Regulating Contaminants Under the Safe Drinking Water Act (SDWA)

Changes from January 8, 2021 to March 3, 2021

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Regulating Contaminants
~~January 8~~March 3, 2021 , 2021
Under the Safe Drinking Water Act (SDWA)
Elena H. Humphreys
Concerns about drinking water quality have resulted in congressional attention to the Safe Concerns about drinking water quality have resulted in congressional attention to the Safe
Analyst in Environmental Analyst in Environmental
Drinking Water Act (SDWA), particularly on the process for evaluating contaminants for Drinking Water Act (SDWA), particularly on the process for evaluating contaminants for
Policy Policy
potential regulation. Detections of unregulated contaminants in public water supplies in potential regulation. Detections of unregulated contaminants in public water supplies in

numerous states have raised concerns about the quality of drinking water and increased numerous states have raised concerns about the quality of drinking water and increased
congressional interest congressional interest toin the U.S. Environmental Protection Agency’s (EPA’s) response to such the U.S. Environmental Protection Agency’s (EPA’s) response to such

detections. Additionally, concerns about the detection of regulated contaminants, such as lead, detections. Additionally, concerns about the detection of regulated contaminants, such as lead,
have raised concerns about the effectiveness of certain existing regulations. have raised concerns about the effectiveness of certain existing regulations.
SDWA is the key federal law that authorizes EPA to promulgate regulations to control contaminants in public water supplies. SDWA is the key federal law that authorizes EPA to promulgate regulations to control contaminants in public water supplies.
Since enactment of the act in 1974, EPA has issued drinking water regulations for over 90 contaminants. Congress has twice Since enactment of the act in 1974, EPA has issued drinking water regulations for over 90 contaminants. Congress has twice
revised the act’s process for evaluating contaminants and developing drinking water regulations (in 1986 and 1996). In 1986, revised the act’s process for evaluating contaminants and developing drinking water regulations (in 1986 and 1996). In 1986,
Congress directed EPA to develop regulations for 83 contaminants within 3 years, and adopt regulations, every 3 years, for at Congress directed EPA to develop regulations for 83 contaminants within 3 years, and adopt regulations, every 3 years, for at
least 25 new contaminants. When this regulatory schedule proved unworkable, Congress amended SDWA in 1996 to least 25 new contaminants. When this regulatory schedule proved unworkable, Congress amended SDWA in 1996 to
establish a risk-based process that prioritizes contaminants for regulation based on the contaminant’s health effects and establish a risk-based process that prioritizes contaminants for regulation based on the contaminant’s health effects and
occurrence. occurrence.
Under SDWA, EPA follows a multistep process to evaluate and prioritize contaminants for regulation. This process includes Under SDWA, EPA follows a multistep process to evaluate and prioritize contaminants for regulation. This process includes
identifying contaminants of potential concern, assessing health risks, collecting national occurrence data (and developing identifying contaminants of potential concern, assessing health risks, collecting national occurrence data (and developing
reliable and field tested analytical methods necessary to do so), and making determinations as to whether a contaminant reliable and field tested analytical methods necessary to do so), and making determinations as to whether a contaminant
warrants regulation. Since 1996, EPA has screened over 7,500 contaminants for potential regulation, revised existing warrants regulation. Since 1996, EPA has screened over 7,500 contaminants for potential regulation, revised existing
regulations, and established new regulations and standards for several contaminants. regulations, and established new regulations and standards for several contaminants.
When EPA determines that a contaminant warrants regulation, SDWA directs EPA to propose a “national primary drinking When EPA determines that a contaminant warrants regulation, SDWA directs EPA to propose a “national primary drinking
water regulation” and request public comment within 24 months. Within 18 months of the proposal, EPA is required to water regulation” and request public comment within 24 months. Within 18 months of the proposal, EPA is required to
promulgate a final rule. As a part of the proposal, EPA is required to establish a nonenforceable maximum contaminant level promulgate a final rule. As a part of the proposal, EPA is required to establish a nonenforceable maximum contaminant level
goal (MCLG) at a level at which no known or anticipated adverse health effects occur and allowing for an adequate margin of goal (MCLG) at a level at which no known or anticipated adverse health effects occur and allowing for an adequate margin of
safety. Drinking water regulations generally specify a maximum contaminant level (MCL)—an enforceable limit for a safety. Drinking water regulations generally specify a maximum contaminant level (MCL)—an enforceable limit for a
contaminant in public water supplies. SDWA requires EPA to set the MCL as close to the MCLG as “feasible,” taking contaminant in public water supplies. SDWA requires EPA to set the MCL as close to the MCLG as “feasible,” taking
treatment costs into consideration. Concurrent with proposing a regulation, SDWA requires EPA to publish a “health risk treatment costs into consideration. Concurrent with proposing a regulation, SDWA requires EPA to publish a “health risk
reduction and cost analysis” for each contaminant covered by the proposed regulation and make a determination whether or reduction and cost analysis” for each contaminant covered by the proposed regulation and make a determination whether or
not the benefits of regulation outweigh the compliance costs. not the benefits of regulation outweigh the compliance costs.
Regulations generally take effect three years after promulgation. SDWA requires EPA to review—and, if necessary, revise— Regulations generally take effect three years after promulgation. SDWA requires EPA to review—and, if necessary, revise—
each existing national primary drinking water regulation every six years. SDWA also requires that any revisions to drinking each existing national primary drinking water regulation every six years. SDWA also requires that any revisions to drinking
water regulations maintain or provide greater health protection. water regulations maintain or provide greater health protection.
Under the current statutory framework, evaluating and developing regulations for contaminants requires data, including peer- Under the current statutory framework, evaluating and developing regulations for contaminants requires data, including peer-
reviewed scientific studies on potential health effects and nationally representative occurrence data. For some contaminants, reviewed scientific studies on potential health effects and nationally representative occurrence data. For some contaminants,
the availability or development of (1) such data, (2) analytical methods to detect contaminants in drinking water, and (3) the availability or development of (1) such data, (2) analytical methods to detect contaminants in drinking water, and (3)
treatment technologies pose technical and resource issues. treatment technologies pose technical and resource issues.
Congressional attention has centered on EPA’s implementation of SDWA regulatory development provisions, as well as the Congressional attention has centered on EPA’s implementation of SDWA regulatory development provisions, as well as the
functionality of the current process established in SDWA. In the 116th Congress, legislation was introduced to prompt EPA to functionality of the current process established in SDWA. In the 116th Congress, legislation was introduced to prompt EPA to
regulate certain contaminants or contaminant groups within specific timeframes or to amend SDWA contaminant regulation regulate certain contaminants or contaminant groups within specific timeframes or to amend SDWA contaminant regulation
provisions. Representatives of water systems have supported EPA’s commitment to following the statutory process for provisions. Representatives of water systems have supported EPA’s commitment to following the statutory process for
regulating contaminants in drinking water that prioritizes reducing health risks. In some cases, state drinking water regulating contaminants in drinking water that prioritizes reducing health risks. In some cases, state drinking water
administrators have urged EPA to issue regulations for specific contaminants to establish uniformity among the states. The administrators have urged EPA to issue regulations for specific contaminants to establish uniformity among the states. The
House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change, held an oversight hearing House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change, held an oversight hearing
in July 2020 regarding EPA’s implementation of SDWA contaminant regulation provisions. In his opening remarks, in July 2020 regarding EPA’s implementation of SDWA contaminant regulation provisions. In his opening remarks,
Chairman Frank Pallone stated that the hearing would contribute to the Chairman Frank Pallone stated that the hearing would contribute to the ~~Subcommittee~~subcommittee’s efforts to revise SDWA regulatory ’s efforts to revise SDWA regulatory
development provisions. Congressional interest in drinking water contaminant regulation under SDWA is likely to continue. development provisions. Congressional interest in drinking water contaminant regulation under SDWA is likely to continue.
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Contacts
Author Information ........................................................................................................................ 2728

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Regulating Contaminants Under the Safe Drinking Water Act (SDWA)

Introduction
Detections of Detections of ~~unregulated~~ contaminants (e.g., per- and polyfluoroalkyl substances [PFAS] and contaminants (e.g., per- and polyfluoroalkyl substances [PFAS] and
1,4-dioxane) in public water supplies have raised questions about the quality of drinking water 1,4-dioxane) in public water supplies have raised questions about the quality of drinking water
and increased congressional interest in the Environmental Protection Agency’s (EPA’s) efforts to and increased congressional interest in the Environmental Protection Agency’s (EPA’s) efforts to
regulate contaminants under the Safe Drinking Water Act (SDWA). regulate contaminants under the Safe Drinking Water Act (SDWA).
Congress enacted SDWA in 1974 to address the quality of public drinking water supplies and Congress enacted SDWA in 1974 to address the quality of public drinking water supplies and
protect public health.1 A key part of the act is the authority for EPA to regulate contaminants in protect public health.1 A key part of the act is the authority for EPA to regulate contaminants in
public water supplies.2 Since enactment, Congress has revised the act’s process for contaminant public water supplies.2 Since enactment, Congress has revised the act’s process for contaminant
regulation twice, in 1986 and in 1996. The 1996 amendments established specific contaminant regulation twice, in 1986 and in 1996. The 1996 amendments established specific contaminant
identification, assessment, and regulatory determination processes for the purpose of focusing identification, assessment, and regulatory determination processes for the purpose of focusing
regulatory resources and requirements toward contaminants of greatest public health concern. regulatory resources and requirements toward contaminants of greatest public health concern.
Since 1996, EPA has updated several drinking water regulations, promulgated regulations for Since 1996, EPA has updated several drinking water regulations, promulgated regulations for
additional contaminants under other SDWA authorities, and evaluated more than 7,500 additional contaminants under other SDWA authorities, and evaluated more than 7,500
contaminants for potential regulation. However, the agency has not promulgated new regulations contaminants for potential regulation. However, the agency has not promulgated new regulations
using the statutory regulatory determination process. using the statutory regulatory determination process.
In response to the detections of unregulated contaminants in drinking water and concerns about In response to the detections of unregulated contaminants in drinking water and concerns about
EPA’s regulatory pace, legislation has been introduced in the 116th Congress and recent EPA’s regulatory pace, legislation has been introduced in the 116th Congress and recent
Congresses to address contaminant regulation under SDWA. Proposals include broadly revising Congresses to address contaminant regulation under SDWA. Proposals include broadly revising
the act’s regulatory provisions and/or requiring EPA to promulgate regulations for specific the act’s regulatory provisions and/or requiring EPA to promulgate regulations for specific
contaminants, among others. contaminants, among others.
Congressional interest in SDWA regulatory development provisions has centered on Congressional interest in SDWA regulatory development provisions has centered on
 EPA’s implementation of the statutory criteria for making a determination to  EPA’s implementation of the statutory criteria for making a determination to
regulate a contaminant; regulate a contaminant;
 how costs and affordability are considered when setting drinking water standards;  how costs and affordability are considered when setting drinking water standards;
and and
 EPA’s regulatory pace under the current framework.  EPA’s regulatory pace under the current framework.
SDWA requires EPA to use the best available, peer-reviewed science to characterize a SDWA requires EPA to use the best available, peer-reviewed science to characterize a
contaminant’s health effects and occurrence in water supplies to determine whether a contaminant contaminant’s health effects and occurrence in water supplies to determine whether a contaminant
warrants national regulation. EPA has long recognized that limited data on unregulated warrants national regulation. EPA has long recognized that limited data on unregulated
contaminants of concern has hindered the agency’s ability to make regulatory determinations.3 In contaminants of concern has hindered the agency’s ability to make regulatory determinations.3 In
a 2011 report, the U.S. Government Accountability Office (GAO) made a similar finding.4 EPA’s a 2011 report, the U.S. Government Accountability Office (GAO) made a similar finding.4 EPA’s
efforts to develop peer-reviewed science necessary to support regulatory determinations for efforts to develop peer-reviewed science necessary to support regulatory determinations for
unregulated contaminants—or to update existing contaminant regulations—have been affected by unregulated contaminants—or to update existing contaminant regulations—have been affected by
data availability and available agency resources, among other factors. data availability and available agency resources, among other factors.

1 Safe Drinking Water Act of 1974 (P.L. 93-523), enacted December 16, 1974. 1 Safe Drinking Water Act of 1974 (P.L. 93-523), enacted December 16, 1974.
2 SDWA §1401(4)(A) defines public water system generally to mean “a system for the provision to the public of water 2 SDWA §1401(4)(A) defines public water system generally to mean “a system for the provision to the public of water
for human consumption through pipes or other constructed conveyances, if such system has at least fifteen service for human consumption through pipes or other constructed conveyances, if such system has at least fifteen service
connections or regularly serves at least twenty-five individuals ...” (42 U.S.C. §300f(4)(A)). connections or regularly serves at least twenty-five individuals ...” (42 U.S.C. §300f(4)(A)).
3 See, for example, Table 2 “Information Gaps for the CCL 2 Chemical Contaminants,” EPA, “Drinking Water: 3 See, for example, Table 2 “Information Gaps for the CCL 2 Chemical Contaminants,” EPA, “Drinking Water:
Regulatory Determinations Regarding Contaminants on the Second Drinking Water Contaminant Candidate List,” 73Regulatory Determinations Regarding Contaminants on the Second Drinking Water Contaminant Candidate List,” 73
Federal Register 44260, July 30, 2008. 44260, July 30, 2008.
4 U.S. Government Accountability Office (GAO), 4 U.S. Government Accountability Office (GAO), EPA Should Improve Implementation of Requirements on Whether to
Regulate Additional Contaminants, 11-254, May 27, 2011, at https://www.gao.gov/products/GAO-11-254. , 11-254, May 27, 2011, at https://www.gao.gov/products/GAO-11-254.
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This report discusses the SDWA provisions relevant to how EPA evaluates contaminants to This report discusses the SDWA provisions relevant to how EPA evaluates contaminants to
determine whether a contaminant warrants a “national primary drinking water regulation” determine whether a contaminant warrants a “national primary drinking water regulation”
(NPDWR), provides an overview of the regulatory development process, and analyzes certain (NPDWR), provides an overview of the regulatory development process, and analyzes certain
issues that may affect implementation of this section. In addition to the agency’s work related to issues that may affect implementation of this section. In addition to the agency’s work related to
contaminant regulation, EPA has issued other SDWA regulations applicable to public water contaminant regulation, EPA has issued other SDWA regulations applicable to public water
systems. These include regulations to reduce lead content in drinking water pipes and plumbing systems. These include regulations to reduce lead content in drinking water pipes and plumbing
and to increase consumer information and public notification about drinking water quality and and to increase consumer information and public notification about drinking water quality and
compliance.5 The report is primarily limited to EPA’s implementation of the process outlined in compliance.5 The report is primarily limited to EPA’s implementation of the process outlined in
SDWA Section 1412 “National Drinking Water Regulations” for evaluating contaminants for SDWA Section 1412 “National Drinking Water Regulations” for evaluating contaminants for
regulation.6 regulation.6
History of SDWA Section 1412 “National Drinking
Water Regulations”
The Safe Drinking Water Act of 1974 established the federal role in regulating contaminants in The Safe Drinking Water Act of 1974 established the federal role in regulating contaminants in
public water supplies. The 1974 act directed EPA to promulgate “national interim primary public water supplies. The 1974 act directed EPA to promulgate “national interim primary
drinking water regulations,” with enforceable standards (i.e., maximum contaminant levels), for a drinking water regulations,” with enforceable standards (i.e., maximum contaminant levels), for a
list of contaminants based on the 1962 U.S. Public Health Service interstate carrier drinking water list of contaminants based on the 1962 U.S. Public Health Service interstate carrier drinking water
quality standards.7 It also directed the National Academy of Sciences to conduct a study and quality standards.7 It also directed the National Academy of Sciences to conduct a study and
recommend maximum contaminant levels that protect human health. EPA was required to set the recommend maximum contaminant levels that protect human health. EPA was required to set the
interim regulations’ revised levels as close as “feasible” to the National Academies of Sciences’ interim regulations’ revised levels as close as “feasible” to the National Academies of Sciences’
recommended levels—using the best available technology, treatment techniques, and other recommended levels—using the best available technology, treatment techniques, and other
means—taking costs into consideration.8 The act provided EPA with discretionary authority to means—taking costs into consideration.8 The act provided EPA with discretionary authority to
issue drinking water regulations for additional contaminants.9 By 1985, EPA had issued interim issue drinking water regulations for additional contaminants.9 By 1985, EPA had issued interim
regulations with standards for the initial list of contaminants, yet EPA had revised existing regulations with standards for the initial list of contaminants, yet EPA had revised existing
regulations or established regulations for few other contaminants. regulations or established regulations for few other contaminants.
In the 99th Congress, concerns about the pace at which EPA issued drinking water regulations In the 99th Congress, concerns about the pace at which EPA issued drinking water regulations
prompted legislation intended to expedite regulation of drinking water contaminants.10 In the Safe prompted legislation intended to expedite regulation of drinking water contaminants.10 In the Safe

5 Other regulations include the “Use of Lead Free Pipes, Fittings, Fixtures, Solder, and Flux for Drinking Water” rule 5 Other regulations include the “Use of Lead Free Pipes, Fittings, Fixtures, Solder, and Flux for Drinking Water” rule
(85 (85 Federal Register 54235-54259) and “right-to-know” rules (e.g., public notification rule [65 54235-54259) and “right-to-know” rules (e.g., public notification rule [65 Federal Register
25982-26049]25982-26049] and consumer confidence report rule [63 and consumer confidence report rule [63 Federal Register 44512- 44536]). 44512- 44536]).
6 42 U.S.C. §300g-1. 6 42 U.S.C. §300g-1.
7 U.S. Congress, House Committee on Interstate and Foreign Commerce, 7 U.S. Congress, House Committee on Interstate and Foreign Commerce, Safe Drinking Water Act, 93rd Cong., 2nd , 93rd Cong., 2nd
sess., July 10, 1974, H.Rept. 93-1185, pp. 1-11. (SDWA, as amended, comprises Title XIV of the Public Health sess., July 10, 1974, H.Rept. 93-1185, pp. 1-11. (SDWA, as amended, comprises Title XIV of the Public Health
Service Act, 42 U.S.C. §§300f-300j-26.) With congressional approval, the Nixon Administration established the U.S. Service Act, 42 U.S.C. §§300f-300j-26.) With congressional approval, the Nixon Administration established the U.S.
Environmental Protection Agency (EPA) in 1970 under an executive branch reorganization plan, which consolidated Environmental Protection Agency (EPA) in 1970 under an executive branch reorganization plan, which consolidated
numerous federal pollution control responsibilities that had been divided among several federal agencies. In 1970, numerous federal pollution control responsibilities that had been divided among several federal agencies. In 1970,
Congress transferred responsibility for implementation and enforcement of the interstate carrier drinking water Congress transferred responsibility for implementation and enforcement of the interstate carrier drinking water
standards from the Public Health Service to EPA. See Appendix B for the 1962 standards, EPA, standards from the Public Health Service to EPA. See Appendix B for the 1962 standards, EPA, 25 Years of the Safe
Drinking Water Act: History and Trends, EPA 816-R-99-0007, Washington, DC, December 1999, p. 6. , EPA 816-R-99-0007, Washington, DC, December 1999, p. 6.
8 According to the House report accompanying the 1974 act, “the level (i.e., drinking water standard) should be 8 According to the House report accompanying the 1974 act, “the level (i.e., drinking water standard) should be
achievable by large metropolitan water systems treating relatively clean source water.” U.S. Congress, House achievable by large metropolitan water systems treating relatively clean source water.” U.S. Congress, House
Committee on Interstate and Foreign Commerce, Committee on Interstate and Foreign Commerce, Safe Drinking Water Act, 93rd Cong., 2nd sess., July 10, 1974, H.Rept. , 93rd Cong., 2nd sess., July 10, 1974, H.Rept.
93-1185, p. 18. 93-1185, p. 18.
9 Safe Drinking Water Act (P.L. 93-523), Section 2(a). As discussed in U.S. Congress, Senate Committee on 9 Safe Drinking Water Act (P.L. 93-523), Section 2(a). As discussed in U.S. Congress, Senate Committee on
Environment and Public Works, Safe Drinking Water Act Amendments of 1985, 99th Cong., 1st sess., May 15, 1985, Environment and Public Works, Safe Drinking Water Act Amendments of 1985, 99th Cong., 1st sess., May 15, 1985,
S.Rept. 99-56. S.Rept. 99-56.
10 U.S. Congress, Senate Committee on Environment and Public Works, 10 U.S. Congress, Senate Committee on Environment and Public Works, Safe Drinking Water Act Amendments of 1985, ,
99th Cong., 1st sess., May 15, 1985, S.Rept. 99-56. 99th Cong., 1st sess., May 15, 1985, S.Rept. 99-56.
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Drinking Water Amendments of 1986 (P.L. 99-339), Congress directed EPA to promulgate Drinking Water Amendments of 1986 (P.L. 99-339), Congress directed EPA to promulgate
drinking water regulations for 83 contaminants by June 1989 and for 25 additional contaminants drinking water regulations for 83 contaminants by June 1989 and for 25 additional contaminants
every 3 years thereafter.11 Following the 1986 amendments, EPA promulgated new regulations every 3 years thereafter.11 Following the 1986 amendments, EPA promulgated new regulations
and revised existing regulations for more than 80 contaminants, attempting to keep pace with the and revised existing regulations for more than 80 contaminants, attempting to keep pace with the
statutory requirements. Water utilities, state drinking water regulators, and EPA expressed statutory requirements. Water utilities, state drinking water regulators, and EPA expressed
concern that the regulatory schedule imposed significant burdens and did not prioritize concern that the regulatory schedule imposed significant burdens and did not prioritize
contaminants based on risk to public health.12 In its report on the 1996 SDWA amendments, the contaminants based on risk to public health.12 In its report on the 1996 SDWA amendments, the
House Committee on Commerce stated that, particularly for small water systems, the 1986 House Committee on Commerce stated that, particularly for small water systems, the 1986
regulatory schedule resulted in increased compliance costs without a commensurate increase in regulatory schedule resulted in increased compliance costs without a commensurate increase in
public health protection.13 public health protection.13
Adding to these findings, a 1993 outbreak of Adding to these findings, a 1993 outbreak of Cryptosporidiosis in Milwaukee’s public water in Milwaukee’s public water
supply focused congressional attention to whether the regulatory pace established by the 1986 supply focused congressional attention to whether the regulatory pace established by the 1986
SDWA amendments reduced EPA’s focus on high-risk contaminants, such as microbial pathogens SDWA amendments reduced EPA’s focus on high-risk contaminants, such as microbial pathogens
that pose acute health risks. In response to calls for “a more streamlined and flexible approach to that pose acute health risks. In response to calls for “a more streamlined and flexible approach to
controlling drinking water contamination consistent with continued protection of the public controlling drinking water contamination consistent with continued protection of the public
health,”14 the 104th Congress amended SDWA to establish the current health risk-based regulatory health,”14 the 104th Congress amended SDWA to establish the current health risk-based regulatory
process.15 The House Committee on Commerce stated that the purpose of the Safe Drinking process.15 The House Committee on Commerce stated that the purpose of the Safe Drinking
Water Act Amendments of 1996 was Water Act Amendments of 1996 was
~~...~~ to help make more effective and more cost-effective Federal regulation of drinking water to help make more effective and more cost-effective Federal regulation of drinking water
and to help small communities pay for improvements to their public water systems, while and to help small communities pay for improvements to their public water systems, while
ensuring that health protections are maintained or improved.16 ensuring that health protections are maintained or improved.16
Table 1 outlines EPA actions and timelines regarding the regulation of contaminants since the outlines EPA actions and timelines regarding the regulation of contaminants since the
1974 enactment of SDWA. 1974 enactment of SDWA.

11 According to the Senate Debate on these amendments, setting regulatory schedules for specific contaminants is not 11 According to the Senate Debate on these amendments, setting regulatory schedules for specific contaminants is not
normally a legislative function (Sen. Durenberger, “The Safe Drinking Water Act Amendments Conference Report,” normally a legislative function (Sen. Durenberger, “The Safe Drinking Water Act Amendments Conference Report,”
Senate debate, Senate debate, Congressional Record, May 21, 1986, pp. 6284-6301). , May 21, 1986, pp. 6284-6301).
12 U.S. Congress, House Committee on Commerce, 12 U.S. Congress, House Committee on Commerce, Safe Drinking Water Act Amendments of 1996, 104th Cong., 2nd , 104th Cong., 2nd
sess., June 24, 1996, H.Rept. 104-632, p. 6. sess., June 24, 1996, H.Rept. 104-632, p. 6.
13 U.S. Congress, House Committee on Commerce, 13 U.S. Congress, House Committee on Commerce, Safe Drinking Water Act Amendments of 1996, 104th Cong., 2nd , 104th Cong., 2nd
sess., June 24, 1996, H.Rept. 104-632, p. 10. sess., June 24, 1996, H.Rept. 104-632, p. 10.
14 U.S. Congress, House Committee on Commerce, 14 U.S. Congress, House Committee on Commerce, Safe Drinking Water Act Amendments of 1996, 104th Cong., 2nd , 104th Cong., 2nd
sess., June 24, 1996, H.Rept. 104-632, p. 6. sess., June 24, 1996, H.Rept. 104-632, p. 6.
15 P.L. 104-182. 15 P.L. 104-182.
16 U.S. Congress, House Committee on Commerce, 16 U.S. Congress, House Committee on Commerce, Safe Drinking Water Act Amendments of 1996, 104th Cong., 2nd , 104th Cong., 2nd
sess., June 24, 1996, H.Rept. 104-632, p. 6. sess., June 24, 1996, H.Rept. 104-632, p. 6.
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Table 1. SDWA Contaminant Regulation Timeline
National Primary Drinking
Type of Regulatory
Cumulative # of
Water Regulations
Action (# of
Regulated
Date
(NPDWRs)
Contaminants)
Contaminants
December 1975 and July December 1975 and July
National Interim Primary National Interim Primary
New (22) New (22)
22 22
1976 1976
Drinking Water Regulations Drinking Water Regulations
November 1979 November 1979
Total Trihalomethanes Rule Total Trihalomethanes Rule
New (1) New (1)
23 23
April 1986 April 1986
Fluoride Rule Fluoride Rule
Revised (1) Revised (1)
23 23
July 1987 July 1987
Phase I NPDWRs Phase I NPDWRs
New (8) New (8)
31 31
June 1989 June 1989
Total Coliform Rule Total Coliform Rule
Revised (1) Revised (1)
31 31
June 1989 June 1989
Surface Water Treatment Rule Surface Water Treatment Rule
New (4) and Revised New (4) and Revised
35 35
(1) (1)
January 1991 and July 1991 January 1991 and July 1991
Phase II NPDWRs Phase II NPDWRs
New (27), Revised (11), New (27), Revised (11), 61 61
and Deleted (1) and Deleted (1)
June 1991 June 1991
Lead and Copper Rule Lead and Copper Rule
New (1) and Revised New (1) and Revised
62 62
(1) (1)
July 1992 July 1992
Phase V NPDWRs Phase V NPDWRs
New (22) and Revised New (22) and Revised
84 84
(1) (1)
June 1995 June 1995
Nickel NPDWR Nickel NPDWR
Remanded (1) Remanded (1)
83 83
December 1998 December 1998
Stage I Disinfectant and Stage I Disinfectant and
New (6) and Revised New (6) and Revised
89 89
Disinfection Byproduct Rule Disinfection Byproduct Rule
(1) (1)
December 1998 December 1998
Interim Enhanced Surface Water Interim Enhanced Surface Water
New (1) and Revised New (1) and Revised
90 90
Treatment Rule Treatment Rule
(2) (2)
January 2000 January 2000
Lead and Copper Rule Lead and Copper Rule
Revised (2) Revised (2)
90 90
December 2000 December 2000
Radionuclides Rule Radionuclides Rule
New (1) and Revised New (1) and Revised
91 91
(4) (4)
January 2001 January 2001
Arsenic Rule Arsenic Rule
Revised (1) Revised (1)
91 91
June 2001 June 2001
Filter Backwash Recycling Rule Filter Backwash Recycling Rule
Revised (1) Revised (1)
91 91
January 2002 January 2002
Long Term I Enhanced Surface Long Term I Enhanced Surface
Revised (2) Revised (2)
91 91
Water Treatment Rule Water Treatment Rule
January 2006 January 2006
Long Term II Enhanced Surface Long Term II Enhanced Surface
Revised (1) Revised (1)
91 91
Water Treatment Rule Water Treatment Rule
November 2006 November 2006
Groundwater Rule Groundwater Rule
New (3) New (3)
94 94
October 2007 October 2007
Lead and Copper Rule Lead and Copper Rule
Revised (2) Revised (2)
94 94
October 2009 October 2009
Aircraft Drinking Water Rule Aircraft Drinking Water Rule
Newa Newa
94 94
February 2013 February 2013
Revised Total Coliform Rule Revised Total Coliform Rule
Revised (1) Revised (1)
94 94
December 2020 December 2020
Lead and Copper Rule Lead and Copper Rule
Revised (1) Revised (1)
94 94
Source: Compiled by CRS from the U.S. Environmental Protection Agency (EPA) website “Regulation Timeline: Compiled by CRS from the U.S. Environmental Protection Agency (EPA) website “Regulation Timeline:
Contaminants Regulated Under the Safe Drinking Water Act” at https://www.epa.gov/sdwa/regulation-timeline-Contaminants Regulated Under the Safe Drinking Water Act” at https://www.epa.gov/sdwa/regulation-timeline-
contaminants-regulated-under-safe-drinking-water-act. contaminants-regulated-under-safe-drinking-water-act.
a. The Aircraft Drinking Water Rule addresses microbial contaminants in water served by aircraft that meet a. The Aircraft Drinking Water Rule addresses microbial contaminants in water served by aircraft that meet
the SDWA definition of public water system. The contaminants addressed in the rule, total coliform and the SDWA definition of public water system. The contaminants addressed in the rule, total coliform and
Escherichia coli ( (E. coli), are regulated under an existing rule for other public water systems. , are regulated under an existing rule for other public water systems.
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Regulated Public Water Systems
National primary drinking water regulations apply to National primary drinking water regulations apply to public water systems. SDWA generally . SDWA generally
defines a defines a public water system as a system that provides water through pipes or other conveyances as a system that provides water through pipes or other conveyances
to at least 15 service connections or that regularly serves at least 25 individuals.17 Primary to at least 15 service connections or that regularly serves at least 25 individuals.17 Primary
enforcement responsibility (primacy) of public water system compliance with SDWA enforcement responsibility (primacy) of public water system compliance with SDWA
requirements, including drinking water regulations, may be assumed by states that meet statutory requirements, including drinking water regulations, may be assumed by states that meet statutory
criteria, under SDWA Section 1413.18 criteria, under SDWA Section 1413.18
Public water systems can be divided into three subset categories. Public water systems can be divided into three subset categories. Community water systems are are
systems that regularly serve at least 25 individuals year-round.19 Federal drinking water systems that regularly serve at least 25 individuals year-round.19 Federal drinking water
regulations apply to these systems, which provide drinking water to more than 312 million regulations apply to these systems, which provide drinking water to more than 312 million
individuals. As presented inindividuals. As presented in Table 2, more than 50% (26,885) of community water systems serve more than 50% (26,885) of community water systems serve
500 or fewer individuals, yet these systems serve roughly 1.5% of the total population served by 500 or fewer individuals, yet these systems serve roughly 1.5% of the total population served by
such systems. such systems. Non-transient non-community water systems, such as schools or factories, have , such as schools or factories, have
their own water supplies and generally serve the same individuals for more than six months but their own water supplies and generally serve the same individuals for more than six months but
not year-round. Most drinking water regulations apply to these systems. not year-round. Most drinking water regulations apply to these systems. Transient non-community
water systems, such as campgrounds and gas stations, provide their own water to transitory , such as campgrounds and gas stations, provide their own water to transitory
customers. Only regulations for contaminants that pose immediate health risks apply to these customers. Only regulations for contaminants that pose immediate health risks apply to these
systems. systems.
Table 2. Public Water System Statistics

Very Small Small
Medium
Large
Very Large Total
Population served
500 or 500 or
501 to 501 to
3,301 to 3,301 to
10,001 to 10,001 to
100,001 or 100,001 or
fewer fewer
3,300 3,300
10,000 10,000
100,000 100,000
more more

Community
# of Systems # of Systems
26,885 26,885
13,291 13,291
5,018 5,018
3,954 3,954
443 443
49,591 49,591
water
system
Pop. Served Pop. Served
4,538,205 4,538,205
19,139,653 19,139,653
29,480,771 29,480,771
113,932,781 113,932,781
145,630,947 145,630,947
312,722,357 312,722,357
% of Systems % of Systems
54.21% 54.21%
26.80% 26.80%
10.12% 10.12%
7.97% 7.97%
0.89% 0.89%
100% 100%
% of Pop. Served % of Pop. Served
1.45% 1.45%
6.12% 6.12%
9.43% 9.43%
36.43% 36.43%
46.57% 46.57%
100% 100%
Non-
# of Systems # of Systems
14,806 14,806
2,454 2,454
158 158
38 38
1 1
17,457 17,457
Transient
non-
Pop. Served Pop. Served
2,061,850 2,061,850
2,633,440 2,633,440
858,567 858,567
801,416 801,416
203,375 203,375
6,558,648 6,558,648
community
% of Systems % of Systems
84.81% 84.81%
14.06% 14.06%
0.9% 0.9%
0.22% 0.22%
0.01% 0.01%
100% 100%
system
% of Pop. Served % of Pop. Served
31.44% 31.44%
40.15% 40.15%
13.09% 13.09%
12.22% 12.22%
3.10% 3.10%
100% 100%
Transient
# of Systems # of Systems
74,597 74,597
2,921 2,921
74 74
12 12
1 1
77,605 77,605
non-
community
Pop. Served Pop. Served
6,942,296 6,942,296
2,739,119 2,739,119
383,603 383,603
247,616 247,616
2,000,000 2,000,000
12,312,634 12,312,634
system
% of Systems % of Systems
96.12% 96.12%
3.76% 3.76%
0.10% 0.10%
0.02% 0.02%
0.00% 0.00%
100% 100%
% of Pop. Served % of Pop. Served
56.38% 56.38%
22.25% 22.25%
3.12% 3.12%
2.01% 2.01%
16.24% 16.24%
100% 100%
Total
# of Systems # of Systems
116,288 116,288
18,666 18,666
5,250 5,250
4,004 4,004
445 445
144,653 144,653

17 42 U.S.C. §300f(4). The act does not specify ownership of public water systems. 17 42 U.S.C. §300f(4). The act does not specify ownership of public water systems.
18 42 U.S.C. §300g-2. Currently, 49 states, the territories, and the Navajo Nation have applied for and received primacy 18 42 U.S.C. §300g-2. Currently, 49 states, the territories, and the Navajo Nation have applied for and received primacy
for the drinking water program. EPA retains implementation and enforcement authority for Wyoming, the District of for the drinking water program. EPA retains implementation and enforcement authority for Wyoming, the District of
Columbia, and Indian tribes other than the Navajo Nation. Columbia, and Indian tribes other than the Navajo Nation.
19 42 U.S.C. §300f(15). 19 42 U.S.C. §300f(15).
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Source: Prepared by CRS from EPA’s Safe Drinking Water Information Systems, Water System Summary Prepared by CRS from EPA’s Safe Drinking Water Information Systems, Water System Summary
report generated on October 23, 2020. The search parameters were “public water systems.” report generated on October 23, 2020. The search parameters were “public water systems.”
Regulating Contaminants in Public Water Supplies
As revised in 1996, the act’s regulatory development provisions reflect themes of prioritizing As revised in 1996, the act’s regulatory development provisions reflect themes of prioritizing
contaminants for regulation based on public health risk, considering compliance costs to contaminants for regulation based on public health risk, considering compliance costs to
communities with health risk reduction benefits, and science-based decisionmaking. The act communities with health risk reduction benefits, and science-based decisionmaking. The act
requires EPA to identify contaminants that may require regulation, assess health risks based on requires EPA to identify contaminants that may require regulation, assess health risks based on
the best available peer-reviewed science, conduct a monitoring program to estimate the frequency the best available peer-reviewed science, conduct a monitoring program to estimate the frequency
and levels of a contaminant’s occurrence, and make determinations of whether a drinking water and levels of a contaminant’s occurrence, and make determinations of whether a drinking water
regulation is warranted. regulation is warranted.
EPA’s ability to implement these provisions—and to set scientifically sound standards—depends EPA’s ability to implement these provisions—and to set scientifically sound standards—depends
on the availability of health effects and occurrence data as well as agency resources to develop on the availability of health effects and occurrence data as well as agency resources to develop
such data, among other factors. For many unregulated contaminants, health effects and such data, among other factors. For many unregulated contaminants, health effects and
occurrence data may not be available and may take some time to generate. The availability, as occurrence data may not be available and may take some time to generate. The availability, as
well as the development, of such data poses challenges for EPA in evaluating contaminants for well as the development, of such data poses challenges for EPA in evaluating contaminants for
regulation and for establishing regulations with enforceable standards for contaminants. (For regulation and for establishing regulations with enforceable standards for contaminants. (For
further discussion, see further discussion, see “Data Availability and Quality.”) )
Identifying Contaminants for Consideration
SDWA requires EPA, every five years, to publish a list of unregulated contaminants known or SDWA requires EPA, every five years, to publish a list of unregulated contaminants known or
anticipated to occur in public water systems that may warrant regulation.20 EPA has termed this anticipated to occur in public water systems that may warrant regulation.20 EPA has termed this
list the list the contaminant candidate list (CCL). Prior to publishing a final CCL, EPA is required to (CCL). Prior to publishing a final CCL, EPA is required to
consider contaminant occurrence, to give notice and provide an opportunity for public comment, consider contaminant occurrence, to give notice and provide an opportunity for public comment,
and to consult with the scientific community, including the Science Advisory Board.21 In selecting and to consult with the scientific community, including the Science Advisory Board.21 In selecting
contaminants for regulatory consideration, SDWA requires EPA to select contaminants that contaminants for regulatory consideration, SDWA requires EPA to select contaminants that
present the greatest public health concern, taking into consideration a contaminant’s health effects present the greatest public health concern, taking into consideration a contaminant’s health effects
on specified population subgroups (e.g., infants, children, and pregnant women) who may be at on specified population subgroups (e.g., infants, children, and pregnant women) who may be at
greater risk due to exposure to a contaminant.22 greater risk due to exposure to a contaminant.22
Over time, EPA has revised the process to identify and list contaminants on the CCL.23 In 2009, Over time, EPA has revised the process to identify and list contaminants on the CCL.23 In 2009,
EPA published CCL 3, which was developed using a revised process based on recommendations EPA published CCL 3, which was developed using a revised process based on recommendations
and advice from the National Research Council and National Drinking Water Advisory Council and advice from the National Research Council and National Drinking Water Advisory Council
(NDWAC).24 For CCL 3, EPA identified a broad “universe” of potential drinking water (NDWAC).24 For CCL 3, EPA identified a broad “universe” of potential drinking water

20 SDWA §1412(b)(1)(B); 42 U.S.C. §300g-1(b)(1)(B). This provision directs EPA to consider contaminants defined as 20 SDWA §1412(b)(1)(B); 42 U.S.C. §300g-1(b)(1)(B). This provision directs EPA to consider contaminants defined as
hazardous substances under §101(14) of the Comprehensive Environmental Response, Compensation, and Liability Act hazardous substances under §101(14) of the Comprehensive Environmental Response, Compensation, and Liability Act
of 1980 (CERCLA; 42 U.S.C. §9601(14)) and substances that are registered as pesticides under the Federal Insecticide, of 1980 (CERCLA; 42 U.S.C. §9601(14)) and substances that are registered as pesticides under the Federal Insecticide,
Fungicide, and Rodenticide Act, as amended (7 U.S.C. §§136 et seq.). Fungicide, and Rodenticide Act, as amended (7 U.S.C. §§136 et seq.).
21 The 1978 Environmental Research, Development, and Demonstration Authorization Act (P.L. 95-477) directed EPA 21 The 1978 Environmental Research, Development, and Demonstration Authorization Act (P.L. 95-477) directed EPA
to establish the Science Advisory Board to provide scientific advice to the Administrator (42 U.S.C. §4365). to establish the Science Advisory Board to provide scientific advice to the Administrator (42 U.S.C. §4365).
22 SDWA §1412(b)(1)(C); 42 U.S.C. §300g-1(b)(1)(C). 22 SDWA §1412(b)(1)(C); 42 U.S.C. §300g-1(b)(1)(C).
23 For the first CCL, EPA used screening and evaluation criteria for chemical contaminants from the National Drinking 23 For the first CCL, EPA used screening and evaluation criteria for chemical contaminants from the National Drinking
Water Advisory Council (NDWAC) and convened an expert panel of microbiologists to recommend microbiological Water Advisory Council (NDWAC) and convened an expert panel of microbiologists to recommend microbiological
contaminants. EPA also solicited public input through a hotline. contaminants. EPA also solicited public input through a hotline.
24 NDWAC, “National Drinking Water Advisory Council Report on the CCL Classification Process to the U.S. 24 NDWAC, “National Drinking Water Advisory Council Report on the CCL Classification Process to the U.S.
Environmental Protection Agency,” May 19, 2004. National Research Council (NRC), “Classifying Drinking Water Environmental Protection Agency,” May 19, 2004. National Research Council (NRC), “Classifying Drinking Water
Contaminants for Regulatory Consideration,” National Academy Press, Washington, DC. EPA, “Drinking Water Contaminants for Regulatory Consideration,” National Academy Press, Washington, DC. EPA, “Drinking Water
Contaminant Candidate List 3-Draft,” 73 Contaminant Candidate List 3-Draft,” 73 Federal Register 9627, February 21, 2008, at https://www.federalregister.gov/ 9627, February 21, 2008, at https://www.federalregister.gov/
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contaminants, which was narrowed through a screening process as well as with public and expert contaminants, which was narrowed through a screening process as well as with public and expert
input.25 This revised process was intended to be more easily reproducible than the process EPA input.25 This revised process was intended to be more easily reproducible than the process EPA
used to develop the first and second CCLs.26 used to develop the first and second CCLs.26
Once the CCL is developed, EPA continues to evaluate listed contaminants to inform regulatory Once the CCL is developed, EPA continues to evaluate listed contaminants to inform regulatory
decisionmaking.27 EPA typically divides the listed contaminants into groups: those prioritized for decisionmaking.27 EPA typically divides the listed contaminants into groups: those prioritized for
drinking water research (e.g., health effects, analytical methods, treatment technologies), those drinking water research (e.g., health effects, analytical methods, treatment technologies), those
that required additional occurrence data, and those prioritized for future drinking water that required additional occurrence data, and those prioritized for future drinking water
regulations. regulations.
EPA is developing the fifth CCL (or CCL 5), and typically the agency carries forward EPA is developing the fifth CCL (or CCL 5), and typically the agency carries forward
contaminants from one CCL to the next to continue evaluating contaminants from one CCL to the next to continue evaluating ~~contaminant~~scontaminants. Appendix A
includes details about the first, second, third, and fourth contaminant candidate list. includes details about the first, second, third, and fourth contaminant candidate list.
Evaluating Contaminant Occurrence
To gather data on contaminant occurrence at a national level, EPA is required to administer a To gather data on contaminant occurrence at a national level, EPA is required to administer a
monitoring program for unregulated contaminants in public water supplies. SDWA directs EPA to monitoring program for unregulated contaminants in public water supplies. SDWA directs EPA to
publish, every five years, a rule (Unregulated Contaminant Monitoring Rule [UCMR]) listing no publish, every five years, a rule (Unregulated Contaminant Monitoring Rule [UCMR]) listing no
more than 30 unregulated contaminants to be monitored by public water systems.28 Only a more than 30 unregulated contaminants to be monitored by public water systems.28 Only a
nationally representative sample of public water systems serving 10,000 individuals or fewer are nationally representative sample of public water systems serving 10,000 individuals or fewer are
required to conduct monitoring.29 EPA funds the monitoring costs for this representative sample required to conduct monitoring.29 EPA funds the monitoring costs for this representative sample
of small public water systems.30 EPA uses monitoring results from the UCMR to assess the of small public water systems.30 EPA uses monitoring results from the UCMR to assess the
frequency and levels of a contaminant’s occurrence nationwide. frequency and levels of a contaminant’s occurrence nationwide.
EPA generally selects the list of unregulated contaminants for a UCMR based on the CCLs, but EPA generally selects the list of unregulated contaminants for a UCMR based on the CCLs, but
may select other unregulated contaminants as well. SDWA directs EPA to include specific may select other unregulated contaminants as well. SDWA directs EPA to include specific

documents/2008/02/21/E8-3114/drinking-water-contaminant-candidate-list-3-draft.documents/2008/02/21/E8-3114/drinking-water-contaminant-candidate-list-3-draft.
25 To develop CCL 3, EPA evaluated 284 data sources and selected approximately 7,500 contaminants. EPA then used 25 To develop CCL 3, EPA evaluated 284 data sources and selected approximately 7,500 contaminants. EPA then used
specified criteria (i.e., potential to occur in public water systems and potential for public health concern) to reduce the specified criteria (i.e., potential to occur in public water systems and potential for public health concern) to reduce the
number of contaminants that EPA included on the preliminary CCL. For the preliminary CCL 3, EPA included 532 number of contaminants that EPA included on the preliminary CCL. For the preliminary CCL 3, EPA included 532
contaminants. The agency then evaluated contaminants listed on the preliminary CCL further for their occurrence and contaminants. The agency then evaluated contaminants listed on the preliminary CCL further for their occurrence and
health effects through scoring and “structured classification models” to identify priority contaminants to include on the health effects through scoring and “structured classification models” to identify priority contaminants to include on the
final CCL. EPA solicited public input and expert review throughout the development of CCL 3. When finalized, CCL 3 final CCL. EPA solicited public input and expert review throughout the development of CCL 3. When finalized, CCL 3
included 116 contaminants. included 116 contaminants.
26 EPA, “Drinking Water Contaminant Candidate List 3-Draft,” 73 26 EPA, “Drinking Water Contaminant Candidate List 3-Draft,” 73 Federal Register 9631, February 21, 2008, at 9631, February 21, 2008, at
https://www.federalregister.gov/documents/2008/02/21/E8-3114/drinking-water-contaminant-candidate-list-3-draft. https://www.federalregister.gov/documents/2008/02/21/E8-3114/drinking-water-contaminant-candidate-list-3-draft.
27 For more information, see EPA website 27 For more information, see EPA website, “Basic Information on the CCL and Regulatory Determination” at “Basic Information on the CCL and Regulatory Determination” at
https://www.epa.gov/ccl/basic-information-ccl-and-regulatory-determination. https://www.epa.gov/ccl/basic-information-ccl-and-regulatory-determination.
28 SDWA §1445(a)(2); 42 U.S.C. §300j-4(a)(2). This provision requires all systems serving more than 10,000 people 28 SDWA §1445(a)(2); 42 U.S.C. §300j-4(a)(2). This provision requires all systems serving more than 10,000 people
and a sample of smaller systems to monitor for the contaminants. In America’s Water Infrastructure Act, P.L. 115-270, and a sample of smaller systems to monitor for the contaminants. In America’s Water Infrastructure Act, P.L. 115-270,
Congress amended §1445 to require public water systems serving between 3,300 and 10,000 to conduct monitoring—Congress amended §1445 to require public water systems serving between 3,300 and 10,000 to conduct monitoring—
subject to the availability of appropriations. This requirement is to take effect three years after the date of enactment of subject to the availability of appropriations. This requirement is to take effect three years after the date of enactment of
P.L. 115-270 (i.e., October 23, 2021). The National Defense Authorization Act, Fiscal Year 2020 specified for the fifth P.L. 115-270 (i.e., October 23, 2021). The National Defense Authorization Act, Fiscal Year 2020 specified for the fifth
UCMR that any PFAS with a validated test method not count toward the 30 contaminant limit (P.L. 116-92, §7311; 15 UCMR that any PFAS with a validated test method not count toward the 30 contaminant limit (P.L. 116-92, §7311; 15
U.S.C. §8911). U.S.C. §8911).
29 SDWA §1445(a)(2); 42 U.S.C. §300j-4(a)(2). EPA estimates that approximately 83% of the population receives 29 SDWA §1445(a)(2); 42 U.S.C. §300j-4(a)(2). EPA estimates that approximately 83% of the population receives
water from public water systems that serve more than 10,000 individuals. This requirement enters into effect three water from public water systems that serve more than 10,000 individuals. This requirement enters into effect three
years after the date of enactment of P.L. 115-270 (i.e., October 23, 2021). years after the date of enactment of P.L. 115-270 (i.e., October 23, 2021).
30 SDWA §1445(a)(2)(C)(ii); 42 U.S.C. §300j-4(a)(2)(C)(ii). This provision directs EPA to cover testing and laboratory 30 SDWA §1445(a)(2)(C)(ii); 42 U.S.C. §300j-4(a)(2)(C)(ii). This provision directs EPA to cover testing and laboratory
analysis costs for small systems, using funds reserved from the annual DWSRF capitalization grant (SDWA §1452(o); analysis costs for small systems, using funds reserved from the annual DWSRF capitalization grant (SDWA §1452(o);
42 U.S.C. §300j-12(o)). 42 U.S.C. §300j-12(o)).
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contaminants in the UCMR, when such contaminants have been nominated by the governors of contaminants in the UCMR, when such contaminants have been nominated by the governors of
seven or more states.31 seven or more states.31
For each contaminant included in an UCMR, EPA specifies an analytical method that water For each contaminant included in an UCMR, EPA specifies an analytical method that water
system operators and laboratories may use to measure the contaminant in drinking water.32 EPA system operators and laboratories may use to measure the contaminant in drinking water.32 EPA
may be unable to include one or more contaminants of concern in a particular monitoring may be unable to include one or more contaminants of concern in a particular monitoring
rule/cycle if no validated analytical method is available to detect and measure the contaminant in rule/cycle if no validated analytical method is available to detect and measure the contaminant in
drinking water. UCMRs set a minimum reporting level (MRL) for each contaminant. MRLs are drinking water. UCMRs set a minimum reporting level (MRL) for each contaminant. MRLs are
based on the capability of the analytical method and often are set at levels below health-based based on the capability of the analytical method and often are set at levels below health-based
reference levels, where established. Prior to finalizing the UCMR, EPA seeks public input by reference levels, where established. Prior to finalizing the UCMR, EPA seeks public input by
publishing a proposed contaminant list in the publishing a proposed contaminant list in the Federal Register.
SDWA requires community water system operators to include the results of UCMR monitoring to SDWA requires community water system operators to include the results of UCMR monitoring to
their customers in the annual consumer confidence report.33 Additionally, EPA may require public their customers in the annual consumer confidence report.33 Additionally, EPA may require public
water systems to notify consumers specifically about the levels of contaminants for which UCMR water systems to notify consumers specifically about the levels of contaminants for which UCMR
monitoring was required.34 EPA publishes the UCMR monitoring results and reports the number monitoring was required.34 EPA publishes the UCMR monitoring results and reports the number
of detections at or above the MRL, as well as detections above EPA’s health-based reference of detections at or above the MRL, as well as detections above EPA’s health-based reference
levels, when available. levels, when available.
The agency uses UCMRs to gather national occurrence data. These data support evaluation and The agency uses UCMRs to gather national occurrence data. These data support evaluation and
prioritization of contaminants on the CCL and inform EPA’s review of contaminants that may prioritization of contaminants on the CCL and inform EPA’s review of contaminants that may
warrant regulation.35warrant regulation.35 Appendix B contains information on the first, second, third, and fourth contains information on the first, second, third, and fourth
UCMRs. UCMRs.
Determining Whether or Not to Regulate
Using occurrence and health effects data, EPA is required, every five years, to make a Using occurrence and health effects data, EPA is required, every five years, to make a
determination of whether or not to regulate (a regulatory determination [RD]) for at least five determination of whether or not to regulate (a regulatory determination [RD]) for at least five
contaminants on the CCL.36 Under SDWA, to make a positive determination to regulate a contaminants on the CCL.36 Under SDWA, to make a positive determination to regulate a
contaminant, EPA must find that contaminant, EPA must find that
 a contaminant may have an adverse health effect;  a contaminant may have an adverse health effect;
 it is known to occur or there is a substantial likelihood that it will occur in public  it is known to occur or there is a substantial likelihood that it will occur in public
water systems with a frequency and at levels of public health concern; and water systems with a frequency and at levels of public health concern; and
 in the sole judgment of the Administrator, regulation of the contaminant presents  in the sole judgment of the Administrator, regulation of the contaminant presents
a meaningful opportunity for health risk reduction for persons served by water a meaningful opportunity for health risk reduction for persons served by water
systems.37 systems.37

31 SDWA §1445(a)(2)(B)(ii); 42 U.S.C. §300j-4(a)(2)(B)(ii). 31 SDWA §1445(a)(2)(B)(ii); 42 U.S.C. §300j-4(a)(2)(B)(ii).
32 The contaminants for which monitoring is required are divided into those for “assessment monitoring” (using test 32 The contaminants for which monitoring is required are divided into those for “assessment monitoring” (using test
methods that are widely used) and for “screening survey” (using test methods that are newer and less available). methods that are widely used) and for “screening survey” (using test methods that are newer and less available).
33 SDWA §1414(c)(4)(B)(v); 42 U.S.C. §300g-3(c)(4)(B)(v). Community water system operators are required to 33 SDWA §1414(c)(4)(B)(v); 42 U.S.C. §300g-3(c)(4)(B)(v). Community water system operators are required to
provide their customers with an annual consumer confidence report on their drinking water quality and SDWA provide their customers with an annual consumer confidence report on their drinking water quality and SDWA
compliance. Community water systems serving more than 10,000 individuals are required to biannually produce and compliance. Community water systems serving more than 10,000 individuals are required to biannually produce and
distribute such reports. distribute such reports.
34 SDWA §1414(c)(1)(C); 42 U.S.C. §300g-3(c)(1)(C); and SDWA §1414(c)(2)(F); 42 U.S.C. §300g-3(c)(2)(F). 34 SDWA §1414(c)(1)(C); 42 U.S.C. §300g-3(c)(1)(C); and SDWA §1414(c)(2)(F); 42 U.S.C. §300g-3(c)(2)(F).
35 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation for Public Water Systems,” 6435 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation for Public Water Systems,” 64 Federal
Register 50559, September 17, 1999. 50559, September 17, 1999.
36 SDWA §1412(b)(1)(B)(ii); 42 U.S.C. 300g-1(b)(1)(B)(ii). Nothing in the statute prevents EPA from making a 36 SDWA §1412(b)(1)(B)(ii); 42 U.S.C. 300g-1(b)(1)(B)(ii). Nothing in the statute prevents EPA from making a
regulatory determination outside of the five-year timeline. regulatory determination outside of the five-year timeline.
37 SDWA §1412(b)(1)(A); 42 U.S.C. §300g-1(b)(1)(A). 37 SDWA §1412(b)(1)(A); 42 U.S.C. §300g-1(b)(1)(A).
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In selecting unregulated contaminants for regulatory consideration, SDWA requires EPA to give In selecting unregulated contaminants for regulatory consideration, SDWA requires EPA to give
priority to contaminants that present the greatest public health concern. EPA is specifically priority to contaminants that present the greatest public health concern. EPA is specifically
required to take into consideration a contaminant’s health effects on specified population required to take into consideration a contaminant’s health effects on specified population
subgroups (e.g., infants, children, pregnant women) that may be at greater risk due to exposure to subgroups (e.g., infants, children, pregnant women) that may be at greater risk due to exposure to
a contaminant.38 a contaminant.38
Before making a final determination, EPA is required to provide notice and opportunity for public Before making a final determination, EPA is required to provide notice and opportunity for public
comment on the preliminary RD.39 If EPA makes a determination to regulate a contaminant, the comment on the preliminary RD.39 If EPA makes a determination to regulate a contaminant, the
agency then begins to develop a drinking water regulation. Under the statute, a determination not agency then begins to develop a drinking water regulation. Under the statute, a determination not
to regulate a contaminant is a final agency action and subject to judicial review.40 However, EPA to regulate a contaminant is a final agency action and subject to judicial review.40 However, EPA
reconsiders such contaminants for inclusion on the CCL if new occurrence or health effects reconsiders such contaminants for inclusion on the CCL if new occurrence or health effects
information becomes available.41 information becomes available.41
To evaluate contaminants for regulatory determinations for CCL 3 and CCL 4, EPA used a To evaluate contaminants for regulatory determinations for CCL 3 and CCL 4, EPA used a
process that included three phases—(1) data availability assessment, (2) data evaluation, and (3) process that included three phases—(1) data availability assessment, (2) data evaluation, and (3)
regulatory determination assessment.42 In the final phase, Regulatory Determination Assessment regulatory determination assessment.42 In the final phase, Regulatory Determination Assessment
Phase, EPA evaluates each contaminant using the statutory criteria outlined in SDWA Section Phase, EPA evaluates each contaminant using the statutory criteria outlined in SDWA Section
1412(b)(1)(A). Under these criteria, EPA evaluates uncertainties or limitations of the health 1412(b)(1)(A). Under these criteria, EPA evaluates uncertainties or limitations of the health
effects and occurrence data for a contaminant.43 effects and occurrence data for a contaminant.43
EPA uses available peer-reviewed health effects assessments to derive health reference levels EPA uses available peer-reviewed health effects assessments to derive health reference levels
(HRLs). HRLs are a preliminary estimate of the concentration below which adverse health effects (HRLs). HRLs are a preliminary estimate of the concentration below which adverse health effects
are unlikely to occur.44 For contaminants with carcinogenic effects (i.e., potential increased risk of are unlikely to occur.44 For contaminants with carcinogenic effects (i.e., potential increased risk of
developing certain cancers), EPA develops an HRL using a quantitative estimate of carcinogenic developing certain cancers), EPA develops an HRL using a quantitative estimate of carcinogenic
risk to calculate a level in drinking water equivalent to a one-in-a-million increased risk of cancer risk to calculate a level in drinking water equivalent to a one-in-a-million increased risk of cancer
from a lifetime of exposure.45 For noncarcinogenic contaminants, EPA estimates the relative from a lifetime of exposure.45 For noncarcinogenic contaminants, EPA estimates the relative
source contribution, which is the percentage of the general population’s potential exposure from source contribution, which is the percentage of the general population’s potential exposure from
drinking water to a contaminant (relative to other exposure pathways [including food, inhalation, drinking water to a contaminant (relative to other exposure pathways [including food, inhalation,
and dermal contact]). and dermal contact]).
EPA reviews the occurrence data for each contaminant, evaluating the number of public water EPA reviews the occurrence data for each contaminant, evaluating the number of public water
systems (and the population served) with detections at or above the HRL and above one-half of systems (and the population served) with detections at or above the HRL and above one-half of
the HRL.46 Using these data, EPA evaluates whether the contaminant occurs locally, regionally, or the HRL.46 Using these data, EPA evaluates whether the contaminant occurs locally, regionally, or

38 SDWA §1412(b)(1)(C); 42 U.S.C. §300g-1(b)(1)(C). 38 SDWA §1412(b)(1)(C); 42 U.S.C. §300g-1(b)(1)(C).
39 SDWA §1412(b)(1)(B)(ii); 42 U.S.C. §300g-1(b)(1)(B)(ii). 39 SDWA §1412(b)(1)(B)(ii); 42 U.S.C. §300g-1(b)(1)(B)(ii).
40 SDWA §1412(b)(1)(B)(ii)(IV); 42 U.S.C. §300g-1(b)(1)(B)(ii)(IV). 40 SDWA §1412(b)(1)(B)(ii)(IV); 42 U.S.C. §300g-1(b)(1)(B)(ii)(IV).
41 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water 41 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water
Contaminant Candidate List,” 79Contaminant Candidate List,” 79 Federal Register 62727, October 20, 2014. 62727, October 20, 2014.
42 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water 42 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water
Contaminant Candidate List,” 79Contaminant Candidate List,” 79 Federal Register 62720, October 20, 2014. 62720, October 20, 2014.
43 EPA, 43 EPA, Chapter 2: Evaluation of Health and Occurrence Data, EPA Report 815-R-08-012, Washington, DC, June , EPA Report 815-R-08-012, Washington, DC, June
2008. 2008.
44 EPA, “Regulatory Determination 3 Supporting Document,” EPA 815-R-15-014, December 2015. For a non- 44 EPA, “Regulatory Determination 3 Supporting Document,” EPA 815-R-15-014, December 2015. For a non-
threshold toxicant, such as a carcinogen, EPA derives an estimated concentration below which adverse health effects threshold toxicant, such as a carcinogen, EPA derives an estimated concentration below which adverse health effects
have a defined low probability of occurring. EPA states that “an HRL is not a final determination on establishing a have a defined low probability of occurring. EPA states that “an HRL is not a final determination on establishing a
protective level of a contaminant in drinking water for a particular population; it is derived prior to development of a protective level of a contaminant in drinking water for a particular population; it is derived prior to development of a
complete health and exposure assessment and can be considered a screening value.” EPA, “Announcement of complete health and exposure assessment and can be considered a screening value.” EPA, “Announcement of
Preliminary Regulatory Determinations for Contaminants on the Fourth Drinking Water Contaminant Candidate List,” Preliminary Regulatory Determinations for Contaminants on the Fourth Drinking Water Contaminant Candidate List,”
85 85 Federal Register 14102, March 10, 2020. 14102, March 10, 2020.
45 EPA, 45 EPA, Chapter 2: Evaluation of Health and Occurrence Data, EPA Report 815-R-08-012, Washington, DC, June , EPA Report 815-R-08-012, Washington, DC, June
2008. 2008.
46 EPA, “Announcement of Preliminary Regulatory Determinations 46 EPA, “Announcement of Preliminary Regulatory Determinations ~~For~~for Priority Contaminants on the Contaminant Priority Contaminants on the Contaminant
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nationally, and uses these findings to assess whether the contaminant warrants regulation under nationally, and uses these findings to assess whether the contaminant warrants regulation under
the statutory criteria. the statutory criteria.
The first, second, third, and fourth regulatory determinations are discussed briefly below. (See The first, second, third, and fourth regulatory determinations are discussed briefly below. (See
Appendix C for additional details.) for additional details.)
Regulatory Determination Cycles
In the first CCL, EPA initially categorized 20 contaminants as having sufficient health effects data In the first CCL, EPA initially categorized 20 contaminants as having sufficient health effects data
and occurrence information to support RDs, and noted that the agency would use this list to select and occurrence information to support RDs, and noted that the agency would use this list to select
five or more contaminants to make regulatory determinations in 2001.47 Subsequently, EPA found five or more contaminants to make regulatory determinations in 2001.47 Subsequently, EPA found
that the available health effects and occurrence data were insufficient to support RDs for 12 of the that the available health effects and occurrence data were insufficient to support RDs for 12 of the
20 contaminants.48 EPA selected nine contaminants for the first cycle of regulatory 20 contaminants.48 EPA selected nine contaminants for the first cycle of regulatory
determinations, and determined that none presented a meaningful opportunity of health-risk determinations, and determined that none presented a meaningful opportunity of health-risk
reduction, citing few detections or low risk of adverse health effects, among other reasons.49 reduction, citing few detections or low risk of adverse health effects, among other reasons.49
For the second cycle in 2007, EPA made final determinations not to regulate 11 contaminants, due For the second cycle in 2007, EPA made final determinations not to regulate 11 contaminants, due
to highly regionalized contaminant occurrence or few detections at levels of public health to highly regionalized contaminant occurrence or few detections at levels of public health
concern.50 EPA solicited comments and provided an update on assessments of other CCL 2 concern.50 EPA solicited comments and provided an update on assessments of other CCL 2
contaminants, including perchlorate and methyl tertiary-butyl ether (MTBE).51 contaminants, including perchlorate and methyl tertiary-butyl ether (MTBE).51
For the third cycle in 2014, EPA made a preliminary determination to regulate strontium, and For the third cycle in 2014, EPA made a preliminary determination to regulate strontium, and
proposed not to regulate four other contaminants.52 In the final RD 3, EPA determined not to proposed not to regulate four other contaminants.52 In the final RD 3, EPA determined not to
regulate four contaminants due to low detections and/or low risk to public health.53 For strontium, regulate four contaminants due to low detections and/or low risk to public health.53 For strontium,
EPA delayed a final determination to consider additional newly identified scientific data about the EPA delayed a final determination to consider additional newly identified scientific data about the
contribution of other sources of strontium exposure.54 contribution of other sources of strontium exposure.54

Candidate List,” 67Candidate List,” 67 Federal Register 38226-38231, June 3, 2002. EPA added sodium to the initial list of eight 38226-38231, June 3, 2002. EPA added sodium to the initial list of eight
contaminants evaluated for possible regulation. contaminants evaluated for possible regulation.
47 EPA, “Announcement of the Drinking Water Contaminant Candidate List,” 63 47 EPA, “Announcement of the Drinking Water Contaminant Candidate List,” 63 Federal Register 10285-10286, 10285-10286,
March 2, 1998. March 2, 1998.
48 EPA, “Announcement of Preliminary Regulatory Determinations 48 EPA, “Announcement of Preliminary Regulatory Determinations ~~For~~for Priority Contaminants on the Contaminant Priority Contaminants on the Contaminant
Candidate List,” 67Candidate List,” 67 Federal Register 38224, June 3, 2002. 38224, June 3, 2002.
49 EPA, “Announcement of Preliminary Regulatory Determinations 49 EPA, “Announcement of Preliminary Regulatory Determinations ~~For~~for Priority Contaminants on the Contaminant Priority Contaminants on the Contaminant
Candidate List,” 67Candidate List,” 67 Federal Register 38234, June 3, 2002. 38234, June 3, 2002.
50 EPA, “Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water 50 EPA, “Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water
Contaminant Candidate List—Preliminary Determinations,” 72Contaminant Candidate List—Preliminary Determinations,” 72 Federal Register 24027-24038, May 1, 2007. EPA 24027-24038, May 1, 2007. EPA
stated its intent to finalize a determination by December 2008. On October 10, 2008, EPA made a preliminary negative stated its intent to finalize a determination by December 2008. On October 10, 2008, EPA made a preliminary negative
determination, but did not finalize the determination in the final RD 2. In 2011, EPA reversed the proposed negative determination, but did not finalize the determination in the final RD 2. In 2011, EPA reversed the proposed negative
determination and published a final regulatory determination that perchlorate warranted regulation, noting that the determination and published a final regulatory determination that perchlorate warranted regulation, noting that the
agency would begin the process of proposing a drinking water regulation. In July 2020, EPA published a “Notice of agency would begin the process of proposing a drinking water regulation. In July 2020, EPA published a “Notice of
Final Action” in the Final Action” in the Federal Register withdrawing the 2011 positive regulatory determination for perchlorate. (EPA, withdrawing the 2011 positive regulatory determination for perchlorate. (EPA,
“Drinking Water: Final Action on Perchlorate,” 85“Drinking Water: Final Action on Perchlorate,” 85 Federal Register 43990, July 21, 2020.) 43990, July 21, 2020.)
51 EPA, “Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water 51 EPA, “Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water
Contaminant Candidate List-Preliminary Determinations,” 72Contaminant Candidate List-Preliminary Determinations,” 72 Federal Register 24038-24052, May 1, 2007. For 24038-24052, May 1, 2007. For
perchlorate, EPA solicited additional information on exposure and associated health effects, and EPA delayed the RD perchlorate, EPA solicited additional information on exposure and associated health effects, and EPA delayed the RD
for MTBE while the agency revised the health risk assessment. for MTBE while the agency revised the health risk assessment.
52 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water 52 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water
Contaminant Candidate List,” 79Contaminant Candidate List,” 79 Federal Register 62718, October 20, 2014. 62718, October 20, 2014.
53 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water 53 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water
Contaminant Candidate List,” 79Contaminant Candidate List,” 79 Federal Register 62741, October 20, 2014. 62741, October 20, 2014.
54 EPA, “Announcement of Final Regulatory Determinations for Contaminants on the Third Drinking Water 54 EPA, “Announcement of Final Regulatory Determinations for Contaminants on the Third Drinking Water
Contaminant Candidate List,” 81Contaminant Candidate List,” 81 Federal Register 18, January 4, 2016. 18, January 4, 2016.
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In March In March ~~2020, EPA proposed~~2021, EPA finalized regulatory determinations for contaminants on CCL 4. EPA regulatory determinations for contaminants on CCL 4. EPA
~~proposed~~determined to regulate two PFAS (i.e., perfluorooctanoic acid [PFOA] and perfluorooctane to regulate two PFAS (i.e., perfluorooctanoic acid [PFOA] and perfluorooctane
sulfonate [PFOS]) and not to regulate six other chemicalssulfonate [PFOS]) and not to regulate six other chemicals ~~in early 2020.55 The~~ ~~Fall 2020 Unified~~
~~Agenda of Regulatory and Deregulatory Action~~ ~~states that EPA intends to finalize these proposed~~
~~RDs by January 2021.~~.55 In the In the Federal Register notice for the preliminary RDs, EPA provided an notice for the preliminary RDs, EPA provided an
update on the agency’s efforts to evaluate strontium for regulation.56 update on the agency’s efforts to evaluate strontium for regulation.56
Promulgating a Drinking Water Regulation
Once the Administrator determines to regulate a contaminant, SDWA requires EPA to propose a Once the Administrator determines to regulate a contaminant, SDWA requires EPA to propose a
“national primary drinking water regulation” within 24 months and request public comment on “national primary drinking water regulation” within 24 months and request public comment on
the proposal. EPA is required to promulgate a final rule within 18 months after the proposal.57 the proposal. EPA is required to promulgate a final rule within 18 months after the proposal.57
EPA can extend the deadline to publish a final rule for up to nine months by notice in the EPA can extend the deadline to publish a final rule for up to nine months by notice in the Federal
Register.58 58
For each contaminant that EPA determines to regulate, EPA is required to establish a maximum For each contaminant that EPA determines to regulate, EPA is required to establish a maximum
contaminant level goal (MCLG) at a level at which no known or anticipated adverse health contaminant level goal (MCLG) at a level at which no known or anticipated adverse health
effects occur and which allows an adequate margin of safety.59 Regulations also include a effects occur and which allows an adequate margin of safety.59 Regulations also include a
maximum contaminant level (MCL)—an enforceable limit for a contaminant in public water maximum contaminant level (MCL)—an enforceable limit for a contaminant in public water
supplies—or a treatment technique if an MCL is not feasible.60 These regulations can cover supplies—or a treatment technique if an MCL is not feasible.60 These regulations can cover
multiple contaminants and generally establish an MCL for each contaminant covered by the multiple contaminants and generally establish an MCL for each contaminant covered by the
regulation.61 regulation.61
For each drinking water regulation, SDWA requires EPA to identify a list of best available For each drinking water regulation, SDWA requires EPA to identify a list of best available
technologies, treatment techniques, and other means that EPA finds to be feasible for the purposes technologies, treatment techniques, and other means that EPA finds to be feasible for the purposes
of meeting the MCL. In addition, EPA is required to identify treatment technologies that achieve of meeting the MCL. In addition, EPA is required to identify treatment technologies that achieve
the MCL and are affordable for small systems.62 Each regulation also establishes associated the MCL and are affordable for small systems.62 Each regulation also establishes associated
monitoring and reporting requirements. monitoring and reporting requirements.
When developing regulations, EPA is required to (1) use the best available, peer-reviewed science When developing regulations, EPA is required to (1) use the best available, peer-reviewed science
and supporting studies and data; and (2) make publicly available a risk assessment document that and supporting studies and data; and (2) make publicly available a risk assessment document that
discusses estimated risks, uncertainties, and studies used in the assessment.63 discusses estimated risks, uncertainties, and studies used in the assessment.63
Once finalized, regulations generally take effect three years after promulgation.64 EPA may allow Once finalized, regulations generally take effect three years after promulgation.64 EPA may allow
up to two additional years if the Administrator determines that more time is needed for public up to two additional years if the Administrator determines that more time is needed for public
water systems to make capital improvements (states have the same authority for individual water systems).65
55 EPA, “Announcement of 55 EPA, “Announcement of ~~Preliminary~~Final Regulatory Determinations for Contaminants on the Fourth Drinking Water Regulatory Determinations for Contaminants on the Fourth Drinking Water
Contaminant Candidate List,” Contaminant Candidate List,” 8586 Federal Register ~~14098~~12272-12291, March , March ~~10, 2020~~3, 2021. .
56 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Fourth Drinking Water 56 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Fourth Drinking Water
Contaminant Candidate List,” 85Contaminant Candidate List,” 85 Federal Register 14132, March 10, 2020. 14132, March 10, 2020.
57 SDWA §1412(b)(1)(E); 42 U.S.C. §300g-1(b)(1)(E). 57 SDWA §1412(b)(1)(E); 42 U.S.C. §300g-1(b)(1)(E).
58 SDWA §1412(b)(1)(E); 42 U.S.C. §300g-1(b)(1)(E). 58 SDWA §1412(b)(1)(E); 42 U.S.C. §300g-1(b)(1)(E).
59 SDWA §1412(b)(4)(A); 42 U.S.C. §300g-1(b)(4)(A). 59 SDWA §1412(b)(4)(A); 42 U.S.C. §300g-1(b)(4)(A).
60 SDWA §1412(b)(4)(B); 42 U.S.C. §300g-1(b)(4)(B). 60 SDWA §1412(b)(4)(B); 42 U.S.C. §300g-1(b)(4)(B).
61 By definition, a “primary drinking water regulation” includes an MCL and an MCLG for each contaminant, if 61 By definition, a “primary drinking water regulation” includes an MCL and an MCLG for each contaminant, if
technically and economically feasible. SDWA §1401(1); 42 U.S.C. §300f(1). technically and economically feasible. SDWA §1401(1); 42 U.S.C. §300f(1).
62 SDWA §1412(b)(4)(E)(ii); 42 U.S.C. §300g-1(b)(4)(E)(ii). 62 SDWA §1412(b)(4)(E)(ii); 42 U.S.C. §300g-1(b)(4)(E)(ii).
63 SDWA §1412(b)(3); 42 U.S.C. §300g-1(b)(3). 63 SDWA §1412(b)(3); 42 U.S.C. §300g-1(b)(3).
64 SDWA §1412(b)(10); 42 U.S.C. §300g-1(b)(10). 64 SDWA §1412(b)(10); 42 U.S.C. §300g-1(b)(10).
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~~water systems to make capital improvements (states have the same authority for individual water~~
~~systems).65~~
SDWA requires EPA to review each existing national primary drinking water regulation every six SDWA requires EPA to review each existing national primary drinking water regulation every six
years. The review is intended to identify current health effects assessments, changes in years. The review is intended to identify current health effects assessments, changes in
technology, and/or other factors that would support the revision of a regulation to be more technology, and/or other factors that would support the revision of a regulation to be more
protective of public health. protective of public health.
Figure 1 outlines the SDWA processes for contaminant evaluation, regulation, and regulatory outlines the SDWA processes for contaminant evaluation, regulation, and regulatory
review. review.
Figure 1. Simplified Process for Regulating Contaminants Under SDWA

Source: Modified by CRS from EPA.gov. Modified by CRS from EPA.gov.
Notes: CCL = contaminant candidate list, UCMR = unregulated contaminant monitoring rule, NPDWR = CCL = contaminant candidate list, UCMR = unregulated contaminant monitoring rule, NPDWR =
national primary drinking water regulation. national primary drinking water regulation.
Maximum Contaminant Level Goals
Drinking water regulations specify a nonenforceable MCLG, which is based solely on health Drinking water regulations specify a nonenforceable MCLG, which is based solely on health
effects data. Unlike an MCL, the MCLG does not reflect cost or technical feasibility effects data. Unlike an MCL, the MCLG does not reflect cost or technical feasibility
considerations. For contaminants with carcinogenic effects and for microbial contaminants, EPA considerations. For contaminants with carcinogenic effects and for microbial contaminants, EPA
typically sets the MCLG at zero.66 typically sets the MCLG at zero.66
For contaminants with noncarcinogenic effects, EPA derives an MCLG based on a reference dose, For contaminants with noncarcinogenic effects, EPA derives an MCLG based on a reference dose,
which is an estimate of the amount of a contaminant that a person can be exposed to on a daily which is an estimate of the amount of a contaminant that a person can be exposed to on a daily
basis that is not anticipated to cause adverse health effects for sensitive life stages and meaningful basis that is not anticipated to cause adverse health effects for sensitive life stages and meaningful
populations (e.g., infants, children, pregnant women, the elderly, individuals with a history of populations (e.g., infants, children, pregnant women, the elderly, individuals with a history of
serious illness, or other sensitive subpopulations) over a lifetime.67 This amount incorporates serious illness, or other sensitive subpopulations) over a lifetime.67 This amount incorporates

~~65 SDWA §1412(b)(10); 42 U.S.C. §300g-1(b)(10). EPA used this authority to provide two additional years for~~
community water systems serving 10,000 or fewer people to comply with the revised arsenic rule. EPA, “Proposed community water systems serving 10,000 or fewer people to comply with the revised arsenic rule. EPA, “Proposed
Rule: Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring,” 65Rule: Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring,” 65 Federal Register
38892, June 22, 2000. 38892, June 22, 2000.
66 For more information, see EPA website “How EPA Regulates Drinking Water Contaminants” at 66 For more information, see EPA website “How EPA Regulates Drinking Water Contaminants” at
https://www.epa.gov/sdwa/how-epa-regulates-drinking-water-contaminants#standards. https://www.epa.gov/sdwa/how-epa-regulates-drinking-water-contaminants#standards.
67 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Fourth Drinking Water 67 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Fourth Drinking Water
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uncertainty factors to provide a margin of protection for sensitive subpopulations and to account uncertainty factors to provide a margin of protection for sensitive subpopulations and to account
for uncertainties in the data.68 for uncertainties in the data.68
In developing an MCLG for noncarcinogens, EPA also estimates the general population’s In developing an MCLG for noncarcinogens, EPA also estimates the general population’s
exposure to a contaminant from drinking water and other sources (e.g., food, dust, soil, and air). exposure to a contaminant from drinking water and other sources (e.g., food, dust, soil, and air).
After considering other exposure routes, EPA estimates the proportion of exposure attributable to After considering other exposure routes, EPA estimates the proportion of exposure attributable to
drinking water (i.e., the relative source contribution [RSC]).69 When exposure information is not drinking water (i.e., the relative source contribution [RSC]).69 When exposure information is not
available, EPA uses a default assumption that 20% of exposure to a contaminant is attributable to available, EPA uses a default assumption that 20% of exposure to a contaminant is attributable to
drinking water. EPA applies the RSC to ensure that an individual’s total exposure from all sources drinking water. EPA applies the RSC to ensure that an individual’s total exposure from all sources
remains within the estimated protective level.70 The MCLG provides the basis for calculating an remains within the estimated protective level.70 The MCLG provides the basis for calculating an
MCL.71 MCL.71
Feasibility and Maximum Contaminant Levels
SDWA generally requires EPA to set the MCL as close to the MCLG as “feasible.”72 The act SDWA generally requires EPA to set the MCL as close to the MCLG as “feasible.”72 The act
defines “feasible” to mean feasible with the use of the best available (and field demonstrated) defines “feasible” to mean feasible with the use of the best available (and field demonstrated)
treatment technologies, taking cost into consideration.73 The level at which EPA is able to set the treatment technologies, taking cost into consideration.73 The level at which EPA is able to set the
MCL is determined by the ability of a treatment technology to reduce a contaminant to a certain MCL is determined by the ability of a treatment technology to reduce a contaminant to a certain
level. EPA’s ability to set the MCL at the MCLG also depends on the availability of a test method level. EPA’s ability to set the MCL at the MCLG also depends on the availability of a test method
that is sensitive enough to detect the contaminant at the MCLG. For contaminants regulated for that is sensitive enough to detect the contaminant at the MCLG. For contaminants regulated for
noncarcinogenic effects, EPA generally has set the enforceable standard at the same level as the noncarcinogenic effects, EPA generally has set the enforceable standard at the same level as the
MCLG. If it is not technologically or economically feasible to ascertain the level of a contaminant MCLG. If it is not technologically or economically feasible to ascertain the level of a contaminant
in drinking water, EPA may establish a treatment technique in lieu of an MCL.74 For example, in drinking water, EPA may establish a treatment technique in lieu of an MCL.74 For example,
EPA’s Lead and Copper Rule includes a treatment technique—primarily relying on corrosion EPA’s Lead and Copper Rule includes a treatment technique—primarily relying on corrosion
control, among other actions—because lead and/or copper generally enters the water after it control, among other actions—because lead and/or copper generally enters the water after it
leaves the plant.75 leaves the plant.75
When developing an MCL that is feasible, EPA identifies and considers the costs to “large” water When developing an MCL that is feasible, EPA identifies and considers the costs to “large” water
systems, as guided by legislative history.76 Large water systems, serving more than 10,000 systems, as guided by legislative history.76 Large water systems, serving more than 10,000
individuals, comprise roughly 9% of the number of community water systems, but serve a individuals, comprise roughly 9% of the number of community water systems, but serve a
majority (83%) of individuals regularly served by such systems.77 By considering the costs to majority (83%) of individuals regularly served by such systems.77 By considering the costs to

~~Contaminant Candidate List,” 85 Federal Register 14108, March 10, 2020.~~
68 Ibid. 68 Ibid.
69 Other exposure routes include food ingestion, inhalation, and dermal contact. 69 Other exposure routes include food ingestion, inhalation, and dermal contact.
70 See, for example, EPA, 70 See, for example, EPA, Drinking ~~water~~Water Health Advisory for ~~perfluorooctanoic~~Perfluorooctanoic Acid (PFOA), EPA 822-R-16-005, , EPA 822-R-16-005,
May 2016, p. 32, https://www.epa.gov/ground-water-and-drinking-water/supporting-documents-drinking-water-health-May 2016, p. 32, https://www.epa.gov/ground-water-and-drinking-water/supporting-documents-drinking-water-health-
advisories-pfoa-and-pfos. advisories-pfoa-and-pfos.
71 The Safe Drinking Water Act does not prohibit states from setting stricter standards. 71 The Safe Drinking Water Act does not prohibit states from setting stricter standards.
72 SDWA §1412(b)(4)(B); 42 U.S.C. §300g-1(b)(4)(B). EPA may set a standard at other than the feasible level if the 72 SDWA §1412(b)(4)(B); 42 U.S.C. §300g-1(b)(4)(B). EPA may set a standard at other than the feasible level if the
feasible level would lead to an increase in health risks by increasing the concentration of other contaminants or by feasible level would lead to an increase in health risks by increasing the concentration of other contaminants or by
interfering with the treatment processes used to comply with other SDWA regulations. In such cases, the standard or interfering with the treatment processes used to comply with other SDWA regulations. In such cases, the standard or
treatment techniques must minimize the overall health risk (SDWA §1412(b)(5); 42 U.S.C. §300g-1(b)(5)). treatment techniques must minimize the overall health risk (SDWA §1412(b)(5); 42 U.S.C. §300g-1(b)(5)).
73 SDWA §1412(b)(4)(D); 42 U.S.C. §300g-1(b)(4)(D). 73 SDWA §1412(b)(4)(D); 42 U.S.C. §300g-1(b)(4)(D).
74 SDWA §1412(b)(7)(A); 42 U.S.C. §300g-1(b)(7)(A). 74 SDWA §1412(b)(7)(A); 42 U.S.C. §300g-1(b)(7)(A).
75 40 C.F.R. §§141.80-141.91. 75 40 C.F.R. §§141.80-141.91.
76 The meaning of “large” water system has changed over time. Prior to the 1996 SDWA amendments, EPA’s 1991 76 The meaning of “large” water system has changed over time. Prior to the 1996 SDWA amendments, EPA’s 1991
Lead and Copper Rule identified large systems as those serving 50,000 or more individuals, as guided by legislative Lead and Copper Rule identified large systems as those serving 50,000 or more individuals, as guided by legislative
history. The 1996 SDWA Amendments added SDWA §1412(b)(4)(ii), which required EPA to identify compliance history. The 1996 SDWA Amendments added SDWA §1412(b)(4)(ii), which required EPA to identify compliance
technologies for small water systems defined as those serving 10,000 or fewer individuals. technologies for small water systems defined as those serving 10,000 or fewer individuals.
77 From EPA’s “Safe Drinking Water Information Systems: Water System Summary” report at https://ofmpub.epa.gov/ 77 From EPA’s “Safe Drinking Water Information Systems: Water System Summary” report at https://ofmpub.epa.gov/
apex/sfdw/f?p=108:1:::NO:1::. Report generated on October 23, 2020. The search parameters were “public water Congressional Research Service Congressional Research Service

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these systems, Congress intended that MCLs would be established at protective levels that are these systems, Congress intended that MCLs would be established at protective levels that are
achievable for large systems, and thus provide affordable drinking water to a majority of achievable for large systems, and thus provide affordable drinking water to a majority of
individuals served by public water systems. This approach may make compliance with certain individuals served by public water systems. This approach may make compliance with certain
regulations less affordable for small water systems. To address affordability, SDWA includes regulations less affordable for small water systems. To address affordability, SDWA includes
numerous provisions intended to support small system compliance. For discussion of some of numerous provisions intended to support small system compliance. For discussion of some of
these provisions, see these provisions, see “Variances and Exemptions.”
Additional Health Risk Reduction and Cost Considerations
SDWA provides EPA with limited authority to establish an MCL at a level other than the SDWA provides EPA with limited authority to establish an MCL at a level other than the
“feasible” level in certain circumstances. EPA may use this authority if, based on a “Health Risk “feasible” level in certain circumstances. EPA may use this authority if, based on a “Health Risk
Reduction Cost Analysis,” the Administrator determines that the benefits of the feasible level Reduction Cost Analysis,” the Administrator determines that the benefits of the feasible level
“would not justify the costs of complying with the level.”78 In such a case, EPA may—after “would not justify the costs of complying with the level.”78 In such a case, EPA may—after
providing opportunity for public comment—set the standard at a level that “maximizes health risk providing opportunity for public comment—set the standard at a level that “maximizes health risk
reduction benefits at a cost that is justified by the benefits.” However, this authority is not reduction benefits at a cost that is justified by the benefits.” However, this authority is not
available if the benefits that would be experienced by (1) large water systems, and (2) those other available if the benefits that would be experienced by (1) large water systems, and (2) those other
systems unlikely to receive small system variances (e.g., systems serving up to 10,000 persons), systems unlikely to receive small system variances (e.g., systems serving up to 10,000 persons),
would justify the costs.79 EPA has used this authority to establish MCLs at a level higher than would justify the costs.79 EPA has used this authority to establish MCLs at a level higher than
what would be “feasible” for two contaminants—uranium and arsenic.80 For both contaminants, what would be “feasible” for two contaminants—uranium and arsenic.80 For both contaminants,
EPA established the MCL at a level higher than was determined “feasible” because the agency EPA established the MCL at a level higher than was determined “feasible” because the agency
estimated that the costs to treat these contaminants would be incurred primarily by small water estimated that the costs to treat these contaminants would be incurred primarily by small water
systems.81 systems.81
Health Risk Reduction Cost Analysis
Concurrent with proposing a regulation, SDWA requires that EPA publish and seek public Concurrent with proposing a regulation, SDWA requires that EPA publish and seek public
comment on a “health risk reduction and cost analysis” (HRRCA) for each contaminant covered comment on a “health risk reduction and cost analysis” (HRRCA) for each contaminant covered
by the proposed regulation.82 While several congressional and presidential initiatives require by the proposed regulation.82 While several congressional and presidential initiatives require

~~apex/sfdw/f?p=108:1:::NO:1::. Report generated on October 23, 2020. The search parameters were “public water~~
systems.” systems.”
78 SDWA §1412(b)(6)(A); 42 U.S.C. §300g-1(b)(6)(A). 78 SDWA §1412(b)(6)(A); 42 U.S.C. §300g-1(b)(6)(A).
79 SDWA §1412(b)(6)(B); 42 U.S.C. §300g-1(b)(6)(B). 79 SDWA §1412(b)(6)(B); 42 U.S.C. §300g-1(b)(6)(B).
80 For uranium, EPA revised the MCL from 20 µg/L—which EPA considered the “feasible” level—to 30 µg/L due to 80 For uranium, EPA revised the MCL from 20 µg/L—which EPA considered the “feasible” level—to 30 µg/L due to
(1) the generation of additional health effects studies that indicate that “there is not a predictable difference in health (1) the generation of additional health effects studies that indicate that “there is not a predictable difference in health
effects due to exposure” between the two levels, and (2) the cost differences between treating to the two different levels effects due to exposure” between the two levels, and (2) the cost differences between treating to the two different levels
(65 (65 Federal Register 76713-76714). In EPA’s proposed arsenic rule, EPA determined that 3 µg/L was “feasible.” EPA 76713-76714). In EPA’s proposed arsenic rule, EPA determined that 3 µg/L was “feasible.” EPA
used this authority to set the revised MCL at a level where the benefits from health risk reduction outweigh the costs, at used this authority to set the revised MCL at a level where the benefits from health risk reduction outweigh the costs, at
10 µg/L (66 10 µg/L (66 Federal Register 6975-7066). As with the previous standard (set at 50 µg/L), the MCL applies only to 6975-7066). As with the previous standard (set at 50 µg/L), the MCL applies only to
community water systems. community water systems.
81 EPA, “National Primary Drinking Water Regulations; Radionuclides; Final Rule,” 65 81 EPA, “National Primary Drinking Water Regulations; Radionuclides; Final Rule,” 65 Federal Register 76715, 76715,
December 7, 2000. EPA, “National Primary Drinking Water Regulations; Arsenic and Clarifications to Compliance December 7, 2000. EPA, “National Primary Drinking Water Regulations; Arsenic and Clarifications to Compliance
and New Source Contaminants Monitoring,” 66and New Source Contaminants Monitoring,” 66 Federal Register 7033-7034, January 22, 2001. Small water systems 7033-7034, January 22, 2001. Small water systems
primarily rely on groundwater for their drinking water source. Some groundwater sources have naturally occurring primarily rely on groundwater for their drinking water source. Some groundwater sources have naturally occurring
contaminants such as arsenic and radionuclides (including uranium). Under these rules, such system that rely on contaminants such as arsenic and radionuclides (including uranium). Under these rules, such system that rely on
groundwater, which are primarily small water systems, would face costs to treat for such naturally occurring groundwater, which are primarily small water systems, would face costs to treat for such naturally occurring
contaminants. contaminants.
82 EPA may promulgate an interim standard without first preparing a health risk reduction and cost analysis or making 82 EPA may promulgate an interim standard without first preparing a health risk reduction and cost analysis or making
a determination as to whether the benefits of a regulation would justify the costs if the Administrator determines that a a determination as to whether the benefits of a regulation would justify the costs if the Administrator determines that a
contaminant presents an urgent threat to public health. SDWA §1412(b)(1)(D); 42 U.S.C. 300g-1(b)(1)(D). contaminant presents an urgent threat to public health. SDWA §1412(b)(1)(D); 42 U.S.C. 300g-1(b)(1)(D).
Cryptosporidium is exempt from the health risk reduction and cost analysis requirement (SDWA §1412(b)(6)(C); 42 is exempt from the health risk reduction and cost analysis requirement (SDWA §1412(b)(6)(C); 42
U.S.C. 300g-1(b)(6)(C)). U.S.C. 300g-1(b)(6)(C)).
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certain federal agencies to evaluate costs and benefits of rulemakings,83 SDWA outlines the certain federal agencies to evaluate costs and benefits of rulemakings,83 SDWA outlines the
specific costs and benefits that EPA is required to estimate when preparing an HRRCA and specific costs and benefits that EPA is required to estimate when preparing an HRRCA and
requires EPA to present the uncertainties of such an analysis.84 The HRRCA is intended to requires EPA to present the uncertainties of such an analysis.84 The HRRCA is intended to
provide a transparent analysis of the costs and benefits, calculated using the available science, as provide a transparent analysis of the costs and benefits, calculated using the available science, as
well as EPA’s assumptions when developing a drinking water regulation. To prepare an HRRCA, well as EPA’s assumptions when developing a drinking water regulation. To prepare an HRRCA,
EPA estimates the baseline conditions prior to drinking water regulation (based on contaminant EPA estimates the baseline conditions prior to drinking water regulation (based on contaminant
occurrence and effectiveness of existing treatment technologies already in use); estimates occurrence and effectiveness of existing treatment technologies already in use); estimates
national-level costs and benefits associated with the regulation of a specific contaminant; and national-level costs and benefits associated with the regulation of a specific contaminant; and
assesses distributional impacts and equity concerns.85 assesses distributional impacts and equity concerns.85
At the public water system level, EPA estimates costs associated with treatment (e.g., installation At the public water system level, EPA estimates costs associated with treatment (e.g., installation
and operation of contaminant removal technologies), training for staff, monitoring and analyzing and operation of contaminant removal technologies), training for staff, monitoring and analyzing
water samples, and management and oversight.86 In addition, the analysis may include costs to water samples, and management and oversight.86 In addition, the analysis may include costs to
primacy agencies to enforce regulations. SDWA directs EPA to evaluate costs for compliance primacy agencies to enforce regulations. SDWA directs EPA to evaluate costs for compliance
with the proposed MCL (and alternative MCLs), but specifically excludes compliance costs for with the proposed MCL (and alternative MCLs), but specifically excludes compliance costs for
other proposed or promulgated drinking water regulations.87 other proposed or promulgated drinking water regulations.87
When developing an HRRCA, EPA calculates primarily the benefits of avoided mortality or When developing an HRRCA, EPA calculates primarily the benefits of avoided mortality or
morbidity (illness) from reduced exposure to a contaminant through drinking water for specified morbidity (illness) from reduced exposure to a contaminant through drinking water for specified
sensitive subpopulations and for the general population. As provided in SDWA, sensitive sensitive subpopulations and for the general population. As provided in SDWA, sensitive
subpopulations include subpopulations include
infants, children, pregnant women, the elderly, individuals with a history of serious illness, infants, children, pregnant women, the elderly, individuals with a history of serious illness,
or other subpopulations that are identified as likely to be at greater risk of adverse health or other subpopulations that are identified as likely to be at greater risk of adverse health
effects due to exposure to contaminants in drinking water than the general population.88 effects due to exposure to contaminants in drinking water than the general population.88
EPA quantifies health benefits through a variety of methods, primarily estimating the cost of EPA quantifies health benefits through a variety of methods, primarily estimating the cost of
illness or the cost of reduced physical and mental well-being. Other methods include estimating illness or the cost of reduced physical and mental well-being. Other methods include estimating
willingness-to-pay to avoid negative health impacts. EPA may include other quantifiable and willingness-to-pay to avoid negative health impacts. EPA may include other quantifiable and
nonquantifiable benefits such as “enhanced aesthetic benefitsnonquantifiable benefits such as “enhanced aesthetic benefits,” (e.g., improved taste), avoided ” (e.g., improved taste), avoided
materials damage (e.g., reduced corrosivity of drinking water), avoided costs of household or materials damage (e.g., reduced corrosivity of drinking water), avoided costs of household or
water system actions to prevent contamination, as well as non-use benefits, among others.89 water system actions to prevent contamination, as well as non-use benefits, among others.89

83 For more information, see CRS Report R41974, 83 For more information, see CRS Report R41974, Cost-Benefit and Other Analysis Requirements in the Rulemaking
Process, coordinated by Maeve P. Carey. , coordinated by Maeve P. Carey.
84 SDWA §1412(b)(3)(C); 42 U.S.C. 300g-1(b)(3)(C). 84 SDWA §1412(b)(3)(C); 42 U.S.C. 300g-1(b)(3)(C).
85 EPA, 85 EPA, Preliminary Health Risk Reduction and Cost Analysis: Revised National Primary Drinking Water Standards
for Radionuclides, Cambridge, MA, January 2000. , Cambridge, MA, January 2000.
86 For more information, see EPA website, “SDWA Economic Analysis” at https://www.epa.gov/dwregdev/economic- 86 For more information, see EPA website, “SDWA Economic Analysis” at https://www.epa.gov/dwregdev/economic-
analysis-and-statutory-requirements. analysis-and-statutory-requirements.
87 SDWA §1412(b)(3)(C)(i)(III); 42 U.S.C. 300g-1(b)(3)(C)(i)(III). 87 SDWA §1412(b)(3)(C)(i)(III); 42 U.S.C. 300g-1(b)(3)(C)(i)(III).
88 SDWA §1412(b)(3)(C)(i)(V); 42 U.S.C. §300g-1(b)(3)(C)(i)(V). 88 SDWA §1412(b)(3)(C)(i)(V); 42 U.S.C. §300g-1(b)(3)(C)(i)(V).
89 For more information, see EPA website89 For more information, see EPA website, “National Benefits Analysis for Drinking Water Regulations” at “National Benefits Analysis for Drinking Water Regulations” at
https://www.epa.gov/sdwa/national-benefits-analysis-drinking-water-regulations. https://www.epa.gov/sdwa/national-benefits-analysis-drinking-water-regulations.
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Health Advisories
For unregulated contaminants, health effects and/or occurrence data often are limited. SDWA authorizes EPA to For unregulated contaminants, health effects and/or occurrence data often are limited. SDWA authorizes EPA to
issue health advisories for contaminants in drinking water that are not regulated under the act.90 Health advisories issue health advisories for contaminants in drinking water that are not regulated under the act.90 Health advisories
provide information for states, water suppliers, and public health officials on health effects, test methods, and provide information for states, water suppliers, and public health officials on health effects, test methods, and
treatment technologies for specific contaminants. Health advisories are non-enforceable and intended to help treatment technologies for specific contaminants. Health advisories are non-enforceable and intended to help
states, water suppliers, and others address contaminants for which federal drinking water standards have not been states, water suppliers, and others address contaminants for which federal drinking water standards have not been
established. Health advisories include levels for contaminants in drinking water that can be used to address established. Health advisories include levels for contaminants in drinking water that can be used to address
different circumstances and exposure durations (e.g., 1 day, 10 days, a lifetime) and technical guidance on different circumstances and exposure durations (e.g., 1 day, 10 days, a lifetime) and technical guidance on
identifying, measuring, and treating contaminants. EPA has issued health advisories to address various identifying, measuring, and treating contaminants. EPA has issued health advisories to address various
circumstances: when contaminants do not meet the statutory criteria to warrant a national primary drinking water circumstances: when contaminants do not meet the statutory criteria to warrant a national primary drinking water
regulation, as an interim measure while EPA evaluates a contaminant for regulation, or to address a short-term regulation, as an interim measure while EPA evaluates a contaminant for regulation, or to address a short-term
incident or spil . incident or spil .
EPA sets the health advisory levels at concentrations that are expected to be protective of the most sensitive EPA sets the health advisory levels at concentrations that are expected to be protective of the most sensitive
subpopulations (e.g., nursing infants) from any deleterious health effects, with a margin of protection, over the subpopulations (e.g., nursing infants) from any deleterious health effects, with a margin of protection, over the
specified duration of exposure. Similar to the calculation of an MCLG, health advisory levels account for exposure specified duration of exposure. Similar to the calculation of an MCLG, health advisory levels account for exposure
from other contaminant sources (e.g., dermal contact, inhalation, and food ingestion). from other contaminant sources (e.g., dermal contact, inhalation, and food ingestion).
Some states have used health advisories to inform their own state-specific drinking water regulations. EPA has Some states have used health advisories to inform their own state-specific drinking water regulations. EPA has
issued health advisories for more than 200 contaminants to address different circumstances and subsequently issued health advisories for more than 200 contaminants to address different circumstances and subsequently
established regulations for many of these contaminants.91 established regulations for many of these contaminants.91
Variances and Exemptions
As discussed above, national primary drinking water regulations consider the costs to large water As discussed above, national primary drinking water regulations consider the costs to large water
systems, which provide water to 83% of the total population regularly served by public water systems, which provide water to 83% of the total population regularly served by public water
systems, yet comprise roughly 9% of the total number of community water systems.92 The systems, yet comprise roughly 9% of the total number of community water systems.92 The
remaining 91% of water systems that serve 10,000 or fewer individuals may lack technical, remaining 91% of water systems that serve 10,000 or fewer individuals may lack technical,
managerial, and financial capacity, leading to regulatory compliance challenges. Congress has managerial, and financial capacity, leading to regulatory compliance challenges. Congress has
long recognized the compliance challenges of “small” systems and has added a suite of provisions long recognized the compliance challenges of “small” systems and has added a suite of provisions
to SDWA to address such challenges. Among these, SDWA includes provisions that provide for to SDWA to address such challenges. Among these, SDWA includes provisions that provide for
“variances” from a drinking water standard and “exemptions” (i.e., additional time for “variances” from a drinking water standard and “exemptions” (i.e., additional time for
compliance with a standard) from drinking water regulations, under specified circumstances. compliance with a standard) from drinking water regulations, under specified circumstances.
Specifically for small systems, states may provide variances if EPA cannot identify an affordable Specifically for small systems, states may provide variances if EPA cannot identify an affordable
technology that reduces the contaminant to the MCL.93 If EPA identifies no such technology, then technology that reduces the contaminant to the MCL.93 If EPA identifies no such technology, then
the agency is required to identify affordable variance technologies that may not meet the MCL.94 the agency is required to identify affordable variance technologies that may not meet the MCL.94
After identifying variance technologies, states may grant small system variances to systems After identifying variance technologies, states may grant small system variances to systems
serving 3,300 or fewer persons if through treatment, an alternative water source, or restructuring, serving 3,300 or fewer persons if through treatment, an alternative water source, or restructuring,
a system cannot afford to comply with the MCL and the variance ensures adequate protection of a system cannot afford to comply with the MCL and the variance ensures adequate protection of
public health.95 Under this type of variance, a state would allow the system to use a variance public health.95 Under this type of variance, a state would allow the system to use a variance
technology to comply with a regulation. With EPA approval, states may also grant variances to technology to comply with a regulation. With EPA approval, states may also grant variances to

90 SDWA §1412(b)(1)(F); 42 U.S.C. §300g-1(b)(1)(F). 90 SDWA §1412(b)(1)(F); 42 U.S.C. §300g-1(b)(1)(F).
91 EPA, 91 EPA, 2018 Edition of the Drinking Water Standards and Health Advisories Tables, March 2018, , March 2018,
https://www.epa.gov/sites/production/files/2018-03/documents/dwtable2018.pdf. https://www.epa.gov/sites/production/files/2018-03/documents/dwtable2018.pdf.
92 From EPA’s “Safe Drinking Water Information Systems: Water System Summary” report at https://ofmpub.epa.gov/ 92 From EPA’s “Safe Drinking Water Information Systems: Water System Summary” report at https://ofmpub.epa.gov/
apex/sfdw/f?p=108:1:::NO:1::. Report generated on October 23, 2020. The search parameters were “public water apex/sfdw/f?p=108:1:::NO:1::. Report generated on October 23, 2020. The search parameters were “public water
systems.” systems.”
93 SDWA §1415(e); 42 U.S.C. §300g-4(e). In addition, SDWA §1415 authorizes states to grant a public water system a 93 SDWA §1415(e); 42 U.S.C. §300g-4(e). In addition, SDWA §1415 authorizes states to grant a public water system a
variance from an MCL if the untreated source water quality prevents meeting MCL even after application of best variance from an MCL if the untreated source water quality prevents meeting MCL even after application of best
technology, and the variance does not result in an unreasonable risk to health. technology, and the variance does not result in an unreasonable risk to health.
94 SDWA §1412(b)(15); 42 U.S.C. §300g-1(b)(15). 94 SDWA §1412(b)(15); 42 U.S.C. §300g-1(b)(15).
95 SDWA §1415(e); 42 U.S.C. §300g-4(e). 95 SDWA §1415(e); 42 U.S.C. §300g-4(e).
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systems serving between 3,301 and 10,000 persons. Variances are not available for microbial systems serving between 3,301 and 10,000 persons. Variances are not available for microbial
contaminants. For every drinking water regulation, EPA has determined that compliance contaminants. For every drinking water regulation, EPA has determined that compliance
technologies for all MCLs are affordable for small systems; and as such, small system variances technologies for all MCLs are affordable for small systems; and as such, small system variances
are not available. are not available.
SDWA Section 1416 authorizes states to grant public water systems temporary exemptions from SDWA Section 1416 authorizes states to grant public water systems temporary exemptions from
drinking water regulations if a system cannot comply for other compelling reasons (including drinking water regulations if a system cannot comply for other compelling reasons (including
costs). An exemption is intended to give a water system additional time to come into compliance costs). An exemption is intended to give a water system additional time to come into compliance
with a regulation and is limited to situations where an exemption would not result in an with a regulation and is limited to situations where an exemption would not result in an
unreasonable health risk. Exemptions can be issued to a qualified system for up to three unreasonable health risk. Exemptions can be issued to a qualified system for up to three
additional years beyond the regulation’s effective date. Systems serving 3,300 or fewer persons additional years beyond the regulation’s effective date. Systems serving 3,300 or fewer persons
may receive a maximum of three additional two-year extensions for total exemption duration of may receive a maximum of three additional two-year extensions for total exemption duration of
nine years. nine years.
Six-Year Reviews
SDWA directs EPA, every six years, to review and revise, if necessary, each regulation and SDWA directs EPA, every six years, to review and revise, if necessary, each regulation and
requires that any revision maintain or provide greater health protection.96 EPA considers possible requires that any revision maintain or provide greater health protection.96 EPA considers possible
revisions, if the revision could improve the level of public health protection or achieve cost revisions, if the revision could improve the level of public health protection or achieve cost
savings while maintaining or improving public health protection. savings while maintaining or improving public health protection.
Since 1996, EPA has completed three cycles of the “Six-Year Review.” For the first cycle, EPA Since 1996, EPA has completed three cycles of the “Six-Year Review.” For the first cycle, EPA
determined to revise the Total Coliform Rule.97 For the second cycle in 2010, EPA determined to determined to revise the Total Coliform Rule.97 For the second cycle in 2010, EPA determined to
revise the regulations for four contaminants (i.e., acrylamide, epichlorohydrin, revise the regulations for four contaminants (i.e., acrylamide, epichlorohydrin,
tetrachloroethylene, and trichloroethylene).98 For the third cycle in 2017, EPA determined to tetrachloroethylene, and trichloroethylene).98 For the third cycle in 2017, EPA determined to
revise eight regulations, which are part of the following rules: (1) the Stage 1 and the Stage 2 revise eight regulations, which are part of the following rules: (1) the Stage 1 and the Stage 2
Disinfectants and Disinfection Byproducts Rules, (2) the Surface Water Treatment Rule, (3) the Disinfectants and Disinfection Byproducts Rules, (2) the Surface Water Treatment Rule, (3) the
Interim Enhanced Surface Water Treatment Rule, and (4) the Long Term Enhanced Surface Interim Enhanced Surface Water Treatment Rule, and (4) the Long Term Enhanced Surface
Water Treatment Rule.99 EPA has promulgated revisions for a number of these regulations. Water Treatment Rule.99 EPA has promulgated revisions for a number of these regulations.
Table 3 includes a summary of EPA’s actions to evaluate or revise contaminants for regulation includes a summary of EPA’s actions to evaluate or revise contaminants for regulation
under the Safe Drinking Water Act, since the 1996 SDWA amendments that established the act’s under the Safe Drinking Water Act, since the 1996 SDWA amendments that established the act’s
current process. current process.

96 SDWA §1412(b)(9); 42 U.S.C. §300g-1(b)(9). 96 SDWA §1412(b)(9); 42 U.S.C. §300g-1(b)(9).
97 EPA, “National Primary Drinking Water Regulations; Announcement of Completion of EPA’s Review of Existing 97 EPA, “National Primary Drinking Water Regulations; Announcement of Completion of EPA’s Review of Existing
Drinking Water Standards,” 68Drinking Water Standards,” 68 Federal Register 42907-42929, July 18, 2003. 42907-42929, July 18, 2003.
98 EPA, “National Primary Drinking Water Regulations; Announcement of the Results of EPA’s Review of Existing 98 EPA, “National Primary Drinking Water Regulations; Announcement of the Results of EPA’s Review of Existing
Drinking Water Standards and Request for Public Comment and/or Information on Related Issues,” 75Drinking Water Standards and Request for Public Comment and/or Information on Related Issues,” 75 Federal
Register 15499-15572, March 29, 2010. 15499-15572, March 29, 2010.
99 EPA, “National Primary Drinking Water Regulations; Announcement of the Results of EPA’s Review of Existing 99 EPA, “National Primary Drinking Water Regulations; Announcement of the Results of EPA’s Review of Existing
Drinking Water Standards and Request for Public Comment and/or Information on Related Issues,” 82Drinking Water Standards and Request for Public Comment and/or Information on Related Issues,” 82 Federal
Register 3518-3552, January 11, 2017. 3518-3552, January 11, 2017.
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Table 3. EPA’s Drinking Water Contaminant Regulatory Development Actions

First
Second
Third
Fourth
CCL
1998
2005
2009
2016

60 contaminants 60 contaminants
51 contaminants 51 contaminants
116 contaminants 116 contaminants
109 contaminants 109 contaminants
UCMR
1999
2007
2012
2016

36 contaminants 36 contaminants
25 contaminants 25 contaminants
30 contaminants 30 contaminants
30 contaminants 30 contaminants
RD
2003
2008
2016
2021
Evaluated
9 contaminants 9 contaminants
11 contaminants 11 contaminants
5 contaminants 5 contaminants
8 contaminants
(including (including
perchlorate) perchlorate)
Determination to
None None
~~Nonea~~
~~Noneb~~
Nonea Noneb EPA proposed to
Regulate
regulate PFOA and
~~PFOS~~PFOScc
Six-Year Reviews
2003
2010
2017
2023
Evaluated
69 national primary 69 national primary
71 NPDWRs 71 NPDWRs
76 NPDWRs 76 NPDWRs
Forthcoming
drinking water drinking water

regulations regulations
(NPDWRs) (NPDWRs)
Chosen for Revision
1 NPDWR 1 NPDWR
4 NPDWRs 4 NPDWRs
8 NPDWRs 8 NPDWRs

Source: Compiled by CRS from epa.gov. For additional detail on CCLs, UCMRs and RDs, and specific Compiled by CRS from epa.gov. For additional detail on CCLs, UCMRs and RDs, and specific
references, references, see see Appendix A, Appendix B, and and Appendix C, r~~espectively~~respectively. .
a. In 2011, the Administrator determined that regulation was needed for perchlorate, reversing the 2008 a. In 2011, the Administrator determined that regulation was needed for perchlorate, reversing the 2008
negative determination (76 negative determination (76 Federal Register 7762). In July 2020, the Administrator withdrew the 2011 7762). In July 2020, the Administrator withdrew the 2011
determination to regulate perchlorate, and made a final determination not to regulate perchlorate (85 determination to regulate perchlorate, and made a final determination not to regulate perchlorate (85
Federal Register 43990). 43990).
b. EPA delayed the determination for strontium to consider additional data (81 b. EPA delayed the determination for strontium to consider additional data (81 Federal Register 13). 13).
c. In February 2020, EPA published preliminary determinations to regulate PFOA and PFOS in 85 c. In February 2020, EPA published preliminary determinations to regulate PFOA and PFOS in 85 Federal
Register 14098. The agency stated its intents to finalize these proposed RDs by January 2021 in the 14098. The agency stated its intents to finalize these proposed RDs by January 2021 in the Fall 2020
Unified Agenda of Regulatory and Deregulatory Action. .
Considerations for Contaminant Regulation
SDWA broadly outlines the regulatory assessment and development process, yet several technical SDWA broadly outlines the regulatory assessment and development process, yet several technical
and policy considerations arise when implementing the process. Technical considerations include and policy considerations arise when implementing the process. Technical considerations include
the availability and quality of health effects and occurrence data, and the availability of validated the availability and quality of health effects and occurrence data, and the availability of validated
analytical test methods, as well as sufficient laboratory capacity and availability of a feasible analytical test methods, as well as sufficient laboratory capacity and availability of a feasible
treatment technology. Overarching considerations include prioritizing among thousands of treatment technology. Overarching considerations include prioritizing among thousands of
potential contaminants, addressing contaminants that may not meet the act’s criteria to warrant potential contaminants, addressing contaminants that may not meet the act’s criteria to warrant
regulation but still generate public health concern, and competing priorities for agency resources regulation but still generate public health concern, and competing priorities for agency resources
to support drinking water contaminant evaluation and regulation development. to support drinking water contaminant evaluation and regulation development.
Data Availability and Quality
Implementation of the act’s process for evaluating contaminants for regulation and developing Implementation of the act’s process for evaluating contaminants for regulation and developing
drinking water regulations depends on data availability and quality. For unregulated drinking water regulations depends on data availability and quality. For unregulated
contaminants, EPA may lack the necessary health effects and/or occurrence data to consider such contaminants, EPA may lack the necessary health effects and/or occurrence data to consider such
contaminants for regulation. To add a contaminant to the CCL, EPA requires initial data to contaminants for regulation. To add a contaminant to the CCL, EPA requires initial data to
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characterize the contaminant’s occurrence and adverse health effects.100 Similarly, when selecting characterize the contaminant’s occurrence and adverse health effects.100 Similarly, when selecting
contaminants for monitoring as a part of a UCMR, EPA evaluates a contaminant’s health effects, contaminants for monitoring as a part of a UCMR, EPA evaluates a contaminant’s health effects,
prioritizing contaminants associated with carcinogenic health effects.101 To make a regulatory prioritizing contaminants associated with carcinogenic health effects.101 To make a regulatory
determination for a contaminant, EPA requires a peer-reviewed risk assessment and nationally determination for a contaminant, EPA requires a peer-reviewed risk assessment and nationally
representative occurrence data.102 Without these data, EPA is unable to evaluate whether a representative occurrence data.102 Without these data, EPA is unable to evaluate whether a
contaminant meets the statutory criteria for regulation. contaminant meets the statutory criteria for regulation.
To establish an MCLG and drinking water standard, EPA requires a peer-reviewed risk To establish an MCLG and drinking water standard, EPA requires a peer-reviewed risk
assessment to evaluate a contaminant’s health effects, as well as to identify and account for assessment to evaluate a contaminant’s health effects, as well as to identify and account for
effects on the most sensitive subpopulations.103 When developing an HRRCA, EPA requires effects on the most sensitive subpopulations.103 When developing an HRRCA, EPA requires
health effects data to estimate benefits associated with reducing the risk of exposure as well as health effects data to estimate benefits associated with reducing the risk of exposure as well as
occurrence data and field-tested treatment technologies to estimate the cost of treatment needed to occurrence data and field-tested treatment technologies to estimate the cost of treatment needed to
comply. Without data to estimate the costs and benefits of regulating a contaminant, EPA is comply. Without data to estimate the costs and benefits of regulating a contaminant, EPA is
unable to calculate the benefits from reduced health risks or the regulatory costs to communities unable to calculate the benefits from reduced health risks or the regulatory costs to communities
and others. and others.
The absence of sufficient data for unregulated contaminants has limited EPA’s implementation of The absence of sufficient data for unregulated contaminants has limited EPA’s implementation of
SDWA regulatory development provisions.104 EPA has often been unable to include unregulated SDWA regulatory development provisions.104 EPA has often been unable to include unregulated
contaminants for regulatory determinations due to an absence of a peer-reviewed risk assessment contaminants for regulatory determinations due to an absence of a peer-reviewed risk assessment
or nationally representative occurrence data. For several contaminants evaluated for RDs (e.g., or nationally representative occurrence data. For several contaminants evaluated for RDs (e.g.,
perchlorate, strontium), EPA delayed finalizing determinations to collect additional data.105 In perchlorate, strontium), EPA delayed finalizing determinations to collect additional data.105 In
2011, GAO released its report 2011, GAO released its report EPA Should Improve Implementation of Requirements on Whether
to Regulate Additional Contaminants. GAO concluded that insufficient data to characterize . GAO concluded that insufficient data to characterize
contaminant occurrence or health effects had impeded EPA progress in regulating contaminants in contaminant occurrence or health effects had impeded EPA progress in regulating contaminants in
drinking water.106 drinking water.106
Availability of Analytical Methods and Laboratory Capacity
EPA’s ability to develop contaminant occurrence data for the SDWA regulatory determinations EPA’s ability to develop contaminant occurrence data for the SDWA regulatory determinations
depends on the availability of analytical test methods and laboratory capacity. For each depends on the availability of analytical test methods and laboratory capacity. For each
contaminant in an UCMR, EPA requires a widely available analytical test method and sufficient contaminant in an UCMR, EPA requires a widely available analytical test method and sufficient
laboratory capacity to support nationwide monitoring.107 As a part of the UCMR, EPA may assist laboratory capacity to support nationwide monitoring.107 As a part of the UCMR, EPA may assist

100 EPA, “Drinking Water Contaminant Candidate List 3-Draft,” 73 100 EPA, “Drinking Water Contaminant Candidate List 3-Draft,” 73 Federal Register 9631, February 21, 2008. 9631, February 21, 2008.
101 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems,” 76101 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems,” 76
Federal Register 11713-11737, March 3, 2011. 11713-11737, March 3, 2011.
102 EPA, “Drinking Water Contaminant Candidate List 4-Draft,” 80 102 EPA, “Drinking Water Contaminant Candidate List 4-Draft,” 80 Federal Register 6078, February 4, 2015. 6078, February 4, 2015.
103 EPA, “Preliminary Regulatory Determinations for Contaminants on the Third Contaminant Candidate List,” 79103 EPA, “Preliminary Regulatory Determinations for Contaminants on the Third Contaminant Candidate List,” 79
Federal Register 62715-62750, October 20, 2014. 62715-62750, October 20, 2014.
104 See, for example, Table 2, “Information Gaps for the CCL 2 Chemical Contaminants,” EPA, “Drinking Water: 104 See, for example, Table 2, “Information Gaps for the CCL 2 Chemical Contaminants,” EPA, “Drinking Water:
Regulatory Determinations Regarding Contaminants on the Second Drinking Water Contaminant Candidate List,” 73Regulatory Determinations Regarding Contaminants on the Second Drinking Water Contaminant Candidate List,” 73
Federal Register 44260, July 30, 2008. 44260, July 30, 2008.
105 EPA, “Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water 105 EPA, “Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water
Contaminant Candidate List-Preliminary Determinations,” 72Contaminant Candidate List-Preliminary Determinations,” 72 Federal Register 24038-24052, May 1, 2007. EPA, 24038-24052, May 1, 2007. EPA,
“Announcement of Final Regulatory Determinations for Contaminants on the Third Drinking Water Contaminant “Announcement of Final Regulatory Determinations for Contaminants on the Third Drinking Water Contaminant
Candidate List,” 81Candidate List,” 81 Federal Register 18, January 4, 2016. 18, January 4, 2016.
106 GAO, 106 GAO, EPA Should Improve Implementation of Requirements on Whether to Regulate Additional Contaminants, 11-, 11-
254, May 27, 2011, at https://www.gao.gov/products/GAO-11-254. 254, May 27, 2011, at https://www.gao.gov/products/GAO-11-254.
107 EPA, “Drinking Water Contaminant Candidate List 4-Draft,” 80 107 EPA, “Drinking Water Contaminant Candidate List 4-Draft,” 80 Federal Register 6078, February 4, 2015. 6078, February 4, 2015.
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with the development of new analytical methods and/or identify consensus organization- with the development of new analytical methods and/or identify consensus organization-
developed methods.108 developed methods.108
In preparation of a UCMR, laboratories across the country must receive EPA approval certifying In preparation of a UCMR, laboratories across the country must receive EPA approval certifying
that they have demonstrated that they can perform the method with replicable results.109 EPA that they have demonstrated that they can perform the method with replicable results.109 EPA
requires laboratories that wish to participate in UCMRs to apply and receive approval through requires laboratories that wish to participate in UCMRs to apply and receive approval through
EPA’s Laboratory Approval Program, which requires demonstrated method proficiency with EPA’s Laboratory Approval Program, which requires demonstrated method proficiency with
analytical standards.110 EPA cannot select a contaminant for a UCMR without a validated analytical standards.110 EPA cannot select a contaminant for a UCMR without a validated
analytical method and sufficient laboratory capacity to support a national monitoring program. analytical method and sufficient laboratory capacity to support a national monitoring program.
The availability of an analytical test method also informs EPA’s ability to establish an MCL as The availability of an analytical test method also informs EPA’s ability to establish an MCL as
close to the MCLG as “feasible.” To assess feasibility, EPA first evaluates the sensitivity of the close to the MCLG as “feasible.” To assess feasibility, EPA first evaluates the sensitivity of the
test method to detect a contaminant at levels close to the MCLG. Without a method that could test method to detect a contaminant at levels close to the MCLG. Without a method that could
detect a noncarcinogenic contaminant at the “goal” level, EPA would not be able to set an MCL at detect a noncarcinogenic contaminant at the “goal” level, EPA would not be able to set an MCL at
the MCLG.111 the MCLG.111

108 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems,” 76108 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems,” 76
Federal Register 11713-11737, March 3, 2011. For UCMR 3, EPA developed six analytical methods and identified 11713-11737, March 3, 2011. For UCMR 3, EPA developed six analytical methods and identified
four equivalent methods from consensus organizations (e.g., Standard Methods and ASTM International). four equivalent methods from consensus organizations (e.g., Standard Methods and ASTM International).
109 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems,” 76 109 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems,” 76
Federal Register 11720- 11721, March 3, 2011. 11720- 11721, March 3, 2011.
110 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems,” 76 110 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems,” 76
Federal Register 11713-11737, March 3, 2011. 11713-11737, March 3, 2011.
111 For contaminants with carcinogenic effects, EPA sets the MCLG at zero. Without an available treatment technology 111 For contaminants with carcinogenic effects, EPA sets the MCLG at zero. Without an available treatment technology
to reduce a carcinogen to zero, EPA would be unable to set the MCL at the MCLG. to reduce a carcinogen to zero, EPA would be unable to set the MCL at the MCLG.
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Consideration of Contaminant Group Regulations
In the 116th Congress, legislation was introduced to regulate certain contaminants (i.e., some or all PFAS) as a In the 116th Congress, legislation was introduced to regulate certain contaminants (i.e., some or all PFAS) as a
group. The SDWA definition of a “primary drinking water regulation” specifies that each contaminant has an MCL group. The SDWA definition of a “primary drinking water regulation” specifies that each contaminant has an MCL
or a treatment technique. EPA has regulated some contaminants as groups (e.g., different types of disinfection or a treatment technique. EPA has regulated some contaminants as groups (e.g., different types of disinfection
byproduct groups [total trihalomethanes and total haloacetic acids], and gross alpha radionuclides, etc.). Thus far, byproduct groups [total trihalomethanes and total haloacetic acids], and gross alpha radionuclides, etc.). Thus far,
EPA has made regulatory determinations for individual contaminants, although, the agency has considered making EPA has made regulatory determinations for individual contaminants, although, the agency has considered making
regulatory determinations for contaminant groups. regulatory determinations for contaminant groups.
In 2010, EPA released its Drinking Water Strategy, which included a principle to address drinking water In 2010, EPA released its Drinking Water Strategy, which included a principle to address drinking water
contaminants as groups so that drinking water protection can be achieved cost effectively.112 To issue a single contaminants as groups so that drinking water protection can be achieved cost effectively.112 To issue a single
drinking water regulation for a group of contaminants, EPA stated that, at a minimum, all the contaminants must drinking water regulation for a group of contaminants, EPA stated that, at a minimum, all the contaminants must
have the same specific adverse health effect (e.g., cancer, endocrine effects, or developmental effects), be have the same specific adverse health effect (e.g., cancer, endocrine effects, or developmental effects), be
measured by the same analytical methods, be treated with the same treatment technology or treatment technique, measured by the same analytical methods, be treated with the same treatment technology or treatment technique,
and/or been shown to occur individually (and possibly co-occur).113 For RD 3, EPA considered regulating several and/or been shown to occur individually (and possibly co-occur).113 For RD 3, EPA considered regulating several
contaminants as a group, but ultimately decided to address one group of drinking water compounds, carcinogenic contaminants as a group, but ultimately decided to address one group of drinking water compounds, carcinogenic
volatile organic compounds, through a separate regulatory process.114 volatile organic compounds, through a separate regulatory process.114
For certain contaminants, group regulation may pose challenges. Certain contaminants may have some broad For certain contaminants, group regulation may pose challenges. Certain contaminants may have some broad
chemical similarities; however, such contaminants may have different health effects or require different sampling chemical similarities; however, such contaminants may have different health effects or require different sampling
methods and treatment technologies or do not yet have analytical methods developed to detect their occurrence methods and treatment technologies or do not yet have analytical methods developed to detect their occurrence
in drinking water. Establishing an enforceable standard for a group of contaminants also poses a technical challenge in drinking water. Establishing an enforceable standard for a group of contaminants also poses a technical challenge
as the health risk reduction and cost analysis requires assessment of the risk reduction benefits and compliance as the health risk reduction and cost analysis requires assessment of the risk reduction benefits and compliance
costs for each contaminant. Individual contaminants may have varying MCLs depending on the treatment costs and costs for each contaminant. Individual contaminants may have varying MCLs depending on the treatment costs and
health effects for each contaminant, which would affect the treatment technologies available to public water health effects for each contaminant, which would affect the treatment technologies available to public water
systems to comply with such a regulation. systems to comply with such a regulation.
Congressional Actions
Congressional interest in SDWA regulatory development provisions Congressional interest in SDWA regulatory development provisions ~~have~~has centered on EPA’s centered on EPA’s
implementation of these provisions, as well as the functionality of the current process. Since the implementation of these provisions, as well as the functionality of the current process. Since the
1996 SDWA amendments, EPA has finalized a positive regulatory determination for one 1996 SDWA amendments, EPA has finalized a positive regulatory determination for one
contaminant, perchlorate. After initially proposing a determination not to regulate perchlorate in contaminant, perchlorate. After initially proposing a determination not to regulate perchlorate in
2008, EPA reversed the proposal and finalized a positive determination in 2011. In 2020, EPA 2008, EPA reversed the proposal and finalized a positive determination in 2011. In 2020, EPA
withdrew the 2011 positive determination, and separately proposed to regulate two per- and withdrew the 2011 positive determination, and separately proposed to regulate two per- and
polyfluoroalkyl substances (PFAS). polyfluoroalkyl substances (PFAS). EPA finalized positive regulatory determinations for the two PFAS in March 2021. Since 1996, EPA has evaluated thousands of chemicals for Since 1996, EPA has evaluated thousands of chemicals for
potential regulation, and developed health effects and occurrence data for numerous unregulated potential regulation, and developed health effects and occurrence data for numerous unregulated
contaminants. The agency has revised several drinking water regulations to tighten standards and contaminants. The agency has revised several drinking water regulations to tighten standards and
has revised and expanded other existing regulations to establish MCLs for additional has revised and expanded other existing regulations to establish MCLs for additional
contaminants, but has not promulgated a national primary drinking water regulation based on a contaminants, but has not promulgated a national primary drinking water regulation based on a
finalized positive regulatory determination. finalized positive regulatory determination.
Some Members of Congress have raised concerns that the act’s process is lengthy and Some Members of Congress have raised concerns that the act’s process is lengthy and
complicated and does not allow for the timely regulation of contaminants of concern in drinking complicated and does not allow for the timely regulation of contaminants of concern in drinking
~~water.115 Others have expressed concern that proposals to expedite regulation by removing~~

112 EPA, 112 EPA, A New Approach to Protecting Drinking Water and Public Health, EPA 815F10001, March 2010, at , EPA 815F10001, March 2010, at
https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1006RG2.txt. https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1006RG2.txt.
113 EPA, “Preliminary Regulatory Determinations for Contaminants on the Third Contaminant Candidate List,” 79 113 EPA, “Preliminary Regulatory Determinations for Contaminants on the Third Contaminant Candidate List,” 79
Federal Register 62715-62750, October 20, 2014, at https://www.regulations.gov/document?D=EPA-HQ-OW-2012- 62715-62750, October 20, 2014, at https://www.regulations.gov/document?D=EPA-HQ-OW-2012-
0155-0001. 0155-0001.
114 EPA also considered regulating other contaminants as a group. For further discussion, see EPA, “Preliminary 114 EPA also considered regulating other contaminants as a group. For further discussion, see EPA, “Preliminary
Regulatory Determinations for Contaminants on the Third Contaminant Candidate List,” 79Regulatory Determinations for Contaminants on the Third Contaminant Candidate List,” 79 Federal Register 62715- 62715-
62750. 62750.
~~115 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change,~~
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water.115 Others have expressed concern that proposals to expedite regulation by removing elements of SDWA regulatory development provisions (e.g., the requirement to use peer-reviewed elements of SDWA regulatory development provisions (e.g., the requirement to use peer-reviewed
science or a health risk-based approach) may result in compliance costs and affordability science or a health risk-based approach) may result in compliance costs and affordability
challenges for communities to address contaminants that may not pose a significant threat to challenges for communities to address contaminants that may not pose a significant threat to
public health.116 In the absence of federal drinking water standards, some states have issued public health.116 In the absence of federal drinking water standards, some states have issued
regulations for contaminants, such as specific PFAS, that vary from state to state. Some Members regulations for contaminants, such as specific PFAS, that vary from state to state. Some Members
have argued that this patchwork of regulation undermines public confidence in drinking water have argued that this patchwork of regulation undermines public confidence in drinking water
quality.117 Other quality.117 Other ~~members~~Members caution that proposals to amend SDWA to increase regulatory pace caution that proposals to amend SDWA to increase regulatory pace
would add to states’ financial burdens without meaningful health protection, as drinking water would add to states’ financial burdens without meaningful health protection, as drinking water
regulation enforcement is generally a state responsibility.118 Other issues include how costs are regulation enforcement is generally a state responsibility.118 Other issues include how costs are
considered in the standard-setting process, whether the development of a “feasible” standard is considered in the standard-setting process, whether the development of a “feasible” standard is
sufficiently protective of sensitive subpopulations, and the affordability of regulations for small sufficiently protective of sensitive subpopulations, and the affordability of regulations for small
and disadvantaged communities. In addition, EPA’s implementation of these provisions and the and disadvantaged communities. In addition, EPA’s implementation of these provisions and the
number of positive regulatory determinations has garnered congressional interest. number of positive regulatory determinations has garnered congressional interest.
In the 116th Congress, legislation was introduced to direct EPA to regulate specific contaminants In the 116th Congress, legislation was introduced to direct EPA to regulate specific contaminants
(e.g., PFOA and PFOS).119 Other bills would have established a different regulatory process and (e.g., PFOA and PFOS).119 Other bills would have established a different regulatory process and
deadlines for specific contaminants or group of contaminants (i.e., PFAS).120 Representatives of deadlines for specific contaminants or group of contaminants (i.e., PFAS).120 Representatives of
water systems have supported EPA’s commitment to following the statutory process for water systems have supported EPA’s commitment to following the statutory process for
regulating contaminants that prioritizes reducing health risks, and state drinking water regulating contaminants that prioritizes reducing health risks, and state drinking water
administrators have urged EPA to issue PFAS regulations to establish uniformity among the administrators have urged EPA to issue PFAS regulations to establish uniformity among the
states.121 Recent appropriations acts have directed EPA to use specified funds to support MCL states.121 Recent appropriations acts have directed EPA to use specified funds to support MCL
~~development and to brief the conferees on the agency’s plans to develop MCLs for specific~~

115 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change, There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, Testimony of Subcommittee , Testimony of Subcommittee
Chairman Tonko, 116th Cong., 2nd sess., July 28, 2020, at https://energycommerce.house.gov/sites/Chairman Tonko, 116th Cong., 2nd sess., July 28, 2020, at https://energycommerce.house.gov/sites/
democrats.energycommerce.house.gov/files/documents/democrats.energycommerce.house.gov/files/documents/
072820%20ECC%20SDWA%20Reform%20Hearing%20PT%20Opening_0.pdf. 072820%20ECC%20SDWA%20Reform%20Hearing%20PT%20Opening_0.pdf.
116 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change, 116 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change,
There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, Testimony of Ranking Member , Testimony of Ranking Member
Walden, 116th Cong., 2nd sess., July 28, 2020, at https://republicans-energycommerce.house.gov/news/walden-facts-Walden, 116th Cong., 2nd sess., July 28, 2020, at https://republicans-energycommerce.house.gov/news/walden-facts-
and-science-matter/. and-science-matter/.
117 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change, 117 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change,
There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, Testimony of Subcommittee , Testimony of Subcommittee
Chairman Tonko, 116th Cong., 2nd sess., July 28, 2020, at https://energycommerce.house.gov/sites/Chairman Tonko, 116th Cong., 2nd sess., July 28, 2020, at https://energycommerce.house.gov/sites/
democrats.energycommerce.house.gov/files/documents/democrats.energycommerce.house.gov/files/documents/
072820%20ECC%20SDWA%20Reform%20Hearing%20PT%20Opening_0.pdf. 072820%20ECC%20SDWA%20Reform%20Hearing%20PT%20Opening_0.pdf.
118 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change, 118 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change,
There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, Testimony of Ranking Member , Testimony of Ranking Member
Walden, 116th Cong., 2nd sess., July 28, 2020. SDWA §1413 (42 U.S.C. §300g-2) requires EPA to delegate primary Walden, 116th Cong., 2nd sess., July 28, 2020. SDWA §1413 (42 U.S.C. §300g-2) requires EPA to delegate primary
enforcement authority for SDWA regulations to states that meet certain criteria. Currently, 49 states, the territories, and enforcement authority for SDWA regulations to states that meet certain criteria. Currently, 49 states, the territories, and
the Navajo Nation have applied for and received primacy for the drinking water program. EPA retains implementation the Navajo Nation have applied for and received primacy for the drinking water program. EPA retains implementation
and enforcement authority for Wyoming, the District of Columbia, and Indian tribes other than the Navajo Nation. and enforcement authority for Wyoming, the District of Columbia, and Indian tribes other than the Navajo Nation.
119 On occasion, Congress has directed EPA to promulgate a regulation for a particular contaminant within a specified 119 On occasion, Congress has directed EPA to promulgate a regulation for a particular contaminant within a specified
timeframe. For example, in the Safe Drinking Water Amendments of 1996 (P.L. 104-182), the 104th Congress directed timeframe. For example, in the Safe Drinking Water Amendments of 1996 (P.L. 104-182), the 104th Congress directed
EPA to regulate radon, propose a new arsenic standard, and evaluate sulfate for regulation (SDWA §1412(b)(12); 42 EPA to regulate radon, propose a new arsenic standard, and evaluate sulfate for regulation (SDWA §1412(b)(12); 42
U.S.C. §300g(b)(12); SDWA §1412(b)(13); 42 U.S.C. §300g(b)(13)). U.S.C. §300g(b)(12); SDWA §1412(b)(13); 42 U.S.C. §300g(b)(13)).
120 For a discussion of such bills, see CRS Report R45793, 120 For a discussion of such bills, see CRS Report R45793, PFAS and Drinking Water: Selected EPA and
Congressional Actions, by Elena H. Humphreys and Mary Tiemann. , by Elena H. Humphreys and Mary Tiemann.
121 See for example, testimonies of Tracy Mehan for the American Water Works Association and Lisa Daniels for the 121 See for example, testimonies of Tracy Mehan for the American Water Works Association and Lisa Daniels for the
Association of State Drinking Water Administrators before the House Committee on Energy and Commerce, Association of State Drinking Water Administrators before the House Committee on Energy and Commerce,
Subcommittee on Environment and Climate Change, hearing on Protecting Americans at Risk of PFAS Contamination Subcommittee on Environment and Climate Change, hearing on Protecting Americans at Risk of PFAS Contamination
and Exposure, May 15, 2019, at https://energycommerce.house.gov/committee-activity/hearings/hearing-on-protecting-and Exposure, May 15, 2019, at https://energycommerce.house.gov/committee-activity/hearings/hearing-on-protecting-
~~americans-at-risk-of-pfas-contamination-exposure.~~
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development and to brief the conferees on the agency’s plans to develop MCLs for specific drinking water contaminants. For example, the explanatory statement for the Consolidated drinking water contaminants. For example, the explanatory statement for the Consolidated
Appropriations Act, 2021 (P.L. 116-260) directed EPA to dedicate $1.5 million to the agency’s Appropriations Act, 2021 (P.L. 116-260) directed EPA to dedicate $1.5 million to the agency’s
ongoing work to develop PFAS MCLs.122 ongoing work to develop PFAS MCLs.122
In July 2020, the House Committee on Energy and Commerce, Subcommittee on Environment In July 2020, the House Committee on Energy and Commerce, Subcommittee on Environment
and Climate Change, held an oversight hearing on the subject of EPA implementation of SDWA and Climate Change, held an oversight hearing on the subject of EPA implementation of SDWA
standard-setting provisions.123 The standard-setting provisions.123 The ~~Chairman~~chairman of the of the ~~Committee~~committee, Frank Pallone, stated that “there , Frank Pallone, stated that “there
are fundamental weaknesses in both the design and the implementation of the Safe Drinking are fundamental weaknesses in both the design and the implementation of the Safe Drinking
Water Act....Water Act.... ”124 Citing the lack of positive regulatory determinations, Chairman Pallone stated ”124 Citing the lack of positive regulatory determinations, Chairman Pallone stated
that the act’s current standardthat the act’s current standard -setting process “simply, does not work.”125 In the hearing, concerns setting process “simply, does not work.”125 In the hearing, concerns
over EPA’s regulatory pace paralleled those that spurred the 1986 SDWA amendments. Ranking over EPA’s regulatory pace paralleled those that spurred the 1986 SDWA amendments. Ranking
~~Committee Member~~committee member Greg Walden cautioned against eliminating EPA’s flexibility to set a Greg Walden cautioned against eliminating EPA’s flexibility to set a
drinking water standard at a level other than what is “feasible” for large systems, which may drinking water standard at a level other than what is “feasible” for large systems, which may
result in cost and affordability challenges for certain communities to comply with regulations that result in cost and affordability challenges for certain communities to comply with regulations that
do not provide commensurate public health protection.126 Other concerns involved the third do not provide commensurate public health protection.126 Other concerns involved the third
regulatory determination criterion, which gives some discretion to the Administrator to assess regulatory determination criterion, which gives some discretion to the Administrator to assess
what constitutes a “meaningful opportunity for health risk reduction.”127 Others argued that what constitutes a “meaningful opportunity for health risk reduction.”127 Others argued that
proposals that focus on the quantity of drinking water regulations, or the presence of a proposals that focus on the quantity of drinking water regulations, or the presence of a
contaminant rather than risk, may lead EPA to focus agency resources on promulgating contaminant rather than risk, may lead EPA to focus agency resources on promulgating
regulations without a scientific basis or on regulating “lower priority” contaminants with fewer regulations without a scientific basis or on regulating “lower priority” contaminants with fewer
health impacts to meet quotas, as happened with the 1986 amendments.128 health impacts to meet quotas, as happened with the 1986 amendments.128
Other concerns involved how, under SDWA, regulatory costs to water systems and customer Other concerns involved how, under SDWA, regulatory costs to water systems and customer
affordability are considered when EPA sets a drinking water standard. Particularly for small water affordability are considered when EPA sets a drinking water standard. Particularly for small water
~~systems, and communities with declining populations or economies, efforts to accelerate~~
~~regulatory pace by removing consideration of a contaminant’s health risk reduction benefits or~~
~~occurrence may increase the cost of providing water and result in more water affordability~~

americans-at-risk-of-pfas-contamination-exposure. 122 U.S. Congress, House Committee on Appropriations, 122 U.S. Congress, House Committee on Appropriations, Department of the Interior, Environmental, and Related
Agencies Appropriation Bill, 2021, report to accompany H.R. 7612, 116th Cong., 2nd sess., July 14, 2020, H.Rept. 116-, report to accompany H.R. 7612, 116th Cong., 2nd sess., July 14, 2020, H.Rept. 116-
448, p. 96. 448, p. 96.
123 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change, 123 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change,
There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, 116th Cong., 2nd sess., July 28, , 116th Cong., 2nd sess., July 28,
2020, at https://energycommerce.house.gov/committee-activity/hearings/hearing-on-theres-something-in-the-water-2020, at https://energycommerce.house.gov/committee-activity/hearings/hearing-on-theres-something-in-the-water-
reforming-our-nations-drinking. reforming-our-nations-drinking.
124 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change, 124 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change,
There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, 116th Cong., 2nd sess., July 28, , 116th Cong., 2nd sess., July 28,
2020, Testimony of Chairman Pallone, at https://energycommerce.house.gov/sites/2020, Testimony of Chairman Pallone, at https://energycommerce.house.gov/sites/
democrats.energycommerce.house.gov/files/documents/democrats.energycommerce.house.gov/files/documents/
072820%20ECC%20SDWA%20Reform%20Hearing%20FP%20Opening.pdf. 072820%20ECC%20SDWA%20Reform%20Hearing%20FP%20Opening.pdf.
125 Ibid. 125 Ibid.
126 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change, 126 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change,
There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, Testimony of Ranking Member , Testimony of Ranking Member
Walden, 116th Cong., 2nd sess., July 28, 2020, at https://republicans-energycommerce.house.gov/news/walden-facts-Walden, 116th Cong., 2nd sess., July 28, 2020, at https://republicans-energycommerce.house.gov/news/walden-facts-
and-science-matter/. and-science-matter/.
127 See, for example, U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and 127 See, for example, U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and
Climate Change, Climate Change, There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, 116th Cong., 2nd , 116th Cong., 2nd
sess., July 28, 2020, testimony from Natural Resources Defense Council, at https://energycommerce.house.gov/sites/sess., July 28, 2020, testimony from Natural Resources Defense Council, at https://energycommerce.house.gov/sites/
democrats.energycommerce.house.gov/files/documents/Witness%20Testimony_07.28.20_Wu.pdf. democrats.energycommerce.house.gov/files/documents/Witness%20Testimony_07.28.20_Wu.pdf.
128 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change, 128 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change,
There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, Testimony of Subcommittee , Testimony of Subcommittee
Ranking Member Shimkus, 116th Cong., 2nd sess., July 28, 2020, at http://docs.house.gov/meetings/IF/IF18/20200728/Ranking Member Shimkus, 116th Cong., 2nd sess., July 28, 2020, at http://docs.house.gov/meetings/IF/IF18/20200728/
110952/HHRG-116-IF18-MState-S000364-20200728.pdf. 110952/HHRG-116-IF18-MState-S000364-20200728.pdf.
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systems, and communities with declining populations or economies, efforts to accelerate regulatory pace by removing consideration of a contaminant’s health risk reduction benefits or occurrence may increase the cost of providing water and result in more water affordability challenges for people served by such systems. Similarly, representatives of state drinking water challenges for people served by such systems. Similarly, representatives of state drinking water
administrators raised concerns over their current resources to enforce the current (and any new) administrators raised concerns over their current resources to enforce the current (and any new)
drinking water regulations, given the financial impacts from drinking water regulations, given the financial impacts from ~~the~~ Coronavirus Disease 2019 Coronavirus Disease 2019
(COVID-19).129 Others argued that the act’s current consideration of regulatory costs must be (COVID-19).129 Others argued that the act’s current consideration of regulatory costs must be
maintained to ensure that the benefits of public health protection are maximized.130 Congressional maintained to ensure that the benefits of public health protection are maximized.130 Congressional
interest in these issues is likely to continue, especially as EPA interest in these issues is likely to continue, especially as EPA ~~finalizes the regulatory~~
~~determination for PFOS and PFOS and potentially develops drinking water regulations~~develops, proposes, and finalizes drinking water regulations for PFOS and PFOS. .

129 See, for example, U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and 129 See, for example, U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and
Climate Change, Climate Change, There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, 116th Cong., 2nd , 116th Cong., 2nd
sess., July 28, 2020, testimony from Association for State Drinking Water Administrators, at sess., July 28, 2020, testimony from Association for State Drinking Water Administrators, at
https://energycommerce.house.gov/sites/democrats.energycommerce.house.gov/files/documents/https://energycommerce.house.gov/sites/democrats.energycommerce.house.gov/files/documents/
Witness%20Testimony_07.28.20_Chard.pdf. Witness%20Testimony_07.28.20_Chard.pdf.
130 See, for example, U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and 130 See, for example, U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and
Climate Change, Climate Change, There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, 116th Cong., 2nd , 116th Cong., 2nd
sess., July 28, 2020, testimony from Association for State Drinking Water Administrators, at sess., July 28, 2020, testimony from Association for State Drinking Water Administrators, at
https://energycommerce.house.gov/sites/democrats.energycommerce.house.gov/files/documents/https://energycommerce.house.gov/sites/democrats.energycommerce.house.gov/files/documents/
Witness%20Testimony_07.28.20_Chard.pdf, and Association of Metropolitan Water Agencies, at Witness%20Testimony_07.28.20_Chard.pdf, and Association of Metropolitan Water Agencies, at
https://energycommerce.house.gov/sites/democrats.energycommerce.house.gov/files/documents/https://energycommerce.house.gov/sites/democrats.energycommerce.house.gov/files/documents/
Witness%20Testimony_07.28.20_VanDe%20Hei.pdf. Witness%20Testimony_07.28.20_VanDe%20Hei.pdf.
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Appendix A. Contaminant Candidate Lists
Table A-1. Contaminant Candidate Lists (CCLs)
CCL
Date Issued
Contaminants and Notes
CCL 1
1998 1998
60 contaminants (50 chemical contaminants and 10 60 contaminants (50 chemical contaminants and 10
63 63 FR 10274-10287 10274-10287
microbiological contaminants) microbiological contaminants)
CCL 2
2005 2005
51 contaminants (42 chemical contaminants or 51 contaminants (42 chemical contaminants or
70 70 FR 9071-9077 9071-9077
contaminant groups and 9 microbiological contaminants) contaminant groups and 9 microbiological contaminants)
CCL 3
2009 2009
116 contaminants (104 chemicals or chemical groups and 116 contaminants (104 chemicals or chemical groups and
74 74 FR 51850-5186251850-51862
12 microbiological contaminants) 12 microbiological contaminants)
CCL 4
2016 2016
109 contaminants (97 chemicals or chemical groups and 12 109 contaminants (97 chemicals or chemical groups and 12
81 81 FR 81099-81114 81099-81114
microbial contaminants) microbial contaminants)
Source: Prepared by CRS from Prepared by CRS from Federal Register notices. notices.
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Appendix B. Unregulated Contaminant Monitoring
Rules
Table B-1. Unregulated Contaminant Monitoring Rules (UCMRs)
UCMR
Date Issued
Monitoring Period
Contaminants
UCMR 1
1999 1999
2001-2005 2001-2005
36 contaminants (28 chemical contaminants and 36 contaminants (28 chemical contaminants and
(64 (64 FR 50556-50620) 50556-50620)

8 microbiological contaminants or contaminant 8 microbiological contaminants or contaminant
groups)a groups)a
UCMR 2
2007 2007
2008-2010 2008-2010
25 unregulated chemical contaminants (3 25 unregulated chemical contaminants (3
(72 (72 FR 367-398) 367-398)

explosives, 3 acetanilide compounds and 4 explosives, 3 acetanilide compounds and 4
associated degradation products, 6 nitrosamines, associated degradation products, 6 nitrosamines,
5 flame retardants) 5 flame retardants)
UCMR 3
2012 2012
2013-2015 2013-2015
30 contaminants: 29 unregulated contaminants 30 contaminants: 29 unregulated contaminants
(77 (77 FR 26071-26101) 26071-26101)
(27 chemical contaminants and 2 viruses) and 1 (27 chemical contaminants and 2 viruses) and 1
regulated contaminant (total chromium) regulated contaminant (total chromium)
UCMR 4
2016 2016
2018-2020 2018-2020
30 chemical contaminants (9 cyanotoxins and 1 30 chemical contaminants (9 cyanotoxins and 1
(81 (81 FR 92666-92692) 92666-92692)
cyanotoxin group; 2 metals; 9 pesticides; 3 cyanotoxin group; 2 metals; 9 pesticides; 3
brominated haloacetic acid disinfection brominated haloacetic acid disinfection
byproducts groups, 3 alcohols, and 3 semivolatile byproducts groups, 3 alcohols, and 3 semivolatile
organic chemicals) organic chemicals)
29 of these contaminants are unregulated and 1 29 of these contaminants are unregulated and 1
(Haloacetic Acids 5) is regulated under the (Haloacetic Acids 5) is regulated under the
Disinfectant Byproduct Rule Disinfectant Byproduct Rule
Source: Prepared by CRS from epa.gov and Prepared by CRS from epa.gov and Federal Register notices. notices.
Notes: For the fifth rule, the National Defense Authorization Act for Fiscal Year 2020 (P.L. 116-92), Section For the fifth rule, the National Defense Authorization Act for Fiscal Year 2020 (P.L. 116-92), Section
7311 directs EPA to include any PFAS (or class of PFAS) with a validated test method and excludes such 7311 directs EPA to include any PFAS (or class of PFAS) with a validated test method and excludes such
substances from counting toward the 30 contaminant limit. substances from counting toward the 30 contaminant limit.
a. For UCMR 1, EPA interpreted SDWA Section 1445(a)(2)(B)(i) to mean “that the UCMR list may contain a. For UCMR 1, EPA interpreted SDWA Section 1445(a)(2)(B)(i) to mean “that the UCMR list may contain
more than 30 contaminants, as long as monitoring is not required for more than 30 contaminants during a more than 30 contaminants, as long as monitoring is not required for more than 30 contaminants during a
five-year listing cyclefive-year listing cycle.” (64 ” (64 FR 50566). 50566).
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Appendix C. Regulatory Determinations
Table C-1. Regulatory Determinations (RDs)
Date
Other Actions
RD Cycle
Issued
Contaminants Evaluated
Taken

Positive
Negative
Notes

RD1
June 3, 2002 June 3, 2002
None None
Acanthamoeba, aldrin, , aldrin,

EPA issued guidance EPA issued guidance
(67 (67 FR 38222-38244) 38222-38244)
dieldrin, dieldrin,
on on Acanthamoeba and and
hexachlorobutadiene, hexachlorobutadiene,
health advisories for health advisories for
manganese, manganese,
magnesium, sodium, magnesium, sodium,
metribuzin, metribuzin,
and sulfate and sulfate
naphthalene, sodium, naphthalene, sodium,
and sulfate and sulfate
RD 2
July 30, 2008 None July 30, 2008 None
Boron, Dacthal mono- Boron, Dacthal mono-
EPA intended to finalize EPA intended to finalize
EPA issued or revised EPA issued or revised
(73 (73 FR 44251-44261) 44251-44261)
acid (MTP) degradate, acid (MTP) degradate, an RD for perchlorate by an RD for perchlorate by
health advisories for health advisories for
Dacthal di-acid (TPA) Dacthal di-acid (TPA)
December 2008 December 2008
boron, dacthal boron, dacthal
degradate, 1,1- degradate, 1,1-
degradates, 2,4- degradates, 2,4-
Dichloro-2,2-bis(p- Dichloro-2,2-bis(p-
dinitrotoluene, 2,6- dinitrotoluene, 2,6-
chlorophenyl)ethylene chlorophenyl)ethylene
dinitrotoluene, and dinitrotoluene, and
(DDE), 1,3- (DDE), 1,3-
1,1,2,2- 1,1,2,2-
Dichloropropene Dichloropropene
tetrachloroethane tetrachloroethane
(Telone), 2,4- (Telone), 2,4-
Dinitrotoluene, 2,6-Dinitrotoluene, 2,6-
Dinitrotoluene, s-Ethyl Dinitrotoluene, s-Ethyl
propylthiocarbamate propylthiocarbamate
(EPTC), Fonofos, (EPTC), Fonofos,
Terbacil, 1,1,2,2-Terbacil, 1,1,2,2-
Tetrachloroethane Tetrachloroethane
RD 3
January 4, January 4,
None None
Dimethoate, 1,3- Dimethoate, 1,3-
EPA delayed a final EPA delayed a final

(81 (81 FR 13-19) 13-19)
2016 2016
dinitrobenzene, dinitrobenzene,
regulatory determination regulatory determination
terbufos, and terbufos terbufos, and terbufos
on strontium on strontium
sulfone sulfone
RD 4
March 103,
PFOS ~~and~~ 1,1-dichloroethane,
EPA presented an update

~~(85 FR 14098-14142) 2020~~
~~PFOA~~
(86 FR 12272-12291) 2021 and acetochlor, methyl
on strontium and 1,4-
PFOA bromide, metolachlor,
dioxane and 1,2,3-
nitrobenzene, and ~~RDX~~
~~trichloropropane~~ trichloropropane in the RDX proposed RD Federal Register notice (85 FR 14098-14142)
Source: Prepared by CRS from epa.gov and Prepared by CRS from epa.gov and Federal Register notices. notices.
Notes: EPA proposed regulatory determinations for the fourth cycle. In EPA proposed regulatory determinations for the fourth cycle. In Fall 2020 Unified Agenda of Regulatory
and Deregulatory Action, EPA states that it intends to finalize these proposed RDs by January 2021. EPA states that it intends to finalize these proposed RDs by January 2021.

~~Author Information~~

~~Elena H. Humphreys~~

~~Analyst in Environmental Policy~~

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Author Information Elena H. Humphreys Analyst in Environmental Policy
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