[Federal Register Volume 72, Number 83 (Tuesday, May 1, 2007)]
[Proposed Rules]
[Pages 24016-24058]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-7539]



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Part III





Environmental Protection Agency





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40 CFR Part 141



 Drinking Water: Regulatory Determinations Regarding Contaminants on 
the Second Drinking Water Contaminant Candidate List--Preliminary 
Determinations; Proposed Rule

  Federal Register / Vol. 72, No. 83 / Tuesday, May 1, 2007 / Proposed 
Rules  

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 141

[EPA-HQ-OW-2007-0068 FRL-8301-3]
RIN 2040-AE58


Drinking Water: Regulatory Determinations Regarding Contaminants 
on the Second Drinking Water Contaminant Candidate List--Preliminary 
Determinations

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice.

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SUMMARY: The Safe Drinking Water Act (SDWA), as amended in 1996, 
requires the Environmental Protection Agency (EPA) to make regulatory 
determinations on at least five unregulated contaminants and decide 
whether to regulate these contaminants with a national primary drinking 
water regulation (NPDWR). SDWA requires that these determinations be 
made every five years. These unregulated contaminants are typically 
chosen from a list known as the Contaminant Candidate List (CCL), which 
SDWA requires the Agency to publish every five years. EPA published the 
second CCL (CCL 2) in the Federal Register on February 24, 2005 (70 FR 
9071 (USEPA, 2005a)). This action presents the preliminary regulatory 
determinations for 11 of the 51 contaminants listed on CCL 2 and 
describes the supporting rationale for each. The preliminary 
determination is that an NPDWR is not appropriate for any of the 11 
contaminants considered for regulatory determinations. The Agency seeks 
comment on these 11 preliminary determinations. While the Agency has 
not made a preliminary determination for perchlorate, this action 
provides an update on the Agency's evaluation of perchlorate. The 
Agency requests public comment on the information and the options that 
the Agency is considering in evaluating perchlorate and welcomes the 
submission of relevant, new information and/or data that may assist the 
Agency in its regulatory determination.

DATES: Comments must be received on or before July 2, 2007.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2007-0068, by one of the following methods:
     http://www.regulations.gov: Follow the online instructions 
for submitting comments.
     Mail: Water Docket, Environmental Protection Agency, 
Mailcode: 2822T, 1200 Pennsylvania Ave., NW., Washington, DC 20460.
     Hand Delivery: Water Docket, EPA Docket Center (EPA/DC). 
Such deliveries are only accepted during the Docket's normal hours of 
operation, and special arrangements should be made for deliveries of 
boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OW-2007-
0068. EPA's policy is that all comments received will be included in 
the public docket without change and may be made available online at 
http://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through http://www.regulations.gov. The http://www.regulations.gov Web site is an 
``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA without 
going through http://www.regulations.gov your e-mail address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses. For additional instructions on submitting 
comments, go to Unit I.B of the SUPPLEMENTARY INFORMATION section of 
this document.
    Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the Water Docket, EPA/
DC, EPA West, Room 3334, 1301 Constitution Ave., NW., Washington, DC. 
The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday 
through Friday, excluding legal holidays. The telephone number for the 
Public Reading Room is (202) 566-1744, and the telephone number for the 
EPA Docket Center is (202) 566-2426.

FOR FURTHER INFORMATION CONTACT: Wynne Miller, Office of Ground Water 
and Drinking Water, Standards and Risk Management Division, at (202) 
564-4887 or e-mail [email protected]. For general information 
contact the EPA Safe Drinking Water Hotline at (800) 426-4791 or e-
mail: [email protected].

SUPPLEMENTARY INFORMATION:

Abbreviations and Acronyms

a. i.--active ingredient
<--less than
<=--less than or equal to
>--greater than
>=--greater than or equal to
[mu]--microgram, one-millionth of a gram
[mu]g/g--micrograms per gram
[mu]g/kg--micrograms per kilogram
[mu]g/L--micrograms per liter
ATSDR--Agency for Toxic Substances and Disease Registry
AWWARF--American Water Works Association Research Foundation
BMD--bench mark dose
BMDL--bench mark dose level
BW--body weight for an adult, assumed to be 70 kilograms (kg)
CASRN--Chemical Abstract Services Registry Number
CBI--confidential business information
CDC--Centers for Disease Control and Prevention
ChE--cholinesterase
CCL--Contaminant Candidate List
CCL 1--EPA's First Contaminant Candidate List
CCL 2--EPA's Second Contaminant Candidate List
CFR--Code of Federal Regulations
CMR--Chemical Monitoring Reform
CWS--community water system
1,3-DCP--1,3-dichloropropene
DCPA--dimethyl tetrachloroterephthalate (dacthal)
DDE--1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene
DDT--1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane
DNT--dinitrotoluene
DW--dry weight
DWEL--drinking water equivalent level
DWI--drinking water intake, assumed to be 2 L/day
EPA--United States Environmental Protection Agency
EPCRA--Emergency Planning and Community Right-to-Know Act
EPTC--s-ethyl dipropylthiocarbamate
ESA--ethane sulfonic acid
FDA--United States Food and Drug Administration
FQPA--Food Quality Protection Act
FR--Federal Register
FW--fresh weight
g--gram
g/day--grams per day

[[Page 24017]]

HRL--health reference level
IOC--inorganic compound
IRIS--Integrated Risk Information System
kg--kilogram
L--liter
LD50--an estimate of a single dose that is expected to 
cause the death of 50 percent of the exposed animals; it is derived 
from experimental data.
LOAEL--lowest-observed-adverse-effect level
MAC--mycobacterium avium intercellulare
MCL--maximum contaminant level
MCLG--maximum contaminant level goal
mg--milligram, one-thousandth of a gram
mg/kg--milligrams per kilogram body weight
mg/kg/day--milligrams per kilogram body weight per day
mg/L--milligrams per liter
mg/m3--milligrams per cubic meter
MRL--minimum or method reporting limit (depending on the study or 
suvey cited)
MTBE--methyl tertiary butyl ether
MTP--monomethyl-2,3,5,6-tetrachloroterephthalate
N--number of samples
NAS--National Academies of Sciences
NAWQA--National Water Quality Assessment (USGS Program)
NCEH--National Center for Environmental Health (CDC)
NCFAP--National Center for Food and Agricultural Policy
NCI--National Cancer Institute
NCWS--non community water system
ND--not detected (or non detect)
NDWAC--National Drinking Water Advisory Council
NHANES--National Health and Nutrition Examination Survey (CDC)
NIRS--National Inorganic and Radionuclide Survey
NIS--sodium iodide symporter
NOEL--no-observed-effect-level
NOAEL--no-observed-adverse-effect level
NPS--National Pesticide Survey
NQ--not quantifiable (or non quantifiable)
NRC--National Research Council
NPDWR--National Primary Drinking Water Regulation
NTP--National Toxicology Program
OA--oxanilic acid
OW--Office of Water
OPP--Office of Pesticide Programs
PCR--Polymerase Chain Reaction
PGWDB--pesticides in ground water data base
PWS--public water system
RED--Reregistration Eligibility Decision
RfC--reference concentration
RfD--reference dose
RSC--relative source contribution
SAB--Science Advisory Board
SDWA--Safe Drinking Water Act
SOC--synthetic organic compound
SVOC--semi-volatile organic compound
T3--triiodothyronine
T4--thyroxine
TDS--Total Diet Study (FDA)
Tg-DNT--technical grade DNT
TPA--2,3,5,6-tetrachchloroterephthalic acid
TRI--Toxics Release Inventory
TSH--thyroid stimulating hormone
TT--treatment technique
UCM--Unregulated Contaminant Monitoring
UCMR 1--First Unregulated Contaminant Monitoring Regulation
UF--uncertainty factor
US--United States of America
USDA--United States Department of Agriculture
USGS--United States Geological Survey
UST--underground storage tanks
VOC--volatile organic compound
I. General Information
    A. Does This Action Impose Any Requirements on My Public Water 
System?
    B. What Should I Consider as I Prepare My Comments for EPA?
II. Purpose, Background and Summary of This Action
    A. What Is the Purpose of This Action?
    B. Background on the CCL and Regulatory Determinations
    C. Summary of the Approach Used To Identify and Evaluate 
Candidates for Regulatory Determination 2
    D. What Are EPA's Preliminary Determinations and What Happens 
Next?
    E. Supporting Documentation for EPA's Preliminary Determinations
III. What Analyses Did EPA Use To Support the Preliminary Regulatory 
Determinations?
    A. Evaluation of Adverse Health Effects
    B. Evaluation of Contaminant Occurrence and Exposure
IV. Preliminary Regulatory Determinations
    A. Summary of the Preliminary Regulatory Determination
    B. Contaminant Profiles
    1. Boron
    2. and 3. Mono- and Di-Acid Degradates of Dimethyl 
Tetrachloroterephthalate (DCPA)
    4. 1,1-Dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE)
    5. 1,3-Dichloropropene (1,3-DCP; Telone)
    6. and 7. 2,4- and 2,6-Dinitrotoluenes (2,4- and 2,6-DNT)
    8. s-Ethyl dipropylthiocarbamate (EPTC)
    9. Fonofos
    10. Terbacil
    11. 1,1,2,2-Tetrachloroethane
V. What Is the Status of the Agency's Evaluation of Perchlorate?
    A. Sources of Perchlorate
    B. Health Effects
    C. Occurrence in Water, Food, and Humans.
    D. Occurrence Studies on Perchlorate in Human Urine, Breast 
Milk, and Amniotic Fluid
    E. Status of the Preliminary Regulatory Determination for 
Perchlorate
    F. What Are the Potential Options for Characterizing Perchlorate 
Exposure and Proceeding With the Preliminary Regulatory 
Determination for Perchlorate?
    G. Next Steps
VI. What About the Remaining CCL 2 Contaminants?
    A. Metolachlor
    B. Methyl tertiary-butyl ether
    C. Microbial Contaminants
VII. EPA's Next Steps
VIII. References

I. General Information

A. Does This Action Impose Any Requirements on My Public Water System?

    None of these preliminary regulatory determinations or the final 
regulatory determinations, when published, will impose any requirements 
on anyone. Instead, this action notifies interested parties of the 
availability of EPA's preliminary regulatory determinations for 11 of 
the 51 contaminants listed on CCL 2 and seeks comment on these 
preliminary determinations. This action also provides an update on the 
Agency's review of perchlorate and methyl tertiary butyl ether (MTBE).

B. What Should I Consider as I Prepare My Comments for EPA?

    You may find the following suggestions helpful for preparing your 
comments:
    1. Explain your views as clearly as possible.
    2. Describe any assumptions that you used.
    3. Provide any technical information and/or data you used that 
support your views.
    4. If you estimate potential burden or costs, explain how you 
arrived at your estimate.
    5. Provide specific examples to illustrate your concerns.
    6. Offer alternatives.
    7. Make sure to submit your comments by the comment period 
deadline.
    8. To ensure proper receipt by EPA, identify the appropriate docket 
identification number in the subject line on the first page of your 
response. It would also be helpful if you provided the name, date, and 
Federal Register citation related to your comments.

II. Purpose, Background and Summary of This Action

    This section briefly summarizes the purpose of this action, the 
statutory requirements, previous activities related to the Contaminant 
Candidate List and regulatory determinations, and the approach used and 
outcome of these preliminary regulatory determinations.

A. What Is the Purpose of This Action?

    The Safe Drinking Water Act (SDWA), as amended in 1996, requires 
EPA to publish a list of currently unregulated contaminants that may 
pose risks for drinking water (referred to as the Contaminant Candidate 
List, or CCL) and to make determinations on whether to regulate at 
least five contaminants from the CCL with a national primary drinking 
water regulation (NPDWR)

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(section 1412(b)(1)). The 1996 SDWA requires the Agency to publish both 
the CCL and the regulatory determinations every five years. The purpose 
of this action is to present (1) EPA's preliminary regulatory 
determinations for 11 candidates selected from the 51 contaminants 
listed on the second CCL (CCL 2), (2) the process and the rationale 
used to make these determinations, and (3) a brief summary of the 
supporting documentation. This action also includes a request for 
comment(s) on the Agency's preliminary determinations.
    The 11 regulatory determination contaminants candidates discussed 
in this action are boron, the dacthal mono- and di-acid degradates, 
1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), 1,3-
dichloropropene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, s-ethyl 
propylthiocarbamate (EPTC), fonofos, terbacil, and 1,1,2,2-
tetrachloroethane.

B. Background on the CCL and Regulatory Determinations

    1. Statutory Requirements for CCL and Regulatory Determinations. 
The specific statutory requirements for the CCL and regulatory 
determinations can be found in SDWA section 1412(b)(1). The 1996 SDWA 
Amendments require EPA to publish the CCL every five years. The CCL is 
a list of contaminants that are not subject to any proposed or 
promulgated NPDWRs, are known or anticipated to occur in public water 
systems (PWSs), and may require regulation under SDWA. The 1996 SDWA 
Amendments also direct EPA to determine whether to regulate at least 
five contaminants from the CCL every five years (within three and one-
half years after publication of the final list). In making regulatory 
determinations, SDWA requires EPA to publish a Maximum Contaminant 
Level Goal \1\ (MCLG) and promulgate an NPDWR \2\ for a contaminant if 
the Administrator determines that:
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    \1\ The 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, and which allows an adequate margin of 
safety. Maximum contaminant level goals are nonenforceable health 
goals'' (40 CFR 141.2).
    \2\ An NPDWR is a legally enforceable standard that applies to 
public water systems. An NPDWR sets a legal limit (called a maximum 
contaminant level or MCL) or specifies a certain treatment technique 
(TT) for public water systems for a specific contaminant or group of 
contaminants.
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    (a) The contaminant may have an adverse effect on the health of 
persons;
    (b) the contaminant is known to occur or there is a substantial 
likelihood that the contaminant will occur in public water systems with 
a frequency and at levels of public health concern; and
    (c) In the sole judgment of the Administrator, regulation of such 
contaminant presents a meaningful opportunity for health risk reduction 
for persons served by public water systems.
    If EPA determines that all three of these statutory criteria are 
met and makes a final determination that a national primary drinking 
water regulation is needed, the Agency has 24 months to publish a 
proposed MCLG and NPDWR. After the proposal, the Agency has 18 months 
to publish and promulgate a final MCLG and NPDWR (SDWA section 
1412(b)(1)(E)).\3\
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    \3\ The statute authorizes a nine month extension of this 
promulgation date.
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    2. The First Contaminant Candidate List (CCL 1). Following the 1996 
SDWA Amendments, EPA sought input from the National Drinking Water 
Advisory Council (NDWAC) on the process that should be used to identify 
contaminants for inclusion on the CCL. For chemical contaminants, the 
Agency developed screening and evaluation criteria based on 
recommendations from NDWAC. For microbiological contaminants, NDWAC 
recommended that the Agency seek external expertise to identify and 
select potential waterborne pathogens. As a result, the Agency convened 
a workshop of microbiologists and public health experts who developed 
criteria for screening and evaluation and subsequently developed an 
initial list of potential microbiological contaminants.
    The first CCL process benefited from considerable input from the 
NDWAC, the scientific community, and the public through stakeholder 
meetings and the public comments received on the draft CCL published on 
October 6, 1997 (62 FR 52193 (USEPA, 1997a)). EPA published the final 
CCL, which contained 50 chemical and 10 microbiological contaminants, 
on March 2, 1998 (63 FR 10273 (USEPA, 1998a)). A more detailed 
discussion of how EPA developed CCL 1 can be found in the 1997 and the 
1998 Federal Register notices (62 FR 52193 (USEPA, 1997a) and 63 FR 
10273 (USEPA, 1998a)).
    3. The Regulatory Determinations for CCL 1. EPA published its 
preliminary regulatory determinations for a subset of contaminants 
listed on CCL 1 on June 3, 2002 (67 FR 38222 (USEPA, 2002a)). The 
Agency published its final regulatory determinations on July 18, 2003 
(68 FR 42898 (USEPA, 2003a)). EPA identified 9 contaminants from the 60 
contaminants listed on CCL 1 that had sufficient data and information 
available to make regulatory determinations. The 9 contaminants were 
Acanthamoeba, aldrin, dieldrin, hexachlorobutadiene, manganese, 
metribuzin, naphthalene, sodium, and sulfate. The Agency determined 
that a national primary drinking water regulation was not necessary for 
any of these 9 contaminants. The Agency issued guidance on Acanthamoeba 
and health advisories for magnesium, sodium, and sulfate.
    The decision-making process that EPA used to make its regulatory 
determinations for CCL 1 was based on substantial expert input and 
recommendations from different groups including stakeholders, the 
National Research Council (NRC) and NDWAC. In June 2002, EPA consulted 
with the Science Advisory Board (SAB) Drinking Water Committee and 
requested its review and comment on whether the protocol EPA developed, 
based on the NDWAC recommendations, was consistently applied and 
appropriately documented. SAB provided verbal feedback regarding the 
use of the NRC and NDWAC recommendations in EPA's decision criteria for 
making its regulatory determinations. SAB recommended that the Agency 
provide a transparent and clear explanation of the process for making 
regulatory determinations. The Agency took SAB's recommendation into 
consideration and further explained the CCL 1 regulatory determination 
evaluation process in the July 18, 2003 (68 FR 42898 (USEPA, 2003a)) 
notice and in the supporting documentation.
    EPA has used the same approach to develop the regulatory 
determinations discussed in this action. While this action includes a 
short description of the decision process used to make regulatory 
determinations (section II.C), a more detailed discussion can be found 
in the 2002 and the 2003 Federal Register notices (67 FR 38222 (USEPA, 
2002a) and 68 FR 42898 (USEPA, 2003a)).
    4. The Second Contaminant Candidate List (CCL 2). The Agency 
published its draft CCL 2 Federal Register notice on April 2, 2004 (69 
FR 17406 (USEPA, 2004a)) and the final CCL 2 Federal Register notice on 
February 24, 2005 (70 FR 9071 (USEPA, 2005a)). The CCL 2 carried 
forward the 51 remaining chemical and microbial contaminants that were 
listed on CCL 1.
    5. The Regulatory Determinations for CCL 2. This current action 
discusses EPA's preliminary determinations for 11 of the 51 
contaminants listed on the CCL 2.

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C. Summary of the Approach Used To Identify and Evaluate Candidates for 
Regulatory Determination 2

    Figure 1 provides a brief overview of the process EPA used to 
identify which CCL 2 contaminants are candidates for regulatory 
determinations and the SDWA statutory criteria considered in making the 
regulatory determinations.
BILLING CODE 6560-50-P
[GRAPHIC] [TIFF OMITTED] TP01MY07.050

BILLING CODE 6560-50-C
    In identifying which CCL 2 contaminants are candidates for 
regulatory determinations, the Agency considered whether sufficient 
information and/or data were available to characterize the potential 
health effects and the known/likely occurrence in and exposure from 
drinking water. With regards to sufficient health effects information/
data, the Agency considered whether an Agency-approved health risk 
assessment \4\ was available to identify any potential adverse health 
effect(s) and derive an estimated level at which adverse health 
effect(s) are likely to occur. With regards to sufficient occurrence 
information/data, the Agency considered whether information/data were 
available to

[[Page 24020]]

evaluate and give a generally representative idea of known and/or 
likely occurrence in public water systems. If sufficient information/
data were available to characterize adverse human health effects and 
known/likely occurrence in public water systems, the Agency identified 
the contaminant as a potential candidate for regulatory determinations. 
In addition to information/data for health and occurrence, EPA also 
considered the availability and adequacy of analytical methods (for 
monitoring) and treatment.
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    \4\ Health information used for the regulatory determinations 
process includes but is not limited to health assessments available 
from the Agency's Integrated Risk Information System (IRIS), the 
Agency's Office of Pesticide Programs (OPP) in a Reregistration 
Eligibility Decision (RED), the National Academy of Sciences (NAS), 
and/or the Agency for Toxic Substances and Disease Registry (ATSDR).
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    If EPA chose a contaminant as a candidate for regulatory 
determination, the Agency used an approach similar to the first 
regulatory determination process to answer the three statutory criteria 
(listed in section II.B.1).
    For the current regulatory determination process, the Agency 
considered the following in evaluating each of the three statutory 
criteria.
    (1) First statutory criterion--Is the contaminant likely to cause 
an adverse effect on the health of persons? The Agency evaluated the 
best available, peer-reviewed assessments and studies to characterize 
the human health effects that may result from exposure to the 
contaminant when found in drinking water. Based on this 
characterization, the Agency estimated a health reference level (HRL) 
for each contaminant. Section III.A provides more detailed information 
about the approach used to evaluate and analyze the health information.
    (2) Second statutory criterion--Is the contaminant known or likely 
to occur in public water systems at a frequency and level of concern? 
To evaluate known occurrence in PWSs, the Agency compiled, screened, 
and analyzed data from several occurrence data sets to develop 
representative occurrence estimates for public drinking water systems. 
EPA used the HRL estimates for each contaminant as a benchmark against 
which to conduct an initial evaluation or screening of the occurrence 
data. For each contaminant, EPA estimated the number of PWSs (and the 
population served by these PWSs) with detections greater than one-half 
the HRL (> 1/2 HRL) and greater than the HRL (> HRL). To evaluate the 
likelihood of a contaminant to occur in drinking water, the Agency 
considered information on the use and release of a contaminant into the 
environment and supplemental information on occurrence in water (e.g., 
ambient water quality data, State ambient or finished water data, and/
or special studies performed by other agencies, organizations and/or 
entities). Section III.B provides more details on the approach used to 
analyze the occurrence information/data.
    (3) Third statutory criterion--In the sole judgment of the 
Administrator, does regulation of the contaminant present a meaningful 
opportunity for health risk reduction for persons served by public 
water systems? EPA evaluated the potential health effects and the 
results of the occurrence and exposure estimates (i.e., the population 
exposed and the sources of exposure) at the health level of concern to 
determine if regulation presents a meaningful opportunity for health 
risk reduction. EPA has made a preliminary determination regarding the 
meaningful opportunity for health risk reduction for 11 contaminants 
based upon the population exposed to these contaminants at levels of 
concern.
    If the answers to all three statutory criteria are affirmative for 
a particular contaminant, then the Agency makes a determination that a 
national drinking water regulation is necessary and proceeds to develop 
an MCLG and a national primary drinking water regulation for that 
contaminant. It should be noted that this regulatory determination 
process is independent of the more detailed analyses needed to develop 
a national primary drinking water regulation. Thus, a decision to 
regulate is the beginning of the Agency regulatory development process, 
not the end.
    If the answer to any of the three statutory criteria is negative, 
then the Agency makes a determination that a national drinking water 
regulation is not necessary for that contaminant.

D. What Are EPA's Preliminary Determinations and What Happens Next?

    EPA has made preliminary determinations that no regulatory actions 
are appropriate for the 11 contaminants evaluated for this second round 
of regulatory determinations. EPA will make final determinations on 
these 11 contaminants after a 60-day comment period. EPA is making 
preliminary regulatory determinations only on those CCL 2 contaminants 
that have sufficient information to support such a determination at 
this time. The Agency continues to conduct research and/or to collect 
information on the remaining CCL 2 contaminants to fill identified data 
gaps. The Agency is not precluded from taking action when information 
becomes available and will not necessarily wait until the end of the 
next regulatory determination cycle before making other regulatory 
determinations.

E. Supporting Documentation for EPA's Preliminary Determinations

    For this action, EPA prepared several support documents that are 
available for review and comment in the EPA Water Docket and at http://www.regulations.gov. These support documents include:
     A comprehensive regulatory support document entitled, 
``Regulatory Determinations Support Document for Selected Contaminants 
from the Second Drinking Water Contaminant Candidate List'' (CCL 2) 
(USEPA, 2006a). This support document summarizes the information and 
data on the physical and chemical properties, uses and environmental 
release, environmental fate, potential health effects, occurrence and 
exposure estimates, the preliminary determination for each contaminant 
candidate, and the Agency's rationale for its determination. The 
technical health and occurrence support documents listed next served as 
the basis for the health information and the drinking water occurrence 
estimates summarized in this comprehensive regulatory support document.
     Technical health support documents. These documents 
address exposure from drinking water and other media, toxicokinetics, 
hazard identification, and dose-response assessment, and provide an 
overall characterization of the risk from drinking water for the 
contaminants considered for regulatory determination. These documents 
are listed in the reference section as ``USEPA, 2006j'' through 
``USEPA, 2006r.''
     Technical occurrence support documents (USEPA, 2006b and 
USEPA, 2006c). These documents include more detailed information about 
the sources of the data, how EPA assessed the data quality, 
completeness, and representativeness, and how the data were used to 
generate estimates of drinking water contaminant occurrence in support 
of these regulatory determinations. Section III.B.3 provides more 
information about the title and content of these technical support 
documents.

III. What Analyses Did EPA Use To Support the Preliminary Regulatory 
Determinations?

    Sections III.A and B of this action outline the health effects and 
occurrence/exposure evaluation process EPA used to support these 
preliminary determinations.

A. Evaluation of Adverse Health Effects

    Section 1412(b)(1)(A)(i) of SDWA requires EPA to determine whether 
each

[[Page 24021]]

candidate contaminant may have an adverse effect on public health. This 
section describes the overall process the Agency used to evaluate 
health effects information, the approach used to estimate a contaminant 
HRL (a benchmark against which to conduct the initial evaluation of the 
occurrence data), and the approach used to identify and evaluate 
information on hazard and dose-response for the contaminants under 
consideration. More specific information about the potential for 
adverse health effects for each contaminant is presented in section 
IV.B of this action.
    There are two different approaches to the derivation of an HRL. One 
approach is used for chemicals that cause cancer and exhibit a linear 
response to dose and the other applies to noncarcinogens and 
carcinogens evaluated using a non-linear approach.
    1. Use of Carcinogenicity Data for the Derivation of a Health 
Reference Level. For those contaminants considered to be likely or 
probable human carcinogens, EPA evaluated data on the mode of action of 
the chemical to determine the method of low dose extrapolation. When 
this analysis indicates that a linear low dose extrapolation is 
appropriate or when data on the mode of action are lacking, EPA uses a 
low dose linear extrapolation to calculate risk-specific doses. The 
risk-specific doses are the estimated oral exposures associated with 
lifetime excess risk levels that range from one cancer in ten thousand 
(10-4) to one cancer in a million (10-6). The 
risk-specific doses (expressed as mg/kg of body weight per day) are 
combined with adult body weight and drinking water consumption data to 
estimate drinking water concentrations corresponding to this risk 
range. EPA generally used the one-in-a-million (10-6) cancer 
risk in the initial screening of the occurrence data for carcinogens 
evaluated using linear low dose extrapolation. Five of the eleven 
contaminants discussed in this action had data available to classify 
them as likely or probable human carcinogens. These five are also the 
only contaminants for which low dose linear extrapolations were 
performed. These five are p,p-dichlorodiphenyldichloroethylene (DDE), 
1,3-dichloropropene (1,3-DCP or Telone), 2,4-dinitrotoluene, 2,6-
dinitrotoluene, and 1,1,2,2-tetrachloroethane. The remaining 6 
contaminants have not been identified as known, likely or probable 
carcinogens.
    2. Use of Non-carcinogenic Health Effects Data for Derivation of an 
HRL. For those chemicals not considered to be carcinogenic to humans, 
EPA generally calculates a reference dose (RfD). A RfD is an estimate 
of a daily oral exposure to the human population (including sensitive 
subgroups) that is likely to be without an appreciable risk of 
deleterious effects during a lifetime. It can be derived from either a 
``no-observed-adverse-effect level'' (NOAEL), a ``lowest-observed-
adverse-effect level'' (LOAEL), or a benchmark dose, with uncertainty 
factors applied to reflect limitations of the data used.
    The Agency uses uncertainty factors (UFs) to address uncertainty 
resulting from incompleteness of the toxicological database. The 
individual UFs (usually applied as integers of 1, 3, or 10) are 
multiplied together and used to derive the RfD from experimental data. 
Individual UFs are intended to account for:
    (1) The variation in sensitivity among the members of the human 
population (i.e., intraspecies variability);
    (2) the uncertainty in extrapolating animal data to humans (i.e., 
interspecies variability);
    (3) the uncertainty in extrapolating from data obtained in a study 
with less-than-lifetime exposure to lifetime exposure (i.e., 
extrapolating from subchronic to chronic exposure);
    (4) the uncertainty in extrapolating from a LOAEL rather than from 
a NOAEL; and/or
    (5) the uncertainty associated with an incomplete database.
    For boron, the dacthal (DCPA) mono and di acid degradates, s-ethyl 
dipropylthiocarbamate (EPTC), fonofos and terbacil, EPA derived the 
HRLs using the RfD approach as follows:

HRL = [(RfD x BW)/DWI] x RSC

Where:

RfD = Reference Dose
BW = Body Weight for an adult, assumed to be 70 kilograms (kg)
DWI = Drinking Water Intake, assumed to be 2 L/day (90th percentile)
RSC = Relative Source Contribution, or the level of exposure 
believed to result from drinking water when compared to other 
sources (e.g., food, ambient air). A 20 percent RSC is being used to 
estimate the HRL and screen the occurrence data because it is the 
lowest and most conservative RSC used in the derivation of an MCLG 
for drinking water. For each of the 6 aforementioned non-
carcinogenic compounds for which the Agency has made a preliminary 
regulatory determination in this action, EPA used the RfD in 
conjunction with a 20 percent RSC to derive a conservative HRL 
estimate and perform an initial screening of the drinking water 
occurrence data. Since the initial screening of the occurrence data 
at this conservative HRL value resulted in a preliminary negative 
determination for each of these 6 compounds, the Agency determined 
that it was not necessary to further evaluate the RSC in making the 
regulatory determination.

    As discussed in section IV.B.2 and 3, the HRL for the two dacthal 
degradates is based on the HRL value derived for the DCPA parent 
following the guidance provided by EPA's Office of Pesticide Programs.
    3. Sources of Data/Information for Health Effects. EPA used the 
best available peer-reviewed data and analyses in evaluating adverse 
health effects. Peer-reviewed health-risk assessments were available 
for all chemicals considered for regulatory determinations from the 
Agency's Integrated Risk Information System (IRIS) Program\5\ and/or 
the Office of Pesticide Programs (OPP) Reregistration Eligibility 
Decisions (RED).\6\ Table 1 summarizes the sources of the health 
assessment data for each chemical under regulatory determination 
consideration. The Agency performed a literature search for studies 
published after the IRIS or OPP health-risk assessment was completed to 
determine if new information suggested a different outcome. The Agency 
collected and evaluated any peer-reviewed publications identified 
through the literature search for their impact on the RfD and/or cancer 
assessment. In cases where the recent data indicated that a change to 
the existing RfD or cancer assessment was needed, the updated OW 
assessment, as described in the health effects support document, was 
independently peer-reviewed. All quantitative cancer assessments 
conducted under the Guidelines for Carcinogen Risk Assessment (51 FR 
33992 (USEPA, 1986)) were updated using the Guidelines for Carcinogen 
Risk Assessment (USEPA, 1999a) as directed in the November 2001 (66 FR 
59593 (USEPA, 2001a)) Federal Register notice.
---------------------------------------------------------------------------

    \5\ IRIS is an electronic EPA database (http://www.epa.gov/iris/index.html) containing peer-reviewed information on human health 
effects that may result from exposure to various chemicals in the 
environment. These chemical files contain descriptive and 
quantitative information on hazard identification and dose response, 
RfDs for chronic noncarcinogenic health effects, as well as slope 
factors and unit risks for carcinogenic effects.
    \6\ The OPP is required under the Federal Insecticide Fungicide 
and Rodenticide Act (FIFRA) to review all pesticides registered 
prior to 1984 and determine whether to reregister them for continued 
use. The results of the reregistration analysis are included in the 
REDs. Copies of the REDs are located at the following Web site: 
http://cfpub.epa.gov/oppref/rereg/status.cfm?show=rereg.
---------------------------------------------------------------------------

    In March 2005, EPA updated and finalized the Cancer Guidelines and 
a Supplementary Children's Guidance,

[[Page 24022]]

which include new considerations for mode of action and added 
guidelines related to potential risks due to early childhood exposure 
(USEPA, 2005b; USEPA, 2005c). EPA updated the earlier assessments 
(based on the 1986 Guidelines) for DDE, the dinitrotoluenes (2,4 and 
2,6 as a mixture), and 1,1,2,2-tetrachloroethane following the 1999 
Guidelines. None of these chemicals have been determined to have a 
mutagenic mode of action, which would require an extra factor of safety 
for children's health protection. Therefore, conducting the cancer 
evaluation using the 2005 Cancer Guidelines would not result in any 
change from the assessment updated following the 1999 Guidelines.
    The cancer assessment for 1,3-dichloropropene was done by OPP and 
IRIS (USEPA, 1998b and 2000a) under the Proposed Guidelines for 
Carcinogen Risk Assessment (61 FR 17960 (USEPA, 1996a)). The 
Administrator (USEPA, 2005d) has directed that current completed 
assessments can be considered to be scientifically sound based on the 
guidance used when the assessment was completed until a new assessment 
is performed by one of the responsible program offices.

                           Table 1.--Sources and Dates of EPA Health Risk Assessments
----------------------------------------------------------------------------------------------------------------
                         Chemical                               IRIS          Date        OPP RED        Date
----------------------------------------------------------------------------------------------------------------
Boron.....................................................            X          2004  ............  ...........
Dacthal and its mono- and di-acid degradates..............            X          1994            X          1998
1,3-Dichloropropene.......................................            X          2000            X          1998
DDE.......................................................            X          1988  ............  ...........
2,4-Dinitrotoluene........................................            X     1990/1992  ............  ...........
2,6-Dinitrotoluene........................................          * X          1990  ............  ...........
EPTC......................................................            X          1990            X          1999
Fonofos...................................................            X          1991         ** X          1996
Terbacil..................................................            X          1989            X          1998
1,1,2,2-Tetrachloroethane.................................            X          1986  ............  ...........
----------------------------------------------------------------------------------------------------------------
* Applies to a mixture of 98 percent 2,4-dinitrotoluene and 2 percent 2,6-dinitrotoluene.
** Health Risk Assessment; RED not completed due to pesticide cancellation.

    As noted in section II.E, EPA has prepared several technical health 
effects support documents for the contaminants considered for this 
round of regulatory determinations. These documents address the 
exposure from drinking water and other media, toxicokinetics, hazard 
identification, and dose-response assessment, and provide an overall 
characterization of risk from drinking water.

B. Evaluation of Contaminant Occurrence and Exposure

    EPA used data from several sources to evaluate occurrence and 
exposure for the 11 contaminants considered in these regulatory 
determinations. The major or primary sources of the drinking water 
occurrence data used to support these determinations include the 
following sources:
     The first Unregulated Contaminant Monitoring Regulation 
(UCMR 1),
     The Unregulated Contaminant Monitoring (UCM) program, and
     The National Inorganic and Radionuclide Survey (NIRS).
    In addition to these primary sources of occurrence data, the Agency 
also evaluated supplemental sources of occurrence information. Section 
III.B.1 of this action provides a brief summary of the primary sources 
of drinking water occurrence data and section III.B.2 provides brief 
summary descriptions of the supplemental sources of occurrence 
information and/or data. A summary of the occurrence data and the 
results or findings for each of the 11 contaminants considered for 
regulatory determination is presented in Section IV.B, the contaminant 
profiles section.
    1. Primary Data Sources. As previously mentioned, the primary 
sources of the drinking water occurrence data used to support this 
action are the UCMR 1, the UCM program, and NIRS. The following 
sections provide a brief summary of the data sources and the approach 
used to estimate a given contaminant's occurrence. Table 2 lists the 
primary data sources the Agency used for each of the 11 contaminants 
considered for regulatory determinations.

                        Table 2.--Primary Sources of Drinking Water Occurrence Data Used in the Regulatory Determination Process
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                         Primary data sources
                                                                             ---------------------------------------------------------------------------
                                                                                           UCMR 1                              UCM
                   Number                               Contaminant          --------------------------------------------------------------------
                                                                                   List 1           List 2                                         NIRS
                                                                                 assessment       screening      Round 1  cross   Round 2  cross
                                                                                 monitoring         survey          section          section
--------------------------------------------------------------------------------------------------------------------------------------------------------
1...........................................  Boron.........................                                                                        1 X
2...........................................  Dacthal mono- and
3...........................................  di-acid degradates............               X
4...........................................  DDE...........................               X
5...........................................  1,3-Dichloropropene...........             2 X                                 X                X
6...........................................  2,4-Dinitrotoluene............               X
7...........................................  2,6-Dinitrotoluene............               X
8...........................................  EPTC..........................               X
9...........................................  Fonofos.......................                                X
10..........................................  Terbacil......................               X

[[Page 24023]]

 
11..........................................  1,1,2,2-Tetrachloroethane.....                                                 X                X
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 For boron, EPA also considered the results of a study funded by AWWARF (Frey et al., 2004).
2 1,3-Dichloropropene was sampled as a UCM Round 1 and 2 analyte but due to sample degradation concerns the contaminant was re-analyzed using the
  samples provided by the small systems that participated in the UCMR 1 List 1 Assessment Monitoring.

    a. The Unregulated Contaminant Monitoring Regulation. In 1999, EPA 
developed the UCMR program in coordination with the CCL and the 
National Drinking Water Contaminant Occurrence Database (NCOD) to 
provide national occurrence information on unregulated contaminants 
(September 17, 1999, 64 FR 50556 (USEPA, 1999b); March 2, 2000, 65 FR 
11372 (USEPA, 2000b); and January 11, 2001, 66 FR 2273 (USEPA, 2001b)). 
EPA used data from the UCMR 1 program to evaluate occurrence for 9 of 
the 11 contaminants considered for these regulatory determinations. 
These 9 contaminants include the dacthal mono- and di-acid degradates, 
DDE, 1,3-dichloropropene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, EPTC, 
fonofos, and terbacil.
    EPA designed the UCMR 1 data collection with three parts (or tiers) 
primarily based on the availability of analytical methods. Occurrence 
data for 8 of the 9 contaminants listed in the preceding paragraph are 
from the first tier of UCMR (also known as UCMR 1 List 1 Assessment 
Monitoring). Occurrence data for fonofos are from the second tier of 
UCMR 1 (also known as the UCMR 1 List 2 Screening Survey). EPA has not 
collected data as part of the third tier due to the lack of adequate 
analytical methods.
    The UCMR 1 List 1 Assessment Monitoring was performed for a 
specified number of chemical contaminants for which analytical methods 
have been developed. EPA required all large\7\ PWSs, plus a 
statistically representative national sample of 800 small \8\ PWSs to 
conduct Assessment Monitoring.\9\ Approximately one-third of the 
participating small systems were scheduled to monitor for these 
contaminants during each calendar year from 2001 through 2003. Large 
systems could conduct one year of monitoring anytime during the 2001-
2003 UCMR 1 period. EPA specified a quarterly monitoring schedule for 
surface water systems and a twice-a-year, six-month interval monitoring 
schedule for ground water systems. The objective of the UCMR 1 sampling 
approach for small systems was to collect contaminant occurrence data 
from a statistically selected, nationally representative sample of 
small systems. The small system sample was stratified and population-
weighted, and included some other sampling adjustments such as 
allocating a selection of at least 2 systems from each State. With 
contaminant monitoring data from all large PWSs and a statistical, 
nationally representative sample of small PWSs, the UCMR 1 List 1 
Assessment Monitoring program provides a contaminant occurrence data 
set suitable for national drinking water estimates.
---------------------------------------------------------------------------

    \7\ Systems serving more than 10,000 people.
    \8\ Systems serving 10,000 people or fewer.
    \9\ Large and small systems that purchase 100% of their water 
supply were not required to participate in the UCMR 1 Assessment 
Monitoring or the UCMR 1 Screening Survey.
---------------------------------------------------------------------------

    In total, 370,312 sample results have been collected under the UCMR 
1 List 1 Assessment Monitoring program at approximately 3,083 large 
systems and 797 small systems. Approximately 33,600 samples were 
collected for each contaminant. The UCMR 1 List 1 Monitoring program 
included systems from all 50 States, the District of Columbia, 4 U.S. 
Territories, and Tribal lands in 5 EPA Regions. An additional 3,719 
samples were collected for 1,3-DCP at all small systems that conducted 
UCMR 1 List 1 Assessment Monitoring.
    In addition to the UCMR 1 List 1 Assessment Monitoring, EPA 
required monitoring for selected contaminants (including fonofos) for 
which analytical methods were developed but not widely used. Known as 
the UCMR 1 List 2 Screening Survey, EPA randomly selected 300 public 
water systems (120 large and 180 small systems) from the pool of 
systems required to conduct UCMR 1 List 1 Assessment Monitoring. In 
total, 29,765 sample results have been collected under the UCMR 1 List 
2 Screening Survey from the participating large and small systems. 
Approximately 2,300 samples were collected for each contaminant. The 
UCMR 1 List 2 Screening Survey included systems from 48 States, 2 U.S. 
Territories, and Tribal lands in 1 EPA Region. EPA used the occurrence 
data from this survey to evaluate fonofos.
    EPA analyzed the UCMR 1 List 1 Assessment Monitoring and List 2 
Screening Survey data to generate the following initial occurrence and 
exposure summary statistics:
     The total number of systems and the total population 
served by these systems,
     The number and percentage of systems with at least 1 
observed detection that has a concentration greater than \1/2\ the HRL 
and greater than the HRL (or in some cases greater than or equal to the 
minimum reporting limit or MRL), and
     The number of people and percentage of the population 
served by systems with at least one observed detection greater than \1/
2\ the HRL and greater than the HRL (or in some cases greater than or 
equal to the MRL).\10\
---------------------------------------------------------------------------

    \10\ EPA's support documents (USEPA, 2006a and 2006b) provide 
summary statistics for the median and 99th percentile concentrations 
of all analytical detections and detailed occurrence results based 
on UCMR data according to source water type (surface versus ground 
water), system size, and State.
---------------------------------------------------------------------------

    The initial UCMR 1 summary occurrence statistics for dacthal mono- 
and di-acid degradates, DDE, 1,3-dichloropropene, 2,4-dinitrotoluene, 
2,6-dinitrotoluene, EPTC, fonofos, and terbacil are presented in 
section IV.B of this action.
    b. The Unregulated Contaminant Monitoring Program Rounds 1 and 2. 
In 1987, EPA initiated the UCM program to fulfill a 1986 SDWA Amendment 
that required monitoring of specified unregulated contaminants to 
gather information on their occurrence in drinking water for future 
regulatory decision-making purposes. EPA used data from the UCM program 
to evaluate

[[Page 24024]]

occurrence for 2 of the 11 contaminants considered for these regulatory 
determinations. These two contaminants are 1,3-dichloropropene and 
1,1,2,2-tetrachloroethane.
    EPA implemented the UCM program in two phases or rounds. The first 
round of UCM monitoring generally extended from 1988 to 1992 and is 
referred to as UCM Round 1 monitoring. The second round of UCM 
monitoring generally extended from 1993 to 1997 and is referred to as 
UCM Round 2 monitoring.
    UCM Round 1 monitored for 34 volatile organic compounds (VOCs), 
including 1,3-dichloropropene and 1,1,2,2-tetrachloroethane (52 FR 
25720 (USEPA, 1987)). UCM Round 2 monitored for 13 synthetic organic 
compounds (SOCs), sulfate and the same 34 VOCs from UCM Round 1 
monitoring (57 FR 31776 (USEPA, 1992a)).
    The UCM Round 1 database contains contaminant occurrence data from 
38 States, Washington, DC, and the U.S. Virgin Islands. The UCM Round 2 
database contains data from 34 States and several Tribes. Due to 
incomplete State data sets, national occurrence estimates based on raw 
(unedited) UCM Round 1 or Round 2 data could be skewed to low-
occurrence or high-occurrence settings (e.g., some States only reported 
detections). To address potential biases in the data,\11\ EPA developed 
national cross-sections from the UCM Round 1 and Round 2 State data 
using an approach similar to that used for EPA's 1999 Chemical 
Monitoring Reform (CMR), the first Six Year Review, and the first CCL 
Regulatory Determinations. This national cross-section approach was 
developed to support occurrence analyses and was supported by 
scientific peer reviewers and stakeholders. This approach identified 24 
of the original 38 States from the UCM Round 1 database and 20 of the 
original 34 States from the UCM Round 2 data base for the national 
cross-section.
---------------------------------------------------------------------------

    \11\ The potential bias in the raw UCM data are due to lack of 
representativeness (since not all States provided UCM data) and 
incompleteness (since some States that provided data had incomplete 
data sets).
---------------------------------------------------------------------------

    Because UCM Round 1 and Round 2 data represent different time 
periods and include occurrence data from different States, EPA 
developed separate national cross-sections for each data set. The UCM 
Round 1 national cross-section consists of data from 24 States, with 
approximately 3.3 million total analytical data points from 
approximately 22,000 unique PWSs. The UCM Round 2 national cross-
section consists of data from 20 States, with approximately 3.7 million 
analytical data points from slightly more than 27,000 unique PWSs. The 
UCM Round 1 and 2 national cross-sections represent significantly large 
samples of national occurrence data. Within each cross-section, the 
actual number of systems and analytical records for each contaminant 
varies. The support document, ``The Analysis of Occurrence Data from 
the Unregulated Contaminant Monitoring (UCM) Program and National 
Inorganics and Radionuclides Survey (NIRS) in Support of Regulatory 
Determinations for the Second Drinking Water Contaminant Candidate 
List'' (USEPA, 2006c), provides a description of how the national 
cross-sections for the Round 1 and Round 2 data sets were developed.
    EPA constructed the national cross-sections in a way that provides 
a balance and range of States with varying pollution potential 
indicators, a wide range of the geologic and hydrologic conditions, and 
a very large sample of monitoring data points. While EPA recognizes 
that some limitations exist, the Agency believes that the national 
cross-sections do provide a reasonable estimate of the overall 
distribution and the central tendency of contaminant occurrence across 
the United States.
    EPA analyzed the UCM Round 1 and 2 National Cross-Section data to 
generate the following initial occurrence and exposure summary 
statistics:
     The total number of systems and the total population 
served by these systems,
     The number and percentage of systems with at least 1 
observed detection that has a concentration greater than \1/2\ the HRL 
and greater than the HRL (or in some cases greater than or equal to the 
MRL), and
     The number of people and percentage of the population 
served by systems with at least 1 observed detection that has a 
concentration greater than \1/2\ the HRL and greater than the HRL (or 
in some cases greater than or equal to the MRL).\12\
---------------------------------------------------------------------------

    \12\ EPA's support documents (USEPA, 2006a and 2006c) provide 
summary statistics for the median and 99th percentile concentrations 
of all analytical detections and detailed occurrence results based 
on the UCM Round 1 and 2 Nationals Cross-Sectons according to source 
water type (surface versus ground water), system size, and State.
---------------------------------------------------------------------------

    The initial UCM summary occurrence statistics for 1,3-
dichloropropene and 1,1,2,2-tetrachloroethane are presented in section 
IV.B of this action.
    c. National Inorganic and Radionuclide Survey. In the mid-1980's, 
EPA conducted the NIRS to provide a statistically representative sample 
\13\ of the national occurrence of inorganic contaminants in community 
water systems (CWSs) served by ground water. EPA used data from NIRS, 
as well as a supplemental survey, to evaluate occurrence for boron.
---------------------------------------------------------------------------

    \13\ NIRS was designed to provide results that are statistically 
representative of natioal occurrence at CWSs using ground water 
sources and is stratified based on system size (population served by 
the system). Most of the NIRS data are from smaller systems (92 
percent from systems serving 3,300 persons or fewer).
---------------------------------------------------------------------------

    The NIRS database includes 36 radionuclides and inorganic compounds 
(IOCs), including boron. The NIRS provides contaminant occurrence data 
from 989 ground water CWSs covering 49 States (all except Hawaii) and 
does not include surface water systems. The survey focused on ground 
water systems, in part because IOCs tend to occur more frequently and 
at higher concentrations in ground water than in surface water. Each of 
the 989 randomly selected CWSs was sampled at a single time between 
1984 and 1986.
    EPA analyzed the NIRS data to generate the following occurrence and 
exposure summary statistics for boron:
     The total number of systems and the total population 
served by these systems,
     The number and the percentage of systems with at least 1 
detection that has a concentration greater than \1/2\ the HRL and 
greater than the HRL,
     The number of people and percentage of the population 
served by systems with at least 1 observed detection that has a 
concentration greater than \1/2\ the HRL and greater than the HRL.\14\
---------------------------------------------------------------------------

    \14\ EPA's support documents (USEPA, 2006a and 2006c) provide 
the number and percentage of systems with detections, the 99th 
percentile concentration of all samples, the 99th percentile 
concentration of samples with detections, and the median 
concentration of samples with detections.
---------------------------------------------------------------------------

    Similar to the treatment of the UCM cross-section data, the actual 
values for the NIRS analyses of boron are reported in section IV.B. 
Because the NIRS data were collected in a randomly designed sample 
survey, these summary statistics are representative of national 
occurrence in ground water CWSs.
    One limitation of the NIRS is a lack of occurrence data for surface 
water systems. To provide perspective on the occurrence of boron in 
surface water systems relative to ground water systems, EPA reviewed 
and took into consideration a recent boron occurrence survey funded by 
American Water Works Association Research Foundation (AWWARF) (Frey et 
al., 2004). A short description of the AWWARF study is provided in the 
supplemental section

[[Page 24025]]

(section III.B.2) and the results of the AWWARF survey are presented in 
section IV.B of this action.
    d. Presentation of Occurrence Data and Analytical Approach. As 
noted previously, the occurrence values and summary statistics 
presented in this action are the actual data from the UCMR 1, UCM, and 
NIRS data sets. These occurrence values represent direct counts of the 
number and percent of systems, and population served by systems, with 
at least 1 analytical detection above some specified concentration 
threshold. EPA considered this to be the most straightforward and 
accurate way to present these data for the regulatory determination 
process.
    While both UCMR 1 and UCM data could support more involved 
statistical modeling to characterize occurrence based on mean (rather 
than peak) concentrations, EPA chose not to perform this step for the 
regulatory determinations proposed in this action. EPA believes that 
presenting the actual results of the occurrence monitoring is straight-
forward and the use of an analysis based on peak concentrations 
provides conservative estimates of occurrence and potential exposure 
from drinking water. Given that the preliminary determinations for the 
11 contaminants discussed in this action are negative, it is not 
necessary to go beyond the conservative (peak concentration) approach 
used for this analysis.
    2. Supplemental Data. The Agency evaluated several sources of 
supplemental occurrence information to augment the primary drinking 
water occurrence data, to evaluate the likelihood of contaminant 
occurrence, and/or to more fully characterize a contaminant's presence 
in the environment. Sections II.B.2.a through II.B.2.f provide brief 
descriptions of the main supplemental information/data sources cited in 
this action. Summarized occurrence findings from these supplemental 
sources are presented in Section IV.B, the contaminant profiles 
section. While the following descriptions cover the more commonly 
referenced supplemental sources of information/data, they do not 
include every study and survey cited in the contaminant discussions. A 
more detailed discussion of the supplemental sources of information/
data that EPA evaluated for each contaminant can be found in the 
comprehensive regulatory determination support document (USEPA, 2006a).
    a. USGS NAWQA Information/Data. The United States Geological Survey 
(USGS) collects long-term and nationally consistent data describing 
water quality in ground water and surface water. In 1991, USGS 
implemented the National Water-Quality Assessment (NAWQA) Program for 
10-year cyclical data collection and data analyses. During the first 
cycle (1991-2001), the NAWQA program monitored 51 major watersheds and 
aquifers (study units), which supply more than 60% of the nation's 
drinking water and water used for agriculture and industry in the U.S. 
(Hamilton et al., 2004). NAWQA has collected data from over 6,400 
surface water and 7,000 ground water sampling points. USGS National 
Synthesis teams prepare comprehensive analyses of data on topics of 
particular concern. EPA evaluated information/data from the following 
USGS National Synthesis reports/projects:
    (1) The NAWQA Pesticide National Synthesis Project. In 2003, USGS 
posted the preliminary results from the first cycle of monitoring for 
pesticides in streams and ground water. USGS considers these results to 
be provisional. The results and the data can be accessed at http://ca.water.usgs.gov/pnsp/. Data are presented separately for surface 
water and ground water, as well as bed sediments and biota. In each 
case, results are subdivided by land use category. Land use categories 
include agricultural, urban, mixed (deeper aquifers of regional extent 
in the case of ground water), and undeveloped. In this action, the 
NAWQA pesticide data for surface water are referenced as Martin et al. 
(2003) and the ground water data are referenced as Kolpin and Martin 
(2003).
    (2) The National Survey of MTBE and Other VOCs in Community 
Drinking Water Sources (part of the VOC National Synthesis Project). In 
2003, USGS published the survey findings for MTBE, other ether gasoline 
oxygenates, and other volatile organic compounds (VOCs) in source water 
used by CWSs in the United States. The survey was funded by AWWARF and 
performed by USGS in collaboration with the Metropolitan Water District 
of Southern California and the Oregon Health and Science University. 
USGS performed the survey in two independent stages designed to provide 
representative sampling of all CWSs in the United States (Random 
Source-Water Survey) and to improve understanding of the temporal 
variability of MTBE and other compounds in selected water sources 
(Focused Source-Water Survey). Participating water utilities provided 
samples that were analyzed for 66 VOCs. The random survey design 
selected 954 CWSs to be nationally representative of surface and ground 
waters sources used by CWSs. The focused survey studied source waters 
from 134 CWSs suspected or known to contain MTBE. The reports/results 
and data sets from the survey can be accessed at http://sd.water.usgs.gov/nawqa/vocns/nat_survey.html. The random survey 
results can be found in the USGS Water Resources Investigations Report 
02-4079, referenced as Grady (2003). The focused survey results can be 
found in the USGS Water Resources Investigations Report 02-4084, 
referenced as Delzer and Ivahnenko (2003a).
    b. USGS National Highway Runoff Data and Methodology Synthesis. In 
addition to the NAWQA project, USGS has prepared additional surveys of 
national contaminant occurrence. For the National Highway Runoff Data 
and Methodology Synthesis, USGS conducted a review of 44 studies of 
semi-volatile organic compounds (SVOCs) and VOCs in runoff conducted 
since 1970. The USGS Synthesis sought to evaluate data quality 
parameters for comparison between and among these studies, including 
documentation of sampling protocols and methods, limits of reporting 
and detection, and protocols of quality-control and quality-assurance. 
The complete USGS report is Open-File Report 98-409 and is referenced 
as Lopes and Dionne (1998).
    c. Toxics Release Inventory. EPA established the Toxics Release 
Inventory (TRI) in 1987 in response to section 313 of the Emergency 
Planning and Community Right-to-Know Act (EPCRA). EPCRA section 313 
requires facilities to report to both EPA and the States annual 
information on toxic chemical releases from facilities that meet 
reporting criteria. EPCRA section 313 also requires EPA to make this 
information available to the public through a computer database. This 
database is accessible through TRI Explorer, which can be accessed at 
http://www.epa.gov/triexplorer. In 1990 Congress passed the Pollution 
Prevention Act, which required that additional data on waste management 
and source reduction activities be reported under TRI. The TRI database 
details not only the types and quantities of toxic chemicals released 
to the air, water, and land by facilities, but also provides 
information on the quantities of chemicals sent to other facilities for 
further management (USEPA, 2002b and 2003b).
    Facilities are required to report releases and other waste 
management activities related to TRI chemicals if they manufacture, 
process, or otherwise use more than established threshold quantities of 
these chemicals. Currently

[[Page 24026]]

for most chemicals, the thresholds are 25,000 pounds for manufacturing 
and processing and 10,000 pounds for use. Although TRI can provide a 
general idea of release trends, it is far from exhaustive and should 
not be used to estimate general public exposure to a chemical (USEPA, 
2002b and 2003b).
    d. Pesticides in Ground Water Database. The Pesticides in Ground 
Water Database (PGWDB) is a compilation of data from ground water 
studies conducted by Federal, State, and local governments, the 
pesticide industry, and other institutions between 1971 and 1991 
(USEPA, 1992b). Data from 68,824 wells in 45 states are included. The 
vast majority of the wells (65,865) were drinking water wells. 
Monitoring was conducted for 258 pesticides and 45 degradates. Not all 
studies tested for every compound.
    e. The National Pesticide Survey. In 1990, EPA completed a national 
survey of pesticides in drinking water wells. The purpose of the 
National Pesticide Survey (NPS) was to determine the national 
occurrence frequencies and concentrations of select pesticides in the 
nation's drinking water wells, and to improve EPA's understanding of 
how pesticide occurrence in ground water correlates with patterns of 
pesticide usage and ground water vulnerability. The survey included 
approximately 1,300 CWS wells and rural domestic wells. Sampling was 
conducted between 1988 and 1990. Wells were sampled for 101 pesticides, 
25 pesticide degradates, and nitrate. The survey targeted areas 
representing a variety of pesticide usage levels and ground water 
vulnerability. The survey was designed to provide a statistically 
reliable estimate of pesticide occurrence in the nation's drinking 
water wells (USEPA, 1990a).
    f. The AWWARF Boron Study. The American Water Works Research 
Foundation funded a survey to evaluate the occurrence of boron (as well 
as hexavalent chromium) in drinking water sources (Frey et al., 2004). 
The AWWARF study recruited 189 PWSs representing 407 source waters in 
41 states. Of the 407 source water sample kits distributed in 2003, 
approximately 342 were returned. Of these 342 samples, 341 were 
analyzed for boron. Approximately 67 percent (or 228) represented 
ground water sources and 33 percent (or 113) represented surface water 
sources. The results of the AWWARF survey for boron are presented in 
section IV.B of this action.
    3. Supporting Documentation for Occurrence. As mentioned in section 
II.E, EPA prepared several technical occurrence documents to support 
this action. These technical occurrence documents include the 
following:
     ``The Analysis of Occurrence Data from the Unregulated 
Contaminant Monitoring (UCM) Program and National Inorganics and 
Radionuclides Survey (NIRS) in Support of Regulatory Determinations for 
the Second Drinking Water Contaminant Candidate List'' (USEPA, 2006c), 
which this action refers to as the ``UCM and NIRS Occurrence Report.''
     ``The Analysis of Occurrence Data from the First 
Unregulated Contaminant Monitoring Regulation (UCMR 1) in Support of 
Regulatory Determinations for the Second Drinking Water Contaminant 
Candidate List'' (USEPA, 2006b), which this action refers to as the 
``UCMR 1 Occurrence Report.''
    The ``UCM and NIRS Occurrence Report'' provides more detailed 
information about the UCM and the NIRS data, how EPA assessed the data 
quality, completeness, and representativeness, and how the data were 
used to generate estimates of contaminant occurrence. The ``UCMR 1 
Occurrence Report'' provides more detailed information about the UCMR 1 
data, how EPA assessed the data quality, completeness, 
representativeness, and how the data were used to generate estimates of 
contaminant occurrence.
    The comprehensive regulatory support document (USEPA, 2006a) 
provides a summary of the results from the drinking water occurrence 
analyses discussed in the aforementioned technical support documents, 
as well as information on production and use, environmental releases, 
and/or occurrence in ambient water, potential health effects, the 
Agency's preliminary determination, and the rationale for the 
determination.

IV. Preliminary Regulatory Determinations

A. Summary of the Preliminary Regulatory Determination

    The Agency has made a preliminary determination that each of the 11 
contaminants listed in Table 3 do not meet all three of the SDWA 
criteria (discussed in section II.C) and thus do not warrant regulation 
with an NPDWR. Table 3 also summarizes the primary information used to 
make these regulatory determinations. Section IV.B of this action 
provides a more detailed summary of the information and the rationale 
used by the Agency to reach its preliminary decisions. The Agency 
solicits public comment on the preliminary determinations for these 11 
contaminants.
BILLING CODE 6560-50-P

[[Page 24027]]

[GRAPHIC] [TIFF OMITTED] TP01MY07.051

BILLING CODE 6560-50-C

B. Contaminant Profiles

    This section provides further details on the background, health, 
and occurrence information that the Agency used to evaluate each of the 
11 candidate contaminants considered for regulatory determination. For 
each candidate, the Agency evaluated the available human and 
toxicological data, derived a health reference level, and evaluated the 
potential and/or likely occurrence and exposed population for the 
contaminant in public water systems. The Agency used the findings from 
these evaluations to determine whether the three SDWA statutory 
requirements were satisfied.
    As discussed in section II.E, the Agency has also prepared a 
regulatory support document (USEPA, 2006a) that provides more details 
on the background, health, and occurrence information/analyses used to 
evaluate and make preliminary determinations for these 11 candidates.
1. Boron
    a. Background. Boron, a metalloid, tends to occur in nature in the 
form of borates (e.g., boric acid, borax, boron oxide). Man-made 
releases are typically in the form of borates or boron halides (e.g., 
boron trichloride, boron trifluoride). Boron compounds are used in the 
production of glass, ceramics, soaps, fire retardants, pesticides, 
cosmetics, photographic materials, and high energy fuels (USGS, 2004; 
ATSDR, 1992).
    Natural processes such as the weathering of rocks, volcanic 
activity, and geothermal steam contribute to the release of boron in 
the environment. Releases to the environment from human activities 
occur through the production, use, and disposal of boron-containing 
compounds (e.g., industrial emissions, fertilizer and herbicide runoff, 
hazardous waste deposits, and municipal sewage) (HSDB, 2004a; ATSDR, 
1992).
    Although quantitative data are not available on the man-made 
releases of most borates in the United States, two boron halide 
compounds, boron trichloride and boron trifluoride, are listed as 
Toxics Release Inventory (TRI) chemicals. TRI data for boron 
trichloride and boron trifluoride are reported for the years 1995 to 
2003 (USEPA, 2006d). The TRI data show boron trichloride releases from 
facilities in 6 States and indicate that air emissions account for all 
of the total releases of boron trichloride (on- and off-site), which 
generally fluctuated in the range of hundreds of pounds per year during 
the period of record. The TRI data show boron trifluoride releases from 
facilities in 14 States and indicate that air emissions also account 
for nearly all of the boron trifluoride releases, which ranged in the 
tens of thousands of pounds annually.
    b. Health Effects. The Institute of Medicine (IOM, 2001) of the 
National Academies categorizes boron as a possible trace mineral 
nutrient for humans. Boron is essential for plant growth and deficiency 
studies in animals and humans have provided some evidence that low 
intakes of boron affects cellular function and the activity of other 
nutrients. It may interact with Vitamin D and calcium homeostasis, 
influence estrogen metabolism, and play a role in cognitive function 
(IOM, 2001). Iyengar et al. (1988) reported an average dietary intake 
of 1.5 mg/day for male adults based on the Food and Drug Administration 
(FDA) Total Diet Study (TDS).
    Some human oral data are available from cases where boron was 
ingested as a medical treatment. When the amount ingested was less than 
3.68 mg/kg, subjects were asymptomatic, while doses of 20 and 25 mg/kg 
resulted in nausea and vomiting. Case reports and surveys of accidental 
poisonings indicate that the lethal doses of boron range from 15 to 20 
grams (approximately 200 to 300 mg/kg) for adults, 5 to 6 grams 
(approximately 70 to 85 mg/kg) for children, and 2 to 3 grams 
(approximately 30 to 45 mg/kg) for infants (USEPA, 2004b).
    The primary adverse effects seen in animals after chronic exposure 
to low doses of boron generally involve the testes and developing 
fetus. Chronic effects of dietary boron exposure in two-year studies 
included testicular atrophy and spermatogenic arrest in dogs, decreased 
food consumption,

[[Page 24028]]

suppressed growth, and testicular atrophy in rats, and decreased 
survival, testicular atrophy, and interstitial cell hyperplasia in 
mice. Although researchers observed some increases in tumor incidences 
in the liver and in subcutaneous tissues in mice, based on comparisons 
to historic controls, these tumors were determined not to be associated 
with exposure to boron from boric acid (USEPA, 2004b). Boron is not 
considered mutagenic and the Agency determined that there are 
inadequate data to assess the human carcinogenic potential for boron 
(USEPA, 2004c).
    In developmental studies with rats, mice, and rabbits, oral 
exposure to boric acid resulted in decreased pregnancy rate, increased 
prenatal mortality, decreased fetal weights, and increased 
malformations in fetuses and pups. However, these reproductive effects 
were associated with maternal toxicity including changes in maternal 
organ weights, body weights, weight gain, and increased renal tubular 
dilation and/or regeneration (Price et al., 1990, 1994, 1996; Heindel 
et al., 1992, 1994; Field et al., 1989). Reproductive effects in males 
were noted in the subchronic and chronic studies described in the 
preceding paragraphs.
    The EPA RfD for boron is 0.2 mg/kg/day (USEPA, 2004c) based on 
developmental effects in rats from two studies (Price et al., 1996; 
Heindel et al., 1992). The RfD was derived using the benchmark dose 
(BMD) method (bench mark dose level or BMDL from Allen et al., 1996). 
EPA calculated the HRL of 1.4 mg/L or 1,400 [mu]g/L for boron using the 
RfD of 0.2 mg/kg-day and a 20 percent screening relative source 
contribution.
    EPA also evaluated whether health information is available 
regarding the potential effects on children and other sensitive 
populations. Studies in rats, mice, and rabbits identify the developing 
fetus as potentially sensitive to boron. Price et al. (1996) identified 
a LOAEL of 13.3 mg/kg-day and an NOAEL of 9.6 mg/kg-day in the 
developing fetus, based on decreased fetal body weight in rats. 
Accordingly, boron at concentrations greater than the HRL might have an 
effect on prenatal development. Individuals with severely impaired 
kidney function might also be sensitive to boron exposure since the 
kidney is the most important route for excretion.
    c. Occurrence Analyses. The National Inorganics and Radionuclides 
Survey (NIRS) included boron as an analyte. Using data from NIRS, EPA 
performed an initial evaluation of occurrence and exposure at levels 
greater than 700 [mu]g/L (\1/2\ the HRL) and greater than 1,400 [mu]g/L 
(the HRL for boron). The NIRS data indicate that approximately 4.3 
percent (or 43) of the 989 ground water PWSs sampled had detections of 
boron at levels greater than 700 [mu]g/L, affecting approximately 2.9 
percent of the population served (or 42,700 people from 1.48 million). 
Approximately 1.7 percent (or 17) of 989 ground water PWSs sampled had 
detections of boron at levels greater than 1,400 [mu]g/L, affecting 
approximately 0.4 percent of the population served (6,400 people from 
1.48 million) (USEPA, 2006a and 2006c).
    Because NIRS did not contain data for surface water systems, the 
Agency evaluated the results of a survey funded by the American Water 
Works Association Research Foundation (Frey et al., 2004) to gain a 
better understanding of the potential occurrence of boron in surface 
water systems. The AWWARF study recruited 189 PWSs representing 407 
source waters that covered 41 states. Of these 407 PWS source water 
samples, 342 were returned and 341 were analyzed for boron. Of these 
341 samples, approximately 67 percent (or 228) represented ground water 
sources and 33 percent (or 113) represented surface water sources. None 
of the 113 surface water sources exceeded the boron HRL of 1,400 [mu]g/
L and the maximum concentration observed in surface water was 345 
[mu]g/L. Extrapolation of the data indicates that 95 percent of the 
ground water detections had boron levels less than 1,054 [mu]g/L; the 
maximum observed concentration in ground water was approximately 3,300 
[mu]g/L. Seven of the 228 ground water sources (from 5 systems) had 
boron concentrations greater than 1,400 [mu]g/L (Seidel, 2006).
    d. Preliminary Determination. The Agency has made a preliminary 
determination not to regulate boron with an NPDWR. While boron was 
found at levels greater than the HRL (and \1/2\ the HRL) in several of 
the ground water systems surveyed by NIRS, it was not found at levels 
greater than the HRL (or \1/2\ the HRL) in the surface waters sources 
evaluated in the AWWARF study. Taking this surface water information 
into account, the Agency believes that the overall national occurrence 
and exposure from both surface and ground water systems together is 
likely to be lower than the values observed for the NIRS ground water 
data. Because boron is not likely to occur at levels of concern when 
considering both surface and ground waters systems, the Agency believes 
that a national primary drinking water regulation does not present a 
meaningful opportunity for health risk reduction.
    The Agency encourages those States with public water systems that 
have boron at concentrations above the HRL to evaluate site-specific 
protective measures and to consider whether State-level guidance (or 
some other type of action) is appropriate. The Agency also plans to 
update the Health Advisory for boron to provide more recent health 
information. The updated Health Advisory will provide information to 
any States with public water systems that may have boron above the HRL.
2 and 3. Mono- and Di-Acid Degradates of Dimethyl 
Tetrachloroterephthalate (DCPA)
    a. Background. Dimethyl tetrachloroterephthalate (DCPA), a 
synthetic organic compound (SOC) marketed under the trade name 
``Dacthal,'' is a pre-emergent herbicide historically used to control 
weeds in ornamental turf and plants, strawberries, seeded and 
transplanted vegetables, cotton, and field beans. As of 1990, more than 
80 percent of its use was for turf, including golf courses and home 
lawns (USEPA, 1990b). On July 27, 2005, in response to concerns about 
groundwater contamination (especially for one of the DCPA degradates), 
the Agency published a Federal Register notice announcing that the 
registrant for Dacthal had voluntarily terminated a number of uses for 
products containing DCPA (70 FR 43408; USEPA, 2005f). The only uses 
retained were those for use on sweet potatoes, eggplant, kale and 
turnips.
    DCPA is not especially mobile or persistent in the environment. 
Biodegradation and volatilization are the primary dissipation routes. 
Degradation of DCPA forms two breakdown products, the mono-acid 
degradate (or monomethyl tetrachloroterephthalate or MTP) and the di-
acid degradate (tetrachloroterephthalic acid or TPA). The di-acid, 
which is the major degradate, is unusually mobile and persistent in the 
field, with a potential to leach into water (USEPA, 1998c).
    Several studies and reports provide estimates of the amount of DCPA 
used during the 1990s in the United States. The Agency estimated that 
1.6 million pounds of DCPA active ingredient a.i. were used annually in 
the early 1990s (USEPA, 1998c). USGS estimated that approximately 998 
thousand pounds of DCPA a.i. were used annually circa 1992 (Thelin and 
Gianessi, 2000). The National Center for Food and Agricultural Policy 
(NCFAP, 2004) estimates that approximately 1.7 million

[[Page 24029]]

pounds of DCPA a.i. were used in 1992 and approximately 600 thousand 
pounds a.i. were used in 1997 (NCFAP, 2004). The NCFAP data suggest a 
decrease in the use of DCPA from the early to the late 1990s.
    b. Health Effects. Currently, no subchronic or chronic studies are 
available to assess the toxicological effects of MTP (the mono-acid 
degradate) and 3 studies in rats (30 and 90-day feeding studies and a 
one-generation reproductive study) are available for TPA (the di-acid 
degradate). The effects of exposure were mild (weight loss and 
diarrhea) and occurred at doses greater than or equal to 2,000 mg/kg/
day. No reproductive effects were observed.
    The present toxicity database for MTP and TPA is not sufficient to 
derive RfDs for these two chemicals. However, since the available data 
indicate that neither MTP nor TPA are more toxic than their parent 
compound, DCPA, the Agency suggests that the RfD for the DCPA parent 
would be protective against exposure from these two DCPA metabolites 
(USEPA, 1998c). Both compounds are formed in the body from the DCPA 
parent and therefore, the toxicity of these degradates is reflected in 
the toxicity of the parent. The RfD for DCPA is 0.01 mg/kg/day based on 
a chronic rat study (ISK Biotech Corporation, 1993) with a NOAEL of 1.0 
mg/kg/day and an uncertainty factor of 100 for rat to human 
extrapolation and intra-species variability.
    No carcinogenicity studies have been performed using either TPA or 
MTP. Based on the cancer data for the parent and lack of mutagenicity 
for TPA and DCPA, the Agency (USEPA, 2004d) concludes that TPA is 
unlikely to pose a cancer risk. Klopman et al. (1996) evaluated the 
carcinogenic potential of TPA based on its chemical and biological 
properties, as well as by a variety of computational tools, and 
determined that it did not present any substantial carcinogenic risk. 
There was suggestive evidence that DCPA could be carcinogenic based on 
an increased incidence of thyroid and liver tumors in rats. The 
presence of hexachlorobenzene and dioxin as impurities in the material 
tested could have contributed to the cancer risk.
    Using the DCPA RfD of 0.01 mg/kg/day (USEPA, 1994) and a 20 percent 
screening relative source contribution, the Agency calculated an HRL of 
0.07 mg/L or 70 [mu]g/L for DCPA and used this HRL for TPA and MTP.
    EPA also evaluated whether health information is available 
regarding the potential effects on children and other sensitive 
populations. There are no data that identify a particular sensitive 
population for DCPA exposure. Results of a single developmental study 
indicate that exposure to pregnant dams with doses less than or equal 
to 2,500 mg/kg/day of TPA via gavage did not have an adverse effect on 
the fetus. EPA did not identify any data that suggest gender-related 
differences in toxicity or sensitivity in the elderly.
    c. Occurrence. EPA included the DCPA mono- and di-acid degradates 
(MTP and TPA) as analytes in the UCMR 1. The analysis results reported 
for UCMR 1 are the sum of both the mono- and di-acid degradates. EPA 
converted the analysis result for the degradates to the parent DCPA 
equivalent and performed an initial evaluation of occurrence and 
exposure at levels greater than 35 [mu]g/L (\1/2\ the HRL) and greater 
than 70 [mu]g/L (the HRL). As previously discussed, EPA used the HRL 
derived for the DCPA parent because it includes the toxicity for the 
mono- and di-acid degradates. While the UCMR 1 data indicate that the 
DCPA degradates were the most commonly reported analytes in the 
monitoring survey (detected at an MRL of 1 [mu]g/L in 772 samples from 
175 of the 3,868 PWSs sampled), very few systems exceeded the health 
level of concern. PWSs with detections were found in 24 States and 1 
Territory. The UCMR 1 data indicate that approximately 0.05 percent (or 
2) of the 3,868 PWSs sampled had a detection of the DCPA degradates at 
levels greater than 35 [mu]g/L, affecting approximately 0.33 percent of 
the population served (or 739,000 people from 225 million). 
Approximately 0.03 percent (or 1) of the 3,868 PWSs sampled have a 
detection of the DCPA degradates at levels greater than 70 [mu]g/L, 
affecting less than 0.01 percent of the population served (or 500 
people from 225 million) (USEPA, 2006a and 2006b).
    EPA also evaluated several sources of supplemental occurrence 
information for the DCPA parent, the mono-acid degradate and/or the di-
acid degradate. These supplemental sources include:
     The National Pesticide Survey (NPS),
     The provisional pesticide results from the 1992-2001 USGS 
NAWQA survey of ambient surface and ground waters across the U.S., and
     Studies performed by the DCPA or dacthal registrant.
    As part of the National Pesticide Survey, EPA collected samples 
from approximately 1,300 community water systems and rural drinking 
water wells between 1988 and 1990. The NPS included monitoring for the 
DCPA parent and the di-acid degradate. The DCPA parent was not detected 
in any wells (using a detection limit of 0.06 [mu]g/L). While the di-
acid degradate was detected in 49 of 1,347 wells (using a detection 
limit of 0.1 [mu]g/L), the maximum reported concentration of 7.2 [mu]g/
L did not exceed the HRL of 70 [mu]g/L (USEPA, 1990a).
    The USGS NAWQA program included the DCPA parent and the mono-acid 
degradate as analytes in its 1992-2001 monitoring survey of ambient 
surface and ground waters across the United States. EPA evaluated the 
results of the provisional data, which are available on the Web (Martin 
et al., 2003; Kolpin and Martin, 2003). While the USGS detected the 
DCPA parent in both surface and ground waters, at least 95 percent of 
the samples from the various land use settings were less than or equal 
to 0.007 [mu]g/L. The estimated maximum surface water concentration, 40 
[mu]g/L (agricultural setting), and the estimated maximum ground water 
concentration, 10 [mu]g/L (agricultural setting), are both less than 70 
[mu]g/L (the DCPA HRL). While the USGS detected the mono-acid degradate 
in both surface waters and ground waters, at least 95 percent of the 
samples from the various land use settings were less than 0.07 [mu]g/L 
(the reporting limit for the mono-acid degradate). The maximum surface 
water concentration, 0.43 [mu]g/L (agricultural setting), and the 
maximum ground water concentration, 1.1 [mu]g/L (agricultural setting), 
are both less than 70 [mu]g/L (the DCPA HRL, which includes the 
toxicity of the degradates).
    Beginning in 1992, the registrant for DCPA performed two small-
scale ground water occurrence studies in New York and California over a 
period of 17 and 22 months, respectively. The registrant monitored for 
the DCPA parent and both of its degradates. The average reported 
values, which are the sum of the parent and its degradates, were 50.36 
[mu]g/L in New York and 12.75 [mu]g/L in California. Neither average 
value exceeded the HRL of 70 [mu]g/L (USEPA, 1998c).
    d. Preliminary Determination. The Agency has made a preliminary 
determination not to regulate the DCPA mono-acid degradate and/or the 
DCPA di-acid degradate with an NPDWR. Because these degradates appear 
to occur infrequently at health levels of concern in PWSs, the Agency 
believes that a national primary drinking water regulation does not 
present a meaningful opportunity for health risk reduction. While the 
Agency recognizes that these degradates have been detected in the PWSs 
monitored under the UCMR 1, only 1 PWS had a detect above the HRL.

[[Page 24030]]

    The Agency encourages those States with public water systems that 
have detects for these degradates to evaluate site-specific protective 
measures and to consider whether State-level guidance (or some other 
type of action) is appropriate. The Agency also plans to update the 
Health Advisory for the DCPA parent to include the mono and di acid 
degradates, as well as any recent health information related to these 
compounds. The updated Health Advisory will provide information to any 
States with public water systems that may have DCPA degradates at 
levels above the HRL.
4. 1,1-Dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE)
    a. Background. DDE is a primary metabolite of DDT,\15\ a pesticide 
once used to protect crops and eliminate disease-carrying insects in 
the U.S. until it was banned in 1973. DDE itself has no commercial use 
and is only found in the environment as a result of contamination and/
or breakdown of DDT. While DDE tends to adsorb strongly to surface soil 
and is fairly insoluble in water, it may enter surface waters from 
runoff that contains soil particles contaminated with DDE. In both soil 
and water, DDE is subject to photodegradation, biodegradation, and 
volatilization (ATSDR, 2002).
---------------------------------------------------------------------------

    \15\ 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane.
---------------------------------------------------------------------------

    b. Health Effects. DDE is not produced as a commercial product. 
This has limited the numbers of conventional studies that have been 
performed to assess toxicological properties. Limited data on DDE, 
mostly from a National Cancer Institute (NCI) bioassay, suggest that 
the liver is the primary target organ in mammalian species. However, 
the NCI study did not evaluate a full array of noncancer endpoints. 
There is an RfD of 0.0005 mg/kg/day for the parent pesticide DDT based 
on a NOAEL of 0.05 mg/kg/day from a dietary subchronic study (USEPA, 
1996b). In this study, liver lesions were identified at a LOAEL of 0.25 
mg/kg/day. Data on DDT identify effects on the nervous and hormonal 
systems as adverse effects that might also be seen with DDE because it 
is one of DDT's primary metabolites. The limited data for DDE suggest 
that any effects on the nervous system are less severe than those seen 
with DDT. Endocrine effects from DDE are discussed in this section.
    Based on animal studies DDE is likely to be carcinogenic to humans. 
This classification is based on increases in the incidence of liver 
tumors, including carcinomas, in two strains of mice and in hamsters 
after dietary exposure to DDE. Some epidemiological studies suggest a 
possible association of the levels of DDE in serum with breast cancer. 
However, other studies with similar methodologies do not show any 
association. DDE was mutagenic in mouse lymphoma L5178Y and Chinese 
hamster V79 cells but negative in the Ames assay. In the 1988 IRIS, EPA 
calculated an oral slope factor of 0.34 (mg/kg/day)-1 for 
DDE (USEPA, 1988a). For this regulatory determination, EPA calculated 
an oral slope factor from the same data set (from the 1988 IRIS) using 
the EPA 1999 Cancer Guidelines (USEPA, 1999a). The revised slope factor 
is 1.67 x 10-1 (mg/kg/day)-1 resulting in a one-
in-a-million cancer-risk (HRL) of 0.2 [mu]g/L.
    There are some indications that DDE has an adverse impact on the 
immune system (Banerjee et al., 1996). Oral exposures to 22 mg/kg/day 
for 6 weeks suppressed serum immunoglobin levels and antibody titers. 
Inhibition of leucocytes and macrophage migration were observed at the 
cellular level. Considerable evidence exists that DDE can act as an 
endocrine disruptor since it binds to the estrogen and androgen 
receptors. DDE has a stronger affinity for the androgen receptor than 
for the estrogen receptor. It competes with testicular hormones for the 
androgen receptor leading to receptor-related changes in gene 
expression (Kelce et al., 1995).
    EPA evaluated whether health information is available regarding the 
potential effects on children and other sensitive populations. Children 
and adolescents may be sensitive populations for exposure to DDE due to 
its endocrine disruption properties. Some data suggest that DDE can 
delay puberty in males (ATSDR, 2002).
    c. Occurrence. EPA included DDE as an analyte in the UCMR 1. 
Because the HRL for DDE (0.2 [mu]g/L) is lower than the minimum 
reporting limit (MRL) used for monitoring (0.8 [mu]g/L), EPA used the 
MRL value to evaluate occurrence and exposure. The MRL is within the 
10-4 to the 10-6 cancer risk range for DDE. In 
evaluating the UCMR 1 data, EPA found that approximately 0.03 percent 
(or 1) of the 3,867 PWSs sampled had a detection of DDE at the MRL of 
0.8 [mu]g/L, affecting approximately 0.01 percent of the population 
served (or 18,000 people from 226 million) (USEPA, 2006a and 2006b).
    The USGS NAWQA program included DDE as an analyte in its 1992-2001 
monitoring survey of ambient surface and ground waters across the 
United States. EPA evaluated the results of the provisional data, which 
are available on the Web (Martin et al., 2003; Kolpin and Martin, 
2003), as a supplemental source of occurrence information. While the 
USGS detected DDE in both surface and ground waters, 95 percent of the 
samples from the various land use settings were less than 0.006 [mu]g/L 
(the USGS reporting limit). The maximum surface water concentration, 
0.062 [mu]g/L (agricultural setting), and the maximum ground water 
concentration, 0.008 [mu]g/L (agricultural setting), are both less than 
0.2 [mu]g/L (the DDE HRL).
    d. Preliminary Determination. The Agency has made a preliminary 
determination not to regulate DDE with an NPDWR. Because DDE appears to 
occur infrequently at levels of concern in PWSs, the Agency believes 
that a national primary drinking water regulation does not present a 
meaningful opportunity for health risk reduction. DDE was detected in 
only one of the PWSs monitored under the UCMR 1 at a level greater than 
the MRL (0.8 [mu]g/L), a concentration that is within the 
10-4 to the 10-6 cancer risk range. In addition, 
ambient water data from the USGS indicate that the maximum 
concentrations detected in surface and ground water were less than the 
HRL of 0.2 [mu]g/L.
    EPA recognizes that DDE is listed as a probable human carcinogen. 
For this reason, the Agency encourages those States with public water 
systems that might have DDE above the HRL to evaluate site-specific 
protective measures and to consider whether State-level guidance (or 
some other type of action) is appropriate.
5. 1,3-Dichloropropene (1,3-DCP; Telone)
    a. Background. 1,3-Dichloropropene (1,3-DCP), a synthetic volatile 
organic compound, is used as a pre-plant soil fumigant to control 
nematodes and other pests in soils to be planted with all types of food 
and feed crops. 1,3-DCP is typically injected 12'' to 18'' beneath the 
soil surface and can only be used by certified handlers (USEPA, 1998b). 
To mitigate risks to drinking water, 1999 labeling requirements 
restrict the use of 1,3-DCP:
     In areas with shallow ground water and vulnerable soils in 
certain northern tier States (ND, SD, WI, MN, NY, ME, NH, VT, MA, UT, 
and MT);
     In fields within 100 feet of a drinking water well; and
     In areas overlying karst \16\ geology.
---------------------------------------------------------------------------

    \16\ Karst is a type of typography that is formed by the 
dissolution and collapse of soluble rocks (typically limestone and 
dolomite). According to the Karst Waters Institute, as excerpted by 
USGS (2006), common geological characteristics of karst regions that 
influence human use of its land and water resources include ground 
subsidence, sinkhole collapse, ground water contamination, and 
unpredictable water supply.

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[[Page 24031]]

    Estimates of national annual use during the 1990s vary widely, from 
approximately 23 to 40 million pounds of active ingredient a.i. Based 
on information from a 1991 data call-in and other sources, EPA 
estimates that approximately 23 million pounds of 1,3-DCP a.i. were 
used annually from 1990 to 1995 (USEPA, 1998b). NCFAP (2004) estimates 
that approximately 40 million pounds a.i. were used in 1992 and 
approximately 35 million pounds a.i. were used in 1997.
    1,3-Dichloropropene is listed as a TRI chemical and releases are 
reported from facilities in 17 States over a time period covering 1988 
to 2003 (although not all States had facilities reporting releases 
every year) (USEPA, 2006e). Air emissions appear to account for most of 
the on-site (and total) releases and generally declined between 1988 
and 2003. A sharp decrease in air emissions is evident between 1995 and 
1996. Surface water discharges are minor compared to air emissions and 
no obvious trend is evident between 1988 and 2003. Reported underground 
injection, releases to land, and off-site releases are generally 
insignificant.
    b. Health Effects. Chronic and subchronic exposures to 1,3-DCP at 
doses of 12.5 mg/kg/day and above in animal dietary studies indicate 
that 1,3-DCP is toxic to organs involved in metabolism (liver), 
excretion of conjugated metabolites (e.g., urinary bladder and the 
kidney) and organs along the portals of entry (e.g., forestomach for 
oral administration; mucous membrane of the nasal passage and lungs for 
inhalation exposure). Exposure to 1,3-DCP has not been shown to cause 
reproductive or developmental effects. Neither reproductive nor 
developmental toxicity were observed in a two-generation reproductive 
study in rats or in developmental studies in rats and rabbits at 
maternal inhalation concentrations up to 376 mg/m\3\ (USEPA, 2000a). 
Even concentrations that produced parental toxicity did not produce 
reproductive or developmental effects (USEPA, 2000a).
    An RfD of 0.03 mg/kg/day for 1,3-DCP (USEPA, 2000a) has been 
established using a benchmark dose (BMD) analysis based on a two-year 
chronic bioassay (Stott et al., 1995) in which chronic irritation 
(forestomach hyperplasia) and significant body weight reduction were 
the critical and co-critical effects, respectively. A reference 
concentration (RfC) of 0.02 mg/m\3\ was derived from a two-year 
bioassay (Lomax et al., 1989), which observed histopathology in the 
nasal epithelium.
    Under the proposed cancer risk assessment guidelines, the weight of 
evidence for evaluation of 1,3-DCP's ability to cause cancer suggest 
that it is likely to be carcinogenic to humans (USEPA, 2000a). This 
characterization is supported by tumor observations in chronic animal 
bioassays for both inhalation and oral routes of exposure.
    The oral cancer slope factors calculated from chronic dietary, 
gavage and inhalation data ranged from 5 x 10-\2\ to 1 x 
10-\1\ (mg/kg/day)-\1\. Due to uncertainties in 
the delivered doses in some studies, EPA (IRIS) recommended using the 
oral slope factor of 1 x 10-\1\ (mg/kg/day)-\1\ 
from an NTP (1985) study. Using this oral slope factor, EPA calculated 
an HRL of 0.4 [mu]g/L at the 10-\6\ cancer risk level.
    EPA also evaluated whether health information is available 
regarding the potential effects on children and other sensitive 
populations. No human or animal studies are available that have 
examined the effect of 1,3-DCP exposure on juvenile subjects. 
Therefore, its effects on children are unknown. Developmental studies 
in rats and rabbits show no evidence of developmental effects and 
therefore it is unlikely that 1,3-DCP causes developmental toxicity.
    c. Occurrence. EPA included 1,3-DCP as an analyte in the UCM Round 
1 and UCM Round 2 surveys. The MRLs for UCM Round 1 ranged from 0.02 to 
10 [mu]g/L and the MRLs for UCM Round 2 ranged from 0.08 to 1 [mu]g/L. 
EPA also analyzed for 1,3-DCP using the samples from the small systems 
that were included in the UCMR 1 survey. The MRL used for the UCMR 1 
survey was 0.5 [mu]g/L. Because some of these reporting limits exceeded 
the thresholds of interest, the occurrence analyses may result in an 
underestimate of systems affected (USEPA, 2006a, 2006b and 2006c). 
However, the MRL values used for UCM Round 1 and UCM Round 2 as well as 
UCMR 1 are within the 10-\4\ to the 10-\6\ cancer 
risk range.
    The UCM Round 1 Cross Section data indicate that approximately 0.16 
percent (or 15) of the 9,164 PWSs sampled had detections of 1,3-DCP at 
levels greater than 0.2 [mu]g/L (\1/2\ the HRL), affecting 
approximately 0.86 percent of the population served (or 438,000 of 51 
million). The UCM Round 1 Cross Section data also indicate the same 
values when the data are analyzed using 0.4 [mu]g/L (the HRL). That is, 
0.16 percent (or 15) of 9,164 PWSs sampled had detections greater than 
0.4 [mu]g/L (the HRL), affecting approximately 0.86 percent of the 
population served (or 438,000 of 51 million people). The 99th 
percentile of all detections is 2 [mu]g/L and the maximum reported 
value is 2 [mu]g/L.
    The UCM Round 2 Cross Section data indicate that approximately 0.30 
percent (or 50) of the 16,787 PWSs sampled had detections of 1,3-DCP at 
levels greater than 0.2 [mu]g/L (\1/2\ the HRL), affecting 
approximately 0.42 percent of the population served (or 193,000 of 46 
million). The UCM Round 2 Cross Section data indicate that 
approximately 0.23 percent (or 38) of the 16,787 PWSs sampled had 
detections of 1,3-DCP at levels greater than 0.4 [mu]g/L (the HRL), 
affecting approximately 0.33 percent of the population served (or 
152,000 of 46 million). The 99th percentile of all detections is 39 
[mu]g/L and the maximum reported value is 39 [mu]g/L.
    Because the sample preservative used may have resulted in potential 
underestimates of occurrence for the UCM Rounds 1 and 2 data, EPA 
subsequently analyzed for 1,3-DCP using the samples provided by 796 of 
the small systems included in the recent UCMR 1 survey. None of the 
3,719 samples from these 796 small systems (serving a population of 2.8 
million) had detects of 1,3-DCP at levels greater than 0.5 [mu]g/L (the 
minimum reporting limit used for the analysis of 1,3-DCP and a level 
that is slightly higher than the HRL).
    EPA also evaluated several sources of supplemental information, 
which included:
     The National Pesticide Survey,
     The Pesticides in Ground Water Database,
     A well water survey submitted by the registrant of Telone 
(1,3-DCP),
     The USGS VOC National Synthesis Random Source Water 
Survey, and
     The USGS VOC National Synthesis Focused Source Water 
Survey.
    As part of the National Pesticide Survey, EPA collected samples 
from approximately 1,300 community water systems and rural drinking 
water wells between 1988 and 1990. The NPS included cis and trans 1,3-
DCP as analytes in the monitoring survey. Neither compound was detected 
in the survey using a minimum reporting limit of 0.010 [mu]g/L (USEPA, 
1990a).
    The Pesticides in Ground Water Database (USEPA, 1992b) indicates 
that 1,3-DCP was found in 6 of 21,270 ground water wells sampled in 7 
States. The 6 wells with positive detections for 1,3-DCP included 3 
wells in California (at concentrations ranging from 0.890 to 31.0 
[mu]g/L), 2 wells in Florida (at concentrations of 0.279 to 7.83 [mu]g/
L), and 1 well in Montana (at concentrations of 18 to 140 [mu]g/L). 
While most or all of these 6 wells had

[[Page 24032]]

concentrations greater than the HRL for 1,3-DCP, the overall percentage 
of positive wells detections was less than 0.1 percent.
    In 1998, the registrant for Telone (1,3-DCP) submitted a private 
well water study to the Agency. The well water survey covered 5 regions 
where Telone was used intensively and evaluated 518 wells (~5,800 
samples) for the presence of 1,3-DCP. Of the 518 wells, 65 had 
detectable levels of 1,3-DCP and/or its metabolites at levels greater 
than 0.015 [mu]g/L (the detection limit for 1,3-DCP was 0.015 [mu]g/L 
and the metabolites were 0.023 [mu]g/L). None of the wells exceeded 0.2 
[mu]g/L (a level half the EPA-derived HRL for 1,3-DCP) (USEPA, 2004e 
and 2004f).
    For the Random Source Water Survey, the USGS collected samples from 
954 source waters that supply community water systems between 1999 and 
2000. For the Focused Source Water Survey, the USGS collected 451 
samples from 134 source waters that supply community water systems 
between 1999 and 2001. The USGS included 1,3-DCP as an analyte in both 
surveys. The USGS did not detect 1,3-DCP in any of the source water 
samples from the Random Source Water Survey using a reporting limit of 
0.2 [mu]g/L (a level that is one-half the HRL for 1,3-DCP). In 
addition, the USGS did not detect 1,3-DCP in any of the source water 
samples in the Focused Source Water Survey using a detection limit of 
0.024 [mu]g/L for cis-1,3-dichloropropene and 0.026 [mu]g/L for trans-
1,3-dichloropropene (levels that are about 16 times lower than the HRL 
for 1,3-DCP) (Ivahnenko et al., 2001; Grady, 2003; Delzer and 
Ivahnenko, 2003a).
    d. Preliminary Determination. The Agency has made a preliminary 
determination not to regulate 1,3-DCP with an NPDWR. Because 1,3-DCP 
appears to occur infrequently at health levels of concern in PWSs, the 
Agency believes that a national primary drinking water regulation does 
not present a meaningful opportunity for health risk reduction. While 
1,3-DCP was detected in the UCM Round 1 (late 1980s) and the UCM Round 
2 (mid 1990s) surveys, it was not detected in a subsequent evaluation 
of 796 small systems from the UCMR 1 survey. In addition, the USGS did 
not detect 1,3-DCP in two occurrence studies performed between 1999 and 
2001 using monitoring levels that were lower than the HRL. EPA believes 
the 1999 pesticide labeling requirements, which are intended to 
mitigate risks to drinking water, may be one reason for the lack of 
occurrence of 1,3-DCP at levels of concern in subsequent monitoring 
surveys.
    EPA recognizes that 1,3-dichloropropene is listed as a probable 
human carcinogen. For this reason, the Agency encourages those States 
with public water systems that may have 1,3-dichloropropene above the 
HRL to evaluate site-specific protective measures and to consider 
whether State-level (or some other type of action) is appropriate. The 
Agency also plans to update the Health Advisory document for 1,3-DCP to 
provide more recent health information. The updated Health Advisory 
will provide information to any States with public water systems that 
may have 1,3-DCP above the HRL.
6 and 7. 2,4- and 2,6-Dinitrotoluenes (2,4- and 2,6-DNT)
    a. Background. 2,4- and 2,6-dinitrotoluene (DNT), semi-volatile 
organic compounds, are two of 6 isomers of dinitrotoluene. 
Dinitrotoluenes are used in the production of polyurethane foams, 
automobile air bags, dyes, ammunition, and explosives, including 
trinitrotoluene or TNT (HSDB, 2004b and 2004c; ATSDR, 1998). Neither 
2,4-nor 2,6-DNT occur naturally. They are generally produced as 
individual isomers or as a mixture called technical grade DNT (tg-DNT). 
Technical grade DNT primarily contains a mixture of 2,4-DNT and 2,6-DNT 
with the remainder consisting of the other isomers and minor 
contaminants such as TNT and mononitrotoluenes (HSDB, 2004b).
    No recent quantitative estimates of DNT production or use are 
available. The Hazardous Substances Data Bank (HSDB, 2004b) cites a 
1980 EPA Ambient Water Quality Criteria Document that places combined 
2,4- and 2,6-DNT production at 272,610,000 pounds in 1975.
    Both 2,4-DNT and 2,6-DNT are listed as TRI chemicals. TRI data for 
2,4-DNT are reported from facilities in 21 States over a time period 
covering 1988 to 2003. Total releases nationally in 2003 were 14,899 
lbs. Releases of all kinds (off-site releases and on-site air, surface, 
underground injection, and land releases) declined in the early 1990s, 
and then peaked again around 1999-2001. On-site air emissions and 
surface water releases of 2,4-DNT were generally the most consistent 
(least fluctuating) types of releases, with surface water releases 
generally declining over the period on record (USEPA, 2006f).
    TRI data for 2,6-DNT are reported from facilities in 10 States over 
a time period covering 1988 to 2003 (with no more than 9 States having 
reporting facilities in any one year). Total reported releases for 2003 
were 10,937 lbs. Trends for 2,6-DNT are similar to those for 2,4-DNT. 
The TRI data for 2,6-DNT show a trend of declining releases in the late 
1980s and early 1990s, and a subsequent peak around 1999-2001. On-site 
air emissions and surface water discharges are the most consistent 
types of release for 2,6-DNT and surface water discharges exhibit a 
declining trend (USEPA, 2006f).
    In addition, TRI lists mixed DNT isomer releases as a separate 
category over the same time period (1990-2003). TRI releases of mixed 
isomers were reported from facilities in 9 States, with no more than 7 
States having reporting facilities in any one year. Total releases in 
2003 were 13,790 lbs. Underground injections made up the bulk of on-
site releases during the 1990s, but diminished thereafter. Air 
emissions remained relatively constant. Surface water discharges and 
releases to land were generally insignificant but peaked in 2003. Off-
site releases varied widely. Total releases peaked in 1993 and 1997, 
and generally diminished in recent years (USEPA, 2006f).
    b. Health Effects. In experimental animal studies, 2,4- and 2,6-DNT 
appear to be acutely toxic at moderate to high levels 
(LD50's \17\ ranging from 180 to 1,954 mg/kg) when 
administered orally. In subacute studies (4 weeks) conducted by Lee et 
al. (1978), dogs, rats, and mice were fed 2,4-DNT and studied for toxic 
effects. A NOAEL of 5 mg/kg/day was established; decreased body weight 
gain and food consumption, neurotoxic signs, and lesions in the brain, 
kidneys, and testes occurred at 25 mg/kg/day (the highest dose tested).
---------------------------------------------------------------------------

    \17\ LD50 = An estimate of a single dose that is 
expected to cause the death of 50% of the exposed animals. It is 
derived from experimental data.
---------------------------------------------------------------------------

    Subchronic studies in mice, rats, and dogs that administered 2,4- 
and 2,6-DNT in the diet produced similar effects in all species. All 
species exposed to 2,4-DNT exhibited methemoglobinemia, anemia, bile 
duct hyperplasia sometimes accompanied by hepatic degeneration, and 
depressed spermatogenesis. Neurotoxicity and renal degeneration 
occurred in dogs at a dose level of 20 mg/kg/day of 2,6-DNT (Lee et 
al., 1976). At a dose level of 25 mg/kg/day of 2,4-DNT, male and female 
dogs developed impaired muscle movement and paralysis, 
methemoglobinemia, aspermatogenesis, hemosiderosis of the spleen and 
liver, cloudy swelling of the kidneys, and lesions of the brain (Ellis 
et al., 1985).

[[Page 24033]]

These doses were determined to be LOAELs for these studies.
    2,4-DNT has been shown to cause reproductive effects in rats, mice, 
and dogs (Ellis et al., 1979; Lee et al., 1985; Hong et al., 1985; 
Ellis et al., 1985). Ellis et al. (1979) observed effects in rats 
following dietary exposure after a dose of 35 mg/kg/day but not 5 mg/
kg/day over 3 generations. Male mice fed 2,4-DNT for 13 weeks exhibited 
testicular degeneration and atrophy and decreased spermatogenesis at 95 
mg/kg/day (Hong et al., 1985). In another reproductive study, dogs 
exhibited mild to severe testicular degeneration and reduced 
spermatogenesis (Ellis et al., 1985) when administered 2,4-DNT in 
capsules at 25 mg/kg/day. There are currently no studies of the 
reproductive or developmental toxicity of 2,6-DNT although a subchronic 
study in dogs identified atrophy of spermatogenic cells in males 
suggesting a one- or two-generation study as a data need for 2,6-DNT.
    Some studies evaluated the effects of DNT in the form of a 
technical mixture (tg-DNT). In a study by Price et al. (1985), the 
teratogenic potential of tg-DNT (containing approximately 76 percent 
2,4-DNT and 19 percent 2,6-DNT) was investigated in rats. The study was 
conducted in two phases to evaluate the possible teratogenicity of DNT 
as well as DNT effects on postnatal development. For the first phase, 
rats were administered 0, 14, 35, 37.5, 75, 100, or 150 mg/kg/day of 
DNT in corn oil by gavage. In the postnatal phase, rats were 
administered 14, 35, 37.5, 75, or 100 mg/kg/day of DNT in corn oil by 
gavage. The NOAEL and LOAEL for developmental toxicity were 14 and 35 
mg/kg/day, respectively, based on significant increases in relative 
liver and spleen weight in the fetuses of dams administered DNT at 
levels of 35 mg/kg/day or greater. No teratogenic toxicity was seen in 
the study rats.
    In chronic exposures, oral dietary administration of 2,4-DNT to 
dogs primarily affected the nervous system, erythrocytes, and biliary 
tract (Ellis et al., 1979, 1985). Based on neurotoxicity, hematologic 
changes, and effects on the bile ducts in dogs, the LOAEL was 
determined to be 1.5 mg/kg/day and the NOAEL was 0.2 mg/kg/day. EPA 
established an RfD of 0.002 mg/kg/day for 2,4-DNT (USEPA, 1992c) based 
on this study. An uncertainty factor of 100, to account for 
interspecies and intraspecies variability, was applied to derive the 
RfD.
    EPA established an RfD of 0.001 mg/kg/day for 2,6-DNT (USEPA, 
1992c). This RfD was also based on neurotoxicity, Heinz body formation, 
biliary tract hyperplasia, liver and kidney histopathology, and death 
in beagle dogs that were fed gelatin capsules containing 2,6-DNT daily 
for up to 13 weeks (Lee et al., 1976). The NOAEL for this study was 4 
mg/kg/day, and an uncertainty factor of 3,000 (100 for inter- and 
intra-species variability, 10 for the use of a subchronic study, 3 to 
account for the limited database) was applied to derive the RfD.
    DNT is likely to be carcinogenic to humans (classified as a B2 
carcinogen; USEPA, 1990c). This is based on significant increases in 
hepatocellular carcinoma and mammary gland tumors in female rats fed 
DNT (98 percent 2,4-DNT with 2 percent 2,6-DNT) in the diet in a two-
year study (Ellis et al., 1979). The tumor incidence in the female rats 
was used to establish a slope factor of 6.67 x 10-1 
according to the 1999 EPA guidelines. Concentrations of 5 [mu]g/L, 0.5 
[mu]g/L, and 0.05 [mu]g/L are associated with carcinogenic risks of 
10-4, 10-5, and 10-6 respectively. 
There were no studies found in the literature that evaluated the 
effects of 2,4- or 2,6-DNT on children. There is evidence that the pups 
and fetuses from dams administered tg-DNT had significant increases in 
relative liver and spleen weights (Price et al., 1985). DNT toxicity 
may be different in children, compared to adults, since it undergoes 
bioactivation in the liver and by the intestinal microflora (ATSDR, 
1998). Newborns may be more sensitive to DNT-related methemoglobinemia 
because an enzyme that protects against increased levels of 
methemoglobin is inactive for a short duration immediately after birth 
(Gruener 1976; ATSDR, 1998). However, there are no experimental data on 
differences in children's responses to 2,4-/2,6-DNT.
    c. Occurrence. EPA included both 2,4- and 2,6-DNT as analytes in 
the UCMR 1. Because the HRL for both 2,4- and 2,6-DNT (0.05 [mu]g/L) is 
lower than the minimum reporting limit used for monitoring (MRL of 2 
[mu]g/L), EPA used the MRL to evaluate occurrence and exposure. The MRL 
is within the 10-\4\ to the 10-\6\ cancer risk 
range for either 2,4- or 2,6-DNT. In evaluating the UCMR 1 data, EPA 
found that 1 of the 3,866 PWSs sampled (or 0.03 percent) detected 2,4-
DNT at the MRL of 2 [mu]g/L, affecting 0.02 percent of the population 
served (or 38,000 people from 226 million). None of the 3,866 PWSs 
sampled (serving 226 million) detected 2,6-DNT at the MRL of 2 [mu]g/L 
(USEPA, 2006a and 2006b).
    EPA also evaluated the results of a USGS review of 3 highway and 
urban runoff studies (Lopes and Dionne, 1998). These studies showed no 
detects for either 2,4- or 2,6-DNT using a reporting limit of 5 [mu]g/L 
(a value within the 10-\4\ to 10-\6\ risk range).
    d. Preliminary Determination. The Agency has made a preliminary 
determination not to regulate 2,4- or 2,6-DNT with an NPDWR. Because 
2,4- and 2,6-DNT appear to occur infrequently at levels of concern in 
PWSs, the Agency believes that a national primary drinking water 
regulation does not present a meaningful opportunity for health risk 
reduction. 2,4-DNT was detected only once at a minimum reporting level 
that is within the 10-\4\ to the 10-\6\ cancer 
risk range, while 2,6-DNT was not detected at this same level in any of 
the PWSs monitored under the UCMR 1.
    EPA recognizes that 2,4- and 2,6-DNT are listed as probable human 
carcinogens. For this reason, the Agency encourages those States with 
public water systems that may have either 2,4- or 2,6-DNT above the HRL 
to evaluate site-specific protective measures and to consider whether 
State-level guidance (or some other type of action) is appropriate. The 
Agency's original Health Advisories for 2,4- and 2,6-DNT were developed 
for military installations. Because the Agency recognizes that 2,4- and 
2,6-DNT may still be found at some military sites, the Agency has 
updated the Health Advisories to reflect recent health effects 
publications. The Health Advisories are available for review in the 
docket. The updated Health Advisories will provide information to any 
States with public water systems that may have either 2,4- or 2,6-DNT 
above the HRL.
8. s-Ethyl dipropylthiocarbamate (EPTC)
    a. Background. EPTC, a synthetic organic compound, is a 
thiocarbamate herbicide used to control weed growth during the pre-
emergence and early post-emergence stages of weed germination. First 
registered for use in 1958, EPTC is used across the U.S. in the 
agricultural production of a number of crops, most notably corn, 
potatoes, dried beans, alfalfa, and snap beans. EPTC is also used 
residentially on shade trees, annual and perennial ornamentals, and 
evergreens (USEPA, 1999c).
    Estimates of EPTC usage in the United States suggest a decline from 
approximately 17 to 21 million pounds active ingredient in 1987 to 
approximately 7 to 9 million pounds active ingredient in 1999. TRI data 
from 1995 to 2003 indicate that most on-site industrial releases of 
EPTC tend to be releases to air and underground injections. Surface 
water discharges are

[[Page 24034]]

minimal in comparison (USEPA, 2006g). Total releases for 2003 were 
2,183 lbs.
    Environmental fate data indicate that EPTC would not be persistent 
under most environmental conditions. Volatilization into the atmosphere 
and degradation by soil organisms appear to be the primary dissipation 
routes. EPTC has a low affinity for binding to the soil so the 
potential to leach to ground water does exist. If EPTC reaches ground 
water, volatilization is less likely to occur (USEPA, 1999c).
    b. Health Effects. In acute animal toxicity studies, EPTC was shown 
to be moderately toxic via oral and dermal routes and highly toxic via 
inhalation exposures. EPTC is a reversible cholinesterase (ChE) 
inhibitor. Similar to other thiocarbamates, it does not produce a 
consistent ChE inhibition profile. There was no consistent pattern 
observed in any of the toxicity studies with regard to species, 
duration of treatment, or the type of ChE enzyme measured. Typically, 
studies showed inhibition of plasma ChE with dose-related decreases in 
red blood cell and brain ChE activity. Some studies have shown that 
brain ChE activity was inhibited without any effect on either plasma or 
erythrocyte ChE activities. Other studies illustrated erythrocyte ChE 
inhibition with no effect on either plasma or brain ChE (USEPA, 1999c). 
In a primary eye irritation study in rabbits, technical grade EPTC was 
shown to be slightly irritating (USEPA, 1999c).
    In subchronic and chronic studies performed in both rats and dogs, 
there was a dose-related increase in the incidence and severity of 
cardiomyopathy, a disorder of the heart muscle (Mackenzie, 1986; USEPA, 
1999c). An increase in the incidence and severity of degenerative 
effects (neuronal and/or necrotic degeneration) in both the central and 
peripheral nervous system was observed in rats and dogs following 
exposure to EPTC (USEPA, 1999c).
    EPA derived an RfD of 0.025 mg/kg/day for EPTC (USEPA, 1990d; 
USEPA, 1999c). This value was calculated using a NOAEL of 2.5 mg/kg/day 
from a study by Mackenzie (1986). An uncertainty factor of 100 was 
applied for inter- and intraspecies differences. The critical effect 
associated with the RfD is cardiomyopathy (disease of the heart 
muscle). In the reregistration of EPTC, the application of a ten-fold 
Food Quality Protection Act (FQPA) factor was recommended in order to 
be protective against residential exposures of infants and children. 
The Agency derived the HRL for EPTC using the RfD of 0.025 mg/kg/day 
and a 20 percent relative source contribution. The HRL is calculated to 
be 0.175 mg/L or 175 [mu]g/L.
    The Agency used long-term studies in mice and rats and short-term 
studies of mutagenicity to evaluate the potential for carcinogenicity 
(USEPA, 1990d). Based on these data and using EPA's 1999 Guidelines for 
Carcinogen Risk Assessment, EPTC is not likely to be carcinogenic to 
humans (USEPA, 1999a).
    EPA also evaluated whether health information is available 
regarding the potential effects on children and other sensitive 
populations. Data do not suggest increased pre- or post-natal 
sensitivity of children and infants to EPTC exposure. In animal 
studies, adverse developmental effects (i.e., decreased fetal body 
weight and decreased litter size) were only seen at doses that were 
toxic to the mother (USEPA, 1999c). Results from both developmental and 
reproductive studies indicate that there are only minimal adverse 
effects. The behavior patterns of children that lead to heightened 
opportunities for exposure in the indoor environment and the need for a 
developmental neurotoxicity study lead OPP to recommend the application 
of a ten-fold FQPA factor for EPTC. However, EPA did not apply this 
factor in the screening analysis because it does not apply to programs 
other than the pesticide registrations.
    c. Occurrence. EPA included EPTC as an analyte in the UCMR 1. None 
of the 3,866 PWSs sampled (serving a population of 226 million) had 
detects of EPTC at the MRL of 1 [mu]g/L. Hence, these data indicate 
that no occurrence and exposure is expected at levels greater than 87.5 
[mu]g/L (\1/2\ the HRL) and greater than 175 [mu]g/L (the HRL) (USEPA, 
2006a and 2006b).
    EPA also evaluated several sources of supplemental information, 
which included:
     The National Pesticide Survey,
     The Pesticides in Ground Water Database, and
     The provisional pesticide results from the 1992-2001 USGS 
NAWQA survey of ambient surface and ground waters across the U.S.
    As part of the National Pesticide Survey, EPA collected samples 
from approximately 1,300 community water systems and rural drinking 
water wells between 1988 and 1990. The NPS included EPTC as an analyte 
in the monitoring survey. EPTC was not detected using a minimum 
reporting limit of 0.15 [mu]g/L (USEPA, 1990a).
    The Pesticides in Ground Water Database (USEPA, 1992b) indicates 
that EPTC was found in 2 of 1,752 ground water wells that were sampled 
in 10 States. Both contaminated wells were in Minnesota. The detected 
concentrations ranged from 0.01 to 0.33 [mu]g/L. All of these positive 
detections are less than the HRL of 175 [mu]g/L, as well as 87.5 [mu]g/
L (\1/2\ the HRL).
    The USGS NAWQA program included EPTC as an analyte in its 1992-2001 
monitoring survey of ambient surface and ground waters across the 
United States. EPA evaluated the results of the provisional data, which 
are available on the Web (Martin et al., 2003; Kolpin and Martin, 
2003). While the USGS detected EPTC in both surface and ground waters, 
95 percent of the samples from the various land use settings were less 
than or equal to 0.018 [mu]g/L. The estimated maximum surface water 
concentration, 29.6 [mu]g/L (mixed land use settings), and the maximum 
ground water concentration, 0.45 [mu]g/L (agricultural settings), are 
both less than 175 [mu]g/L (the EPTC HRL).
    d. Preliminary Determination. The Agency has made a preliminary 
determination not to regulate EPTC with an NPDWR. Because EPTC does not 
appear to occur at health levels of concern in PWSs, the Agency 
believes that a national primary drinking water regulation does not 
present a meaningful opportunity for health risk reduction. While EPTC 
has been found in ambient waters, it was detected only at levels less 
than the HRL (as well as \1/2\ the HRL) and it was not found in the 
UCMR 1 survey of public water supplies.
9. Fonofos
    a. Background. Fonofos, an organophosphate, is a soil insecticide 
used to control pests such as corn rootworms, cutworms, symphylans 
(i.e., garden centipedes), and wireworms. Primarily used on corn crops, 
fonofos was also used on other crops such as asparagus, beans, beets, 
corn, onions, peppers, tomatoes, cole crops, sweet potatoes, peanuts, 
peas, peppermint, plantains, sorghum, soybeans, spearmint, 
strawberries, sugarcane, sugar beets, white (Irish) potatoes, and 
tobacco (USEPA, 1999d).
    Fonofos was scheduled for a reregistration decision in 1999. 
However, before the review was completed, the registrant requested 
voluntary cancellation. The cancellation was announced in the Federal 
Register on May 6, 1998 (63 FR 25033 (USEPA, 1998d)), with an effective 
date of November 2, 1998, plus a one-year grace period to permit the 
exhaustion of existing stocks (USEPA, 1999d).
    NCFAP data indicate that fonofos use declined significantly during 
the 1990s (NCFAP, 2004). According to NCFAP,

[[Page 24035]]

approximately 3.2 million pounds of fonofos a.i. were applied annually 
around 1992 and approximately 0.4 million pounds a.i. were applied 
annually around 1997. The U.S. Geological Survey (USGS) estimates an 
average of 2.7 million pounds a.i. were used annually around 1992 
(Thelin and Gianessi, 2000).
    Fonofos is moderately persistent in soil and its persistence 
depends on soil type, organic matter, rainfall, and sunlight. Since 
fonofos adsorbs moderately well to soil, it is not readily leached or 
transported to ground water but it can be transported to surface waters 
in runoff. Fonofos is rapidly degraded by soil microorganisms 
(Extoxnet, 1993). Fonofos tends to volatilize from wet soil and water 
surfaces, but the process is slowed by adsorption to organic material 
in soil, suspended solids, and sediment (HSDB, 2004d).
    b. Health Effects. Fonofos (like many organophosphates) is toxic to 
humans and animals. Case reports and acute oral toxicity studies in 
animals indicate that oral exposure to fonofos induces clinical signs 
of toxicity that are typical of cholinesterase inhibitors. In humans, 
accidental exposures produced symptoms of acute intoxication, nausea, 
vomiting, salivation, sweating, muscle twitches, decreased blood 
pressure and pulse rate, pinpoint pupils, profuse salivary and 
bronchial secretions, cardiorespiratory arrest, and even death in 1 
exposed individual (Hayes, 1982; Pena Gonzalez et al., 1996).
    In animals, clinical signs of exposure included tremors, 
salivation, diarrhea, and labored breathing (USEPA, 1996c). Chronic 
exposure studies also indicated that oral administration of fonofos 
inhibits cholinesterase (Banerjee et al., 1968; Cockrell et al., 1966; 
Hodge, 1995; Horner, 1993; Miller, 1987; Miller et al., 1979; Pavkov 
and Taylor, 1988; Woodard et al., 1969). Cholinesterase inhibition is 
one of the critical effects associated with the RfD, which was verified 
by EPA (USEPA, 1991) at 0.002 mg/kg/day. EPA derived the RfD of 0.002 
mg/kg/day using a NOAEL of 0.2 mg/kg/day (Hodge, 1995) and a 100-fold 
uncertainty factor to account for inter- and intraspecies differences.
    Fonofos is classified as an unlikely human carcinogen (Group E) 
because there is no evidence of carcinogenic potential in the available 
long-term feeding studies in rats and mice (Banerjee et al., 1968; 
Pavkov and Taylor, 1988; Sprague and Zwicker, 1987). In addition, 
fonofos does not appear to be mutagenic (USEPA, 1996c).
    EPA evaluated whether health information is available regarding the 
potential effects on children and other sensitive populations. In the 
available developmental studies with rabbits (Sauerhoff, 1987) and mice 
(Minor et al., 1982; Pulsford, 1991), no developmental effects were 
observed at oral doses as high as 1.5 mg/kg/day in the rabbit (highest 
dose tested) nor in mice at doses as high as 2.0 mg/kg/day (Minor et 
al., 1982; Pulsford, 1991). However, in mice, effects were noted at 
higher dose levels. These effects included an increase in the incidence 
of variant sternebrae ossifications (at 6 mg/kg/day or greater) and a 
slight dilation of the fourth brain ventricle in offspring (at 4 mg/kg/
day or greater). No developmental neurotoxicity study with fonofos is 
available for further assessment of this endpoint. In a three-
generation reproduction study in rats (Woodard et al., 1968), no 
treatment-related adverse effects were observed at the 2 dose levels 
used in this study, 0.5 and 1.58 mg/kg/day.
    The Agency believes that the current RfD is adequately protective 
of children. The current fonofos RfD of 0.002 mg/kg/day is 1000-fold 
lower than the NOAEL observed in the Woodard et al. (1968) 
developmental studies.
    Using the RfD of 0.002 mg/kg/day for fonofos and a 20 percent 
screening relative source contribution, the Agency derived an HRL of 
0.014 mg/L and rounded to 0.01 mg/L (or 10 [mu]g/L).
    c. Occurrence. EPA included fonofos as an analyte in the UCMR 1 
List 2 Screening Survey. None of the 2,306 samples from the 295 PWSs 
sampled (serving a population of 41 million) contained detects for 
fonofos at the MRL of 0.5 [mu]g/L. Hence, these data indicate that no 
occurrence and exposure is expected at levels greater than 5 [mu]g/L 
(\1/2\ the HRL) and greater than 10 [mu]g/L (the HRL) (USEPA, 2006a and 
2006b).
    The USGS NAWQA program included fonofos as an analyte in its 1992-
2001 monitoring survey of ambient surface and ground waters across the 
United States. EPA evaluated the results of the provisional data, which 
are available on the Web (Martin et al., 2003; Kolpin and Martin, 
2003). While the USGS detected fonofos in both surface and ground 
waters, 95 percent of the samples from the various land use settings 
were less than 0.003 [mu]g/L (the reporting limit). The maximum surface 
water concentration, 1.20 [mu]g/L (agricultural setting), and the 
maximum ground water concentration, 0.009 [mu]g/L (agricultural 
setting), are both less than 10 [mu]g/L and less than 5 [mu]g/L (the 
fonofos HRL and \1/2\ the HRL).
    d. Preliminary Determination. The Agency has made a preliminary 
determination not to regulate fonofos with an NPDWR. Because fonofos 
does not appear to occur at health levels of concern in PWSs, the 
Agency believes that a national primary drinking water regulation does 
not present a meaningful opportunity for health risk reduction. While 
fonofos has been found in ambient waters, it was detected only at 
levels less than the HRL (as well as \1/2\ the HRL) and it was not 
found in UCMR 1 Screening Survey of public water supplies. Fonofos was 
voluntarily cancelled in 1998 and the Agency expects any remaining 
stocks and releases into the environment to decline. In addition, since 
fonofos tends to bind strongly to soil, any releases to the environment 
are not likely to contaminant source waters.
10. Terbacil
    a. Background. Terbacil, a synthetic organic compound, is a 
selective herbicide used to control broadleaf weeds and grasses on 
terrestrial food/feed crops (e.g., apples, mint, peppermint, spearmint, 
and sugarcane), terrestrial food (e.g., asparagus, blackberry, 
boysenberry, dewberry, loganberry, peach, raspberry, youngberry, and 
strawberry), terrestrial feed (e.g., alfalfa, forage, and hay) and 
forest trees (e.g., cottonwood) (USEPA, 1998e).
    In 1998, EPA estimated that agricultural usage of terbacil consumed 
approximately 221,000 to 447,000 pounds of active ingredient annually 
and non-agricultural usage consumed approximately 9,000 to 14,000 
pounds. These estimates are based on data collected mostly between 1990 
and 1995, and in some cases as early as 1987 (USEPA, 1998e). According 
to NCFAP (2004), approximately 298,000 pounds of terbacil a.i. were 
applied annually in agriculture around 1992 and approximately 342,000 
pounds a.i. were applied around 1997.
    Terbacil is listed as a TRI chemical and data are reported from one 
or more facilities in a single state, Texas, for the time period 
covering 1995 to 1997. During this three-year period, all reported 
releases were on-site releases to surface water that varied between 
3,000 to 10,000 pounds annually (USEPA, 2006h).
    Terbacil is considered a persistent and potentially mobile 
herbicide in terrestrial environments. Because of its low affinity to 
soils, it can potentially leach into ground and/or surface waters 
(USEPA, 1998e; Extoxnet, 1994).
    b. Health Effects. In acute and subchronic toxicity studies, 
terbacil is practically non-toxic (Haskell Laboratories, 1965a and 
1965b). Terbacil does not cause dermal sensitivity in

[[Page 24036]]

rabbits or guinea pigs and causes mild conjunctival eye irritation in 
rabbits (Henry, 1986; Hood, 1966). In rats exposed subchronically to 
dietary terbacil, effects were seen at a LOAEL of 25 mg/kg/day and 
included increased absolute and relative liver weights, vacuolization, 
and enlargement of liver cells (Wazeter et al.,1964; Haskell 
Laboratories, 1965c).
    A primary target organ in rats following exposure to terbacil is 
the liver. Chronic effects of dietary terbacil exposure in two-year 
studies included increases in thyroid-to-body weight ratios, slight 
increases in liver weights and elevated alkaline phosphatase levels in 
beagle dogs, significant decreases in body weight in rats, increases in 
serum cholesterol levels and increases in liver to body weight ratios 
in rats (Wazeter et al.,1967a; Malek, 1993). In beagle dogs, effects 
were seen at or above 6.25 mg/kg/day (NOAEL = 1.25 mg/kg/day). In rats, 
effects (i.e., decreases in body weight, increases in liver weights and 
cholesterol levels) were seen at higher levels (LOAELs = 56 mg/kg/day 
for males and 83 mg/kg/day for females).
    Terbacil is not considered to be a developmental or reproductive 
toxicant. In developmental studies, maternal effects were generally 
seen prior to or at the same levels as developmental effects. Haskell 
Laboratories (1980) reported maternal effects (i.e., decreased body 
weight) and significant decreases in the number of live fetuses per 
litter due to early fetal resorption at a LOAEL of 62.5 mg/kg/day in 
rats. In rabbits administered terbacil via gavage, the maternal and 
developmental LOAELs were equal (600 mg/kg/day). Maternal toxicity was 
based on the death of the dams and developmental toxicity was based on 
a decrease in live fetal weights (Solomon, 1984). No reproductive 
effects were seen in a three-generation study where terbacil was 
administered to male and female rats at dose levels of 2.5 and 12.5 mg/
kg/day (Wazeter et al., 1967b).
    Terbacil is not mutagenic. Terbacil was tested and found negative 
in a chromosomal aberration study in rat bone marrow cells, found 
negative in a gene mutation assay (with and without S9 activation), and 
found negative for DNA synthesis when tested up to cytotoxic levels in 
rats (Cortina, 1984; Haskell Laboratories,1984). Terbacil shows no 
evidence of carcinogenicity and is unlikely to be carcinogenic to 
humans (Group E) (USEPA, 1998e).
    The RfD of 0.013 mg/kg/day for terbacil (USEPA, 1998e) is 
calculated from a two-year chronic study in beagle dogs. The LOAEL of 
6.25 mg/kg/day was based on increased thyroid-to-body weight ratios, 
slight increases in liver weights, and elevated alkaline phosphatase 
levels with a NOAEL of 1.25 mg/kg/day. In deriving the RfD, the Agency 
applied an uncertainty factor of 100 to account for interspecies and 
intraspecies differences. Using the RfD of 0.013 mg/kg/day and applying 
a 20 percent screening relative source contribution, the Agency derived 
an HRL of 0.090 mg/L (or 90 g/L) for terbacil.
    EPA also evaluated whether health information is available 
regarding the potential effects on children and other sensitive 
populations. In the case of terbacil, the Agency determined that there 
was no need to apply an FQPA factor to the RfD in order to protect 
children (USEPA, 1998e). Other potentially sensitive subpopulations 
have not been identified.
    c. Occurrence. EPA included terbacil as an analyte in UCMR 1. None 
of the 3,866 PWSs sampled (serving a population of 226 million) had 
detects for terbacil at the MRL of 2 g/L. Hence, these data indicate 
that no occurrence and exposure is expected at levels greater than 45 
g/L (\1/2\ the HRL) and greater than 90 [mu]g/L (the terbacil HRL) 
(USEPA, 2006a and 2006b).
    EPA also evaluated several sources of supplemental information, 
which included:
     The National Pesticide Survey,
     The Pesticides in Ground Water Database, and
     The provisional pesticide results from the 1992-2001 USGS 
NAWQA survey of ambient surface and ground waters across the U.S.
    As part of the National Pesticide Survey, EPA collected samples 
from approximately 1,300 community water systems and rural drinking 
water wells between 1988 and 1990. The NPS included terbacil as an 
analyte in the monitoring survey. Terbacil was not detected using a 
minimum reporting limit of 1.7 [mu]g/L (USEPA, 1990a).
    The Pesticides in Ground Water Database (USEPA, 1992b) indicates 
that terbacil was found in 6 of the 288 ground water wells tested for 
this contaminant in 6 States. Terbacil was found in 1 ground water well 
in Oregon (at a concentration of 8.9 [mu]g/L) and 5 ground water wells 
in West Virginia (with concentrations ranging from 0.3 to 1.2 [mu]g/L). 
All of the positive detections are less than the HRL of 90 [mu]g/L, as 
well as 45 [mu]g/L (\1/2\ the HRL).
    The USGS NAWQA program included terbacil as an analyte in its 1992-
2001 monitoring survey of ambient surface and ground waters across the 
United States. EPA evaluated the results of the provisional data, which 
are available on the Web (Martin et al., 2003; Kolpin and Martin, 
2003). While the USGS detected terbacil in both surface and ground 
waters, 95 percent of the samples from the various land use settings 
were less than 0.034 [mu]g/L (the USGS reporting limit). The maximum 
surface water concentration, 0.54 [mu]g/L (agricultural setting), and 
the maximum ground water concentration, 0.891 [mu]g/L (mixed land use 
setting), are both less than 90 [mu]g/L and less than 45 [mu]g/L (the 
terbacil HRL and \1/2\ the HRL).
    d. Preliminary Determination. The Agency has made a preliminary 
determination not to regulate terbacil with an NPDWR. Because terbacil 
does not appear to occur at health levels of concern in PWSs, the 
Agency believes that a national primary drinking water regulation does 
not present a meaningful opportunity for health risk reduction. 
Terbacil has been found in ambient waters but the levels were less than 
the HRL (as well as \1/2\ the HRL). It was not found in the UCMR 1 
survey of public water supplies.
11. 1,1,2,2-Tetrachloroethane
    a. Background. 1,1,2,2-Tetrachloroethane, a volatile organic 
compound, is not known to occur naturally in the environment (IARC, 
1979). Prior to the 1980s, 1,1,2,2-tetrachloroethane was synthesized 
for use in the production of other chemicals, primarily chlorinated 
ethylenes. 1,1,2,2-Tetrachloroethane was also once used as a solvent to 
clean and degrease metals, in paint removers, varnishes, lacquers, and 
photographic films, and for oil/fat extraction (Hawley, 1981). 
Commercial production of 1,1,2,2-tetrachloroethane in the U.S. ceased 
in the 1980s when other processes to generate chlorinated ethylenes 
were discovered (ATSDR, 1996).
    Production of 1,1,2,2-tetrachloroethane in the U.S. was 
approximately 440 million pounds in 1967 (Konietzko, 1984). Production 
declined to an estimated 34 million pounds by 1974 (ATSDR, 1996). 
Although U.S. commercial production ceased in the 1980s, 1,1,2,2-
tetrachloroethane is still generated as a byproduct and/or intermediate 
in the production of other chemicals. TRI data indicate that 
environmental releases have generally declined from a high of about 
175,000 pounds in 1988 to a low of 3,500 pounds in 2003. Most releases 
took the form of air emissions, though surface water discharges were 
also documented nearly every year (USEPA, 2006i).

[[Page 24037]]

    Volatilization from water or soil surfaces to the atmosphere 
appears to be the primary dissipation route for 1,1,2,2-
tetrachloroethane. In subsurface soils and ground water, 1,1,2,2-
tetrachloroethane is subject to biodegradation by soil organisms and/or 
chemical hydrolysis by water (ATSDR, 1996).
    b. Health Effects. Data on the toxicity of 1,1,2,2-
tetrachloroethane in humans are limited, consisting of one experimental 
inhalation study, a few case reports of suicidal or accidental 
ingestion, and dated occupational studies. In most cases, there was no 
quantification of the exposure. Respiratory and mucosal effects, eye 
irritation, nausea, vomiting, and dizziness were reported by human 
volunteers exposed to 1,1,2,2-tetrachloroethane vapors under controlled 
chamber conditions (Lehmann and Schmidt-Kehl, 1936). Effects from non-
lethal occupational exposures included gastric distress (i.e., pain, 
nausea, vomiting), headache, loss of appetite, an enlarged liver, and 
cirrhosis (Jeney et al., 1957; Lobo-Mendonca, 1963; Minot and Smith, 
1921).
    There have been a variety of animal studies in rats and mice using 
both the inhalation and oral exposure routes. Recent studies by the 
National Toxicology Program (NTP, 2004) provide a detailed evaluation 
of the short-term and subchronic oral toxicity of 1,1,2,2-
tetrachloroethane and confirm many of the observations from earlier 
studies. In rats and mice exposed orally, the liver appears to be the 
primary target organ. The RfD (10 [mu]g/kg/day) for 1,1,2,2-
tetrachloroethane was derived from the BMDL for a 1 standard deviation 
change in relative liver weight, a biomarker for liver toxicity. A 
1,000-fold uncertainty factor was applied in the RfD determination.
    A National Cancer Institute (1978) bioassay of 1,1,2,2-
tetrachloroethane found clear evidence of carcinogenicity in male and 
female B6C3F1 mice based on a dose-related statistically significant 
increase in liver tumors. There was equivocal evidence for 
carcinogenicity in Osborn Mendel rats because of the occurrence of a 
small number of rare-for-the species neoplastic and preneoplastic 
lesions in the livers of the high dose animals. The Agency used the 
slope factor of 8.5 x 10-2 for the tumors in female mice to 
derive the HRL of 0.4 [mu]g/L for use in the analysis of the occurrence 
data for 1,1,2,2-tetrachloroethane. Information on the reproductive 
effects of 1,1,2,2-tetrachloroethane is limited. There is a single one-
generation inhalation study that does not follow a standard methodology 
and examined a small number of rats (5 females and 7 males) exposed via 
inhalation to 1 dose (13.3 mg/m\3\). There were no statistically 
significant differences in the percentage of females having offspring, 
number of pups per litter, average birth weight, sex ratio, or post 
natal offspring mortality (Schmidt et al., 1972). Effects on sperm in 
male rats were seen after oral (27 mg/kg/day; NTP, 2004) and inhalation 
(13 mg/m\3\; Schmidt et al., 1972) exposures. Similar effects were seen 
in mice but at higher doses. Fetal toxicity did not occur in the 
absence of maternal toxicity.
    Developmental range-finding studies conducted for NTP (1991a and b) 
found that 1,1,2,2-tetrachloroethane was toxic to the dams and pups of 
Sprague Dawley rats and CD-1 Swiss mice. Rats were more sensitive than 
mice. The NOAEL in the rats for both maternal toxicity and associated 
fetal toxicity was 34 mg/kg/day with a LOAEL of 98 mg/kg/day. In mice, 
the NOAEL was 987 mg/kg/day and the LOAEL was 2,120 mg/kg/day.
    EPA also evaluated whether health information is available 
regarding the potential effects on children and other sensitive 
populations. Individuals with preexisting liver and kidney damage would 
likely be sensitive to 1,1,2,2-tetrachloroethane exposure. Low intake 
of antioxidant nutrients (e.g., Vitamin E, Vitamin C, and selenium) 
could be a predisposing factor for liver damage. In addition, 
individuals with a genetically low capacity to metabolize 
dichloroacetic acid (the primary metabolite of 1,1,2,2-
tetrachloroethane) may be at greater risk than the general population 
as a result of 1,1,2,2-tetrachloroethane exposure.
    c. Occurrence. EPA included 1,1,2,2-tetrachloroethane as an analyte 
in the UCM Round 1 and UCM Round 2 surveys. EPA evaluated the UCM Round 
1 Cross Section and the UCM Round 2 Cross Section data at levels 
greater than 0.2 [mu]g/L (\1/2\ the HRL) and greater than 0.4 [mu]g/L 
(the HRL) (USEPA, 2006a and 2006c). The MRLs for UCM Round 1 ranged 
from 0.1 to 10 [mu]g/L and the MRLs for UCM Round 2 ranged from 0.1 to 
2.5 [mu]g/L. Because some of the reporting limits exceeded the 
thresholds of interest, the occurrence analyses may result in an 
underestimate of systems affected. However, all the MRL values used for 
UCM Round 1 and UCM Round 2 are within the 10-4 to the 
10-6 cancer risk range.
    Analysis of UCM Round 1 Cross Section data indicates that 
approximately 0.22 percent (or 44) of the 20,407 PWSs sampled had 
detections of 1,1,2,2-tetrachloroethane at levels greater than 0.20 
[mu]g/L (\1/2\ the HRL), affecting approximately 1.69 percent of the 
population served (or 1.6 million of 95 million). The UCM Round 1 Cross 
Section data indicate that approximately 0.20 percent (or 41) of the 
20,407 PWSs sampled had detections of 1,1,2,2-tetrachloroethane at 
levels greater than 0.4 [mu]g/L (the HRL), affecting approximately 1.63 
percent of the population served (or 1.5 million of 95 million). The 
99th percentile of all detects is 112 [mu]g/L and the maximum reported 
value is 200 [mu]g/L.
    Analysis of the UCM Round 2 Cross Section data indicate that 
approximately 0.07 percent (or 18) of the 24,800 PWSs sampled had 
detections of 1,1,2,2-tetrachloroethane at levels greater than 0.2 
[mu]g/L (\1/2\ the HRL), affecting approximately 0.51 percent of the 
population served (or 362,000 of 71 million). The UCM Round 2 Cross 
Section data indicate that approximately the same percentage and number 
of the PWSs sampled (0.07 percent or 17 of the 24,800) had detections 
of 1,1,2,2-tetrachloroethane at levels greater than 0.4 [mu]g/L (the 
HRL), affecting approximately 0.08 percent of the population served (or 
56,000 of 71 million). The 99th percentile of all detects is 2 [mu]g/L 
and the maximum reported value is 2 [mu]g/L.
    EPA also evaluated several sources of supplemental information, 
which included the USGS VOC National Synthesis Random Source Water 
Survey and the Focused Source Water Survey. For the Random Source Water 
Survey, the USGS collected samples from 954 source waters that supply 
community water systems between 1999 and 2000. For the Focused Source 
Water Survey, the USGS collected 451 samples from 134 source waters 
that supply community water systems between 1999 and 2001. The USGS 
included 1,1,2,2-tetrachloroethane as an analyte in both surveys and 
did not detect it in any of the source water samples using a reporting 
limit of 0.2 [mu]g/L (a level that is less than the 1,1,2,2-
tetrachloroethane HRL). In addition, USGS did not detect 1,1,2,2-
tetrachloroethane when using a detection level of 0.026 [mu]g/L (a 
level that is over 10 times lower than the 1,1,2,2-tetrachloroethane 
HRL) in the focused survey (Ivahnenko et al., 2001, Grady, 2003, Delzer 
and Ivahnenko, 2003a).
    d. Preliminary Determination. The Agency has made a preliminary 
determination not to regulate 1,1,2,2-tetrachloroethane with an NPDWR. 
Because 1,1,2,2-tetrachloroethane appears to occur infrequently at 
health levels of concern in PWSs, the Agency

[[Page 24038]]

believes that a national primary drinking water regulation does not 
present a meaningful opportunity for health risk reduction. While 
1,1,2,2-tetrachloroethane was detected in both the UCM Round 1 and the 
UCM Round 2 surveys, the percentage of detections had decreased by the 
time the UCM Round 2 survey was performed in the mid-1990's. In 
addition, the USGS did not detect 1,1,2,2-tetrachloroethane in two 
subsequent monitoring surveys of source waters that supply community 
water systems using a reporting limit that is less than the 1,1,2,2-
tetrachloroethane HRL. The Agency believes that this decrease in 
detections occurred because commercial production of 1,1,2,2-
tetrachloroethane ceased in the mid-1980's. Hence, the Agency does not 
expect 1,1,2,2-tetrachloroethane to occur in many public water systems 
today.
    EPA recognizes that 1,1,2,2-tetrachloroethane is listed as a likely 
human carcinogen. For this reason, the Agency encourages those States 
with public water systems that may have 1,1,2,2-tetrachloroethane above 
the HRL to evaluate site-specific protective measures and to consider 
whether State-level guidance (or some other type of action) is 
appropriate. The Agency also plans to update the Health Advisory 
document for 1,1,2,2-tetrachloroethane to provide more recent health 
information. The updated Health Advisory will provide information to 
any States with public water systems that may have 1,1,2,2-
tetrachloroethane at levels above the HRL.

V. What Is the Status of the Agency's Evaluation of Perchlorate?

    At this time, the Agency is not making a preliminary determination 
as to whether a national primary drinking water regulation is needed 
for perchlorate. However, the Agency has placed a high priority on 
making a regulatory determination for perchlorate and will publish a 
preliminary determination as soon as possible. EPA is not able to make 
a preliminary determination at this time because, in order to evaluate 
perchlorate against the three SDWA statutory criteria, the Agency 
believes additional information may be needed to more fully 
characterize perchlorate exposure and determine whether regulating 
perchlorate in drinking water presents a meaningful opportunity for 
health risk reduction. This is particularly true if the Agency uses 
food exposure data to first calculate a relative source contribution 
(RSC) and corresponding health reference level (HRL) below the drinking 
water equivalent level (DWEL) \18\ in order to determine whether 
regulating perchlorate would present a meaningful opportunity for 
health risk reduction. However, the Agency is considering several other 
approaches, discussed below, for making this statutory determination 
and is requesting public comment on the strengths and limitations of 
these approaches.
---------------------------------------------------------------------------

    \18\ DWEL = [(Reference Dose x Body Weight of 70 kg) / Drinking 
Water Intake of 2 L per day].
---------------------------------------------------------------------------

    The following sections explain why EPA is not making a preliminary 
regulatory determination for perchlorate at this time, and discusses 
the information the Agency has collected to date (that may be relevant 
to making a preliminary regulatory determination), the additional 
information the Agency is soliciting in this action, and options for 
additional analyses that the Agency may conduct to support a regulatory 
determination. Sections V.A through V.D provide a summary of the 
available and relevant information/data that the Agency has collected 
and reviewed regarding the sources of perchlorate in the environment, 
its potential health effects, and its occurrence in drinking water, 
food, human urine, breast milk, and amniotic fluid. Section V.E 
explains the Agency's basis for not making a preliminary regulatory 
determination for perchlorate at this time and Section V.F. presents 
the options the Agency is considering to better characterize 
perchlorate exposure and the alternate approaches that EPA is 
considering for making a preliminary regulatory determination. This 
action provides an opportunity for the public to submit other relevant 
data that may further characterize exposure to perchlorate through the 
consumption of foods and/or through other pathways and to comment on 
these alternate approaches. The Agency in particular seeks comment on 
the use of urine biomonitoring data in estimating perchlorate exposure. 
The Agency will consider any relevant information/data provided in 
response to this action as the Agency determines whether to regulate 
perchlorate with a national primary drinking water regulation and how 
best to proceed to address perchlorate.

A. Sources of Perchlorate

    Perchlorate (ClO4-) is an anion commonly 
associated with the solid salts of ammonium, magnesium, potassium, and 
sodium perchlorate. Perchlorate salts are highly soluble in water, and 
because perchlorate sorbs poorly to mineral surfaces and organic 
material, perchlorate can be mobile in surface and subsurface aqueous 
environments. Although commonly known as a man-made chemical, 
perchlorate also may be derived from natural processes.
    While perchlorate has a wide variety of industrial uses, it is 
primarily used in the form of ammonium perchlorate as an oxidizer in 
solid fuels used to power rockets, missiles, and fireworks. 
Approximately 90 percent of perchlorate is manufactured for this 
application (Wang et al., 2002). Perchlorate can also be present as an 
ingredient or as an impurity in road flares, lubricating oils, matches, 
aluminum refining, rubber manufacturing, paint and enamel 
manufacturing, leather tanning, paper and pulp processing (as an 
ingredient in bleaching powder), and as a dye mordant.
    Perchlorate can also occur naturally in the environment. Chile 
possesses caliche ores rich in sodium nitrate (NaNO3), which 
are also a natural source of perchlorate (Schilt, 1979 and Ericksen, 
1983). These Chilean nitrate salts (saltpeter) have been mined and 
refined to produce commercial fertilizers, which before 2001 accounted 
for about 0.14 percent of U.S. fertilizer application (USEPA, 2001d). 
The USEPA (2001d) conducted a broad survey of fertilizers and other raw 
materials and found that all products surveyed were devoid of 
perchlorate except for those known to contain or to be derived from 
mined Chilean saltpeter.
    Perchlorate has also been found in other geologic materials. Orris 
et al. (2003) measured perchlorate at levels exceeding 1,000 parts per 
million (ppm or mg/kg) in several samples of natural minerals, 
including potash ore from New Mexico and Saskatchewan (Canada), playa 
crust from Bolivia, and hanksite from California.
    Texas Tech University Water Resources Center conducted a large-
scale sampling program to determine the source and distribution of 
perchlorate in northwest Texas groundwater (Jackson et al., 2004; 
Rajagopalan et al., 2006). Perchlorate was detected at concentrations 
greater than 0.5 g/L in 46 percent of public wells and 47 percent of 
private wells. Jackson et al. (2004) hypothesized that atmospheric 
production and/or surface oxidative weathering is the source of the 
perchlorate. In related research, Dasgupta et al. (2005) detected 
perchlorate in many rain and snow samples and demonstrated that 
perchlorate is formed by a variety of simulated atmospheric processes 
suggesting that natural, atmospherically-

[[Page 24039]]

derived perchlorate exists in the environment. Barron et al. (2006) 
developed a method for the rapid determination of perchlorate in 
rainwater samples, with a detection limit between 70 and 80 ng/L. Of 
the ten rainwater samples collected in Ireland in 2005, perchlorate was 
detected in 4 samples at concentrations between 0.075 and 0.113 g/L, 
and in 1 other sample at 2.8 g/L. Kang et al. (2006) conducted seven-
day experiments to determine if it was possible to produce perchlorate 
by exposing various chlorine intermediates to UV radiation in the form 
of high intensity UV lamps and/or ambient solar radiation. Perchlorate 
formation was demonstrated in aqueous salt solutions with initial 
concentrations of hypochlorite, chlorite, or chlorate between 100 and 
10,000 mg/L.
    After a limited investigation, the Massachusetts Department of 
Environmental Quality (MA DEP, 2005) found that perchlorate may be 
present in sodium hypochlorite solutions used in water and wastewater 
treatment plants, and that the level of occurrence depends upon storage 
conditions and the initial purity of the stock solution (MA DEP, 2005). 
According to MA DEP (2005), the Town of Tewksbury conducted a small 
study to evaluate the impact of storage conditions (temperature and 
light) on a new shipment of sodium hypochlorite stock solution. 
Tewksbury found that the perchlorate concentration in the new stock 
solution increased from 0.2 g/L to levels ranging from 995 to 6,750 g/L 
depending on the storage conditions. Accounting for the large dilution 
factor (e.g., 20,000 to 1 ratio) used in chlorination processes at 
drinking water treatment plants, MA DEP (2005) concluded that ``absent 
additional efforts to minimize breakdown of hypochlorite solutions, it 
would appear that low levels of the perchlorate ion (0.2 to 0.4 g/L) 
detected in a drinking water supply disinfected with sodium 
hypochlorite solutions could be attributable to the chlorination 
process.''
    It is not clear at this time what proportion of perchlorate found 
in public water supplies or entering the food chain comes from these 
various anthropogenic and natural sources. The significance of 
different sources probably varies regionally. A study by Dasgupta et 
al. (2006) analyzes the three principal sources of perchlorate and 
their relative contributions to the food chain. These are its use as an 
oxidizer including rocket propellants, Chilean nitrate used principally 
as fertilizer, and that produced by natural atmospheric processes.

B. Health Effects

    Perchlorate can interfere with the normal functioning of the 
thyroid gland by competitively inhibiting the transport of iodide into 
the thyroid. Iodide is an important component of two thyroid hormones, 
T4 and T3, and the transfer of iodide from the blood into the thyroid 
is an essential step in the synthesis of these two hormones. Iodide 
transport into the thyroid is mediated by a protein molecule known as 
the sodium (Na+)--iodide (I-) symporter (NIS). NIS molecules bind 
iodide with very high affinity, but they also bind other ions that have 
a similar shape and electric charge, such as perchlorate. The binding 
of these other ions to the NIS inhibits iodide transport into the 
thyroid, which can result in intrathyroidal iodide deficiency and 
consequently decreased synthesis of T4 and T3. There is compensation 
for iodide deficiency, however, such that the body maintains the serum 
concentrations of thyroid hormones within narrow limits through 
feedback control mechanisms. This feedback includes increased secretion 
of thyroid stimulating hormone (TSH) from the pituitary gland, which 
has among its effects the increased production of T4 and T3 (USEPA, 
2005e). Sustained changes in thyroid hormone and TSH secretion can 
result in thyroid hypertrophy and hyperplasia (abnormal growth or 
enlargement of the thyroid) (USEPA, 2005e).
    In January 2005, the National Research Council (NRC) of the 
National Academies of Science (NAS) published ``Health Implications of 
Perchlorate Ingestion,'' a review of the current state of the science 
regarding potential adverse health effects of perchlorate exposure and 
mode-of-action for perchlorate toxicity (NRC, 2005). Based on 
recommendations of the NRC, EPA chose data from the Greer et al. (2002) 
human clinical study as the basis for deriving a reference dose (RfD) 
for perchlorate (USEPA, 2005e). Greer et al. (2002) report the results 
of a well-controlled study that measured thyroid iodide uptake, hormone 
levels, and urinary iodide excretion in a group of 24 healthy adults 
administered perchlorate doses orally over a period of 14 days. Dose 
levels ranged from 0.007 to 0.5 mg/kg/day in the different experimental 
groups. No significant differences were seen in measured serum thyroid 
hormone levels (T3, T4, total and free) in any dose group. The 
statistical no observed effect level (NOEL) for perchlorate-induced 
inhibition of thyroid iodide uptake was 0.007 mg/kg/day. Although the 
NRC committee concluded that hypothyroidism is the first adverse effect 
in the continuum of effects of perchlorate exposure, NRC recommended 
that ``the most health-protective and scientifically valid approach'' 
was to base the perchlorate RfD on the inhibition of iodide uptake by 
the thyroid (NRC, 2005). NRC concluded that iodide uptake inhibition, 
although not adverse, is the key biochemical event in the continuum of 
possible effects of perchlorate exposure and would precede any adverse 
health effects of perchlorate exposure. The lowest dose (0.007 mg/kg/
day) administered in the Greer et al. (2002) study was considered a 
NOEL (rather than a NOAEL) because iodide uptake inhibition is not an 
adverse effect but a biochemical change (USEPA, 2005e). A summary of 
the data considered and the NRC deliberations can be found in the NRC 
report (2005) and the EPA Integrated Risk Information System (IRIS) 
summary (USEPA, 2005e).
    The NRC recommended that EPA apply an intraspecies uncertainty 
factor of 10 to the NOEL to account for differences in sensitivity 
between the healthy adults in the Greer et al. (2002) study and the 
most sensitive population, fetuses of pregnant women who might have 
hypothyroidism or iodide deficiency. Because the fetus depends on an 
adequate supply of maternal thyroid hormone for its central nervous 
system development during the first trimester of pregnancy, iodide 
uptake inhibition from low-level perchlorate exposure has been 
identified as a concern in connection with increasing the risk of 
neurodevelopmental impairment in fetuses of high-risk mothers (NRC, 
2005). The NRC (2005) viewed the uncertainty factor of 10 as 
conservative and health protective given that the point of departure is 
based on a non-adverse effect (iodide uptake inhibition) that precedes 
the adverse effect in a continuum of possible effects of perchlorate 
exposure. NRC concluded that no uncertainty factor was needed for the 
use of a less-than chronic study, for deficiencies in the database, or 
for interspecies variability. To protect the most sensitive human 
population from chronic perchlorate exposure, EPA derived an RfD of 
0.0007 mg/kg/day with a ten-fold total uncertainty factor from the NOEL 
of 0.007 mg/kg/day (USEPA, 2005e).
    Blount et al. (2006b) recently published a study examining the 
relationship between urinary levels of perchlorate and serum levels of 
TSH and total T4 in 2,299 men and women (ages 12 years and older), who 
participated in CDC's 2001-2002

[[Page 24040]]

National Health and Nutrition Examination Survey (NHANES).\19\ Blount 
et al. (2006b) evaluated perchlorate along with covariates known or 
likely to be associated with T4 or TSH levels to assess the 
relationship between perchlorate and these hormones, and the influence 
of other factors on this relationship. These covariates included sex, 
age, race/ethnicity, body mass index, serum albumin, serum cotinine (a 
marker of tobacco smoke exposure), estimated total caloric intake, 
pregnancy status, post-menopausal status, premenarche status, serum C-
reactive protein, hours fasting before sample collection, urinary 
thiocyanate, urinary nitrate, and use of selected medications. The 
study found that perchlorate was a significant predictor of thyroid 
hormones in women, but not men. After finding evidence of gender 
differences, the researchers focused on further analyzing the NHANES 
data for the 1,111 women participants. They divided these 1,111 women 
into two categories, higher-iodide and lower-iodide, using a cut point 
of 100 [mu]g/L of urinary iodide based on the World Health Organization 
(WHO) definition of sufficient iodide intake.\20\ Hypothyroid women 
were excluded from the analysis. According to the study authors, about 
36 percent of women living in the United States have urinary iodide 
levels less than 100 [mu]g/L (Caldwell et al., 2005). For women with 
urinary iodide levels less than 100 [mu]g/L, the study found that 
urinary perchlorate is associated with a decrease in (a negative 
predictor for) T4 levels and an increase in (a positive predictor for) 
TSH levels. For women with urinary iodide levels greater than or equal 
to 100 [mu]g/L, the researchers found that perchlorate is a significant 
positive predictor of TSH but not a predictor of T4. The study found 
that perchlorate was not a significant predictor of T4 or TSH in men. 
The researchers state that perchlorate could be a surrogate for another 
unrecognized determinant of thyroid function. Also, the study reports 
that while large doses of perchlorate are known to decrease thyroid 
function, this is the first time an association of decreased thyroid 
function has been observed at these low levels of perchlorate exposure. 
Of note is that the vast majority of the participants in this group had 
urinary levels of perchlorate corresponding to estimated dose levels 
that are below the RfD of 0.0007 mg/kg/day. The clinical significance 
of the variations in T4/TSH levels, which were generally within normal 
limits, has not been determined. The researchers noted several 
limitations of the study (e.g., assumption that urinary perchlorate 
correlates with perchlorate levels in the stroma and tissue and 
preference for measurement of free T4 as opposed to total T4) and 
recommended that these findings be confirmed in at least one more large 
study focusing on women with low urine iodide levels. It is also not 
known whether the association between perchlorate and thyroid hormone 
levels is causal or mediated by some other correlate of both, although 
the relationship between urine perchlorate and total TSH and T4 levels 
persisted after statistical adjustments for some additional covariates 
known to predict thyroid hormone levels (e.g., total kilocalorie 
intake, estrogen use, and serum C-reactive protein levels). A planned 
follow-up study will include additional measures of thyroid health and 
function (e.g., TPO-antibodies, free T4). As EPA proceeds towards a 
regulatory determination for perchlorate, the Agency will continue to 
review any new findings/studies on perchlorate and their relationship 
to thyroid function as they become available.
---------------------------------------------------------------------------

    \19\ While CDC researchers measured urinary perchlorate 
concentration for 2,820 NHANES participants, TSH and total T4 serum 
levels were only available for 2,299 of these participants.
    \20\ WHO notes that the prevalence of goiter begins to increase 
in populations with a median iodide intake level below 100 [mu]g/L 
(WHO, 1994).
---------------------------------------------------------------------------

C. Occurrence in Water, Food, and Humans

    1. Sources of Perchlorate. Section V.A. summarizes the potential 
sources of perchlorate in the environment.
    2. Studies on Perchlorate Occurrence in Public Drinking Water 
Systems and/or Drinking Water Sources. EPA included perchlorate as an 
analyte in the 1999 Unregulated Contaminant Monitoring Regulation (UCMR 
1) and collected drinking water occurrence data for perchlorate from 
3,858 public water systems (PWSs) between 2001 and 2005. EPA analyzed 
the available UCMR 1 data on perchlorate at concentrations greater than 
or equal to 4 [mu]g/L, the minimum reporting limit (MRL) for EPA Method 
314.0.\21\ The Agency found that approximately 4.1 percent (or 160) of 
3,858 PWSs that sampled and reported under UCMR 1 had at least 1 
analytical detection of perchlorate (in at least 1 entry/sampling 
point) at levels greater than or equal to 4 [mu]g/L. These 160 systems 
are located in 26 states and 2 territories. Of these 160 PWSs, 8 are 
small systems (serving 10,000 or fewer people) and 152 are large 
systems (serving more than 10,000 people). Approximately 1.9 percent 
(or 637) of the 34,193 samples collected (by these 3,858 PWSs) had 
positive detections of perchlorate at levels greater than or equal to 4 
[mu]g/L. The maximum reported concentration of perchlorate was 420 
[mu]g/L, which was found in a surface water sample from a PWS in Puerto 
Rico. The average concentration of perchlorate for those samples with 
positive detections for perchlorate was 9.85 [mu]g/L and the median 
concentration was 6.40 [mu]g/L.
---------------------------------------------------------------------------

    \21\ EPA Method 314.0 was the analytical method approved and 
used for UCMR 1 at the time of data collection.
---------------------------------------------------------------------------

    These 160 PWSs (with at least 1 analytical detection for 
perchlorate at levels greater than or equal to 4 [mu]g/L) serve 
approximately 7.5 percent (or 16.8 million) of the 225 million people 
served by the 3,858 PWSs that sampled and reported results under UCMR 
1. The 16.8 million population-served value represents the total number 
of people served by the 160 PWSs with at least one detect. Not all 
people served by these systems necessarily have perchlorate in their 
drinking water. Some of these 160 public water systems have multiple 
entry points to the distribution system and not all of the entry points 
sampled had positive detections for perchlorate in the UCMR 1 survey. 
An alternative approach to the system-level assessment of populations 
served is to use an assessment at the entry (sampling) point level.\22\ 
EPA does not have population-served values for each entry point at the 
system level. However, an assessment can be performed by assuming that 
each entry (or sampling) point at a public water system serves an equal 
proportion of the total population-served by the system. In other 
words, for the alternative assessment, the population served by each 
system is assumed to be equally distributed across all entry (or 
sampling) points at each system. For example, if a system serves a 
million people and has 5 entry points, it is assumed that each entry 
point serves 200,000 people. Using this approach and counting only

[[Page 24041]]

the population served for the entry points with positive detections 
(concentrations greater than or equal to 4 [mu]g/L), the total 
population served by these entry points with perchlorate detections is 
approximately 5 million. Section V.E provides the number of systems and 
population-served estimates for other thresholds of interest.
---------------------------------------------------------------------------

    \22\ EPA acknowledges that uncertainties exist in the 
population-served estimates for this alternative assessment since 
the population for a system is assumed to be equally distributed 
across the entry points for that system. Because the actual 
population-served by an entry point is not known, this alternative 
approach has an equal chance of underestimating or overestimating 
the actual population-served by entry points with positive 
detections for perchlorate. In addition, this approach could 
underestimate the population served that is potentially exposed to 
perchlorate and overestimate the level of exposure because it can 
not incorporate the effects of mixing of water between different 
entry points within the distribution system. This is because the 
approach cannot account for the dilution that may occur when water 
that has no detections of perchlorate is mixed within the 
distribution system with water that has positive detections for 
perchlorate.
---------------------------------------------------------------------------

    The California Department of Health Services (CA DHS) began 
monitoring for perchlorate in 1997. In 1999, CA DHS began requiring 
monitoring for perchlorate for drinking water sources that were 
identified as vulnerable to perchlorate contamination under 
California's own State monitoring program (i.e., Unregulated Chemicals 
for which Monitoring is Required). About 60 percent (or 7,100) of all 
drinking water sources in California (about 12,000) were monitored for 
perchlorate under the State monitoring program. Between June 2001 and 
June 2006, CA DHS (2006) reports that 284 (about 4%) of the 
approximately 7,100 water sources that monitored had at least 2 or more 
positive detections for perchlorate at concentrations greater than or 
equal to 4 [mu]g/L (the reporting limit). These 284 sources supply 
water for 77 drinking water systems (CA DHS, 2006) and represent active 
and standby sources (and exclude inactive, destroyed, and abandoned 
sources, and monitoring and agricultural wells) (CA DHS, 2006).
    In 2005, the State of Massachusetts's Department of Environment 
Protection (MA DEP) reported monitoring results for 85 percent (379 of 
450) of its community water systems and 86 percent (212 of 250) of its 
non-transient, non-community water systems. MA DEP found that 9 (1.5%) 
of the 591 public water systems detected perchlorate at levels greater 
than or equal to 1 [mu]g/L (the reporting limit used for a modified 
version of EPA Method 314.0). MA DEP found that the occurrence of 
perchlorate for these water systems could be traced to the use of 
blasting agents, military munitions, fireworks, and, to a lesser 
degree, sodium hypochlorite disinfectant (MA DEP, 2005).
    3. Studies on Perchlorate Occurrence in Foods, Plants, Beverages, 
and Dietary Supplements. The Food and Drug Administration (FDA), the 
United States Department of Agriculture (USDA), and researchers from 
academia and industry have studied perchlorate in foods. Some of these 
studies are described briefly in this section, and also summarized in 
Table 4. EPA has concluded that the sampling results described in this 
section and Table 4 are too limited to characterize food-borne exposure 
to perchlorate on a national scale. The sampling data are limited in 
the types of foods sampled, sample sizes, geographic coverage, and/or 
analytical method adequacy and many were targeted to foods or areas 
known or likely to have elevated levels of perchlorate. Section V.F of 
this action describes the limitations of the food sampling data and 
also describes plans for including perchlorate as part of the FDA's 
Total Diet Study. EPA requests that commenters provide the Agency with 
any additional data that may further characterize the concentrations of 
perchlorate in foods commercially available in the U.S. When providing 
data to the Agency, please describe the specific locations where the 
samples were collected, including geographic location, type of location 
(e.g., grocery store, farmer's market, commercial field, home garden), 
and the methodologies used to select, collect, prepare, and analyze the 
samples. Please include available laboratory data reports as well as 
all relevant quality assurance/quality control information.
BILLING CODE 6560-50-P
[GRAPHIC] [TIFF OMITTED] TP01MY07.052


[[Page 24042]]


[GRAPHIC] [TIFF OMITTED] TP01MY07.053

[GRAPHIC] [TIFF OMITTED] TP01MY07.054

BILLING CODE 6560-50-C
    a. FDA Targeted Sampling. The FDA released data on perchlorate in 
milk, lettuce, and bottled water in November 2004. To analyze food 
samples, FDA used ion chromatography (IC)-tandem mass spectrometry (MS/
MS), referred to as IC-MS/MS. The quantitation limits for perchlorate 
in these analyses were 0.5 [mu]g/L for bottled water, 1 [mu]g/kg by 
fresh weight (FW) for lettuce, and 3 [mu]g/L for dairy milk. The mean 
concentration of perchlorate in 128 lettuce samples collected in 5 
states (AZ, CA, FL, NJ, TX) was 10.3 [mu]g/kg FW (FDA, 2004), and 
ranged from not quantifiable (NQ) to 129 [mu]g/kg FW. The mean 
concentrations of perchlorate in several varieties of lettuce are 
reported in Table 4. The mean concentration of perchlorate in 104 dairy 
milk samples collected in 14 states (AZ, CA, GA, KS, LA, MD, MO, NJ, 
NC, PA, SC, TX, VA, WA) was 5.76 [mu]g/L (FDA, 2004), with a range from 
NQ to 11.3 [mu]g/L. FDA (2004) detected perchlorate in 2 of the 51 
bottled water samples representing 34 distinct sources collected in 12 
states (CA, CO, GA, MD, MN, MO, NC, NE, PA, SC, TX, WI) at levels of 
0.56 [mu]g/L and 0.45 [mu]g/L.
    b. Other Published Studies. Sanchez (2004) and Sanchez et al. 
(2005a) report the results of an analysis of agricultural products 
sampled from the lower Colorado River region of Arizona and California, 
the Imperial Valley of California, and the Coachella Valley of 
California, where irrigation water is known or suspected to contain 
perchlorate. The studies were partially supported by the U.S. 
Department of

[[Page 24043]]

Agriculture--Agricultural Research Service (USDA-ARS). Samples of 
iceberg, romaine, and leaf lettuce, carrots, onions, sweet corn, 
squash, melons, tomatoes, peppers, broccoli, cauliflower, cabbage, 
durum wheat, and alfalfa were analyzed for perchlorate using ion 
chromatography (IC) as the primary analytical method. For these 
analyses, the fresh-weight method reporting limit was not identified in 
most cases, but was reported to range from 20 to 50 [mu]g/kg FW, 
depending on the moisture content of the samples (Sanchez, 2004). 
Sanchez et al. (2005a) report that the method reporting level for 
iceberg lettuce was approximately 20 [mu]g/kg FW and for other types of 
lettuce was 25-30 [mu]g/kg FW. Perchlorate in the irrigation water 
ranged from 1.5 to 8.0 [mu]g/L over the period of the survey (Sanchez 
et al., 2005a).
    Sanchez et al. (2005a) analyzed 44 samples of iceberg lettuce heads 
that had been trimmed of frame and wrapper leaves, which are usually 
removed before the lettuce is consumed. Perchlorate was quantified in 5 
of the samples (ranging from 23 to 26 [mu]g/kg FW),\23\ perchlorate was 
not detectable in 6 samples, and the results of the remaining samples 
were less than the method reporting limit, which the authors defined as 
``a detectable peak among duplicates and/or replicates but below a 
level that can be quantitated.'' Perchlorate concentrations in 10 
samples of romaine and green leaf lettuce ranged from less than the 
method reporting limit to 81[mu]g/kg FW (Sanchez, 2004).
---------------------------------------------------------------------------

    \23\ Sanchez (2004) presents somewhat different results. 
Specifically, of the 44 samples of ``edible head'' lettuce, 
perchlorate was quantified in one of the samples (26 [mu]g/kg), 
perchlorate was not detectable in 6 samples, and the remaining 
sampling results were qualified as  threshold of  detection > threshold of    detection >       at least 1
                                              scenarios \b\                 interest                 interest \c\         threshold of     detection >
                                                                                                                          interest \d\     threshold of
                                                                                                                                           interest \e\
--------------------------------------------------------------------------------------------------------------------------------------------------------
20....................................  5 [mu]g/L................  3.16% (122 of 3,858).....  1.88% (281 of 14,984)...          14.6 M            4.0 M
30....................................  7 [mu]g/L................  2.13% (82 of 3,858)......  1.14% (171 of 14,984)...           7.2 M            2.2 M
40....................................  10 [mu]g/L...............  1.35% (52 of 3,858)......  0.65% (97 of 14,984)....           5.0 M            1.5 M
50....................................  12 [mu]g/L...............  1.09% (42 of 3,858)......  0.42% (63 of 14,984)....           3.6 M            1.2 M
60....................................  15 [mu]g/L...............  0.80% (31 of 3,858)......  0.29% (44 of 14,984)....           2.0 M            0.9 M
70....................................  17 [mu]g/L...............  0.70% (27 of 3,858)......  0.24% (36 of 14,984)....           1.9 M            0.8 M
80....................................  20 [mu]g/L...............  0.49% (19 of 3,858)......  0.16% (24 of 14,984)....           1.5 M            0.7 M
100...................................  25 [mu]g/L...............  0.36% (14 of 3,858)......  0.12% (18 of 14,984)....           1.0 M            0.4 M
--------------------------------------------------------------------------------------------------------------------------------------------------------
Footnotes:
\a\ These data represent summary statistics for the 3,858 public water systems that have sampled for perchlorate as a part of the UCMR 1 survey.
\b\ HRL threshold = [(RfD of 0.0007 mg/kg/day x 70 kg BW for pregnant female) / (2 L DWI)] x the RSC scenario. Each HRL threshold value is converted
  from mg/L to [mu]g/L units and then rounded to the nearest whole number.
\c\ The entry/sample-point-level population served estimate is based on the system entry/sample points that had at least 1analytical detection for
  perchlorate greater than the HRL threshold of interest. The UCMR 1 small system survey was designed to be representative of the nation's small
  systems, not necessarily to be representative of small system entry points.
\d\ The system-level population served estimate is based on the systems that had at least 1analytical detection for perchlorate greater than the HRL
  threshold of interest.
\e\ Because the population served by each entry/sample point is not known, EPA assumed that the total population served by a particular system is
  equally distributed across all entry/sample points. To derive the entry/sample point-level population estimate, EPA summed the population values for
  the entry/sample points that had at least 1 analytical detection greater than the threshold of interest.

    Table 5 also includes information on the effects of using an RSC of 
100% (that is, using an HRL set at the DWEL of 24.5 [mu]g/L, rounded to 
a whole number). Crawford-Brown et al. (2006), in an estimate of risk 
variability from perchlorate exposure through community water systems, 
noted that the subjects in the original 2002 Greer et al., study (on 
which the RfD of .0007 mg/L was based) presumably had other sources of 
perchlorate exposure outside of the study and suggested that it may be 
appropriate to view their results as reflecting the effects of 
incremental exposure to perchlorate above the background levels already 
in food and water rather than the effects of total exposure, as is 
implicitly assumed when the HRL is derived using an RSC to account for 
other sources of exposure. Use of an RSC to derive the HRL is clearly 
appropriate when the RfD or cancer slope factor is derived from animal 
studies with carefully controlled exposure. Crawford-Brown et al. 
suggest, however, that an RSC is not necessary for perchlorate because 
there is no reason to assume that the background exposure of the study 
subjects was different than that of the general population. EPA notes 
that the sample size in the Greer study was small and EPA is not aware 
of data on their background exposure to perchlorate or how 
representative it may be. EPA requests comment on whether information 
is available on the background exposure of subjects in the Greer study 
and whether it should consider the background exposure of these 
subjects in determining an HRL for perchlorate.
    While several States have recommended guidelines or public health 
goals for perchlorate, EPA recognizes that at least 1 state, 
Massachusetts,\25\ has already promulgated a final drinking water 
standard for perchlorate, that other States may set drinking water 
standards in the future, and that these standards

[[Page 24047]]

could impact national occurrence estimates once these standards are 
fully implemented.
---------------------------------------------------------------------------

    \25\ Massachusetts promulgated a final drinking water standard 
of 2 [mu]g/L for perchlorate on July 28, 2006. For more information 
about the final standard, see http://www.mass.gov/dep/public/press/pchl0706.htm (MA DEP, 2006).
---------------------------------------------------------------------------

F. What Are the Potential Options for Characterizing Perchlorate 
Exposure and Proceeding With the Preliminary Regulatory Determination 
for Perchlorate?

    While the Agency recognizes that food and other pathways may be 
important sources of perchlorate exposure, the Agency believes the 
currently available food data (summarized in section V.C.3) are 
inadequate to develop a better informed RSC (and HRL). First, some of 
the existing data are limited in their sample numbers, geographic 
coverage, and analytical method adequacy. Second, the current studies 
provide little or no data for several food groups (e.g., meat, poultry, 
fish, eggs, root and tuber vegetables, brassica vegetables, bulb 
vegetables, tree fruits, legumes, and cereal grains) that account for 
about half of the diet (by mass) for females of reproductive age (mid-
teens to mid-forties).
    This section presents and requests comment on data EPA might use to 
estimate an RSC based on food-borne exposure as well as on several 
other options that the Agency is considering to better characterize 
perchlorate exposure and assist the Agency in making its regulatory 
determination for perchlorate. These options could serve as a 
supplement or an alternative to developing an HRL based on a better 
informed RSC derived from food concentration and consumption data. The 
Agency specifically seeks comment on the use of urine biomonitoring 
data in estimating perchlorate exposure. If the Agency decides to use 
any of the approaches discussed in V.F.2, EPA will need to determine 
what statistics (e.g., mean, median, percentile, etc.) are most 
appropriate for consideration in a regulatory determination. The Agency 
will also conduct a peer review, as appropriate, of any new methodology 
it decides to use.
    The Agency also invites the public to submit relevant data that may 
further characterize exposure to perchlorate through consumption of 
foods and/or through other pathways. The Agency will consider any new, 
relevant information/data provided in response to this action as the 
Agency determines whether to regulate perchlorate with a national 
primary drinking water regulation.
    1. Use of Food Concentration and Consumption Data to Estimate an 
RSC. In the past, the Agency has relied on dietary exposure information 
from the FDA Total Diet Study (TDS) to determine the RSC allowed for 
drinking water and to set health goals (i.e., Maximum Contaminant Level 
Goals) for several inorganic compounds (e.g., antimony, cadmium, 
chromium, and selenium). Under the TDS, foods are sampled at retail 
outlets, prepared as they would be consumed, and analyzed for a variety 
of analytes (e.g., nutrients, pesticides, industrial chemicals). 
Approximately 280 foods, covering a broad spectrum of the diet, are 
currently sampled in each sampling event. Sampling events (known as 
``market baskets'') occur about 4 times per year, with each event being 
confined to 1 of the 4 regions of the country. The dietary intake of 
the analyzed compounds can be calculated for the U.S. population by 
multiplying the concentrations found in TDS foods by the consumption 
amounts for each food. FDA compiles food consumption amounts for the 
total U.S. population by gender and by age group.\26\
---------------------------------------------------------------------------

    \26\ Information about FDA's TDS design, food list, analytes, 
and analytical results can be found at http://www.cfsan.fda.gov/
~comm/tds-toc.html. (FDA, 2006)
---------------------------------------------------------------------------

    FDA is including perchlorate as an analyte in the 2006 TDS. EPA 
believes that a comprehensive dietary intake estimate for perchlorate 
will be useful in evaluating dietary exposure relative to drinking 
water. When sufficient quantitative exposure data are available (such 
as the data published by FDA in conjunction with the TDS), EPA can use 
the procedure used previously for several regulated inorganic compounds 
(i.e., chromium and selenium) to calculate the relative source 
contribution for perchlorate. In these cases where dietary intake 
values were available, EPA subtracted the dietary intake value from the 
Drinking Water Equivalent Level DWEL and used the remainder as the 
allowance for water. This procedure assures that total exposure does 
not exceed the RfD.
    The Agency invites the public to submit relevant data that may 
further characterize exposure to perchlorate through consumption of 
foods and/or through other pathways. This information may help the 
Agency in the evaluation of currently available food data and the 2006 
TDS.
    2. Use of Urinary Biomonitoring Data to Evaluate Exposure to 
Perchlorate. Researchers at CDC's National Center for Environmental 
Health (NCEH) have conducted a large national study of total 
perchlorate exposure through analysis of urine samples collected for 
NHANES 2001-2002 (Blount et al., 2006b and 2006c). The use of urinary 
perchlorate excretion to estimate perchlorate exposure has been 
demonstrated in Valentin-Blasini et al. (2005), Tollez et al. (2005), 
and Blount et al. (2006c). While this would be the first time the 
Agency has used biomonitoring data to assist EPA in making a 
preliminary regulatory determination for a CCL contaminant, the Agency 
believes that estimating perchlorate exposure among large populations 
using urinary perchlorate excretion data may be appropriate for the 
following reasons:
     Perchlorate is not metabolized in the body and is excreted 
unchanged primarily via the renal pathway (Merrill et al., 2005),
     Perchlorate does not bioaccumulate, that is, it is 
excreted essentially completely (Merrill et al., 2005),
     Perchlorate has a short half-life in the human body 
(approximately 8 hours), simplifying the estimation of daily exposure 
(Greer et al., 2002), and
     A methodology exists that allows estimation of daily 
perchlorate intake from all sources (e.g., water, food) using standard 
creatinine adjustment factors to account for variations in urine 
concentration (Mage et al., 2004).
    The Agency could use the 2001-2002 NHANES urine data in several 
ways as described in the following paragraphs. The Agency welcomes 
comment from the public on these approaches, as well as suggestions for 
other analyses that may inform the preliminary regulatory determination 
for perchlorate.
    One potential approach is to use the 2001-2002 NHANES urine data to 
directly determine whether regulation of perchlorate in drinking water 
presents a meaningful opportunity for health risk reduction. More 
specifically, we could use the urine data (as in Blount et al., 2006b 
and c) to evaluate whether total exposure from food and water is likely 
to result in an appreciable risk of adverse health effects for the U.S. 
population. If the Agency concluded that total exposure, as estimated 
from the urine data, does not pose an appreciable risk, even at the 
upper end of the exposure distribution, then it would follow logically 
that reducing this exposure by regulating drinking water would not 
present a meaningful opportunity for health risk reduction. As 
summarized above, Blount et al. (2006c) estimated a median total daily 
perchlorate dose for adults of 0.066 [mu]g/kg/day (about one tenth of 
the RfD) and a 95th percentile dose of 0.234 [mu]g/kg/day (about one 
third of the RfD). Only eleven adults (0.7%) had an estimated dose in 
excess of the RfD (0.7 [mu]g/kg/day). EPA requests comment on whether 
or not these data provide an adequate basis to support a regulatory

[[Page 24048]]

determination for perchlorate. EPA also requests comment on the 
relevance, if any, to a regulatory determination for perchlorate, of 
the Blount et al (2006b) study, which showed an association between T4/
TSH levels in women and urinary perchlorate concentrations at levels 
below the RfD (see Section V.B).
    EPA could also use the 2001-2002 NHANES urine data to qualitatively 
evaluate the importance of the water contribution to overall exposure. 
For this approach, the Agency could merge data from the 2001-2002 
NHANES and UCMR 1 and compare the total perchlorate exposure values 
(based on the urine data) for the population of individuals whose 
drinking water contains perchlorate at various concentration levels, 
ranging from non-detect to the upper end of the occurrence 
distribution. The intent of this analysis would be to permit the Agency 
to determine whether total perchlorate exposure (as measured in urine) 
is meaningfully correlated with concentrations in local public drinking 
water supplies, though EPA would only use these results qualitatively 
because it is not possible to match up individual urine samples with 
individual drinking water exposures. However, the results could be 
useful in determining at least qualitatively the potential significance 
of drinking water exposure for total exposure. If there were not a 
significant correlation between public water system perchlorate 
occurrence and individual exposure as measured through biomonitoring, 
this might suggest that there is not a meaningful opportunity for 
health risk reduction through regulation of drinking water.
    The Agency could also potentially use the 2001-2002 NHANES urine 
data to derive an RSC to use for drinking water. This could potentially 
be done in several different ways as follows.
    a. Use of Urinary Biomonitoring Total Exposure Value to Estimate an 
RSC. One possible approach to estimating an RSC for water would be to 
use the urine data to estimate total perchlorate exposure, then 
subtract this exposure value from the reference dose and allow the 
remainder as the exposure limit for water. The allowed remainder 
divided by the RfD would be the RSC for drinking water. This approach 
would yield a conservative RSC value because the exposure used to 
represent food would actually correspond to both food and drinking 
water exposure, whereas, if it were possible to estimate the exposure 
from food alone, the relative amount allowed for water would be larger 
(resulting in a higher RSC and higher health reference value). As 
discussed in Section V.D, Blount et al. (2006c) estimated a total daily 
perchlorate dose for adults from urine data and found a median dose of 
0.066 [mu]g/kg/day (about one tenth of the RfD) and a 95th percentile 
of 0.234 [mu]g/kg/day (about one third of the RfD). If EPA were to use 
the estimated 95th percentile total dose from the Blount study as if it 
represented the exposure from food alone, this would suggest a residual 
screening-level RSC of about 70% allocated to water. One possible 
limitation of this approach is that the Blount study estimates exposure 
for adults only. Therefore, an RSC developed based upon this data would 
not necessarily be representative of children. EPA requests comment on 
using this approach as the basis for deriving a screening-level RSC.
    b. Use of the Urine Data and UCMR 1 to Deduce Exposure from Other 
Sources and Derive the RSC. Alternately, for those NHANES survey 
subjects served by public drinking water systems with positive 
detections for perchlorate (based on UCMR 1), EPA could estimate the 
expected perchlorate dose contributed by drinking water (using 
individual water consumption data from the NHANES survey combined with 
UCMR 1 data for the area in which they live) and subtract it from the 
total perchlorate dose (based on urinary perchlorate excretion data) to 
calculate the amount contributed by food. Subtraction of this 
calculated food contribution from the RfD would yield the amount 
allowed for drinking water, which could be divided by the RfD to 
calculate an RSC. One limitation of this methodology would be the 
assumption that subjects in the NHANES study are uniformly consuming 
drinking water that contains perchlorate at the concentration indicated 
in the UCMR 1 data for their area.
    c. Use of Urinary Biomonitoring Data from Exclusive Bottled Water 
Drinkers to Estimate an RSC. The 2001-2002 NHANES data includes urinary 
perchlorate data for populations who exclusively drink bottled water. 
As noted in section V.C.3.a, FDA (2004) tested 51 samples of bottled 
water from 34 distinct sources in 12 states and detected perchlorate in 
2 samples (at levels of 0.56 [mu]g/L and 0.45 [mu]g/L). These levels 
are well below the MRL for the UCMR 1 data and would not contribute 
significant amounts of perchlorate relative to the RfD. If the 
population of exclusive bottled water drinkers is sufficiently 
representative of the U.S. population, these data potentially could be 
used to estimate the contribution of perchlorate exposure coming from 
food and allow the Agency to estimate an RSC for drinking water. The 
RSC value could be derived by subtracting the estimated perchlorate 
exposure for exclusive bottled water drinkers from the RfD of 0.0007 
mg/kg/day, using the remainder as the allowance for drinking water. One 
limitation of this methodology is that the perchlorate concentration of 
the bottled water used by this NHANES population is not known. Hence, 
we would have to assume that the bottled water concentration data 
collected by FDA (2004) is representative of the perchlorate 
concentration in the bottled water used by the NHANES exclusive bottled 
water population. Another limitation of this approach is that it would 
not subtract out the fraction of the drinking water intake that comes 
from water used for cooking purposes (since bottled water is probably 
not used by most subjects in cooking and household food preparation). 
It would thus produce a conservative (health protective) estimate of 
the RSC as it would overestimate the fraction of total exposure coming 
from food.

G. Next Steps

    After the Agency evaluates and thoroughly reviews public comments 
and any new information/data on perchlorate obtained following this 
notice, and performs the necessary analyses, the Agency intends to move 
expeditiously to publish a preliminary regulatory determination for 
perchlorate. Depending on how quickly the Agency is able to complete 
the necessary analyses and determine the best approach for making this 
determination, EPA may be able to publish the preliminary determination 
in time to include a final determination for perchlorate as part of the 
final CCL 2 regulatory determination, which is due by July, 2008. If 
not, the Agency will publish its final determination for perchlorate as 
soon thereafter as possible. EPA does not intend to wait until the CCL 
3 regulatory determination cycle to complete its determination for 
perchlorate.

VI. What About the Remaining CCL 2 Contaminants?

    As previously stated, EPA is only making regulatory determinations 
on CCL 2 contaminants that have sufficient information to support a 
regulatory determination at this time. Section V discusses the status 
of EPA's review of perchlorate. For the 30 remaining chemicals and the 
9 microbial pathogens, the Agency lacks adequate information in the 
areas of health effects or occurrence or both.
    The Agency continues to conduct research and/or to collect 
information

[[Page 24049]]

on the remaining CCL 2 contaminants to fill identified data gaps. 
Stakeholders may be concerned that regulatory determinations for such 
contaminants should not necessarily wait until the end of the next 
regulatory determination cycle. In this regard, it is important to 
recognize that the Agency is not precluded from conducting research, 
monitoring, developing guidance or health advisories, and/or making a 
determination prior to the end of the next cycle. In addition, the 
Agency is not precluded from regulating a contaminant at any time when 
it is necessary to address an urgent threat to public health, including 
any contaminant not listed on the CCL.
    Because the focus of this action is to announce and solicit public 
comment on the Agency's preliminary determinations for 11 of the 51 CCL 
2 contaminants, this action primarily provides information on these 11 
contaminants. The Agency recognizes that the public may have a 
particular interest in metolachlor, methyl tertiary butyl ether (MTBE), 
and the microbial contaminants. Therefore, this action includes some 
additional information for these contaminants in the following sections 
and requests public comment on any further data, information and/or 
analyses that the Agency should be aware of.

A. Metolachlor

    1. Background. Metolachlor is a broad spectrum herbicide used for 
general weed control in many agricultural food and feed crops 
(primarily corn, soybeans and sorghum), on lawns and turf, ornamental 
plants, trees, shrubs and vines, rights of way, fencerows and 
hedgerows, and in forestry. Metolachlor appears to be moderately 
persistent to persistent and depending on the type of soil, can be 
highly mobile. Degradation of metolachlor in the environment is 
dependent on microbially-mediated and abiotic processes. Metolachlor 
has at least 5 major degradates. Two of the more common degradates are 
metolachlor ethane sulfonic acid (ESA) and metolachlor oxanilic acid 
(OA).
    2. Health. The Agency established an RfD for metolachlor of 0.1 mg/
kg/day based on an NOAEL of 9.7 mg/kg/day and a UF of 100 (USEPA, 
1995). The Agency derived the NOAEL from a one-year chronic feeding 
study in beagle dogs where the critical effect was decreased body 
weight gain. Metolachlor shows some evidence of causing developmental 
toxicity effects in rats but none in rabbits. The doses associated with 
the developmental effect in rats are greater than the NOAEL and 
therefore the NOAEL would be protective against developmental toxicity.
    Metolachlor has been evaluated for carcinogenic activity in both 
rats and mice. No treatment-related cancer effects were observed in 2 
studies using mice. In studies using rats, metolachlor caused a 
significant increase in liver nodules and carcinomas in high dose 
females. Negative results from mutagenicity studies suggest that tumors 
may result from a nonmutagenic mode of action. In 1991, a peer review 
committee recommended that metolachlor be classified as a possible 
human carcinogen based on increases in liver tumors in the female rat. 
However, a peer review conducted in July 1994 recommended that the 
evidence for cancer was suggestive and should not be quantified. This 
recommendation was supported by negative mutagenicity data and recent 
metabolism data indicating that the formation of the metabolite 
presumed to be the ultimate carcinogen is very low (USEPA, 1995).
    3. Occurrence. EPA included metolachlor as an analyte in the UCM 
Round 2 survey. EPA evaluated the UCM Round 2 Cross Section data and 
found that metolachlor was detected at or above the reporting limit of 
0.1 [mu]g/L in 0.83% of the 12,953 systems that sampled for metolachlor 
(USEPA, 2006a).
    The USGS NAWQA program included metolachlor as an analyte in its 
1992-2001 monitoring survey of ambient surface and ground waters across 
the United States. EPA evaluated the results of the provisional data, 
which are available on the Web at http://ca.water.usgs.gov/pnsp/ 
(Martin et al., 2003; Kolpin and Martin, 2003). While the USGS detected 
metolachlor in both surface and ground waters, 95 percent of the 
samples from the various land use settings were less than 1.38 [mu]g/L. 
The maximum surface water concentration is 77.6 [mu]g/L (agricultural 
setting) and the maximum estimated ground water concentration is 32.8 
[mu]g/L (agricultural setting).
    4. Consideration of the ESA and OA degradates. While EPA has health 
and occurrence information for metolachlor itself, the Agency believes 
it is prudent to also consider the occurrence and exposure of the ESA 
and OA degradates as well. At this time, there is no finished water 
occurrence and exposure information for these 2 degradates from a 
nationally representative sample of PWSs. However, a few small-scale 
studies indicate that the ESA and the OA degradates may be occurring at 
greater frequencies and at higher concentrations than the metolachlor 
parent (Phillips et al., 1999a and 1999b; Rheineck and Postle, 2000). 
In order to gather more information about the occurrence of the ESA and 
OA degradates in finished water (along with the metolachlor parent), 
the Agency has added these degradates and their parent to the second 
unregulated contaminant monitoring regulation (UCMR 2; 70 FR 49093; 
USEPA, 2005g). While EPA awaits the results of the UCMR 2 survey, the 
Agency is planning to update the health advisory for metolachlor to 
include the ESA and OA degradates. The Agency requests comment from the 
public as to whether updating the health advisory to include these 
degradates will be useful for States and public water utilities.
    In addition, the Agency requests answers to the following questions 
and any available data:
     Are States collecting data on the co-occurrence of 
metolachlor and its degradates in source waters on a state-wide basis? 
In drinking water on a state-wide basis?
     If available, are States willing to provide data on the 
co-occurrence of metolachlor and its ESA and OA degradates in community 
and public water systems? What analytical method and reporting limit 
were used to gather these data?
     Do States have any information on the number of PWSs 
impacted by metolachlor and/or its degradates?
     Have States seen an increase or decrease in the number of 
PWSs impacted by metolachlor and/or its degradates?
     How many systems have taken wells or sources offline due 
to impacts from metolachlor and/or its degradates?

B. Methyl tertiary-butyl ether

1. Background
    Methyl tertiary-butyl ether (MTBE) is a volatile organic compound 
synthesized for use as a gasoline additive. First used as an octane 
enhancer to improve engine performance, MTBE is also used to reduce 
emissions that form carbon monoxide and ozone. Leaking underground 
storage tanks, gasoline distribution facilities, and even recreational 
boating can release MTBE into the environment.
    In 1997, EPA issued a drinking water advisory of 20 to 40 [mu]g/L 
based on taste and odor (USEPA, 1997b). EPA is currently revising its 
health risk assessment for MTBE, and thus, will not be making a 
regulatory determination for MTBE as part of this action. The IRIS 
Chemical Assessment Tracking System http://cfpub.epa.gov/iristrac/index.cfm has the most up-to-date information on

[[Page 24050]]

the status of the MTBF health risk assessment and interested members of 
the public should check that Web site to find out the latest schedule.
    The Agency collected data on MTBE occurrence as part of the UCMR 1 
survey. In addition, EPA evaluated several sources of supplemental 
occurrence information described in the supporting documentation for 
this action entitled ``Regulatory Determinations Support Document for 
Selected Contaminants from the Second Drinking Water Contaminant 
Candidate List (CCL 2)'' (USEPA, 2006a). Section VI.B.2 provides a 
summary of some of the data and information on MTBE occurrence 
collected to date.
2. Occurrence Information
    a. UCMR 1. EPA collected sampling results for MTBE from over 98.9 
percent (3,068 of 3,100) of the large PWSs and over 99.5 percent (796 
of 800) of the small systems required to sample under UCMR 1. Based on 
these data, 19 public water systems (0.49 percent of the 3,864 sampled) 
in 14 states (CA, CT, GA, IL, MA, MO, NH, NJ, NM, NY, PA, SD, TN, and 
WV) reported MTBE occurrence in drinking water. These 19 systems 
reported MTBE in 26 samples at the minimum reporting level of 5 [mu]g/L 
or above, representing approximately 0.33 percent (or 754 thousand of 
226 million) of the population served by the public water systems that 
sampled for MTBE. (USEPA, 2006a)
    Of the PWSs reporting detections at or above 5 [mu]g/L (the MRL), 
15 were ground water systems and 4 were surface water systems. One 
small ground water system (49 [mu]g/L) and 3 large ground water PWSs 
(48 [mu]g/L, 36 [mu]g/L, and 33.2 [mu]g/L) reported MTBE at levels 
greater than 20 [mu]g/L (the lower end of the taste and odor 
threshold). One large surface water system (33 [mu]g/L) reported MTBE 
at levels greater than 20 [mu]g/L. The remaining 14 systems had detects 
between 5 [mu]g/L and 20 [mu]g/L (USEPA, 2006a).
    b. USGS studies/surveys/reviews. In 2003, the USGS reported results 
of national source water sampling (previously introduced in section 
III.B.2.a.(2)). USGS sampling included a random study of a 
representative sample of untreated source waters (known as the ``Random 
Survey'') and a study of source waters from areas known or suspected of 
having MTBE (known as the ``Focused Survey''). In the Random Survey, 
USGS found that none of the source waters exceeded 20 [mu]g/L, and the 
three highest concentration sources ranged from 6 [mu]g/L to 19.5 
[mu]g/L (Grady, 2003). Of the areas known or suspected of having MTBE 
in the Focused Survey, USGS found that 5 percent (e.g., ground waters 
for 7 of the 134 systems) had concentrations greater than 20 [mu]g/L 
(Delzer and Ivahnenko, 2003a).
    USGS also reviewed the literature for national, regional, and State 
MTBE information (Delzer and Ivahnenko, 2003b), including 13 state-wide 
assessments. This information is summarized in Table 6. USGS noted that 
because study objectives varied, information varied in terms of 
reporting levels, sampling frequencies, and sources (e.g., ambient 
water, public and homeowner wells, treated drinking water).
    Previously, USGS (Grady and Casey, 2001) studied MTBE occurrence in 
the drinking water of 12 States (New England and the Mid-Atlantic). The 
study found less than 1 percent of the CWSs had drinking water samples 
at or above 20 [mu]g/L, while 7.8 percent of the CWSs had MTBE at 1 
[mu]g/L or higher.
BILLING CODE 6560-50-P
[GRAPHIC] [TIFF OMITTED] TP01MY07.055

BILLING CODE 6560-50-C
    c. New England Interstate Water Pollution Control Commission 
(NEIWPCC). In 2003, the NEIWPCC surveyed the States under a grant from 
EPA's Office of Underground Storage Tanks (UST). Twenty-six States 
estimated that they had public wells that were contaminated by MTBE at 
some level, and of those, 5 States (ME,

[[Page 24051]]

NH, NJ, DE, and MD) estimated having detectable levels of MTBE in at 
least 100 public water supply wells. Thirteen States did not know the 
answer, 8 States did not respond, and 3 States reported that no PWS 
wells were impacted. The survey established no reporting level to 
define ``contamination.'' Only 3 States documented the basis for their 
estimates (projected from several studies, raw and treated water 
analyses, and a survey of funded petroleum spill projects) (NEIWPCC, 
2003).
    d. California Department of Health Services. In 2000, California 
developed a drinking water standard of 13 [mu]g/L for MTBE (CA DHS, 
2000). According to California's annual compliance reports, there were 
no violations of the 13 [mu]g/L standard by public water systems in 
2002 and 2003, and 2 violations at 2 public water systems (serving 
almost 14,000 people) in 2004 (CA DHS, 2002; CA DHS, 2003; CA DHS, 
2004).
    e. Other Sources of Data. In April 2005, the Environmental Working 
Group (EWG, 2005) released a report, Like Oil and Water, on their Web 
page. In response to Freedom of Information Act requests, 29 State 
agencies submitted data to EWG. EPA informally evaluated the data 
posted by EWG to determine if this information might be useful in 
projecting state-wide occurrence. While EPA found the report 
interesting, the data as reported on the Web lacked some of the 
information needed to assess the representativeness and the quality of 
the data. For example, States submitted different time periods of 
monitoring data (e.g., Alaska submitted 7 months of data for 1 system 
during the 2000 timeframe and Illinois submitted data that spanned 1990 
to 2002). States did not report monitoring results for every system. 
Also, the data do not indicate if the samples came from source water or 
finished water, from ground water or surface water, the analytical 
method used for analysis nor the reporting level, the frequency of the 
sampling (e.g., annual, quarterly), number of samples from each water 
system, number of non-detects, etc.
3. Request for Additional MTBE Occurrence Information
    As discussed earlier, EPA is not making a regulatory determination 
for MTBE; however, EPA is presenting this information because of 
ongoing interest in MTBE. And as noted earlier, additional information 
is presented in the regulatory support document for this action (i.e., 
USEPA, 2006a). While the Agency waits for the final health risk 
assessment, EPA will continue to collect and evaluate occurrence 
information. The Agency requests any data, information, or analyses 
that may be available on the following topics:
     Are there additional occurrence data for MTBE in community 
and non-community public water systems on a state-wide or more local 
basis? As noted in the previous section, the State data submitted to 
EWG lack some elements needed to assess the quality of the data, as 
required in EPA's guidance for information quality guidelines (USEPA, 
2003c), and project state-wide occurrence.
     What analytical method and reporting limit were used to 
gather these data?
     Has there been an increase or decrease in the number of 
impacted PWSs? Over what time frame?
     For those PWSs whose water supplies have been impacted, 
has there been an increase or a decrease in the concentration of MTBE?
     How many systems have taken wells or sources offline, 
consolidated with other PWSs, or added customers due to impacts from 
MTBE?
     What treatments are being used in the field? What range of 
treatment effectiveness is being achieved?
     Is the listing of State bans for MTBE shown in Table 7 
complete? Have state-wide bans decreased MTBE contamination in drinking 
water?

            Table 7.--State Actions Banning MTBE (State-wide)
       [Adapted from USEPA, 2004g and McCarthy and Tiemann, 2005]
------------------------------------------------------------------------
            State                Effective date      Extent of MTBE ban
------------------------------------------------------------------------
Arizona.....................  January 1, 2005.....  0.3% max volume in
                                                     gasoline.
California..................  December 31, 2003...  complete ban in
                                                     gasoline.
Colorado....................  April 30, 2002......  complete ban in
                                                     gasoline.
Connecticut.................  January 1, 2004.....  complete ban in
                                                     gasoline.
Illinois....................  July 24, 2004.......  0.5% max volume in
                                                     gasoline.
Indiana.....................  July 24, 2004.......  0.5% max volume in
                                                     gasoline.
Iowa........................  July 1, 2000........  0.5% max volume in
                                                     gasoline.
Kansas......................  July 1, 2004........  0.5% max volume in
                                                     gasoline.
Kentucky....................  January 1, 2006.....  0.5% max volume in
                                                     gasoline.
Maine.......................  January 1, 2007.....  0.5% max volume in
                                                     gasoline.
Michigan....................  June 1, 2003........  complete ban in
                                                     gasoline.
Minnesota...................  July 2, 2005........  complete ban in
                                                     gasoline.
                                                     (following partial
                                                     ban in 2000).
Missouri....................  July 1, 2005........  0.5% max volume in
                                                     gasoline.
Montana.....................  January 1, 2006.....  no more than trace
                                                     amounts in
                                                     gasoline.
Nebraska....................  July 13, 2000.......  1% max volume in
                                                     gasoline.
New Hampshire...............  January 1, 2007.....  0.5% max volume in
                                                     gasoline.
New Jersey..................  January 1, 2009.....  0.5% max volume in
                                                     gasoline.
New York....................  January 1, 2004.....  complete ban in
                                                     gasoline.
North Carolina..............  January 1, 2008.....  0.5% max volume in
                                                     gasoline.
Ohio........................  July 1, 2005........  0.5% max volume in
                                                     gasoline.
Rhode Island................  June 1, 2007........  0.5% max volume in
                                                     gasoline.
South Dakota................  July 1, 2001........  0.5% max volume in
                                                     gasoline.
Vermont.....................  January 1, 2007.....  0.5% max volume in
                                                     gasoline.
Washington..................  January 1, 2004.....  0.6% max volume in
                                                     gasoline.
Wisconsin...................  August 1, 2004......  0.5% max volume in
                                                     gasoline.
------------------------------------------------------------------------


[[Page 24052]]

C. Microbial Contaminants

    1. Evaluation of Microbial Contaminants for Regulatory 
Determination. The 9 microbial contaminants listed on CCL 2 include:
     Four virus groups--Caliciviruses, Echoviruses, 
Coxsackieviruses, and Adenoviruses
     Four bacteria/bacterial groups-Aeromonas hydrophila; 
Helicobacter pylori; Mycobacterium avium intercellulare (or MAC); and 
Cyanobacteria (called blue-green algae\27\), fresh water algae, and the 
associated toxins
---------------------------------------------------------------------------

    \27\ Cyanobacteria are called blue-green algae even though they 
are technically bacteria.
---------------------------------------------------------------------------

     One group of protozoa--Microsporidia (Enterocytozoon 
bieneusi and Septata intestinalis, now renamed Encephalitozoon 
intestinalis).
    In addition to considering if the Agency had sufficient information 
to address the three statutory criteria listed in section II.B.1 (i.e., 
adverse health effects, known/likely occurrence, and meaningful 
opportunity for health risk reduction), the Agency also considered 
whether sufficient information was available to determine whether 
current treatment requirements adequately controlled for any of the 9 
microbial contaminants. After consideration of these factors, the 
Agency determined that none of the 9 microbial contaminants have 
sufficient information at this time to address the three statutory 
criteria to make a regulatory determination. Table 8 identifies the 
specific areas for which information is insufficient.

                            Table 8.--Information Gaps for the Microbial Contaminants
----------------------------------------------------------------------------------------------------------------
            Health effects                    Treatment           Analytical  methods           Occurrence
----------------------------------------------------------------------------------------------------------------
Microsporidia........................  Aeromonas..............  Aeromonas..............  Aeromonas.
Some Cyanotoxins.....................  MAC....................  MAC....................  MAC.
                                       Adenoviruses...........  Helicobacter...........  Helicobacter.
                                       Caliciviruses..........  Microsporidia..........  Adenoviruses.
                                       Coxsackieviruses.......  Some Cyanotoxins.......  Caliciviruses.
                                       Echoviruses............  .......................  Coxsackieviruses.
                                       Microsporidia..........  .......................  Echoviruses.
                                       Some Cyanotoxins.......  .......................  Microsporidia.
                                       Helicobacter...........  .......................  Some Cyanotoxins.
----------------------------------------------------------------------------------------------------------------

    2. Research and Other Ongoing Activities. EPA has supported an 
active research program to fill the information gaps on the CCL 2 
microorganisms. While several examples of the ongoing research 
activities are listed below, further information on these and other 
projects can be found on EPA's Drinking Water Research Information 
Network (DRINK). DRINK is a publicly-accessible, Web-based system that 
tracks over 1,000 ongoing research projects and can be accessed at: 
http://www.epa.gov/safewater/drink/intro.html.
    a. Virus. For the CCL virus groups (or surrogates), the Agency has 
initiated treatment studies that simulate realistic conditions where 
viruses may be protected in aggregates. EPA also plans to conduct virus 
removal/inactivation studies in drinking water treatment plants and/or 
pilot plants. In order to assess the effectiveness of treatment and to 
perform monitoring studies, methods development for viruses is also in 
progress.
    b. Bacteria. For Aeromonas spp., EPA recently completed a one-year 
UCMR 1 survey of 293 public water systems. The Agency is currently 
attempting to characterize and distinguish pathogenic from non-
pathogenic strains, as well as develop methods to detect Aeromonas 
virulence factors. For H. pylori, the Agency is in the process of 
developing a culture method and method for its identification. For MAC, 
preliminary drinking water surveys have been conducted using a culture 
method followed by genetic detection. EPA is also conducting further 
research into methods development and the characterization of virulence 
factors for this organism.
    EPA has funded projects to evaluate the effect of disinfectants on 
cyanotoxins, and on the removal of algal cells and cyanotoxins in a 
pilot scale treatment plant. EPA is developing analytical methods for 
potential use for future monitoring and has available analytical 
chemistry standards for the toxins of most concern in the United 
States--microcystin, cylindrospermopsin, and anatoxin-a. EPA has 
conducted several small-scale preliminary occurrence surveys for 
cyanotoxins using a screening method followed by confirmation by 
instrumental analysis. A number of health effects studies are also in 
progress on several high priority cyanotoxins. These include behavioral 
studies in mice, acute and subacute effects in neonatal mice, and 
biomarkers of human exposure. Risk assessments are being conducted at 
EPA on the cyanotoxins to determine reference doses where possible. The 
Agency has organized and participated in several workshops on 
cyanotoxins to assess the state-of-the-science.
    As an interim measure to assist public water utilities, the Agency 
is planning to develop an information sheet that discusses pertinent 
information on cyanobacteria and some of its key toxins. The document 
will discuss the state of the knowledge on the prevention and treatment 
of cyanobacteria and its toxins, as well as the available information 
on the potential health effects of some of the toxins. EPA requests 
comment from the public as to whether such a document would be useful 
for public water utilities.
    c. Protozoa. EPA has several ongoing projects to evaluate the 
susceptibility of microsporidia to chlorine and chloramine 
disinfectants. EPA has sponsored methods-related projects for 
microsporidia, which have included the use of fluorescent gene probes, 
real-time PCR, concentration methods, and immunomagnetic separation. 
Ongoing monitoring at EPA has revealed that microsporidia are present 
in ground water. EPA has funded work to determine exposure to 
microsporidia, and to determine strains (animal and human) of 
Enterocytozoon bieneusi found in water. EPA also held a workshop in 
2003 on microsporidia to assess the state-of-the-science.

VII. EPA's Next Steps

    EPA intends to respond to the public comments it receives on the 11

[[Page 24053]]

preliminary determinations and subsequently issue its final regulatory 
determinations. Although the preliminary determinations for all 11 
contaminants are not to regulate, if after consideration of public 
comments, the Agency determines that a national primary drinking water 
regulation is warranted for any of these 11 contaminants, the 
regulation would then need to be formally proposed within 24 months of 
the determination and promulgated 18 months following the proposal.\28\
---------------------------------------------------------------------------

    \28\ The statute authorizes a nine-month extension of this 
promulgation date.
---------------------------------------------------------------------------

VIII. References

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Selected Contaminants from the Second Drinking Water Contaminant 
Candidate List (CCL 2). EPA Report 815-D-06-007. Draft. December 
2006.
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Unregulated Contaminant Monitoring Regulation (UCMR 1) in Support of 
Regulatory Determinations for the Second Drinking Water Contaminant 
Candidate List. EPA Report 815-D-06-007. Draft. December 2006.
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Unregulated Contaminant Monitoring (UCM) Program and National 
Inorganics and Radionuclides Survey (NIRS) in Support of Regulatory 
Determinations for the Second Drinking Water Contaminant Candidate 
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trifluoride.] Accessed February 8, 2006.
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Last modified June 8, 2005. Available on the internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for 1,3-
dichloropropylene.] Accessed February 8, 2006.
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2,6-Dinitrotoluene.'' Last modified June 8, 2005. Available on the 
Internet at: http://www.epa.gov/triexplorer/trends.htm. [Search for 
2,4-dinitrotoluene, 2,6-dinitrotoluene, and dinitrotoluene (mixed 
isomers).] Accessed February 8, 2006.
    USEPA. 2006g. ``TRI Explorer: Trends--EPTC.'' Last modified June 
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2006.
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Tetrachloroethane.'' Last modified June 8, 2005. Available on the 
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Report 822-R-06-005. December 2006.
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Degradates: Tetrachloroterephthalic Acid (TPA) and Monomethyl 
Tetrachloroterephthalic Acid (MTP). EPA Report 822-R-06-006. 
December 2006.
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2,2-bis(p-chlorophenyl)ethylene (DDE). EPA Report 822-R-06-0007. 
December 2006.
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dipropylthiocarbamate (EPTC). EPA Report 822-R-06-008. December 
2006.
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Report 822-R-06-009. December 2006.
    USEPA. 2006o. Health Effects Support Document for Terbacil. EPA 
Report 822-R-06-010. December 2006.

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    Dated: April 12, 2007.
Stephen L. Johnson,
Administrator.
 [FR Doc. E7-7539 Filed 4-30-07; 8:45 am]
BILLING CODE 6560-50-P