37948 Federal Register / Vol. 86, No. 135 / Monday, July 19, 2021 / Proposed Rules 

Technology Transfer and Advancement 

Act of 1995 (15 U.S.C. 272 note) because 

application of those requirements would 

be inconsistent with the CAA; and 

• Do not provide EPA with the 

discretionary authority to address, as 

appropriate, disproportionate human 

health or environmental effects, using 

practicable and legally permissible 

methods, under Executive Order 12898 

(59 FR 7629, February 16, 1994). 

The SIP is not approved to apply on 

any Indian reservation land or in any 

other area where EPA or an Indian tribe 

has demonstrated that a tribe has 

jurisdiction. In those areas of Indian 

country, the rule does not have tribal 

implications as specified by Executive 

Order 13175 (65 FR 67249, November 9, 

2000), nor will it impose substantial 

direct costs on tribal governments or 

preempt tribal law. 

For South Carolina, because this 

proposed action merely proposes to 

approve state law as meeting Federal 

requirements and does not impose 

additional requirements beyond those 

imposed by state law, this action for the 

state of South Carolina does not have 

Tribal implications as specified by 

Executive Order 13175 (65 FR 67249, 

November 9, 2000). Therefore, this 

proposed action will not impose 

substantial direct costs on Tribal 

governments or preempt Tribal law. The 

Catawba Indian Nation Reservation is 

located within the boundary of York 

County, South Carolina. Pursuant to the 

Catawba Indian Claims Settlement Act, 

S.C. Code Ann. 27–16–120 (Settlement 

Act), ‘‘all state and local environmental 

laws and regulations apply to the 

Catawba Indian Nation and Reservation 

and are fully enforceable by all relevant 

state and local agencies and 

authorities.’’ The Catawba Indian Nation 

also retains authority to impose 

regulations applying higher 

environmental standards to the 

Reservation than those imposed by state 

law or local governing bodies, in 

accordance with the Settlement Act. 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Intergovernmental 

relations, Nitrogen dioxide, Ozone, 

Reporting and recordkeeping 

requirements, Volatile organic 

compounds. 

Authority: 42 U.S.C. 7401 et seq 

Dated: July 12, 2021. 

John Blevins, 

Acting Regional Administrator, Region 4. 

[FR Doc. 2021–15097 Filed 7–16–21; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 141 

[EPA–HQ–OW–2018–0594; FRL–7251–01– 

OW] 

Drinking Water Contaminant Candidate 

List 5—Draft 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Notice of availability; request 

for comments. 

SUMMARY: The U.S. Environmental 

Protection Agency (EPA) is publishing a 

draft list of contaminants that are 

currently not subject to any proposed or 

promulgated national primary drinking 

water regulations for public review and 

comment. These contaminants are 

known or anticipated to occur in public 

water systems and may require 

regulation under the Safe Drinking 

Water Act (SDWA). This draft list is the 

Fifth Contaminant Candidate List (CCL 

5) published by the agency since the 

SDWA amendments of 1996. The Draft 

CCL 5 includes 66 chemicals, 3 

chemical groups (per- and 

polyfluoroalkyl substances (PFAS), 

cyanotoxins, and disinfection 

byproducts) and 12 microbial 

contaminants. EPA seeks comment on 

the Draft CCL 5 and on improvements 

implemented in the CCL 5 process for 

consideration in developing future 

CCLs. 

DATES: Comments must be received on 

or before September 17, 2021. 

ADDRESSES: You may send comments, 

identified by Docket ID Number EPA– 

HQ–OW–2018–0594, by any of the 

following methods: 

Federal eRulemaking Portal: https://

www.regulations.gov (our preferred 

method). Follow the online instructions 

for submitting comments. 

Mail: U.S. Environmental Protection 

Agency, EPA Docket Center, Water 

Docket, Environmental Protection 

Agency, Mail code: 28221T, 1200 

Pennsylvania Ave. NW, Washington, DC 

20460. 

Hand Delivery/Courier (by scheduled 

appointment only): EPA Docket Center, 

WJC West Building, Room 3334, 1301 

Constitution Ave. NW, Washington, DC 

20004. The Docket Center’s hours of 

operations are 8:30 a.m. to 4:30 p.m., 

Monday through Friday (except federal 

holidays). 

Instructions: All submissions received 

must include the Docket ID No. EPA– 

HQ–OW–2018–0594 for this 

rulemaking. Comments received may be 

posted without change to https://

www.regulations.gov, including any 

personal information provided. For 

detailed instructions on sending 

comments and additional information 

on the rulemaking process, see the 

‘‘Public Participation’’ heading of the 

SUPPLEMENTARY INFORMATION section of 

this document. Out of an abundance of 

caution for members of the public and 

our staff, the EPA Docket Center and 

Reading Room are closed to the public, 

with limited exceptions, to reduce the 

risk of transmitting COVID–19. Our 

Docket Center staff will continue to 

provide remote customer service via 

email, phone, and webform. We 

encourage the public to submit 

comments via https://

www.regulations.gov, as there may be 

delay in processing mail. Hand 

deliveries and couriers may be received 

by scheduled appointment only. For 

further information of EPA Docket 

Center Services and the current status, 

please visit us online at https://

www.epa.gov/dockets. 

FOR FURTHER INFORMATION CONTACT: For 

information on chemical contaminants 

contact Kesha Forrest, Office of Ground 

Water and Drinking Water, Standards 

and Risk Management Division, at (202) 

564–3632 or email forrest.kesha@

epa.gov. For information on microbial 

contaminants contact Nicole Tucker, 

Office of Ground Water and Drinking 

Water, Standards and Risk Management 

Division, at (202) 564–1946 or email 

tucker.nicole@epa.gov. 

For more information visit https://

www.epa.gov/ccl. 

SUPPLEMENTARY INFORMATION: 

Table of Contents 

I. General Information 

A. Does this action impose any 

requirements on public water systems? 

B. Public Participation 

C. What should I consider as I prepare my 

comments for EPA? 

II. Purpose, Background, and Statutory 

Requirements of This Action 

A. What is the purpose of this action? 

B. Background and Statutory Requirements 

for CCL, Regulatory Determinations and 

Unregulated Contaminant Monitoring 

Rule 

1. Contaminant Candidate List 

2. Regulatory Determinations 

3. Unregulated Contaminant Monitoring 

Rule 

C. Interrelationship of the CCL, Regulatory 

Determinations, and Unregulated 

Contaminant Monitoring 

D. Summary of Previous CCLs and 

Regulatory Determinations 

1. The First Contaminant Candidate List 

2. The Regulatory Determinations for CCL 

1 Contaminants 

3. The Second Contaminant Candidate List 

4. The Regulatory Determinations for CCL 

2 Contaminants 


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5. The Third Contaminant Candidate List 

6. The Regulatory Determinations for CCL 

3 Contaminants 

7. The Fourth Contaminant Candidate List 

8. The Regulatory Determinations for CCL 

4 Contaminants 

E. Summary of the Approach Used To 

Identify Contaminants for the Draft CCL 

5 

1. Chemical Contaminants 

2. Microbial Contaminants 

F. What is included on the Draft CCL 5? 

III. Developing the Draft CCL 5 

A. Approach Used To Identify Chemical 

Candidates for the Draft CCL 5 

1. Building the Chemical Universe 

2. Screening Chemicals to a PCCL 

a. Screening the Chemical Universe 

b. Publicly Nominated Chemicals 

c. Chemicals Excluded From the PCCL 

i. Regulatory Determinations 

ii. Canceled Pesticides 

d. Summary of the PCCL 

3. Classification of PCCL Chemicals To 

Select the Draft CCL 

a. Supplemental Data Collection 

i. Occurrence 

ii. Health Effects 

b. Calculated Data Elements 

i. Health Reference Levels and CCL 

Screening Levels 

ii. Final Hazard Quotients 

iii. Attribute Scores 

c. Evaluation Team Listing Decision 

Process 

d. Logistic Regression 

e. Chemical Groups on the Draft CCL 5 

B. Approach Used To Identify Microbial 

Candidates for the Draft CCL 5 

1. Building the Microbial Universe 

2. Screening the Microbial Universe to the 

PCCL 

3. The PCCL to Draft CCL Process 

a. Waterborne Disease Outbreak (WBDO) 

Protocol 

b. Occurrence Protocol 

c. Health Effects Protocol 

d. Combining Protocol Scores to Rank 

Pathogens 

e. Selection of the Draft CCL Microbes 

f. Organisms Covered by Existing 

Regulations 

C. Summary of Nominated Candidates for 

the Draft CCL 5 

1. Data Sources for the Nominated 

Chemical and Microbial Contaminants 

a. Chemical Nominations 

b. Microbial Nominations 

2. Listing Outcomes for the Nominated 

Chemical Contaminants 

3. Listing Outcomes for the Nominated 

Microbial Contaminants 

D. Data Availability Assessment for the 

Draft CCL 5 Chemicals 

IV. Request for Comments 

V. EPA’s Next Steps 

VI. References 

I. General Information 

A. Does this action impose any 

requirements on public water systems? 

The Draft Contaminant Candidate List 

5 (CCL 5) and the Final CCL 5, when 

published, will not impose any 

requirements on regulated entities. 

B. Public Participation 

Submit your comments, identified by 

Docket ID No. EPA–HQ–OW–2018– 

0594, at https://www.regulations.gov 

(our preferred method), or the other 

methods identified in the ADDRESSES

section of this document. Once 

submitted, comments cannot be edited 

or removed from the docket. EPA may 

publish any comment received to its 

public docket. Do not submit 

electronically any information you 

consider to be Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Multimedia submissions (audio, video, 

etc.) must be accompanied by a written 

comment. The written comment is 

considered the official comment and 

should include discussion of all points 

you wish to make. EPA will generally 

not consider comments or comment 

contents located outside of the primary 

submission (i.e., on the web, cloud, or 

other file sharing system). For 

additional submission methods, the full 

EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

https://www.epa.gov/dockets/ 

commenting-epa-dockets. 

EPA is temporarily suspending its 

Docket Center and Reading Room for 

public visitors, with limited exceptions, 

to reduce the risk of transmitting 

COVID–19. Our Docket Center Staff will 

continue to provide remote customer 

service via email, phone, and webform. 

We encourage the public to submit 

comments via https://

www.regulations.gov/ as there may be a 

delay in processing mail. Hand 

deliveries or couriers will be received 

by scheduled appointment only. For 

further information and updates on EPA 

Docket Center services, please visit us 

online at https://www.epa.gov/dockets. 

EPA continues to carefully monitor 

information from the Centers for Disease 

Control and Prevention (CDC), local area 

health departments, and our federal 

partners so that we can respond rapidly 

as conditions change regarding COVID– 

19. 

C. What should I consider as I prepare 

my comments for EPA? 

You may find the following 

suggestions helpful for preparing your 

comments: 

Explain your views as clearly as 

possible. 

Describe any assumptions that you 

used. 

Provide any technical information 

and/or data you used that support your 

views. 

Provide full references for any peer 

reviewed publication you used that 

support your views. 

Provide specific examples to illustrate 

your concerns. 

Offer alternatives. 

Make sure to submit your comments 

by the comment period deadline. To 

ensure proper receipt by EPA, identify 

the appropriate docket identification 

number in the subject line on the first 

page of your response. It would also be 

helpful if you provided the name, date, 

and Federal Register citation related to 

your comments. 

II. Purpose, Background, and Statutory 

Requirements of This Action 

This section briefly summarizes the 

purpose of this action, the statutory 

requirements, previous activities related 

to the CCL and the approach used to 

develop the Draft CCL 5. 

A. What is the purpose of this action? 

The purpose of this action is to 

present EPA’s Draft CCL 5 and the 

rationale for the selection process used 

to make the list. This Draft CCL 5, when 

finalized, is subsequently used to make 

regulatory determinations on whether to 

regulate at least five contaminants from 

the CCL with national primary drinking 

water regulations (NPDWRs) under the 

Safe Drinking Water Act (SDWA), 

section 1412(b)(1)(B)(ii). This action 

only addresses the Draft CCL 5. The 

regulatory determinations process for 

contaminants on the CCL is a separate 

agency action. EPA requests comment 

on the Draft CCL 5 and on 

improvements implemented in the CCL 

5 process for consideration in 

developing future CCLs. 

B. Background and Statutory 

Requirements for CCL, Regulatory 

Determinations and Unregulated 

Contaminant Monitoring 

1. Contaminant Candidate List 

SDWA section 1412(b)(1)(B)(i), as 

amended in 1996, requires EPA to 

publish the CCL every five years. The 

SDWA specifies that the list must 

include contaminants that are not 

subject to any proposed or promulgated 

NPDWRs, are known or anticipated to 

occur in public water systems (PWSs), 

and may require regulation under the 

SDWA. The unregulated contaminants 

considered for listing shall include, but 

not be limited to, hazardous substances 

identified in section 101(14) of the 

Comprehensive Environmental 

Response, Compensation, and Liability 

Act (CERCLA) of 1980, and substances 

registered as pesticides under the 

Federal Insecticide, Fungicide, and 


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1An NPDWR is a legally enforceable standard 

that applies to public water systems. An NPDWR 

sets a legal limit (called a maximum contaminant 

level or MCL) or specifies a certain treatment 

technique for public water systems for a specific 

contaminant or group of contaminants. The MCL is 

the highest level of a contaminant that is allowed 

in drinking water and is set as close to the MCLG 

as feasible, using the best available treatment 

technology and taking cost into consideration. 

Rodenticide Act (FIFRA). The SDWA 

directs EPA to consider the health 

effects and occurrence information for 

unregulated contaminants to identify 

those contaminants that present the 

greatest public health concern related to 

exposure from drinking water. The 

statute further directs EPA to take into 

consideration the effect of contaminants 

upon subgroups that comprise a 

meaningful portion of the general 

population (such as infants, children, 

pregnant women, the elderly, and 

individuals with a history of serious 

illness or other subpopulations) that are 

identifiable as being at greater risk of 

adverse health effects due to exposure to 

contaminants in drinking water than the 

general population. EPA considers agerelated subgroups as ‘‘lifestages’’ in 

reference to a distinguishable time 

frame in an individual’s life 

characterized by unique and relatively 

stable behavioral and/or physiological 

characteristics that are associated with 

development and growth. Thus, 

childhood is viewed as a sequence of 

stages, from conception through fetal 

development, infancy and adolescence 

(see http://www2.epa.gov/children/ 

early-life-stages). 

2. Regulatory Determinations 

SDWA section 1412(b)(1)(B)(ii), as 

amended in 1996, requires EPA, at fiveyear intervals, to make determinations 

of whether or not to regulate no fewer 

than five contaminants from the CCL. 

The 1996 SDWA Amendments specify 

three criteria to determine whether a 

contaminant may require regulation: 

The contaminant may have an adverse 

effect on the health of persons; 

The contaminant is known to occur or 

there is a substantial likelihood that the 

contaminant will occur in public water 

systems with a frequency and at levels of 

public health concern; and 

In the sole judgment of the Administrator, 

regulation of such contaminant presents a 

meaningful opportunity for health risk 

reduction for persons served by public water 

systems. 

If, after considering public comment on 

a preliminary determination, EPA 

makes a determination to regulate a 

contaminant, the agency will initiate the 

process to propose an NPDWR.1 In that 

case, the statutory time frame provides 

for EPA proposal of a regulation within 

24 months and action on a final 

regulation within 18 months of 

proposal. 

3. Unregulated Contaminant Monitoring 

Rule 

SDWA section 1445(a)(2), as amended 

in 1996, requires that once every five 

years, beginning in 1999, EPA issues a 

new list of no more than 30 unregulated 

contaminants to be monitored in 

drinking water by PWSs. Monitoring is 

required by all PWSs serving more than 

10,000 persons. The SDWA, as amended 

by America’s Water Infrastructure Act of 

2018, expands the requirements of the 

program and specifies that, subject to 

availability of appropriations and 

laboratory capacity, the UCMR program 

shall include all systems serving 

between 3,300 and 10,000 persons and 

a nationally representative sample of 

PWSs serving fewer than 3,300 persons. 

The program would continue to require 

monitoring by PWSs serving more than 

10,000 persons. The SDWA also 

requires EPA to enter the monitoring 

data into the publicly available National 

Contaminant Occurrence Database 

(NCOD). This national occurrence data 

is used to inform regulatory decisions 

for emerging contaminants in drinking 

water. Since the development of the 

UCMR program, EPA has issued four 

UCMRs. The UCMR 1 was published in 

the Federal Register on September 17, 

1999 (64 FR 50556, USEPA, 1999), and 

required monitoring for 26 

contaminants from 2001 to 2005. The 

UCMR 2 was published in the Federal 

Register on January 4, 2007 (72 FR 368, 

USEPA, 2007), and required monitoring 

for 25 contaminants from 2008 to 2010. 

The UCMR 3 was published in the 

Federal Register on May 2, 2012 (77 FR 

26072, USEPA, 2012a), and required 

monitoring for 30 contaminants: 28 

chemicals and two viruses from 2013 to 

2015. The UCMR 4 was published in the 

Federal Register on December 20, 2016 

(81 FR 92666, USEPA, 2016a), and 

required monitoring for 30 

contaminants from 2018 to 2020. 

Seventeen of the contaminants being 

monitored under the UCMR 4 were 

included on the CCL 4 and 13 chemicals 

or chemical groups monitored under the 

UCMR 4 are included on the Draft CCL 

5. EPA published the UCMR 5 proposal 

in the Federal Register on March 11, 

2021 (86 FR 13846, USEPA, 2021a). The 

proposed UCMR 5 would require 

monitoring for 29 per- and 

polyfluoroalkyl substances (PFAS) and 

lithium in drinking water from 2023 to 

2025. The Draft CCL 5 includes all of 

the contaminants that are proposed for 

monitoring on the UCMR 5. 

C. Interrelationship of the CCL, 

Regulatory Determinations, and 

Unregulated Contaminant Monitoring 

The CCL is the first step in the SDWA 

regulatory framework for screening and 

evaluating the subset of contaminants 

that may require future regulation. The 

CCL serves as the initial screening of 

potential contaminants to consider for 

regulatory determinations. However, 

inclusion on the CCL does not mean 

that any particular contaminant will 

necessarily be regulated in the future. 

The UCMR provides a mechanism to 

obtain nationally representative 

occurrence data for contaminants in 

drinking water. Historically, most 

unregulated contaminants chosen by 

EPA for monitoring have been selected 

from the CCL. When selecting 

contaminants for monitoring under the 

UCMR, EPA considers the availability of 

health effects data and the need for 

national occurrence data for 

contaminants, as well as analytical 

method availability, availability of 

analytical standards, sampling costs, 

and laboratory capacity to support a 

nationwide monitoring program. The 

contaminant occurrence data collected 

under the UCMR serves to better inform 

future CCLs and regulatory 

determinations. Contaminants on the 

CCL are evaluated based on health 

effects and occurrence information and 

those contaminants with sufficient 

information to make a regulatory 

determination are then evaluated based 

on the three statutory criteria in SDWA 

section 1412(b)(1), to determine whether 

a regulation is required (called a 

positive determination) or not required 

(called a negative determination). Under 

the SDWA, EPA must make regulatory 

determinations for at least five 

contaminants listed on the CCL every 

five years. For those contaminants 

without sufficient information to allow 

EPA to make a regulatory determination, 

the agency encourages research to 

provide the information needed to fill 

the data gaps to determine whether to 

regulate the contaminant. 

This action addresses only the CCL 5 

and not the UCMR or regulatory 

determinations. 

D. Summary of Previous CCLs and 

Regulatory Determinations 

1. The First Contaminant Candidate List 

The first CCL (CCL 1) was published 

on March 2, 1998 (63 FR 10274, USEPA, 

1998). The CCL 1 was developed based 

on recommendations by the National 

Drinking Water Advisory Council 

(NDWAC) and reviewed by technical 

experts. It contained 50 chemicals and 

10 microbial contaminants/groups. 


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2. The Regulatory Determinations for 

CCL 1 Contaminants 

EPA published its final regulatory 

determinations for a subset of 

contaminants listed on the CCL 1 on 

July 18, 2003 (68 FR 42898, USEPA, 

2003). EPA identified 9 contaminants 

from the 60 contaminants listed on the 

CCL 1 that had sufficient data and 

information available to make regulatory 

determinations. The nine contaminants 

were Acanthamoeba, aldrin, dieldrin, 

hexachlorobutadiene, manganese, 

metribuzin, naphthalene, sodium, and 

sulfate. EPA determined that no 

regulatory action was appropriate or 

necessary for any of the nine 

contaminants at that time. EPA 

subsequently issued guidance on 

Acanthamoeba and Health Advisories 

for manganese, sodium, and sulfate. 

3. The Second Contaminant Candidate 

List 

EPA published the Final CCL 2 on 

February 24, 2005 (70 FR 9071, USEPA, 

2005). EPA carried forward the 51 

remaining chemical and microbial 

contaminants from the CCL 1 (that did 

not have regulatory determinations) to 

the CCL 2. 

4. The Regulatory Determinations for 

CCL 2 Contaminants 

EPA published its final regulatory 

determinations for a subset of 

contaminants listed on the CCL 2 on 

July 30, 2008 (73 FR 44251, USEPA, 

2008). EPA identified 11 contaminants 

from the 51 contaminants listed on the 

CCL 2 that had sufficient data and 

information available to make regulatory 

determinations. The 11 contaminants 

were boron, the dacthal mono- and diacid degradates, 1,1-dichloro-2,2-bis (pchlorophenyl) ethylene (DDE), 1,3- 

dichloropropene, 2,4-dinitrotoluene, 

2,6-dinitrotoluene, s-ethyl 

propylthiocarbamate (EPTC), fonofos, 

terbacil, and 1,1,2,2-tetrachloroethane. 

EPA made a final determination that no 

regulatory action was appropriate or 

necessary for any of the 11 

contaminants. New or updated Health 

Advisories were subsequently issued 

for: Boron, the dacthal degradates, 2,4- 

dinitrotoluene, 2,6-dinitrotoluene, and 

1,1,2,2-tetrachloroethane. 

5. The Third Contaminant Candidate 

List 

EPA published the Final CCL 3 on 

October 8, 2009 (74 FR 51850, USEPA, 

2009). In developing the CCL 3, EPA 

implemented an improved, stepwise 

process which built on the previous 

CCL process and was based on expert 

input and recommendations from the 

National Academy of Sciences’ National 

Research Council (NRC), the National 

Drinking Water Advisory Council 

(NDWAC), and the Science Advisory 

Board (SAB). The CCL 3 contained 104 

chemicals or chemical groups and 12 

microbial contaminants. 

6. The Regulatory Determinations for 

CCL 3 Contaminants 

On February 11, 2011, EPA published 

in the Federal Register (76 FR 7762, 

USEPA, 2011) a determination that 

perchlorate (a CCL 3 contaminant) met 

the criteria for regulating a contaminant 

under the SDWA based upon the 

information available at that time. On 

January 4, 2016, EPA published in the 

Federal Register (81 FR 13, USEPA, 

2016b) final determinations not to 

regulate four additional CCL 3 

contaminants—dimethoate, 1,3- 

dinitrobenzene, terbufos and terbufos 

sulfone. 

EPA published a proposed 

rulemaking for perchlorate in the 

Federal Register on June 26, 2019 (85 

FR 43990, USEPA, 2019a), and sought 

public input on regulatory alternatives 

for perchlorate, including withdrawal of 

the previous regulatory determination. 

Based on the evaluation of public 

comments, and review of the updated 

scientific data, EPA withdrew the 2011 

regulatory determination and made a 

final determination not to regulate 

perchlorate on July 21, 2020 (85 FR 

43990, USEPA, 2020). EPA is reviewing 

this final determination in accordance 

with President Biden’s Executive Order 

No. 13990 (86 FR 7037, Executive Office 

of the President, 2021). 

7. The Fourth Contaminant Candidate 

List 

EPA published the Final CCL 4 in the 

Federal Register on November 17, 2016 

(81 FR 81099, USEPA, 2016c). The Final 

CCL 4 contained 97 chemicals or 

chemical groups and 12 microbial 

contaminants. All contaminants listed 

on the Final CCL 4 were carried forward 

from CCL 3, except for manganese and 

nonylphenol, which were nominated by 

the public to be included on the CCL 4. 

For information about publicly 

nominated contaminants for the CCL 5, 

see Section III.C.1 of this document. 

8. The Regulatory Determinations for 

CCL 4 Contaminants 

On March 3, 2021, EPA published 

final regulatory determinations for eight 

contaminants on the CCL 4 (86 FR 

12272, USEPA, 2021b). EPA made final 

determinations to regulate 

perfluorooctanesulfonic acid (PFOS) 

and perfluorooctanoic acid (PFOA) in 

drinking water and to not regulate six 

contaminants 1,1-dichloroethane, 

acetochlor, methyl bromide 

(bromomethane), metolachlor, 

nitrobenzene, and 1,3,5-Trinitro-1,3,5- 

triazinane (RDX). 

E. Summary of the Approach Used To 

Identify Contaminants for the Draft CCL 

5 

In developing the Draft CCL 5, EPA 

followed the stepwise process used in 

developing the CCL 3 and CCL 4, which 

was based on expert input and 

recommendations from the SAB, NRC 

and NDWAC. Note that EPA used an 

abbreviated process for the CCL 4 by 

carrying forward the CCL 3 

contaminants (81 FR 81099, USEPA, 

2016c). In each cycle of the CCL, EPA 

attempts to improve the CCL 

development process in response to 

comments from the SAB and the public. 

Therefore, in developing the Draft CCL 

5, EPA implemented improvements to 

the CCL process to better identify, 

screen, and classify potential drinking 

water contaminants. EPA’s approach 

utilizes the best available data to 

characterize the occurrence and adverse 

health risks a chemical may pose from 

potential drinking water exposure. 

Exhibit 1 illustrates a generalized 3- 

step process EPA applied to both 

chemical and microbial contaminants 

for the Draft CCL 5. The agency began 

with a large Universe of contaminants, 

screened it down to a Preliminary CCL 

5, then finally selected the Draft CCL 5. 

The specific execution of particular 

steps differed in detail for the chemical 

and microbial contaminants. Each step 

of the Draft CCL 5 process and 

associated number of chemical and 

microbial contaminants are described in 

Section III of this document. 


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1. Chemical Contaminants 

EPA followed 3 three-step process 

illustrated in Exhibit 1 to identify 

chemicals for inclusion on the Draft 

CCL 5. These steps included: 

Step 1. Building a broad universe of 

potential drinking water contaminants 

(called the CCL 5 Chemical Universe). 

EPA evaluated 134 data sources and 

identified 43 that were related to 

potential drinking water chemical 

contaminants and met established CCL 

assessment factors. From these data 

sources, EPA identified and extracted 

occurrence and health effects data for 

the 21,894 chemicals that form the CCL 

5 Chemical Universe. 

Step 2. Screening the CCL 5 Chemical 

Universe to identify a list of chemicals 

that should be further evaluated (called 

the Preliminary CCL 5 (PCCL 5)). EPA 

established and applied a data-driven 

screening points system to identify and 

prioritize a subset of chemicals with the 

greatest potential for public health 

concern. The agency also incorporated 

publicly nominated chemicals to the 

PCCL 5. 

Step 3. Classifying PCCL 5 chemicals 

to select the Draft CCL 5 chemicals. EPA 

compiled occurrence and health effects 

information for use by two evaluation 

teams of EPA scientists. The evaluation 

teams reviewed this information for 

each chemical before reaching a group 

decision on whether to list a chemical 

on the Draft CCL 5. 

A more detailed description of the 

processes used to develop the Draft CCL 

5 of chemicals using these steps can be 

found in the Technical Support 

Document for the Draft Fifth 

Contaminant Candidate List (CCL 5)— 

Chemical Contaminants (USEPA, 

2021c). 

2. Microbial Contaminants 

EPA followed the 3-step process 

illustrated in Exhibit 1 to identify 

microbes for inclusion on the Draft CCL 

5. For microbial contaminants, these 

steps included: 

Step 1. Building a broad universe of 

all microbes that may cause human 

disease. 

Step 2. Screening that universe of 

microbial contaminants to produce a 

PCCL 5. 

Step 3. Selecting the Draft CCL 5 

microbial list by ranking the PCCL 5 

contaminants based on occurrence in 

drinking water (including waterborne 

disease outbreaks) and human health 

effects. 

This approach is similar to that used 

by EPA for the CCL 3, with updates 

made to the microbial screening process 

in response to SAB and stakeholder 

comments. EPA re-examined all 12 

microbial exclusionary screening 

criteria used in previous CCLs and 

modified one criterion for the CCL 5. 

More details on the screening process 

are presented in the Technical Support 

Document for the Draft Fifth Candidate 

List (CCL 5)—Microbial Contaminants 

(USEPA, 2021d). (Note, referred to as 

the Microbial Technical Support 

Document thereafter.) 

F. What is included on the Draft CCL 5? 

The Draft CCL 5 includes 81 

contaminants or groups (Exhibits 2a, 2b, 

and 2c). The list is comprised of 69 

chemicals or chemical groups and 12 

microbes. The 69 chemicals or chemical 

groups include 66 chemicals 

recommended for listing following an 

improved process to evaluate the PCCL, 

one group of cyanotoxins, one group of 

disinfection byproducts (DBPs), and one 

group of PFAS chemicals. The 12 

microbes include 8 bacteria, 3 viruses, 

and 1 protozoa recommended for listing 

based on the scores for waterborne 

disease outbreaks, occurrence, health 

effects, and recommendations from 

various experts. 


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Exhibit 1-Generalized Draft CCL 5 Development Process and Contaminant Counts 

Number of Number of 

Chemical Microbial 

Contaminants Contaminants 

~22,000 

275 

66 + 3 

chemical 

groups 

1,435 

35 

12 
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EXHIBIT 2a—CHEMICAL CONTAMINANTS ON THE DRAFT CCL 5 

Chemical name CASRN 1 DTXSID 2

1,2,3-Trichloropropane .................................................................................................................................. 96–18–4 DTXSID9021390 

1,4-Dioxane ................................................................................................................................................... 123–91–1 DTXSID4020533 

17-alpha ethynyl estradiol ............................................................................................................................. 57–63–6 DTXSID5020576 

2,4-Dinitrophenol ........................................................................................................................................... 51–28–5 DTXSID0020523 

2-Aminotoluene ............................................................................................................................................. 95–53–4 DTXSID1026164 

2-Hydroxyatrazine ......................................................................................................................................... 2163–68–0 DTXSID6037807 

4-Nonylphenol (all isomers) .......................................................................................................................... 25154–52–3 DTXSID3021857 

6-Chloro-1,3,5-triazine-2,4-diamine ............................................................................................................... 3397–62–4 DTXSID1037806 

Acephate ....................................................................................................................................................... 30560–19–1 DTXSID8023846 

Acrolein .......................................................................................................................................................... 107–02–8 DTXSID5020023 

alpha-Hexachlorocyclohexane (alpha-HCH) ................................................................................................. 319–84–6 DTXSID2020684 

Anthraquinone ............................................................................................................................................... 84–65–1 DTXSID3020095 

Bensulide ....................................................................................................................................................... 741–58–2 DTXSID9032329 

Bisphenol A ................................................................................................................................................... 80–05–7 DTXSID7020182 

Boron ............................................................................................................................................................. 7440–42–8 DTXSID3023922 

Bromoxynil ..................................................................................................................................................... 1689–84–5 DTXSID3022162 

Carbaryl ......................................................................................................................................................... 63–25–2 DTXSID9020247 

Carbendazim (MBC) ...................................................................................................................................... 10605–21–7 DTXSID4024729 

Chlordecone (Kepone) .................................................................................................................................. 143–50–0 DTXSID1020770 

Chlorpyrifos ................................................................................................................................................... 2921–88–2 DTXSID4020458 

Cobalt ............................................................................................................................................................ 7440–48–4 DTXSID1031040 

Cyanotoxins 3 ................................................................................................................................................. Multiple Multiple 

Deethylatrazine .............................................................................................................................................. 6190–65–4 DTXSID5037494 

Desisopropyl atrazine .................................................................................................................................... 1007–28–9 DTXSID0037495 

Desvenlafaxine .............................................................................................................................................. 93413–62–8 DTXSID40869118 

Diazinon ......................................................................................................................................................... 333–41–5 DTXSID9020407 

Dicrotophos ................................................................................................................................................... 141–66–2 DTXSID9023914 

Dieldrin .......................................................................................................................................................... 60–57–1 DTXSID9020453 

Dimethoate .................................................................................................................................................... 60–51–5 DTXSID7020479 

Disinfection byproducts (DBPs) 4 .................................................................................................................. Multiple Multiple 

Diuron ............................................................................................................................................................ 330–54–1 DTXSID0020446 

Ethalfluralin .................................................................................................................................................... 55283–68–6 DTXSID8032386 

Ethoprop ........................................................................................................................................................ 13194–48–4 DTXSID4032611 

Fipronil ........................................................................................................................................................... 120068–37–3 DTXSID4034609 

Fluconazole ................................................................................................................................................... 86386–73–4 DTXSID3020627 

Flufenacet ...................................................................................................................................................... 142459–58–3 DTXSID2032552 

Fluometuron .................................................................................................................................................. 2164–17–2 DTXSID8020628 

Iprodione ........................................................................................................................................................ 36734–19–7 DTXSID3024154 

Lithium ........................................................................................................................................................... 7439–93–2 DTXSID5036761 

Malathion ....................................................................................................................................................... 121–75–5 DTXSID4020791 

Manganese .................................................................................................................................................... 7439–96–5 DTXSID2024169 

Methomyl ....................................................................................................................................................... 16752–77–5 DTXSID1022267 

Methyl tert-butyl ether (MTBE) ...................................................................................................................... 1634–04–4 DTXSID3020833 

Methylmercury ............................................................................................................................................... 22967–92–6 DTXSID9024198 

Molybdenum .................................................................................................................................................. 7439–98–7 DTXSID1024207 

Norflurazon .................................................................................................................................................... 27314–13–2 DTXSID8024234 

Oxyfluorfen .................................................................................................................................................... 42874–03–3 DTXSID7024241 

Per- and polyfluoroalkyl substances (PFAS) 5 .............................................................................................. Multiple Multiple 

Permethrin ..................................................................................................................................................... 52645–53–1 DTXSID8022292 

Phorate .......................................................................................................................................................... 298–02–2 DTXSID4032459 

Phosmet ........................................................................................................................................................ 732–11–6 DTXSID5024261 

Phostebupirim ................................................................................................................................................ 96182–53–5 DTXSID1032482 

Profenofos ..................................................................................................................................................... 41198–08–7 DTXSID3032464 

Propachlor ..................................................................................................................................................... 1918–16–7 DTXSID4024274 

Propanil ......................................................................................................................................................... 709–98–8 DTXSID8022111 

Propargite ...................................................................................................................................................... 2312–35–8 DTXSID4024276 

Propazine ...................................................................................................................................................... 139–40–2 DTXSID3021196 

Propoxur ........................................................................................................................................................ 114–26–1 DTXSID7021948 

Quinoline ....................................................................................................................................................... 91–22–5 DTXSID1021798 

Tebuconazole ................................................................................................................................................ 107534–96–3 DTXSID9032113 

Terbufos ........................................................................................................................................................ 13071–79–9 DTXSID2022254 

Thiamethoxam ............................................................................................................................................... 153719–23–4 DTXSID2034962 

Tri-allate ......................................................................................................................................................... 2303–17–5 DTXSID5024344 

Tribufos .......................................................................................................................................................... 78–48–8 DTXSID1024174 

Tributyl phosphate ......................................................................................................................................... 126–73–8 DTXSID3021986 

Trimethylbenzene (1,2,4-) ............................................................................................................................. 95–63–6 DTXSID6021402 

Tris(2-chloroethyl) phosphate (TCEP) .......................................................................................................... 115–96–8 DTXSID5021411 

Tungsten ........................................................................................................................................................ 7440–33–7 DTXSID8052481 

Vanadium ...................................................................................................................................................... 7440–62–2 DTXSID2040282 

1 Chemical Abstracts Service Registry Number (CASRN) is a unique identifier assigned by the Chemical Abstracts Service (a division of the 

American Chemical Society) to every chemical substance (organic and inorganic compounds, polymers, elements, nuclear particles, etc.) in the 

open scientific literature. It contains up to 10 digits, seperated by hyphens into three parts. 


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2 Distributed Structure Searchable Toxicity Substance Identifiers (DTXSID) is a unique substance identifier used in EPA’s CompTox Chemicals 

database, where a substance can be any single chemical, mixture or polymer. 3Toxins naturally produced and released by some species of cyanobacteria (previously known as ‘‘blue-green algae’’). The group of 

cyanotoxins includes, but is not limited to: Anatoxin-a, cylindrospermopsin, microcystins, and saxitoxin. 4This group includes 23 unregulated DBPs as shown in Exhibit 2b. 

5This group is inclusive of any PFAS (except for PFOA and PFOS). For the purposes of this document, the structural definition of PFAS includes per- and polyfluorinated substances that structurally contain the unit R-(CF2)-C(F)(R′)R′′. Both the CF2 and CF moieties are saturated 

carbons and none of the R groups (R, R′ or R′′) can be hydrogen (USEPA, 2021f). 

EXHIBIT 2b—UNREGULATED DBPS IN THE DBP GROUP ON THE DRAFT CCL 5 

Chemical name CASRN DTXSID 

Haloacetic Acids: 

Bromochloroacetic acid (BCAA) ............................................................................................................ 5589–96–8 DTXSID4024642 

Bromodichloroacetic acid (BDCAA) ....................................................................................................... 71133–14–7 DTXSID4024644 

Dibromochloroacetic acid (DBCAA) ....................................................................................................... 631–64–1 DTXSID3031151 

Tribromoacetic acid (TBAA) ................................................................................................................... 75–96–7 DTXSID6021668 

Haloacetonitriles: 

Dichloroacetonitrile (DCAN) ................................................................................................................... 3018–12–0 DTXSID3021562 

Dibromoacetonitrile (DBAN) ................................................................................................................... 3252–43–5 DTXSID3024940 

Halonitromethanes: 

Bromodichloronitromethane (BDCNM) .................................................................................................. 918–01–4 DTXSID4021509 

Chloropicrin (trichloronitromethane, TCNM) .......................................................................................... 76–96–2 DTXSID0020315 

Dibromochloronitromethane (DBCNM) .................................................................................................. 1184–89–0 DTXSID00152114 

Iodinated Trihalomethanes: 

Bromochloroiodomethane (BCIM) .......................................................................................................... 34970–00–8 DTXSID4021503 

Bromodiiodomethane (BDIM) ................................................................................................................. 557–95–9 DTXSID70204235 

Chlorodiiodomethane (CDIM) ................................................................................................................ 638–73–3 DTXSID20213251 

Dibromoiodomethane (DBIM) ................................................................................................................ 557–68–6 DTXSID60208040 

Dichloroiodomethane (DCIM) ................................................................................................................. 594–04–7 DTXSID7021570 

Iodoform (triiodomethane, TIM) ............................................................................................................. 75–47–8 DTXSID4020743 

Nitrosamines: 

Nitrosodibutylamine (NDBA) .................................................................................................................. 924–16–3 DTXSID2021026 

N-Nitrosodiethylamine (NDEA) .............................................................................................................. 55–18–5 DTXSID2021028 

N-Nitrosodimethylamine (NDMA) ........................................................................................................... 62–75–9 DTXSID7021029 

N-Nitrosodi-n-propylamine (NDPA) ........................................................................................................ 621–64–7 DTXSID6021032 

N-Nitrosodiphenylamine (NDPhA) ......................................................................................................... 86–30–6 DTXSID6021030 

Nitrosopyrrolidine (NPYR) ...................................................................................................................... 930–55–2 DTXSID8021062 

Others: 

Chlorate .................................................................................................................................................. 14866–68–3 DTXSID3073137 

Formaldehyde ........................................................................................................................................ 50–00–0 DTXSID7020637 

EXHIBIT 2c—MICROBIAL

CONTAMINANTS ON THE DRAFT CCL 5 

Microbial name Microbial 

class 

Adenovirus .................................. Virus. 

Caliciviruses ................................ Virus. 

Campylobacter jejuni .................. Bacteria. 

Escherichia coli (O157) .............. Bacteria. 

Enteroviruses .............................. Virus. 

Helicobacter pylori ...................... Bacteria. 

Legionella pneumophila .............. Bacteria. 

Mycobacterium abscessus ......... Bacteria. 

Mycobacterium avium ................. Bacteria. 

Naegleria fowleri ......................... Protozoa. 

Pseudomonas aeruginosa .......... Bacteria. 

Shigella sonnei ........................... Bacteria. 

III. Developing the Draft CCL 5 

A. Approach Used To Identify Chemical 

Candidates for the Draft CCL 5 

The SDWA directs EPA to consider 

health effects and occurrence 

information on unregulated 

contaminants to identify those that 

present the greatest public health 

concern related to exposure from 

drinking water. EPA gathered this 

information into a data directory that 

supports the evaluation of contaminants 

over the three steps of the CCL 5 

development process, as outlined in 

Section II.E.1 of this document. 

1. Building the Chemical Universe 

The goal of the first step of the CCL 

5 development process for chemical 

candidates is to identify a broad 

universe of potential drinking water 

contaminants. EPA began the CCL 5 

development process by compiling data 

sources to identify chemicals that would 

form a broad CCL 5 Chemical Universe 

(e.g., a list of contaminants identified 

through health and occurrence data 

sources that are relevant, complete, 

retrievable, and not redundant). EPA 

compiled data sources identified from 

the CCL 3 and the CCL 4, along with 

data sources recommended by the CCL 

5 EPA workgroup and subject matter 

experts. Information on how EPA 

addressed data sources provided 

through the public nomination process 

is described in Section III.C.1 of this 

document. As a result of this effort, EPA 

identified 134 potential data sources 

and further assessed their potential use 

for the CCL 5 development process. EPA 

accessed each potential data source 

online and evaluated them using the 

following assessment factors: 

Relevance: The data source contains 

information on demonstrated or 

potential health effects, occurrence, or 

potential occurrence of contaminants 

using surrogate information (e.g., 

environmental release, environmental 

fate and transport properties); 

Completeness: The data source either 

(a) has been peer-reviewed, or (b) 

provides a description of the data, 

information on how the data were 

obtained, and contact information 

regarding the data source; 

Redundancy: The data source does 

not contain information identical to 

other more comprehensive data sources 

also being considered; and, 

Retrievability: The data are formatted 

for automated retrieval (e.g., data are 

stored in a tabular format) and publicly 

accessible. 

Out of the 134 potential data sources, 

43 met all four assessment factors and 

were therefore considered ‘‘primary data 

sources’’ that were used to build the 

CCL 5 Chemical Universe. Data sources 

that met the first three assessment 


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factors but were not retrievable were set 

aside as potential supplemental sources, 

some of which were used as part of the 

CCL 5 classification process, as 

discussed further in this section as well 

as Sections III.A.4 and III.C of this 

document. More information on how 

data sources were assessed and 

extracted is provided in Sections 2.2 

and 2.3, respectively, of the Chemical 

Technical Support Document (USEPA, 

2021c). 

EPA downloaded data from the 43 

primary data sources and categorized 

them as sources of health effects 

(Exhibit 3) or occurrence (Exhibit 4) 

data. In total, 21,894 chemicals were 

identified from the 43 primary data 

sources. 

Out of the 43 primary data sources, 

EPA identified 17 sources of health 

effects data that met the assessment 

factors of relevance, completeness, 

redundancy, and retrievability. One 

additional health effects data source, the 

Hazardous Substances Data Bank 

(HSDB), did not meet the retrievability 

factor but was designated as a primary 

data source. The HSDB is a data rich 

source, and the only source of Lethal 

Dose, 50% (LD50s) for the CCL 5 

development process. 

Therefore, additional effort was taken 

to extract this data, as was done with 

the CCL 3 development process 

(USEPA, 2009a). These 18 data sources, 

listed in Exhibit 3, include both 

qualitative and quantitative data. 

EXHIBIT 3—CCL 5 HEALTH EFFECTS PRIMARY DATA SOURCES

Data source Agency or author 1

Agency for Toxic Substances and Disease Registry (ATSDR) Minimal 

Risk Levels (MRLs).

Centers for Disease Control and Prevention (CDC). 

Cancer Potency Data Bank ...................................................................... National Library of Medicine, U.S. Department of Health and Human 

Services (HHS). 

Drinking Water Standards and Health Advisory Tables .......................... EPA. 

Guidelines for Canadian Drinking Water Quality ..................................... Health Canada. 

Guidelines for Drinking-Water Quality ...................................................... World Health Organization (WHO). 

Hazardous Substances Data Bank .......................................................... National Library of Medicine, HHS. 

Health-Based Screening Levels (HBSLs) ................................................ U.S. Geological Survey (USGS). 

Human Health-Based Water Guidance Table .......................................... Minnesota Department of Health. 

Human Health Benchmarks for Pesticides .............................................. EPA. 

Integrated Risk Information System (IRIS) .............................................. EPA. 

International Agency for Research on Cancer Classifications ................. WHO. 

Maximum Recommended Daily Dose (MRDD) Database ....................... U.S. Food and Drug Administration (FDA). 

National Recommended Water Quality Criteria—Human Health Criteria EPA. 

National Toxicology Program (NTP) Cancer Classifications ................... HHS. 

Provisional Peer-Reviewed Toxicity Values (PPRTVs) ........................... EPA. 

Screening Levels for Pharmaceuticals ..................................................... FDA Drugs@FDA database, National Institutes of Health (NIH) 

DailyMed Database. 

Toxicity Criteria Database ........................................................................ California Environmental Protection Agency (CalEPA) Office of Environmental Health Hazard Assessment. 

Toxicity Reference Database (ToxRefDB) ............................................... EPA 

1 References for the data sources listed in Exhibit 3 are provided in Appendix N of the Chemical Technical Support Document (USEPA, 

2021c). 

EPA identified 25 sources of 

occurrence related data that met the 

assessment factors of relevance, 

completeness, redundancy, and 

retrievability. These data sources, listed 

in Exhibit 4, include both qualitative 

and quantitative data. 

EXHIBIT 4—CCL 5 OCCURRENCE PRIMARY DATA SOURCES

Data source Agency or author 1

ATSDR Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) 

Substance Priority List.

CDC. 

Chemical Data Reporting (CDR) Results ...................................................................................... EPA.

‘‘Concentrations of prioritized pharmaceuticals in effluents from 50 large wastewater treatment 

plants in the US and implications for risk estimation’’.

Kostich et al. 2014. 

Disinfection By-product Information Collection Rule (DBP ICR) ................................................... EPA. 

‘‘Evaluating the extent of pharmaceuticals in surface waters of the United States using a National-scale Rivers and Streams Assessment survey’’.Batt et al. 2016. 

‘‘Expanded target-chemical analysis reveals extensive mixed-organic-contaminant exposure in 

U.S. streams’’.

Bradley et al. 2017. 

Federal Insecticide Fungicide, and Rodenticide Act (FIFRA) List ................................................. EPA. 

‘‘Legacy and emerging perfluoroalkyl substances are important emerging water contaminants 

in the Cape Fear River Watershed of North Carolina’’.

Sun et al. 2016. 

National Health and Nutrition Examination Survey (NHANES) ..................................................... CDC. 

National Inorganics and Radionuclides Survey (NIRS) ................................................................. EPA. 

National Water Information System (NWIS) .................................................................................. Water Quality Portal, USGS. 

National Water-Quality Assessment (NAWQA) ............................................................................. Water Quality Portal, USGS. 

‘‘Nationwide reconnaissance of contaminants of emerging concern in source and treated drinking waters of the United States’’.Glassmeyer et al. 2017. 

‘‘Nationwide reconnaissance of contaminants of emerging concern in source and treated drinking waters of the United States: Pharmaceuticals’’.Furlong et al. 2017. 


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EXHIBIT 4—CCL 5 OCCURRENCE PRIMARY DATA SOURCES—Continued 

Data source Agency or author 1

Pesticide Data Program ................................................................................................................. U.S. Department of Agriculture (USDA). 

Pesticide Use Estimates ................................................................................................................ USGS. 

‘‘Pharmaceutical manufacturing facility discharges can substantially increase the pharmaceutical load to US wastewaters’’.Scott et al. 2018. 

‘‘Predicting variability of aquatic concentrations of human pharmaceuticals’’ ............................... Kostich et al. 2010. 

‘‘Reconnaissance of mixed organic and inorganic chemicals in private and public supply 

tapwaters at selected residential and workplace sites in the United States’’.

Bradley et al. 2018. 

Surface Water Database (SURF) .................................................................................................. California Department of Pesticide Regulation. 

‘‘Suspect screening and non-targeted analysis of drinking water using point-of-use filters’’ ........ Newton et al. 2018. 

Toxics Release Inventory (TRI) ..................................................................................................... EPA. 

Unregulated Contaminant Monitoring Rule (UCMR) Cycles 1–3 .................................................. EPA. 

UCMR Cycle 4 ............................................................................................................................... EPA. 

Unregulated Contaminant Monitoring-State (UCM-State) Rounds 1 and 2 .................................. EPA. 

1 References for the data sources listed in Exhibit 4 are provided in Appendix N of the Chemical Technical Support Document (USEPA, 

2021c). 

To ensure consistency and accuracy 

of the data across such a large data 

directory with a multitude of sources, 

EPA utilized the Distributed Structure— 

Searchable Toxicity Substance 

Identifiers (DTXSIDs) and tools 

provided in EPA’s CompTox Chemicals 

Dashboard (Williams et al., 2017). This 

dashboard provides easy access to 

results from several models developed 

by EPA and others that predict toxicity 

endpoints, physicochemical properties, 

and environmental fate and exposure 

parameters for specific chemicals, as 

well as tools to efficiently and 

accurately match chemicals with 

DTXSIDs. With these tools and 

identifiers, EPA was able to match a 

chemical that may have been reported 

differently (i.e., with different names or 

other identifiers) across CCL 5 data 

sources to one DTXSID. EPA linked 

these identifiers with descriptors that 

characterize toxicological and 

occurrence information, referred to as 

‘‘data elements,’’ to ensure that data for 

each chemical would be available for 

use in later steps of the CCL 5 

development process. EPA also 

considered the CompTox Chemicals 

Dashboard as a supplemental data 

source, as described in Section 2.4.3 of 

the Chemical Technical Support 

Document (USEPA, 2021c). 

While building the CCL 5 Chemical 

Universe, EPA took several steps to 

ensure that the chemical identifiers 

were accurate, and that the data 

elements gathered across sources were 

uniform and comparable, as described 

in Section 2.4.4 of the Chemical 

Technical Support Document (USEPA, 

2021c). The result of the first step of the 

CCL 5 development process was the 

CCL 5 Chemical Universe that provided 

a starting point for screening chemicals 

for inclusion on the PCCL 5, as 

described in Section III.A.2 of this 

document. 

At later stages in the CCL 5 

development process, EPA also 

collected data from supplemental data 

sources, which, along with data from 

the 43 primary data sources, was used 

to aid in further evaluation of chemicals 

for listing on the Draft CCL 5. As 

described in Section 2.2.3 of the 

Chemical Technical Support Document 

(USEPA, 2021c), supplemental sources 

were used to fill data gaps as part of the 

CCL 5 classification step (see Section 

III.A.3 of this document). For example, 

EPA conducted literature searches to 

identify peer-reviewed studies that are 

considered supplemental data sources 

to aid in the evaluations of chemicals of 

interest (see Section III.A.3.a of this 

document). Supplemental data could 

also come from sources cited in public 

nominations (see Section III.C of this 

document). While these sources could 

most often not be efficiently or 

effectively incorporated into the 

screening process, they were often an 

important source of detail and 

description that supported CCL 5 listing 

decisions. This effort to combine data 

collected from primary data sources 

along with data from supplemental data 

sources resulted in the most 

comprehensive data compilation for 

universe chemicals collected for any 

CCL iteration to date. For more 

information about the specific iterative 

steps taken to build the CCL 5 Chemical 

Universe, see Chapter 2 of the Chemical 

Technical Support Document (USEPA, 

2021c). 

2. Screening Chemicals to a PCCL 

The goal of the second step of the CCL 

5 development process was to screen 

chemicals for inclusion on the PCCL 5 

using the data compiled in Step 1. The 

PCCL 5 is comprised of the top scoring 

universe chemicals that were advanced 

for further evaluation and publicly 

nominated chemicals. A number of top 

scoring chemicals and publicly 

nominated chemicals were not included 

on the PCCL 5 because they had ongoing 

agency actions or did not warrant 

further evaluation, such as canceled 

pesticides as described in this section. 

a. Screening the Chemical Universe 

EPA developed a screening process to 

determine which contaminants require 

further consideration through the PCCL 

to CCL step. EPA modified the CCL 3 

screening process for this CCL cycle to 

accommodate new data types and 

sources that have become available, but 

maintained the framework of screening 

chemicals to the PCCL based on their 

available toxicity properties and 

occurrence data (USEPA, 2009b). To 

screen chemicals for the CCL 5, EPA 

developed a transparent and 

reproducible scoring rubric and pointbased screening system. This pointbased screening system is an 

improvement over the Toxicity 

Categories and Occurrence Hierarchies 

developed for the CCL 3 (USEPA, 

2009b) because it incorporates data from 

all the available data elements identified 

for use in screening rather than relying 

on an individual data element that 

indicates the highest toxicity or 

occurrence for a chemical. 

EPA developed a scoring rubric to 

assign points across health effects and 

occurrence data elements based on (1) 

the relevance of the data element to 

drinking water exposure and (2) the 

relative toxicity or relative occurrence 

indicated by the value of a chemical’s 

data element compared to the values of 

that data element for all other 

chemicals, as described here and in 

more detail in Section 3.2 of the 

Chemical Technical Support Document 

(USEPA, 2021c). EPA used this scoring 

rubric to assign points to health effects 

and occurrence data elements and 

calculate cumulative point scores, 


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called ‘‘screening scores,’’ for each 

chemical. EPA then used these 

screening scores as a tool to prioritize 

chemicals along with statistical models 

and analyses to inform the PCCL 5. The 

statistical models and analyses are 

described in Section III.A.4.d of this 

document and Section 4.6 of the 

Chemical Technical Support Document 

(USEPA, 2021c). During the CCL 5 

development process, EPA compiled 68 

different data elements that could be 

assigned points or used as 

supplementary data for individual 

chemicals. Of these 68 data elements, 

EPA assigned points to 22 data elements 

related to health effects and 13 data 

elements related to occurrence, but did 

not assign points to the remaining 33 

data elements. Generally, EPA did not 

assign points to data elements if: 

The data element was not available for a 

large number of chemicals. 

The data element was not considered 

highly relevant to hazards associated with 

drinking water. 

The data element required chemicalspecific data manipulation (e.g., unit 

conversions requiring chemical molecular 

weight) and/or was not comparable to others 

in the universe. 

Another data element extracted from the 

same data source and describing the same 

data was assigned points. 

Or, the data element was not relevant to 

unregulated chemicals. 

Many of the data elements assigned 

points in CCL 5 are the same data 

elements that were used in the CCL 3 

screening and classification processes. 

These data elements include health 

effects information such as categories of 

cancer classifications and toxicity 

values (e.g., Reference Dose (RfD), No 

Observed Adverse Effect Level 

(NOAEL), Lowest Observed Adverse 

Effect Level (LOAEL), and Lethal Dose, 

50% (LD50)), as well as occurrence 

information such as measures of 

chemical concentration and frequency 

of detections in drinking water, 

production volume, and chemical 

release data. There are also new data 

elements related to both health and 

occurrence endpoints that EPA included 

in the CCL 5 screening process that were 

not available in a retrievable format or 

not used in previous CCL cycles, 

including National Health and Nutrition 

Examination Survey (NHANES) 

biomonitoring data and results from 

EPA’s ToxCast in vitro screening assays. 

EPA designed the CCL 5 screening 

process to accommodate quantitative, 

calculated, and descriptive types of 

data. A full list of the data elements 

assigned points for the CCL 5 screening 

process is described in Chapter 3 of the 

Chemical Technical Support Document 

(USEPA, 2021c). 

EPA divided the CCL 5 health effects 

and occurrence data elements that were 

assigned points into five categories, 

referred to as ‘‘tiers,’’ based on the 

relevance of the data to public health 

concerns over drinking water exposure. 

Tier 1 contains data most relevant to 

understanding potential drinking water 

risk and Tier 5 contains data that 

provide indirect indication of potential 

risk associated with drinking water 

exposure. For example, Tier 1 health 

effects data elements include RfD, 

cancer slope factor (CSF), and chronic 

benchmark value, which are generally 

only available for chemicals that have 

relevant risk or hazard assessments from 

at least one health agency. Tier 1 

occurrence data element is the screening 

Hazard Quotient (sHQ), a calculated 

data element based on the ratio of the 

maximum concentration of a chemical 

in finished drinking water (the 

occurrence element most applicable to 

drinking water risk) to the lowest (i.e., 

most health-protective) health screening 

level for a chemical (see Section 3.2 of 

the Chemical Technical Support 

Document (USEPA, 2021c) for more 

details). The list of data elements 

assigned points for CCL 5 screening 

purposes and their corresponding tier is 

presented in Exhibit 5. 

EXHIBIT 5—TIERS OF HEALTH AND OCCURRENCE DATA ELEMENTS ASSIGNED POINTS DURING THE CCL 5 SCREENING

PROCESS

Tier Data element 

Health Effects Data Elements 

Tier 1 ................ Reference dose (RfD), cancer slope factor (CSF), chronic benchmark. 

Tier 2 ................ Chronic no observed adverse effect level (NOAEL), chronic lowest observed adverse effect level (LOAEL). 

Tier 3 ................ Numeric cancer classification,1 subchronic benchmark, subchronic RfD. 

Tier 4 ................ Acute benchmark, acute RfD, subchronic NOAEL, subchronic LOAEL, MRDD, mined literature for neurotoxins,2 human 

neurotoxicants,2 developmental neurotoxins,2 developmental neurotoxins (in vivo),2 androgen receptor chemicals.2

Tier 5 ................ TD50, LD50, percent active in ToxCast assays,2 PubMed articles.2

Occurrence Data Elements 

Tier 1 ................ Screening hazard quotient. 

Tier 2 ................ National finished water detection rates. 

Tier 3 ................ National ambient water detection rates, non-national finished water detection rates. 

Tier 4 ................ Non-national ambient water detection rates. 

Tier 5 ................ Chemical release quantity, estimated pesticide application rate, chemical production volume, presence on FIFRA and 

CERCLA lists, NHANES blood, urine, and serum concentrations, OPERA model biodegradation half-life.2

1EPA converted categorial cancer classifications to a numeric scheme (1–3) which were assigned screening points. See Section 2.4.4 of the 

Chemical Technical Support Document (USEPA, 2021c) for more information. 2These data elements were extracted from the CompTox Chemicals Dashboard. 

A more detailed discussion on the 

inclusion and exclusion of data 

elements for point assignment is 

included in Chapter 3 of the Chemical 

Technical Support Document (USEPA, 

2021c). 

For a specific chemical, the number of 

points assigned to each individual data 

element depends on the relative toxicity 

or relative occurrence indicated by the 

data element compared to values of that 

data element available for all other 

chemicals in the universe. Further 

descriptions of data element category 

calculations and point assignments can 

be found in Section 3.3.2 of the 

Chemical Technical Support Document 

(USEPA, 2021c). Altogether, a chemical 

can receive points for each data element 

in every tier. The lower tiers of 

information are assigned fewer points 

because the data elements included in 

these tiers are considered less relevant 


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to hazards associated with chemical 

exposure via drinking water. 

EPA developed the screening points 

system to ensure the agency considers 

chemicals of emerging concern in 

drinking water in addition to wellstudied chemicals with more robust 

human health and drinking water 

occurrence data. The point system 

allows a chemical with limited health 

effects data, but high occurrence, to be 

included on the PCCL 5. Similarly, a 

chemical with limited or no drinking 

water occurrence data but with health 

effects information potentially 

indicating higher toxicity could also be 

included in the PCCL. The screening 

score for a chemical is the sum of health 

effects and occurrence points assigned 

for each data element. The maximum 

screening score a chemical could be 

assigned is 14,050. 

EPA identified the 250 highest scoring 

chemicals for inclusion in the PCCL 5 

and further evaluation for listing on the 

Draft CCL 5. This resulted in all 

chemicals scoring at or above 3,320 

points were advanced for further 

consideration for the Draft CCL 5. 

Because three chemicals (2,4- 

Dinitrophenol, Phosmet, and 4- 

Androstene-3,17-dione) have the same 

screening score of 3,320, a total of 252 

chemicals were advanced for further 

consideration and potential inclusion 

on the PCCL 5 (Note: The 252 chemicals 

are referred to as the ‘‘top 250’’ in this 

document). EPA validated the selection 

of the top 250 highest scoring chemicals 

and the screening score framework 

using a statistical modeling approach. A 

complete description of the results of 

this approach can be found in Section 

4.6 of the Chemical Technical Support 

Document (USEPA, 2021c). 

b. Publicly Nominated Chemicals 

EPA added 53 publicly nominated 

chemicals to the 252 highest scoring 

chemicals to be included on the PCCL. 

Publicly nominated chemicals are 

described further in Section III.C of this 

document and Section 3.6 of the 

Chemical Technical Support Document 

(USEPA, 2021c). 

c. Chemicals Excluded From the PCCL 

i. Regulatory Determinations 

In March 2021, under the fourth 

Regulatory Determination process, EPA 

made final regulatory determinations for 

eight chemicals including: PFOS; PFOA; 

1,1-dichloroethane; acetochlor; methyl 

bromide (bromomethane); metolachlor; 

nitrobenzene; and RDX (86 FR 12272, 

USEPA, 2021b). EPA also made a 

preliminary positive determination on 

strontium under the third Regulatory 

Determination process (79 FR 62715, 

USEPA, 2014). Therefore, EPA excluded 

these nine chemicals from the PCCL 5. 

ii. Canceled Pesticides 

EPA evaluated canceled pesticides 

and excluded those that are not 

persistent in the environment from the 

PCCL 5. The persistence and occurrence 

of canceled pesticides were evaluated 

by their biodegradation half-life, end-ofuse date, and the timeframe of 

monitoring data in finished and/or 

ambient water. Canceled pesticides 

were assigned a persistence score based 

on the scale described in EPA’s 2012 

TSCA Work Plan Chemicals: Methods 

Document (USEPA, 2012b). Canceled 

pesticides’ biodegradation half-life 

information was downloaded from 

EPA’s CompTox Chemicals Dashboard. 

Based on half-life ranges, a persistence 

score of 1 to 3 was assigned to each 

canceled pesticide with 1 indicative of 

lowest persistence and 3 highest 

persistence. A canceled pesticide 

received a persistence score of 1, 2, or 

3 if its half-life was less than two 

months, greater than or equal to two 

months, or greater than six months, 

respectively. 

Additionally, end-of-use dates of 

canceled pesticides were compared to 

the dates of occurrence monitoring data 

in finished and/or ambient water. Only 

the occurrence monitoring data 

collected after the end-of-use dates were 

used to determine if a canceled 

pesticide had any detects and/or data 

spikes that would pose a public health 

concern. A canceled pesticide was 

included in the PCCL if it received a 

persistence score of 3 and had detects in 

finished or ambient water, or if it 

received a score of 1 or 2 but had detects 

in finished water. A canceled pesticide 

was excluded from the PCCL if it 

received a score of 1 or 2 and had no 

detects in finished water or no or few 

detects in ambient water. 

In total, 26 canceled pesticides were 

assessed for persistence. Four 

pesticides, including dieldrin, aldrin, 

chlordecone (kepone), and ethion, were 

assigned a persistence score of 3 and 

showed detects in finished or ambient 

water; thus, they were included in the 

PCCL 5. Alpha-hexachlorocyclohexane, 

although received a persistence score of 

1, was also included in the PCCL 5 

because it had detects in the UCMR 4 

occurrence data (collected 2018–2019). 

Alpha-hexachlorocyclohexane is an 

organochloride, which is one of the 

isomers of hexachlorocyclohexane, and 

is a byproduct of the production of the 

canceled insecticide lindane. 

The 21 remaining pesticides were 

assigned a score of 2 or 1 and showed 

no or very few detections in finished or 

ambient water; and therefore were 

excluded from the PCCL 5. Their 

finished or ambient water monitoring 

results were consistent with the low 

persistence scores, indicating that these 

canceled pesticides are likely of low 

public health concern. 

d. Summary of the PCCL 

The resulting PCCL 5 is comprised of 

a total of 275 chemicals. As shown in 

Exhibit 6, the PCCL 5 includes 252 of 

the highest scoring chemicals and 53 

publicly nominated chemicals, of which 

30 were excluded because they had 

other ongoing agency actions or did not 

warrant further evaluation. A summary 

of the PCCL 5 is included in Section 3.8 

of the Chemical Technical Support 

Document (USEPA, 2021c). 

EXHIBIT 6—CHEMICAL COUNTS ON DRAFT PCCL 5 AND DRAFT CCL 5 

Counting process Number of 

chemicals Total count 

Highest scoring chemicals (screened from Universe) ................................................. 252 275 (PCCL). 

(+) Add public nominated chemicals (not screened) ................................................... 53 

(¥) Exclude chemicals with Regulatory Determinations ............................................. 9 

(¥) Exclude canceled pesticides ................................................................................. 21 

(¥) Exclude Disinfection Byproducts (listed as a chemical group instead) ................ 23 214 (Reviewed by Evaluation Teams). 

(¥) Exclude cyanotoxins (listed as a chemical group instead) ................................... 7 

(¥) Exclude PFAS (listed as a chemical group instead) ............................................ 18 

(¥) Exclude public nominated chemicals lacking occurrence Data ............................ 13 

Evaluation Teams’ Listing Recommendation ............................................................... ........................ 66. 

Draft CCL 5 Chemicals ......................................................................................... ........................ 66 and 3 groups. 


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3. Classification of PCCL Chemicals To 

Select the Draft CCL 

In the third step of the CCL 5 process, 

chemical contaminants screened to the 

PCCL 5 in Step 2 passed through a 

classification process. Classification is 

the process by which the agency 

incorporates the knowledge and 

evaluation of EPA scientists, referred to 

as ‘‘chemical evaluators,’’ to narrow the 

PCCL down to a draft CCL. During this 

process, chemical evaluators assessed 

health and occurrence data on the PCCL 

5 chemical contaminants and reached a 

consensus on whether to recommend 

them for listing on the Draft CCL 5. 

To facilitate the classification process, 

EPA conducted health and occurrence 

literature searches to gather 

supplemental data for the remaining 

PCCL 5 chemicals. For more 

information, see Sections III.A.3.i and 

III.C.2 of this document, and Section 

4.2.1.1 of the Chemical Technical 

Support Document (USEPA, 2021c). 

Literature searches acquired 

supplemental health effects and/or 

occurrence data from qualifying studies 

that may not have been available in a 

retrievable format during the 

identification of the universe. The 

supplemental data resources 

encountered during the literature 

searches were compiled by chemical, 

and relevant health effects and 

occurrence data metrics were imported 

into a standardized document format, 

called the Contaminant Information 

Sheet (CIS) (USEPA, 2021e). 

EPA formed two evaluation teams to 

review the qualifying health effects and 

occurrence information provided in 

supplemental studies and on the CISs to 

make consensus listing 

recommendations for the PCCL 5 

chemicals. Each evaluation team was 

composed of seven chemical evaluators 

with professional experience and 

expertise in relevant technical fields, 

including public health, public policy, 

toxicology, chemistry, biology, and 

pesticide exposure. 

The supplemental studies provided to 

the chemical evaluators during the 

review process can be found in the EPA 

docket at https://www.regulations.gov 

(Docket ID No. EPA–HQ–OW–2018– 

0594). The CISs can be viewed in the 

Technical Support Document for the 

Draft Fifth Contaminant Candidate List 

(CCL 5)—Contaminant Information 

Sheets, hereafter referred to as the CIS 

Technical Support Document (USEPA, 

2021e). 

The following sections provide a 

detailed explanation of the classification 

process broken down into individual 

components. 

a. Supplemental Data Collection 

Primary data sources play a crucial 

role in the entire CCL process (see 

Section III.A.1 of this document); 

however, it is often necessary to gather 

and extract data from supplemental 

sources to aid in further evaluation of 

chemicals for listing on the Draft CCL 5. 

As described in Section III.A.1 of this 

document, EPA assessed data sources 

for potential use in the CCL 5 

development process and set aside, as 

supplemental sources, those that met 

the relevance, completeness, and 

redundancy assessment factors but were 

not retrievable. EPA utilized these 

supplemental sources to fill data gaps as 

part of the CCL classification process. 

EPA also identified supplemental 

sources from data sources cited in 

public nominations (see Section III.C.1 

of this document) and conducted 

literature searches to identify further 

supplemental occurrence and health 

effects data as described in this section. 

i. Occurrence 

For PCCL 5 chemicals that reached 

the classification step but lacked 

national drinking water data within the 

last 10 years, EPA conducted a search of 

peer-reviewed literature relevant to the 

occurrence of contaminants in drinking 

water to identify studies that provided 

supplemental occurrence data for 

drinking water or ambient water not 

captured in the primary data sources. 

The literature review was limited to 

journal articles published between 2010 

and 2020. 

Each of the supplemental data sources 

was reviewed to determine the 

availability of data for any of the PCCL 

5 chemicals that required further 

evaluation through the CCL 5 

classification process. EPA identified 

and compiled 12 supplemental 

literature sources for contaminant 

occurrence in drinking and ambient 

water. All supplemental occurrence data 

identified through the literature search 

were included in the CISs. More 

information on CISs can be found in 

Section III.A.4.c of this document and in 

the CIS Technical Support Document 

(USEPA, 2021e). 

EPA’s occurrence literature search 

was conducted in a systematic manner 

to fill the occurrence data gaps for 

contaminants on the PCCL. For 

example, EPA did not conduct 

occurrence literature searches for PCCL 

chemicals that had national drinking 

water occurrence data from the UCMR 

3 or UCMR 4. These chemicals were 

considered to already have the best 

available occurrence data to inform 

whether a contaminant was known to 

occur in public water systems and 

therefore supplemental drinking or 

ambient water occurrence data was not 

needed. A full description of the 

occurrence literature search protocol 

and a list of supplemental occurrence 

literature utilized for CCL 5 can be 

found in the Appendix E of the 

Chemical Technical Support Document 

(USEPA, 2021c). In addition to 

supplemental occurrence data extracted 

through a targeted literature search, EPA 

compiled additional occurrence data 

from the 2006 Community Water 

Systems Survey (CWSS) (USEPA, 2009c; 

2009d), EPA’s Third Six-Year Review 

(SYR 3) (USEPA, 2017), and modeled 

concentrations from EPA’s Office of 

Pesticide Programs (OPP). 

The 2006 CWSS gathered data on the 

financial and operating characteristics 

of a random sample of CWSs 

nationwide. Systems serving more than 

500,000 people were included in the 

sample, and systems in that size 

category were surveyed about 

concentrations of unregulated 

contaminants in their raw and finished 

water. EPA supplemented the data set 

by gathering additional information on 

contaminant occurrence at the systems 

in this size category from publicly 

available sources. The 2006 CWSS was 

used as supplemental source for the 

CCL 5 because the information is not 

statistically representative for the 

purpose of the CCL evaluation. For the 

SYR 3, EPA requested, through an 

Information Collection Request (ICR), 

that primacy agencies voluntarily 

submit drinking water compliance 

monitoring data collected during 2006– 

2011 to EPA. Some primacy agencies 

submitted occurrence data for 

unregulated contaminants in addition to 

the data on regulated contaminants. 

EPA extracted drinking water data on 

PCCL 5 chemicals from the SYR 3 ICR 

data, and supplemented these data by 

downloading additional publicly 

available monitoring data from state 

websites. These data were used as a 

supplemental data source and were 

included on the CISs. 

Modeled concentration data were 

gathered for pesticides on the PCCL 5 

that lack nationally representative 

drinking and/or nationally 

representative ambient water data. The 

modeled concentrations, known as 

estimated environmental concentrations 

(EECs) or estimated drinking water 

concentrations (EDWCs), of pesticides 

in water are often included in EPA’s 

OPP registration and re-registration 

evaluation documentation, but are not 

in a retrievable format that could be 

efficiently extracted for all CCL 5 

Chemical Universe pesticides. 


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Specific information on the 

systematic occurrence literature review, 

SYR 3 ICR, and state occurrence 

monitoring data sets, 2006 CWSS data 

set, and OPP modeled concentrations 

used in the Draft CCL 5 can be found in 

Section 4.2.1 of the Chemical Technical 

Support Document (USEPA, 2021c). 

The data search efforts did not yield 

occurrence data for 13 publicly 

nominated chemicals that were lacking 

occurrence data in the CCL 5 Chemical 

Universe. As a result, these chemicals 

were not evaluated for listing on the 

Draft CCL 5 (Exhibit 6). More 

information is provided on this decision 

in Section III.C.2 of this document and 

Section 4.2.1.1 of the Chemical 

Technical Support Document (USEPA, 

2021c). 

ii. Health Effects 

EPA developed the rapid systematic 

review (RSR) protocol to identify 

supplemental health effects data for 

PCCL 5 chemicals. The RSR process 

encompassed the identification of 

health effects information, including 

epidemiological and toxicological data, 

as well as physiologically-based 

pharmacokinetic models, and 

subsequent extraction of relevant data 

elements (i.e., NOAELs and LOAELs) 

that could be used to derive toxicity 

values and CCL Screening Levels, 

further described in Section III.A.4.b.i of 

this document. The CCL 5 RSR process 

was designed to allow for screening and 

data synthesis of a large number of 

chemicals in a relatively short time 

frame. As such, the RSR process was 

comprised of: 

A targeted chemical-specific literature 

search; 

Machine learning-based screening to 

identify relevant literature; 

A streamlined full-text review and 

study quality evaluation of relevant 

literature; and, 

Data extraction components of 

traditional systematic reviews. 

Studies targeted by the RSR literature 

search included those deemed relevant 

to health effects found in animal models 

after repeated oral exposure lasting at 

least 28 days. Epidemiological studies 

were also identified and catalogued for 

future use (i.e., for Regulatory 

Determination). If available, NOAELs 

and LOAELs, along with their 

corresponding health effects, were 

extracted from all relevant studies. 

These toxicity values were populated on 

the CISs and were used as a 

supplemental source of information for 

chemical evaluators to understand 

potential health effects that could result 

from chronic exposure to PCCL 5 

chemicals. A detailed description of the 

RSR process can be found in Section 

4.2.1 of the Chemical Technical Support 

Document (USEPA, 2021c). 

b. Calculated Data Elements 

i. Health Reference Levels and CCL 

Screening Levels 

Health Reference Levels (HRLs) and 

CCL Screening Levels are referred to 

collectively as ‘‘health concentrations.’’ 

Health concentrations are nonregulatory health-based toxicity values, 

expressed as concentrations of a 

contaminant in drinking water (in mg/L), 

which a person could consume over a 

lifetime and be unlikely to experience 

adverse health effects. HRLs are based 

on data elements (toxicity values 

including RfD, population-adjusted dose 

(PAD), CSF, etc.) extracted from 

‘‘qualifying’’ health assessments, peerreviewed, publicly available health 

assessments published by EPA and 

other health agencies. Assessments used 

to derive HRLs generally follow 

methodology that is consistent with 

EPA’s current guidelines and guidance 

documents, are externally reviewed by 

experts in the field, and have been used 

during EPA regulatory efforts in the 

past. CCL Screening Levels are based on 

data elements (toxicity values including 

RfD equivalents, CSF equivalents, etc.) 

extracted from ‘‘non-qualifying’’ health 

assessments, publicly available 

assessments that are published by 

health agencies and provide valuable 

health information, but do not 

necessarily follow standard EPA 

methodologies and/or are not externally 

peer-reviewed. Alternatively, CCL 

Screening Levels can be based on data 

elements (NOAEL or LOAEL) extracted 

from peer-reviewed studies identified 

through the CCL 5 RSR process 

previously described. 

The process for determining the 

toxicity value most appropriate for use 

in deriving the health concentration is 

similar to the process EPA uses for 

Regulatory Determination. Generally, 

EPA relies on its most recently 

published health assessment as the 

source of these toxicity values unless a 

qualifying assessment from another 

source incorporates new scientific 

information published after the 

publication date of the most recent EPA 

health assessment. If no qualifying 

health assessments are available, EPA 

extracts toxicity values from the most 

recently published non-qualifying 

health assessment. If no qualifying or 

non-qualifying health assessments are 

available, EPA relies on toxicity values 

extracted from studies identified 

through the health effects RSR process. 

For carcinogens, the derived health 

concentration is the one-in-a-million 

cancer risk expressed as a drinking 

water concentration. For noncarcinogens, health concentrations are 

obtained by dividing the RfD (or 

equivalent) by an exposure factor, also 

known as the drinking water intake 

(DWI), and multiplying by a 20% 

relative source contribution (USEPA, 

2000). All health concentrations were 

converted to units of mg/L to compare 

with CCL 5 occurrence concentrations 

and for use in derivation of the final 

Hazard Quotient. If a chemical had no 

available qualifying or non-qualifying 

health assessments or studies identified 

through the RSR process, or the 

available health assessments did not 

provide toxicity values, EPA did not 

derive a health concentration. 

The health concentration used to 

derive the hazard quotient is presented 

on the summary page of the CIS 

alongside the critical effect and data 

element from which it was derived. EPA 

also provides health concentrations 

derived from supplementary 

assessments on the second page of the 

CIS as additional resources. Refer to 

Section 4.3.1 of the Chemical Technical 

Support Document (USEPA, 2021c) for 

more information about the sources and 

process for derivation of CCL 5 health 

concentrations. 

ii. Final Hazard Quotients 

Final hazard quotients (fHQ) are an 

important metric used in the evaluation 

of PCCL chemicals during the 

classification step. The fHQ is the ratio 

of a chemical’s 90th percentile (of 

detections) water concentration over its 

health concentration (HRL or CCL 

screening level) at which no adverse 

effects are expected to occur. The fHQ 

serves as a benchmark for chemical 

evaluators to gauge the potential level of 

concern posed by the exposure to each 

chemical in drinking water. 

A relatively higher fHQ value for a 

given chemical can generally be 

interpreted as an increase to the level of 

concern for exposure to the chemical in 

drinking water; as the ratio increases 

beyond 0, the expected exposure 

concerns also increase; an fHQ value 

equal to or greater than 1.0 indicates a 

chemical with water concentration 

exceeding its health concentration. 

EPA followed the CCL 3 and CCL 4 

protocol to select the concentration 

input values for the ratio as closely as 

possible while incorporating newly 

available data sources. Depending on 

data availability, the fHQ was calculated 

by first using the 90th percentile of 

detections from national drinking water 

monitoring data sources, such as UCMR. 


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If the 90th percentile was not available, 

EPA used the next highest percentile 

(95th or 99th) or maximum reported 

concentration value. For contaminants 

that lacked finished water data but had 

robust ambient water monitoring data 

from sources such as NAWQA, the ratio 

was developed by using the ambient 

water concentration. Similarly, if the 

90th percentile was not available, the 

next highest percentile or maximum 

reported concentration was used. If no 

measured water data were available, 

EPA used modeled water data for 

pesticides developed by EPA’s OPP to 

calculate the fHQ. For contaminants 

with no water data (either measured or 

modeled), the occurrence to health 

concentration ratio could not be 

calculated and the entry for the fHQ was 

left blank on the CIS. 

Similarly, HRLs were the preferred 

health concentration used to derive the 

fHQ. If a chemical did not have data 

available to calculate an HRL, a CCL 

screening level was used to derive the 

fHQ. For chemicals with no relevant 

health effects data (i.e., no HRL or CCL 

screening level), the occurrence to 

health concentration ratio could not be 

calculated and the entry for the fHQ was 

left blank on the CIS. 

A more detailed description of the 

protocol used to calculate the final 

hazard quotients for CCL 5 can be found 

in Section 4.3.2 the Chemical Technical 

Support Document (USEPA, 2021c). 

iii. Attribute Scores 

During the CCL process, EPA 

evaluates relatively new and emerging 

contaminants not currently subject to 

EPA drinking water regulations. Some 

of these contaminants do not have 

readily available information on their 

health effects in humans and animal 

models and/or their occurrence in 

water. Recognizing the need to establish 

consistent relationships and enable 

comparison among different types of 

data, EPA developed a scaling system of 

attribute scores for the CCL 3 based on 

recommendations from the National 

Academy of Science’s National Research 

Council (NRC, 2001) and the National 

Drinking Water Advisory Council 

(NDWAC, 2004). Attributes are defined 

as the properties used to categorize 

contaminants based on their potential to 

cause adverse health effects and occur 

in drinking water. The associated scores 

for these attributes provide a consistent, 

comparative framework for evaluation 

purposes that accommodate a variety of 

input data. 

The health effects of a contaminant 

are categorized using the attributes of 

potency and severity, while the actual 

or potential occurrence of a contaminant 

is categorized using the attributes of 

prevalence and magnitude. 

Potency reflects the potential for a 

chemical to cause adverse health effects 

based on the dose required to elicit the 

most sensitive adverse effect. Severity is 

a descriptive measure of the adverse 

health effect associated with the 

potency score. Unlike the other 

attributes, which are numerical, severity 

is categorical; contaminants are assigned 

to one of eight severity categories (noncancer effects, no adverse effects, 

cosmetic effects, carcinogen with a 

linear mode of action, carcinogen with 

a mutagenic mode of action, carcinogen 

with a non-linear mode of action, 

reproductive and developmental effects, 

or reduced longevity) depending on the 

reported health endpoint. 

Prevalence provides some indicator of 

how widespread the occurrence of the 

contaminant is in the environment, such 

as the percentage of public water 

systems or sample locations in a study 

reporting detections. 

Magnitude describes the quantity of a 

contaminant that may be in the 

environment (e.g., median concentration 

of detections or pounds applied 

annually). When direct occurrence data 

are not available, EPA uses PersistenceMobility data as surrogate indicators of 

potential occurrence of a contaminant. 

Persistence-Mobility is defined by 

chemical properties that measure or 

estimate environmental fate 

characteristics of a contaminant and 

affect their likelihood to occur in water. 

EPA used the attribute scoring 

developed for CCL 3 to evaluate PCCL 

5 chemicals, with some adjustments 

made to the calibrations for potency and 

descriptions for severity. Those 

adjustments, along with the scoring 

scales and categories, are explained in 

detail in the Chemical Technical 

Support Document (USEPA, 2021c). 

c. Evaluation Team Listing Decision 

Process 

The EPA scientists on the two 

evaluation teams shared a broad range 

of professional experience and expertise 

across the agency and with the CCL 

process. These ‘‘chemical evaluators’’ 

were provided training, which included 

a detailed overview of the goals and 

general principles of the CCL process, 

types of data, and materials compiled to 

aid in evaluating chemicals for listing, 

the evaluation process steps, and the 

format of the discussion meetings. Of 

the 275 PCCL 5 chemicals, the 

evaluation teams reviewed 214 

chemicals (Exhibit 6). The evaluation 

teams did not review 7 cyanotoxins, 23 

DBPs, and 18 PFAS chemicals because 

they were listed as three chemical 

groups on the Draft CCL 5 (as discussed 

further in Section III.A.3.e of this 

document). Additionally, the evaluation 

teams did not evaluate the 13 publicly 

nominated chemicals due to lack of 

occurrence data. 

The chemical evaluators on the two 

evaluation teams met over 20 times 

between March 19 and July 2, 2020, to 

discuss their individual reviews and 

reach consensus listing decisions as a 

group for batches of approximately 10– 

20 chemicals per batch. To prepare for 

these discussion meetings, the chemical 

evaluators independently reviewed the 

relevant health effects and occurrence 

information on CISs for each chemical 

in a batch. For each chemical on the 

PCCL 5 that was evaluated for potential 

listing, a CIS was developed to 

summarize the data and assist the 

chemical evaluators in making listing 

recommendations for the Draft CCL 5. 

Each CIS presents the health and 

occurrence data gathered from primary 

and supplemental data sources, as well 

as health and occurrence statistical 

measures described in Section III.A.4.b 

of this document. CISs also include 

additional information about the 

contaminant, such as the identity of the 

contaminant and its usage, whether it 

was subject to past negative regulatory 

determinations, listed on past CCLs, and 

publicly nominated for the CCL 5. Due 

to the inclusion of more data in the CCL 

5 process, CISs for the Draft CCL 5 

contain more information than those of 

past CCLs. CISs for contaminants 

evaluated for the Draft CCL 5 and 

further information on what data the 

CISs provide can be found in the CIS 

Technical Support Document (USEPA, 

2021e). 

Upon completing their independent 

reviews, the chemical evaluators 

submitted their listing decisions along 

with written justifications through a 

survey tool. The results from the survey 

were collected and tabulated before 

each facilitated group discussion. 

Numerical values were assigned to the 

individual evaluator’s listing decision 

for each chemical (i.e., 1 = No List, 2 = 

No List?, 3 = List?, and 4 = List) so that 

an average listing decision could be 

calculated. A question mark (?) signified 

that the chemical evaluator was leaning 

toward listing (List?) or toward not 

listing (No List?) but had some 

uncertainty. These average listing 

decisions helped inform the facilitator 

and the chemical evaluators of their 

collective decisions and guided the 

teams towards making the final listing 

recommendations for each chemical. In 

total, the evaluation teams 

recommended 66 chemicals for listing 

on the Draft CCL 5. A more detailed 


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description of the team listing process 

can be found in Section 4.5 of the 

Chemical Technical Support Document 

(USEPA, 2021c). 

d. Logistic Regression 

EPA conducted statistical analyses 

and developed a simple logistic 

regression model to validate the 

selection of the top 250 highest scoring 

chemicals for inclusion on the PCCL 5 

and provide diagnostic feedback on the 

screening system during the evaluation 

team meetings. EPA hypothesized that 

screening scores have a positive 

association with listing decisions, and 

that the higher the screening score of a 

PCCL 5 chemical, the higher the 

probability of the chemical being 

recommended for listing by the 

evaluation teams. Additional analyses 

and logistic regression models were 

developed to further examine the 

efficacy of the screening scores and to 

determine additional factors, such as 

fHQs and health and occurrence 

attribute scores, associated with listing 

decisions. 

The simple logistic regression models 

the statistical relationship between 

screening scores and the evaluation 

teams’ list or not list decision. The 

model was used to obtain probabilities 

of listing at the highest screening score 

(top of the PCCL 5) and screening score 

directly below the PCCL 5 top 250. 

Results of this analysis indicate 

chemicals with higher screening scores 

are more likely to be listed than 

chemicals with lower screening scores. 

The predicted mean probability of 

listing at the top of the PCCL 5 is 0.90 

and at the screening score directly 

below the PCCL 5 top 250 is 0.12. A full 

description of the modeling approach 

and results can be found in Section 

4.6.2 of the Chemical Technical Support 

Document (USEPA, 2021c). 

Following the evaluation team 

decisions, EPA explored other factors 

that may have impacted listing 

decisions and further evaluated how 

well the screening scores performed as 

a predictor of listing decisions. To 

accomplish this, EPA compiled a 

dataset that contained the chemical 

screening scores, health effects and 

occurrence attribute scores, fHQs, and 

other information. See Section 4.6.1 of 

the Chemical Technical Support 

Document (USEPA, 2021c) for details on 

the compiled dataset used in the 

statistical analyses. The first step of the 

analysis was to calculate descriptive 

statistics for each variable stratified by 

listing decision. Next, several simple 

logistic regression models were 

explored to obtain odds ratios (OR) and 

establish statistical significance of the 

predictor variables. Lastly, an area 

under the curve–receiver operator 

characteristic (AUC–ROC) curve 

analysis was conducted to examine the 

performance of simple logistic 

regression models and multivariable 

logistic models as predictors of listing 

decisions. The results of the simple 

logistic regression found the screening 

scores, attributes scores, and fHQs 

(adjusted for outliers) to be statistically 

significant predictors of listing 

decisions. The AUC–ROC analysis 

provided further evidence that the 

screening scores were a moderate-togood predictor of listing decisions (AUC 

= 0.72) and led to the discovery of a 

multivariable logistic regression model 

that was a very good-to-excellent 

predictor of listing decisions (AUC = 

0.89). A complete description of the 

results of the statistical analyses 

conducted for the Draft CCL 5 can be 

found in Section 4.6 of the Chemical 

Technical Support Document (USEPA, 

2021c). 

e. Chemical Groups on the Draft CCL 5 

In addition to the 66 chemicals 

recommended for listing on the Draft 

CCL 5 by the evaluation teams (Exhibit 

6), EPA proposes to list three chemical 

groups (cyanotoxins, DBPs, and PFAS) 

instead of listing them as individual 

chemicals. These chemical groups have 

been identified as agency priorities and 

contaminants of concern for drinking 

water under other EPA actions. Listing 

these three chemical groups on the Draft 

CCL 5 does not necessarily mean that 

EPA will make subsequent regulatory 

decisions for the entire group. EPA will 

evaluate scientific data on the listed 

groups, subgroups, and individual 

contaminants included in the group to 

inform any regulatory determinations 

for the group, subgroup, or individual 

contaminants in the group. Addressing 

the public health concerns of 

cyanotoxins in drinking water remains a 

priority as specified in the 2015 Algal 

Toxin Risk Assessment and 

Management Strategic Plan for Drinking 

Water (USEPA, 2015). Cyanotoxins are 

toxins naturally produced and released 

by some species of cyanobacteria 

(previously known as ‘‘blue-green 

algae’’), were listed on the CCL 3 and 

CCL 4 as a group. EPA is listing a 

cyanotoxin group on the Draft CCL 5, 

identical to the CCL 3 and CCL 4 listing. 

The group of cyanotoxins includes, but 

is not limited to: Anatoxin-a, 

cylindrospermopsin, microcystins, and 

saxitoxin. Cyanotoxins were also 

monitored under the UCMR 4. 

EPA is also proposing to list 23 

unregulated DBPs (as shown in Exhibit 

2b) as a group on the Draft CCL 5. DBPs 

are formed when disinfectants react 

with naturally-occurring materials in 

water. Under the Stage 2 Disinfectants 

and Disinfection Byproducts Rule, there 

are currently 11 regulated DBPs from 

three subgroups that include four 

trihalomethanes, five haloacetic acids, 

and two inorganic compounds (bromate 

and chlorite). Under the Six-Year 

Review 3 (SYR 3), EPA identified 10 

regulated DBPs (all but bromate) as 

‘‘candidates for revision’’ (USEPA, 

2017). For the Draft CCL 5, the group of 

23 unregulated DBPs were either 

publicly nominated or among the top 

250 chemicals. Listing these 

unregulated DBPs as a group on the 

Draft CCL 5 would be consistent with 

the decision that EPA has identified a 

number of microbial and disinfection 

byproduct (MDBP) drinking water 

regulations as candidates for revision in 

the agency’s SYR 3 . 

PFAS are a class of synthetic 

chemicals that are most commonly used 

to make products resistant to water, 

heat, and stains and are consequently 

found in industrial and consumer 

products like clothing, food packaging, 

cookware, cosmetics, carpeting, and 

fire-fighting foam (AAAS, 2020; USEPA, 

2018b). Over 4,000 PFAS have been 

manufactured and used globally since 

the 1940s (USEPA, 2019b), which 

would make listing PFAS individually 

on the Draft CCL 5 difficult and 

challenging. EPA proposes to list PFAS 

as a group inclusive of any PFAS 

(except for PFOA and PFOS). For the 

purposes of this document, the 

structural definition of PFAS includes 

per- and polyfluorinated substances that 

structurally contain the unit R-(CF2)- 

C(F)(R′)R′′. Both the CF2 and CF 

moieties are saturated carbons and none 

of the R groups (R, R′ or R′′) can be 

hydrogen (USEPA, 2021f). This proposal 

is responsive to public nominations 

which stated that EPA should ‘‘include 

PFAS chemicals as a class on CCL 5.’’ 

This action is in keeping with the 

agency’s commitment to better 

understand and ultimately reduce the 

potential risks caused by this broad 

class of chemicals. Including the broad 

group of PFAS on the Draft CCL 5 

demonstrates the agency’s commitment 

to prioritizing and building a strong 

foundation of science on PFAS while 

working to harmonize multiple 

authorities to address the impacts of 

PFAS on public health and the 

environment. EPA is also committed to 

a flexible approach and working 

collaboratively with states, tribes, water 

systems, and local communities that 

have been impacted by PFAS. 


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B. Approach Used To Identify Microbial 

Candidates for the Draft CCL 5 

1. Building the Microbial Universe 

EPA defined the microbial Universe 

for the CCL 5 as all known human 

pathogens. The microbial Universe was 

built on the CCL 3 and the CCL 4 

Universe of 1,425 pathogens. EPA 

conducted a literature search, sought 

input from subject matter experts, and 

reviewed nominations for additional 

microbes to add to the Universe. As a 

result, 14 organisms were added to the 

CCL 5 Microbial Universe (Exhibit 7). 

Changes to nomenclature of the 

microbes were made as necessary (in 

most cases combining two species into 

one organism group), making the total 

number of organisms in the microbial 

Universe 1,435. The full CCL 5 

microbial Universe list is available in 

the Technical Support Document for the 

Draft fifth Contaminant Candidate List 

(CCL 5)—Microbial Contaminants 

(USEPA, 2021d). 

EXHIBIT 7—MICROBIAL CONTAMINANTS

ADDED TO THE MICROBIAL UNIVERSE

FOR THE CCL 5 

Microbial contaminant Microbe 

class 

Alloscardovia omnicolens ............. Bacteria. 

Elizabethkingia anophelis ............. Bacteria. 

Neoehrlichia mikurensis ............... Bacteria. 

Parachlamydia acanthamoebae ... Bacteria. 

Waddia chondrophila .................... Bacteria. 

EXHIBIT 7—MICROBIAL CONTAMINANTS

ADDED TO THE MICROBIAL UNIVERSE

FOR THE CCL 5—Continued 

Microbial contaminant Microbe 

class 

Human bocavirus ......................... Virus. 

Human coronavirus SARS–CoV– 

2.

Virus. 

KI polyomavirus ............................ Virus. 

Kobuvirus ...................................... Virus. 

Lujo virus ...................................... Virus. 

Parovovirus 4 ............................... Virus. 

WU polyomavirus ......................... Virus. 

Botrytsis cinerea ........................... Fungi. 

Epiccocum purpurascens ............. Fungi. 

2. Screening the Microbial Universe to 

the PCCL 

During the CCL 3 process, EPA 

developed 12 screening criteria (Exhibit 

8) to focus the Universe of all human 

pathogens to only those pathogens that 

could be transmitted through drinking 

water. Screening is based on a 

pathogen’s epidemiology, geographical 

distribution, and biological properties in 

their host and in the environment. All 

pathogens that are not excluded by any 

screening criteria are moved to the 

PCCL. In addition, any pathogen 

documented to cause disease 

transmitted through drinking water 

regardless of the screening criteria, is 

also considered for the PCCL. The 

screening criteria restrict the microbial 

PCCL to human pathogens that may 

cause drinking water-related diseases 

resulting from ingestion of, inhalation 

of, or dermal contact with drinking 

water. For the Draft CCL 5, EPA reevaluated the screening criteria for 

applicability to microbes and reviewed 

certain criterion in depth per 

recommendations received from the 

SAB and stakeholders during the 

development of the CCL 3 and the CCL 

4. In particular, Criterion 1 (anaerobes), 

Criterion 9 (natural habitat is in the 

environment without epidemiological 

evidence of drinking water-related 

disease) and Criterion 10 (not endemic 

to North America) were closely reevaluated based on previous comments 

for the CCL 3 and the CCL 4 from 

NDWAC, SAB, and the public. Upon 

further evaluation, EPA did not find 

supporting evidence to modify Criterion 

1 and Criterion 10. 

EPA modified the screening Criterion 

9 to include pathogens on the PCCL 

with nosocomial infections where 

drinking water is implicated due to 

recent increases in and recognition of 

antimicrobial resistance and nosocomial 

infections. Modifying Criterion 9 

addresses a SAB comment that the 

screening criteria for the CCL 4 

microbial process were too restrictive. 

As a result, Criterion 9 was modified to 

include pathogens that cause 

nosocomial infections where drinking 

water is implicated so that it is less 

restrictive. 

EXHIBIT 8—SCREENING CRITERIA FOR PATHOGENS

All anaerobes. 

Obligate intracellular fastidious pathogens. 

Transmitted by contact with blood or body fluids. 

Transmitted by vectors. 

Indigenous to the gastrointestinal tract, skin and mucous membranes. 

Transmitted solely by respiratory secretions. 

Life cycle incompatible with drinking water transmission. 

Drinking water-related transmission is not implicated. 

Natural habitat is in the environment without epidemiological evidence of drinking water-related disease and without evidence of drinking 

water-related nosocomial infection. 

Not endemic to North America. 

Represented by a pathogen for the entire genus or species (that are closely related). 

Current taxonomy changed from taxonomy used in Universe. 

Bolded text indicates the modification made to Criterion 9. 

Based upon the screening criteria, 

1,400 of the 1,435 pathogens were 

excluded; therefore 35 pathogens 

advanced to the PCCL. The results of the 

screening process are summarized in 

Exhibit 9. The criteria and results of the 

screening process are discussed in 

greater detail in the Technical Support 

Document for the Draft Fifth 

Contaminant Candidate List (CCL 5)— 

Microbial Contaminants (USEPA, 

2021d). 

EXHIBIT 9—APPLICATION OF 12 SCREENING CRITERIA TO PATHOGENS IN THE MICROBIAL CCL UNIVERSE

Pathogen 

class Total 

Screening criteria and number of pathogens screened out per criterion Pathogens 

screened 

out 

On 

PCCL 1 2 3 4 5 6 7 8 9 10 11 12 

Bacteria ... 545 ........................... 121 16 10 38 121 7 0 29 150 2 28 5 527 1 18 

Viruses .... 225 ........................... 0 0 29 104 0 20 1 20 0 36 8 0 218 7 

Protozoa 2 66 ............................. 0 0 1 29 3 0 4 7 7 0 6 0 59 7 

Helminths 286 ........................... 0 0 0 25 0 0 105 0 0 156 0 0 286 0 


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EXHIBIT 9—APPLICATION OF 12 SCREENING CRITERIA TO PATHOGENS IN THE MICROBIAL CCL UNIVERSE—Continued 

Pathogen 

class Total 

Screening criteria and number of pathogens screened out per criterion Pathogens 

screened 

out 

On 

PCCL 1 2 3 4 5 6 7 8 9 10 11 12 

Fungi ....... 313 ........................... 0 0 0 0 12 3 0 0 295 0 0 0 310 3 

Total 1,435 ........................ 121 16 40 196 136 30 110 56 452 194 42 5 1,400 35 

1 NTM are included on the PCCL as a group. 

2 Cryptosporidium and Giardia (both protozoa) are considered to be regulated by the Long Term Surface Water Treatment Rule (LT–2); even though counted in the

Microbial universe, they were not evaluated for screening. 

3. The PCCL to Draft CCL Process 

Pathogens on the PCCL were scored 

for placement on the Draft CCL 5. In 

developing the CCL 3, EPA devised a 

scoring system to assign a numerical 

value to each pathogen on the PCCL. 

Each pathogen on the PCCL was scored 

using three scoring protocols, one 

protocol each for waterborne disease 

outbreaks (WBDO), occurrence in 

drinking water, and health effects. The 

higher of the WBDO score or the 

occurrence score was added to the 

normalized health effects score to 

produce a composite pathogen score. 

Pathogens receiving high scores were 

considered for placement on the CCL. 

EPA normalized the health effects 

score so that occurrence and health 

effects had equal weight in determining 

the ranking of the Draft CCL. The equal 

weighting of occurrence and health 

effects information closely mirrors the 

risk estimate methods used by EPA in 

drinking water regulation development. 

This scoring system prioritizes and 

restricts the number of pathogens on the 

CCL to only those that have been 

strongly associated with drinking waterrelated disease. Pathogens that scored 

low will remain on the PCCL until 

additional occurrence data, 

epidemiological surveillance data, or 

health effects data become available to 

support their reevaluation. It is 

important to note that pathogens for 

which there are no documented WBDO 

in drinking water earn a low score 

under the protocols. Pathogens that 

have caused a WBDO and have health 

effects data are rank higher than 

pathogens that only have health effect 

data but no evidence of a WBDO. The 

following sections describe the three 

protocols used to score the pathogens on 

the PCCL and the process by which the 

scores are combined. 

a. Waterborne Disease Outbreak 

(WBDO) Protocol 

The Centers for Disease Control and 

Prevention (CDC), EPA, and the Council 

of State and Territorial Epidemiologists 

(CSTE) have maintained a collaborative 

surveillance system for collecting and 

periodically reporting data related to 

occurrence and causes of WBDOs since 

1971. In recent years, CDC has 

developed National Outbreak Reporting 

System (NORS) (CDC, 2020a) for WBDO 

reporting, in collaboration with CSTE 

and EPA, to improve the quality, 

quantity, and availability of data 

submitted to the Waterborne Disease 

and Outbreak Surveillance System 

(WBDOSS). For the Draft CCL 5, EPA 

used CDC’s NORS as the primary data 

source for the WBDO protocol. Reports 

from the CDC system were published 

periodically in Morbidity and Mortality 

Weekly Report (MMWR) until 2017. For 

the CCL 3 and the CCL 4, EPA used 

MMWRs for the WBDO protocol. 

For the Draft CCL 5, EPA used CDC’s 

NORS for more recent outbreak 

information due to the most recent 

MMWR being published in 2014. For 

the WBDO protocol (Exhibit 10), a 

pathogen is scored as having a WBDO(s) 

in the U.S. if that pathogen is listed in 

a CDC waterborne disease drinking 

water surveillance summary (i.e., on 

NORS from 2009–2017). Outbreaks that 

occurred in 2009 and after were used to 

capture microbes causing concern since 

the publication of the CCL 3. A 

pathogen with multiple WBDOs listed 

by CDC was given the highest score 

under this protocol. In addition, EPA 

scored non-CDC reported WBDOs and 

WBDOs outside the U.S. with lower 

scores. WBDOs outside the U.S. were 

scored when information was available 

from World Health Organization or 

other peer-reviewed publications. 

In addition, CDC and EPA 

acknowledge that the WBDOs reported 

in the surveillance system represent 

only a portion of the burden of illness 

associated with drinking water exposure 

(CDC, 2008). The surveillance 

information does not include endemic 

waterborne disease risks, nor are 

reliable estimates available of the 

number of unrecognized WBDOs and 

associated cases of illness. Therefore, 

EPA also considered the non-CDC data 

as indicating a WBDO (even though 

CDC did not list it in their NORS) if the 

data showed a link between human 

illness defined by a common water 

source, a common time period of 

exposure and/or similar symptoms. 

Additionally, EPA considered the use of 

molecular typing methods to link 

patients and environmental isolates. 

EXHIBIT 10—WATERBORNE DISEASE OUTBREAK SCORING PROTOCOL

Category Score 

Has caused multiple (2 or more) documented WBDOs in the U.S. as reported by CDC surveillance between 2009–2017 ................... 5 

Has caused at least one documented WBDO in the U.S. as reported by CDC surveillance 2009–2017 ................................................. 4 

Has caused documented WBDOs at any time in the U.S. ......................................................................................................................... 3 

Has caused documented WBDOs in countries other than the U.S. ........................................................................................................... 2 

Has never caused WBDOs in any country, but has been epidemiologically associated with water-related disease ................................ 1 

b. Occurrence Protocol 

The second attribute of the scoring 

process evaluates the occurrence of a 

pathogen in drinking water and source 

water. Because water-related illness may 

also occur in the absence of recognized 

outbreaks, EPA scored the occurrence 

(direct detection) of microbes using 

cultural, immunochemical, or molecular 

detection of pathogens in drinking water 

under the Occurrence Protocol (Exhibit 

11). Occurrence characterizes pathogen 

introduction, survival, and distribution 

in the environment. Occurrence implies 

that pathogens are present in water and 

that they may be capable of surviving 

and moving through water to cause 


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illness in persons exposed to drinking 

water by ingestion, inhalation, or 

dermal contact. 

Pathogen occurrence is considered 

broadly to include treated drinking 

water, and all waters using a drinking 

water source for recreational purposes, 

ground water, and surface water bodies. 

This attribute does not characterize the 

extent to which a pathogen’s occurrence 

poses a public health threat from 

drinking water exposure. 

EXHIBIT 11—OCCURRENCE AND HEALTH EFFECTS SCORING PROTOCOLS FOR PATHOGENS

Category Score 

Occurrence Scoring Protocol: 

Detected in drinking water in the U.S. 3 

Detected in source water in the U.S. 2 

Not detected in the U.S. 1 

Health Effects Scoring Protocol: 

Does the organism cause significant mortality (>1/1,000 cases)? ...................................................................................................... 7 

Does the organism cause pneumonia, meningitis, hepatitis, encephalitis, endocarditis, cancer, or other severe manifestations of

illness necessitating long term hospitalization (>week)? ................................................................................................................. 6 

Does the illness result in long term or permanent dysfunction or disability (e.g., sequelae)? ............................................................ 5 

Does the illness require short term hospitalization? (<week)? ............................................................................................................ 4 

Does the illness require physician intervention? .................................................................................................................................. 3 

Is the illness self-limiting within 72 hours (without requiring medical intervention)? ........................................................................... 2 

Does the illness result in mild symptoms with minimal or no impact on daily activities? ................................................................... 1 

c. Health Effects Protocol 

EPA’s health effects protocol 

evaluates the extent or severity of 

human illness produced by a pathogen 

across a range of potential endpoints. 

The seven-level hierarchy developed for 

this protocol (Exhibit 11) begins with 

mild, self-limiting illness (score of 1) 

and progresses to death (score of 7). 

The final outcome of a host-pathogen 

relationship resulting from drinking 

water exposure is a function of viability, 

infectivity, and pathogenicity of the 

microbe to which the host is exposed 

and the host’s susceptibility and 

immune response. SDWA directs EPA to 

consider subgroups of the population at 

greater risk of adverse health effects (i.e., 

sensitive populations) in the selection of 

unregulated contaminants for the CCL. 

Sensitive populations may have 

increased susceptibility and may 

experience increased severity of 

symptoms, compared to the general 

population. The SDWA refers to several 

categories of sensitive populations 

including children and infants, elderly, 

pregnant women, and persons with a 

history of serious illness. Health effects 

for individuals with marked 

immunosuppression (e.g., primary or 

acquired severe immunodeficiency, 

transplant recipients, individuals 

undergoing potent cytoreductive 

treatments) are not included in this 

health effect scoring. While such 

populations are considered sensitive 

subpopulations, immunosuppressed 

individuals often have a higher standard 

of ongoing health care and protection 

required than the other sensitive 

populations under medical care. More 

importantly, nearly all pathogens have 

very high health effect scores for the 

markedly immunosuppressed 

individuals; therefore, there is little 

differentiation between pathogens based 

on health effects for the 

immunosuppressed subpopulation. 

This protocol scores the 

representative or common clinical 

presentation for the specific pathogen 

for the population category under 

consideration. Pathogens may produce a 

range of illness from asymptomatic 

infection to fulminate illness 

progressing rapidly to death. Scoring 

decisions are based upon the more 

common clinical presentation and 

clinical course for the population under 

consideration, rather than the extremes. 

EPA used recently published clinical 

microbiology manuals (Carroll et al., 

2019; Murray et al., 2011) as the primary 

data source for the common clinical 

presentation. These manuals took a 

broad epidemiological view of health 

effects rather than focusing on narrow 

research investigations or single cases. 

To obtain a representative 

characterization of health effects in all 

populations, EPA evaluated (separately) 

the general population and four 

sensitive populations (children, elderly, 

pregnant woman, and persons with 

chronic diseases) as to the common 

clinical presentation of illness for that 

population. EPA added the general 

population score to the highest score 

among the four sensitive subpopulations 

for an overall health effects score. The 

resulting score reflects that sensitive 

populations have increased risk for 

waterborne diseases. 

d. Combining Protocol Scores To Rank 

Pathogens 

EPA scored and ranked the microbes 

on the PCCL using the three attribute 

scoring protocols for WBDOs, 

occurrence, and health effects. These 

protocols are designed in a hierarchical 

manner so that each pathogen is 

evaluated using the same criteria and 

that the criteria range for each protocol 

varies from high to low significance. 

The three attribute scores are then 

combined into a total score. 

EPA scored pathogens first using the 

WBDO and occurrence protocols, and 

then selected the higher score of the two 

scores. Selection of the higher score 

from the WBDO or occurrence protocol 

elevates pathogens that have been 

detected in drinking water or source 

water in the U.S. (occurrence score of 2 

or 3) above pathogens that have caused 

WBDOs in other countries but not in the 

U.S. (WBDO score of 2). 

The CCL selection process placed 

more weight on pathogens causing 

recent WBDOs than on those detected in 

drinking water without documented 

waterborne disease from that exposure. 

Direct detection of pathogens indicates 

the potential for waterborne 

transmission of disease. Documented 

WBDOs provide an additional weight of 

evidence that illness was transmitted 

and that there was a waterborne route of 

exposure. 

Next, pathogens were scored using the 

Health Effects Protocol. The pathogen’s 

score for the general population was 

added to the highest score among the 

four sensitive populations to produce a 

sum score between 2 and 14. 

Finally, EPA normalizes the Health 

Effects score and WBDO/Occurrence 

score because these are of equal 

importance. The highest possible score 

for WBDO/Occurrence is 5 and the 

highest possible Health Effects score is 

14. To equalize this imbalance, EPA 


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multiplies the health effect score by 

5/14. Combining health effects data with 

the WBDO/occurrence data by adding 

the scores from these protocols provides 

a system that evaluates both the severity 

of potential disease and the potential 

magnitude of exposure through drinking 

water. Exhibit 12 presents the scores for 

all the 35 PCCL pathogens. 

EXHIBIT 12—SCORES FOR ALL THE PCCL 5 PATHOGENS

Pathogen Ranking WBDO Occurrence 

Normalized 

health 

score 

Total 

score 1

Naegleria fowleri ...................................................................................... 1 5 3 5.0 10.0 

Legionella pneumophila ........................................................................... 2 5 3 3.6 8.6 

Escherichia coli (O157) ............................................................................ 3 5 3 3.2 8.2 

Pseudomonas aeruginosa ....................................................................... 4 5 3 3.2 8.2 

Helicobacter pylori ................................................................................... 5 1 3 5.0 8.0 

Campylobacter jejuni ............................................................................... 6 5 3 2.5 7.5 

Mycobacterium abcessus ........................................................................ 7 4 3 3.2 7.2 

Shigella sonnei ........................................................................................ 8 4 3 3.2 7.2 

Caliciviruses ............................................................................................. 9 5 3 2.1 7.1 

Mycobacterium avium .............................................................................. 10 4 3 2.9 6.9 

Adenovirus ............................................................................................... 11 2 3 3.6 6.6 

Enterovirus ............................................................................................... 12 2 3 3.6 6.6 

Pantoea agglomerans .............................................................................. 13 4 3 2.5 6.5 

Hepatitis A virus ....................................................................................... 14 3 2 3.2 6.2 

Arcobacter butzleri ................................................................................... 15 4 3 2.1 6.1 

Fusarium solani ........................................................................................ 16 1 3 2.9 5.9 

Nontuberculous Mycobacteria (NTM) ...................................................... 17 3 3 2.9 5.9 

Hepatitis E virus ....................................................................................... 18 2 1 3.6 5.6 

Cyclospora cayetanensis ......................................................................... 19 3 3 2.5 5.5 

Rotavirus .................................................................................................. 20 2 3 2.5 5.5 

Salmonella enterica ................................................................................. 21 3 3 2.5 5.5 

Toxoplasma gondii ................................................................................... 22 2 1 3.2 5.2 

Aspergillus fumigatus group .................................................................... 23 1 3 2.1 5.1 

Entamoeba histolytica .............................................................................. 24 3 3 2.1 5.1 

Exophiala jeanselmei ............................................................................... 25 1 3 2.1 5.1 

Vibrio cholerae ......................................................................................... 26 3 3 2.1 5.1 

Aeromonas hydrophila ............................................................................. 27 1 3 1.8 4.8 

Plesiomonas shigelloides ......................................................................... 28 3 3 1.8 4.8 

Blastocystis hominis ................................................................................. 29 4 1 0.7 4.7 

Acinetobacter baumannii ......................................................................... 30 1 2 2.5 4.5 

Comanonas testosteroni .......................................................................... 31 1 2 2.5 4.5 

Yersinia enterocolitica .............................................................................. 32 3 3 1.4 4.4 

Astrovirus ................................................................................................. 33 2 2 1.4 3.4 

Microsporidia ............................................................................................ 34 1 2 1.4 3.4 

Isospora belli ............................................................................................ 35 2 1 1.1 3.1 

1Total Score = Normalized Health Score + the higher of WBDO or Occurrence. 

e. Selection of the Draft CCL Microbes 

The 35 PCCL pathogens, listed in 

Exhibit 12, are ranked according to an 

equal weighting of their summed scores 

for normalized health effects and the 

higher of the individual scores for 

WBDO and occurrence in drinking 

water. EPA believes this ranking 

indicates the most important pathogens 

to consider for the Draft CCL 5. To 

determine which of the 35 PCCL 

pathogens should be the highest priority 

for EPA’s drinking water program and 

included on the Draft CCL 5, EPA 

considered scientific factors and the 

opportunity to advance public health 

protection. The factors included the 

PCCL scores for WBDO, occurrence, and 

health effects; and comments and 

recommendations from the various 

expert panels, including EPA’s internal 

workgroup and CDC subject matter 

experts. The evaluation prioritizes the 

pathogens that provide the best 

opportunities to advance public health 

protection. After consideration of these 

factors, EPA has decided to include in 

the Draft CCL 5 the 12 highest ranked 

pathogens shown in Exhibit 12. The 

selection of microbial pathogens for the 

CCL 5 was similar to the method used 

for the CCL 3 and the CCL 4 with the 

exception that with the CCL 5, there 

were no ‘‘natural’’ break points in the 

ranked scores for the 35 pathogens. 

EPA believes that the overall rankings 

strongly reflect the best available 

scientific data and high quality expert 

input employed in the CCL selection 

process, and therefore should be 

important factors in helping to identify 

the top priority pathogens for the Draft 

CCL 5. 

f. Organisms Covered by Existing 

Regulations 

According to Section 1412(b)(1) of the 

1996 SDWA Amendments, EPA must 

select CCL contaminants that ‘‘at the 

time of publication, are not subject to 

any proposed or promulgated national 

primary drinking water regulation.’’ In 

promulgating regulations for 

contaminants in drinking water, EPA 

can set either a legal limit (maximum 

contaminant level or MCL) and require 

monitoring for the contaminant in 

drinking water or, for those 

contaminants that are difficult to 

measure, EPA can establish a treatment 

technique requirement. The Surface 

Water Treatment Rule (54 FR 27486, 

USEPA, 1989a) established maximum 

contaminant level goals (MCLGs) of zero 

for Legionella, Giardia, and viruses 

because any amount of exposure to 

these contaminants represents some 

public health risk. Since measuring 

disease-causing microbes in drinking 

water was not considered to be feasible 

at the time of the development of the 

SWTR, EPA established treatment 


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technique requirements for these 

contaminants. The purpose of 

subsequent treatment technique 

requirements (Interim Enhanced Surface 

Water Treatment Rule (63 FR 69478, 

USEPA 1998a), Long Term 1 Surface 

Water Treatment Rule (67 FR 1813, 

USEPA, 2002a), and the Long Term 2 

Surface Water Treatment Rule (71 FR 

654, USEPA, 2006a), which included an 

MCLG of zero for Cryptosporidium, is to 

reduce disease incidence associated 

with Cryptosporidium and other 

pathogenic microorganisms in drinking 

water. These rules apply to all public 

water systems that use surface water or 

ground water under the direct influence 

of surface water. 

The Ground Water Rule (GWR) (71 FR 

65573; USEPA, 2006c) set treatment 

technique requirements to control for 

viruses (and pathogenic bacteria) 

because it was not feasible to monitor 

for viruses (or pathogenic bacteria) in 

drinking water. Under the GWR, if 

systems detect total coliforms in the 

distribution system, they are required to 

monitor for a fecal indicator (E. coli, 

coliphage, or enterococci) in the source 

water. If fecal contamination is found in 

the source water, the system must take 

remedial action to address 

contamination. 

EPA considered Legionella and 

specific viruses in CCL even though 

they are regulated under the Surface 

Water Treatment Rules (SWTR). In this 

draft document, EPA proposes to 

specifically list Legionella 

pneumophila, the primary pathogenic 

bacterium, on the Draft CCL 5 because 

it has been identified in numerous 

WBDOs and is the most common cause 

of reported drinking water-associated 

outbreaks in the U.S. Furthermore, 

reported Legionnaires’ disease has 

increased 10-fold in the last 20 years 

(CDC, 2020b). A recent National 

Academies of Science report estimated 

52,000–70,000 cases of Legionnaires’ 

disease annually, with 3–30% mortality 

(NASEM, 2020). 

EPA is also proposing to list certain 

viruses on the Draft CCL 5. Viruses 

include a wide range of taxa and 

different viral taxa have been implicated 

in various WBDOs for which EPA did 

not have dose response or treatment 

data when promulgating its treatment 

technique requirements. 

Even though there are MCLGs for 

Legionella and viruses, and these 

contaminants are subject to limitations 

as a class through the treatment 

techniques under the Surface Water 

Treatment Rules, there are no 

monitoring, treatment, or notification 

requirements within those NPDWRs that 

are specific to Legionella pneumophila 

or the specific viruses listed on CCL5 

(although systems may use coliphage for 

source water monitoring for ground 

water systems). Therefore, EPA 

considers Legionella pneumophila and 

the specific viruses listed on CCL5 to be 

unregulated contaminants for purposes 

of eligibility for the CCL. Additionally, 

EPA received public nomination for 

viruses and Legionella for the Draft CCL 

5, with Legionella pneumophila 

receiving the highest number of 

nominations. 

C. Summary of Nominated Candidates 

for the Draft CCL 5 

EPA sought public nominations in a 

Federal Register notice on October 5, 

2018, for unregulated chemical and 

microbial contaminants to be 

considered for possible inclusion in the 

CCL 5 (83 FR 50364, USEPA, 2018a). In 

accordance with the SDWA, which 

directs EPA to consider health effects 

and occurrence information when 

deciding whether to place contaminants 

on the CCL, EPA asked that nominations 

include responses to the following 

questions: 

What is the contaminant’s name, CAS 

registry number, and/or common 

synonym (if applicable)? Please do not 

nominate a contaminant that is already 

subject to a national primary drinking 

water regulation. 

What are the data that you believe 

support the conclusion that the 

contaminant is known or anticipated to 

occur in public water systems? For 

example, provide information that 

shows measured occurrence of the 

contaminant in drinking water or 

measured occurrence in sources of 

drinking water or provide information 

that shows the contaminant is released 

in the environment or is manufactured 

in large quantities and has a potential 

for contaminating sources of drinking 

water. Please provide the source of this 

information with complete citations for 

published information (i.e., author(s), 

title, journal, and date) or contact 

information for the primary investigator. 

What are the data that you believe 

support the conclusion that the 

contaminant may require regulation? 

For example, provide information that 

shows the contaminant may have an 

adverse health effect on the general 

population or that the contaminant is 

potentially harmful to subgroups that 

comprise a meaningful proportion of the 

population (such as children, pregnant 

women, the elderly, individuals with a 

history of serious illness, or others). 

Please provide the source of this 

information with complete citations for 

published information (i.e., author(s), 

title, journal, and date) or contact 

information for the primary investigator. 

EPA compiled and reviewed the 

information from the nominations 

process to identify the contaminants 

nominated and any sources of 

supporting data submitted that could be 

used to supplement the data gathered by 

EPA to inform selection of the Draft CCL 

5. 

EPA received nominations for 89 

unique contaminants for the CCL 5, 

including 73 chemicals and 16 

microbes. Nominated contaminants 

included chemicals used in commerce, 

pesticides, disinfection byproducts, 

pharmaceuticals, naturally occurring 

elements, biological toxins, and 

waterborne pathogens. Contaminants 

nominated for consideration for the CCL 

5 are shown in Exhibit 13. 

EPA received nominations from 29 

different organizations and/or 

individuals. There were three general 

types of nominations: specific 

individual chemicals, specific 

individual organisms, and groups of 

contaminants (e.g., PFAS). Seven 

chemicals and eight microbes were 

nominated by more than one 

organization or individual. Legionella 

pneumophila received the most 

nominations, nominated by 18 

organizations or individuals. Among 

chemicals, perfluorononanoic acid 

(PFNA), PFOS, and PFOA received the 

most nominations, each nominated by 

three organizations or individuals. In 

addition to individual contaminants, 

groups of contaminants were 

nominated, such as brominated 

haloacetic acids known as ‘‘HAA6Br,’’ 

cyanotoxins, GenX chemicals 

(hexafluoropropylene oxide dimer acid 

(HFPO–DA) and its ammonium salt), all 

the PFAS approved by the EPA Method 

537.1, PFAS, and the top 200 prescribed 

drugs of 2016 and their parents and 

metabolites. A public commenter also 

proposed that all CCL 4 contaminants be 

retained on the CCL 5. 

EPA also received recommendations 

for the CCL process. All public 

nominations can be viewed in the EPA 

docket at https://www.regulations.gov 

(Docket ID No. EPA–HQ–OW–2018– 

0594). A more detailed summary of the 

nomination process is included in 

Section 3.6 of the Chemical Technical 

Support Document (USEPA, 2021c) and 

in Section 2.1 of the Microbial 

Technical Support Document (USEPA, 

2021d). 


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EXHIBIT 13—CONTAMINANTS NOMINATED FOR CONSIDERATION ON THE DRAFT CCL 5: NOMINATED CHEMICAL

CONTAMINANT

Chemical name CASRN DTXSID 

1,1-Dichloroethane ........................................................................................................................................ 75–34–3 DTXSID1020437 

1,4-Dioxane ................................................................................................................................................... 123–91–1 DTXSID4020533 

1-Phenylacetone 1 ......................................................................................................................................... 103–79–7 DTXSID1059280 

2-(N-Methylperfluorooctane sulfonamido)acetic acid (Me-PFOSA-AcOH) ................................................... 2355–31–9 DTXSID10624392 

2-(N-Ethyl perfluorooctane sulfonamido) acetic acid (Et-PFOSA-AcOH) ..................................................... 2991–50–6 DTXSID5062760 

2-[(8-Chloro-1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-Hexadecafluorooctyl)oxy]-1,1,2,2-tetrafluoroethane-1-sulfonic 

acid (11Cl-PF3OUdS).

763051–92–9 DTXSID40892507 

3-Hydroxycarbofuran ..................................................................................................................................... 16655–82–6 DTXSID2037506 

3-Monoacetylmorphine 1 ................................................................................................................................ 29593–26–8 DTXSID30183774 

4,8-Dioxa-3H-perfluorononanoic acid (ADONA) ........................................................................................... 919005–14–4 DTXSID40881350 

6-Monoacetylmorphine 1 ................................................................................................................................ 2784–73–8 DTXSID60182154 

Ammonium perfluoro-2-methyl-3-oxahexanoate ........................................................................................... 62037–80–3 DTXSID40108559 

Anatoxin A ..................................................................................................................................................... 64285–06–9 DTXSID50867064 

Azinphos-methyl ............................................................................................................................................ 86–50–0 DTXSID3020122 

Benzoic acid 1 ................................................................................................................................................ 65–85–0 DTXSID6020143 

Benzoic acid glucuronide 1 ............................................................................................................................ 19237–53–7 DTXSID90940901 

Bromochloroacetic acid (BCAA) .................................................................................................................... 5589–96–8 DTXSID4024642 

Bromochloroiodomethane (BCIM) ................................................................................................................. 34970–00–8 DTXSID9021502 

Bromodichloroacetic acid (BDCAA) .............................................................................................................. 71133–14–7 DTXSID4024644 

Bromodichloronitromethane (BDCNM) .......................................................................................................... 918–01–4 DTXSID4021509 

Bromodiiodomethane (BDIM) ........................................................................................................................ 557–95–9 DTXSID70204235 

Chlorate ......................................................................................................................................................... 14866–68–3 DTXSID3073137 

Chlorodibromoacetic acid (CDBAA) .............................................................................................................. 5278–95–5 DTXSID3031151 

Chloro-diiodo-methane (CDIM) ..................................................................................................................... 638–73–3 DTXSID20213251 

Chloropicrin (trichloro-nitromethane; TCNM) ................................................................................................ 76–06–2 DTXSID0020315 

Chlorpyrifos ................................................................................................................................................... 2921–88–2 DTXSID4020458 

Cylindrospermopsin ....................................................................................................................................... 143545–90–8 DTXSID2031083 

Dibromochloronitromethane (DBCNM) ......................................................................................................... 1184–89–0 DTXSID00152114 

Dibromoiodomethane (DBIM) ........................................................................................................................ 593–94–2 DTXSID60208040 

Dichloroiodomethane (DCIM) ........................................................................................................................ 594–04–7 DTXSID7021570 

Fluoxetine ...................................................................................................................................................... 5491–89–3 DTXSID7023067 

Gemfibrozil .................................................................................................................................................... 25812–30–0 DTXSID0020652 

Heroin ............................................................................................................................................................ 561–27–3 DTXSID6046761 

Hippuric acid 1 ............................................................................................................................................... 495–69–2 DTXSID9046073 

Hydromorphone 1 ........................................................................................................................................... 466–99–9 DTXSID8023133 

Hydromorphone-3-glucuronide 1 .................................................................................................................... No CASRN NO_DTXSID 

Hydroxyamphetamide 1 ................................................................................................................................. 103–86–6 DTXSID3023134 

Isodrin (Pholedrine, 4-Hydroxymethamphetamine) 1 .................................................................................... 465–73–6 DTXSID7042065 

Manganese .................................................................................................................................................... 7439–96–5 DTXSID2024169 

Methamphetamine 1 ....................................................................................................................................... 537–46–2 DTXSID8037128 

Microcystin LA ............................................................................................................................................... 96180–79–9 DTXSID3031656 

Microcystin LR ............................................................................................................................................... 101043–37–2 DTXSID3031654 

Microcystin LW .............................................................................................................................................. No CASRN DTXSID70891285 

Microcystin RR .............................................................................................................................................. 111755–37–4 DTXSID40880085 

Microcystin YR .............................................................................................................................................. 101064–48–6 DTXSID00880086 

Molybdenum .................................................................................................................................................. 7439–98–7 DTXSID1024207 

Morphine ........................................................................................................................................................ 57–27–2 DTXSID9023336 

Morphine-3-glucuronide ................................................................................................................................. 20290–09–9 DTXSID80174157 

Morphine-6-glucuronide 1 .............................................................................................................................. 20290–10–2 DTXSID40174158 

N-Nitrosodiethylamine (NDEA) ...................................................................................................................... 55–18–5 DTXSID2021028 

N-Nitrosodimethylamine (NDMA) .................................................................................................................. 62–75–9 DTXSID7021029 

N-Nitroso-di-n-propylamine (NDPA) .............................................................................................................. 621–64–7 DTXSID6021032 

N-Nitrosodiphenylamine (NDPhA) ................................................................................................................. 86–30–6 DTXSID6021030 

N-Nitrosopyrrolidine (NPYR) ......................................................................................................................... 930–55–2 DTXSID8021062 

Perfluoro(2-((6-chlorohexyl)oxy)ethanesulfonic acid) (9Cl-PF3ONS) ........................................................... 756426–58–1 DTXSID80892506 

Perfluoro-2-methyl-3-oxahexanoic acid ......................................................................................................... 13252–13–6 DTXSID70880215 

Perfluorobutane sulfonic acid (PFBS) ........................................................................................................... 375–73–5 DTXSID5030030 

Perfluorobutyric acid (PFBA) ......................................................................................................................... 375–22–4 DTXSID4059916 

Perfluorodecanoic acid (PFDeA/PFDA) ........................................................................................................ 335–76–2 DTXSID3031860 

Perfluorododecanoic acid (PFDoA) ............................................................................................................... 307–55–1 DTXSID8031861 

Perfluoroheptanoic acid (PFHpA) ................................................................................................................. 375–85–9 DTXSID1037303 

Perfluorohexane sulfonic acid (PFHxS) ........................................................................................................ 355–46–4 DTXSID7040150 

Perfluorohexanoic acid (PFHxA) ................................................................................................................... 307–24–4 DTXSID3031862 

Perfluoronononanoic acid (PFNA) ................................................................................................................ 375–95–1 DTXSID8031863 

Perfluorooctanesulfonamide (PFOSA) .......................................................................................................... 754–91–6 DTXSID3038939 

Perfluorooctane sulfonic acid (PFOS) ........................................................................................................... 1763–23–1 DTXSID3031864 

Perfluorooctanoic acid (PFOA) ..................................................................................................................... 335–67–1 DTXSID8031865 

Perfluorotetradecanoic acid (PFTA) .............................................................................................................. 376–06–7 DTXSID3059921 

Perfluorotridecanoic acid (PFTrDA) .............................................................................................................. 72629–94–8 DTXSID90868151 

Perfluoroundecanoic acid (PFUA/PFUnA) .................................................................................................... 2058–94–8 DTXSID8047553 

Phenylpropanolamine 1 .................................................................................................................................. 37577–28–9 DTXSID4023466 


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EXHIBIT 13—CONTAMINANTS NOMINATED FOR CONSIDERATION ON THE DRAFT CCL 5: NOMINATED CHEMICAL

CONTAMINANT—Continued 

Chemical name CASRN DTXSID 

Strontium ....................................................................................................................................................... 7440–24–6 DTXSID3024312 

Tribromoacetic acid (TBAA) .......................................................................................................................... 75–96–7 DTXSID6021668 

Triiodomethane (TIM) .................................................................................................................................... 75–47–8 DTXSID4020743 

1Thirteen nominated chemicals did not have available water occurrence data, even after a systematic literature search was conducted, and 

therefore were not evaluated for listing on the Draft CCL 5. See Section 4.2.1.1 of the Chemical Technical Support Document for more 

information. 

NOMINATED MICROBIAL CONTAMINANTS

Microbial name 

Adenovirus. 

Aeromonas hydrophila. 

Caliciviruses. 

Campylobacter jejuni. 

Enterovirus. 

Escherichia coli (0157). 

Helicobacter pylori. 

Hepatitis A virus. 

Legionella pneumophila. 

Mycobacterium species predominantly found 

in drinking water. 

Mycobacterium avium. 

Naegleria fowleri. 

Non-tuberculous Mycobacterium (NTM). 

Pseudomonas aeruginosa. 

Salmonella enterica. 

Shigella sonnei. 

1. Data Sources for the Nominated 

Chemical and Microbial Contaminants 

a. Chemical Nominations 

EPA reviewed the public nominations 

for the 73 chemicals and determined 

which nominated chemicals were 

already included in the CCL 5 Chemical 

Universe and which ones were not. If a 

chemical was already part of the CCL 5 

Chemical Universe, this meant that EPA 

had identified and extracted health 

effects and occurrence data on this 

chemical from primary data sources in 

Step 1, Building the Chemical Universe. 

However, most of these chemicals did 

not have sufficiently high screening 

scores and therefore required additional 

data to evaluate them. For the 

nominated chemicals that were not 

included in the CCL 5 Chemical 

Universe, they would require further 

data collection to be evaluated for 

listing on the Draft CCL 5. To identify 

additional data for these nominated 

chemicals, EPA assessed data sources 

cited with public nominations using the 

assessment factors described in Section 

III.A.1 of this document and extracted 

health effects and occurrence data from 

sources that were relevant, complete, 

and not redundant. Sources that met 

these three assessment factors were 

considered supplemental data sources 

and could serve as references to fill any 

data gaps for particular chemical 

contaminants during Step 3 of the CCL 

5 process (see Section III.A.3 of this 

document). EPA also conducted 

literature searches to identify additional 

health effects and occurrence data; more 

information can be found on the 

literature searches in Section III.A.3.a of 

this document and in Chapter 4 of the 

Chemical Technical Support Document 

(USEPA, 2021c). A complete list of 

supplemental sources can be found in 

Appendix B of the Chemical Technical 

Support Document (USEPA, 2021c). 

b. Microbial Nominations 

EPA reviewed the nominated 

microbial contaminants and the 

supporting information provided by 

nominators to determine if any new data 

were provided that had not been 

previously evaluated. EPA also 

collected additional data for the 

nominated microbial contaminants, 

when available, from both the CCL 3 

and CCL 4 data sources that had been 

updated and from literature searches 

covering the time between the CCL 4 

and the CCL 5 (2016–2019). If new data 

were available, EPA screened and 

scored the microbial contaminants 

nominated for CCL 5 using the same 

process that was used for the CCL 3 and 

the CCL 4. There were no new publicly 

nominated microbial data sources for 

the CCL 5. A more detailed description 

of the data sources used to evaluate 

microbial contaminants for the Draft 

CCL 5 can be found in the Microbial 

Technical Support Document (USEPA, 

2021d). 

2. Listing Outcomes for the Nominated 

Chemical Contaminants 

EPA reviewed the nominated 

chemical contaminants and identified 

which chemicals were (i) not already on 

the PCCL 5, and (ii) not subject to 

proposed or promulgated NPDWRs, and 

needed to be considered for further 

analysis. EPA did not add publicly 

nominated groups like ‘‘the top 200 

most prescribed drugs in 2016 and their 

parents and metabolites’’ to the PCCL 5 

because health effects and occurrence 

data must be linked to specific 

individual contaminants in order to be 

evaluated. However, individual 

chemicals in a nominated group could 

still be listed on the PCCL if they were 

also nominated individually or if they 

were part of the CCL 5 Chemical 

Universe and screened to the PCCL. 

EPA could not identify occurrence 

data for 13 nominated chemicals 

(Exhibit 13) from either primary or 

supplemental data sources nor was data 

provided in the public nominations. 

Without available data regarding 

measured occurrence in water or 

relevant data provided by the 

nominators, the two evaluation teams 

agreed that they could not determine 

whether these chemicals were likely to 

present the greatest public health 

concern through drinking water 

exposure and therefore should not 

advance further in the CCL 5 process. 

However, some were evaluated for 

possible research needs (see Chapter 5 

of the Chemical Technical Support 

Document; USEPA, 2021c). More 

detailed information about how 

nominated chemicals were considered 

for the Draft CCL 5 can be found in 

Section 3.6 of the Chemical Technical 

Support Document (USEPA, 2021c). 

Four publicly nominated chemicals 

were included on the Draft CCL 5 as a 

result of evaluation team listing 

decisions, including 1,4-dioxane, 

chlorpyrifos, manganese, and 

molybdenum. In addition, 43 nominated 

chemicals consisting of 7 cyanotoxins, 

18 DBPs, and 18 PFAS chemicals were 

included in the three chemical groups 

listed on the Draft CCL 5 (e.g., the 

cyanotoxin, DBP, and PFAS groups). 

The PFAS group is inclusive of any 

PFAS, except for PFOA and PFOS. 

Although PFOA and PFOS were 

nominated, EPA has made a positive 

final regulatory determination for these 

two chemicals; and therefore, did not 

include them in the PFAS group. 

3. Listing Outcomes for the Nominated 

Microbial Contaminants 

All the microbes nominated for the 

CCL 5, with the exception of Salmonella 

enterica, and Aeromonas hydrophila, 

and Hepatitis A, are listed on the Draft 

CCL 5. Salmonella enterica, Aeromonas 

hydrophila and Hepatitis A did not 

produce sufficient composite scores to 

place them on the Draft CCL 5. 


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Although Salmonella enterica and 

Hepatitis A have numerous WBDOs, the 

route of exposure was not explicitly 

waterborne. Non-tuberculous 

Mycobacterium (NTM) and 

Mycobacterium (species broadly found 

in drinking water) were nominated for 

the CCL 5 and are not listed on the Draft 

CCL 5 as a group; instead, they were 

listed as Mycobacterium avium and 

Mycobacterium abscessus, two species 

of NTM that are found in drinking 

water. 

D. Data Availability Assessment for the 

Draft CCL 5 Chemicals 

In an effort to provide the current data 

availability of the Draft CCL 5 

contaminants with respect to 

occurrence, health effects, and 

analytical methods data, EPA provides a 

summary table (Exhibit 14) depicting 

chemicals categorized into six groups 

depending upon the availability of their 

occurrence data and health assessment. 

EPA did not assess data availability for 

individual chemicals of the 

cyanotoxins, DBPs and PFAS groups 

because the availability of health effects 

and occurrence data varies with 

individual chemicals in each group. The 

agency is addressing these groups 

broadly in drinking water based on a 

subset of chemicals in these groups that 

are known to occur in public water 

systems and may cause adverse health 

effects. 

EXHIBIT 14—DATA AVAILABILITY/INFORMATION FOR THE DRAFT CCL 5 CONTAMINANTS

CASRN DTXSID Common name Best available occurrence data 

Is a health 

assessment 

available? 

Is an 

analytical 

method 

available? 

A. Contaminants with Nationally Representative Finished Water Occurrence Data and Qualifying Health Assessments 

96–18–4 ................ DTXSID9021390 1,2,3-Trichloropropane ........................................ National Finished Water ............ Yes .................... Yes. 

123–91–1 .............. DTXSID4020533 1,4-dioxane .......................................................... National Finished Water ............ Yes .................... Yes. 

319–84–6 .............. DTXSID2020684 alpha-Hexachlorocyclohexane ............................. National Finished Water ............ Yes .................... Yes. 

7440–42–8 ............ DTXSID3023922 Boron ................................................................... National Finished Water ............ Yes .................... Yes. 

63–25–2 ................ DTXSID9020247 Carbaryl ............................................................... National Finished Water ............ Yes .................... Yes. 

2921–88–2 ............ DTXSID4020458 Chlorpyrifos .......................................................... National Finished Water ............ Yes .................... Yes. 

7440–48–4 ............ DTXSID1031040 Cobalt .................................................................. National Finished Water ............ Yes .................... Yes. 

60–57–1 ................ DTXSID9020453 Dieldrin ................................................................. National Finished Water ............ Yes .................... Yes. 

330–54–2 .............. DTXSID0020446 Diuron .................................................................. National Finished Water ............ Yes .................... Yes. 

13194–84–4 .......... DTXSID4032611 Ethoprop .............................................................. National Finished Water ............ Yes .................... Yes. 

7439–93–2 ............ DTXSID5036761 Lithium ................................................................. National Finished Water ............ Yes .................... Yes. 

7439–96–5 ............ DTXSID2024169 Manganese .......................................................... National Finished Water ............ Yes .................... Yes. 

7439–98–7 ............ DTXSID1024207 Molybdenum ........................................................ National Finished Water ............ Yes .................... Yes. 

42874–03–3 .......... DTXSID7024241 Oxyfluorfen .......................................................... National Finished Water ............ Yes .................... Yes. 

52645–53–1 .......... DTXSID8022292 Permethrin ........................................................... National Finished Water ............ Yes .................... Yes. 

41198–08–7 .......... DTXSID3032464 Profenofos ........................................................... National Finished Water ............ Yes .................... Yes. 

1918–16–7 ............ DTXSID4024274 Propachlor ........................................................... National Finished Water ............ Yes .................... Yes. 

91–22–5 ................ DTXSID1021798 Quinoline .............................................................. National Finished Water ............ Yes .................... Yes. 

107534–96–3 ........ DTXSID9032113 Tebuconazole ...................................................... National Finished Water ............ Yes .................... Yes. 

78–48–8 ................ DTXSID1024174 Tribufos ................................................................ National Finished Water ............ Yes .................... Yes. 

7440–62–2 ............ DTXSID2040282 Vanadium ............................................................. National Finished Water ............ Yes .................... Yes. 

95–53–4 ................ DTXSID1026164 2-Aminotoluene .................................................... National Finished Water ............ Yes .................... Yes. 

51–28–5 ................ DTXSID0020523 2,4-Dinitrophenol ................................................. National Finished Water ............ Yes .................... Yes. 

B. Contaminants with Non-Nationally Representative Finished Water Occurrence Data and Qualifying Health Assessments 

2163–68–0 ............ DTXSID6037807 2-Hydroxyatrazine ................................................ Non-National Finished Water .... Yes .................... No. 

120068–37–3 ........ DTXSID4034609 Fipronil ................................................................. Non-National Finished Water .... Yes .................... No. 

121–74–5 .............. DTXSID4020791 Malathion ............................................................. Non-National Finished Water .... Yes .................... Yes. 

36734–19–7 .......... DTXSID3024154 Iprodione .............................................................. Non-National Finished Water .... Yes .................... No. 

298–02–2 .............. DTXSID4032459 Phorate ................................................................ Non-National Finished Water .... Yes .................... Yes. 

27314–13 .............. DTXSID8024234 Norflurazon .......................................................... Non-National Finished Water .... Yes .................... Yes. 

2303–17–5 ............ DTXSID5024344 Tri-allate ............................................................... Non-National Finished Water .... Yes .................... No. 

139–40–2 .............. DTXSID3021196 Propazine ............................................................. Non-National Finished Water .... Yes .................... Yes. 

1689–84–5 ............ DTXSID3022162 Bromoxynil ........................................................... Non-National Finished Water .... Yes .................... No. 

2312–35–8 ............ DTXSID4024276 Propargite ............................................................ Non-National Finished Water .... Yes .................... No. 

141–66–2 .............. DTXSID9023914 Dicrotophos .......................................................... Non-National Finished Water .... Yes .................... Yes. 

709–98–8 .............. DTXSID8022111 Propanil ................................................................ Non-National Finished Water .... Yes .................... Yes. 

153719–23–4 ........ DTXSID2034962 Thiamethoxam ..................................................... Non-National Finished Water .... Yes .................... No. 

10605–21–7 .......... DTXSID4024729 Carbendazim (MBC) ............................................ Non-National Finished Water .... Yes .................... No. 

55283–68 .............. DTXSID8032386 Ethalfluralin .......................................................... Non-National Finished Water .... Yes .................... No. 

3397624 ................ DTXSID1037806 Diaminochlorotriazine (DACT) ............................. Non-National Finished Water .... Yes .................... No. 

96182535 .............. DTXSID1032482 Tebupirimfos ........................................................ Non-National Finished Water .... Yes .................... Yes. 

114261 .................. DTXSID7021948 Propoxur .............................................................. Non-National Finished Water .... Yes .................... Yes. 

732116 .................. DTXSID5024261 Phosmet ............................................................... Non-National Finished Water .... Yes .................... Yes. 

2164–17–2 ............ DTXSID8020628 Fluometuron ......................................................... Non-National Finished Water .... Yes .................... Yes. 

C. Contaminant with Nationally Representative Finished Water Occurrence Data Lacking Qualifying Health Assessments 

1634–04–4 ............ DTXSID3020833 Methyl tert-butyl ether (MTBE) ............................ National Finished Water ............ No ...................... Yes. 

D. Contaminants with Qualifying Health Assessments Lacking Finished Water Occurrence Data 

3397–62–4 ............ DTXSID1037806 6-Chloro-1,3,5-triazine-2,4-diamine ..................... National Ambient Water ............ Yes .................... Yes. 

30560–19–1 .......... DTXSID8023846 Acephate .............................................................. National Ambient Water ............ Yes .................... Yes. 

84–65–1 ................ DTXSID3020095 Anthraquinone ..................................................... National Ambient Water ............ Yes .................... No. 

6190–65–4 ............ DTXSID5037494 Deethylatrazine .................................................... National Ambient Water ............ Yes .................... No. 

3397–62–4 ............ DTXSID0037495 Desisopropyl atrazine .......................................... National Ambient Water ............ Yes .................... Yes. 

333–41–5 .............. DTXSID9020407 Diazinon ............................................................... National Ambient Water ............ Yes .................... Yes. 

60–51–5 ................ DTXSID7020479 Dimethoate .......................................................... National Ambient Water ............ Yes .................... Yes. 


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I I 
Federal Register / Vol. 86, No. 135 / Monday, July 19, 2021 / Proposed Rules 37971 

EXHIBIT 14—DATA AVAILABILITY/INFORMATION FOR THE DRAFT CCL 5 CONTAMINANTS—Continued 

CASRN DTXSID Common name Best available occurrence data 

Is a health 

assessment 

available? 

Is an 

analytical 

method 

available? 

142459–58–3 ........ DTXSID2032552 Flufenacet (Thiaflumide) ...................................... National Ambient Water ............ Yes .................... No. 

22967–92–6 .......... DTXSID9024198 Methylmercury ..................................................... National Ambient Water ............ Yes .................... No. 

13071–79–9 .......... DTXSID2022254 Terbufos ............................................................... National Ambient Water ............ Yes .................... Yes. 

126–73–8 .............. DTXSID3021986 Tributyl phosphate (TNBP) .................................. National Ambient Water ............ Yes .................... No. 

103476–24–0 ........ DTXSID5021411 Tris(2-chloroethyl) phosphate (TCEP) ................. National Ambient Water ............ Yes .................... No. 

7440–33–7 ............ DTXSID8052481 Tungsten .............................................................. National Ambient Water ............ Yes .................... No. 

107–02–8 .............. DTXSID5020023 Acrolein ................................................................ National Ambient Water ............ Yes .................... Yes. 

95–63–6 ................ DTXSID6021402 Trimethylbenzene (1,2,4-) ................................... National Ambient Water ............ Yes .................... Yes. 

80–05–7 ................ DTXSID7020182 Bisphenol A ......................................................... National Ambient Water ............ Yes .................... No. 

143–50–0 .............. DTXSID1020770 Chlordecone (Kepone)2 ....................................... Non-national Ambient Water ..... Yes .................... Yes. 

741–58–2 .............. DTXSID9032329 Bensulide ............................................................. Non-national Ambient Water ..... Yes .................... Yes. 

16752–77–5 .......... DTXSID1022267 Methomyl ............................................................. Non-National Finished Water .... Yes .................... Yes. 

E. Contaminants Lacking Nationally Representative Finished Water Occurrence Data and Qualifying Health Assessments 

104–40–5 .............. DTXSID3021857 4-Nonylphenol (all isomers) ................................. Non-National Finished Water .... No ...................... Method in review. 

86386–73–4 .......... DTXSID3020627 Fluconazole ......................................................... Non-National Finished Water .... No ...................... No. 

93413628 .............. DTXSID40869118 Desvenlafaxine .................................................... Non-National Finished Water .... No ...................... No. 

Key to Exhibit 

National = Occurrence data that are nationally representative are available 

Non-National = Occurrence data that are not nationally representative are available 

Note: Data availability was not assessed for cyanotoxins, DBPs and PFAS. 

Contaminants in Group A have 

nationally representative finished 

drinking water occurrence data and 

qualifying health assessments. 

Contaminants in Group B have finished 

drinking water occurrence data that is 

not nationally representative and 

qualifying health assessments. 

Contaminants in groups C, D, and E lack 

either a qualifying health assessment or 

finished water occurrence data and have 

more substantial data needs. 

In addition, EPA assessed the data 

availability of the PCCL 5 chemicals that 

are not included on the Draft CCL 5. For 

more information on EPA methodology 

to identify data availability and 

summary tables, see Section 5.3 of the 

Chemical Technical Support Document 

(USEPA, 2021c). 

IV. Request for Comments 

The purpose of this document is to 

present the Draft CCL 5. EPA seeks 

comments on the following: 

A. Contaminants selected for the Draft 

CCL 5, including any supporting data 

that can be used in developing the Final 

CCL 5. 

B. Data that EPA obtained and 

evaluated for developing the Draft CCL 

5 may be found in the Chemical 

Technical Support Document and 

Microbial Technical Support Document 

located in the docket for this document. 

C. The improvements EPA 

implemented in the CCL 5 process. 

EPA will take these comments into 

consideration when developing future 

CCLs. EPA will consider all information 

and comments received in determining 

the Final CCL 5, in the development of 

future CCLs, and in the agency’s efforts 

to set drinking water priorities in the 

future. 

V. EPA’s Next Steps 

Between now and the publication of 

the Final CCL 5, EPA will evaluate 

comments received during the public 

comment period for this document, 

consult with EPA’s Science Advisory 

Board, and prepare the Final CCL 5 

considering this input. 

VI. References 

American Association for the Advancement 

of Science (AAAS). 2020. Per- and 

Polyfluoroalkyl Substances (PFAS) in 

Drinking Water. Available on the 

internet at: https://www.aaas.org/ 

programs/epi-center/pfas. 

Carroll, K.C., Pfaller, M.A., Landry, M.L., 

McAdam, A.J., Patel, R., Richter, S.S. and 

Warnock, David W. (ed). 2019. Manual of 

Clinical Microbiology, Twelfth Edition. 

CDC. 2008. Surveillance for Waterborne 

Disease and Outbreaks Associated with 

Drinking Water and Water not Intended 

for Drinking—United States, 2005–2006. 

MMWR 57 (SS–9). 

CDC, 2020a. National Outbreak Reporting 

System (NORS)—United States, 2009– 

2017. 

CDC, 2020b. Legionella (Legionnaires’ 

Disease and Pontiac Fever). https://

cdc.gov/legionella/about/history.html. 

Executive Office of the President. 2021. 

Protecting Public Health and the 

Environment and Restoring Science To 

Tackle the Climate Crisis; Federal 

Register. Vol. 86, E.O. 13990. p. 7037, 

January 20, 2021. 

Murray, P.R., E.J. Baron, J.H. Jorgensen, M.L. 

Landry, and M.A. Pfaller (ed.). 2011. 

Manual of Clinical Microbiology, 10th 

Edition, ASM Press, Washington, DC. 

National Academies of Sciences, 

Engineering, and Medicine (NASEM). 

2020. Management of Legionella in 

Water Systems. The National Academies 

Press, Washington, DC. 

National Drinking Water Advisory Council 

(NDWAC). 2004. National Drinking 

Water Advisory Council Report on the 

CCL Classification Process to the U.S. 

Environmental Protection Agency. 

Available on the internet at: https://

www.epa.gov/sites/production/files/ 

2015-11/documents/report_ccl_ndwac_

07-06-04.pdf. 

National Research Council (NRC). 2001. 

Classifying Drinking Water 

Contaminants for Regulatory 

Consideration. National Academy Press, 

Washington, DC. 

USEPA. 1998. Announcement of the 

Drinking Water Contaminant Candidate 

List; Notice. Federal Register. Vol. 63, 

No. 40. p. 10274, March 2, 1998. 

USEPA. 1999. Revisions to the Unregulated 

Contaminant Monitoring Regulation for 

Public Water Systems. Federal Register. 

Vol. 64, No. 180, p. 50556, September 17, 

1999. 

USEPA. 2000. Methodology for Deriving 

Ambient Water Quality Criteria for the 

Protection of Human Health (2000). 

https://www.epa.gov/sites/production/ 

files/2018-10/documents/methodologywqc-protection-hh-2000.pdf. 

USEPA. 2003. Announcement of Regulatory 

Determinations for Priority 

Contaminants on the Drinking Water 

Contaminant Candidate List. Federal 

Register. Vol. 68, No. 138. p. 42898, July 

18, 2003. 

USEPA. 2005. Drinking Water Contaminant 

Candidate List 2; Final Notice. Federal 

Register. Vol. 70, No. 36. p. 9071, 

February 24, 2005. 

USEPA. 2007. Unregulated Contaminant 

Monitoring Regulation (UCMR) for 

Public Water Systems Revisions; 

Correction. Federal Register. Vol. 72, No. 

19, p. 4328, January 30, 2007. 


lotter on DSK11XQN23PROD with PROPOSALS1
37972 Federal Register / Vol. 86, No. 135 / Monday, July 19, 2021 / Proposed Rules 

USEPA. 2008. Drinking Water: Regulatory 

Determinations Regarding Contaminants 

on the Second Drinking Water 

Contaminant Candidate List. Federal 

Register. Vol. 73, No. 174. p. 44251, July 

30, 2008. 

USEPA. 2009a. Final Contaminant Candidate 

List 3 Chemicals: Identifying the 

Universe. EPA 815–R09–006. August 

2009. 

USEPA. 2009b. Final Contaminant Candidate 

List 3 Chemicals: Screening to a PCCL. 

EPA. 815–R09–007. August 2009. 

USEPA. 2009c. Community Water System 

Survey 2006. Volume 1: Overview. EPA 

815–R–09–001. February 2009. 

USEPA. 2009d. Community Water System 

Survey 2006. Volume II: Detailed Tables 

and Survey Methodology. EPA 815–R– 

09–002. May 2009. 

USEPA. 2009e. Drinking Water Contaminant 

Candidate List 3—Final. Federal 

Register. Vol. 74, No. 194. p. 51850, 

October 8, 2009. 

USEPA. 2011. Drinking Water: Regulatory 

Determination on Perchlorate. Federal 

Register. Vol. 76, No. 29. p. 7762, 

February 11, 2011. 

USEPA. 2012a. Revisions to the Unregulated 

Contaminant Monitoring Regulation 

(UCMR 3) for Public Water Systems. 

Federal Register. Vol. 77, No. 85. p. 

26071, May 2, 2012. 

USEPA. 2012b. TSCA Work Plan Chemicals: 

Methods Document. February 2012. 

Available on the internet at: https://

www.epa.gov/sites/production/files/ 

2014-03/documents/work_plan_

methods_document_web_final.pdf. 

USEPA. 2014. Announcement of Preliminary 

Regulatory Determination for 

Contaminants on the Third Drinking 

Water Contaminant Candidate List. 

Federal Register. Vol. 79, No. 202, p. 

62716, October 20, 2014. 

USEPA. 2015. Algal Toxin Risk Assessment 

and Management Strategic Plan for 

Drinking Water, Strategy Submitted to 

Congress to Meet the Requirements of 

P.L. 114–45. EPA 810–R–04–003. 

USEPA. 2016a. Revisions to the Unregulated 

Contaminant Monitoring Regulation 

(UCMR 4) for Public Water Systems. 

Federal Register. Vol. 81, No. 244. p. 

92666, December 20, 2016. 

USEPA. 2016b. Final Regulatory 

Determinations on the Third Drinking 

Water Contaminant Candidate List. 

Federal Register. Vol. 81, No. 1. P. 13– 

19, January 4, 2016. 

USEPA. 2016c. Drinking Water Contaminant 

Candidate List 4-Final. Federal Register. 

Vol. 81, No. 222. P. 81099, November 17, 

2016. 

USEPA. 2017. Analysis of Occurrence Data 

from the Third Six-Year Review of 

Existing National Primary Drinking 

Water Regulations: Chemical Phase 

Rules and Radionuclides Rules. EPA– 

810–R–16–014. December 2016. 

USEPA. 2018a. Request for Nominations of 

Drinking Water Contaminants for the 

Fifth Contaminant Candidate List. 

Notice. Federal Register. Vol. 83, No. 

194. p. 50364, October 5, 2018. 

USEPA. 2018b. Basic Information on PFAS. 

Available at: https://www.epa.gov/pfas/ 

basic-information-pfas. 

USEPA. 2019a. Drinking Water: Final Action 

on Perchlorate. Federal Register. Vol. 84, 

No. 123, p. 30524. June 26, 2019. 

USEPA. 2019b. EPA’s Per- and 

Polyfluoroalkyl Substances (PFAS) 

Action Plan. EPA 823–R–18–004, 

February 2019. Available at: https://

www.epa.gov/sites/production/files/ 

2019-02/documents/pfas_action_plan_

021319_508compliant_1.pdf. 

USEPA. 2020. Drinking Water: Perchlorate. 

Federal Register. Vol. 85, No. 140, p. 

43990, July 2020. EPA–HQ–OW–2018– 

0780–0302. 

USEPA. 2021a. Revisions to the Unregulated 

Contaminant Monitoring Regulation 

(UCMR 5) for Public Water Systems. 

Federal Register. Vol. 86, No. 46. p. 

13846, March 11, 2021. 

USEPA. 2021b. Announcement of Final 

Regulatory Determinations for 

Contaminants on the Fourth Drinking 

Water Contaminant Candidate List. 

Federal Register. Vol. 86, No. 40, p. 

12272, March 3, 2021. EPA–HQ–OW– 

2019–0583. 

USEPA. 2021c. Technical Support Document 

for the Draft Fifth Contaminant 

Candidate List (CCL 5)—Chemical 

Contaminants. EPA 815–R–21–005, July 

2021. 

USEPA. 2021d. Technical Support Document 

for the Draft Fifth Contaminant 

Candidate List (CCL 5)—Microbial 

Contaminants. EPA 815–R–21–007, July 

2021. 

USEPA. 2021e. Technical Support Document 

for the Draft Fifth Contaminant 

Candidate List (CCL 5)—Contaminant 

Information Sheets. EPA 815–R–21–006, 

July 2021. 

USEPA. 2021f. TSCA Section 8(a)(7) 

Reporting and Recordkeeping 

Requirements for Perfluoroalkyl and 

Polyfluoroalkyl Substances. Proposed 

Rule. 86 FR 33926. June 28, 2021. 

Williams, A.J., C.M. Grulke, J. Edwards, A.D. 

McEachran, K. Mansouri, N.C. Baker, G. 

Patlewicz, I. Shah, J.F. Wambaugh, R.S. 

Judson, and A.M. Richard. 2017. The 

CompTox Chemistry Dashboard: a 

community data resource for 

environmental chemistry. Journal of 

Cheminformatics. 9:61. doi:10.1186/ 

s13321–017–0247–6. 

Radhika Fox, 

Assistant Administrator, Office of Water. 

[FR Doc. 2021–15121 Filed 7–16–21; 8:45 am] 

BILLING CODE 6560–50–P 

FEDERAL COMMUNICATIONS 

COMMISSION 

47 CFR Parts 1 and 73 

[AU Docket No. 21–284; DA 21–801; FR ID 

37717] 

Auction of Construction Permits for 

Low Power Television and TV 

Translator Stations; Comment Sought 

on Competitive Bidding Procedures for 

Auction 111 

AGENCY: Federal Communications 

Commission. 

ACTION: Proposed rule; proposed auction 

procedures. 

SUMMARY: The Office of Economics and 

Analytics and the Media Bureau 

announce a closed auction of 

construction permits for new or 

modified low power television (LPTV) 

stations and TV translator stations 

(collectively, LPTV/translator stations). 

This document seeks comment on the 

procedures to be used for this auction, 

which is designated as Auction 111. 

DATES: Comments are due on or before 

August 3, 2021, and reply comments are 

due on or before August 13, 2021. 

Bidding in this auction is expected to 

commence in February 2022. 

ADDRESSES: Interested parties may file 

comments or reply comments in AU 

Docket No. 21–284. Comments may be 

filed using the Commission’s Electronic 

Comment Filing System (ECFS). All 

filings in response to the Auction 111 

Comment Public Notice must refer to 

AU Docket No. 21–284. 

• Electronic Filers: Comments may be 

filed electronically using the internet by 

accessing the ECFS at https://

www.fcc.gov/ecfs/. 

• Paper Filers: Parties who choose to 

file by paper must file an original and 

one copy of each filing. 

• Filings in response to the Public 

Notice can be sent by commercial 

courier or by first-class or overnight U.S. 

Postal Service mail. All filings must be 

addressed to the Commission’s 

Secretary, Office of the Secretary, 

Federal Communications Commission 

• Commercial deliveries (other than 

U.S. Postal Service Express Mail and 

Priority Mail) must be sent to 9050 

Junction Dr., Annapolis Junction, MD 

20701. 

• U.S. Postal Service first-class, 

Express, or Priority mail must be 

addressed to 45 L Street NE, 

Washington, DC 20554. 

• Until further notice, the 

Commission no longer accepts any hand 

or messenger delivered filings. This is a 

temporary measure taken to help protect 

the health and safety of individuals, and 


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