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

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

detections. Additionally, concerns about the detection of regulated contaminants, such as lead,
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.
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,
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
establish a risk-based process that prioritizes contaminants for regulation based on the contaminant’s health effects and
occurrence.
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
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
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
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
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
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
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.
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
water regulations maintain or provide greater health protection.
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,
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.
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
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
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
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,
Chairman Frank Pallone stated that the hearing would contribute to the Subcommittee’s efforts to revise SDWA regulatory
development provisions. Congressional interest in drinking water contaminant regulation under SDWA is likely to continue.
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Contacts
Author Information ........................................................................................................................ 27

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Regulating Contaminants Under the Safe Drinking Water Act (SDWA)

Introduction
Detections of unregulated 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
and increased congressional interest in the Environmental Protection Agency’s (EPA’s) efforts to
regulate contaminants under the Safe Drinking Water Act (SDWA).
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
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
identification, assessment, and regulatory determination processes for the purpose of focusing
regulatory resources and requirements toward contaminants of greatest public health concern.
Since 1996, EPA has updated several drinking water regulations, promulgated regulations for
additional contaminants under other SDWA authorities, and evaluated more than 7,500
contaminants for potential regulation. However, the agency has not promulgated new regulations
using the statutory regulatory determination process.
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
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
contaminants, among others.
Congressional interest in SDWA regulatory development provisions has centered on
 EPA’s implementation of the statutory criteria for making a determination to
regulate a contaminant;
 how costs and affordability are considered when setting drinking water standards;
and
 EPA’s regulatory pace under the current framework.
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
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
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
unregulated contaminants—or to update existing contaminant regulations—have been affected by
data availability and available agency resources, among other factors.

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
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)).
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,” 73
Federal Register 44260, July 30, 2008.
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.
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This report discusses the SDWA provisions relevant to how EPA evaluates contaminants to
determine whether a contaminant warrants a “national primary drinking water regulation”
(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
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
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
SDWA Section 1412 “National Drinking Water Regulations” for evaluating contaminants for
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
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
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
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’
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
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 or established regulations for few other contaminants.
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

5 Other regulations include the “Use of Lead Free Pipes, Fittings, Fixtures, Solder, and Flux for Drinking Water” rule
(85 Federal Register 54235-54259) and “right-to-know” rules (e.g., public notification rule [65 Federal Register
25982-26049] and consumer confidence report rule [63 Federal Register 44512- 44536]).
6 42 U.S.C. §300g-1.
7 U.S. Congress, House Committee on Interstate and Foreign Commerce, Safe Drinking Water Act, 93rd Cong., 2nd
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.
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,
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, 25 Years of the Safe
Drinking Water Act: History and Trends, 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
achievable by large metropolitan water systems treating relatively clean source water.” U.S. Congress, House
Committee on Interstate and Foreign Commerce, Safe Drinking Water Act, 93rd Cong., 2nd sess., July 10, 1974, H.Rept.
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
Environment and Public Works, Safe Drinking Water Act Amendments of 1985, 99th Cong., 1st sess., May 15, 1985,
S.Rept. 99-56.
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.
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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
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
statutory requirements. Water utilities, state drinking water regulators, and EPA expressed
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
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
public health protection.13
Adding to these findings, a 1993 outbreak of Cryptosporidiosis in Milwaukee’s public water
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
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
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
Water Act Amendments of 1996 was
... 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
ensuring that health protections are maintained or improved.16
Table 1 outlines EPA actions and timelines regarding the regulation of contaminants since the
1974 enactment of SDWA.

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,”
Senate debate, Congressional Record, May 21, 1986, pp. 6284-6301).
12 U.S. Congress, House Committee on Commerce, Safe Drinking Water Act Amendments of 1996, 104th Cong., 2nd
sess., June 24, 1996, H.Rept. 104-632, p. 6.
13 U.S. Congress, House Committee on Commerce, Safe Drinking Water Act Amendments of 1996, 104th Cong., 2nd
sess., June 24, 1996, H.Rept. 104-632, p. 10.
14 U.S. Congress, House Committee on Commerce, Safe Drinking Water Act Amendments of 1996, 104th Cong., 2nd
sess., June 24, 1996, H.Rept. 104-632, p. 6.
15 P.L. 104-182.
16 U.S. Congress, House Committee on Commerce, Safe Drinking Water Act Amendments of 1996, 104th Cong., 2nd
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
National Interim Primary
New (22)
22
1976
Drinking Water Regulations
November 1979
Total Trihalomethanes Rule
New (1)
23
April 1986
Fluoride Rule
Revised (1)
23
July 1987
Phase I NPDWRs
New (8)
31
June 1989
Total Coliform Rule
Revised (1)
31
June 1989
Surface Water Treatment Rule
New (4) and Revised
35
(1)
January 1991 and July 1991
Phase II NPDWRs
New (27), Revised (11), 61
and Deleted (1)
June 1991
Lead and Copper Rule
New (1) and Revised
62
(1)
July 1992
Phase V NPDWRs
New (22) and Revised
84
(1)
June 1995
Nickel NPDWR
Remanded (1)
83
December 1998
Stage I Disinfectant and
New (6) and Revised
89
Disinfection Byproduct Rule
(1)
December 1998
Interim Enhanced Surface Water
New (1) and Revised
90
Treatment Rule
(2)
January 2000
Lead and Copper Rule
Revised (2)
90
December 2000
Radionuclides Rule
New (1) and Revised
91
(4)
January 2001
Arsenic Rule
Revised (1)
91
June 2001
Filter Backwash Recycling Rule
Revised (1)
91
January 2002
Long Term I Enhanced Surface
Revised (2)
91
Water Treatment Rule
January 2006
Long Term II Enhanced Surface
Revised (1)
91
Water Treatment Rule
November 2006
Groundwater Rule
New (3)
94
October 2007
Lead and Copper Rule
Revised (2)
94
October 2009
Aircraft Drinking Water Rule
Newa
94
February 2013
Revised Total Coliform Rule
Revised (1)
94
December 2020
Lead and Copper Rule
Revised (1)
94
Source: 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-safe-drinking-water-act.
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
Escherichia coli (E. coli), 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 public water systems. SDWA generally
defines a public water system 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
enforcement responsibility (primacy) of public water system compliance with SDWA
requirements, including drinking water regulations, may be assumed by states that meet statutory
criteria, under SDWA Section 1413.18
Public water systems can be divided into three subset categories. Community water systems are
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
individuals. As presented in Table 2, 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
such systems. Non-transient non-community water systems, such as schools or factories, have
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. Transient non-community
water systems, 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
systems.
Table 2. Public Water System Statistics

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

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

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
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.
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
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
contaminants for regulation based on public health risk, considering compliance costs to
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
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
regulation is warranted.
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
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
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
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
anticipated to occur in public water systems that may warrant regulation.20 EPA has termed this
list the contaminant candidate list (CCL). Prior to publishing a final CCL, EPA is required to
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
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
on specified population subgroups (e.g., infants, children, and pregnant women) who may be at
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,
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
(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
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,
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
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).
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
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.
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
Contaminant Candidate List 3-Draft,” 73 Federal Register 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
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
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
drinking water research (e.g., health effects, analytical methods, treatment technologies), those
that required additional occurrence data, and those prioritized for future drinking water
regulations.
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. Appendix A
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
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
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
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
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
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.
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
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
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
included 116 contaminants.
26 EPA, “Drinking Water Contaminant Candidate List 3-Draft,” 73 Federal Register 9631, February 21, 2008, at
https://www.federalregister.gov/documents/2008/02/21/E8-3114/drinking-water-contaminant-candidate-list-3-draft.
27 For more information, see EPA website, “Basic Information on the CCL and Regulatory Determination” at
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
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—
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
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).
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
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
analysis costs for small systems, using funds reserved from the annual DWSRF capitalization grant (SDWA §1452(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
seven or more states.31
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
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
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
reference levels, where established. Prior to finalizing the UCMR, EPA seeks public input by
publishing a proposed contaminant list in the Federal Register.
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
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
of detections at or above the MRL, as well as detections above EPA’s health-based reference
levels, when available.
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
warrant regulation.35 Appendix B contains information on the first, second, third, and fourth
UCMRs.
Determining Whether or Not to Regulate
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
contaminants on the CCL.36 Under SDWA, to make a positive determination to regulate a
contaminant, EPA must find that
 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
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
a meaningful opportunity for health risk reduction for persons served by water
systems.37

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
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
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
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).
35 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation for Public Water Systems,” 64 Federal
Register 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
regulatory determination outside of the five-year timeline.
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
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
subgroups (e.g., infants, children, pregnant women) that may be at greater risk due to exposure to
a contaminant.38
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
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
reconsiders such contaminants for inclusion on the CCL if new occurrence or health effects
information becomes available.41
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)
regulatory determination assessment.42 In the final phase, Regulatory Determination Assessment
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
effects and occurrence data for a contaminant.43
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
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
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
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,
and dermal contact]).
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
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).
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).
41 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water
Contaminant Candidate List,” 79 Federal Register 62727, October 20, 2014.
42 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water
Contaminant Candidate List,” 79 Federal Register 62720, October 20, 2014.
43 EPA, Chapter 2: Evaluation of Health and Occurrence Data, EPA Report 815-R-08-012, Washington, DC, June
2008.
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
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
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,”
85 Federal Register 14102, March 10, 2020.
45 EPA, Chapter 2: Evaluation of Health and Occurrence Data, EPA Report 815-R-08-012, Washington, DC, June
2008.
46 EPA, “Announcement of Preliminary Regulatory Determinations For Priority Contaminants on the Contaminant
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nationally, and uses these findings to assess whether the contaminant warrants regulation under
the statutory criteria.
The first, second, third, and fourth regulatory determinations are discussed briefly below. (See
Appendix C for additional details.)
Regulatory Determination Cycles
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
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
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
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
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
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
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,
EPA delayed a final determination to consider additional newly identified scientific data about the
contribution of other sources of strontium exposure.54

Candidate List,” 67 Federal Register 38226-38231, June 3, 2002. EPA added sodium to the initial list of eight
contaminants evaluated for possible regulation.
47 EPA, “Announcement of the Drinking Water Contaminant Candidate List,” 63 Federal Register 10285-10286,
March 2, 1998.
48 EPA, “Announcement of Preliminary Regulatory Determinations For Priority Contaminants on the Contaminant
Candidate List,” 67 Federal Register 38224, June 3, 2002.
49 EPA, “Announcement of Preliminary Regulatory Determinations For Priority Contaminants on the Contaminant
Candidate List,” 67 Federal Register 38234, June 3, 2002.
50 EPA, “Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water
Contaminant Candidate List—Preliminary Determinations,” 72 Federal Register 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
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
agency would begin the process of proposing a drinking water regulation. In July 2020, EPA published a “Notice of
Final Action” in the Federal Register withdrawing the 2011 positive regulatory determination for perchlorate. (EPA,
“Drinking Water: Final Action on Perchlorate,” 85 Federal Register 43990, July 21, 2020.)
51 EPA, “Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water
Contaminant Candidate List-Preliminary Determinations,” 72 Federal Register 24038-24052, May 1, 2007. For
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.
52 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water
Contaminant Candidate List,” 79 Federal Register 62718, October 20, 2014.
53 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water
Contaminant Candidate List,” 79 Federal Register 62741, October 20, 2014.
54 EPA, “Announcement of Final Regulatory Determinations for Contaminants on the Third Drinking Water
Contaminant Candidate List,” 81 Federal Register 18, January 4, 2016.
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In March 2020, EPA proposed regulatory determinations for contaminants on CCL 4. EPA
proposed to regulate two PFAS (i.e., perfluorooctanoic acid [PFOA] and perfluorooctane
sulfonate [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. In the Federal Register notice for the preliminary RDs, EPA provided an
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
“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
EPA can extend the deadline to publish a final rule for up to nine months by notice in the Federal
Register.58
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
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
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
regulation.61
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
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
monitoring and reporting requirements.
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
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
up to two additional years if the Administrator determines that more time is needed for public

55 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Fourth Drinking Water
Contaminant Candidate List,” 85 Federal Register 14098, March 10, 2020.
56 EPA, “Announcement of Preliminary Regulatory Determinations for Contaminants on the Fourth Drinking Water
Contaminant Candidate List,” 85 Federal Register 14132, March 10, 2020.
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).
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).
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).
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).
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
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
protective of public health.
Figure 1 outlines the SDWA processes for contaminant evaluation, regulation, and regulatory
review.
Figure 1. Simplified Process for Regulating Contaminants Under SDWA

Source: Modified by CRS from EPA.gov.
Notes: CCL = contaminant candidate list, UCMR = unregulated contaminant monitoring rule, NPDWR =
national primary drinking water regulation.
Maximum Contaminant Level Goals
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
considerations. For contaminants with carcinogenic effects and for microbial contaminants, EPA
typically sets the MCLG at zero.66
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
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
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
Rule: Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring,” 65 Federal Register
38892, June 22, 2000.
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.
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
for uncertainties in the data.68
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).
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
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
remains within the estimated protective level.70 The MCLG provides the basis for calculating an
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
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
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
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
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,
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
leaves the plant.75
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
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

Contaminant Candidate List,” 85 Federal Register 14108, March 10, 2020.
68 Ibid.
69 Other exposure routes include food ingestion, inhalation, and dermal contact.
70 See, for example, EPA, Drinking water Health Advisory for perfluorooctanoic Acid (PFOA), EPA 822-R-16-005,
May 2016, p. 32, https://www.epa.gov/ground-water-and-drinking-water/supporting-documents-drinking-water-health-
advisories-pfoa-and-pfos.
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
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
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).
74 SDWA §1412(b)(7)(A); 42 U.S.C. §300g-1(b)(7)(A).
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
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
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/
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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
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
numerous provisions intended to support small system compliance. For discussion of some of
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
“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
“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
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
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
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
estimated that the costs to treat these contaminants would be incurred primarily by small water
systems.81
Health Risk Reduction Cost Analysis
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
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.”
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).
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
effects due to exposure” between the two levels, and (2) the cost differences between treating to the two different levels
(65 Federal Register 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
10 µg/L (66 Federal Register 6975-7066). As with the previous standard (set at 50 µg/L), the MCL applies only to
community water systems.
81 EPA, “National Primary Drinking Water Regulations; Radionuclides; Final Rule,” 65 Federal Register 76715,
December 7, 2000. EPA, “National Primary Drinking Water Regulations; Arsenic and Clarifications to Compliance
and New Source Contaminants Monitoring,” 66 Federal Register 7033-7034, January 22, 2001. Small water systems
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
groundwater, which are primarily small water systems, would face costs to treat for such naturally occurring
contaminants.
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
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
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
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
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,
EPA estimates the baseline conditions prior to drinking water regulation (based on contaminant
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
assesses distributional impacts and equity concerns.85
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
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
with the proposed MCL (and alternative MCLs), but specifically excludes compliance costs for
other proposed or promulgated drinking water regulations.87
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
sensitive subpopulations and for the general population. As provided in SDWA, sensitive
subpopulations include
infants, children, pregnant women, the elderly, individuals with a history of serious illness,
or other subpopulations that are identified as likely to be at greater risk of adverse health
effects due to exposure to contaminants in drinking water than the general population.88
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
willingness-to-pay to avoid negative health impacts. EPA may include other quantifiable and
nonquantifiable benefits such as “enhanced aesthetic benefits,” (e.g., improved taste), avoided
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

83 For more information, see CRS Report R41974, Cost-Benefit and Other Analysis Requirements in the Rulemaking
Process, coordinated by Maeve P. Carey.
84 SDWA §1412(b)(3)(C); 42 U.S.C. 300g-1(b)(3)(C).
85 EPA, Preliminary Health Risk Reduction and Cost Analysis: Revised National Primary Drinking Water Standards
for Radionuclides, Cambridge, MA, January 2000.
86 For more information, see EPA website, “SDWA Economic Analysis” at https://www.epa.gov/dwregdev/economic-
analysis-and-statutory-requirements.
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).
89 For more information, see EPA website, “National Benefits Analysis for Drinking Water Regulations” at
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
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
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
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
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
regulation, as an interim measure while EPA evaluates a contaminant for regulation, or to address a short-term
incident or spil .
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
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).
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
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
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
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
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
“variances” from a drinking water standard and “exemptions” (i.e., additional time for
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
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
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,
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
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).
91 EPA, 2018 Edition of the Drinking Water Standards and Health Advisories Tables, March 2018,
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/
apex/sfdw/f?p=108:1:::NO:1::. Report generated on October 23, 2020. The search parameters were “public water
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
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.
94 SDWA §1412(b)(15); 42 U.S.C. §300g-1(b)(15).
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
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
are not available.
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
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
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
may receive a maximum of three additional two-year extensions for total exemption duration of
nine years.
Six-Year Reviews
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
revisions, if the revision could improve the level of public health protection or achieve cost
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
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,
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
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
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
under the Safe Drinking Water Act, since the 1996 SDWA amendments that established the act’s
current process.

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
Drinking Water Standards,” 68 Federal Register 42907-42929, July 18, 2003.
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,” 75 Federal
Register 15499-15572, March 29, 2010.
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,” 82 Federal
Register 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
51 contaminants
116 contaminants
109 contaminants
UCMR
1999
2007
2012
2016

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

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

Source: Compiled by CRS from epa.gov. For additional detail on CCLs, UCMRs and RDs, and specific
references, see Appendix A, Appendix B, and Appendix C, respectively.
a. In 2011, the Administrator determined that regulation was needed for perchlorate, reversing the 2008
negative determination (76 Federal Register 7762). In July 2020, the Administrator withdrew the 2011
determination to regulate perchlorate, and made a final determination not to regulate perchlorate (85
Federal Register 43990).
b. EPA delayed the determination for strontium to consider additional data (81 Federal Register 13).
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 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
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
analytical test methods, as well as sufficient laboratory capacity and availability of a feasible
treatment technology. Overarching considerations include prioritizing among thousands of
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
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
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 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
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
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
contaminant meets the statutory criteria for regulation.
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
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
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
unable to calculate the benefits from reduced health risks or the regulatory costs to communities
and others.
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
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.,
perchlorate, strontium), EPA delayed finalizing determinations to collect additional data.105 In
2011, GAO released its report EPA Should Improve Implementation of Requirements on Whether
to Regulate Additional Contaminants. GAO concluded that insufficient data to characterize
contaminant occurrence or health effects had impeded EPA progress in regulating contaminants in
drinking water.106
Availability of Analytical Methods and Laboratory Capacity
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
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

100 EPA, “Drinking Water Contaminant Candidate List 3-Draft,” 73 Federal Register 9631, February 21, 2008.
101 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems,” 76
Federal Register 11713-11737, March 3, 2011.
102 EPA, “Drinking Water Contaminant Candidate List 4-Draft,” 80 Federal Register 6078, February 4, 2015.
103 EPA, “Preliminary Regulatory Determinations for Contaminants on the Third Contaminant Candidate List,” 79
Federal Register 62715-62750, October 20, 2014.
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,” 73
Federal Register 44260, July 30, 2008.
105 EPA, “Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water
Contaminant Candidate List-Preliminary Determinations,” 72 Federal Register 24038-24052, May 1, 2007. EPA,
“Announcement of Final Regulatory Determinations for Contaminants on the Third Drinking Water Contaminant
Candidate List,” 81 Federal Register 18, January 4, 2016.
106 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.
107 EPA, “Drinking Water Contaminant Candidate List 4-Draft,” 80 Federal Register 6078, February 4, 2015.
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with the development of new analytical methods and/or identify consensus organization-
developed methods.108
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
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
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.
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
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
the MCLG.111

108 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
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
Federal Register 11720- 11721, March 3, 2011.
110 EPA, “Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems,” 76
Federal Register 11713-11737, March 3, 2011.
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.
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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
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
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
regulatory determinations for contaminant groups.
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
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
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
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
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
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
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
health effects for each contaminant, which would affect the treatment technologies available to public water
systems to comply with such a regulation.
Congressional Actions
Congressional interest in SDWA regulatory development provisions have centered on EPA’s
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
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
withdrew the 2011 positive determination, and separately proposed to regulate two per- and
polyfluoroalkyl substances (PFAS). Since 1996, EPA has evaluated thousands of chemicals for
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
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
finalized positive regulatory determination.
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
water.115 Others have expressed concern that proposals to expedite regulation by removing

112 EPA, A New Approach to Protecting Drinking Water and Public Health, EPA 815F10001, March 2010, at
https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1006RG2.txt.
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-
0155-0001.
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,” 79 Federal Register 62715-
62750.
115 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Environment and Climate Change,
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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
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
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
quality.117 Other members caution that proposals to amend SDWA to increase regulatory pace
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
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
and disadvantaged communities. In addition, EPA’s implementation of these provisions and the
number of positive regulatory determinations has garnered congressional interest.
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
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
regulating contaminants that prioritizes reducing health risks, and state drinking water
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
development and to brief the conferees on the agency’s plans to develop MCLs for specific

There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, Testimony of Subcommittee
Chairman Tonko, 116th Cong., 2nd sess., July 28, 2020, at https://energycommerce.house.gov/sites/
democrats.energycommerce.house.gov/files/documents/
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,
There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, Testimony of Ranking Member
Walden, 116th Cong., 2nd sess., July 28, 2020, at https://republicans-energycommerce.house.gov/news/walden-facts-
and-science-matter/.
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
Chairman Tonko, 116th Cong., 2nd sess., July 28, 2020, at https://energycommerce.house.gov/sites/
democrats.energycommerce.house.gov/files/documents/
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,
There’s Something in the Water: Reforming Our Nation’s Drinking Water Standards, 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
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
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
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
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, PFAS and Drinking Water: Selected EPA and
Congressional Actions, 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
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
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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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
ongoing work to develop PFAS MCLs.122
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
standard-setting provisions.123 The Chairman of the Committee, Frank Pallone, stated that “there
are fundamental weaknesses in both the design and the implementation of the Safe Drinking
Water Act....”124 Citing the lack of positive regulatory determinations, Chairman Pallone stated
that the act’s current standard 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
Committee Member 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
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
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
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
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
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
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

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-
448, p. 96.
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,
2020, at https://energycommerce.house.gov/committee-activity/hearings/hearing-on-theres-something-in-the-water-
reforming-our-nations-drinking.
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,
2020, Testimony of Chairman Pallone, at https://energycommerce.house.gov/sites/
democrats.energycommerce.house.gov/files/documents/
072820%20ECC%20SDWA%20Reform%20Hearing%20FP%20Opening.pdf.
125 Ibid.
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
Walden, 116th Cong., 2nd sess., July 28, 2020, at https://republicans-energycommerce.house.gov/news/walden-facts-
and-science-matter/.
127 See, for example, 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, 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.
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
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.
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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)
drinking water regulations, given the financial impacts from the Coronavirus Disease 2019
(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
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.

129 See, for example, 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, 2020, testimony from Association for State Drinking Water Administrators, at
https://energycommerce.house.gov/sites/democrats.energycommerce.house.gov/files/documents/
Witness%20Testimony_07.28.20_Chard.pdf.
130 See, for example, 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, 2020, testimony from Association for State Drinking Water Administrators, at
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
https://energycommerce.house.gov/sites/democrats.energycommerce.house.gov/files/documents/
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
60 contaminants (50 chemical contaminants and 10
63 FR 10274-10287
microbiological contaminants)
CCL 2
2005
51 contaminants (42 chemical contaminants or
70 FR 9071-9077
contaminant groups and 9 microbiological contaminants)
CCL 3
2009
116 contaminants (104 chemicals or chemical groups and
74 FR 51850-51862
12 microbiological contaminants)
CCL 4
2016
109 contaminants (97 chemicals or chemical groups and 12
81 FR 81099-81114
microbial contaminants)
Source: Prepared by CRS from Federal Register 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
2001-2005
36 contaminants (28 chemical contaminants and
(64 FR 50556-50620)

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

explosives, 3 acetanilide compounds and 4
associated degradation products, 6 nitrosamines,
5 flame retardants)
UCMR 3
2012
2013-2015
30 contaminants: 29 unregulated contaminants
(77 FR 26071-26101)
(27 chemical contaminants and 2 viruses) and 1
regulated contaminant (total chromium)
UCMR 4
2016
2018-2020
30 chemical contaminants (9 cyanotoxins and 1
(81 FR 92666-92692)
cyanotoxin group; 2 metals; 9 pesticides; 3
brominated haloacetic acid disinfection
byproducts groups, 3 alcohols, and 3 semivolatile
organic chemicals)
29 of these contaminants are unregulated and 1
(Haloacetic Acids 5) is regulated under the
Disinfectant Byproduct Rule
Source: Prepared by CRS from epa.gov and Federal Register notices.
Notes: 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
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
more than 30 contaminants, as long as monitoring is not required for more than 30 contaminants during a
five-year listing cycle.” (64 FR 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
None
Acanthamoeba, aldrin,

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

(81 FR 13-19)
2016
dinitrobenzene,
regulatory determination
terbufos, and terbufos
on strontium
sulfone
RD 4
March 10,
PFOS and 1,1-dichloroethane,
EPA presented an update

(85 FR 14098-14142) 2020
PFOA
acetochlor, methyl
on strontium and 1,4-
bromide, metolachlor,
dioxane and 1,2,3-
nitrobenzene, and RDX
trichloropropane
Source: Prepared by CRS from epa.gov and Federal Register notices.
Notes: 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.

Author Information

Elena H. Humphreys

Analyst in Environmental Policy

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Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan
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under the direction of Congress. Information in a CRS Report should not be relied upon for purposes other
than public understanding of information that has been provided by CRS to Members of Congress in
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