Document ID: EPA-HQ-OW-2012-0155-0027
Agency: epa
Document Type: Rule
Title: Final Regulatory Determinations: Contaminants on the Third Drinking Water Contaminant Candidate List,
Posted Date: 2016-01-04T05:00Z

[Federal Register Volume 81, Number 1 (Monday, January 4, 2016)]
[Rules and Regulations]
[Pages 13-19]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-32760]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 141

[EPA-HQ-OW-2012-0155; FRL-9940-64-OW]

Announcement of Final Regulatory Determinations for Contaminants 
on the Third Drinking Water Contaminant Candidate List

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final regulatory determinations.

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SUMMARY: The U.S. Environmental Protection Agency (EPA) is announcing 
final regulatory determinations not to issue national primary drinking 
water regulations for four of the 116 contaminants listed on the Third 
Contaminant Candidate List. The Safe Drinking Water Act, as amended in 
1996, requires the EPA to make regulatory determinations every five 
years on at least five unregulated contaminants. A regulatory 
determination is a decision about whether or not to begin the process 
to propose and promulgate a national primary drinking water regulation 
for an unregulated contaminant. On October 20, 2014, the agency 
published its preliminary determinations not to regulate dimethoate, 
1,3-dinitrobenzene, terbufos, terbufos sulfone and begin the process to 
regulate strontium. The agency requested public comment on the 
determinations, process, rationale and supporting technical 
information. The agency received comments from 14 individuals or 
organizations on the preliminary regulatory determinations. After 
careful review and consideration of the public comments, the agency is 
making a final determination not to regulate dimethoate, 1,3-
dinitrobenzene, terbufos and terbufos sulfone. The agency, however, is 
delaying the final regulatory determination on strontium in order to 
consider additional data and decide whether there is a meaningful 
opportunity for health risk reduction by regulating strontium in 
drinking water.

DATES: In accordance with 40 CFR 23.7 for purposes of judicial review, 
the regulatory determinations in this document are issued as of January 
4, 2016.

FOR FURTHER INFORMATION CONTACT: Zeno Bain, Standards and Risk 
Management Division, Office of Ground Water and Drinking Water, Office 
of Water (Mailcode 4607M), Environmental Protection Agency, 1200 
Pennsylvania Ave. NW., Washington, DC 20460; telephone number: (202) 
564-5970; email address: bain.zeno@epa.gov. For general information, 
contact the Safe Drinking Water Hotline, telephone number: (800) 426-
4791. The Safe Drinking Water Hotline is open Monday through Friday, 
excluding legal holidays, from 10 a.m. to 4 p.m., eastern time.

SUPPLEMENTARY INFORMATION: 

I. General Information

A. Does this action apply to me?

    These final regulatory determinations will not impose any 
requirements on anyone. Instead, this action notifies interested 
parties of the EPA's final regulatory determinations for four 
contaminants and provides a summary of the major comments received on 
the October 20, 2014, preliminary determinations (USEPA, 2014c).

B. How can I get copies of this document and other related information?

    Docket: The EPA has established a docket for this action under 
Docket ID No. EPA-HQ-OW-2012-0155. Publicly available docket materials 
are available either electronically at 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 Water Docket 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 Water Docket 
is (202) 566-2426.
    Electronic Access: You may access this Federal Register document 
electronically from the Government Printing Office under the ``Federal 
Register'' listings at http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR.

Abbreviations Used in This Document

CCL Contaminant Candidate List
CCL 3 Third Contaminant Candidate List
CFR Code of Federal Regulations
EPA Environmental Protection Agency
FR Federal Register
HRL Health Reference Level
MCL Maximum Contaminant Level
MCLG Maximum Contaminant Level Goal
MRL Minimum Reporting Limit

[[Page 14]]

NPDWR National Primary Drinking Water Regulation
PWS Public Water System
RD Regulatory Determination
RD 3 Third Regulatory Determination
RSC Relative Source Contribution
SDWA Safe Drinking Water Act
STORET Storage and Retrieval Data System
UCMR Unregulated Contaminant Monitoring Regulation
UCMR 1 First Unregulated Contaminant Monitoring Regulation
UCMR 2 Second Unregulated Contaminant Monitoring Regulation
UCMR 3 Third Unregulated Contaminant Monitoring Regulation
USDA United States Department of Agriculture
USGS United States Geological Survey
[mu]g/L micrograms per Liter

Table of Contents

I. General Information
    A. Does this action apply to me?
    B. How can I get copies of this document and other related 
information?
II. Purpose and Background
    A. What is the purpose of this action?
    B. What are the statutory requirements for the Contaminant 
Candidate List (CCL) and regulatory determinations?
    C. What contaminants did the EPA consider for regulations?
III. What process did the EPA use to make the regulatory 
determinations?
IV. Summary of the EPA's Findings on the Four Contaminants With 
Final Regulatory Determinations
    A. Dimethoate
    1. Description
    2. Agency Findings
    B. 1,3-Dinitrobenzene
    1. Description
    2. Agency Findings
    C. Terbufos and Terbufos Sulfone
    1. Description
    2. Agency Findings
    D. Public Comments on Four Contaminants With Final Regulatory 
Determinations
V. Summary of Public Comments on Strontium and the Agency's 
Responses
    A. Background on Strontium and the EPA's Preliminary 
Determination
    B. What comments did the EPA receive on strontium?
VI. Next Steps
VII. References

II. Purpose and Background

A. What is the purpose of this action?

    The purpose of this action is to present a summary of the EPA's 
findings related to the final regulatory determinations for four 
contaminants listed on the Third Contaminant Candidate List (CCL 3) 
(USEPA, 2009). The four contaminants include: Dimethoate, 1,3-
dinitrobenzene, terbufos and terbufos sulfone. Today's action briefly 
summarizes the statutory requirements for targeting drinking water 
contaminants for regulatory determination, provides an overview of the 
contaminants the agency considered for regulation and describes the 
approach used to make the final regulatory determinations. In addition, 
today's action summarizes the public comments received on the agency's 
preliminary determinations and the agency's responses to those 
comments, including the status of the EPA's evaluation of strontium.

B. What are the statutory requirements for the Contaminant Candidate 
List (CCL) and regulatory determinations?

    The specific statutory requirements for the CCL and regulatory 
determinations can be found in the Safe Drinking Water Act (SDWA), 
section 1412(b)(1). The 1996 SDWA Amendments require the 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 the agency to determine whether to regulate 
at least five contaminants from the CCL every five years. SDWA requires 
the agency to publish a Maximum Contaminant Level Goal (MCLG) \1\ 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 
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 the agency 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 up to a nine-month extension of this 
promulgation date.
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C. What contaminants did the EPA consider for regulation?

    On October 20, 2014, the EPA published preliminary regulatory 
determinations for five contaminants on the third Contaminant Candidate 
List (CCL 3) that had sufficient information to support a regulatory 
determination (USEPA, 2014c). The five contaminants are 1,3-
dinitrobenzene, dimethoate, terbufos, terbufos sulfone and strontium. 
The agency is making final regulatory determinations not to regulate 
dimethoate, 1,3-dinitrobenzene, terbufos and terbufos sulfone. The 
agency is not making a final regulatory determination for strontium at 
this time. The agency's decision to delay a final determination for 
strontium is based on public comments received and the plan to further 
evaluate scientific information that became available after publication 
of the preliminary regulatory determinations. The agency is currently 
conducting additional scientific analyses to determine if there is a 
need to develop a national drinking water regulation for strontium. For 
more information about the comments the agency received on strontium 
and the analyses that are underway, see section V.A of this notice.
    Information on the five contaminants can be found in the Regulatory 
Determinations 3 Support Document (USEPA, 2014b). More information is 
available at the Water Docket (Docket ID No. EPA-HQ-OW-2012-0155) and 
also on EPA's Regulatory Determination 3 Web site at http://www2.epa.gov/ccl/regulatory-determination-3.

III. What process did the EPA use to make the regulatory 
determinations?

    This section gives a summary of the regulatory determination 
process the agency followed to identify and evaluate contaminants for 
the Third Regulatory Determination. For more detailed information on 
the process and the analyses performed, please refer to the ``Protocol 
for the Regulatory Determination 3'' document (USEPA, 2014a) and the 
Federal Register notice for the Preliminary Regulatory Determinations 
for Contaminants on CCL 3 (USEPA, 2014c).
    The CCL 3 identified 116 contaminants that are currently not 
subject to any proposed or promulgated national drinking water 
regulation, are known or anticipated to occur in public water systems, 
and may require

[[Page 15]]

regulation under SDWA (USEPA, 2009). Since some of the CCL 3 
contaminants do not have adequate health and/or occurrence data to 
evaluate against the three statutory criteria (see section II.B of this 
notice), the agency used a three-phase process to identify which of the 
contaminants are candidates for regulatory determinations. Priority was 
given to identifying contaminants known to occur or with substantial 
likelihood to occur at frequencies and levels of public health concern.
    The three phases of the Third Regulatory Determination process are 
(1) the Data Availability Phase, (2) the Data Evaluation Phase and (3) 
the Regulatory Determination Assessment Phase. The overall process is 
displayed in Exhibit 1.
BILLING CODE 6560-50-P
[GRAPHIC] [TIFF OMITTED] TR04JA16.000

BILLING CODE 6560-50-C
    The purpose of the first phase, the Data Availability Phase, is to 
determine if the agency ``may have'' sufficient data to characterize 
the potential health effects and known or likely occurrence in drinking 
water. Although contaminants must have sufficient data to evaluate the 
statutory criteria in Phase 3, the agency does not want to rule out any 
contaminants too early in the process; therefore, if sufficient health 
and occurrence data are likely available, the contaminants are 
considered in the Data Evaluation Phase, the second phase of the 
regulatory determination process. From the 116 CCL 3 contaminants, the 
agency identified 37 contaminants (35 CCL 3 contaminants and two non-
CCL 3 contaminants \4\) to further evaluate in the second phase.
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    \4\ The non-CCL 3 contaminants, N-Nitroso-di-n-butylamine (NDBA) 
and N-Nitrosomethylethylamine (NMEA), were included because they are 
part of a larger group (nitrosamines) that also includes a number of 
CCL 3 contaminants.
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    During the second phase, the agency further evaluates each 
contaminant on the short list to identify those that have sufficient 
data (or are expected to have sufficient data within the timeframe 
allotted for the second phase) for the EPA to assess the three 
statutory criteria. As part of the second phase, the agency 
specifically focuses its efforts on identifying those contaminants or 
contaminant groups that are occurring or have substantial likelihood to 
occur at levels and frequencies of public health concern, based on the 
best available peer reviewed data. If the agency finds that sufficient 
data are not available or not likely to be available to evaluate the 
three statutory criteria during the first and second phases, then the 
contaminant is not considered a candidate for making a regulatory 
determination.
    If sufficient data are available for a contaminant to characterize 
the potential health effects and known or likely occurrence in drinking 
water, the contaminant is evaluated against the three statutory 
criteria in the Regulatory Determination Assessment Phase, which is the 
third phase of the process. Of the 37 contaminants that were evaluated 
under Phase 2, 12 were designated for further evaluation in Phase 3.

[[Page 16]]

    Of the 12 contaminants that were evaluated in Phase 3, the agency 
did not make preliminary regulatory determinations for seven 
contaminants. The seven contaminants include chlorate and six 
nitrosamines. Chlorate and the six nitrosamines are disinfection 
byproducts, and the agency is further evaluating these contaminants as 
part of the regulatory review of existing Microbial and Disinfection 
Byproduct regulations, as announced in the Preliminary Regulatory 
Determination 3 Federal Register notice published on October 20, 2014 
(USEPA, 2014c).
    After evaluating the five remaining CCL 3 contaminants (dimethoate, 
1,3-dinitrobenzene, terbufos, terbufos sulfone and strontium) against 
the three statutory criteria and considering other relevant information 
(such as level and frequency of occurrence, population exposed and 
information on sensitive populations and lifestages), the agency made 
preliminary regulatory determinations to regulate strontium and to not 
regulate the remaining four contaminants. These preliminary 
determinations, with their supporting analyses and documentation, were 
published in the Federal Register on October 20, 2014, for public 
comment (USEPA, 2014c).
    The EPA received comments from 14 organizations and individuals on 
the October 20, 2014, Federal Register notice. These 14 organizations 
and individuals include four environmental organizations, six industry 
groups, one state association and three anonymous individuals. The 
agency prepared a Response to Comments document for this action that is 
available in the Public Docket at www.regulations.gov under Docket ID 
No. EPA-HQ-OW-2012-0155. Comments on specific contaminants, and the 
EPA's responses, are briefly summarized in the sections below.

IV. Summary of the EPA's Findings on the Four Contaminants With Final 
Regulatory Determinations

    After considering the public comments, the EPA is making final 
regulatory determinations not to regulate dimethoate, 1,3-
dinitrobenzene, terbufos and terbufos sulfone.
    This notice provides a brief description of the agency findings on 
these contaminants. Details on the background, health and occurrence 
information and analyses used to evaluate and make final determinations 
for these contaminants can be found in the Regulatory Determinations 3 
Support Document (USEPA, 2015b) and the Federal Register notice for the 
Preliminary Regulatory Determination 3 (USEPA, 2014c).
    For each contaminant, the agency evaluated the available human and 
toxicological data, derived a health reference level (HRL),\5\ 
evaluated the potential and/or likely occurrence and examined the 
likely exposed population for the contaminant in public water systems. 
The agency also considered whether information was available on 
sensitive populations. The agency used the findings from these 
evaluations to determine whether the three SDWA statutory criteria are 
satisfied. Table 1 gives a summary of the health and occurrence 
information for the four contaminants with final determinations under 
RD 3.
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    \5\ HRLs are risk derived concentrations against which to 
evaluate the occurrence data to determine if contaminants may occur 
at levels of public health concern. They are not the level of a 
contaminant in drinking water that must not be exceeded to protect 
any particular population (i.e., an HRL is not an MCL).

                             Table 1--Summary of the Health and Occurrence Information and the Final Determinations for Four of the Contaminants Considered for RD 3
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                                  Health                                             Occurrence findings from primary data sources
                                reference ----------------------------------------------------------------------------------------------------------------------------------
       RD 3 contaminants          level                                                 Population served by PWSs                                Population served by PWSs          Final
                                  (HRL)        Primary        PWSs with at least 1     with at least 1  detection      PWSs with at least 1     with at least 1  detection      determination
                                ([mu]g/L)     database       detection >=\1/2\ HRL             >=\1/2\ HRL               detection >=HRL                   >=HRL
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Dimethoate....................       15.4  UCMR 2........  0% (0 of 4140)...........  0% (0 of 229M)..............  0% (0 of 4140)...........  0% (0 of 229M)..............  Do not regulate.
1,3-Dinitrobenzene............        0.7  UCMR 2........  0% (0 of 4139)...........  0% (0 of 229M)..............  0% (0 of 4139)...........  0% (0 of 229M)..............  Do not regulate.
Terbufos......................       0.35  UCMR 1........  0% (0 of 295)............  0% (0 of 41M)...............  0% (0 of 295)............  0% (0 of 41M)...............  Do not regulate
Terbufos sulfone..............       0.35  UCMR 2........  0.02% (1 of 4140)........  0.01% (44.6K of 229M).......  0.02% (1 of 4140)........  0.01% (44.6K of 229M).......  Do not regulate.
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A. Dimethoate

1. Description
    Dimethoate is an organophosphate pesticide, commonly used as an 
insecticide on field crops (e.g., wheat, alfalfa, corn and cotton), 
orchard crops, vegetable crops and in forestry. Synonyms for dimethoate 
include dimethogen, dimeton, dimevur and cygon (HSDB, 2010; USEPA, 
2007). Dimethoate is considered highly mobile and relatively non-
persistent in the environment (USEPA, 2007).
2. Agency Findings
    The agency is making a determination not to regulate dimethoate 
with an NPDWR. It does not occur at levels and frequencies of public 
health concern. As a result, the agency finds that an NPDWR does not 
present a meaningful opportunity for health risk reduction.
    The primary data for dimethoate are the 2008-2010 nationally 
representative drinking water monitoring data, generated through the 
EPA's Second Unregulated Contaminant Monitoring Regulation (UCMR 2). 
Dimethoate was not detected in any of the 32,150 UCMR 2 samples 
collected by 4,140 PWSs (serving ~230 million people) at levels greater 
than the \1/2\ HRL (7.7 [mu]g/L), the HRL (15.4 [mu]g/L), or the 
minimum reporting level (MRL) (0.7 [mu]g/L) (USEPA, 2015c). Based on 
the results of the UCMR 2 samples, the estimated population exposed to 
dimethoate at levels of public health concern is 0%.
    Other supplementary sources of finished water data from the State 
of California, the U.S. Department of Agriculture (USDA) and the U.S. 
Geologic Survey (USGS) indicate that the occurrence of dimethoate in 
PWSs is likely to be low to non-existent. Dimethoate occurrence data 
for ambient water from the USGS and the Storage and Retrieval (STORET) 
Data System are consistent with those for finished water. These data 
sources are discussed in the October 2014 Federal Register notice of 
the Preliminary Regulatory Determination 3 (USEPA, 2014c).

[[Page 17]]

B. 1,3-Dinitrobenzene

1. Description
    1,3-Dinitrobenzene is a nitro aromatic compound that is used as an 
industrial chemical and formed as a by-product in the manufacture of 
munitions, as well as in the production of other substances (HSDB, 
2009). There are no known natural sources of 1,3-dinitrobenzene. 1,3-
Dinitrobenzene appears to be moderately persistent in environmental 
media and moderately mobile in soil and water, although in soils with 
high clay content it will be less mobile (USEPA, 2015b).
2. Agency Findings
    The agency is making a determination not to regulate 1,3-
dinitrobenzene with an NPDWR. It does not occur at levels and 
frequencies of public health concern. As a result, the agency finds 
that an NPDWR does not present a meaningful opportunity for health risk 
reduction.
    The primary data for 1,3-dinitrobenzene are the 2008-2010 
nationally representative drinking water monitoring data generated 
through the EPA's UCMR 2 (USEPA, 2015c). UCMR 2 is the only dataset 
with finished water data for this contaminant. UCMR 2 collected 32,152 
samples from 4,139 PWSs for 1,3-dinitrobenzene and it was not detected 
above the MRL (0.8 [mu]g/L), which is only slightly higher than the HRL 
(0.7 [mu]g/L). Based on the results of the UCMR 2 samples, the 
estimated population exposed to 1,3-dinitrobenzene at or above the MRL 
is 0%.
    Findings from the available ambient water data for 1,3-
dinitrobenzene are consistent with the results in finished water. 
Ambient water data in STORET included no measured results above 0.33 
[mu]g/L in 143 samples from 70 sites (USEPA, 2012). It should be noted 
that some occurrence above the HRL may have gone undetected since 
reporting levels are not documented. These data sources are discussed 
in the October 2014 Federal Register notice of the Preliminary 
Regulatory Determination 3 (USEPA, 2014c).

C. Terbufos and Terbufos Sulfone

1. Description
    Terbufos is a phosphorodithioate pesticide (i.e., an 
organophosphate) used as an insecticide-nematicide to control a variety 
of insect pests, primarily used on corn and sugar beets (USEPA, 2006). 
Terbufos sulfone is a degradate of terbufos. Total toxic residues of 
terbufos and degradates are highly mobile and persistent in the 
environment, with terbufos sulfone being more mobile and substantially 
more persistent than terbufos (USEPA, 2006).
2. Agency Findings
    The agency is making determinations not to regulate terbufos and 
terbufos sulfone with NPDWRs. They do not occur at levels and 
frequencies of public health concern. As a result, the agency finds 
that an NPDWR does not present a meaningful opportunity for health risk 
reduction.
    The primary data for terbufos are from the First Unregulated 
Contaminant Monitoring Regulation (UCMR 1) screening survey (2001-2003) 
(USEPA, 2008). The UCMR 1 screening survey collected 2,301 finished 
water samples from 295 PWSs for terbufos and it was not detected at 
levels at or above the MRL (0.5 [mu]g/L), which is slightly higher than 
the HRL (0.35 [mu]g/L) (USEPA, 2008). Based on the results of the UCMR 
1 screening survey, the estimated population exposed to terbufos at or 
above the MRL is 0%.
    The primary data for terbufos sulfone are nationally representative 
finished water monitoring data generated through the EPA's UCMR 2 
(2008-2010) (USEPA, 2015c). UCMR 2 collected 32,149 finished water 
samples from 4,140 PWSs (serving ~230 million people) for terbufos 
sulfone and it was detected in only one sample, at a concentration of 
0.42 [mu]g/L. The MRL is 0.4 [mu]g/L, which is slightly higher than the 
HRL (0.35 [mu]g/L) (USEPA, 2015c). Based on the results of the UCMR 2 
samples, the estimated population exposed to terbufos sulfone at a 
level of public health concern (based on the HRL for terbufos) is 
44,600 (0.02% of the population served by PWSs).
    Finished water data for terbufos and terbufos sulfone from 
California, Iowa, USDA and USGS are consistent with the UCMR 1 and UCMR 
2 data. Terbufos and (very limited) terbufos sulfone occurrence data 
for ambient water from the EPA, STORET and several USGS programs or 
studies are also consistent with those for finished water. These data 
sources are discussed in the October 2014 Federal Register notice of 
the Preliminary Regulatory Determination 3 (USEPA, 2014c).

D. Public Comments on Four Contaminants With Final Regulatory 
Determinations

    The agency received comments in support of the agency's preliminary 
determinations not to regulate dimethoate, 1,3-dinitrobenzene, terbufos 
and terbufos sulfone. The agency did not receive any comments to the 
contrary.
    Agency Response: EPA agrees with the comments and, as previously 
explained, is making final determinations not to regulate dimethoate, 
1,3-dinitrobenzene, terbufos and terbufos sulfone.

V. Summary of Public Comments on Strontium and the Agency's Responses

A. Background on Strontium and the EPA's Preliminary Determination

    Strontium is a naturally occurring element (atomic number 38) and a 
member of the alkaline earth metals (ANL, 2007). There are several 
radioactive strontium isotopes formed by nuclear fission of uranium or 
plutonium. Since drinking water contamination by radioactive isotopes, 
including beta particle emitters, is covered under the existing 
Radionuclides Rule, this section describes the stable \88\Sr isotope.
    In October 2014, the agency made a preliminary determination to 
regulate strontium with an NPDWR after evaluating the available health, 
occurrence and other related information against the three SDWA 
statutory criteria. Specifically, EPA made a preliminary determination 
that (a) strontium may have an adverse effect on the health of persons, 
(b) it is known to occur or there is substantial likelihood that 
strontium will occur in public water systems with a frequency and at 
levels of public health concern and (c) regulation of strontium with an 
NPDWR presents a meaningful opportunity to reduce health risks for 
persons served by PWSs. EPA describes the underlying science in support 
of these criteria in the Federal Register notice of the Preliminary 
Regulatory Determination 3 (USEPA, 2014c).
    In the Federal Register notice of the Preliminary Regulatory 
Determination 3, EPA calculated a non-cancer HRL of 1500 [micro]g/L for 
strontium using the reference dose of 0.3 mg/kg/day, a default Relative 
Source Contribution (RSC) of 20% and age-specific exposure factors 
(i.e., drinking water intake expressed as liters per kg of body weight) 
for the sensitive population of birth through 18 years to reflect the 
most active period of bone growth and development. The RSC is the level 
of exposure believed to result from drinking water when compared to 
other sources (e.g., food, ambient air). In the Preliminary Regulatory 
Determination 3 EPA used the default 20% RSC to calculate the HRL. For 
more detailed information see the October 20, 2014, Federal Register 
notice of the

[[Page 18]]

Preliminary Regulatory Determination 3 (USEPA, 2014c).
    After consideration of public comments on the preliminary 
regulatory determination for strontium (see Section V.B.), the agency 
is delaying the final determination for strontium in order to consider 
additional scientific data and decide whether there is a meaningful 
opportunity for health risk reduction by regulating strontium in 
drinking water.

B. What comments did the EPA receive on strontium?

    Some commenters supported the preliminary determination to regulate 
strontium. These commenters supported a regulation due to the adverse 
effect on bone growth and/or the potential for elevated levels of 
strontium in the environment as a result of spills and disposal of 
waste products related to gas production.
    Many comments called upon the agency to delay the final 
determination, collect more data and perform additional analyses before 
making a final determination for strontium. Specifically, the comments 
were focused on the following areas: The relationship between 
occurrence and health risk, the RSC of strontium, the costs and 
benefits of a potential strontium regulation and the feasibility of 
treating strontium.
    Three commenters questioned whether enough water systems show 
strontium at levels and frequency of concern that a meaningful 
reduction in health risk can be achieved through a national regulation. 
Two of these commenters suggested conducting an epidemiology study that 
evaluates whether adverse human health effects are occurring and at 
what drinking water concentrations (and frequency of occurrence) to 
determine whether there is a meaningful opportunity for health risk 
reduction of a regulation.
    Two commenters indicated the agency should quantify the RSC or 
provide stronger justification for using an RSC of 20%. One commenter 
stated the RSC has a significant impact on the reference dose. One 
commenter stated that defaults of 20% and 80% have utility in 
relatively simple circumstances where it is accepted that the drinking 
water component is either very small or large. The commenter indicated 
that it is essential to analyze and quantify the RSC when it is 
intermediate and there are data to perform a meaningful estimate. The 
commenter asserted that it is essential because the impact on the MCLG 
and ultimately the MCL and compliance costs can become significant.
    Several commenters indicated concerns with the costs and benefits 
of a potential strontium regulation. One commenter urged the agency to 
update the current affordability standard under SDWA before 
promulgating any new NPDWRs in order to allow rural and small 
communities to utilize the most economical and safe treatment options. 
One commenter stated that the agency failed to estimate the social 
benefits and social costs in its analysis for the strontium 
determination, specifically the additional energy usage and its 
externalities. Several commenters compared the cost of a potential 
strontium regulation to that of the arsenic regulation, based on the 
percentage and type of systems with strontium occurrence at levels of 
concern.
    Several commenters supported the agency's commitment to conducting 
more extensive treatment research prior to promulgating a regulation 
for strontium. Two commenters indicated that the treatment technology 
to remove strontium may remove beneficial alkaline earth metals, such 
as calcium, that partially counter the uptake of strontium.
    Agency Response: The agency is delaying the final determination for 
strontium in order to consider additional scientific data and decide 
whether there is a meaningful opportunity for health risk reduction by 
regulating strontium in drinking water.
    Strontium is known to occur in food, ambient air and soil. While 
data on levels in those media and estimates of intake from those 
sources were limited when EPA made the preliminary determination to 
regulate strontium, the EPA is evaluating recent additions to the 
exposure database to determine if the agency can develop a data-derived 
RSC rather than using a default 20% RSC in the calculation of the HRL. 
In the absence of this type of relevant exposure information, the 
agency supports the use of the default RSC and may ultimately use the 
default 20% RSC in the final regulatory determination for strontium and 
for other compounds in the future. The agency selects the default RSCs 
for regulatory determinations based on the Methodology for Deriving 
Ambient Water Quality Criteria for the Protection of Human Health 
(USEPA, 2000).
    If the agency makes a final determination to regulate strontium, 
the EPA will conduct tests on treatment technologies for strontium 
prior to developing a regulation. The agency understands that strontium 
may co-occur with beneficial calcium in some drinking water systems and 
treatment technologies that remove strontium may also remove calcium. 
The agency is evaluating the effectiveness of treatment technologies 
under different water conditions, including calcium concentrations. The 
agency will continue to work with stakeholders in evaluating treatment 
technologies for strontium.
    At this time, the agency does not plan to initiate any longer term 
health effect studies, including human epidemiological studies on the 
relationship of skeletal effects and strontium exposure levels through 
consumption of drinking water and foods. The agency will continue to 
evaluate new health studies related to strontium exposure, including 
any epidemiology studies. It should be noted that while the agency is 
not precluded from conducting epidemiological studies, the agency is 
not required to do so to support the decision to regulate a 
contaminant.
    An evaluation of the costs and benefits of a potential strontium 
regulation is outside the scope of the regulatory determination 
process. If the agency decides to regulate strontium, as part of the 
regulation development process, the agency will conduct a health risk 
reduction and cost analysis, including an evaluation of the costs and 
benefits of regulating strontium.

VI. Next Steps

    Prior to making a final regulatory determination for strontium, the 
agency will consider additional data gathered and analyses completed 
after publication of the preliminary determination (for further 
information, see discussion in section V.B. of this notice). The agency 
published the Draft Contaminant Candidate List 4 (CCL 4) on February 4, 
2015 (USEPA, 2015a) and will issue a Final CCL 4 after consideration of 
public comments received. The agency will evaluate and consider 
contaminants on the Final CCL 4 for the Fourth Regulatory 
Determination.

VII. References

Argonne National Laboratory (ANL). 2007. Radiological and Chemical 
Fact Sheets to Support Health Risk Analyses for Contaminated Areas. 
Environmental Science Division. Available on the Internet at: http://www.gfxtechnology.com/ArgonneRadFacts.pdf.
HSDB. 2010. Available on the Internet at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?HSDB. Accessed September 2010.
USEPA. 2000. Methodology for Deriving Ambient Water Quality Criteria 
for the

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Protection of Human Health (2000). EPA 822-B-00-004.
USEPA. 2006. Reregistration Eligibility Decision for Terbufos. 
Office of Pesticide Programs. Available on the Internet at: http://archive.epa.gov/pesticides/reregistration/web/pdf/terbufos_red.pdf. 
Accessed Oct 2015.
USEPA. 2007. Revised Interim Reregistration Decision for Dimethoate. 
Available on the Internet at: http://archive.epa.gov/pesticides/reregistration/web/pdf/dimethoate_ired_revised.pdf. Accessed October 
2015.
USEPA. 2008. 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 815-R-08-012. June 2008.
USEPA. 2009. Drinking Water Contaminant Candidate List 3--Final. 
Federal Register. Vol. 74, No. 194, p. 51850. October 8, 2009.
USEPA. 2012. Storage and Retrieval (STORET) Data Warehouse. 
Available on the Internet at: http://www.epa.gov/storet/index.html. 
Data Warehouse. Accessed March 2012.
USEPA. 2014a. Protocol for the Regulatory Determinations 3. 
Including Appendices A-F. EPA 815-R14-005. April 2014.
USEPA. 2014b. Regulatory Determinations 3 Support Document. EPA 815-
R14-003. April 2014.
USEPA. 2014c. Announcement of the Preliminary Regulatory 
Determinations for Contaminants on the Third Drinking Water 
Contaminant Candidate List; Proposed Rule. Federal Register. Vol. 
79, No. 202, p. 62716. October 20, 2014.
USEPA. 2015a. Drinking Water Contaminant Candidate List 4--Draft. 
Federal Register. Vol. 80, No. 23, p. 6076. February 4, 2015.
USEPA. 2015b. Regulatory Determinations 3 Support Document (Final). 
EPA 815-R15-014. December 2015.
USEPA. 2015c. Occurrence Data from the Second Unregulated 
Contaminant Monitoring Regulation (UCMR 2). EPA 815-R15-013. 
December 2015.

    Dated: December 22, 2015.
Gina McCarthy,
Administrator.
[FR Doc. 2015-32760 Filed 12-31-15; 8:45 am]
 BILLING CODE 6560-50-P