one new well is installed per 500 GPM of water production capacity
required
A well depth of 250 feet
500 feet of distance between the new wells and the
distribution system.
The T&C document (USEPA, 2024m) provides a comprehensive discussion
of these and other key inputs and assumptions.
d. Incremental Treatment Costs
The EPA has estimated the national level costs of the final rule
associated with PFOA, PFOS, and PFHxS. As discussed in chapter 4 of the
EA and detailed in the Technical Support Document for PFAS Occurrence
and Contaminant Background chapter 10.1 and 10.3, there are limitations
with nationally representative occurrence information for the other
contaminants in the final rule (PFNA, HFPO-DA and PFBS). Specifically,
HFPO-DA does not currently have a completed nationally representative
dataset while PFNA and PFBS were not included in the national
occurrence model because of limited results reported above the minimum
reporting levels in UCMR 3. As described in the Technical Support
Document for PFAS Occurrence and Contaminant Background chapter 10.3.2,
non-targeted state monitoring datasets were used for extrapolation of
PFNA, HFPO-DA, and PFBS in lieu of a nationally representative dataset.
The EPA used conservative assumptions in this extrapolation to generate
conservative cost estimates. As demonstrated in this analysis, the
Hazard Index, PFNA, and HFPO-DA MCLs meaningfully increase public
health protection at modest additional costs. Because of the increased
uncertainty associated with PFNA, HFPO-DA and PFBS, the additional
treatment cost from co-occurrence of PFNA, HFPO-DA, PFBS at systems
already required to treat because of PFOA, PFOS, or PFHxS MCL and
Hazard Index exceedances are not quantitatively assessed in the
national cost estimates. These three PFAS' treatment costs are
summarized here in this section and detailed in appendix N.3 of the EA
(USEPA, 2024e). Likewise, treatment costs for systems that exceed the
Hazard Index based on the combined occurrence of PFNA, HFPO-DA, PFBS,
and PFHxS (where PFHxS itself does not exceed its HBWC of 10 ng/L) are
not included in the national monetized cost estimates and are also
summarized in this section and detailed in appendix N.3 of the EA
(USEPA, 2024e).
In the EA for the proposed PFAS NPDWR, the EPA used a model system
approach to illustrate the potential incremental costs for removing
PFAS not included in the national economic model. After considering
public comments on the incremental cost analysis, the EPA decided to
further explore the incremental costs associated with the Hazard Index
and MCLs with a national level sensitivity analysis for the final rule.
When the modeled occurrence data for PFNA, HFPO-DA, PFBS is
incorporated into the SafeWater MCBC model, the estimated number of EP
[[Page 32660]]
exceeding one or more MCLs, and therefore required to treat or use a
different water source, increases to 9,471 from 9,043. This results in
an increase in the expected national costs. Under the primary analyses,
the expected total national cost is $1,549 million over the EPA's
period of analysis (2024-2105) for the PFOA, PFOS, and PFHxS MCLs. When
considering the additional incremental national cost impacts of the
Hazard Index MCL for, PFNA, HFPO-DA, and PFBS (and individual MCLs for
PFNA and HFPO-DA) the expected national costs of the final rule
increase to $1,631 million at, or approximately a 5 percent national
cost increase.
For further detail on the assumptions and findings of the EPA's
analysis of incremental costs of other PFAS, see appendix N.3 and
section XII.A of this preamble.
e. PWS Implementation Administration Costs
The EPA estimated PWS costs associated with one-time actions to
begin implementation of the rule including reading and understanding
the rule and attending training provided by primacy agencies. The
average unit costs for PWSs are based on the following burden
assumptions: (1) The EPA anticipates that the majority of water systems
will likely not read the entirety of the rule preamble (as they are not
required to do so) but focus their time and attention on understanding
the regulatory requirements through the CFR regulatory text, relevant
portions of the preamble, the EPA provided fact sheets and small system
guidance documents, and state provided summaries documents; (2)
Additionally, the EPA anticipates that system staff will attend primacy
agency PFAS rule trainings to reenforce the systems' understanding of
the final rule. The EPA assumes that systems will conduct these
activities during years one through three of the analysis period. Table
34 lists the data elements and corresponding values associated with
calculating the costs of these one-time implementation administration
actions.
[GRAPHIC] [TIFF OMITTED] TR26AP24.039
Estimated national annualized PWS implementation and administration
startup costs for the final rule are $1.33 million. National annualized
PWS cost estimates are further summarized in Table 39.
f. PWS Monitoring Costs
The final rule requires initial and long-term monitoring. As Table
35 shows, surface and ground water systems serving greater than 10,000
people will collect one sample each quarter, at each EP, during the
initial 12-month monitoring period. Surface water systems serving
10,000 or fewer people are also required to collect a quarterly sample
at each EP during the initial 12-month period. Ground water systems
that serve 10,000 or fewer people will be required to sample once at
each EP on a semi-annual basis for the first 12-month monitoring
period.
Long-term monitoring schedules are based on specific EP sampling
results (i.e., water systems can have different EP within the system on
different monitoring schedules). Long-term monitoring requirements
differ based on whether a system can demonstrate during the initial
monitoring period or once conducting long-term monitoring that an EP is
below the trigger levels for regulated PFAS. The trigger levels are set
as one-half the MCLs: 2.0 ng/L for PFOA and PFOS, 5 ng/L each for
PFHxS, PFNA, and HFPO-DA, and 0.5 for the Hazard Index. EP below the
trigger level values during the initial 12-month monitoring period and
in future long-term monitoring periods may conduct triennial monitoring
and collect one triennial sample at that EP. For EP with concentration
values at or above a trigger level, a quarterly sample must be taken at
that EP following initial monitoring. EP that demonstrate they are
``reliably and consistently'' \21\ below the MCLs following four
consecutive quarterly samples are eligible to conduct annual
monitoring. After three annual samples at that EP showing no results at
or above a trigger level, the location can further reduce to triennial
monitoring.
---------------------------------------------------------------------------
\21\ The definition of reliably and consistently below the MCL
means that each of the samples contains regulated PFAS
concentrations below the applicable MCLs. For the PFAS NPDWR, this
demonstration of reliably and consistently below the MCL would
include consideration of at least four quarterly samples at an EP
below the MCL, but states will make their own determination as to
whether the detected concentrations are reliably and consistently
below the MCL.
---------------------------------------------------------------------------
For any samples that are above detection, the system will analyze
the FRB samples collected at the same time as the monitoring sample.
Systems that have an MCL exceedance will collect one additional sample
from the relevant EP to confirm the results.
[[Page 32661]]
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For the national cost analysis, the EPA assumes that systems with
either UCMR 5 data or monitoring data in the State PFAS Database (see
section 3.1.4 in USEPA, 2024g) will not conduct the initial year of
monitoring as allowed by the final rule. As a simplifying assumption
for the cost analysis, the EPA assumes all systems serving a population
of greater than 3,300 have UCMR 5 data and those with 3,300 or less do
not. For the State PFAS Database, the EPA relied on the PWSIDs stored
in the database and exempted those systems from the first year of
monitoring in the cost analysis. Note these simplifying assumptions may
result in a small underestimate of initial monitoring costs. Under UCMR
5, individual water systems would be able to request the full release
of data from the labs for use in determining their compliance
monitoring frequency. PWSs may be able to use these lab analyses to
demonstrate a ``below trigger level'' concentration using the UCMR 5
analyses by following up with the lab for a more detailed results
report.
The EPA used system-level distributions of PFOA, PFOS, and PFHxS,
as described in Cadwallader et al. (2022), to simulate EP
concentrations and estimate PFAS occurrence relative to the final rule
MCLs and trigger levels. Based on these occurrence distributions, the
EPA estimates that the large majority of water systems subject to the
rule (approx. 52,000-57,000) will have EP with concentrations below the
trigger levels and would conduct reduced monitoring on a triennial
basis. The EPA estimates that the remainder of water systems subject to
the rule (approx. 9,000-15,000) will have at least one or more EP
exceed the trigger level and therefore would be required to conduct
quarterly monitoring.
The EPA assumes that systems with an MCL exceedance will implement
actions to comply with the MCL by the compliance date. The EPA assumes
a treatment target,\22\ for systems required to treat for PFAS, that
includes a margin of safety so finished water PFAS levels at these
systems are 80 percent of the MCLs. In the final rule, in order to
reduce burden associated with monitoring, the EPA is adding an annual
tier of sampling for any system with concentrations ``reliably and
consistently'' \23\ below the MCL but not consistently below the
trigger level. The EPA believes this tier would likely
[[Page 32662]]
apply to most systems treating their water for regulated PFAS, at least
for the first three years of treatment. Therefore, in the model, the
EPA assumes EP that have installed treatment will take one year of
quarterly samples, then continue to sample on an annual basis after
that. The final rule allows EP showing no results at or above a trigger
level after three annual samples to further reduce to triennial
monitoring. In the national cost analysis, the EPA does not model this
possibility nor does the EPA model instances where water systems are
triggered back into quarterly monitoring after installing treatment.
---------------------------------------------------------------------------
\22\ A treatment target is a contaminant concentration that a
PWS has designed and operated their water system to meet. The EPA
assumes all PWS will target 80% of the MCLs.
\23\ The definition of reliably and consistently below the MCL
means that each of the samples contains regulated PFAS
concentrations below the applicable MCLs. For the PFAS NPDWR, this
demonstration of reliably and consistently below the MCL would
include consideration of at least four quarterly samples at an EP
below the MCL, but states will make their own determination as to
whether the detected concentrations are reliably and consistently
below the MCL.
---------------------------------------------------------------------------
For all systems, the activities associated with the sample
collection in the initial 12-month monitoring period are the labor
burden and cost for the sample collection and analysis, as well as a
review of the sample results. Table 36 presents the data elements and
corresponding values associated with calculating sampling costs during
the implementation monitoring period.
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[[Page 32663]]
Estimated national annualized PWS sampling costs for the final rule
have an expected value of $36.23 million. National annualized PWS cost
estimates are further summarized in Table 39.
g. Treatment Administration Costs
Any system with an MCL exceedance adopts either a treatment or
nontreatment alternative to comply with the rule. The majority of
systems are anticipated to install treatment technologies while a
subset of systems will choose alternative methods. The EPA assumes that
systems will bear administrative costs associated with these treatment
or nontreatment compliance actions (i.e., permitting costs). The EPA
assumes that systems will install treatment in the fifth year of the
period of analysis. In addition, after installation of treatment, the
EPA assumes that systems will spend an additional 2 hours per treating
EP compiling data for and reviewing treatment efficacy with their
primacy agency during their triennial sanitary survey. Table 37
presents the data elements and corresponding values associated with
calculating treatment administration costs.
[GRAPHIC] [TIFF OMITTED] TR26AP24.042
h. Public Notification (PN) Costs
The EPA's cost analysis assumes full compliance with the rule
throughout the period of analysis and, as a result, the EPA does not
estimate costs for the PN requirements in the final rule for systems
with certain violations. The final rule designates MCL violations for
PFAS as Tier 2, which requires systems to provide PN as soon as
practical, but no later than 30 days after the system learns of the
violation. The system must repeat notice every three months if the
violation or situation persists unless the primacy agency determines
otherwise. At a minimum, systems must give repeat notice at least once
per year. The final rule also designates monitoring and testing
procedure violations as Tier 3, which requires systems to provide
public notice no later than one year after the system learns of the
violation. The system must repeat the notice annually for as long as
the violation persists. CWSs may deliver Tier 3 PNs in their CCR if the
timing, content, and delivery requirements are met according to 40 CFR
141.204(d). Using the CCR to deliver Tier 3 PNs can minimize the burden
on systems by reducing delivery costs. For approximate estimates of the
potential burden associated with Tier 2 and 3 PNs, please see USEPA
(2024g).
i. Primacy Agency Costs
The EPA assumes that primacy agencies will have upfront
implementation costs as well as costs associated with system actions
related to sampling and treatment. The activities that primacy agencies
are expected to carry out under the final rule include:
Reading and understanding the rule, providing internal
primacy agency officials training for the rule implementation, updating
sanitary survey standard operating procedures,
Primacy package application, including making regulatory
changes to the Federal rule where applicable,
Providing systems with training and technical assistance
during the rule implementation,
Reporting to the EPA on an ongoing basis any PFAS-specific
information under 40 CFR 142.15 regarding violations as well as
enforcement actions and general operations of PWS programs,
Performing inspection of PFAS related treatment during
sanitary surveys every three years
[[Page 32664]]
Reviewing the sample results during the implementation
monitoring period and the SMF period, and
Reviewing and consulting with systems on the installation
of treatment technology or alternative methods, including source water
change.
For the last three activities listed above, the primary agency
burdens are incurred in response to action taken by PWSs; for instance,
the cost to primacy agencies of reviewing sample results depends on the
number of samples taken at each EP by each system under an agency's
jurisdiction. Table 38 presents the data elements and corresponding
values associated with calculating primacy agency costs.
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Estimated national annualized primacy agency costs for the final
rule have an expected value of $4.65 million. National annualized cost
estimates are further summarized in Table 39.
[[Page 32665]]
In addition to the costs described above, a primacy agency may also
have to review the certification of any Tier 2 or 3 PNs sent out by
systems. The EPA assumes full compliance with the final rule and
therefore does not include this cost in national estimated cost totals
but provides a brief discussion of the possible primacy agency burden
associated with this component in USEPA (2024g).
In Table 39, the EPA summarizes the total annualized quantified
cost of the final rule at a 2 percent discount rate expressed in
millions of 2022 dollars. The first three rows show the annualized PWS
sampling costs, the annualized PWS implementation and administrative
costs, and the annualized PWS treatment costs. The fourth row shows the
sum of the annualized PWS costs. The expected annualized PWS costs are
$1,544 million. The uncertainty range for annualized PWS costs are
$1,431 million to $1,667 million. Finally, annualized primacy agency
implementation and administrative costs are added to the annualized PWS
costs to calculate the total annualized cost of the final rule. The
expected total annualized cost of the final rule is $1,549 million. The
uncertainty range for the total annualized costs of the final rule is
$1,436 million to $1,672 million. The EPA notes that treatment costs
associated with the rule are the most significant contribution to
overall rule costs for the final rule and the regulatory alternatives.
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In Tables 40, 41, and 42, the EPA summarizes the total annualized
quantified cost of options 1a, 1b, and 1c, respectively.
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j. Data Limitations and Uncertainties in the Cost Analysis
Table 43 lists data limitations and characterizes the impact on the
quantitative cost analysis. The EPA notes that in most cases it is not
possible to judge the extent to which a particular limitation or
uncertainty could affect the cost analysis. The EPA provides the
potential direction of the impact on the cost estimates when possible
but does not prioritize the entries with respect to the impact
magnitude.
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E. Nonquantifiable costs of the final rule
As described in section j. (Data Limitations and Uncertainties in
the Cost Analysis) above, given the available occurrence data for the
other compounds in the rule (PFNA, HFPO-DA, and PFBS) and the
regulatory thresholds under consideration, the EPA considered national
costs associated with potential Hazard Index exceedances as a direct
result of these compounds in a sensitivity analysis; therefore, the
additional treatment cost,
[[Page 32672]]
from co-occurrence of PFNA, HFPO-DA, PFBS, at systems already required
to treat because of PFOA, PFOS, or PFHxS MCL and Hazard Index
exceedances are not presented in the national cost estimates above. Nor
are treatment costs for systems that exceed the Hazard Index based on
the combined occurrence of PFHxS (where PFHxS itself does not exceed 10
ng/L), PFNA, HFPO-DA, and PFBS presented in the national monetized cost
estimates above. Treatment costs for the individual PFNA and HFPO-DA
MCLs are also not considered above. For further discussion of how the
EPA considered the costs of the five individual MCLs and the HI MCL,
see section XII.A.4 of this preamble. These potential additional costs
are described in greater detail in section 5.3.1.4 of USEPA (2024g) and
appendix N.3 of USEPA (2024e). When considering the national cost
impacts of the Hazard Index MCL for PFNA, HFPO-DA, and PFBS (and
individual MCLs for PFNA and HFPO-DA) the expected national costs
increase from $1,549 million to $1,631 million, or approximately a 5
percent national cost increase.
PFAS-contaminated wastes are not considered RCRA regulatory or
characteristic hazardous wastes at this time and therefore total costs
reported in this table do not include costs associated with hazardous
waste disposal of spent filtration materials. To address stakeholder
concerns, including those raised during the Small Business Regulatory
Enforcement Fairness Act (SBREFA) process, the EPA conducted a
sensitivity analysis with an assumption of hazardous waste disposal for
illustrative purposes only. As part of this analysis, the EPA generated
a second full set of unit cost curves that are identical to the curves
used for the national cost analysis with the exception that spent GAC
and spent IX resin are considered hazardous. If in the future PFAS-
contaminated wastes require handling as hazardous wastes, the residuals
management costs are expected to be higher. See appendix N.2 of the EA
for a sensitivity analysis describing the potential increase in costs
associated with hazardous waste disposal (USEPA, 2024e).
F. Method for Estimating Benefits
The EPA's quantification of health benefits resulting from reduced
PFAS exposure in drinking water was driven by PFAS occurrence
estimates, PK model availability, information on exposure-response
relationships, and economic data to monetize the impacts. In the EA,
the EPA either quantitatively assesses or qualitatively discusses
health endpoints associated with exposure to PFAS. The EPA assesses
potential benefits quantitatively if there is evidence of an
association between PFAS exposure and health effects, if it is possible
to link the outcome to risk of a health effect, and if there is no
overlap in effect with another quantified endpoint in the same outcome
group. Particularly, the most consistent epidemiological associations
with PFOA and PFOS include decreased immune system response, decreased
birthweight, increased serum lipids, and increased serum liver enzymes
(particularly alanine transaminase, ALT). The available evidence
indicates effects across immune, developmental, cardiovascular, and
hepatic organ systems at the same or approximately the same level of
exposure.
Table 44 presents an overview of the categories of health benefits
expected to result from the implementation of treatment that reduces
PFAS levels in drinking water. Of the PFAS compounds included in the
final rule, the EPA quantifies some of the adverse health effects
associated with PFOA and PFOS. These compounds have likely evidence
linking exposure to a particular health endpoint and have reliable PK
models connecting the compound to PFAS blood serum. PK models are tools
for quantifying the relationship between external measures of exposure
and internal measures of dose. Benefits from avoided adverse health
effects of PFHxS, PFNA, HFPO-DA, and PFBS are discussed qualitatively
in this section.
As Table 44 demonstrates, only a subset of the potential health
effects of reduced PFAS in drinking water can be quantified and
monetized. The monetized benefits evaluated in the EA for the final
rule include changes in human health risks associated with CVD and
infant birth weight from reduced exposure to PFOA and PFOS in drinking
water and RCC from reduced exposure to PFOA. The EPA also quantified
benefits from reducing bladder cancer risk due to the co-removal of
non-PFAS pollutants via the installation of drinking water treatment,
discussed in greater detail in USEPA (2024g). The EPA quantified
benefits associated with PFOS effects on liver cancer and PFNA effects
on birth weight in sensitivity analyses.
The EPA was not able to quantify or monetize other benefits,
including those related to other reported health effects including
immune, liver, endocrine, metabolic, reproductive, musculoskeletal, or
other cancers. The EPA discusses these benefits qualitatively in more
detail in this section, as well as in section 6.2 of USEPA (2024g).
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The EPA developed PK models to evaluate blood serum PFAS levels in
adults resulting from exposure to PFAS via drinking water. To date, the
EPA has developed PK models for PFOA and PFOS. The EPA used baseline
and regulatory alternative PFOA/PFOS drinking water concentrations as
inputs to its PK model to estimate blood serum PFOA/PFOS concentrations
for adult males and females. For further detail on the PK model and its
application in the EPA's benefits analysis, please see the EPA's Final
Human Health Toxicity Assessments for PFOA and PFOS (USEPA, 2024c;
USEPA, 2024d) and section 6.3 of USEPA (2024g).
1. Quantified Developmental Effects
Exposure to PFOA and PFOS is linked to developmental effects,
including decreased infant birth weight (Steenland et al., 2018;
Dzierlenga et al., 2020; Verner et al., 2015; USEPA, 2016c; USEPA,
2016d; USEPA, 2024c; USEPA, 2024d; Negri et al., 2017; ATSDR, 2021;
Waterfield et al., 2020). The route through which infants are exposed
prenatally to PFOA and PFOS is through maternal blood via the placenta.
Most studies of the association between maternal serum PFOA/PFOS and
birth weight report inverse relationships (Verner et al., 2015; Negri
et al., 2017; Steenland et al., 2018; Dzierlenga et al., 2020). The
EPA's PK model assumes that mothers were exposed to PFOA/PFOS from
birth to the year in which pregnancy occurred.
The EPA quantified and valued changes in birth weight-related risks
associated with reductions in exposure to PFOA and PFOS in drinking
water. EP-specific time series of the differences between serum PFOA/
PFOS concentrations under baseline and regulatory alternatives are
inputs into this analysis. For each EP, evaluation of the changes in
birth weight impacts involves the following key steps:
1. Estimating the changes in birth weight based on modeled changes
in serum PFOA/PFOS levels and exposure-response functions for the
effect of serum PFOA/PFOS on birth weight;
2. Estimating the difference in infant mortality probability
between the baseline and regulatory alternatives based on changes in
birth weight under the regulatory alternatives and the association
between birth weight and mortality;
3. Identifying the infant population affected by reduced exposure
to PFOA/PFOS in drinking water under the regulatory alternatives;
4. Estimating the changes in the expected number of infant deaths
under the regulatory alternatives based on the difference in infant
mortality rates and
[[Page 32675]]
the population of surviving infants affected by increases in birth
weight due to reduced PFOA/PFOS exposure; and
5. Estimating the economic value of reducing infant mortality based
on the Value of a Statistical Life and infant morbidity based on
reductions in medical costs associated with changes in birth weight for
the surviving infants based on the cost of illness.
The EPA also considered the potential benefits from reduced
exposure to PFNA that may be realized as a direct result of the final
rule. The agency explored the birth weight impacts of PFNA in a
sensitivity analysis based on epidemiological studies published before
2018 cited in the current, best available final human health analysis
of PFNA (ATSDR, 2021), as well as a recently published meta-analysis of
mean birth weight that indicates the birth weight results for PFNA are
robust and consistent, even if associations in some studies may be
small in magnitude (Wright et al., 2023). The EPA used a unit PFNA
reduction scenario (i.e., 1.0 ng/L change) and the PFAS serum
calculator developed by Lu and Bartell (2020) to estimate PFNA blood
serum levels resulting from PFNA exposures in drinking water. To
estimate blood serum PFNA based on its drinking water concentration,
the EPA used a first-order single-compartment model whose behavior was
previously demonstrated to be consistent with PFOA pharmacokinetics in
humans (Bartell et al., 2010). In addition to the PFOA-birth weight and
PFOS-birth weight effects analyzed in the EA, the EPA examined the
effect of inclusion of PFNA-birth weight effects using estimates from
two studies (Lenters et al., 2016; Valvi et al., 2017). The EPA found
that inclusion of a 1.0 ng/L PFNA reduction increased annualized birth
weight benefits by between a factor of 5.6 to 7.8, relative to the
scenario that quantifies a 1.0 ng/L reduction in PFOA and a 1.0 ng/L
reduction in PFOS only. The range of estimated PFNA-related increases
in benefits is driven by the exposure-response, with smaller estimates
produced using the slope factors from Lenters et al. (2016), followed
by Valvi et al. (2017). The EPA notes that the PFNA slope factor
estimates are orders of magnitude larger than the slope factor
estimates used to evaluate the impacts of PFOA/PFOS reductions. The EPA
also notes that the PFNA slope factor estimates in this analysis are
not precise, with 95 percent CIs covering wide ranges that include zero
(i.e., serum PFNA slope factor estimates are not statistically
significant at 5 percent level). Caution should be exercised in making
judgements about the potential magnitude of change in the national
benefits estimates based on the results of these sensitivity analyses,
although conclusions about the directionality of these effects can be
inferred. The EPA did not include PFNA effects in the national benefits
estimates for the final rule because there was insufficient data above
the UCMR 3 MRL to reasonably fit model parameters for PFNA. For the
EPA's PFNA sensitivity analysis, see appendix K of USEPA (2024g).
To estimate changes in birth weight resulting from reduced exposure
to PFOA and PFOS under the regulatory alternatives, the EPA relied on
the estimated time series of changes in serum PFOA/PFOS concentrations
specific to women of childbearing age and serum-birth weight exposure-
response functions provided in recently published meta-analyses. For
more detail on the evaluation of the studies used in these meta-
analyses, please see the EPA's Final Human Health Toxicity Assessments
for PFOA and PFOS (USEPA, 2024c; USEPA, 2024d) and section 6.4 of USEPA
(2024g).
Changes in serum PFOA and PFOS concentrations are calculated for
each PWS EP during each year in the analysis period. The EPA assumes
that, given the long half-lives of PFOS and PFOA (with median half-
lives of 2.7 and 3.5 years, respectively (Li et al., 2018)), any one-
time measurement during or near pregnancy is reflective of a critical
exposure window and not subject to considerable error. In other words,
blood serum concentrations in a single year are expected to correlate
with past exposures and are reflective of maternal exposures regardless
of the timing of pregnancy. The mean change in birth weight per
increment in long-term PFOA and PFOS exposure is calculated by
multiplying each annual change in PFOA and PFOS serum concentration
(ng/mL serum) by the PFOA and PFOS serum-birth weight exposure-response
slope factors (g birth weight per ng/mL serum) provided in Table 45,
respectively. The mean annual change in birth weight attributable to
changes in both PFOA and PFOS exposure is the sum of the annual PFOA
and PFOS-birth weight change estimates. Additional detail on the
derivation of the exposure-response functions can be found in appendix
D in USEPA (2024e). appendix K in USEPA (2024e) presents an analysis of
birth weight risk reduction considering slope factors specific to the
first trimester.
[GRAPHIC] [TIFF OMITTED] TR26AP24.052
The EPA places a cap on estimated birth weight changes in excess of
200 g, assuming that such changes in birth weight are unreasonable
based on existing studies that found that changes to environmental
exposures result in relatively modest birth weight changes (Windham and
Fenster, 2008; Klein and Lynch, 2018; Kamai et al., 2019). Modest
changes in birth weight even as a result of large changes in PFOA/PFOS
serum concentrations may be due to potential bias from studies only
including live births (Liew et al., 2015). Additionally, the magnitude
of birth
[[Page 32676]]
weight changes may be correlated with other developmental outcomes such
as preterm birth, gestational duration, fetal loss, birth defects, and
developmental delays.
Low birth weight is linked to a number of health effects that may
be a source of economic burden to society in the form of medical costs,
infant mortality, parental and caregiver costs, labor market
productivity loss, and education costs (Chaikind and Corman, 1991;
Behrman and Butler, 2007; Behrman and Rosenzweig, 2004; Joyce et al.,
2012; Kowlessar et al., 2013; Colaizy et al., 2016; Nicoletti et al.,
2018; Klein and Lynch, 2018). Recent literature also linked low birth
weight to educational attainment and required remediation to improve
student outcomes, childhood disability, and future earnings (Jelenkovic
et al., 2018; Temple et al., 2010; Elder et al., 2020; Hines et al.,
2020; Chatterji et al., 2014; Dobson et al., 2018).
The EPA's analysis focuses on two categories of birth weight
impacts that are amenable to monetization associated with incremental
changes in birth weight: (1) medical costs associated with changes in
infant birth weight and (2) the value of avoiding infant mortality at
various birth weights. The birth weight literature related to other
sources of economic burden to society (e.g., parental and caregiver
costs and productivity losses) is limited in geographic coverage,
population size, and range of birth weights evaluated and therefore
cannot be used in the EA of birth weight effects from exposure to PFOA/
PFOS in drinking water (ICF, 2021).
Two studies showed statistically significant relationships between
incremental changes in birth weight and infant mortality: Almond et al.
(2005) and Ma and Finch (2010). Ma and Finch (2010) used 2001 NCHS
linked birth/infant death data for singleton and multiple birth infants
among subpopulations defined by sex and race/ethnicity to estimate a
regression model assessing the associations between 14 key birth
outcome measures, including birth weight and infant mortality. They
found notable variation in the relationship between birth weight and
mortality across race/ethnicity subpopulations, with odds ratios for
best-fit birth weight-mortality models ranging from 0.8-1 (per 100 g
birth weight change). Almond et al. (2005) used 1989-1991 NCHS linked
birth/infant death data for multiple birth infants to analyze
relationships between birth weight and infant mortality within birth
weight increment ranges. For their preferred model, they reported
coefficients in deaths per 1,000 births per 1 g increase in birth
weight that range from -0.420 to -0.002. However, the data used in
these studies (Almond et al., 2005 and Ma and Finch, 2010) are outdated
(1989-1991 and 2001, respectively). Given the significant decline in
infant mortality over the last 30 years (ICF, 2020) and other maternal
and birth characteristics that are likely to influence infant mortality
(e.g., average maternal age and rates of maternal smoking), the birth
weight-mortality relationship estimates from Almond et al. (2005) and
Ma and Finch (2010) are likely to overestimate the benefits of birth
weight changes.
Considering the discernible changes in infant mortality over the
last 30 years, the EPA developed a regression analysis to estimate the
relationship between birth weight and infant mortality using the
Period/Cohort Linked Birth-Infant Death Data Files published by NCHS
from the 2017 period/2016 cohort and the 2018 period/2017 cohort (CDC,
2017; CDC, 2018). These data provide information on infants who are
delivered alive and receive a birth certificate. The EPA selected
variables of interest for the regression analysis, including maternal
demographic and socioeconomic characteristics, maternal risk, and risk
mitigation factors (e.g., number of prenatal care visits, smoker
status), and infant birth characteristics. The EPA included several
variables used in Ma and Finch (2010) (maternal age, maternal
education, marital status, and others) as well as additional variables
to augment the set of covariates included in the analyses. In addition,
the EPA developed separate models for different race/ethnicity
categories (non-Hispanic Black, non-Hispanic White, and Hispanic) and
interacted birth weight with categories of gestational age, similar to
Ma and Finch (2010). Appendix E of USEPA (2024e) provides details on
model development and regression results.
Table 46 presents the resulting odds ratios and marginal effects
(in terms of deaths per 1,000 births for every 1 g increase in birth
weight) estimated for changes in birth weight among different
gestational age categories in the mortality regression models for non-
Hispanic Black, non-Hispanic White, and Hispanic race/ethnicity
subpopulations. Marginal effects for birth weight among gestational age
categories vary across different race/ethnicity subpopulations. The
marginal effects for birth weight among different gestational age
categories are higher in the non-Hispanic Black model than in the non-
Hispanic White and Hispanic models, particularly for extremely and very
preterm infants, indicating that low birth weight increases the
probability of mortality within the first year more so among non-
Hispanic Black infants than among non-Hispanic White and Hispanic
infants.
The EPA relies on odds ratios estimated using the birth weight-
mortality regression model to assess mortality outcomes of reduced
exposures to PFOA/PFOS in drinking water under the regulatory
alternatives. To obtain odds ratios specific to each race/ethnicity and
100 g birth weight increment considered in the birth weight benefits
model,\24\ the EPA averaged the estimated odds ratios for 1 g increase
in birth weight over the gestational age categories using the number of
infants (both singleton and multiple birth) that fall into each
gestational age category as weights. Separate gestational age category
weights were computed for each 100 g birth weight increment and race/
ethnicity subpopulation within the 2017 period/2016 cohort and 2018
period/2017 cohort Linked Birth-Infant Death Data Files. The weighted
birth weight odds ratios are then used in conjunction with the
estimated change in birth weight and baseline infant mortality rates to
determine the probability of infant death under the regulatory
alternatives, as described further in section 6.4 of USEPA (2024g).
---------------------------------------------------------------------------
\24\ The birth weight risk reduction model evaluates changes in
birth weight in response to PFOA/PFOS drinking water level
reductions for infants who fall into 100 g birth weight increments
(e.g., birth weight 0-99 g, 100-199 g, 200-299 g. . . 8,000-8,099 g,
8,100-8,165 g).
---------------------------------------------------------------------------
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The EPA weighted the race/ethnicity-specific odds ratios in Table
46 by the proportions of the infant populations who fell into each
gestational age within a 100 g birth weight increment, based on the
2016/17 and 2017/18 period cohort data, to obtain a weighted odds ratio
estimate for each modeled race/ethnicity subpopulation and 100 g birth
weight increment.
Based on reduced serum PFOA/PFOS exposures under the regulatory
alternatives and the estimated relationship between birth weight and
infant mortality, the EPA estimates the subsequent change in birth
weight for those infants affected by decreases in PFOA/PFOS and changes
in the number of infant deaths. The EPA evaluated these changes at each
PWS EP affected by the regulatory alternatives and the calculations are
performed for each race/ethnicity group, 100 g birth weight category,
and year of the analysis. Additional detail on the calculations the EPA
used to estimate changes in birth
[[Page 32678]]
weight, the affected population size, and infant deaths avoided, and
the number of surviving infants is provided in chapter 6 of USEPA
(2024g).
The EPA used the Value of a Statistical Life to estimate the
benefits of reducing infant mortality and the cost of illness to
estimate the economic value of increasing birth weight in the
population of surviving infants born to mothers exposed to PFOA and
PFOS in drinking water. The EPA's approach to monetizing benefits
associated with incremental increases in birth weight resulting from
reductions in drinking water PFOA/PFOS levels relies on avoided medical
costs associated with various ranges of birth weight. Although the
economic burden of treating infants at various birth weights also
includes non-medical costs, very few studies to date have quantified
such costs (Klein and Lynch, 2018; ICF, 2021). The EPA selected the
medical cost function from Klein and Lynch (2018) to monetize benefits
associated with the estimated changes in infant birth weight resulting
from reduced maternal exposure to PFOA/PFOS.\25\
---------------------------------------------------------------------------
\25\ The Klein and Lynch (2018) report was externally peer
reviewed by three experts with qualifications in economics and
public health sciences. The EPA's charge questions to the peer
reviewers sought input on the methodology for developing medical
cost estimates associated with changes in birth weight. The agency's
charge questions, and peer reviewer responses are available in the
docket.
---------------------------------------------------------------------------
Using the incremental cost changes from Klein and Lynch (2018), the
EPA calculates the change in medical costs resulting from changes in
birth weight among infants in the affected population who survived the
first year following birth, provided in Table 47.
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Tables 48 to 51 provide the health effects avoided and valuation
associated with birth weight impacts. The EPA estimated that, over the
evaluation period, the final rule will result in annualized benefits
from avoided reductions in birth weight of $209 million.
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2. Quantified Cardiovascular Effects
CVD is one of the leading causes of premature mortality in the
United States (D'Agostino et al., 2008; Goff et al., 2014; Lloyd-Jones
et al., 2017). As discussed in the EPA's Final Human Health Toxicity
Assessments for PFOA and PFOS, exposure to PFOA and PFOS through
drinking water contributes to increased serum PFOA and PFOS
concentrations and elevated levels of TC, as well as suggestive
evidence of changes in levels of HDLC and elevated levels of systolic
blood pressure (USEPA, 2024c; USEPA, 2024d). Changes in TC and blood
pressure are associated with changes in incidence of CVD events such as
myocardial infarction (i.e., heart attack), ischemic stroke, and
cardiovascular mortality occurring in populations without prior CVD
event experience (D'Agostino et al., 2008; Goff et al., 2014; Lloyd-
Jones et al., 2017).
The EPA recognizes that the epidemiologic literature that provides
strong support for an effect of PFOA and PFOS on cholesterol and blood
pressure does not provide direct support for an effect of PFOA and PFOS
on the risk of CVD. Therefore, the EPA uses the approach outlined here
to link changes in CVD risk biomarkers (i.e., cholesterol and blood
pressure) to changes in CVD risk.
For each EP, evaluation of the changes in CVD risk involves the
following key steps:
1. Estimation of annual changes in TC and blood pressure levels
using exposure-response functions for the potential effects of serum
PFOA/PFOS on these biomarkers;
2. Estimation of the annual incidence of fatal and non-fatal first
hard CVD events, defined as fatal and non-fatal myocardial infarction,
fatal and non-fatal ischemic stroke or other coronary heart disease
death occurring in populations without prior CVD event experience
(D'Agostino et al., 2008; Goff et al., 2014; Lloyd-Jones et al., 2017),
and post-acute CVD mortality corresponding to baseline and regulatory
alternative TC and blood pressure levels in all populations alive
during or born after the start of the evaluation period; and
3. Estimation of the economic value of reducing CVD mortality and
morbidity from baseline to regulatory alternative levels, using the
Value of a Statistical Life and cost of illness measures, respectively.
Given the breadth of evidence linking PFOA and PFOS exposure to
effects on TC and blood pressure in general adult populations, the EPA
quantified public health impacts of changes in these well-established
CVD risk biomarkers (D'Agostino et al., 2008; Goff et al., 2014; Lloyd-
Jones et al., 2017) by estimating changes in incidence of several CVD
events. Specifically, the EPA assumed that PFOA/PFOS-related changes in
TC and blood pressure had the same effect on the CVD risk as the
changes unrelated to chemical exposure and used the Pooled Cohort ASCVD
model (Goff et al., 2014) to evaluate their impacts on the incidence of
myocardial infarction, ischemic stroke, and cardiovascular mortality
occurring in populations without prior CVD event experience.
The ASCVD model includes TC as a predictor of first hard CVD
events. The EPA did not identify any readily available relationships
for PFOA or PFOS and TC that were specifically relevant to the age
group of interest (40-89 years, the years for which the ASCVD model
estimates the probability of a first hard CVD event). Therefore, the
agency developed a meta-analysis of studies reporting associations
between serum PFOA or PFOS and TC in general populations (e.g.,
populations that are not a subset of workers or pregnant women).
Statistical analyses that combine the results of multiple studies, such
as meta-analyses, are widely applied to investigate the associations
between contaminant levels and associated health effects. Such analyses
are suitable for economic assessments because they can improve
precision and statistical power (Engels et al., 2000; Deeks, 2002;
R[uuml]cker et al., 2009).
The EPA identified 14 studies from which to derive slope estimates
for PFOA and PFOS associations with serum TC levels. Appendix F of
USEPA (2024e) provides further detail on the studies selection
criteria, meta-data development, meta-analysis results, and discussion
of the uncertainty and limitations inherent in the EPA's exposure-
response analysis.
The EPA developed exposure-response relationships between serum
PFOA/PFOS and TC for use in the CVD analysis using the meta-analyses
restricted to studies of adults in the general population reporting
similar models. When using studies reporting linear associations
between TC and serum PFOA or PFOS, the EPA estimated a positive
increase in TC of 1.57 (95 percent CI: 0.02, 3.13) mg/dL per ng/mL
serum PFOA (p-value=0.048), and of 0.08 (95 percent CI: -0.01, 0.16)
mg/dL per ng/mL serum PFOS (p-value=0.064). Based on the systematic
review conducted by the EPA to develop the EPA's Final Human Health
Toxicity Assessments for PFOA and PFOS, the available evidence supports
a positive association between PFOS and TC in the general population.
For more information on the systematic review and results, see USEPA
(2024c) and USEPA (2024d).
PFOS exposure has been linked to other cardiovascular outcomes,
such as systolic blood pressure and hypertension (Liao et al., 2020;
USEPA, 2024d). Because systolic blood pressure is another predictor
used by the ASCVD model, the EPA included the estimated changes in
blood pressure from reduced exposure to PFOS in the CVD analysis. The
EPA selected the slope from the Liao et al. (2020) study--a high
confidence study conducted based on U.S. general population data from
NHANES cycles 2003-2012. The evidence on the associations between PFOA
and blood pressure is not as consistent as for PFOS. Therefore, the EPA
is not including effect estimates for the serum PFOA-blood pressure
associations in the CVD analysis.
The EPA relies on the life table-based approach to estimate CVD
risk reductions because (1) changes in serum PFOA/PFOS in response to
changes in drinking water PFOA/PFOS occur over multiple years, (2) CVD
risk, relying on the ASCVD model, can be modeled only for those older
than 40 years without prior CVD history, and (3) individuals who have
experienced non-fatal CVD events have elevated mortality implications
immediately and within at least five years of the first occurrence.
Recurrent life table calculations are used to estimate a PWS EP-
specific annual time series of CVD event incidence for a population
cohort characterized by sex, race/ethnicity, birth year, age at the
start of the PFOA/PFOS evaluation period (i.e., 2024), and age- and
sex-specific time series of changes in TC and blood pressure levels
obtained by combining serum PFOA/PFOS concentration time series with
exposure-response information. Baseline and regulatory alternatives are
evaluated separately, with regulatory alternative TC and blood pressure
levels estimated using baseline information on these biomarkers from
external statistical data sources and modeled changes in TC and blood
pressure due to conditions under the regulatory alternatives.
The EPA estimated the incidence of first hard CVD events based on
TC serum and blood pressure levels using the ASCVD model (Goff et al.,
2014), which predicts the 10-year probability of a hard CVD event to be
experienced by a person without a prior CVD history. The EPA adjusted
the modeled
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population cohort to exclude individuals with pre-existing conditions,
as the ASCVD risk model does not apply to these individuals. For blood
pressure effects estimation, the EPA further restricts the modeled
population to those not using antihypertensive medications for
consistency with the exposure-response relationship. Modeled first hard
CVD events include fatal and non-fatal myocardial infarction, fatal and
non-fatal ischemic stroke, and other coronary heart disease mortality.
The EPA has also estimated the incidence of post-acute CVD mortality
among survivors of the first myocardial infarction or ischemic stroke
within 6 years of the initial event.
The estimated CVD risk reduction resulting from reducing serum PFOA
and serum PFOS concentrations is the difference in annual incidence of
CVD events (i.e., mortality and morbidity associated with first-time
CVD events and post-acute CVD mortality) under the baseline and
regulatory alternatives. Appendix G of USEPA (2024e) provides detailed
information on all CVD model components, computations, and sources of
data used in modeling.
The EPA uses the Value of a Statistical Life to estimate the
benefits of reducing mortality associated with hard CVD events in the
population exposed to PFOA and PFOS in drinking water. The EPA relies
on cost of illness-based valuation that represents the medical costs of
treating or mitigating non-fatal first hard CVD events (myocardial
infarction, ischemic stroke) during the three years following an event
among those without prior CVD history, adjusted for post-acute
mortality.
The annual medical expenditure estimates for myocardial infarction
and ischemic stroke are based on O'Sullivan et al. (2011). The
estimated expenditures do not include long-term institutional and home
health care. For non-fatal myocardial infarction, O'Sullivan et al.
(2011) estimated medical expenditures are $53,246 ($2022) for the
initial event and then $33,162, $14,635, $13,078 annually within 1, 2,
and 3 years after the initial event, respectively. For non-fatal
ischemic stroke, O'Sullivan et al. (2011) estimated medical
expenditures are $16,503 ($2022) for the initial event and then
$11,988, $788, $1,868 annually within 1, 2, and 3 years after the
initial event, respectively. Annual estimates within 1, 2, and 3 years
after the initial event include the incidence of secondary CVD events
among survivors of first myocardial infarction and ischemic stroke
events.
To estimate the present discounted value of medical expenditures
within 3 years of the initial non-fatal myocardial infarction, the EPA
combined O'Sullivan et al. (2011) myocardial infarction-specific
estimates with post-acute survival probabilities based on Thom et al.
(2001) (for myocardial infarction survivors aged 40-64) and Li et al.
(2019) (for myocardial infarction survivors aged 65+). To estimate the
present discounted value of medical expenditures within 3 years of the
initial non-fatal ischemic stroke, the EPA combined O'Sullivan et al.
(2011) ischemic stroke-specific estimates with post-acute survival
probabilities based on Thom et al. (2001) (for ischemic stroke
survivors aged 40-64, assuming post-acute myocardial infarction
survival probabilities reasonably approximate post-acute ischemic
stroke survival probabilities) and Li et al. (2019) (for ischemic
stroke survivors aged 65+). The EPA did not identify post-acute
ischemic stroke mortality information in this age group, but instead
applied post-acute myocardial infarction mortality estimates for
ischemic stroke valuation. Table 52 presents the resulting myocardial
infarction and ischemic stroke unit values.
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Tables 53 to 56 provide the health effects avoided and valuation
associated with CVD. The EPA estimated that, over the evaluation
period, the final rule will result in annualized benefits from avoided
CVD cases and deaths of $606 million.
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3. Quantified Kidney Cancer Effects
Data on the association between PFOA exposure and kidney cancer
(i.e., RCC), particularly from epidemiological studies, indicate a
positive association between exposure and increased risk of RCC.
Epidemiology studies indicated that exposure to PFOA was associated
with an increased risk of RCC (CalEPA, 2021; ATSDR, 2021; USEPA, 2016c;
USEPA, 2024c, USEPA, 2024j). In the PFOA HESD (USEPA, 2016c), the EPA
determined that PFOA is likely to be carcinogenic to humans (USEPA,
2005a) based in part on evidence of associations between PFOA exposure
and kidney cancer in humans. A recent study of the relationship between
PFOA and RCC in U.S. general populations found strong evidence of a
positive association between exposure to PFOA and RCC in humans
(Shearer et al., 2021). A meta-analysis of epidemiological literature
also concluded that there was an increased risk of kidney cancer
associated with increased PFOA serum concentrations (Bartell and
Vieira, 2021). As such, the EPA selected RCC as a key outcome when
assessing the health impacts of reduced PFOA exposures.
The EPA quantified and valued the changes in RCC risk associated
with reductions in serum PFOA levels that are in turn associated with
reductions in drinking water PFOA concentrations under the regulatory
alternatives. PWS EP-specific time series of the differences between
serum PFOA concentrations under baseline and regulatory alternatives
are inputs into this analysis. For each PWS EP, evaluation of the
changes in RCC impacts involves the following key steps:
1. Estimating the changes in RCC risk based on modeled changes in
serum PFOA levels and the exposure-response function for the effect of
serum PFOA on RCC;
2. Estimating the annual incidence of RCC cases and excess
mortality among those with RCC in all populations corresponding to
baseline and regulatory alternative RCC risk levels, as well as
estimating the regulatory alternative-specific reduction in cases
relative to the baseline, and
3. Estimating the economic value of reducing RCC mortality from
baseline to regulatory alternative levels, using the Value of a
Statistical Life and cost of illness measures, respectively.
To identify an exposure-response function, the EPA reviewed studies
highlighted in the HESD for PFOA (USEPA, 2016c) and a recent study
discussed in both the California Environmental Protection Agency's
Office of Environmental Health Hazard Assessment (OEHHA) PFOA Public
Health Goals report (CalEPA, 2021) and the EPA's Final Human Health
Toxicity Assessment for PFOA (USEPA, 2024c; USEPA, 2024j). Steenland et
al. (2015) observed an increase in kidney cancer deaths among workers
with high exposures to PFOA. Vieira et al. (2013) found that kidney
cancer was positively associated with ``high'' and ``very high'' PFOA
exposures. Barry et al. (2013) found a slight trend in cumulative PFOA
serum exposures and kidney cancer among the C8 Health Project
population. In a large case-control general population study of the
relationship between PFOA and kidney cancer in 10 locations across the
U.S., Shearer et al. (2021) found evidence that exposure to PFOA is
associated with RCC, the most common form of kidney cancer, in humans.
To evaluate changes between baseline and regulatory alternative RCC
risk resulting from reduced exposure to PFOA, the EPA relied on the
estimated time series of changes in serum PFOA concentrations (section
6.3) and the
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serum-RCC exposure-response function provided by Shearer et al. (2021):
0.00178 (ng/mL)-1. The analysis reported in Shearer et al.
(2021) was designed as a case-control study with population controls
based on 10 sites within the U.S. population. Shearer et al. (2021)
accounted for age, sex, race, ethnicity, study center, year of blood
draw, smoking, and hypertension in modeling the association between
PFOA and RCC. Results showed a strong and statistically significant
association between PFOA and RCC. The EPA selected the exposure-
response relationship from Shearer et al. (2021) because it included
exposure levels typical in the general population and the study was
found to have a low risk of bias when assessed in the EPA's Final Human
Health Toxicity Assessment for PFOA (USEPA, 2024c; USEPA, 2024j).
The linear slope factor developed by the agency (see section 4.2 of
USEPA, 2024c) based on Shearer et al. (2021) enables estimation of the
changes in the lifetime RCC risk associated with reduced lifetime serum
PFOA levels. Because baseline RCC incidence statistics are not readily
available from the National Cancer Institute (NCI) public use data, the
EPA used kidney cancer statistics in conjunction with an assumption
that RCC comprises 90 percent of all kidney cancer cases to estimate
baseline lifetime probability of RCC (USEPA, 2024c; American Cancer
Society, 2020). The EPA estimated the baseline lifetime RCC incidence
for males at 1.89 percent and the baseline lifetime RCC incidence for
females at 1.05 percent. Details of these calculations are provided in
appendix H of USEPA (2024e).
Similar to the EPA's approach for estimating CVD risk reductions,
the EPA relies on the life table approach to estimate RCC risk
reductions. The outputs of the life table calculations are the PWS EP-
specific estimates of the annual change in the number of RCC cases and
the annual change in excess RCC population mortality. For more detail
on the EPA's application of the life table to cancer benefits analyses,
please see appendix H of USEPA (2024e).
Although the change in PFOA exposure likely affects the risk of
developing RCC beyond the end of the analysis period (the majority of
RCC cases manifest during the latter half of the average individual
lifespan; see appendix H of USEPA (2024e), the EPA does not capture
effects after the end of the period of analysis, 2105. Individuals
alive after the end of the period of analysis likely benefit from lower
lifetime exposure to PFOA. Lifetime health risk model data sources
include the EPA SDWIS, age-, sex-, and race/ethnicity-specific
population estimates from the U.S. Census Bureau (2020), the
Surveillance, Epidemiology, and End Results (SEER) program database
(Surveillance Research Program--National Cancer Institute, 2020a;
National Cancer Institute, 2020b), and the CDC NCHS. Appendix H of
USEPA (2024e) provides additional detail on the data sources and
information used in this analysis as well as baseline kidney cancer
statistics. Appendix B of USEPA (2024e) describes estimation of the
affected population.
The EPA uses the Value of a Statistical Life to estimate the
benefits of reducing mortality associated with RCC in the population
exposed to PFOA in drinking water. The EPA uses the cost of illness-
based valuation to estimate the benefits of reducing morbidity
associated with RCC.
The EPA used the medical cost information from a recent RCC cost-
effectiveness study by Ambavane et al. (2020) to develop cost of
illness estimates for RCC morbidity. Ambavane et al. (2020) used a
discrete event simulation model to estimate the lifetime treatment
costs of several RCC treatment sequences, which included first and
second line treatment medication costs, medication administration
costs, adverse effect management costs, and disease management costs
on- and off-treatment. To this end, the authors combined RCC cohort
data from CheckMate 214 clinical trial and recent US-based healthcare
cost information assembled from multiple sources (see supplementary
information from Ambavane et al. (2020)).
The EPA received public comments on the EA for the proposed rule
related to the EPA's use of cost of illness information for morbidity
valuation. Specifically, some commenters recommended that the EPA use
willingness to pay information (instead of cost of illness information)
when valuing the costs associated with non-fatal illnesses, stating
that willingness to pay information better accounts for lost
opportunity costs (e.g., lost productivity and pain and suffering)
associated with non-fatal illnesses (USEPA, 2024k). To better account
for these opportunity costs, the EPA used recently available
willingness to pay values in a sensitivity analysis for morbidity
associated with RCC. The sensitivity analysis results show that when
willingness to pay values are used in RCC benefits analysis, morbidity
benefits are increased by approximately 2 percent. See appendix O of
the EA for full details and results on the willingness to pay
sensitivity analyses.
Table 57 summarizes RCC morbidity cost of illness estimates derived
by the EPA using Ambavane et al. (2020)-reported disease management
costs on- and off-treatment along with medication, administration, and
adverse effect management costs for the first line treatment that
initiated the most cost-effective treatment sequences as identified by
Ambavane et al. (2020), i.e., the nivolumab and ipilimumab drug
combination. This is a forward-looking valuation approach in that it
assumes that the clinical practice would follow the treatment
recommendations in Ambavane et al. (2020) and other recent studies
cited therein. The EPA notes that the second line treatment costs are
not reflected in the EPA's cost of illness estimates, because Ambavane
et al. (2020) did not report information on the expected durations of
the treatment-free interval (between the first line treatment
discontinuation and the second line treatment initiation) and the
second line treatment phase, conditional on survival beyond
discontinuation of the second line treatment. As such, the EPA valued
RCC morbidity at $261,175 ($2022) during year 1 of the diagnosis,
$198,705 ($2022) during year 2 of the diagnosis, and $1,661 ($2022)
starting from year 3 of the diagnosis. Additionally, the EPA assumed
that for individuals with RCC who die during the specific year, the
entire year-specific cancer treatment regimen is applied prior to the
death event. This may overestimate benefits if a person does not
survive the entire year.
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Tables 58 to 61 provide the health effects avoided and valuation
associated with RCC. The EPA estimated that, over the evaluation
period, the final rule will result in annualized benefits from avoided
RCC cases and deaths of $354 million.
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4. Key Limitations and Uncertainties in the Benefits Analysis
The following section discusses the uncertainty information
incorporated in the quantitative benefits analysis. There are
additional sources of uncertainty and limitations that could not be
modeled quantitatively as part of the national benefits analysis. These
sources of uncertainty are characterized in detail in section 6.8 of
USEPA (2024g). This summary includes uncertainties that are specific to
application of PK models for blood serum PFAS concentration estimation,
developmental effects (i.e., infant birth weight) modeling, CVD impacts
modeling, RCC impacts modeling, and modeling of bladder cancer impacts
from GAC treatment-related reductions in the sum of four
trihalomethanes (THM4). Table 62 presents the key limitations and
uncertainties that apply to the benefits analysis for the final rule.
The EPA notes that in most cases it is not possible to judge the extent
to which a particular limitation or uncertainty could affect the
magnitude of the estimated benefits. Therefore, in each of the
following tables, the EPA notes the potential direction of the impact
on the quantified benefits (e.g., a source of uncertainty that tends to
underestimate quantified benefits indicates expectation for larger
quantified benefits) but does not prioritize the entries with respect
to the impact magnitude.
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G. Nonquantifiable Benefits of PFOA and PFOS Exposure Reduction
In this section, the EPA qualitatively discusses the potential
health benefits resulting from reduced exposure to PFOA and PFOS in
drinking water. These nonquantifiable benefits are expected to be
realized as avoided adverse health effects as a result of the final
NPDWR, in addition to the benefits that the EPA has quantified, because
of their known toxicity and additive health concerns as well as
occurrence and likely co-occurrence in drinking water. The EPA
anticipates additional benefits associated with developmental,
cardiovascular, liver, immune, endocrine, metabolic, reproductive,
musculoskeletal, and carcinogenic effects beyond those benefits that
the EPA has quantified. The evidence for these adverse health effects
is briefly summarized here.
The EPA identified a wide range of potential health effects
associated with exposure to PFOA and PFOS using five comprehensive
Federal Government health effects assessments that summarize the recent
literature on PFAS (mainly PFOA and PFOS, although many of the same
health effects have been observed for the other PFAS in this rule)
exposure and its health impacts: the EPA's HESDs for PFOA and PFOS,
hereafter referred to as the EPA HESDs (USEPA, 2016c; USEPA, 2016d);
the EPA's Final Human Health Toxicity Assessments for PFOA and
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PFOS (USEPA, 2024c; USEPA, 2024d); and the U.S. Department of Health
and Human Services (HHS) ATSDR Toxicological Profile for
Perfluoroalkyls (ATSDR, 2021). Each source presents comprehensive
literature reviews on adverse health effects associated with PFOA and
PFOS. The EPA notes that NASEM also published a report which includes a
review of the adverse health effects for numerous PFAS (NASEM, 2022).
That document is included in the docket for this final rule.
The most recent literature reviews on PFAS exposures and health
impacts, which are included in the EPA's Final Human Health Toxicity
Assessments for PFOA and PFOS (USEPA, 2024c; USEPA, 2024d), describe
the weight of evidence supporting PFOA and PFOS associations with
health outcomes as either demonstrative, indicative (likely),
suggestive, inadequate, or strong evidence supportive of no effect
according to the evidence integration judgments outlined in the ORD
Staff Handbook for Developing IRIS Assessments (USEPA, 2022f; USEPA,
2024c; USEPA, 2024d). For the purposes of the reviews conducted to
develop the Final Human Health Toxicity Assessments for PFOA and PFOS,
an association is deemed demonstrative when there is a strong evidence
base demonstrating that the chemical exposure causes a health effect in
humans. The association is deemed indicative (likely) when the evidence
base indicates that the chemical exposure likely causes a health effect
in humans, although there might be outstanding questions or limitations
that remain, and the evidence is insufficient for the higher conclusion
level. The association is suggestive if the evidence base suggests that
the chemical exposure might cause a health effect in humans, but there
are very few studies that contributed to the evaluation, the evidence
is very weak or conflicting, or the methodological conduct of the
studies is poor. The association is inadequate if there is a lack of
information or an inability to interpret the available evidence (e.g.,
findings across studies). The association supports no effect when
extensive evidence across a range of populations and exposure levels
has identified no effects/associations. Note that the EPA considered
information available as of September 2023 for the analyses presented
herein.
Developmental effects: Exposure to PFOA and PFOS is linked to
developmental effects including but not limited to the infant birth
weight effects that the EPA quantified. Other developmental effects
include small for gestational age (SGA), birth length, head
circumference at birth, and other effects (Verner et al., 2015; Negri
et al., 2017; ATSDR, 2021; Waterfield et al., 2020; USEPA, 2016c;
USEPA, 2016d; USEPA, 2024c; USEPA, 2024d). SGA is a developmental
health outcome of interest when studying potential effects of PFOA/PFOS
exposure because SGA infants have increased health risks during
pregnancy and delivery as well as post-delivery (Osuchukwu and Reed,
2022). The majority of epidemiology studies indicated increased risk of
SGA with PFOA/PFOS exposure, although some studies reported null
results (USEPA, 2024c; USEPA, 2024d). For instance, some studies
suggested a potentially positive association between PFOA exposure and
SGA (Govarts et al., 2018; Lauritzen et al., 2017; Wang et al., 2016;
Souza et al., 2020; Wikstr[ouml]m et al., 2020; Chang et al., 2022;
USEPA, 2024c). In addition to decreases in offspring weight, toxicology
studies on PFOA and PFOS exposures in rodents demonstrated
relationships with multiple other developmental toxicity endpoints,
including increased offspring mortality, decreased maternal body weight
and body weight change, skeletal and soft tissue effects, and delayed
eye-opening (USEPA, 2024c; USEPA, 2024d). For additional details on
developmental studies and their individual outcomes, see chapter 3.4.4
(Developmental) in USEPA (2024c) and USEPA (2024d).
Cardiovascular effects: In addition to the CVD effects that the EPA
quantified associated with changes in TC and blood pressure from
exposure to PFOA and PFOS (see section 6.2 of USEPA (2024g)), available
evidence suggests an association between exposure to PFOA and PFOS and
increased low-density lipoprotein cholesterol (LDLC) (ATSDR, 2021;
USEPA, 2024c; USEPA, 2024d). High levels of LDLC are known as the `bad'
cholesterol because it can lead to the buildup of cholesterol in the
arteries, which can raise the risk of heart disease and stroke.
Epidemiology studies showed a positive association between PFOA or PFOS
exposure and LDLC levels in adults and children (USEPA, 2024c; USEPA,
2024d). In particular, the evidence suggested positive associations
between serum PFOA and PFOS levels and LDLC levels in adolescents ages
12-18, while positive associations between serum levels and LDLC levels
in younger children were observed only for PFOA (ATSDR, 2021).
Additionally, available evidence supports a relatively consistent
positive association between PFOA or PFOS and low-density lipoprotein
(LDL) in adults, especially those who are obese or prediabetic.
Associations with other lipoprotein cholesterol known to increase
cardiovascular risks were also positive, which increased confidence in
the findings for LDLC. Available evidence regarding the impact of PFOA
and PFOS exposure on pregnant women was too limited for the EPA to
determine an association (ATSDR, 2021; USEPA, 2024c; USEPA, 2024d).
Toxicology studies generally reported alterations in serum lipid levels
in mice and rats following oral exposure to PFOA (USEPA, 2024d) or PFOS
(USEPA, 2024c), indicating a disruption in lipid metabolism, which is
coherent with effects observed in humans. For additional details on
LDLC studies and their individual outcomes, see chapter 3.4.3
(Cardiovascular) in USEPA (2024c) and USEPA (2024d).
Liver effects: Several biomarkers can be used clinically to
diagnose liver diseases, including alanine aminotransferase (ALT).
Serum ALT measures are considered a reliable indicator of impaired
liver function because increased serum ALT is indicative of leakage of
ALT from damaged hepatocytes (Boone et al., 2005; Z. Liu et al., 2014;
USEPA, 2002d). Additionally, evidence from both human epidemiological
and animal toxicological studies indicates that increased serum ALT is
associated with liver disease (Ioannou et al., 2006a; Ioannou et al.,
2006b; Kwo et al., 2017; Roth et al., 2021). Human epidemiological
studies have demonstrated that even low magnitude increases in serum
ALT can be clinically significant (Mathiesen et al., 1999; Park et al.,
2019). Additionally, numerous studies have demonstrated an association
between elevated ALT and liver-related mortality (reviewed by Kwo et
al., 2017). Furthermore, the American Association for the Study of
Liver Diseases (AASLD) recognizes serum ALT as an indicator of overall
human health and mortality (Kim et al., 2008). Epidemiology data
provides consistent evidence of a positive association between PFOS/
PFOA exposure and ALT levels in adults (ATSDR, 2021; USEPA, 2024c;
USEPA, 2024d). Studies of adults showed consistent evidence of a
positive association between PFOA exposure and elevated ALT levels at
both high exposure levels and exposure levels typical of the general
population (USEPA, 2024c). There is also consistent epidemiology
evidence of associations between PFOS and elevated ALT levels. A
limited number of studies reported
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inconsistent evidence on whether PFOA/PFOS exposure is associated with
increased risk of liver disease (USEPA, 2024d). It is also important to
note that while evaluation of direct liver damage is possible in animal
studies, it is difficult to obtain biopsy-confirmed histological data
in humans. Therefore, liver injury is typically assessed using serum
biomarkers of hepatotoxicity (Costello et al., 2022). Associations
between PFOA/PFOS exposure and ALT levels in children were less
consistent than in adults (USEPA, 2024c; USEPA, 2024d).
PFOA toxicology studies showed increases in ALT and other serum
liver enzymes across multiple species, sexes, and exposure paradigms
(USEPA, 2024c). Toxicology studies on the impact of PFOS exposure on
ALT also reported increases in ALT and other serum liver enzyme levels
in rodents, though these increases were modest (USEPA, 2024d). Several
studies in animals also reported increases in the incidence of liver
lesions or cellular alterations, such as hepatocellular cell death
(USEPA, 2024c; USEPA, 2024d). For additional details on the ALT studies
and their individual outcomes, see section 3.4.1 (Hepatic) in USEPA
(2024c) and USEPA (2024d).
Immune effects: Proper antibody response helps maintain the immune
system by recognizing and responding to antigens. The available
evidence indicates a relationship between PFOA exposure and
immunosuppression; epidemiology studies showed suppression of at least
one measure of the antibody response for tetanus and diphtheria among
people with higher prenatal and childhood serum concentrations of PFOA
(ATSDR, 2021; USEPA, 2024c). Data reporting on associations between
PFOA exposure and antibody response to vaccinations other than tetanus
and diphtheria (i.e., rubella and hand, foot, and mouth disease) are
limited but supportive of associations between PFOA and decreased
immune response in children (USEPA, 2024c). Available studies supported
an association between PFOS exposure and immunosuppression in children,
where increased PFOS serum levels were associated with decreased
antibody production in response to tetanus, diphtheria, and rubella
vaccinations (USEPA, 2024d). Studies reporting associations between
PFOA or PFOS exposure and immunosuppression in adults are less
consistent, though this may be due to a lack of high confidence data
(USEPA, 2024c; USEPA, 2024d). Toxicology evidence suggested that PFOA
and PFOS exposure results in effects similarly indicating immune
suppression, such as reduced response of immune cells to challenges
(e.g., reduced natural killer cell activity and immunoglobulin
production) (USEPA, 2024c; USEPA, 2024d). For additional details on
immune studies and their individual outcomes, see section 3.4.2
(Immune) in USEPA (2024c) and USEPA (2024d).
Endocrine effects: Elevated circulating thyroid hormone levels can
accelerate metabolism and cause irregular heartbeat; low levels of
thyroid hormones can cause neurodevelopmental effects, tiredness,
weight gain, and increased susceptibility to the common cold. There is
suggestive evidence of a positive association between PFOA/PFOS
exposure and thyroid hormone disruption (ATSDR, 2021; USEPA, 2024c;
USEPA, 2024d). Epidemiology studies reported inconsistent evidence
regarding associations between PFOA and PFOS exposure and general
endocrine outcomes, such as thyroid disease, hypothyroidism, and
hypothyroxinemia (USEPA, 2024c; USEPA, 2024d). However, for PFOA,
epidemiological studies reported suggestive evidence of positive
associations for serum levels of thyroid stimulating hormone (TSH) and
the thyroid hormone triiodothyronine (T3) in adults, and the thyroid
hormone thyroxine (T4) in children (USEPA, 2024c; USEPA, 2024d). For
PFOS, epidemiological studies reported suggestive evidence of positive
associations for TSH in adults, positive associations for T3 in
children, and inverse associations for T4 in children (USEPA, 2024d).
Toxicology studies indicated that PFOA and PFOS exposure leads to
decreases in serum thyroid hormone levels \26\ and adverse effects to
the endocrine system (ATSDR, 2021; USEPA, 2024c; USEPA, 2024d; USEPA,
2024h). Overall, changes in serum thyroid hormone levels in animals
indicate PFOS and PFOA toxicity potentially relevant to humans (USEPA,
2024c; USEPA, 2024d). For additional details on endocrine effects
studies and their individual outcomes, see appendix C.2 (Endocrine) in
USEPA (2024h) and USEPA (2024i).
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\26\ Decreased thyroid hormone levels are associated with
effects such as changes in thyroid and adrenal gland weight, hormone
fluctuations, and organ histopathology, as well as adverse
neurodevelopmental outcomes (ATSDR, 2021; USEPA, 2024c).
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Metabolic effects: Leptin is a hormone that, along with
adiponectin, can be a marker of adipose tissue dysfunction. Chronic
high levels of leptin lead to leptin resistance that mirrors many of
the characteristics associated with diet-induced obesity, including
reduced leptin receptors and diminished signaling. Therefore, high
leptin levels are associated with higher body fat mass, a larger size
of individual fat cells, overeating, and inflammation (e.g., of adipose
tissue, the hypothalamus, blood vessels, and other areas). Evidence
suggests an association between PFOA exposure and leptin levels in the
general adult population (ATSDR, 2021; USEPA, 2024c). Based on a review
of human epidemiology studies, evidence of associations between PFOS
and metabolic outcomes appears inconsistent, but in some studies,
positive associations were observed between PFOS exposure and leptin
levels (USEPA, 2024d). Studies examining newborn leptin levels did not
find associations with maternal PFOA levels (ATSDR, 2021). Maternal
PFOS levels were also not associated with alterations in leptin levels
(ATSDR, 2021). For additional details on metabolic effect studies and
their individual outcomes, see appendix C.3 (Metabolic/Systemic) in
USEPA (2024h) and USEPA (2024i).
Reproductive effects: Studies of the reproductive effects from
PFOA/PFOS exposure have focused on associations between exposure to
these contaminants and increased risk of gestational hypertension and
preeclampsia in pregnant women (ATSDR, 2021; USEPA, 2024c; USEPA,
2024d). Gestational hypertension (high blood pressure during pregnancy)
can lead to fetal problems such as poor growth and stillbirth.
Preeclampsia--instances of gestational hypertension where the mother
also has increased levels of protein in her urine--can similarly pose
significant risks to both the fetus and mother. Risks to the fetus
include impaired fetal growth due to the lack of oxygen and nutrients,
stillbirth, preterm birth, and infant death (NIH, 2017). Even if born
full term, the infant may be at risk for later problems such as
diabetes, high blood pressure, and congestive heart failure. Effects of
preeclampsia on the mother may include kidney and liver damage, blood
clotting problems, brain injury, fluid on the lungs, seizures, and
mortality (NIH, 2018). The epidemiology evidence yields mixed (positive
and null) associations, with some suggestive evidence supporting
positive associations between PFOA/PFOS exposure and both preeclampsia
and gestational hypertension (ATSDR, 2021; USEPA, 2024c; USEPA, 2024d).
For additional details on reproductive effects studies and their
individual
[[Page 32699]]
outcomes, see appendix C.1 (Reproductive) in USEPA (2024h) and USEPA
(2024i).
Musculoskeletal effects: Adverse musculoskeletal effects such as
osteoarthritis and decreased bone mineral density impact bone integrity
and cause bones to become brittle and more prone to fracture. The
available epidemiology evidence suggests that PFOA exposure may be
linked to decreased bone mineral density, bone mineral density relative
to bone area, height in adolescence, osteoporosis, and osteoarthritis
(ATSDR, 2021; USEPA, 2024c). Some studies found that PFOA/PFOS exposure
was linked to osteoarthritis, in particular among women under 50 years
of age (ATSDR, 2021). There is limited evidence from studies pointing
to effects of PFOS on skeletal size (height), lean body mass, and
osteoarthritis (USEPA, 2024d). Evidence from some studies suggests that
PFOS exposure has a harmful effect on bone health, particularly
measures of bone mineral density, with greater statistically
significance of effects occurring among females (USEPA, 2024d).
However, other reviews reported mixed findings on the effects of PFOS
exposure including decreased risk of osteoarthritis, increased risk for
some demographic subgroups, or no association (ATSDR, 2021). For
additional details on musculoskeletal effects studies and their
individual outcomes, see appendix C.8 (Musculoskeletal) in USEPA
(2024h) and USEPA (2024i).
Cancer Effects: In the EPA's Final Human Health Toxicity Assessment
for PFOA, the agency evaluates the evidence for carcinogenicity of PFOA
that has been documented in both epidemiological and animal toxicity
studies (USEPA, 2024c; USEPA, 2024j). The evidence in epidemiological
studies is primarily based on the incidence of kidney and testicular
cancer, as well as potential incidence of breast cancer in genetically
susceptible subpopulations or for particular breast cancer types. Other
cancer types have been observed in humans, although the evidence for
these is generally limited to low confidence studies. The evidence of
carcinogenicity in animal models is provided in three chronic oral
animal bioassays in Sprague-Dawley rats which identified neoplastic
lesions of the liver, pancreas, and testes (USEPA, 2024c; USEPA,
2024j). The EPA determined that PFOA is Likely to Be Carcinogenic to
Humans, as ``the evidence is adequate to demonstrate carcinogenic
potential to humans but does not reach the weight of evidence for the
descriptor Carcinogenic to Humans.'' This determination is based on the
evidence of kidney and testicular cancer in humans and LCTs, PACTs, and
hepatocellular adenomas in rats (USEPA, 2024c; USEPA, 2024j). The EPA's
benefits analysis for avoided RCC cases from reduced PFOA exposure is
discussed in section XII.E of this preamble and in section 6.6 of USEPA
(2024g).
In the EPA's Final Human Health Toxicity Assessment for PFOS, the
agency evaluates the evidence for carcinogenicity of PFOS and found
that several epidemiological studies and a chronic cancer bioassay
comprise the evidence database for the carcinogenicity of PFOS (USEPA,
2024d; USEPA 2024j). The available epidemiology studies report elevated
risk of liver cancer, consistent with increased incidence of liver
tumors reported in male and female rats. There is also mixed but
plausible evidence of bladder, prostate, kidney, and breast cancers in
humans. The animal chronic cancer bioassay study also provides evidence
of increased incidence of pancreatic islet cell tumors in male rats.
The EPA reviewed the weight of the evidence and determined that PFOS is
Likely to Be Carcinogenic to Humans, as ``the evidence is adequate to
demonstrate carcinogenic potential to humans but does not reach the
weight of evidence for the descriptor Carcinogenic to Humans.'' The
EPA's national-level benefits sensitivity analysis for avoided liver
cancer cases from reduced PFOS exposure is detailed in appendix O of
the EA.
The EPA anticipates there are additional nonquantifiable benefits
related to potential testicular, bladder, prostate, and breast cancer
effects summarized above. Benefits associated with avoiding cancer
cases not quantified in the EPA's analysis could be substantial. For
example, a study by Obsekov et al. (2023) reports the number of breast
cancer cases attributable to PFAS exposure ranges from 421 to 3,095
annually, with an estimated direct cost of 6-month treatment ranging
from $27.1 to $198.4 million per year ($2022). This study also finds
that approximately 5 (0.076 percent) annual testicular cases are
attributable to PFOA exposure with an estimated direct cost of
treatment of $173,450 per year ($2022). Although the methods used by
Obsekov et al. (2023) differ from those used to support the national
quantified benefits of the rule, the information provided in the study
is helpful in portraying the costs of cancers that are associated with
PFAS exposures. For additional details on cancer studies and their
individual outcomes, see chapter 3.5 (Cancer) in USEPA (2024c) and
USEPA (2024d).
After assessing available health and economic information, the EPA
was unable to quantify the benefits of avoided health effects discussed
above. The agency prioritized health endpoints with the strongest
weight of evidence conclusions and readily available data for
monetization, namely cardiovascular effects, developmental effects, and
carcinogenic effects. Several other health endpoints that had
indicative or suggestive evidence of associations with exposure to PFOA
and PFOS have not been selected for the EA:
While immune effects had indicative evidence of
associations with exposure to PFOA and PFOS, the EPA did not identify
the necessary information to connect the measured biomarker responses
(i.e., decrease in antibodies) to a disease that could be valued in the
EA;
Evidence indicates associations between PFOA and PFOS
exposure and hepatic effects, such as increases in ALT. While increased
ALT is considered an adverse effect, ALT can be one of several
contributors to a variety of diseases, including liver disease, and it
is difficult to therefore quantify the relationship between this
biomarker and a disease that can be monetized. Similar challenges with
the biomarkers representing metabolic effects (i.e., leptin) and
musculoskeletal effects (i.e., bone density) prevented economic
analysis of these endpoints;
There is evidence of association between exposure to PFOA
and testicular cancer in human and animal studies; however, the
available slope factor in rats implied small changes in the risk of
this endpoint. Because testicular cancer is rarely fatal and the Value
of Statistical Life is the driver of economic benefits evaluated in the
EA, the benefit of decreased testicular cancer expected with this rule
was smaller in comparison and not quantified;
There is evidence of association between exposure to PFOS
and hepatic carcinogenicity in human and animal studies. The EPA
quantified benefits associated with reduced liver cancer cases and
deaths as part of a sensitivity analysis for the final rule in response
to public comments received on the proposed rule requesting that the
EPA quantify additional health benefits (see appendix O of the EA
(USEPA, 2024e));
Finally, other health endpoints, such as SGA and LDLC
effects, were not modeled in the EA because they overlap with effects
that the EPA did model. More specifically, SGA infants are often born
with decreased birth weight or
[[Page 32700]]
receive similar care to infants born with decreased birth weight. LDLC
is a component of TC and could not be modeled separately as the EPA
used TC as an input to the ASCVD model to estimate CVD outcomes.
H. Nonquantifiable Benefits of Removal of PFAS Included in the Final
Regulation and Co-Removed PFAS
The EPA also qualitatively summarized the potential health benefits
resulting from reduced exposure to PFAS other than PFOA and PFOS in
drinking water. The final rule and all regulatory alternatives are
expected to result in additional benefits that have not been
quantified. The final rule will reduce exposure to PFHxS, HFPO-DA, and
PFNA to below their individual MCLs. It will also reduce exposure to
PFBS to below the Hazard Index MCLG and MCL of 1 when the mixture
contains two or more of PFHxS, PFNA, HFPO-DA, and PFBS. Benefits from
avoided cases of the adverse health effects discussed in this section
are expected from the final rule due to co-occurrence of these
contaminants in source waters containing PFOA and/or PFOS, as described
in the Per- and Polyfluoroalkyl Substances (PFAS) Occurrence &
Contaminant Background Support Document (USEPA, 2024b) and part VI of
this preamble. In addition, PFAS, including PFHxS, PFNA, HFPO-DA, and
PFBS and their mixtures affect common target organs, tissues, or
systems to produce dose-additive effects from their co-exposures with
each other, as well as PFOA and PFOS (USEPA, 2024a). The EPA expects
that compliance actions taken under the final rule will remove
additional unregulated co-occurring PFAS contaminants where present
because the best available technologies have been demonstrated to co-
remove additional PFAS. Treatment responses implemented to reduce PFOA
and PFOS exposure under the final rule and Options 1a-c are likely to
remove some amount of additional PFAS contaminants where they co-occur.
Ion exchange (IX) and granulated activated carbon (GAC) are
effective at removing PFAS; there is generally a linear relationship
between PFAS chain length and removal efficiency, shifted by functional
group (McCleaf et al., 2017; S[ouml]reng[aring]rd, 2020).
Perfluoroalkyl sulfonates (PFSAs), such as PFOS, are removed with
greater efficiency than corresponding perfluoroalkyl carboxylates
(PFCAs), such as PFOA, of the same carbon backbone length (Appleman et
al., 2014; Du et al., 2014; Eschauzier et al., 2012; Ochoa-Herrera and
Sierra-Alvarez, 2008; Zaggia et al., 2016). Generally, for a given
water type and concentration, PFSAs are removed approximately as
effectively as PFCAs, which have two additional fully perfluorinated
carbons in the carbon backbone. For example, PFHxS (i.e., sulfonic acid
with a six-carbon backbone) is removed approximately as well as PFOA
(i.e., carboxylic acid with an eight-carbon backbone) and PFHxA (i.e.,
carboxylic acid with a six-carbon backbone) is removed approximately as
well as PFBS (i.e., sulfonic acid with a four-carbon backbone).
Further, PFAS compounds with longer carbon chains display lower
percentage decreases in average removal efficiency over time (McCleaf
et al., 2017).
In cases where the six PFAS included in the final rule occur at
concentrations above their respective regulatory standards, there is
also an increased probability of co-occurrence of additional
unregulated PFAS. Further, as the same technologies also remove other
long-chain and higher carbon/higher molecular weight PFAS, the EPA
expects that treatment will provide additional public health protection
and benefits due to co-removal of unregulated PFAS that may have
adverse health effects. While the EPA has not quantified these
additional benefits, the agency expects that these important co-removal
benefits will further enhance public health protection.
The EPA identified a wide range of potential health effects
associated with exposure to PFAS other than PFOA and PFOS using
documents that summarize the recent literature on exposure and
associated health impacts: the ATSDR's Toxicological Profile for
Perfluoroalkyls (ATSDR, 2021); the EPA's toxicity assessment of HFPO-DA
(USEPA, 2021b); publicly available IRIS assessments for PFBA and PFHxA
(USEPA, 2022g; USEPA, 2023p); the EPA's toxicity assessment of PFBS
(USEPA, 2021a); and the recent National Academies of Sciences,
Engineering, and Medicine Guidance on PFAS Exposure, Testing, and
Clinical Follow-up (NASEM, 2022). Note that the determinations of
associations between PFAS and associated health effects are based on
information available as of September 2023.
Developmental effects: Toxicology and/or epidemiology studies
observed evidence of associations between birth weight and/or other
developmental effects and exposure to PFBA, PFDA, PFHxS, PFHxA, PFNA,
HFPO-DA, PFUnA, and PFBS. Specifically, data from toxicology studies
support this association for PFBS, PFBA, PFHxA, and HFPO-DA, while both
toxicology and epidemiology studies support this association for PFHxS,
PFDA, PFUnA, and PFNA (ATSDR, 2021; USEPA, 2021b; USEPA, 2022g; USEPA,
2023e; Wright et al., 2023). In general, epidemiological studies did
not find associations between exposure and adverse pregnancy outcomes
(miscarriage, preterm birth, or gestational age) for PFNA, PFUnA and
PFHxS (ATSDR, 2021; NASEM, 2022). Epidemiological studies support an
association between PFNA, PFHxS or PFDA exposure and developmental
effects such as decreases in infant birth weight and birth length,
small for gestational age and increased risk of low birth weight (Valvi
et al., 2017; Bach et al., 2016; Louis et al., 2018; Wright et al.,
2023; Manzano-Salgado et al., 2017; Starling et al., 2017). Few
epidemiologic studies also indicate that PFDA exposure is associated
with developmental effects (Wikstr[ouml]m et al., 2020; Valvi et al.,
2017; Luo et al., 2021; Yao et al., 2021). The EPA has determined that
evidence indicates that exposure to PFBA or PFHxA likely causes
developmental effects, based on moderate evidence from animal studies
and indeterminate evidence from human studies (USEPA, 2022g; USEPA,
2023p).
Cardiovascular effects: Epidemiology and/or toxicology studies
observed evidence of associations between PFNA, PFDA, and PFHxS
exposures and effects on total cholesterol, LDLC, and HDLC.
Epidemiological studies report consistent associations between PFHxS
and total cholesterol in adults (Cakmak et al., 2022; Dunder et al.,
2022; Canova et al., 2020; Lin et al., 2019; Liu et al., 2020; Fisher
et al., 2013).
In an analysis based on studies published before 2018, evidence for
associations between PFNA exposure and serum lipid levels in
epidemiology studies was mixed; associations have been observed between
serum PFNA levels and total cholesterol in general populations of
adults but not in pregnant women, and evidence in children is
inconsistent (ATSDR, 2021). Most epidemiology studies did not observe
associations between PFNA and LDLC or HDLC. Epidemiological studies
report consistent associations between PFDA and effects on total
cholesterol in adults (Cakmak et al., 2022; Dunder et al, 2022; Liu et
al., 2020; Dong et al., 2019). Positive associations between PFDA and
other serum lipids, adiposity, cardiovascular disease, and
atherosclerosis were observed in some epidemiology studies, but
findings were inconsistent (Huang et al., 2018; Mattsson et al., 2015;
Christensen et al., 2016). A single animal study observed
[[Page 32701]]
decreases in cholesterol and triglyceride levels in rats at PFDA doses
above 1.25 mg/kg/d for 28 days (NTP, 2018b). There was no association
between PFBA and serum lipids in a single epidemiology study and no
animal studies on PFBA evaluated cardiovascular endpoints (USEPA,
2022g).
Other PFAS for which lipid outcomes were examined in toxicology or
epidemiology studies showed limited to no evidence of associations.
Studies have examined possible associations between various PFAS and
blood pressure in humans or heart histopathology in animals.
Epidemiological studies report positive associations between PFHxS and
hypertension in adolescents and young adults (Averina et al., 2021; Li
et al., 2021; Pitter et al., 2020), but not in other adults (Lin et
al., 2020; Chen et al., 2019; Christensen et al., 2018; Liu et al.,
2018; Bao et al., 2017; Christensen et al., 2016) or children
(Papadopoulou et al., 2021; Khalil et al., 2018; Manzano-Salgado et
al., 2017). No evidence was observed of associations between PFHxS and
cardiovascular diseases (Huang et al., 2018; Mattsson et al., 2015).
Overall, studies did not find likely evidence of cardiovascular effects
for other PFAS except for PFOA and PFOS (USEPA, 2024c; USEPA, 2024d).
Hepatic effects: Toxicology and/or epidemiology studies have
reported associations between exposure to PFAS (PFBA, PFDA, PFUnA,
PFDoDA, PFHxA, PFHxS, HFPO-DA, and PFBS) and hepatotoxicity. The
results of the animal toxicology studies provide strong evidence that
the liver is a sensitive target of PFHxS, PFNA, PFDA, PFUnA, PFBS,
PFBA, PFDoDA, HFPO-DA and PFHxA toxicity. Observed effects in rodents
include increases in liver weight, hepatocellular hypertrophy,
hyperplasia, and necrosis (ATSDR, 2021; USEPA, 2021b; USEPA, 2022g;
USEPA, 2023p). Increases in serum enzymes (such as ALT) and decreases
in serum bilirubin were observed in several epidemiological studies of
PFNA and PFDA (Nian et al., 2019; Jain and Ducatman, 2019; Liu et al.,
2022; Cakmak et al., 2022). Associations between exposure to PFHxS and
effects on serum hepatic enzymes are less consistent (Cakmak et al.,
2022; Liu et al., 2022; Jain and Ducatman, 2019; Salihovic et al.,
2018; Gleason et al., 2015). Mixed effects were observed for serum
liver enzymes in epidemiological studies for PFNA (ATSDR, 2021).
Immune effects: Epidemiology studies have reported evidence of
associations between PFDA or PFHxS exposure and antibody response to
tetanus or diphtheria (Grandjean et al., 2012; Grandjean et al., 2017a;
Grandjean et al., 2017b; Budtz-J[oslash]rgensen and Grandjean, 2018).
There is also some limited evidence for decreased antibody response for
PFNA, PFUnA, and PFDoDA, although there were notable inconsistencies
across studies examining associations for these compounds (ATSDR,
2021). There is limited evidence for associations between PFHxS, PFNA,
PFDA, PFBS, and PFDoDA and increased risk of asthma due to the small
number of studies evaluating the outcome and/or inconsistent study
results (ATSDR, 2021). The small number of studies investigating
immunotoxicity in humans following exposure to PFHpA and PFHxA did not
find associations (ATSDR, 2021; USEPA, 2023p; NASEM, 2022). Toxicology
studies have reported evidence of associations between HFPO-DA exposure
and effects on various immune-related endpoints in animals (ATSDR,
2021; USEPA, 2021b). No laboratory animal studies were identified for
PFUnA, PFHpA, PFDoDA, or FOSA. A small number of toxicology studies
evaluated the immunotoxicity of other perfluoroalkyls and most did not
evaluate immune function. No alterations in spleen or thymus organ
weights or morphology were observed in studies on PFHxS and PFBA. A
study on PFNA found decreases in spleen and thymus weights and
alterations in splenic lymphocyte phenotypes (ATSDR, 2021). Changes in
spleen and thymus weights were reported in female mice and male/female
rats in two 28-day gavage studies of PFDA, although the direction and
dose-dependency of these changes in rats was inconsistent across
studies (Frawley et al., 2018; NTP, 2018b).
COVID-19: A cross-sectional study in Denmark (Grandjean et al.,
2020) showed that PFBA exposure was associated with increasing severity
of COVID-19, with an OR of 1.77 (95% CI: 1.09, 2.87) after adjustment
for age, sex, sampling site, and interval between blood sampling and
diagnosis. A case-control study showed increased risk of COVID-19
infection with high urinary PFAS (including PFOA, PFOS, PFHxA, PFHpA,
PFHxS, PFNA, PFBS, PFDA, PFUnA, PFDoA, PFTrDA, PFTeDA) levels (Ji et
al., 2021). Adjusted odds ratios were 1.94 (95% CI: 1.39, 2.96) for
PFOS, 2.73 (95% CI: 1.71, 4.55) for PFOA, and 2.82 (95% CI: 1.97-3.51)
for total PFAS (sum of 12 PFAS), while other PFAS were not
significantly associated with COVID-19 susceptibility after adjusting
for confounders. In a spatial ecological analysis, Catelan et al.
(2021) showed higher mortality risk for COVID-19 in a population
heavily exposed to PFAS (including PFOA, PFOS, PFHxS, PFBS, PFBA,
PFPeA, PFHxA, and PFHpA) via drinking water. Overall, results suggested
a general immunosuppressive effect of PFAS and/or increased COVID-19
respiratory toxicity due to a concentration of PFBA in the lungs.
Although these studies provide a suggestion of possible associations,
the body of evidence does not permit conclusions about the relationship
between COVID-19 infection, severity, or mortality, and exposures to
PFAS.
In addition to the adverse health effects listed above, there was
little or no evidence that exposure to the various PFAS is associated
with the additional health effects summarized in this section.
Endocrine effects: Epidemiology studies have observed associations
between serum PFHxS, PFNA, PFDA, and PFUnA and effects on thyroid
stimulating hormone (TSH), triiodothyronine (T3), or thyroxine (T4)
levels in serum or thyroid disease; however, there are notable
inconsistencies across the studies identified in the available reports
(ATSDR, 2021; NASEM, 2022). Toxicology studies have reported consistent
associations between exposure to PFHxS, PFBA, PFHxA, and PFBS and
effects on thyroid hormones, thyroid organ weight, and thyroid
histopathology in animals; the endocrine system was a notable target of
PFBS and PFHxS toxicity (ATSDR, 2021; USEPA, 2021a; USEPA, 2022g;
USEPA, 2023p; NTP, 2018b; Ramh[oslash]j et al., 2018; Ramh[oslash]j et
al., 2020; Butenhoff et al., 2009).
Metabolic effects: Epidemiology and toxicology studies have
examined possible associations between various PFAS and metabolic
effects, including leptin, body weight, or body fat in humans or
animals (ATSDR, 2021). Exposure to PFDA has been associated with an
increase in adiposity in adults (Blake et al., 2018; Christensen et
al., 2018; Liu et al., 2018). However, evidence of associations was not
suggestive or likely for any PFAS in this summary except for PFOA and
PFOS (USEPA, 2024c; USEPA, 2024d). Evidence for changes such as
maternal body weight gain, pup body weight, or other developmentally
focused weight outcomes is strong but is considered under the
Developmental effects category (ATSDR, 2021; NASEM, 2022).
Renal effects: A small number of epidemiology studies with
inconsistent results evaluated possible associations
[[Page 32702]]
between PFHxS, PFNA, PFDA, PFBS, PFDoDA, or PFHxA and renal functions
(including estimated glomerular filtration rate and increases in uric
acid levels) (ATSDR, 2021; NASEM 2022; USEPA, 2023p). Toxicology
studies have not observed impaired renal function or morphological
damage following exposure to PFHxS, PFDA, PFUnA, PFBS, PFBA, PFDoDA, or
PFHxA (ATSDR, 2021). Associations with kidney weight in animals were
observed for PFBS and HFPO-DA and was a notable target for PFBS
toxicity (ATSDR, 2021; USEPA, 2021a; USEPA, 2021b; USEPA, 2023p).
Reproductive effects: A small number of epidemiology studies with
inconsistent results evaluated possible associations between
reproductive hormone levels and PFHxS, PFNA, PFDA, PFUnA, PFDoDA, or
PFHxA. Some associations between PFAS (PFHxS, PFHxA, PFNA, PFDA)
exposures and sperm parameters have been observed, but often only one
sperm parameter was altered. While there is suggestive evidence of an
association between PFHxS or PFNA exposure and an increased risk of
early menopause, this may be due to reverse causation since an earlier
onset of menopause would result in a decrease in the removal of PFAS in
menstrual blood. Epidemiological studies provide mixed evidence of
impaired fertility (increased risks of longer time to pregnancy and
infertility), with some evidence for PFHxS, PFNA, PFHpA, and PFBS but
the results are inconsistent across studies or were only based on one
study (ATSDR, 2021; Bach et al., 2018; V[eacute]lez et al., 2015).
Toxicology studies have evaluated the potential histological
alterations in reproductive tissues, alterations in reproductive
hormones, and impaired reproductive functions. No effect on fertility
was observed for PFBS and PFDoDA, and no histological alterations were
observed for PFBS and PFBA. One study found alterations in sperm
parameters and decreases in fertility in mice exposed to PFNA, and one
study for PFDoDA observed ultrastructural alterations in the testes
(ATSDR, 2021). Decreased uterine weights, changes in hormone levels,
and increased time spent in diestrus were observed in studies of PFDA
or PFHxS exposures (NTP, 2018b; Yin et al., 2021).
Musculoskeletal effects: Epidemiology studies observed evidence of
associations between PFNA and PFHxS and musculoskeletal effects
including osteoarthritis and bone mineral density, but data are limited
to two studies (ATSDR, 2021; Khalil et al., 2016; Khalil et al., 2018).
Toxicology studies reported no morphological alterations in bone or
skeletal muscle in animals exposed to PFBA, PFDA, PFHxA, PFHxS, or
PFBS, but evidence is based on a very small number of studies (NTP,
2018b; ATSDR, 2021; USEPA, 2022g; USEPA, 2023p).
Hematological effects: A single uninformative epidemiological study
reported on blood counts in pregnant women exposed to PFHxA (USEPA,
2023p). Epidemiological data were not identified for the other PFAS
(ATSDR, 2021). A limited number of toxicology studies observed
alterations in hematological indices following exposure to relatively
high doses of PFHxS, PFDA, PFUnA, PFBS, PFBA, or PFDoDA (ATSDR, 2021;
USEPA, 2022g; NTP, 2018b; 3M Company, 2000; Frawley et al., 2018).
Toxicology studies observed robust evidence of association between
PFHxA or HFPO-DA exposure and hematological effects, including
decreases in red blood cell (RBC) number, hemoglobin, and percentage of
RBCs in the blood (USEPA, 2021b; USEPA, 2023p). A small number of
toxicology studies observed slight evidence of associations between
exposure to PFHxS, PFDA, or PFBA and decreases in multiple red blood
cell parameters and in prothrombin time; however, effects were not
consistent (USEPA, 2022g; Butenhoff et al., 2009).
Other non-cancer effects: A limited number of epidemiology and
toxicology studies have examined possible associations between various
PFAS and dermal, ocular, and other non-cancer effects. However, the
evidence does not support associations for any PFAS in this summary
except for PFOA and PFOS (ATSDR, 2021; USEPA, 2021a; USEPA, 2023p).
Cancer effects: A small number of epidemiology studies reported
limited associations between multiple PFAS (i.e., PFHxS, PFDA, PFUnA,
and FOSA) and cancer effects. No consistent associations were observed
for breast cancer risk for PFHxS, PFHxA, PFNA, PFHpA, or PFDoDA;
increased breast cancer risks were observed for PFDA and FOSA, but this
was based on a single study (Bonefeld-J[oslash]rgensen et al., 2014),
and one study observed non-significant increased risk for breast cancer
risk and PFDA (Tsai et al., 2020). Exposure to PFHxS was associated
with increased breast cancer risk in one study and with decreased
breast cancer risk in two related studies (Bonefeld-J[oslash]rgensen et
al., 2014; Ghisari et al., 2017; Tsai et al., 2020). No associations
between exposure to PFHxS, PFNA, PFDA, or PFUnA and prostate cancer
risk were observed. However, among men with a first-degree relative
with prostate cancer, associations were observed for PFHxS, PFDA
(Hardell et al., 2014), and PFUnA, but not for PFNA (ATSDR, 2021;
USEPA, 2022g; USEPA, 2023p). A decreased risk of thyroid cancer was
associated with exposure to PFHxS and PFDA in a single study (Liu et
al., 2021). Epidemiological studies examining potential cancer effects
were not identified for PFBS or PFBA (ATSDR, 2021; USEPA 2022g). No
animal studies examined carcinogenicity of PFHxS or PFBA. Aside from a
study that suggested an increased incidence of liver tumors in rats
exposed to high doses of HFPO-DA, the limited number of available
toxicology studies reported no evidence of associations between
exposure to other PFAS (i.e., PFDA and PFHxA) and risk of cancer
(ATSDR, 2021; USEPA, 2021b; USEPA, 2023p). At this time, there is
inadequate information to assess carcinogenic potential for PFAS other
than PFOA, PFOS, and HFPO-DA.
I. Benefits Resulting From Disinfection By-Product Co-Removal
As part of its HRRCA, the EPA is directed by SDWA to evaluate
quantifiable and nonquantifiable health risk reduction benefits for
which there is a factual basis in the rulemaking record to conclude
that such benefits are likely to occur from reductions in co-occurring
contaminants that may be attributed solely to compliance with the MCL
(SDWA 1412(b)(3)(C)(II)). These co-occurring contaminants are expected
to include additional PFAS contaminants not directly regulated by the
final PFAS NPDWR, co-occurring chemical contaminants such as SOCs,
VOCs, and DBP precursors. In this section, the EPA presents a
quantified estimate of the reductions in DBP formation potential that
are likely to occur as a result of compliance with the final PFAS
NPDWR. The methodology detailed here and in section 6.7.1 of USEPA
(2024g) to estimate DBP reductions was externally peer reviewed by
three experts in GAC treatment for PFAS removal and DBP formation
potential (USEPA, 2023m). The external peer reviewers supported the
EPA's approach and edits based on their recommendations for clarity and
completeness are reflected in the following analysis and discussion.
DBPs are formed when disinfectants react with naturally occurring
materials in water. There is a substantial body of literature on DBP
precursor occurrence and THM4 formation mechanisms in drinking water
treatment. Under the Stage 2 Disinfectants and Disinfection Byproducts
Rule (Stage 2 DBP Rule, USEPA, 2006a), the EPA regulates 11
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individual DBPs from three subgroups: THM4, HAA5, and two inorganic
compounds (bromate and chlorite). The formation of THM4 in a particular
drinking water treatment plant is a function of several factors
including disinfectant type, disinfectant dose, bromide concentration,
organic material type and concentration, temperature, pH, and system
residence times. Epidemiology studies have shown that THM4 exposure, a
surrogate for chlorinated drinking water, is associated with an
increased risk of bladder cancer, among other diseases (Cantor et al.,
1998; Cantor et al., 2010; Costet et al., 2011; Beane Freeman et al.,
2017; King and Marrett, 1996; Regli et al., 2015; USEPA, 2019d;
Villanueva et al., 2004; Villanueva et al., 2006; Villanueva et al.,
2007). These studies considered THM4 as surrogate measures for DBPs
formed from the use of chlorination that may co-occur. The
relationships between exposure to DBPs, specifically THM4 and other
halogenated compounds resulting from water chlorination, and bladder
cancer are further discussed in section 6.7 of USEPA (2024g).
Reductions in exposure to THM4 is expected to yield public health
benefits, including a decrease in bladder cancer incidence (Regli et
al., 2015). Among other things, Weisman et al. (2022) found that there
is even a stronger weight of evidence linking DBPs and bladder cancer
since the promulgation of the 2006 Stage 2 DBP regulations (USEPA,
2006a) and publication of Regli et al. (2015). While not the regulated
contaminant for this rulemaking, the expected reduction of DBP
precursors and subsequent DBPs that result from this rulemaking are
anticipated to reduce cancer risk in the U.S. population.
GAC adsorption has been used to remove SOCs, taste and odor
compounds, and natural organic matter (NOM) during drinking water
treatment (Chowdhury et al., 2013). Recently, many water utilities have
installed or are considering installing GAC and/or other advanced
technologies as a protective or mitigation measure to remove various
contaminants of emerging concern, such as PFAS (Dickenson and Higgins,
2016). Because NOM often exists in a much higher concentration (in mg/
L) than trace organics (in [mu]g/L or ng/L) in water, NOM, often
measured as TOC, can interfere with the adsorption of trace organics by
outcompeting the contaminants for adsorption sites and by general
fouling (blockage of adsorption pores) of the GAC.
NOM and inorganic matter are precursors for the formation of THMs
and other DBPs when water is disinfected using chlorine and other
disinfectants to control microbial contaminants in finished drinking
water. Removal of DBP precursors through adsorption onto GAC has been
included as a treatment technology for compliance with the existing DBP
Rules and is a BAT for the Stage 2 DBP Rule. Dissolved organic matter
(DOM) can be removed by GAC through adsorption and biodegradation
(Crittenden et al., 1993; Kim et al., 1997; Yapsakli et al., 2010). GAC
is well-established for removal of THM and HAA precursors (Cheng et
al., 2005; Dastgheib et al., 2004; Iriarte-Velasco et al., 2008;
Summers et al., 2013; Cuthbertson et al., 2019; Wang et al., 2019). In
addition to removal of organic DBPs, GAC also exhibits some capacity
for removal of inorganic DBPs such as bromate and chlorite (Kirisits et
al., 2000; Sorlini et al., 2005) and removal of preformed organic DBPs
via adsorption and biodegradation (Jiang et al., 2017; Terry and
Summers, 2018). Further, GAC may offer limited removal of dissolved
organic nitrogen (Chili et al., 2012).
Based on an extensive review of published literature in sampling
studies where both contaminant groups (PFAS and DBPs) were sampled,
there is limited information about PFAS removal and co-occurring
reductions in DBPs, specifically THMs. To help inform its EA, the EPA
relied on the DBP Information Collection Rule Treatment Study Database
and DBP formation studies to estimate reductions in THM4 ([Delta]THM4)
that may occur when GAC is used to remove PFAS. Subsequently, these
results were compared to THM4 data from PWSs that have detected PFAS
and have indicated use of GAC.
The objective of the EPA's co-removal benefits analysis is to
determine the reduction in bladder cancer cases associated with the
decrease of regulated THM4 in treatment plants due to the installation
of GAC for PFAS removal. Evaluation of the expected reductions in
bladder cancer risk resulting from treatment of PFAS in drinking water
involves five steps:
1. Estimating the number of systems expected to install GAC
treatment in compliance with the final PFAS NPDWR and affected
population size;
2. Estimating changes in THM4 levels that may occur when GAC is
installed for PFAS removal based on influent TOC levels;
3. Estimating changes in the cumulative risk of bladder cancer
using an exposure-response function linking lifetime risk of bladder
cancer to THM4 concentrations in residential water supply (Regli et
al., 2015);
4. Estimating annual changes in the number of bladder cancer cases
and excess mortality in the bladder cancer population corresponding to
changes in THM4 levels under the regulatory alternative in all
populations alive during or born after the start of the evaluation
period; and
5. Estimating the economic value of reducing bladder cancer
morbidity and mortality from baseline to regulatory alternative levels,
using COI measures and the Value of a Statistical Life, respectively.
The EPA expects PWSs that exceed the PFAS MCLs to consider both
treatment and nontreatment options to achieve compliance with the
drinking water standard. The EPA assumes that the populations served by
systems with EP expected to install GAC based on the compliance
forecast detailed in section 5.3 of USEPA (2024g) will receive the DBP
exposure reduction benefits. The EPA notes that other compliance
actions included in the compliance forecast could result in DBP
exposure reductions, including installation of RO. However, these
compliance actions are not included in the DBP benefits analysis
because this DBP exposure reduction function is specific to GAC.
Switching water sources may or may not result in DBP exposure
reductions, therefore the EPA assumed no additional DBP benefits for an
estimated percentage of systems that elect this compliance option.
Lastly, the EPA assumed no change in DBP exposure at water systems that
install IX, as that treatment technology is not expected to remove a
substantial amount of DBP precursors. The EPA also assumed that the
PWSs included in this analysis use chlorine only for disinfection and
have conventional treatment in place prior to GAC installation.
The EPA used the relationship between median raw water TOC levels
and changes in THM4 levels estimated in the 1998 DBP Information
Collection Rule to estimate changes in THM4 concentrations in the
finished water of PWSs fitted with GAC treatment. For more detail on
the approach the EPA used to apply changes in THM4 levels to PWSs
treating for PFAS under the final rule, please see section 6.7 of USEPA
(2024g).
The EPA models a scenario where reduced exposures to THM4 begin in
2029. Therefore, the EPA assumed that the population affected by
reduced THM4 levels resulting from implementation of GAC treatment is
exposed to baseline THM4 levels prior to actions to comply with the
rule (i.e.,
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prior to 2029) and to reduced THM4 levels from 2029 through 2105.
Rather than modeling individual locations (e.g., PWS), the EPA
evaluates changes in bladder cancer cases among the aggregate
population per treatment scenario and source water type that is
expected to install GAC treatment to reduce PFAS levels. Because of
this aggregate modeling approach, the EPA used national-level
population estimates to distribute the SDWIS populations based on
single-year age and sex and to extrapolate the age- and sex-specific
populations to future years. Appendix B of USEPA (2024g) provides
additional details on estimation of the affected population.
Regli et al. (2015) analyzed the potential lifetime bladder cancer
risks associated with increased bromide levels in surface source water
resulting in increased THM4 levels in finished water. To account for
variable levels of uncertainty across the range of THM4 exposures from
the pooled analysis of Villanueva et al. (2004), they derived a
weighted mean slope factor from the odds ratios reported in Villanueva
et al. (2004). They showed that, while the original analysis deviated
from linearity, particularly at low concentrations, the overall pooled
exposure-response relationship for THM4 could be well-approximated by a
linear slope factor that predicted an incremental lifetime cancer risk
of 1 in 10,000 exposed individuals (10-\4\) per 1 [micro]g/L
increase in THM4. The linear slope factor developed by Regli et al.
(2015) enables estimation of the changes in the lifetime bladder cancer
risk associated with lifetime exposures to reduced THM4 levels. Weisman
et al. (2022) applied the dose-response information from Regli et al.
(2015) and developed a robust, national-level risk assessment of DBP
impacts, where the authors estimated that approximately 8,000 of 79,000
annual U.S. bladder cancer cases are attributable to chlorination DBPs,
specifically associated with THM4 concentrations.
The EPA estimated changes in annual bladder cancer cases and annual
excess mortality in the bladder cancer population due to estimated
reductions in lifetime THM4 exposure using a life table-based approach.
This approach was used because (1) annual risk of new bladder cancer
should be quantified only among those not already experiencing this
chronic condition, and (2) bladder cancer has elevated mortality
implications.
The EPA used recurrent life table calculations to estimate a water
source type-specific time series of bladder cancer incidence for a
population cohort characterized by sex, birth year, and age at the
beginning of the PFOA/PFOS evaluation period under the baseline
scenario and the GAC regulatory alternative. The estimated risk
reduction from lower exposure to DBPs in drinking water was calculated
based on changes in THM4 levels used as inputs to the Regli et al.
(2015)-based health impact function, described in more detail in
section 6.7 of USEPA (2024g). The life table analysis accounts for the
gradual changes in lifetime exposures to THM4 following implementation
of GAC treatment under the regulatory alternative compared to the
baseline. The outputs of the life table calculations are the water
source type-specific estimates of the annual change in the number of
bladder cancer cases and the annual change in excess bladder cancer
population mortality.
The EPA used the Value of a Statistical Life to estimate the
benefits of reducing mortality associated with bladder cancer in the
affected population. The EPA used the cost of illness-based valuation
to estimate the benefits of reducing morbidity associated with bladder
cancer. Specifically, the EPA used bladder cancer treatment-related
medical care and opportunity cost estimates from Greco et al. (2019).
Table 63 shows the original cost of illness estimates from Greco et al.
(2019), along with the values updated to $2022 used in this analysis.
The EPA received public comments on the EA for the proposed rule
related to the EPA's use of cost of illness information for morbidity
valuation. Specifically, a couple of commenters recommended that the
EPA use willingness to pay information (instead of cost of illness
information) when valuing the costs associated with non-fatal
illnesses, stating that willingness to pay information better accounts
for lost opportunity costs (e.g., lost productivity and pain and
suffering) associated with non-fatal illnesses (USEPA, 2024k). To
better account for these opportunity costs, the EPA used recently
available willingness to pay values in a sensitivity analysis for
morbidity associated with bladder cancer. The sensitivity analysis
results show that when willingness to pay values are used in bladder
cancer benefits analysis, morbidity benefits are increased by
approximately 19.9 percent. See appendix O of the EA for full details
and results on the willingness to pay sensitivity analyses.
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Tables 64 to 67 presents the estimated changes in non-fatal bladder
cancer cases and bladder cancer-related deaths from exposure to THM4
due to implementation of GAC treatment by option. The EPA estimated
that, over the evaluation period, the final rule will result in
annualized benefits from avoided bladder cancer cases and deaths of
$380 million.
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J. Comparison of Costs and Benefits
This section provides a comparison of the incremental costs and
benefits of the final rule, as described in chapter 7 of the EA.
Included here are estimates of total quantified annualized costs and
benefits for the final rule and regulatory alternative MCLs under
options 1a-1c, as well as considerations for the nonquantifiable costs
and benefits. The EPA's determinations as to whether the costs are
justified by the benefits must be based on an analysis of both the
quantified costs and benefits as well as the nonquantifiable benefits
and nonquantifiable costs, per SDWA 1412(b)(3)(C)(I)-(III).
The incremental cost is the difference between quantified costs
that will be incurred if the final rule is enacted over current
baseline conditions. Incremental benefits reflect the avoided future
adverse health outcomes attributable to PFAS reductions and co-removal
of additional contaminants due to actions undertaken to comply with the
final rule.
Table 68 provides the incremental quantified costs and benefits of
the final rule at a 2 percent discount rate in 2022 dollars. The top
row shows total monetized annualized costs including total PWS costs
and primacy agency costs. The second row shows total monetized
annualized benefits including all endpoints that could be quantified
and valued. For both, the estimates are the expected (mean) values and
the 5th percentile and 95th percentile quantified estimates from the
uncertainty distribution. These percentile estimates come from the
distributions of annualized costs and annualized benefits generated by
the 4,000 iterations of SafeWater MCBC. Therefore, these distributions
reflect the joint effect of the multiple sources of variability and
uncertainty for quantified costs, quantified benefits, and the baseline
uncertainties such as PFAS occurrence, as detailed in sections 5.1.2,
6.1.2, and chapter 4 of the EA, respectively (USEPA, 2024g). For
further discussion of the quantified uncertainties in the EA, see
section XII.K of this preamble.
The third row shows net quantified benefits (benefits minus costs).
The net annual quantified incremental benefits are $760,000. Because of
the variation associated with the use of statistical models such as
SafeWater MCBC, the modeled quantified net benefits are nearly at
parity. The uncertainty range for net benefits is a negative $622
million to $725 million. Additional uncertainties are presented in
Table 72.
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Tables 69 to 71 summarize the total annual costs and benefits for
options 1a, 1b, and 1c, respectively.
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The benefit-cost analysis reported dollar figures presented above
reflect benefits and costs that could be quantified for each regulatory
alternative MCL given the best available scientific data. The EPA notes
that these quantified benefits are estimated using a cost-of-illness
approach. In the sensitivity analysis, the EPA also calculated
quantified benefits using a willingness-to-pay approach instead of cost
of illness information, for non-fatal RCC and bladder cancer illnesses.
In this case, the estimated expected quantified annualized costs are
approximately $1,549 million and the estimated expected quantified
annualized benefits increase to approximately $1,632 million, resulting
in approximately $84 million in expected annualized net benefits. See
appendix O of the EA for further discussion.
The quantified benefit-cost results above are not representative of
all benefits and costs anticipated under the final NPDWR. Due to
occurrence, health, and economic data limitations, there are several
adverse health effects associated with PFAS exposure and costs
associated with treatment that the EPA could not estimate
quantitatively.
PFAS exposure is associated with a wide range of adverse health
effects, including reproductive effects such as decreased fertility;
increased high blood pressure in pregnant women; developmental effects
or delays in children, including low birth weight, accelerated puberty,
bone variations, or behavioral changes; increased risk of some cancers,
including prostate, kidney, and testicular cancers; reduced ability of
the body's immune system to fight infections, including reduced vaccine
response; interference with the body's natural hormones; and increased
cholesterol levels and/or risk of obesity. Based on the available data
at rule proposal and submitted by public commenters, the EPA is only
able to quantify three PFOA- and PFOS-related health endpoints (i.e.,
changes in birth weight, CVD, and RCC) in the national analysis.
The EPA also evaluated the impacts of PFNA on birth weight and PFOS
on liver cancer in quantitative sensitivity analyses (See appendices K
and O of USEPA, 2024e, respectively). Those analyses demonstrate that
there are potentially significant other quantified benefits not
included in the national quantified benefits above: for example, the
EPA's quantitative sensitivity analysis for PFNA (found in appendix K
of USEPA, 2024e) found that the inclusion of a 1 ng/L PFNA reduction
could increase annualized birth weight benefits by a factor of 5.6-7.8
in a model system serving 100,000 people, relative to a scenario that
quantified a 1 ng/L reduction in PFOA and a 1 ng/L reduction in PFOS
only. In the case of PFOS impacts on liver cancer, the EPA has
estimated an expected value of $4.79 million in benefits via the
reduction in liver cancer cases anticipated to be realized by the final
rule. All regulatory alternatives are
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expected to produce substantial additional benefits from all the other
adverse health effects avoided, but that cannot be quantified at this
time. Treatment responses implemented to remove PFOA and PFOS under
regulatory alternative MCLs under options 1a-1c are likely to remove
some amount of additional PFAS contaminants where they co-occur. Co-
occurrence among PFAS compounds has been observed frequently as
discussed in the PFAS Occurrence & Contaminant Background Support
Document (USEPA, 2024b). The final rule is expected to produce the
greatest reduction in exposure to PFAS compounds as compared to the
three regulatory alternative MCLs because it includes PFHxS, PFNA,
HFPO-DA, and PFBS in the regulation. Inclusion of the Hazard Index will
trigger more systems to treat (as shown in section 4.4.4 of the EA) and
provides enhanced public health protection by ensuring reductions of
these additional compounds when present above the Hazard Index of 1.
Specifically, as Hazard Index PFAS are reduced, the EPA anticipates
additional public health benefits from avoided cardiovascular,
developmental, and immune effects. For further discussion of the
quantitative and qualitative benefits associated with the final rule,
see section 6.2 of the EA.
The EPA also expects that the final rule will result in additional
nonquantifiable costs. As noted above, the Hazard Index and individual
MCLs are expected to trigger more systems into more frequent monitoring
and treatment. In the national cost analysis, the EPA quantified the
national treatment and monitoring costs associated with the PFHxS
individual MCL and the Hazard Index associated costs based on PFHxS
occurrence only. Due to occurrence data limitations, cost estimates for
PFNA, PFBS, and HFPO-DA are less precise relative to those for PFOA,
PFOS, and PFHxS compounds, and as such, the EPA performed a
quantitative sensitivity analysis of the national cost impacts
associated with Hazard Index exceedances resulting from PFNA, PFBS, and
HFPO-DA and the PNFA and HFPO-DA individual MCLs to understand and
consider the potential magnitude of costs associated with treating
these three PFAS. The EPA found that in addition to the costs
associated with PFHxS exceedances, which are included in the national
cost estimate, the Hazard Index and individual MCLs for PFNA and HFPO-
DA could cost an additional $82.4 million per year. In cases where
these compounds co-occur at locations where PFAS treatment is
implemented because of nationally modeled PFOA, PFOS, and PFHxS
occurrence, treatment costs are likely to be marginally higher as
treatment media estimated bed-life is shortened. In instances where
concentrations of PFNA, HFPO-DA, and PFBS are high enough to cause or
contribute to a Hazard Index exceedance when the concentrations of
PFOA, PFOS, and PFHxS would not have already otherwise triggered
treatment, the national modeled costs may be underestimated. If these
PFAS occur in isolation at levels that affect treatment decisions, or
if these PFAS occur in combination with PFHxS when PFHxS concentrations
were otherwise below its respective HBWC in isolation (i.e., less than
10 ng/L) then the quantified costs underestimate the impacts of the
final rule. See appendix N.3 of the EA for a sensitivity analysis of
additional treatment costs at systems with Hazard Index exceedances
(USEPA, 2024e). See appendix N.4 for a sensitivity analysis of the
marginal costs of HFPO-DA and PFNA MCLs. For further discussion of how
the EPA considered the costs of the five individual MCLs and the HI
MCL, see section XII.A.4 of this preamble.
Commenters suggested that another potential source of non-
quantified cost comes from the fact that the EPA has proposed
designating PFOA and PFOS as CERCLA hazardous substances (USEPA,
2022l). Stakeholders have expressed concern to the EPA that a hazardous
substance designation for certain PFAS may limit their disposal options
for drinking water treatment residuals (e.g., spent media, concentrated
waste streams) and/or potentially increase costs. The designation of
PFOA and PFOS as CERCLA hazardous substances would not require waste
(e.g., biosolids, treatment residuals, etc.) to be treated in any
particular fashion, nor disposed of at any specific particular type of
landfill. The designation also would not restrict, change, or recommend
any specific activity or type of waste at landfills. In its estimated
national costs, the EPA has maintained the assumption that disposal
does not have to occur in accordance with hazardous waste standards
thus national costs may be underestimated. The EPA has conducted a
sensitivity analysis that assumes hazardous waste disposal at all
systems treating for PFAS to assess the potential increase in costs
(see appendix N of USEPA, 2024e).
Table 72 provides a summary of the likely impact of nonquantifiable
benefit-cost categories. In each case, the EPA notes the potential
direction of the impact on costs and/or benefits. For example, benefits
are underestimated if the PFOA and PFOS reductions result in avoided
adverse health outcomes that cannot be quantified and valued. Sections
5.7 and 6.8 of the EA identify the key methodological limitations and
the potential effect on the cost or benefit estimates, respectively.
Additionally, Table 73 summarizes benefits and costs that are
quantified and nonquantifiable under the final rule.
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Sections XII.B to XII.K of this preamble summarize the results of
this final rule analysis. The EPA discounted the estimated monetized
cost and benefit values using a 2 percent discount rate, consistent
with OMB Circular A-4 (OMB, 2003; OMB, 2023) guidance. The U.S. White
House and Office of Management and Budget recently finalized and re-
issued the A-4 and A-94 benefit-cost analysis guidance (see OMB
Circular A-4, 2023), and the update includes new guidance to use a
social discount rate of 2 percent. The updated OMB Circular A-4 states
that the discount rate should equal the real (inflation-adjusted) rate
of return on long-term U.S. government debt, which provides an
approximation of the social rate of time preference. This rate for the
past 30 years has averaged around 2.0 percent per year in real terms on
a pre-tax basis. OMB arrived at the 2 percent discount rate figure by
considering the 30-year average of the yield on 10-year Treasury
marketable securities, and the approach taken by OMB produces a real
rate of 1.7 percent per year, to which OMB added a 0.3 percent per-year
rate to reflect inflation as measured by the personal consumption
expenditure (PCE) inflation index. The OMB guidance states that
Agencies must begin using the 2 percent discount rate for draft final
rules that are formally submitted to OIRA after December 31, 2024. The
updated OMB Circular A-4 guidance further states that ``to the extent
feasible and appropriate, as determined in consultation with OMB,
agencies should follow this Circular's guidance earlier than these
effective dates.'' Given the updated default social discount rate
prescribed in the OMB Circular A-4 and also public input received on
the discount rates considered by the EPA in the proposed NPDWR, for
this final rule, the EPA estimated national benefits and costs at the 2
percent discount rate for the final rule and incorporated those results
into the final economic analysis. Since the EPA proposed this NPDWR
with the 3 and 7 percent discount rates based on guidance in the
previous version of OMB Circular A-4, the EPA has kept the presentation
of results using these discount rates in appendix P. The Administrator
reaffirms his determination that the benefits of the rule justify the
costs. The EPA's determination is based on its analysis under in SDWA
section 1412(b)(3)(C) of the quantifiable benefits and costs at the 2
percent discount rate, in addition to at the 3 and 7 percent discount
rate, as well as the nonquantifiable benefits and costs. The EPA found
that significant nonquantifiable benefits are likely to occur from the
final PFAS NPDWR.
The quantified analysis is limited in its characterization of
uncertainty. In section XII.I, Table 68 of this preamble, the EPA
provides 5th and 95th percentile values associated with the 2 percent
discounted expected values for net benefits. These values represent the
quantified, or modeled, potential range in the expected net benefit
values associated with the uncertainty resulting from the following
variables; the baseline PFAS occurrence; the affected population size;
the compliance technology unit cost curves, which are selected as a
function of baseline PFAS concentrations and population size, the
distribution of feasible treatment technologies, and the three
alternative levels of treatment capital costs; the concentration of TOC
in a system's source water (which impacts GAC O&M costs); the
demographic composition of the system's population; the magnitude of
PFAS concentration reductions; the health effect-serum PFOA and PFOS
slope factors that quantify the relationship between changes in PFAS
serum level and health outcomes for birth weight, CVD, and RCC; and the
cap placed on the cumulative RCC risk reductions due to reductions in
serum PFOA. These modeled sources of uncertainty are discussed in more
detail in section XII.K of this preamble. While the agency reports only
the 5th and 95th percentile values, the EPA notes that additional
information can be obtained from looking at the whole uncertainty
distribution of annualized net benefits (i.e., the distribution of
annualized differences between total monetize benefits and total
monetized costs).
The quantified 5th and 95th percentile values do not include a
number of factors that impact both costs and benefits but for which the
agency did not have sufficient data to include in the quantification of
uncertainty. The factors influencing the final rule cost estimates that
are not quantified in the uncertainty analysis are detailed in Table 43
of this preamble. These uncertainty sources include: the specific
design and operating assumptions used in developing treatment unit
cost; the use of national average costs that may differ from the
geographic distribution of affected systems; the possible future
deviation from the compliance technology forecast; and the degree to
which actual TOC source water values differ from the EPA's estimated
distribution. The EPA has no information to indicate a directional
influence of the estimated costs with regard to these uncertainty
sources. To the degree that uncertainty exists across the remaining
factors it would most likely influence the estimated 5th and 95th
percentile range and not significantly impact the expected value
estimate of costs.
Table 62 of this preamble discusses the sources of uncertainty
affecting the estimated benefits not captured in the estimated 5th and
95th reported values. The modeled values do not capture the uncertainty
in: the exposure that results from daily population changes at NTNCWSs
or routine population shifting between PWSs, for example spending
working hours at a NTNCWS or CWS and home hours at a different CWS; the
exposure-response functions used in the benefits analyses assume that
the effects of serum PFOA/PFOS on the health outcomes considered are
independent, additive, and that there are no threshold serum
concentrations below which effects (cardiovascular, developmental, and
renal cell carcinoma) do not occur; the distribution of population by
size and demographics across EP within modeled systems and future
population size and demographic changes; and the Value of Statistical
Life reference value or income elasticity used to update the Value of
Statistical Life. Given information available to the agency, four of
the listed uncertainty sources would not affect the benefits expected
value but the dispersion around that estimate. They are the unmodeled
movements of populations between PWSs with potentially differing PFAS
concentrations; the independence and additivity assumptions with regard
to the effects of serum PFOA/PFOS on the health outcomes; the
uncertainty in the population and demographic distributions among EP
within individual systems; and the Value of Statistical Life value and
the income elasticity measures. Two of the areas of uncertainty not
captured in the analysis would tend to indicate that the quantified
benefits numbers are overestimates. First, the data available to the
EPA with regard to population size at NTNCWSs, while likely capturing
peaks in populations utilizing the systems, does not account for the
variation in use and population and would tend to overestimate the
exposed population. The second source of uncertainty, which
definitionally would indicate overestimates in the quantified benefits
values, is the assumption that there are no threshold serum
concentrations below which health effects (cardiovascular,
developmental, and renal cell carcinoma) do not occur. One source of
possible underestimation of benefits not accounted for in the
[[Page 32717]]
quantified analysis is the impact of general population growth over the
extended period of analysis.
In addition to the quantified cost and benefit expected values, the
modeled uncertainty associated within the 5th and 95th percentile
values, and the un-modeled uncertainty associated with a number of
factors listed above, there are also significant nonquantifiable costs
and benefits which are important to the overall weighing of costs and
benefits. Table 72 provides a summary of these nonquantifiable cost and
benefit categories along with an indication of the directional impact
each category would have on total costs and benefits. Tables 43 and 62
also provide additional information on a number of these
nonquantifiable categories.
For the nonquantifiable costs, the EPA had insufficient nationally
representative data to precisely characterize occurrence of HFPO-DA,
PFNA, and PFBS at the national level and therefore could not include
complete treatment costs associated with: the co-occurrence of these
PFAS at systems already required to treat as a result of estimated
PFOA, PFOS, or PFHxS levels, which would shorten the filtration media
life and therefore increase operation costs; and the occurrence of
HFPO-DA, PFNA, and/or PFBS at levels high enough to cause systems to
exceed the individual MCLs for PFNA and HFPO-DA or the Hazard Index and
have to install PFAS treatment. The EPA expects that the quantified
national costs, which do not include HFPO-DA, PFNA, and PFBS treatment
costs are marginally underestimated (on the order of 5%) as a result of
this lack of sufficient nationally representative occurrence data. In
an effort to better understand and consider the costs associated with
treatment of the PFNA and HFPO-DA MCLs and potentially co-occurring
HFPO-DA, PFNA, and PFBS at systems both with and without PFOA, PFOS and
PFHxS occurrence in exceedance of the MCLs the EPA performed a
quantitative sensitivity analysis of the national cost impacts
associated with Hazard Index MCL exceedances resulting from HFPO-DA,
PFNA, and PFBS and/or individual MCL exceedances of PFNA and HFPO-DA.
The analysis is discussed in section 5.3.1.4 and appendix N.3 of the EA
(USEPA, 2024l; USEPA, 2024e). Two additional nonquantifiable cost
impacts stemming from insufficient co-occurrence data could also
potentially shorten filtration media life and increase operation costs.
The co-occurrence of other PFAS and other non-PFAS contaminants not
regulated in the final rule could both increase costs to the extent
that they reduce media life. The EPA did not include POU treatment in
the compliance technology forecast because current POU units are not
certified to remove PFAS to the standards required in the final rule.
Once certified, this technology may be a low-cost treatment alternative
for some subset of small systems. Not including POU treatment in this
analysis has resulted in a likely overestimate of costs. Additionally,
appendix N.2 of the EA (USEPA, 2024e) contains a sensitivity analysis
that estimates possible additional national annualized costs of $99
million, which would accrue to systems if the waste filtration media
from GAC and IX were handled as RCRA regulatory or characteristic
hazardous waste. This sensitivity analysis includes only disposal costs
and does not consider other potential environmental benefits and costs
associated with the disposal of the waste filtration media.
There are significant nonquantifiable sources of benefits that were
not captured in the quantified benefits estimated for the proposed
rule. While the EPA was able to monetize some of the PFOA and PFOS
benefits related to CVD, infant birth weight, and RCC effects, the
agency was unable to quantify additional reductions in negative health
impacts in the national quantitative analysis. In addition to the
national analysis for the final rule, the agency developed a
sensitivity analysis assessing liver cancer impacts, which is detailed
in appendix O of the EA (USEPA, 2024e). The EPA did not quantify PFOA
and PFOS benefits related to health endpoints including developmental,
cardiovascular, hepatic, immune, endocrine, metabolic, reproductive,
musculoskeletal, and other types of carcinogenic effects. See section
XII.F of this preamble for additional information on the
nonquantifiable impacts of PFOA and PFOS. Further, the agency did not
quantify any health benefits associated with the potential reductions
in Hazard Index PFAS, which include PFHxS, HFPO-DA, PFNA, and PFBS, or
other co-occurring non-regulated PFAS which would be removed due to the
installation of required filtration technology at those systems that
exceed the final MCLs. The nonquantifiable benefits categories
associated with exposure to PFHxS, HFPO-DA, PFNA, and PFBS include
developmental, cardiovascular, immune, hepatic, endocrine, metabolic,
reproductive, musculoskeletal, and carcinogenic effects. In addition,
the EPA did not quantify the potential developmental, cardiovascular,
immune, hepatic, endocrine, metabolic, reproductive, musculoskeletal,
or carcinogenic impacts related to the removal of other co-occurring
non-regulated PFAS. See section XII.G of this preamble for additional
information on the nonquantifiable impacts of PFHxS, HFPO-DA, PFNA, and
PFBS and other non-regulated co-occurring PFAS.
The treatment technologies installed to remove PFAS can also remove
numerous other non-PFAS drinking water contaminants which have negative
health impacts including additional regulated and unregulated DBPs (the
quantified benefits assessment does estimate benefits associated with
THM4), heavy metals, organic contaminants, and pesticides, among
others. The removal of these co-occurring non-PFAS contaminants could
have additional positive health benefits. In total these
nonquantifiable benefits are anticipated to be significant and are
discussed qualitatively in section 6.2 of the EA (USEPA, 2024g).
To fully weigh the costs and benefits of the action, the agency
considered the totality of the monetized values, the potential impacts
of the nonquantifiable uncertainties described above, the
nonquantifiable costs and benefits, and public comments received by the
agency related to the quantified and qualitative assessment of the
costs and benefits. For the final rule, the EPA is reaffirming the
Administrator's determination made at proposal that the quantified and
nonquantifiable benefits of the rule justify its quantified and
nonquantifiable costs (88 FR 18638; USEPA, 2023f).
K. Quantified Uncertainties in the Economic Analysis
The EPA characterized sources of uncertainty in its estimates of
costs expected to result from the final rule. The EPA conducted Monte-
Carlo based uncertainty analysis as part of SafeWater MCBC. With
respect to the cost analysis, the EPA modeled the sources of
uncertainty in Table 74.
[[Page 32718]]
[GRAPHIC] [TIFF OMITTED] TR26AP24.082
For each iteration, SafeWater MCBC assigned new values to the three
sources of modeled uncertainty as described in Table 74, and then
calculated costs for each of the model PWSs. This was repeated 4,000
times to reach an effective sample size for each parameter. At the end
of the 4,000 iterations, SafeWater MCBC outputs the expected value as
well as the 90 percent CI for each cost metric (i.e., bounded by the
5th and 95th percentile estimates for each cost component). Detailed
information on the data used to model uncertainty is provided in
appendices A and L of USEPA (2024e).
Additionally, the EPA characterized sources of uncertainty in its
analysis of potential benefits resulting from changes in PFAS levels in
drinking water. The analysis reports uncertainty bounds for benefits
estimated in each health endpoint category modeled for the final rule.
Each lower (upper) bound value is the 5th (95th) percentile of the
category-specific benefits estimate distribution represented by 4,000
Monte Carlo draws.
Table 75 provides an overview of the specific sources of
uncertainty that the EPA quantified in the benefits analysis. In
addition to these sources of uncertainty, reported uncertainty bounds
also reflect the following upstream sources of uncertainty: baseline
PFAS occurrence, affected population size and demographic composition,
and the magnitude of PFAS concentration reductions. These analysis-
specific sources of uncertainty are further described in appendix L of
USEPA (2024e).
[[Page 32719]]
[GRAPHIC] [TIFF OMITTED] TR26AP24.138
XIII. Statutory and Executive Order Reviews
Additional information about these statutes and Executive orders
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.
A. Executive Order 12866: Regulatory Planning and Review and Executive
Order 14094 Modernizing Regulatory Review
1. Significant Regulatory Action
This action is a ``significant regulatory action,'' as defined
under section 3(f)(1) of Executive Order (E.O.) 12866, as amended by
E.O. 14094. Accordingly, the EPA submitted this action to the Office of
Management and Budget (OMB) for E.O. 12866 review. Documentation of any
changes made in response to E.O. 12866 review is available in the
docket. The EPA prepared an analysis of the potential costs and
benefits associated with this action. This analysis, the Economic
Analysis (EA; USEPA, 2024g), is also available in the docket and is
summarized in section XII of this preamble.
2. Additional Analysis Under E.O. 12866
The EPA evaluated commenters recommendations summarized in this
section to quantify the greenhouse gas (GHG) impacts associated with
the rule in light of E.O. 12866, Regulatory Planning and Review, and
E.O. 13990, Protecting Public Health and the Environment and Restoring
Science to Tackle the Climate Crisis. For the final rule, the EPA has
conducted an additional analysis of the disbenefits associated with
operation of treatment technologies to comply with the standard. This
analysis is summarized here and detailed in the EA for the Final per-
and polyfluoroalkyl substances (PFAS) National Primary Drinking Water
Regulation (NPDWR; USEPA, 2024g).
a. Proposed Rule
In the proposed rule, the EPA did not quantify and monetize
potential GHG emissions impacts that would occur as a result of
operating treatment technologies to comply with the proposed rule
because quantification of such impacts is not required for the Health
Risk Reduction and Cost Analysis (HRRCA) under the Safe Drinking Water
Act (SDWA). The EPA evaluated commenters recommendations and summarized
that the EPA should quantify and monetize the GHG emissions impacts
associated with the rule in light of E.O. 13990, Protecting Public
Health and the Environment and Restoring Science to Tackle the Climate
Crisis.
b. Summary of Major Public Comments and EPA Responses
Several commenters recommend ``. . . that the agency consider the
social costs of carbon as part of any PFAS rule's cost analysis to be
comprehensive as well as to understand how this rule may have
unintended consequences like increased social costs relating to carbon
dioxide emissions.'' Commenters asserted that ``[n]ot including the
social costs of carbon and other social costs hinders the Administrator
from having all necessary information to set the perfluorooctanoic acid
(PFOA) and perfluorooctane sulfonic acid (PFOS) drinking water standard
at a level that maximizes health risk reduction benefits at a cost that
is justified, given those benefits.'' Commenters pointed to the GHG
emissions associated with production, reactivation, and delivery of
treatment media, focusing on granular activated carbon (GAC) in
particular; construction associated with the installation of the
treatment technology at the entry point (EP); electricity used to
operate treatment technologies; and transportation and disposal of
drinking water treatment residuals to comply with the PFAS NPDWR. Two
commenters provided their own quantified estimates for some aspects of
CO2 emissions. One commenter estimated that the climate
disbenefits from CO2 emissions associated with increased
electricity use for additional pumping, lighting, and ventilation in
[[Page 32720]]
treatment plants would be ``$2.5M to $6.8M at 2.5 and 1.5 percent
discount rates, respectively, in 2026; and $3.6M to $8.6M at 2.5 and
1.5 percent discount rates, respectively, in 2046.'' Another commenter
used a life cycle analysis paper that provides one estimate for the
carbon footprint of producing and using GAC and estimates that the
climate damages from the CO2 emissions associated with
increased GAC media use ``. . . could have a social cost of more than
$160 million annually.'' One commenter stated that the EPA has
performed this analysis in other rulemakings, specifically a 2023
proposed air rulemaking (88 FR 25080), and notes that in that
regulatory impact analysis (RIA; USEPA, 2023u), ``EPA included the
social cost of carbon for the electricity required to operate the air
pollution controls.''
The EPA disagrees with commenters that SDWA requires the EPA to
quantify and consider the climate disbenefits associated with GHG
emission increases from this final rule in the HRRCA. The HRRCA
requirements of SDWA 1412 (b)(3)(C) require the agency to analyze
``quantifiable and nonquantifiable costs . . . that are likely to occur
solely as a result of compliance with the maximum contaminant level''
(emphasis added). Therefore, the EPA considered as part of its HRRCA
analysis the compliance costs to facilities, including the costs to
purchase electricity required to operate the treatment technologies.
Since the climate disbenefits from GHG emissions associated with
producing electricity necessary to operate the treatment technologies
account for climate impacts associated with the CO2
emissions and associated costs to society, they do not qualify as
compliance costs to public water systems (PWSs) that are part of the
required HRRCA analysis under SDWA. For this reason, the EPA included
compliance costs to PWSs but not climate disbenefits from GHG emissions
associated with the production, reactivation, and delivery of treatment
media; construction associated with the installation of the treatment
technology at EP; electricity used to operate treatment technologies;
and transportation and disposal of drinking water treatment residuals
in the cost consideration for the final PFAS NPDWR.
The EPA is committed to understanding and addressing climate change
impacts in carrying out the agency's mission of protecting human health
and the environment. While the EPA is not required by SDWA
1412(b)(3)(C) to consider climate disbenefits under the HRRCA the
agency has estimated the potential climate disbenefits caused by
increased on-site electricity demand associated with removing PFAS from
drinking water. As explained in section V of this preamble, the EPA's
final rule is based on the EPA's record-based analysis of the statutory
factors in SDWA 1412(b), and this disbenefits analysis is presented
solely for the purpose of complying with E.O. 12866. Circular A-4
states ``[l]ike other benefits and costs, an effort should be made to
quantify and monetize additional effects when feasible and
appropriate'' (OMB, 2023). The scope of the monetized climate
disbenefits analysis is limited to the climate impacts associated with
the CO2 emissions from increased electricity to operate the
treatment technologies that will be installed to comply with the PFAS
NPDWR.
The EPA did not quantify the potential CO2 emissions
changes associated with the production and delivery of treatment media,
construction required for the installation of treatment technology, and
transportation and disposal of treatment residuals. The EPA recognizes
that many activities directly and indirectly associated with drinking
water treatment produce GHG emissions; however, the agency determined
that it could not accurately quantify all the potential factors that
could increase and decrease greenhouse gas emissions that are not
solely attributable to the direct onsite operations of the plant beyond
increased electricity use at the plant. The EPA has information, to
varying degrees, that the agency could use to potentially estimate
emissions from some of these activities. To accurately understand the
total potential climate disbenefits of this rule, the EPA should
consider GHG emissions in the baseline scenario where the agency also
takes no action. However, the EPA lacks the data needed to consider the
potentially significant climate disbenefits and other costs to society
of the EPA taking no action (i.e., not finalizing the PFAS NPDWR). If
the EPA were to not finalize the rule, this could likely trigger other
activities that would increase GHG emissions. For example, significant
climate disbenefits may be realized from the public increasing
purchases of bottled water in an effort to avoid PFAS exposure from
drinking water provided by PWSs. More members of the public switch to
drinking bottled water if they do not trust the safety of their utility
supplied drinking water (Grupper et al. 2021, Lev[ecirc]que and Burns,
2017). Bottled water has a substantially larger carbon footprint than
the most highly treated tap water, including the significant energy
necessary to produce plastic bottles and transport water from where it
is bottled to the point of consumption (Gleick and Cooley, 2009). This
carbon footprint can be hundreds of times greater than tap water on a
per volume basis (e.g., see Botto, 2009). In addition, this is the
first drinking water regulation in which the EPA has estimated
disbenefits associated with increases or reductions in GHG emissions.
The EPA expects that the approach for quantifying such benefits or
disbenefits will continue to evolve as our understanding of the
potential relationships between quality of drinking water treatment,
impacts on consumer behavior, and other factors influencing GHG
emissions improves. Considering the limitations described above and
consistent with past EPA rulemakings,\27\ the EPA is limiting the scope
of the analysis to the major sources of emissions from the direct
operation of treatment technologies. The EPA did not quantify the
CO2 emissions associated with production of treatment
technologies, construction, transportation, and disposal, as these
activities are not solely attributable to the direct onsite operations
of the plant and are beyond the scope of this analysis.
---------------------------------------------------------------------------
\27\ Recent examples include New Source Performance Standards
(NSPS) for the SOC Manufacturing Industry and National Emission
Standards for Hazardous Air Pollutants (NESHAP) for the SOC
Manufacturing Industry and Group I and Group II polymers and Resins
Industry, NESHAP Gasoline Distribution NRPM, Supplemental Effluent
Limitations Guidelines (ELGs) and Standards for the Steam Electric
Power Generating Point Source Category.
---------------------------------------------------------------------------
Furthermore, while some data exists to inform an estimate of the
CO2 emissions associated with production and reactivation of
GAC, the EPA did not do so in this analysis due to significant
uncertainties associated with the future CO2 emissions
associated with these technologies. The carbon footprint of GAC is
likely to reduce over time, as research continues on novel applications
for PFAS removal (e.g., advanced reduction/oxidation processes, novel
sorbents, foam fractionation, sonolysis, among others), alternative
sources of materials to produce GAC (e.g., biomass and other waste
materials), and use of carbon capture technology expands in the future.
Given these compounding uncertainties, the EPA did not quantify the
climate disbenefits of GAC production and reactivation.
In this rule, the EPA determined that increased electricity use is
the major source of emissions from the direct operation of treatment
technologies to
[[Page 32721]]
remove PFAS. In this analysis conducted pursuant to E.O. 12866, the EPA
first quantified the CO2 emissions from the additional
electricity that is expected to be used for pumping, building lighting,
heating, ventilation, and operation of other technology-specific
equipment to remove PFAS. The EPA then monetized the climate
disbenefits resulting from these CO2 emissions by applying
the social cost of carbon dioxide (SC-CO2) estimates
recommended by the commenter, as described in the following paragraphs.
After considering public comments that recommended the EPA consider
the climate disbenefits of the rule, the EPA conducted an analysis
similar to the one recommended by one commenter. As suggested by the
commenter, the EPA used the estimates of consumption of purchased
electricity available from the EPA's peer reviewed work breakdown
structure (WBS) cost models to estimate the national electricity use
associated with operation of PFAS removal treatment technologies. The
EPA deviated from the commenter's suggested approach when estimating
associated CO2 emissions over time from producing
electricity. The commenter estimates carbon emissions in a single year
and presents that value as a constant reoccurring annual cost. Instead,
the EPA estimated how CO2 emissions would change through
2070, the calendar year to which the EPA has estimated CO2
emissions from electricity production. The EPA applied readily
available information from the latest reference case of the EPA's
Integrated Planning Model (IPM) to represent CO2 emissions
associated with electricity production over time.\28\ Given that
emissions from producing electricity are expected to significantly
decrease over time, this is a logical application consistent with other
agency rulemakings estimating future emissions from the power sector
including the EPA's final Good Neighbor Plan (USEPA, 2023q) and the
EPA's New Source Performance Standards for GHG Emissions from New,
Modified, and Reconstructed Electric Utility Generating Units (USEPA,
2023r). Finally, the EPA monetized the climate disbenefits resulting
from the estimated CO2 emissions by applying the SC-
CO2 estimates presented in the regulatory impact analysis of
the EPA's December 2023 Final Rule, ``Standards of Performance for New,
Reconstructed, and Modified Sources and Emissions Guidelines for
Existing Sources: Oil and Natural Gas Sector Climate Review'' (USEPA
2023s). These are the same SC-CO2 estimates the EPA
presented in a sensitivity analysis in the RIA for the agency's
December 2022 supplemental proposed Oil and Gas rulemaking that the
commenter recommended for use in this action. The SC-CO2
estimates incorporate recent research addressing recommendations of the
National Academies of Science, Engineering, and Medicine (NASEM 2017),
responses to public comments on the December 2022 supplemental proposed
Oil and Gas rulemaking, and comments from a 2023 external peer review
of the accompanying technical report. The methodology underlying the
SC-CO2 estimates is described in the agency's technical
report Report on the Social Cost of Greenhouse Gases: Estimates
Incorporating Recent Scientific Advances (USEPA, 2023t), and is
included in the docket for this final rule. For additional details on
the climate disbenefits analysis see chapter 9.1 of the EPA's EA for
the final PFAS NPDWR.
---------------------------------------------------------------------------
\28\ See https://www.epa.gov/power-sector-modeling.
---------------------------------------------------------------------------
c. Final Analysis
The EPA did not include an estimate of the monetized climate
disbenefits from increased GHG emissions associated with the rule in
the HRRCA as recommended by commenters because under the SDWA, the EPA
only analyzes compliance costs to PWSs solely as a result of the
Maximum Contaminant Level (MCL). The EPA analyzed the climate
disbenefits of CO2 emissions associated with the increased
electricity use at PWSs as a result of compliance with the PFAS NPDWR,
the EPA estimates annualized climate disbenefits associated with this
rule of $5.5 million per year \29\ (under a 2 percent near term
discount rate \30\), which constitutes less than 0.4 percent of the
monetized benefits of the rule at a 2 percent discount rate. As noted
earlier, the EPA's action is justified based on the statutory factors
in SDWA section 1412(b) and this disbenefits analysis is presented
solely for the purposes of complying with E.O. 12866.
---------------------------------------------------------------------------
\29\ Disbenefits are annualized over the years 2024-2080.
\30\ See the EPA's EA for the Final PFAS NPDWR for results at
all discount rates.
---------------------------------------------------------------------------
B. Paperwork Reduction Act (PRA)
The information collection activities in this final rule have been
submitted for approval to the Office of Management and Budget under the
PRA. The Information Collection Request (ICR) document that the EPA
prepared has been assigned the EPA ICR number 2732.02 and OMB control
number 2040-0307. You can find a copy of the ICR in the docket for this
rule at https://www.regulations.gov/docket/EPA-HQ-OW-2022-0114, and it
is briefly summarized here. The information collection requirements are
not enforceable until OMB approves them.
The monitoring information collected as a result of the final rule
should allow primacy agencies and the EPA to determine appropriate
requirements for specific systems and evaluate compliance with the
NPDWR. For the first three-year period following rule promulgation, the
major information requirements concern primacy agency activities to
implement the rule including adopting the NPDWR into state regulations,
providing training to state and PWS employees, updating their
monitoring data systems, and reviewing system monitoring data and other
requests. Certain compliance actions for drinking water systems,
specifically initial monitoring, would be completed during the three
years following rule promulgation. Other compliance actions for
drinking water systems (including ongoing compliance monitoring,
administration, and treatment costs) would not begin until after three
years due to the MCL compliance date of this rule. More information on
these actions is described in section XII of this preamble and in
chapter 9 from the EA of the Final PFAS NPDWR (USEPA, 2024g).
Respondents/affected entities: The respondents/affected entities
are PWSs and primacy agencies.
Respondent's obligation to respond: The collection requirements are
mandatory under SDWA (42 U.S.C. 300g-7).
Estimated number of respondents: For the first three years after
publication of the rule in the Federal Register, information
requirements apply to an average of 33,594 respondents annually,
including 33,538 PWSs and 56 primacy agencies.
Frequency of response: During the initial three-year period, PWSs
will conduct one-time startup activities. The one-time burden
associated with reading and understanding the rule and adopting the
rule is estimated to be an average of 4 hours per system. The one-time
burden associated with attending one-time training provided by primacy
agencies is an average of 16 hours for systems serving <=3,300 people
and 32 hours for systems serving >3,300 people. The burden associated
with initial sampling requirements is an estimated 207,000 hours. The
total burden for these activities, for the three-year period, for all
systems is estimated to be 1,519,000 hours. During the initial
[[Page 32722]]
three-year period, primacy agencies will incur burdens associated with
one-time startup activities. The burden associated with reading and
understanding the rule, adopting the regulatory requirements, and
training internal staff is estimated to be an average of 4,320 hours
per primacy agency. The burden associated with primacy agency review of
initial monitoring data is 207,000 hours. The total burden for these
activities, for the three-year period, for all 56 primacy agencies is
estimated to be 533,000 hours.
Total estimated burden: For the first three years after the final
rule is published, water systems and primacy agencies will implement
several requirements related to one-time startup activities and
monitoring. The total burden hours for public water systems are
1,519,000 hours. The total burden for primacy agencies is 533,000
hours. The total combined burden is 2,052,000 hours.
Total estimated cost: The total costs over the three-year period is
$176.8 million, for an average of $58.9million per year (simple average
over three years).
An agency may not conduct or sponsor, and a person is not required
to respond to, a collected for information unless it displays a
currently valid OMB control number. The OMB control numbers for the
EPA's regulations in 40 CFR are listed in 40 CFR part 9. When OMB
approves this ICR, the agency will announce that approval in the
Federal Register and publish a technical amendment to 40 CFR part 9 to
display the OMB control number for the approved information collection
activities contained in this final rule.
C. Regulatory Flexibility Act (RFA)
Pursuant to sections 603 and 609(b) of the RFA, the EPA prepared an
initial regulatory flexibility analysis (IRFA) for the proposed rule
and convened a Small Business Advocacy Review (SBAR) Panel to obtain
advice and recommendations from small entity representatives (SERs)
that potentially would be subject to the rule's requirements. Summaries
of the IRFA and Panel recommendations are presented in the proposed
rule (USEPA, 2023f).
As required by section 604 of the RFA, the EPA prepared a final
regulatory flexibility analysis (FRFA) for this action. The FRFA
addresses the issues raised by public comments on the IRFA for the
proposed rule. The complete FRFA is available for review in section 9.4
of the EA in the docket and is summarized here.
For purposes of assessing the impacts of the final rule on small
entities, the EPA considered small entities to be water systems serving
10,000 people or fewer. This is the threshold specified by Congress in
the 1996 Amendments to SDWA for small water system flexibility
provisions. As required by the RFA, the EPA proposed using this
alternative definition in the Federal Register (USEPA, 1998d), sought
public comment, consulted with the Small Business Administration (SBA),
and finalized the small water system threshold in the agency's Consumer
Confidence Report (CCR) Regulation (USEPA, 1998e). As stated in the
document, the alternative definition would apply to all future drinking
water regulations.
The SDWA is the core statute addressing drinking water at the
Federal level. Under the SDWA, the EPA sets public health goals and
enforceable standards for drinking water quality. As previously
described, the final PFAS NPDWR requires water systems to reduce
certain PFAS in drinking water below regulatory levels. The EPA is
regulating these PFAS in drinking water to improve public health
protection by reducing drinking water exposure to these and other PFAS
in drinking water.
The final rule contains provisions affecting approximately 62,000
small PWSs. A small PWS serves between 25 and 10,000 people. These
water systems include approximately 45,000 community water systems
(CWSs) that serve the year-round residents and approximately 17,000
non-transient non-community water systems (NTNCWSs) that serve the same
persons over six months per year (e.g., a PWS that is an office or
school). The final PFAS NPDWR includes legally enforceable regulatory
standards with requirements for monitoring, public notification, and
treatment or nontreatment options for water systems exceeding the
regulatory standards. This final rule also includes reporting,
recordkeeping, and other administrative requirements. States are
required to implement operator certification (and recertification)
programs under SDWA section 1419 to ensure operators of CWSs and
NTNCWSs, including small water system operators, have the appropriate
level of certification.
Under the final rule requirements, small CWSs and NTNCWs serving
10,000 or fewer people are required to conduct initial monitoring or
demonstrate recent, previously collected monitoring data to determine
the level of certain PFAS in their water system. Based on these initial
monitoring results, systems are required to conduct ongoing monitoring
at least every three years or as often as four times per year. Systems
that exceed a drinking water standard will be required to choose
between treatment and nontreatment as the compliance option. Under the
final rule, the EPA estimates that approximately 16,542 small CWSs (37
percent of small CWSs) could incur annual total PFAS NPDWR related
costs of more than one percent of revenues, and that approximately
8,199 small CWSs (18 percent of small CWSs) could incur annual total
costs of three percent or greater of revenue. See section 9.3 of the
final PFAS NPDWR EA for more information on the characterization of the
impacts under the final rule.
The EPA took a number of steps to solicit small entity stakeholder
input during the development of the final PFAS NPDWR. Sections XIII.E
and XIII.F of this preamble contain detailed information on stakeholder
outreach during the rulemaking process, including material on the
Federalism and Tribal consultation processes. The EPA also specifically
sought input from small entity stakeholders through the SBAR Panel
process. On May 24, 2022, the EPA's Small Business Advocacy Chairperson
convened the Panel, which consisted of the Chairperson, the Director of
the Standards and Risk Management Division within the EPA's Office of
Ground Water and Drinking Water, the Administrator of the Office of
Information and Regulatory Affairs within OMB, and the Chief Counsel
for Advocacy of the SBA. Detailed information on the overall panel
process can be found in the panel report available in the PFAS NPDWR
docket (EPA-HQ-OW-2022-0114).
In response to the proposal, the EPA received one comment
specifically on the analytical approach used in the IRFA. The commenter
states that ``[d]etailed analysis on the impacts to NTNCWSs should be
conducted to inform the cost/benefit analysis. For example, treating
PFAS with GAC at the low levels proposed is much more costly than
current treatment for currently regulated contaminants, and a 2008
study is not a reliable indicator of future costs. Lack of both actual
data on occurrence in these systems and reliable information on cost of
compliance makes finalizing the MCL as to NTNCWSs too uncertain.'' The
EPA disagrees that the agency has not analyzed the impacts of the PFAS
NPDWR on NTNCWS. The EPA has used both actual data on occurrence at
NTNCWSs from the third Unregulated Contaminant Monitoring Rule (UCMR 3)
and state data, as well as reliable information on costs to NTNCWSs
using
[[Page 32723]]
the WBS treatment cost models to assess the impact of the rule on
NTNCWSs. As the EPA stated in the proposal, the EPA lacks information
on the revenues of NTNCWS, therefore the agency does not take the same
approach used for CWSs in the Significant Economic Impact on a
Substantial Number of Small Entities (SISNOSE) screening analysis where
costs are compared to 1 and 3 percent of revenues. Instead, the EPA
used the best available data, the EPA's Assessment of the Vulnerability
of Noncommunity Water Systems to SDWA Cost Increases (USEPA, 1998f), to
find that NTNCWSs are less vulnerable to SDWA related increases than a
typical CWS. The EPA proceeded with the SBAR Panel process, as
previously detailed in this section.
The EPA received many comments on the rule proposal, including from
the Chief Counsel for Advocacy of the SBA, on small system and IRFA
related topics including lack of funding availability for small water
systems, the EPA's alleged underestimation of the impacts of the rule
on small systems, the EPA's alleged overestimation of reliance on
Federal funding to defray compliance costs for small water systems, and
``other factors that will further deter timely compliance'' such as
personnel shortages, supply chain disruptions, limited lab and disposal
capacity, and availability of treatment technologies. The EPA has
addressed these comments and provided for maximum flexibility for small
systems while ensuring sufficient public health protection for
populations served by these systems. For the EPA's response to SBA and
other comments on funding availability, please see section II of this
preamble. For the EPA's response to SBA and other comments on the
estimated costs to small water systems, please see section XII of this
preamble. For the EPA's response to SBA and other comments on lab
capacity, see sections V and VIII. For the EPA's response to SBA and
other comments on technology and disposal capacity, see section X. For
responses to SBA's and other commenters' recommendations to the EPA to
provide burden-reducing flexibilities for small water systems,
including finalizing one of the regulatory alternatives and phasing in
the MCL, as well as providing additional time for compliance, see
section V of this preamble. For response to SBA and other commenters
concerned about the EPA's concurrent proposal of a preliminary
determination and a proposed regulation for four PFAS, see section III
of the preamble. The FRFA, available for review in section 9.4 of the
EA in the docket, also provides detailed information on the
recommendations of the SBAR Panel and the EPA's actions taken to
minimize the significant economic impact of the final rule on small
systems.
As a mechanism to reduce the burden of the final rule requirements
on small entities the EPA has promulgated compliance flexibilities for
small CWSs serving 10,000 or fewer persons. These flexibilities include
the use of previously collected PFAS monitoring data to satisfy initial
monitoring requirements, allowing reduced initial monitoring for small
groundwater systems serving 10,000 or fewer, the addition of annual
monitoring to the ongoing compliance monitoring framework, and modified
rule trigger levels for reduced monitoring eligibility. For more
information on these flexibilities, see section VIII of this preamble.
The EPA is also exercising its authority under SDWA section 1412(b)(10)
to implement a nationwide two-year capital improvement extension to
comply with MCL. The agency notes that SDWA section 1416(a) and
(b)(2)(C) describe how the primacy agencies may also grant an exemption
for systems meeting specified criteria that provides an additional
period for compliance. PWSs that meet the minimum criteria outlined in
the SDWA section 1416 may be eligible for an exemption of up to three
years. Exemptions for smaller water systems (<=3,300 population),
meeting certain specified criteria may be renewed for one or more two-
year periods, but not to exceed six years. States exercising primacy
enforcement responsibility must have adopted the 1998 Variance and
Exemption Regulation for a water system to be eligible for an exemption
in that state. Finally, the EPA notes that if point-of-use (POU)
devices are certified to meet the NPDWR standard in the future, this
could reduce the economic impact of the final regulation on small PWSs,
particularly on water systems in the smallest size category (e.g.,
those serving between 25 and 500 people).
The EPA also assessed the degree to which the final PFAS NPDWR
small system flexibilities would mitigate compliance costs. The EPA
estimates that the use of previously collected PFAS monitoring data
will reduce the economic burden on small systems nationally by $7
million dollars per year for three years. The EPA expects that reduced
monitoring for small groundwater systems will reduce the economic
burden on small systems nationally by $21 million per year for three
years. The EPA estimates that under the final rule approximately 4,300
to 7,000 small PWSs may have regulated PFAS occurrence between the
trigger levels and the MCLs, and therefore may be eligible for annual
monitoring following four consecutive quarterly samples demonstrating
they are ``reliably and consistently'' below the MCLs. The EPA
anticipates further compliance cost mitigations stemming from the
decision to set the reduced monitoring trigger levels at one-half of
the MCLs, rather than one-third of the MCLs as proposed. While the MCL
compliance period extension does not change the treatment or non-
treatment actions that small systems will be compelled to undertake, it
will reduce the compliance burden faced by small water systems by
allowing for more time for them to obtain and install capital
improvements. Finally, the EPA recognizes the possibility of small
system compliance cost reduction particularly for very small water
systems should POU certifications be updated in the future and POUs
meet the small system compliance technology (SSCT) criteria for the
final NPDWR. See chapter 9, section 9.3.4 of the final PFAS NPDWR EA
(USEPA, 2024g) for more information on the characterization of the
impacts under the final rule.
In addition, the EPA is preparing a Small Entity Compliance Guide
to help small entities comply with this rule. The EPA expects the Small
System Compliance Guide will be developed in the first three years
after rule promulgation and will be made available on the EPA's PFAS
NPDWR website.
D. Unfunded Mandates Reform Act (UMRA)
This action contains a Federal mandate under UMRA, 2 U.S.C. 1531-
1538, that may result in expenditures of $100 million or more for
state, local, and Tribal governments, in the aggregate, or the private
sector in any one year. Accordingly, the EPA has prepared a written
statement required under section 202 of UMRA that is included in the
docket for this action (see chapter 9 of the EA for the Final PFAS
NPDWR) and briefly summarized here.
Consistent with UMRA section 205, the EPA identified and analyzed a
reasonable number of regulatory alternatives to determine the MCL
requirement in the final rule. The agency notes, however, that the
provisions of section 205 do not apply when they are inconsistent with
applicable law; in the case of NPDWRs, the UMRA section 205 requirement
to adopt the least costly, most cost-
[[Page 32724]]
effective, or least burdensome option is inconsistent with SDWA
regulatory development requirements. See section XII of this preamble
and chapter 9 of the EA for the Final PFAS NPDWR (USEPA, 2024g) for
alternative options that were considered. Consistent with the
intergovernmental consultation provisions of UMRA section 204, the EPA
consulted with governmental entities affected by this rule. The EPA
describes the government-to-government dialogue and comments from
state, local, and Tribal governments in sections XIII.E. (E.O. 13132:
Federalism) and XIII.F. (E.O. 13175: Consultation and Coordination with
Indian Tribal Governments) of this document.
This action may significantly or uniquely affect small governments.
The EPA consulted with small governments concerning the regulatory
requirements that might significantly or uniquely affect them. The EPA
describes this consultation in the RFA, section XIII.C. of this
preamble.
E. Executive Order 13132: Federalism
The EPA has concluded that this action has federalism implications
because it imposes substantial direct compliance costs on state or
local governments, and the Federal Government will not provide the
funds necessary to pay those costs. However, the EPA notes that the
Federal Government will provide a potential source of funds necessary
to offset some of those direct compliance costs through the Bipartisan
Infrastructure Law (BIL). The EPA estimates that the net change in
primacy agency related cost for state, local, and Tribal governments in
the aggregate to be $4.7 million.
The EPA provides the following federalism summary impact statement.
The EPA consulted with state and local governments early in the process
of developing the proposed action to allow them to provide meaningful
and timely input into its development. The EPA held a federalism
consultation on February 24, 2022. The EPA invited the following
national organizations representing state and local elected officials
to a virtual meeting on February 24, 2022: The National Governors'
Association, the National Conference of State Legislatures, the Council
of State Governments, the National League of Cities, the U.S.
Conference of Mayors, the National Association of Counties, the
International City/County Management Association, the National
Association of Towns and Townships, the County Executives of America,
and the Environmental Council of States. Additionally, the EPA invited
the Association of State Drinking Water Administrators (ASDWA), the
Association of Metropolitan Water Agencies (AMWA), the National Rural
Water Association (NRWA), the American Water Works Association (AWWA),
the American Public Works Association, the Western Governors'
Association, the Association of State and Territorial Health Officials,
the National Association of Country and City Health Officials, and
other organizations to participate in the meeting. In addition to input
received during the meeting, the EPA provided an opportunity to receive
written input within 60 days after the initial meeting. A summary
report of the views expressed during federalism consultations is
available in the rule docket (EPA-HQ-OW-2022-0114). The EPA also
received public comments from some of these organizations during the
public comment period following the rule proposal. These individual
organization comments are available in the docket.
Comments provided by the organizations during both the consultation
and public comment periods covered a range of topics. The overarching
comments from multiple organizations related to the NPDWR compliance
timeframe and implementation flexibilities, the proposed MCLs for PFOA
and PFOS and the Hazard Index PFAS, the EPA's estimated costs of the
NPDWR and funding considerations, PFAS treatment disposal, and other
EPA actions to address PFAS in the environment. Specifically, several
of these organizations expressed that the EPA should allow an extended
compliance timeframe to comply with the MCLs due to supply chain
disruptions and availability of treatment materials, as well as
maximize the implementation flexibilities for water systems and primacy
agencies, including those related to monitoring. Regarding rule costs,
some organizations contended that the EPA's costs were underestimated,
and that the EPA should consider the disposal of PFAS treatment
residuals and associated costs particularly if determined to be
hazardous wastes in the future under other EPA statutes such as the
Resource Conservation and Recovery Act (RCRA). A couple of
organizations requested that the EPA should provide more direct funding
for local governments to comply with the NPDWR noting the available BIL
funding would not be sufficient to cover the rule costs and these funds
cannot be used for certain rule compliance costs. A few organizations
suggested that the agency should raise the proposed PFOA and PFOS MCLs,
with some of these commenters offering that the EPA should not move
forward with the Hazard Index MCL for perfluorohexane sulfonic acid
(PFHxS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer
acid (HFPO-DA), and perfluorobutane sulfonic acid (PFBS). Finally,
several organizations provided that the agency should focus on
addressing PFAS holistically and expedite its efforts on source water
protection and other actions to address PFAS in the environment beyond
drinking water. The EPA considered these organizations' concerns and
has taken this input to address many of these in the final PFAS NPDWR
while ensuring sufficient public health protection those served by
PWSs.
Related to compliance timeline and other rule implementation
flexibilities, the EPA is exercising its authority under SDWA section
1412(b)(10) to implement a nationwide two-year capital improvement
extension to comply with MCL. The agency notes that SDWA section
1416(a) and (b)(2)(C) describe how the EPA or states may also grant an
exemption for systems meeting specified criteria that provides an
additional period for compliance. See section XI.D for more information
on extensions and exemptions. The EPA has promulgated compliance
flexibilities for monitoring implementation including the use of
previously collected PFAS monitoring data to satisfy initial monitoring
requirements and allowing reduced initial monitoring for small
groundwater systems serving 10,000 or fewer. Other monitoring
implementation flexibilities include the addition of annual monitoring
to the ongoing compliance monitoring framework and higher rule trigger
levels for reduced monitoring eligibility. For more information on
these flexibilities, see section VIII of this preamble.
For the final rule, the EPA has evaluated the concerns related to
the rule costs and maintains that the estimated benefits of the rule
justify the costs. Regarding financial costs to water systems if
regulated PFAS were to be required to be disposed of as hazardous waste
in the future, the EPA reaffirms that no PFAS are currently listed, or
proposed to be listed, as hazardous wastes under RCRA. However, the EPA
has included a sensitivity analysis to determine the impact on this
action should be PFAS-containing treatment materials be considered RCRA
[[Page 32725]]
regulatory or characteristic hazardous waste in the future (see section
X.C. for more detail). For funding concerns and information, the EPA
has provided information, detailed further in section II.G. of this
preamble related to potential funding opportunities, particularly those
available through BIL funds including the EPA's Emerging Contaminants
in Small or Disadvantaged Communities (EC-SDC) grants program.
For organizations recommending that the EPA raise the proposed PFOS
and PFOS MCLs, with some of these organizations suggesting that the
Hazard Index MCL is not justified and should not be finalized, as
described in section V of this preamble, the EPA has demonstrated these
levels are justified under the requirements of SDWA. Therefore, the
agency is maintaining these MCLs for the final rule but has offered
compliance flexibilities as described previously.
Lastly, several organizations provided that the agency should focus
on addressing PFAS through source water protection efforts beyond
drinking water, under the agency's PFAS Strategic Roadmap and
associated actions, the EPA is swiftly working to address PFAS
contamination in the environment and reduce human health PFAS exposure
through all pathways. While beyond the scope of this rulemaking, the
EPA is making progress implementing many of the commitments in the
Roadmap, including those that may significantly reduce PFAS source
water concentrations.
In addition to the federalism consultation, regarding state
engagement more specifically, the EPA notes there were multiple
meetings held by ASDWA where the EPA gathered input from state
officials and utilized this input to inform this rule. The EPA also
considered all comments provided by individual states and state
organizations provided during the public comment period and used these
comments to inform the final rule.
F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments
This action has Tribal implications, it imposes direct compliance
costs on Tribal governments, and the Federal Government will not
provide funds necessary to pay those direct compliance costs. However,
the EPA notes that the Federal Government will provide a potential
source of funds necessary to offset some of those direct compliance
costs through the BIL.
The EPA has identified 998 PWSs serving Tribal communities, 84 of
which are federally owned. The EPA estimates that Tribal governments
will incur PWS compliance costs of $9.0 million per year attributable
to monitoring, treatment or nontreatment actions to reduce PFAS in
drinking water, and administrative costs, and that these estimated
impacts will not fall evenly across all Tribal systems. The final PFAS
NPDWR does offer regulatory relief by providing flexibilities for all
water systems to potentially utilize pre-existing monitoring data in
lieu of initial monitoring requirements and for groundwater CWSs and
NTNCWSs serving 10,000 or fewer to reduce initial monitoring from
quarterly monitoring during a consecutive 12-month period to only
monitoring twice during a consecutive 12-month period. These
flexibilities may result in implementation cost savings for many Tribal
systems since 98 percent of Tribal CWSs and 94 percent of NTNCWs serve
10,000 or fewer people.
Accordingly, the EPA provides the following Tribal summary impact
statement as required by section 5(b) of E.O. 13175. The EPA consulted
with federally recognized Tribal governments early in the process of
developing this action to permit them to have meaningful and timely
input into its development. The EPA conducted consultation with Indian
Tribes beginning on February 7, 2022, and ending on April 16, 2022. The
consultation included two national webinars with interested Tribes on
February 23, 2022, and March 8, 2022, where the EPA provided proposed
rulemaking information and requested input. A total of approximately 35
Tribal representatives participated in the two webinars. Updates on the
consultation process were provided to the National Tribal Water Council
and the EPA Region 6's Regional Tribal Operations Committee upon
request at regularly scheduled monthly meetings during the consultation
process. As part of the consultation, the EPA received written comments
from the following Tribes: Little Traverse Bay Bands of Odawa Indians
and Sault Ste. Marie Tribe of Chippewa Indians. In addition to the
comments from these Tribal governments, the EPA received comments the
National Tribal Water Council. A summary report of the consultation,
webinars, and views expressed during the consultation is available in
the Docket (EPA-HQ-OW-2022-0114).
The EPA received a variety of comments from Tribal officials and
representatives during both the consultation and public comment
periods. These comments can be found in more detail within the Docket
through the individual public comments and within the consultation
summary report. Specifically, comments included those related to
initial monitoring requirements, use of monitoring waivers, concerns
related to treatment options and disposal of treatment materials,
particularly if determined to be hazardous in the future, as well as
funding concerns. The EPA has addressed these officials' comments
through finalizing monitoring requirements which allow for small
systems flexibilities including the use of previously collected
monitoring data to be used to satisfy initial monitoring requirements
and not allowing the use of monitoring waivers (see section VIII) of
this preamble. Related to treatment considerations, the EPA has
identified best available technologies (BATs) as described in section X
which have been shown to reduce regulated PFAS levels, but also allows
for other treatment technologies not identified as BATs to be used to
address MCL exceedances if they can remove PFAS to the regulatory
standards. Additionally, the EPA has developed a sensitivity cost
analysis to describe the additional financial costs to water systems if
the regulated PFAS were to be required to be disposed of as hazardous
waste in the future (see appendix N, section 2 of the EA for additional
detail). For funding concerns, the EPA has provided information,
detailed further in section II of this preamble, related to potential
funding opportunities, particularly those available through the EPA's
EC-SDC grants program.
The EPA reviewed these comments received from Tribal groups, the
estimated cost data, and the quantified and nonquantifiable benefits
associated with the PFAS NPDWR and determined that the regulatory
burden placed on Tribes is outweighed by the positive benefits. Given
that the majority of Tribal systems serve fewer than 10,000 persons, as
noted previously, the EPA has provided regulatory relief in the form of
small system compliance flexibilities related to monitoring
requirements. For additional information on these compliance
flexibilities and their estimated impacts see sections VIII of this
preamble and chapter 9.4, of the final PFAS NPDWR EA (USEPA, 2024g).
As required by section 7(a) of E.O. 13175, the EPA's Tribal
Official has certified that the requirements of the E.O. have been met
in a meaningful and timely manner. A copy of the
[[Page 32726]]
certification is included in the docket for this action.
G. Executive Order 13045: Protection of Children From Environmental
Health and Safety Risks
Executive Order 13045 directs Federal agencies to include an
evaluation of the health and safety effects of the planned regulation
on children in Federal health and safety standards and explain why the
regulation is preferable to potentially effective and reasonably
feasible alternatives. This action is subject to E.O. 13045 because it
is a significant regulatory action under section 3(f)(1) of E.O. 12866,
and the EPA believes that the environmental health or safety risk
addressed by this action has a disproportionate effect on children.
Accordingly, the EPA has evaluated the environmental health or safety
effects of the regulated PFAS found in drinking water on children and
estimated the risk reduction and health endpoint impacts to children
associated with adoption of treatment or nontreatment options to reduce
these PFAS in drinking water. The results of these evaluations are
contained in the EA of the Final PFAS NPDWR (USEPA, 2024g) and
described in section XII of this preamble. Copies of the EA of the
Final PFAS NPDWR and supporting information are available in the Docket
(EPA-HQ-OW-2022-0114).
Furthermore, the EPA's Policy on Children's Health also applies to
this action. Information on how the Policy was applied is available in
section II.B. of this preamble.
H. Executive Order 13211: Actions That Significantly Affect Energy
Supply, Distribution, or Use
This action is not a ``significant energy action'' because it is
not likely to have a significant adverse effect on the supply,
distribution, or use of energy. The public and private water systems
affected by this action do not, as a rule, generate power. This action
does not regulate any aspect of energy distribution as the water
systems that are proposed to be regulated by this rule already have
electrical service. Finally, the EPA has determined that the
incremental energy used to implement the identified treatment
technologies at drinking water systems in response to the regulatory
requirements is minimal. The EPA estimates that the final rule will
result in an increased electricity use of approximately 229 GWh per
year, for more information see section XIII.A; total U.S. electricity
consumption in 2022 was approximately 4.05 million GWh (USEIA, 2023).
Therefore, the electricity consumed as a result of the final rule
represents approximately 0.005 percent of total U.S. electricity
consumption. Based on these findings, the EPA does not anticipate that
this rule will have a significant adverse effect on the supply,
distribution, or use of energy.
I. National Technology Transfer and Advancement Act of 1995
This action involves technical standards. The rule could involve
voluntary consensus standards in that it requires monitoring for
regulated PFAS, and analysis of the samples obtained from monitoring
based on required methods. As part of complying with this final rule,
two analytical methods are required to be used for the identification
and quantification of PFAS in drinking water. The EPA Methods 533 and
537.1 incorporate quality control criteria which allow accurate
quantitation of PFAS. Additional information about the analytical
methods is available in section VII of this preamble. The EPA has made,
and will continue to make, these documents generally available through
www.regulations.gov and at the U.S. Environmental Protection Agency
Drinking Water Docket, William Jefferson Clinton West Building, 1301
Constitution Ave. NW, Room 3334, Washington, DC 20460, call (202) 566-
2426.
J. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations and
Executive Order 14096: Revitalizing Our Nation's Commitment to
Environmental Justice for All
1. Proposal
The EPA believes that the human health or environmental conditions
that exist prior to this action result in or have the potential to
result in disproportionate and adverse human health or environmental
effects on communities with environmental justice (EJ) concerns.
Consistent with the agency's Technical Guidance for Assessing
Environmental Justice in Regulatory Analysis (USEPA, 2016f), for the
proposed rule, the EPA conducted an EJ analysis to assess the
demographic distribution of baseline PFAS drinking water exposure and
impacts anticipated to result from the proposed PFAS NPDWR. The EPA
conducted two separate analyses: an EJ exposure analysis using the
agency's EJSCREENbatch R package, which utilizes data from EJScreen,
the agency's Environmental Justice Screening and Mapping Tool (USEPA,
2019e), and from the U.S. Census Bureau's American Community Survey
(ACS) 2015-2019 five-year sample (United States Census Bureau, 2022),
and an analysis of the EPA's proposed regulatory option and
alternatives using SafeWater Multi-Contaminant Benefit Cost Model
(MCBC; detailed in section XII of this preamble). The EPA's analyses
examined EJ impacts on a subset of PWSs across the country, based on
availability of PFAS occurrence data and information on PWS service
area boundaries. In the EPA's analysis, results for income, race, and
ethnicity groups were generally summarized separately due to how
underlying ACS statistics are aggregated at the census block group
level; for more information, please see: https://www.census.gov/data/developers/data-sets/acs-5year.html (United States Census Bureau,
2022). Additional information on both analyses can be found in chapter
8 of USEPA (2024g) and appendix M of USEPA (2024e).
The EPA's EJ exposure analysis using the EJSCREENbatch R package
utilized hypothetical regulatory scenarios, which differed from the
EPA's proposed option and regulatory alternatives presented in the
proposed rule. The EPA's analysis demonstrated that across hypothetical
regulatory scenarios evaluated, elevated baseline PFAS drinking water
exposures, and thus greater anticipated reductions in exposure, were
estimated to occur in communities of color and/or low-income
populations. For this analysis, the EPA examined individuals served by
PWSs with modeled PFAS exposure above baseline concentration thresholds
or a specific alternative policy threshold. The EPA also summarized
population-weighted average concentrations in the baseline as well as
reductions that would accrue to each demographic group from
hypothetical regulatory scenarios.
The EPA's analysis in SafeWater MCBC evaluated the demographic
distribution of health benefits and incremental household costs
anticipated to result from the PFAS NPDWR. The EPA's proposed option
and all regulatory alternatives were anticipated to provide benefits
across all health endpoint categories for all race/ethnicity groups.
Across all health endpoints, communities of color were anticipated to
experience the greatest reductions in adverse health effects associated
with PFAS exposure, resulting in the greatest quantified benefits
associated with the EPA's proposed rule, likely due to disproportionate
baseline exposure. When examining costs anticipated to result from the
rule, the EPA found that cost differences across demographic
[[Page 32727]]
groups were typically small, with no clear unidirectional trend in cost
differences based on demographic group. In some cases, the EPA found
that communities of color were anticipated to bear minimally increased
costs but in other cases, costs to communities of color were
anticipated to be lower than those across all demographic groups. In
general, incremental household costs to all race/ethnicity groups were
found to decrease with increasing system size, an expected result due
to economies of scale.
Additionally, on March 2, 2022, and April 5, 2022, the EPA held
public meetings related to EJ and the development of the proposed
NPDWR. The meetings provided an opportunity for the EPA to share
information and for communities to offer input on EJ considerations
related to the development of the proposed rule. During the meetings
and in subsequent written comments, the EPA received public comment on
topics including establishing an MCL for PFAS, affordability of PFAS
abatement options, limiting industrial discharge of PFAS, and the EPA's
relationship with community groups. For more information on the public
meetings, please refer to the Environmental Justice Considerations for
the Development of the Proposed PFAS Drinking Water Regulation Public
Meeting Summary for each of the meeting dates in the public docket at
https://www.regulations.gov/docket/EPA-HQ-OW-2022-0114. Additionally,
the written public comments are included within the public docket.
2. Summary of Major Public Comments and EPA Responses
Many commenters expressed support for the rule and the EPA's EJ
analysis, underscoring the rule's alignment with the administration's
commitment to advancing EJ. Commenters point to evidence which suggests
that PFAS exposure disproportionately affects communities with EJ
concerns. Further, commenters state that these communities are
particularly vulnerable to PFAS exposure and the associated health
outcomes. Several commenters also assert that the rule is anticipated
to benefit these communities with EJ concerns who are at a higher risk
of PFAS exposure. Through this rule, the EPA reaffirms the importance
of EJ considerations in agency activities, including rulemaking.
Many commenters expressed concern about potential EJ implications
of the final rule and urged the EPA to further consider these
implications prior to final rule promulgation. Specifically, commenters
presented concerns that the rule will disproportionately impact
communities that already are overburdened with sociodemographic and
environmental stressors. Additionally, several commenters voiced EJ
concerns associated with implementation of the rule. Many commenters
asserted that communities with EJ concerns may not have sufficient
financial capacity to implement the rule (e.g., install treatment) and
that this may further exacerbate existing disparities associated with
PFAS exposure. Additionally, commenters stated that additional
resources would likely be needed for communities with EJ concerns to
successfully implement the rule, including targeted monitoring and
sampling in these areas.
The EPA acknowledges commenters' concerns regarding potential EJ
implications of the rule. Under E.O. 14096, the EPA is directed to
identify, analyze, and address disproportionate and adverse human
health or environmental effects of agency actions on communities with
environmental justice concerns (USEPA, 2023v). The EPA believes that
its EJ analysis accompanying the final rule has achieved this
directive, as the EPA has assessed the demographic distribution of
baseline PFAS exposure in drinking water as well as the anticipated
distribution of benefits and costs that will result from the rule. For
more information on the EPA's EJ analysis, please see chapter 8 of
USEPA (2024g) and appendix M of USEPA (2024e). The EPA acknowledges the
potential for implementation challenges for communities with EJ
concerns; however, there may be opportunities for many communities to
utilize external funding streams to address such challenges. The BIL,
the Low-Income Water Household Assistance Program through the American
Rescue Plan, and other funding sources may be able to provide financial
assistance for addressing emerging contaminants. In particular, the BIL
funding has specific allocations for disadvantaged and/or small
communities to address emerging contaminants, including PFAS. For
example, the Emerging Contaminants in Small or Disadvantaged
Communities (EC-SDC) grants program, which does not have a cost-sharing
requirement, will provide states and territories with $5 billion to
provide grants to public water systems in small or disadvantaged
communities to address emerging contaminants, including PFAS. Grants
will be awarded non-competitively to states and territories.
Many commenters stated that the costs of the rule will
disproportionately fall on communities with EJ concerns. Additionally,
some commenters asserted that the EPA's EJ analysis does not
appropriately consider the distributional impacts of rule costs, with
one commenter incorrectly stating that the analysis ``fails to consider
how these increased compliance costs will impact EJ communities, as
required by Executive Order 12898''. Commenters recommended that the
EPA revise its analysis to reflect the impact that compliance costs of
the rule will have on communities with potential EJ concerns.
The EPA disagrees with commenters that the EPA has failed to
appropriately consider the impact that costs required to implement the
rule may have on communities with potential EJ concerns. The agency has
fulfilled its commitments in this rulemaking by conducting an analysis
consistent with E.O. 14096 and has shared information on the
demographic distribution of impacts evaluated in its EJ analysis to
facilitate the public's understanding on potential environmental
justice impacts of the rule. In section 8.4.2.2 of its EJ Analysis
(found in chapter 8 of the HRRCA (USEPA, 2024l)), the EPA estimated the
distribution of annualized incremental household costs across different
race/ethnicity groups. As described in section XIII.J.1 above, the EPA
found that cost differences across demographic groups are typically
small, with no clear unidirectional trend in cost differences based on
demographic group. In some cases, the EPA found that communities of
color are anticipated to bear minimally increased costs but in other
cases, costs to communities of color are lower than those across all
demographic groups. In response to commenters, the EPA has updated its
analysis to also examine the distribution of benefits and costs across
income groups. With respect to the distribution of costs, the EPA found
that, similar to its findings based on race/ethnicity group,
differences in annual incremental household costs across income groups
were small with no unidirectional trend in cost differences based on
income level.
Additionally, one commenter recommended that the EPA disaggregate
Asian and Pacific Islander data in its EJ analysis, asserting that the
``EPA must comply with OMB Statistical Directive 15''. The EPA
disagrees that its EJ analysis must disaggregate Asian and Pacific
Islander data in order to comply with OMB Statistical Directive 15 (SPD
15). SPD 15 establishes standards for maintaining, collecting, and
presenting
[[Page 32728]]
Federal data on race and ethnicity and applies to ``all Federal
reporting purposes'' (OMB, 1977). This term is not defined and does not
clearly apply to analyses developed to support rulemaking efforts. SPD
15 is targeted primarily toward data collection efforts, the
development of data for public consumption, and the enforcement of
civil rights laws. As SPD 15 is not applicable in the context of
rulemakings, the EPA is not required to revise its EJ analysis in
accordance with the standards for data disaggregation set forth in the
OMB directive. However, the EPA acknowledges that reporting results
separately for these groups can help to reveal potential disparities
that may exist across Asian and Pacific Islander subpopulations. In
response to this comment, the EPA has added a qualitative summary of
the literature provided by the commenter and has updated its analysis
to include separate Asian and Pacific Islander demographic groups.
These updates are reflected in chapter 8 of USEPA (2024g) and appendix
M of USEPA (2024e) for the public's information and understanding.
3. Final Rule
The EPA's EJ exposure analysis for the final rule demonstrates that
some communities of color are anticipated to experience elevated
baseline PFAS drinking water exposures compared to the entire sample
population. The percentage of non-Hispanic Black and Hispanic
populations with PFAS in drinking water detected above baseline
thresholds is greater than the percentage of the total population
served with PFAS exposure above these thresholds for all PFAS analytes
examined in the EPA's analysis. Similarly, when results are separately
analyzed by system size, non-Hispanic Black and Hispanic populations
are more likely to be served by large systems with PFAS detected above
baseline thresholds compared to the percentage of the total population
served across all demographic groups. For small systems, non-Hispanic
Asian and non-Hispanic Black populations are more likely to be served
by systems with PFAS concentrations above baseline thresholds for some
PFAS analytes compared to the total population served across all
demographic groups.
The EPA believes that this action is likely to reduce existing
disproportionate and adverse effects on communities with EJ concerns.
Across all hypothetical regulatory thresholds, elevated exposure--and
thus reductions in exposure under the hypothetical regulatory
scenarios--is anticipated to occur in communities of color and/or low-
income populations. The EPA estimates that the most notable reductions
in exposure would be experienced by Hispanic populations, specifically
when using UCMR 5 minimum reporting level values as hypothetical
regulatory thresholds. Hispanic populations are estimated to experience
exposure rates that are at least two percentage points higher than
exposure for the total population served across all demographic groups
and for all PFAS analytes included in this analysis. Hispanic
populations are therefore also expected to have greater reductions in
exposure compared to the entire sample population. In addition, under
hypothetical regulatory thresholds set at the UCMR 5 minimum reporting
levels, the EPA anticipates some of the largest reductions in exposure
to PFOA and PFHxS occur for non-Hispanic Native American or Alaska
Native and non-Hispanic Pacific Islander populations due to relatively
high concentration levels when these PFAS are detected at PWSs serving
these groups. For more information on the results of this EJ exposure
analysis, see chapter 8 of USEPA (2024g) and appendix M of USEPA
(2024e).
For the final rule, the EPA has updated its EJ exposure analysis to
include separate Asian and Pacific Islander demographic groups, which
were previously combined for the proposed rule. Additionally, the EPA
has updated the demographic categories utilized in the EJ exposure
analysis to ensure that consistent information is used or applied
throughout the PFAS NPDWR EA to the extent possible and to reduce
double counting across demographic categories. For the proposed rule,
the EPA's EJ exposure analysis used different demographic categories
than its distributional analysis conducted in SafeWater, with the
former partly including racial groups that were inclusive of Hispanic
individuals and the latter including racial groups that were exclusive
of Hispanic individuals. Because the EPA's EJ exposure analysis for the
proposed rule employed some demographic categories that were inclusive
of Hispanic individuals (e.g., American Indian or Alaska Native) and
others that were not (e.g., non-Hispanic White), this introduced double
counting across groups in the analysis, which complicated making
comparisons of exposure across populations of concern. This issue was
described in the EJ analysis at proposal, and the EPA solicited comment
on alternative methods for defining affected population groups.
Additionally, after considering public comments, the EPA has also
updated its EJ analysis conducted in SafeWater MCBC to include an
assessment of the distribution of benefits and costs anticipated to
result from the final rule across income groups. Findings from the
EPA's EJ analysis conducted in SafeWater MCBC for the final rule
reaffirm the conclusions of the assessment of the distribution of
benefits and costs conducted for the proposed rule across demographic
groups. Across all health endpoints evaluated by the EPA, communities
of color (i.e., Hispanic, non-Hispanic Black, and/or Other race/
ethnicity groups) are anticipated to experience the greatest reductions
in adverse health effects associated with PFAS exposure, resulting in
the greatest quantified benefits associated with the final rule. For
instance, non-Hispanic Black populations are expected to experience
7.48 avoided non-fatal ischemic stroke (IS) cases and 3.90 avoided
cardiovascular disease (CVD) deaths per 100,000 people per year, as
compared to 3.78 avoided non-fatal IS cases and 1.26 avoided CVD deaths
per 100,000 people per year for non-Hispanic White populations.
Additionally, under the final rule, while in most cases the difference
in cases of illnesses and deaths avoided across income groups is small,
quantified health benefits are higher for low-income communities (i.e.,
populations with income below twice the poverty level) across all
health endpoints evaluated, compared to populations with income above
twice the poverty level.
As found in its analysis for the rule proposal, when examining
costs anticipated to result from the final rule, the EPA found that
cost differences across both race/ethnicity and income groups are
typically small, with no clear unidirectional trend in cost differences
based on demographic group. In some cases, the EPA found that
communities of color and low-income communities are anticipated to bear
minimally increased costs but in other cases, costs to communities of
color and low-income communities are anticipated to be lower than those
across all race/ethnicity groups or populations with income above twice
the poverty level, respectively. Additionally, incremental household
costs to all race/ethnicity and income groups generally decrease as
system size increases, which is expected due to economies of scale.
This is especially true if systems serving these communities are
required to install treatment to comply with the final rule. For
example, systems serving 3,300 to 10,000 people that will be required
to install treatment to comply with the
[[Page 32729]]
final rule have substantially higher costs than systems in all larger
size categories, irrespective of demographic group. To alleviate
potential cost disparities identified by the EPA's analysis, there may
be an opportunity for many communities to utilize BIL (Pub. L. 117-58)
funding to provide financial assistance for addressing emerging
contaminants. BIL funding has specific allocations for both
disadvantaged and/or small communities and emerging contaminants,
including PFAS.
The information supporting this E.O. 12898 review is contained in
chapter 8 of USEPA (2024g) and appendix M of USEPA (2024e) and is
available in the public docket for this action. This documentation
includes additional detail on the methodology, results, and conclusions
of the EPA's EJ analysis.
K. Consultations With the Science Advisory Board, National Drinking
Water Advisory Council, and the Secretary of Health and Human Services
In accordance with sections 1412(d) and 1412(e) of the SDWA, the
agency consulted with the National Drinking Water Advisory Council
(NDWAC, or the Council); the Secretary of U.S. Department of Health and
Human Services (HHS); and with the EPA Science Advisory Board (SAB).
1. Science Advisory Board
The SAB PFAS Review Panel met virtually via a video meeting
platform on December 16, 2021, and then at three (3) subsequent
meetings on January 4, 6, and 7, 2022, to deliberate on the agency's
charge questions. Another virtual meeting was held on May 3, 2022, to
discuss their draft report. Oral and written public comments were
considered throughout the advisory process. The EPA sought guidance
from the SAB on how best to consider and interpret life stage
information, epidemiological and biomonitoring data, the agency's
physiologically based pharmacokinetic (PBPK) analyses, and the totality
of PFAS health information to derive an MCLG for PFOA and PFOS,
combined toxicity framework, and CVD. The documents sent to SAB were
the EPA's Proposed Approaches to the Derivation of a Draft Maximum
Contaminant Level Goal for Perfluorooctanoic Acid (PFOA) (CASRN 335-67-
1) in Drinking Water (USEPA, 2021i); the EPA's Proposed Approaches to
the Derivation of a Draft Maximum Contaminant Level Goal for
Perfluorooctane Sulfonic Acid (PFOS) (CASRN 1763-23-1) in Drinking
Water (USEPA, 2021j); the EPA's Draft Framework for Estimating
Noncancer Health Risks Associated with Mixtures of Per- and
Polyfluoroalkyl Substances (PFAS) (USEPA, 2021e); and the EPA's
Analysis of Cardiovascular Disease Risk Reduction as a Result of
Reduced PFOA and PFOS Exposure in Drinking Water. On May 3 and July 20,
2022, the EPA received input from SAB, summarized in the report Review
of EPA's Analyses to Support EPA's National Primary Drinking Water
Rulemaking for PFAS (USEPA, 2022i).
In response to the EPA's request that the SAB review the EPA's four
draft documents listed above, the SAB identified subject matter experts
to augment the SAB Chemical Assessment Advisory Committee (CAAC) and
assembled the SAB PFAS Review Panel to conduct the review.
In general, the SAB recognized the time constraints for completing
the rulemaking process and was supportive of the EPA's efforts to the
utilize the latest scientific finding to inform their decisions. The
SAB applauded the agency's efforts to develop new approaches for
assessing the risk of PFAS mixtures and the benefits arising from
reducing exposure to these chemicals as adopted by the EPA in the
Hazard Index approach in this rule. In general, the SAB agreed with
many of the conclusions presented in the assessments, framework, and
analysis. The SAB also identified many areas that would benefit from
further clarification to enhance their transparency and increase their
utility. The SAB provided numerous recommendations which can be found
in the SAB's final report (USEPA, 2022i) and some highlights are
outlined in the following section.
a. Approaches to the Derivation of Draft MCLGs for PFOA and PFOS
The primary purpose of the Proposed Approaches to the Derivation of
Draft MCLGs for PFOA and PFOS (USEPA, 2021i; USEPA, 2021j) was to
develop Maximum Contaminant Level Goals (MCLGs) based on the best
available health effects information for PFOA and PFOS. Each MCLG draft
document includes derivation of an updated chronic oral reference dose
(RfD), cancer slope factor (CSF) when relevant data were available, and
a relative source contribution (RSC) for SAB review. The health effects
information used to derive these toxicity values and RSC values built
upon the information in the 2016 EPA PFOA and PFOS Health Effects
Support Documents (HESDs; USEPA, 2016c; USEPA, 2016d). The EPA has
considered all SAB consensus advice in the development of the final
values derived in this health effects assessment and subsequently
derived MCLGs for the NPDWRs for PFOA and PFOS based on the best
available science and the EPA guidance and precedent. Please see
section IV of this preamble for discussions on the process for
derivation of the MCLGs and the resulting proposed MCLG values for this
final action.
The SAB charge questions for the MCLG draft documents addressed the
systematic review study identification and inclusion, non-cancer hazard
identification, cancer hazard identification and slope factor,
toxicokinetic (TK) modeling, RfD derivation, and RSC. The complete list
of charge questions was included in the EPA's documents prepared for
the SAB (USEPA, 2022i). The SAB provided numerous specific
recommendations to consider alternative approaches, expand the
systematic review steps for the health effects assessment, and to
develop additional analyses in order to improve the rigor and
transparency of the EPA's documents. The complete list of SAB consensus
advice is described in their final report (USEPA, 2022i).
Regarding the approaches to deriving MCLG draft documents, the SAB
stated that the systematic review methods could be more transparent and
complete. Specifically, study identification and criteria for inclusion
could be improved. The EPA made revisions to the systematic review
description and process by updating and expanding the scope of the
literature search; providing greater transparency regarding the study
inclusion criteria; and adding additional systematic review steps and
transparently describing each of these steps in the PFOA and PFOS
systematic review protocols.
In the charge questions, the EPA sought advice on the noncancer
health assessment, and the SAB recommended that the EPA separate hazard
and dose-response assessment systematic review steps. In response, the
EPA made revisions to the noncancer hazard identification by expanding
systematic review steps beyond study quality evaluation to include
evidence integration to address the need to separate hazard
identification and dose-response assessment and to ensure consistent
hazard decisions; and strengthening rationales for selection of points
of departure for the noncancer health outcomes. Additionally, the SAB
advised the EPA to focus on the health endpoints with the strongest
evidence (i.e., liver, immune, serum lipids, development, and cancer).
The EPA consulted with the SAB on the cancer risk assessment. On
the cancer Hazard Index and CSF, the SAB agreed that PFOA was a
``likely''
[[Page 32730]]
designation but recommended undertaking and describing a more
structured and transparent discussion of the ``weight of evidence'' for
both PFOA and PFOS. The EPA revised this assessment by following the
structured approach in the EPA cancer guidelines (USEPA, 2005a) to
develop a weight of evidence narrative for cancer, to consider the data
for selecting the cancer classification, evaluating and integrating
mechanistic information, and strengthening the rationales for
decisions.
With respect to the TK model for which the EPA sought advice, SAB
requested more details on the TK modeling including model code and
parameters and recommended that the EPA consider expressing the RfD in
water concentration equivalents to better account for possible life-
stage specific differences in exposure rates and TKs. The EPA
considered the alternate approach suggested by SAB and made revisions
by evaluating alternative TK models and further validating the selected
model.
The EPA also sought advice on the draft RfD derivation. The SAB
advised that the EPA consider multiple human and animal studies for a
variety of endpoints and populations. The SAB also stated a need for
stronger and more transparent justification of BMR selections and asked
the EPA to consider adopting a probabilistic framework to calculate
risk-specific doses. SAB also recommended that the EPA clearly state
that RfDs apply to both short-term and chronic exposure. The EPA made
revisions based on these recommendations by providing additional
descriptions and rationale for the selected modeling approaches and
conducting new dose-response analyses of additional studies and
endpoints.
On the RSC charge question, SAB supported the selection of a 20
percent RSC, but asked that the EPA provide clarity and rationale to
support the value. To address this recommendation, the EPA added
clarifying language related to the RSC determination from the EPA
guidance (USEPA, 2000d), including the relevance of drinking water
exposures and the relationship between the RfD and the RSC.
b. Combined Toxicity Framework
The EPA sought advice from the SAB on the Draft Framework for
Estimating Noncancer Health Risks Associated with Mixtures of PFAS
document (USEPA, 2021e). The main purpose of this document was to
provide a data-driven framework for estimating human health risks
associated with oral exposures to mixtures of PFAS. The charge
questions for the SAB pertaining to the framework draft documents
included whether the EPA provided clear support for the assumption of
dose additivity, and application of the Hazard Index, relative potency
factor (RPF), and mixtures benchmark dose (BMD) approaches for the
evaluation of mixtures of PFAS. The full list of charge questions was
included in the EPA's documents prepared for the SAB (USEPA, 2022i).
The SAB agreed in general with dose additivity at the level of common
health effect, and application of the Hazard Index, RPF and mixture BMD
approaches for the evaluation of mixtures of PFAS. The SAB identified
instances in which the communication of the analyses and approaches in
the EPA's framework document could be improved to be clearer.
On the EPA's charge question for dose additivity, the SAB agreed
with the use of the dose additivity assumption when evaluating PFAS
mixtures that have similar effects and concluded that this approach was
health protective. The SAB recommended a more thoroughly and clearly
presented list of the uncertainties associated with dose additivity
along with information supporting this approach. The EPA made revisions
that added clarity to the text by expanding upon the uncertainties and
including additional support for using dose additivity.
The SAB panel agreed with the use of the Hazard Index as a
screening method and decision-making tool. The SAB advised that the EPA
should consider using a menu-based framework to support selection of
fit-for-purpose approaches, rather than a tiered approach as described
in the draft mixtures document. Based on this feedback, the EPA has
since reorganized the approach to provide a data-driven ``menu of
options'' to remove the tiered logic flow and is adding text to clarify
the flexibility in implementation.
The EPA sought the SAB's opinion on the RPF approach for estimating
health risks associated with PFAS mixtures and the SAB panel considered
the RPF approach to be a reasonable methodology for assessing mixtures.
On the mixture BMD, the SAB agreed that the mixture BMD approach was a
reasonable methodology for estimating a mixture-based point of
departure (POD). For both the RPF and mixture BMD approach, the SAB
recommended that the EPA's approach be strengthened by the use of PODs
from animal studies that are based on HEDs rather than administered
doses. The SAB also requested clarification as to the similarities and
differences among the RPF and mixture BMD approaches. The SAB also
asked the EPA to provide additional information on how the proposed
mixtures BMD approach would be applied in practice. To address these
recommendations, the EPA made revisions to provide better context and
delineation about the applicability of the data across these
approaches.
c. Cardiovascular Disease Analysis
The EPA consulted with the SAB on the agency's methodology to
determine the avoided cases of CVD events (e.g., heart attack, stroke,
death from coronary heart disease) associated with reductions in
exposure to PFOA and PFOS in drinking water to support a benefits
analysis. Specifically, the EPA sought SAB comment on the extent to
which the approach to estimating reductions in CVD risk is
scientifically supported and clearly described. The EPA posed specific
charge questions on the exposure-response information used in the
analysis, the risk model and approach used to estimate the avoided
cases of CVD events, and the EPA's discussion of limitations and
uncertainties of the analysis. Overall, the SAB supported the EPA's
approach to estimating reductions in CVD risk associated with
reductions in exposure to PFOA and PFOS in drinking water. The SAB
provided feedback on several areas of the analysis; main points of
their feedback and the EPA's responses are discussed in this section.
The SAB noted a discrepancy between the draft CVD document's focus
on CVD risk, and the draft MCLG documents' conclusions that the
evidence of CVD was not sufficient to form the basis of a RfD. Based on
SAB feedback on the draft MCLG document's assessment of CVD related
risks, the EPA has developed an RfD for total cholesterol (TC). (For
more information see USEPA, 2024c; USEPA, 2024d.) The derivation of an
RfD for this endpoint addresses the SAB's concerns about inconsistency
between the two documents. The SAB also recommended that the EPA ensure
that recommendations for the draft MCLG documents relating to evidence
identification and synthesis are applied to the CVD endpoint. All
studies in the EPA's CVD benefits analysis were evaluated for risk of
bias, selective reporting, and sensitivity as applied in the EPA's
Public Comment Draft--Toxicity Assessment and Proposed MCLGs for PFOA
and PFOS in Drinking Water (USEPA, 2023g; USEPA, 2023h).
The SAB recommended that the EPA provide more discussion as to the
rationale for selecting CVD for risk reduction analysis and that the
[[Page 32731]]
approach follows the pathway that links cholesterol to cardiovascular
events rather than looking at the reported effects of PFAS directly on
CVD. The SAB also recommended that the EPA consider risk reduction
analyses for other endpoints. In section 6.5 of the EA, the EPA
discusses the rationale for quantifying CVD and analytical assumptions.
Sections 6.4 and 6.6 discusses the agency's quantified risk reduction
analyses for other adverse health effects, including infant birthweight
effects and renal cell carcinoma (RCC), respectively. In section 6.2.2,
the EPA assesses the qualitative benefits of other adverse health
effects of PFAS.
Although the SAB generally agreed with the meta-analysis, life
table and risk estimation methods, the SAB recommended that the EPA
provide additional clarity as to the application of these approaches
and conduct additional sensitivity analyses. In response to these
comments, the EPA expanded documentation and conducted additional
sensitivity analyses to evaluate the impact of inclusion or exclusion
of certain studies in the meta-analyses of exposure-response estimates.
Further, the EPA expanded documentation and conducted additional
sensitivity analyses to assess the effects of using a key single study
approach versus the meta-analysis approach to inform the exposure-
response estimates. The EPA identified two suitable key studies for use
in the single study approach. The EPA found that the single study
approach resulted in increased benefits, and this trend was driven by
the larger estimates of PFAS-TC slope factors and inverse associations
in the high-density lipoprotein cholesterol (HDLC) effect for one or
both contaminants in the key single studies. The EPA elected to retain
the meta-analysis approach in the benefits analysis because the agency
identified several studies on adults in the general population with
large numbers of participants and low risk of bias, and in this case
the meta-analytical approach offers an increased statistical power over
the single study approach. While the single study approach is common
for RfD derivations, the meta-analysis pooled estimate provides a slope
factor that represents the average response across a larger number of
studies, which is useful in evaluating benefits resulting from changes
in CVD risk on a national scale.
The SAB also recommended that the EPA evaluate how inclusion of
HDLC effects would influence the results and provide further
justification for the inclusion or exclusion of HDLC and blood pressure
effects. The EPA found that, as expected, inclusion of HDLC effects
decreases annualized CVD benefits and inclusion of blood pressure
effects slightly increases annualized CVD benefits. Because HDLC was
shown to have a stronger effect than blood pressure on annualized CVD
benefits, inclusion of blood pressure and HDLC effects together
decreases annualized CVD benefits. For more information see sensitivity
analyses evaluating these effects in appendix K of the EA. Inclusion of
HDLC effects into the national analysis would reduce national benefits
estimates but would not change the EPA's bottom-line conclusion that
the quantifiable and nonquantifiable benefits of the rule justify the
quantifiable and nonquantifiable costs. After further examination of
the evidence for HDLC and blood pressure effects, the EPA elected to
include blood pressure effects because the findings from a single high
confidence study and several medium confidence studies conducted among
the general population provided consistent evidence of an association
between PFOS exposure and blood pressure. The EPA did not include HDLC
effects in the national benefits analysis because available evidence of
associations between PFOS exposures and HDLC levels is inconsistent and
there is no evidence of an association between PFOA exposures and HDLC
levels.
Finally, the SAB noted that while the Atherosclerotic
Cardiovascular Disease (ASCVD) model is a reasonable choice for
estimating the probability of first time CVD events, it is not without
limitations. The panel recommended that the EPA include more discussion
of the accuracy of its predictions, particularly for sub-populations.
The EPA expanded its evaluation of the ASCVD model's limitations,
including a comparison of the ASCVD model predictions with race/
ethnicity and sex-specific CVD incidence from Centers for Disease
Control and Prevention's (CDC's) public health surveys (See section
6.5.3.2 and appendix G of the EA for details). Results show that the
ASCVD model coefficients for the non-Hispanic Black model are more
consistent with data on CVD prevalence and mortality for Hispanic and
non-Hispanic other race subpopulations than the ASCVD model
coefficients for the non-Hispanic White model.
Comments on the SAB consultation and review were raised by public
commenters. As a result, the comments have been addressed by the EPA in
the final rule, supporting documents in the record, and throughout this
preamble, specifically in sections III.B, IV, and XII.A.
2. National Drinking Water Advisory Council (NDWAC)
The agency consulted with the NDWAC prior to the rule proposal
during the Council's April 19, 2022, virtual meeting. During the
meeting, the EPA provided information related to the development of the
proposed rule. A summary of the NDWAC input from that meeting is
available in the NDWAC, Fall 2022 Meeting Summary Report (NDWAC, 2022)
and the docket.
On August 8, 2023, the EPA consulted with the NDWAC prior to the
final rule during a virtual meeting where the EPA presented on the
proposed PFAS NPDWR, including the proposed MCLs, monitoring and PN
requirements, and treatment and economic considerations. The EPA
reiterated that the PFAS NPDWR was developed with extensive
consultation from state, local and Tribal partners to identify avenues
that would reduce PFAS in drinking water and reaffirmed its commitment
to working with these partners on rule implementation. The EPA
carefully considered the information provided by the NDWAC during the
development of a final PFAS NPDWR. A summary of the NDWAC input from
that meeting is available in the NDWAC Summary Report (NDWAC, 2023) and
the docket.
3. Department of Health and Human Service
On September 28, 2022, the EPA consulted with the Department of HHS
on the proposed PFAS NPDWR. On November 2, 2023, the EPA consulted with
the HHS on the final rule. The EPA received and considered comments
from the HHS for both the proposed and final rules through the
interagency review process described in section XIII.A.
L. Congressional Review Act (CRA)
This action is subject to the CRA, and the EPA will submit a rule
report to each House of the Congress and to the Comptroller General of
the United States. This action meets the criteria set forth in 5
U.S.C.804(2).
XIV. Severability
The purpose of this section is to clarify the EPA's intent with
respect to the severability of provisions of this rule. Each Maximum
Contaminant Level (MCL) is independent of the others and can be
implemented on its own. For that reason, if any individual or Hazard
Index MCL is determined by judicial review or operation of law to be
invalid, the EPA intends that the partial invalidation will not render
any other
[[Page 32732]]
MCL invalid. In addition, each per- and polyfluoroalkyl substance
(PFAS) included in the Hazard Index is independent from any other PFAS
included in the Hazard Index. As a result, if any PFAS regulation is
determined by judicial review or operation of law to be invalid, that
partial invalidation should not render any other PFAS regulation
included in the Hazard Index or the Hazard Index PFAS MCL invalid.
Moreover, the Hazard Index approach and Hazard Index PFAS MCL can
remain operable and applicable so long as there are at least two
contaminants subject to the Hazard Index as a mixture because the EPA's
definition of mixture in this final rule is of two or more of the
Hazard Index PFAS. In addition, each individual Maximum Contaminant
Level Goal (MCLG) is independent of each of the other MCLGs and,
because they perform different functions under the Act, of each of the
MCLs. As a result, if an MCL is determined to be invalid, that partial
invalidation should not render the associated MCLG invalid. The
monitoring requirements are independent and capable of operating
without any MCLs. Likewise, if any provision of this rule other than
the MCLGs, or MCLs, is determined to be invalid (such as monitoring
waivers or the capital improvements extension), the remainder of the
rule can still be sensibly implemented; as a result, the EPA intends
that the rest of the rule (such as monitoring requirements) remain
operable and applicable.
XV. Incorporation by Reference
In this action, the EPA requires that systems must only use the
analytical methods specified to demonstrate compliance with the rule.
EPA Method 533: Determination of Per- and Polyfluoroalkyl Substances in
Drinking Water by Isotope Dilution Anion Exchange Solid Phase
Extraction and Liquid Chromatography/Tandem Mass Spectrometry, November
2019, 815-B-19-020, and EPA Method 537.1,Version 2.0: Determination of
Selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by
Solid Phase Extraction and Liquid Chromatography/Tandem Mass
Spectrometry (LC/MS/MS), March 2020, EPA/600/R-20/006, are incorporated
by reference in this final rule and are publicly available in the EPA's
Docket ID No. EPA-HQ-OW-2022-0114. The EPA Method 533 and EPA Method
537.1, Version 2.0 are solid phase extraction liquid chromatography-
tandem mass spectrometry methods for the detection and determination of
select per-and polyfluoroalkyl substances in drinking water. In
addition to being available in the aforementioned rule docket, both
methods can be accessed online at https://www.epa.gov/pfas/epa-pfas-drinking-water-laboratory-methods.
XVI. References
3M (3M Company). 2000. Sanitized report: Exploratory 28-day oral
toxicity study with telomer alcohol, telomer acrylate, PFHS and PFOS
(positive control) by daily gavage in the rat followed by a 14/28-
day recovery period [TSCA Submission]. (FYI-0500-01378 B; DCN
84000000018). St. Paul, MN. https://yosemite.epa.gov/oppts/epatscat8.nsf/ReportSearchView/05ADDF3067814C978525703B004B4119.
Adamson, D.T., Pi[ntilde]a, E.A., Cartwright, A.E., Rauch, S.R.,
Anderson, R.H., Mohr, T., and Connor, J.A. 2017. 1,4-Dioxane
drinking water occurrence data from the third unregulated
contaminant monitoring rule. Science of the Total Environment,
596:236-245.
Aguilera, P.A., Fern[aacute]ndez, A., Fern[aacute]ndez, R.,
Rum[iacute], R., and Salmer[oacute]n, A. 2011. Bayesian networks in
environmental modelling. Environmental Modelling & Software,
26(12):1376-1388.
Almond, D., Chay, K.Y., and Lee, D.S. 2005. The Costs of Low Birth
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Guidance. March 2018 Update. Available on the internet at: https://www.epa.gov/sites/default/files/2018-03/documents/hhra_regional_supplemental_guidance_report-march-2018_update.pdf.
USEPA. 2019a. Update for Chapter 3 of the Exposure Factors Handbook:
Ingestion of Water and Other Select Liquids. EPA 600-R-18-259F.
Available on the internet at: https://www.epa.gov/sites/default/files/2019-02/documents/efh_-_chapter_3_update.pdf.
[[Page 32741]]
USEPA. 2019b. Method 533: Determination of Per- and Polyfluoroalkyl
Substances in Drinking Water by Isotope Dilution Anion Exchange
Solid Phase Extraction and Liquid Chromatography/Tandem Mass
Spectrometry. EPA 815-B-19-020. Available on the internet at:
https://www.epa.gov/sites/default/files/2019-12/documents/method-533-815b19020.pdf.
USEPA. 2019c. Health Risk Reduction and Cost Analysis of the
Proposed Perchlorate National Primary Drinking Water Regulation. EPA
816-R-19-004.
USEPA. 2019d. Supplemental Environmental Assessment for Proposed
Revisions to Effluent Limitations Guidelines and Standards for the
Steam Electric Power Generating Point Source Category (EA).
USEPA. 2019e. EJSCREEN Technical Documentation. Available on the
internet at: https://www.epa.gov/sites/default/files/2021-04/documents/ejscreen_technical_document.pdf.
USEPA. 2020a. Announcement of Preliminary Regulatory Determinations
for Contaminants on the Fourth Drinking Water Contaminant Candidate
List. Federal Register. 85 FR 14098, March 10, 2020.
USEPA. 2020b. UCMR 5 Laboratory Approval Manual Version 2.0.
December 2021. EPA 815-B-21-010. Available on the internet at:
https://www.regulations.gov/document/EPA-HQ-OW-2020-0530-0129.
USEPA. 2020c. Determination of Selected Per- and Polyfluorinated
Alkyl Substances in Drinking Water by Solid Phase Extraction and
Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS). EPA 600-
R-20-006, Version 2.0, March 2020. Available on the internet at:
https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NERL&dirEntryId=348508.
USEPA. 2020d. Interim Guidance on the Destruction and Disposal of
Perfluoroalkyl and Polyfluoroalkyl Substances and Materials
Containing Perfluoroalkyl and Polyfluoroalkyl Substances. EPA-HQ-
OLEM-2020-0527-0002. Available on the internet at: https://www.epa.gov/system/files/documents/2021-11/epa-hq-olem-2020-0527-0002_content.pdf.
USEPA. 2020e. Labor Costs for National Drinking Water Rules. Report
prepared for EPA under Contract # EP-B16C-0001.
USEPA. 2020f. Economic Analysis for the Final Lead and Copper Rule
Revisions. EPA 816-R-20-008.
USEPA. 2021a. Human Health Toxicity Values for Perfluorobutane
Sulfonic Acid (CASRN 375-73-5) and Related Compound Potassium
Perfluorobutane Sulfonate (CASRN 29420-49-3). EPA/600/R-20/345F.
Available on the internet at: https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=350888.
USEPA. 2021b. Human Health Toxicity Values for Hexafluoropropylene
Oxide (HFPO) Dimer Acid and Its Ammonium Salt (CASRN 13252-13-6 and
CASRN 62037-80-3). Also Known as ``GenX Chemicals.'' EPA/822/R-21/
010. Available on the internet at: https://www.epa.gov/system/files/documents/2021-10/genx-chemicals-toxicity-assessment_tech-edited_oct-21-508.pdf.
USEPA. 2021c. Assessing and Managing Chemicals under TSCA: Fact
Sheet PFOA Stewardship Program. Available on the internet at:
https://www.epa.gov/assessing-and-managing-chemicals-under-tsca/fact-sheet-20102015-pfoa-stewardship-program.
USEPA. 2021d. Announcement of Final Regulatory Determinations for
Contaminants on the Fourth Drinking Water Contaminant Candidate
List. Federal Register. 86 FR 12272, March 3, 2021.
USEPA. 2021e. Draft Framework for Estimating Noncancer Health Risks
Associated with Mixtures of Per- and Polyfluoroalkyl Substances
(PFAS). EPA-822-D-21-003. Available on the internet at: https://sab.epa.gov/ords/sab/f?p=100:18:10311539418988:::18:P18_ID:2601.
USEPA. 2021f. Response To Additional Focused External Peer Review of
Draft Human Health Toxicity Values for Hexafluoropropylene Oxide
(HFPO) Dimer Acid and Its Ammonium Salt (GenX Chemicals). Available
on the internet at: https://www.epa.gov/system/files/documents/2021-10/epa_2nd-response-to-peer-review_genx_508.pdf.
USEPA. 2021g. EPA Response to Public Comments on Draft Human Health
Toxicity Values for Hexafluoropropylene Oxide (HFPO) Dimer Acid and
Its Ammonium Salt (CASRN 13252-13-6 and CASRN 62037-80-3) Also Known
as ``GenX Chemicals''. EPA 822R-21-008. October 2021. Available on
the internet at: https://www.epa.gov/system/files/documents/2021-10/final-genx-assessment-resp-to-public-comments_508.pdf.
USEPA. 2021h. Systematic Review Protocol for the PFAS IRIS
Assessments. EPA/635/R-19/050, 2019. Available on the internet at:
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USEPA. 2021i. Proposed Approaches to the Derivation of a Draft
Maximum Contaminant Level Goal for Perfluorooctanoic Acid (PFOA)
(CASRN 335-67-1) in Drinking Water. EPA 822-D-21-001. Available on
the internet at: https://sab.epa.gov/ords/sab/f?p=100:18:16490947993:::RP,18:P18_ID:2601.
USEPA. 2021j. Proposed Approaches to the Derivation of a Draft
Maximum Contaminant Level Goal for Perfluorooctane Sulfonic Acid
(PFOS) (CASRN 1763-23-1) in Drinking Water. EPA 822-D-21-002.
Available on the internet at: https://sab.epa.gov/ords/sab/f?p=100:18:16490947993:::RP,18:P18_ID:2601.
USEPA. 2021k. Analysis of Cardiovascular Disease Risk Reduction as a
Result of Reduced PFOA and PFOS Exposure in Drinking Water. EPA 815-
D-21-001. Available on the internet at: https://sab.epa.gov/ords/sab/f?p=100:18:16490947993:::RP,18:P18_ID:2601.
USEPA. 2022a. Changes to Reporting Requirements for Per- and
Polyfluoroalkyl Substances and to Supplier Notifications for
Chemicals of Special Concern; Community Right-to-Know Toxic Chemical
Release Reporting. Federal Register. 87 FR 74379, December 5, 2022.
USEPA. 2022b. Drinking Water Contaminant Candidate List 5--Final.
Federal Register. 87 FR 68060, November 14, 2022.
USEPA. 2022c. PFAS Strategic Roadmap: EPA's Commitments to Action
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USEPA. 2022e. Addressing PFAS discharges in NPDES permits and
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(RFC) received by the USEPA from Arnold & Porter Kaye Scholer LLP
(A&P) on March 18, 2022. Available on the internet at: https://www.epa.gov/system/files/documents/2022-06/RFC_22001_Response_June2022.pdf.
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Perfluorooctanoic Acid and Perfluorooctanesulfonic Acid. EPA-HQ-
OLEM-2019-0341-0001. Washington, DC. Retrieved from https://
[[Page 32742]]
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USEPA. 2023c. Advances in Dose Addition for Chemical Mixtures: A
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USEPA. 2023e. Public Comment Draft--Maximum Contaminant Level Goal
(MCLG) Summary Document for a Mixture of Four Per- and
Polyfluoroalkyl Substances (PFAS): GenX Chemicals, PFBS, PFNA and
PFHxS. EPA-822-P-23-004.
USEPA. 2023f. PFAS National Primary Drinking Water Regulation
Rulemaking. Federal Register. 88 FR 18638. March 29, 2023.
USEPA. 2023g. Public Comment Draft--Toxicity Assessment and Proposed
Maximum Contaminant Level Goal (MCLG) for Perfluorooctanoic Acid
(PFOA) (CASRN 335-67-1) in Drinking Water. EPA-822-P-23-005.
USEPA. 2023h. Public Comment Draft--Toxicity Assessment and Proposed
Maximum Contaminant Level Goal (MCLG) for Perfluorooctane Sulfonic
Acid (PFOS) (CASRN 1763-23-1) in Drinking Water. EPA-822-P-23-007.
USEPA. 2023i. Public Comment Draft--Appendix: Proposed Maximum
Contaminant Level Goal for Perfluorooctanoic Acid (PFOA) (CASRN 335-
67-1) in Drinking Water.
USEPA. 2023j. Public Comment Draft--Appendix: Proposed Maximum
Contaminant Level Goal for Perfluorooctane Sulfonic Acid (PFOS)
(CASRN 1763-23-1) in Drinking Water.
USEPA. 2023k. EPA Response to Final Science Advisory Board
Recommendations (August 2022) on Four Draft Support Documents for
the EPA's Proposed PFAS National Primary Drinking Water Regulation.
EPA-822-D-23-001.
USEPA. 2023l. PFAS Occurrence and Contaminant Background Support
Document. EPA-822-P-23-010.
USEPA. 2023m. EPA Response to Letter of Peer Review for Disinfectant
Byproduct Reduction as a Result of Granular Activated Carbon
Treatment for PFOA and PFOS in Drinking Water: Benefits Analysis
Related to Bladder Cancer. EPA-815-B23-001.
USEPA. 2023n. Economic Analysis of the Proposed National Primary
Drinking Water Regulation for Per- and Polyfluoroalkyl Substances.
EPA-822-P-23-001.
USEPA. 2023o. Appendix: Economic Analysis of the Proposed National
Primary Drinking Water Regulation for Per- and Polyfluoroalkyl
Substances. EPA-822-P-23-002.
USEPA. 2023p. IRIS Toxicological Review of Perfluorohexanoic Acid
[PFHxA, CASRN 307-24-4] and Related Salts (EPA/635/R-23/027Fa).
Retrieved from https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0704tr.pdf.
USEPA. 2023q. Federal ``Good Neighbor Plan'' for the 2015 Ozone
National Ambient Air Quality Standards. Federal Register. 88 FR
36654. June 5, 2023.
USEPA. 2023r. New Source Performance Standards for Greenhouse Gas
Emissions From New, Modified, and Reconstructed Fossil Fuel-Fired
Electric Generating Units; Emission Guidelines for Greenhouse Gas
Emissions From Existing Fossil Fuel-Fired Electric Generating Units;
and Repeal of the Affordable Clean Energy Rule. Federal Register. 88
FR 33240. May 23, 2023.
USEPA. 2023s. Regulatory Impact Analysis of the Standards of
Performance for New, Reconstructed, and Modified Sources and
Emissions Guidelines for Existing Sources: Oil and Natural Gas
Sector Climate Review. EPA-452/R-23-013.
USEPA. 2023t. Supplementary Material for the Regulatory Impact
Analysis for the Final Rulemaking, ``Standards of Performance for
New, Reconstructed, and Modified Sources and Emissions Guidelines
for Existing Sources: Oil and Natural Gas Sector Climate Review'';
EPA Report on the Social Cost of Greenhouse Gases: Estimates
Incorporating Recent Scientific Advances.
USEPA. 2023u. New Source Performance Standards for the Synthetic
Organic Chemical Manufacturing Industry and National Emission
Standards for Hazardous Air Pollutants for the Synthetic Organic
Chemical Manufacturing Industry and Group I & II Polymers and Resins
Industry. Federal Register. 88 FR 25080. April 25, 2023.
USEPA. 2023v. Executive Order 14096--Revitalizing Our Nation's
Commitment to Environmental Justice for All. Federal Register. 88 FR
25251, April 26, 2023.
USEPA. 2023w. Framework for Estimating Noncancer Health Risks
Associated with Mixtures of Per- and Polyfluoroalkyl Substances
(PFAS). EPA-822-P-23-003.
USEPA. 2024a. Framework for Estimating Noncancer Health Risks
Associated with Mixtures of Per- and Polyfluoroalkyl Substances
(PFAS). 815-R-24-003.
USEPA. 2024b. PFAS Occurrence and Contaminant Background Support
Document for the Final PFAS NPDWR. 815-R-24-013.
USEPA. 2024c. Office of Water Final Human Health Toxicity Assessment
for Perfluorooctanoic Acid (PFOA). 815-R-24-006.
USEPA 2024d. Office of Water Final Human Health Toxicity Assessment
for Perfluorooctane Sulfonic Acid (PFOS). 815-R-24-007.
USEPA. 2024e. Economic Analysis for the Final Per- and
Polyfluoroalkyl Substances National Primary Drinking Water
Regulation Appendices. 815-R-24-002.
USEPA 2024f. Maximum Contaminant Level Goals (MCLGs) for Three
Individual Per- and Polyfluoroalkyl Substances (PFAS) and a Mixture
of Four PFAS. 815-R-24-004.
USEPA. 2024g. Economic Analysis for the Final Per- and
Polyfluoroalkyl Substances National Primary Drinking Water
Regulation. 815-R-24-001.
USEPA. 2024h. Appendix--Office of Water Final Human Health Toxicity
Assessment for Perfluorooctanoic Acid (PFOA). 815-R-24-008.
USEPA. 2024i. Appendix--Office of Water Final Human Health Toxicity
Assessment for Perfluorooctane Sulfonic Acid (PFOS). 815-R-24-009.
USEPA. 2024j. OW Final Maximum Contaminant Level Goals (MCLGs) for
Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonic Acid
(PFOS) in Drinking Water. 815-R-24-010.
USEPA. 2024k. EPA's Responses to Public Comments on the Proposed
PFAS National Primary Drinking Water Regulation. 815-R-24-005.
USEPA. 2024l. Best Available Technologies and Small System
Compliance Technologies Per- and Polyfluoroalkyl Substances (PFAS)
in Drinking Water. 815-R-24-011.
USEPA. 2024m. Technologies and Costs for Removing Per- and
Polyfluoroalkyl Substances from Drinking Water. 815-R-24-012.
USEPA. 2024n. Fifth Unregulated Contaminant Monitoring Rule:
Occurrence Data. Available on the internet at: https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-monitoring-rule#5.
USEPA. 2024o. Fluoride Informational Links. Available on the
internet at: https://tdb.epa.gov/tdb/contaminant?id=10700.
USEPA. 2024p. Work Breakdown Structure-Based Cost Model for Granular
Activated Carbon Drinking Water Treatment.
USEPA. 2024q. Work Breakdown Structure-Based Cost Model for Ion
Exchange Treatment of Per- and Polyfluoroalkyl Substances (PFAS) in
Drinking Water.
USEPA. 2024r. Work Breakdown Structure-Based Cost Model for
Nontreatment Options for Drinking Water Compliance.
United States Office of Science and Technology Policy (OSTP). 2023.
Per- and Polyfluoroalkyl Substances (PFAS) Report, A Report by the
Joint Subcommittee on Environment, Innovation, and Public Health.
Available on the internet at: https://www.whitehouse.gov/wpcontent/uploads/2023/03/OSTP-March-2023-PFASReport.pdf.
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List of Subjects
40 CFR Part 141
Environmental protection, Incorporation by reference, Indians--
lands, Intergovernmental relations, Monitoring and analytical
requirements, Per- and polyfluoroalkyl substances, Reporting and
recordkeeping requirements, Water supply.
40 CFR Part 142
Environmental protection, Administrative practice and procedure,
Indians--lands, Intergovernmental relations, Monitoring and analytical
requirements, Per- and polyfluoroalkyl substances, Reporting and
recordkeeping requirements, Water supply.
Michael S. Regan,
Administrator.
For the reasons stated in the preamble, the Environmental
Protection Agency amends 40 CFR parts 141 and 142 as follows:
PART 141--NATIONAL PRIMARY DRINKING WATER REGULATIONS
0
1. The authority citation for part 141 continues to read as follows:
Authority: 42 U.S.C. 300f, 300g-1, 300g-2, 300g-3, 300g-4,
300g-5, 300g-6, 300j-4, 300j-9, and 300j-11.
0
2. Amend Sec. 141.2 by adding in alphabetical order the definitions
for ``Hazard Index (HI)'', ``Hazard quotient (HQ)'', ``Health-based
water concentration (HBWC)'', ``HFPO-DA or GenX chemicals'', ``PFBS'',
``PFHxS'', ``PFNA'', ``PFOA'', and ``PFOS'' to read as follows:
Sec. 141.2 Definitions.
* * * * *
Hazard Index (HI) is the sum of component hazard quotients (HQs),
which are calculated by dividing the measured regulated PFAS component
contaminant concentration in water (e.g., expressed as parts per
trillion (ppt) or nanograms per liter (ng/l)) by the associated health-
based water concentration (HBWC) expressed in the same units as the
measured concentration (e.g., ppt or ng/l). For PFAS, a mixture Hazard
Index greater than 1 (unitless) is an exceedance of the MCL.
Hazard quotient (HQ) means the ratio of the measured concentration
in drinking water to the health-based water concentration (HBWC).
Health-based water concentration (HBWC) means level below which
there are no known or anticipated adverse health effects over a
lifetime of
[[Page 32744]]
exposure, including sensitive populations and life stages, and allows
for an adequate margin of safety.
HFPO-DA or GenX chemicals means Chemical Abstract Service
registration number 122499-17-6, chemical formula C6F11O3-,
International Union of Pure and Applied Chemistry preferred name
2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoate, along with its
conjugate acid and any salts, derivatives, isomers, or combinations
thereof.
* * * * *
PFBS means Chemical Abstract Service registration number 45187-15-
3, chemical formula C4F9SO3-, perfluorobutane sulfonate, along with its
conjugate acid and any salts, derivatives, isomers, or combinations
thereof.
PFHxS means Chemical Abstract Service registration number 108427-
53-8, chemical formula C6F13SO3-, perfluorohexane sulfonate, along with
its conjugate acid and any salts, derivatives, isomers, or combinations
thereof.
PFNA means Chemical Abstract Service registration number 72007-68-
2, chemical formula C9F17O2-, perfluorononanoate, along with its
conjugate acid and any salts, derivatives, isomers, or combinations
thereof.
PFOA means Chemical Abstract Service registration number 45285-51-
6, chemical formula C8F15O2-, perfluorooctanoate, along with its
conjugate acid and any salts, derivatives, isomers, or combinations
thereof.
PFOS means Chemical Abstract Service registration number 45298-90-
6, chemical formula C8F17SO3-, perfluorooctanesulfonate, along with its
conjugate acid and any salts, derivatives, isomers, or combinations
thereof.
* * * * *
0
3. Amend Sec. 141.6 by revising paragraph (a) and adding paragraph (l)
to read as follows:
Sec. 141.6 Effective dates.
(a) Except as provided in paragraphs (b) through (l) of this
section the regulations set forth in this part take effect on June 24,
1977.
* * * * *
(l) The regulations pertaining to the per- and polyfluoroalkyl
substances (PFAS) chemicals set forth in subpart Z of this part are
effective June 25, 2024. See Sec. 141.900 for the compliance dates for
provisions under subpart Z. Compliance with reporting requirements
under subpart Z, in accordance with subparts O (the consumer confidence
rule) and Q (the public notification rule) of this part are required on
April 26, 2027, except for notification requirements in Sec. 141.203
related to violations of the MCLs. The compliance date for the PFAS
MCLs in Sec. 141.61, as specified in Sec. 141.60, and for Sec.
141.203 notifications of violations of the PFAS MCLs is April 26, 2029.
0
4. Amend Sec. 141.24 by revising paragraph (h) introductory text to
read as follows:
Sec. 141.24 Organic chemicals, sampling and analytical requirements.
* * * * *
(h) Analysis of the contaminants listed in Sec. 141.61(c) for the
purposes of determining compliance with the maximum contaminant level
shall be conducted as follows, with the exceptions that this paragraph
(h) does not apply to regulated PFAS (see Sec. 141.902) and no
monitoring is required for aldicarb, aldicarb sulfoxide, or aldicarb
sulfone:
* * * * *
0
5. Amend Sec. 141.28 by revising paragraph (a) to read as follows:
Sec. 141.28 Certified laboratories.
(a) For the purpose of determining compliance with Sec. Sec.
141.21 through 141.27, 141.40, 141.74, 141.89, 141.402, 141.901, and
141.902, samples may be considered only if they have been analyzed by a
laboratory certified by EPA or the State except that measurements of
alkalinity, disinfectant residual, orthophosphate, pH, silica,
temperature, and turbidity may be performed by any person acceptable to
the State.
* * * * *
0
6. Amend Sec. 141.50 by:
0
a. Adding periods at the ends of paragraphs (a)(1) through (23);
0
b. Adding paragraphs (a)(24) and (25); and
0
c. In the table to paragraph (b), revising the heading for the second
column and adding in numerical order the entries ``(34),'' ``(35),''
``(36),'' and ``(37)'' and footnote 1.
The additions and revision read as follows:
Sec. 141.50 Maximum contaminant level goals for organic contaminants.
(a) * * *
(24) PFOA.
(25) PFOS.
(b) * * *
MCLG in mg/l (unless otherwise
Contaminant noted)
* * * * * * *
(34) Hazard Index PFAS (HFPO-DA, PFBS, 1 (unitless).\1\
PFHxS, and PFNA).
(35) HFPO-DA........................... 0.00001.
(36) PFHxS............................. 0.00001.
(37) PFNA.............................. 0.00001.
\1\ The PFAS Mixture Hazard Index (HI) is the sum of component hazard
quotients (HQs), which are calculated by dividing the measured
component PFAS concentration in water by the corresponding
contaminant's health-based water concentration (HBWC) when expressed
in the same units (shown in ng/l). The HBWC for PFHxS is 10 ng/l; the
HBWC for HFPO-DA is 10 ng/l; the HBWC for PFNA is 10 ng/l; and the
HBWC for PFBS is 2000 ng/l. A PFAS Mixture Hazard Index greater than 1
(unitless) indicates an exceedance of the health protective level and
indicates potential human health risk from the PFAS mixture in
drinking water.
Hazard Index = ([HFPO-DAwater ng/l]/[10 ng/l]) +
([PFBSwater ng/l]/[2000 ng/l]) + ([PFNAwater ng/
l]/[10 ng/l]]) + ([PFHxSwater ng/l]/[10 ng/l])
HBWC = health-based water concentration
HQ = hazard quotient
ng/l = nanograms per liter
PFASwater = the concentration of a specific PFAS in water
0
7. Amend Sec. 141.60 by adding paragraph (a)(4) to read as follows:
Sec. 141.60 Effective dates.
(a) * * *
(4) The effective date for paragraphs (c)(34) through (40) of Sec.
141.61 (listed in table 4 to paragraph (c)) is April 26, 2029.
* * * * *
0
8. Amend Sec. 141.61 by:
[[Page 32745]]
0
a. In paragraph (a), revising the introductory text and adding a table
heading;
0
b. In paragraph (b), revising the introductory text and the table
heading;
0
c. Revising and republishing paragraph (c); and
0
d. Adding paragraphs (d) and (e).
The revisions and additions read as follows:
Sec. 141.61 Maximum contaminant levels for organic contaminants.
(a) The following maximum contaminant levels for volatile organic
contaminants apply to community and non-transient, non-community water
systems.
Table 1 to Paragraph (a)--Maximum Contaminant Levels for Volatile
Organic Contaminants
* * * * *
(b) The Administrator, pursuant to section 1412 of the Act, hereby
identifies as indicated in table 2 to this paragraph (b) granular
activated carbon (GAC), packed tower aeration (PTA), or oxidation (OX)
as the best technology, treatment technique, or other means available
for achieving compliance with the maximum contaminant level for organic
contaminants identified in paragraphs (a) and (c) of this section,
except for per- and polyfluoroalkyl substances (PFAS).
Table 2 to Paragraph (b)--BAT for Organic Contaminants in Paragraphs (a)
and (c) of This Section, Except for PFAS
------------------------------------------------------------------------
* * * * *
(c) The following maximum contaminant levels (MCLs) in tables 3 and
4 to this paragraph (c) for synthetic organic contaminants apply to
community water systems and non-transient, non-community water systems;
table 4 also contains health-based water concentrations (HBWCs) for
selected per- and poly-fluoroalkyl substances (PFAS) used in
calculating the Hazard Index.
Table 3 to Paragraph (c)--MCLs for Synthetic Organic Contaminants,
Except for PFAS
------------------------------------------------------------------------
CAS No. Contaminant MCL (mg/l)
------------------------------------------------------------------------
(1) 15972-60-8.................... Alachlor............ 0.002
(2) 116-06-3...................... Aldicarb............ 0.003
(3) 1646-87-3..................... Aldicarb sulfoxide.. 0.004
(4) 1646-87-4..................... Aldicarb sulfone.... 0.002
(5) 1912-24-9..................... Atrazine............ 0.003
(6) 1563-66-2..................... Carbofuran.......... 0.04
(7) 57-74-9....................... Chlordane........... 0.002
(8) 96-12-8....................... Dibromochloropropane 0.0002
(9) 94-75-7....................... 2,4-D............... 0.07
(10) 106-93-4..................... Ethylene dibromide.. 0.00005
(11) 76-44-8...................... Heptachlor.......... 0.0004
(12) 1024-57-3.................... Heptachlor epoxide.. 0.0002
(13) 58-89-9...................... Lindane............. 0.0002
(14) 72-43-5...................... Methoxychlor........ 0.04
(15) 1336-36-3.................... Polychlorinated 0.0005
biphenyls.
(16) 87-86-5...................... Pentachlorophenol... 0.001
(17) 8001-35-2.................... Toxaphene........... 0.003
(18) 93-72-1...................... 2,4,5-TP............ 0.05
(19) 50-32-8...................... Benzo[a]pyrene...... 0.0002
(20) 75-99-0...................... Dalapon............. 0.2
(21) 103-23-1..................... Di(2-ethylhexyl) 0.4
adipate.
(22) 117-81-7..................... Di(2-ethylhexyl) 0.006
phthalate.
(23) 88-85-7...................... Dinoseb............. 0.007
(24) 85-00-7...................... Diquat.............. 0.02
(25) 145-73-3..................... Endothall........... 0.1
(26) 72-20-8...................... Endrin.............. 0.002
(27) 1071-53-6.................... Glyphosate.......... 0.7
(28) 118-74-1..................... Hexacholorbenzene... 0.001
(29) 77-47-4...................... Hexachlorocyclopenta 0.05
diene.
(30) 23135-22-0................... Oxamyl (Vydate)..... 0.2
(31) 1918-02-1.................... Picloram............ 0.5
(32) 122-34-9..................... Simazine............ 0.004
(33) 1746-01-6.................... 2,3,7,8-TCDD 3 x 10-8
(Dioxin).
------------------------------------------------------------------------
Table 4 to Paragraph (c)--MCLs and HBWCs for PFAS
----------------------------------------------------------------------------------------------------------------
HBWC (mg/l) for
CAS. No. Contaminant MCL (mg/l) (unless hazard index
otherwise noted) calculation
----------------------------------------------------------------------------------------------------------------
(34) Not applicable.................. Hazard Index PFAS (HFPO-DA, 1 (unitless) \1\....... Not applicable
PFBS, PFHxS, and PFNA).
(35) 122499-17-6..................... HFPO-DA...................... 0.00001................ 0.00001
(36) 45187-15-3...................... PFBS......................... No individual MCL...... 0.002
(37) 108427-53-8..................... PFHxS........................ 0.00001................ 0.00001
(38) 72007-68-2...................... PFNA......................... 0.00001................ 0.00001
(39) 45285-51-6...................... PFOA......................... 0.0000040.............. Not applicable
[[Page 32746]]
(40) 45298-90-6...................... PFOS......................... 0.0000040.............. Not applicable
----------------------------------------------------------------------------------------------------------------
\1\ The PFAS Mixture Hazard Index (HI) is the sum of component hazard quotients (HQs), which are calculated by
dividing the measured component PFAS concentration in water by the relevant health-based water concentration
when expressed in the same units (shown in ng/l for simplification). The HBWC for PFHxS is 10 ng/l; the HBWC
for HFPO-DA is 10 ng/l; the HBWC for PFNA is 10 ng/l; and the HBWC for PFBS is 2000 ng/l.
Hazard Index = ([HFPO-DAwater ng/l]/[10 ng/l]) +
([PFBSwater ng/l]/[2000 ng/l]) + ([PFNAwater ng/
l]/[10 ng/l]) + ([PFHxSwater ng/l]/[10 ng/l])
HBWC = health-based water concentration
HQ = hazard quotient
ng/l = nanograms per liter
PFASwater = the concentration of a specific PFAS in water
(d) The Administrator, pursuant to section 1412 of the Act, hereby
identifies in table 5 to this paragraph (d) the best technology,
treatment technique, or other means available for achieving compliance
with the maximum contaminant levels for all regulated PFAS identified
in paragraph (c) of this section:
Table 5 to Paragraph (d)--Best Available Technologies for PFAS Listed in
Paragraph (c) of This Section
------------------------------------------------------------------------
Contaminant BAT
------------------------------------------------------------------------
Hazard Index PFAS (HFPO-DA, PFBS, Anion exchange, GAC, reverse
PFHxS, and PFNA). osmosis, nanofiltration.
HFPO-DA................................ Anion exchange, GAC, reverse
osmosis, nanofiltration.
PFHxS.................................. Anion exchange, GAC, reverse
osmosis, nanofiltration.
PFNA................................... Anion exchange, GAC, reverse
osmosis, nanofiltration.
PFOA................................... Anion exchange, GAC, reverse
osmosis, nanofiltration.
PFOS................................... Anion exchange, GAC, reverse
osmosis, nanofiltration.
------------------------------------------------------------------------
(e) The Administrator, pursuant to section 1412 of the Act, hereby
identifies in table 6 to this paragraph (e) the affordable technology,
treatment technique, or other means available to systems serving 10,000
persons or fewer for achieving compliance with the maximum contaminant
levels for all regulated PFAS identified in paragraph (c) of this
section:
Table 6 to Paragraph (e)--Small System Compliance Technologies (SSCTs)
for PFAS
------------------------------------------------------------------------
Affordable for listed small
Small system compliance technology \1\ system categories \2\
------------------------------------------------------------------------
Granular Activated Carbon................. All size categories.
Anion Exchange............................ All size categories.
Reverse Osmosis, Nanofiltration \3\....... 3,301-10,000.
------------------------------------------------------------------------
\1\ Section 1412(b)(4)(E)(ii) of SDWA specifies that SSCTs must be
affordable and technically feasible for small systems.
\2\ The Act (ibid.) specifies three categories of small systems: (i)
those serving 25 or more, but fewer than 501, (ii) those serving more
than 500, but fewer than 3,301, and (iii) those serving more than
3,300, but fewer than 10,001.
\3\ Technologies reject a large volume of water and may not be
appropriate for areas where water quantity may be an issue.
0
9. Amend Sec. 141.151 by revising paragraph (d) to read as follows:
Sec. 141.151 Purpose and applicability of this subpart.
* * * * *
(d) For the purpose of this subpart, detected means: at or above
the levels prescribed by Sec. 141.23(a)(4) for inorganic contaminants,
at or above the levels prescribed by Sec. 141.24(f)(7) for the
contaminants listed in Sec. 141.61(a), at or above the levels
prescribed by Sec. 141.24(h)(18) for the contaminants listed in Sec.
141.61(c) (except PFAS), at or above the levels prescribed by Sec.
141.131(b)(2)(iv) for the contaminants or contaminant groups listed in
Sec. 141.64, at or above the levels prescribed by Sec. 141.25(c) for
radioactive contaminants, and at or above the levels prescribed in
Sec. 141.902(a)(5) for PFAS listed in Sec. 141.61(c).
* * * * *
0
10. Amend Sec. 141.153 by adding paragraph (c)(3)(v) to read as
follows:
Sec. 141.153 Content of the reports.
* * * * *
(c) * * *
(3) * * *
(v) Hazard Index or HI. The Hazard Index is an approach that
determines the health concerns associated with mixtures of certain PFAS
in finished drinking water. Low levels of multiple PFAS that
individually would not likely result in adverse health effects may pose
health concerns when combined in a mixture. The Hazard Index MCL
represents the maximum level for mixtures of PFHxS, PFNA, HFPO-DA, and/
or PFBS allowed in water delivered by a public water system. A Hazard
Index greater than 1 requires a system to take action.
* * * * *
0
11. Amend appendix A to subpart O, under the Contaminant heading
``Synthetic organic contaminants including pesticides and
herbicides:'', by adding in alphabetical order entries for ``Hazard
Index PFAS (HFPO-DA, PFBS, PFHxS, and PFNA) (unitless)'', ``HFPO-DA
(ng/l)'', ``PFHxS (ng/l)'', ``PFNA (ng/l)'', ``PFOA (ng/l)'', and
``PFOS (ng/l)'' to read as follows:
[[Page 32747]]
Appendix A to Subpart O of Part 141--Regulated Contaminants
--------------------------------------------------------------------------------------------------------------------------------------------------------
To convert for
Contaminant (units) Traditional CCR, multiply MCL in CCR MCLG Major sources in drinking Health effects language
MCL in mg/L by units water
--------------------------------------------------------------------------------------------------------------------------------------------------------
* * * * * * *
Synthetic organic contaminants * * * * * *
including pesticides and
herbicides:
* * * * * * *
Hazard Index PFAS (HFPO-DA, PFBS, 1 (unitless) .............. 1 1 Discharge from Per- and polyfluoroalkyl
PFHxS, and PFNA) (unitless). manufacturing and substances (PFAS) can
industrial chemical persist in the human
facilities, use of body and exposure may
certain consumer lead to increased risk
products, occupational of adverse health
exposures, and certain effects. Low levels of
firefighting activities. multiple PFAS that
individually would not
likely result in
increased risk of
adverse health effects
may result in adverse
health effects when
combined in a mixture.
Some people who consume
drinking water
containing mixtures of
PFAS in excess of the
Hazard Index (HI) MCL
may have increased
health risks such as
liver, immune, and
thyroid effects
following exposure over
many years and
developmental and
thyroid effects
following repeated
exposure during
pregnancy and/or
childhood.
* * * * * * *
HFPO-DA (ng/l).................... 0.00001 1,000,000 10 10 Discharge from Some people who drink
manufacturing and water containing HFPO-DA
industrial chemical in excess of the MCL
facilities, use of over many years may have
certain consumer increased health risks
products, occupational such as immune, liver,
exposures, and certain and kidney effects.
firefighting activities. There is also a
potential concern for
cancer associated with
HFPO-DA exposure. In
addition, there may be
increased risks of
developmental effects
for people who drink
water containing HFPO-DA
in excess of the MCL
following repeated
exposure during
pregnancy and/or
childhood.
[[Page 32748]]
* * * * * * *
PFHxS (ng/l)...................... 0.00001 1,000,000 10 10 Discharge from Some people who drink
manufacturing and water containing PFHxS
industrial chemical in excess of the MCL
facilities, use of over many years may have
certain consumer increased health risks
products, occupational such as immune, thyroid,
exposures, and certain and liver effects. In
firefighting activities. addition, there may be
increased risks of
developmental effects
for people who drink
water containing PFHxS
in excess of the MCL
following repeated
exposure during
pregnancy and/or
childhood.
PFNA (ng/l)....................... 0.00001 1,000,000 10 10 Discharge from Some people who drink
manufacturing and water containing PFNA in
industrial chemical excess of the MCL over
facilities, use of many years may have
certain consumer increased health risks
products, occupational such as elevated
exposures, and certain cholesterol levels,
firefighting activities. immune effects, and
liver effects. In
addition, there may be
increased risks of
developmental effects
for people who drink
water containing PFNA in
excess of the MCL
following repeated
exposure during
pregnancy and/or
childhood.
PFOA (ng/l)....................... 0.0000040 1,000,000 4.0 0 Discharge from Some people who drink
manufacturing and water containing PFOA in
industrial chemical excess of the MCL over
facilities, use of many years may have
certain consumer increased health risks
products, occupational such as cardiovascular,
exposures, and certain immune, and liver
firefighting activities. effects, as well as
increased incidence of
certain types of cancers
including kidney and
testicular cancer. In
addition, there may be
increased risks of
developmental and immune
effects for people who
drink water containing
PFOA in excess of the
MCL following repeated
exposure during
pregnancy and/or
childhood.
[[Page 32749]]
PFOS (ng/l)....................... 0.0000040 1,000,000 4.0 0 Discharge from Some people who drink
manufacturing and water containing PFOS in
industrial chemical excess of the MCL over
facilities, use of many years may have
certain consumer increased health risks
products, occupational such as cardiovascular,
exposures, and certain immune, and liver
firefighting activities. effects, as well as
increased incidence of
certain types of cancers
including liver cancer.
In addition, there may
be increased risks of
developmental and immune
effects for people who
drink water containing
PFOS in excess of the
MCL following repeated
exposure during
pregnancy and/or
childhood.
* * * * * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------
* * * * *
0
12. Amend appendix A to subpart Q by:
0
a. Adding under the Contaminant heading ``D. Synthetic Organic
Chemicals (SOCs)'' entries for ``31'', ``32'', ``33'', ``34'', ``35'',
and ``36'' in numerical order;
0
b. Adding, immediately before footnote 1, footnote *; and
0
c. Adding footnote 23 at the end of the table.
The additions read as follows:
Appendix A to Subpart Q of Part 141--NPDWR Violations and Other
Situations Requiring Public Notice \1\
----------------------------------------------------------------------------------------------------------------
MCL/MRDL/TT violations \2\ Monitoring & testing procedure
-------------------------------- violations
-------------------------------
Contaminant Tier of public Tier of public
notice Citation notice Citation
required required
----------------------------------------------------------------------------------------------------------------
* * * * * * *
D. Synthetic Organic Chemicals (SOCs)
----------------------------------------------------------------------------------------------------------------
* * * * * * *
31. Hazard Index PFAS........................... \23\ * 2 141.61(c) 3 141.905(c)
32. HFPO-DA..................................... * 2 141.61(c) 3 141.905(c)
33. PFHxS....................................... * 2 141.61(c) 3 141.905(c)
34. PFNA........................................ * 2 141.61(c) 3 141.905(c)
35. PFOA........................................ * 2 141.61(c) 3 141.905(c)
36. PFOS........................................ * 2 141.61(c) 3 141.905(c)
* * * * * * *
----------------------------------------------------------------------------------------------------------------
Appendix A--Endnotes
* * * * * * *
* Beginning April 26, 2029.
\1\ Violations and other situations not listed in this table (e.g., failure to prepare Consumer Confidence
Reports), do not require notice, unless otherwise determined by the primacy agency. Primacy agencies may, at
their option, also require a more stringent public notice tier (e.g., Tier 1 instead of Tier 2 or Tier 2
instead of Tier 3) for specific violations and situations listed in this Appendix, as authorized under Sec.
141.202(a) and Sec. 141.203(a).
\2\ MCL--Maximum contaminant level, MRDL--Maximum residual disinfectant level, TT--Treatment technique.
* * * * * * *
\23\ Systems that violate the Hazard Index MCL and one or more individual MCLs based on the same contaminants
may issue one notification to satisfy the public notification requirements for multiple violations pursuant to
Sec. 141.203.
0
13. Amend appendix B to subpart Q by redesignating entries ``55''
through ``89'' as entries ``61'' through ``95'' and adding new entries
``55'' through ``60'' under the heading ``E. Synthetic Organic
Chemicals (SOCs)'' to read as follows:
Appendix B to Subpart Q of Part 141--Standard Health Effects Language
for Public Notification
[[Page 32750]]
----------------------------------------------------------------------------------------------------------------
Standard health effects language for
Contaminant MCLG \1\ mg/L MCL \2\ mg/L public notification
----------------------------------------------------------------------------------------------------------------
* * * * * * *
----------------------------------------------------------------------------------------------------------------
E. Synthetic Organic Chemicals (SOCs)
----------------------------------------------------------------------------------------------------------------
* * * * * * *
55. Hazard Index PFAS (HFPO-DA, 1 (unitless) 1 (unitless) Per- and polyfluoroalkyl substances
PFBS, PFHxS, and PFNA). (PFAS) can persist in the human body
and exposure may lead to increased
risk of adverse health effects. Low
levels of multiple PFAS that
individually would not likely result
in increased risk of adverse health
effects may result in adverse health
effects when combined in a mixture.
Some people who consume drinking
water containing mixtures of PFAS in
excess of the Hazard Index (HI) MCL
may have increased health risks such
as liver, immune, and thyroid
effects following exposure over many
years and developmental and thyroid
effects following repeated exposure
during pregnancy and/or childhood.
56. HFPO-DA........................ 0.00001 0.00001 Some people who drink water
containing HFPO-DA in excess of the
MCL over many years may have
increased health risks such as
immune, liver, and kidney effects.
There is also a potential concern
for cancer associated with HFPO-DA
exposure. In addition, there may be
increased risks of developmental
effects for people who drink water
containing HFPO-DA in excess of the
MCL following repeated exposure
during pregnancy and/or childhood.
57. PFHxS.......................... 0.00001 0.00001 Some people who drink water
containing PFHxS in excess of the
MCL over many years may have
increased health risks such as
immune, thyroid, and liver effects.
In addition, there may be increased
risks of developmental effects for
people who drink water containing
PFHxS in excess of the MCL following
repeated exposure during pregnancy
and/or childhood.
58. PFNA........................... 0.00001 0.00001 Some people who drink water
containing PFNA in excess of the MCL
over many years may have increased
health risks such as elevated
cholesterol levels, immune effects,
and liver effects. In addition,
there may be increased risks of
developmental effects for people who
drink water containing PFNA in
excess of the MCL following repeated
exposure during pregnancy and/or
childhood.
59. PFOA........................... Zero 0.0000040 Some people who drink water
containing PFOA in excess of the MCL
over many years may have increased
health risks such as cardiovascular,
immune, and liver effects, as well
as increased incidence of certain
types of cancers including kidney
and testicular cancer. In addition,
there may be increased risks of
developmental and immune effects for
people who drink water containing
PFOA in excess of the MCL following
repeated exposure during pregnancy
and/or childhood.
60. PFOS........................... Zero 0.0000040 Some people who drink water
containing PFOS in excess of the MCL
over many years may have increased
health risks such as cardiovascular,
immune, and liver effects, as well
as increased incidence of certain
types of cancers including liver
cancer. In addition, there may be
increased risks of developmental and
immune effects for people who drink
water containing PFOS in excess of
the MCL following repeated exposure
during pregnancy and/or childhood.
* * * * * * *
----------------------------------------------------------------------------------------------------------------
* * * * * * *
\1\ MCLG--Maximum contaminant level goal.
\2\ MCL--Maximum contaminant level.
* * * * *
0
14. Amend appendix C to subpart Q by adding entries for the acronyms
``HI'' and ``PFAS'' in alphabetical order to read as follows:
Appendix C to Subpart Q of Part 141--List of Acronyms Used in Public
Notification Regulation
* * * * *
HI Hazard Index
* * * * *
PFAS Per- and Polyfluoroalkyl Substances
* * * * *
0
15. Add subpart Z to read as follows:
Subpart Z--Control of Per- and Polyfluoroalkyl Substances (PFAS)
Sec.
141.900 General requirements.
141.901 Analytical requirements.
141.902 Monitoring requirements.
141.903 Compliance requirements.
141.904 Reporting and recordkeeping requirements.
141.905 Violations.
Subpart Z--Control of Per- and Polyfluoroalkyl Substances (PFAS)
Sec. 141.900 General requirements.
(a) The requirements of this subpart constitute the national
primary drinking water regulations for PFAS. Each community water
system (CWS) and non-transient, non-community water system (NTNCWS)
must meet the requirements of this subpart including the maximum
contaminant levels for the PFAS identified in Sec. 141.61(c).
[[Page 32751]]
(b) The deadlines for complying with the provisions of this subpart
are as follows:
(1) Each system must meet the analytical requirements in Sec.
141.901 by June 25, 2024.
(2) Each system must report the results of initial monitoring, as
described in Sec. 141.902(b)(1), to the State by April 26, 2027.
(3) Each system must meet the compliance monitoring requirements in
Sec. 141.902(b)(2) by April 26, 2027.
(4) Each system must meet the MCL compliance requirements in Sec.
141.903 by April 26, 2029.
(5) Each system must meet the reporting and recordkeeping
requirements in Sec. 141.904 by April 26, 2027.
(6) Violations described in Sec. 141.905 include monitoring and
reporting violations and violations of MCLs. Monitoring and reporting
violations may be assessed beginning on April 26, 2027. MCL violations
may be assessed beginning on April 26, 2029.
Sec. 141.901 Analytical requirements.
(a) General. (1) Systems must use only the analytical methods
specified in this section to demonstrate compliance with the
requirements of this subpart.
(2) The following documents are incorporated by reference with the
approval of the Director of the Federal Register in accordance with 5
U.S.C. 552(a) and 1 CFR part 51. This material is available for
inspection at the EPA and at the National Archives and Records
Administration (NARA). Contact the EPA's Drinking Water Docket at: 1301
Constitution Avenue NW., EPA West, Room 3334, Washington, DC 20460;
phone: 202-566-2426. For information on the availability of this
material at NARA, email: [email protected], or go to:
www.archives.gov/federal-register/cfr/ibr-locations. The material may
be obtained from the EPA at 1301 Constitution Avenue NW, the EPA West,
Room 3334, Washington, DC 20460; phone: 202-566-2426; website: https://www.epa.gov/pfas/epa-pfas-drinking-water-laboratory-methods.
(i) EPA Method 533: Determination of Per- and Polyfluoroalkyl
Substances in Drinking Water by Isotope Dilution Anion Exchange Solid
Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry,
815-B-19-020, November 2019.
(ii) Method 537.1, Version 2.0: Determination of Selected Per- and
Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase
Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/
MS), EPA/600/R-20/006, March 2020.
(b) PFAS-(1) Analytical methods. Systems must measure regulated
PFAS by the methods listed in the following table:
Table 1 to Paragraph (b)(1)--Analytical Methods for PFAS Contaminants
------------------------------------------------------------------------
EPA method
(incorporated by
Contaminant Methodology reference, see
paragraph (a) of
this section)
------------------------------------------------------------------------
Perfluorobutane Sulfonate (PFBS) SPE LC-MS/MS...... 533, 537.1,
version 2.0.
Perfluorohexane Sulfonate SPE LC-MS/MS...... 533, 537.1,
(PFHxS). version 2.0.
Perfluorononanoate (PFNA)....... SPE LC-MS/MS...... 533, 537.1,
version 2.0.
Perfluorooctanesulfonic Acid SPE LC-MS/MS...... 533, 537.1,
(PFOS). version 2.0.
Perfluorooctanoic Acid (PFOA)... SPE LC-MS/MS...... 533, 537.1,
version 2.0.
2,3,3,3-Tetrafluoro-2- SPE LC-MS/MS...... 533, 537.1,
(heptafluoropropoxy)propanoate version 2.0.
(HFPO-DA or GenX Chemicals).
------------------------------------------------------------------------
(2) Laboratory certification. Analyses under this section for
regulated PFAS must only be conducted by laboratories that have been
certified by EPA or the State. To receive certification to conduct
analyses for the regulated PFAS, the laboratory must:
(i) Analyze Performance Evaluation (PE) samples that are acceptable
to the State at least once during each consecutive 12-month period by
each method for which the laboratory desires certification.
(ii) Beginning June 25, 2024, achieve quantitative results on the
PE sample analyses that are within the following acceptance limits:
Table 2 to Paragraph (b)(2)(ii)--Acceptance Limits for PFAS Performance
Evaluation Samples
------------------------------------------------------------------------
Acceptance
limits
Contaminant (percent of
true value)
------------------------------------------------------------------------
Perfluorobutane Sulfonate (PFBS)........................ 70-130
Perfluorohexane Sulfonate (PFHxS)....................... 70-130
Perfluorononanoate (PFNA)............................... 70-130
Perfluorooctanesulfonic Acid (PFOS)..................... 70-130
Perfluorooctanoic Acid (PFOA)........................... 70-130
2,3,3,3-Tetrafluoro-2-(heptafluoropropoxy)propanoate 70-130
(HFPO-DA or GenX Chemicals)............................
------------------------------------------------------------------------
(iii) For all samples analyzed for regulated PFAS in compliance
with Sec. 141.902, beginning June 25, 2024, report data for
concentrations as low as the trigger levels as defined in Sec.
141.902(a)(5).
Sec. 141.902 Monitoring requirements.
(a) General requirements. (1) Systems must take all samples during
normal operating conditions at all entry points to the distribution
system.
(2) If the system draws water from more than one source and the
sources are combined before distribution, the system must sample at an
entry point to the distribution system during periods of representative
operating conditions.
(3) Systems must use only data collected under the provisions of
this subpart to qualify for reduced monitoring.
(4) All new systems that begin operation after, or systems that use
a new source of water after April 26, 2027, must demonstrate compliance
with the MCLs within a period of time specified by the State. A system
must also comply with initial sampling frequencies required by the
State to ensure that the system can demonstrate compliance with the
MCLs. Compliance monitoring frequencies must be conducted in accordance
with the requirements in this section.
[[Page 32752]]
(5) For purposes of this section, the trigger levels are defined as
shown in the following table.
Table 1 to Paragraph (a)(5)--Trigger Levels for PFAS Contaminants
------------------------------------------------------------------------
Contaminant Trigger level
------------------------------------------------------------------------
Hazard Index PFAS (HFPO-DA, PFBS, PFHxS, 0.5 (unitless).
PFNA).
HFPO-DA................................... 5 nanograms per liter (ng/
l).
PFHxS..................................... 5 ng/l.
PFNA...................................... 5 ng/l.
PFOA...................................... 2.0 ng/l.
PFOS...................................... 2.0 ng/l.
------------------------------------------------------------------------
(6) Based on initial monitoring results, for each sampling point at
which a regulated PFAS listed in Sec. 141.61(c) is detected at a level
greater than or equal to the trigger level, the system must monitor
quarterly for all regulated PFAS beginning April 26, 2027, in
accordance with paragraph (b)(2) of this section.
(7) For purposes of this section, each water system must ensure
that all results provided by a laboratory are reported to the State and
used for determining the required sampling frequencies. This includes
values below the practical quantitation levels defined in Sec.
141.903(f)(1)(iv); zero must not be used in place of reported values.
(b) Monitoring requirements for PFAS--(1) Initial monitoring. (i)
Groundwater CWS and NTNCWS serving greater than 10,000 persons and all
surface water CWS and NTNCWS must take four consecutive samples 2 to 4
months apart within a 12-month period (quarterly samples) for each
regulated PFAS listed in Sec. 141.61(c).
(ii) All groundwater CWS and NTNCWS serving 10,000 or fewer persons
must take two samples for each regulated PFAS listed in Sec. 141.61(c)
five to seven months apart within a 12-month period.
(iii) All groundwater under the direct influence of surface water
(GWUDI) CWS and NTNCWS must follow the surface water CWS and NTNCWS
monitoring schedule in paragraph (b)(1)(i) of this section.
(iv) All systems that use both surface water and groundwater must
apply the requirements in paragraphs (b)(1)(i) through (iii) of this
section depending on the source(s) of water provided at a given entry
point to the distribution system (EPTDS). If the EPTDS provides surface
water, the requirements for a surface water CWS/NTNCWS apply. If the
EPTDS provides groundwater, the requirements for a groundwater CWS/
NTNCWS apply, based on system size. If an EPTDS provides a blend of
surface water and groundwater, the requirements for a surface water
system apply. For systems that change the source water type at an EPTDS
during the initial monitoring period (i.e., one part of the year it is
surface water and the remaining part of the year it is groundwater),
the sampling requirements for a surface water system apply.
(v) Systems must monitor at a frequency indicated in the following
table, though a State may require more frequent monitoring on a system-
specific basis:
Table 2 to Paragraph (b)(1)(v)--Initial Monitoring Requirements
------------------------------------------------------------------------
Minimum monitoring
Type of system frequency Sample location
------------------------------------------------------------------------
Groundwater CWS and NTNCWS Four consecutive Sampling point
serving greater than 10,000 quarters of samples for EPTDS.
persons, all surface water per entry point to
CWS and NTNCWS, and all GWUDI the distribution
systems. system (EPTDS) within
a 12-month period,
unless the exception
in paragraph
(b)(1)(viii) of this
section applies.
Samples must be taken
two to four months
apart..
Groundwater CWS and NTNCWS Two consecutive Sampling point
serving 10,000 or fewer samples per EPTDS for EPTDS.
persons. within a 12-month
period, unless the
exception in
paragraph
(b)(1)(viii) of this
section applies.
Samples must be taken
five to seven months
apart..
------------------------------------------------------------------------
(vi) A State may accept data that has been previously acquired by a
water system to count toward the initial monitoring requirements if the
data meet the requirements of Sec. 141.901(b)(1), samples were
collected starting on or after January 1, 2019, and otherwise meet the
timing requirements specified in table 2 to paragraph (b)(1)(v) of this
section. For the purposes of satisfying initial monitoring
requirements, acceptable data may be reported to a concentration no
greater than the MCLs. However, a system is only eligible for triennial
monitoring at the start of the compliance monitoring period if the
system demonstrates that concentrations in all samples it uses to
satisfy the initial monitoring requirements are below the trigger
levels as defined in paragraph (a)(5) of this section.
(vii) If systems have multiple years of data, the most recent data
must be used.
(viii) For systems using previously acquired data that have fewer
than the number of samples required in a continuous 12-month period for
initial monitoring as listed in table 2 to paragraph (b)(1)(v) of this
section: All surface water systems, GWUDI systems, and groundwater
systems serving greater than 10,000 persons must collect in a calendar
year one sample in each quarter that was not represented, two to four
months apart from the months with available data; All groundwater
systems serving 10,000 or fewer persons must collect one sample in the
month that is five to seven months apart from the month in which the
previous sample was taken.
(ix) In determining the most recent data to report, a system must
include all results provided by a laboratory whether above or below the
practical quantitation levels. These results must be used for the
purposes of determining the frequency with which a system must monitor
at that sampling point at the start of the compliance monitoring
period.
(x) States may delete results of obvious sampling errors. If the
State deletes a result because of an obvious sampling error and the
system fails to collect another sample this is a monitoring violation
as described in Sec. 141.905(c).
(xi) Initial monitoring requirements, including reporting results
to the State, must be completed by April 26, 2027.
(2) Compliance monitoring. (i) Based on initial monitoring results,
at the start of the monitoring period that begins on April 26, 2027,
systems may reduce monitoring at each sampling point at which all
reported sample concentrations were below all trigger levels defined in
paragraph (a)(5) of this section, unless otherwise provided for by the
State. At eligible sampling points,
[[Page 32753]]
each water system must analyze one sample for all regulated PFAS during
each three-year monitoring period, at a time specified by the State, in
the quarter in which the highest analytical result was detected during
the most recent round of quarterly or semi-annual monitoring. If a
sampling point is not eligible for triennial monitoring, then the water
system must monitor quarterly at the start of the compliance monitoring
period.
(ii) If, during the compliance monitoring period, a system is
monitoring triennially and a PFAS listed in Sec. 141.61(c) is detected
at a level equal to or exceeding the trigger levels defined in
paragraph (a)(5) of this section in any sample, then the system must
monitor quarterly for all regulated PFAS beginning in the next quarter
at the sampling point. The triggering sample must be used as the first
quarter of monitoring for the running annual average calculation.
(iii) For all source water types, a State may determine that all
regulated PFAS at a sampling point are reliably and consistently below
the MCL after considering, at a minimum, four consecutive quarterly
samples collected during the compliance monitoring period. A sampling
point that a State has determined to be reliably and consistently below
the MCL is required to collect annual samples for at least the first
three years after that determination is made. Annual samples must be
collected in the quarter in which detected concentrations were highest
during the most recent year of quarterly monitoring. If, after three
consecutive years, annual samples all contain results that are below
the trigger levels defined in paragraph (a)(5) of this section, the
State may allow a system to begin triennial monitoring at the sampling
point. The water system must collect triennial samples in the quarter
with the highest concentrations during the most recent round of
quarterly sampling. If an annual sample meets or exceeds an MCL or the
State determines that the result is not reliably and consistently below
the MCL for all regulated PFAS, then the system must monitor quarterly
for all regulated PFAS beginning in the next quarter at the sampling
point.
(iv) The three different compliance monitoring sampling schedules
that may be assigned and the criteria for each are summarized in the
following table:
Table 3 to paragraph (b)(2)(iv)--Compliance Monitoring Schedules
and Requirements
----------------------------------------------------------------------------------------------------------------
Sampling frequency Eligibility requirements \1\ Sample timing requirements
----------------------------------------------------------------------------------------------------------------
Triennial............................. At an individual sampling point, either: Sample must be collected at a
(1) All initial monitoring results time within the three-year
demonstrate concentrations of all period designated by the
regulated PFAS below trigger levels;. State, in the quarter that
(2) The most recent three consecutive yielded the highest
annual monitoring results all analytical result during the
demonstrated concentrations of all most recent round of
regulated PFAS below trigger levels; or. quarterly sampling (or the
(3) The previous triennial sample most recent semi-annual
demonstrated all regulated PFAS sampling, if no quarterly
concentrations below trigger levels.. sampling has occurred).
Note: After beginning compliance
monitoring, a system may not transition
directly from quarterly monitoring to
triennial monitoring..
Annual................................ A State makes a determination that all Sample must be collected at a
regulated PFAS concentrations at the time designated by the State,
sampling point are reliably and within the quarter that
consistently below PFAS MCLs, after yielded the highest
considering, at a minimum, 4 analytical result during the
consecutive quarterly samples collected most recent round of
during the compliance monitoring quarterly sampling.
period..
Quarterly............................. At an individual sampling point, either: Samples must be collected in
(1) Any regulated PFAS concentration four consecutive quarters, on
meets or exceeds a trigger level during dates designated by the
initial monitoring;. State.
(2) Sampling is occurring quarterly
during compliance monitoring and a
State has not made a determination that
all levels of regulated PFAS at the
sampling point are reliably and
consistently below the regulated PFAS
MCLs; or.
(3) A sample collected by a system
required to conduct triennial
monitoring contains regulated PFAS
concentrations that meet or exceed
trigger levels. The first of these
samples meeting or exceeding the
trigger level is considered the first
quarterly sample..
(4) A sample collected by a system
required to conduct annual monitoring
contains regulated PFAS concentrations
that meet or exceed an MCL. The first
of these samples meeting or exceeding
the MCL is considered the first
quarterly sample..
----------------------------------------------------------------------------------------------------------------
\1\ The monitoring frequency at a sampling point must be the same for all regulated PFAS and is determined based
on the most frequent sampling required for any regulated PFAS detected at a level at or exceeding the trigger
level.
(v) The State may require a confirmation sample for any sampling
result. If a confirmation sample is required by the State, the system
must average the result with the first sampling result and the average
must be used for the determination of compliance with MCLs as specified
by Sec. 141.903. A State may delete results of obvious sampling errors
from the MCL compliance calculations described in Sec. 141.903. If the
State deletes a result because of an obvious sampling error and the
system fails to collect another sample this is a monitoring violation
as described in Sec. 141.905(c).
(vi) The State may increase the required monitoring frequency,
where necessary, to detect variations within the system (e.g.,
fluctuations in concentration due to seasonal use, changes in water
source).
(vii) Each public water system must monitor at the time designated
by the State within each monitoring period.
(viii) When a system reduces its sampling frequency to annual or
triennial sampling, the next compliance sample must be collected in the
monitoring period that begins the calendar year following State
approval of a reduction in monitoring frequency.
Sec. 141.903 Compliance requirements.
(a) Compliance with MCLs for regulated PFAS in Sec. 141.61(c) must
be determined based on the analytical results obtained at each sampling
point.
[[Page 32754]]
(b) For systems monitoring quarterly, compliance with the MCL is
determined by the running annual average at each sampling point.
(c) If a system fails to collect the required number of samples
specified in Sec. 141.902, this is a monitoring violation as described
in Sec. 141.905(c), and compliance calculations must be based on the
total number of samples collected.
(d) Systems monitoring triennially whose sample result equals or
exceeds the trigger level of 2.0 ng/l for either PFOS or PFOA, 5 ng/l
for HFPO-DA, PFHxS, or PFNA, or a Hazard Index of 0.5 for the Hazard
Index PFAS, must begin quarterly sampling for all regulated PFAS in the
next quarter at the sampling point. Systems monitoring annually whose
sample result equals or exceeds the MCL of 4.0 ng/l for either PFOS or
PFOA, 10 ng/l for HFPO-DA, PFHxS, or PFNA, or a Hazard Index of 1 for
the Hazard Index PFAS, must begin quarterly sampling for all regulated
PFAS in the next quarter at the sampling point.
(e) Except as provided in this paragraph (e), if a sample result
exceeds an MCL, the system will not be considered in violation of the
MCL until it has completed one year of quarterly sampling at the
sampling point with the triggering sample used as the first quarter of
monitoring for the running annual average calculation. However,
whenever a sample result in any quarter (or quarterly average, if more
than one compliance sample is available in a quarter because a
confirmation sample was required by the State) causes the running
annual average to exceed the MCL at a sampling point regardless of the
subsequent quarterly monitoring results required to complete a full
year of monitoring (e.g., the results from a single sample are more
than 4 times the MCL), the system is out of compliance with the MCL
immediately.
(f) Systems must calculate compliance using the following method to
determine MCL compliance at each sampling point:
(1) For each PFAS regulated by an individual MCL:
(i) For systems monitoring quarterly, divide the sum of the
measured quarterly concentrations for each analyte by the number of
quarters samples were collected for that analyte during the consecutive
quarters included in the calculation. If more than one compliance
sample for that analyte is available in a quarter because a
confirmation sample was required by the State, systems must average all
the results in a quarter then average the quarterly averages. Rounding
does not occur until the end of the calculation. If the running annual
average exceeds the MCL, the system is not in compliance with the MCL
requirements.
(ii) For systems monitoring annually, if the concentration measured
is equal to or exceeds an MCL for regulated PFAS, the system is
required to initiate quarterly monitoring for all regulated PFAS
beginning in the next quarter at the sampling point, with the
triggering sample result used as the first quarter of monitoring for
the running annual average calculation.
(iii) For systems monitoring triennially, if the concentration
measured is equal to or exceeds the trigger level, the system is
required to initiate quarterly monitoring for all regulated PFAS
beginning in the next quarter at the sampling point, with the
triggering sample result used as the first quarter of monitoring for
the running annual average calculation.
(iv) For the purpose of calculating MCL compliance, if a sample
result is less than the practical quantitation level (PQL) for a
regulated PFAS, in accordance with the following table, zero is used
for that analyte solely to calculate the running annual average.
Table 1 to Paragraph (f)(1)(iv)--Practical Quantitation Levels (PQLs)
for PFAS Contaminants
------------------------------------------------------------------------
PQL (in parts
Contaminant per trillion)
------------------------------------------------------------------------
HFPO-DA................................................. 5.0
PFBS.................................................... 3.0
PFHxS................................................... 3.0
PFNA.................................................... 4.0
PFOA.................................................... 4.0
PFOS.................................................... 4.0
------------------------------------------------------------------------
(2) For each PFAS regulated under the Hazard Index MCL:
(i) For systems monitoring quarterly, divide the observed sample
analytical result for each analyte included in the Hazard Index by the
corresponding HBWC listed in Sec. 141.61(c) to obtain a hazard
quotient for each analyte for each sampling event at each sampling
point. Sum the resulting hazard quotients together to determine the
Hazard Index for the quarter. If the State requires a confirmation
sample for an analyte in the quarter, systems must average these
results for each analyte in that quarter and then determine the hazard
quotient(s) from those average values, then sum the hazard quotients.
Once the Hazard Indices for the individual quarters are calculated,
they are averaged to determine a running annual average. If the running
annual average Hazard Index exceeds the MCL and two or more Hazard
Index analytes had an observed sample analytical result at or above the
PQL in any of the quarterly samples collected to determine the running
annual average, the system is in violation of the Hazard Index MCL. No
rounding occurs until after the running annual average Hazard Index is
calculated.
(ii) If the Hazard Index calculated using the results of an annual
sample equals or exceeds the Hazard Index MCL, the system must initiate
quarterly sampling for all regulated PFAS beginning in the next quarter
at the sampling point, with the triggering sample result used as the
first quarter of monitoring.
(iii) If the Hazard Index calculated using the results of a
triennial sample equals or exceeds the Hazard Index trigger level, the
system must initiate quarterly sampling for all regulated PFAS
beginning in the next quarter at the sampling point, with the
triggering sample result used as the first quarter of monitoring.
(iv) If a sample result is less than the practical quantitation
level for a regulated PFAS, in accordance with the table 1 to paragraph
(f)(1)(iv) of this section, zero is used for that analyte solely to
calculate the running annual average.
Sec. 141.904 Reporting and recordkeeping requirements.
Systems required to sample must report to the State according to
the timeframes and provisions of Sec. 141.31 and retain records
according to the provisions in Sec. 141.33.
(a) Systems must report the information from initial monitoring
specified in the following table:
[[Page 32755]]
Table 1 to Paragraph (a)--Data To Report From Initial Monitoring
------------------------------------------------------------------------
If you are a . . . You must report . . .
------------------------------------------------------------------------
System monitoring for regulated PFAS 1. All sample results,
under the requirements of Sec. including the locations,
141.902(b)(1) on a quarterly basis. number of samples taken at
each location, dates, and
concentrations reported.
2. Whether a trigger level,
defined in Sec.
141.902(a)(5), was met or
exceeded in any samples.
System monitoring for regulated PFAS 1. All sample results,
under the requirements of Sec. including the locations,
141.902(b)(1) less frequently than number of samples taken at
quarterly. each location, dates, and
concentrations reported.
2. Whether a trigger level,
defined in Sec.
141.902(a)(5), was met or
exceeded in any samples.
------------------------------------------------------------------------
(b) Systems must report the information collected during the
compliance monitoring period specified in the following table:
Table 2 to Paragraph (b)--Data To Report From Compliance Monitoring
------------------------------------------------------------------------
If you are a . . . You must report . . .
------------------------------------------------------------------------
System monitoring for regulated PFAS 1. All sample results,
under the requirements of Sec. including the locations,
141.902(b)(2) on a quarterly basis. number of samples taken at
each location, dates, and
concentrations during the
previous quarter.
2. The running annual average
at each sampling point of all
compliance samples.
3. Whether a trigger level,
defined in Sec.
141.902(a)(5), was met or
exceeded in any samples.
4. Whether an MCL for a
regulated PFAS in Sec.
141.61(c) was met or exceeded
in any samples.
5. Whether, based on Sec.
141.903, an MCL was violated.
System monitoring for regulated PFAS 1. All sample results,
under the requirements of Sec. including the locations,
141.902(b)(2) less frequently than number of samples taken at
quarterly. each location, dates, and
concentrations during the
previous monitoring period.
2. Whether a trigger level,
defined in Sec.
141.902(a)(5), was met or
exceeded in any samples.
3. Whether an MCL for a
regulated PFAS in Sec.
141.61(c) was met or exceeded
in any samples.
4. Whether, based on Sec.
141.903, an MCL was violated
(e.g., the results from a
single sample are more than 4
times the MCL).
------------------------------------------------------------------------
Sec. 141.905 Violations.
(a) PFAS MCL violations, both for the individual PFOA, PFOS, HFPO-
DA, PFHxS, and PFNA MCLs, as well as the Hazard Index MCL, as listed in
Sec. 141.61(c), are based on a running annual average, as outlined
under Sec. 141.903.
(b) Compliance with Sec. 141.61(c) must be determined based on the
analytical results obtained at each sampling point. If one sampling
point is in violation of an MCL, the system is in violation of the MCL.
(c) Each failure to monitor in accordance with the requirements
under Sec. 141.902 is a monitoring violation.
(d) Failure to notify the State following a MCL violation and
failure to submit monitoring data in accordance with the requirements
of Sec. Sec. 141.904 and 141.31 are reporting violations.
(e) Results for PFAS with individual MCLs as listed in Sec.
141.61(c) are compared to their respective MCLs, and results for
mixtures of two or more of the Hazard Index PFAS (HFPO-DA, PFBS, PFHxS,
and PFNA) are compared to the Hazard Index MCL as listed in Sec.
141.61(c). For determining compliance with the Hazard Index MCL, if
only PFBS is reported at any concentration and no other regulated PFAS
are in the mixture, it is not violation of the Hazard Index MCL. If
only one of the other PFAS within the Hazard Index (HFPO-DA, PFHxS, and
PFNA) is detected and the level of this PFAS exceeds its MCL as
determined by Sec. 141.903(f)(1)(i), only an individual MCL violation
is assessed for the individual PFAS detected, and it is not a violation
of the Hazard Index MCL. Exceedances of the Hazard Index caused by two
or more of the Hazard Index PFAS (HFPO-DA, PFBS, PFHxS, and PFNA) and
exceedances of one or more individual MCLs can result in multiple MCL
exceedances. However, in this instance, for purposes of public
notification under appendix A to subpart Q of this part, a PWS must
only report the Hazard Index MCL exceedance.
PART 142--NATIONAL PRIMARY DRINKING WATER REGULATIONS
IMPLEMENTATION
0
16. The authority citation for part 142 continues to read as follows:
Authority: 42 U.S.C. 300f, 300g-1, 300g-2, 300g-3, 300g-4,
300g-5, 300g-6, 300j-4, 300j-9, and 300j-11.
0
17. Amend Sec. 142.16 by adding paragraph (r) to read as follows:
Sec. 142.16 Special primacy requirements.
* * * * *
(r) Requirements for States to adopt 40 CFR part 141, subpart Z,
PFAS. In addition to the general primacy requirements elsewhere in this
part, including the requirements that State regulations be at least as
stringent as Federal requirements, an application for approval of a
State program revision that adopts 40 CFR part 141, subpart Z, must
contain the following, in lieu of meeting the requirements of paragraph
(e) of this section:
(1) The State's procedures for reviewing the water system's use of
pre-existing data to meet the initial
[[Page 32756]]
monitoring requirements specified in Sec. 141.902, including the
criteria that will be used to determine if the data are acceptable.
This paragraph (r)(1) is no longer applicable after the initial
monitoring period ends on April 26, 2027.
(2) The State's procedures for ensuring all systems complete the
initial monitoring period requirements that will result in a high
degree of monitoring compliance by the regulatory deadlines. This
paragraph (r)(2) is no longer applicable after the initial monitoring
period ends on April 26, 2027.
(3) After the initial monitoring period, States establish the
initial monitoring requirements for new public water systems and
existing public water systems that plan to use a new source. States
must explain their initial monitoring schedules and how these
monitoring schedules ensure that new public water systems and existing
public water systems that plan to use new sources comply with MCLs and
monitoring requirements. States must also specify the time frame in
which a new system or existing system that plans to use a new source
must demonstrate compliance with the MCLs.
0
18. Amend Sec. 142.62 by revising and republishing paragraph (a) to
read as follows:
Sec. 142.62 Variances and exemptions from the maximum contaminant
levels for organic and inorganic chemicals.
(a) The Administrator, pursuant to section 1415(a)(1)(A) of the
Act, hereby identifies the technologies listed in tables 1 and 2 to
this paragraph (a) as the best available technology, treatment
techniques, or other means available for achieving compliance with the
maximum contaminant levels for the organic chemicals, including per-
and polyfluoroalkyl substances (PFAS), listed in Sec. 141.61(a) and
(c) of this chapter, for the purposes of issuing variances and
exemptions. A list of small system compliance technologies for the
regulated PFAS for the purposes of providing variances and exemptions
is provided in table 3 to this paragraph (a); for the purpose of this
paragraph (a), small system is defined as a system serving 10,000
persons or fewer.
Table 1 to Paragraph (a)--BATs for PFAS Listed in Sec. 141.61(c)
------------------------------------------------------------------------
Contaminant BAT
------------------------------------------------------------------------
Hazard Index PFAS (HFPO-DA, PFBS, Anion exchange, GAC, reverse
PFHxS, and PFNA). osmosis, nanofiltration.
HFPO-DA................................ Anion exchange, GAC, reverse
osmosis, nanofiltration.
PFHxS.................................. Anion exchange, GAC, reverse
osmosis, nanofiltration.
PFNA................................... Anion exchange, GAC, reverse
osmosis, nanofiltration.
PFOA................................... Anion exchange, GAC, reverse
osmosis, nanofiltration.
PFOS................................... Anion exchange, GAC, reverse
osmosis, nanofiltration.
------------------------------------------------------------------------
Table 2 to Paragraph (a)--BATs for Other Synthetic Organic Contaminants Listed in Sec. 141.61(c) and Volatile
Organic Chemicals Listed in Sec. 141.61(a)
----------------------------------------------------------------------------------------------------------------
Best available technologies
Contaminant -----------------------------------------------
PTA \1\ GAC \2\ OX \3\
----------------------------------------------------------------------------------------------------------------
(1) Benzene..................................................... X X
(2) Carbon tetrachloride........................................ X X
(3) 1,2-Dichloroethane.......................................... X X
(4) Trichloroethylene........................................... X X
(5) para-Dichlorobenzene........................................ X X
(6) 1,1-Dichloroethylene........................................ X X
(7) 1,1,1-Trichloroethane....................................... X X
(8) Vinyl chloride.............................................. X
(9) cis-1,2-Dichloroethylene.................................... X X
(10) 1,2-Dichloropropane........................................ X X
(11) Ethylbenzene............................................... X X
(12) Monochlorobenzene.......................................... X X
(13) o-Dichlorobenzene.......................................... X X
(14) Styrene.................................................... X X
(15) Tetrachloroethylene........................................ X X
(16) Toluene.................................................... X X
(17) trans-1,2-Dichloroethylene................................. X X
(18) Xylense (total)............................................ X X
(19) Alachlor................................................... .............. X
(20) Aldicarb................................................... .............. X
(21) Aldicarb sulfoxide......................................... .............. X
(22) Aldicarb sulfone........................................... .............. X
(23) Atrazine................................................... .............. X
(24) Carbofuran................................................. .............. X
(25) Chlordane.................................................. .............. X
(26) Dibromochloropropane....................................... X X
(27) 2,4-D...................................................... .............. X
(28) Ethylene dibromide......................................... X X
(29) Heptachlor................................................. .............. X
(30) Heptachlor epoxide......................................... .............. X
(31) Lindane.................................................... .............. X
(32) Methoxychlor............................................... .............. X
(33) PCBs....................................................... .............. X
(34) Pentachlorophenol.......................................... .............. X
[[Page 32757]]
(35) Toxaphene.................................................. .............. X
(36) 2,4,5-TP................................................... .............. X
(37) Benzo[a]pyrene............................................. .............. X
(38) Dalapon.................................................... .............. X
(39) Dichloromethane............................................ X
(40) Di(2-ethylhexyl)adipate.................................... X X
(41) Di(2-ethylhexyl)phthalate.................................. .............. X
(42) Dinoseb.................................................... .............. X
(43) Diquat..................................................... .............. X
(44) Endothall.................................................. .............. X
(45) Endrin..................................................... .............. X
(46) Glyphosate................................................. .............. .............. X
(47) Hexachlorobenzene.......................................... .............. X
(48) Hexachlorocyclopentadiene.................................. X X
(49) Oxamyl (Vydate)............................................ .............. X
(50) Picloram................................................... .............. X
(51) Simazine................................................... .............. X
(52) 1,2,4-Trichlorobenzene..................................... X X
(53) 1,1,2-Trichloroethane...................................... X X
(54) 2,3,7,8-TCDD (Dioxin)...................................... .............. X
----------------------------------------------------------------------------------------------------------------
\1\ Packed Tower Aeration.
\2\ Granular Activated Carbon.
\3\ Oxidation (Chlorination or Ozonation).
Table 3 to Paragraph (a)--List of Small System Compliance Technologies
(SSCTs) \1\ for PFAS Listed in Sec. 141.61(c)
------------------------------------------------------------------------
Affordable for listed small
Small system compliance technologies system categories \2\
------------------------------------------------------------------------
Anion Exchange............................ All size categories.
GAC....................................... All size categories.
Reverse Osmosis,\3\ Nanofiltration \3\.... 3,301-10,000.
------------------------------------------------------------------------
\1\ Section 1412(b)(4)(E)(ii) of SDWA specifies that SSCTs must be
affordable and technically feasible for small systems.
\2\ The Act (ibid.) specifies three categories of small systems: (i)
those serving 25 or more, but fewer than 501, (ii) those serving more
than 500, but fewer than 3,301, and (iii) those serving more than
3,300, but fewer than 10,001.
\3\ Technologies reject a large volume of water and may not be
appropriate for areas where water quantity may be an issue.
* * * * *
[FR Doc. 2024-07773 Filed 4-25-24; 8:45 am]
BILLING CODE 6560-50-P