Screening Document 

for the Draft PCCL 4 

Nominated 

Contaminants 
Office of Water (4607M) 

EPA 815-R-15-002 

January 2015
EPA-OGWDW Screening Document for the Draft

PCCL 4 Nominated Contaminants

EPA 815-R-15-002

Contents

1.0 Introduction ............................................................................................................................. 1

2.0 Summary of the CCL 3 Chemicals Screening Process ........................................................ 3

2.1 Health Effects Data Elements ............................................................................................... 4

2.2 Occurrence Data Elements .................................................................................................... 6

2.3 Selection of the PCCL .......................................................................................................... 7

3.0 Screening the Nominated Chemicals from the CCL 4 Universe to the PCCL ................. 8

4.0 Summary of the CCL 3 Microbes Screening Process and Screening of the Nominated 

Microbes from the CCL 4 Universe to the PCCL 4 ....................................................... 8

5.0 References ............................................................................................................................. 10

6.0 Appendices ............................................................................................................................ A1

Appendix 1. Screening data for the Nominated Chemicals in the CCL 4 Universe ................ A1

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Exhibits

Exhibit 1: Partition for Screening the Universe .............................................................................. 4

Exhibit 2: Potency Measures for Universe Data Element Partitioned Based on Toxicity 

(mg/kg/day or mg/kg) ......................................................................................................... 5

Exhibit 3: Partitioning of Cancer Data Based on TD50 Values and Weight of Evidence .............. 6

Exhibit 4: Criteria for a Chemical to Pass to the PCCL ................................................................. 7

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Acronyms and Abbreviations

< Less than

< Less than or equal to

> Greater than

> Greater than or equal to

μ Microgram, one

μg/L Micrograms per liter

ADI Acceptable Daily Intake

AWWARF American Water Works Association Research Foundation

CASRN Chemical Abstract Services Registry Number

CCL Contaminant Candidate List

CCL 1 EPA’s First Contaminant Candidate List

CCL 2 EPA’s Second Contaminant Candidate List 

CCL 3 EPA’s Third Contaminant Candidate List 

CCL 4 EPA’s Fourth Contaminant Candidate List 

CE Clear evidence of carcinogenicity

CUS/IUR Chemical Update System/Inventory Update Rule 

DBP-CAN EPA Water Disinfection By-Products with Carcinogenicity Estimates 

DSSTOX Distributed Structure-Searchable Toxicity Database Network

E Equivocal 

EE Equivocal evidence of carcinogenicity 

EPA United States Environmental Protection Agency 

EPA HA EPA Health Advisory 

FR Federal Register

g Gram

H High probability of causing cancer 

HM High moderate probability of causing cancer 

IARC International Agency for Research on Cancer

ITER International Toxicity Estimates for Risk

JECFA Joint FAO/WHO Expert Committee on Food Additives

kg Kilogram

L Liter

LD50 Lethal dose 50; an estimate of a single dose that is expected to cause the death

of 50 percent of the exposed animals; it is derived from experimental data.

M Moderate probability of causing cancer 

LM Low moderate probability of causing cancer 

LOAEL Lowest Observed Adverse Effect Level

MCL Maximum Contaminant Level 

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MCLG Maximum Contaminant Level Goal 

mg/kg Milligrams per kilogram body weight 

mg/kg/day Milligrams per kilogram body weight per day 

mg/L Milligrams per liter

MRDD Maximum Recommended Daily Dose 

N Negative 

NAWQA National Water Quality Assessment 

NE No evidence of carcinogenicity

NIRS National Inorganics and Radionuclides Survey

NOAEL No Observed Adverse Effect Level

NCI National Cancer Institute

NCFAP National Center for Food and Agricultural Policy 

NDWAC National Drinking Water Advisory Council 

NRC National Academy of Science’s National Research Council

NREC National Reconnaissance of Emerging Contaminants 

NTP National Toxicology Program 

OPP Office of Pesticide Programs

P Positive

PFOA Perfluorooctanoic acid 

PWS Public water system

QSAR Quantitative Structure Activity Relationship

RfD Reference dose

RAIS Risk Assessment Information System

RTECS Registry of Toxic Effects of Chemical Substances

SDWA Safe Drinking Water Act

SE Some evidence of carcinogenicity

TD50 Tumorigenic dose 50; The dose-rate which if administered chronically for the 

standard life-span of the species will have a 50% probability of causing 

tumors at some point during that period. 

TRI Toxics Release Inventory

UCM Round 1 Unregulated Contaminant Monitoring Round 1 

US United States of America

WHO World Health Organization 

yr Year

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1.0 Introduction 

Section 1412(b)(1) of the Safe Drinking Water Act (SDWA), as amended in 1996, requires EPA 

to publish the Contaminant Candidate List (CCL) every five years. The SDWA specifies that the 

list must include contaminants that are not subject to any proposed or promulgated National 

Primary Drinking Water Regulations (NPDWRs), are known or anticipated to occur in public 

water systems (PWSs) and may require regulation under the SDWA. EPA uses this list of 

unregulated contaminants to help the agency identify priority contaminants for regulatory 

decision making and to prioritize research and data collection efforts. SDWA also requires the 

agency to consult with the scientific community, including the Science Advisory Board, and 

provide notice and opportunity for public comment prior to the publication of the Final CCL. In 

addition, SDWA directs the agency 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. 

EPA published the third CCL (CCL 3), which listed 116 contaminants on October 8, 2009 (74 

FR 51850 (USEPA, 2009a)). In developing the CCL 3, EPA implemented a multi-step process to 

select contaminants for the final CCL 3, which included the following key steps: 

(1) The identification of a broad universe of potential drinking water contaminants (CCL 3 

Universe); 

(2) Screening the CCL 3 Universe to a Preliminary CCL (PCCL) using screening criteria 

based on the potential to occur in PWSs and the potential for public health concern; 

(3) Evaluation of the PCCL contaminants based on a more detailed review of the occurrence 

and health effects data using a scoring and classification system to identify a final list of 

116 CCL 3 contaminants; and 

(4) Incorporating public input and expert review in the CCL 3 process. 

Steps 1, 2 and 3 in the process are described in detail in the CCL 3 support documents: 

• Final CCL 3 Chemicals: Identifying the Universe (USEPA, 2009b);

• Final CCL 3 Chemicals: Screening to a PCCL (USEPA, 2009c);

• Final Contaminant Candidate List 3 Chemicals: Classification of the PCCL to the CCL

(USEPA, 2009d);

• Final CCL 3 Microbes: Identifying the Universe (USEPA, 2009e);

• Final CCL 3 Microbes: Screening to the PCCL (USEPA, 2009f); and

• Final CCL 3 Microbes: PCCL to CCL Process (USEPA, 2009g).

These documents can be found on the EPA web site at: http://www2.epa.gov/ccl/contaminantcandidate-list-3-ccl-3 or at http://www.regulations.gov (docket ID: EPA-HQ-OW-2007-1189). 

After a Final CCL is published, SDWA section 1412(b)(1)(B)(ii) as amended in 1996, requires 

EPA at five year intervals to make determinations of whether to regulate or not to regulate no 

fewer than five contaminants from the CCL in a process called regulatory determinations. This is 

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a separate process from the listing of contaminants on 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 PWSs 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 PWSs.

If EPA determines that these three statutory criteria are met and makes a final determination to 

regulate a contaminant, the agency has 24 months to publish a proposed Maximum Contaminant 

Level Goal1 (MCLG) and NPDWR2. After the proposal, the agency has 18 months to publish 

and promulgate a final MCLG and NPDWR (SDWA section 1412(b)(1)(E))3

. 

On February 11, 2011, as a separate action, the agency issued a positive regulatory determination

for perchlorate, a chemical listed in CCL 1, CCL 2 and CCL 3 (76 FR 7762 (USEPA, 2011)). 

Recently, EPA has published preliminary regulatory determinations for five unregulated 

contaminants on the CCL 3 (79 FR 62716 (USEPA, 2014)). The five contaminants include: 

dimethoate; 1,3-dinitrobenzene; strontium; terbufos and terbufos sulfone. The agency is making 

preliminary determinations to regulate one contaminant (strontium) and to not regulate four 

contaminants (dimethoate; 1,3-dinitrobenzene; terbufos; and terbufos sulfone). Therefore, the 

agency is removing perchlorate and these five contaminants from the Draft Fourth CCL (CCL 4), 

pending the result of the final regulatory determinations for CCL 3. 

EPA conducted an abbreviated evaluation and selection process for the CCL 4. This abbreviated 

CCL 4 process includes a three pronged approach: (1) carrying forward CCL 3 contaminants 

(minus those with regulatory determinations), (2) seeking and evaluating nominations from the 

public for additional contaminants to consider and (3) evaluating any new data for those 

contaminants with previous negative regulatory determinations from CCL 1 or CCL 2 for 

potential inclusion on the CCL 4. 

As part of the process to develop the CCL 4, EPA published a Federal Register notice (77 FR

27057 (USEPA, 2012)) requesting that the public submit nominations for chemical and 

microbial contaminants to be considered for inclusion in the CCL 4. EPA also requested 

supporting information that has been made available since the development of the CCL 3, or 

existing information that was not considered in the development of the CCL 3, which shows that 

the nominated contaminant may have an adverse health effect on people, and occurs or is likely 

1 The MCLG is the "maximum level of a contaminant in drinking water at which no known or anticipated adverse 

effect on the health of persons would occur, and which allows an adequate margin of safety. Maximum contaminant 

level goals are non-enforceable health goals." (40 C.F.R. 141.2; 42 U.S.C. 300g-1) 2 An NPDWR is a legally enforceable standard that applies to public water systems. An NPDWR sets a legal limit 

(called a maximum contaminant level or MCL) or specifies a certain treatment technique (TT) for public water 

systems for a specific contaminant or group of contaminants. 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 analytical methods and taking cost into consideration.

3

 The statute authorizes a nine month extension of this promulgation date. 

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to occur in public water systems. EPA reviewed the nominations and supporting information 

provided by nominators to determine if any new data were provided that had not been previously 

evaluated for CCL 3. The agency also collected additional data for the nominated contaminants, 

when it was available, from both CCL 3 data sources that had been updated and from new data 

sources that were not available at the time of CCL 3. A complete list of references provided by 

nominators can be found in the support document Summary of Nominations for the Fourth CCL

(USEPA, 2015a). A more detailed description of the CCL data sources collected by EPA may be 

found in the support document Data Sources for the CCL 4 (USEPA, 2015b). EPA evaluated the 

nominated contaminants utilizing the best available health effects and occurrence data and the 

same process for screening and scoring contaminants that was used for CCL 3. 

This document focuses on describing the second step in the CCL 4 process, in which EPA 

applied screening criteria to the nominated contaminants in the CCL 4 Universe to identify a 

Preliminary CCL (PCCL) based on a contaminant’s potential to occur in public water systems 

and the potential for public health concern. Appendix 1 shows the health effects and occurrence 

data used to screen the nominated chemicals in the CCL 4 Universe to the PCCL 4. 

2.0 Summary of the CCL 3 Chemicals Screening Process

The agency evaluated the nominated contaminants for CCL 4 utilizing the best available health 

effects and occurrence data and the same process for screening and scoring contaminants that 

was used for CCL 3. This section summarizes the process developed under CCL 3 to screen 

chemicals from the Universe to the PCCL. A more detailed description of the screening process 

can be found in the CCL 3 support document: Final CCL 3 Chemicals: Screening to a PCCL

(USEPA, 2009c). EPA developed criteria to screen chemicals from the CCL 3 Universe to the 

PCCL 3. These screening criteria utilized available data (e.g., occurrence and health) to examine 

a chemical’s health effects relative to its occurrence. 

The health effects information used included quantitative, descriptive or categorical information. 

Within the aforementioned categories, there were various types of reported health related values 

(e.g., RfD, LOAEL, NOAEL, LD50 or cancer classifications) from several data sources. A list 

and detailed description of the data sources used in CCL 3 can be found in Final CCL 3 

Chemicals: Identifying the Universe (USEPA, 2009b). 

The occurrence information also included many types of available data representative of a 

chemical’s potential to occur in water. Occurrence data ranged from concentrations in finished 

drinking water from PWSs, to concentrations of a chemical in ambient water, to environmental 

release and production data. The basic framework EPA used in screening is shown in Exhibit 1. 

EPA categorized the CCL Chemical Universe contaminants by their toxicity along the vertical 

axis and by their occurrence on the horizontal axis. This allows for separation of chemicals into 

those that move to the PCCL based on their toxicity and occurrence properties (e.g., upper right 

in Exhibit 1) and those that are not further evaluated and remain in the CCL Chemical Universe 

(e.g., lower left in Exhibit 1). EPA used a set of test chemicals to develop the screening criteria. 

This set of chemicals included regulated and unregulated chemicals that provided comprehensive 

information on health effects and occurrence in finished and/or ambient water as well as 

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environmental release and production volume. EPA then used these criteria to select chemicals 

for the PCCL for further consideration. 

Exhibit 1: Partition for Screening the Universe

Health Effects Occurrence

blank Low to High Occurrence 

Increasing 

Toxicity

Do not pass to PCCL Pass to the PCCL

2.1 Health Effects Data Elements

EPA evaluated the toxicity information and health effects data compiled from the data sources in 

the Universe and these data varied greatly. Some of these data are quantitative (e.g.,

RfD, LOAEL, NOAEL, LD50) and some are descriptive (e.g., cancer classifications or 

predictions). EPA designed the screening process to accommodate both types of health effects 

data.

EPA divided the chemicals in the Universe into five toxicity categories for screening based upon 

the distribution of the toxicity value for each type of quantitative data element and/or the 

qualitative information on cancer weight-of-evidence. The five toxicity categories are designated 

1 through 5, with Toxicity Category 1 containing chemicals in the most toxic grouping and 

Toxicity Category 5 the least toxic grouping. Based upon the distribution of the chemicals for 

each quantitative data element, EPA selected ranges of toxicity values for each toxicity category 

that differed based upon the type of data element used. For example, the range of toxicity values 

that places a LOAEL in Toxicity Category 1 differs from the values used to place LD50 values 

into Toxicity Category 1. Placing contaminants into Toxicity Categories allows for a comparison 

of the relative toxicity of contaminants that have different types of available data. Exhibit 2 

displays the ranges for each non-cancer health effects data element and their respective Toxicity 

Categories. 

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Exhibit 2: Potency Measures for Universe Data Element Partitioned 

Based on Toxicity (mg/kg/day or mg/kg)

blankblank RfD NOAEL LOAEL MRDD LD50

Toxicity Category 1 <0.0001 <0.01 <0.01 <0.01 <1

Toxicity Category 2 0.0001 - <0.001 0.01 - < 1 0.01 - <1 0.01 - < 1 1 - <50

Toxicity Category 3 0.001 - <0.05 1 - <10 1 - <10 1 - <10 50 - <500

Toxicity Category 4 0.05 - <0.1 10 - < 1000 10 - <1000 10 - < 1000 500 - <5000

Toxicity Category 5 ≥0.1 ≥1000 ≥1000 ≥1000 ≥5000

EPA used descriptive (or categorical) cancer data to group data elements into toxicity categories 

that provide gradation based upon the strength of the data. Sources for the descriptive cancer data 

included: 

• US EPA Cancer Groupings

• International Agency for Research on Cancer (IARC) Cancer Groupings

• National Toxicology Program weight-of-evidence findings from cancer bioassays

• National Cancer Institute (NCI) weight-of-evidence findings from cancer bioassays

• EPA Water Disinfection By-Products with Carcinogenicity Estimates (DBP-CAN)

groupings based on carcinogenic potential derived from Quantitative Structure Activity

Relationship (QSAR) projections and expert judgment

EPA partitioned the cancer-related data elements in the Universe as described in Exhibit 3. The 

cancer data placed chemicals in only the three highest Toxicity Categories. EPA did not use 

quantitative measures of dose-response for carcinogenicity in the screening criteria because more 

chemicals can be analyzed using the descriptive data than by cancer slope factors. In addition, 

EPA did not use descriptors indicating lack of carcinogenic potential or insufficient data to 

determine carcinogenic potential in categorizing chemicals because those descriptors apply only 

to the cancer endpoint and do not consider non-cancer effects associated with exposure to the 

chemical.

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Exhibit 3: Partitioning of Cancer Data Based on TD50 Values and 

Weight of Evidence

blanblankk TD50 EPA IARC /HC NTP NCI DSS-Tox

Toxicity 

Category 1 <0.1

Group A;

Human 

Carcinogen

Group 1

CE 2 species/2 

sexes; or 2 

species; or 2 

sexes

P 2 species/2 

sexes; or 2 

species; or 2 

sexes

H 

Toxicity 

Category 2 0.1 - 100

Groups B1 and 

B2; Likely 

carcinogens

Group 2A

Combinations of 

CE, SE, EE, and 

NE

Combinations 

of P, E and N HM

Toxicity 

Category 3 >100

Group C; 

Suggestive 

evidence of 

carcinogenicity

Group 2B Combinations of 

SE, EE, and NE

Combinations 

of E and N M and LM

** Cancer data placed chemicals in only the three highest Toxicity Categories

CE = clear evidence, SE = some evidence, EE = equivocal evidence, NE = no evidence P = positive, N = Negative, E 

= equivocal

H = high probability, HM = high to medium probability, M = medium probability, LM = medium to low probability

EPA chose a conservative approach to categorize each chemical’s toxicity for screening and 

evaluated all the available health effects dose-response and categorical data elements for a given 

chemical in the screening process. Chemicals were assigned to the highest toxicity category 

indicated after an evaluation of all the available data. Accordingly, if a chemical had just one 

data element that places it in Toxicity Category 1, it was categorized as such even if some of the 

other data elements for that same chemical may place it in a lower toxicity category. For 

example, if a chemical is classified as a 2A carcinogen by IARC it will be placed in Toxicity 

Category 2 using the descriptive cancer data even if a quantified LOAEL from a different study 

places it in Toxicity Category 3. 

2.2 Occurrence Data Elements

EPA evaluated the occurrence data elements for each chemical and placed them on the horizontal 

axis of the screening table. In assessing the data, EPA found that the data elements that represent 

a chemical’s potential to occur in drinking water vary greatly. EPA’s goal was to determine 

which data elements best represented the potential to occur in drinking water. EPA considered 

and evaluated data elements in the following categories: 

• Finished Water – measures of concentration and frequency of detections

• Ambient Water – measures of concentration and frequency of detections

• Total Releases in the Environment – pounds per year and number of states

• Pesticide Application Rates – pounds per year and number of states

• Production volume – pounds per year

In addition to evaluating quantitative data elements listed above, EPA also considered chemicals 

with descriptive data based upon their likelihood of occurring in drinking water. Examples of 

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descriptive occurrence data elements include characterization as a disinfection by-product or a 

drinking water treatment chemical. 

EPA used the following hierarchal approach to select the occurrence data element used to screen 

a chemical:

Finished Water = Ambient Water > Environmental Release Data > Production Data.

The highest data elements in the hierarchy are the finished and ambient water data; the lowest is

production data. Environmental release data from TRI and pesticide application data occupy the 

middle position in the hierarchy. EPA also decided that when multiple data values exist for the 

chemicals within a given component of the hierarchy, the most conservative data value is used. 

For example, in the case of a chemical that has finished water data and ambient water data, EPA 

selected the highest available numerical concentration value as the occurrence screening data 

element. 

2.3 Selection of the PCCL

The last step in the screening process used the health effects and occurrence data elements shown 

in Exhibit 4 to establish the PCCL. As mentioned earlier, the health data elements were grouped 

into 5 toxicity categories and the highest toxicity category indicated after an evaluation of all the 

available data for a particular chemical was used in screening. EPA selected the highest available 

data element in the occurrence hierarchy to screen the contaminant. Because the chemicals were

evaluated using a hierarchical approach for their occurrence elements, EPA developed separate 

criteria for each of the occurrence elements. EPA tested the screening criteria using a set of 200 

chemicals including regulated and prior CCL chemicals and some chemicals from the Universe 

that had fairly complete data for all of the occurrence data elements. EPA screened these test 

chemicals and then adjusted the position of the PCCL selection line. In general, the PCCL 

selection line was positioned so that regulated chemicals and most prior CCL chemicals would 

be selected for the PCCL. 

Exhibit 4: Criteria for a Chemical to Pass to the PCCL

Health Effects Occurrence (by data type)

blank Finished/Ambient Water 

Concentrations

Release Amount 

(per year)

Production Volume 

(per year)

Toxicity Category 1 All Concentrations All Amounts All Amounts

Toxicity Category 2 ≥ 1 μg/l ≥ 10,000 lbs/yr ≥ 500,000 lbs/yr

Toxicity Category 3 ≥ 10 μg/l ≥ 100,000 lbs/yr ≥ 10 M lbs/yr

Toxicity Category 4 ≥ 100 μg/l ≥ 1 M lbs/yr ≥ 50 M lbs/yr

Toxicity Category 5 ≥ 1000 μg/l ≥ 10 M lbs/yr ≥ 100 M lbs/yr

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3.0 Screening the Nominated Chemicals from the CCL 4 

Universe to the PCCL 4

EPA received nominations for 59 unique contaminants for the CCL 4 including 54 chemicals and 

five microbials (see section 4.0). Forty three of the nominated chemicals were included in the 

CCL 4 Universe. Forty of the nominated chemicals were previously included in the CCL 3

Universe, and were carried forward to the CCL 4 Universe. In addition to these forty, EPA has

added three nominated chemicals to the CCL 4 Universe (octylphenol ethoxylate, oxacillin and 

virginiamycin) based on health effects and/or occurrence data that was newly available since the 

development of the CCL 3. A complete list of the nominated contaminants for the CCL 4 can be 

found in the support document: Summary of Nominations for the Fourth CCL (USEPA, 2015a). 

EPA screened all of the nominated chemicals in the CCL 4 Universe according to the screening 

criteria developed for CCL 3, and based on that evaluation; twenty of the nominated chemicals 

were included in the PCCL 4. Eighteen of those 20 chemicals were also included in the PCCL 3, 

and EPA added two new chemicals (manganese and nonylphenol) to the PCCL 4. The data used 

to screen the nominated chemicals from the CCL 4 Universe to the PCCL 4, and whether or not 

the chemical moved from the Universe to the PCCL 4 is shown in Appendix 1 of this document. 

4.0 Summary of the CCL 3 Microbes Screening Process and 

Screening of the Nominated Microbes from the CCL 4 

Universe to the PCCL 4

The microbial CCL 3 Universe was defined as microbes that are known to cause disease in 

humans. A literature review identified a list of 1,415 known human pathogens including 

bacterial, viral, protozoan, helminth and fungal pathogens (Taylor et al., 2001). This list was 

recommended as the basis of the microbial CCL 3 Universe. EPA requested nominations from 

the public for additions to the microbial CCL 3 Universe, and two microbes and two viral groups 

were added to the list through the nomination process (USEPA, 2006; USEPA, 2009e). EPA also 

added six fungi that did not appear on the list of Taylor et al. (2001) but were identified in 

drinking water distribution systems, thus bringing the total number of microbes in the CCL 3 

Universe to 1,425 pathogens. These microbes remain in the CCL 4 Universe.

The National Academy of Science’s National Research Council (NRC) workgroup report did not 

make specific recommendations for selection and screening of microbial contaminants to a 

PCCL, and because occurrence data for microbes are not readily available to support the 

screening process envisioned by the NRC workgroup, the agency requested further study of these 

issues by a workgroup convened by the National Drinking Water Advisory Council (NDWAC). 

NDWAC recommended selecting microbial contaminants for the PCCL based upon an 

assessment of occurrence attributes and health effects attributes relating to the plausibility of 

pathogen presence, survival, and transport through drinking water resulting in disease 

manifestations from drinking water exposure. These recommendations are described further in, 

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National Drinking Water Advisory Council Report on the CCL Classification Process (NDWAC, 

2004). 

Selection of microbes from the CCL Universe for placement on the PCCL is based upon 

exclusionary screening criteria that assess the potential of water-related transmission 

(occurrence) and the plausibility of causing waterborne disease by ingestion, inhalation or 

dermal contact (health effects). Microbes that met any of the exclusionary criteria were not 

included on the PCCL. The screening criteria developed for CCL 3, which are listed below, were 

also used for CCL 4. 

Criterion 1: Anaerobes (microorganisms that cannot survive in oxygenated environments) 

Criterion 2: Fastidious or obligate intracellular pathogens (environmental survival in water 

implausible)

Criterion 3: Pathogens exclusively transmitted by direct or indirect contact with blood or body 

fluids (including sexually transmitted diseases)

Criterion 4: Pathogens transmitted by vectors 

Criterion 5: Microflora indigenous to the gastrointestinal tract, skin and mucous membranes 

Criterion 6: Pathogens transmitted solely by respiratory secretions

Criterion 7: Pathogens whose life cycle is incompatible with drinking water transmission

Criterion 8: Pathogens where drinking water-related transmission is not implicated

Criterion 9: Natural habitat is in the environment without epidemiological evidence of drinking 

water-related disease

Criterion 10: Pathogens not endemic to North America

Criterion 11: A genus and species or serotype may be chosen to represent a group of closely 

related organisms

Criterion 12: Current taxonomy does not support the classification listed by Taylor et al. (2001). 

Four of the five nominated microbial contaminants, with the exception of heterotrophic plate 

count bacteria, (e.g. Vibrio cholerae, Toxoplasma gondii, Naegleria fowleri and Adenovirus) 

were on the PCCL 3 and are being carried forward to the PCCL 4 since no new data were found 

that would support a change to the contaminants listed in the PCCL 3. For additional information 

on the screening process please see Final Contaminant Candidate List 3 Microbes: Screening to 

the PCCL (USEPA, 2009f). For detailed information on the scoring protocols used to rank the 

nominated pathogens on the PCCL to produce a CCL please see Final Contaminant Candidate 

List 3 Microbes: PCCL to CCL Process (USEPA, 2009g) and for the most recent versions of the 

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contaminant information sheets, which summarize the data used for scoring the microbial 

contaminants nominated for CCL 4 see Contaminant Information Sheets for the Draft PCCL 

4 Nominated Contaminants (USEPA, 2015c). 

5.0 References

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, May 19, 2004 

Taylor, L. H., S. M. Latham, and M. E. Woolhouse. 2001. Risk factors for human disease 

emergence Philosophical Transactions of the Royal Society of London B. Vol. 356, pp. 983-989 

(See electronic Appendix A, No. 1411, pp. 1-9). 

USEPA. 2006. Request for Nominations of Drinking Water Contaminants for the Contaminant 

Candidate List. Federal Register. Vol. 71. No. 199. p. 60704. October 16, 2006.

USEPA. 2009a. Drinking Water Contaminant Candidate List 3—Final Notice. Federal Register.

Vol. 74. No 194. p. 51850. October 8, 2009. 

USEPA. 2009b. Final Contaminant Candidate List 3 Chemicals: Identifying the Universe. 

EPA 815-R-09-006. August, 2009. 

USEPA. 2009c. Final Contaminant Candidate List 3 Chemicals: Screening to a PCCL. 

EPA 815-R-09-007. August, 2009. 

USEPA. 2009d. Final Contaminant Candidate List 3 Chemicals: Classification of PCCL to the 

CCL. EPA 815-R-09-008. August 2009. 

USEPA. 2009e. Final Contaminant Candidate List 3 Microbes: Identifying the Universe. 

EPA 815-R-09-008. August 2009. 

USEPA. 2009f. Final Contaminant Candidate List 3 Microbes: Screening to the PCCL. 

EPA 815-R-09-008. August 2009. 

USEPA. 2009g. Final Contaminant Candidate List 3 Microbes: PCCL to CCL Process. 

EPA 815-R-09-009. August, 2009. 

USEPA, 2012. Request for Nominations of Drinking Water Contaminants for the Fourth 

Contaminant Candidate List. Federal Register. Vol. 77. No 89. p. 27057. May 8, 2012 

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. 

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PCCL 4 Nominated Contaminants

USEPA. 2015a. Summary of Nominations for the Fourth Contaminant Candidate List. EPA 815-

R-15-001. January, 2015. 

USEPA. 2015b. Data Sources for the CCL 4. EPA 815-R-15-004. January, 2015. 

USEPA. 2015c. Contaminant Information Sheets (CISs) for the Draft Fourth Preliminary 

Contaminant Candidate List (PCCL 4) Nominated Contaminants. EPA 815-R-15-003. January, 

2015. 

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EPA-OGWDW Screening Document for the Draft

PCCL 4 Nominated Contaminants

EPA 815-R-15-002

6.0 Appendices

Appendix 1. Screening data for the Nominated Chemicals in the 

CCL 4 Universe

Appendix 1 presents the CASRN, names of the nominated contaminants in the CCL 4 Universe, 

the health effects and occurrence data elements that were used in their screening. The CCL 4 

Screening Notes column includes a brief explanation of whether or not the chemical made the 

PCCL 4, and if it did not make the PCCL 4, the reason is included (i.e., the chemical failed based 

on the screening criteria, or incomplete data were available, so the chemical could not be 

screened). Some chemicals had some type of occurrence/ health information that allowed them to 

be included in the CCL 4 Universe, but this data was not sufficient for screening. An example of 

this is a chemical that was an analyte in a supplemental occurrence study, but was not detected; 

therefore, no concentration value was available to be used in the screening process. Thus, this 

chemical would remain in the Universe. The screening process is summarized in the text of this 

report, and a detailed description of the screening process developed under CCL 3 can be found 

in the Final CCL 3 Chemicals: Screening to a PCCL (USEPA, 2009c). 

When the health effects data element is designated as Cancer Studies NTP, the results shown are 

from cancer assays for two species and two sexes (male rat/female rat/ male mouse/female 

mouse) The NTP cancer data were partitioned into Toxicity Categories as described in Exhibit 3 

of this document and the data source is described further in USEPA, 2009b. For the occurrence 

data elements, the release data may be either national TRI data or pesticide application data. The 

notation “FW/AW” indicates the data are finished or ambient water data. Also noted, for some 

contaminants, supplemental data were used.

Further data and information for the nominated contaminants that made the PCCL 4 are 

available in the Contaminant Information Sheets (USEPA, 2015c) available in the CCL 4 water 

docket and on the CCL 4 Web site at: http://www2.epa.gov/ccl/contaminant-candidate-list-4-

ccl-4. 

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Appendix 1. Screening Data for the Nominated Chemicals in the CCL 4 Universe

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Key CASRN Common Name Health Effect Data 

Element Value Units Data Source

Toxicity 

Screening 

Category 

Occurrence Data 

Element Value Units Data Source CCL 4 Screening 

Notes

74233 77439760 

3-chloro-4-

dichloromethyl-5-

hydroxy-2(5H)-

furanone

Lethal Dose 50 (LD50) 120 mg/kg RTECS Toxicity 

Category 3 

No Occurrence data 

for screening blank blank blank 

Incomplete data for 

screening/ remains 

in CCL 4 Universe 

6535 319846 

alphaHexachlorocyclohe

xane

Risk Specific Dose (RSD) 0.000002 mg/kg-day ITER Toxicity 

Category 1 FW/AW-Max Value 0.21 ug/L NAWQA Makes PCCL 4 

3200 86500 Azinphos-methyl 

Lowest Observed 

Adverse Effect Level 

(LOAEL)

0.91 mg/kg-day RTECS Toxicity 

Category 2 FW/AW-Max Value 3.37 ug/L NAWQA Makes PCCL 4 

28242 25057890 Bentazon Reference Dose (RfD) 0.03 mg/kg-day OPP Toxicity 

Category 3 FW/AW-Max Value 11.46 ug/L NAWQA Makes PCCL 4 

2918 80057 Bisphenol A (BPA) 

Lowest Observed 

Adverse Effect Level 

(LOAEL)

2.5 mg/kg-day RTECS Toxicity 

Category 3 FW/AW-Max Value 12 ug/L Kolpin et al., 2002 (Max) Makes PCCL 4 

12023 1689845 Bromoxynil Reference Dose (RfD) 0.015 mg/kg-day OPP Toxicity 

Category 3 FW/AW-Max Value 6.1 ug/L NAWQA

Fails Screen/ 

remains in CCL 4 

Universe

3168 85687 Butyl benzyl 

phthalate Cancer Studies, NTP IS/P/P/N blank NTP Toxicity Category 2 Production Volume >50M - 100M lbs/yr CUS/IUR Makes PCCL 4 

2448 63252 Carbaryl 

Lowest Observed 

Adverse Effect Level 

(LOAEL)

0.23 mg/kg-day RTECS Toxicity 

Category 2 FW/AW-Max Value 33.5 ug/L NAWQA Makes PCCL 4 

12375 1897456 Chlorothalonil Cancer Studies, NTP P/P/N/N blank NTP Toxicity 

Category 1 FW/AW-Max Value 0.71 ug/L NAWQA Makes PCCL 4 

14098 2921882 Chlorpyrifos Reference Dose (RfD) 0.0003 mg/kg-day OPP Toxicity 

Category 2 FW/AW-Max Value 0.57 ug/L NAWQA

Fails Screen/ 

remains in CCL 4 

Universe

3122 84742 Dibutyl phthalate Tolerable Daily Intake 

(TDI) 0.063 mg/kg-day ITER Toxicity Category 4 Release 177,489 lbs/yr TRI

Fails Screen/ 

remains in CCL 4 

Universe

5106 115322 Dicofol Tumorigenic Dose 50 

(TD50) 32.9 mg/kg-day DSSTOX Toxicity Category 2 Release 788,527 lbs/yr NCFAP Makes PCCL 4 

3114 84617 Dicyclohexyl 

phthalate No HE data for screening blank blank blank blank Production Volume >500K - 1M lbs/yr CUS/IUR 

Incomplete data for 

screening/ remains 

in CCL 4 Universe

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Key CASRN Common Name Health Effect Data 

Element Value Units Data Source

Toxicity 

Screening 

Category

Occurrence Data 

Element Value Units Data Source CCL 4 Screening Notes

3118 84662 Diethyl phthalate No Observed Adverse 

Effect Level (NOAEL) 750 mg/kg-day ITER Toxicity Category 4 FW/AW-Med Value 0.2 ug/L NREC 

Fails Screen/ 

remains in CCL 4 

Universe 

30533 28553120 Di-isononyl 

phthalate 

Lowest Observed 

Adverse Effect Level 

(LOAEL)

402 mg/kg-day RTECS Toxicity 

Category 4 Production Volume >10M - 50M lbs/yr CUS/IUR 

Fails Screen/ 

remains in CCL 4 

Universe 

5769 131113 Dimethyl phthalate Reference Dose (RfD) 10 mg/kg-day RAIS Toxicity 

Category 5 Release 414093 lbs/yr TRI

Fails Screen/ 

remains in CCL 4 

Universe 

5200 117840 Di-n-octyl 

phthalate Reference Dose (RfD) 0.04 mg/kg-day RAIS Toxicity Category 3 Production Volume >1M - 10M lbs/yr CUS/IUR 

Fails Screen/ 

remains in CCL 4 

Universe 

5104 115297 Endosulfan No Observed Adverse 

Effect Level (NOAEL) 0.7 mg/kg-day ITER Toxicity Category 2 Release 1,604,700 lbs/yr NCFAP Makes PCCL 4 

12839 2164172 Fluometuron Reference Dose (RfD) 0.01 mg/kg-day EPA HA Toxicity 

Category 3 FW/AW-Max Value 37.8 ug/L NAWQA Makes PCCL 4 

6584 330552 Linuron Lowest Observed Effect 

Level (LOEL) 0.63 mg/kg-day ITER Toxicity Category 2 FW/AW-Max Value 1.4 ug/L NAWQA Makes PCCL 4 

5402 121755 Malathion No Observed Effect Level 

(NOEL) 0.23 mg/kg-day ITER Toxicity Category 2 FW/AW-Max Value 9.58 ug/L NAWQA Makes PCCL 4 

18823 7439965 Manganese No Observed Adverse 

Effect Level (NOAEL) 0.14 mg/kg-day ITER Toxicity Category 2 FW/AW 1,314 ug/L NIRS Makes PCCL 4 

6419 298000 Methyl parathion Reference Dose (RfD) 0.0002 mg/kg-day EPA HA Toxicity 

Category 2 FW/AW-Max Value 0.521 ug/L NAWQA

Fails Screen/ 

remains in CCL 4 

Universe

11918 1634044 Methyl tert-butyl 

ether 

Tolerable Daily Intake 

(TDI) 0.01 mg/kg-day ITER Toxicity Category 3 FW/AW-Max Value 23,000 ug/L NAWQA Makes PCCL 4 

76859 101043372 Microcystin-LR Reference Dose (RfD) 0.000003 mg/kg-day Ueno et 

al., 1999 

Toxicity 

Category 1 FW/AW 1,200 ug/L AWWARF, 2001 (Max) Makes PCCL 4 

28410 25154523 Nonylphenol 

Lowest Observed 

Adverse Effect Level 

(LOAEL)

2 mg/kg-day RTECS Toxicity 

Category 3 FW/AW-Max Value 40 ug/L Kolpin et al., 2002 (Max) Makes PCCL 4 

20331 9016459 Nonylphenol 

ethoxylate Lethal Dose 50 (LD50) 1310 mg/kg RTECS Toxicity Category 4 

FW/AW-Median 

Value 1 ug/L NREC 

Fails Screen/ 

remains in CCL 4 

Universe 

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Key CASRN Common Name Health Effect Data 

Element Value Units Data Source

Toxicity 

Screening 

Category

Occurrence Data 

Element Value Units Data Source CCL 4 Screening Notes

29943 27193288 Octylphenol No HE data for screening blank blank blank blank Production Volume >10M - 50M lbs/yr CUS/IUR 

Incomplete data for 

screening/ remains 

in CCL 4 Universe

20418 9036195 Octylphenol 

ethoxylate Lethal Dose 50 (LD50) 3500 mg/kg RTECS Toxicity Category 4 Production Volume < 500,000 

lbs lbs/yr CUS/IUR 

Fails Screen/ 

remains in CCL 4 

Universe 

81717 66795 Oxacillin Maximum Recommended 

Daily Dose (MRDD) 100 mg/kg-day DSSTOX Toxicity Category 4 

No Occurrence data 

for screening blank blank blank

Incomplete data for 

screening/ remains 

in CCL 4 Universe 

75565 61336 Penicillin Maximum Recommended 

Daily Dose (MRDD) 25 mg/kg-day DSSTOX Toxicity Category 4 

No Occurrence data 

for screening blank blank blank

Incomplete data for 

screening/ remains 

in CCL 4 Universe 

6614 335671 Perfluorooctanoic 

acid (PFOA)

Lowest Observed 

Adverse Effect Level 

(LOAEL)

0.46 mg/kg-day Lau et al., 

2006 

Toxicity 

Category 2 FW/AW 7.2 ug/L 

Emmett et 

al., 2006 

(Max)

Makes PCCL 4 

35815 52645531 Permethrin No Observed Effect Level 

(NOEL) 5 mg/kg-day ITER Toxicity Category 3 Release 1,068,390 lbs/yr NCFAP Makes PCCL 4 

9544 732116 Phosmet Lethal Dose 50 (LD50) 26 mg/kg RTECS Toxicity 

Category 2 Release 1,336,387 lbs/yr NCFAP Makes PCCL 4 

2334 57830 Progesterone Acceptable Daily Intake 

(ADI) 0.03 mg/kg-day JECFA Toxicity Category 3 FW/AW 0.199 ug/L Kolpin et al., 2002 (Max) 

Fails Screen/ 

remains in CCL 4 

Universe 

2343 58220 Testosterone Acceptable Daily Intake 

(ADI) 0.002 mg/kg-day JECFA Toxicity Category 3 FW/AW 0.214 ug/L Kolpin et al., 2002 (Max) 

Fails Screen/ 

remains in CCL 4 

Universe 

2202 52686 Trichlorfon Reference Dose (RfD) 0.002 mg/kg-day OPP Toxicity 

Category 3 Release 861 lbs/yr TRI

Fails Screen/ 

remains in CCL 4 

Universe 

4164 101202 Triclocarban No Observed Adverse 

Effect Level (NOAEL) 25 mg/kg-day OCSPP Toxicity Category 4 Production Volume >1M - 10M lbs/yr CUS/IUR 

Fails Screen/ 

remains in CCL 4 

Universe 

14798 3380345 Triclosan Lethal Dose 50 (LD50) 3700 mg/kg RTECS Toxicity 

Category 4 

FW/AW-Median 

Value 0.19 ug/L NREC 

Fails Screen/ 

remains in CCL 4 

Universe 

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Element Value Units Data Source

Toxicity 

Screening 

Category

Occurrence Data 

Element Value Units Data Source CCL 4 Screening Notes

75792 1401690 Tylosin Lethal Dose 50 (LD50) 800 mg/kg RTECS Toxicity 

Category 4 

FW/AW-Median 

Value 0.04 ug/L NREC 

Fails Screen/ 

remains in CCL 4 

Universe 

75932 11006761 Virginiamycin No HE data for screening blank blank blank blank No Occurrence data 

for screening blank blank blank

Incomplete data for 

screening/ remains 

in CCL 4 Universe

AWWARF - Carmichael, W.W. 2001. Assessment of Blue-Green Algal Toxins in Raw and Finished Drinking Water. Denver, CO: American Water Works Association Research 

Foundation

CUS/IUR - Chemical Update System/ Inventory Update Rule 

DSSTOX - Distributed Structure-Searchable Toxicity Database Network

Emmett et al., 2006 - Emmett, et al., 2006. J. Occ. Env. Med. Little Hocking, OH

EPA HA - EPA Health Advisory 

ITER - International Toxicity Estimates for Risk

JECFA - Joint FAO/WHO Expert Committee on Food Additives

Kolpin et al., 2002 - Kolpin, D.W., et al., 2002. Env. Sci. & Technol., 36(6), pp. 1202-1211.

Lau et al., 2006 - Lau, 2006. Tox. Sci., 90, 2, pp. 510-518.

NAWQA - National Water Quality Assessment

NCFAP - National Center for Food and Agricultural Policy 

NIRS - National Inorganics and Radionuclides Survey

NREC - National Reconnaissance of Emerging Contaminants 

NTP - National Toxicology Program; Values: P=positive; N=negative; IS=insufficient study. Results for male rat/female rat/male mouse/female mouse.

OCSPP - Office of Chemical Safety and Pollution Prevention

OPP - Office of Pesticide Programs

RAIS - Risk Assessment Information System

RTECS - Registry of Toxic Effects of Chemical Substances

TRI - Toxics Release Inventory 

UCM Round 1 - Unregulated Contaminant Monitoring

Ueno et al., 1999 - Ueno, Y., Y. Makita, S. Nagata et al. 1999. Environ. Toxicol. 14(1):45-55

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