Document ID: EPA-HQ-OW-2007-0068-0171
Agency: epa
Document Type: Notice
Title: Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water Contaminant Candidate List
Posted Date: 2008-07-30T04:00Z

[Federal Register: July 30, 2008 (Volume 73, Number 147)]
[Notices]               
[Page 44251-44261]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr30jy08-72]                         

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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OW-2007-0068; FRL-8699-1]
RIN 2040-AE60

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

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice.

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SUMMARY: The Safe Drinking Water Act (SDWA), as amended in 1996, 
requires the United States Environmental Protection Agency (EPA) to 
periodically publish a list of unregulated contaminants (known as the 
Contaminant Candidate List or CCL) and determine whether to regulate at 
least five contaminants on each list. Today's action announces the 
Agency's final determinations on whether to issue national primary 
drinking water regulations (NPDWRs) for 11 contaminants listed on the 
second Contaminant Candidate List (CCL 2).
    On May 1, 2007, EPA published preliminary regulatory determinations 
for 11 of the 51 contaminants listed on CCL 2 and requested public 
comment on the determinations, process, rationale, and supporting 
technical information for each contaminant. The 11 regulatory 
determination contaminants 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 
dipropylthiocarbamate (EPTC); fonofos; terbacil; and 1,1,2,2-
tetrachloroethane. In the May 2007 notice, the Agency made a 
preliminary determination that no regulatory action was appropriate for 
any of these 11 contaminants.
    EPA received comments from nine individuals or organizations on the 
preliminary regulatory determinations for the 11 contaminants and 
additional comments for other contaminants on CCL 2: perchlorate, 
methyl tertiary butyl ether (MTBE), metolachlor, and cyanotoxins. After 
careful review and consideration of these comments, the Agency is 
making a final determination that no regulatory action is appropriate 
at this time for any of the 11 CCL 2 contaminants for which the Agency 
made preliminary regulatory determinations in the May 2007 notice.

DATES: For purposes of judicial review, the regulatory determinations 
in this notice are issued as of July 30, 2008, as provided in 40 CFR 
23.7.

ADDRESSES: EPA has established a docket for this action under Docket ID 
No. EPA-HQ-OW-2007-0068. All documents in the docket are listed on the 
http://www.regulations.gov Web site. Although listed in the index, some 
information is not publicly available, e.g., Confidential Business 
Information or other information whose disclosure is restricted by 
statute. Certain other material, such as copyrighted material, is not 
placed on the Internet and will be publicly available only in hard copy 
form. Publicly available docket materials are available either 
electronically through 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: Yvette Selby-Mohamadu, Standards and 
Risk Management Division, Office of Ground Water and Drinking Water, 
4607M, Environmental Protection Agency, 1200 Pennsylvania Ave., NW., 
Washington, DC 20460; telephone number: (202) 564-5245; e-mail address: 
selby-mohamadu.yvette@epa.gov. For general information contact the EPA 
Safe Drinking Water Hotline at (800) 426-4791, or (703) 412-3330, from 
10 a.m. to 4 p.m., Eastern Time, Monday through Friday, excluding legal 
holidays.

Abbreviations and Acronyms

[mu]g/L--micrograms per liter
ATSDR--Agency for Toxic Substances and Disease Registry
AwwaRF--American Water Works Association Research Foundation
CCL--Contaminant Candidate List
CCL 1--EPA's First Contaminant Candidate List
CCL 2--EPA's Second Contaminant Candidate List
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
EPA--United States Environmental Protection Agency
EPTC--s-ethyl dipropylthiocarbamate
ESA--ethane sulfonic acid
FR--Federal Register
HRL--health reference level
IRIS--Integrated Risk Information System
kg--kilogram
L--liter
MAC--Mycobacterium avium
MCL--maximum contaminant level
MCLG--maximum contaminant level goal
MRL--minimum or method reporting limit (depending on the study or 
survey cited)
MTBE--methyl tertiary butyl ether
MTP--monomethyl-2,3,5,6-tetrachloroterephthalate
NDWAC--National Drinking Water Advisory Council
NIRS--National Inorganic and Radionuclide Survey
NRC--National Research Council
NPDWR--national primary drinking water regulation
OA--oxanilic acid
OPP--Office of Pesticide Programs
PWS--public water system
RSC--relative source contribution
SDWA--Safe Drinking Water Act
SOT--Society of Toxicology
TPA--2,3,5,6-tetrachchloroterephthalic acid
TRI--Toxics Release Inventory
TT--treatment technique
UCM--Unregulated Contaminant Monitoring
UCMR 1--First Unregulated Contaminant Monitoring Regulation issued 
after the 1996 SDWA Amendments
US--United States of America
USGS--United States Geological Survey

SUPPLEMENTARY INFORMATION: 

I. General Information
    A. Does This Action Impose Any Requirements on My Public Water 
System?
II. Purpose, Background, and Summary of This Action
    A. What Is the Purpose of This Action?
    B. What Is the Statutory Requirement for the Contaminant 
Candidate List (CCL) and Regulatory Determinations?
    C. What Contaminants Did EPA Consider for Regulation?
III. What Approach and Analyses Did EPA Use To Make the Regulatory 
Determinations?
    A. Approach
    B. Analyses
IV. Summary of Public Comments and the Agency's Responses on the CCL 
Regulatory Determination Process
    A. Regulatory Determinations for the 11 Contaminants
    B. Regulatory Determinations Approach
    C. Occurrence and Exposure Evaluation
    D. Comments on Boron, Perchlorate, MTBE, Metolachlor, and 
Cyanobacteria and Its Toxins
V. Summary of the Agency's Findings on the 11 CCL 2 Contaminants
    A. Boron
    B. Dacthal mono- and di-acid degradates

[[Page 44252]]

    C. 1,1-Dichloro-2,2-bis(p-chlorophenyl) ethylene
    D. 1,3-Dichloropropene
    E. 2,4- and 2,6-Dinitrotoluenes
    F. s-Ethyl dipropylthiocarbamate
    G. Fonofos
    H. Terbacil
    I. 1,1,2,2-Tetrachloroethane
VI. How Will EPA Address the Data Needs of the Remaining CCL 2 
Contaminants?
VII. References

SUPPLEMENTARY INFORMATION: 

I. General Information

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

    None of these regulatory determinations will impose any 
requirements on anyone. Instead, this action notifies interested 
parties of EPA's determinations for 11 CCL 2 contaminants and provides 
a summary of the major comments received on the May 1, 2007, 
preliminary determinations (72 FR 24016 (USEPA, 2007a)).

II. Purpose, Background and Summary of This Action

A. What Is the Purpose of This Action?

    Today's action briefly describes the statutory requirements for 
targeting potential drinking water contaminants for regulatory 
development and the approach EPA used to make regulatory determinations 
for 11 CCL 2 contaminants. In addition, today's action (1) summarizes 
the public comments received on EPA's preliminary determinations and 
the Agency's responses to those comments, (2) presents the Agency's 
findings and final regulatory determination for 11 CCL 2 contaminants, 
and (3) provides information regarding the other CCL 2 contaminants.

B. What Is the Statutory Requirement for the Contaminant Candidate List 
(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 national primary drinking water regulations (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. 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, it makes a determination that a national primary drinking water 
regulation is needed. In that case, the Agency has 24 months to publish 
a proposed MCLG and NPDWR. After the proposal, the Agency has 18 months 
to publish a final MCLG and promulgate a final 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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C. What Contaminants Did EPA Consider for Regulation?

    On May 1, 2007 (72 FR 24016 (USEPA, 2007a)), EPA published 
preliminary regulatory determinations for 11 CCL 2 contaminants that 
have sufficient information to support a regulatory determination. The 
11 contaminants 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 (DNT); 2,6-dinitrotoluene; s-ethyl 
dipropylthiocarbamate (EPTC); fonofos; terbacil; and 1,1,2,2-
tetrachloroethane.
    Information for the 11 contaminants is available in the regulatory 
determination support document (USEPA, 2008a), the occurrence technical 
support documents (USEPA, 2008b-c), and the Health Effects Support 
Documents or Drinking Water Advisories for each of the contaminants 
(USEPA, 2008d-l). This information is available at the Water Docket 
(Docket ID No. EPA-HQ-OW-2007-0068) and is also available on EPA's Safe 
Drinking Water Regulatory Determination Web site at http://www.epa.gov/
safewater/ccl/reg_determine2.html. Brief descriptions of each of the 
11 contaminants considered for regulatory determinations are included 
in section V of this notice.

III. What Approach and Analyses Did EPA Use To Make the Regulatory 
Determinations?

A. Approach

    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. For health effects, 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 no adverse health effect(s) are likely to occur. For occurrence, 
the Agency considered whether available information/data provided a 
representative picture 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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    In cases where EPA chose a contaminant as a candidate for 
regulatory determination, the Agency considered the following in 
evaluating each of the three statutory criteria.
    (a) 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.

[[Page 44253]]

    (b) Second statutory criterion--Is the contaminant known or likely 
to occur in public water systems at a frequency and level of public 
health 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 estimate 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 further evaluate the likelihood of a contaminant occurring in 
drinking water, the Agency considered information on the use and 
release of the 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).
    (c) 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 estimates, as well as 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.
    If the answers to all three statutory criteria are affirmative for 
a particular contaminant, then the Agency makes a determination that 
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 distinct from the 
more detailed analyses needed to develop a national primary drinking 
water regulation. Thus, a decision to regulate is the beginning of the 
Agency's regulatory development process, not the end.
    If the answer to any of the three statutory criteria is negative 
based on the available data, then the Agency makes a determination that 
a national primary drinking water regulation is not necessary for that 
contaminant at that time.

B. Analyses

    EPA has prepared Health Effects Support Documents or Drinking Water 
Advisories (USEPA, 2008d-l) for each of the 11 contaminants. In these 
documents, EPA characterized the human health effects that may result 
from exposure to a contaminant found in drinking water. The support 
documents address exposure from drinking water and other media, 
toxicokinetics, hazard identification, dose-response assessment, and an 
overall characterization of risk from drinking water. Based on this 
characterization, EPA estimated a health reference level (HRL) or 
benchmark value for each contaminant.
    To analyze occurrence and exposure, the Agency used data from the 
first Unregulated Contaminant Monitoring Regulation (UCMR 1) for 9 of 
the contaminants: 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 dipropylthiocarbamate 
(EPTC), fonofos, and terbacil.\5\ In addition, the Unregulated 
Contaminant Monitoring (UCM \6\) program provided additional data for 
1,3-dichloropropene and 1,1,2,2-tetrachloroethane and the National 
Inorganic and Radionuclide Survey (NIRS \7\) provided data for boron. 
The Agency used the UCMR 1, UCM, and NIRS data to estimate the number 
and percentage of PWSs and the population served by these PWSs at 
concentrations above the HRL benchmark values, and \1/2\ the HRL 
values. The Agency also used these data to evaluate the geographic 
distribution of occurrence for these 11 CCL 2 contaminants.
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    \5\ The UCMR 1 monitoring survey began in 2001. As discussed in 
the May 2007 notice, fonofos was sampled as part of UCMR 1 Screening 
Monitoring and the remaining 8 contaminants were sampled as part of 
UCMR 1 Assessment Monitoring.
    \6\ 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.
    \7\ The monitoring for NIRS spanned from 1984 to 1986.
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    EPA also employed State drinking water data, use and environmental 
release information (e.g., EPA's Toxic Release Inventory (TRI), 
academic and private sector publications), as well as ambient water 
quality data (e.g., data from the U.S. Geological Survey's National 
Water Quality Assessment program) as secondary sources of information 
to evaluate the likelihood of contaminant occurrence.
    A detailed discussion of the data collected and analyses for each 
contaminant can be found in the regulatory determination support 
document (USEPA, 2008a) and the occurrence technical support documents 
(USEPA, 2008b-c). In addition, a summary of the occurrence and exposure 
findings are included in Table 1. Table 1 in this notice is similar to 
Table 3 in the May 2007 notice (72 FR 24016 (USEPA, 2007a)); however, 
note that EPA updated the occurrence data for the UCMR 1 results to 
include final results for 17 additional drinking water systems that 
were not available when the Agency was in the process of making its 
preliminary regulatory determinations. Updating these numbers did not 
change the outcome of today's decisions.

     Table 1--Summary of the Health and Occurrence Information and the Final Determinations for the 11 Contaminants Considered Under CCL Regulatory
                                                                    Determinations 2
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                                                                       Occurrence findings from primary data sources (UCMR 1, UCM round 1 and 2 cross
                                                                                                      sections, NIRS)
              Contaminant and                                     --------------------------------------------------------------------------------------
               its chemical                      Health reference                                         Population                        Population
        abstract        Determination      level (HRL)                        PWSs with at     served by PWSs    PWSs with at    served by PWSs
              registry number                                          Database           least 1      with at least 1      least 1      with at least 1
                  (CASRN)                                                            detection  > \1/  detection  > \1/   detection  >     detection  >
                                                                                          2\ HRL            2\ HRL            HRL              HRL
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1..........  Boron (7440-42-   Do not regulate   1,400 [mu]g/L...  NIRS............  4.3% (43 of 989)  2.9% (42.7K of   1.7% or (17 of   0.4% (6.4K of
              8).               \1\.                                                                    1.48M).          989) \1\.        1.48M)
2..........  Dacthal di acid   Do not regulate.  70 [mu]g/L \4\..  UCMR 1 \5\......  0.05% (2 of       0.33% (739K of   0.03% (1 of      < 0.01% (500 of
              degradate \2\                                                           3,876).           225M).           3,876).          225M)
              (2136-79-0).

[[Page 44254]]

3..........  Dacthal mono
              acid degradate
              \3\ (887-54-7).
4..........  DDE \6\ (72-55-   Do not regulate.  0.2 [mu]g/L.....  UCMR 1..........  \7\.............  \7\............  0.03% \7\ (1 of  0.01% (18K of
              9).                                                                                                        3,874) \8\.      226M) \8\
5..........  1,3-              Do not regulate.  0.4 [mu]g/L.....  UCM Rd1.........  0.16% (15 of      0.86% (436K of   0.16% (15 of     0.86% (436K of
              Dichloropropene                                      UCM Rd2.........   9,164) \9\.       51M) \9\.        9,164) \9\.      51M) \9\
              (Telone) (542-                                       UCMR 1..........  0.30% (50 of      0.42% (193K of   0.23% (38 of     0.33% (152K of
              75-6).                                                                  16,787) \9\.      46M) \9\.        16,787) \9\.     46M) \9\
                                                                                     \7\.............  \7\............  0.00% (0 of      0.00% (0 of
                                                                                                                         796) \8\.        2.8M) \8\
6..........  2,4-              Do not regulate.  0.05 [mu]g/L....  UCMR 1..........  \7\.............  \7\............  0.03% (1 of      0.02% (38K of
              Dinitrotoluene                                                                                             3,873) \8\.      226M) \8\
              (121-14-2).
7..........  2,6-              Do not regulate.  0.05 [mu]g/L....  UCMR 1..........  \7\.............  \7\............  0.00% (0 of      0.00% (0 of
              Dinitrotoluene                                                                                             3,873) \8\.      226M) \8\
              (606-20-2).
8..........  EPTC \10\ (759-   Do not regulate.  175 [mu]g/L.....  UCMR 1..........  0.00% (0 of       0.00% (0 of      0.00% (0 of      0.00% (0 of
              94-4).                                                                  3,873).           226M).           3,873).          226M)
9..........  Fonofos (944-22-  Do not regulate.  10 [mu]g/L......  UCMR 1..........  0.00% (0 of 295)  0.00% (0 of      0.00% (0 of      0.00% (0 of
              9).                                                                                       41M).            295).            41M)
10.........  Terbacil (5902-   Do not regulate.  90 [mu]g/L......  UCMR 1..........  0.00% (0 of       0.00% (0 of      0.00% (0 of      0.00% (0 of
              51-2).                                                                  3,873).           226M).           3,873).          226M)
11.........  1,1,2,2-          Do not regulate.  0.4 [mu]g/L.....  UCM Rd1.........  0.22% (44 of      1.69% (1.6M of   0.20% (41 of     1.63% (1.5M of
              Tetrachloroetha                                      UCM Rd2.........   20,407) \9\.      95M) \9\.        20,407) \9\.     95M) \9\
              ne (79-34-5).                                                          0.07% (18 of      0.51% (362K of   0.07% (17 of     0.08% (56K of
                                                                                      24,800) \9\.      71M) \9\.        24,800) \9\.     71M) \9\
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\1\ EPA also considered the results of an AwwaRF study of PWSs indicating that surface water sources are unlikely to contain boron at levels > the HRL
  of 1,400 [mu]g/L (Frey et al., 2004).
\2\ 2,3,5,6-tetrachloroterephthalic acid (TPA).
\3\ monomethyl-2,3,5,6-tetrachloroterephthalate (MTP).
\4\ Using the dacthal parent HRL since it includes the toxicity for the degradates.
\5\ Degradates monitored in aggregate and converted to the parent equivalent.
\6\ 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene.
\7\ Not reported since MRL > \1/2\ the HRL.
\8\ Shows results > MRL, rather than > HRL, since MRL is greater than the HRL. In all cases the MRL is within the 10-4 to 10-6 risk range.
\9\ The MRLs used in UCM varied from below the \1/2\ HRL to above the HRL. However, even the highest MRLs used are within the 10-4 to 10-6 risk range.
\10\ s-ethyl dipropylthiocarbamate.

IV. Summary of Public Comments and the Agency's Responses on the CCL 
Regulatory Determination Process

    EPA received comments from nine organizations or individuals on the 
May 1, 2007, Federal Register notice. These nine organizations/
individuals include five water-related associations, one industry 
group, one State agency, one State-related association, and one 
anonymous person. A majority of the comments focused on the following 
four over-arching topic areas:
     The regulatory determinations for the 11 contaminants;
     The regulatory determinations approach;
     The occurrence and exposure evaluation; and
     Comments on specific CCL 2 contaminants: boron, 
perchlorate, MTBE, metolachlor, and cyanobacteria and its toxins.
    A complete copy of the public comments and the Agency's responses 
are included in the Docket for today's action (USEPA, 2008m). The 
remainder of this section discusses the four key topic areas identified 
by commenters in response to the May 2007 preliminary regulatory 
determination notice (72 FR 24016, (USEPA, 2007a)).

A. Regulatory Determinations for the 11 Contaminants

    Comment Summary: Most of the commenters agreed with EPA's decisions 
not to regulate the 11 contaminants. However, one State agency 
recommended that EPA reconsider its position of not regulating 2,4- and 
2,6-DNT because they found these two contaminants in ground water in 
numerous locations in and around ammunition and military sites in their 
State.
    Agency Response: EPA agrees with the commenters who believe that no 
regulation is warranted at this time for the 11 contaminants. In 
response to reconsidering the Agency's decision for 2,4- and 2,6-DNT, 
EPA respectfully disagrees. Monitoring data collected on 2,4- and 2,6-
DNT from UCMR 1 do not indicate that either of these chemicals occurs 
nationally in public drinking water systems at health levels of 
concern. EPA found only one detection of 2,4-DNT from among the 3,873 
public water systems evaluated and no detections of 2,6-DNT. The 
information submitted by the commenter does not lead the Agency to 
change its decision because the occurrence appears to be highly 
localized and therefore, does not meet statutory criterion 2 (likely to 
occur in PWSs with a frequency and at a level of concern). To assist 
State and local communities that may have localized occurrence of 2,4- 
and/or 2,6-DNT, the Agency has updated the Health Advisory for both of 
these compounds as part of the regulatory determination process. If a 
State finds that it has highly localized levels of 2,4- and/or 2,6-DNT 
above the HRL of 0.05 [mu]g/L, the Agency encourages States to consider 
whether State-level guidance (or some other type of action) may be 
appropriate.

B. Regulatory Determinations Approach

    Comment Summary: One commenter recommended that EPA expand its 
discussion of the logic underlying the determinations for these 11 
contaminants. The commenter stated that EPA needs to raise the level of 
transparency in its decision logic so that stakeholders can understand 
how data and information translate to determinations and to ensure

[[Page 44255]]

consistency across the two parallel regulatory efforts (regulatory 
determinations and six-year reviews). The commenter asked for a 
discussion about the status of the remaining CCL 2 contaminants. In 
addition, the commenter recommended that EPA's drinking water research 
agenda be integrated with the regulatory development process.
    Another commenter agreed with the determinations not to regulate 
the 11 contaminants but recommended that EPA include affordability 
criteria when evaluating whether regulation will result in a meaningful 
health benefit in future determinations. The commenter submitted a 
paper in support of their comment.\8\
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    \8\ This paper can be found in the Docket for this notice at 
http://www.regulations.gov under the Docket ID No. EPA-HQ-OW-2007-
0068.
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    Agency Response: In response to the first comment, EPA developed a 
consistent regulatory determination approach for evaluating CCL 2 
contaminants that followed the National Drinking Water Advisory 
Council's (NDWAC, 2000) recommended protocol for both health effects 
and occurrence analyses. In this notice (section VI), EPA added a 
narrative and tables that summarize the data gaps for the other 40 CCL 
2 contaminants, which kept the Agency from making a regulatory 
determination at this time. EPA does not believe that it is appropriate 
to consider a research agenda specifically for those contaminants at 
this time because the Agency is in the process of developing a new CCL 
(CCL 3). The new process considers the knowledge and experience gained 
from evaluating unregulated contaminants on CCL 1 and CCL 2 and the 
recommendations and advice from the National Academies of Sciences' 
National Research Council (NRC, 2001) and NDWAC (2004). The Agency 
anticipates that future CCL research needs will be directed at filling 
data gaps for contaminants on the new list (i.e., CCL 3), not CCL 2. 
All CCL 2 contaminants will be examined for inclusion on CCL 3 and 
those that remain a high priority will be examined for research needs.
    In response to the second comment, the SDWA requires that EPA 
consider the costs and benefits, as well as affordability, as NPDWRs 
are developed. Specifically, SDWA requires that EPA perform a health 
risk reduction and cost analysis and an affordability analysis for 
proposed NPDWRs. EPA respectfully disagrees that an affordability 
analysis is necessary or required for regulatory determinations. For 
regulatory determination, SDWA requires that EPA use the three criteria 
discussed in section III.A. As a result, EPA will evaluate costs and 
affordability in more detail, including whether small system variances 
are appropriate, as part of the regulatory process after the Agency 
makes a positive regulatory determination.

C. Occurrence and Exposure Evaluation

    Comment Summary: One commenter stated that ``based on the first 
round of regulatory determinations, a range of 0.02%-3.2% for national 
occurrence could be considered as the minimum threshold for development 
of a new regulation'' and ``national occurrence estimates for these 
eleven contaminants are well below this threshold, with boron having 
the highest prevalence of occurrence, at 1.7% of systems sampled in the 
National Inorganics and Radionuclides Survey (NIRS).''
    Another commenter provided a report by Phillips and Chambless \9\ 
that evaluated compliance data for seven contaminants from five States 
obtained from a cross section of State regulatory agencies. Based on a 
preliminary analysis, the authors found that the variability in the 
means of quarterly samples taken for compliance purposes was 
consistently large. The commenter expressed the opinion that the 
variability (standard error of the mean divided by the mean) is 
significant enough (100 percent or more in many cases) to question the 
validity of decisions made based on the UCMR data (for unregulated 
contaminants). Based on that study, the commenter stated that there is 
no reason to assume that the quality of the occurrence data from the 
UCMR effort would be any better than the quality of the compliance 
data. The second commenter urged EPA to resolve this quality issue 
before trying to make CCL 2 regulatory decisions that are based on 
rather precise calculations of occurrence levels and the number of 
persons exposed.
---------------------------------------------------------------------------

    \9\ This paper can be found in the Docket for this notice at 
http://www.regulations.gov under the Docket ID No. EPA-HQ-OW-2007-
0068.
---------------------------------------------------------------------------

    Agency Response: In response to the first comment, EPA considers 
both the extent of national occurrence and the severity of health 
effects for a contaminant, as well as other factors (e.g., sources of 
exposure), when deciding whether regulation presents a meaningful 
opportunity for health risk reduction. As a result, the Agency does not 
believe it is appropriate to set minimum occurrence thresholds for 
regulatory determinations.
    In response to the second comment regarding variability in 
occurrence measures based on the compliance monitoring data for 
regulated contaminants, the Agency believes the variability issues 
identified by Phillips and Chambless do not directly reflect the 
dependability of the UCMR 1 data used to support the Agency's 
regulatory determinations. Compliance monitoring data is State data 
resulting from individual public water systems efforts to comply with 
regulatory monitoring requirements. The UCMR 1 is EPA's program to 
collect data for contaminants suspected to be present in drinking water 
based upon a statistically-valid data set for nationwide occurrence 
estimates. The UCMR 1 program was designed to address this variability 
issue at the national level by defining a vulnerable period (the season 
of greatest vulnerability of contaminant occurrence, the season of 
increased flux of water movement) and requiring at least one UCMR 1 
sample during that period. In addition, the monitoring periods for the 
large and small systems were performed over a three year period. 
Approximately one-third of all small UCMR 1 systems throughout the 
country conducted monitoring in each of the three years of UCMR 1 
monitoring. Furthermore, the monitoring schedules for these systems 
were conducted to include monitoring in every month and every season 
around the country. Large systems could conduct their one year of 
monitoring anytime during the UCMR 1 period from 2001 to 2003. Like 
small systems, their monitoring schedules were spread throughout the 
year and were to include one sample during what was considered the most 
vulnerable season. In this way, the UCMR 1 monitoring results reflect 
multiple seasons and multiple years of climatic conditions throughout 
the country and are not directly affected (or biased) by weather 
conditions of a single season, year, or geographic region. Whereas some 
variability might still be expected, EPA believes this is unlikely to 
be a source of bias for national level occurrence estimates.
    In addition, it should be noted that EPA used peak occurrence 
estimates (the number and percent of systems with at least one observed 
detection greater than \1/2\ the HRL and the HRL) as opposed to mean 
values in making its final decisions not to regulate the 11 CCL 2 
contaminants. Hence, taking variability around the mean into account 
would not have influenced the outcome of the final determinations for 
these 11 contaminants. The characterization of national occurrence 
provided by the UCMR 1 monitoring

[[Page 44256]]

data is adequate and the best available data to support today's 
decisions.

D. Comments on Boron, Perchlorate, MTBE, Metolachlor, and Cyanobacteria 
and Its Toxins

    1. Boron. One anonymous commenter agreed with our determination for 
boron but commented on the fact that the health reference level does 
not incorporate the results of the preliminary chemical-specific Health 
Advisory Level (HAL) derived recently by EPA and presented at the 2007 
Society of Toxicology (SOT) meeting.
    Agency Response: The HRL used in making regulatory determinations 
is not equivalent to a lifetime health advisory value. As stated in the 
Health Effects Support Document for Boron (USEPA, 2008d) and the May 1, 
2007, notice (72 FR 24016 (USEPA, 2007a)), an HRL is a benchmark 
against which to measure the occurrence data; it is not a Health 
Advisory guideline. For noncarcinogens such as boron, the HRL is 
calculated by multiplying the Agency Reference Dose by a 70 kg body 
weight and a 20 percent default Relative Source Contribution (RSC) and 
dividing the product by a drinking water intake of 2 L/day.
    As described in the May 2007 notice (72 FR 24016 (USEPA, 2007a)) 
and in evaluating contaminants for regulatory determinations, the 
Agency initially uses a default 20 percent RSC to estimate the HRLs for 
non-carcinogens because this approach derives the lowest and most 
conservative HRL value to use in screening the occurrence data. EPA 
used this approach to calculate the HRL benchmark for boron and to 
determine if boron might be occurring nationally at a level of 
potential health concern. In developing the health advisory for boron, 
the Agency performed a more refined assessment of the risk for those 
PWSs that occasionally find levels of boron that exceed the lifetime or 
shorter term health advisory values. While the Agency derived a more 
refined RSC for the determination of the lifetime Health Advisory for 
boron, this value is still limited by the RSC ceiling of 80 percent as 
a matter of policy. The derivation of health advisory values also 
incorporates the use of appropriate body weights for the target 
population. The 2007 SOT poster presentation used a body weight of 67 
kg for a pregnant woman, consistent with the Human Health Methodology 
(USEPA, 2000) guidelines. There may be changes to that policy based on 
more recent data on pregnancy weights, and if so, the draft Health 
Advisory will be revised to reflect the new policy.
    2. Perchlorate. EPA received comment letters on perchlorate from 
eight commenters. The major areas of concern raised in the comments 
related to (1) the Agency's decision not to make a regulatory 
determination for perchlorate at the same time as for the 11 
contaminants for which a regulatory determination is being finalized 
today, and (2) the Agency's discussion of potential analyses to more 
fully characterize total perchlorate exposure in order to assess the 
opportunity for public health protection through a drinking water 
regulation.
    Agency Response: EPA will soon publish a preliminary determination 
for perchlorate. EPA will request public comment as part of that 
notice. EPA will consider the comments received on the May 2007 notice 
(72 FR 24016 (USEPA, 2007a)) with respect to perchlorate as a part of 
that regulatory determination and will respond to such public comments 
at the time the Agency issues a regulatory determination for 
perchlorate. EPA intends to finalize a regulatory determination for 
perchlorate by December 2008.
    3. MTBE. Most commenters supported EPA's decision not to make a 
regulatory determination for methyl tertiary-butyl ether (MTBE) at this 
time because the IRIS assessment is currently being revised. Also, one 
commenter felt that UCMR 1 would provide valuable occurrence data for 
MTBE when the risk assessment becomes available.
    Agency Response: EPA agrees that UCMR 1 data provides important 
occurrence information on MTBE and will be useful in making a 
regulatory determination once the final risk assessment is available.
    4. Metolachlor. Some commenters noted that additional research for 
the health effects and occurrence of metolachlor and its degradates is 
needed. One commenter felt that UCMR 2 would provide valuable 
occurrence information for metolachlor and its degradates. One 
commenter did not have additional data but believes more information is 
needed on the occurrence and health effects of many herbicides and 
pesticides and their degradates. The results of this research should be 
appropriately included in regulatory decisions by the Office of 
Pesticide Programs (OPP) and the Office of Ground Water and Drinking 
Water. The commenter stated that EPA should promote further research to 
definitively determine whether metolachlor, a very widely used 
pesticide, is carcinogenic, as acetochlor, alachlor and metolachlor 
have very similar chemical structures.
    Agency Response: The Agency agrees that more information on the 
occurrence of metolachlor and its degradates is needed in order to 
determine if the combined parent compound and its degradates are 
occurring at levels of health concern. The available metolachlor data 
from earlier unregulated contaminant monitoring surveys indicate that 
metolachlor is found in finished water in many locations but at levels 
below the HRL. The occurrence data on the parent metolachlor, combined 
with the knowledge that it decomposes to several degradates that are 
more persistent than the parent, supported the inclusion of both 
metolachlor and its degradates in UCMR 2. Once available, the UCMR 2 
data will be useful in evaluating the occurrence of metolachlor and its 
degradates in public water systems and will assist the Agency in 
deciding whether to regulate these compounds.
    5. Cyanobacteria and its toxins. In the May 2007 notice (72 FR 
24016 (USEPA, 2007a)), EPA asked for comment on the usefulness of 
providing an information summary about cyanobacteria and its toxins. 
One commenter responded and recommended that EPA provide an information 
summary describing the state of the knowledge on the prevention, 
treatment, and health effects of cyanobacteria and its toxins. The 
commenter felt that a document would be useful for utilities and State 
agencies. The commenter recommended that the summary include 
information on occurrence, conditions that might favor growth of algae 
and production of toxins, and a strategy for communicating this 
information to utility customers. In addition, the commenter suggested 
that the summary include information on research funded by other 
organizations, particularly the AWWA Research Foundation (AwwaRF).
    Agency Response: EPA is developing an information sheet that will 
include the information suggested by the commenter and links to 
organizations performing research on the cyanobacteria and its toxins. 
The Agency anticipates making this information sheet available on its 
Safewater Web site (http://www.epa.gov/safewater) shortly after the 
publication of this notice.

V. Summary of the Agency's Findings on the 11 CCL 2 Contaminants

A. Boron

    1. Description. 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

[[Page 44257]]

trifluoride). Boron compounds are used in the production of glass, 
ceramics, cleaning agents, fire retardants, pesticides, cosmetics, 
photographic materials, and high energy fuels (USGS, 2004; ATSDR, 
1992).
    2. Agency Findings. The Agency is making a determination not to 
regulate boron with a national primary drinking water regulation. As 
noted in the May 2007 notice (72 FR 24016 (USEPA, 2007a)), EPA used 
data from NIRS and an AwwaRF study (Frey et al., 2004) to evaluate 
occurrence and exposure at the HRL of 1,400 [mu]g/L (as well as \1/2\ 
the HRL). The NIRS data indicate that approximately 4.3 percent (or 43) 
of the 989 ground water PWSs sampled had at least one detection 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 
at least one detection 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, 2008c and 2008d).
    Because NIRS did not contain data for surface water systems, the 
Agency evaluated the results of the AwwaRF study (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 at 
least one sample with a boron concentration greater than 1,400 [mu]g/L 
(Seidel, 2006).
    While boron was found at levels greater than the HRL of 1,400 
[mu]g/L (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 water sources evaluated in the AwwaRF 
study. Taking this surface water information into account, the Agency 
believes the overall 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 health levels of concern when considering both surface and 
ground water systems, the Agency believes that a national primary 
drinking water regulation does not present a meaningful opportunity for 
health risk reduction.
    The Agency presented a complete review of our analysis of the 
health effects, occurrence, and exposure for boron in the May 2007 
notice (72 FR 24016 (USEPA, 2007a)), the final regulatory support 
document (USEPA, 2008a), and the health effects support document for 
boron (USEPA, 2008d). 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. If a State 
finds highly localized occurrence of boron at concentrations above the 
HRL, the Agency encourages States to consider whether State-level 
guidance (or some other type of action) may be appropriate.

B. Dacthal Mono- and Di-Acid Degradates

    1. Description. 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. 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 (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, 1998a).
    2. Agency Findings. The Agency is making a determination not to 
regulate the DCPA mono-acid degradate and/or the DCPA di-acid degradate 
with a national primary drinking water regulation. As noted in the May 
2007 notice (72 FR 24016 (USEPA, 2007a)), these degradates appear to 
occur infrequently at health levels of concern in PWSs, and 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 one PWS detected these degradates at a 
concentration above the HRL of 70 [mu]g/L.
    The Agency presented a complete review of our analysis of the 
health effects, occurrence, and exposure for dacthal mono- and di-acid 
degradates in the May 2007 notice (72 FR 24016 (USEPA, 2007a)), the 
final regulatory support document (USEPA, 2008a), and the health 
effects support document (USEPA, 2008e). 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. If a State finds highly localized occurrence 
of DCPA degradates at concentrations above the HRL, the Agency 
encourages States to consider whether State-level guidance (or some 
other type of action) may be appropriate.

C. 1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene

    1. Description. DDE is a primary metabolite of 1,1,1-trichloro-2,2-
bis(p-chlorophenyl)ethane (DDT), a pesticide 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 prior contamination with 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 DDE bound 
to soil particles. In both soil and water, DDE is subject to 
photodegradation, biodegradation, and volatilization (ATSDR, 2002).
    2. Agency Findings. The Agency is making a determination not to 
regulate DDE with a national primary drinking water regulation. As 
noted in the May 2007 notice (72 FR 24016 (USEPA, 2007a)), DDE appears 
to occur infrequently at health levels of concern in PWSs, and 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). The MRL is greater than the HRL of 
0.2 [mu]g/L but represents a concentration that is within the 
10-4 to the 10-6 cancer risk range targeted by

[[Page 44258]]

the Agency. In addition, ambient water data from the USGS (Martin et 
al., 2003; Kolpin and Martin, 2003) indicate that the maximum 
concentrations detected in surface and ground water were less than the 
HRL.
    The Agency presented a complete review of our analysis of the 
health effects, occurrence, and exposure for DDE in the May 2007 notice 
(72 FR 24016 (USEPA, 2007a)), the final regulatory support document 
(USEPA, 2008a), and the health effects support document (USEPA, 2008f). 
If a State finds highly localized occurrence of DDE at concentrations 
above the HRL, the Agency encourages States to consider whether State-
level guidance (or some other type of action) may be appropriate.

D. 1,3-Dichloropropene

    1. Description. 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 planted with all types of food and 
feed crops. 1,3-DCP is typically injected 12 inches to 18 inches 
beneath the soil surface and can only be used by certified handlers 
(USEPA, 1998b).
    2. Agency Findings. The Agency is making a determination not to 
regulate 1,3-DCP with a national primary drinking water regulation. As 
noted in the May 2007 notice (72 FR 24016 (USEPA, 2007a)), 1,3-DCP 
appears to occur infrequently at health levels of concern in PWSs, and 
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 application requirements, which 
are intended to mitigate risks to drinking water, may be one reason for 
the lack of occurrence of 1,3-DCP at health levels of concern in 
subsequent monitoring surveys.
    The Agency presented a complete review of our analysis of the 
health effects, occurrence, and exposure for 1,3-DCP in the May 2007 
notice (72 FR 24016 (USEPA, 2007a)) and in the health effects support 
document (USEPA, 2008j). The Agency also plans to update the Health 
Advisory document for 1,3-DCP with 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. If a State 
finds a highly localized occurrence of 1,3-DCP at concentrations above 
the HRL, the Agency encourages States to consider whether State-level 
guidance (or some other type of action) may be appropriate.

E. 2,4-Dinitrotoluene and 2,6-Dinitrotoluene

    1. Description. 2,4- and 2,6-dinitrotoluene (DNT), semi-volatile 
organic compounds, are two of the six isomers of dinitrotoluene. 
Dinitrotoluenes are used in the production of polyurethane foams, 
automobile air bags, dyes, ammunition, and explosives, including 
trinitrotoluene or TNT (HSDB, 2004a and 2004b; ATSDR, 1998). Neither 
2,4-DNT nor 2,6-DNT occurs naturally. They are generally produced as 
individual isomers or as a mixture called technical grade 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, 2004c).
    2. Agency Findings. The Agency is making a determination not to 
regulate 2,4-or 2,6-DNT with a national primary drinking water 
regulation. As noted in the May 2007 notice (72 FR 24016 (USEPA, 
2007a)), 2,4- and 2,6-DNT appear to occur infrequently at health levels 
of concern in PWSs, and 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 (MRL) of 2 [mu]g/L and 2,6-DNT was not detected at this 
same level in any of the PWSs monitored under the UCMR 1. While the MRL 
is slightly greater than the HRL of 0.05 [mu]g/L, this concentration is 
within the acceptable 10-4 to the 10-6 cancer 
risk range targeted by the Agency.
    The Agency presented a complete review of our analysis of the 
health effects, occurrence, and exposure for 2,4- and 2,6-DNT in the 
May 2007 notice (72 FR 24016 (USEPA, 2007a)) and in the health effects 
support document (USEPA, 2008l). 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. EPA 
published a draft of the updated Health Advisory document for both 2,4 
and 2,6-DNT as part of the regulatory determinations for these two 
isomers. The updated document is available on the Web at: http://
www.epa.gov/safewater/ccl/reg_determine2.html. The final Health 
Advisory document will be published in 2008 and will provide 
information to States with public water systems that may have either 
2,4- or 2,6-DNT at concentrations above health levels of concern. If a 
State finds highly localized occurrence of 2,4- and/or 2,6-DNT at 
concentrations above the HRL, the Agency encourages States to consider 
whether State-level guidance (or some other type of action) may be 
appropriate.

F. s-Ethyl dipropylthiocarbamate

    1. Description. 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).
    2. Agency Findings. The Agency is making a determination not to 
regulate EPTC with a national primary drinking water regulation. As 
noted in the May 2007 notice (72 FR 24016 (USEPA, 2007a)), EPTC does 
not appear to occur at health levels of concern in PWSs, and 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 at levels less than the HRL of 175 
[mu]g/L (as well as \1/2\ the HRL), it was not found in the UCMR 1 
survey of public water supplies. The Agency presented a complete review 
of our analysis of the health effects, occurrence, and exposure for 
EPTC in the May 2007 notice (72 FR 24016 (USEPA, 2007a)), the final 
regulatory support document (USEPA, 2008a), and in the health effects 
support document (USEPA, 2008g).

G. Fonofos

    1. Description. 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, 
onions, peppers, tomatoes, cole crops, sweet

[[Page 44259]]

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).
    2. Agency Findings. The Agency is making a determination not to 
regulate fonofos with a national primary drinking water regulation. As 
noted in the May 2007 notice (72 FR 24016 (USEPA, 2007a)), fonofos does 
not appear to occur at health levels of concern in PWSs and 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 at levels less than the HRL of 
10 [mu]g/L (as well as \1/2\ the HRL), it was not found in the 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 contaminate source waters. The Agency presented a complete 
review of our analysis of the health effects, occurrence, and exposure 
for fonofos in the May 2007 notice (72 FR 24016 (USEPA, 2007a)), the 
final regulatory support document (USEPA, 2008a), and in the health 
effects support document (USEPA, 2008h).

H. Terbacil

    1. Description. 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, 1998c).
    2. Agency Findings. The Agency is making a determination not to 
regulate terbacil with a national primary drinking water regulation. As 
noted in the May 2007 notice (72 FR 24016 (USEPA, 2007a)), terbacil 
does not appear to occur at health levels of concern in PWSs. 
Accordingly, the Agency believes that a national primary drinking water 
regulation does not present a meaningful opportunity for health risk 
reduction. While terbacil has been found in ambient waters at the 
levels less than the HRL of 90 [mu]g/L (as well as \1/2\ the HRL), it 
was not found in the UCMR 1 survey of public water supplies. The Agency 
presented a complete review of our analysis of the health effects, 
occurrence, and exposure for terbacil in the May 2007 notice (72 FR 
24016 (USEPA, 2007a)), the final regulatory support document (USEPA, 
2008a), and in the health effects support document (USEPA, 2008i).

I. 1,1,2,2-Tetrachloroethane

    1. Description. 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).
    2. Agency Findings. The Agency is making a determination not to 
regulate 1,1,2,2-tetrachloroethane with a national primary drinking 
water regulation. As noted in the May 2007 notice (72 FR 24016 (USEPA, 
2007a)), 1,1,2,2-tetrachloroethane appears to occur infrequently at 
health levels of concern in PWSs. Accordingly, the Agency 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.\10\ 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 of 0.4 [mu]g/L. 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.
---------------------------------------------------------------------------

    \10\ The UCM Round 1 and 2 surveys were performed in the late 
1980's and the mid 1990's. These surveys should not be confused with 
the UCMR 1 Screening and Assessment Monitoring that began in 2001.
---------------------------------------------------------------------------

    The Agency presented a complete review of our analysis of the 
health effects, occurrence, and exposure for 1,1,2,2-tetrachloroethane 
in the May 2007 notice (72 FR 24016 (USEPA, 2007a)), the final 
regulatory support document (USEPA, 2008a), and in the health effects 
support document (USEPA, 2008k). 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. If a State finds 
highly localized occurrence of 1,1,2,2-tetrachloroethane at 
concentrations above the HRL, the Agency encourages States to consider 
whether State-level guidance (or some other type of action) may be 
appropriate.

VI. How Will EPA Address the Data Needs of the Remaining CCL 2 
Contaminants?

    To support decisions on CCL contaminants, the Agency evaluates when 
and where these contaminants occur, the extent of exposure, and their 
risk to public health. EPA must also determine if regulating the 
contaminant presents a meaningful opportunity for reducing public 
health risk. Contaminants deemed ready for regulatory determination are 
those that have sufficient health and occurrence data to evaluate both 
exposure and risk to public health and support a decision as to whether 
a regulation is appropriate. The remaining CCL 2 contaminants for which 
decisions are not being made today do not have sufficient data to 
support regulatory decisions at this time, except for perchlorate, 
which is the subject of a separate regulatory determination effort (see 
section IV.D.2 in this notice). Tables 2 and 3 list each contaminant 
and the type of data lacking for each contaminant.
    In addition, the Agency is evaluating the contaminants on CCL 2 as 
part of the new CCL 3 classification process. The new process is an 
expanded comprehensive system that evaluates a wider range of existing 
information, including data published after the CCL 2 preliminary 
regulatory determinations. The new process also applies revised 
screening criteria to

[[Page 44260]]

generate the CCL 3 based upon recommendations from NRC (2001) and NDWAC 
(2004). EPA anticipates determining future research needs once the CCL 
3 is finalized.

Table 2--Information Gaps for the CCL 2 Chemical Contaminants (As of May
                                 2007)*
------------------------------------------------------------------------
                                                     Health effects and
       Health effects              Occurrence            occurrence
------------------------------------------------------------------------
 Acetochlor \3\.............   Diazinon \6\.......   Alachlor ESA \4\
                                                     \7\
 Aluminum \4\ \5\...........   2,4-Dichloropheno     Metolachlor \7\ \8\
                               \6\.
 Bromobenzene \3\...........   2,4-Dinitrophenol     Organotins \1\ \3\
                               \6\.                  \5\ \7\
 1,1-Dichloroethane \4\.....   1,2-                  Prometon \3\ \6\
                               Diphenylhydrazine
                               \6\.
 1,3-Dichloropropane \4\....   Disulfoton \6\.....   RDX \3\ \7\
 2,2-Dichloropropane \4\....   Diuron \6\.........
 1,1-Dichloropropene \4\....   Linuron \6\........
 p-Isopropyltoluane \4\.....   2-Methylphenol \6\.
 Methyl Bromide \4\.........   Terbufos \6\.......
 Methyl Tertiary-Butyl Ether   Triazines \2\ \5\
 (MTBE) \3\.                   \7\.
 Molinate \3\...............   2,4,6-
                               Trichlorophenol \6\.
 Nitrobenzene \3\
 1,2,4-Trimethylbenzene \4\
 Vanadium \4\
------------------------------------------------------------------------
* Perchlorate is not included in this table (see section IV.D.2).
\1\ Organotins include dimethyl tin, dibutyl tin, monomethyl tin,
  monobutyl tin from PVC stabilizers and triphenyl tin pesticide.
\2\ Triazines include the chlorodegradates (DEA, DIA, and DACT) of
  regulated contaminants--atrazine and simazine.
\3\ IRIS or OPP assessment in progress or needs an updated risk
  assessment.
\4\ Insufficient data to do a quantitative risk assessment, health
  assessment incomplete, or no risk assessment available.
\5\ These chemicals also have analytical methods (i.e., organotins) and/
  or treatment (i.e. triazines, aluminum) gaps.
\6\ Insufficient occurrence (sampling) data for a national estimate.
\7\ Lack of finished water occurrence (monitoring) data.
\8\ Lack of occurrence data for metolachlor's degradates (ESA & OA).
  Metolachlor and its degradates are on UCMR 2.

                    Table 3--Information Gaps for the Microbial Contaminants (as of May 2007)
----------------------------------------------------------------------------------------------------------------
            Health effects                    Occurrence               Treatment            Analytical methods
----------------------------------------------------------------------------------------------------------------
 Microsporidia.......................   Microsporidia.........   Microsporidia.........   Microsporidia
Some Cyanotoxins.....................  Some Cyanotoxins.......  Some Cyanotoxins.......  Some Cyanotoxins
                                       Aeromonas..............  Aeromonas..............  Aeromonas
                                       Helicobacter...........  Helicobacter...........  Helicobacter
                                       MAC....................  MAC....................  MAC
                                       Adenoviruses...........  Adenoviruses...........
                                       Caliciviruses..........  Caliciviruses..........
                                       Coxsackieviruses.......  Coxsackieviruses.......
                                       Echoviruses............  Echoviruses............
----------------------------------------------------------------------------------------------------------------

VII. References

Agency for Toxic Substances and Disease Registry (ATSDR). 1992. 
Toxicological Profile for Boron. Atlanta, GA: Agency for Toxic 
Substances and Disease Registry, Public Health Service, U.S. 
Department of Health and Human Services. Available on the Internet 
at: http://www.atsdr.cdc.gov/toxprofiles/tp26.html.
ATSDR. 1996. Toxicological Profile for 1,1,2,2-Tetrachloroethane. 
Available on the Internet at: http://www.atsdr.cdc.gov/toxprofiles/
tp93.html.
ATSDR. 1998. Toxicological Profile for 2,4- and 2,6-Dinitrotoluene. 
Available on the Internet at: http://www.atsdr.cdc.gov/toxprofiles/
tp109.html.
ATSDR. 2002. Toxicological Profile DDT, DDE, and DDD. Available on 
the Internet at: http://www.atsdr.cdc.gov/toxprofiles/tp35.html.
Frey, M.M., C. Seidel, M. Edwards, J. Parks, and L. McNeill. 2004. 
Occurrence Survey for Boron and Hexavalent Chromium. AwwaRF Report 
91044F.
Hawley, G.G. 1981. Condensed Chemical Dictionary. 10th ed. New York, 
NY: Van Nostrand Reinhold Co. (As cited in ATSDR, 1996)
Hazardous Substances Database (HSDB). 2004a. ``TOXNET: Toxicology 
Data Network--2,4-Dinitrotoluene.'' Available on the Internet at: 
http://toxnet.nlm.nih.gov. [Search for 2,4-dinitrotoluene.] Accessed 
November 1, 2004.
HSDB. 2004b. ``TOXNET: Toxicology Data Network--2,6-
Dinitrotoluene.'' Available on the Internet at: http://
toxnet.nlm.nih.gov. [Search for 2,6-dinitrotoluene.] Accessed 
November 1, 2004.
International Agency for Research on Cancer (IARC). 1979. 1,1,2,2-
Tetrachloroethane. IARC Monographs on the Evaluation of the 
Carcinogenic Risk of Chemicals to Humans: Some Halogenated 
Hydrocarbons. Vol. 20. pp. 477-489. (As cited in ATSDR, 1996)
Kolpin, D.W. and J.D. Martin. 2003. ``Pesticides in Ground Water: 
Summary Statistics; Preliminary Results from Cycle I of the National 
Water Quality Assessment Program (NAWQA), 1992-2001.'' Available on 
the Internet at: http://ca.water.usgs.gov/pnsp/pestgw/Pest-GW_
2001_Text.html. Accessed August 24, 2004. A copy of this report is 
available in the docket.
Martin, J.D., C.G. Crawford, and S.J. Larson. 2003. ``Pesticides in 
Streams: Summary Statistics; Preliminary Results from Cycle I of the 
National Water Quality Assessment Program (NAWQA), 1992-2001.'' 
Available on the Internet at: http://ca.water.usgs.gov/pnsp/pestsw/ 
Pest-SW--2001--Text.html. Accessed August 24, 2004. A copy of this 
report is available in the docket.
National Drinking Water Advisory Council (NDWAC). 2004. Report on 
the CCL Classification Process to the U.S. Environmental Protection 
Agency; May 19, 2004.
NDWAC. 2000. Proposed Recommendation from the Working Group on CCL 
and 6-Year Review to the U.S. Environmental Protection Agency; May 
23, 2000.
National Research Council. 2001. Classifying Drinking Water 
Contaminants for Regulatory Consideration. National Academy Press, 
Washington DC.

[[Page 44261]]

Seidel, C. 2006. Email Communication from C. Seidel to Brent Ranalli 
at The Cadmus Group, Inc. [concerning boron data from an AwwaRF-
sponsored study, with data in an attached spreadsheet]. Denver, CO: 
McGuire Malcolm Pirnie; May 19, 2006.
USEPA. 1998a. Reregistration Eligibility Decision (RED)--DCPA. EPA 
Report 738-R-98-005. Washington, DC: Office of Prevention, 
Pesticides and Toxic Substances. November 1998. Available on the 
Internet at: http://www.epa.gov/oppsrrd1/REDs/0270red.pdf.
USEPA. 1998b. Reregistration Eligibility Decision (RED)--1,3-
Dichloropropene. EPA Report 738-R-98-016. Washington, DC: Office of 
Prevention, Pesticides and Toxic Substances. December 1998. 
Available on the Internet at: http://www.epa.gov/oppsrrd1/REDs/
0328red.pdf.
USEPA. 1998c. Reregistration Eligibility Decision (RED)--Terbacil. 
EPA Report 738-R-97-011. Washington, DC: Office of Prevention, 
Pesticides and Toxic Substances. January 1998. Available on the 
Internet at: http://www.epa.gov/oppsrrd1/REDs/0039red.pdf.
USEPA. 1998d. Notice of Receipt of Requests to Voluntarily Cancel 
Certain Pesticide Registrations. Federal Register. Vol. 63, No. 87. 
p. 25033, May 6, 1998.
USEPA. 1999c. Reregistration Eligibility Decision (RED)--EPTC. EPA 
Report 738-R-99-006. Washington, DC: Office of Prevention, 
Pesticides and Toxic Substances. December 1999. Available on the 
Internet at: http://www.epa.gov/oppsrrd1/REDs/0064red.pdf.
USEPA. 1999d. Reregistration Eligibility Decision (RED) Facts--O-
Ethyl S-phenyl ethylphosphonodithiolate (Fonofos). EPA Report 738-F-
99-019. Washington, DC: Office of Prevention, Pesticides and Toxic 
Substances. November 1999. Available on the Internet at: http://
www.epa.gov/oppsrrd1/REDs/factsheets/0105fact.pdf.
USEPA. 2000. Methodology for Deriving Ambient Water Quality Criteria 
for the Protection of Human Health (2000). EPA Report EPA-822-B-00-
004. Washington, DC: Office of Water. October 2000. Available on the 
Internet at: http://www.epa.gov/waterscience/criteria/humanhealth/
method/method.html
USEPA. 2007a. Drinking Water: Regulatory Determinations Regarding 
Contaminants on the Second Drinking Water Contaminant Candidate 
List--Preliminary Determinations. Notice. Federal Register. Vol. 72, 
No. 83, p. 24016, May 1, 2007.
USEPA. 2008a. Regulatory Determinations Support Document for 
Selected Contaminants from the Second Drinking Water Contaminant 
Candidate List (CCL 2). EPA Report 815-R-08-012. June 2008.
USEPA. 2008b. 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. EPA Report 815-R-08-013. June 2008.
USEPA. 2008c. 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. EPA Report 
815-R-08-014. June 2008.
USEPA. 2008d. Health Effects Support Document for Boron. EPA Report 
822-R-08-002. June 2008.
USEPA. 2008e. Health Effects Support Document for Dacthal 
Degradates: Tetrachloroterephthalic Acid (TPA) and Monomethyl 
Tetrachloroterephthalic Acid (MTP). EPA Report 822-R-08-005. June 
2008.
USEPA. 2008f. Health Effects Support Document for 1,1-Dichloro-2,2-
bis(p-chlorophenyl)ethylene (DDE). EPA Report 822-R-08-003. June 
2008.
USEPA. 2008g. Health Effects Support Document for S-Ethyl 
dipropylthiocarbamate (EPTC). EPA Report 822-R-08-006. June 2008.
USEPA. 2008h. Health Effects Support Document for Fonofos. EPA 
Report 822-R-08-009. June 2008.
USEPA. 2008i. Health Effects Support Document for Terbacil. EPA 
Report 822-R-08-004. June 2008.
USEPA. 2008j. Health Effects Support Document for 1,3-
Dichloropropene. EPA Report 822-R-08-008. June 2008.
USEPA. 2008k. Health Effects Support Document for 1,1,2,2-
Tetrachloroethane. EPA Report 822-R-08-007. June 2008.
USEPA. 2008l. Health Advisory for 2,4- and 2,6-Dinitrotoluene. EPA 
Report 822-R-08-010. June 2008.
USEPA. 2008m. Comment Response Document for the Regulatory 
Determinations on the Second Drinking Water Contaminant Candidate 
List 2 (Categorized Public Comments). June 2008.
USGS. 2004. ``Mineral Commodity Summaries, January 2004--Boron.'' 
January 2004. Available on the Internet at: http://
minerals.usgs.gov/minerals/pubs/commodity/boron/boronmcs04.pdf.

    Dated: July 24, 2008.
Stephen L. Johnson,
Administrator.
[FR Doc. E8-17463 Filed 7-29-08; 8:45 am]

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