[Federal Register Volume 88, Number 60 (Wednesday, March 29, 2023)]
[Proposed Rules]
[Pages 18638-18754]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-05471]
[[Page 18637]]
Vol. 88
Wednesday,
No. 60
March 29, 2023
Part II
Environmental Protection Agency
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40 CFR Parts 141 and 142
PFAS National Primary Drinking Water Regulation Rulemaking; Proposed
Rule
Federal Register / Vol. 88, No. 60 / Wednesday, March 29, 2023 /
Proposed Rules
[[Page 18638]]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 141 and 142
[EPA-HQ-OW-2022-0114; FRL 8543-01-OW]
RIN 2040-AG18
PFAS National Primary Drinking Water Regulation Rulemaking
AGENCY: Environmental Protection Agency (EPA).
ACTION: Preliminary regulatory determination and proposed rule; request
for public comment; notice of public hearing.
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SUMMARY: The Environmental Protection Agency (EPA) is committed to
using and advancing the best available science to tackle per- and
polyfluoroalkyl substances (PFAS) pollution, protect public health, and
harmonize policies that strengthen public health protections with
infrastructure funding to help communities, especially disadvantaged
communities, deliver safe drinking water. In March 2021, EPA issued a
final regulatory determination to regulate perfluorooctanoic acid
(PFOA) and perfluorooctane sulfonic acid (PFOS) as contaminants under
Safe Drinking Water Act (SDWA). In this notice, EPA is issuing a
preliminary regulatory determination to regulate perfluorohexane
sulfonic acid (PFHxS), hexafluoropropylene oxide dimer acid (HFPO-DA)
and its ammonium salt (also known as a GenX chemicals),
perfluorononanoic acid (PFNA), and perfluorobutane sulfonic acid
(PFBS), and mixtures of these PFAS as contaminants under SDWA. Through
this action, EPA is also proposing a National Primary Drinking Water
Regulation (NPDWR) and health-based Maximum Contaminant Level Goals
(MCLG) for these four PFAS and their mixtures as well as for PFOA and
PFOS. EPA is proposing to set the health-based value, the MCLG, for
PFOA and PFOS at zero. Considering feasibility, including currently
available analytical methods to measure and treat these chemicals in
drinking water, EPA is proposing individual MCLs of 4.0 nanograms per
liter (ng/L) or parts per trillion (ppt) for PFOA and PFOS. EPA is
proposing to use a Hazard Index (HI) approach to protecting public
health from mixtures of PFHxS, HFPO-DA and its ammonium salt, PFNA, and
PFBS because of their known and additive toxic effects and occurrence
and likely co-occurrence in drinking water. EPA is proposing an HI of
1.0 as the MCLGs for these four PFAS and any mixture containing one or
more of them because it represents a level at which no known or
anticipated adverse effects on the health of persons is expected to
occur and which allows for an adequate margin of safety. EPA has
determined it is also feasible to set the MCLs for these four PFAS and
for a mixture containing one or more of PFHxS, HFPO-DA and its ammonium
salt, PFNA, PFBS as an HI of unitless 1.0. The Agency is requesting
comment on this action, including this proposed NPDWR and MCLGs, and
have identified specific areas where public input will be helpful for
EPA in developing the final rule. In addition to seeking written input,
the EPA will be holding a public hearing on May 4, 2023.
DATES: Comments must be received on or before May 30, 2023. Comments on
the information collection provisions submitted to the Office of
Management and Budget (OMB) under the Paperwork Reduction Act (PRA) are
best assured of consideration by OMB if OMB receives a copy of your
comments on or before April 28, 2023. Public hearing: EPA will hold a
virtual public hearing on May 4, 2023, at https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas. Please refer to the SUPPLEMENTARY
INFORMATION section for additional information on the public hearing.
ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OW-2022-0114 by any of the following methods:
Federal eRulemaking Portal: https://www.regulations.gov/
(our preferred method). Follow the online instructions for submitting
comments.
Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Office of Ground Water and Drinking Water Docket, Mail Code
2822IT, 1200 Pennsylvania Avenue NW, Washington, DC 20460.
Hand Delivery or Courier: EPA Docket Center, WJC West
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004.
The Docket Center's hours of operations are 8:30 a.m. to 4:30 p.m.,
Monday through Friday (except Federal Holidays).
Instructions: All submissions received must include the Docket ID
No. for this rulemaking. Comments received may be posted without change
to https://www.regulations.gov/, including any personal information
provided. For detailed instructions on sending comments and additional
information on the rulemaking process, see the ``Public Participation''
heading of the SUPPLEMENTARY INFORMATION section of this document.
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
In March 2021, EPA issued a final regulatory determination to
regulate perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic
acid (PFOS) as contaminants under Safe Drinking Water Act (SDWA). EPA
is issuing a preliminary regulatory determination to regulate
perfluorohexane sulfonic acid (PFHxS), hexafluoropropylene oxide dimer
acid (HFPO-DA) and its ammonium salt (also known as a GenX chemicals),
perfluorononanoic acid (PFNA), and perfluorobutane sulfonic acid
(PFBS), and mixtures of these PFAS as contaminants under SDWA (see
section III of this preamble for additional discussion on EPA's
preliminary regulatory determination). Through this action, EPA is also
proposing a National Primary Drinking Water Regulation (NPDWR) and
health-based Maximum Contaminant Level Goals (MCLG) for these four PFAS
and their mixtures as well as for PFOA and PFOS. Exposure to these PFAS
may cause adverse health effects, and all are likely to occur in
drinking water.
PFAS are a large family of synthetic chemicals that have been in
use since the 1940s. Many of these compounds have unique physical and
chemical properties that make them highly stable and resistant to
degradation in the environment--colloquially termed ``forever
chemicals.'' People can be exposed to PFAS through certain consumer
products, occupational contact, and/or by consuming food and drinking
water that contain PFAS (see section II.C of this preamble for
additional discussion on PFAS chemistry, production, and uses). Current
scientific evidence indicates that consuming water containing the PFAS
covered in this proposed regulation above certain levels can result in
harmful health effects. Depending on the individual PFAS, health
effects can include negative impacts on fetal growth after exposure
during pregnancy, on other aspects of development, reproduction, liver,
thyroid, immune function, and/or the nervous system; and increased risk
of cardiovascular and/or certain types of cancers, and other health
impacts (see
[[Page 18639]]
section II.B and III.B of this preamble for additional discussion on
health effects).
This proposed PFAS drinking water regulation contains several key
features. Based on a review of the best available health effects data,
EPA is proposing MCLGs that address six PFAS. An MCLG is the maximum
level of a contaminant in drinking water at which no known or
anticipated adverse effect on the health of persons would occur,
allowing an adequate margin of safety. A contaminant means any
``physical, chemical or biological or radiological substance or matter
in water.'' This proposal addresses contaminants and certain mixtures
of contaminants. Through this action, EPA is also proposing enforceable
standards which takes the form of maximum contaminant levels (MCLs) in
this proposed regulation. An MCL is the maximum level allowed of a
contaminant or a group of contaminants (i.e., mixture of contaminants)
in water which is delivered to any user of a public water system (PWS).
The SDWA generally requires EPA to set an MCL ``as close as feasible
to'' the MCLG. EPA has also included monitoring, reporting, and other
requirements to ensure regulated drinking water systems, known as a
PWS, meet the PFAS limits in the regulation.
Following a systematic review of available human epidemiological
and animal toxicity studies, EPA has determined that PFOA and PFOS are
likely to cause cancer (e.g., kidney and liver cancer) and that there
is no dose below which either chemical is considered safe (see section
IV.A and V.A through B of this preamble for additional discussion).
Therefore, EPA is proposing to set the health-based value, the MCLG,
for both of these contaminants at zero. Considering feasibility,
including currently available analytical methods to measure and treat
these chemicals in drinking water, EPA is proposing individual MCLs of
4.0 nanograms per liter (ng/L) or parts per trillion (ppt) for PFOA and
PFOS (see sections VI.C and VIII of this preamble for additional
discussion on the MCLs and practical quantitation limits [PQLs]).
Due to their widespread use and persistence, many PFAS are known to
co-occur in drinking water and the environment--meaning that these
compounds are often found together and in different combinations as
mixtures (see section III.C and VII of this preamble for additional
discussion on occurrence). PFAS 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, and immune and liver
function. Additionally, EPA's examination of health effects information
found that exposure through drinking water to a mixture of PFAS can be
assumed to act in a dose-additive manner (see sections III.B and IV.B
of this preamble for additional discussion on mixture toxicity). This
dose additivity means that low levels of multiple PFAS, that
individually would not likely result in adverse health effects, when
combined in a mixture are expected to result in adverse health effects.
As a result, EPA is proposing to use a Hazard Index (HI) approach to
protecting public health from mixtures of four PFAS: PFHxS, HFPO-DA and
its ammonium salt (also known as GenX chemicals), PFNA, and PFBS
because of their known and additive toxic effects and occurrence and
likely co-occurrence in drinking water. PFOA and PFOS are being
proposed for separate MCLs and not included in the HI because their
individual proposed MCLGs are zero, and the level at which no known or
anticipated adverse effects on the health of persons is expected to
occur is well below current analytical quantitation levels. Based on
our current understanding of health effects, this is not the case for
the other covered PFAS. Because of the analytical limitations for PFOA
and PFOS, the MCL for these two PFAS is set at the lowest feasible
quantitation level and any exceedance of this limit requires action to
protect public health, regardless of any mixture in which they are
found. As a result, EPA is not proposing to include PFOA or PFOS in the
HI.
The HI is a commonly used risk management approach for mixtures of
chemicals (USEPA, 1986a; 2000a). In this approach, a ratio called a
hazard quotient (HQ) is calculated for each of the four PFAS (PFHxS,
HFPO-DA and its ammonium salt (also known as GenX chemicals), PFNA, and
PFBS) by dividing an exposure metric, in this case, the measured level
of each of the four PFAS in drinking water, by a health reference value
for that particular PFAS. For health reference values, in this
proposal, EPA is using Health Based Water Concentration (HBWCs) as
follows: 9.0 ppt for PFHxS, 10.0 ppt for HFPO-DA; 10.0 ppt for PFNA;
and 2000 ppt for PFBS (USEPA, 2023a). The individual PFAS ratios (HQs)
are then summed across the mixture to yield the HI. If the resulting HI
is greater than one (1.0), then the exposure metric is greater than the
health metric and potential risk is indicated. EPA's Science Advisory
Board (SAB) opined that where the health endpoints of the chosen
compounds are similar, it is reasonable to use an HI as ``a reasonable
approach for estimating the potential aggregate health hazards
associated with the occurrence of chemical mixtures in environmental
media.'' (USEPA, 2022a). The HI provides an indication of overall
potential risk of a mixture as well as individual PFAS that are
potential drivers of risk (those PFAS(s) with high(er) ratios of
exposure to health metrics) (USEPA, 2000a; see section IV.B and V.C of
this preamble for additional discussion on the HI and its derivation).
Therefore, EPA is proposing an HI of 1.0 as the MCLGs for these four
PFAS and any mixture containing one or more of them because it
represents a level at which no known or anticipated adverse effects on
the health of persons is expected to occur and which allows for an
adequate margin of safety. EPA has determined it is also feasible to
set the MCLs for these four PFAS and for a mixture containing one or
more of PFHxS, HFPO-DA and its ammonium salt, PFNA, PFBS as an HI of
unitless 1.0 (see sections V.C and VI.B of this preamble for discussion
of the HI MCLG and MCL, respectively).
Monitoring is a core component of a NPDWR and assures that water
systems are providing necessary public health protections (see section
IX of this preamble for additional discussion on monitoring and
compliance requirements). EPA is therefore proposing requirements for
systems to monitor for PFOA, PFOS, PFHxS, HFPO-DA and its ammonium
salt, PFNA, and PFBS in drinking water that build upon EPA's
Standardized Monitoring Framework (SMF) for Synthetic Organic Compounds
(SOCs) where the monitoring frequency for any PWS depends on previous
monitoring results. This proposal includes flexibilities related to
monitoring, including flexibilities for systems to use certain,
previously collected data to satisfy initial monitoring requirements in
this proposal as well as reduced monitoring requirements in certain
circumstances (see section IX.E of this preamble for additional
discussion on monitoring waivers).
In summary, the proposed MCLs for PFOA and PFOS are 4 ng/L
(individually), and the proposed MCL of an HI of 1.0 for any mixture
containing PFHxS, HFPO-DA and its ammonium salt, PFNA, and/or PFBS.
Water systems with PFAS levels that exceed the proposed MCLs would need
to take action to provide safe and reliable drinking water. These
systems may install water treatment or consider other
[[Page 18640]]
options such as using a new uncontaminated source water or connecting
to an uncontaminated water system. Activated carbon, anion exchange
(AIX) and high-pressure membrane technologies have all been
demonstrated to remove PFAS, including PFOA, PFOS, PFHxS, HFPO-DA and
its ammonium salt, PFNA, and PFBS, from drinking water systems. These
treatment technologies can be installed at a water system's treatment
plant and are also available through in-home filter options (see
section XI of this preamble for additional discussion on available
treatment technologies).
As part of its health risk reduction and cost analysis, SDWA
requires an evaluation of quantifiable and nonquantifiable health risk
reduction benefits and costs. SDWA also requires that EPA considers
quantifiable and nonquantifiable health risk reduction benefits from
reductions in co-occurring contaminants. The SDWA also requires that
EPA determine if the benefits of the proposed rule justify the costs.
In accordance with these requirements, the EPA Administrator has
determined that the quantified and nonquantifiable benefits of the
proposed PFAS NPDWR justify the costs (see section XIII of this
preamble for additional discussion on EPA's Health Risk Reduction and
Cost Analysis [HRRCA]). Among other things, EPA evaluated which
entities which would be affected by the rule, quantified costs using
available data and statical models, and described unquantifiable costs.
EPA also quantified benefits by estimating reduced cardiovascular
events (e.g., heart attacks and strokes), developmental impacts to
fetuses and infants, and reduced cases of kidney cancer. EPA has also
quantified benefits by estimating reduced bladder cancer cases caused
by reduced disinfection byproduct (DBP) formation in some systems that
install treatment to meet the requirements of this rule. EPA has also
developed a qualitative summary of benefits expected to result from the
removal of regulated PFAS and additional co-removed PFAS contaminants.
To help communities on the frontlines of PFAS contamination, the
passage of the Infrastructure Investment and Jobs Act, also referred to
as the Bipartisan Infrastructure Law (BIL), invests over $11.7 billion
in the Drinking Water State Revolving Fund (SRF); $4 billion to the
Drinking Water SRF for Emerging Contaminants; and $5 billion to Small,
Underserved, and Disadvantaged Communities Grants. 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.
Public participation and consultations with key stakeholders are
critical in developing an implementable and public health protective
rule. EPA has engaged with many stakeholders and consulted with
entities such as the SAB, and the National Drinking Water Advisory
Council (NDWAC) in developing this proposed rule (see section XV of
this preamble on EPA's Statutory and Executive Order reviews). The
Agency is requesting comment on this action, including this proposed
NPDWR and MCLGs, and have identified specific areas where public input
will be helpful for EPA in developing the final rule (see section XIV
of this preamble on specific topics highlighted for public comment). In
addition to seeking written input, EPA will be holding a public hearing
on May 4th, 2023.
I. Public Participation
A. Written Comments
Submit your comments, identified by Docket ID No. EPA-HQ-OW-2022-
0114, at https://www.regulations.gov (our preferred method), or the
other methods identified in the ADDRESSES section. Once submitted,
comments cannot be edited or removed from the docket. EPA may publish
any comment received to its public docket. Do not submit to EPA's
docket at https://www.regulations.gov any information you consider to
be Confidential Business Information (CBI), Proprietary Business
Information (PBI), or other information whose disclosure is restricted
by statute. Multimedia submissions (audio, video, etc.) must be
accompanied by a written comment. The written comment is considered the
official comment and should include discussion of all points you wish
to make. EPA will generally not consider comments or comment contents
located outside of the primary submission (i.e., on the web, cloud, or
other file sharing system). Please visit https://www.epa.gov/dockets/commenting-epa-dockets for additional submission methods; the full EPA
public comment policy; information about CBI, PBI, or multimedia
submissions; and general guidance on making effective comments.
B. Participation in Virtual Public Hearing
EPA will hold a public hearing on May 4th, 2023, to receive public
comment and will present the proposed requirements of the draft NPDWR.
The hearing will be held virtually from approximately 11 a.m. until 7
p.m. eastern time. EPA will begin registering speakers for the hearing
upon publication of this document in the Federal Register (FR). To
attend and register to speak at the virtual hearing, please use the
online registration form available at https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas. The last day to pre-register to speak
at the hearing will be April 28, 2023. On May 3, 2023, EPA will post a
general agenda for the hearing that will list pre-registered speakers
in approximate order at: https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas. The number of online connections available for the
hearing is limited and will be offered on a first- come, first-served
basis. To submit visual aids to support your oral comment, please
contact [email protected] for guidelines and instructions. Registration
will remain open for the duration of the hearing itself for those
wishing to provide oral comment during unscheduled testimony; however,
early registration is strongly encouraged to ensure proper
accommodations and adequate timing.
EPA will make every effort to follow the schedule as closely as
possible on the day of the hearing; however, please plan for the
hearings to run either ahead of schedule or behind schedule. Please
note that the public hearing may close early if all business is
finished.
EPA encourages commenters to provide EPA with a written copy of
their oral testimony electronically by submitting it to the public
docket at www.regulations.gov, Docket ID: EPA-HQ-OW-2022-0114. Oral
comments will be time limited to allow for maximum participation, which
may result in the full statement not being heard. Therefore, EPA also
recommends submitting the text of your oral comments as written
comments to the rulemaking docket. Any person not making an oral
statement may also submit a written statement. Written statements and
supporting information submitted during the comment period will be
considered with the same weight as oral comments and supporting
information presented at the public hearing.
Please note that any updates made to any aspect of the hearing are
posted online at https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas. While EPA expects the hearing to go forward as set
forth above, please monitor our website or contact [email protected] to
determine if there are any updates. EPA does not
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intend to publish a document in the Federal Register announcing
updates.
If you require any accommodations such as language translation,
captioning, or other special accommodations for the day of the hearing,
please indicate this as a part of your registration and describe your
needs by April 28, 2023. EPA may not be able to arrange accommodations
without advance notice. Please contact [email protected] with any
questions related to the public hearing.
This proposed rule is organized as follows:
I. General Information
A. What is EPA proposing?
B. Does this action apply to me?
II. Background
A. What are PFAS?
B. Definitions
C. Chemistry, Production and Uses
D. Human Health Effects
E. Statutory Authority
F. Statutory Framework and PFAS Regulatory History
G. Bipartisan Infrastructure Law
H. EPA PFAS Strategic Roadmap
III. Preliminary 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. EPA's Preliminary Regulatory Determination Summary for PFHxS,
HFPO-DA, PFNA, and PFBS
F. Request for Comment on EPA's Preliminary Regulatory
Determination for PFHxS, HFPO-DA, PFNA, and PFBS
IV. Approaches to MCLG Derivation
A. Approach to MCLG Derivation for Individual PFAS
B. Approach to MCLG Derivation for a PFAS Mixture
V. Maximum Contaminant Level Goals
A. PFOA
B. PFOS
C. PFAS Hazard Index: PFHxS, HFPO-DA, PFNA, and PFBS
VI. Maximum Contaminant Levels
A. PFOA and PFOS
B. PFAS Hazard Index: PFHxS, HFPO-DA, PFNA, and PFBS
C. Reducing Public Health Risk by Protecting Against Dose
Additive Noncancer Health Effects From PFAS
D. Regulatory Alternatives
E. MCL-Specific Requests for Comment
VII. Occurrence
A. UCMR 3
B. State Drinking Water Data
C. 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
VIII. Analytical Methods
A. Practical Quantitation Levels (PQLs) for Regulated PFAS
IX. 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?
X. 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?
XI. 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)?
XII. Rule Implementation and Enforcement
A. What are the requirements for primacy?
B. What are the primacy agency record keeping requirements?
C. What are the primacy agency reporting requirements?
D. Exemptions and Extensions
XIII. Health Risk Reduction and Cost Analysis
A. Affected Entities and Major Data Sources Used To Develop the
Baseline Water System Characterization
B. Overview of the Cost-Benefit Model
C. Method for Estimating Costs
D. Method for Estimating Benefits
E. Nonquantifiable Benefits of PFOA and PFOS Exposure Reduction
F. Nonquantifiable Benefits of Removal of PFAS Included in the
Proposed Regulation and Co-Removed PFAS
G. Benefits Resulting From Disinfection By-Product Co-Removal
H. Comparison of Costs and Benefits
I. Quantified Uncertainties in the Economic Analysis
J. Cost-Benefit Determination
XIV. Request for Comment on Proposed Rule
Section III--Regulatory Determinations for Additional PFAS
Section V--Maximum Contaminant Level Goals
Section VI--Maximum Contaminant Levels
Section VII--Occurrence
Section IX--Monitoring and Compliance Requirements
Section X--Safe Drinking Water Right to Know
Section XI--Treatment Technologies
Section XII--Rule Implementation and Enforcement
Section XIII--HRRCA
Section XV--Statutory and Executive Order Reviews
XV. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563 Improving Regulation and 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
K. Consultations With the Science Advisory Board, National
Drinking Water Advisory Council, and the Secretary of Health and
Human Services
XVI. References
I. General Information
A. What is EPA proposing?
EPA is proposing for public comment a drinking water regulation
that includes six PFAS. EPA is proposing to establish MCLGs and an
NPDWR for these PFAS in public drinking water supplies. EPA proposes
MCLGs for PFOA and PFOS at zero (0) and an enforceable MCL for PFOA and
PFOS in drinking water at 4.0 ppt. Additionally, the Agency is
requesting comment on a preliminary determination to regulate
additional PFAS to include PFHxS, HFPO-DA \1\ (also known as and
referred to as ``GenX Chemicals'' in this proposal), PFNA, and PFBS.
Concurrent with this preliminary determination, EPA is proposing an HI
of 1.0 as the MCLG and enforceable MCL to address individual and
mixtures of these four contaminants where they occur in drinking water.
EPA is proposing to calculate the HI as the sum total of component PFAS
HQs, calculated by dividing the measured component PFAS concentration
in water by the relevant HBWC. In this proposal, EPA is using HBWCs of
9.0 ppt for PFHxS, 10.0 ppt
[[Page 18642]]
for HFPO-DA; 10.0 ppt for PFNA; and 2000 ppt for PFBS. The proposed
approach to calculating the HI for this set of four PFAS compounds is
designed to be protective against all adverse effects, not a single
outcome/effect, and is a health protective decision aid for use in
determining the level at which there are no adverse effects on the
health of persons with an adequate margin of safety, thus is
appropriate for MCLG development.
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\1\ PFAS may exist in multiple forms, such as acids and organic
or metal salts. Each of these forms may be listed as a separate
entry in certain databases and have separate Chemical Abstract
Service (CAS) Registry numbers. However, PFAS are expected to
dissociate in water to their anionic form. For example, the term
``GenX Chemicals'' acknowledges the ``acid'' and ``ammonium salt''
forms of HFPO-DA as two different chemicals. In water, though, these
chemicals dissociate and therefore the resulting anion appears as a
single analyte for the purposes of detection and quantitation.
Please see ``definitions'' for more information. EPA notes that the
chemical HFPO-DA is used in a processing aid technology developed by
DuPont to make fluoropolymers without using PFOA. The chemicals
associated with this process are commonly known as GenX Chemicals
and the term is often used interchangeably for HFPO-DA along with
its ammonium salt (USEPA, 2021b).
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The requirements in this proposal that apply to (1) PFOA, (2) PFOS,
and (3) PFHxS, HFPO-DA, PFNA, and PFBS and their mixtures are distinct
and capable of operating independently.
B. Does this action apply to me?
The preliminary regulatory determination to establish drinking
water regulations for certain PFAS and their mixtures and the proposed
regulation are proposals for public comment and are not requirements or
regulations. Instead, this action notifies interested parties of the
availability of information supporting the preliminary regulatory
determinations for four PFAS and their mixtures, the development of the
NPDWR for six PFAS, and proposed rule requirements for public comment.
If EPA proceeds to a final regulatory determination and final
regulation, once promulgated, this action will potentially affect the
following:
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Examples of potentially affected
Category entities
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Public water systems \2\............. Community water systems (CWSs);
Non-transient, non-community
water systems (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 that could be affected by this
action once promulgated. To determine whether a facility or activities
could be affected by this action, this proposed rule should be
carefully examined. Questions regarding the applicability of this
action to a particular entity may be directed to the person listed in
the FOR FURTHER INFORMATION CONTACT section.
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\2\ The term ``public water system'' means a system for the
provision to the public of water for human consumption through pipes
or other constructed conveyances, if such system has at least
fifteen service connections or regularly serves at least twenty-five
individuals. Such term includes (i) any collection, treatment,
storage, and distribution facilities under control of the operator
of such system and used primarily in connection with such system,
and (ii) any collection or pretreatment storage facilities not under
such control which are used primarily in connection with such
system.
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II. Background
A. What are PFAS?
PFAS are a large class of specialized synthetic chemicals that have
been in use since the 1940s (USEPA, 2018a). This proposed regulation
only applies to certain PFAS: PFOA, PFOS, PFHxS, HFPO-DA, PFNA, and
PFBS. People may potentially be exposed to these PFAS through certain
consumer products such as textiles (e.g., seat covers, sail covers,
weather protection (Janousek et al., 2019)), leather shoes as well as
shoe polish/wax (Norden, 2013; Borg and Ivarsson, 2017), along with
cooking/baking wares (Blom and Hanssen 2015; KEMI, 2015; Gl[uuml]ge et
al., 2020), occupational contact, and/or by consuming food and drinking
water that contain PFAS. Due to their widespread use, physicochemical
properties, and prolonged persistence, many PFAS co-occur in exposure
media (e.g., air, water, ice, sediment), and bioaccumulate in tissues
and blood of aquatic as well as terrestrial organisms, including humans
(Domingo and Nadal, 2019; Fromme et al., 2009). Industrial workers who
are involved in manufacturing or processing fluoropolymers, or people
who live or recreate near fluoropolymer facilities, may encounter
greater exposures; particularly of PFOA, PFNA, as well as HFPO-DA.
Firefighters as well as people who live near airfields or military
bases may have especially higher exposure to PFHxS and PFBS due to the
use of aqueous foam forming film as a fire suppressant. Pregnant and
lactating women, as well as children, may be more sensitive to the
harmful effects of certain PFAS, for example, 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, cancer, immunological effects, among others
(USEPA, 2023b; USEPA, 2023c). Other PFAS are also documented to result
in a range of adverse health effects (USEPA, 2021a; USEPA, 2021b;
ATSDR, 2021; NASEM 2022).
Although most United States production of PFOS, PFOA, and PFNA,
along with other long-chain PFAS, was phased out and then generally
replaced by production of PFBS, PFHxS, HFPO-DA and other PFAS, EPA is
aware of ongoing use of PFOS, PFOA, PFNA, and other long-chain PFAS.
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 and some uses of PFOS are ongoing (see 40 Code of
Federal Regulations (CFR) Sec. 721.9582). EPA is also aware of ongoing
use of the chemicals available from existing stocks or newly introduced
via imports. Additionally, the environmental persistence of these
chemicals and formation as degradation products from other compounds
may still contribute to their release in the environment.
B. Definitions
The six PFAS proposed for regulation and their relevant Chemical
Abstract Service (CAS) registry numbers are:
PFOA (C8F15CO2-; CAS: 45285-51-6)
PFOS (C8F17SO3-; CAS: 45298-90-6)
PFHxS (C6F13SO3-; CAS: 108427-53-8)
HFPO-DA (C6F11O3-; CAS: 122499-17-6)
PFNA (C9F17CO2-; CAS: 72007-68-2)
PFBS (C4F9SO3-; CAS: 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 CAS 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 (CAS: 122499-17-6), also known as HFPO-
DA, is an anionic molecule which has an ammonium salt (CAS: 62037-80-
3), a conjugate acid (CAS: 13252-13-6), a potassium salt (CAS: 67118-
55-2), and an acyl fluoride precursor (CAS: 2062-98-8), among other
variations. At environmentally relevant pHs these all dissociate into
the propanoate/anion form (CAS: 122499-17-6). Each PFAS listed has
multiple variants with differing chemical connectivity but the same
molecular composition; these are known as
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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. The proposed regulation covers all salts, isomers
and derivatives of the chemicals listed, including derivatives other
than the anionic form which might be created or identified.
C. Chemistry, Production and Uses
PFAS are most commonly and widely used to make products resistant
to water, heat, and stains. As a result, they are found in industrial
and consumer products such as clothing, food packaging, cookware,
cosmetics, carpeting, and fire-fighting foam (AAAS, 2020). Facilities
associated with PFAS releases into the air, soil, and water include
those for manufacturing, chemical as well as well as product production
and military installations (USEPA, 2016a; USEPA, 2016b).
The chemical structures of some PFAS cause them to repel water as
well as oil, remain chemically and thermally stable, and exhibit
surfactant properties. PFAS have strong, stable carbon-fluorine (C-F)
bonds, making them resistant to hydrolysis, photolysis, microbial
degradation, and metabolism (Ahrens, 2011; Beach et al., 2006; Buck et
al., 2011). These properties are what make PFAS useful for commercial
and industrial applications and purposes. However, these are also what
make some PFAS extremely persistent in the human body and the
environment (Calafat et al., 2007, 2019).
PFOA, PFOS, PFHxS, HFPO-DA, PFNA, and PFBS belong to a subset of
PFAS known as perfluoroalkyl acids (PFAAs), all of which consist of a
perfluorinated alkyl chain connected to an acidic headgroup. Humans are
exposed to PFAS due to wide-ranging commercial and industrial
applications along with long range migration from sources. The
structure of these PFAS contribute to their persistence in the
environment as well as their resistance to chemical, biological, and
physical degradation processes.
PFOA and PFOS are two of the most widely studied and longest used
PFAS. These two compounds have been detected in up to 98 percent of
human serum samples taken in biomonitoring studies that are
representative of the U.S. general population; however, since PFOA and
PFOS have been voluntarily phased out in the U.S., serum concentrations
have been declining (CDC, 2019). The sole U.S. manufacturer of PFOS
agreed to a voluntary phaseout in 2000, and the last reported
production was in 2002 (USEPA, 2000b; USEPA, 2018b; USEPA, 2021c). PFOS
has been used as a surfactant or emulsifier in firefighting foam,
circuit board etching acids, alkaline cleaners, floor polish, and as a
pesticide active ingredient for insect bait traps (HSBD, 2016). PFOA
has been used as an emulsifier and surfactant in fluoropolymers (such
as in the manufacturing of non-stick products like Teflon(copyright)),
firefighting foams, cosmetics, grease and lubricants, paints, polishes,
and adhesives (HSBD, 2016).
PFNA was historically the second most used surfactant for emulsion
polymerization (after PFOA) which was its main use (Buck et al., 2012).
Fluorinated surfactants improve the physical properties of the polymer
as well as improving the polymerization rate (Gl[uuml]ge et al., 2020).
Fluoropolymers are used in many applications because of their unique
physical properties such as resistance to high and low temperatures,
resistance to chemical and environmental degradation, and nonstick
characteristics. Fluoropolymers also have dielectric and fire-resistant
properties that have a wide range of electrical and electronic
applications, including architecture, fabrics, automotive uses, cabling
materials, electronics, pharmaceutical and biotech manufacturing, and
semiconductor manufacturing (Gardiner, 2014). Although drying processes
can release the surfactants when manufacturing is complete, surfactant
residues remain in the finished products (KEMI, 2015). Legacy stocks
may still be used and products containing PFNA may still be produced
internationally and imported to the U.S. (ATSDR, 2021).
The voluntary phase out caused a shift to alternatives such as per-
and polyfluoroalkyl ether carboxylic acids (PFECAs). The chemical HFPO-
DA is the most prevalent of these and is used in a processing aid
technology developed by DuPont to make fluoropolymers without using
PFOA. The chemicals associated with this process are commonly known as
GenX Chemicals and the term is often used interchangeably for HFPO-DA
along with its ammonium salt (USEPA, 2021b). The most common use for
GenX Chemicals is for emulsion polymerization.
Another alternative, PFBS, is mainly used as a water and stain
repellent protection for leather, textiles, carpets, and porous hard
surfaces, representing 25-50 tons/year of PFBS in mixtures (Norwegian
Environment Agency, 2017). PFBS and related chemicals are also used in
curatives for fluoroelastomers (Gl[uuml]ge et al., 2020). The curatives
are used for manufacturing O-rings, seals, linings, protective
clothing, cooking wares, and flame retardants (Norwegian Environment
Agency, 2017; Blom and Hanssen, 2015).
PFHxS is used in stain-resistant fabrics, fire-fighting foams,
flame retardants, insecticides, and as a surfactant in industrial
processes (Gl[uuml]ge et al., 2020). Additionally, particle
accelerators including the Delphi Detector at Stanford University rely
on liquid PFHxS (Gl[uuml]ge et al., 2020). PFHxS production, along with
PFOS, was phased out in 2002 nationwide however, production continues
in other countries and products containing PFHxS may be imported into
the U.S. (USEPA, 2000c). Legacy stocks may also still be used.
D. 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 linear carboxylic and sulfonic acid
species such as PFOA, PFOS, PFHxS, PFNA, and PFBS (ATSDR, 2021). Many
other PFAS have preliminary human health effects data (Mahoney et al.,
2022) and some PFAS, such as PFBS and HFPO-DA, have sufficient data
that has allowed EPA to derive toxicity values and publish toxicity
assessments (USEPA, 2021a; USEPA, 2021b). The adverse health effects
observed following oral exposure to such PFAS are significant and
diverse and include (but are not limited to): cancer and effects on the
liver (e.g., liver cell death), growth and development (e.g., low birth
weight), hormone levels, kidney, immune system, lipid levels (e.g.,
high cholesterol), the nervous system, and reproduction. Please see
sections III.B, IV, and V of this preamble for additional discussion on
health considerations for the six PFAS EPA is proposing to regulate in
this document.
E. Statutory Authority
Section 1412(b)(1)(A) of SDWA requires EPA to establish 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 with a frequency and at levels of public health concern;
and (3) where in the sole
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judgment of the Administrator, regulation of such contaminant presents
a meaningful opportunity for health risk reduction for persons served
by PWSs.
F. Statutory Framework and PFAS Regulatory History
Section 1412(b)(1)(B)(i) of SDWA requires 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 and are not
currently subject to any proposed or promulgated NPDWRs. EPA uses the
CCL to identify priority contaminants for regulatory decision-making
(i.e., regulatory determinations), and information collection.
Contaminants listed on the CCL may require future regulation under
SDWA. EPA included PFOA and PFOS on the third and fourth CCLs published
in 2009 (USEPA, 2009a) and 2016 (USEPA, 2016c). The Agency published
the fifth CCL (CCL 5) earlier this year and it includes PFAS as a
chemical group (USEPA, 2022b).
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, EPA issue a final regulatory determination to
regulate or not regulate at least five contaminants on each CCL. In
addition, Section 1412(b)(1)(B)(ii)(III) authorizes EPA to make a
determination to regulate a contaminant not listed on the CCL 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, EPA
issues preliminary regulatory determinations subject to public comment
and then issues a final regulatory determination after consideration of
public comment. For any contaminant that EPA determines meets the
criteria for regulation under SDWA 1412(b)(1)(A), Section 1412(b)(1)(E)
requires that EPA propose a NPDWR within two years and promulgate a
final regulation within 18 months of the proposal (which may be
extended by 9 additional months).
EPA implements a monitoring program for unregulated contaminants
under SDWA 1445(a)(2) which requires that once every five years, EPA
issue a list of priority unregulated contaminants to be monitored by
PWSs. This monitoring is implemented through the Unregulated
Contaminant Monitoring Rule (UCMR), which collects data from CWSs and
NTNCWSs. 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). Water system monitoring data for six PFAS were
collected during the third UCMR (UCMR3) between 2013 to 2015. The fifth
UCMR (UCMR5), published December 2021, requires sample collection and
analysis for 29 PFAS to occur between 2023 and 2025 using analytical
methods developed by EPA and consensus organizations. 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 EPA
appropriations for such purpose and sufficient laboratory capacity, EPA
must require all 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 VII of this preamble
provides additional discussion on PFAS occurrence. Additionally, while
the UCMR 5 information will not be available to inform this proposal,
EPA is proposing to consider the UCMR 5 data to support implementation
of monitoring requirements under the proposed rule. Section IX of this
preamble further discusses monitoring and compliance requirements.
After careful consideration of public comments, EPA issued final
regulatory determinations for contaminants on the fourth CCL in March
of 2021 (USEPA, 2021d) which included determinations to regulate two
contaminants, PFOA and PFOS, in drinking water. EPA found that PFOA and
PFOS may have 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 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 preliminarily finds that
additional PFAS compounds also meet SDWA criteria for regulation. EPA's
preliminary 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 a
proposed drinking water regulation concurrent ``with a determination to
regulate.'' This provision authorizes a more expedited process by
allowing EPA to make concurrent the regulatory determination and
rulemaking processes. As a result, EPA interprets the 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 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
EPA to act efficiently to issue a final determination to regulate
concurrently with a final NPDWR to avoid delays to address contaminants
that meet the statutory criteria. As a result, this proposal contains
both a preliminary determination to regulate four PFAS contaminants and
proposed regulations for those contaminants as well as the two PFAS
contaminants (PFOA and PFOS) for which EPA has already issued a final
Regulatory Determination. EPA developed a proposed MCLG and a proposed
NPDWR for six PFAS compounds pursuant to the requirements under section
1412(b)(1)(B) of SDWA. The proposed MCLGs and proposed NPDWR are
discussed in more detail below.
G. Bipartisan Infrastructure Law
The Agency notes that the passage of the Infrastructure Investment
and Jobs Act, also referred to as the BIL, invests over $11.7 billion
in the Drinking Water SRF; $4 billion to the Drinking Water SRF for
Emerging Contaminants; and $5 billion to Small, Underserved, and
Disadvantaged Communities Grants. 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.
These funds can also be used to address emerging contaminants like PFAS
in drinking water through actions such as technical assistance, water
quality testing, and contractor training, which will allow communities
supplemental funding to meet their obligations under
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this proposed regulation and help ensure protection from PFAS
contamination of drinking water.
H. EPA PFAS Strategic Roadmap
In October 2021, EPA published the PFAS Strategic Roadmap that
outlined the Agency's plan 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). Described in the Roadmap are key
commitments the Agency made toward addressing these contaminants in the
environment. With this proposal, EPA is delivering on a key commitment
in the Roadmap to ``establish a National Primary Drinking Water
Regulation'' for proposal and is working toward promulgating the final
NPDWR in Fall of 2023.
III. Preliminary Regulatory Determinations for Additional PFAS
Since 2021 when EPA determined to regulate two PFAS contaminants,
PFOA and PFOS, EPA has evaluated additional PFAS compounds for
regulatory consideration and has preliminarily determined that an
additional four individual PFAS and mixtures of these PFAS meet SDWA
criteria for regulation. 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
``contaminants'' 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 is making a preliminary determination to regulate
PFHxS, HFPO-DA, PFNA, and PFBS in drinking water, and mixtures of these
PFAS contaminants. PFHxS, HFPO-DA, PFNA, and PFBS, and mixtures of
these PFAS, are known to cause adverse human health effects; there is
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, HFPO-DA, PFNA, PFBS and mixtures of
these PFAS present a meaningful opportunity for health risk reductions
for people served by PWSs. This section describes the best available
science and information used by the Agency to support this preliminary
Regulatory Determination. The proposed MCLG and enforceable standard
for these four PFAS and mixtures of these PFAS are discussed further in
sections V to VI of this preamble.
A. Agency Findings
To support the Agency's preliminary Regulatory Determination, EPA
examined health effects information from available peer reviewed human
health assessments as well as drinking water monitoring data collected
as part of the UCMR 3 and state-led monitoring efforts. EPA finds that
oral exposure to PFHxS, HFPO-DA, PFNA, and PFBS may individually and in
a mixture each result in adverse health effects, including disrupting
multiple biological pathways that result in common adverse effects on
several biological systems including the endocrine, cardiovascular,
developmental, immune, and hepatic systems (USEPA, 2023a). PFAS,
including PFHxS, HFPO-DA, PFNA, and PFBS and their mixtures are
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, EPA finds that
PFHxS, HFPO-DA, PFNA, and PFBS each have a substantial likelihood to
occur in finished drinking water and that these PFAS are also likely to
co-occur as mixtures and result in increased exposure above levels of
health concern. Therefore, given this high occurrence and co-occurrence
likelihood and that adverse health effects arise as a result of both
these PFAS individually and as mixtures, the Agency is preliminarily
determining that PFHxS, HFPO-DA, PFNA, and PFBS and their mixtures may
have adverse human health effects; there is a substantial likelihood
that PFHxS, HFPO-DA, PFNA, PFBS and mixtures of these PFAS, will occur
and co-occur in PWSs with a frequency and at levels of public health
concern; and in the sole judgment of the Administrator, regulation of
PFHxS, HFPO-DA, PFNA, and PFBS, and their mixtures, presents a
meaningful opportunity for health risk reductions for persons served by
PWSs.
B. Statutory Criterion 1--Adverse Health Effects
The Agency finds that PFHxS, HFPO-DA, PFNA, PFBS and their mixtures
may have an adverse effect on the health of persons. Discussion related
to health effects for each of the four PFAS is below. For this
proposal, the Agency is developing HBWCs for PFHxS, HFPO-DA, PFNA and
PFBS, defined as a level protective of health effects over a lifetime
of exposure, including sensitive populations and life stages. Each of
the four HBWCs is used in this proposal to evaluate occurrence data and
the likelihood of potential risk to human health to justify the
agency's preliminary regulatory determinations for PFHxS, HFPO-DA, PFNA
and PFBS. The chemical-specific HBWCs are also used to assess the
potential human health risk associated with mixtures of the four PFAS
in drinking water using the HI approach. Additional details on the HBWC
for PFHxS, HFPO-DA, PFNA and PFBS are found in section IV of this
preamble. More information supporting EPA's preliminary regulatory
determination relating to adverse health effects for these PFAS and the
HI approach for mixtures is available in section V of this preamble.
1. PFHxS
Toxicity studies of oral PFHxS exposure in animals have reported
adverse health effects on the liver, thyroid, and development (ATSDR,
2021). EPA has not yet classified the carcinogenicity of PFHxS. For a
detailed discussion on adverse effects of oral exposure to PFHxS,
please see ATSDR (2021) and USEPA (2023a).
The HBWC for PFHxS is derived using a chronic reference value based
on an Agency For Toxic Substances And Disease Registry (ATSDR)
intermediate-duration oral Minimal Risk Level, which was based on
thyroid effects seen in male rats after oral PFHxS exposure (ATSDR,
2021). The most sensitive non-cancer effect observed was thyroid
follicular epithelial hypertrophy/hyperplasia in parental male rats
exposed to PFHxS for 42-44 days, identified in the critical
developmental toxicity study selected by ATSDR (no observed adverse
effect level (NOAEL) of 1 mg/kg/day) (Butenhoff et al., 2009; ATSDR,
2021). To derive the intermediate-duration Minimal Risk Level for
PFHxS, ATSDR calculated a human equivalent dose (HED) of 0.0047 mg/kg/
day from the NOAEL of 1 mg/kg/day identified in the principal study.
Then, ATSDR applied a total uncertainty factor (UF)/modifying factor
(MF) of 300X (10X UF for intraspecies variability, 3X UF for
interspecies differences, and a 10X MF for database deficiencies) to
yield an intermediate-duration oral Minimal Risk Level of 0.00002 mg/
kg/day (ATSDR, 2021). Per Agency guidance (USEPA, 2002), to calculate
the HBWC, EPA applied an additional UF of 10 to adjust for subchronic-
to-chronic duration (UFS) because the effect was not in a
developmental life stage (i.e., thyroid follicular epithelial
hypertrophy/hyperplasia in parental male rats). The
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resulting chronic reference value was 0.000002 mg/kg/day.
No sensitive population or life stage was identified for
bodyweight-adjusted drinking water intake (DWI-BW) selection for PFHxS
because the critical effect on which the ATSDR Minimal Risk Level was
based (thyroid alterations) was observed in adult male rats. Since this
exposure life stage does not correspond to a sensitive population or
life stage, a DWI-BW 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) was
selected for HBWC derivation (USEPA, 2019a).
EPA calculated the HBWC for PFHxS using a relative source
contribution (RSC) of 0.20. This means that 20% of the exposure--equal
to the chronic reference value--is allocated to drinking water, and the
remaining 80% is attributed to all other potential exposure sources.
This was based on EPA's determination that the available data on PFHxS
exposure routes and sources did not permit quantitative
characterization of PFHxS exposure. In such cases, an RSC of 0.20 is
typically used (USEPA, 2000c). See U.S.EPA (2023a) for complete details
on the RSC determination for PFHxS.
As further described in USEPA (2023a) and section V of this
preamble below, the HBWC for PFHxS is calculated to be 9.0 ppt. This
HBWC of 9.0 ppt is also used as the health reference level (HRL) for
this preliminary regulatory determination.
2. HFPO-DA
EPA's 2021 Human Health Toxicity Assessment for GenX Chemicals
describes potential health effects associated with oral exposure to
HFPO-DA (USEPA, 2021b). Toxicity studies in animals indicate that
exposures to HFPO-DA may result in adverse health effects, including
liver and kidney toxicity and immune system, hematological,
reproductive, and developmental effects (USEPA, 2021b). There is
Suggestive Evidence of Carcinogenic Potential of oral exposure to HFPO-
DA in humans, but the available data are insufficient to derive a
cancer risk concentration in water for HFPO-DA. For a detailed
discussion on adverse effects of oral exposure to HFPO-DA, please see
USEPA (2021b).
EPA's noncancer HBWC for HFPO-DA is derived from a reference dose
(RfD) that is based on liver effects observed following oral exposure
of mice to HFPO-DA (USEPA, 2021b). The most sensitive noncancer effect
observed was a constellation of liver lesions in parental female mice
exposed to HFPO-DA by gavage for 53-64 days, identified in the critical
reproductive/developmental toxicity study selected by EPA (NOAEL of 0.1
mg/kg/day) (DuPont, 2010; USEPA, 2021b). To develop the chronic RfD for
HFPO-DA, EPA derived an HED of 0.01 mg/kg/day from the NOAEL of 0.1 mg/
kg/day identified in the principal study. EPA then applied a composite
UF of 3,000 (i.e., 10X for intraspecies variability, 3X for
interspecies differences, 10X for extrapolation from a subchronic to a
chronic dosing duration, and 10X for database deficiencies) to yield
the chronic RfD (USEPA, 2021b).
To select an appropriate DWI-BW for use in derivation of the
noncancer HBWC values for HFPO-DA, EPA considered the HFPO-DA exposure
interval used in the oral reproductive/developmental toxicity study in
mice that was 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 exposure for
HFPO-DA: women of childbearing age, pregnant women, and lactating women
(Table 3-63 in USEPA, 2019a). Of these three, the DWI-BW for lactating
women (0.0469 L/kg/day) is anticipated to be protective of the other
two sensitive life stages. Therefore, EPA used the DWI-BW for lactating
women to calculate the HBWC for the proposed regulation, which is also
used for the HRL for the preliminary regulatory determination.
The HBWC value for HFPO-DA was calculated using an RSC of 0.20.
This means that 20% of the exposure--equal to the RfD--is allocated to
drinking water, and the remaining 80% is attributed to all other
potential exposure sources (USEPA, 2022d). Selection of this RSC was
based on EPA's determination that the available exposure data for HFPO-
DA did not enable a quantitative characterization of relative HFPO-DA
exposure sources and routes. In such cases, an RSC of 0.20 is typically
used (USEPA, 2000c).
As further described in USEPA (2023a) and USEPA (2022d), the HBWC
for HFPO-DA is calculated to be 10.0 ppt. This value is consistent with
EPA's 2022 drinking water health advisory for HFPO-DA (USEPA, 2022d),
but was derived from EPA's 2021 Human Health Toxicity Assessment for
HFPO-DA (USEPA, 2021b). This HBWC of 10 ppt is also used as the HRL for
this preliminary Regulatory Determination for HFPO-DA.
3. PFNA
Animal toxicity studies have reported adverse health effects,
specifically on development, reproduction, immune function, and the
liver, after oral exposure to PFNA (ATSDR, 2021). EPA has not yet
classified the carcinogenicity of PFNA. For a detailed discussion on
adverse effects of oral exposure to PFNA, please see ATSDR (2021) and
USEPA (2023a).
The HBWC for PFNA is derived using a chronic reference value based
on an ATSDR intermediate-duration oral Minimal Risk Level, which was
based on developmental effects seen in mice after oral PFHxS exposure
(ATSDR, 2021). The most sensitive non-cancer effects were decreased
body weight (BW) gain and developmental delays (i.e., delayed eye
opening, preputial separation, and vaginal opening) in mice born to
mothers that were gavaged with PFNA from gestational days (GD) 1-17,
with continued exposure through lactation and monitoring until
postnatal day (PND) 287, identified in the critical developmental
toxicity study selected by ATSDR (NOAEL of 1 mg/kg/day) (Das et al.,
2015; ATSDR, 2021). To derive the intermediate-duration Minimal Risk
Level, ATSDR calculated an HED of 0.001 mg/kg/day from the NOAEL of 1
mg/kg/day identified in the principal study. Then, ATSDR applied a
total UF/MF of 300X (total UF of 30X and a MF of 10X for database
deficiencies) to yield an intermediate-duration Minimal Risk Level of
0.000003 mg/kg/day. EPA did not apply an additional UF to adjust for
subchronic-to-chronic duration (i.e., UFS) to calculate the
chronic reference value because the critical effects were observed
during a developmental life stage (USEPA, 2002). The chronic reference
value of 0.000003 mg/kg/day was used to derive the HBWC for PFNA.
Based on the life stages of exposure in the principal study from
which the intermediate-duration Minimal Risk Level was derived (i.e.,
during gestation and lactation), EPA identified three potentially
sensitive life stages that may represent critical windows of exposure
for PFNA: women of childbearing age (13 to < 50 years), pregnant women,
and lactating women (Table 3-63 in USEPA, 2019a). The DWI-BW for
lactating women (0.0469 L/kg/day; 90th percentile direct and indirect
consumption of community water, consumer-only two-day average) was
selected to calculate the HBWC for PFNA because it is the highest of
the three DWI-BWs and is anticipated to be protective of the other two
sensitive life stages.
[[Page 18647]]
EPA calculated the HBWC for PFNA using an RSC of 0.20. This means
that 20% of the exposure--equal to the chronic reference value--is
allocated to drinking water, and the remaining 80% is attributed to all
other potential exposure sources. This was based on EPA's determination
that the available data on PFNA exposure routes and sources did not
permit quantitative characterization of PFNA exposure. In such cases,
an RSC of 0.20 is typically used (USEPA, 2000c). See USEPA (2023a) for
complete details on the RSC determination for PFNA.
As further described in USEPA (2023a), the HBWC for PFNA is
calculated to be 100 ppt. This HBWC of 10.0 ppt is also used as the HRL
for this preliminary Regulatory Determination for PFNA.
4. PFBS
EPA's 2021 PFBS Toxicity Assessment describe potential health
effects associated with oral PFBS exposure (USEPA, 2021a). Toxicity
studies of oral PFBS exposures in animals have reported adverse health
effects on development, as well as 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. EPA concluded that there is ``Inadequate Information to
Assess Carcinogenic Potential'' for PFBS and K+PFBS by any route of
exposure. For a detailed discussion on adverse effects of oral exposure
to PFBS, please see USEPA (2021a).
EPA's noncancer HBWC for PFBS is derived from a chronic RfD that is
based on thyroid effects observed following gestational exposure of
mice to K+PFBS (USEPA, 2021a; USEPA, 2022e). The most sensitive non-
cancer effect observed was decreased serum total thyroxine (T4) in
newborn (PND 1) mice gestationally exposed to K+PFBS from GD 1-20,
identified in the critical developmental toxicity study selected by EPA
(benchmark dose lower confidence limit HED or BMDLHED) of 0.095 mg/kg/
day) (Feng et al., 2017; USEPA, 2021a). To develop the chronic RfD for
PFBS, EPA applied a composite UF of 300 (i.e., 10X for intraspecies
uncertainty factor (UFH), 3X for interspecies uncertainty
factor (UFA), and 10X for database uncertainty factor
(UFD)) to yield a value of 0.0003 mg/kg/day (USEPA, 2021a).
To select an appropriate DWI-BW for use in deriving the noncancer
HBWC value, EPA considered 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 embryo or fetus (Table 3-63 in USEPA, 2019a). Of these
two, EPA selected the DWI-BW for women of child-bearing age (0.0354 L/
kg/day) to derive the noncancer HBWC for PFBS because it was higher and
therefore more health-protective (USEPA, 2022e).
The HBWC value for PFBS was calculated using an RSC of 0.20. This
means that 20% of the exposure--equal to the RfD--is allocated to
drinking water, and the remaining 80% is attributed to all other
potential exposure sources (USEPA, 2022e). This was based on EPA's
determination that the available data on PFBS exposure routes and
sources did not enable a quantitative characterization of PFBS
exposure. In such cases, an RSC of 0.20 is typically used (USEPA,
2000c).
As further described in USEPA (2022e), the HBWC for PFBS is
calculated to be 2000 ppt. This value is consistent with EPA's 2022
drinking water health advisory for PFBS (USEPA, 2022d), but was derived
from EPA's 2021 PFBS Toxicity Assessment (USEPA, 2021a). This HBWC of
2000 ppt is also used as the HRL for this preliminary Regulatory
Determination for PFBS.
5. Mixtures of PFHxS, HFPO-DA, PFNA, and PFBS
PFAAs, including PFHxS, HFPO-DA, PFNA, and PFBS, disrupt signaling
of multiple biological pathways resulting in common adverse effects on
several biological systems including thyroid hormone levels, lipid
synthesis and metabolism, as well as on development, and immune and
liver function (ATSDR, 2021; EFSA, 2018, 2020; USEPA, 2023a).
Studies with PFAS and other classes of chemicals support the health
protective assumption that a mixture of chemicals with similar observed
effects should be assumed to also act in a dose additive manner unless
data demonstrate otherwise (USEPA, 2023d). Dose additivity means that
each of the component chemicals in the mixture (in this case, PFHxS,
HFPO-DA, PFNA, and PFBS) behaves as a concentration or dilution of
every other chemical in the mixture differing only in relative toxicity
(USEPA, 2000a). See additional discussion of PFAS dose additivity in
Section V.C of this preamble.
C. Statutory Criterion 2--Occurrence
With this proposal, EPA is preliminarily determining that PFHxS,
HFPO-DA, PFNA, and PFBS, both individually and as mixtures of these
PFAS, meet SDWA's second statutory criterion for regulatory
determination: there is a substantial likelihood that the contaminants
will occur and co-occur with a frequency and at levels of public health
concern in PWSs based on EPA's evaluation of the best available
occurrence information. EPA is seeking public comment on whether
additional data or studies exist which EPA should consider that support
or do not support this preliminary determination.
EPA has made its preliminary determination based on the most
recent, publicly available data, which includes UCMR 3 data and more
recent PFAS drinking water data collected by several states. Informed
by these data, EPA determined that there is a substantial likelihood
PFHxS, HFPO-DA, PFNA, and PFBS will occur and co-occur with a frequency
of public health concern. Additionally, when determining that there is
a substantial likelihood these PFAS will occur at levels of public
health concern, EPA considered both the occurrence concentration levels
for each contaminant individually, as well as their collective co-
occurrence and corresponding dose additive health effects from co-
exposures. Furthermore, the Agency notes that it does not have a
bright-line threshold for occurrence in drinking water that triggers
whether a contaminant is of public health concern. A determination of
public health concern 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. Given the many possible combinations of factors, a simple
threshold is not viable and is a highly contaminant-specific decision
that takes into consideration multiple factors.
UCMR 3 monitoring occurred between 2013 and 2015 for PFHxS,
[[Page 18648]]
PFNA, and PFBS. HFPO-DA were not monitored for as part of the UCMR 3.
Under the UCMR 3, 36,972 samples from 4,920 PWSs were analyzed for
PFHxS, PFNA, and PFBS. The minimum reporting levels (MRLs) for PFHxS,
PFNA, and PFBS were 30 ppt, 20 ppt, and 90 ppt, respectively. EPA notes
that these UCMR 3 MRLs are higher than those utilized within the
majority of state monitoring data and for the upcoming UCMR 5. A total
of 233 samples and 70 systems serving a total population of
approximately 6.7 million people had reported detections (greater than
or equal to the MRL) of at least one of the three compounds. Moreover,
the large majority of these UCMR 3 reported detections were found at
concentrations at or above levels of public health concern as described
previously in section III.B of this preamble and below within this
section. USEPA (2023e) presents sample and system level summaries of
the results for the individual contaminants. More information
supporting EPA's regulatory determination relating to the occurrence of
these PFAS and their mixtures is included in section VII.A. of this
preamble.
EPA has also collected more recent finished drinking water data
from 23 states who have made their data publicly available as of August
2021 (USEPA, 2023e). EPA used this cutoff date to allow the Agency to
conduct thorough analyses of the state information. EPA further refined
this dataset based on representativeness and reporting limitations,
resulting in detailed technical analyses using a subset of the
available state data (i.e., all 23 states' data were not included
within the detailed technical analyses). For example, a few states only
reported results as a combination of analytes which was not conducive
for analyzing PFAS. In general, the state data which were more recently
collected using newer analytical methods that have lower reporting
limits than those under UCMR 3 show widespread occurrence of PFOA,
PFOS, PFHxS, PFNA, and PFBS in multiple geographic locations. These
data also show that there is a substantial likelihood that these PFAS
occur at concentrations below UCMR 3 reporting limits. Furthermore,
these data include results for more PFAS than were included in the UCMR
3, including HFPO-DA, and show that PFHxS, HFPO-DA, PFNA, and PFBS, and
mixtures of these PFAS, occur and co-occur at levels of public health
concern as they are measured at concentrations above their respective
individual HRLs or, when considering their dose additive impacts,
exceed these levels. The Agency notes that the data vary in terms of
quantity and coverage, including that some of these available data are
from targeted or site-specific sampling efforts (i.e., monitoring
specifically in areas of known or potential contamination) and thus may
be expected to have higher detection rates or not be representative of
levels found in all PWSs within the state.
Tables 1 and 2 below show the percent of samples with state
reported detections of PFHxS, HFPO-DA, PFNA, and PFBS, and the
percentage of monitored systems with detections of PFHxS, HFPO-DA,
PFNA, and PFBS, respectively, across the non-targeted or non-site
specific (i.e., monitoring not conducted specifically in areas of known
or potential contamination) state finished water monitoring data.
EPA notes that different states utilized various reporting
thresholds or limits when presenting their data, and for some states
there were no clearly defined limits publicly provided. Further, the
limits often varied within the data for each state depending on the
specific analyte, as well as the laboratory analyzing the data. When
conducting data analyses, EPA incorporated individual state-specific
reporting limits where possible. In some cases, states reported data at
concentrations below EPA's proposed rule trigger level for reduced
compliance monitoring frequency and/or PQLs described in sections
VIII.A., IX.A., and IX.B of this preamble. However, to present the best
available occurrence data, EPA collected and evaluated the data based
on the information as reported directly by the states. EPA also notes,
and as described in further detail in section VIII.A. of this preamble,
some laboratories are able to detect and measure the PFAS addressed in
this document at lower concentrations than EPA's proposed rule trigger
level and PQLs which account for differences in the capability of
laboratories across the country. As such, EPA believes this data can
reasonably support EPA's evaluation of PFOA, PFOS, PFHxS, HFPO-DA,
PFNA, and PFBS occurrence and co-occurrence in drinking water. Specific
details on state data reporting thresholds are available in Table 1
within USEPA (2023e).
Table 1--Non-Targeted State PFAS Finished Water Data--Summary of Samples With State Reported Detections \1\ of
PFHxS, HFPO-DA, PFNA, and PFBS
----------------------------------------------------------------------------------------------------------------
State PFHxS (%) PFNA (%) PFBS (%) HFPO-DA (%)
----------------------------------------------------------------------------------------------------------------
Colorado........................................ 10.8 0.9 11.0 0.2
Illinois........................................ 5.1 0.2 7.8 0.0
Kentucky........................................ 8.6 2.5 12.3 13.6
Massachusetts................................... 31.9 4.6 35.5 0.0
Michigan........................................ 2.9 0.1 5.2 0.04
New Hampshire................................... 16.6 3.3 31.4 3.8
New Jersey...................................... 24.7 8.0 24.9 N/A
North Dakota.................................... 1.6 0.0 0.0 0.0
Ohio............................................ 5.8 0.3 4.7 0.1
South Carolina.................................. 13.5 2.1 38.3 6.0
Vermont......................................... 2.2 1.7 4.8 0.2
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Detections determined by individual state reported limits which are not defined consistently across all
states.
[[Page 18649]]
Table 2--Non-Targeted State PFAS Finished Water Data--Summary of Monitored Systems With State Reported \1\
Detections of PFHxS, HFPO-DA, PFNA, and PFBS
----------------------------------------------------------------------------------------------------------------
State PFHxS (%) PFNA (%) PFBS (%) HFPO-DA (%)
----------------------------------------------------------------------------------------------------------------
Colorado........................................ 13.4 1.0 13.4 0.3
Illinois........................................ 4.3 0.2 6.6 0.0
Kentucky........................................ 8.6 2.5 12.3 13.6
Massachusetts................................... 30.2 8.4 39.4 0.0
Michigan........................................ 3.0 0.2 5.3 0.1
New Hampshire................................... 22.5 5.5 37.9 5.1
New Jersey...................................... 32.6 13.3 34.0 N/A
North Dakota.................................... 1.6 0.0 0.0 0.0
Ohio............................................ 2.2 0.3 2.4 0.1
South Carolina.................................. 20.0 6.1 56.0 10.9
Vermont......................................... 1.6 1.3 5.2 0.5
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Detections determined by individual state reported limits which are not defined consistently across all
states.
As shown in Tables 1 and 2, all states except one 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 0.1 to 38.3 percent and 0.1 to 56.0
percent, respectively. While these percentages show occurrence
variability across states, several of these states demonstrate a
significant number of samples (e.g., detections of PFHxS in 31.9
percent of Massachusetts samples) and systems (e.g., detections of
HFPO-DA in 13.9 percent of monitored systems in Kentucky) with some or
all of the four PFAS, which supports the Agency's preliminary
determination that there is a substantial likelihood these PFAS and
their mixtures occur and co-occur with a frequency of public health
concern. Specific discussion related to occurrence for each of the four
PFAS is below.
1. PFHxS
The occurrence data presented above, throughout section VII. of
this preamble and discussed in the USEPA (2023e) support the Agency's
preliminary 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% of systems using an MRL of 30 ppt. All
UCMR 3 reported values are greater than the HRL of 9.0 ppt.
Additionally, through analysis of available non-targeted state data all
states in Tables 1 and 2 had reported detections of PFHxS within 1.6 to
32.6 percent of their systems and reported concentrations ranging from
0.46 to 310 ppt with median sample concentrations ranging from 2.14 to
11.3 ppt. Results from targeted state monitoring data of PFHxS are also
consistent with non-targeted state data. For example, California
reported 29.2 percent of monitored systems found PFHxS, where
concentrations ranged from 1.1 to 140.0 ppt. Therefore, in addition to
the UCMR 3 results, these state data reflect PFHxS at frequencies and
levels of public health concern. 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 and results are described in
section VII.E of this preamble. Hundreds of systems serving millions of
people were estimated to have mean concentrations exceeding the PFHxS
HRL (9.0 ppt). Further supporting this preliminary determination, PFAS
have dose additive impacts and PFHxS co-occurs in mixtures with other
PFAS, including PFOA, PFOS, HFPO-DA, PFNA, and PFBS. More information
on PFHxS co-occurrence is available in section VII.C. and VII.D. of
this preamble.
2. HFPO-DA
The occurrence data presented above, throughout section VII of this
preamble, and discussed in the USEPA (2023e) support the Agency's
preliminary 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 United States. Through analysis of
available non-targeted state data over half of the states in Tables 1
and 2 had state reported detections of HFPO-DA within 0.1 to 13.6
percent of their systems. State reported sample results were also
reported above the HRL of 10.0 ppt with sample results ranging from 1.7
to 29.7 ppt and median sample results ranging from 1.7 to 9.7 ppt.
Additionally, targeted state monitoring in North Carolina which
conducted sampling across six finished drinking water sites where 438
samples showed HFPO-DA ranging from 9.2 to 1100 ppt, with a median
concentration of 40 ppt. Therefore, these state data demonstrate
concentrations of HFPO-DA at levels of public health concern. Further
supporting this preliminary determination, PFAS have dose additive
impacts and HFPO-DA occur in mixtures with other PFAS, including PFOA,
PFOS, PFHxS, PFNA, and PFBS. More information on HFPO-DA co-occurrence
is available in section VII.C. and VII.D. of this preamble.
3. PFNA
The occurrence data presented above, throughout section VII of this
preamble, and discussed in USEPA (2023e) support the Agency's
preliminary 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 United States. PFNA was found under
UCMR 3 using an MRL of 20 ppt. Thus, all UCMR 3 reported detections are
greater than the HRL of 10.0 ppt. Additionally, through analysis of
available non-targeted state data all states except one in Tables 1 and
2 had state reported detections of PFNA within 0.2 to 13.3 percent of
their systems, and state reported sample results ranging from 0.25 to
94.2 ppt with median sample results range from 2.1 to 7.46 ppt.
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 ppt. Thus, in addition to the UCMR 3 results, these state data
also reflect PFNA concentrations at levels of public health concern.
Further supporting this preliminary
[[Page 18650]]
determination, PFAS have dose additive impacts and PFNA co-occurs in
mixtures with other PFAS, including PFOA, PFOS, PFHxS, HFPO-DA, and
PFBS. More information on PFNA co-occurrence is available in section
VII.C. and VII.D. of this preamble.
4. PFBS
The occurrence data presented above, throughout section VII of this
preamble, and discussed in USEPA (2023e) support the Agency's
preliminary determination that there is a substantial likelihood PFBS
occurs with a frequency and at levels of public health concern in
drinking water systems across the United States. PFBS was found under
UCMR 3 using an MRL of 90 ppt. Additionally, through analysis of
available non-targeted state data all states except one in Tables 1 and
2 had state reported detections of PFBS within 2.4 to 56 percent of
their systems, with four states finding PFBS in over 34 percent of
their systems. Furthermore, PFBS occurred at a greater frequency in all
but one state than the other three PFAS. State reported sample results
ranged from 1 to 310 ppt with median sample results ranging from 1.99
to 7.26 ppt. Targeted state monitoring data of PFBS are consistent with
non-targeted state data. Maryland reported 51.5 percent of monitored
systems found PFBS, where concentrations ranged from 1.01 to 21.29 ppt.
Further supporting this preliminary determination, PFAS have dose
additive impacts and PFBS occurs in mixtures with other PFAS, including
PFOA, PFOS, PFHxS, HFPO-DA, and PFNA. Moreover, given the considerable
prevalence of PFBS in state data reviewed by EPA and frequency in which
it has been shown to have other PFAS co-occurring with it, PFBS may
serve as an indicator of broad contamination of other PFAS. Those other
PFAS are also likely dose additive to PFBS and other PFAS being
proposed for regulation. EPA notes that PFBS concentrations do not
exceed their HRL of 2000 ppt when considered in isolation; however,
when considering dose additivity and the elevated frequency to which
PFBS occurrence has been observed over time, EPA has determined that
PFBS is an important component of regulated PFAS mixtures and because
of their pervasiveness, there is a substantial likelihood of its
occurrence with a frequency and at levels of public health concern.
More information on PFBS co-occurrence is available in section VII.C.
and VII.D. of this preamble. Based on the occurrence and co-occurrence
information above and throughout section VII of this preamble, EPA has
preliminarily determined that there is substantial likelihood PFBS
occurs with a considerable frequency and at levels of public health
concern.
5. Preliminary Occurrence Determination for PFHxS, HFPO-DA, PFNA, and
PFBS
Through the information presented within this section and in USEPA
(2023e), along with the co-occurrence information presented in section
VII.C. and VII.D. of this preamble, EPA's evaluation of the UCMR 3 data
and state data collected more recently demonstrates that as analytical
methods improved, monitoring has increased, and minimum reporting
thresholds are lowered, there is a sustained upward trend that there is
a substantial likelihood that these contaminants will occur and co-
occur at a frequency and at levels of public health concern. The UCMR 3
results showed there were over 6.5 million people served by PWSs that
had reported detections of PFHxS, PFNA, and PFBS, with many of the
detections for PFHxS and PFNA above the HRLs. EPA's evaluation of
monitoring data from multiple states that was primarily gathered
following the UCMR 3 using improved analytical methods that could
measure more PFAS at lower concentrations found that there is even
greater demonstrated occurrence and co-occurrence of these PFAS, as
well as for HFPO-DA, at significantly greater frequencies and at levels
of public health concern. EPA anticipates that national monitoring with
newer analytical methods capable of quantifying PFAS occurrence to
lower levels, significant occurrence and co-occurrence of these PFAS
are likely to be observed.
EPA notes that it focused the evaluation of the state data on the
non-targeted monitoring efforts from 12 states, given that these types
of monitoring efforts are likely to be more representative of PFHxS,
HFPO-DA, PFNA, and PFBS occurrence as they are not specifically
conducted in areas of known or potential contamination. In these 12
states, there were reported detections of PFHxS, HFPO-DA, PFNA, or
PFBS, with nearly all states reporting detections of at least three of
these four PFAS. EPA considered the targeted state 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
additional targeted state data that EPA analyzed, EPA also found that
these states reported detections at systems serving millions of
additional people, as well as at levels of public health concern,
particularly when considering PFAS mixtures and dose additive impacts.
State data detection frequency and concentration results vary for
PFHxS, HFPO-DA, PFNA, 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 when compared to
other states. However, given the overall results, this demonstrates the
substantial likelihood that these PFAS and their mixtures will occur at
frequencies and levels of public health concern, and where these PFAS
have been monitored they are very commonly found. Furthermore, EPA
notes that as described in section VII.C.1. of this preamble, when
evaluating only a subset of the available state data representing non-
targeted monitoring, that one or more of PFHxS, HFPO-DA, PFNA, and PFBS
were reported in approximately 13.9 percent of monitored systems; if
these results were extrapolated to the nation, one or more of these
four PFAS would be detectable in over 9,000 PWSs. Moreover, as shown in
section VII.C.2. of this preamble, PFHxS, HFPO-DA, PFNA, and PFBS
generally co-occur with each other, as well as with PFOA and PFOS,
supporting that there is substantial likelihood that these PFAS will
co-occur in mixtures with dose additive impacts. For all of these
reasons, EPA has determined that there is sufficient occurrence
information available to support this preliminary determination that
there is a substantial likelihood that PFHxS, HFPO-DA, PFNA, and PFBS
will occur at frequencies and levels of public health concern.
D. Statutory Criterion 3--Meaningful Opportunity
EPA has preliminarily determined that regulation of PFHxS, HFPO-DA,
PFNA, and PFBS, both individually and in a mixture, presents a
meaningful opportunity for health risk reduction for persons served by
PWSs. EPA has made this preliminary determination after evaluating
health, occurrence, treatment, and other related information against
the three SDWA statutory criteria including consideration of the
following for the four PFAS and their mixtures:
PFHxS, HFPO-DA, PFNA, and PFBS, individually and in a
mixture, may cause adverse human health effects on several biological
systems including the endocrine, cardiovascular, developmental, immune,
and hepatic systems. Additionally, these four PFAS, as well as other
PFAS, are likely to
[[Page 18651]]
produce dose-additive effects from co-exposures.
The substantial likelihood that PFHxS, HFPO-DA, PFNA, and
PFBS, individually occur and 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 VII of this preamble, and the
corresponding significant populations served by these water systems.
PFHxS, HFPO-DA, PFNA, and PFBS, individually and in a
mixture, are expected to be environmentally persistent.
Validated EPA-approved measurement methods are available
to measure PFHxS, HFPO-DA, PFNA, and PFBS, individually and in
mixtures. See section VIII of this preamble for further discussion.
Treatment technologies are available to remove PFHxS,
HFPO-DA, PFNA, and PFBS, and mixtures of these contaminants, from
drinking water. See section XI of this preamble for further discussion.
Regulating PFHxS, HFPO-DA, PFNA, and PFBS, in addition to
PFOA and PFOS, is anticipated to reduce the overall public health risk
from all other PFAS that co-occur and are co-removed. Their regulation
is anticipated to provide public health protection at the majority of
known sites with PFAS-impacted drinking water.
There are achievable steps to manage drinking water that
can be taken to reduce risk.
Due to the environmental persistence of these chemicals, there is
potential for toxicity at environmentally relevant concentrations as
studies show it can take years for many PFAS to leave the human body
(NIEHS, 2020). See section III of this preamble above and section V of
this preamble for discussion about the human health effects of PFHxS,
HFPO-DA, PFNA, and PFBS.
Data from both the UCMR 3 and state monitoring efforts demonstrates
occurrence or likely occurrence and co-occurrence of PFHxS, HFPO-DA,
PFNA, and PFBS, and their mixtures, at frequencies and levels of public
health concern. Under UCMR 3, 1.4% of systems serving approximately 6.7
million people had reported detections (greater than or equal to their
MRLs) of PFHxS, PFNA, and PFBS of at least one of the three compounds.
Additionally, based on the available state monitoring data presented
earlier in this section, in the 11 states shown in Table 2 that
conducted non-targeted sampling of the four PFAS, monitored systems
that reported detections of PFHxS, HFPO-DA, PFNA, and PFBS serve
approximate populations of 8.3 million, 1.8 million, 2.6 million, and
8.8 million people, respectively. Further, as demonstrated in the UCMR
3 and state data, concentrations of these PFAS, as well as PFOA and
PFOS, and their mixtures co-occur at levels of public health concern as
described in more detail in section VII.C. and VII.D. of this preamble
and USEPA (2023e).
Analytical methods are available to measure PFHxS, HFPO-DA, PFNA,
and PFBS in drinking water. EPA has published two multi-laboratory
validated drinking water methods for individually measuring PFHxS,
HFPO-DA, PFNA, and PFBS: EPA Method 537.1 which measures 18 PFAS and
EPA Method 533 which measures 25 PFAS. There are 14 PFAS which overlap
between methods and both methods measure PFOA and PFOS). Additional
discussion on analytical methods can be found in section VIII of this
preamble.
EPA's analysis, summarized in section XI of this preamble, found
there are available technologies capable of reducing PFHxS, HFPO-DA,
PFNA, and PFBS. These technologies include granular activated carbon
(GAC), AIX resins, reverse osmosis (RO), and nanofiltration (NF). See
discussion in section XI of this preamble for information about these
treatment technologies. Due to the inherent nature of sorptive and
high-pressure membrane technologies such as these, treatment
technologies that remove PFHxS, HFPO-DA, PFNA, and PFBS and their
mixtures 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 VII of this
preamble, PFHxS, HFPO-DA, PFNA, and PFBS also co-occur with PFAS for
which the Agency is not currently making a preliminary 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 EPA's findings that PFHxS,
HFPO-DA, PFNA, and PFBS have a substantial likelihood to co-occur in
drinking water with other PFAS and treating for PFHxS, HFPO-DA, PFNA,
and PFBS is anticipated to result in removing these and other PFAS,
regulation of PFHxS, HFPO-DA, PFNA, PFBS (as well as PFOA and PFOS)
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, HFPO-DA, PFNA, 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, EPA has
identified meaningful and achievable actions that can be taken to
reduce the human health risk of PFAS.
EPA is preliminarily determining that regulation of PFHxS, HFPO-DA,
PFNA, and PFBS presents a meaningful opportunity for health risk
reduction for persons served by PWSs.
E. EPA's Preliminary Regulatory Determination Summary for PFHxS, HFPO-
DA, PFNA, and PFBS
The statute provides EPA significant discretion when making a
preliminary determination under Section 1412(b)(1)(A). This decision to
make a preliminary regulatory determination for PFHxS, HFPO-DA, PFNA
and PFBS and their mixtures is based on consideration of the evidence
supporting the factors individually and as a whole.
EPA's preliminary determination that PFHxS, HFPO-DA, PFNA, and PFBS
``may have an adverse effect on the health of persons'' is strongly
supported by numerous studies where multiple health effects are
demonstrated following exposure. EPA's preliminary determination
regarding occurrence is supported by evidence documenting the trend
demonstrated first by the UCMR 3 data and then subsequent state
occurrence data that measured occurrence of the four PFAS has increased
with more widespread monitoring primarily using EPA approved methods
that have, lower reporting thresholds. The statute contemplates that
there may be instances where exact occurrence may not be ``known'' and
in these instances EPA need only demonstrate that that it has a basis
to determine that there is a ``substantial likelihood that the
contaminant will occur.'' Additional nationwide monitoring data will be
conducted between 2023-2025 under the UCMR 5. This data will serve to
demonstrate whether the four PFAS are known to occur, however, EPA has
sufficient evidence now to support a preliminary determination there is
a substantial likelihood that these PFAS will occur frequently and at
concentrations where they are likely to exceed their respective HRLs
based on the increased occurrence trends documented by available
information. This finding is further supported by available dose
additive impacts and co-occurrence information that demonstrates that
there is a substantial likelihood that these PFAS co-occur in PWSs with
a frequency and at levels of public health concern at hundreds of
systems serving millions of people.
[[Page 18652]]
Finally, EPA's preliminary determination that regulating these four
PFAS presents a meaningful opportunity for health risks reductions is
strongly supported by numerous bases, including the potential adverse
human health effects and potential for exposure and co-exposure of
these PFAS, and the availability of both analytical methods to measure
and treatment technologies to remove these contaminants in drinking
water.
After considering these factors individually and together, EPA has
preliminarily determined that now is the appropriate time to exercise
its discretion under the statute to regulate the four PFAS and their
mixtures as contaminants under SDWA. EPA recognizes the public health
burden of PFHxS, HFPO-DA, PFNA, and PFBS, as well as PFOA, PFOS, and
other PFAS, a public urgency to reduce PFAS concentrations in drinking
water, and that the proposed regulation provides a mechanism to reduce
these PFAS expeditiously and efficiently for regulated utilities,
States, and Tribes. Furthermore, in addition to making this preliminary
regulatory determination, EPA is concurrently proposing an NPDWR to
include all four of these PFAS, 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 as
effectively and quickly as feasible, maximizing the protection of
drinking water for the American public.
F. Request for Comment on EPA's Preliminary Regulatory Determination
for PFHxS, HFPO-DA, PFNA, and PFBS
EPA specifically requests comment on its preliminary regulatory
determination for PFHxS, HFPO-DA, PFNA, and PFBS and their mixtures. In
particular, EPA requests comment on whether there is additional health
information the Agency should consider as to whether PFHxS, HFPO-DA,
PFNA, and PFBS and their mixtures may have an adverse effect on the
health of persons. EPA also requests comment on whether there are other
peer-reviewed health or toxicity assessments for other PFAS the Agency
should consider as part of this action. Additionally, EPA requests
comment on additional occurrence data the Agency should consider
regarding its decision that PFHxS, HFPO-DA, PFNA, and PFBS and their
mixtures occur or are substantially likely to occur in PWSs with a
frequency and at levels of public health concern. EPA also requests
public comment on its evaluation that regulation of PFHxS, HFPO-DA,
PFNA, and PFBS and their mixtures, in addition to PFOA and PFOS, will
provide protection from PFAS that will not be regulated as part of this
proposed PFAS NPDWR.
IV. Approaches to MCLG Derivation
Section 1412(a)(3) of the SDWA requires the Administrator of the
EPA to propose a 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
1412(b)(3)(C)(i)(V), in developing the MCLG, 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 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.
EPA is proposing individual MCLGs for two PFAS (PFOA and PFOS; see
USEPA, 2023b; USEPA, 2023c) and a separate MCLG to account for dose
additive noncancer effects for a mixture of four PFAS (PFHxS, HFPO-DA,
PFNA, and PFBS; see USEPA, 2023d). The derivation of the proposed MCLG
for the mixture is based on an HI approach (USEPA, 2023a).
The SAB, discussed further in section XV.K.1. of this preamble
below, supported many of EPA's conclusions presented in the PFOA and
PFOS MCLG approaches, mixtures framework, and economics benefits
documents including health effects and economic benefits analyses
(USEPA, 2022a). Regarding the Proposed Approaches to the Derivation of
Draft MCLGs for PFOA and PFOS (USEPA, 2021e; USEPA, 2021f), SAB agreed
with the selection of the UFs used in deriving the noncancer RfDs,
supported the selection of an RSC of 20%, and agreed with the
``likely'' designation for PFOA carcinogenicity.
The SAB commented that EPA should ``focus on those health outcomes
that have been concluded to have the strongest evidence'' and
``consider multiple human and animal studies for a variety of endpoints
in different populations so as to provide convergent evidence that is
more reliable than any single study or health endpoint in isolation.''
EPA applied these recommendations when deriving points of departure and
selecting critical studies used for toxicity value development in the
MCLG documents for PFOA and PFOS (USEPA, 2023b; USEPA, 2023c).
Specifically, EPA focused on the five health outcomes with the
strongest weight of evidence--liver, immune, cardiovascular,
developmental, and cancer--during quantitative analyses.
However, the SAB had a number of consensus recommendations and
identified ``methodological concerns in the draft MCLG documents for
PFOA and PFOS.'' EPA has addressed these concerns by providing
additional clarity and transparency on the systematic literature review
process and expanding the systematic review steps included in the
health effects assessment. The systematic review protocols, which were
developed to be consistent with EPA's Office of Research and
Development (ORD) Integrated Risk Information System (IRIS) Staff
Handbook (USEPA, 2022f), are available in the Appendices of the MCLG
documents for PFOA and PFOS (USEPA, 2023b; USEPA, 2023c). In order to
base the MCLG derivation on the best available science, EPA has updated
the draft MCLG documents to reflect the results of conducting an update
to the literature search and performing new evaluations of models,
methods, and data. More information is available in section XV.K.1. of
this preamble.
EPA expects to conduct a final literature search update before the
final rule is promulgated. The SAB input has made this product more
scientifically sound and ensures that it reflects the best available
science. The updated supporting information can be found in the MCLG
documents for PFOA and PFOS (USEPA, 2023b; USEPA, 2023c).
A. Approach to MCLG Derivation for Individual PFAS
To establish the MCLG, EPA assesses the peer reviewed science
examining cancer and noncancer health effects associated with oral
exposure to the contaminant. For linear carcinogenic contaminants,
where there is a proportional relationship between dose and
carcinogenicity at low concentrations, EPA has a long-standing practice
of establishing the MCLG at zero (see USEPA, 1998a; USEPA, 2000d;
USEPA, 2001). For nonlinear carcinogenic contaminants, contaminants
that are suggestive carcinogens, and non-carcinogenic contaminants, EPA
typically establishes the MCLG based on an RfD. An RfD is an estimate
of a daily exposure to the
[[Page 18653]]
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.
The MCLG is derived depending on the noncancer and cancer evidence
for a particular contaminant. Establishing the MCLG for a chemical has
historically been accomplished in one of three ways depending upon a
three-category classification approach (USEPA, 1985; USEPA, 1991a). The
categories are based on the available evidence of carcinogenicity after
exposure via ingestion. The starting point in categorizing a chemical
is through assigning a cancer descriptor using EPA's current Guidelines
for Carcinogen Risk Assessment (USEPA, 2005). The 2005 Guidelines
replaced the prior alphanumeric groupings although the basis for the
classifications is similar. In prior rulemakings, the Agency typically
placed Group A, B1, and B2 contaminants into Category I, Group C into
Category II, and Group D and E into Category III based on the Agency's
previous cancer classification guidelines (i.e., Guidelines for
Carcinogen Risk Assessment, published in 51 FR 33992, September 24,
1986 (USEPA, 1986b) and the 1999 draft revised final guidelines (USEPA,
1999):
Category I chemicals have ``strong evidence [of
carcinogenicity] considering weight of evidence, pharmacokinetics, and
exposure'' (USEPA, 1985; USEPA, 1991a). EPA's 2005 Cancer descriptors
associated with this category are: ``Carcinogenic to Humans'' or
``Likely to be Carcinogenic to Humans'' (USEPA, 2005). EPA's policy
under SDWA is to set MCLGs for Category I chemicals at zero, based on
the principle that there is no known threshold for carcinogenicity
(USEPA, 1985; USEPA, 1991a; USEPA, 2016d). In cases when there is
sufficient evidence to determine a nonlinear cancer mode of action
(MOA), the MCLG is based on the RfD approach described below.
Category II chemicals have ``limited evidence [of
carcinogenicity] considering weight of evidence, pharmacokinetics, and
exposure'' (USEPA, 1985; USEPA, 1991a). EPA's 2005 Cancer descriptor
associated with this category is: ``Suggestive Evidence of Carcinogenic
Potential'' (USEPA, 2005). The MCLG for Category II contaminants is
based on noncancer effects (USEPA, 1985; USEPA, 1991a) as described
below.
Category III chemicals have ``inadequate or no animal
evidence [of carcinogenicity]'' (USEPA, 1985; USEPA, 1991a). EPA's 2005
Cancer descriptors associated with this category are: ``Inadequate
Information to Assess Carcinogenic Potential'' and ``Not Likely to Be
Carcinogenic to Humans'' (USEPA, 2005). The MCLG for Category III
contaminants is based on noncancer effects as described below.
For chemicals exhibiting a noncancer threshold for toxic effects
(e.g., Category II or III; e.g., see USEPA, 1985 and USEPA, 1991a) and
nonlinear carcinogens (e.g., see USEPA, 2006a), EPA establishes the
MCLG based on a toxicity value, typically an RfD, but similar toxicity
values may also be used when they represent the best available science
(e.g., ATSDR Minimal Risk Level). A noncancer MCLG is designed to be
protective of noncancer effects over a lifetime of exposure with an
adequate margin of safety, including for sensitive populations and life
stages, consistent with SDWA 1412(b)(3)(C)(i)(V) and 1412(b)(4)(A). The
calculation of a noncancer MCLG includes an oral toxicity reference
value such as an RfD (or Minimal Risk Level), DWI-BW, and RSC as
presented in the equation below:
[GRAPHIC] [TIFF OMITTED] TP29MR23.060
Where:
RfD \3\ = reference dose--an estimate (with uncertainty spanning
perhaps an order of magnitude) of a daily oral exposure of the human
population to a substance that is likely to be without an
appreciable risk of deleterious effects during a lifetime. The RfD
is equal to a point-of-departure (POD) divided by a composite UF.
---------------------------------------------------------------------------
\3\ A reference dose (RfD) is an estimate of the amount of a
chemical a person can ingest daily over a lifetime (chronic RfD) or
less (subchronic RfD) that is unlikely to lead to adverse health
effects in humans.
---------------------------------------------------------------------------
DWI-BW = An exposure factor in the form of the 90th percentile DWI-
BW for the identified population or life stage, in units of liters
of water consumed per kilogram BW per day (L/kg/day). The DWI-BW
considers both direct and indirect consumption of drinking water
(indirect water consumption encompasses water added in the
preparation of foods or beverages, such as tea or coffee). Chapter 3
of EPA's Exposure Factors Handbook (USEPA, 2019a) provides DWI-BWs
for various populations or life stages within the general population
for which there are publicly available, peer-reviewed data such as
National Health and Nutrition Examination Survey (NHANES) data.
RSC = relative source contribution--the percentage of the total
exposure attributed to drinking water sources (USEPA, 2000c), with
the remainder of the exposure allocated to all other routes or
sources.
EPA established internal protocols for the systematic review steps
of literature search, Population, Exposure, Comparator, and Outcomes
(PECO) development, literature screening, study quality evaluation, and
data extraction prior to conducting the systematic review for PFOA and
PFOS. However, EPA recognizes that while components of the protocols
were included in the November 2021 draft Proposed Approaches documents
(USEPA, 2021e; USEPA, 2021f), the protocols were only partially
described in those documents. EPA has incorporated detailed,
transparent, and complete protocols for all steps of the systematic
review process into the Proposed MCLG documents (USEPA, 2023b; USEPA,
2023c). Additionally, the protocols and methods have been updated and
expanded based on SAB recommendations to improve the transparency of
the process used to derive the MCLGs for PFOA and PFOS and to be
consistent with the ORD Staff Handbook for Developing IRIS Assessments
(USEPA, 2022f). For additional details of EPA's systematic review
methods, see USEPA (2023b, 2023c; Chapter 2 and Appendix A).
EPA evaluated strengths and limitations of each study to determine
an overall classification of high, medium, low, or uninformative with
respect to confidence in the quality and reliability of the study (this
was done for each endpoint evaluated in each study). High, medium, and
low confidence studies were prioritized for qualitative assessments,
while only high and medium confidence studies were prioritized for
quantitative assessments. Within each health outcome, the evidence from
epidemiology and animal toxicity studies was synthesized. For noncancer
health outcomes, the animal toxicological and epidemiological evidence
for each health outcome was classified as either robust, moderate,
slight, indeterminate, or compelling evidence of no effect. The weight
of evidence for each health outcome across all available evidence
(i.e., epidemiology, animal toxicity, and mechanistic studies) was
classified as either evidence demonstrates, evidence indicates
(likely), evidence suggests, evidence inadequate, or strong evidence
supports no effect. To characterize the weight of evidence for cancer
effects,
[[Page 18654]]
EPA followed recommendations of the Guidelines for Carcinogen Risk
Assessment (USEPA, 2005). Further description of the methods used to
make these determinations for PFOA and PFOS is provided in USEPA
(2023b; 2023c). Consistent with the recommendations of the SAB and to
ensure that the rule reflects the best available science, EPA continues
to evaluate the literature using systematic review methods.
The approach to select the DWI-BW and RSC for MCLG derivation
includes a step to identify sensitive population(s) or life stage(s)
(i.e., populations or life stages that may be more susceptible or
sensitive to a chemical exposure) by considering the available data for
the contaminant, including the adverse health effects reported in the
toxicity study on which the RfD 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 or health outcomes may have been
assessed in available studies), the critical effect and 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 within the low dose range among the available data.
Evaluation of the critical study, including the exposure window or
interval, may identify a sensitive population or life stage (e.g.,
pregnant women, formula-fed infants, lactating women). In such cases,
EPA can select the corresponding DWI-BW for that sensitive population
or life stage from the Exposure Factors Handbook (USEPA, 2019a) to
derive the MCLG. In the absence of information indicating a sensitive
population or life stage, the DWI-BW corresponding to the general
population may be selected for use in MCLG derivation.
To account for potential aggregate risk from exposures and exposure
pathways other than oral ingestion of drinking water, EPA applies an
RSC when calculating MCLGs to ensure that total exposure to a
contaminant does not exceed the daily exposure associated with the
toxicity value, consistent with USEPA (2000c) and long-standing EPA
methodology for establishing drinking water MCLGs and NPDWRs. 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
transfer to 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, 2000c). The purpose of the RSC is to ensure that the
level of a contaminant (e.g., MCLG), when combined with other
identified potential sources of exposure for the population of concern,
will not result in exposures that exceed the RfD (or Minimal Risk
Level) (USEPA, 2000c).
To determine the RSC, EPA follows the Exposure Decision Tree for
Defining Proposed RfD (or POD/UF) Apportionment in EPA's Methodology
for Deriving Ambient Water Quality Criteria for the Protection of Human
Health (USEPA, 2000c). EPA considers whether there are significant
known or potential uses/sources of the contaminant other than drinking
water, the adequacy of data and strength of evidence available for each
relevant exposure medium and pathway, and whether adequate information
on each exposure source is available to quantitatively characterize the
exposure profile. The RSC is developed to reflect the exposure to the
general population or a sensitive population within the general
population. When exposure data are available for multiple sensitive
populations or life stages, the most health-protective RSC is selected.
In the absence of adequate data to quantitatively characterize exposure
to a contaminant, EPA typically selects an RSC of 20 percent (0.2).
When scientific data demonstrating that sources and routes of exposure
other than drinking water are not anticipated for a specific pollutant,
the RSC can be raised as high as 80 percent based on the available
data, thereby allocating the remaining 20 percent to other potential
exposure sources (USEPA, 2000c).
B. Approach to MCLG Derivation for a PFAS Mixture
There has been a lot of work evaluating parameters that best inform
the combining of PFAS components identified in environmental matrices
into mixtures analyses. Indeed, there is currently no consensus on
whether or how PFAS should be combined for risk assessment purposes.
EPA considered several approaches to account for dose additive
noncancer effects associated with PFHxS, HFPO-DA, PFNA, and PFBS in
mixtures. PFAS can affect multiple human health endpoints and differ in
their impact (i.e., potency of effect) on target organs/systems. PFAS
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,
and immune and liver function (ATSDR, 2021; EFSA, 2018, 2020; EPA,
2023d). For example, one PFAS may be most toxic to the liver, and
another may be most toxic to the thyroid but both chemicals affect the
liver and the thyroid. Other chemicals regulated as groups operate
through a common MOA and predominately affect one human health
endpoint. This supports a flexible data-driven approach that
facilitates the evaluation of multiple health endpoints, such as the
HI.
EPA is proposing to establish an MCLG for a mixture of chemicals
that are expected to impact multiple endpoints. SDWA requires the
agency to establish a health-based MCLG set at, ``a level at which no
known or anticipated adverse effects on the health of persons occur and
which allow for an adequate margin of safety. EPA's SAB opined that
where the health endpoints of the chosen compounds are similar, ``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 EPA'' (USEPA,
2022a). This proposal is based on the Agency's finding that the general
HI approach is the most efficient and effective approach for
establishing an MCLG for PFAS mixtures consistent with the statutory
requirement described above. This finding is based on the level of
protection afforded by both the HBWCs for the individual PFAS as
components of a mixture and the resulting HI itself, which provides an
added margin of safety with respect to potential health hazards of
mixtures of these PFAS. An HI greater than 1.0 is generally regarded as
an indicator of potential adverse health risks associated with exposure
to the mixture (USEPA, 1986a; USEPA, 1991b; USEPA, 2000a). A HI less
than or equal to 1.0 is generally regarded as having no appreciable
risk (USEPA, 1986a; USEPA, 1991b; USEPA, 2000a). The proposed MCLG is
based on using this HI of 1.0, and the HBWCs of each mixture component,
which in turn is based on its respective health-based reference value
(RfV; RfD or MRL). Because the RfV represents an estimate at which no
appreciable risk of deleterious effects exists (USEPA, 1986a, 1991a,
2000a), the use of the HBWCs means that the HI of 1.0 will ensure that
there are no known or anticipated effects on the health of persons and
allow for an adequate
[[Page 18655]]
margin of safety. In addition, the resulting HI adds an additional
margin of safety for mixtures of the four PFAS, to address the
potential for additive toxicity where the contaminants co-occur and the
HBWCs for the individual components are less than 1.0. The Agency
therefore proposes the general HI approach as the basis for the MCLG,
and because treatment to this level is also feasible, the MCL for these
PFAS, (see additional discussion in section VI of this preamble) and
welcomes public comment on its findings.
EPA considered the two main types of HI approaches: (1) the general
HI which allows for component chemicals in the mixture to have
different health effects or endpoints as the basis for the component
chemical reference values (e.g., RfDs), and (2) the target-organ
specific HI which relies on reference values based on the same organ or
organ system (e.g., liver-, thyroid-, or developmental-specific). The
general HI approach is based on the overall RfD which is protective of
all effects for a given chemical, and thus is a more health protective
indicator of risk. The target-organ specific HI approach produces a
less health protective estimate of risk than the general HI when a
contaminant impacts multiple organs because the range of potential
effects has been scoped to a specific target organ, which may be one of
the less potent effects or for which there may be significant currently
unquantified effects. Additionally, a target-organ specific HI approach
relies on toxicity values aggregated by the ``same'' target organ
endpoint/effect, and the absence of information about a specific
endpoint may result in the contaminant not being adequately considered
in a target-organ specific approach, and thus, underestimating
potential health risk. A target-organ specific HI can only be performed
for those PFAS for which a health effect specific RfD is calculated.
For example, for some PFAS a given health effect might be poorly
characterized or not studied at all, or, as a function of dose may be
one of the less(er) potent effects in the profile of toxicity for that
particular PFAS. Another limitation is that so many PFAS lack human
epidemiological or experimental animal hazard and dose-response
information across a broad(er) effect range thus limiting derivation of
target-organ specific values. A similar, effect/endpoint-specific
method called the relative potency factor (RPF) approach, which
represents the relative difference in potency of an effect/endpoint
between an index chemical and other members of the mixture, was also
considered. (Further background on all of these approaches, plus
illustrative examples, and a discussion of the advantages and
challenges associated with each approach can be found in Section 5 and
6 in USEPA, 2023d).
EPA also considered setting individual MCLGs instead of and in
addition to using a mixtures-based approach for PFHxS, HFPO-DA, PFNA,
and/or PFBS in mixtures. EPA ultimately selected the general HI
approach for establishing an MCLG for these four PFAS, as described in
greater detail below, because it provides the most health protective
endpoint for multiple PFAS in a mixture to ensure there would be no
known or anticipated adverse effects on the health of persons. EPA also
considered a target-specific HI or RPF approach but, because of
information gaps, EPA may not be able to ensure that the MCLG is
sufficiently health protective. If the Agency only established an
individual MCLG, the Agency would not provide any protection against
dose-additivity from regulated co-occurring PFAS. EPA is seeking
comments on the merits and drawbacks of each of the approaches
described above. As discussed later in this proposal, EPA is also
seeking comment on whether to set MCLGs for the individual PFAS in
addition to or instead of setting them for the mixture.
EPA is proposing use of the general HI approach. Although EPA's SAB
opined that it is reasonable to use a HI for evaluation of mixtures of
PFAS in drinking water for situations where the profile of health
effects of the chosen compounds share similarity in one or more effect
domains, the SAB emphasized that using a HI in the context of
developing regulations for PFAS should not be directly interpreted as a
quantitative estimate of mixture risk. Rather the SAB agreed that the
HI can be used as an indicator of potential health risk(s) associated
with exposure to mixtures of PFAS; see discussion in USEPA (2023d) and
Section V of this preamble for further information. EPA addresses the
full range of responses to SAB comments in a response to comment
document; that document is included in the docket for this action
(USEPA, 2023f).
EPA proposes that the general HI is the most appropriate and
justified approach for considering PFAS mixtures in this rulemaking
because of the level of protection afforded for the evaluation of
chemicals with diverse (but in many cases shared) health endpoints.
SDWA requires the agency to establish a MCLG set at, ``a level at which
no known or anticipated adverse effects on the health of persons occur
and which allow for an adequate margin of safety.'' In this context,
EPA has made a reasonable policy choice for regulating a mixture of
chemicals that are expected to adversely impact multiple health
endpoints. Because mixture component chemical HBWCs are based on
overall lowest RfDs across candidate critical effects, the approach is
protective against all health effects across component chemicals and
therefore meets the statutory requirements of establishing an MCLG
under SDWA. Basing the mixture MCLG on overall RfDs ensures that there
are no known or anticipated effects, and using the HI adds an
appropriate margin of safety for a class of contaminants that have been
shown to co-occur and evidence suggests that they may have dose
additive toxicity. Conversely, by definition, a target-organ specific
(e.g., liver-, thyroid-, or developmental-specific) HI or RPF approach
would not be protective of all health effects across the four PFAS
proposed for regulation with the mixture MCLG.
Use of the general HI approach over the target-organ specific HI
for these four PFAS is supported by EPA guidance (EPA, 2000a) and
available health assessments and toxicity values (overall RfDs).
Target-organ specific reference values and RPFs are not currently
available for HFPO-DA, PFBS, PFHxS, and PFNA.
EPA's protocol for MCLG development for the mixture of PFHxS, HFPO-
DA, PFNA, and PFBS follows existing Agency guidance, policies, and
procedures related to the three key inputs (i.e., RfD/Minimal Risk
Level, DWI-BW, and RSC) and longstanding Agency mixtures guidance
(USEPA, 1986a; USEPA, 2000a) to address dose additive health effects.
First, EPA identifies or derives a HBWC, calculated using the MCLG
equation above, for each of the four individual PFAS in the mixture.
More information on HBWCs for PFHxS, HFPO-DA, PFNA, and PFBS is
available in section III.B of this preamble. Peer reviewed, publicly
available assessments for PFHxS (ATSDR, 2021), HFPO-DA (USEPA, 2021b),
PFNA (ATSDR, 2021), and PFBS (USEPA, 2021a) provide the chronic
reference values (RfD, adjusted Minimal Risk Level) used to calculate
the HBWCs for these four PFAS. The DWI-BW and RSC for each of the four
PFAS are determined as described using the processes described for
individual PFAS (Section IV.A of this preamble). Briefly, the DWI-BW
for each of the four PFAS is selected from the EPA Exposure Factors
Handbook (USEPA, 2019a), taking into account the relevant
[[Page 18656]]
sensitive population(s) or life stage(s). RSCs are determined based on
a literature review of potential exposure sources of the four PFAS and
using the Exposure Decision Tree approach (USEPA, 2000c).
The HI is based on an assumption of dose addition (DA) among the
mixture components (Svendsgaard and Hertzberg, 1994; USEPA, 2000a). An
important aspect of the proposed `general HI' approach is that it is
based on the availability of a reference value regardless of the
critical effect for each mixture component. Unlike a target-organ
specific Hazard Index which is typically based on either shared mode-
of-action or shared health outcome of mixture components, the general
HI is based on a non-cancer reference value (RfD or Minimal Risk Level)
for the critical (usually the most sensitive) effect of each component
(USEPA, 2000a; USEPA, 1989). Importantly, while many PFAS share some
common target organs/health outcomes such as liver toxicity, the
potency--and in some cases, even the overall most sensitive target
organ--differs among PFAS. As an example, the most sensitive organ to
HFPO-DA is the liver while the most sensitive organ to PFBS is the
thyroid. Integrating the overall RfDs for each mixture PFAS in the
calculation of component HQs and a corresponding mixture HI, regardless
of the critical (most sensitive) effect, ensures health protection
under an assumption of dose additivity. The alternative may
underestimate potential health risk(s) associated with exposure to a
PFAS mixture as a given effect-specific HI might entail the use of
target-organ specific reference values that are not protective of
effects at a given mixture component's corresponding overall RfD.
Further, effect-specific RfDs are not typically derived for chemicals
beyond the critical effect for the overall RfD which might prohibit the
inclusion of a chemical in a target-organ specific HI. Recognizing the
various nuances to the HI approach, EPA welcomes public comment.
In the HI approach, an HQ is calculated as the ratio of human
exposure (E) to a health-based reference value (RfV) for each mixture
component chemical (i) (USEPA, 1986a). The HI involves the use of RfVs
for each PFAS mixture component (in this case, PFHxS, HFPO-DA, PFNA,
and PFBS), which have been selected based on sensitive health outcomes
that are protective of all other adverse health effects observed after
exposure to the individual PFAS. Thus, this approach, which protects
against all adverse effects, not only a single adverse outcome/effect
(e.g., as would be the case using other mixture approaches such as the
target-organ specific HI or RPF approach), is a health protective risk
indicator and appropriate for MCLG development. The HI is unitless; in
the HI formula, E and the RfV must be in the same units. For example,
if E is the oral intake rate (mg/kg/day), then the RfV could be the RfD
or Minimal Risk Level, which have the same units. Alternatively, the
exposure metric can be a media-specific metric such as a measured water
concentration (e.g., nanograms per liter or ng/L) and the RfV can be an
HBWC (e.g., ng/L). The component chemical HQs are then summed across
the mixture to yield the HI. A mixture HI exceeding 1.0 indicates that
the exposure metric is greater than the toxicity metric and there is
potential concern for a given environmental medium or site, in this
case, drinking water served to consumers from a PWS. The HI provides an
indication of: (1) concern for the overall mixture and (2) potential
driver PFAS (i.e., those PFAS with high[er] HQs). The HI accounts for
differences in toxicity among the mixture component chemicals rather
than weighting them all equally. For a detailed discussion of PFAS dose
additivity and the HI approach, see the PFAS Mixtures Framework (USEPA,
2023d). The HI is calculated through the following equation:
[GRAPHIC] [TIFF OMITTED] TP29MR23.061
Where:
HI = Hazard Index
HQi = Hazard Quotient for chemical i
Ei = Exposure, i.e., dose (mg/kg/day) or occurrence
concentration, such as in drinking water (mg/L), for chemical i
RfVi = Reference value (e.g., oral RfD or Minimal Risk
Level) [mg/kg/day], or corresponding HBWC; e.g., such as an MCLG for
chemical i (in milligrams per liter or mg/L)
V. Maximum Contaminant Level Goals
A. PFOA
1. Carcinogenicity Assessment and Cancer Slope Factor (CSF) Derivation
a. Summary of Cancer Health Effects
The carcinogenicity of PFOA has been observed in both human
epidemiological and animal toxicity studies. The evidence in high and
medium confidence epidemiological studies is primarily based on the
incidence of kidney and testicular cancer, as well as some medium
quality studies providing limited evidence of breast cancer associated
with exposure to PFOA. Other cancer types have been observed in human
studies, although the evidence for these is largely from low confidence
studies. The evidence of carcinogenicity in animal models was observed
in three medium or high quality chronic oral animal studies in adult
Sprague-Dawley rats which identified neoplastic lesions in the liver,
pancreas, and testes after PFOA exposure.
Since publication of the 2016 PFOA Health Effects Support Document
(HESD) (USEPA, 2016e), the evidence supporting the carcinogenicity of
PFOA has been strengthened by additional published studies. In
particular, the evidence of kidney cancer from highly exposed community
studies (Vieira et al., 2013; Barry et al., 2013) is now supported by
new evidence of renal cell carcinoma (RCC) from a nested case-control
study in the general population (Shearer et al., 2021). In animal
models, the evidence of multi-site tumorigenesis reported in two
chronic bioassays in rats (Butenhoff et al., 2012a; Biegel et al.,
2001) is now supported by new evidence from a third chronic bioassay in
rats that also reports multi-site tumorigenesis (NTP, 2020).
The available evidence indicates that PFOA has carcinogenic
potential in humans and at least one animal species. A plausible,
though not definitively causal, association between human exposure to
PFOA and kidney and testicular cancers in the general population and
highly exposed populations is supported by the available evidence. As
stated in the Guidelines for Carcinogen Risk Assessment (USEPA, 2005),
``an inference of causality is strengthened when a pattern of elevated
risks is observed across several independent studies.'' Two medium
confidence studies in independent populations provide evidence of an
association between elevated PFOA serum concentrations and kidney
cancer (Shearer et al., 2021; Vieira et al., 2013), while two studies
from the same cohort provide evidence of an association between
testicular cancer and elevated PFOA serum concentrations (Vieira et
al., 2013; Barry et al., 2013). A recent National Academies of Science,
Engineering, and Mathematics report on PFAS similarly ``concluded that
there is sufficient evidence for an association between PFAS and kidney
cancer'' (NASEM, 2022). The evidence of carcinogenicity in animals is
from three studies in rats of the same strain. The results from these
studies provide evidence of increased incidence of three tumor types
(Leydig cell tumors (LCTs), pancreatic acinar cell tumors (PACTs),
[[Page 18657]]
and hepatocellular adenomas) in males administered diets dosed with
PFOA. Importantly, site concordance is not always assumed between
humans and animal models; agents observed to produce tumors may do so
at the same or different sites in humans and animals, as appears to be
the case for PFOA (USEPA, 2005).
b. CSF Derivation
When a chemical is a linear carcinogen, a value that numerically
describes the relationship between the dose of a chemical and the risk
of cancer, is calculated. This is known as a cancer slope factor (CSF).
The CSF is the cancer risk (i.e., proportion affected) per unit of dose
(USEPA, 2005). In addition to reevaluating the CSF previously derived
and described in the 2016 HESD (USEPA, 2016e) based on LCTs in male
rats observed by Butenhoff et al. (2012a), EPA derived CSFs for
combined hepatocellular adenomas and carcinomas and pancreatic acinar
cell adenomas in male rats observed by NTP (2020) and kidney cancer in
humans reported by Shearer et al. (2021) and Vieira et al. (2013). EPA
focused on the CSFs derived from the epidemiological data consistent
with the EPA ORD handbook which states ``when both laboratory animal
data and human data with sufficient information to perform exposure-
response modeling are available, human data are generally preferred for
the derivation of toxicity values'' (USEPA, 2022f).
EPA selected the critical effect of RCCs in human males reported by
Shearer et al. (2021) as the basis of the CSF for PFOA. Shearer et al.
(2021) is a multi-center case-control epidemiological study nested
within the National Cancer Institute's (NCI) Prostate, Lung,
Colorectal, and Ovarian Screening Trial (PLCO) with median PFOA levels
relevant to the general U.S. population. The PLCO is a randomized
clinical trial of the use of serum biomarkers for cancer screening. The
cases in Shearer et al. (2021) included all the participants in the
screening arm of the PLCO trial who were newly diagnosed with RCC
during the follow-up period (N = 326) and all cases were
histopathologically confirmed. Controls were selected among
participants in the PLCO trial screening arm based on those who had
never had RCC and were individually matched to the RCC cases by age at
enrollment, sex, race/ethnicity, study center, and year of blood draw.
Additionally, analyses conducted by the authors accounted for numerous
confounders, including the potential for confounding by other PFAS.
Study design advantages of the Shearer et al. (2021) compared with the
Vieira et al. (2013) include specificity in the health outcome
considered (RCC vs. any kidney cancer), the type of exposure assessment
(serum biomarker vs. modeled exposure), source population (multi-center
vs. Ohio and West Virginia regions), and study size (324 cases and 324
matched controls vs. 59 cases and 7,585 registry-based controls). The
resulting CSF is 0.0293 (ng/kg/day)-\1\.
Selection of RCCs as the critical effect is supported by similar
findings from other studies of a highly exposed community (Barry et
al., 2013; Vieira et al., 2013), an occupational kidney cancer
mortality study (Steenland and Woskie, 2012), as well as a meta-
analysis of epidemiological literature that concluded that there was an
increased risk of kidney tumors correlated with increased PFOA serum
concentrations (Bartell et al., 2021). Further discussion of the
rationale for endpoint and study selection and descriptions of the
modeling methods are described in USEPA (2023b).
2. Assessment of Noncancer Health Effects and Reference Dose (RfD)
Derivation
The Agency has also considered noncancer effects in its assessment
of the best available science to derive the MCLG. As described in USEPA
(2023b), there is evidence from both human epidemiological and animal
toxicological studies that oral PFOA exposure may result in adverse
health effects across many health outcomes, including but not limited
to: immune, hepatic, developmental, cardiovascular, reproductive, and
endocrine outcomes. As recommended by the SAB (USEPA, 2022a), EPA has
largely focused its systematic literature review, health outcome
synthesis, and toxicity value derivation efforts ``on those health
outcomes that have been concluded to have the strongest evidence,
including the liver disease, immune system dysfunction, serum lipid
aberration, impaired fetal growth, and cancer.'' Conclusions regarding
the four noncancer adverse health outcome categories (i.e., judgements
for human, animal, and integrated evidence streams (USEPA, 2023b)) are
described in the subsections below. Descriptions of studies and the
basis for conclusions about the non-prioritized health outcomes are
described in USEPA (2023b).
a. Summary of Noncancer Health Effects
EPA determined that the evidence indicates that oral PFOA exposure
is associated with adverse hepatic effects based on the study quality
evaluation, evidence synthesis and evidence integration of the relevant
human epidemiological and animal toxicity studies. There is moderate
evidence from epidemiological studies supporting an association between
PFOA exposure and hepatic outcomes such as elevated serum liver enzymes
indicative of hepatic damage. Overall, there is consistent evidence of
a positive association between PFOA serum concentrations and alanine
aminotransferase (ALT), a liver enzyme marker. The evidence of hepatic
effects in humans was supported by robust evidence of hepatic effects
resulting from PFOA exposure in animal studies. Several studies provide
comprehensive histopathological reports of non-neoplastic hepatic
lesions (e.g., hepatocellular death and necrosis) in PFOA-treated
rodents, as well as increases in serum liver enzymes similar to the
trends observed in humans.
EPA determined that the evidence indicates that oral PFOA exposure
is associated with adverse immunological effects based on the study
quality evaluation, evidence synthesis and evidence integration of the
relevant human epidemiological and animal toxicity studies. There is
moderate evidence from epidemiological studies supporting an
association between PFOA and immune outcomes such as immunosuppression.
Overall, there is consistent evidence of an association between PFOA
serum concentrations and developmental immune effects (i.e., reduced
antibody response to vaccination in children). Associations between
PFOA and other immune system effects (e.g., hypersensitivity and
autoimmune disease) were mixed. The evidence for developmental
immunological effects in humans was supported by moderate evidence of
immunotoxicity resulting from PFOA exposure in animal studies. Studies
report varying manifestations of immune system effects including
altered immune cell populations and altered spleen and thymus
cellularity and weight. PFOA treatment resulted in reduced globulin and
immunoglobulin levels in animals that are consistent with the decreased
antibody response seen in human populations (i.e., the observed animal
and human study health outcomes are both indicators of
immunosuppression).
EPA determined that the evidence indicates that oral PFOA exposure
is associated with adverse developmental effects based on the study
quality evaluation, evidence synthesis and evidence integration of the
relevant human epidemiological and animal
[[Page 18658]]
toxicity studies. There is moderate evidence from epidemiological
studies supporting an association between PFOA and developmental
outcomes such as fetal growth. Overall, there is consistent evidence of
a relationship between PFOA concentrations and low birth weight.
Associations between PFOA and other developmental effects (e.g.,
postnatal growth, fetal loss, and birth defects) were mixed. The
evidence for developmental effects in humans was supported by robust
evidence of developmental toxicity resulting from PFOA exposure in
animal studies. Several studies in rodents provide evidence of
decreased fetal and pup weight due to gestational PFOA exposure,
consistent with the evidence of low birth weight in humans. Other pre-
and post-natal effects observed in animal models include decreased
offspring survival and developmental delays (e.g., delayed eye
opening).
EPA determined that the evidence indicates that oral PFOA exposure
is associated with adverse cardiovascular effects based on the study
quality evaluation, evidence synthesis and evidence integration of the
relevant human epidemiological and animal toxicity studies. There is
moderate evidence from epidemiological studies supporting an
association between PFOA and cardiovascular outcomes such as
alterations in serum lipids. Overall, there is consistent evidence of
positive relationships between PFOA serum concentrations and serum
total cholesterol, low-density lipoproteins, and triglycerides. There
is also limited evidence of positive associations of PFOA with blood
pressure and hypertension among adult populations. The evidence for
cardiovascular effects in humans was supported by moderate evidence of
cardiovascular effects resulting from PFOA exposure in animal studies.
Several studies in rodents provide evidence of alterations in serum
total cholesterol and triglycerides, though the effect direction varied
with dose. Regardless, these effects indicate a disruption in lipid
metabolism resulting from PFOA treatment, consistent with the
alterations in serum lipids observed in humans.
b. RfD Derivation
The databases for the four prioritized health outcomes were
evaluated further for identification of medium and high confidence
studies and endpoints to select for dose-response modeling. EPA
prioritized endpoints with the strongest overall weight of evidence
based on human and animal evidence for POD derivation. Specifically,
EPA focused the dose response assessment on the health outcomes where
the evidence indicated that PFOA causes health effects in humans under
relevant exposure circumstances. The focus of this Federal Register
Notice (FRN) is on epidemiological studies for the four prioritized
health outcomes for which studies meeting this consideration were
available, as human data are generally preferred ``when both laboratory
animal data and human data with sufficient information to perform
exposure-response modeling are available'' (USEPA, 2023b). EPA presents
PODs and candidate RfDs for animal studies, as well as other health
outcomes determined to have sufficient strength of evidence and studies
suitable for dose-response modeling in USEPA (2023b).
EPA identified four candidate critical effects across the four
prioritized health outcomes, all of which were represented by several
candidate critical studies. These candidate critical effects are
decreased antibody production in response to vaccinations (immune), low
birth weight (developmental), increased serum total cholesterol
(cardiovascular), and elevated ALT (hepatic). As described in the
following paragraphs and in further detail in USEPA (2023b), EPA
selected studies from each health outcome to proceed with candidate RfD
derivation. For all selected candidate RfDs, the composite UF was 10
(10x for intraspecies variability). The candidate RfDs are presented in
Table 3.
Two medium confidence studies were considered for POD derivation
for the decreased antibody production in response to various
vaccinations in children Budtz-J[oslash]rgensen and Grandjean (2018);
and Timmerman et al. (2021). These candidate studies offer a variety of
PFOA exposure measures across various populations and various
vaccinations. Budtz-J[oslash]rgensen and Grandjean (2018) investigated
anti-tetanus and anti-diphtheria responses in Faroese children aged 5-7
and Timmerman et al. (2021) investigated anti-tetanus and anti-
diphtheria responses in Greenlandic children aged 7-12. Though the
Timmerman et al. (2021) study is also a medium confidence study, the
study by Budtz-J[oslash]rgensen and Grandjean (2018) has two additional
features that strengthen the confidence in this RfD: (1) the response
reported by this study was more precise in that it reached statistical
significance, and (2) the analysis considered co-exposures of other
PFAS. The RfD for anti-tetanus response in 7-year-old Faroese children
and anti-diphtheria response in 7-year-old Faroese children, both from
Budtz-J[oslash]rgensen and Grandjean (2018) were ultimately selected
for the immune outcome as they are the same and have no distinguishing
characteristics that would facilitate selection of one over the other.
Six high confidence studies (Chu et al., 2020; Govarts et al.,
2016; Sagiv et al., 2018; Starling et al., 2017; Wikstr[ouml]m et al.,
2020; Yao et al., 2021) reported decreased birth weight in infants
whose mothers were exposed to PFOA. These candidate studies offer a
variety of PFOA exposure measures across the fetal and neonatal window.
All six studies reported their exposure metric in units of ng/mL and
reported the [beta] coefficients per ng/mL or ln(ng/mL), along with 95%
confidence intervals (CIs), estimated from linear regression models. Of
the six individual studies, Sagiv et al. (2018) and Wikstr[ouml]m et
al. (2020) assessed maternal PFOA serum concentrations primarily or
exclusively in the first trimester, minimizing concerns surrounding
bias due to pregnancy-related hemodynamic effects. Therefore, the RfDs
from these two studies were considered further for candidate RfD
selection. Both were high confidence prospective cohort studies with
many study strengths including sufficient study sensitivity and largely
sound methodological approaches, analysis, and design, as well as no
evidence of bias. The RfD from Wikstr[ouml]m et al. (2020) was
ultimately selected for the developmental outcome as it was the lowest
candidate RfD from these two studies.
Three medium confidence studies were considered for POD derivation
for the cholesterol endpoint (Dong et al., 2019; Lin et al., 2019;
Steenland et al., 2009). These candidate studies offer a variety of
PFOA exposure measures across various populations. Dong et al. (2019)
investigated the NHANES population (2003-2014), while Steenland et al.
(2009) investigated effects in a high-exposure community (the C8 Health
Project study population). Lin et al. (2019) collected data from
prediabetic adults from the Diabetes Prevention Program (DPP) and DPP
Outcomes Study at baseline (1996-1999). Of the three studies, Dong et
al. (2019) and Steenland et al. (2009) exclude those prescribed
cholesterol medication, minimizing concerns surrounding confounding due
to the medical intervention altering serum total cholesterol levels.
Additionally, Dong et al. (2019) reported measured serum total
cholesterol whereas Steenland et al. (2009) reported regression
coefficients as the response variable. Since EPA prefers dose response
modeling of endpoint data, the RfD from Dong et al. (2019) was selected
for the cardiovascular outcome, as there
[[Page 18659]]
is increased confidence in the modeling results from this study.
Four medium confidence studies were selected as candidates for POD
derivation for the ALT endpoint (Gallo et al., 2012; Darrow et al.,
2016; Nian et al., 2019; Lin et al., 2010). The two largest studies of
PFOA and ALT in adults are Gallo et al. (2012) and Darrow et al.
(2016), both conducted in over 30,000 adults from the C8 Study. Gallo
et al. (2012) reported measured serum ALT levels, unlike Darrow et al.
(2016) which reported a modeled regression coefficient as the response
variable. Another difference between the two studies is reflected in
exposure assessment: Gallo et al. (2012) includes measured PFOA serum
concentrations, while Darrow et al. (2016) based PFOA exposure on
modeled PFOA serum levels. Two additional studies (Lin et al., 2010;
Nian et al., 2019) were considered by EPA for POD derivation because
they reported significant associations in general populations in the
U.S and a high exposed population in China, respectively. Nian et al.
(2019) examined a large population of adults in Shenyang (one of the
largest fluoropolymer manufacturing centers in China) part of the
Isomers of C8 Health Project. In an NHANES adult population, Lin et al.
(2010) observed elevated ALT levels per log-unit increase in PFOA.
While this is a large nationally representative population, several
methodological limitations, including lack of clarity about base of
logarithmic transformation applied to PFOA concentrations in regression
models and the choice to model ALT as an untransformed variable
preclude its use for POD derivation. While both Nian et al. (2019) and
Gallo et al. (2012) provide measured PFOA serum concentrations and a
measure of serum ALT levels, the RfD for increased ALT from Gallo et
al. (2012) was ultimately selected for the hepatic outcome as it was
conducted in a community exposed predominately to PFOA whereas Nian et
al. (2019) was in a community exposed predominately to PFOS, which
reduces concerns about confounding from other PFAS.
Table 3--Candidate Reference Doses for PFOA for the Four Prioritized
Health Outcomes
------------------------------------------------------------------------
Measurement of Candidate RfD \1\
Study reference exposure and endpoint (mg/kg/day)
------------------------------------------------------------------------
Immune
------------------------------------------------------------------------
Budtz-J[oslash]rgensen and PFOA at age five 3 x 10-
Grandjean, 2018. years and anti-
tetanus antibody
concentrations at
age seven years.
Budtz-J[oslash]rgensen and PFOA at age five 3 x 10-
Grandjean, 2018. years on anti-
diphtheria antibody
concentrations at
age seven years.
Timmerman et al., 2021....... PFOA and anti-tetanus 3 x 10-\8\
antibody
concentrations at
ages 7-10 years.
Timmerman et al., 2021....... PFOA and anti- 2 x 10-\8\
diphtheria antibody
concentrations at
ages 7-10 years.
------------------------------------------------------------------------
Developmental
------------------------------------------------------------------------
Sagiv et al., 2018........... PFOA in first 1 x 10-\7\
trimester and
decreased birth
weight.
Wikstr[ouml]m et al., 2020... PFOA in first and 3 x 10-
second trimesters
and decreased birth
weight.
------------------------------------------------------------------------
Cardiovascular
------------------------------------------------------------------------
Dong et al., 2019............ Increased serum total 3 x 10-
cholesterol.
Steenland et al., 2009....... Increased serum total 5 x 10-\8\
cholesterol.
------------------------------------------------------------------------
Hepatic
------------------------------------------------------------------------
Gallo et al., 2012........... Increased serum ALT.. 2 x 10-
Darrow et al., 2016.......... Increased serum ALT.. 8 x 10-\7\
Nian et al., 2019............ Increased serum ALT.. 5 x 10-\8\
------------------------------------------------------------------------
Notes:
\1\ RfDs are rounded to 1 significant digit.
Bolded values indicate selected health outcome-specific RfDs.
The available evidence indicates there are effects across immune,
developmental, cardiovascular, and hepatic organ systems at the same or
approximately the same level of PFOA exposure. Candidate RfDs within
the immune, developmental, and cardiovascular outcomes are the same
value (i.e., 3 x 10-8 mg/kg/day). Therefore, EPA has selected an
overall RfD for PFOA of 3 x 10-8 mg/kg/day. The immune, developmental
and cholesterol RfDs and serve as co-critical effects and are
protective of effects that may occur in sensitive populations (i.e.,
infants and children), as well as hepatic effects that may result from
PFOA exposure.
c. MCLG Derivation
Consistent with the Guidelines for Carcinogen Risk Assessment
(USEPA, 2005), EPA reviewed the weight of the evidence and 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, pancreatic acinar cell tumors,
and hepatocellular adenomas in rats as described in USEPA (2023b).
Consistent with the statutory definition of MCLG, EPA establishes
MCLGs of zero for carcinogens classified as Carcinogenic to Humans or
Likely to be Carcinogenic to Humans where there is insufficient
information to determine that a carcinogen has a threshold dose below
which no carcinogenic effects have been observed. In this situation,
EPA takes a health protective approach of assuming that there is no
such threshold and that carcinogenic effects should therefore be
extrapolated linearly to zero. This approach ensures that the MCLG is
set at a level where there are no anticipated adverse health effects
with a margin of safety. This is the linear default extrapolation
[[Page 18660]]
approach. Here, EPA has determined that PFOA is Likely to be
Carcinogenic to Humans based on sufficient evidence of carcinogenicity
in humans and animals and 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, 2005) and therefore, it is assumed that
there is no known threshold for carcinogenicity (USEPA, 2016d). Based
upon a consideration of the best available peer reviewed science and a
consideration of an adequate margin of safety, EPA proposes a MCLG of
zero for PFOA in drinking water.
EPA is seeking comment on the derivation of the proposed MCLG for
PFOA and its determination that PFOA is Likely to be Carcinogenic to
Humans and whether the proposed MCLG is set at the level at which there
are no adverse effects to the health of persons and which provides an
adequate margin of safety. EPA is also seeking comment on its
assessment of the noncancer effects associated with exposure to PFOA
and the toxicity values described in USEPA (2023b).
B. PFOS
1. Carcinogenicity Assessment and CSF Derivation
a. Summary of Cancer Health Effects
Several medium and high confidence human epidemiological studies
and one high confidence animal chronic cancer bioassay comprise the
evidence database for the carcinogenicity of PFOS. The available
epidemiology studies reported elevated risk of bladder, prostate,
kidney, and breast cancers after chronic PFOS exposure. While there are
reports of cancer incidence from epidemiological studies, the study
designs, analyses, and mixed results preclude a definitive conclusion
about the relationship between PFOS exposure and cancer outcomes in
humans. The one high confidence animal chronic cancer bioassay study
provides evidence of multi-site tumorigenesis in both male and female
rats.
While the epidemiological evidence of associations between PFOS and
cancer found mixed results across tumor types, the available study
findings support a plausible correlation between PFOS exposure and
carcinogenicity in humans. The single chronic cancer bioassay performed
in rats is positive for multi-site and -sex tumorigenesis (Thomford,
2002; Butenhoff et al., 2012b). In this study, statistically
significant increases in the incidences of hepatocellular adenomas or
combined hepatocellular adenomas and carcinomas were observed in both
male and female rats. There was also a statistically significant dose-
response trend of these tumors in both sexes. As described in USEPA
(2023c), the available mechanistic evidence is consistent with multiple
potential MOAs for this tumor type; therefore, the hepatocellular
tumors observed by Thomford (2002)/Butenhoff et al. (2012b) may be
relevant to humans. In addition to hepatocellular tumors, Thomford
(2002)/Butenhoff et al. (2012b) reported increased incidences of
pancreatic islet cell tumors with a statistically significant dose-
dependent positive trend, as well as modest increases in the incidence
of thyroid follicular cell tumors. The findings of multiple tumor types
provide additional support for potential multi-site tumorigenesis
resulting from PFOS exposure. Structural similarities between PFOS and
PFOA add to the weight of evidence for carcinogenicity of PFOS.
Notably, a similar set of noncancer effects have been observed after
exposure to either PFOA or PFOS in humans and animal studies including
similarities in hepatic, developmental, immunological, cardiovascular,
and endocrine effects.
Under the Guidelines for Carcinogen Risk Assessment (USEPA, 2005),
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.'' As
described in USEPA (2023c), EPA determined that the available data for
PFOS surpass many of the descriptions for the descriptor of Suggestive
Evidence of Carcinogenic Potential.
b. CSF Derivation
The Thomford (2002)/Butenhoff et al. (2012b) chronic cancer study
in male and female rats is of high confidence and provides multi-dose
tumor incidence findings that are suitable for dose-response modeling
and subsequent CSF derivation. As described in USEPA (2023c), EPA
derived PODs and candidate CSFs for three endpoints reported by this
study: hepatocellular adenomas in male rats; combined hepatocellular
adenomas and carcinomas in female rats; and pancreatic islet cell
carcinomas in male rats.
EPA selected the hepatocellular adenomas and carcinomas in female
rats reported by Thomford (2002)/Butenhoff et al. (2012b) as the basis
of the CSF for PFOS because there was a statistically significant
increase in tumor incidence in the highest dose group, a trend of
increased incidence with increasing PFOS concentrations across dose
groups, and it was the most health-protective value. The resulting CSF
is 39.5 (mg/kg/day)-1. Selection of hepatocellular adenomas and
carcinomas in female rats is supported by statistically significant
increases in hepatocellular tumor incidence in the high dose group as
well as a statistically significant trend of this response observed in
the male rats. The critical effect of pancreatic islet cell carcinomas
was not selected as the basis of the CSF because the response of the
high dose group was not statistically different from the control group,
though the trend of response across dose groups was statistically
significant. Further discussion on the rationale for endpoint selection
and descriptions of the modeling methods are described in USEPA
(2023c).
In support of the selection of hepatocellular tumors as the basis
of the CSF for PFOS, a recently published study (Goodrich et al., 2022)
reports associations between hepatocellular carcinomas and PFOS serum
concentrations in humans. These findings provide further support for
both MOA conclusions in USEPA (2023c) and the ``Likely to Be
Carcinogenic to Humans'' designation. This study was published after
the systematic literature review cutoff date for the proposed MCLG for
PFOS (USEPA, 2023c), therefore EPA requests comment on the Goodrich et
al. (2022) study and whether it supports EPA's ``Likely to Be
Carcinogenic to Humans'' designation.
2. Assessment of Noncancer Health Effects and Reference Dose (RfD)
Derivation
The Agency has also considered noncancer effects in its assessment
of the best available science to derive the MCLG. As described in USEPA
(2023c), there is evidence from both human epidemiological and animal
toxicological studies that oral PFOS exposure may result in adverse
health effects across many health outcomes, including but not limited
to immune, hepatic, developmental, cardiovascular, nervous system, and
endocrine outcomes. As recommended by the SAB (USEPA, 2022a), EPA has
focused its systematic literature review, health outcome synthesis, and
toxicity value derivation efforts ``on those health outcomes that have
been concluded to have the strongest evidence, including
[[Page 18661]]
the liver disease, immune system dysfunction, serum lipid aberration,
impaired fetal growth, and cancer.'' Conclusions regarding the four
noncancer adverse health outcome categories (i.e., judgements for
human, animal, and integrated evidence streams (USEPA, 2022f)) are
described in the subsections below. Descriptions and conclusions about
the non-priority health outcomes are described in USEPA (2023c).
a. Summary of Noncancer Health Effects
EPA determined that the evidence indicates that oral PFOS exposure
is associated with adverse hepatic effects based on the study quality
evaluation, evidence synthesis and evidence integration of the relevant
human epidemiological and animal toxicity studies. Specifically, there
is moderate evidence from epidemiological studies supporting an
association between PFOS exposure and hepatic outcomes such as elevated
serum liver enzymes indicative of hepatic damage. Overall, there is
consistent evidence of a positive association between PFOS serum
concentrations and ALT, a liver enzyme marker. The evidence of hepatic
effects in humans was supported by robust evidence of hepatotoxicity
resulting from PFOS exposure in animal studies. Studies in rodents
observed several manifestations of hepatic toxicity including
histopathological reports of non-neoplastic hepatic lesions (e.g.,
hepatic necrosis and inflammation) and increases in serum liver enzymes
similar to the trends observed in humans.
EPA determined that the evidence indicates that oral PFOS exposure
is associated with adverse immunological effects based on the study
quality evaluation, evidence synthesis and evidence integration of the
relevant human epidemiological and animal toxicity studies. There is
moderate evidence from epidemiological studies supporting an
association between PFOS and immune outcomes such immunosuppression.
Overall, there is generally consistent evidence of an association
between PFOS serum concentrations and reduced antibody response to
vaccination in children. Associations between PFOS and other immune
system effects (e.g., hypersensitivity and asthma) were mixed. The
evidence for immunological effects in humans was supported by moderate
evidence of immunotoxicity resulting from PFOS exposure in animal
studies. Studies in rodents report immune system effects including
altered activity of plaque-forming cells and natural killer cells,
altered spleen and thymus cellularity, and bone marrow hypocellularity
and extramedullary hematopoiesis. The alterations in plaque-forming and
natural killer cells in animals are consistent with the decreased
antibody response seen in human populations (i.e., the observed animal
and human study health outcomes are both indicators of
immunosuppression).
EPA determined that the evidence indicates that oral PFOS exposure
is associated with adverse developmental effects, based on the study
quality evaluation, evidence synthesis and evidence integration of the
relevant human epidemiological and animal toxicity studies. There is
moderate evidence from epidemiological studies supporting an
association between PFOS and developmental outcomes such as fetal
growth and gestational duration. Overall, there is consistent evidence
of a relationship between PFOS concentrations and low birth weight,
preterm birth, and gestational age. Associations between PFOS and
postnatal growth were inconsistent while there was limited evidence for
other developmental effects (e.g., fetal loss and birth defects). The
evidence for developmental effects in humans was supported by moderate
evidence of developmental toxicity resulting from PFOS exposure in
animal studies. Several studies in rodents provide evidence of
decreased fetal and pup weight due to gestational PFOS exposure,
consistent with the evidence of low birth weight in humans. Decreased
maternal BW was also observed. Other pre- and post-natal effects
observed in animal models include increased offspring mortality,
skeletal and soft tissue effects, and developmental delays (e.g.,
delayed eye opening). However, some studies reported no indications of
developmental toxicity.
EPA determined that the evidence indicates that oral PFOS exposure
is associated with adverse cardiovascular effects, based on the study
quality evaluation, evidence synthesis and evidence integration of the
relevant human epidemiological and animal toxicity studies. There is
moderate evidence from epidemiological studies supporting an
association between PFOS and cardiovascular outcomes such as
alterations in serum lipids. Overall, there is consistent evidence of
positive relationships between PFOS serum concentrations and serum
total cholesterol and low-density lipoproteins. There is also evidence
of positive associations of PFOS with blood pressure and hypertension
in adults. The evidence for cardiovascular effects in humans was
supported by moderate evidence of cardiovascular effects resulting from
PFOS exposure in animal studies. Several studies in rodents provide
evidence of alterations in serum total cholesterol and triglycerides,
though the effect direction varied with dose. Regardless, these effects
indicate a disruption in lipid metabolism resulting from PFOS
treatment, consistent with the alterations in serum lipids observed in
humans.
b. RfD Derivation
The databases for the four prioritized health outcomes were
evaluated further for identification of medium and high confidence
studies and endpoints to select for dose-response modeling. EPA
prioritized endpoints with the strongest overall weight of evidence
based on human and animal evidence for POD derivation. Specifically,
EPA focused the dose response assessment on the health outcomes where
the evidence indicated that PFOS causes health effects in humans under
relevant exposure circumstances. The focus of this FRN is on
epidemiological studies for the four prioritized health outcomes for
which studies meeting this consideration were available, as human data
are generally preferred ``when both laboratory animal data and human
data with sufficient information to perform exposure-response modeling
are available'' (USEPA, 2022f). EPA presents PODs and candidate RfDs
for animal studies, as well as other health outcomes determined to have
sufficient strength of evidence and studies suitable for dose-response
modeling in USEPA (2023c).
EPA identified four candidate critical effects across the four
prioritized health outcomes, all of which were represented by several
candidate critical studies. These candidate critical effects are
decreased antibody production in response to vaccinations (immune), low
birth weight (developmental), increased serum total cholesterol
(cardiovascular), and elevated ALT (hepatic). As described in the
following paragraphs and in further detail in USEPA (2023c), EPA
selected studies from each health outcome to proceed with candidate RfD
derivation. For all selected candidate RfDs, presented in Table 4, the
composite UF was 10 (10x for intraspecies variability).
Two medium confidence studies were considered for POD derivation
for the decreased antibody production in response to various
vaccinations in children Budtz-J[oslash]rgensen and Grandjean (2018)
and Timmerman et al. (2021). These candidate studies offer a variety
[[Page 18662]]
of PFOS exposure measures across various populations and various
vaccinations. Budtz-J[oslash]rgensen and Grandjean (2018) investigated
anti-tetanus and anti-diphtheria responses in Faroese children aged 5-7
and Timmerman et al. (2021) investigated anti-tetanus and anti-
diphtheria responses in Greenlandic children aged 7-12. Though the
Timmerman et al. (2021) study is also a medium confidence study, the
study by Budtz-J[oslash]rgensen and Grandjean (2018) has two features
that strengthen the results: (1) the response reported by this study
reached statistical significance, and (2) the analysis considered co-
exposures of other PFAS. The RfD for anti-diphtheria response in 7-
year-old Faroese children from Budtz-J[oslash]rgensen and Grandjean
(2018) was ultimately selected for the immune outcome because the
response reported by this study reached statistical significance, this
analysis considered co-exposures of other PFAS, and it was the more
health-protective of the two vaccine-specific responses reported by
Budtz-J[oslash]rgensen and Grandjean (2018).
Six high confidence studies (Chu et al., 2020; Sagiv et al., 2018;
Starling et al., 2017; Wikstr[ouml]m et al., 2020; Darrow et al., 2013;
Yao et al., 2021) reported decreased birth weight in infants whose
mothers were exposed to PFOS. These candidate studies offer a variety
of PFOS exposure measures across the fetal and neonatal window. All six
studies reported their exposure metric in units of ng/mL and reported
the [beta] coefficients per ng/mL or ln(ng/mL), along with 95% CIs,
estimated from linear regression models. Of the six individual studies,
Sagiv et al. (2018) and Wikstr[ouml]m et al. (2020) assessed maternal
PFOS serum concentrations primarily or exclusively in the first
trimester, minimizing concerns surrounding bias due to pregnancy-
related hemodynamic effects. Therefore, the RfDs from these two studies
were considered further for candidate RfD selection. Both were high
confidence prospective cohort studies with many study strengths
including sufficient study sensitivity and largely sound methodological
approaches, analysis, and design, as well as no evidence of bias. The
RfD from Wikstr[ouml]m et al. (2020) was ultimately selected for the
developmental outcome as it was the lowest candidate RfD from these two
studies.
Three medium confidence studies were considered for POD derivation
for the cholesterol endpoint (Dong et al., 2019; Lin et al., 2019;
Steenland et al., 2009). These candidate studies offer a variety of
PFOS exposure measures across various populations. Dong et al. (2019)
investigated the NHANES population (2003-2014), while Steenland et al.
(2009) investigated effects in a high-exposure community (the C8 Health
Project study population). Lin et al. (2019) collected data from
prediabetic adults from the DPP and DPP Outcomes Study at baseline
(1996-1999). Of the three studies, Dong et al. (2019) and Steenland et
al. (2009) exclude those prescribed cholesterol medication, minimizing
concerns surrounding confounding due to the medical intervention
altering serum total cholesterol levels. Additionally, Dong et al.
(2019) reported measured serum total cholesterol whereas Steenland et
al. (2009) reported modeled regression coefficients as the response
variable. Since EPA prefers dose response modeling of measured data,
the RfD from Dong et al. (2019) was selected for cardiovascular
endpoint as there is increased confidence in the modeling from this
study.
Three medium confidence studies were selected as candidates for POD
derivation for the ALT endpoint (Gallo et al., 2012; Nian et al., 2019;
Lin et al., 2010). The largest study of PFOS and ALT in adults is Gallo
et al. (2012), conducted in over 30,000 adults from the C8 Study
Project. Two additional studies (Lin et al., 2010; Nian et al., 2019)
were considered by EPA for POD derivation because they reported
significant associations in general populations in the U.S and a high
exposed population in China, respectively. Nian et al. (2019) examined
a large population of adults in Shenyang (one of the largest
fluoropolymer manufacturing centers in China) part of the Isomers of C8
Health Project. In an NHANES adult population, Lin et al. (2010)
observed elevated ALT levels per log-unit increase in PFOS. While this
is a large nationally representative population, several methodological
limitations, including lack of clarity about base of logarithmic
transformation applied to PFOS concentrations in regression models and
the choice to model ALT as an untransformed variable preclude its use
for POD derivation. The RfD from Nian et al., 2019 was ultimately
selected for the hepatic outcome as PFOS was the predominating PFAS in
this study which reduces concern about potential confounding by other
PFAS.
Table 4--Candidate Reference Doses for PFOS for the Four Prioritized
Health Outcomes
------------------------------------------------------------------------
Candidate RfD \1\
Study Endpoint (mg/kg/day)
------------------------------------------------------------------------
Immune
------------------------------------------------------------------------
Budtz-J[oslash]rgensen and PFOS at age five 3 x 10-\7\
Grandjean, 2018. years and anti-
tetanus antibody
concentrations at
age seven years.
Budtz-J[oslash]rgensen and PFOS at age five 2 x 10-
Grandjean, 2018. years on anti-
diphtheria antibody
concentrations at
age seven years.
Timmerman et al., 2021....... PFOS and anti-tetanus 2 x 10-\7\
antibody
concentrations at
ages 7-10 years.
Timmerman et al., 2021....... PFOS and anti- 1 x 10-\7\
diphtheria antibody
concentrations at
ages 7-10 years.
------------------------------------------------------------------------
Developmental
------------------------------------------------------------------------
Sagiv et al., 2018........... PFOS in first 6 x 10-\7\
trimester and
decreased birth
weight.
Wikstr[ouml]m et al., 2020... PFOS in first and 1 x 10-
second trimesters
and decreased birth
weight.
------------------------------------------------------------------------
Cardiovascular
------------------------------------------------------------------------
Dong et al., 2019............ Increased serum total 1 x 10-
cholesterol.
Steenland et al., 2009....... Increased serum total 1 x 10-\7\
cholesterol.
------------------------------------------------------------------------
Hepatic
------------------------------------------------------------------------
Gallo et al., 2012........... Increased serum ALT.. 7 x 10-\7\
[[Page 18663]]
Nian et al., 2019............ Increased serum ALT.. 2 x 10-
------------------------------------------------------------------------
Notes:
\1\ RfDs are rounded to 1 significant digit.
Bolded values indicate selected health outcome-specific RfDs.
The available evidence indicates there are effects across immune,
developmental, cardiovascular, and hepatic organ systems at the same or
approximately the same level of PFOS exposure. Candidate RfDs within
the developmental and cardiovascular outcomes are the same value (i.e.,
1 x 10-7 mg/kg/day). Therefore, EPA has selected an overall RfD for
PFOS of 1 x 10-7 mg/kg/day. The developmental and cholesterol RfDs
serve as co-critical effects and are protective of immune and hepatic
effects that may result from PFOS exposure.
c. MCLG Derivation
Consistent with the Guidelines for Carcinogen Risk Assessment
(USEPA, 2005), 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.'' This determination is based on the evidence of hepatocellular
tumors in male and female rats, pancreatic islet cell carcinomas in
male rats, and mixed but plausible evidence of bladder, prostate,
kidney, and breast cancers in humans. As previously noted, the results
provided by one chronic cancer bioassay in rats exceeds the descriptor
of Suggestive Evidence of Carcinogenic Potential as it provides
evidence of multi-site and multi-sex tumorigenesis (Thomford, 2002;
Butenhoff et al., 2012b).
Consistent with the statutory definition of MCLG, EPA establishes
MCLGs of zero for carcinogens classified as Carcinogenic to Humans or
Likely to be Carcinogenic to Humans, described in Section V.A. of this
preamble above as the linear default extrapolation approach. EPA has
determined that PFOS is Likely to be Carcinogenic to Humans based on
sufficient evidence of carcinogenicity in humans and animals and 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, 2005)
and therefore, it is assumed that there is no known threshold for
carcinogenicity (USEPA, 2016d). Based upon a consideration of the best
available peer reviewed science and a consideration of an adequate
margin of safety, EPA proposes a MCLG of zero for PFOS in drinking
water.
EPA is seeking comment on the derivation of the proposed MCLG for
PFOS, its determination that PFOS is Likely to be Carcinogenic to
Humans and whether the proposed MCLG is set at the level at which there
are no adverse effects to the health of persons and which provides an
adequate margin of safety. EPA is also seeking comment on its
assessment of the noncancer effects associated with exposure to PFOS
and the toxicity values described in USEPA (2023c).
C. PFAS Hazard Index: PFHxS, HFPO-DA, PFNA, and PFBS
1. Background
Although it would be optimal to leverage whole mixture data for
human health risk assessment, such data for PFAS and other chemicals
are extremely rare, particularly at component-chemical (i.e.,
individual PFAS) proportions consistent with environmental mixtures. As
such, mixtures assessment commonly relies upon integration of toxicity
information for the individual component chemicals that co-occur in
environmental media. In order to assess the potential health risks
associated with PFAS mixtures, EPA has developed a Framework for
Estimating Noncancer Health Risks Associated with Mixtures of Per- and
Polyfluoroalkyl Substances (PFAS) (``PFAS Mixtures Framework'') (USEPA,
2023d), based on existing EPA mixtures guidelines and guidance (USEPA,
1986a, 2000a). The PFAS Mixtures Framework describes a flexible
approach that facilitates practical component-based mixtures evaluation
of two or more PFAS based on dose additivity. Studies with PFAS and
other classes of chemicals support the assumption that a mixture of
chemicals with similar apical effects should be assumed to also act in
a dose additive manner unless data demonstrate otherwise. This health
protective assumption for PFAS mixture assessment was supported by the
SAB in their recent review of the draft PFAS Mixtures Framework (USEPA,
2022a). All of the approaches described in the PFAS Mixtures Framework,
including the HI approach (Section III of this preamble), involve
integrating dose-response metrics that have been scaled based on the
potency of each PFAS in the mixture. As discussed in section XV of this
preamble, the SAB has reviewed the PFAS Mixtures Framework, and
concluded that the approaches in that document, including the HI
approach, are scientifically robust and defensible for assessing dose
additive effects from co-occurring PFAS (USEPA, 2022a).
The MOA is considered a key determinant of chemical toxicity. It
describes key changes in cellular interaction that may lead to
functional or anatomical changes. Toxicants are classified by their
type of toxic actions. Yet, because PFAS are an emerging chemical class
of note for toxicological evaluations and human health risk assessment,
MOA data may be limited or not available at all for many PFAS.
Component-based approaches for assessing risks of PFAS mixtures are
focused on evaluation of similarity of toxicity endpoint/effect rather
than similarity in MOA, consistent with EPA mixtures guidance (USEPA,
2000a). Precedents of prior research conducted on mixtures of various
chemical classes with common key events and adverse outcomes support
the use of dose additive models for estimating mixture-based effects,
even in instances where chemicals with disparate molecular initiating
events were included. Thus, in the absence of detailed characterization
of molecular mechanisms for most PFAS, it is considered a reasonable
health-protective assumption, consistent with the statute's admonition
to ensure an adequate margin of safety (1412(b)(4)(A)), that PFAS which
can be demonstrated to share one or more key events or adverse outcomes
will produce dose-additive effects from co-exposure (USEPA, 2022c,
2023a). This assumption of dose additivity and the HI approach was
supported by the SAB in its review of the draft PFAS Mixtures
[[Page 18664]]
Framework (USEPA, 2022a). For a detailed description of the evidence
supporting dose additivity for PFOA, PFOS, and other PFAS, see the
revised PFAS Mixtures Framework (USEPA, 2023d).
Following EPA's data-driven approach for component-based mixtures
assessment based on dose additivity (i.e., see Figure 4-1 in USEPA,
2023d), the Agency selected the HI approach for MCLG development to
ensure the Agency is protecting against dose additive risk from
mixtures of PFHxS, HFPO-DA, PFNA, and PFBS. While a single PFAS may
occur in concentrations below where EPA might establish an individual
MCLG, PFAS tend to co-occur (see discussion in sections III.C and VII
of this preamble). Hence, there are some situations where setting an
MCLG while only considering the concentration of an individual PFAS
without considering the dose additive effects that would occur from
other PFAS that may be present in a mixture may not provide a
sufficiently protective MCLG with an adequate margin of safety. For
this proposed rule, in addition to the PFOA and PFOS assessments
discussed above, peer reviewed, publicly available assessments with
final toxicity values (i.e., RfDs, Minimal Risk Levels) are available
for HFPO-DA (USEPA, 2021b), PFBS (USEPA, 2021a), PFNA (ATSDR, 2021),
and PFHxS (ATSDR, 2021). These toxicity values (along with DWI-BW and
RSC) are used to derive the HBWCs for the HI approach for PFHxS, HFPO-
DA, PFNA, and PFBS. EPA is seeking comment on derivation of the HBWCs
for each of the four PFAS considered as part of the HI. See discussion
in section VI.C of this preamble as to why EPA is not proposing to
include PFOA and PFOS in the HI MCLG at this time.
As discussed previously in this document, the Agency is proposing
the general HI as the most appropriate and justified approach for
considering PFAS mixtures in this rulemaking because of the level of
protection afforded for diverse endpoints. SDWA requires the Agency to
establish a health-based MCLG set at, ``a level at which no known or
anticipated adverse effects on the health of persons occur and which
allow for an adequate margin of safety.'' The Safe Drinking Water Act
defines the term ``contaminant'' very broadly to mean any ``physical,
chemical, biological, or radiological substance or matter in water
(SDWA 1401 4(A)(ii)(C)(6)).'' In this context, this proposal addresses
contaminants and certain mixtures of contaminants. A mixture of two or
more ``contaminants'' qualifies as a ``contaminant'' because the
mixture itself is ``any physical, chemical or biological or
radiological substance or matter in water.'' (emphasis added). EPA has
a long-standing history of regulating contaminants in this manner
(i.e., as contaminant groups or mixtures). For instance, the TTHM Rule
(U.S. EPA, 1979) EPA regulated total trihalomethanes as a group due to
their concurrent formation during the chlorination of drinking water;
EPA stating that the four regulated THMs were ``also indicative of the
presence of a host of other halogenated and oxidized, potentially
harmful byproducts of the chlorination process that are concurrently
formed in even larger quantities but which cannot be characterized
chemically'' (USEPA, 1979). In the Stage I and II Disinfection
Byproduct (DBPs) Rules, EPA regulates a second group of DBPs, in this
instance setting regulatory standards for a group of five haloacetic
acids (HAA5) (USEPA, 1998a; 2006a). A third example is EPA's regulation
of radionuclides, where, among other things, EPA regulates
radionuclides mixtures for gross alpha radiation that account for both
natural and man-made alpha emitters as a group rather than individually
(USEPA, 2000d). In summary, EPA has the statutory authority to regulate
groups and/or mixtures of contaminants, EPA has a history of regulating
groups and mixtures of contaminants that have improved public health
protection, and EPA has made a reasonable policy choice for
establishing an MCLG for a mixture of chemicals that are expected to
impact multiple endpoints. Because mixture component chemical HBWCs are
based on overall (i.e., not target-organ specific) RfDs, the approach
is protective against all health effects across component chemicals and
therefore meets the statutory requirements of establishing an MCLG
under SDWA. Basing the mixture MCLG on overall RfDs ensures that there
are no known or anticipated effects, and using the HI adds an
appropriate margin of safety for a class of contaminants that have been
shown to co-occur and evidence indicates that they have additive
toxicity.
2. PFAS Mixture MCLG Derivation
To account for dose additive noncancer effects associated with
PFHxS, HFPO-DA, PFNA, and PFBS, EPA is proposing an MCLG for the
mixture of these four PFAS based on the HI approach (USEPA, 2023a). As
described in Section IV of this preamble, a mixture HI can be
calculated when HBWCs for a set of PFAS are available or can be
calculated. The health effects information including relevant studies
mentioned in this section are summarized from USEPA (2023a) and are
also described in Section III of this preamble.
There is currently no EPA RfD available for PFHxS; however, EPA's
IRIS program is developing a human health toxicity assessment for PFHxS
(expected to undergo public comment and external peer review in 2023).
The HBWC for PFHxS is derived using an ATSDR intermediate-duration oral
Minimal Risk Level based on thyroid effects seen in male rats after
oral PFHxS exposure (ATSDR, 2021; USEPA, 2023a). ATSDR calculated an
HED of 0.0047 mg/kg/day and applied a combined UF/MF factor of 300X
(total UF of 30X and a MF of 10X for database deficiencies) to yield an
intermediate-duration oral Minimal Risk Level of 2E-05 mg/kg/day
(ATSDR, 2021). To calculate the HBWC, EPA applied an additional UF of
10 to adjust for subchronic-to-chronic duration, per Agency guidance
(USEPA, 2002), because the effect is not in a developmental population
(i.e., thyroid follicular epithelial hypertrophy/hyperplasia in
parental male rats). The resulting chronic reference value for use in
HBWC calculation was 2E-06 mg/kg/day. EPA selected a DWI-BW for adults
within the general population (0.034 L/kg/day) and applied an RSC of 20
percent (USEPA, 2022c). The resulting HBWC for PFHxS is 9 ng/L (ppt)
(USEPA, 2022c).
Like EPA's drinking water health advisory for HFPO-DA and its
ammonium salt (USEPA, 2022d), the HBWC that the agency is using for the
HI MCLG was derived from the agency's 2021 human health toxicity
assessment, specifically the chronic RfD of 3E-06 mg/kg/day based on
liver effects observed following oral exposure of mice to HFPO-DA
(USEPA, 2021b). EPA selected a DWI-BW for lactating women (0.0469 L/kg/
day) and applied an RSC of 20 percent (USEPA, 2023a) to calculate the
HBWC for HFPO-DA. The HBWC for HFPO-DA is 10 ng/L (ppt) (USEPA, 2023a).
There is currently no EPA RfD available for PFNA; however, EPA's
IRIS program is developing a human health toxicity assessment for PFNA.
The HBWC for PFNA is derived using an ATSDR intermediate-duration oral
Minimal Risk Level that was based on developmental effects seen in mice
after oral PFNA exposure (ATSDR, 2021; USEPA, 2023a). ATSDR calculated
an HED of 0.001 mg/kg/day and applied a combined UF/MF factor of 300X
(total UF of 30X and a MF of 10X for database
[[Page 18665]]
deficiencies) to yield an intermediate-duration oral Minimal Risk Level
of 3E-06 mg/kg/day (ATSDR, 2021). EPA did not apply an additional UF to
adjust for subchronic-to-chronic duration for PFNA because the critical
effects were observed during a developmental life stage (USEPA, 2002).
EPA used the chronic reference value of 3E-06 mg/kg/day to calculate
the HBWC for PFNA. EPA selected a DWI-BW for lactating women (0.0469 L/
kg/day) and applied an RSC of 20 percent (USEPA, 2023a). The resulting
HBWC for PFNA is 10 ng/L (ppt) (USEPA, 2023a).
Like EPA's drinking water health advisory for PFBS (USEPA, 2022e),
the HBWC that the agency is using for the HI MCLG was derived from the
agency's 2021 human health toxicity assessment, specifically the
chronic RfD of 3E-04 mg/kg/day based on thyroid effects observed seen
in newborn mice born to mothers that had been orally exposed to PFBS
throughout gestation (USEPA, 2021a; 2023a). EPA selected a DWI-BW for
women of child-bearing age (0.0354 L/kg/day) and applied an RSC of 20
percent (USEPA, 2023a) to calculate the HBWC for PFBS. The HBWC for
PFBS is 2,000 ng/L (ppt) (USEPA, 2023a).
As described above, the HBWCs for PFHxS, HFPO-DA, PFNA, and PFBS
are 9, 10, 10, and 2000 ppt respectively (see Section III.A of this
preamble, as well as in USEPA (2022c)). HQs are calculated by dividing
the measured component PFAS concentration in water (e.g., expressed as
ppt) by the relevant HBWC (e.g., expressed as ppt), as shown in the
equation below. Component HQs are then summed across the PFAS mixture
to yield the PFAS mixture HI MCLG. Thus, the HI accounts for
differences in toxicity among the mixture component chemicals rather
than weighting them all equally in the mixture. A PFAS mixture HI
greater than 1.0 indicates an exceedance of the health protective level
and indicates potential human health risk for noncancer effects from
the PFAS mixture in water. For more details on this approach, please
see USEPA (2023a). The proposed mixture HI MCLG for PFHxS, HFPO-DA,
PFNA, and PFBS is as follows:
[GRAPHIC] [TIFF OMITTED] TP29MR23.062
Where:
[PFASwater] = the measured component PFAS concentration
in water and
[PFASHBWC] = the HBWC of a component PFAS.
For example, if each of the four PFAS are measured at their
respective proposed PQLs described in section VIII.A. of this preamble,
the HI calculation would be as follows:
[GRAPHIC] [TIFF OMITTED] TP29MR23.063
In this scenario, while none of the individual PFAS contaminants
exceed their relative HBWC, when considered in the HI, the sum of the
four PFAS in the HI exceeds 1.0, and therefore is higher than the MCLG.
In the following example, if only PFNA and PFHxS were measured at 8 ppt
each, while also below their individual HWBCs, the two would sum to an
exceedance of the HI.
[GRAPHIC] [TIFF OMITTED] TP29MR23.064
[[Page 18666]]
In a final example, if only a single PFAS, PFHxS were reported
above its PQL, but that value was 20, this would also result in an HI
higher than 1.0.
[GRAPHIC] [TIFF OMITTED] TP29MR23.065
EPA requests comment on significant figure use when calculating
both the HI MCLG and the MCL (see discussion in section VI of this
preamble). EPA has set the HI MCLG and MCL using two significant
figures (i.e., 1.0). EPA requests comment on the proposed use of two
significant figures for the MCLG when considering underlying health
information and for the MCL when considering the precision of the
analytical methods.
In conclusion, while current weight of evidence suggests that PFAS
vary in their precise structure and function, exposure to different
PFAS can result in similar health effects. As a result, PFAS exposures
are likely to result in dose-additive effects (ATSDR, 2021; USEPA,
2023a) and therefore the assumption of dose-additivity is reasonable.
While individual PFAS can pose a potential risk to human health if the
exposure level exceeds the chemical-specific toxicity value (RfD or
Minimal Risk Level) (i.e., individual PFAS HQ >1.0), mixtures of PFAS
can result in dose additive health effects when lower individual
concentrations of PFAS are present in that mixture. For example, if the
individual HQs for PFHxS, HFPO-DA, PFNA, and PFBS were each 0.9 that
would indicate that the measured concentration of each PFAS in drinking
water is below the level of appreciable risk (recall that an RfV, such
as an oral RfD, represents an estimate at which no appreciable risk of
deleterious effects exists). However, the overall HI for that mixture
would be 3.6 (i.e., sum of four HQs of 0.9). An HI of 3.6 means that
the total measured concentration of PFAS is 3.6 times the level
associated with potential health risks. Thus, setting an MCLG while
only considering the concentration of an individual PFAS without
considering the dose additive effects from other PFAS in a mixture
would not provide a sufficiently protective MCLG with an adequate
margin of safety. In order to account for dose additive noncancer
effects associated with co-occurring PFAS and PFAS in mixtures, to
protect against health impacts from likely multi-chemical exposures of
PFHxS, HFPO-DA, PFNA, and PFBS, with an adequate margin of safety, the
Agency is proposing to use of the HI approach, a commonly used
component-based mixture risk assessment method, for the MCLG for these
four PFAS (USEPA, 2022). Consistent with the statutory requirement
under 1412(b)(4)(A), establishing the MCLG for PFHxS, HFPO-DA, PFNA,
and PFBS at an HI = 1.0 ensures that MCLG is set at a level where there
are no known or anticipated adverse effect on the health of persons and
ensuring an adequate margin of safety.
VI. Maximum Contaminant Level
Under section 1412(b)(4)(B) of SDWA, EPA must generally establish
an enforceable MCL as close to the MCLG as is feasible, taking costs
into consideration. The Agency evaluates feasibility according to
several factors including the availability of analytical methods
capable of measuring the targeted compounds in drinking water and
examining available treatment technologies capable of contaminant
removal examined under laboratory and field conditions.
A. PFOA and PFOS
The Agency evaluated available analytical methods to determine the
lowest concentration at which PFOA and PFOS can reliably be measured in
finished drinking water. There are two analytical methods approved by
EPA for analyzing PFAS regulated under this proposed rule, USEPA
Methods 537.1 and 533. In this evaluation, EPA determined that 4.0 ppt
is the lowest concentration that PFOA and PFOS can be reliably
quantified within specific limits of precision and accuracy during
routine laboratory operating conditions. EPA has historically called
this level the ``practical quantitation level,'' also known as a PQL
(USEPA, 1987). Under UCMR5, EPA published MRLs of 4.0 ppt each for PFOA
and PFOS (USEPA, 2022g). As described in the UCMR 5 rulemaking, this
reporting level is the minimum quantitation level that, with 95 percent
confidence, can be achieved by capable analysts at 75 percent or more
of the laboratories using a specified analytical method (i.e., Method
533 and 537.1, discussed in more detail in section VIII of this
preamble). Based on the multi-laboratory data acquired for the UCMR 5
rule, EPA has defined the PQL for PFOA and PFOS to be equal to the UCMR
5 MRL of 0.0000040 mg/L or 4.0 ppt. This quantitation level provides an
allowance for the degree of measurement precision and accuracy that EPA
estimates can be achieved across laboratories nationwide. Furthermore,
the PQLs provide for consistency in data quality from a diverse group
of laboratories across the country and provide routine performance
goals that many laboratories must strive to achieve. 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. Please see section VIII of this preamble
for more information on analytical methods for PFAS and a detailed
discussion of the PQL and other levels below this quantitation level
that may be appropriate for screening values.
EPA has promulgated and successfully implemented NPDWRs with MCLs
equal to the contaminant PQLs. In 1987, 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, p-
dichlorobenzene, trichloroethylene, vinyl chloride, 1,1,1-
trichloroethane, 1,1-dichloroethylene and 1,2-dichloroethane. In that
rule, EPA set the PQL at a level consistent with what was then the
``general rule of five to ten times the [method detection limit] MDL.''
While some commenters at the time stated they believed implementation
would be challenging, EPA notes that those rules have been
[[Page 18667]]
implemented successfully and provided an incentive for laboratories to
improve analytical capabilities and reduce method quantitation and
detection limits.
EPA requests comment on whether setting the MCL at the PQLs for
PFOA and PFOS is similarly implementable and feasible. As in the 1987
rule, EPA recognizes that quantitation of the contaminants can be
achieved between the MDL (e.g., see Method 537.1, section 9.2.8) and
the PQL, albeit not necessarily with the same precision and accuracy
that is possible at and above the PQL. Measuring PFOA and PFOS results
below the PQLs may not be achievable from all laboratories and may not
have the same precision as higher-level measurements, nor does EPA
believe it is appropriate to make potentially costly compliance
decisions based on such lower-level measurements. Nonetheless, the
ability to know that PFOA and PFOS may be present within a certain
range at these low concentrations (i.e., below the PQLs) can be used to
inform decisions for already installed treatment (e.g., a utility can
evaluate when break though is most likely to occur or is imminent) and
to judge appropriate monitoring frequency. In addition, further support
for considering measurement levels below PQL, and the demonstrated
capability of laboratories to support screening at these lower levels,
was found within laboratory calibration standard data submitted as part
of the UCMR 5 Laboratory Approval Program.\4\ These data revealed that
49 of the 54 laboratories seeking EPA approval included a lowest PFAS
calibration standard level at 1 ppt or lower, with the median lowest
calibration level among all laboratories at 0.5 ppt. Therefore, for
almost all laboratories, the proposed PQLs for PFOA and PFOS of 4.0 ppt
are at least 4 times greater than the lowest calibration standard. This
suggests the overwhelming majority of laboratories with the necessary
instrumentation to support PFAS monitoring have the capability to
provide screening measurement results above the proposed trigger level
of \1/3\ of the MCL (i.e., 1.3 ppt for PFOS or PFOS). Hence, a utility
may use the lower-level measurements as a warning that they may be
nearing the PFOA and PFOS MCLs of 4.0 ppt prior to exceeding them and
can make informed treatment decisions about managing their systems
(e.g., replacing GAC). For more information on the proposed trigger
level, please see sections VIII and IX of this preamble. EPA requests
comment on implementation challenges and considerations for setting the
MCL at the PQLs for PFOA and PFOS, including on the costs and benefits
related to this approach.
---------------------------------------------------------------------------
\4\ Instrument calibration for the approved methods is defined
by analyzing a set of at least five standard solutions spanning a
20-fold concentration range, in which the lowest concentration must
be at or below the quantitation level. Calibration standards below
the quantitation level must meet defined precision requirements. The
resulting calibration curve is validated by measuring standard
solutions of known concentration prepared from commercially
available reference materials. Calibration is confirmed at multiple
points, including by performing an initial calibration and initial
demonstration of capability prior to analysis, through the addition
of internal and surrogate standards, and by incorporating continuous
calibration check samples into the analysis routine.
---------------------------------------------------------------------------
Additionally, consistent with EPA's SMF for many drinking water
contaminants, EPA is proposing to utilize a running annual average
approach to calculate compliance with this proposed rule. As a result,
a single occurrence of PFOA or PFOS that is slightly above the proposed
MCLs would not result in an MCL violation, assuming other quarterly
samples remain below the MCLs. For example, if a system had a sample
result of PFOA at 5.0 ppt and the remaining quarter sample results were
all 2.0 ppt each, the system would not be violation. In addition, when
calculating the running annual averages, if a sample result is less
than the PQL for the monitored PFAS, EPA is also proposing to use zero
to calculate the average for compliance purposes. For further
discussion on monitoring and compliance, please see section IX of this
preamble. Hence, while EPA believes utilities should endeavor for all
samples to remain below the MCL, the proposed rule allows for temporal
fluctuations in concentrations that may occur because of unexpected
events such as premature PFOA and PFOS breakthrough or temporary
increased source water concentrations. This extra buffer provides the
utilities additional operational safety margins in the event of minor
management or treatment issues. As an alternative, and as described in
more detail in section IX of this preamble, when calculating the
running annual averages, rather than using zero for sample results less
than the PQL, EPA seeks comment on instead using the proposed rule
trigger levels (i.e., 1.3 ppt for PFOA and PFOS) in the case where PFAS
are detected but below their proposed PQLs. This would have the
potential to be more protective in the long run than counting sampling
results below the PQL as zero and provide PWSs greater forewarning that
their results may exceed the MCLs.
EPA anticipates there would not be sufficient laboratory capacity
if the quantitation level were set at a level below 4.0 ppt. The
rigorous laboratory certification and quality assurance/quality control
(QA/QC) procedures could limit the number of laboratories that can
achieve lower quantitation levels and many water systems would not be
able to secure the services of laboratories that are capable of
consistently providing precise and accurate quantitation of
concentrations of PFOA and PFOS at levels lower than 4.0 ppt. The
Agency has determined that high confidence in the accuracy of
analytical results is necessary to demonstrate that any treatment
technologies are effectively reducing levels of PFOA and PFOS to the
levels as close as feasible to the proposed MCLGs for these
contaminants. To achieve this intended purpose, the Agency is proposing
to establish the MCLs for PFOA and PFOS at this PQL of 4.0 ppt.
While EPA anticipates potential laboratory capacity issues if the
Agency were to propose MCLs below 4.0 ppt, EPA believes there will be
sufficient laboratory capacity with the MCLs set at 4.0 ppt. As of
September 2022, as a part of the UCMR 5 laboratory approval program,
fifty-four (54) laboratories submitted applications to EPA for approval
to analyze PFOA and PFOS to quantification limits of 4.0 ppt using EPA
Method 533. Each of these 54 laboratories had acquired the analytical
equipment necessary to run both EPA Method 533 and 537.1 and
laboratories are required to achieve and demonstrate they can meet the
PFOA and PFOS PQLs of 4.0 ppt to receive EPA Method 533 approval. EPA
received strong interest from a significant number of laboratories
seeking UCMR 5 laboratory approval, demonstrating there is effective
laboratory capacity to support the program. The commercial market for
PFAS analysis is likely to remain strong and, in fact, grow as more
laboratories develop the technical capability further enhancing lab
capacity to analyze PFAS for drinking water rule compliance purposes.
The various State regulatory monitoring programs established in recent
years for PFAS incorporate laboratory certification/accreditation
programs that further elevate commercial laboratory interest and expand
laboratory capacity. Additionally, because EPA is proposing to allow
the use of existing PFAS monitoring data to meet the initial monitoring
requirements of this proposed rule where available (see section IX of
this preamble for further discussion), EPA anticipates the sudden spike
in laboratory demands that could
[[Page 18668]]
otherwise accompany a proposed rule such as this will instead be
distributed during the initial rule implementation timeframe. EPA
requests comment on the underlying assumptions that sufficient
laboratory capacity will be available with the MCLs set at 4.0 ppt;
that demand will be sufficiently distributed during rule implementation
to allow for laboratory capacity; and on the cost estimates related to
these assumptions.
SDWA 1412(b)(4)(d) defines feasibility as, ``feasible with the use
of the best technology, treatment techniques and other means which the
Administrator finds, after examination for efficacy under field
conditions and not solely under laboratory conditions, are available
(taking cost into consideration).'' Further, Section 1412(b)(4)(E) of
SDWA requires identification of technologies, referred to as best
available technologies (BATs) ``which the Administrator finds to be
feasible for purposes of meeting [the MCL].'' As described in section
XI.A. of this preamble, the Agency identifies the BATs as those meeting
certain criteria including: (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 and
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. In section XI of
this preamble, EPA evaluated treatment technologies for the removal of
PFOA and PFOS that would meet these criteria and determined there are
multiple technologies (i.e., GAC, AIX, RO, and NF) that are both
available and have reliably demonstrated PFAS removal efficiencies that
may exceed >99 percent and can achieve concentrations less than the
proposed MCLs for PFOA and PFOS. Based on its evaluation, the Agency
proposes to determine that it is feasible to treat PFOA and PFOS to 4.0
ppt because multiple treatment technologies are effective and available
and there are methods available to reliably quantify PFOA and PFOS at
4.0 ppt. For more information about treatment technologies, please see
section XI of this preamble. For more information about available
analytical methods, please see section VIII of this preamble.
For purposes of its proposed feasibility determination, EPA also
considered costs when setting the MCLs for PFOA and PFOS at 4.0 ppt and
that analysis supports a finding that 4.0 ppt represents the level of
what is ``feasible'' under the standard of Section 1412(b)(4)(D). Based
on legislative history (A Legislative History of the Safe Drinking
Water Act, Committee Print, 97th Cong., 2d Sess. (1982) at 550), EPA
interprets ``taking cost into consideration'' in Section 1412(b)(4)(D)
to be limited to ``reasonable cost based on large and metropolitan
water systems.'' EPA has determined that 4.0 ppt represents what is
achievable for BATs given the standard of ``reasonable cost based on
large and metropolitan water systems.'' As discussed in section XII of
this preamble, EPA evaluated quantifiable and nonquantifiable costs for
MCLs for PFOA and PFOS at 4.0, 5.0, and 10.0 ppt. As part of that
evaluation, EPA considered capital, operational, administrative,
monitoring, and other costs. In addition to estimating national level
costs associated with the proposed rule and potential regulatory
alternatives, EPA assessed PWS level costs, costs to small systems, and
costs at the household level. For more information about EPA's cost
estimates, please see Best Available Technologies and Small System
Compliance Technologies Per- and Polyfluoroalkyl Substances (PFAS) in
Drinking Water (USEPA, 2023g). EPA considered these cost analyses, in
addition to analytical methods, quantitation levels, and treatment
technologies in coming to its proposed finding that MCLs of 4.0 ppt for
PFOA and PFOS represents levels that are as close as feasible to the
MCLGs. EPA seeks comment on its PFOA and PFOS evaluation of feasibility
for the proposal, including analytical measurement and treatment
capability, as well as reasonable costs, as defined by SDWA.
B. PFAS Hazard Index: PFHxS, HFPO-DA, PFNA, and PFBS
To protect against the potential for dose additive health impacts
from likely multi-chemical exposures when they occur as mixtures in
drinking water, EPA is proposing an MCL for mixtures of PFHxS, HFPO-DA,
PFNA, and PFBS expressed as an HI. An HI is the sum of HQs from
multiple substances. HQs are the ratio of potential exposure to a
substance and the level at which no health effects are expected. EPA is
proposing the MCL for mixtures of PFHxS, HFPO-DA, PFNA, and PFBS as
equal to the MCLG: as proposed, the HI must be equal to or less than
1.0. SDWA section 1401(3) defines an MCL as the ``maximum permissible
level of a contaminant in water which is delivered to any user of a
public water system.'' This approach, as proposed, sets a permissible
level for the contaminant mixture (i.e., a resulting PFAS mixture HI
greater than 1.0 indicates an exceedance of the health protective level
and indicates potential human health risk for noncancer effects from
the PFAS mixture in water). If there is only one contaminant PFAS
present, the HI approach in practice also sets a permissible level for
the individual contaminant through the use of its respective HBWC (see
example and discussion in section V.C2 of this preamble). As discussed
below in this section (section VI.D. of this preamble) and in section
XIII of this preamble, the Agency is also inviting comment on whether
establishing a traditional MCLG and MCL for PFHxS, HFPO-DA, PFNA, and
PFBS instead of or in addition to the HI approach would change public
health protection, improve clarity for the rule, or change costs.
EPA asked the SAB for advice on using an HI approach as an option
for PFAS mixture assessment under an assumption of dose additivity.
Consistent with EPA Guidance (e.g., USEPA, 2000a; USEPA, 1989) the HI
is used here as a decision aid, and determination of dose additivity
among chemicals is relaxed from the level of common MOA to common
target organ(s)/health outcome(s). Per SAB's suggestion, EPA outlines
here the validity of, and procedures for, calculating the HI given a
mixture such as this one that includes PFAS with varying levels of
available information across health outcomes.
Consistent with advice from the SAB, EPA considers it an
appropriately health protective approach to assume dose additivity for
PFAS co-occurring in mixtures as they share similar profiles of health
effect domains (e.g., liver, thyroid, developmental, etc.). EPA's
analysis of finished water monitoring data demonstrates that PFAS often
have a substantial likelihood to co-occur in mixtures (see section
III.D of this preamble). While PFAS are well documented to co-occur,
the exact chemical composition is often site-specific in nature (i.e.,
each location of PFAS mixture is influenced by different environmental
point and diffuse sources that results in a unique PFAS profile)
(Banzhaf et al., 2017). Yet, EPA finds that PFHxS, HFPO-DA, PFNA, and
PFBS often co-occur in mixtures in drinking water, including with other
PFAS (USEPA, 2023e). To protect against the potential for dose additive
health impacts from likely multi-chemical exposures of PFHxS, HFPO-DA,
PFNA, and PFBS when they occur as mixtures in drinking water, the
Agency is proposing to use the HI approach. Both EPA's recent PFAS
mixture's framework (USEPA, 2023d), and SAB's review of the prior draft
of
[[Page 18669]]
this document discuss the strengths and limitations associated with
using an HI approach as the basis for evaluating potential health risks
associated with exposure to mixtures of PFAS, and consideration as a
metric to inform health-based decision-making for regulatory purposes
(USEPA, 2022a). For a full discussion of the strengths and limitations
identified during SAB's review and how EPA responded, please see USEPA,
2022a and 2023f. The HI approach is used regularly by EPA (and States)
to inform potential health risks of chemical mixtures associated with
contaminated sites/locations under the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA)/the Superfund
Amendments and Reauthorization Act (SARA); as such, the application of
the HI approach under a regulatory purview is not novel for the Agency
though this is the first use of an HI approach for a SDWA National
Primary Drinking Water Regulation.
EPA is proposing an MCL based on a HI composed of the four PFAS for
which there are validated EPA methods for measurement and treatment,
evidence of co-occurrence, the potential for similar health effects,
and the availability of finalized peer reviewed toxicity values to use
in generating the HI. For this proposal, those PFAS are PFHxS, HFPO-DA,
PFNA, and PFBS. The MCL for mixtures of PFHxS, HFPO-DA, PFNA, and PFBS
would be an HI = 1.0. In this proposal, the HBWCs that EPA uses to
calculate the HI are proposed to be 9.0 ppt for PFHxS; 10.0 ppt for
HFPO-DA; 10.0 ppt for PFNA; and 2000 ppt for PFBS (USEPA, 2023a). To
calculate the proposed HI, regulated PWSs would be required to monitor
to determine the concentrations of PFHxS, HFPO-DA, PFNA, and PFBS in
their finished drinking water. See section IX of this preamble for
proposed requirements related to monitoring and determining compliance.
See equation below for calculation of the PFHxS, HFPO-DA, PFNA, and
PFBS HI MCL:
[GRAPHIC] [TIFF OMITTED] TP29MR23.066
Where:
HFPO-DAwater = monitored concentration of HFPO-DA;
PFBSwater = monitored concentration of PFBS;
PFNAwater = monitored concentration of PFNA; and
PFHxSwater = monitored concentration of PFHxS
See discussion in section IV of this preamble above for how EPA
derived these values for these contaminants.
As described in section VI.A. of this preamble for PFOA and PFOS,
the Agency has similarly considered feasibility as defined by SDWA
1412(b)(4)(D) for PFHxS, HFPO-DA, PFNA, and PFBS. The Agency has
determined that there are validated analytical methods that can measure
below the HBWC for each of these PFAS. Additionally, as discussed
above, the Agency proposes to determine that it is feasible to treat
each of these PFAS to below their PQL (between 3.0-5.0 ppt) and it is
feasible to treat these PFAS to below their PQLs individually and as a
group. When identifying BATs, EPA evaluated the same factors as defined
previously in Section VI.A. and in Section XI.A. of this preamble and
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 achieve concentrations less than the
proposed HI MCL for PFHxS, HFPO-DA, PFNA, and PFBS.
As described in section VI.A. of this preamble for PFOA and PFOS,
the Agency similarly considered costs as part of its proposed
feasibility determination for PFHxS, HFPO-DA, PFNA, and PFBS and
setting the HI MCL at 1.0. EPA's analysis supports a finding that an HI
of 1.0 is ``feasible'' under standard of SDWA 1412(b)(4)(D) because it
is achievable for BATs given the standard of ``reasonable cost based on
large and metropolitan water systems.'' For more information about
EPA's cost estimates, please see Best Available Technologies and Small
System Compliance Technologies Per- and Polyfluoroalkyl Substances
(PFAS) in Drinking Water (USEPA, 2023g; USEPA, 2023h). EPA considered
these cost analyses, in addition to analytical methods, quantitation
levels, and treatment technologies in coming to its proposal that an HI
MCL of 1.0 for PFHxS, HFPO-DA, PFNA, and PFBS represents a level that
is as close as feasible to the MCLG. EPA seeks comment on its
evaluation of feasibility for the proposed HI MCL finding, including
analytical measurement and treatment capability, as well as reasonable
costs, as defined by SDWA.
C. Reducing Public Health Risk by Protecting Against Dose Additive
Noncancer Health Effects From PFAS
As described above, PFOA and PFOS are demonstrated to have the
potential for adverse health effects at low levels of exposure. The
level at which no known or anticipated adverse effects on the health of
persons would occur is well below current analytical quantitation level
for PFOA and PFOS. To ensure maximum public health protection for these
contaminants, the statute generally requires that exposure be driven to
the lowest feasible concentration.
Because of the analytical limitations discussed in the preceding
section VI.A of this preamble, EPA is not proposing to include PFOA and
PFOS in the HI. The only feasible way to represent PFOA and PFOS in the
HI approach would be to only consider values for PFOA and PFOS at or
above the PQL of 4.0 ppt. As a result, any measured concentration above
4.0 ppt for PFOA and PFOS would result in an exceedance of the HI of
1.0. Therefore, regulating PFOA and PFOS under a HI approach would not
add any meaningful health protection over setting an individual MCL for
these PFAS. Additionally, EPA believes that adding PFOA or PFOS to the
HI could increase potential compliance challenges with the rule as
there could be confusion created by how to consider screening level
values above detection but below quantitation (see additional
discussion in section VIII of the preamble for discussion on screening
and trigger levels). Therefore, EPA is proposing to set MCLs for PFOA
and PFOS individually and not part of the HI.
Some PFAS (such as PFHxS, HFPO-DA, PFNA, and PFBS) have HBWCs at
thresholds higher than current analytical quantitation levels. As a
result of assuming dose-additivity, PFHxS, HFPO-DA, PFNA, and PFBS
[[Page 18670]]
may have individual detectable or quantifiable concentrations below
their individual HBWCs, but their combined concentrations can be above
levels of health concern. As proposed, the HI MCL provides a protective
approach to avoiding these potential health risks associated with
mixtures of PFAS that are below the public health goals individually,
yet exceed the PFAS mixture limit (i.e., HI MCL = 1.0). Separating PFOA
and PFOS away from a HI approach is not meant to ignore the potential
dose additive health impacts for these compounds in mixtures. As
described in the preceding paragraph, EPA is not including PFOA and
PFOS as part of the HI approach because the Agency believes doing so
would not add meaningful health protection over setting an individual
MCL for these PFAS.
EPA recognizes that some PFAS such as PFOA, PFOS, and PFNA have
been voluntarily phased out of production and replaced in the United
States so their relative concentrations in source waters may decrease
over time. However, other PFAS that have been shown to also cause
adverse health effects (e.g., perfluorobutanoic acid [PFBA], PFBS,
HFPO-DA) may increase in concentration as their production, use, and
discharges into source water continues. The HI framework is designed to
inform protection of human health for any source water PFAS, with
available human health assessment values, still in production and use.
Under the HI approach, additional PFAS can be added over time once more
information on health effects, analytics, exposure and/or treatment
becomes available, and merits additional regulation as determined by
EPA. As such, this approach provides a framework for Federal and State
public health agencies to consider using to address other PFAS in the
future as needed.
D. Regulatory Alternatives
As discussed in section VI.A of this preamble above, EPA proposes
to determine that it is feasible to set MCLs for PFOA and PFOS at 4.0
ppt each and that the level is as close as feasible to the MCLGs. As
discussed in Section VI.B of this preamble, EPA proposes to determine
it is feasible to set an MCL for mixtures of PFHxS, HFPO-DA, PFNA, and
PFBS as a HI = 1.0 which is the same level as the MCLG.
In section XIII of this preamble, the HRRCA section of this
proposal, EPA is presenting estimated costs and benefits of regulatory
alternatives for PFOA and PFOS of MCLs at 4.0, 5.0 ppt and 10.0 ppt.
Quantified costs and benefits for the proposed option and alternative
options considered are summarized in section XIII.H of this preamble,
specifically tables 66-69. Tables 70-71 summarize the non-quantified
benefits and costs and assess the potential impact of non-quantifiable
benefits and costs on the overall benefits and costs estimate.
Establishing only MCLs at 4.0 ppt for PFOA and PFOS instead of the
proposed rule (MCLs at 4.0 ppt for PFOA and PFOS and the HI) would
result in a reduction of $16 million in quantified costs and $17
million in quantified benefits at the 3% discount level and $27 million
in quantified costs and $13 million in quantified benefits at the 7%
discount level. Establishing MCLs at 5.0 ppt for PFOA and PFOS instead
of 4.0 ppt would result in a reduction of $145 million in quantified
costs and $169 million in quantified benefits at the 3% discount level
and $235 million in quantified costs and $122 million in quantified
benefits at the 7% discount level. Establishing MCLs at 10.0 ppt for
PFOA and PFOS instead of 5.0 ppt would result in a reduction of $318
million in quantified costs and $462 million in quantified benefits at
the 3% discount level and $511 million in quantified costs and $337
million in quantified benefits at the 7% discount level. EPA notes that
there would also be commensurate reduction in the nonquantifiable
benefits and costs among these options. As discussed elsewhere in this
proposal, the nonquantifiable benefits are anticipated to be
significant. EPA evaluated these regulatory alternatives in its HRRCA,
discussed in Section XIII of this preamble below and is requesting
comment on these alternatives.
EPA considered an MCL of 5.0 ppt for PFOA and PFOS because it is 25
percent above the PQL of 4.0 ppt. A commenter in EPA's outreach
consultations for this regulation suggested the Agency consider a
buffer of approximately 20 percent if the MCL is close to the
quantitation level because water systems operate with a margin of
safety and plan for performance that maintains water quality below
quantitation levels. Therefore, in this commenter's opinion, having an
increased buffer between the PQL and the MCL may allow utilities to
manage treatment technology performance more efficiently because
utilities typically aim to achieve lower than the MCL to avoid a
violation. With the MCL at the PQL, the commenter believes that
utilities would not have the early warning that they may exceed the MCL
prior to doing so. EPA disagrees that utilities would not have early
warning prior to exceeding the MCL; see discussion above in section
VI.A of this preamble for more information. For results between the
detection limit and the PQL, EPA has determined that utilities would be
able to reliably conclude analyte presence, though this detection is
less precise regarding specific concentration. Knowledge regarding the
presence of PFOA and PFAS at concentrations below PQLs can inform
decisions related to monitoring frequency and existing treatment. EPA
requests comment on this approach.
EPA also considered the MCL of 10.0 ppt to evaluate the national
costs and benefits and whether the expected reduction in costs would
change EPA's determination of the level at which the benefits would
justify the costs. See SDWA Section 1412(b)(6)(A). The Agency notes
that this regulatory alternative level is consistent with State-enacted
MCLs for certain PFAS (NYDOH, 2020). Because there is significant
expected occurrence of PFOA and PFOS between 4.0 ppt and 10.0 ppt,
raising the MCL from 4.0 to 10.0 would be expected to significantly
decrease the number of utilities that must take action to manage PFOA
and PFOS concentrations in their finished drinking water. However, it
would also result in millions of Americans continuing to be exposed to
levels that have the potential for harmful levels of PFOA and PFOS that
can feasibly be removed through treatment, thereby decreasing the
quantified and non-quantified benefits delivered by this proposed
regulation. Furthermore, since EPA has found proposed PFOA and PFOS
MCLs of 4.0 ppt to be feasible, the Agency must set the MCL as close to
the MCLG as feasible, the Administrator determined the costs were
justified by the benefits at a PFOA and PFOS proposed MCL at 4.0 (see
discussion in section XIII of this preamble), and setting the PFOA and
PFOS MCLs at 10.0 ppt would not reduce PFOA and PFOS exposure risks for
millions of Americans to the extent feasible, EPA preliminarily
determined that proposing PFOA and PFOS MCLs at 10.0 ppt would not be
appropriate or justifiable under the SDWA statutory criteria.
EPA also considered the traditional approach of establishing
individual MCLGs and MCLs for PFHxS, HFPO-DA, PFNA, and PFBS in lieu of
or in addition to separate rule language for the HI approach. As noted
earlier, this action includes a preliminary determination to regulate
these additional PFAS and their mixtures. EPA's proposed HI approach
addresses both the particular PFAS and their mixtures. If EPA does not
finalize a
[[Page 18671]]
regulatory determination for mixtures of these PFAS, then a more
traditional approach may be warranted. Under this alternative, the
proposed MCLG and MCL for PFHxS would be 9.0 ppt; for HFPO-DA the MCLG
and MCL would be 10 ppt; for PFNA the MCLG and MCL would be 10 ppt; and
for PFBS the MCLG and MCL would be 2000 ppt (i.e., 2.0x103 or 2.0e+3).
As discussed in section XIII of this preamble, EPA has not separately
presented changes in quantified costs and benefits for these
approaches. If EPA adds individual MCLs in addition to using the HI
approach, EPA anticipates there will be no change in costs and benefits
relative to the proposed rule (i.e., the same number of systems will
incur identical costs to the proposed option and the same benefits will
be realized). EPA has not separately quantified the benefits and costs
for the approach to regulate PFHxS, PFNA, PFBS, and HFPO-DA with
individual MCLs instead of the HI. However, EPA expects both the costs
and benefits would be reduced under this approach as fewer systems may
be triggered into treatment and its associated costs. Additionally,
systems that exceed one or more of the individual MCLs will treat to a
less stringent and public health-protective standard. Furthermore,
while EPA recognized that regulating these PFAS with individual MCLs
and MCLGs might be simpler to implement for some states or operators,
if EPA were to regulate these PFAS individually and not under the HI
MCL approach, it would not provide equivalent protection against
potential dose additive impacts for these PFAS, nor would it establish
a framework to consider potential dose additive impacts for future PFAS
components or groups as EPA develops a better understanding of the
adverse health effects of other PFAS. The Agency is requesting comment
on whether establishing a traditional MCLG and MCL for PFHxS, HFPO-DA,
PFNA, and PFBS instead of or in addition to the HI approach would
change public health protection, improve clarity of the rule, or change
costs.
EPA also considered an alternative regulatory construct of
establishing both MCLGs and MCLs for these four PFAS in addition to
separate rule language for the HI MCL. Hence, these four PFAS would
expressly be subject to two MCLs: the individual MCLs and the HI MCL
for the mixture. However, this approach has the potential to function
the same as the proposed rule because a system cannot have MCL
violations of an individually regulated PFAS without also exceeding the
HI MCL. EPA considered this approach because it may improve the ability
to communicate about PFAS risks with PWSs and the public, while still
providing the important benefit of protection against dose additive
impacts from these PFAS with the HI approach, as well as building a
potential framework for considering future PFAS regulation. Moreover,
this approach may improve the ability to communicate about PFAS
concentrations and their relative importance with operators and the
public although there may be challenges in risk communication with
respect to those small number of facilities that would not exceed an
individual MCL but would exceed the HI MCL.
While EPA evaluated these regulatory alternatives, EPA proposal is
based upon its proposed finding that an MCL of 4.0 ppt for PFOA and
PFOS and an HI of 1.0 for PFHxS, HFPO-DA, PFNA, and PFBS are feasible
because treatment technologies are available that treat to below these
levels and there are analytical methods that can reliably quantify at
these levels (See discussion above in Section VI.A and Section VIII of
this preamble). Additionally, EPA determined that the benefits justify
the costs with the current rule's proposed MCLs of 4.0 ppt and an HI of
1.0 for PFHxS, HFPO-DA, PFNA, and PFBS.
When proposing an MCL, EPA must publish, and seek public comment
on, the HRRCA for the proposed MCL and each alternative standard
considered under paragraphs 5 and 6(a) of Section 1412(b) (SDWA Section
1412(b)(3)(C)(i)), including:
the quantifiable and nonquantifiable health risk reduction
benefits attributable to MCL compliance;
the quantifiable and nonquantifiable health risk reduction
benefits of reduced exposure to co-occurring contaminants attributable
to MCL compliance;
the quantifiable and nonquantifiable costs of MCL
compliance including monitoring, treatment, and other costs;
the incremental costs and benefits of each alternative
MCL;
the effects of the contaminant on the general population
and sensitive subpopulations likely to be at greater risk of exposure;
and
any adverse health risks posed by compliance; and
other factors such as data quality and uncertainty.
EPA provides this information in section XIII in this preamble. EPA
must base its action on the best available, peer-reviewed science and
supporting studies, taking into consideration the quality of the
information and the uncertainties in the benefit-cost analysis (SDWA
Section 1412(b)(3)). The following sections, as well as the health
effects discussion in sections IV and V of this preamble document the
science and studies that EPA relied upon to develop estimates of
benefits and costs and understand the impact of uncertainty on the
Agency's analysis.
E. MCL-Specific Requests for Comment
EPA specifically requests comment on its proposal to set MCLs at
4.0 ppt for PFOA and PFOS and whether 4.0 ppt is the lowest PQL that
can be achieved by laboratories nationwide. EPA also requests comment
on implementation challenges and considerations for setting the MCL at
the PQLs for PFOA and PFOS. EPA requests comment on its evaluation of
feasibility under SDWA for the proposed PFOA and PFOS MCLs and the
proposed HI MCL. EPA also requests comment on using an HI approach for
PFHxS, HFPO-DA, PFNA, and PFBS. Additionally, EPA requests comment on
its decision to establish stand-alone MCLs for PFOA and PFOS in lieu of
including them in the HI approach. Finally, EPA specifically requests
comment on whether establishing a traditional MCLG and MCL for each of
the following: PFHxS, HFPO-DA, PFNA, and PFBS instead of or in addition
to the HI approach would change public health protection or improve
clarity of the rule; or change anticipated costs.
VII. Occurrence
EPA relied on multiple data sources, including UCMR 3 and state
finished water data to evaluate the occurrence and probability of co-
occurrence of PFOA, PFOS, PFHxS, HFPO-DA, PFNA, and PFBS. 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. EPA has utilized
similar statistical approaches in past regulatory actions to inform its
decision making, particularly where a contaminant's occurrence is
infrequent or at low concentrations (USEPA, 2006b). 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
[[Page 18672]]
water systems (and associated population) expected to be exposed to
levels of PFOA and PFOS which would potentially exceed the proposed and
alternative MCLs, and to levels of PFHxS, HFPO-DA, PFNA, and PFBS that
would potentially exceed the HI.
EPA relied on the UCMR 3 as the primary source of nationwide
occurrence data to inform the occurrence model's exposure estimates for
four PFAS: PFOA, PFOS, perfluoroheptanoic acid (PFHpA), and PFHxS.
Additionally, as described in the final regulatory determination for
PFOA and PFOS (USEPA, 2021d), EPA has also considered and evaluated
publicly-available state finished water PFAS monitoring data, including
data on PFOA, PFOS, PFHxS, HFPO-DA, PFNA, and PFBS.
A. UCMR 3
As discussed in section III.B. of this preamble, UCMR 3 monitoring
occurred between 2013 and 2015 and is currently the best nationally
representative finished water dataset for any PFAS, including PFOA,
PFOS, PFNA, PFBS, and PFHxS. Under UCMR 3, 36,972 samples from 4,920
PWSs were analyzed for these five PFAS.
PFOA was found above the UCMR 3 MRL (20 ppt) 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 MRL (40 ppt). 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
MRL (30 ppt) 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
MRL (90 ppt). 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 MRL (20 ppt) in 19 samples at 14 systems
serving a population of approximately 526,000 people located in 7
states, tribes, and U.S. territories.
B. State Drinking Water Data
As discussed in section III.B of this preamble, the Agency has
supplemented its 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, PFBS, and PFNA 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. Furthermore, these data include results for more PFAS
than were included in the UCMR 3, including HFPO-DA.
EPA evaluated publicly available monitoring data from the following
23 states: Alabama, Arizona, California, Colorado, Delaware, George,
Illinois, Kentucky, Maine, Massachusetts, Maryland, Michigan, Missouri,
New Hampshire, New Mexico, New Jersey, North Carolina, North Dakota,
Ohio, Pennsylvania, Rhode Island, South Carolina, and Vermont. The data
EPA used in its analyses were collected from public state websites
through August 2021, but represent sampling conducted on or before May
2021.
The available data are varied in terms of quantity as well as
coverage, and some are from targeted sampling efforts (i.e., monitoring
in areas of known or potential PFAS contamination) so may not be
representative of levels found in all PWSs within the state or
represent occurrence in other states. EPA further refined this dataset
based on representativeness and reporting limitations, resulting in
detailed technical analyses using a subset of the available state data
(i.e., all 23 states' data were not included within the detailed
technical analyses). USEPA (2023e) presents a comprehensive discussion
of all the available state PFAS drinking water occurrence data.
Tables 5 and 6 in this section demonstrate the number and percent
of samples with PFOA and PFOS state reported detections, and the number
and percent of monitored systems with PFOA and PFOS 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, HFPO-DA, PFNA, and
PFBS data.
Different states utilized various reporting thresholds when
presenting their data, and for some states there were no clearly
defined limits. Further, the limits often varied within the data for
each state depending on the specific analyte, as well as the laboratory
analyzing the data. In some cases, states reported data at
concentrations below EPA's proposed rule trigger level and/or PQLs in
this document. However, to present the best available occurrence
information, EPA collected and evaluated the data based on the
information as reported directly by the states. When conducting data
analyses, EPA incorporated individual state-specific reporting limits
where possible. Specific details on state data reporting thresholds are
available in USEPA (2023e).
Table 5--Non-Targeted State PFOS and PFOA Finished Water Data--Summary of Samples With State Reported Detections
\1\
----------------------------------------------------------------------------------------------------------------
PFOS samples PFOS state PFOA samples PFOA state
with state reported sample with state reported sample
State reported percent reported percent
detections detection detections detections
----------------------------------------------------------------------------------------------------------------
Alabama \2\............................. 140 N/A 80 N/A
Colorado................................ 60 10.3 54 9.3
Illinois................................ 55 5.2 56 5.3
Kentucky................................ 33 40.7 24 29.6
Massachusetts........................... 441 49.1 506 66.5
Michigan................................ 70 2.5 103 3.6
New Hampshire........................... 495 27.1 1,010 55.3
New Jersey.............................. 3,512 37.2 4,379 46.4
North Dakota............................ 0 0.0 0 0.0
Ohio.................................... 93 4.9 93 4.9
South Carolina.......................... 88 57.9 82 53.9
[[Page 18673]]
Vermont................................. 87 6.9 109 8.7
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Detections determined by individual state reported limits which are not defined consistently across all
states.
\2\ Only reported detections.
Table 6--Non-Targeted State PFOS and PFOA Finished Water Data--Summary of Monitored Systems With State Reported
Detections \1\
----------------------------------------------------------------------------------------------------------------
PFOS state PFOA state
PFOS monitored reported PFOA monitored reported
State systems with monitored systems with monitored
state reported system percent state reported system percent
detections detection detections detections
----------------------------------------------------------------------------------------------------------------
Alabama \2\............................. 49 N/A 28 N/A
Colorado................................ 50 12.6 45 11.3
Illinois................................ 36 5.5 32 4.9
Kentucky................................ 33 40.7 24 29.6
Massachusetts........................... 107 47.3 126 55.5
Michigan................................ 55 2.6 82 3.8
New Hampshire........................... 189 33.8 310 55.4
New Jersey.............................. 494 45.9 564 52.4
North Dakota............................ 0 0.0 0 0.0
Ohio.................................... 29 2.0 32 2.2
South Carolina.......................... 42 82.4 40 78.4
Vermont................................. 35 6.3 44 7.9
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Detections determined by individual state reported limits which are not defined consistently across all
states.
\2\ Only reported detections.
As illustrated in Tables 5 and 6, there is a wide range in PFOA and
PFOS results between states, however in nearly half of states that
conducted non-targeted monitoring, more than 25 percent of the
monitored systems found PFOA and/or PFOS. Additionally, considering all
states in Tables 5 and 6, PFOA detected concentrations ranged from 0.51
to 153 ppt with a range of median detected concentrations from 1.98 to
9.4 ppt, and PFOS detected concentrations ranged from 0.5 to 350 ppt
with a range of median detected concentrations from 3 to 11.9 ppt.
Monitoring data for PFOA and PFOS from states that conducted
targeted sampling efforts, including California, Maryland, and
Pennsylvania, 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 ppt and PFOS ranging
from 1.8 to 94 ppt. California reported 26.2 and 29.9 percent of
monitored systems found PFOA and PFOS, respectively, including reported
concentrations of PFOA ranging from 0.9 to 120 ppt and reported
concentrations of PFOS from 0.4 to 250 ppt. 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 ppt and
reported concentrations of PFOS ranging from 2.05 to 235 ppt.
As discussed above in section VI of this preamble, EPA is proposing
individual MCLs of 4.0 ppt for PFOA and PFOS, and an HI level of 1.0
for PFHxS, PFNA, PFBS, and HFPO-DA. EPA also evaluated occurrence for
the regulatory alternatives discussed in section VI of this preamble
including alternative MCLs for PFOA and PFOS of 5.0 ppt and 10.0 ppt.
Table 7, Table 8, and Table 9 demonstrate, based on available state
data, the total state reported number and percentages of monitored
systems that exceed these proposed and alternative MCL values across
the non-targeted state finished water monitoring data.
Table 7--Non-Targeted State PFOS and PFOA Finished Water Data--Summary of Monitored Systems With State Reported
Detections \1\ >=4.0 ppt
----------------------------------------------------------------------------------------------------------------
PFOS state PFOA state
PFOS monitored reported PFOA monitored reported
State systems with monitored systems with monitored
state reported systems percent state reported systems percent
detections detection detections detection
----------------------------------------------------------------------------------------------------------------
Alabama \2\............................. 37 N/A 19 N/A
Colorado................................ 22 5.5 18 4.5
Illinois................................ 17 2.6 16 2.5
Kentucky................................ 4 4.9 9 11.1
[[Page 18674]]
Massachusetts........................... 72 31.9 90 39.6
Michigan................................ 15 0.7 24 1.1
New Hampshire........................... 107 19.1 210 37.5
New Jersey.............................. 315 29.3 411 38.2
North Dakota............................ 0 0.0 0 0.0
Ohio.................................... 29 2.0 32 2.2
South Carolina.......................... 27 52.9 30 58.8
Vermont................................. 16 2.9 24 4.3
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Detections determined by individual state reported limits which are not defined consistently across all
states.
\2\ Only reported detections.
Table 8--Non-Targeted State PFOS and PFOA Finished Water Data--Summary of Monitored Systems With State Reported
Detections \1\ >=5.0 ppt
----------------------------------------------------------------------------------------------------------------
PFOS state PFOA state
PFOS monitored reported PFOA monitored reported
State systems with monitored systems with monitored
state reported systems percent state reported systems percent
detections detection detections detection
----------------------------------------------------------------------------------------------------------------
Alabama \2\............................. 31 N/A 15 N/A
Colorado................................ 16 4.0 14 3.5
Illinois................................ 12 1.8 11 1.7
Kentucky................................ 3 3.7 4 4.9
Massachusetts........................... 64 28.3 83 36.6
Michigan................................ 12 0.6 17 0.8
New Hampshire........................... 86 15.4 186 33.2
New Jersey.............................. 272 25.3 363 33.7
North Dakota............................ 0 0.0 0 0.0
Ohio.................................... 29 2.0 32 2.2
South Carolina.......................... 25 49.0 25 49.0
Vermont................................. 13 2.33 16 2.9
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Detections determined by individual state reported limits which are not defined consistently across all
states.
\2\ Only reported detections.
Table 9--Non-Targeted State PFOS and PFOA Finished Water Data--Summary of Monitored Systems With State Reported
Detections \1\ >=10.0 ppt
----------------------------------------------------------------------------------------------------------------
PFOS state PFOA state
PFOS monitored reported PFOA monitored reported
State systems with monitored systems with monitored
state reported systems percent state reported systems percent
detections detection detections detection
----------------------------------------------------------------------------------------------------------------
Alabama \2\............................. 23 N/A 8 N/A
Colorado................................ 3 0.8 2 0.5
Illinois................................ 3 0.5 6 0.9
Kentucky................................ 1 1.2 1 1.2
Massachusetts........................... 32 14.2 32 14.1
Michigan................................ 6 0.3 7 0.3
New Hampshire........................... 39 7.0 83 14.8
New Jersey.............................. 133 12.4 189 17.6
North Dakota............................ 0 0.0 0 0.0
Ohio.................................... 20 1.4 15 1.0
South Carolina.......................... 3 5.9 3 5.9
Vermont................................. 4 0.7 7 1.3
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Detections determined by individual state reported limits which are not defined consistently across all
states.
\2\ Only reported detections.
Based on the available state data evaluated and presented in Table
7, Table 8, and Table 9, within 12 states that conducted non-targeted
monitoring there are 661 systems that show exceedances of the proposed
PFOS MCL
[[Page 18675]]
of 4.0 ppt and 883 systems with exceedances of the proposed PFOA MCL of
4.0 ppt. These systems serve populations of approximately 8.8 and 10.5
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 ppt, would still be 267 and 353 systems with
exceedances, serving populations of approximately 3.7 and 4.4 million
people, respectively.
Monitoring data for PFOA and PFOS from states that conducted
targeted sampling efforts shows additional systems that would exceed
the proposed and alternative MCLs. For example, in California, Maine,
Maryland, and Pennsylvania, 23.4 percent (25 PWSs), 30.4 percent (7
PWSs), 22.7 percent (15 PWSs), and 19.3 percent (66 PWSs) of monitored
systems exceeded the proposed PFOS MCL of 4.0 ppt, respectively, and
20.6 percent (22 PWSs), 21.7 percent (5 PWSs), 25.8 percent (17 PWSs),
and 21.1 percent (72 PWSs) of monitored systems exceeded the proposed
PFOA MCL of 4.0 ppt, respectively. While these frequencies may be
anticipated given the sampling locations, within only these four states
that conducted limited, targeted monitoring, the monitored systems
exceeding the proposed PFOS MCL and proposed PFOA MCL serve significant
populations of approximately 4.6 million people and approximately 4.4
million people, respectively.
C. Co-Occurrence
While the discussions in sections III.B, VII.A. and VII.B of this
preamble describe how PFOA, PFOS, PFHxS, HFPO-DA, PFNA, and PFBS occur
individually, PFAS have been documented to co-occur in finished
drinking water (Adamson et al., 2017; Cadwallader et al., 2022; Guelfo
and Adamson, 2018). As discussed in section VI of this preamble, EPA is
proposing regulation of four PFAS including PFHxS, HFPO-DA, PFNA, and
PFBS (collectively referred to as ``HI PFAS'') as part of an HI
approach. Sampling results in the aggregated state dataset were
examined to determine the extent to which the HI PFAS occurred with
each other as well as with PFOA and/or PFOS. This involved considering
the observed occurrence in terms of grouping (i.e., groups of HI PFAS
and ``PFOS or PFOA'') as well as pairwise by means of odds ratios. For
the group assessment, the aggregated state dataset was limited to
samples from non-targeted monitoring efforts where at least one HI PFAS
was analyzed and PFOS and PFOA were analyzed sufficiently to determine
whether one was present.
1. Groupwise Chemical Co-Occurrence
Table 10 shows the distribution of systems and samples according to
whether states report detections for any HI PFAS (PFHxS, HFPO-DA, PFNA
and PFBS) and whether they also reported detections of PFOS or PFOA.
USEPA (2023e) provides additional information for this analysis.
Table 10--Non-Targeted State PFAS Finished Water Data--Samples and Systems Binned According to Whether PFOS or
PFOA Were Reported by States and Whether Additional HI PFAS Were Reported
----------------------------------------------------------------------------------------------------------------
No PFOS or PFOA reported PFOS or PFOA reported
----------------------------------------------------------------------
Type At least one At least one Total
No HI PFAS HI PFAS No HI PFAS HI PFAS count
reported reported reported reported
----------------------------------------------------------------------------------------------------------------
Samples.......................... 12,704 (65.2%) 357 (1.8%) 3,380 (17.3%) 3,041 (15.6%) 19,482
Systems.......................... 5,560 (78.8%) 196 (2.8%) 516 (7.3%) 784 (11.1%) 7,056
----------------------------------------------------------------------------------------------------------------
Considering eligible samples and systems within the aggregated
state dataset, states reported detections of either PFOS, PFOA, or one
or more HI PFAS in 34.8 percent (6,778 of 19,482) of samples and 21.2
percent (1,496 of 7,056) of systems. When any PFAS (among PFOA, PFOS,
and the HI PFAS) were reported detected, at least one HI PFAS was also
reported in 50.1 percent (3,398 of 6,778) of samples and at 65.5
percent (980 of 1,496) of systems. Further, among samples and systems
that reported detections of PFOS or PFOA, at least one HI PFAS was
detected in 47.4 percent (3,041 of 6,421) of samples and at 60.3
percent (784 of 1,300) of systems. This demonstrated strong co-
occurrence of HI PFAS with PFOA and PFOS and a substantial likelihood
(over 50 percent) of at least one HI PFAS being present at systems with
reported detections of PFOS or PFOA. Overall, one or more HI PFAS were
reported at about 13.9 percent (980 of 7,056) of systems included in
the aggregated state dataset of non-targeted monitoring. If this
percentage were extrapolated to the nation, one or more HI PFAS would
be at detectable levels in over 9,000 systems. Table 11 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 HI PFAS.
Table 11--Non-Targeted State PFAS Finished Water Data--Systems That Sampled for 3 or 4 HI PFAS Binned According
to Whether PFOS or PFOA Were Reported and Whether Any Additional HI PFAS Were Reported by State
----------------------------------------------------------------------------------------------------------------
No PFOA/S detected PFOA/S detected Total
State ------------------------------------------------------------------------ system
No HI detected HI detected No HI detected HI detected count
----------------------------------------------------------------------------------------------------------------
CO............................ 270 (68.0%) 26 (6.5%) 11 (2.8%) 90 (22.7%) 397
IL............................ 582 (89.7%) 22 (3.4%) 15 (2.3%) 30 (4.6%) 649
KY............................ 37 (52.9%) 2 (2.9%) 16 (22.9%) 15 (21.4%) 70
MA............................ 60 (35.5%) 2 (1.2%) 12 (7.1%) 95 (56.2%) 169
MI............................ 1,969 (91.5%) 82 (3.8%) 43 (2.0%) 58 (2.7%) 2,152
ND............................ 49 (98%) 1 (2.0%) 0 (0.0%) 0 (0.0%) 50
NH............................ 60 (43.2%) 2 (1.4%) 34 (24.5%) 43 (30.9%) 139
NJ............................ 225 (36.3%) 7 (1.1%) 127 (20.5%) 261 (42.1%) 620
[[Page 18676]]
OH............................ 1,397 (94.5%) 31 (2.1%) 25 (1.7%) 26 (1.8%) 1,479
SC............................ 10 (22.2%) 1 (2.2%) 10 (22.2%) 24 (53.3%) 45
VT............................ 488 (87.6%) 15 (2.7%) 31 (5.6%) 23 (4.1%) 557
----------------------------------------------------------------------------------------------------------------
The percentage of systems included in Table 11 that reported
detections of any HI PFAS ranged from 2.0 to 57.4 percent of systems
when broken down by state, with six states exceeding 20 percent of
systems. The percentage of systems that reported detections of any PFAS
ranged from 2.0 to 77.8 percent. Many systems and/or samples that were
included in the aggregated state dataset did not monitor for all four
HI PFAS. It is possible that more systems would have detected HI PFAS
if they had monitored for all four HI PFAS. Additionally, as
demonstrated in Table 11, when PFOA and/or PFOS were reported, at least
one of the HI PFAS chemicals were also frequently reported. Table 12
presents system counts for systems where PFOS or PFOA were detected
according to (a) how many HI PFAS were monitored and (b) how many HI
PFAS were reported to be detected.
Table 12--Non-Targeted State PFAS Finished Water Data--System Counts According to HI PFAS Analyzed and Reported Present for Systems Where PFOS and PFOA
Were Reported
--------------------------------------------------------------------------------------------------------------------------------------------------------
HI reported present
HI analyzed -------------------------------------------------------------------------------- Total
0 1 2 3 4
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.............................................................. 143 (70.1%) 61 (29.9%) .............. .............. .............. 204
2.............................................................. 49 (45.8%) 41 (38.3%) 17 (15.9%) .............. .............. 107
3.............................................................. 153 (34.7%) 95 (21.5%) 137 (31.1%) 56 (12.7%) .............. 441
4.............................................................. 171 (31.2%) 135 (24.6%) 179 (32.7%) 61 (11.1%) 2 (0.4%) 548
----------------------------------------------------------------------------------------
Total...................................................... 516 332 333 117 2 .......
--------------------------------------------------------------------------------------------------------------------------------------------------------
Among systems that reported detections of PFOS and/or PFOA, the
fraction of systems that also reported detections of any HI PFAS tended
to increase as systems monitored for more of the HI PFAS. At systems
monitoring for a single HI PFAS, 29.9 percent reported a detection at
some point during sampling. This increased to 68.8 percent of systems
reporting detections of at least one HI PFAS when monitoring for all
four HI PFAS. Not only did the fraction of systems reporting detections
of any HI PFAS increase as the number of HI PFAS increased, so did the
number of HI PFAS that were reported. When three or four HI PFAS were
monitored, over 40 percent of systems reported detections of two to
three of the HI PFAS. Thus, if PFOS or PFOA are reported, there is a
reasonable likelihood that multiple HI PFAS would be present as well.
2. Pairwise Chemical Co-Occurrence
In addition to considering the co-occurrence of six PFAS as two
groups, EPA conducted a pairwise analysis to further explore co-
occurrence relationships. Table 13 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 (2023e) and a brief explanation is described following
Table 13.
Table 13--Non-Targeted State PFAS Finished Water Data--System-Level Counts of Pairwise Chemical Occurrence and Odds Ratios Calculated From Aggregated
State Dataset PFAS Samples for PFOS, PFOA, and HI PFAS
--------------------------------------------------------------------------------------------------------------------------------------------------------
Chems A and B Only Chem B Only Chem A Neither Chem
Chem A Chem B reported reported reported reported Odds ratio [95% CI]
--------------------------------------------------------------------------------------------------------------------------------------------------------
HFPO-DA............................... PFBS..................... 10 452 10 5,116 11.3 [4.8-26.7]
HFPO-DA............................... PFHxS.................... 2 339 18 5,229 1.7 [0.4-6.7]
HFPO-DA............................... PFNA..................... 2 77 18 5,491 7.9 [2.0-31.4]
HFPO-DA............................... PFOA..................... 16 438 4 5,129 46.8 [16.3-134.1]
HFPO-DA............................... PFOS..................... 14 399 6 5,168 30.2 [11.9-76.5]
PFBS.................................. PFHxS.................... 433 133 261 5,501 68.6 [54.5-86.5]
PFBS.................................. PFNA..................... 135 33 560 5,601 40.9 [27.7-60.4]
PFBS.................................. PFOA..................... 517 360 178 5,273 42.5 [34.8-52.0]
PFBS.................................. PFOS..................... 503 278 192 5,355 50.5 [41.1-62.0]
PFHxS................................. PFNA..................... 150 38 473 5,939 49.6 [34.3-71.6]
PFHxS................................. PFOA..................... 510 466 113 5,510 53.4 [42.6-66.9]
PFHxS................................. PFOS..................... 507 353 116 5,623 69.6 [55.4-87.6]
[[Page 18677]]
PFNA.................................. PFOA..................... 236 934 15 5,871 98.9 [58.7-166.5]
PFNA.................................. PFOS..................... 234 789 17 6,016 105.0 [64.1-171.9]
PFOA.................................. PFOS..................... 893 130 277 5,756 142.7 [114.5-177.9]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Odds ratios reflect the change in the odds of detecting 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 detecting if
the second chemical is not present. For example, as shown in Table 13,
the point estimate of 142.7 for the odds ratio between PFOA and PFOS
indicates that the odds of detecting PFOA after knowing that PFOS has
been observed are 142.7 times what the odds would have been if PFOS was
not observed, and vice versa. For every pair of chemicals, except for
HFPO-DA and PFHxS, both the point estimate and 95 percent CI were above
1, indicating significant increases in the likelihood of detecting one
chemical if the other is present. For HFPO-DA and PFHxS, 1 fell within
the 95 percent CI, and thus the odds ratio was not determined to be
statistically significantly different from 1.
Both as a group and as individual chemicals, the HI PFAS had a
higher likelihood of being reported if PFOS or PFOA were present.
PFHxS, HFPO-DA, PFNA and PFBS (the individual HI PFAS) are demonstrated
to generally co-occur with each other, as well. As such, these data
support that there is a substantial likelihood PFHxS, HFPO-DA, PFNA,
and PFBS co-occur with a frequency of public health concern in drinking
water systems.
D. Occurrence Relative to the Hazard Index
EPA analyzed the available state data in comparison to the proposed
HI MCL of 1.0 to evaluate the co-occurrence of PFHxS, HFPO-DA, PFNA,
and PFBS. Table 14 presents the total number and percentage of
monitored systems that exceeded the proposed HI MCL based on state
reported HI PFAS detections for the states that conducted non-targeted
monitoring and that sampled all four HI PFAS as a part of their overall
monitoring efforts. EPA notes that for equivalent comparison purposes
Table 14 only accounts for samples that included reported values
(including non-detects) of all four HI PFAS. As shown within the table,
the majority of states evaluated had monitored systems exceed the
proposed HI MCL, ranging from 0.72 to 7.41 percent of total monitored
systems.
Table 14--Non-Targeted State PFAS Finished Water Data--Summary of Total
Number and Percent of Monitored Systems Exceeding the HI With Samples
Containing Reported Values of All HI PFAS
------------------------------------------------------------------------
Total monitored
State systems > proposed Percent systems >
HI of 1.0 proposed HI of 1.0
------------------------------------------------------------------------
Colorado.................... 5 1.26
Illinois.................... 10 1.54
Kentucky.................... 6 7.41
Massachusetts............... 8 6.40
Michigan.................... 14 0.65
New Hampshire............... 4 2.99
North Dakota................ 0 0.00
Ohio........................ 25 1.69
South Carolina.............. 0 0.00
Vermont..................... 4 0.72
------------------------------------------------------------------------
Further evaluating the available state data related to the proposed
HI MCL of 1.0, Table 15 presents the total number of systems and
associated populations served that exceed the proposed HI of 1.0 based
on state reported HI PFAS detections for the same states shown in Table
15. However, in this case, EPA also analyzed the same non-targeted
state data adding in additional samples even if those samples did not
contain reported values (including non-detects) for all four HI PFAS
(i.e., exceeding the HI based on only one to three HI PFAS with
reported values included within a sample). Moreover, while these states
did monitor for all four HI PFAS as a part of their overall monitoring,
in a subset of those states some samples did not include reported data
on all four HI PFAS (i.e., values of one or more of the HI PFAS were
not reported as non-detect, rather no value was reported). This
analysis, presented in Table 15, shows an increase in the number of
monitored systems exceeding the proposed HI of 1.0 and demonstrates
prevalence of these PFAS at levels of concern, even when all four PFAS
may not be included within a sample.
[[Page 18678]]
Table 15--Non-Targeted State PFAS Finished Water Data--Summary of Total
Monitored Systems Exceeding the HI With Samples Containing Reported
Values of Any Number of HI PFAS
------------------------------------------------------------------------
Total monitored
State systems > proposed Population served
HI of 1.0
------------------------------------------------------------------------
Colorado.................... 5 5,429
Illinois.................... 10 107,461
Kentucky.................... 6 103,315
Massachusetts............... 19 302,482
Michigan.................... 14 221,484
New Hampshire............... 25 36,463
North Dakota................ 0 0
Ohio........................ 25 234,834
South Carolina.............. 0 0
Vermont..................... 4 410
------------------------------------------------------------------------
Combining the non-targeted monitoring results shown previously with
targeted state monitoring conducted for all four HI PFAS showed at
least 917 samples from 157 PWSs in 15 states that exceed the proposed
HI of 1.0 for PFHxS, HFPO-DA, PFNA, and PFBS. These systems serve
approximately 3.08 million people. Additionally, data from New Jersey,
which conducted non-targeted monitoring but did not conduct any
monitoring that included all four HI PFAS, showed an additional 243
samples within 57 systems serving a total population of approximately
1.43 million people exceeding the proposed HI of 1.0 based solely upon
the reported detections of three of the four HI PFAS (i.e., PFHxS,
PFNA, and PFBS). USEPA (2023e) presents a detailed discussion on state
PFAS monitoring information. More information on occurrence in state
monitoring is available in section III.B. of this preamble.
In summary, the finished water data collected under both non-
targeted and targeted state monitoring efforts from 22 states showed
there are at least 1,007 PWSs serving a total population of
approximately 15.3 million people that have at least one result
exceeding the proposed PFOA MCL of 4.0 ppt. In those same 22 states,
there are also at least 805 PWSs serving a total population of
approximately 13.6 million people that have at least one result
exceeding the proposed PFOS MCL of 4.0 ppt. Related to the proposed HI,
finished water data collected under both non-targeted and targeted
state monitoring efforts in 16 states showed there are at least 214
systems serving a total population of approximately 4.5 million people
that exceed the proposed HI value of 1.0 for PFHxS, HFPO-DA, PFNA, and
PFBS. USEPA (2023e) presents a detailed discussion on state PFAS
monitoring information. Additionally, EPA is aware that since the data
were collected some of these states may have updated data available and
that additional states have or intend to conduct monitoring of finished
drinking water, such as New York and Virginia. EPA will consider, and
as appropriate, analyze additional data submitted in response to this
proposal to inform future regulatory decision making.
E. Occurrence Model
A Bayesian hierarchical occurrence model was developed to explore
national occurrence of the four PFAS that were most frequently detected
in the UCMR 3: PFOS, PFOA, PFHxS, and PFHpA. While PFNA and PFBS were
included in the UCMR 3 as well, they lacked sufficient reported values
above the UCMR 3 MRLs to be incorporated into the model. The model has
been peer reviewed and is described extensively in Cadwallader et al.
(2022). Briefly, inputs to the model include the UCMR 3 dataset as well
as subsequent data in publicly available state datasets that were
collected at PWSs that took part in the UCMR 3. 23,130 analytical
results from state datasets were used to supplement the UCMR 3. These
results were derived from 17 state datasets. The objective of the model
was to enable national estimates of PFAS occurrence by using available
UCMR 3 and state data to inform occurrence distributions both within
and across PWSs. Note that while PFHpA was included in the model
because of its UCMR 3 occurrence data availability, EPA is not
proposing to regulate it in this document.
The model uses Markov chain Monte Carlo (MCMC) and the assumption
of lognormality in PFAS chemical occurrence. After log-transforming all
available data, 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 are
distributed 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 MRLs. EPA has
used similar hierarchical statistical models to inform regulatory
decision making in the past, such as for development of the NPDWR for
Arsenic and Cryptosporidium parvum (USEPA, 2006b; USEPA, 2000e).
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 CWS and 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. Using population data
retrieved from SDWIS, the total number of systems with system-level
mean concentrations of each chemical, as well as their associated
population served, could be estimated. The median estimate and the 90
percent credible interval are shown for the systems with system-level
means at or above various PFAS concentrations in Table 16 and the
population served by those systems in Table 17.
[[Page 18679]]
Table 16--National Occurrence Model Estimate--Estimated Number of Systems With System-Level Means at or Above
Various Concentrations
----------------------------------------------------------------------------------------------------------------
Concentration (ppt) PFHxS [90% CI] PFOA [90% CI] PFOS [90% CI]
----------------------------------------------------------------------------------------------------------------
4.0........................................ 1,697 [1,053-2,702] 1,987 [1,338-3,016] 3,427 [2,326-4,900]
5.0........................................ 1,232 [745-2,009] 1,351 [903-2,083] 2,593 [1,737-3,770]
10.0....................................... 417 [241-730] 349 [223-577] 986 [627-1,531]
----------------------------------------------------------------------------------------------------------------
Table 17--National Occurrence Model Estimate--Estimated Population Served by Systems With System-Level Means at
or Above Various Concentrations
----------------------------------------------------------------------------------------------------------------
Concentration (ppt) PFHxS [90% CI] PFOA [90% CI] PFOS [90% CI]
----------------------------------------------------------------------------------------------------------------
4.0......................... 18,641,000 28,051,000 30,627,000
[15,669,000-21,693,000] [24,966,000-33,071,000] [27,407,000-35,665,000]
5.0......................... 14,092,000 20,844,000 24,405,000
[11,129,000-16,887,000] [18,193,000-24,239,000] [21,611,000-28,440,000]
10.0........................ 4,608,000 7,111,000 10,561,000
[3,432,000-7,262,000] [5,566,000-9,335,000] [7,858,000-12,866,000]
----------------------------------------------------------------------------------------------------------------
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
ppt) presented in Tables 16 and 17 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. Untransformed
estimates of system-level means were assessed for correlation across
each unique pair of the four modeled chemicals included in the model.
Estimates of the Pearson correlation coefficient are shown in Table 18.
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).
Table 18--National Occurrence Model Estimate--Median Estimated Pearson
Correlation Coefficient and 90% Credible Interval Among System-Level
Means
------------------------------------------------------------------------
Pearson correlation
Chemical pair coefficient [90% CI]
------------------------------------------------------------------------
PFOS-PFOA........................................ 0.71 [0.60-0.79]
PFOS-PFHpA....................................... 0.69 [0.57-0.78]
PFOS-PFHxS....................................... 0.85 [0.74-0.92]
PFOA-PFHpA....................................... 0.85 [0.80-0.89]
PFOA-PFHxS....................................... 0.55 [0.41-0.65]
PFHpA-PFHxS...................................... 0.62 [0.47-0.72]
------------------------------------------------------------------------
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% credible interval
above 0.7. PFOS-PFOA and PFOS-PFHpA had similar point estimates and 90%
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 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 VII.C
of this preamble that indicated extensive co-occurrence of PFOA, PFOS,
and the HI 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 proposed regulation, including MCLs of 4.0 ppt for PFOA
and PFOS alongside an HI of 1.0 for PFHxS, HFPO-DA, PFNA, 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 (2023e). Briefly, information collected from non-targeted
state datasets included the fractions of systems that reported a
measurement at or above the UCMR 5 MRL 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 MRLs for HFPO-DA, PFNA, and PFBS are equivalent to
5.0 ppt, 4.0 ppt, and 3.0 ppt, respectively (USEPA, 2021e). This
applies the assumption that
[[Page 18680]]
the fraction of systems that observed HFPO-DA, PFNA, and PFBS at or
above UCMR 5 MRLs and the maximum concentrations observed at those
systems are reasonably representative of the nation.
The model was used to simulate entry point-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 entry points (thus a given entry point is assumed to
have a constant concentration) For each system, the maximum estimated
entry point PFOA or PFOS concentration was selected to determine
whether the system exceeded either of the proposed MCLs of 4.0 ppt. The
entry point with the maximum concentration is the point that determines
whether a system has an entry point that is above an MCL. Estimates of
the system-level maximum for PFHxS were also selected for the HI
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 HI chemicals (HFPO-DA, PFNA, 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 HFPO-DA, PFNA, and PFBS would occur at the same
location within a system. Substantial co-occurrence among PFAS was
observed in the model output, state datasets, and the UCMR 3 dataset.
Combination of system-level maximums independently pulled from chemical
eCDFs is a reasonable simplifying assumption given this co-occurrence.
This is particularly true given that the 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 resulting range of systems estimated to be impacted by the
proposed regulation of an MCL of 4.0 ppt for PFOA and PFOS and an HI of
1.0 for a mixture of PFHxS, HFPO-DA, PFNA, and PFBS was 3,400-6,300
systems serving a total population of 70-94 million people. Among these
systems, 100-500 were estimated to be systems exceeding the HI for
PFHxS, HFPO-DA, PFNA, and PFBS that had not already exceeded the MCLs
for PFOA and/or PFOS. The total population served by these systems was
estimated to be 0.6 to 6.3 million people.
In summary, using the MCMC occurrence model, EPA estimated baseline
occurrence to derive occurrence and exposure estimates for the proposed
MCLs for PFOA and PFOS, as well as alternative MCLs. EPA then used
these modeled estimates to inform the costs and benefits determination
as described in section XIII of this preamble. Here and in section XIII
of this preamble, EPA requests comment on the number of systems
estimated to solely exceed the HI (but not the PFOA or PFOS MCLs)
according to the approach outlined in USEPA (2023e).
VIII. Analytical Methods
EPA developed the following 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, 2009b; USEPA, 2020a). All six PFAS
proposed for regulation can be measured by both EPA Methods 533 and
537.1 and both methods are acceptable for meeting the monitoring
requirements of this regulation.
EPA Method 533 monitors for 25 select PFAS, including PFOA, PFOS,
PFHxS, HFPO-DA, PFNA, and PFBS, with published measurement accuracy and
precision data for PFOA in reagent water, finished ground water, and
finished surface water. For further details about the procedures for
this analytical method, please see 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 (USEPA, 2019b).
EPA Method 537.1 (an update to EPA Method 537), monitors for 18
select PFAS, including PFOA, PFOS, PFHxS, HFPO-DA, PFNA, and PFBS, with
published measurement accuracy and precision data for PFOA in reagent
water, finished ground water, and finished surface water. For further
details about the procedures for this analytical method, please see
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) (USEPA, 2020a).
A. Practical Quantitation Levels (PQLs) for Regulated PFAS
As described in section VI of this preamble, a PQL is defined as
the ``lowest concentration of an analyte that can be reliably measured
within specified limits of precision and accuracy during routine
laboratory operating conditions'' (USEPA, 1985). EPA uses the PQL to
estimate or evaluate the minimum, reliable quantitation level that most
laboratories can be expected to meet during day-to-day operations. The
basis for setting PQLs is (1) quantitation, (2) precision and accuracy,
(3) normal operations of a laboratory, and (4) the fundamental need (in
the compliance monitoring program) to have a sufficient number of
laboratories available to conduct the analyses. For the PFAS regulated
in this proposal, EPA is proposing the following PQLs outlined in Table
19:
Table 19--PQLs for Regulated PFAS
------------------------------------------------------------------------
PQL
Contaminant (ppt)
------------------------------------------------------------------------
PFOA......................................................... 4.0
PFOS......................................................... 4.0
HFPO-DA...................................................... 5.0
PFHxS........................................................ 3.0
PFNA......................................................... 4.0
PFBS......................................................... 3.0
------------------------------------------------------------------------
Drinking water analytical laboratories have different performance
capabilities dependent upon their instrumentation (manufacturer, age,
usage, routine maintenance, operating configuration, etc.) and analyst
experience. Some laboratories will effectively generate accurate,
precise, quantifiable results at lower concentrations than others.
Organizations that collect data need to establish data quality
objectives (DQOs) to meet the needs of their program. These DQOs should
consider establishing reasonable quantitation levels that laboratories
can routinely meet. Establishing a quantitation level that is too low
may result in recurring QC failures that will necessitate repeating
sample analyses, increase
[[Page 18681]]
costs, and potentially reduce laboratory capacity. Establishing a
quantitation level that is too high may result in important lower-
concentration results not being quantitated.
EPA's approach to establishing DQOs within the UCMR program serves
as an example. EPA established MRLs for UCMR 5, finalized in December
2021, and requires laboratories approved to analyze UCMR samples to
demonstrate that they can make quality measurements at or below the
established MRLs. EPA calculated the UCMR 5 MRLs using quantitation-
limit data from multiple laboratories participating in an MRL-setting
study. An MRL is set after a statistical determination that 75% of
laboratories will be able to meet that level with a 95% CI (USEPA,
2022g). The UCMR 5 MRLs are not intended to represent the lowest
achievable measurement level an individual laboratory may achieve. As
noted above, these MRLs are derived using the quantitation level
results from multiple laboratories participating in an analytical study
and account for differences in the capability of laboratories across
the country.
For UCMR 5, EPA calculated and published the following multi-
laboratory MRLs for the PFAS addressed in this proposed rule: PFOA:
0.004 [micro]g/L (4.0 ppt); PFOS: 0.004 [micro]g/L (4.0 ppt); PFHxS:
0.003 [micro]g/L (3.0 ppt); HFPO-DA: 0.005 [micro]g/L (5.0 ppt); PFNA:
0.004 [micro]g/L (4.0 ppt); PFBS: 0.003 [micro]g/L (3.0 ppt). Based on
the multi-laboratory data acquired for the UCMR 5 rule, EPA has defined
the PQL for PFAS addressed in this proposed rule to be equal to the
UCMR 5 MRL (see Table 19, above).
Some laboratories are capable of measuring the PFAS addressed in
this proposed rule at lower concentrations. Indeed, EPA received some
public comments prior to developing the final UCMR 5 recommending lower
MRLs than those that were ultimately promulgated (USEPA, 2022g).
However, after reviewing the data from laboratories that participated
in the MRL-setting study for UCMR 5, EPA concluded that the MRLs set in
that rule represented ``lowest feasible'' levels for a national
measurement program. Based on laboratory performance in EPA's UCMR 5
Laboratory Approval Program, during 2021-2022, EPA believes that the
UCMR 5 MRLs are appropriate for using as PQL for this proposed
rulemaking. EPA recognizes that as more laboratories upgrade their
instrumentation and gain more experience analyzing drinking water
samples for PFAS, more laboratories may become capable of
quantitatively measuring PFAS at lower concentrations.
While the values below the PQL will not be used to calculate
compliance with the proposed MCLs under this proposed rule (see
discussion above in Section VI of this preamble), values lower than the
PQL are achievable by individual laboratories, and therefore lower
levels can be used for purposes of screening and to determine
compliance monitoring frequency. EPA is proposing the use of a rule
trigger level for less frequent compliance monitoring under certain
circumstances in which systems can demonstrate PFAS concentrations in
finished drinking water are below:
one-third of the MCLs for PFOA and PFOS, i.e., 1.3 ppt;
and
one-third of the HI MCL for the HI PFAS (PFHxS, HFPO-DA,
PFNA, and PFBS), i.e., 0.33.
Based on laboratory calibration standard data submitted as part of
the UCMR 5 Laboratory Approval Program, described in more detail in
section VI.A. of this preamble, EPA maintains that laboratories are
capable of screening to this level. For additional discussion on this
rule trigger level and monitoring requirements for this proposal,
please see sections VI.A. and IX of this preamble.
IX. Monitoring and Compliance Requirements
A. What are the monitoring requirements?
EPA is proposing requirements for CWS and NTNCWSs to monitor for
certain PFAS. The Agency is proposing to amend 40 CFR part 141 by
adding a new subpart to incorporate the regulated PFAS discussed in
this preamble. Under this new subpart, PWSs must sample entry points to
the distribution system using a monitoring regime based on EPA's SMF
for SOCs. Under the SMF for SOCs, the monitoring frequency for a PWS is
dependent on previous monitoring results, among other things (USEPA,
2004). EPA is proposing that, consistent with the SMF for SOCs,
groundwater systems serving greater than 10,000 and all surface water
systems are initially required to monitor quarterly within a 12-month
period for regulated PFAS. To provide additional flexibilities for
small groundwater systems, EPA is also proposing and taking comment on
a modification to the SMF for SOCs in that groundwater systems serving
10,000 or fewer are initially required to only monitor twice for
regulated PFAS within a 12-month period, each sample at least 90 days
apart. In this proposal, all systems would be allowed to use previously
acquired monitoring data to satisfy the initial monitoring requirements
(see subsection (C) of this preamble below for additional details about
using previously acquired monitoring data to satisfy initial monitoring
requirements). Based on the SMF, EPA is also proposing that based upon
the initial monitoring results, primacy agencies would be able 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 rule trigger level (defined below).
EPA is proposing that water systems will conduct compliance
monitoring to demonstrate that finished drinking water does not exceed
the MCLs for regulated PFAS. Water systems must show the primacy agency
that the contaminant is not present in the drinking water supply or, if
present, it does not exceed the proposed MCLs for regulated PFAS. For
compliance monitoring frequency purposes only, EPA is proposing a rule
trigger level of one-third the MCLs (1.3 ppt for PFOA and PFOS and 0.33
for HI PFAS (PFHxS, HFPO-DA, PFNA, and PFBS)). As such, EPA is
proposing amendments for a new subpart to include the following term to
describe the circumstances in which water systems may be eligible for
reduced monitoring for PFOA and PFOS and the HI PFAS if below this:
Rule Trigger Level: One-third of the MCLs for regulated
PFAS, i.e., 1.3 ppt for PFOA and PFOS and 0.33 for PFAS regulated by
the HI (PFHxS, HFPO-DA, PFNA, and PFBS).
For more information, including the basis of the rule trigger
level, please see sections VI.A. and VIII.A. of this preamble.
EPA notes that for some proposed regulated PFAS, the values used to
determine reduced monitoring may be below their PQLs (e.g., PFOA and
PFOS at 1.3 ppt when the PQL is 4.0 ppt). For purposes of screening to
determine monitoring frequency, however, EPA has sufficient confidence
that while measurements below the PQL may be slightly less precise and
accurate, they are achievable by individual laboratories and
appropriate for this intended purpose. EPA requests comment on this
finding regarding feasibility of the proposed MCLs and more generally
on laboratory capacity. As noted earlier, EPA anticipates laboratories
will be able to adjust to demand (including possible price effects),
which the Agency anticipates will be distributed across the
implementation period. Further, at the proposed rule trigger level, the
measurement is primarily useful in determining whether the contaminant
is
[[Page 18682]]
present in a sample and for evaluating monitoring flexibilities, rather
than to determine its specific concentration. EPA has set these values
below the MCLs to allow systems the opportunity to reduce their
monitoring schedule and burden, while minimizing the chance of random
normal variation resulting in a single sample close to, but below the
MCLs, when the ``true'' annual average value would be above the MCL.
For additional discussion on PQL, please see section VII of this
preamble. Systems below the rule trigger level would be required to
conduct compliance monitoring according to the following schedule:
Systems that do not detect regulated PFAS in their systems
at or above the rule trigger level (1.3 ppt for PFOA and PFOS and 0.33
for the HI PFAS (PFHxS, HFPO-DA, PFNA, and PFBS)), and that serve 3,300
or fewer customers will be required to analyze one sample for all
regulated PFAS per three-year compliance period at each entry point to
the distribution system (EPTDS) that does not meet or exceed the rule
trigger level.
Systems that do not detect regulated PFAS in their systems
at or above the rule trigger level (1.3 ppt for PFOA and PFOS and 0.33
for the HI PFAS (PFHxS, HFPO-DA, PFNA, and PFBS), and that serve a
population of greater than 3,300 will 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 EPTDS that does not meet
or exceed the rule trigger level.
If a water system is not below the rule trigger level for regulated
PFAS at a given EPTDS, it will be required to monitor for all regulated
PFAS quarterly at that EPTDS. Systems monitoring less frequently than
quarterly whose sample result is at or exceeds the rule trigger level
must also begin quarterly sampling at the EPTDS where regulated PFAS
were observed at or above the trigger level. In either case, the
primacy agency may allow a system to move to a reduced monitoring
frequency when the primacy agency determines that the system is below
the rule trigger level and reliably and consistently below the MCL.
However, primacy agencies cannot determine that the system is below the
rule trigger level and reliably and consistently below the MCL until at
least four consecutive quarters of quarterly monitoring have occurred.
EPA notes that, as described above, systems may have EPTDS within a
system on different compliance monitoring schedules depending on
monitoring results.
In this document, EPA requests comment on the reduced monitoring
approach the Agency is proposing which will save resources for many
lower-risk water systems. First, EPA is requesting comment on the
allowance of a water system to potentially have each EPTDS on a
different compliance monitoring schedule based on specific entry point
sampling results (i.e., some EPTDS being sampled quarterly and other
EPTDS sampled only once or twice during each three-year compliance
period), and if instead, compliance monitoring frequency should be
consistent across all of the system's sampling points. EPA is also
requesting comment on establishing the proposed rule trigger level
values of 1.3 ppt for PFOA and PFOS and 0.33 for the PFAS regulated by
the HI (PFHxS, HFPO-DA, PFNA, and PFBS). EPA is seeking comment on
establishing the trigger level at other levels, specifically
alternative values of 2.0 ppt for PFOA and PFOS and 0.50 for the HI
PFAS. EPA notes that adjusting the trigger levels to 2.0 ppt for PFOA
and PFOS and 0.50 for the HI PFAS would result in a considerable number
of additional water systems significantly reducing their monitoring
frequency from at least four times each year to once or twice every
three years. EPA also notes that the higher trigger may provide
slightly less assurance of the water systems' current regulated PFAS
levels as a result of the more intermittent monitoring. EPA is seeking
comment on the merits and drawbacks of these higher trigger levels
compared to those proposed in this document.
B. How are PWS compliance and violations determined?
Consistent with existing rules for determining compliance with
NPDWRs, EPA is proposing that compliance with this rule will be
determined based on the analytical results obtained at each sampling
point. For systems monitoring quarterly, compliance with the proposed
MCLs for regulated PFAS will be determined by running annual averages
at the sampling point. Systems monitoring less frequently whose sample
result(s) are at or exceed the rule trigger level must revert to
quarterly sampling at each EPTDS where the trigger level is met or
exceeded for all regulated PFAS in the next quarter, with the triggered
sample result being used for the first quarter of monitoring in
calculating the running annual average.
A running annual average is an average of sample analytical results
for samples taken at a particular monitoring location during the
previous four consecutive quarters. 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 averages to be used in
calculating the running annual averages. Conversely, if a system does
not collect required samples for a quarter, the running annual average
will be based on the total number of samples collected for the quarters
in which sampling was conducted. A system will not be considered in
violation of an MCL until it has completed one year of quarterly
sampling, except in the case where, if a quarterly sampling result will
cause the running annual averages to exceed an MCL at any sampling
point (i.e., the analytical result is greater than four times the MCL).
In that case, the system is out of compliance with the MCL immediately.
When calculating the running annual averages, if a sample result is
less than the PQL for the monitored PFAS, EPA is proposing to use zero
to calculate the average for compliance purposes. For example, if a
system has sample results for PFOA that are 2.0, 1.5, 5.0, and 1.5 ppt
for their last four quarters at a sample location, the values used to
calculate the running annual average would be 0.0, 0.0, 5.0, and 0.0
with a resulting PFOA running annual average of 1.3 ppt. As described
in sections VI and VIII of this preamble, EPA is proposing that values
below the PQL will not be used to determine compliance with the
proposed MCLs as these PQLs are the lowest concentration of analyte
that can be reliably measured within specified limits of precision and
accuracy during routine laboratory conditions. As such, quantifying
concentrations below the PQL for compliance purposes may decrease the
precision and accuracy of the measured value and may not be achievable
for some individual laboratories. In this document, EPA is requesting
comment on whether EPA should consider an alternative approach when
calculating the running annual averages for compliance. Specifically,
in the case where a regulated PFAS is detected but below its proposed
PQL, that the proposed rule trigger level (1.3 ppt for PFOA and PFOS
and 0.33 of each of the HI PFAS PQLs (i.e., PFHxS=1.0, HFPO-DA=1.7,
PFNA=1.3, and PFBS=1.0)) be used as the value in calculating the
running annual average for compliance purposes. While this approach may
be more complicated to implement than using zero when below the PQL, it
is largely consistent with EPA's NPDWRs related to other SOCs and has
the
[[Page 18683]]
potential to slightly increase the public health protection provided by
this proposed regulation.
C. Can systems use previously collected data to satisfy the initial
monitoring requirement?
As proposed, systems would 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
distribution system entry point, 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.
EPA is proposing that systems with previously acquired monitoring
data from UCMR 5 will not be required to conduct separate initial
monitoring for regulated PFAS. To satisfy the initial monitoring
requirements for these systems using UCMR 5 data, data collected after
January 1st, 2023, can be used for entry point samples.
While EPA expects most systems serving 3,300 or greater will have
UCMR 5 data, EPA is also proposing 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
will also not be required to conduct separate initial monitoring for
regulated PFAS. This addition may allow systems serving fewer than
3,300 to satisfy the initial monitoring requirements. Data collected
after January 1st, 2023, can be used for entry point samples. Data
collected between January 1st, 2019, and December 31, 2022, may also be
used if it is below the proposed rule trigger level of 1.3 ppt for PFOA
and PFOS and an HI of 0.33 for PFHxS, HFPO-DA, PFNA, and PFBS. The
additional analytical requirement for older data is to ensure the use
of these data is adequately representative of current water quality
conditions. If systems have multiple years of data, the most recent
data must be used.
D. Can systems composite samples?
40 CFR 141.24 subpart C describes instances where primacy agencies
may reduce the samples a system must analyze by allowing samples to be
composited. Composite sampling is an approach in which equal volumes of
water from multiple entry points are combined into a single container
and analyzed as a mixture. The reported concentration from the analysis
of the composite sample therefore reflects the average of the analyte
concentrations from the contributing entry points. 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, based on comments EPA
received in 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. For example,
incidental contamination from or adherence to surface laboratory
equipment may artificially lower contaminant concentrations or result
in false negatives. Additionally, PFAS are demonstrated to be
ubiquitous in the environment such that the risk for false positives
may increase when combining samples for composite analysis. Based on
these potential implementation issues, EPA is proposing a deviation
from the SMF for SOCs by not allowing samples to be composited.
E. Can primacy agencies grant monitoring waivers?
40 CFR 141.24 Subpart C 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). Based on EPA's consultation with
state regulators and operators of small PWSs, the Agency believes that
due to the ubiquity, environmental persistence, and transport abilities
of PFAS, granting waivers based on these conditions would be
challenging, therefore EPA is not incorporating this flexibility as a
part of these proposed monitoring requirements. However, in this
proposal, EPA is considering and taking comment on waivers based on
sampling results. Specifically, EPA is requesting comment on whether
water systems should be permitted to apply to the primacy agency for a
monitoring waiver of up to 9-years (one full compliance cycle) for
these proposed PFAS if after at least one year of quarterly sampling
the results are below the rule trigger level of one-third of the MCLs,
or for systems that may be monitoring less frequently than quarterly if
at least two consecutive three year-compliance period sample results
are below the rule trigger level. Additionally, EPA is requesting
comment on allowing similar monitoring waivers to be granted based on
previously acquired monitoring data as described above in subsection
(C) of this preamble. In either case, systems with a monitoring waiver
would be required to take at least one sample per nine-year compliance
cycle in order to maintain or renew an existing waiver. Furthermore,
EPA is seeking comment on the identification of possible alternatives
to traditional vulnerability assessments that should be considered to
identify systems as low risk and potential eligibility for monitoring
waivers.
F. When must systems complete initial monitoring?
Pursuant to Section 1412(b)(10), this proposed rule would require
compliance three years after promulgation. To satisfy initial
monitoring requirements and demonstrate rule compliance, within the
three years following rule promulgation, groundwater systems serving a
population greater than 10,000 and all surface water systems will be
required to demonstrate their baseline concentrations using data from
four quarterly samples collected over a one-year period. Groundwater
systems serving a population 10,000 or fewer may collect two quarterly
samples at least 90 days apart over a one-year period for the purpose
of initial monitoring, rather than collecting four quarterly samples.
Additionally, as described earlier in this section (subsection C of
this preamble), EPA is proposing that systems with appropriate,
previously acquired monitoring data from UCMR 5, state-led, or other
applicable monitoring programs using EPA Methods 533 or 537.1, will not
be required to conduct separate initial monitoring for regulated PFAS.
As such, given the advantageous timing of UCMR 5 monitoring data for
all systems serving greater than 3,300 and the availability of
historical monitoring data that many small systems serving 3,300 or
fewer may utilize from state-level monitoring programs, EPA notes this
proposed allowance will offer significant burden reduction for these
systems and sufficient timing to take necessary actions and ensure rule
compliance. For systems that may not have available data and/or choose
to conduct additional monitoring, as proposed in this document, EPA
would encourage those systems to conduct their initial monitoring as
soon as practicable following rule promulgation to allow for actions
that may need to be taken based on monitoring results and to certify
rule compliance. The Agency seeks comment on EPA's proposed initial
monitoring timeframe, particularly for NTNCWS or all systems serving
3,300 or fewer.
[[Page 18684]]
G. What are the laboratory certification requirements?
EPA is proposing that laboratories demonstrate their ability to
achieve the precision and detection limits necessary to meet the
objectives of this regulation. The proposal would require laboratories
to analyze performance evaluation (PE) samples every year in order to
achieve and maintain certification.
X. Safe Drinking Water Act (SDWA) Right To Know Requirements
A. What are the Consumer Confidence Report requirements?
A CWS must prepare and deliver to its customers an annual Consumer
Confidence Report (CCR) in accordance with requirements in 40 CFR 141
Subpart O. A CCR provides customers with information about their local
drinking water quality as well as information regarding the water
system compliance with drinking water regulations. Under this proposal
CWSs would be required to report detected PFAS in their CCR;
specifically, PFOA, PFOS, PFHxS, HFPO-DA, PFNA, and PFBS, and the HI
for the mixtures of PFHxS, HFPO-DA, PFNA, and PFBS.
B. What are the public notification (PN) requirements?
As part of SDWA, the Public Notification (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 (use of less costly technology); or if the system
has been granted an exemption (more time to comply with a new
regulation).
All PWSs must give the public notice for all violations of NPDWRs
and for other situations. Under this proposal, EPA is proposing that
violations of the three MCLs in the proposal would 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.
XI. Treatment Technologies
Water systems with PFAS levels that exceed the MCLs proposed would
need to take action to provide drinking water which meets the NPDWR by
the compliance dates established in the rule when final. For example,
systems may install water treatment or consider other options such as
source remediation or connecting to an uncontaminated water system.
While conventional treatment technologies are unable to remove PFOS,
PFOA, PFNA, PFHxS, PFBS, or HFPO-DA to levels protective of public
health (McCleaf et al., 2017), there are technologies currently
available that effectively remove these and other PFAS.
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 BATs. These BATs are used by states to
establish conditions for source water variances under Section 1415(a).
Section 1412(b)(4)(E)(ii) also requires that the Agency identify small
system compliance technologies (SSCTs), which are affordable treatment
technologies, or other means that can achieve compliance with the MCL
(or treatment technique [TT], where applicable).
A. What are the best available technologies?
The Agency identifies the BATs as those meeting the following
criteria: (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 and 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. The Agency is proposing the following technologies as BAT
for PFAS removal from drinking water based its review of the treatment
and cost literature (USEPA, 2023g):
GAC
AIX
High pressure membranes (RO and NF)
Operationally, GAC and AIX are sorptive processes meaning a process
where one substance becomes attached to another. Sorption is typically
composed of absorption where one substance is incorporated into
another, adsorption where one substance is incorporated onto another,
or ion exchange (IX) where an aqueous ion (the contaminant) is traded
for a different less dangerous ion (typically chloride in AIX) on an
insoluble matrix. Sorptive processes pour feed water through a vessel
filled with a sorbent known as a contactor. The operation continues
until the sorbent no longer effectively removes the target contaminant;
this is when the contaminant ``breaks through'' the treatment process.
At this point, the sorbent must be disposed then replaced or
regenerated. The length of time until the sorbent must be replaced or
regenerated is known as bed life and is a critical factor in the cost
effectiveness of sorptive technology. One bed life measurement is the
water volume that can be treated before breakthrough and is measured in
bed volumes (BV). BVs are how many times the sorbent (i.e., media) can
be filled in the bed in which the sorbent resides before contaminant
breakthrough. EPA estimates GAC treatment will be sufficiently
available to support cost-effective compliance with this proposed
regulation, and requests comment on whether additional guidance on
applicable circumstances for GAC treatment is needed.
High pressure membranes are a separation process where feed water
is split into two streams across a membrane. One stream has few
contaminants or other solutes left in it and is known as permeate or
produced water. The other stream contains the concentrated contaminant
and other solutes which is known as concentrate, brine, retentate, or
reject water. Membrane flux is how much permeate is produced for a
given surface area and time; different system configurations operating
at the same flux produce differing quantities of finished water. This
means that membrane systems with differing configurations cannot be
directly compared based on flux. Flux can be reduced during membrane
fouling which is where things accumulate on or in the membrane. Fouling
can require membrane cleaning and replacement or operational changes.
There are also non-treatment options which may be used for
compliance such as replacing a PFAS-contaminated drinking water source
with a new uncontaminated source (e.g., a new well), or purchasing
compliant water from another system. Conventional and most advanced
water treatment methods are ineffective at removing PFAS (Rahman et
al., 2014). Further information on the proposed BATs is provided below.
1. Granular Activated Carbon
GAC is a separation process where contaminants become attached to
specially treated carbon with a high surface area. The GAC
manufacturing process can accept any highly carbonaceous material as an
input such as bituminous coal, lignite coal, peat, wood, coconut
shells, and peach pits. Activation is predominantly a thermal process,
although it may also be a chemical process, that creates as well as
[[Page 18685]]
enlarges pores generating a porous structure with a large surface area
per unit mass. Literature suggests that the primary mechanisms of
adsorption include both hydrophobic and electrostatic interactions
(Ateia et al., 2019). In addition to removing PFAS, GAC can remove
contaminants including taste and odor compounds, natural organic matter
(NOM), VOCs, SOCs, DBP precursors, and radon. Organic compounds with
high molecular weights are also readily adsorbable.
Demonstrated PFAS removal efficiencies can exceed >99 percent and
can achieve concentrations less than 4 ng/L (Forrester and Bostardi,
2019; Zeng et al., 2020; Westreich et al., 2018; Belkouteb et al.,
2020; Woodard et al., 2017; and Hopkins et al., 2018). During the
operation, carbon is removed from the system periodically, for disposal
or regeneration, based on treatment objectives. Several factors affect
bed life, including the presence of competing contaminants such as
nitrate and the carbon type used. Most studies found that natural or
dissolved organic matter (NOM/DOM) interferes with PFAS sorption, in
general, and its presence dramatically lowers treatment efficacy
(McNamara et al., 2018; Pramanik et al., 2015; Yu et al., 2012). The
lowered treatment effectiveness was found to be less pronounced for
HFPO-DA than for perfluoroalkyl carboxylic acid (PFCA) C7 and above for
GAC (Park et al., 2020).
Reactivation is a process that removes organic compounds from
adsorption sites on GAC enabling reuse. Although different methods are
available for GAC reactivation, the process most commonly involves high
temperature thermal treatment in a specialized facility such as a
multiple hearth furnace or rotary kiln (Matthis and Carr, 2018; USEPA,
2023g). Reactivated carbon can become totally exhausted with other
contaminants not removed during reactivation and must be replaced.
However, for GAC, the loss of approximately 10 percent of the media due
to abrasion within the reactivation process can result in a somewhat
steady state for performance as new GAC is added each time to replace
the lost GAC. Systems may decide to dispose of GAC (i.e., operate on a
`throw-away' basis) instead of reactivating the media. GAC can be a
cost-effective treatment option despite needing to dispose of
contaminated carbon.
2. Anion Exchange
AIX is a separation process where an anion in the aqueous phase is
exchanged for an ion attached to an exchange resin. Similar to GAC, AIX
uses contactors. These contactors, however, are filled with a bed of
beads or gel known as resin instead of carbon. As feed water moves
through the resin, an anionic contaminant, such as PFAS exchanges, for
an anion, typically chloride, on the resin. For PFAS compounds, vendors
generally recommend using PFAS-selective resins (Boodoo, 2018; Boodoo
et al., 2019; Lombardo et al., 2018; Woodard et al., 2017). AIX may
also have a beneficial effect by removing other undesirable anions from
the treated water such as nitrate or sulfate.
Demonstrated PFAS removal efficiencies may be >99 percent and can
achieve concentrations less than 4 ng/L (Dixit et al., 2021; Dixit et
al., 2020; Zeng et al., 2020; Liu, 2017; Kumarasamy et al., 2020;
Arevalo et al., 2014; and Yan et al., 2020). The operation continues
until enough of the resin's available IX sites have ions from the feed
water and the resin no longer effectively removes the target
contaminant, also known as ``breaks through.'' At this point, the resin
must be disposed and replaced or regenerated. The length of time until
resin must be replaced or regenerated is known as bed life and is a
critical factor in the cost effectiveness of IX as a treatment
technology. Several factors affect bed life, including the presence of
competing ions such as nitrate and the resin type used.
Conventional regeneration solutions are not generally effective for
restoring the capacity of PFAS-selective resins (Liu and Sun, 2021).
Regeneration may be possible using organic solvents (Boodoo, 2018;
Zaggia et al., 2016) or proprietary methods (Woodard et al., 2017).
These alternative regeneration practices are generally practical or
cost-effective only with very high influent concentrations, such as in
remediation settings. Therefore, in drinking water applications using
PFAS-selective resin, vendors recommend a single-use approach where the
spent resin is disposed and replaced with fresh resin (Boodoo, 2018;
Lombardo et al., 2018). Exhausted resin must be disposed; due to the
difficulties mentioned earlier and vendor recommendation, resins are
often operated on a `throw-away' basis. This operational mode avoids
generating spent regenerant liquid residuals. AIX can be a cost-
effective treatment option.
3. High Pressure Membranes (RO and NF)
RO and NF are membrane separation processes where water is forced
through a membrane at greater than osmotic pressure. The water that
transverses the membrane is known as permeate or produce water, and has
few solutes left in it; the remaining water is known as concentrate,
brine, retentate, or reject water and forms a waste stream with
concentrated solutes. NF has a less dense active layer than RO, which
enables lower operating pressures but also makes it less effective at
removing contaminants. In drinking water treatment, these membranes are
most often used in a spiral-wound configuration that consists of
several membrane envelopes, layered with feed spacers, and rolled
together in and around a central collection tube. Feed pressures for NF
membranes are typically in the range of 50 to 150 pounds per square
inch (psi). Feed pressures for RO membranes are in the range of 125 to
300 psi in low pressure applications (such as PFAS removal) but can be
as high as 1,200 psi in applications such as seawater desalination
(USEPA, 2023d). RO may remove other contaminants including arsenic and
chromium-VI.
RO and NF may achieve PFAS removal >99 percent (Lipp et al., 2010;
Horst et al., 2018; Liu et al., 2021; Dickenson and Higgins, 2016;
Steinle-Darling et al., 2008; Boonya-Atichart et al., 2016; Appleman et
al., 2014; Thompson et al., 2011; CDM Smith, 2018; Dickenson and
Higgins, 2016; and Dowbiggin et al., 2021). While water quality affects
process design (e.g., recovery rate, cleaning frequency, and
antiscalant selection), it has relatively little effect on PFAS removal
percent. High pressure membranes generate a relatively large
concentrate stream, which will contain PFAS as well as other rejected
dissolved species, which will require disposal or additional treatment.
The large concentrate stream also means less treated water is available
for distribution (e.g., 70 to 85 percent of source water), which is a
disadvantage for systems with limited water supply.
B. PFAS Co-Removal
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 (McCleaf et al., 2017; S[ouml]reng[aring]rd
et al., 2020). Perfluoroalkyl sulfonates (PFSA), such as PFOS, are
removed with greater efficiency than the corresponding PFCA, 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, a PFSA is removed
[[Page 18686]]
about as well as a PFCA which has two more fully perfluorinated carbons
in its backbone. For example, PFHxS (six carbon backbone and a sulfonic
acid functional group) is removed about as well as PFOA (eight carbon
backbone and a carboxylate head) and perfluorohexanoic acid (PFHxA)
(six carbon backbone with a carboxylate head) is removed approximately
as well as PFBS (four carbon backbone and a sulfonic acid functional
group). Additionally, the compounds with longer carbon chain displayed
a smaller percentage decrease in average removal efficiency over time
(McCleaf et al., 2017).
The three technologies discussed above have all been demonstrated
to be effective in removing all six PFAS proposed for regulation as
part of this rulemaking. As discussed in section VII.C. of this
preamble, PFAS have been shown to co-occur. Hence, where the six PFAS
being regulated today occur in concentrations above their respective
regulatory standards there is also an increased probability of other
unregulated PFAS being present. Further, since these same technologies
also remove other long-chain and higher carbon/higher molecular weight
PFAS EPA expects this rulemaking will provide additional public health
benefits and protection by removing unregulated PFAS that may have
adverse health effects. While EPA has not quantified those benefits as
part of this rulemaking, the Agency believes these important secondary
benefits further enhance public protection offered by this proposed
regulation.
C. Management of Treatment Residuals
As part of EPA's BAT evaluation, the Agency assesses the
availability of studies of full-scale treatment of residuals that fully
characterize residual waste streams and disposal options. At present,
the most likely management option for spent material containing PFAS is
reactivation for GAC and incineration for spent IX resin. For disposal
of RO/NF membrane concentrate, most systems use surface water discharge
or discharge to sanitary sewer. The large volume of residuals is a
well-known obstacle to adoption of membrane separation technology in
general. For more information on current residuals management
practices, see Best Available Technologies and Small System Compliance
Technologies for Per- and Polyfluoroalkyl Substances (PFAS) in Drinking
Water (USEPA, 2023g) or Managing and Treating Per- and Polyfluoroalkyl
Substances (PFAS) in Membrane Concentrates (Tow et al., 2021).
EPA recognizes that future actions through several statutory
authorities other than SDWA may have direct or indirect implications
for drinking water treatment facilities and some actions may prevent or
reduce PFAS entering drinking water sources. EPA is addressing PFAS
through statutory authorities including the CERCLA, Resource
Conservation and Recovery Act (RCRA), Toxic Substances Control Act
(TSCA), Clean Water Act, Clean Air Act, and Emergency Planning and
Community Right-to-Know Act (EPCRA). For example, as part of EPA's PFAS
Strategic Roadmap, EPA proposed certain PFAS be designated as CERCLA
hazardous substances to require reporting of PFOA and PFOS releases,
enhance the availability of data, and ensure agencies can recover
cleanup costs (USEPA, 2022c). In the Strategic Roadmap, EPA has also
committed to expanding research on and accelerating the deployment of
emerging PFAS treatment, remediation, destruction, disposal, and
control technologies (USEPA, 2022c). EPA's 2020 Interim Guidance on the
Destruction and Disposal of Perfluoroalkyl and Polyfluoroalkyl
Substances and Materials Containing Perfluoroalkyl and Polyfluoroalkyl
Substances outlines the current state of the science on techniques and
treatments that may be used to destroy or dispose of PFAS (USEPA,
2020b). In accordance with EPA's PFAS Strategic Roadmap, EPA
anticipates releasing an updated version of the Guidance in 2023. As
part of this rulemaking, EPA considered that in drinking water
treatment, large volumes of spent GAC and ion exchange resin must be
removed which does not lend itself to on-site storage over time. The
disposal options identified in the Interim Guidance (USEPA, 2020b) are
landfill disposal and thermal treatment.
Stakeholders have expressed concern to 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. Although EPA
anticipates that designating chemicals as hazardous substances under
CERCLA generally should not result in limits on for disposal of PFAS
drinking water treatment residuals, 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, EPA assessed the potential
impact on PWS treatment costs associated with hazardous residual
management requirements in a sensitivity analysis on the proposed
option. Relative to the national analysis for the proposed option
assuming non-hazardous disposal, the hazardous waste disposal
assumption would increase PWS costs by 4% ($30 million annually) at the
3% discount rate and 5% ($61 million annually) at the 7% discount rate
should spent media need to be disposed of as hazardous waste in the
future because of separate EPA or State regulatory action. EPA's
sensitivity analysis demonstrates that potential hazardous waste
disposal requirements may increase PWS treatment costs marginally,
however the increase in PWS costs are not significant enough to change
the determination that benefits of the rulemaking justify the costs.
These estimates are discussed in greater detail in the HRRCA section of
this proposed rulemaking and in Appendix N of the Economic Analysis
(USEPA, 2023i). These costs are limited to the disposal of the PFAS
contaminated residuals and wastes. Results for small systems are
presented in Section D of this preamble below. EPA is seeking public
input related to PFAS treatment residual disposal in Section XIV of
this preamble.
D. What are small system compliance technologies (SSCTs)?
EPA is proposing the SSCTs shown in Table 20. The table 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. The Agency
identified these technologies based on an analysis of treatment
effectiveness and affordability.
Table 20--Proposed SSCTs for PFAS Removal
----------------------------------------------------------------------------------------------------------------
System size (population Point of use
served) GAC IX RO/NF (POU) RO/NF \1\
----------------------------------------------------------------------------------------------------------------
25-500....................... Yes................ Yes................ No................. Yes.
501-3,300.................... Yes................ Yes................ No................. Yes.
[[Page 18687]]
3,301-10,000................. Yes................ Yes................ Yes................ not applicable.\2\
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ POU RO is not currently listed as a compliance option 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. However, POU treatment is reasonably
anticipated to become a compliance option for small systems in the future if NSF/ANSI or other independent
third-party certification organizations develop a new certification standard that mirrors EPA's proposed
regulatory standard. The affordability conclusions presented here reflect the costs of devices certified under
the current standard, not a future standard, which may change dependent on future device design.
\2\ EPA's work breakdown structure (WBS) model for POU treatment does not cover systems larger than 3,300 people
(greater than 1 million gallons per day [MGD] design flow), because implementing and maintaining a large-scale
POU program is likely to be impractical.
The operating principle for POU RO devices is the same as
centralized RO: Steric exclusion and electrostatic repulsion of ions
from the charged membrane surface. In addition to a RO membrane for
dissolved ion removal, POU RO devices often have a sediment pre-filter
and a carbon filter in front of the RO membrane, a 3- to 5-gallon
treated water storage tank, and a carbon filter between the tank and
the tap.
EPA identified SSCTs using the affordability criteria methodology
developed for drinking water rules (USEPA, 1998b). The analysis method
is a comparison of estimated incremental household costs for PFAS
treatment to an expenditure margin, which is the difference between
baseline household water costs and a threshold equal to 2.5% of median
household income (MHI). Table 21 shows the expenditure margins derived
for the analysis. These margins show the cap on affordable incremental
annual expenditures.
Table 21--Expenditure Margins for SSCT Affordability Analysis
----------------------------------------------------------------------------------------------------------------
Affordability Baseline water Expenditure
System size (population served) MHI \1\ threshold \2\ cost \3\ margin
A B = 2.5% x A C D = B-C
----------------------------------------------------------------------------------------------------------------
25-500.................................... $55,377 $1,384 $507 $877
501-3,300................................. 53,596 1,340 587 753
3,301-10,000.............................. 58,717 1,468 613 855
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ MHI based on U.S. Census Bureau's American Community Survey five-year estimates (United States Census
Bureau, 2010) stated in 2010 dollars, adjusted to 2020 dollars using the Consumer Price Index (CPI) (for all
items) for areas under 2.5 million persons.
\2\ Affordability threshold equals 2.5 percent of MHI.
\3\ Household water costs derived from 2006 Community Water System Survey (USEPA, 2009c), based on residential
revenue per connection within each size category, adjusted to 2020 dollars based on the CPI for All Urban
Consumers: Water and Sewer and Trash Collection Services in U.S. City Average.
Table 21 shows the estimates of per-household costs by treatment
technology and size category generated using the treatment cost method
described in section XII.B of this preamble as well as Best Available
Technologies and Small System Compliance Technologies for Perchlorate
in Drinking Water (USEPA, 2019c) and Technologies and Costs for
Treating Perchlorate-Contaminated Waters (USEPA, 2018c). Based on the
results presented in Table 22, EPA identified candidate technologies
available for which costs do not exceed the corresponding expenditure
margin and, therefore, meet the SSCT affordability criterion. As such,
EPA has determined that affordable SSCTs are available, and the Agency
is not proposing any variance technologies.
Table 22--Total Annual Cost per Household for Candidate Technologies
----------------------------------------------------------------------------------------------------------------
System size (population
served) GAC IX RO/NF POU RO/NF \1\
----------------------------------------------------------------------------------------------------------------
25-500........................ $395 to $727..... $376 to $645..... $3,711 to $4,676. $317 to $326.
501-3,300..................... $139 to $332..... $133 to $235..... $608 to $1,169... $299 to $300.
3,301-10,000.................. $136 to $329..... $121 to $218..... $326 to $462..... not applicable.\2\
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ POU RO is not currently a compliance option because the regulatory options under consideration require
treatment to concentrations below the current NSF/ANSI certification standard for POU device removal of PFAS.
However, POU treatment is reasonably anticipated to become a compliance option for small systems in the future
if NSF/ANSI or other independent third-party certification organizations develop a new certification standard
that mirrors EPA's proposed regulatory standard. Costs presented here reflect the costs of devices certified
under the current testing standard, not a future standard, which may change dependent on future device design.
\2\ EPA's WBS model for POU treatment does not cover systems larger than 3,300 people (greater than 1 MGD design
flow), because implementing and maintaining a large-scale POU program is likely to be impractical.
[[Page 18688]]
The results discussed above assume management of spent GAC and
spent IX resin using current typical management practices (reactivation
for GAC and incineration for resin). EPA is in the process of proposing
some PFAS be designated as hazardous substances under CERCLA and listed
as hazardous constituents under RCRA. If finalized, neither of these
actions should result in limiting disposal options and how PFAS
containing waste, including spent GAC or resin, is required to be
managed. However, waste management facilities may, at their own
discretion, refuse to accept PFAS-containing materials or drinking
water treatment operations may choose to send spent GAC and resin
containing PFAS to facilities permitted to treat and/or dispose of
hazardous wastes. To consider the implications of this possibility, EPA
has developed an assessment of the current unit costs for disposing
spent treatment materials and the costs associated with their disposal
as hazardous waste. Table 23 shows the resulting cost per household if
systems dispose of these residuals as hazardous waste. Although costs
would increase somewhat compared to if they do not treat the spent
media as hazardous waste, those increases are not significant enough to
change the conclusions about affordability.
Table 23--Total Annual Cost per Household Assuming Hazardous Waste
Disposal for Spent GAC and Resin
------------------------------------------------------------------------
System size (population
served) GAC IX
------------------------------------------------------------------------
25-500....................... $417 to $827.... $397 to $678.
501-3,300.................... $149 to $368.... $138 to $243.
3,301-10,000................. $146 to $360.... $124 to $222.
------------------------------------------------------------------------
In addition to the required analysis for small system
affordability, EPA having received a number of recommendations from the
SAB, the NDWAC, and other stakeholders, is exploring the use of
alternative expenditure margins and other potential changes to the
national level affordability methodology to better understand the cost
impacts of new standards on low income and disadvantaged households
served by small drinking water systems. The Agency conducted
supplemental affordability analyses using alternative metrics suggested
to EPA by stakeholders to demonstrate the potential affordability
implications of the proposed NPDWR on the determination of affordable
technologies for small systems at the national level of analysis.
As required under the 1996 amendments to SDWA, EPA lists treatment
technologies for small systems that are affordable and that achieve
compliance with the regulatory standard. As part of its affordability
analysis for the proposed PFAS rule, EPA determined that there are
several affordable treatment technologies for small systems, including
GAC, IX, RO, and POU RO.\5\ EPA is seeking public comment on the
national level analysis of affordability of SSCTs and specifically on
the potential methodologies presented. EPA's national small system
affordability determination can be found in Section 9.12.1 of the EA.
EPA's supplementary affordability analyses can be found in Section
9.12.2 of the EA. EPA is also seeking comment on whether there are
additional technologies which are viable for PFAS removal to the
proposed MCLs as well as any additional costs which may be associated
with non-treatment options such as water rights procurement. Finally,
EPA is seeking comment on the benefits from using treatment
technologies (such as reverse osmosis and GAC) that have been
demonstrated to co-remove other types of contaminants found in drinking
water and whether employing these treatment technologies are sound
strategies to address PFAS and other regulated or unregulated
contaminants that may co-occur in drinking water.
---------------------------------------------------------------------------
\5\ POU RO is not currently a compliance option because the
regulatory options under consideration require treatment to
concentrations below 70 ppt total of PFOA and PFOS, the current
certification standard for POU devices. However, POU treatment is
anticipated to become a compliance option for small systems in the
future should NSF/ANSI or another accredited third-party
certification entity develop a new certification standard that
mirrors (or is demonstrated to treat to concentrations lower than)
EPA's proposed regulatory standard. The affordability conclusions
for POU RO should be considered preliminary because they reflect the
costs of devices certified under the current standard, not a future
standard.
---------------------------------------------------------------------------
Following finalization of the PFAS NPDWR, EPA will work with
primacy agencies to provide assistance to support implementation of the
rule. EPA requests comment on the type of assistance that would help
small public water systems identify laboratories that can perform the
required monitoring, evaluate treatment technologies and determine the
most appropriate way to dispose of PFAS contaminated residuals and
waste the systems may generate when implementing the rule.
XII. Rule Implementation and Enforcement
A. What are the requirements for primacy?
This section describes the regulations, procedures, and policies
primacy entities must adopt, or have in place, to implement the PFAS
rule, when it is final. States, Territories, and Tribes must continue
to meet all other conditions of primacy in 40 CFR part 142. Section
1413 of SDWA establishes requirements that primacy entities (States or
Indian Tribes) must meet to maintain primary enforcement responsibility
(primacy) for its PWSs. These include:
Adopting drinking water regulations that are no less
stringent than Federal NPDWRs in effect under sections 1412(a) and
1412(b) of the Act;
Adopting and implementing adequate procedures for
enforcement;
Keeping records and making reports available on activities
that EPA requires by regulations;
Issuing variances and exemptions (if allowed by the State)
under conditions no less stringent than allowed by SDWA Sections 1415
and 1416; and
Adopting and being capable of implementing an adequate
plan for the provision of safe drinking water under emergency
situations.
40 CFR part 142 sets out the specific program implementation
requirements for States to obtain primacy for the Public Water System
Supervision (PWSS) Program, as authorized under 1413 of the Act.
Under 40 CFR 142.12(b), all primacy States/territories/tribes would
be required to submit a revised program to
[[Page 18689]]
EPA for approval within two years of promulgation of any final PFAS
NPDWR or could request an extension of up to two years in certain
circumstances. To be approved for a program revision, primacy States/
territories/tribes would be required to adopt revisions at least as
stringent as the revised PFAS-related provisions in 40 CFR 141.6
(Effective Dates); 40 CFR 141.900 subpart Z (Control of Per- and
Polyfluoroalkyl Substances); 40 CFR 141.50 (Maximum Contaminant Level
Goals for organic contaminants); 40 CFR 141.60 (Maximum Contaminant
Levels for organic contaminants); appendix A to subpart O ([Consumer
Confidence Report] Regulated contaminants); Appendix A to Subpart Q
((NPDWR violations and other situations requiring public notice);
Appendix B to Subpart Q (Standard health effects language for public
notification); 40 CFR 142.62 (Variances and exemptions from the MCLs
for organic and inorganic contaminants); and 40 CFR 142.16 (Primary
Enforcement Responsibility).
B. What are the primacy agency record keeping requirements?
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. If primacy agencies grant monitoring waivers, they must
record monitoring results that are below the rule trigger level in
order to ensure systems are eligible for reduced monitoring schedules
(for additional discussion on the rule trigger level and monitoring
waivers, please see sections VIII and IX of this preamble). The primacy
agency record keeping requirements remain unchanged and would apply to
PFAS as with any other regulated contaminant.
C. What are the primacy agency reporting requirements?
Currently, primacy agencies must report to EPA information under 40
CFR 142.15 regarding violations, variances and exemptions, enforcement
actions, and general operations of State PWS programs. These reporting
requirements remain unchanged and would apply to PFAS as with any other
regulated contaminant. However, the proposed PFAS MCLs, when final,
could result in a greater frequency of reporting by certain primacy
agencies. See discussion of PRA compliance in Section XV of this
preamble for more information.
D. Exemptions and Extensions
In accordance with SDWA Sec. 1412(b)(10), a state or EPA may grant
an extension of up to two additional years to comply with an NPDWR's
MCL(s) if the state or EPA determines an individual system needs
additional time for capital improvements. At this time, EPA does not
intend to provide a two-year extension nationwide. However, States may
provide such an extension on an individual system basis. Where a State
or EPA chooses to provide such an extension, the system would have up
to five years from the rule's promulgation date to meet the MCLs. In
addition, under SDWA Sec. 1416, EPA or primacy Agencies may grant an
exemption for systems meeting specified criteria that provides an
additional period for compliance not to exceed 3 years beyond the time
period provided by Section 1412(b)(10). Under SDWA Sec. 1416(a), a
State which has primary enforcement responsibility may exempt any
public water system within the State's jurisdiction from any
requirement respecting a MCL of any applicable NPDWR upon a finding
that:
Due to compelling factors (which may include economic
factors, including qualification of the public water system as a system
serving a disadvantaged community pursuant to section 300j-12(d) of
this title), the public water system is unable to comply with such
contaminant level or treatment technique requirement, or to implement
measures to develop an alternative source of water supply,
The public water system was in operation on the effective
date of such contaminant level or treatment technique requirement, or,
for a system that was not in operation by that date, only if no
reasonable alternative source of drinking water is available to such
new system,
The granting of the exemption will not result in an
unreasonable risk to health; and
Management or restructuring changes (or both) cannot
reasonably be made that will result in compliance with this subchapter,
or if compliance cannot be achieved, improve the quality of the
drinking water.
In addition, SDWA Sec. 1416(b)(2)(C) also allows for a small
system that does not serve a population of more than 3,300 and which
needs financial assistance for the necessary improvements to receive up
to three additional two-year exemptions, not to exceed a total of six
years provided that the system establishes that it is taking all
practicable steps to meet the requirements. In total, this means that
some systems could potentially exceed the MCLs' numerical standards for
up to 14 years after the rule promulgation date (or approximately 2037/
2038). EPA is seeking comment as to whether there are specific
conditions that should be mandated for systems to be eligible for
exemptions under 1416 to ensure that they are only used in rare
circumstances where there are no other viable alternatives and what
those conditions would be. EPA has established requirements for EPA
issuance of these exemptions in 40 CFR 142 subpart F but could consider
amending these requirements or establishing requirements for State
exemptions.
XIII. Health Risk Reduction and Cost Analysis
This section summarizes the HRRCA for the proposed NPDWR for PFAS,
which is written in compliance with SDWA section 1412(b)(3)(C). Section
1412(b)(3)(C)(i) lists the analytical elements required in a HRRCA
applicable to a NPDWR that includes an 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 rule options;
(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 and pursuant to Section 1412(b)(4)(C) of
SDWA, the Administrator has determined that the quantified and
nonquantifiable benefits of the proposed regulation justify the costs.
The complete HRRCA for the proposed NPDWR, Economic Analysis for the
Proposed PFAS Rule, is hereafter referred to as the ``Economic
Analysis,'' and can be found in the docket at USEPA (2023j).
For purposes of this Economic Analysis, EPA assumes that the NPDWR
[[Page 18690]]
will be promulgated by the end of 2023. This analysis follows the
standard NPDWR compliance schedule with regulatory requirements taking
effect three years after the date on which the regulation is
promulgated. If EPA issues a final NPDWR for PFAS by the end of 2023,
EPA assumes actions to comply with the rule, including installation of
treatment technologies, will occur by 2026. Based on an assumed mean
human lifespan of 80 years, EPA evaluates costs and benefits under the
proposed rule through the year 2104. 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). EPA annualized the future estimated streams of costs and
benefits symmetrically over this same period of analysis. Capital costs
for installation of treatment technologies are spread over the useful
life of the technologies. EPA does not capture effects of compliance
with the proposed rule after the end of the period of analysis. Costs
and benefits discussed in this section are presented as annualized
present values in 2021 dollars. EPA determined the present value of
these costs using discount rates of 3 and 7 percent, which are discount
rates prescribed by the (OMB Circular A-4, 2003).
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 VII.E.
of this preamble above. The model was fitted using sample data from
systems participating in PFAS sampling under UCMR 3 and included
systems serving over 10,000 customers, as well as a subset of 800
smaller systems. A best-fit model was selected using sample data to
define occurrence and co-occurrence of PFOA, PFOS, PFHpA, and PFHxS 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 EPA's
occurrence model, please see Section VII.E. of this preamble and USEPA
(2023e).
In the Economic Analysis, EPA analyzes the costs and benefits of
the proposed rule, as well as several regulatory alternatives. EPA
analyzed the costs and benefits of setting individual MCLs for PFOA and
PFOS at 4.0 ppt, 5.0 ppt, and 10.0 ppt, referred to as Option 1a,
Option 1b, and Option1c, respectively. EPA assessed these options in
the Economic Analysis to understand the impact of less stringent PFOA
and PFOS MCLs, and the Agency is asking for comment on these
assessments in the Economic Analysis. The Agency is also inviting
comment on whether establishing a traditional MCLG and MCL for PFHxS,
HFPO-DA, PFNA, and PFBS instead of or in addition to the HI approach
would change public health protection, improve clarity of the rule, or
change costs. EPA has not separately presented changes in quantified
costs and benefits for these approaches. If EPA adds individual MCLs in
addition to using the HI approach, EPA anticipates there will be no
change in costs and benefits relative to the proposed rule (i.e., the
same number of systems will incur identical costs to the proposed
option and the same benefits will be realized). EPA has not separately
quantified the benefits and costs for the alternative approach to
regulate PFHxS, PFNA, PFBS, and HFPO-DA with individual MCLs instead of
the HI. However, EPA expects both the costs and benefits would be
reduced under this approach as fewer systems may be triggered into
treatment and its associated costs. Additionally, systems that exceed
one or more of the individual MCLs will treat to a less stringent and
public health-protective standard. Furthermore, under the proposed
option, PWSs are required to treat based on the combined occurrence of
PFAS included in the HI which considers the known and additive toxic
effects and occurrence and likely co-occurrence of PFAS compounds in
the HI, providing more public health protection compared to an
individual MCL approach.
Section A summarizes the entities which would be affected by the
rule and provides a list of key data sources used to develop EPA's
baseline water system characterization. Section B provides an overview
of the cost-benefit model used to estimate the national costs and
benefits of the proposed rule. Section C summarizes the methods EPA
used to estimate costs associated with the proposed rule. Section D
summarizes the methods EPA used to estimate quantified benefits
associated with the proposed rule. Section E provides a summary of the
nonquantifiable benefits associated with reductions in exposure to both
PFOA and PFOS. Section F provides a qualitative summary of benefits
expected to result from the removal of PFAS included in the HI
component of the proposed regulation and additional co-removed PFAS
contaminants. Section G summarizes benefits expected to result from
DBPs co-removal. Section H provides a comparison of cost and benefit
estimates. Section I summarizes and discusses key uncertainties in the
cost and benefit analyses. Quantified costs and benefits for the
proposed option and alternative options considered are summarized in
section H, specifically Tables 66-69. Tables 70-71 summarizes the non-
quantified B-Cs and assess the potential impact of non-quantifiable
benefits and costs on the overall B-C estimate. Finally, Section J
presents the Administrator's cost-benefit determination for the
proposed rule.
A. Affected Entities and Major Data Sources Used To Develop the
Baseline Water System Characterization
The entities potentially affected by the proposed PFAS regulation
are primacy agencies and PWSs. PWSs subject to the proposed 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
a limited number of cases--anticipated costs to reduce PFAS levels in
drinking water to meet this proposed NPDWR using treatment or
nontreatment options. Section C of this preamble below summarizes the
method EPA used to estimate these costs.
The systems that reduce PFAS concentrations will reduce associated
health risks. EPA developed methods to estimate the potential benefits
of reduced PFAS exposure among the service populations of systems with
PFAS levels exceeding the proposed drinking water standard. Section B
of this preamble below summarizes this method used to estimate these
benefits.
In its Guidelines for Preparing Economic Analyses, EPA
characterizes the ``baseline'' as a reference point that reflects the
world without the proposed regulation (USEPA, 2010). It is the starting
point for estimating the potential benefits and costs of the proposed
PFAS NPDWR. EPA used a variety of data sources to develop the baseline
drinking water system characterization for the regulatory analysis.
Table 24 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
[[Page 18691]]
can be found in the Chapter 4 of USEPA (2023j).
Table 24--Data Sources Used To Develop Baseline Water System
Characterization
------------------------------------------------------------------------
Data source Baseline data derived from the source
------------------------------------------------------------------------
SDWIS/Federal version fourth Water System Inventory: PWS
quarter 2021 Q4 ``frozen'' inventory, including system unique
dataset \1\. identifier, population served, number of
service connections, source water type,
and system type.
Population and Households
Served: PWS population served.
Treatment Plant
Characterization: Number of unique
treatment plant facilities per system,
which are used as a proxy for entry
points when UCMR 3 sampling site data
are not available.
UCMR 3 (USEPA, 2017)......... Treatment Plant
Characterization: Number of unique entry
point sampling sites, which are used as
a proxy for entry points.
Treatment Plant
Characterization: PFAS concentration
data collected as part of UCMR 3.
Independent state sampling Treatment Plant
programs. Characterization: PFAS concentration
data collected by states. These data
supplemented the occurrence modeling for
systems included in UCMR 3.
Six-Year Review 4 Information Treatment Plant
Collection Request (SYR4 Characterization: Total organic carbon
ICR) Occurrence Dataset (TOC).
(2012-2019).
Geometries and Treatment Plant
Characteristics of Public Characterization: Design and average
Water Systems (USEPA, 2000f). daily flow per system.
2006 Community Water System Public Water System Labor Rates:
Survey (CWSS; USEPA, 2009c). PWS labor rates.
------------------------------------------------------------------------
Notes:
\1\ Contains information extracted on January 14, 2022.
B. Overview of the Cost-Benefit Model
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 proposed PFAS rule simultaneously regulates
multiple PFAS contaminants, 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
contaminants 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 EPA's economic analysis.
The costs incurred by a PWS depend on water system characteristics;
SDWIS/Fed provides information on PWS characteristics that typically
define PWS categories, or strata, for which EPA has develops 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 PWS state.
Because 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, 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 (2023j). 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 proposed 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 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 (2023j).
For each PWS category, the model then calculates summary statistics
that describe the costs and benefits associated with the proposed rule
compliance. These summary statistics include total quantified costs of
the proposed regulatory requirement, total quantified benefits of the
proposed regulatory requirement, the variability in PWS-level costs
(e.g., 5th and 95th percentile system costs), and the variability in
household-level costs.
C. Method for Estimating Costs
This section summarizes the cost elements and estimates total cost
of compliance for the proposed PFAS NPDWR discounted at 3 and 7
percent. EPA estimated the costs associated with
[[Page 18692]]
monitoring, administrative requirements, and both treatment and non-
treatment compliance actions associated with the proposed rule (USEPA,
2023j).
1. Public Water System (PWS) Costs
a. PWS Treatment and Non-Treatment Compliance Costs
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 non-treatment 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. EPA used SafeWater MCBC to apply costs for one of the treatment
technologies or non-treatment alternatives at each entry point in a PWS
estimated to be out of compliance with the proposed rule. For each
affected entry point, SafeWater MCBC selected from among the compliance
alternatives using a decision tree procedure, described in more detail
in USEPA (2023g) and (2023h). Next, the model estimated the cost of the
chosen compliance alternative using outputs from EPA's WBS cost
estimating models.
Specifically, EPA used cost equations generated from the following
models (USEPA, 2023h):
the GAC WBS model (USEPA, 2021g);
the PFAS-selective IX WBS model (USEPA, 2021h);
the centralized RO/NF WBS model (USEPA, 2021i); and
the non-treatment WBS model (USEPA, 2021j).
The Technologies and Costs (T&C) document (USEPA, 2023h) 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 nearly 3,500 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).
b. Decision Tree for Technology Selection
For entry points at which baseline PFAS concentrations exceed
regulatory thresholds, the decision tree selects a treatment technology
or non-treatment alternative using a two-step process that both:
Determines whether to include or exclude each alternative
from consideration given the entry point'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 the decision tree include the following:
Influent concentrations of individual PFAS contaminants in
ppt;
Entry point design flow in MGD;
TOC influent to the new treatment process in mg/L.
EPA relied on information from the national PFAS occurrence model
to inform influent PFAS concentrations. EPA relied on Geometries and
Characteristics of Public Water Supplies (USEPA, 2000f) and SDWIS
inventory information to derive entry point design flow. SafeWater MCBC
selects influent TOC using the distribution shown below in Table 25.
Table 25--Frequency Distribution To Estimate Influent TOC
[In mg/L]
------------------------------------------------------------------------
Percentile Surface water Ground water
------------------------------------------------------------------------
0.05.............................. 0.65 0.35
0.15.............................. 1.1 0.48
0.25.............................. 1.38 0.5
0.35.............................. 1.6 0.5
0.45.............................. 1.85 0.58
0.5............................... 1.97 0.69
0.55.............................. 2.14 0.75
0.65.............................. 2.54 1
0.75.............................. 3.04 1.39
0.85.............................. 3.63 2.01
0.95.............................. 4.81 3.8
------------------------------------------------------------------------
Source: EPA's analysis of TOC concentrations in the SYR4 ICR database.
Step 1 of the decision tree uses these inputs to determine whether
to include or exclude each treatment alternative from consideration in
the compliance forecast. For the treatment technologies (GAC, IX, and
RO/NF), this determination is based on estimates of each technology's
performance given available data about influent water quality and the
regulatory option under consideration.
EPA assumes a small number of PWSs may be able to take non-
treatment actions in lieu of treatment. The viability of non-treatment
actions is likely to depend on the quantity of water being replaced.
Therefore, the decision tree considers non-treatment only for entry
points with design flows less than or equal to 3.536 MGD. EPA's WBS
model for non-treatment does not generate costs for flows greater than
this value, so the decision tree excludes non-treatment actions from
consideration above this flow. EPA estimates approximately 2% of
systems of this size will develop new wells and approximately 6-7% of
systems will elect to interconnect with another system to achieve
compliance.
Step 2 of the decision tree selects a compliance alternative for
each entry point from among the alternatives that remain in
consideration after Step 1. Table 26 shows the initial compliance
forecast that is the starting point for this step. The percentages in
Table 26 consider data presented in the T&C document (USEPA, 2023h) 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, 2023h). The data in USEPA (2023h) 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. EPA
expects this trend to continue, so the initial percentages include
adjustments to
[[Page 18693]]
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 Economic Analysis (USEPA, 2023j). Accordingly, the table
includes adjusted distributions for systems with higher influent TOC.
The list of compliance alternatives in Table 26 does not include
POU RO for small systems. At this time, EPA is not including POU RO in
the national cost estimates because the regulatory options under
consideration require treatment to concentrations below 70 ppt PFOA and
PFOS summed, the current certification standard for POU devices.
Therefore, the decision tree excludes POU RO from consideration and
proportionally redistributes the percentages among the other
alternatives.
Table 26--Initial Compliance Forecast
--------------------------------------------------------------------------------------------------------------------------------------------------------
Design flow less than 1 MGD Design flow 1 to less than 10 Design flow greater than or
-------------------------------- MGD equal to 10 MGD
---------------------------------------------------------------
Compliance alternative TOC less than TOC greater TOC less than TOC greater TOC less than TOC greater
or equal to than 1.5 mg/L or equal to than 1.5 mg/L or equal to than 1.5 mg/L
1.5 mg/L (%) (%) 1.5 mg/L (%) (%) 1.5 mg/L (%) (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------
GAC..................................................... 75 57 77 50 85 50
PFAS-selective IX....................................... 11 29 10 37 10 45
Central RO/NF........................................... 5 5 5 5 5 5
Interconnection......................................... 7 7 6 6 0 0
New Wells............................................... 2 2 2 2 0 0
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: EPA's analysis of TOC concentrations in the SYR4 ICR database.
Note: EPA is not including POU RO in the national cost estimates for the proposed rule because the regulatory options under consideration require
treatment to concentrations below 70 ppt PFOA and PFOS summed, the current certification standard for POU devices. Therefore, the decision tree
excludes POU RO from consideration and proportionally redistributes the percentages among the other alternatives.
If all the compliance alternatives remain in consideration after
Step 1, the decision tree uses the forecast shown in Table 26 above. If
Step 1 eliminated on one or more of the alternatives, the decision tree
proportionally redistributes the percentages among the remaining
alternatives and uses the redistributed percentages.
EPA's approach to estimating GAC and IX performance under the
proposed option and all alternatives considered is discussed in detail
within the cost chapter of the Economic Analysis (USEPA, 2023j).
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. EPA developed the WBS model approach as part of
an effort to address recommendations made by the Technology Design
Panel (TDP), which convened 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 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
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 a
complete compliance cost estimate.
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, EPA fit cost curves to the WBS estimates
across a range of flow rates, which is described in Chapter 5 of the
Economic Analysis (USEPA, 2023j).
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. 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, EPA models the
potential variability in treatment cost based on the three component/
cost levels. To estimate costs for PFAS treatment, EPA generated
separate cost equations for each of the
[[Page 18694]]
three component levels, thus creating a range of cost estimates for use
in national compliance cost estimates. EPA requests comment on the
range of component levels assumed and the range of estimated PFAS
treatment costs.
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 equations for system
automation are described in Chapter 5 of the Economic Analysis (USEPA,
2023j).
The WBS models generate cost estimates that include a consistent
set of capital, add-on, indirect, and O&M costs. Table 27 below
identified these cost elements, which are common to all the WBS models
and included in the cost estimates below. As described below and
summarized in Tables 28-31 the WBS models also include technology-
specific cost elements. The documentation for the WBS models provide
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, 2021g; USEPA, 2021h; USEPA, 2021i; and USEPA, 2021j).
WBS model accuracy is described in Chapter 5 of the Economic Analysis
(USEPA, 2023j).
Table 27--Cost Elements Included in All WBS Models
------------------------------------------------------------------------
Cost category Components included
------------------------------------------------------------------------
Direct Capital Costs.......... Technology-specific equipment
(e.g., vessels, basins, pumps,
treatment media, piping, valves).
Instrumentation and system
controls.
Buildings.
Residuals management equipment.
Add-on Costs.................. Land.
Permits.
Pilot testing.
Indirect Capital Costs........ Mobilization and
demobilization.
Architectural fees for
treatment building.
Equipment delivery,
installation, and contractor's overhead
and profit.
Sitework.
Yard piping.
Geotechnical.
Standby power.
Electrical infrastructure.
Process engineering.
Contingency.
Miscellaneous allowance.
Legal, fiscal, and
administrative.
Sales tax.
Financing during construction.
Construction management.
O&M Costs: Technology-specific Operator labor for technology-
specific tasks (e.g., managing backwash
and media replacement).
Materials for O&M of technology-
specific equipment.
Technology-specific chemical
usage.
Replacement of technology-
specific equipment that occurs on an
annual basis (e.g., treatment media).
Energy for operation of
technology-specific equipment (e.g.,
mixers).
O&M Costs: Labor.............. Operator labor for O&M of
process equipment.
Operator labor for building
maintenance.
Managerial and clerical labor.
O&M Costs: Materials.......... Materials for maintenance of
booster or influent pumps.
Materials for building
maintenance.
O&M Costs: Energy............. Energy for operation of booster
or influent pumps.
Energy for lighting,
ventilation, cooling, and heating.
O&M Costs: Residuals.......... Residuals management operator
labor, materials, and energy.
Residuals disposal and
discharge costs.
------------------------------------------------------------------------
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 28 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 Cost Elements Included in
All WBS Models table above.
Table 28--Technology-Specific Cost Elements Included in the GAC Model
------------------------------------------------------------------------
Cost category Major components included
------------------------------------------------------------------------
Direct Capital Costs.......... Booster pumps for influent
water.
Contactors (either pressure
vessels or concrete basins) that
contain the GAC bed.
Tanks and pumps for backwashing
the contactors.
GAC transfer and storage
equipment.
Spent GAC reactivation
facilities (if on-site reactivation is
selected).
Associated piping, valves, and
instrumentation.
[[Page 18695]]
O&M Costs: Labor.............. Operator labor for contactor
maintenance (for gravity GAC designs).
Operator labor for managing
backwash events.
Operator labor for backwash
pump maintenance (if backwash occurs
weekly or more frequently).
Operator labor for GAC transfer
and replacement.
O&M Costs: Materials.......... Materials for contactor
maintenance (accounts for vessel
relining in pressure designs, because
GAC can be corrosive, and for concrete
and underdrain maintenance in gravity
designs).
Materials for backwash pump
maintenance (if backwash occurs weekly
or more frequently).
Replacement virgin GAC (loss
replacement only if reactivation is
selected).
O&M Costs: Energy............. Operating energy for backwash
pumps.
O&M Costs: Residuals.......... Discharge fees for spent
backwash.
Fees for reactivating spent GAC
(if off-site reactivation is selected).
Labor, materials, energy, and
natural gas for regeneration facility
(if on-site reactivation is selected).
Disposal of spent GAC (if
disposal is selected).
------------------------------------------------------------------------
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.
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
(2021g) provides complete details on the variant design assumptions
used for package plants.
To generate the GAC cost equations, 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 150,000 BV.
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 and replacement
with virgin GAC (i.e., single use operation).
The T&C document (USEPA, 2023h) provides a comprehensive discussion
of these and other key inputs and assumptions.
Table 29 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 Cost Elements
Included in All WBS Models table above.
Table 29--Technology-Specific Cost Elements Included in the PFAS-
Selective IX Model
------------------------------------------------------------------------
Cost category Major components included
------------------------------------------------------------------------
Direct Capital Costs.......... Booster pumps for influent
water.
Pre-treatment cartridge
filters.
Pressure vessels that contain
the resin bed.
Tanks and pumps for initial
rinse and (optionally) backwash of the
resin bed.
Tanks (with secondary
containment), pumps and mixers for
delivering sodium hydroxide for use in
post-treatment corrosion control
(optional).
Associated piping, valves, and
instrumentation.
O&M Costs: Labor.............. Operator labor for pre-
treatment filters.
Operator labor for managing
backwash/rinse events.
Operator labor for backwash
pump maintenance (only if backwash
occurs weekly or more frequently).
Operator labor for resin
replacement.
O&M Costs: Materials.......... Replacement cartridges for pre-
treatment filters.
Materials for backwash pump
maintenance (only if backwash occurs
weekly or more frequently).
Chemical usage (if post-
treatment corrosion control is
selected).
Replacement virgin PFAS-
selective resin.
O&M Costs: Energy............. Operating energy for backwash/
rinse pumps.
O&M Costs: Residuals.......... Disposal of spent cartridge
filters.
Discharge fees for spent
backwash/rinse.
Disposal of spent resin.
------------------------------------------------------------------------
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 (2021j) provides complete details on the variant design
assumptions used for IX package plants.
To generate the IX cost equations, 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 440,000 BV.
[[Page 18696]]
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, 2023h) provides a comprehensive discussion
of these and other key inputs and assumptions.
Table 30 shows the technology-specific capital equipment and O&M
requirements included in the model for RO/NF (USEPA, 2021i). These
items are in addition to the common WBS cost elements listed in listed
in the Cost Elements Included in All WBS Models table above.
Table 30--Technology-Specific Cost Elements Included in the RO/NF Model
------------------------------------------------------------------------
Cost category Major components included
------------------------------------------------------------------------
Direct Capital Costs.......... High-pressure pumps for
influent water and (optionally)
interstage pressure boost.
Pre-treatment cartridge
filters.
Tanks, pumps, and mixers for
pretreatment chemicals.
Pressure vessels, membrane
elements, piping, connectors, and steel
structure for the membrane racks.
Valves for concentrate control
and (optionally) per-stage throttle.
Tanks, pumps, screens,
cartridge filters, and heaters for
membrane cleaning.
Equipment, including dedicated
concentrate discharge piping, for
managing RO/NF concentrate and spent
cleaning chemicals.
Associated pipes, valves, and
instrumentation.
O&M Costs: Labor.............. Operator labor for pre-
treatment filters.
Operator labor for routine O&M
of membrane units.
Operator labor to maintain
membrane cleaning equipment.
O&M Costs: Materials.......... Replacement cartridges for pre-
treatment filters.
Chemical usage for
pretreatment.
Maintenance materials for pre-
treatment, membrane process, and
cleaning equipment.
Replacement membrane elements.
Chemical usage for cleaning.
O&M Costs: Energy............. Energy for high-pressure
pumping.
O&M Costs: Residuals.......... Disposal costs for spent
cartridge filters and membrane
elements.
------------------------------------------------------------------------
The RO/NF model includes three default ground waters and three
default surface waters, ranging from high to low quality (i.e., from
low to high total dissolved solids and scaling potential). To generate
the cost equations, EPA used the model's default high-quality influent
water parameters to reflect the incremental cost of removing PFAS from
otherwise potable water. EPA used the following additional key inputs
and assumptions:
For systems larger than approximately 0.5 MGD, target
recovery rates of 80 percent for ground water and 85 percent for
surface water.
Target recovery rates of 70 to 75 percent for smaller
systems.
Flux rates of 19 gallons per square foot per day (gfd) for
ground water and 15 to 16 gfd for surface water.
Direct discharge of RO/NF concentrate to a permitted
outfall on a non-potable water body (e.g., ocean or brackish estuary)
via 10,000 feet of buried dedicated piping.
The T&C document (USEPA, 2023h) provides a comprehensive discussion
of these and other key inputs and assumptions.
USEPA (2021j) 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 31 below shows the technology-specific
capital equipment and O&M requirements included in the model for each
alternative.
Table 31--Technology-Specific Cost Elements Included in the Non-
Treatment Model
------------------------------------------------------------------------
Major components Major components
Cost category included for included for new
interconnection wells
------------------------------------------------------------------------
Direct Capital Costs............. Booster Well
pumps or pressure casing, screens,
reducing valves and plugs.
(depending on Well
pressure at installation
supply source). costs including
Concrete drilling,
vaults (buried) development,
for booster pumps gravel pack, and
or pressure surface seals.
reducing valves. Well
pumps.
Interconnecting Piping
piping (buried) (buried) and
and valves. valves to
connect the new
well to the
system.
O&M Costs: Labor................. Operator Operator
labor for O&M of labor for
booster pumps or operating and
pressure reducing maintaining well
valves (depending pumps and
on pressure at valves.
supply source)
and
interconnecting
valves.
O&M Costs: Materials............. Cost of
purchased water. Materials for
Materials maintaining well
for maintaining pumps.
booster pumps (if
required by
pressure at
supply source).
O&M Costs: Energy................ Energy Energy
for operating for operating
booster pumps (if well pumps.
required by
pressure at
supply source).
------------------------------------------------------------------------
To generate the cost equations, EPA used the following key inputs
in the non-treatment model for interconnection:
An interconnection distance of 10,000 feet;
[[Page 18697]]
Minimal differences in pressure between the supplier and
the purchasing system, so that neither booster pumps nor pressure
reducing valves are needed;
An average cost of purchased water of $3.00 per thousand
gallons in 2020 dollars.
For new wells, EPA used the following key inputs:
A maximum well capacity of 500 gallons per minute (gpm),
such that one new well is installed per 500 gpm of water production
capacity required;
A well depth of 250 feet;
500 feet of distance between the new wells and the
distribution system.
The T&C document (USEPA, 2023h) provides a comprehensive discussion
of these and other key inputs and assumptions.
d. Incremental Treatment Costs
EPA has estimated the national level costs of the proposed rule
associated with PFOA, PFOS, and PFHxS. Given the available occurrence
data for the other compounds in the proposed rule (PFNA, HFPO-DA, and
PFBS) and the regulatory thresholds under consideration, EPA did not
model national costs associated with potential HI exceedances as a
direct result of these compounds. To assess the potential impact of
these compounds, EPA conducted an analysis of the additional, or
incremental, system level impact that occurrence of these compounds
would have on treatment costs. To do so, EPA used a model system
approach. For further detail on the assumptions and findings of EPA's
analysis of incremental costs, please see Chapter 5 in USEPA (2023j)
and Appendix N in USEPA (2023i).
e. PWS Implementation Administration Costs
EPA estimated PWS costs associated with one-time actions to begin
implementation of the rule including reading and understanding the rule
and attending training provided by primacy agencies. EPA assumes that
systems will conduct these activities during years one through three of
the period of analysis. Table 32 lists the data elements and
corresponding values associated with calculating the costs of these
one-time implementation administration actions.
Table 32--Implementation Administration Startup Costs
[2021$]
------------------------------------------------------------------------
Data element description Data element value
------------------------------------------------------------------------
The labor rate per hour for systems........ $35.48 (systems <=3,300).
$37.84 (systems 3,301-
10,000).
$39.94 (systems 10,001-
50,000).
$41.70 (systems 50,001-
100,000).
$48.74 (systems >100,000).
The average hours per system to read and 4 hours per system.
adopt the rule.
The average hours per system to attend one- 16 hours per system
time training provided by primacy agencies. (systems <=3,300).
32 hours per system
(systems >3,300).
------------------------------------------------------------------------
Estimated national annualized PWS implementation and administration
startup costs for the proposed option are $1.71 million (3% discount
rate) and $3.52 million (7% discount rate). National annualized PWS
cost estimates are further summarized in Table 37.
f. PWS Monitoring Costs
EPA assumes that the proposed rule will require initial and long-
term monitoring. As Table 33 shows, surface and ground water systems
serving 10,000 or more people will collect one sample each quarter, at
each entry point, 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 entry point during the initial
12-month period. Ground water systems that serve 10,000 or fewer people
will be required to sample once at each entry point on a semi-annual
basis for the first 12-month monitoring period.
Long-term monitoring requirements differ based on two factors: (1)
system size, and (2) whether a system can demonstrate during the
initial monitoring period that they are ``reliably and consistently''
below the proposed MCLs for PFAS. EPA has set the PWS size threshold at
systems serving 3,300 or fewer people. The threshold for systems to
demonstrate that they are ``reliably and consistently'' below the
proposed MCLs is set at a trigger level of one-third the MCLs for PFOA
or PFOS (1.3 ppt) or the HI (0.33). For systems below the trigger level
values during the initial 12-month monitoring period and in future
long-term monitoring periods may conduct triennial monitoring. Systems
serving 3,300 or fewer people will collect one triennial sample per
entry point. Systems providing water for more than 3,300 people will
take one sample in two consecutive quarters at each entry point,
totaling two samples in each triennial period. For systems with
concentration values at or above the trigger level regardless of system
size, a quarterly sample must be taken at each entry point.
For any samples that have a detection, the system will analyze the
field reagent blank samples collected at the same time as the
monitoring sample. Systems that have an MCL exceedance will collect one
additional sample from the relevant entry point to confirm the results.
Table 33--Initial and Long-Term Sampling Frequencies per System Entry Point
----------------------------------------------------------------------------------------------------------------
Long-Term
Long-term monitoring: \a\ Long-term monitoring: \1\ PFAS
Initial monitoring Initial 12-month monitoring PFAS detection detection >=1.3 ppt (PFOA or
system size category monitoring period system size <1.3 ppt (PFOA or PFOS) or HI >=0.33
category PFOS) or HI <0.33
----------------------------------------------------------------------------------------------------------------
<=10,000............. Surface Water: 1 <=3,300 1 triennial sample 1 sample every quarter.
sample every
quarter.
Ground Water: 1
sample every 6-
month period.
[[Page 18698]]
>10,000.............. Surface Water and >3,300 2 triennial 1 sample every quarter.
Ground Water: 1 samples (1 sample
sample every in two
quarter. consecutive
quarters).
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ EPA used the following thresholds to distinguish whether PFAS concentrations are reliably and consistently
below the MCL: PFOA and PFOS--one-third the MCL for each option; PFHxS--one-third the health benchmark of 9
ppt or 3 ppt.
For the national cost analysis, EPA assumes that systems with
either UCMR 5 data or monitoring data in the State PFAS Database (see
Section 3.1.4 in USEPA, 2023j) will not need to conduct the initial
year of monitoring. As a simplifying assumption for the cost analysis,
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, 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. EPA requests comment on these
underlying assumptions.
EPA used system-level distributions, as described in Cadwallader et
al. (2022), to simulate entry point concentrations and estimate PFAS
occurrence relative to the proposed option MCLs and trigger levels.
Based on these occurrence distributions, EPA estimates that the large
majority of water systems subject to the proposed rule (approx. 52,000)
will have EPs with concentrations below the proposed trigger level and
would conduct reduced monitoring on a triennial basis. EPA estimates
that the remainder of water systems subject to the proposed rule
(approx. 14,000) will have at least one or more EPs exceed the proposed
trigger level and therefore would be required to conduct quarterly
monitoring. EPA requests comment on these estimates and the underlying
assumptions.
EPA assumes that systems with an MCL exceedance will implement
actions to comply with the MCL by the compliance date. EPA assumes a
treatment target, 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 MCL or HI. This target is insufficient to meet the
triennial monitoring threshold. Therefore, systems implementing
treatment will continue with quarterly monitoring. All other systems
that do not have PFAS concentrations at or below the trigger level
threshold will also continue quarterly monitoring.
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 34 presents the data elements and
corresponding values associated with calculating sampling costs during
the implementation monitoring period.
Table 34--Sampling Costs
[2021$]
------------------------------------------------------------------------
Data element description Data element value
------------------------------------------------------------------------
The labor rate per hour for systems........ $35.48 (systems <=3,300).
$37.84 (systems 3,301-
10,000).
$39.94 (systems 10,001-
50,000).
$41.70 (systems 50,001-
100,000).
$48.74 (systems >100,000).
The number of samples per entry point per 2 samples (Ground Water
monitoring round for the initial systems <=10,000).
monitoring in Year 1. 4 samples (all systems)
\1\.
The number of samples per entry point per 4 samples (all other
long-term monitoring year for entry points systems).
that exceed the triennial monitoring
threshold.
The number of samples per entry point per 1 sample (systems <=3,300).
long-term monitoring round for entry 2 samples (systems >3,300).
points that meet the triennial threshold.
The hours per sample to travel to sampling 1 hour.
locations, collect samples, record any
additional information, submit samples to
a laboratory, and review results.
The laboratory analysis cost per sample for $376.
EPA Method 533.
The laboratory analysis cost per sample for $302.
EPA Method 537.1.
The laboratory analysis cost per sample for $327.\2\
field reagent blank under EPA Method 533.
The laboratory analysis cost per sample for $266.\ 2\
the field reagent blank under EPA Method
537.1.
------------------------------------------------------------------------
Notes:
\1\ Systems greater than 3,300 will rely on UCMR 5 data and a subset of
other systems will rely on data in the State PFAS Monitoring Database
discussed in USEPA, 2023j.
\2\ This incremental sample cost applies to all samples that exceed
MDLs. EPA used the Method 537.1 detection limits to apply this cost
because Method 533 does not include detection limits.
Estimated national annualized PWS sampling costs for the proposed
option are $90.32 million (3 discount rate) and $92.97 million (7%
discount rate). National annualized PWS cost estimates are further
summarized in Table 37.
[[Page 18699]]
g. Treatment Administration Costs
Any system with an MCL exceedance adopts either a treatment or non-
treatment alternative to comply with the proposed rule. The majority of
systems are anticipated to install treatment technologies while a
subset of systems will choose alternative methods. EPA assumes that
systems will bear administrative costs associated with these treatment
or non-treatment compliance actions (i.e., permitting costs). EPA
assumes that systems will install treatment in the fourth year of the
period of analysis. Table 35 presents the data elements and
corresponding values associated with calculating treatment
administration costs.
Table 35--Treatment Administration Costs
[2021$]
------------------------------------------------------------------------
Data element description Data element value
------------------------------------------------------------------------
The labor rate per hour for systems........ $35.48 (systems <=3,300).
$37.84 (systems 3,301-
10,000).
$39.94 (systems 10,001-
50,000).
$41.70 (systems 50,001-
100,000).
$48.74 (systems >100,000).
The hours per entry point for a system to 3 hours (systems <=100)
notify, consult, and submit a permit 5 hours (systems 101-500).
request for treatment installation \a\.
7 hours (systems 501-
1,000).
12 hours (systems 1,001-
3,300).
22 hours (systems 3,301-
50,000).
42 hours (systems >50,000).
The hours per entry point for a system to 6 hours.
notify, consult, and submit a permit
request for source water change or
alternative method \1\.
------------------------------------------------------------------------
Notes:
\1\ EPA applied the cost per entry point for this economic analysis
because the notification, consultation, and permitting process occurs
for individual entry points.
h. Public Notification (PN) Costs
EPA's cost analysis assumes full compliance with the rule
throughout the period of analysis and, as a result, EPA does not
estimate costs for the PN requirements in the proposed rule for systems
with certain violations. The proposed 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 proposed rule also designates monitoring and testing
procedure violations as Tier 3, which requires systems to provide
public notice not 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. For approximate estimates of the potential
burden associated with Tier 2 and 3 PNs, please see USEPA (2023j).
i. Primacy Agency Costs
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 proposed rule include:
Reading and understanding the rule and adopting regulatory
requirements,
Providing primacy agency officials training for the rule
implementation,
Providing systems with training and technical assistance
during the rule implementation,
Reporting to 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,
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.
With the exception of the first four 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 entry point by
each system under an Agency's jurisdiction. Table 36 presents the data
elements and corresponding values associated with calculating primacy
agency costs.
Table 36--Primacy Agency Costs
[2021$]
------------------------------------------------------------------------
Data element description Data element value
------------------------------------------------------------------------
The labor rate per hour for primacy $58.14.
agencies \1\.
The average hours per primacy Agency to 416 hours per primacy
read and understand the rule, as well as Agency.
adopt regulatory requirements.
The average hours per primacy Agency to 250 hours per primacy
provide initial training to internal staff. Agency.
The average hours per primacy Agency to 2,080 hours per primacy
provide initial training and technical Agency.
assistance to systems.
The average hours per primacy Agency to 0.
report annually to EPA information under
40 CFR 142.15 regarding violations,
variances and exemptions, enforcement
actions and general operations of State
PWS programs.
The hours per sample for a primacy Agency 1 hour.
to review sample results.
[[Page 18700]]
The hours per entry point for a primacy 3 hours (systems <=100).
agency to review and consult on 5 hours (systems 101-500).
installation of a TT \2\. 7 hours (systems 501-
1,000).
12 hours (systems 1,001-
3,300).
22 hours (systems 3,301-
50,000).
42 hours (systems >50,000).
The hours per entry point for a primacy 4 hours.
agency to review and consult on a source
water change \2\.
------------------------------------------------------------------------
Notes:
\1\ In USBLS (2022), State employee wage rate of $33.91 from National
Occupational Employment and Wage Estimates, United States, BLS SOC
Code 19-2041, ``State Government, excluding schools and hospitals--
Environmental Scientists and Specialists, Including Health,'' hourly
mean wage rate. May 2020 data (published in March 2021): https://www.bls.gov/oes/current/oes192041.htm. Wages are loaded using a factor
of 62.2 from the Bureau of Labor Statistics (BLS) Employer Costs for
Employee Compensation report, Table 3, March 2020. Percent of total
compensation--Wages and Salaries--All Workers--State and Local
Government Workers (https://www.bls.gov/news.release/archives/ecec_06182020.pdf). See worksheet BLS Table 3. The final loaded wage
is adjusted for inflation.
\2\ EPA assumes that the proposed PFAS rule will have no discernable
incremental burden for quarterly or annual reports to SDWIS/Fed.
Estimated national annualized primacy agency costs for the proposed
option are $7.96 million (3% discount rate) and $8.76 million (7%
discount rate). National annualized cost estimates are further
summarized in Table 37.
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. EPA assumes full compliance with the proposed 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 (2023j).
In Table 37, EPA summarizes the total annualized quantified cost of
the proposed option at both a 3 percent and 7 percent discount rate
expressed in millions of 2021 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. At a 3 percent
discount rate, the expected annualized PWS costs are $769 million. The
uncertainty range for annualized PWS costs are $699 million to $862
million. Finally, annualized primacy agency implementation and
administrative costs are added to the annualized PWS costs to calculate
the total annualized cost of the proposed option. At a 3 percent
discount rate, the expected total annualized cost of the proposed rule
is $777 million. The uncertainty range for the total annualized costs
of the proposed rule is $706 million to $872 million. At a 7 percent
discount rate, the expected total annualized cost of the proposed
option is $1.211 billion, while the uncertainty range for the total
annualized costs of the proposed option is $1.103 billion to $1.353
billion. Note as described in section j. Data Limitations and
Uncertainties in the Cost Analysis below, given the available
occurrence data for the other compounds in the proposed rule (PFNA,
HFPO-DA, and PFBS) and the regulatory thresholds under consideration,
EPA did not model national costs associated with potential HI
exceedances as a direct result of these compounds; therefore, the
additional treatment cost, from co-occurrence of PFNA, HFPO-DA, PFBS or
other PFAS, at systems already required to treat because of PFOA, PFOS,
or PFHxS MCL and HI exceedances are not quantitatively assessed in the
national cost estimates. Nor are treatment costs for systems that
exceed the HI based on the combined occurrence of PFNA, HFPO-DA, PFBS,
and PFHxS (where PFHxS itself does not exceed 9 ppt) included in the
national monetized cost estimates. These potential additional costs are
described in Section 5.3.1.4 of USEPA (2023j) and Appendix N of USEPA
(2023i).
In these sections of the Economic Analysis, EPA uses a model system
approach to explore the potential costs of treatment at a system that:
(1) has no detections of PFOA, PFOS, or PFHxS (modeled in the national
analysis), but has occurrence of all the other PFAS included in the HI
(HFPO-DA, PFBS, and PFNA), and (2) has occurrence of PFOA, PFOS, and
PFHxS identical to the national model but also has occurrence of all
the other PFAS included in the HI (HFPO-DA, PFBS, and PFNA). The first
type of system represents additional systems that are not currently
captured in the national costs but would incur treatment costs under
the HI. The second type of system illustrates a range of potential
incremental treatment costs for systems that are already treating to
remove PFOA, PFOS, and/or PFHxS in the national cost analysis. EPA
analyzed system costs for GAC, IX, and OR for two scenarios: high
occurrence of the three PFAS not included in the national analysis and
medium occurrence of those PFAS. The model system analysis found for IX
and RO/NF that costs were slightly less or the same as modeled system
treatment costs under a national cost scenario across both types of
systems defined above, the medium and high PFAS scenarios, and across
model system size categories. The assessment of GAC produced more
variability in results. For systems that are not currently captured in
the national costs but would incur treatment costs under the HI, EPA
found under the medium PFAS concentrations cost would be the same or
slightly less than a model system treating for the PFAS included in the
national analysis. The systems representing the potential incremental
treatment costs for systems that are already treating to remove PFOA,
PFOS, and/or PFHxS in the national cost analysis, the model system
analysis under the medium scenario found that costs of treatment would
increase by 1-9 percent, depending on system size and other cost
assumptions associated with bed life changes as a result of TOC
assumptions. Under the high PFAS scenario across both types of systems
GAC treatment costs were found to range from 0 to 77% higher than
treatment of national PFAS values depending on system size and other
costing assumptions like bed life. This high-end cost increase of 77
percent is unlikely to occur at a large number of systems given the
assumed high levels of PFAS and the assumed high levels of
[[Page 18701]]
TOC at 2 mg/L. It is also likely that systems facing these GAC
treatment cost will select IX or RO/NF as lower cost alternative
treatments and therefore national cost estimates are unlikely to be
substantially underestimated. EPA requests comment on these estimated
impacts and the assumption that HI exceedances resulting from these
additional compounds will not significantly impact overall compliance
costs.
The national annualized costs below do not reflect costs of
hazardous waste disposal for GAC and IX media. As a general matter, EPA
notes that such wastes are not currently regulated under Federal law as
a hazardous waste. To address stakeholder concerns, including those
raised during the SBREFA process, EPA conducted a sensitivity analysis
with an assumption of hazardous waste disposal for illustrative
purposes only. As part of this analysis, 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. EPA acknowledges that if Federal
authorities later determine that PFAS-contaminated wastes require
handling as hazardous wastes, the residuals management costs are
expected to be higher. See Appendix N.2 of USEPA (2023j) for a
sensitivity analysis describing the potential increase in costs
associated with hazardous waste disposal (USEPA, 2023i).
Table 37--National Annualized Costs, Proposed Option
[PFOA and PFOS MCLs of 4.0 ppt and HI of 1.0; million $2021]
--------------------------------------------------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
---------------------------------------------------------------------------------------
5th Percentile Expected 95th 5th Percentile Expected 95th
\1\ value Percentile \1\ \1\ value Percentile \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Annualized PWS Sampling Costs................................... $76.12 $90.32 $106.95 $78.54 $92.97 $109.19
Annualized PWS Implementation and Administration Costs.......... 1.71 1.71 1.71 3.52 3.52 3.52
Annualized PWS Treatment Costs.................................. 617.05 676.56 762.05 1,008.88 1,105.66 1,232.92
Total Annualized PWS Costs \2\ \3\ \4\.......................... 698.90 768.57 861.78 1,096.29 1,202.09 1,341.19
Primacy Agency Rule Implementation and Administration Cost...... 6.86 7.96 9.18 7.67 8.76 10.04
Total Annualized Rule Costs \2\ \3\ \4\......................... 705.85 776.54 871.50 1,102.71 1,210.91 1,352.71
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding. Percentiles cannot be summed because cost components are not perfectly correlated.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section XIII.I of this preamble and Table 71. This
range does not include the uncertainty described in Table 41.
\2\ Total quantified national cost values do not include the incremental treatment costs associated with the co-occurrence of HFPO-DA, PFBS, and PFNA at
systems required to treat for PFOA, PFOS, and PFHxS. The total quantified national cost values do not include treatment costs for systems that would
be required to treat based on HI exceedances apart from systems required to treat because of PFHxS occurrence alone. See Appendix N, Section 3 of the
Economic Analysis (USEPA, 2023i) for additional detail on co-occurrence incremental treatment costs and additional treatment costs at systems with HI
exceedances.
\3\ PFAS-contaminated wastes are not considered 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 about potential costs for disposing PFAS-
contaminated wastes as hazardous should they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA, 2023i) for additional detail.
\4\ See Table 70 for a list of the nonquantifiable costs, and the potential direction of impact these costs would have on the estimated monetized total
annualized costs in this table.
In Table 38, Table 39, and Table 40, EPA summarizes the total
annualized quantified cost of options 1a, 1b, and 1c, respectively.
Table 38--National Annualized Costs, Option 1a
[PFOA and PFOS MCLs of 4.0 ppt; million $2021]
--------------------------------------------------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
---------------------------------------------------------------------------------------
5th Percentile Expected 95th 5th Expected 95th
\1\ value Percentile \1\ Percentile\1\ value Percentile \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Annualized PWS Sampling Costs................................... $75.54 $89.45 $105.44 $77.76 $92.10 $108.29
Annualized PWS Implementation and Administration Costs.......... 1.71 1.71 1.71 3.52 3.52 3.52
Annualized PWS Treatment Costs.................................. 601.03 661.40 745.31 984.54 1,079.05 1,205.22
Total Annualized PWS Costs \2\ \3\.............................. 680.76 752.56 848.52 1,066.70 1,174.69 1,314.49
Primacy Agency Rule Implementation and Administration Cost...... 6.83 7.89 9.12 7.59 8.69 9.96
Total Annualized Rule Costs \2\ \3\............................. 687.54 760.45 857.04 1,078.01 1,183.41 1,324.41
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding. Percentiles cannot be summed because cost components are not perfectly correlated.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section XIII.I of this preamble and Table 71. This
range does not include the uncertainty described in Table 41.
[[Page 18702]]
\2\ PFAS-contaminated wastes are not considered 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 about potential costs for disposing PFAS-
contaminated wastes as hazardous should they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA, 2023i) for additional detail.
\3\ See Table 70 for a list of the nonquantifiable costs, and the potential direction of impact these costs would have on the estimated monetized total
annualized costs in this table.
Table 39--National Annualized Costs, Option 1b
[PFOA and PFOS MCLs of 5.0 ppt; million $2021]
--------------------------------------------------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
---------------------------------------------------------------------------------------
5th Percentile Expected 95th 5th Expected 95th
\1\ value Percentile \1\ Percentile\1\ value Percentile \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Annualized PWS Sampling Costs................................... $66.40 $78.38 $93.04 $68.77 $80.92 $95.70
Annualized PWS Implementation and Administration Costs.......... 1.71 1.71 1.71 3.52 3.52 3.52
Annualized PWS Treatment Costs.................................. 479.50 527.00 597.91 778.40 853.94 960.05
Total Annualized PWS Costs \2\ \3\.............................. 549.52 607.08 686.67 854.64 938.38 1,052.52
Primacy Agency Rule Implementation and Administration Cost...... 6.03 6.94 8.03 6.74 7.69 8.84
Total Annualized Rule Costs \2\ \3\............................. 555.94 614.03 694.18 860.01 946.07 1,064.56
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding. Percentiles cannot be summed because cost components are not perfectly correlated.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section XIII.I of this preamble and Table 71. This
range does not include the uncertainty described in Table 41.
\2\ PFAS-contaminated wastes are not considered 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 about potential costs for disposing PFAS-
contaminated wastes as hazardous should they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA, 2023i) for additional detail.
\3\ See Table 70 for a list of the nonquantifiable costs, and the potential direction of impact these costs would have on the estimated monetized total
annualized costs in this table.
Table 40--National Annualized Costs, Option 1c
[PFOA and PFOS MCLs of 10.0 ppt; Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected percentile
\1\ value \1\ \1\ value \1\
----------------------------------------------------------------------------------------------------------------
Annualized PWS Sampling Costs......... $46.19 $52.84 $64.34 $48.33 $55.14 $66.82
Annualized PWS Implementation and 1.71 1.71 1.71 3.52 3.52 3.52
Administration Costs.................
Annualized PWS Treatment Costs........ 214.02 233.87 257.12 336.54 367.40 404.42
Total Annualized PWS Costs \2\ \3\.... 264.49 288.43 317.66 390.39 426.06 468.83
Primacy Agency Rule Implementation and 4.28 4.76 5.65 4.91 5.40 6.28
Administration Cost..................
Total Annualized Rule Costs \2\ \3\... 269.11 293.19 323.45 395.35 431.46 474.75
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding. Percentiles cannot be summed because cost
components are not perfectly correlated.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 71. This range does not include the uncertainty described in Table 41.
\2\ PFAS-contaminated wastes are not considered 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 about potential costs for disposing PFAS-contaminated wastes as hazardous should
they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA,
2023i) for additional detail.
\3\ See Table 70 for a list of the nonquantifiable costs, and the potential direction of impact these costs
would have on the estimated monetized total annualized costs in this table.
j. Data Limitations and Uncertainties in the Cost Analysis
Table 41 lists data limitations and characterizes the impact on the
quantitative cost analysis. 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. 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.
[[Page 18703]]
Table 41--Limitations That Apply to the Cost Analysis for the Proposed PFAS Rule
----------------------------------------------------------------------------------------------------------------
Uncertainty/assumption Effect on quantitative analysis Notes
----------------------------------------------------------------------------------------------------------------
WBS engineering cost model assumptions Uncertain...................... The WBS engineering cost models require
and component costs. many design and operating assumptions
to estimate treatment process
equipment and operating needs. Chapter
5 of the Economic Analysis (USEPA,
2023j) addressed the bed life
assumption. The Technologies and Costs
document (USEPA, 2023h) and individual
WBS models in the rule docket provide
additional information. The component-
level costs approximate national
average costs, which can over- or
under-estimate costs at systems
affected by the proposed rule.
Compliance forecast................... Uncertain...................... The forecast probabilities are based on
historical full-scale compliance
actions. Site-specific water quality
conditions, changes in technology, and
changes in market conditions can
result in future technology selections
that differ from the compliance
forecast.
TOC concentration..................... Uncertain...................... The randomly assigned values from the
two national distributions are based
on a limited dataset. Actual TOC
concentrations at systems affected by
the proposed rule can be higher or
lower than the assigned values.
Insufficient UCMR 3 data for PFBS and Underestimate.................. The HI in the proposed option would
PFNA and no UCMR 3 data for HFPO-DA regulate PFBS, PFNA, and HFPO-DA in
were available to incorporate into addition to the modeled PFAS. In
the Bayesian hierarchical occurrence instances when concentrations of PFBS,
model. PFNA, and/or HFPO-DA are high enough
to cause a HI exceedance, the modeled
costs may be underestimated. If these
PFAS occur in isolation at levels that
affect treatment decisions, or if they
occur in sufficient concentration to
result in an exceedance when the
concentration of PFHxS alone would be
below the HI, then costs would be
underestimated. Note that EPA has
conducted an analysis of the potential
changes in system level treatment cost
associated with the occurrence of
PFBS, PFNA, and HFPO-DA using a model
system approach which is discussed in
detail in Chapter 5 and Appendix N of
the Economic Analysis (USEPA, 2023j;
USEPA, 2023i).
POU not included in compliance Overestimate................... If POU devices can be certified to meet
forecast. concentrations that satisfy the
proposed rule, then small systems may
be able to reduce costs by using a POU
compliance option instead of
centralized treatment or source water
changes.
Process wastes not classified as Underestimate.................. The national cost analysis reflects the
hazardous. assumption that PFAS-contaminated
wastes are not considered hazardous
wastes. As a general matter, EPA notes
that such wastes are not currently
regulated under Federal law as a
hazardous waste. To address
stakeholder concerns, including those
raised during the SBREFA process, EPA
conducted a sensitivity analysis with
an assumption of hazardous waste
disposal for illustrative purposes
only. As part of this analysis, 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. EPA acknowledges that if
Federal authorities later determine
that PFAS-contaminated wastes require
handling as hazardous wastes, the
residuals management costs in the WBS
treatment cost models are expected to
be higher. See Appendix N of the
Economic Analysis (USEPA, 2023j;
USEPA, 2023i) for a sensitivity
analysis describing the potential
increase in costs associated with
hazardous waste disposal at 100% of
systems treating for PFAS. The costs
estimated in Appendix N are consistent
with EPA OLEM's ``Interim Guidance on
the Destruction and Disposal of
Perfluoroalkyl and Polyfluoroalkyl
Substances and Materials Containing
Perfluoroalkyl and Polyfluoroalkyl
Substances.'' \1\
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ EPA Office of Land and Emergency Management's Interim Guidance on the Destruction and Disposal of
Perfluoroalkyl and Polyfluoroalkyl Substances and Materials Containing Perfluoroalkyl and Polyfluoroalkyl
Substances can be found at https://www.epa.gov/system/files/documents/2021-11/epa-hq-olem-2020-0527-0002_content.pdf.
D. Method for Estimating Benefits
EPA's quantification of health benefits resulting from reduced PFAS
exposure in drinking water was driven by PFAS occurrence estimates,
pharmacokinetic (PK) model availability, information on exposure-
response relationships, and available information to monetize avoided
cases of illness. In the Economic Analysis, EPA either quantitatively
assesses or qualitatively discusses health endpoints associated with
exposure to PFAS. EPA assesses potential benefits quantitatively if
evidence of exposure and health effects is likely, it is possible to
link the outcome to risk of a health effect, and 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 liver enzymes
(particularly 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 42 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
proposed rule, EPA quantifies some of the adverse health effects
associated with PFOA and PFOS. EPA also quantifies one adverse health
effect of PFNA in a sensitivity analysis only. 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 describe the distribution of chemicals in the body and
pharmacodynamic relation between blood concentration and clinical
effects. Benefits from avoided adverse health effects of HFPO-DA, PFHxS
and PFBS are discussed qualitatively in this section.
As Table 42 demonstrates, only a subset of the avoided morbidity
and mortality stemming from reduced PFAS levels in drinking water can
be quantified and monetized. The monetized benefits evaluated in the
Economic Analysis for the proposed rule include changes in human health
risks associated with CVD and infant
[[Page 18704]]
birth weight from reduced exposure to PFOA and PFOS in drinking water
and RCC from reduced exposure to PFOA. 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 (2023j).
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, other cancers. EPA
discusses these benefits qualitatively in more detail below, as well as
in Section 6.2 of USEPA (2023j).
Table 42--Overview of Health Benefits Categories Considered in the Analysis of Changes in PFAS Drinking Water Levels
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Health outcome PFAS Compound \1\ \2\ \3\ Benefits analysis \4\
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Discussed Discussed
Category Endpoint PFOA PFOS PFNA PFHxS PFBS HFPO-DA quantitatively qualitatively
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Lipids.................................. Total cholesterol......... X X \e\ X X
High-density lipoprotein \5\ X \5\ X X
cholesterol (HDLC).
Low-density lipoprotein X X \5\ X X
cholesterol (LDLC).
CVD..................................... Blood pressure............ X X
Developmental........................... Birth weight.............. X X X \5\ X \5\ X
Small for gestational age X \5\ X X X
(SGA), non-birth weight
developmental.
Endocrine............................... Thyroid hormone disruption X
Hepatic................................. ALT....................... X X \5\ X X X
Immune.................................. Antibody response X X \5\ X X X
(tetanus, diphtheria).
Metabolic............................... Leptin.................... X X
Renal................................... Organ weight.............. X
Musculoskeletal......................... Osteoarthritis, bone X \5\ X X
mineral density.
Hematologic............................. Vitamin D levels, X
hemoglobin levels,
albumin levels.
Cancer.................................. RCC....................... X X
Testicular................ X X
Other..................... \5\
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
\1\ Fields marked with ``X'' indicate the PFAS compound for which there is evidence of an association with a given health outcome in epidemiological studies.
\2\ Fields marked with ``'' indicate the PFAS compound for which there is evidence of an association with a given health outcome only in toxicological studies.
\3\ Note that only PFOA and PFOS effects were modeled in the assessment of benefits under the proposed rule. PFNA was modeled only in sensitivity analyses of birth weight benefits (See
Economic Analysis Appendix K in USEPA (2023i)).
\4\ Outcomes with likely evidence of an association between a PFAS compound and a health outcome are assessed quantitatively unless (1) there is an overlap within the same outcome group (e.g.,
LDLC overlaps with total cholesterol, and SGA overlaps with low birth weight), or (2) it is not possible to link the outcome to the risk of the health effect (e.g., evidence is inconclusive
regarding the relationship between PFOS exposure and leptin levels and associated health outcomes). Such health outcomes are discussed qualitatively.
\5\ Evidence of the relationship between the PFAS compound and the health outcome is not conclusive. Note that EPA sought comments from the EPA SAB on the CVD exposure-response approach
(USEPA, 2023j). The SAB recommended that EPA evaluate how the inclusion of HDLC effects would influence results. EPA evaluated the inclusion of HDLC effects in a sensitivity analysis,
described in Appendix K.
EPA developed PK models to evaluate blood serum PFAS levels in
adults resulting from exposure to PFAS via drinking water. To date, EPA
has developed PK models for PFOA and PFOS. 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 EPA's benefits analysis, please see EPA's Proposed MCLG
documents (USEPA, 2023b; USEPA, 2023c) and Section 6.3 of USEPA
(2023j).
1. Quantified Developmental Effects
Research indicates that exposure to PFOA and PFOS is associated
with developmental effects, including infant birth weight (Verner et
al., 2015; USEPA, 2016e; USEPA, 2016f; USEPA, 2023b; USEPA, 2023c;
Negri et al., 2017; ATSDR, 2021; Waterfield et al., 2020). The route
through which the embryo and fetus are exposed prenatally to PFOA and
PFOS is maternal blood serum via the placenta. Most studies of the
association between maternal serum PFOA/PFOS and birth weight report
negative relationships (Verner et al., 2015; Negri et al., 2017;
Dzierlenga et al., 2020). EPA's PK model assumes that mothers were
exposed to PFOA/PFOS from birth to the year in which pregnancy
occurred.
EPA quantified and valued changes in birth weight-related risks
associated
[[Page 18705]]
with reductions in exposure to PFOA and PFOS in drinking water. Entry
point-specific time series of the differences between serum PFOA/PFOS
concentrations under baseline and regulatory alternatives are inputs
into this analysis. For each entry point, 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 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.
EPA also considered the potential benefits from reduced exposure to
PFNA that may be realized as a direct result of the proposed rule. The
Agency explored the birth weight impacts of PFNA in a sensitivity
analysis, using a unit PFNA reduction scenario (i.e., 1.0 ppt change)
and 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, EPA used a first-order
single-compartment model whose behavior was previously demonstrated to
be consistent with PFOA PKs in humans (Bartell et al., 2010). In
addition to the PFOA-birth weight and PFOS-birth weight effects
analyzed in the Economic Analysis, EPA examined the effect of inclusion
of PFNA-birth weight effects using estimates from two studies (Lenters
et al., 2016; Valvi et al., 2017). EPA found that inclusion of a 1.0
ppt PFNA reduction could increase annualized birth weight benefits 5.4-
7.7-fold, relative to the scenario that quantifies a 1.0 ppt reduction
in PFOA and a 1.0 ppt 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). 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.
EPA also notes that the PFNA slope factor estimates are not precise,
with 95% CIs covering wide ranges that include zero (i.e., serum PFNA
slope factor estimates are not statistically significant at 5% 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. EPA did not include
PFNA effects in the national benefits estimates for the proposed
rulemaking because of limitations associated with the UCMR 3 PFNA
occurrence data and the slope factor estimates are less precise. For
more information, see Appendix K of USEPA (2023j).
To estimate changes in birth weight resulting from reduced exposure
to PFOA and PFOS under the regulatory alternatives, 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 EPA's Proposed Maximum Contaminant Level Goal for
PFOA and PFOS in Drinking Water (USEPA, 2023b; USEPA, 2023c) and
Section 6.4 of USEPA (2023j).
Changes in serum PFOA and PFOS concentrations are calculated for
each PWS entry point during each year in the analysis period. EPA
assumes that, given long half-lives of PFOS and PFOA, any one-time
measurement during or near pregnancy is reflective of a critical window
and not subject to considerable error. 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 43,
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 (2023i). Appendix K in USEPA (2023i) presents an analysis of
birth weight risk reduction considering slope factors specific to the
first trimester.
Table 43--Serum Exposure-Birth Weight Response Estimates
------------------------------------------------------------------------
Compound g/ng/mL serum (95% CI)
------------------------------------------------------------------------
PFOA \1\....................................... -10.5 (-16.7, -4.4)
PFOS \2\....................................... -3.0 (-4.9, -1.1)
------------------------------------------------------------------------
Notes:
\1\ The serum-birth weight slope factor for PFOA is based on the main
random effects estimate from Negri et al. (2017); Steenland et al.
(2018).
\2b\ The serum-birth weight slope factor for PFOS is based on an EPA
reanalysis of Dzierlenga et al. (2020).
EPA places a cap on estimated birth weight changes in excess of 200
g, assuming that such changes in birth weight are unreasonable even as
a result of large changes in PFOA/PFOS serum concentrations. This cap
is 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).
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
students' 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).
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
[[Page 18706]]
and therefore cannot be used in the economic analysis 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 National
Center for Health Statistics (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,
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 Fitch (2010) are likely to
overestimate the benefits of birth weight changes.
Considering the discernible changes in infant mortality over the
last 30 years, EPA developed a regression analysis to estimate the
relationship between birth weight and infant mortality using the most
recently available 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, 2018). 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. EPA included several variables used in Ma
and Fitch (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, 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 to USEPA (2023i) provides details on model development and
regression results.
Table 44 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.
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,\6\ 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 (2023j).
---------------------------------------------------------------------------
\6\ 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).
Table 44--Race/Ethnicity and Gestational Age-Specific Birth Weight Marginal Effects and Odds Ratios From the
Mortality Regression Models \1\
----------------------------------------------------------------------------------------------------------------
Gestational age Marginal effect per
Race category \2\ 1,000 births (95% CI) Odds ratio (95% CI)
----------------------------------------------------------------------------------------------------------------
Non-Hispanic Black................... Extremely Preterm...... -0.20400 (-0.21910, - 0.99817 (0.99802,
0.18890). 0.99832)
Very Preterm........... -0.04580 (-0.04820, - 0.99816 (0.99804,
0.04340). 0.99827)
Moderately Preterm..... -0.01030 (-0.01080, - 0.99852 (0.99846,
0.009850). 0.99857)
Term................... -0.00453 (-0.00472, - 0.99856 (0.99851,
0.00434). 0.9986)
Non-Hispanic White................... Extremely Preterm...... -0.12160 (-0.13080, - 0.99866 (0.99855,
0.11240). 0.99878)
Very Preterm........... -0.03290 (-0.03430, - 0.9985 (0.99842,
0.03140). 0.99858)
Moderately Preterm..... -0.00677 (-0.00702, - 0.99867 (0.99863,
0.00652). 0.99872)
Term................... -0.00228 (-0.00236, - 0.99865 (0.99861,
0.00221). 0.99868)
[[Page 18707]]
Hispanic............................. Extremely Preterm...... -0.15260 (-0.16770, - 0.99835 (0.99817,
0.13750). 0.99853)
Very Preterm........... -0.03290 (-0.03510, - 0.99846 (0.99835,
0.03070). 0.99858)
Moderately Preterm..... -0.00626 (-0.00659, - 0.99856 (0.99849,
0.00592). 0.99862)
Term................... -0.00219 (-0.00229, - 0.99849 (0.99844,
0.00208). 0.99855)
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Data based on the 2016/17 and 2017/18 CDC Period Cohort Linked Birth-Infant Death Data Files obtained from
NCHS/National Vital Statistics System (NVSS). Marginal effects and odds ratios are estimated using a
regression model that also includes covariates representative of infant birth characteristics in addition to
birth weight, maternal demographic characteristics, and maternal risk factors. All effects were statistically
significant at the 5% level. Additional details are included in Appendix E to the Economic Analysis.
\2\ Gestational age categories defined as extremely preterm (<=28 weeks), very preterm (>28 weeks and <=32
weeks), moderately preterm (>32 weeks and <=37 weeks), and term (>37 weeks).
EPA weighted the race/ethnicity-specific odds ratios in Table 44 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, 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. EPA evaluated these changes at each PWS entry
point 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 EPA
used to estimate changes in birth weight, the affected population size,
and infant deaths avoided, and the number of surviving infants is
provided in Chapter 6 of USEPA (2023j).
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. 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). 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.\7\
---------------------------------------------------------------------------
\7\ The Klein and Lynch (2018) report was externally peer
reviewed by three experts with qualifications in economics and
public health sciences. 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), 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 45.
Table 45--Simulated Cost Changes for Birth Weight Increases
[$2021]
----------------------------------------------------------------------------------------------------------------
Simulated cost changes for birth weight
increases, dollars per gram ($2021) \3\
Birth weight \1\ \2\ -----------------------------------------------
+0.04 lb (+18 +0.11 lb (+50 +0.22 lb (+100
g) g) g)
----------------------------------------------------------------------------------------------------------------
2 lb (907 g).................................................... -$126.53 -$112.87 -$109.39
2.5 lb (1,134 g)................................................ -$94.88 -$84.64 -$82.03
3 lb (1,361 g).................................................. -$71.15 -$63.47 -$61.51
3.3 lb (1,497 g)................................................ -$59.86 -$53.40 -$51.75
4 lb (1,814 g).................................................. -$40.00 -$35.69 -$34.59
4.5 lb (2,041 g)................................................ -$30.00 -$26.76 -$25.93
5 lb (2,268 g).................................................. -$22.49 -$20.07 -$19.45
5.5 lb (2,495 g)................................................ -$0.93 -$0.84 -$0.84
6 lb (2,722 g).................................................. -$0.91 -$0.83 -$0.83
7 lb (3,175 g).................................................. -$0.88 -$0.80 -$0.80
8 lb (3,629 g).................................................. -$0.85 -$0.77 -$0.77
9 lb (4,082 g).................................................. $3.15 $2.87 $2.89
10 lb (4,536 g)................................................. $3.54 $3.23 $3.26
----------------------------------------------------------------------------------------------------------------
Notes:
[[Page 18708]]
\1\ Values for birth weight have been converted from lb to g.
\2\ Note that simulated medical costs increase, rather than decrease, in response to increased birth weight
changes among high birth weight infants (those greater than 8 lb). Among high birth weight infants, there is a
higher risk of birth trauma, metabolic issues, and other health problems (Klein and Lynch, 2018).
\3\ Values scaled from $2010 to $2021 using the medical care CPI (Bureau of Labor Statistics, 2021).
Tables 46 to 49 provide the health effects avoided and valuation
associated with birth weight impacts. EPA estimated that, over the
evaluation period, the proposed rule will result in an average annual
benefit from avoided reductions in birth weight from $139 million
($2021, 7% discount rate) to $178 million ($2021, 3% discount rate).
Table 46--National Birth Weight Benefits, Proposed Option
[PFOA and PFOS MCLs of 4.0 ppt and HI of 1.0]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Increase in Birth Weight (millions of 114.2 209.3 329.7 114.2 209.3 329.7
grams)...............................
Number of Birth Weight-Related Deaths 676.8 1,232.7 1,941.0 676.8 1,232.7 1,941.0
Avoided..............................
Total Annualized Birth Weight Benefits $97.36 $177.66 $279.49 $74.62 $139.01 $219.43
(Million $2021) \2\..................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
Table 47--National Birth Weight Benefits, Option 1a
[PFOA and PFOS MCLs of 4.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Increase in Birth Weight (millions of 111.7 206.3 326.9 111.7 206.3 326.9
grams)...............................
Number of Birth Weight-Related Deaths 665.4 1,214.7 1,915.4 665.4 1,214.7 1,915.4
Avoided..............................
Total Annualized Birth Weight Benefits $95.73 $175.05 $276.44 $74.66 $136.97 $217.02
(Million $2021) \2\..................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
Table 48--National Birth Weight Benefits, Option 1b
[PFOA and PFOS MCLs of 5.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Increase in Birth Weight (millions of 97.6 181.9 292.1 97.6 181.9 292.1
grams)...............................
Number of Birth Weight-Related Deaths 578.9 1,069.5 1,707.3 578.9 1,069.5 1,707.3
Avoided..............................
Total Annualized Birth Weight Benefits $83.27 $154.13 $246.43 $64.94 $120.59 $193.47
(Million $2021) \2\..................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
[[Page 18709]]
Table 49--National Birth Weight Benefits, Option 1c
[PFOA and PFOS MCLs of 10.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Increase in Birth Weight (millions of 51.0 109.2 195.3 51.0 109.2 195.3
grams)...............................
Number of Birth Weight-Related Deaths 299.5 643.3 1,140.5 299.5 643.3 1,140.5
Avoided..............................
Total Annualized Birth Weight Benefits $43.22 $92.70 $164.19 $34.18 $72.51 $125.80
(Million $2021) \2\..................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
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 EPA's Proposed Maximum Contaminant Level
Goals for PFOA and PFOS in Drinking Water, exposure to PFOA and PFOS
through drinking water contributes to increased serum PFOA and PFOS
concentrations and potentially elevated levels of total cholesterol and
elevated levels of systolic blood pressure (USEPA, 2023b; USEPA,
2023c). Changes in total cholesterol 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).
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, EPA uses the approach outlined below to
link changes in CVD risk biomarkers (i.e., cholesterol and blood
pressure) to changes in CVD risk.
For each entry point, evaluation of the changes in CVD risk
involves the following key steps:
1. Estimation of annual changes in total cholesterol 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 total cholesterol 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 total cholesterol and blood pressure in general adult
populations, 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, EPA assumed that PFOA/PFOS-related
changes in total cholesterol and blood pressure had the same effect on
the CVD risk as the changes unrelated to chemical exposure and used the
Pooled Cohort Atherosclerotic Cardiovascular Disease (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 total cholesterol as a predictor of first
hard CVD events. EPA did not identify any readily available
relationships for PFOA or PFOS and total cholesterol 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 total
cholesterol 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).
EPA identified 14 studies from which to derive slope estimates for
PFOA and PFOS associations with serum total cholesterol levels.
Appendix A to USEPA (2023i) provides further detail on the studies
selection criteria, meta-data development, meta-analysis results, and
discussion of the uncertainty and limitations inherent in EPA's
exposure-response analysis.
EPA developed exposure-response relationships between serum PFOA/
PFOS and total cholesterol 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 total cholesterol and serum PFOA or PFOS, EPA
estimated a positive increase in total cholesterol of 1.57 (95% CI:
0.02, 3.13) mg/dL per ng/mL serum PFOA (p-value=0.048), and of 0.08
(95% CI: -0.01, 0.16) mg/dL per ng/mL serum PFOS (p-value=0.064). Based
on the systematic review conducted by EPA to develop EPA's Proposed
Maximum Contaminant Level Goals for PFOA and PFOS in Drinking Water,
the available evidence supports a positive association between PFOS and
total cholesterol in the general population. For more information on
the systematic review and results, see USEPA, 2023b and USEPA, 2023c.
PFOS exposure has been linked to other cardiovascular outcomes,
such as systolic blood pressure and hypertension (Liao et al., 2020;
USEPA,
[[Page 18710]]
2023c). Because systolic blood pressure is another predictor used by
the ASCVD model, EPA included the estimated changes in blood pressure
from reduced exposure to PFOS in the CVD analysis. 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, EPA is not
including effect estimates for the serum PFOA-blood pressure
associations in the CVD analysis.
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 entry
point-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., 2023), and age-
and sex-specific time series of changes in total cholesterol 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
total cholesterol and blood pressure levels estimated using baseline
information on these biomarkers from external statistical data sources
and modeled changes in total cholesterol and blood pressure due to
conditions under the regulatory alternatives.
EPA estimated the incidence of first hard CVD events based on total
cholesterol 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. EPA
adjusted the modeled 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, 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. EPA also has 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 to USEPA (2023i) provides detailed
information on all CVD model components, computations, and sources of
data used in modeling.
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. 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 $51,173 ($2021) for the
initial event and then $31,871, $14,065, $12,569 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 $15,861 ($2021) for the initial event and then
$11,521, $748, $1,796 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, 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, 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+). 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 50 presents the resulting myocardial infarction
and ischemic stroke unit values.
Table 50--Cost of Illness-Based Value of Non-Fatal First CVD Event Used in Modeling
----------------------------------------------------------------------------------------------------------------
Present discounted value of 3-
year medical expenditures
($2021) \1\ \2\, adjusted for
Type of first non-fatal hard CVD event Age group post-acute mortality \3\
-------------------------------
3% discount 7% discount
rate rate
----------------------------------------------------------------------------------------------------------------
Myocardial Infarction (MI).................... 40-65 years..................... $105,419 $104,155
66+ years....................... 92,658 91,881
Ischemic Stroke (IS).......................... 40-65 years..................... 29,154 29,017
66+ years....................... 26,844 26,762
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Estimates of annual medical expenditures are from O'Sullivan et al. (2011);
[[Page 18711]]
\2\ Original values from O'Sullivan et al. (2011) were inflated to $2021 using the medical care CPI (Bureau of
Labor Statistics, 2021);
\3\ Post-acute myocardial infarction mortality data for those aged 40-64 years is from Thom et al. (2001);
probabilities to survive 1 year, 2 years, and 3 years after the initial event are 0.93, 0.92, and 0.90,
respectively. EPA applies these mortality values to derive the ischemic stroke value in this age group. Post-
acute myocardial infarction mortality data and post-acute IS mortality data for persons aged 65 and older are
from Li et al. (2019). For myocardial infarction, probabilities to survive 1 year, 2 years, and 3 years after
the initial event are 0.68, 0.57, and 0.49, respectively. For ischemic stroke, probabilities to survive 1
year, 2 years, and 3 years after the initial event are 0.67, 0.57, and 0.48, respectively.
Table 51 to Table 54 provide the health effects avoided and
valuation associated with CVD. EPA estimated that, over the evaluation
period, the proposed option will result in an average annual benefit
from avoided CVD cases and deaths from $421 million ($2021, 7% discount
rate) to $533 million ($2021, 3% discount rate).
Table 51--National CVD Benefits, Proposed Option
[PFOA and PFOS MCLs of 4.0 ppt and HI of 1.0]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal MI Cases Avoided.. 1,251.5 6,081.0 11,738.7 1,251.5 6,081.0 11,738.7
Number of Non-Fatal IS Cases Avoided.. 1,814.0 8,870.8 17,388.5 1,814.0 8,870.8 17,388.5
Number of CVD Deaths Avoided.......... 753.6 3,584.6 7,030.9 753.6 3,584.6 7,030.9
Total Annualized CVD Benefits (Million $111.78 $533.48 $1,051.00 $85.94 $421.10 $822.88
$2021) \2\...........................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
Table 52--National CVD Benefits, Option 1a
[PFOA and PFOS MCLs of 4.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal MI Cases Avoided.. 1,248.7 5,983.8 11,614.9 1,248.7 5,983.8 11,614.9
Number of Non-Fatal IS Cases Avoided.. 1,786.4 8,729.6 17,149.5 1,786.4 8,729.6 17,149.5
Number of CVD Deaths Avoided.......... 744.6 3,527.8 6,951.5 744.6 3,527.8 6,951.5
Total Annualized CVD Benefits (Million $110.45 $525.05 $1,035.36 $86.32 $414.45 $817.79
$2021) \2\...........................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
Table 53--National CVD Benefits, Option 1b
[PFOA and PFOS MCLs of 5.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal MI Cases Avoided.. 1,105.9 5,220.7 10,215.4 1,105.9 5,220.7 10,215.4
Number of Non-Fatal IS Cases Avoided.. 1,609.3 7,624.2 15,029.5 1,609.3 7,624.2 15,029.5
Number of CVD Deaths Avoided.......... 645.9 3,084.6 6,102.2 645.9 3,084.6 6,102.2
Total Annualized CVD Benefits (Million $99.73 $459.09 $908.82 $72.72 $362.42 $717.85
$2021) \2\...........................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
[[Page 18712]]
Table 54--National CVD Benefits, Option 1c
[PFOA and PFOS MCLs of 10.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal MI Cases Avoided.. 619.0 3,032.5 6,320.7 619.0 3,032.5 6,320.7
Number of Non-Fatal IS Cases Avoided.. 878.1 4,445.9 9,439.4 878.1 4,445.9 9,439.4
Number of CVD Deaths Avoided.......... 343.8 1,806.7 3,835.8 343.8 1,806.7 3,835.8
Total Annualized CVD Benefits (Million $51.00 $268.78 $571.32 $41.85 $212.18 $450.51
$2021) \2\...........................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
3. Quantified Kidney Cancer Effects
Data on the association between PFOA exposure and kidney cancer
(i.e., RCC) are limited but suggest 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
(California Environmental Protection Agency, 2021; USEPA, 2016e; ATSDR,
2021; USEPA, 2023b). In the PFOA HESD (USEPA, 2016e), EPA characterized
the evidence for PFOA effects on RCC as ``probable'' based on two
occupational population studies (Raleigh et al., 2014; Steenland and
Woskie, 2012) and two high-exposure community studies (Vieira et al.,
2013; Barry et al., 2013). A recent study of the relationship between
PFOA and RCC in U.S. general populations found strong evidence that
exposure to PFOA causes RCC in humans (Shearer et al., 2021). As such,
EPA selected RCC as a key outcome when assessing the health impacts of
reduced PFOA exposures.
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 entry point-specific time series of the differences
between serum PFOA concentrations under baseline and regulatory
alternatives are inputs into this analysis. For each PWS entry point,
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, EPA reviewed three
studies highlighted in the HESD for PFOA (USEPA, 2016e) 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 (California Environmental Protection Agency,
2021) and EPA's Proposed Maximum Contaminant Level Goal (MCLG) for PFOA
(USEPA, 2023b). 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 strong evidence that exposure to
PFOA causes 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, EPA relied on the
estimated time series of changes in serum PFOA concentrations (Section
6.3) and the serum-RCC exposure-response function provided by Shearer
et al. (2021): 0.00178 (ng/mL)-1. The analysis from 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)
included controls for age, sex, race, ethnicity, study center, year of
blood draw, smoking, and hypertension. Results showed a strong and
statistically significant association between PFOA and RCC. EPA
selected the exposure-response relationship from Shearer et al. (2021)
because it included exposure levels typical in the general population
and was found to have a low risk of bias based on EPA's Proposed
Maximum Contaminant Level Goal for PFOA (USEPA, 2023b).
The linear slope factor based on Shearer et al. (2021) enables
estimation of the changes in lifetime RCC risk associated with reduced
lifetime serum PFOA levels. Because baseline RCC incidence statistics
are not readily available from the NCI public use data, EPA used kidney
cancer statistics in conjunction with an assumption that RCC comprises
90% of all kidney cancer cases to estimate baseline lifetime
probability of RCC (USEPA, 2023b). EPA estimated the baseline lifetime
RCC incidence for males at 1.89% and the baseline lifetime RCC
incidence for females at 1.05%. Details of these calculations are
provided in Appendix H to USEPA (2023i).
Similar to its approach for estimating of CVD risk reductions, EPA
relies on the life table approach to estimate RCC risk reductions. The
outputs of the life table calculations are the PWS entry point-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
EPA's application of the life table to cancer benefits analyses, please
see Appendix H to USEPA (2023j).
Although the change in PFOA exposure likely affects the risk of
developing RCC beyond the end of the
[[Page 18713]]
analysis period (the majority of RCC cases manifest during the latter
half of the average individual lifespan; see Appendix H to USEPA
(2023j), EPA does not capture effects after the end of the period of
analysis, 2104. 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 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,
202a; 2020b), and the Centers for Disease Control and Prevention (CDC)
NCHS. Appendix H to USEPA (2023i) provides additional detail on the
data sources and information used in this analysis as well as baseline
kidney cancer statistics. Appendix B to USEPA (2023i) describes
estimation of the affected population.
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. EPA uses the cost of illness-based valuation to
estimate the benefits of reducing morbidity associated with RCC.
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)). Ambavane et al. (2020) found
that RCC treatment sequences using a combination of two immunotherapy
drugs as the first line medications were the most cost-effective.
Table 55 summarizes RCC morbidity cost of illness estimates derived
by 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/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. EPA notes that the second line treatment costs are not
reflected in 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, EPA valued RCC
morbidity at $251,007 ($2021) during year 1 of the diagnosis, $190,969
($2021) during year 2 of the diagnosis, and $1,596 ($2021) starting
from year 3 of the diagnosis. Additionally, 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.
Table 55--RCC Morbidity Valuation
--------------------------------------------------------------------------------------------------------------------------------------------------------
First line
First line First line adverse effect Disease
Time interval medication administration management management Total ($2018) Total ($2021)
($2018) \1\ ($2018) \1\ ($2018) \1\ ($2018) \1\ \4\
\3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Monthly cost, month 1-3 from diagnosis \1\ \5\.......... 32,485 516 78 73 33,152 35,927
Monthly cost, month 4-24 from diagnosis \2\ \6\......... 13,887 647 78 73 14,685 15,914
Monthly cost, month 25+ from diagnosis \7\.............. .............. .............. .............. 123 123 133
Annual cost, year 1 from diagnosis...................... 222,438 7,371 934 878 231,621 251,007
Annual cost, year 2 from diagnosis...................... 166,644 7,764 934 878 176,220 190,969
Annual cost, year 3+ from diagnosis..................... .............. .............. .............. 1,473 1,473 1,596
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
\1\ Ambavane et al. (2020) Table 1.
\2\ Ambavane et al. (2020) p. 41, a maximum treatment duration assumption of 2 years.
\3\ The adverse effect management costs of $1,868 in Ambavane et al. (2020) Table 1 were reported for the treatment duration. EPA used the treatment
duration of 24 months (i.e., 2 years) to derive monthly costs of $77.83.
\4\ To adjust for inflation, EPA used U.S. BLS CPI for All Urban Consumers: Medical Care Services in U.S. (City Average).
\5\ First line treatment induction.
\6\ First line treatment maintenance.
\7\ Treatment-free interval.
Tables 56 to 59 provide the health effects avoided and valuation
associated with RCC. EPA estimated that, over the evaluation period,
the proposed rule will result in an average annual benefit from avoided
RCC cases and deaths from $217 million ($2021, 7% discount rate) to
$301 million ($2021, 3% discount rate).
[[Page 18714]]
Table 56--National RCC Benefits, Proposed Option
[PFOA and PFOS MCLs of 4.0 ppt and HI of 1.0]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal RCC Cases Avoided. 1,313.6 6,872.0 17,387.8 1,313.6 6,872.0 17,387.8
Number of RCC-Related Deaths Avoided.. 308.7 1,927.8 5,049.3 308.7 1,927.8 5,049.3
Total Annualized RCC Benefits (Million $54.23 $300.56 $758.03 $45.36 $217.37 $515.89
$2021) \2\...........................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
Table 57--National RCC Benefits, Option 1a
[PFOA and PFOS MCLs of 4.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal RCC Cases Avoided. 1,289.6 6,753.3 17,147.8 1,289.6 6,753.3 17,147.8
Number of RCC-Related Deaths Avoided.. 300.5 1,895.2 4,960.4 300.5 1,895.2 4,960.4
Total Annualized RCC Benefits (Million $52.92 $295.53 $744.64 $45.09 $213.78 $508.56
$2021) \2\...........................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
Table 58--National RCC Benefits, Option 1b
[PFOA and PFOS MCLs of 5.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal RCC Cases Avoided. 1,017.6 5,681.7 14,962.1 1,017.6 5,681.7 14,962.1
Number of RCC-Related Deaths Avoided.. 235.9 1,602.1 4,317.6 235.9 1,602.1 4,317.6
Total Annualized RCC Benefits (Million $42.28 $250.60 $643.71 $36.32 $182.24 $446.80
$2021) \2\...........................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
Table 59--National RCC Benefits, Option 1c
[PFOA and PFOS MCLs of 10.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal RCC Cases Avoided. 433.5 2,903.0 8,205.4 433.5 2,903.0 8,205.4
Number of RCC-Related Deaths Avoided.. 101.1 831.8 2,406.2 101.1 831.8 2,406.2
Total Annualized RCC Benefits (Million $18.58 $131.44 $367.38 $17.34 $97.30 $260.54
$2021) \2\...........................
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
[[Page 18715]]
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized total annualized benefits in this table.
4. Key Limitations and Uncertainties in the Benefits Analysis
The section below 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 (2023j). 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 60 below presents the key limitations and
uncertainties that apply to the benefits analysis for the proposed
rule. 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 table below,
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.
Table 60--Key Limitations and Uncertainties That Apply to Benefits Analyses Considered for the Proposed PFAS
Rule
----------------------------------------------------------------------------------------------------------------
Effect on benefits
Uncertainty/assumption estimate Notes
----------------------------------------------------------------------------------------------------------------
EPA quantified benefits for three health Underestimate.............. For various reasons, EPA has not
endpoints for PFOA and PFOS. quantified the benefit of removing PFOA
and PFOS from drinking water for most of
the health endpoints PFOA and PFOS are
expected to impact. See discussion in
section C for more information about
these nonquantifiable benefits.
EPA has only quantified benefits for one Underestimate.............. Treatment technologies installed to
co-removed contaminant group (THM4). remove PFAS can also removes numerous
other contaminants, including other
unregulated PFAS, additional regulated
and unregulated DBPs, heavy metals,
organic contaminants, pesticides, among
others. These co-removal benefits may be
significant, depending on co-occurrence,
how many facilities install treatment
and which treatment option they select.
EPA has not quantified benefits for any Underestimate.............. PFHxS, PFNA, PFBS, and HFPO-DA each have
health endpoint for PFHxS, PFNA, PFBS, substantial health impacts on multiple
and HFPO-DA. health endpoints. See discussion in
section D for more information about
these nonquantifiable benefits.
The analysis considers PFOA/PFOS Overestimate............... Some SDWIS population served estimates
concentrations from NTNCWSs. for NTNCWSs represent the both the
population that has regular exposure to
the NTNCWS' drinking water (e.g., the
employees at a location) and the peak
day transient population (e.g.,
customers) who have infrequent exposure
to the NTNCWS' drinking water.
Estimating the demographic distribution
and the share of daily drinking water
consumption for these two types of
NTNCWS populations would be difficult
across many of the industries which
operate NTNCWSs. The inclusion of NTNCWS
results is an overestimate of benefits
because daily drinking water consumption
for these populations is also modeled at
their residential CWS.
EPA assumes that the effects of PFOA and Uncertain.................. The exposure-response functions used in
PFOS exposures are independent. benefits analyses assume that the
effects of serum PFOA/PFOS on the health
outcomes considered are independent and
therefore additive. Due to limited
evidence, EPA does not consider
synergies or antagonisms in PFOA/PFOS
exposure-response.
The derivation of PFOA/PFOS exposure- Overestimate............... The new data and EPA's proposed MCLGs
response functions for the relationship indicate that the levels at which
between PFOA/PFOS serum and associated adverse health effects could occur are
health outcomes assumes that there are much lower than previously understood
no threshold serum concentrations below when EPA issued the 2016 health
which effects do not occur. advisories for PFOA and PFOS (70 parts
per trillion or ppt)--including near
zero for certain health effects.
Therefore, the exposure-response
functions used in benefits analyses
assume that there are no threshold serum
concentrations below which effects do
not occur. This could result in a slight
overestimate of benefits for certain
health endpoints.
The exposure-response functions used to Overestimate............... Analyses evaluating the evidence on the
estimate risk assume causality. associations between PFAS exposure and
health outcomes are ongoing and EPA has
not conclusively determined causality.
As described in Section 6.2, EPA modeled
health risks from PFOA/PFOS exposure for
endpoints for which the evidence of
association was found to be likely.
These endpoints include birth weight,
total cholesterol, and RCC. While the
evidence supporting causality between
DBP exposure and bladder cancer has
increased since EPA's Stage 2 DBP Rule
(NTP, 2021; Weisman et al., 2022),
causality has not yet been conclusively
determined (Regli et al., 2015).
[[Page 18716]]
The analysis assumes that quantified Uncertain.................. EPA did not model birth weight, CVD, RCC,
benefits categories are additive. and bladder cancer benefits jointly, in
a competing risk framework. Therefore,
reductions in health risk in a specific
benefits category do not influence
health risk reductions in another
benefits category. For example, lower
risk of CVD and associated mortality
implies a larger population that could
benefit from cancer risk reductions,
because cancer incidence grows
considerably later in life.
The analysis does not take into account Underestimate.............. The benefits analysis does not reflect
population growth and other changes in the effects of growing population that
long-term trends. may benefit from reduction in PFOA/PFOS
exposure. Furthermore, EPA uses present-
day information on life expectancy,
disease, environmental exposure, and
other factors, which are likely to
change in the future.
For PWSs with multiple entry points, the Uncertain.................. Data on the populations served by each
analysis assumes a uniform population entry point are not available and EPA
distribution across the entry points. therefore uniformly distributes system
population across entry points. Effects
of the regulatory alternative may be
greater or smaller than estimated,
depending on actual populations served
by affected entry points. For one large
system serving more than one million
customers EPA has sufficient data on
entry point flow to proportionally
assign effected populations.
EPA does not characterize uncertainty Uncertain.................. EPA did not quantitatively characterize
associated with the Value of the uncertainty for the VSL reference
Statistical Life (VSL) reference value value and income elasticity. Because the
or VSL elasticity. economic value of avoided premature
mortality comprises the majority of the
overall benefits estimate, not
considering uncertainty surrounding the
VSL is a limitation.
----------------------------------------------------------------------------------------------------------------
E. Nonquantifiable Benefits of PFOA and PFOS Exposure Reduction
In this section 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 proposed NPDWR, in
addition to the benefits that EPA has quantified. 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 EPA has quantified. The evidence for these adverse
health effects is briefly summarized below.
EPA identified a wide range of potential health effects associated
with exposure to PFOA and PFOS using five comprehensive Federal
government documents that summarize the recent literature on PFAS
(mainly PFOA and PFOS) exposure and its health impacts: EPA's Health
Effects Support Documents for PFOA and PFOS, hereafter referred to as
EPA HESDs (USEPA, 2016e; USEPA, 2016f); EPA's Proposed Maximum
Contaminant Level Goals for PFOA and PFOS in Drinking Water (USEPA,
2023b; USEPA, 2023c); and the U.S. Department of Health and Human
Services Agency for Toxic Substances and Disease Registry's (ATSDR)
Toxicological Profile for Perfluoroalkyls (ATSDR, 2021). Each source
presents comprehensive literature reviews on adverse health effects
associated with PFOA and PFOS. EPA notes that the National Academies of
Science, Engineering, and Medicine 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 proposed
rulemaking.
The most recent literature reviews on PFAS exposures and health
impacts, which are included in EPA's Proposed Maximum Contaminant Level
Goal for PFOA and PFOS in Drinking Water (USEPA, 2023b; USEPA, 2023c),
discuss the weight of evidence supporting associations between PFOA or
PFOS exposure with health outcomes as indicative (likely), inadequate,
or suggestive. For the purposes of the reviews conducted to develop the
proposed MCLGs, an association is deemed indicative when findings are
consistent and supported by substantial evidence. 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 is suggestive if findings are consistent but supported by a
limited number of studies or analyses, or only observed in certain
populations or species. Note that these determinations are based on
information available as of February 2022.
Developmental effects: Exposure to PFOA and PFOS during
developmental life stages is linked to developmental effects including
but not limited to the infant birth weight effects that EPA quantified.
Other developmental effects include SGA, birth length, head
circumference at birth, and other effects (Verner et al., 2015; USEPA,
2016e; USEPA, 2016f; Negri et al., 2017; ATSDR, 2021; Waterfield et
al., 2020; USEPA, 2023b; USEPA, 2023c). 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). Epidemiology evidence related to PFOA/PFOS exposure was mixed;
some studies reported increased risk of SGA with PFOA/PFOS exposure,
while other studies observed null results (USEPA, 2023b; USEPA, 2023c).
For instance, some studies suggested a potentially positive association
between PFOA exposure and SGA (Govarts et al., 2018; Lauritzen et al.,
2017; Y. Wang et al., 2016; USEPA, 2023b). For PFOS, few patterns were
discernible, and overall confidence of an association between the two
factors was low (USEPA, 2023c). Similarly, ATSDR found no strong
associations between PFOA or PFOS exposure and increases in risk of SGA
infants (ATSDR, 2021). Toxicology studies on PFOS exposures in rodents
reported effects on multiple developmental toxicity endpoints
(including increased mortality, decreased BW and BW change, skeletal
and soft tissue effects, and delayed eye-opening) (USEPA, 2023c). For
additional details on developmental studies and their individual
outcomes, see Chapter 3.4.1 (Developmental) in USEPA (2023b) and USEPA
(2023c).
[[Page 18717]]
Cardiovascular effects: In addition to the CVD effects that EPA
quantified associated with changes in total cholesterol and blood
pressure from exposure to PFOA or PFOS (see Section 6.2 of USEPA
(2023j)), available evidence suggests an association between exposure
to PFOA or PFOS and increased LDLC (ATSDR, 2021; USEPA, 2023b; USEPA,
2023c). High levels of LDLC 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 children (USEPA, 2023b; USEPA, 2023c). 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). Studies conducted
on PFOS showed evidence of an association between exposure and LDLC
levels in adults. For instance, all five epidemiology studies evaluated
in EPA's Proposed MCLGs for PFOA and PFOS in Drinking Water reported
positive associations, although the association was only statistically
significant in obese women. Available evidence regarding the impact of
PFOA and PFOS exposure on pregnant women was too limited for EPA to
determine an association (ATSDR, 2021; USEPA, 2023b; USEPA, 2023c). For
additional details on LDLC studies and their individual outcomes, see
Chapter 3.4.4 (Cardiovascular) in USEPA (2023b) and USEPA (2023c).
Liver effects: Several biomarkers can be used clinically to
diagnose liver diseases, including the ALT. High levels of serum ALT
may indicate liver damage. Epidemiology data provides consistent
evidence of a positive association between PFOS/PFOA exposure and ALT
levels in adults (ATSDR, 2021; USEPA, 2023b; USEPA, 2023c). 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, 2023b). There
is also consistent epidemiology evidence of associations between PFOS
and elevated ALT levels, although the associations observed were not
large in magnitude. Study results showed inconsistent evidence on
whether the observed changes led to changes in specific liver disease
(USEPA, 2023c).
Associations between PFOS/PFOA exposure and ALT levels in children
were less consistent than in adults (USEPA, 2023b; USEPA, 2023c), and
PFOA toxicology studies showed increases in ALT and other liver enzymes
across multiple species, sexes, and exposure paradigms (USEPA, 2023b).
Toxicology studies on the impact of PFOS exposure on ALT in rodents
also reported increases in ALT and other liver enzyme levels in
rodents, though these increases were modest (USEPA, 2023c). For
additional details on the ALT studies and their individual outcomes,
see Section 3.4.2 (Hepatic) in USEPA (2023b) and USEPA (2023c).
Immune effects: Proper antibody response helps maintain the immune
system by recognizing and responding to antigens. Some evidence
suggests 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, childhood, and adult serum concentrations of PFOA (USEPA,
2023b). It is less clear whether PFOA exposure impacts antibody
response to vaccinations other than tetanus and diphtheria (ATSDR,
2021; USEPA, 2023b). Epidemiology evidence suggests that children with
preexisting immunological conditions are particularly susceptible to
immunosuppression associated with PFOA exposure (USEPA, 2023b).
Available studies supported an association between PFOS exposure and
immunosuppression in children, where increased PFOS serum levels were
associated with decreased antibody production (USEPA, 2023c). However,
the association between PFOS exposure and immunosuppression was not
apparent in adults (USEPA, 2023c).\8\ Other potential associations with
PFOS exposure with a high degree of uncertainty included asthma and
infectious diseases (e.g., the common cold, lower respiratory tract
infections, pneumonia, bronchitis, ear infections) (USEPA, 2023c).
Animal toxicology study evidence suggested that PFOA or PFOS exposure
results in effects similarly indicating immune suppression, such as
reduced response of immune cells (e.g., natural killer cell activity
and immunoglobulin production) (USEPA, 2023b; USEPA, 2023c). For
additional details on antibody studies and their individual outcomes,
see Section 3.4.3 (Immune) in USEPA (2023b) and USEPA (2023c).
---------------------------------------------------------------------------
\8\ This may be due to the lack of high-quality data at present.
---------------------------------------------------------------------------
Endocrine effects: Elevated thyroid hormone levels can accelerate
metabolism and cause irregular heartbeat; low levels of thyroid hormone
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, 2023b; USEPA, 2023c).
Epidemiology studies reported inconsistent evidence regarding
associations between PFOA or PFOS exposure and general endocrine
outcomes, such as thyroid disease, hypothyroidism, and hypothyroxinemia
(USEPA, 2023b; USEPA, 2023c). However, studies reported suggestive
evidence of positive associations for thyroid stimulating hormone (TSH)
in adults, and the thyroid hormone thyroxine (T4) in children (USEPA,
2023b; USEPA, 2023c). Toxicology studies indicated that PFOA and PFOS
exposure leads to decreases in thyroid hormone levels \9\ and adverse
effects to the endocrine system (ATSDR, 2021; USEPA, 2023b; USEPA,
2023c). Despite uncertainty around the applicability of animal studies
in this area, changes in thyroid hormone levels in animals did indicate
adverse effects after PFOS and PFOA exposure that is relevant to humans
(USEPA, 2023b; USEPA, 2023c). For additional details on endocrine
effects studies and their individual outcomes, see Chapter C.2
(Endocrine) in USEPA (2023k) and USEPA (2023l).
---------------------------------------------------------------------------
\9\ Decreased thyroid hormone levels are associated with effects
such as changes in thyroid and adrenal gland weight, hormone
fluctuations, and organ histopathology (ATSDR, 2021; USEPA, 2023b;
USEPA, 2023c).
---------------------------------------------------------------------------
Metabolic effects: Leptin is a hormone that controls hunger, and
high leptin levels are associated with obesity, overeating, and
inflammation (e.g., of adipose tissue, the hypothalamus, blood vessels,
and other areas). Evidence suggests a direct association between PFOA
exposure and leptin levels in the general adult population (ATSDR,
2021; USEPA, 2023b). Based on a review of 69 human epidemiology
studies, evidence of associations between PFOS and metabolic outcomes
appears inconsistent, but in some studies, suggestive evidence was
observed between PFOS exposure and leptin levels (USEPA, 2023c).
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 Chapter C.3
[[Page 18718]]
(Metabolic/Systemic) in USEPA (2023k) and USEPA (2023l).
Reproductive effects: Studies of the reproductive effects from
PFOA/PFOS exposure have focused on associations between exposure to
these pollutants and increased risk of gestational hypertension and
preeclampsia in pregnant women (ATSDR, 2021; USEPA, 2023b; USEPA,
2023c). Gestational hypertension (high blood pressure during pregnancy)
can lead to fetal health outcomes 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 lead
to fetal problems and maternal complications. The epidemiology evidence
yields mixed (positive and non-significant) associations, with some
suggestive evidence supporting positive associations between PFOA/PFOS
exposure and both preeclampsia and gestational hypertension (ATSDR,
2021; USEPA, 2023b; USEPA, 2023c). For additional details on
reproductive effects studies and their individual outcomes, see Chapter
C.1 (Reproductive) in USEPA (2023k) and USEPA (2023l).
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. There is
limited evidence from studies pointing to effects of PFOS on skeletal
size (height), lean body mass, and osteoarthritis (USEPA, 2023c).
Epidemiology evidence suggested 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, 2023b). Evidence from four PFOS 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, 2023c). Some studies found that
PFOA/PFOS exposure was linked to osteoarthritis, in particular among
women under 50 years of age (ATSDR, 2021). 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
Chapter C.8 (Musculoskeletal) in USEPA (2023k) and USEPA (2023l).
Cancer Effects: In EPA's Proposed Maximum Contaminant Level Goal
for PFOA in Drinking Water, the Agency evaluates the evidence for
carcinogenicity of PFOA that has been documented in both
epidemiological and animal toxicity studies (USEPA, 2023b). The
evidence in epidemiological studies is primarily based on the incidence
of kidney and testicular cancer, as well as some evidence of breast
cancer, which is most consistent in genetically susceptible
subpopulations. 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, 2023b). 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, 2023b). EPA's benefits analysis
for avoided RCC cases from reduced PFOA exposure is discussed in
Section XII.D of this preamble and in Section 6.6 of USEPA (2023j).
In EPA's Proposed Maximum Contaminant Level Goal for PFOS in
Drinking Water, the Agency evaluates the evidence for carcinogenicity
of PFOS and concluded that several epidemiological studies and a single
chronic cancer bioassay comprise the evidence database for the
carcinogenicity of PFOS (USEPA, 2023c). The available epidemiology
studies report elevated risk of bladder, prostate, kidney, and breast
cancers after chronic PFOS exposure. However, in developing this
proposal, EPA did not identify information to quantify the benefits
that reducing PFOS would have on reducing various cancers in humans.
The sole animal chronic cancer bioassay study provide support for
multi-site tumorigenesis in male and female rats. 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.''
EPA anticipates there are additional nonquantifiable benefits
related to potential testicular, bladder, prostate, kidney, and breast
carcinogenic effects summarized above. For additional details on cancer
studies and their individual outcomes, see Chapter 3.5 (Cancer) in
USEPA (2023b) and USEPA (2023c).
After assessing the available health and economic information, 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 for this assessment and readily
available data for monetization, namely cardiovascular effects,
developmental effects, and carcinogenic effects. Several other health
endpoints that had indicative evidence of associations with exposure to
PFOA or PFOS have not been selected for the Economic Analysis for the
reasons below.
While immune effects had indicative evidence of
associations with exposure to PFOA or PFOS, EPA did not identify the
necessary information to connect the measured biomarker responses
(i.e., decrease in antibodies) to a clinical effect that could be
valued in the Economic Analysis;
Evidence indicates associations between PFOA and PFOS
exposure and hepatic effects, such as increases in ALT. However, EPA is
not able to model this health endpoint because ALT is a non-specific
biomarker. Similar challenges with non-specificity of the biomarkers
representing metabolic effects (i.e., leptin) and musculoskeletal
effects (i.e., bone density) prevented economic analysis of these
endpoints;
There is indicative evidence of association with exposure
to PFOA for testicular cancer; however, the available slope factor
implied small changes in the risk of this endpoint. Furthermore,
testicular cancer is rarely fatal which implies low expected economic
value of reducing this risk because Value of Statistical Life is the
driver of economic benefits evaluated in the Economic Analysis;
Finally, other health endpoints, such as SGA and LDLC
effects, were not modeled in the Economic Analysis because they overlap
with effects that EPA did model. For example, infants that are
considered SGA are often born at low birth weight or receive similar
care to infants born at low birth weight. LDLC is a component of total
cholesterol and could not be modeled separately as EPA used total
cholesterol as an input to the ASCVD model to estimate CVD outcomes.
[[Page 18719]]
F. Nonquantifiable Benefits of Removal of PFAS Included in the Proposed
Regulation and Co-Removed PFAS
EPA also qualitatively summarized the potential health benefits
resulting from reduced exposure to PFAS other than PFOA and PFOS in
drinking water. The proposed option and all regulatory alternatives are
expected to result in benefits that have not been quantified. Treatment
responses implemented to reduce PFOA and PFOS exposure under the
proposed option and Options 1a-c 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 Section VII
of this preamble and USEPA (2023e). The proposed option will require
reduced exposure to PFHxS, HFPO-DA, PFNA, and PFBS to below their
respective HBWCs. EPA also expects that compliance actions taken under
the proposed rule will remove additional unregulated co-occurring PFAS
contaminants where present because the BATs have been demonstrated to
co-remove additional PFAS (see Section XI of this preamble for more
information). EPA identified a wide range of potential health effects
associated with exposure to PFAS compounds other than PFOA and PFOS
using documents that summarize the recent literature on exposure and
associated health impacts: ATSDR's Toxicology Profile for
Perfluoroalkyls (ATSDR, 2021); EPA's summary of HFPO-DA toxicity
(USEPA, 2021b); publicly available draft IRIS assessments for PFBA, and
PFHxA (USEPA, 2021k; USEPA, 2022h); a human health assessment for 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 compounds and associated health effects are
based on information available as of May 2022, and that the
finalization of the IRIS assessments may result in slight changes to
the discussion of evidence. Additional discussion of the evidence from
epidemiology and toxicology studies for associations between different
categories of health effects and exposure to additional PFAS can be
found in Section 6.2 of USEPA (2023j).
Developmental effects: Toxicology and/or epidemiology studies
observed evidence of associations with decreased birth weight and/or
other developmental effects and exposure to PFBA, perfluorodecanoic
acid (PFDA), PFHxS, HFPO-DA, PFNA, and PFBS. Specifically, data from
animal toxicological studies support this association for PFBS, PFBA,
and HFPO-DA while both animal toxicological and epidemiological studies
support this association for PFDA and PFNA (ATSDR 2021) although some
mixed results have been found for birth outcomes, particularly birth
weight. In general, epidemiological studies did not find associations
between perfluoroalkyl exposure and adverse pregnancy outcomes
(miscarriage, preterm birth, or gestational age) for PFHxS, PFNA, PFDA,
or perfluoroundecanoic acid (PFUnA) (ATSDR, 2021; NASEM, 2022).
Cardiovascular effects: Epidemiology and toxicology studies
observed evidence of associations between PFNA or PFDA exposures and
total cholesterol, LDLC, and HDLC. Evidence for associations between
PFNA exposure and serum lipids 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 (ATSDR, 2021).
Similarly inconsistent evidence was observed for PFDA (ATSDR,
2021). Other PFAS for which lipid outcomes were examined in toxicology
or epidemiology studies observed limited to no evidence of
associations. Studies have examined possible associations between
various PFAS and blood pressure in humans or heart histopathology in
animals. However, studies did not find suggestive or likely evidence
for any PFAS in this summary except for PFOS.
Hepatic effects: Toxicology studies reported associations between
exposure to PFAS compounds (PFBA, PFDA, PFHxA, PFHxS, HFPO-DA, and
PFBS) and hepatotoxicity following inhalation, oral, and dermal
exposure in animals. The results of these studies provide strong
evidence that the liver is a sensitive target of PFHxS, PFNA, PFDA,
PFUnA, PFBS, PFBA, perfluorododecanoic acid (PFDoDA), and PFHxA
toxicity. Observed effects in rodents include increases in liver
weight, hepatocellular hypertrophy, hyperplasia, and necrosis (ATSDR,
2021; USEPA, 2021b; USEPA, 2022h). Increases in serum enzymes (such as
ALT) and decreases in serum bilirubin were observed in one
epidemiologic study of PFHxS, and mixed effects were observed for
epidemiologic studies for PFNA (ATSDR, 2021).
Immune effects: Epidemiology studies have reported evidence of
associations between PFDA and PFHxS exposure and antibody response to
tetanus or diphtheria. There is also some limited evidence for
decreased antibody response for PFNA, PFUnA, and PFDoDA, although many
of the studies did not find associations for these compounds. 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 conflicting study results. The small
number of studies investigating immunotoxicity in humans following
exposure to PFHpA and PFHxA did not find associations (ATSDR, 2021).
Toxicology studies have reported evidence of associations between HFPO-
DA and immune-related endpoints in animals (USEPA, 2021b). No
laboratory animal studies were identified for PFUnA, PFHpA, PFDoDA, or
perfluorooctane sulfonamide (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, PFBA,
and PFDA. A study on PFNA found decreases in spleen and thymus weights
and alterations in splenic lymphocyte phenotypes (ATSDR, 2021).
Endocrine effects: Epidemiology studies have observed associations
between serum PFHxS, PFNA, PFDA, and PFUnA and TSH, triiodothyronine
(T3), or thyroxine (T4) levels or thyroid disease, however the results
are not consistent across studies and a large number of studies have
not found associations (ATSDR, 2021; NASEM, 2022). Toxicology studies
have reported associations with thyroid hormone disruption in animals
for PFBA, PFHxA, and PFBS (USEPA, 2021a; 2021k; USEPA, 2022h).
Metabolic effects: Epidemiology and toxicology studies have
examined possible associations between various PFAS and metabolic
effects, including leptin, BW, or body fat in humans or animals (ATSDR,
2021). However, evidence of associations was not suggestive or likely
for any PFAS in this summary except for PFOA. Evidence did not include
changes such as BW gain, pup BW, or other developmentally focused
weight outcomes (ATSDR, 2021; NASEM, 2022).
Renal effects: A small number of epidemiology studies with
inconsistent results evaluated possible associations between PFHxS,
PFNA, PFDA, PFBS, PFDoDA, or PFHxA and renal functions
[[Page 18720]]
(including estimated glomerular filtration rate and increases in uric
acid levels) (ATSDR, 2021; NASEM 2022). Toxicology studies have not
observed impaired renal function or morphological damage following
exposure to PFHxS, PFDA, PFUnA, PFBS, PFBA, PFDoDA, or PFHxA.
Associations with kidney weight in animals were observed for HFPO-DA
and PFBS (ATSDR, 2021; USEPA, 2021b; USEPA, 2021a).
Reproductive effects: A small number of epidemiology studies with
inconsistent results evaluated possible associations between PFHxS,
PFNA, PFUnA, PFDoDA, or PFHxA exposure and reproductive hormone levels
(ATSDR, 2021). Some associations between PFAS (PFHxS, PFNA, or PFDA)
exposures and sperm parameters have been observed. 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 via 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). 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, PFHxS or PFDoDA, and no histological alterations were
observed for PFBS, PFHxS 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).
Musculoskeletal effects: Epidemiology studies observed evidence of
associations between PFNA or PFHxS and musculoskeletal effects
including osteoarthritis and bone mineral density, but data are limited
to two studies (ATSDR, 2021). Epidemiology studies reported limited to
no evidence of associations between exposure to PFDA and
musculoskeletal effects. Toxicology studies reported no morphological
alterations in bone or skeletal muscle in animals exposed to PFBA,
PFHxA, PFHxS, or PFBS (ATSDR, 2021).
Hematological effects: A single epidemiologic study reported on
blood counts in pregnant Chinese women exposed to PFHxA and observed no
correlations with any of the hematological parameters evaluated (total
white blood cell counts, red blood cell (RBC) counts, and hemoglobin)
(USEPA, 2022h). 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 higher doses
of PFHxS, PFDA, PFUnA, PFBS, PFBA, PFDoDA, or PFHxA (ATSDR, 2021).
Toxicology studies observed evidence of association between HFPO-DA
exposure and hematological effects including decreases in RBC number,
hemoglobin, and percentage of RBCs in the blood (USEPA, 2021b).
Other non-cancer effects: A limited number of epidemiology and
toxicology studies have examined possible associations between other
PFAS and dermal, ocular, and other non-cancer effects. However,
evidence of associations was not considered to be suggestive or likely
for any PFAS compound in this summary except for PFOA and PFOS (ATSDR,
2021; USEPA, 2021a; USEPA, 2021k; USEPA, 2022h).
Cancer effects: A small number of epidemiology studies reported
limited associations between exposure to multiple PFAS (i.e., PFHxS,
PFDA, PFUnA, and FOSA) and cancer effects. No consistent associations
were observed for breast cancer risk for PFHxS, 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).
No associations between exposure to PFHxS, PFNA, PFDA, or PFUnA,
individually and prostate cancer risk were observed. However, among men
with a first-degree relative with prostate cancer, associations were
observed for PFHxS, PFDA, and PFUnA, but not for PFNA (ATSDR, 2021).
Epidemiological studies examining potential cancer effects were not
identified for PFBS, PFBA, or PFHxA (ATSDR, 2021). Aside from a study
that suggested an increased incidence of liver tumors in rats exposed
to high doses of HFPO-DA, toxicology studies reported no evidence of
associations between exposure to PFDA or PFHxA and risk of cancer
(ATSDR, 2021; USEPA, 2021b).
Coronavirus Disease 2019 (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% Confidence Interval (CI): 1.09, 2.87] after adjustment for age,
sex, sampling site, and interval between blood sampling and diagnosis.
However, the study design does not allow for causal determinations.
A case-control study showed increased risk for COVID-19 infection
with high urinary PFAS (including PFOA, PFOS, PFHxA, PFHpA, PFHxS,
PFNA, PFBS, PFDA, PFUnA, PFDoDA, perfluorotridecanoic acid [PFTrDA],
and perfluorotetradecanoic acid [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 sum 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, perfluoropentanoic acid
[PFPeA], PFHxA, and PFHpA) via drinking water in Veneto, Italy.
Overall, results may indicate a general immunosuppressive effect of
PFAS and/or increased COVID-19 respiratory toxicity due to a
concentration of PFBA in the lungs, however the study design precludes
causal determinations.
Although these studies provide a suggestion of possible
associations, the body of evidence does not permit any conclusions
about the relationship between COVID-19 infection, severity, or
mortality, and exposures to PFAS.
G. Benefits Resulting From Disinfection By-Product Co-Removal
As part of its health risk reduction and cost analysis, 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 proposed PFAS NPDWR, co-
occurring chemical contaminants such as SOCs, VOCs, and DBP precursors.
In this section, EPA presents a quantified estimate of the reductions
in DBP formation potential that are likely to occur as a result of
compliance with the proposed PFAS NPDWR. The methodology detailed below
and in Section 6.7.1 of USEPA (2023j) 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 EPA's approach
[[Page 18721]]
and edits based on their recommendations for clarity and completeness
are reflected in the following analysis and discussion. Some peer
reviewer comments suggested EPA provide additional baseline data
summaries for TOC and THM4 occurrence information. EPA intends to
evaluate and potentially include these additional summaries in the EA
for the final rule.
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. EPA regulates 11 individual DBPs from three subgroups: THM4,
five haloacetic acids (HAA5), and two inorganic compounds (bromate and
chlorite) under the Stage 2 Disinfectants and Disinfection Byproducts
Rule (USEPA, 2006a). 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 (2023j). 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 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 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 ppt) 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
trihalomethanes (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. 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 haloacetic acid precursors (Cheng et
al., 2005; Dastgheib et al., 2004; Iriarte-Velasco et al., 2008;
Summers et al., 2013; Cuthbertson et al., 2019; L. 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 Economic
Analysis, 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 EPA's co-removal benefits analysis was 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 proposed 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
mortality from baseline to regulatory alternative levels, using the
Value of a Statistical Life and cost of illness measures, respectively.
EPA expects PWSs that exceed the PFAS MCLs to consider both
treatment and non-treatment options to achieve compliance with the
drinking water standard. EPA assumes that the populations served by
systems with entry points expected to install GAC based on the
compliance forecast detailed in Section 5.3 of USEPA (2023j) will
receive the DBP exposure reduction benefits. 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 EPA assumed no additional DBP benefits for an
estimated percentage of systems that elect this compliance option.
Lastly, 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. EPA also assumes that the PWSs in
this analysis use chlorine only for disinfection and have conventional
treatment in place prior to installation of GAC technology.
EPA used the relationship between median raw water TOC levels and
changes in THM4 levels estimated in the 1998 DBP Information Collection
[[Page 18722]]
Rule to estimate changes in THM4 concentrations in the finished water
of PWSs fitted with GAC treatment. For more detail on the approach EPA
used to apply changes in THM4 levels to PWSs treating for PFAS under
the proposed rule, please see Section 6.7 of USEPA (2023j).
EPA models a scenario where reduced exposures to THM4 begin in
2026. Therefore, 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.,
prior to 2026) and to reduced THM4 levels from 2026 through 2104.
Rather than modeling individual locations, 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, EPA used national-level population estimates to distribute
the SDWIS populations based on single-year age and sex and to grow the
age- and sex-specific populations to future years. Appendix B to USEPA
(2023j) 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 ten thousand 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.
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.
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 is 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 (2023j). 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.
EPA uses the Value of a Statistical Life to estimate the benefits
of reducing mortality associated with bladder cancer in the affected
population. EPA uses the cost of illness-based valuation to estimate
the benefits of reducing morbidity associated with bladder cancer.
Specifically, EPA used bladder cancer treatment-related medical care
and opportunity cost estimates from Greco et al. (2019). Table 61 shows
the original cost of illness estimates from Greco et al. (2019), along
with the values updated to $2021 used in this analysis.
Table 61--Bladder Cancer Morbidity Valuation
----------------------------------------------------------------------------------------------------------------
Cost in Cost in
Cost in first subsequent Cost in first subsequent
Bladder cancer subtype \1\ Type of cost year ($2010) years ($2010) year ($2021) years ($2021)
\2\ \2\ \c\ \3\
----------------------------------------------------------------------------------------------------------------
Non-invasive.................. Medical care.... 9,133 916 12,350 1,239
Opportunity cost 4,572 24 5,921 31
---------------------------------------------------------------
Total cost... 13,705 941 18,272 1,270
----------------------------------------------------------------------------------------------------------------
Invasive...................... Medical care.... 26,951 2,455 36,445 3,320
Opportunity cost 10,513 77 13,616 100
---------------------------------------------------------------
Total cost... 37,463 2,532 50,061 3,420
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ The estimates for non-invasive bladder cancer subtype were used to value local, regional, and unstaged
bladder cancer morbidity reductions, while the estimates for the invasive bladder cancer subtype were used to
value distant bladder cancer morbidity reductions.
\2\ The estimates come from Greco et al. (2019).
\3\ To adjust for inflation, EPA used U.S. BLS CPI for All Urban Consumers: Medical Care Services in U.S. (City
Average).
Table 62 to 65 presents the estimated changes in bladder cancer
cases and excess bladder cancer mortality from exposure to THM4 due to
implementation of GAC treatment by option. EPA estimated that, over the
evaluation period, the proposed rule will result in an average annual
benefit from avoided bladder cancer cases and deaths from $131 million
($2021, 7% discount rate) to $221 million ($2021, 3% discount rate).
[[Page 18723]]
Table 62--National Bladder Cancer Benefits, Proposed Option
[PFOA and PFOS MCLs of 4.0 ppt and HI of 1.0]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal Bladder Cancer 4,079.1 5,238.6 6,475.3 4,079.1 5,238.6 6,475.3
Cases Avoided........................
Number of Bladder Cancer-Related 1,436.0 1,844.4 2,280.0 1,436.0 1,844.4 2,280.0
Deaths Avoided.......................
Total Annualized Bladder Cancer $173.09 $221.30 $273.62 $102.08 $130.63 $161.56
Benefits (Million $2021) \2\.........
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized annualized benefits in this table.
Table 63--National Bladder Cancer Benefits, Option 1a
[PFOA and PFOS MCLs of 4.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal Bladder Cancer 4,066.1 5,219.4 6,488.8 4,066.1 5,219.4 6,488.8
Cases Avoided........................
Number of Bladder Cancer-Related 1,431.5 1,837.6 2,284.9 1,431.5 1,837.6 2,284.9
Deaths Avoided.......................
Total Annualized Bladder Cancer $171.72 $220.48 $274.24 $101.34 $130.15 $161.56
Benefits (Million $2021) \2\.........
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized annualized benefits in this table.
Table 64--National Bladder Cancer Benefits, Option 1b
[PFOA and PFOS MCLs of 5.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal Bladder Cancer 3,342.7 4,334.3 5,382.5 3,342.7 4,334.3 5,482.5
Cases Avoided........................
Number of Bladder Cancer-Related 1,176.8 1,526.0 1,895.3 1,176.8 1,526.0 1,895.3
Deaths Avoided.......................
Total Annualized Bladder Cancer $141.17 $183.10 $227.85 $83.31 $108.08 $135.37
Benefits (Million $2021) \2\.........
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized annualized benefits in this table.
Table 65--National Bladder Cancer Benefits, Option 1c
[PFOA and PFOS MCLs of 10.0 ppt]
[Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
Benefits category 5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ benefits \1\ \1\ benefits \1\
----------------------------------------------------------------------------------------------------------------
Number of Non-Fatal Bladder Cancer 1,615.9 2,175.5 2,807.4 1,615.9 2,175.5 2,807.4
Cases Avoided........................
Number of Bladder Cancer-Related 568.9 766.0 988.6 568.9 766.0 988.6
Deaths Avoided.......................
Total Annualized Bladder Cancer $68.26 $91.90 $118.64 $40.29 $54.25 $70.10
Benefits (Million $2021) \2\.........
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 72. This range does not include the uncertainty described in Table 60.
\2\ See Table 70 for a list of the nonquantifiable benefits, and the potential direction of impact these
benefits would have on the estimated monetized annualized benefits in this table.
[[Page 18724]]
H. Comparison of Costs and Benefits
This section provides a comparison of the costs and benefits of the
proposed rule, as described in Chapter 7 of the Economic Analysis.
Included here are estimates of total quantified annualized costs and
benefits for the proposed option and regulatory alternatives
considered, as well as considerations for the nonquantifiable costs and
benefits. EPA notes that it cannot make determinations as to whether
the costs are justified by the benefits based on quantified costs and
benefits alone, as SDWA 1412(b)(3)(C)(I) and (II) mandates that the
Agency must consider nonquantifiable benefits.
The incremental cost is the difference between quantified costs
that will be incurred if the proposed rule is enacted over and above
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 proposed rule.
Table 66 provides the incremental quantified costs and benefits of
the proposed option at both a 3 percent and a 7 percent discount rate
in 2021 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
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 costs, benefits, and PFAS occurrence,
as detailed in Sections 5.1.2, 6.1.2, and Chapter 4 of the Economic
Analysis, respectively (USEPA, 2023j). For further discussion of the
quantified uncertainties in the Economic Analysis, see Section G of
this preamble below.
The third row shows net benefits (benefits minus costs). At a 3
percent discount rate, the net annual incremental benefits are $461
million. The uncertainty range for net benefits is a negative $45
million to $1,141 million. At a 7 percent discount rate, the net annual
incremental quantified benefits are a negative $297 million. The
uncertainty range for net benefits is a negative $628 million to $141
million.
Table 66--Annualized Quantified National Costs and Benefits, Proposed Option
[PFOA and PFOS MCLs of 4.0 ppt and HI of 1.0; Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ value \1\ \1\ value \1\
----------------------------------------------------------------------------------------------------------------
Total Annualized Rule Costs \2\ \3\ $704.53 $771.77 $850.40 $1,106.01 $1,204.61 $1,321.01
\4\..................................
Total Annualized Rule Benefits \4\.... 659.91 1,232.98 1,991.51 477.69 908.11 1,462.43
-------------------------------------------------------------------------
Total Net Benefits................ -44.62 461.21 1,141.11 -628.31 -296.50 141.42
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 71 and Table 72. This range does not include the uncertainty described in
Table 41 for costs and Table 60 for benefits.
\2\ Total quantified national cost values do not include the incremental treatment costs associated with the
cooccurrence of HFPO-DA, PFBS, and PFNA at systems required to treat for PFOA, PFOS, and PFHxS. The total
quantified national cost values do not include treatment costs for systems that would be required to treat
based on HI exceedances apart from systems required to treat because of PFHxS occurrence alone. See Appendix
N, Section 3 of the Economic Analysis (USEPA, 2023i) for additional detail on co-occurrence incremental
treatment costs and additional treatment costs at systems with HI exceedances.
\3\ PFAS-contaminated wastes are not considered 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 about potential costs for disposing PFAS-contaminated wastes as hazardous should
they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA,
2023i) for additional detail.
\4\ See Table 70 for a list of the nonquantifiable benefits and costs, and the potential direction of impact
these benefits and costs would have on the estimated monetized total annualized benefits and costs in this
table.
Tables 67 to 69 summarize the total annual costs and benefits for
Options 1a, 1b, and 1c, respectively.
Table 67--Annualized Quantified National Costs and Benefits, Option 1a
[PFOA and PFOS MCLs of 4.0 ppt; Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ value \1\ \1\ value \1\
----------------------------------------------------------------------------------------------------------------
Total Annualized Rule Costs \2\ \3\... $688.09 $755.82 $833.48 $1,078.51 $1,177.31 $1,292.01
Total Annualized Rule Benefits \3\.... 651.19 1,216.08 1,971.01 471.53 895.36 1,456.23
-------------------------------------------------------------------------
Total Net Benefits................ -36.90 460.26 1,137.53 -606.97 -281.95 164.22
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 71 and Table 72. This range does not include the uncertainty described in
Table 41 for costs and Table 60 for benefits.
[[Page 18725]]
\2\ PFAS-contaminated wastes are not considered 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 about potential costs for disposing PFAS-contaminated wastes as hazardous should
they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA,
2023i) for additional detail.
\3\ See Table 70 for a list of the nonquantifiable benefits and costs, and the potential direction of impact
these benefits and costs would have on the estimated monetized total annualized benefits and costs in this
table.
Table 68--Annualized Quantified National Costs and Benefits, Option 1b
[PFOA and PFOS MCLs of 5.0 ppt; Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ value \1\ \1\ value \1\
----------------------------------------------------------------------------------------------------------------
Total Annualized Rule Costs \2\ \3\... $558.71 $611.01 $674.32 $864.74 $942.28 $1,035.56
Total Annualized Rule Benefits \3\.... 553.37 1,046.91 1,706.81 398.21 773.33 1,292.96
-------------------------------------------------------------------------
Total Net Benefits................ -5.34 435.90 1,032.49 -466.53 -168.95 257.40
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 71 and Table 72. This range does not include the uncertainty described in
Table 41 for costs and Table 60 for benefits.
\2\ PFAS-contaminated wastes are not considered 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 about potential costs for disposing PFAS-contaminated wastes as hazardous should
they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA,
2023i) for additional detail.
\3\ See Table 70 for a list of the nonquantifiable benefits and costs, and the potential direction of impact
these benefits and costs would have on the estimated monetized total annualized benefits and costs in this
table.
Table 69--Annualized Quantified National Costs and Benefits, Option 1c
[PFOA and PFOS MCLs of 10.0 ppt; Million $2021]
----------------------------------------------------------------------------------------------------------------
3% Discount rate 7% Discount rate
-------------------------------------------------------------------------
5th 95th 5th 95th
Percentile Expected Percentile Percentile Expected Percentile
\1\ value \1\ \1\ value \1\
----------------------------------------------------------------------------------------------------------------
Total Annualized Rule Costs \2\ \3\... $269.36 $292.57 $320.76 $396.22 $430.87 $472.20
Total Annualized Rule Benefits \3\.... 280.42 584.80 1,030.56 208.71 436.24 784.59
-------------------------------------------------------------------------
Total Net Benefits................ 11.06 292.23 709.80 -187.51 5.36 312.39
----------------------------------------------------------------------------------------------------------------
Notes:
Detail may not add exactly to total due to independent rounding.
\1\ The 5th and 95th percentile range is based on modeled variability and uncertainty described in section
XIII.I of this preamble and Table 71 and Table 72. This range does not include the uncertainty described in
Table 41 for costs and Table 60 for benefits.
\2\ PFAS-contaminated wastes are not considered 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 about potential costs for disposing PFAS-contaminated wastes as hazardous should
they be regulated as such in the future, EPA conducted a sensitivity analysis with an assumption of hazardous
waste disposal for illustrative purposes only. See Appendix N, Section 2 of the Economic Analysis (USEPA,
2023i) for additional detail.
\3\ See Table 70 for a list of the nonquantifiable benefits and costs, and the potential direction of impact
these benefits and costs would have on the estimated monetized total annualized benefits and costs in this
table.
The benefit-cost analysis reported dollar figures presented above
reflect benefits and costs that could be quantified for each regulatory
alternative given the best available scientific data. EPA notes that
the quantified benefit-cost results above are not representative of all
benefits and costs anticipated under the proposed 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 EPA could not estimate in a quantitative
manner.
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,
EPA is only able to quantify three PFOA- and PFOS-related health
endpoints in this analysis. All regulatory alternatives are expected to
produce substantial benefits that have not been quantified. Treatment
responses implemented to remove PFOA and PFOS under Options 1a-c 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 Technical Support
Document (USEPA, 2023e). The proposed option is expected to produce the
greatest reduction in exposure to PFAS compounds because it includes
PFHxS, HFPO-DA, PFNA, and PFBS in the regulation. Inclusion of the HI
will trigger more systems into treatment (as shown in Section 4.4.4 of
the Economic
[[Page 18726]]
Analysis) and provides enhanced public health protection by ensuring
reductions of these additional compounds when present above the HI of
1.0. EPA conducted a sensitivity analysis to evaluate the additional
benefits anticipated due to regulating PFAS compounds beyond PFOA and
PFOS. Specifically, EPA's sensitivity analysis demonstrates the
potential significant quantified benefits associated with infant birth
weight expected to result from reductions in PFNA under the proposed
rule. For further discussion of the quantitative and qualitative
benefits associated with the proposed rule, see Section 6.2 of the
Economic Analysis.
EPA also expects that the proposed option will result in additional
nonquantifiable costs in comparison to Options 1a-c. As noted above,
the HI is expected to trigger more systems into more frequent
monitoring and treatment. Due to occurrence data limitations, EPA has
quantified the national treatment and monitoring costs associated with
the HI for PFHxS only and has not quantified the cost impacts
associated with HI exceedances resulting from HFPO-DA, PFNA, and PFBS.
In instances when concentrations of HFPO-DA, PFNA, and PFBS are high
enough to cause or contribute to an HI exceedance when the
concentrations of PFOA, PFOS, and PFHxS would not have already
otherwise triggered treatment, the 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 the HI in isolation (i.e., <9.0
ppt) then the quantified costs underestimate the impacts of the
proposed rule. As such, EPA conducted a semi-quantitative analysis of
the anticipated incremental costs associated with regulating HFPO-DA,
PFNA, and PFBS (for additional detail, please see USEPA (2023i)).
Table 70 provides a summary of the likely impact of nonquantifiable
benefit-cost categories. In each case, 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 Economic Analysis identify the key methodological
limitations and the potential effect on the cost or benefit estimates,
respectively. Additionally, Table 71 summarizes benefits and costs that
are quantified and nonquantifiable under the proposed rule.
Table 70--Potential Impact of Nonquantifiable Benefits (B) and Costs (C)
----------------------------------------------------------------------------------------------------------------
Source (Proposed option) Option 1a Option 1b Option 1c
----------------------------------------------------------------------------------------------------------------
Nonquantifiable PFOA and PFOS B: underestimate.. B: underestimate.. B: underestimate.. B: underestimate.
health endpoints.
Limitations with available C: underestimate.. n/a............... n/a............... n/a.
occurrence data for HFPO-DA,
PFNA, and PFBS.
Nonquantifiable HI (HFPO-DA, B: underestimate.. n/a............... n/a............... n/a.
PFNA, PFHxS and PFBS) health
endpoints.
Limitations with available B+C: underestimate B+C: underestimate B+C: underestimate B+C:
occurrence data for additional underestimate.
PFAS compounds.
Removal of co-occurring non-PFAS B+C: underestimate B+C: underestimate B+C: underestimate B+C:
contaminants. underestimate.
POU not in compliance forecast.. C: overestimate... C: overestimate... C: overestimate... C: overestimate.
Unknown future hazardous waste C: underestimate.. C: underestimate.. C: underestimate.. C: underestimate.
management requirements for
PFAS (including HI).
----------------------------------------------------------------------------------------------------------------
Table 71--Summary of Quantified and Nonquantified Benefits and Costs
----------------------------------------------------------------------------------------------------------------
Methods (economic analysis report
Category Quantified Non-quantified section where analysis is
detailed)
----------------------------------------------------------------------------------------------------------------
Costs:
PWS treatment costs \1\......... X Section 5.3.1.
PWS sampling costs.............. X Section 5.3.2.2.
PWS implementation and X Section 5.3.2.1.
administration costs.
Primacy agency rule X Section 5.3.2.
implementation and
administration costs.
Hazardous waste disposal for X Section 5.6.
treatment media.
POU not in compliance forecast.. X Section 5.6.
Benefits:
PFOA and PFOS birth weight X Section 6.4.
effects.
PFOA and PFOS cardiovascular X Section 6.5.
effects.
PFOA and PFOS RCC............... X Section 6.6.
Health effects associated with X Section 6.7.
disinfection byproducts.
Other PFOA and PFOS health X Section 6.2.2.2.
effects.
Health effects associated with X Section 6.2.
HI compounds (HFPO-DA, PFNA,
PFBS, PFHxS).
Health effects associated with X Section 6.2.
other PFAS.
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Due to occurrence data limitations, EPA quantified the national treatment and monitoring costs associated
with the HI for PFHxS only and has not quantified the national cost impacts associated with HI exceedances
resulting from PFNA, PFBS, and HFPO-DA.
[[Page 18727]]
I. Quantified Uncertainties in the Economic Analysis
EPA characterized sources of uncertainty in its estimates of costs
expected to result from the proposed PFAS NPDWR. EPA conducted Monte-
Carlo based uncertainty analysis as part of SafeWater MCBC. With
respect to the cost analysis, EPA modeled the sources of uncertainty in
Table 72.
Table 72--Quantified Sources of Uncertainty in Cost Estimates
------------------------------------------------------------------------
Source Description of uncertainty
------------------------------------------------------------------------
TOC concentration................. The TOC value assigned to each
system is from a distribution
derived from the SYR4 ICR database
(see Section 5.3.1.1 in Economic
Analysis).
Compliance technology unit cost Cost curve selection varies with
curve selection. baseline PFAS concentrations and
also includes a random selection
from a distribution across feasible
technologies (see Section 5.3.1.2
in Economic Analysis), and random
selection from a triangular
distribution of low-, mid-, and
high-cost equipment (25%, 50%, and
25%, respectively).
------------------------------------------------------------------------
For each iteration, SafeWater MCBC assigned new values to the four
sources of modeled uncertainty as described in Table 72, 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% confidence interval 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 Appendix L to USEPA (2023i).
Additionally, 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 proposed
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 73 provides an overview of the specific sources of
uncertainty that 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 to USEPA
(2023i).
Table 73--Quantified Sources of Uncertainty in Benefits Estimates
------------------------------------------------------------------------
Source Description of uncertainty
------------------------------------------------------------------------
Health effect-serum PFAS slope The slope factors that express the
factors. effects of serum PFOA and serum
PFOS on health outcomes (birth
weight, CVD,\1\ and RCC) are based
either on EPA meta-analyses or high-
quality studies that provide a
central estimate and a confidence
interval for the slope factors. EPA
assumed that the slope factors
would have a normal distribution
within their range.
RCC risk reduction cap............ EPA implemented a cap on the
cumulative RCC risk reductions due
to reductions in serum PFOA based
on the population attributable
fraction (PAF) estimates for a
range of cancers and environmental
contaminants. This parameter is
treated as uncertain; its
uncertainty is characterized by a
log-uniform distribution with a
minimum set at the smallest PAF
estimate identified in the
literature and a maximum set at the
largest PAF estimate identified in
the literature. The central
estimate for the PAF is the mean of
this log-uniform distribution.
------------------------------------------------------------------------
Note:
\1\ The slope factors contributing to the CVD benefits analysis include
the relationship between total cholesterol and PFOA and PFOS, the
relationship between HDLC and PFOA and PFOS, and the relationship
between blood pressure and PFOS.
J. Cost-Benefit Determination
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 paragraph
1412(b)(3)(C). With this proposed rule, the Administrator has
determined that the quantified and nonquantifiable benefits of the
proposed PFAS NPDWR justify the costs.
Sections XIII.A to XIII.I of this preamble summarize the results of
this proposed rule analysis. As indicated in section XIII.H of this
preamble, EPA discounted the estimated monetized cost and benefit
values using both 3 and 7 percent discount rates. In Federal regulatory
analyses, EPA follows OMB Circular A4 (OMB, 2003) guidance which
recommends using both 3 percent and 7 percent is intended to account
for the different streams of monetized benefits and costs affected by
regulation. The 7 percent discount rate represents the estimated rate
of return on capital in the U.S. economy, to reflect the opportunity
cost of capital when ``the main effect of a regulation is to displace
or alter the use of capital in the private sector.'' Regulatory
effects, however, can fall on both capital and private consumption.\10\
In 2003, Circular A-4 estimated the rate appropriate for discounting
consumption effects at 3 percent. The estimated monetized costs and
benefits of this rulemaking result in expected annual net benefits
(total monetized annual benefits minus total monetized annual costs) of
$461.21 million at a 3 percent discount rate and -$296.50 at a 7
percent discount rate. There are a variety of considerations with
respect to the capital displacement in this particular proposal. For
example, a meaningful number of PWSs may not be managed as profit-
maximizing private sector investments, which could impact the degree to
which the rate of return on the use of capital in the private sector
applies to PWS costs. Federal funding is expected to defray many such
PWS
[[Page 18728]]
costs; \11\ where that occurs, such costs are transferred to the
government. Additionally, to the extent that the benefits extend over a
long time period into the future, including to future generations,
Circular A-4 advises agencies to consider conducting sensitivity
analyses using lower discount rates. Regardless, the impacts in this
rulemaking are such that costs are expected to occur in the nearer
term, and in particular that larger one-time capital investments are
expected to occur in the near term; and public health benefits are
expected to occur over the much longer term. Discounting across an
appropriate range of rates can help explore how sensitive net benefits
are to assumptions about whether effects fall more to capital or more
to consumption.
---------------------------------------------------------------------------
\10\ Private consumption is the consumption of goods and
services by households for the direct satisfaction of individual
needs (rather than for investment).
\11\ As noted above in this preamble, ``Infrastructure
Investment and Jobs Act, also referred to as the Bipartisan
Infrastructure Law (BIL), invests over $11.7 billion in the Drinking
Water State Revolving Fund (SRF); $4 billion to the Drinking Water
SRF for Emerging Contaminants; and $5 billion to Small, Underserved,
and Disadvantaged Communities Grants.''
---------------------------------------------------------------------------
EPA has followed Circular A-4's default recommendations to use 3
and 7 percent rates to represent the range of potential impacts
accounting for diversity in stakeholders' time preferences. The Agency
views the 3 to 7 percent range of costs and benefits as characterizing
a significant portion of the uncertainty in the discount rate and views
the quantified endpoint values as demonstrating a range of monetized
costs and benefits which encompass a significant portion of the
uncertainty associated with discount rates. Material unquantified
benefits expected as a result of this proposed rulemaking are discussed
in greater detail later in this section.
The quantified analysis is limited in its characterization of
uncertainty. In Section XIII.H, Table 66 of this preamble, EPA provides
5th and 95th percentile values associated with the 3 and 7 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 variability in system characteristics and
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
systems 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 XIII.I
of this preamble. What the quantified 5th and 95th percentile values do
not include are a number of factors which 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 proposed rule cost estimates that are not quantified in the
uncertainty analysis are detailed in section XIII.C.j and Table 41 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 EPA's estimated distribution. 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. Section
XIII.D and Table 60, of this preamble, discuss 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
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 do not occur;
the distribution of population by size and demographics across entry
points 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 VSL. 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 PWS
which 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 entry points within individual systems; and the VSL
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 EPA with regard to population size at NTNCWs 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 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 do not occur. One factor not accounted for in the
quantified analysis associated with the underestimation of benefits 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 70 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 benefit. Tables 41 and 60
also provide additional information on a number of these
nonquantifiable categories.
On the nonquantifiable costs side of the equation 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,
[[Page 18729]]
and/or PFBS at levels high enough to cause systems to exceed the HI and
have to install PFAS treatment. EPA expects that the quantified
national costs are marginally underestimated as a result of this lack
of sufficient nationally representative occurrence data for purposes of
model integration. In an effort to better understand the costs
associated with treatment of potentially co-occurring HFPO-DA, PFNA,
and PFBS at systems already required to treat and the potential costs
resulting from an HI exceedance associated with the same chemicals EPA
estimated the potential unit treatment costs for model systems under
both scenarios for differing assumed HI PFAS concentrations. The
analysis is discussed in section 5.3.1.4 and Appendix N of the Economic
Analysis (USEPA, 2023j; USEPA, 2023i). 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 proposed rule could both increase costs to the extent
that they reduce media life. 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 proposed
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
cost values. Appendix N of the Economic Analysis (USEPA, 2023j; USEPA,
2023i) contains a sensitivity analysis that estimates there may be a
national annual costs of $30 to $61 million, discounted at 3 and 7
percent, respectively, which would accrue to systems if the waste
filtration media from GAC and IX were handled as hazardous waste. This
sensitivity analysis includes only disposal costs and does not consider
other potential environmental 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 EPA was able to monetize some of the PFOA and PFOS benefits
related to CVD, infant birthweight, and RCC effects, the Agency was
unable to quantify additional negative health impacts. 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 XIII.E, of this preamble, for additional information on the
nonquantifiable impacts of PFOA and PFOS. Further, the Agency did not
quantify any health endpoint benefits associated with the potential
reductions in HI PFAS, which include PFHxS, HFPO-DA, PFNA, and PFBS, or
other co-occurring non-regulated PFAS which would be removed by the
installation of required filtration technology at those systems with
PFOA, PFOS, or HI exceedances. The nonquantifiable benefits impact
categories associated with PFHxS, HFPO-DA, and PFBS include
developmental, cardiovascular, immune, hepatic, endocrine, metabolic,
reproductive, musculoskeletal, and carcinogenic effects. In addition,
EPA did not quantify the potential developmental, cardiovascular,
immune, hepatic, endocrine, metabolic, reproductive, musculoskeletal,
and carcinogenic impacts related to the removal of other co-occuring
non-regulated PFAS. See Section XIII.F, 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 significant positive health benefits. In total these
nonquantifiable benefits are anticipated to be significant and are
discussed qualitatively in Section 6.2 of the Economic Analysis (USEPA,
2023j).
To fully weigh the costs and benefits of the action the Agency
considered the totality of the monetized values, the potential impacts
of the unquantified uncertainties described above, and the
nonquantifiable costs and benefits. The Administrator has determined
that the benefits of this proposed regulation justify the costs.
XIV. Request for Comment on Proposed Rule
The Agency is requesting comment on this proposed NPDWR for PFAS.
In the proposal, the Agency highlighted numerous areas where specific
public comment will be helpful for EPA in developing a final rule. EPA
specifically requests comment on the following topics within each
section of this preamble.
Section III--Regulatory Determinations for Additional PFAS
EPA requests comment on its preliminary regulatory
determination for PFHxS and its evaluation of the statutory criteria
that supports the finding. EPA also requests comment on if there are
additional data or studies EPA should consider that support or do not
support the Agency's preliminary regulatory determination for PFHxS,
including additional health information and occurrence data.
EPA requests comment on its preliminary regulatory
determination for HFPO-DA and its evaluation of the statutory criteria
that supports the finding. EPA also requests comment on if there are
additional data or studies EPA should consider that support or do not
support the Agency's preliminary regulatory determination for HFPO-DA,
including additional health information and occurrence data.
EPA requests comment on its preliminary regulatory
determination for PFNA and its evaluation of the statutory criteria
that supports the finding. EPA also requests comment on if there are
additional data or studies EPA should consider that support or do not
support the Agency's preliminary regulatory determination for PFNA,
including additional health information and occurrence data.
EPA requests comment on its preliminary regulatory
determination for PFBS and its evaluation of the statutory criteria
that supports the finding. EPA also requests comment on if there are
additional data or studies EPA should consider that support or do not
support the Agency's preliminary regulatory determination for PFBS,
including additional health information and occurrence data.
EPA requests comment on whether there are other peer-
reviewed health or toxicity assessments for other PFAS the Agency
should consider as a part of this action.
EPA requests comment on its evaluation that regulation of
PFHxS, HFPO-DA, PFNA, PFBS, and their mixtures, in addition to PFOA and
PFOS, will provide protection from PFAS that will not be regulated
under this proposed rule.
Section V--Maximum Contaminant Level Goal
EPA requests comment on the derivation of the proposed
MCLG for PFOA and its determination that PFOA
[[Page 18730]]
is Likely to be Carcinogenic to Humans and whether the proposed MCLG is
set at the level at which there are no adverse effects to the health of
persons and which provides an adequate margin of safety. EPA is also
seeking comment on its assessment of the noncancer effects associated
with exposure to PFOA and the toxicity values described in the support
document on the proposed MCLG for PFOA.
EPA requests comment on the derivation of the proposed
MCLG for PFOS, its determination that PFOS is Likely to be Carcinogenic
to Humans and whether the proposed MCLG is set at the level at which
there are no adverse effects to the health of persons and which
provides an adequate margin of safety. EPA is also seeking comment on
its assessment of the noncancer effects associated with exposure to
PFOS and the toxicity values described in the support document on the
proposed MCLG for PFOS.
EPA requests comment on the general HI approach for the
mixture of four PFAS.
EPA requests comment on the merits and drawbacks of the
target-specific HI or RPF approach.
EPA requests comment on significant figure use when
calculating both the HI MCLG and the MCL. EPA has set the HI MCLG and
MCL using two significant figures (i.e., 1.0). EPA requests comment on
the proposed use of two significant figures for the MCLG when
considering underlying health information and for the MCL when
considering the precision of the analytical methods.
EPA requests comment on the derivation of the HBWCs for
each of the four PFAS considered as part of the HI.
EPA requests comment on whether the HBWCs should instead
be proposed as stand-alone MCLGs in addition to or in lieu of the
mixture MCLGs.
Section VI--Maximum Contaminant Level
EPA requests comment on its proposed determination to set
MCLs at 4.0 ppt for PFOA and PFOS and whether 4.0 ppt is the lowest PQL
that can be achieved by laboratories nationwide.
EPA seeks comment on its PFOA and PFOS evaluation of
feasibility for the proposal, including analytical measurement and
treatment capability, as well as reasonable costs, as defined by SDWA.
EPA seeks comment on its evaluation of feasibility for the
proposed HI MCL finding, including analytical measurement and treatment
capability, as well as reasonable costs, as defined by SDWA.
EPA requests comment on implementation challenges and
considerations for setting the MCL at the PQLs for PFOA and PFOS,
including on the costs and benefits related to this approach.
EPA requests comment on the underlying assumptions that
sufficient laboratory capacity will be available with the proposed
MCLs; that demand will be sufficiently distributed during rule
implementation to allow for laboratory capacity; and on the cost
estimates related to these assumptions.
EPA requests comment on its proposal of using an HI
approach for PFHxS, HFPO-DA, PFNA, and PFBS, including whether it can
be clearly implemented and achieves the goal of protecting against dose
additive noncancer health effects.
EPA requests comment on its proposed decision to establish
stand-alone MCLs for PFOA and PFOS in lieu of including them in the HI
approach.
EPA requests comment on whether establishing a traditional
MCLG and MCL for PFHxS, HFPO-DA, PFNA, and PFBS instead of, or in
addition to, the HI approach would change public health protection,
improve clarity of the rule, or change costs.
Section VII--Occurrence
EPA requests comment on the number of systems estimated to
solely exceed the HI (but not the PFOA or PFOS MCLs) according to the
approach outlined in USEPA (2023e).
Section IX--Monitoring and Compliance Requirements
EPA requests comment on the proposed monitoring
flexibility for groundwater systems serving 10,000 or fewer to only
collect two samples at each EPTDS to satisfy initial monitoring
requirements.
EPA requests comment on monitoring-related flexibilities
that should be considered to further reduce burden while also
maintaining public health protection including a rule trigger level at
different values than the currently proposed values of 1.3 ppt for PFOA
and PFOS and 0.33 for the HI PFAS (PFHxS, HFPO-DA, PFNA, and PFBS),
specifically alternative values of 2.0 ppt for PFOA and PFOS and 0.50
for the HI PFAS. EPA also requests comment other monitoring
flexibilities identified by commenters.
EPA requests comment on the proposed allowance of a water
system to potentially have each EPTDS on a different compliance
monitoring schedule based on specific entry point sampling results
(i.e., some EPTDS being sampled quarterly and other EPTDS sampled only
once or twice during each three-year compliance period), or if
compliance monitoring frequency should be consistent across all of the
system's sampling points.
EPA requests comments on whether water systems should be
permitted to apply to the primacy agency for monitoring waivers.
Specifically, EPA is requesting comment on the allowance of monitoring
waivers of up to nine years if after at least one year of sampling
results are below the proposed rule trigger level. Similarly, EPA also
requests comment on whether allowance of monitoring waivers of up to
nine years should be permitted based on previously acquired monitoring
data results that are below the proposed rule trigger level.
Additionally, EPA is also requesting comment on the identification of
possible alternatives to traditional vulnerability assessments that
should be considered to identify systems as low risk and potentially
eligible for monitoring waivers.
EPA requests comment on if all water systems, regardless
of system size, be allowed to collect and analyze one sample per three-
year compliance period if the system does not detect regulated PFAS in
their system at or above the rule trigger level.
EPA requests comment on its proposal to allow the use of
previously acquired monitoring data to satisfy initial monitoring
requirements including the data collection timeframe requirements and
if other QA requirements should be considered.
EPA requests comment on whether EPA should consider an
alternative approach to what is currently proposed when calculating
compliance with proposed MCLs. Specifically, in the case where a
regulated PFAS is detected but below its proposed PQL, rather than
using zero for the measurement value of the specific PFAS in the
running annual average compliance calculation, that the proposed rule
trigger levels (1.3 ppt for PFOA and PFOS and 0.33 of each of the HI
PFAS PQLs (i.e., PFHxS=1.0, HFPO-DA=1.7, PFNA=1.3, and PFBS=1.0)) be
used as the values in calculating the running annual average for
compliance purposes.
EPA requests comment on other monitoring related
considerations including laboratory capacity and QA/QC of drinking
water sampling.
EPA seeks comment on the Agency's proposed initial
monitoring timeframe, particularly for NTNCWS or all systems serving
3,300 or fewer.
[[Page 18731]]
Section X--Safe Drinking Water Right to Know
EPA requests comment on its proposal to designate
violations of the proposed MCLs as Tier 2.
EPA requests comment on what may be needed for water
systems to effectively communicate information about the PFAS NPDWR to
the public.
Section XI--Treatment Technologies
EPA requests comment on whether PWSs can feasibly treat to
4.0 ppt or below.
EPA requests additional information on PFAS removal
treatment technologies not identified in the proposed rule that have
been shown to reduce levels of PFAS to the proposed regulatory
standard.
EPA requests comment on the co-removal of the HI chemicals
(PFHxS, PFBS, PFNA, and HFPO-DA) when GAC, IX, or RO are used in the
treatment of PFOA and/or PFOS.
EPA requests comment on whether there are additional
technologies which are viable for PFAS removal to the proposed MCLs as
well as any additional costs which may be associated with non-treatment
options such as water rights procurement.
EPA estimates GAC treatment will be sufficiently available
to support cost-effective compliance with this proposed regulation, and
requests comment on whether additional guidance on applicable
circumstances for GAC treatment is needed.
EPA is seeking comment on the benefits from using
treatment technologies (such as reverse osmosis and GAC) that have been
demonstrated to co-remove other types of contaminants found in drinking
water and whether employing these treatment technologies are sound
strategies to address PFAS and other regulated or unregulated
contaminants that may co-occur in drinking water.
EPA requests comment on the estimates for disposing of
drinking water treatment residuals or regenerating drinking water
treatment media including assumptions related to the transport distance
to disposal sites and other costs that arise out of disposal of PFAS
contaminated drinking water treatment residuals.
EPA requests comment on the availability of facilities to
dispose of or regenerate drinking water treatment media that contains
PFAS. EPA requests comment on whether there will be sufficient capacity
to address the increased demand for disposal of drinking water
treatment residuals or to regenerate media for reuse by drinking water
treatment facilities.
EPA requests comment on the impacts that the disposal of
PFAS contaminated treatment residuals may have in communities adjacent
to the disposal facilities.
EPA requests comment on the type of assistance that would
help small public water systems identify laboratories that can perform
the required monitoring, evaluate treatment technologies and determine
the most appropriate way to dispose of PFAS contaminated residuals and
waste the systems may generate when implementing the rule.
Section XII--Rule Implementation and Enforcement