i

Protocol for the 

Regulatory 

Determination 3 
ii

Office of Water (4607M) 

EPA 815-R-14-005 

April 2014 

http://water.epa.gov/drink/
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Disclaimer

This document is designed to provide technical background information for the Regulatory 

Determination 3 (RD 3). 

This document is not a regulation itself, and it does not substitute for the Safe Drinking Water 

Act (SDWA) or the Environmental Protection Agency’s (EPA’s) regulations. Mention of trade 

names or commercial products does not constitute endorsement or recommendation for use. 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Executive Summary

The Safe Drinking Water Act (SDWA), as amended in 1996, requires the Environmental 

Protection Agency (EPA) to make regulatory determinations every five years on at least five 

unregulated contaminants. A regulatory determination is a decision about whether or not to begin 

the process to propose and promulgate a national primary drinking water regulation (NPDWR) 

for an unregulated contaminant. These unregulated contaminants are chosen from the 

Contaminant Candidate List (CCL), which SDWA requires the agency to publish every five 

years. 

In developing CCL 3, EPA improved and built upon the process that was used for CCL 1 and 

CCL 2. The new CCL 3 process was based on substantial expert input and recommendations 

from the National Academy of Science’s (NAS) National Research Council (NRC) and the 

National Drinking Water Advisory Council (NDWAC) as well as input from the public. Based 

on these consultations and input, EPA developed a multi-step process to select candidates for the 

final CCL 3. EPA published the final CCL 3, which listed 116 contaminants, in the FR on 

October 8, 2009. The contaminants on CCL 3 were evaluated for the third round of regulatory 

determination (RD 3). 

In 2011, in response to a Government Accountability Office (GAO) report and a Congressional 

committee hearing, EPA prepared a first iteration of this report, the October 2011 Draft Protocol 

for the Regulatory Determination 3. The draft Protocol described the approach used to select 

contaminants from the CCL 3 for regulatory determination. EPA convened a seven-member 

expert panel to conduct an independent, scientific expert review of the agency’s draft Protocol. 

The goals of the expert review were to ensure that EPA’s protocol adequately addresses the 

GAO’s recommendations for improving the consistency, clarity and transparency in the process 

for identifying unregulated drinking water contaminants that pose the greatest public health 

concern under the SDWA. EPA subsequently updated the draft Protocol to include input 

received from the expert review. This document, Protocol for the Regulatory Determination 3, is 

the result of that revision. The outside experts’ comments, and EPA’s responses that formed the 

basis for the revisions, can be found in Response to External Expert Review of the Regulatory 

Determination 3 Protocol: Expert Review Comments with EPA Responses. 

This document is structured as follows: Section 1 is an introduction that provides an overview of 

the drinking water program risk management processes. Section 2 presents the background of the 

CCL and Regulatory Determination processes and the Unregulated Contaminant Monitoring 

Regulation (UCMR) established under the 1996 SDWA Amendments. Section 3 provides 

background on the CCLs and Regulatory Determinations that preceded CCL 3. Section 4

includes an in-depth discussion of the approach for and development of CCL 3. Section 5 

explains the role of the UCMR and its relationship to the CCL and Regulatory Determination 

processes. Section 6 describes EPA’s new Drinking Water Strategy, including provisions to 

consider regulation of related contaminants as groups rather than individually. Section 7 provides 

an overview of the Regulatory Determination process and outreach/consultation activities 

associated with this process. Section 8 explains in detail the RD 3 protocol, the process by which 

the agency evaluated chemical contaminants from CCL 3 for inclusion in RD 3 and against the 

three statutory criteria for regulatory determinations. RD 3 involved a three-phase process: (1) 
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the Data Availability Phase, (2) the Data Evaluation Phase, and (3) the Regulatory Determination 

Assessment Phase. 

This document also includes seven appendices that provide additional detailed background 

information and supporting materials relevant to the implementation of RD 3. These are: 

• Appendix A – Health Reference Levels provides an explanation of the health reference 

level (HRL), its role in the Regulatory Determination process, and how it is derived for 

carcinogens and non-carcinogens. 

• Appendix B – Health Assessment Data Sources for RD 3 explains how health 

assessments were used for RD 3 and describes the sources of the drinking water health 

data used by EPA to support regulatory determinations. 

• Appendix C – Data Sources for Occurrence describes the data sources EPA used to 

evaluate occurrence and exposure for contaminants considered for regulatory 

determinations.

• Appendix D – Summary of Phase 1: Data Availability provides a summary of the 

outcome of the Phase 1 evaluation of 116 contaminants and includes information about

occurrence data type, best available occurrence data source, primary health effects data 

source, health assessment status, and whether the contaminant was placed on the short list 

for Phase 2. 

• Appendix E – Summary of Phase 2: Data Availability provides a summary of the 

outcome of the Phase 2 evaluation of 35 contaminants and includes information about 

contaminant background (e.g., production/release, fate/transport), health effect findings, 

initial occurrence findings, and the rationale for the outcome of the Phase 2 evaluation. 

• Appendix F – Summary of Phase 3: Regulatory Determination Assessments provides 

a summary of the outcome of the Phase 3 evaluation of ten contaminants and includes 

information about contaminant background, health effect findings, occurrence findings, 

other relevant information (e.g., sensitive subpopulations, mobility), and conclusions. 

• Appendix G - Evaluation of Statutory Criterion #3: explains the factors the EPA 

Administrator may consider when determining whether regulation would provide a 

meaningful opportunity to improve public health. 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Contents

Executive Summary ...........................................................................................................................v

Contents .............................................................................................................................................vii

Exhibits ..............................................................................................................................................x

Abbreviations .....................................................................................................................................xii

1. Introduction ............................................................................................................................1

2. The 1996 SDWA Amendments and the CCL and Regulatory Determination 

Processes ................................................................................................................................2

2.A. The Contaminant Candidate List (CCL) ................................................................................2

2.B. Regulatory Determinations ....................................................................................................2

2.C. The Unregulated Contaminant Monitoring Regulation (UCMR) ..........................................3

3. Regulatory Determination Cycles for CCL ...........................................................................4

3.A. The First Contaminant Candidate List (CCL 1) ....................................................................4

3.B. The Regulatory Determination 1 ...........................................................................................4

3.C. The Second Contaminant Candidate List (CCL 2) ................................................................5

3.D. The Regulatory Determination 2 ...........................................................................................5

3.E. The Regulatory Determination for Perchlorate ......................................................................6

4. The Third Contaminant Candidate List (CCL 3) ...................................................................6

4.A. The Approach for CCL 3 .......................................................................................................6

4.B. Creating the Universe ............................................................................................................8

Chemical Contaminants .........................................................................................................8

Microbial Contaminants.........................................................................................................8

4.C. Screening to the PCCL ...........................................................................................................9

Chemical Contaminants .........................................................................................................9

Microbial Contaminants.........................................................................................................9

4.D. Arriving at the CCL ...............................................................................................................9

Chemical Contaminants .........................................................................................................9

Microbial Contaminants.........................................................................................................10

4.E. All Contaminants – Nominations, Expert Input, and Public Comment .................................10

4.F. Results of CCL 3 ....................................................................................................................10

5. UCMR and Its Relationship to the Regulatory Development Process ..................................13

6. Drinking Water Strategy ........................................................................................................14

7. EPA’s Regulatory Determination Process .............................................................................15

8. The Regulatory Determination 3 Process ..............................................................................16

8.A. Phase 1: Data Availability ....................................................................................................18

8.A.1. Health Data Availability Assessment .......................................................................19

8.A.1.a. Is a Health Assessment Available or In Process? ....................................19

8.A.2. Occurrence Data Availability Assessment ................................................................20

8.A.2.a. Are Nationally Representative Finished Water Occurrence Data 

Available? ......................................................................................................20
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8.A.2.b. Are Non-National Finished Water Occurrence Data Available that 

Show Occurrence at Levels of Public Health Concern? ................................20

8.A.3. Evaluation of Outcomes of Health and Occurrence Data Availability Assessments 21

8.A.4. Outcome of Phase 1 for Regulatory Determination 3 ...............................................22

8.B. Phase 2: Data Evaluation .......................................................................................................24

8.B.1. Phase 2--Step1: Collect and Evaluate Health Information and Derive a Draft HRL 24

8.B.1.a. Derivation of the Draft HRL and Consideration of Sensitive 

Populations .....................................................................................................25

8.B.2. Phase 2--Step 2: Gather and Evaluate Additional Occurrence Data Sources 

Relative to the Draft HRL ..........................................................................................26

8.B.3. Phase 2--Step 3: Identify Contaminants Occurring at Levels and Frequencies of 

Public Health Concern ...............................................................................................26

8.B.4. Phase 2--Step 4: Identify Contaminants That Have No or Low Occurrence at 

Levels of Public Health Concern ...............................................................................27

8.B.5. Outcome of Phase 2 for Regulatory Determination 3 ...............................................28

8.C. Phase 3: Regulatory Determination Assessment ..................................................................29

8.C.1. Evaluation of Statutory Criterion #1 (Adverse Health Effect) .................................29

8.C.2. Evaluation of Statutory Criterion #2 (Known or Likely Occurrence in PWSs with 

a Frequency and Level of Concern) ...........................................................................30

8.C.2.a. Factors of Primary Consideration .............................................................30

8.C.2.b. Additional Factors of Consideration .........................................................30

8.C.3. Evaluation of Statutory Criterion #3 (Meaningful Opportunity) ..............................31

8.C.4. Making a Regulatory Determination Decision .........................................................31

8.C.5. Outcome of the Regulatory Determination Assessment Phase for Regulatory 

Determination 3 .........................................................................................................33

9. References Cited ....................................................................................................................33

Appendix A. Health Reference Levels ................................................................................37

Unidentified Mode of Action .................................................................................................37

Mutagenic Mode of Action ....................................................................................................37

Appendix B. Health Assessment Data Sources for RD 3 ....................................................40

EPA Health Assessments: ..................................................................................................................40

Non-EPA Health Assessments: ..........................................................................................................42

Appendix C. Data Sources for Occurrence .........................................................................44

National Data Sources (National Drinking Water Data) ...................................................................44

Unregulated Contaminant Monitoring Regulation (UCMR) Assessment Monitoring 

(AM): .........................................................................................................................44

Unregulated Contaminant Monitoring Regulation: Screening Surveys (SS): .......................45

Unregulated Contaminant Monitoring (UCM): .....................................................................45

National Inorganic and Radionuclide Survey (NIRS): ..........................................................45

Unregulated Contaminant Monitoring Regulation 1 Screening Survey: ...............................46

Disinfection By-Product Information Collection Rule (DBP ICR): ......................................46

Individual States’ Data ...........................................................................................................46

Supplemental Drinking Water Data Sources .....................................................................................47

Community Water System Survey (CWSS): .........................................................................47
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Consumer Confidence Reports (CCRs): ................................................................................47

Pesticide Data Program (PDP): ..............................................................................................47

United States Geological Survey Pilot Monitoring Program (USGS PMP): .........................47

Environmental Working Group (EWG): ...............................................................................48

Supplemental Ambient/Source Water Data Sources .........................................................................48

USGS National Water Quality Assessment Program (NAWQA): ........................................48

EPA Storage and Retrieval database (STORET): ..................................................................48

USGS National Reconnaissance of Emerging Contaminants (NREC): ................................48

Production/Use/Release Data Sources ...............................................................................................49

Chemical Update System/Inventory Update Rule (CUS IUR): .............................................49

EPA Office of Pesticide Programs (OPP) Reregistration Documents: ..................................49

National Center for Food and Agricultural Policy (NCFAP): ...............................................49

USGS Pesticide Use Maps: ....................................................................................................49

Toxics Release Inventory (TRI): ...........................................................................................50

Appendix D. Summary of Phase 1: Data Availability .........................................................51

Appendix E. Summary of Phase 2 Data Evaluation ...........................................................51

Appendix F. Summary of Phase 3 Regulatory Determination Assessments ......................51

Appendix G. Evaluation of Statutory Criterion #3 ..............................................................52
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Exhibits

Exhibit 1: Drinking Water Program Risk Management Processes ....................................................1

Exhibit 2: CCL, Regulatory Determination, and UCMR Timeline ...................................................4

Exhibit 3: General Overview of the Approach Used to Establish CCL 3 .........................................8

Exhibit 4: CCL 3 Chemicals and Chemical Groups ..........................................................................11

Exhibit 5: CCL 3 Microbiological Contaminants ..............................................................................13

Exhibit 6: The Three Primary Phases of the Technical Assessment of the Regulatory 

Determination 3 Process. .......................................................................................................18

Exhibit 7: Contaminants to be Evaluated in Phase 2 of the Regulatory Determination Process .......22

Exhibit 8: Regulatory Determination Outcomes................................................................................33

Exhibit 1: Drinking Water Program Risk Management Processes ....................................................1

Exhibit 2: CCL, Regulatory Determination, and UCMR Timeline ...................................................4

Exhibit 3: General Overview of the Approach Used to Establish CCL 3 .........................................8

Exhibit 4: CCL 3 Chemicals and Chemical Groups ..........................................................................11

Exhibit 5: CCL 3 Microbiological Contaminants ..............................................................................13

Exhibit 6: The Three Primary Phases of the Technical Assessment of the Regulatory 

Determination 3 Process. .......................................................................................................18

Exhibit 7: Contaminants to be Evaluated in Phase 2 of the Regulatory Determination Process .......22

Exhibit 8: Regulatory Determination Outcomes................................................................................33
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Abbreviations

ADAF Age Dependent Adjustment Factors

AMS Agricultural Marketing Service

ATSDR Agency for Toxic Substances and Disease Registry

AWWA American Water Works Association

BMDL Benchmark Dose Lower Confidence Limit

BW Body Weight

CASRN Chemical Abstract Services Registry Number

CCL Contaminant Candidate List

CCL 1 First Contaminant Candidate List

CCL 2 Second Contaminant Candidate List

CCL 3 Third Contaminant Candidate List

CCR Consumer Confidence Report

CERCLA Comprehensive Environmental Response, Compensations, and Liability Act of 1980

CSF Cancer Slope Factor

CUSIUR Chemical Update System / Inventory Update Rule

CVOC Carcinogenic Volatile Organic Compound

CW Concentration in Water

CWS Community Water System

CWSS Community Water Systems Survey

DBP Disinfection By-Products

DBP ICR Disinfection By-Product Information Collection Rule

DDE 1, 1-Dichloro-2,2-bis(p-chlorophenyl)ethylene

DWI Drinking Water Intake

DWS Drinking Water Strategy

EPA Environmental Protection Agency

EPTC s-Ethyl dipropylthiocarbamate

ESA Acetochlor ethanesulfone acid

EWG Environmental Working Group

FIFRA Federal Insecticide, Fungicide, and Rodenticide Act

FQPA Food Quality Protection Act

FR Federal Register

HA Health Advisory

HRL Health Reference Level

IRIS Integrated Risk Information System

LOAEL Lowest-Observed-Adverse-Effect Level

MCL Maximum Contaminant Level

MCLG Maximum Contaminant Level Goal

MOA Mode of Action

MRL Minimum Reporting Limit
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NAS National Academy of Sciences

NAWQA National Water Quality Assessment 

NCFAP National Center for Food and Agricultural Policy

NCOD National Contaminant Occurrence Database

NDBA N-nitroso-di-n-butylamine

NDEA N-Nitrosodiethylamine

NDMA N-Nitrosodimethylamine

NDPA N-Nitrosodipropylamine

NDPhA N-Nitrosodiphenylamine

NDWAC National Drinking Water Advisory Council

NIRS National Inorganics and Radionuclides Survey

NMEA N-nitrosomethylethylamine

NOAEL No-Observed-Adverse-Effect Level

NPDWR National Primary Drinking Water Regulation

NPYR N-Nitrosodipyrolidene

NRC National Research Council

NREC United States Geological Survey National Reconnaissance of Emerging Contaminants

OA Acetochlor oxanilic acid

OEHHA Office of Environmental Health Hazard Assessment (California)

OGWDW Office of Ground Water and Drinking Water

OPP Office of Pesticide Programs

OPP IRED Office of Pesticide Programs Interim Reregistration Eligibility Decision

OPP TRED Office of Pesticide Programs Tolerance Reregistration Eligibility Decision

ORD Office of Research and Development

OW Office of Water

PCCL Preliminary Contaminant Candidate List

PDP Pesticide Data Program

PFOA Perfluorooctanoic acid

PFOS Perfluorooctane sulfonic acid

PMP United States Geological Survey Pilot Monitoring Program 

PRZM / EXAMS Pesticide Root Zone Model / Exposure Analysis Modeling System

PWS Public Water System

RDX Cyclotrimethylenetrinitramine

RED Reregistration Eligibility Decision

RD 3 Regulatory Determination 3

RfD Reference Dose

RSC Relative Source Contribution

RTECS Registry of Toxic Effects for Chemical Substances

SAB Science Advisory Board

SCI-GROW Screening Concentrations in Ground Water Model

SDWA Safe Drinking Water Act

STORET Storage and Retrieval
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TCP 1,2,3-Trichloropropane

TPTH Triphenyltin hydroxide

TRI Toxics Release Inventory

TSCA Toxic Substances Control Act

UCM Unregulated Contaminant Monitoring

UCMR Unregulated Contaminant Monitoring Regulation

UCMR 1 First Unregulated Contaminant Monitoring Regulation

UCMR 2 Second Unregulated Contaminant Monitoring Regulation

UCMR 3 Third Unregulated Contaminant Monitoring Regulation

UF Uncertainty Factor

USDA United States Department of Agriculture

USGS United States Geological Survey

WBDO Waterborne Disease Outbreak

WHO World Health Organization
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1. Introduction

The 1996 Safe Drinking Water Act (SDWA) Amendments required that EPA develop a revised 

risk management and regulatory development approach for drinking water in order to protect 

public health. To meet these requirements EPA developed an integrated framework (Exhibit 1) 

to: 

(1) List currently unregulated contaminants of public health concern, called the 

Contaminant Candidate List (CCL); 

(2) Evaluate these contaminants and determine whether or not the contaminants warrant a 

national primary drinking water regulation (NPDWR), called Regulatory 

Determination; 

(3) Collect drinking water monitoring data for unregulated contaminants under the 

Unregulated Contaminant Monitoring Regulation (UCMR); and 

(4) Periodically review existing regulations and assess whether revisions are needed that 

maintain or improve public health protection for drinking water consumers (called the 

Six-Year Review). 

Exhibit 1: Drinking Water Program Risk Management Processes

The purpose of this document is to provide a detailed summary of the protocol used for the third 

cycle of Regulatory Determination (i.e., Regulatory Determination 3, or RD 3) and the 

evaluation of the unregulated contaminants listed on the third CCL (CCL 3). In developing CCL 

3 and RD 3, EPA has utilized input from peer reviews and expert consultations, including several 

reports from the National Academy of Sciences’ (NAS’s) National Research Council (NRC), 

reviews by EPA’s Science Advisory Board (SAB), and the National Drinking Water Advisory 

Council (NDWAC), as well as other stakeholder input and public comment. 

At each stage, need increased specificity and confidence in the 

type of supporting data used (e.g., health and occurrence). 

Public consultation is involved in each step of the process.

Draft CCL

Final CCL

Final Rule

(NPDWR) 

Six Year Review of 

Existing NPDWRs

No further action if EPA makes 

decision to not regulate 

(may develop health advisory; 

may consider for future CCL)

Preliminary 

Regulatory 

Determinations

Final Regulatory 

Determinations

Proposed Rule

(NPDWR) Draft UCMR

Final UCMR

UCMR Monitoring

Results
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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2. The 1996 SDWA Amendments and the CCL and Regulatory

Determination Processes

As noted, the 1996 SDWA Amendments direct EPA to periodically publish a list of unregulated 

contaminants that may pose risks to public health from drinking water (the CCL) and to 

periodically make determinations on whether or not to regulate any CCL contaminant with an 

NPDWR. The specific statutory requirements for the CCL and Regulatory Determinations can be 

found in SDWA Section 1412(b)(1). The statutory requirements for a related effort, the UCMR

can be found in SDWA Section 1445(a)(2). 

2.A. The Contaminant Candidate List (CCL)

The 1996 SDWA Amendments required EPA to publish the first CCL (CCL 1) by February 

1998, 18 months after the date of enactment, and to publish a new CCL every 5 years thereafter. 

The CCL is a list of 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 SDWA to protect public health. SDWA also specifies that the CCL must consider 

substances identified in section 101(14) of the Comprehensive Environmental Response, 

Compensation, and Liability Act of 1980 (CERCLA) and substances registered as pesticides 

under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and must consider data 

and information from the National Contaminant Occurrence Database (NCOD), which EPA 

established as required under SDWA Section 1445(g). For the CCL, SDWA requires 

consultation with the scientific community, including EPA’s Science Advisory Board, and 

opportunity for public comment. The CCL is the starting point for the Regulatory Determination 

process and is the list of priority contaminants that are evaluated for potential drinking water 

regulations. 

2.B. Regulatory Determinations

The 1996 SDWA Amendments, section 1412(b)(1)(A), direct EPA to determine whether or not 

to regulate at least five contaminants from the most recent CCL every five years and allow an 

opportunity for public notice and comment. The first Regulatory Determination was due within 

three and one-half years after the publication of CCL 1, and then every five years thereafter. 

When making a regulatory determination, the 1996 SDWA Amendments require that EPA assess

three criteria and decide whether: 

(1) The contaminant may have an adverse effect on the health of persons. 

(2) The contaminant is known to occur or there is substantial likelihood that the 

contaminant will occur in PWSs with a frequency and at levels of public health 

concern. 

(3) 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 finds that all three of these statutory criteria are met, it makes a determination to regulate 

the contaminant (i.e., a positive determination). Following a positive regulatory determination, 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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the agency has 24 months to publish a proposed Maximum Contaminant Level Goal (MCLG)1

and NPDWR2

. After the proposal, the agency has 18 months to publish a final MCLG and 

promulgate a final NPDWR (SDWA section 1412(b)(1)(E)).3 If EPA finds that one or more of 

these statutory criteria are not met, it makes a determination not to regulate the contaminant (i.e., 

a negative determination). A determination not to regulate a contaminant is considered a final 

agency action and is subject to judicial review. 

2.C. The Unregulated Contaminant Monitoring Regulation (UCMR)

The 1996 SDWA Amendments (section 1445(a)(2)) also required that once every five years, 

beginning in August 1999, EPA issue a new list of no more than 30 unregulated contaminants to 

be monitored by PWSs. The UCMR occurrence data are designed to help determine if the 

contaminant occurs “with a frequency and at levels of public health concern” (per the second 

statutory criterion for regulatory determinations, above) to support the Administrator’s 

determination under the Regulatory Determination process of whether or not to regulate a 

contaminant. The 1996 SDWA Amendments require EPA to enter the monitoring data into a 

national drinking water contaminant occurrence database (implemented as NCOD). 

The CCL and UCMR are integral components of the coordinated risk management process that 

inform and support Regulatory Determination (Exhibit 2 illustrates the time-line relationship 

among the programs). The UCMR list of contaminants for each monitoring cycle are developed 

in coordination with the CCL process. The programs continually support and inform each other. 

The UCMR is designed to inform Regulatory Determination, and in some cases may also collect 

data that would support regulation development and help determine whether new or emerging 

contaminants should be listed on future CCLs. 

 

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

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

level goals are nonenforceable health goals.

2 An NPDWR is a legally enforceable standard that applies to PWSs. 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. 3 The statute authorizes a nine-month extension of this promulgation date.
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Exhibit 2: CCL, Regulatory Determination, and UCMR Timeline

3. Regulatory Determination Cycles for CCL

3.A. The First Contaminant Candidate List (CCL 1) 

The 1996 SDWA Amendments required EPA to publish the first CCL (CCL 1) 18 months after 

the date of enactment. Following the 1996 SDWA Amendments, EPA sought input from the 

NDWAC on the process that should be used to identify contaminants for inclusion on the CCL. 

For chemical contaminants, the agency developed screening and evaluation criteria based on 

recommendations from NDWAC. For microbiological contaminants, NDWAC recommended 

that the agency seek external expertise to identify and select potential waterborne pathogens. As 

a result, the agency convened an international panel of microbiologists and public health experts 

who developed criteria for screening and evaluation, and subsequently developed an initial list of 

potential microbiological contaminants.

Within the short time frame required by SDWA, EPA developed the first CCL based largely on 

expert knowledge and the evaluation of readily available information. EPA received beneficial 

input from the NDWAC, the scientific community, and the public (through stakeholder meetings 

and the public comments). EPA published the draft and final CCL 1 in the Federal Register on 

October 6, 1997 (62 FR 52193; USEPA, 1997) and March 2, 1998 (63 FR 10273; USEPA, 

1998), respectively. The final CCL 1 contained 50 chemical and 10 microbiological 

contaminants. 

3.B. The Regulatory Determination 1 

EPA published the preliminary and final regulatory determinations for 9 CCL 1 contaminants in 

the Federal Register on June 3, 2002 (67 FR 38222; USEPA, 2002) and July 18, 2003 (68 FR 

42898; USEPA, 2003), respectively. EPA determined that 9 of the 60 CCL 1 contaminants had 

sufficient data and information available to make regulatory determinations. The nine 

contaminants were Acanthamoeba, aldrin, dieldrin, hexachlorobutadiene, manganese,

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

Regulatory 

Determination 1:

9 Contaminants

Regulatory 

Determination 2:

11 Contaminants

Regulatory 

Determination 3

UCMR 1:

25 Contaminants

(Monitoring 2001-2003)

UCMR 2: 

25 Contaminants

(Monitoring 2008-2010)

UCMR 3: 

30 Contaminants

(Monitoring 2013-2015)

CCL 1:

60 Contaminants

CCL 2: 

51 Contaminants

CCL 3: 

116 Contaminants
EPA – OGWDW Protocol for Regulatory Determination 3   April 2014

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metribuzin, naphthalene, sodium, and sulfate. The agency decided not to regulate any of these 

nine contaminants due to no or low occurrence in PWSs and/or no meaningful opportunity to 

protect public health. The agency posted information about Acanthamoeba2

 on the EPA website 

and issued health advisories for manganese, sodium, and sulfate (available at 

http://water.epa.gov/drink/standards/hascience.cfm). 

The decision-making process that EPA used to make its regulatory determinations for CCL 1 

was based on expert input and recommendations from different groups including the NRC, 

NDWAC, and stakeholders. In June 2002, EPA consulted with the Science Advisory Board 

(SAB) Drinking Water Committee on whether the protocol EPA developed, based on the 

NDWAC recommendations, was consistently applied and appropriately documented. SAB 

provided verbal feedback and recommended that the agency provide a transparent and clear 

explanation of the process for making regulatory determinations. The agency took SAB’s 

recommendation into consideration and further explained the CCL 1 regulatory determination 

evaluation process in the July 18, 2003 (68 FR 42898; USEPA, 2003) notice and in the 

supporting documentation (see also 67 FR 38222; USEPA, 2002).

3.C. The Second Contaminant Candidate List (CCL 2) 

After completing CCL 1, the agency began the process to develop an enhanced, more robust 

approach to evaluating the risk of potential drinking water contaminants for future CCLs. The 

agency asked the National Academy of Sciences’ NRC for guidance on a more rigorous and 

expansive approach for the CCL (see section 4). Since NRC’s evaluation overlapped with the 

statutory timeline for developing the second CCL (CCL 2), the agency continued to develop the 

more rigorous CCL process while simultaneously publishing a CCL 2 that carried forward the 51 

contaminants remaining on CCL 1. The agency published its draft and final CCL 2 in the 

Federal Register on April 2, 2004 (69 FR 17406; USEPA, 2004) and February 24, 2005 (70 FR 

9071; USEPA, 2005a), respectively. 

3.D. The Regulatory Determination 2 

EPA used the same approach for Regulatory Determination 2 as was used for evaluating whether 

or not to regulate contaminants for Regulatory Determination 1. The agency published its 

preliminary and final regulatory determinations for 11 CCL 2 contaminants in the Federal 

Register on May 1, 2007 (72 FR 24106; USEPA, 2007a) and July 30, 2008 (73 FR 44251; 

USEPA, 2008a), respectively. EPA determined that 11 of the 51 CCL 2 contaminants had 

sufficient data and information available to make regulatory determinations. The 11 

contaminants were boron, the dacthal mono- and di-acid degradates, 1,1-dichloro-2,2-bis(pchlorophenyl)ethylene (DDE), 1,3-dichloropropene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, sethyl dipropylthiocarbamate (EPTC), fonofos, terbacil, and 1,1,2,2-tetrachloroethane. The 

agency decided not to regulate any of these 11 contaminants due to no or low occurrence in 

PWSs and/or no meaningful opportunity for public health protection. The agency did, however, 

issue health advisories for boron, dacthal degradates, 2,4-dinitrotoluene, 2,6-dinitrotoluene and 

1,1,2,2-tetrachloroethane (available at http://water.epa.gov/drink/standards/hascience.cfm). 

 

2 Consumer information about Acanthamoeba for people who wear contact lenses can be found at 

http://water.epa.gov/action/advisories/acanthamoeba/index.cfm
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

6

3.E. The Regulatory Determination for Perchlorate 

EPA published a preliminary determination not to regulate perchlorate with a national primary 

drinking water regulation in October 2008 (73 FR 60262; USEPA, 2008b). In 2009, EPA 

solicited input from the public on approaches for analyzing and evaluating perchlorate data (74 

FR 41883; USEPA, 2009a and 74 FR 48541; USPEA, 2009b), and in February 2011, EPA 

issued a final determination to regulate perchlorate (76 FR 7762; USEPA, 2011a). This decision 

is the first time EPA has decided to regulate a substance from the CCL. 

EPA determined that perchlorate met SDWA’s three criteria for regulating a contaminant: 

(1) Perchlorate may have adverse health effects because scientific research indicates that 

perchlorate can disrupt the thyroid’s ability to produce hormones needed for normal 

growth and development (which could be of special concern for fetuses, newborns, 

and children). 

(2) There is a substantial likelihood that perchlorate occurs with frequency at levels of 

health concern in public water systems because monitoring data show over four 

percent of public water systems have detected perchlorate. 

(3) There is a meaningful opportunity for health risk reduction for the 5.2 to 16.6 million 

people who may be served drinking water containing perchlorate. 

The agency is currently developing the proposed drinking water regulation for perchlorate. 

4. The Third Contaminant Candidate List (CCL 3)

4.A. The Approach for CCL 3

In developing CCL 3, EPA improved upon the process that was used to develop CCL 1 and 

CCL 2. This new process was based on substantial expert input and recommendations from the 

NRC, NDWAC and input from the public. 

The NRC recommended a multi-step process including using a prototype classification algorithm 

that evaluates attributes in conjunction with expert judgment to identify contaminants for future 

CCLs. The approach is based on predictive features or attributes that characterize the occurrence 

in drinking water and health effects of each contaminant. The NRC described two health effects 

attributes and three occurrence attributes. The health effects attributes are severity and potency, 

and the occurrence attributes are prevalence, magnitude, and persistence/mobility (used as a 

surrogate for prevalence when a contaminant had no occurrence data). 

The details of the NAS-NRC recommendations are available in the report entitled “Classifying 

Drinking Water Contaminants for Regulatory Considerations” (NAS, 2001). It is important to 

emphasize that the NRC report only gives a broad framework for EPA to develop its own 

prototype classification scheme and then to calibrate the scheme using diagnostic contaminants.

With the NAS-NRC recommendations in hand, the Office of Water turned to the NDWAC to 

provide advice on how to implement the approach recommended in the NAS-NRC report. The 

NDWAC formed a subcommittee to provide advice to the NDWAC and then to EPA. 

Based on the deliberations of the NDWAC Work Group, NDWAC released a report in May 2004 

and noted that EPA may need several CCL cycles to fully develop and implement the NRC 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

7

recommended approach (NDWAC, 2004). While the NDWAC agreed with the overall approach, 

the group noted that not all the data and information needed to develop the NRC-envisioned 

CCL were available at the time. The NDWAC also recognized that the CCL process could be 

refined and improved in successive efforts; therefore, the agency should take advantage of the 

knowledge gained and improve upon the next CCL using an adaptive management approach. 

Based on these consultations with expert groups and stakeholders, EPA developed a multi-step 

approach to select contaminants for the CCL 3, which includes the following key steps: 

(1) Identify a broad universe of potential drinking water contaminants (the CCL 3 

Universe). 

(2) Screen the CCL 3 Universe to develop a preliminary CCL (PCCL) based on the 

potential of contaminants to occur in public water systems and the potential for public 

health concern.

(3) Further evaluate the PCCL contaminants based on a more detailed review of 

occurrence and health effects data to generate the final CCL 3. 

Exhibit 3 illustrates the three-step process used to evaluate contaminants for CCL 3. 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

8

Exhibit 3: General Overview of the Approach Used to Establish CCL 3

4.B. Creating the Universe

Chemical Contaminants

To populate the CCL 3 Universe of Chemicals, an extensive preliminary list (a “pre-universe”) 

of approximately 26,000 substances was compiled from a wide variety of data sources that met 

specific criteria. The preliminary list was refined by focusing on those substances that had some 

health effects and occurrence information and removing chemicals that are currently regulated in 

drinking water and substances that are considered mixtures of chemicals. The public also had an 

opportunity to nominate chemicals to the Universe of Chemicals. The resultant CCL 3 Universe 

included approximately 6,000 chemicals (for further details, see USEPA, 2009c). 

Microbial Contaminants

To assemble the CCL 3 Universe of microbiological contaminants, EPA reviewed the literature 

and compiled a list of known human pathogens. As a result of the literature review and public 

nominations process, the Universe included a total of 1,425 pathogens (for further details, see 

USEPA, 2009d).

Classification 

Tools

Evaluation 

Expert Review 

Universe

PCCL

Proposed CCL

Surveillance

and 

Nomination 

STEP 1

Identify the

STEP 2

Screen 

to a PCCL

STEP 3

Select the CCL

Final CCL
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

9

4.C. Screening to the PCCL

Chemical Contaminants

The chemicals in the CCL 3 Universe were then screened using a framework that took into 

account both health effects and occurrence data. In the case of health effects, EPA evaluated both 

quantitative and qualitative information on the hazard and/or dose-response properties of the 

contaminants. For occurrence, EPA evaluated both quantitative and qualitative information on 

occurrence in water, releases to the environment, and amounts produced. 

EPA categorized contaminants according to their potential to occur in PWSs and their potential 

for public health concern. For occurrence, categories were developed for each available data 

source to evaluate the potential occurrence in PWSs. For public health concern, categories were 

developed for each available toxicity parameter. To be most protective of public health, 

chemicals that had health effects properties that placed them in the highest toxicity category were 

moved forward for further evaluation, even if their occurrence was limited. And because of their 

health concerns and obvious exposure potential, known disinfection by-products (DBPs) were 

considered to have “default” occurrence potential even if no actual occurrence information was 

available, and they were also moved forward for further review. As the result of this screening 

process, 561 chemical contaminants from the approximately 6,000 chemicals in the CCL 3 

Universe were selected to move on to the Preliminary CCL 3 (PCCL 3) (see USEPA, 2009e, for 

details on the screening process).

Microbial Contaminants

EPA developed a set of 12 screening criteria to reduce the Universe of human pathogens to just 

those pathogens that could cause drinking water-related diseases resulting from ingestion of, 

inhalation of, or dermal contact with drinking water in the United States. For example, pathogens 

transmitted solely by animal vectors, pathogens not endemic to North America, and pathogens 

with a life-cycle incompatible with drinking-water transmission were screened out and not 

included on the PCCL. Based upon this screening exercise, 1,396 of the 1,425 pathogens were 

excluded and 29 pathogens moved on to the PCCL. (For more information about the screening 

process for microbial contaminants, see USEPA, 2009f.) 

4.D. Arriving at the CCL

Chemical Contaminants

To select chemical contaminants for the CCL 3 from among the 561 PCCL contaminants, EPA 

used classification models as a support tool to handle larger, more complex assortments of data 

in a consistent and reproducible manner. Classification models are algorithms that use statistical 

approaches for pattern recognition and derive mathematical relationships among input variables 

(measurements or descriptive data) and output from a data set used to train the classification 

model. The classification models were trained by first evaluating chemicals for which regulatory 

decisions had already been made and for which considerable occurrence and health effects 

information was available. A scaling system was developed for four attributes: severity, potency, 

magnitude, and prevalence (see USEPA, 2009g, for details). Contaminants were scored in each 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

10

of these attributes, the results were run through three calibrated models, and EPA made several 

post-modeling refinements to compile the draft list of CCL 3 contaminants. One important 

refinement was the calculation of ratios comparing health reference levels3

 (HRLs) with 

observed or projected concentrations in water. For listing on CCL 3, EPA gave precedence to 

those contaminants with lower ratios (i.e., higher known or anticipated occurrence relative to 

levels of health concern). See Appendix A for more information on HRLs. 

Microbial Contaminants

EPA developed a scoring system to assign a numerical value to each pathogen on the PCCL. 

Each of the pathogens on the PCCL was scored using three scoring protocols, one protocol each 

for (a) waterborne disease outbreaks (WBDO), (b) occurrence in drinking water and other kinds 

of water (e.g., recreational, ground water, surface water), and (c) 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. (For details about the three protocols used to score the 

pathogens on the PCCL and the process by which the scores were combined, see USEPA, 

2009h.) 

To determine which of the 29 PCCL pathogens should be included on the draft CCL 3, the 

agency considered various factors, including the PCCL scores for WBDO, occurrence, and 

health effects. 

4.E. All Contaminants – Nominations, Expert Input, and Public Comment

EPA also put out a special call for nominations to the CCL 3 (USEPA, 2009i), held expert panel 

consultations, consulted with the SAB, had the draft list reviewed by a peer review panel, and 

accepted public comments (USEPA, 2009j) on the draft CCL 3, published on February 21, 2008 

(73 FR 9628; USEPA, 2008c). 

4.F. Results of CCL 3

The final CCL 3 was published on October 8, 2009 (74 FR 51850; USEPA, 2009k). It consists of 

104 chemicals or chemical groups (see Exhibit 4) and 12 microbiological contaminants (Exhibit 

5). These 116 contaminants serve as the starting point to the RD 3 process and the occurrenceand health-data-driven approach of the CCL 3 process provides a narrowed list of priority 

contaminants for a focused and more detailed data evaluation for RD 3. 

 

3 The CCL 3 HRL is a risk-derived concentration developed during the CCL 3 process. The CCL 3 HRLs could be 

developed using an RfD and/or cancer slope factor from a peer-reviewed health assessment or a published scientific 

study.
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Exhibit 4: CCL 3 Chemicals and Chemical Groups

Contaminant CASRN Contaminant CASRN

1,1,1,2-Tetrachloroethane 630206 Halon 1011 (bromochloromethane) 74975

1,1-Dichloroethane 75343 HCFC-22 75456

1,2,3-Trichloropropane 96184 Hexane 110543

1,3-Butadiene 106990 Hydrazine 302012

1,3-Dinitrobenzene 99650 Mestranol 72333

1,4-Dioxane 123911 Methamidophos 10265926

17alpha-estradiol 57910 Methanol 67561

1-Butanol 71363 Methyl bromide (Bromomethane) 74839

2-Methoxyethanol 109864 Methyl tert-butyl ether 1634044

2-Propen-1-ol 107186 Metolachlor 51218452

3-Hydroxycarbofuran 16655826 Metolachlor ESA 171118095

4,4'-Methylenedianiline 101779 Metolachlor OA 152019733

Acephate 30560191 Molinate 2212671

Acetaldehyde 75070 Molybdenum 7439987

Acetamide 60355 Nitrobenzene 98953

Acetochlor 60355 Nitroglycerin 55630

Acetochlor ethanesulfonic acid (ESA) 187022113 N-Methyl-2-pyrrolidone 872504

Acetochlor oxanilic acid (OA) 194992444 N-Nitrosodiethylamine (NDEA) 55185

Acrolein 107028 N-Nitrosodimethylamine (NDMA) 62759

Alachlor ESA 142363539 N-Nitrosodipropylamine (NDPA) 621647

Alachlor OA 171262172 N-Nitrosodiphenylamine (NDPhA) 86306

alpha-Hexachlorocyclohexane 319846 N-Nitrosodipyrrolidine (NPYR) 930552

Aniline 62533 Norethindrone (19-Norethisterone) 68224

Bensulide 741582 n-Propylbenzene 103651

Benzyl chloride 100447 o-Toluidine 95534
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Contaminant CASRN Contaminant CASRN

Butylated hydroxyanisole 25013165 Oxirane, methyl- 75569

Captan 133062 Oxydemeton-methyl 301122

Chlorate 14866683 Oxyfluorfen 42874033

Chloromethane (Methyl chloride) 74873 Perchlorate 14797730

Clethodim 110429624 Perfluorooctane sulfonic acid 

(PFOS)

1763231

Cobalt 7440484 Perfluorooctanoic acid (PFOA) 335671

Cumene hydroperoxide 80159 Permethrin 52645531

Cyanotoxins (microcystin, 

anatoxin-a, cylindrospermopsin)

64285069, 

143545908, 

101043372

Profenofos 41198087

Dicrotophos 141662 Quinoline 91225

Dimethipin 55290647 RDX 121824

Dimethoate 60515 sec-Butylbenzene 135988

Disulfoton 298044 Strontium 7440246

Diuron 330541 Tebuconazole 107534963

Equilenin 517099 Tebufenozide 112410238

Equilin 474862 Tellurium 13494809

Erythromycin 114078 Terbufos 13071799

Estradiol (17-beta estradiol) 50282 Terbufos Sulfone 56070167

Estriol 50271 Thiodicarb 59669260

Estrone 53167 Thiophanate-methyl 23564058

Ethinyl Estradiol (17-alpha ethynyl 

estradiol)

57636 Toluene diisocyanate 26471625

Ethoprop 13194484 Tribufos 78488

Ethylene glycol 107211 Triethylamine 121448

Ethylene oxide 75218 Triphenyltin hydroxide (TPTH) 76879
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Contaminant CASRN Contaminant CASRN

Ethylene thiourea 96457 Urethane 51796

Fenamiphos 22224926 Vanadium 7440622

Formaldehyde 50000 Vinclozolin 50471448

Germanium 7440564 Ziram 137304

Exhibit 5: CCL 3 Microbiological Contaminants

Contaminant Contaminant

Adenovirus Hepatitis A virus

Caliciviruses Legionella pneumophila

Campylobacter jejuni Mycobacterium avium

Enterovirus Naegleria fowleri

Escherichia coli (0157) Salmonella enterica 

Helicobacter pylori Shigella sonnei

5. UCMR and Its Relationship to the Regulatory Development 

Process The UCMR is EPA’s primary authority for collecting monitoring data on the occurrence of 

unregulated contaminants in drinking water. The UCMR is designed to collect nationally 

representative occurrence data for a list of contaminants that is developed in coordination with 

the CCL and Regulatory Determination processes. UCMR is limited by statute to 30 unregulated 

contaminants during any 5-year cycle (SDWA section 1445(a)(2)). Large and very large PWSs 

(those serving between 10,001 and 100,000 people, and those serving over 100,000 people, 

respectively) are required to handle the sampling and laboratory analysis and then report the data 

through EPA’s electronic reporting system. EPA coordinates and pays for the shipping and 

laboratory analysis for a random sample of small systems (those serving 10,000 or fewer people). 

EPA published the first list for the Unregulated Contaminant Monitoring Regulation cycle (i.e., 

UCMR 1) in the Federal Register on September 17, 1999 (64 FR 50556; USEPA, 1999a), with 

monitoring conducted during 2001-2003. UCMR 2 was published on January 4, 2007 (72 FR 

367; USEPA, 2007b), with monitoring conducted during 2008-2010. Monitoring under the third 

UCMR (UCMR 3) is scheduled to be conducted during 2013-2015. (The monitoring lists are 

available at: http://water.epa.gov/lawsregs/rulesregs/sdwa/ucmr/.) 

The UCMR program was designed using a three-tiered approach for monitoring contaminants 

based on the availability of analytical methods. Assessment Monitoring, applied to List 1 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

14

contaminants, typically relies on analytical methods that are in common use in drinking water 

laboratories. The Screening Survey, for List 2 contaminants, uses newly developed analytical 

methods that are not as commonly employed in drinking water laboratories. The Screening 

Survey involves a smaller number of PWSs due to expectations of reduced laboratory capacity. 

Pre-Screen Testing, for List 3 contaminants, is designed to address contaminants that require 

highly specialized analytical methods, or methods that are in the early stage of development. PreScreen Testing will typically involve only a limited number of systems determined to be most 

vulnerable to the targeted contaminants. 

EPA designed the Assessment Monitoring sampling frame to ensure that sample results would 

yield a high level of confidence and a low margin of error (see USEPA, 1999b and 2001, for 

UCMR design details). Assessment Monitoring is required for all large and very large PWSs 

(i.e., a census of these systems) and a statistically representative national sample of 800 small 

PWSs.

Under UCMR 1, the Screening Survey monitoring was conducted by a statistically selected 

sample of 300 large and small PWSs. While the statistical design provided national data, for 

relatively low occurrence contaminants there was concern that there was too much uncertainty in 

the results to extrapolate results for national estimates. 

For the UCMR 2 Screening Survey, the design was improved to include a census of all very 

large systems and a statistical sample of 320 large PWSs and 480 small PWSs (72 FR 367; 

USEPA 2007b). With this larger Screening Survey sample size, sufficient data were generated to 

provide a national estimate of population exposure. 

Under UCMR 1 and UCMR 2, for a variety of reasons that included method availability, 

laboratory capacity, and contaminant priorities, EPA elected not to specify Pre-Screen Testing

under List 3. 

The national design, statistical sampling frame, all new analytical methods, and the data analysis 

approach for the UCMR program have been peer reviewed (USEPA, 2001; USEPA, 2008d). 

Details about the sampling frame for small systems can be found in the original UCMR 1 Rule 

(64 FR 50556; USEPA, 1999a) and an associated support document (USEPA, 1999c). The data 

collected through the UCMR program are stored in NCOD to facilitate analysis and review of 

contaminant occurrence, inform the development of the CCL, help EPA to determine if 

monitored contaminants occur at frequencies and concentrations that would be of public health 

concern under the Regulatory Determination process, and support the development of 

regulations. For more information about the UCMR program, including monitoring lists and the 

results of UCMR 1 and UCMR 2 monitoring, see

http://water.epa.gov/lawsregs/rulesregs/sdwa/ucmr/. 

6. Drinking Water Strategy

In March 2010, EPA announced the agency’s new Drinking Water Strategy (DWS), which aims 

to find ways to strengthen public health protection from contaminants in drinking water. The 

new strategy is intended to streamline decision making and expand protection under existing 

laws and promote cost-effective new technologies to meet the needs of rural, urban and other 

water-stressed communities. The four principles underlying the DWS are: 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

15

(1) Address contaminants as groups rather than one at a time. 

(2) Foster development of new drinking water technologies to address health risks posed 

by a broad array of contaminants. 

(3) Use the authority of multiple statutes to help protect drinking water. 

(4) Partner with states to develop shared access to all PWS monitoring data. 

Only the first principle of the DWS (i.e., addressing contaminants as groups) has a direct bearing 

on regulatory determinations. The agency identified several factors to evaluate which 

contaminants might be addressed effectively as a group. These factors include whether the 

contaminants in the group: (a) have a similar health endpoint, (b) can be measured by the same 

analytical methods, (c) can be treated using the same technologies or treatment techniques, 

and/or (d) have been shown to occur individually and, if data are available, have been shown to 

occur together. EPA conducted extensive national outreach to solicit input from stakeholders on 

the DWS and how best to address groups of contaminants. Stakeholders generally agreed that 

these were the more important factors to consider in evaluating contaminants for a group 

regulation. 

The purpose of grouping contaminants by a similar health endpoint is to better protect public 

health from the potential risk of co-occurring contaminants with common additive or synergistic 

(i.e., greater than additive) adverse health effects. The affected target organ(s), specific 

endpoint(s), mechanism(s)/mode(s) of action, functional molecular group(s) and the potential for 

additive risk based on available data are considered in the selection of endpoints that are used to 

group contaminants for regulatory consideration. The ability to measure a group of contaminants 

by the same analytical method and to treat the contaminants using the same technology or 

treatment technique approach improves cost effectiveness and efficiency of regulating the group 

of contaminants because there is likely a marginal additional cost for monitoring and/or treating 

additional contaminants in the group, if they co-occur. 

The agency’s decisions regarding groups of contaminants are important to consider during the 

RD 3 process. In February 2011, the agency decided to address carcinogenic volatile organic 

compounds (CVOCs) as a group, which include several CVOCs on CCL 3 (e.g., 1,2,3-

trichloropropane, nitrobenzene). The agency decided to move ahead with a CVOC regulation so 

any regulatory determinations for CVOCs listed on CCL 3 will be handled with the CVOC 

regulatory effort. Information about the DWS, including a timeline of decisions and summaries 

of DWS-related listening sessions and stakeholder meetings, is on EPA’s website at: 

http://water.epa.gov/lawsregs/rulesregs/sdwa/dwstrategy/index.cfm. 

7. EPA’s Regulatory Determination Process 

The Regulatory Determination process is not a rulemaking but requires public notice (i.e., a 

Federal Register notice) and an opportunity for public comment, as specified in the 1996 SDWA 

Amendments. The Regulatory Determination process is distinct from the more detailed analyses 

needed to develop an NPDWR. Thus, a determination to regulate a contaminant is the beginning 

of the agency regulatory development process, not the end. 

In developing RD 3, EPA’s OGWDW established a formal workgroup to bring together experts 

from across the agency to share expertise, data, information, and perspectives on the 

contaminants of interest, and most importantly, to provide review of the quality of the data used 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

16

and the analyses conducted. The agency workgroup uses the best available peer-reviewed data 

and analyses to conduct its evaluation. The workgroup reviews the details of the technical 

approach (discussed in section 8 below) and works to develop recommendations for senior 

managers.

EPA has presented information on the Regulatory Determination process at two major public 

meetings: the Environmental Justice Considerations for Drinking Water Regulatory Efforts, on 

March 3, 2011, and the Regulatory Determination 3 Public Meeting, on June 16, 2011 (USEPA, 

2011b). The agency has also engaged stakeholders and experts throughout the RD 3 process, 

giving presentations to explain the process and discuss the available data under consideration to 

various drinking water organizations (e.g., the Association of State Drinking Water 

Administrators, the National Drinking Water Advisory Council, and the American Water Works 

Association). Any key insights or new data or information identified by stakeholders are also 

considered in the agency’s deliberative process.

At a Senate committee hearing on July 12, 2011, in response to a report by the General 

Accounting Office (GAO) (GAO, 2011), EPA Deputy Administrator Robert Perciasepe made a 

commitment to improve the transparency of the Regulatory Determination process. The result 

was a first iteration of this Protocol document, which explains the process that EPA used to make 

decisions under RD 3. The draft Protocol was reviewed by a panel of seven outside experts on 

October 26 and 27, 2011. The panel of experts made a number of helpful suggestions for 

clarification and transparency (USEPA 2011c). The present Protocol document has been revised 

in response to feedback from the expert panel. The questions posed to the panel of experts, their 

responses, and EPA’s acknowledgement of those responses and explanations of how it has acted 

on them, are contained in a companion comment-response document (USEPA, 2013).

The Administrator makes the preliminary and final Regulatory Determination decisions. The 

preliminary Regulatory Determination, positives and negatives, are announced in the Federal 

Register. EPA then accepts, reviews, and responds to comments received from the public and 

interested stakeholders during the comment-response period. After the review and response to 

public comments, EPA formulates and publishes the final Regulatory Determination in a 

subsequent Federal Register notice. For positive determinations (i.e., determinations to regulate 

a contaminant) this notice initiates the Regulation Development phase. Negative determinations 

(i.e., determinations not to regulate a contaminant) are considered a final agency action and this 

action is subject to judicial review. Negative determinations establish that contaminants are not 

occurring at levels and frequencies of public health concern in PWSs nationally,, and thus 

provide confidence in the safety of the nation’s drinking water. When the agency decides not to 

regulate a contaminant, EPA may develop and issue a Health Advisory to guide state initiatives 

when a contaminant may be a local, but not a national concern. Contaminants that receive 

negative determinations are evaluated in future CCL development processes to determine if new 

data are available on health effects and/or occurrence that warrant listing on future CCLs. 

The following sections outline the technical protocol and analyses conducted by EPA to inform 

the RD 3 effort.

8. The Regulatory Determination 3 Process

As noted in section 2B, EPA is required to evaluate the following three statutory criteria when 

making regulatory determinations for CCL contaminants: 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

17

(1) The contaminant may have an adverse effect on the health of persons. 

(2) The contaminant is known to occur or there is substantial likelihood that the 

contaminant will occur in PWSs with a frequency and at levels of public health 

concern. 

(3) In the sole judgment of the Administrator, regulation of such contaminant presents a 

meaningful opportunity for health risk reduction for persons served by PWSs. 

The agency is not able to make a regulatory determination for every contaminant on CCL 3 at 

this time. For some of the 116 CCL 3 contaminants, there is inadequate health and/or occurrence 

data to evaluate the contaminant against the three statutory criteria. As a result, EPA has 

developed a three-phased protocol to identify contaminants that have sufficient information to 

apply the three statutory criteria, with a priority of identifying contaminants known to occur or 

with substantial likelihood to occur with a frequency and at levels of public health concern. 

The three phases of the RD 3 Process are (1) the Data Availability Phase, (2) the Data 

Evaluation Phase, and (3) the Regulatory Determination Assessment Phase. The overall RD 3 

Process is displayed in Exhibit 6. The purpose of the first phase, the Data Availability Phase, is 

to determine if EPA “may have” sufficient data to characterize the potential health effects and 

known or likely occurrence in drinking water. Although contaminants must have sufficient data 

to evaluate the statutory criteria in Phase 3, EPA does not want to rule out any contaminants too 

early in the process therefore, if sufficient health and occurrence data “are likely” available, the 

contaminants are placed on a “short list” for the Data Evaluation Phase, the second phase of the 

regulatory determination process.

During this second phase, EPA further evaluates each contaminant on the short list to identify 

those which have sufficient data (or were expected to have sufficient data by Fall 2011) for EPA 

to assess the three statutory criteria. As part of the second phase, EPA specifically focuses its 

efforts to identify those contaminants or contaminant groups that are occurring or have 

substantial likelihood to occur at levels and frequencies of public health concern, based on the 

best available data. If EPA finds that sufficient data are not available or likely to be available to 

evaluate the three statutory criteria during the first and second phases, then the contaminant is 

not considered a candidate for making a regulatory determination and the contaminant is referred 

to the OGWDW Research Team to find potential avenues to fill data gaps4

. 

If sufficient data are (or will be) available for a contaminant to characterize the potential health 

effects and known or likely occurrence in drinking water, the contaminant is evaluated against 

the three statutory criteria in the Regulatory Determination Assessment Phase, which is the third 

 

4 OGWDW has a separate process for identifying and prioritizing research needs for the various drinking water 

projects. OGWDW coordinates with the Office of Research and Development (ORD) as well as other partners to 

find avenues to fill these data gaps (e.g., including a contaminant on the next round of UCMR, developing an 

analytical method, conducting a health assessment).
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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phase of the approach. The following sections discuss the steps involved in the three primary 

phases of the RD 3 Process. 

The results of these three phases, information from the expert panel review, and other relevant 

information (such as population exposed and information on sensitive populations and lifestages) 

will be presented to the Administrator to determine whether regulation of the contaminant 

presents a meaningful opportunity for public health protection and to make preliminary decisions 

for RD 3. These preliminary decisions will be published in the Federal Register for public 

comment. EPA will analyze and respond to the comments and issue the final Regulatory 

Determination 3 in the Federal Register. 

Exhibit 6: The Three Primary Phases of the Technical Assessment of the 

Regulatory Determination 3 Process.

Health Data Availability 

Assessment 

•Health Assessment 

available or in process

Occurrence Data 

Availability Assessment

•Nationally representative 

finished water data “or” 

•Other finished water data 

with detects greater than 

CCL3 derived HRL

Evaluation of Outcomes of Health & 

Occurrence Data Availability Assessments

Does it potentially have sufficient health and 

occurrence data available?

Phase 1: Data Availability

Phase 2: Data Evaluation

Phase 3:

Regulatory Determination Assessment

Step 1: Collect & 

Evaluate Health 

Information and Derive 

a Draft HRL

Step 2: Gather & 

Evaluate Additional 

Occurrence Data 

Sources Relative to the 

Draft HRL

Evaluate Statutory Criterion #2: 

Occurrence Assessment

Is the contaminant known to occur or is 

there substantial likelihood that the 

contaminant will occur above the HRL at a 

frequency and level of public health 

concern?

Evaluate Statutory Criterion #1: 

Health Assessment

May the contaminant have an 

adverse effect on the health of 

persons?

Evaluate Statutory Criterion #3: 

Meaningful Opportunity Assessment 

(Administrator’s Decision)

In the sole judgment of the Administrator, 

does regulation of such contaminant 

present a meaningful opportunity for 

health risk reduction for persons served by 

public water systems?

CCL 3 

Step 3: Identify 

Contaminants Occurring 

at Levels and Frequencies 

of Public Health Concern

Step 4: Identify 

Contaminants with No or 

Low Occurrence at Levels 

of Public Health Concern

8.A. Phase 1: Data Availability

Within the Data Availability Phase, two primary assessments are conducted in parallel: the 

Health Data Availability Assessment and the Occurrence Data Availability Assessment. 

Performing both assessments in parallel helps the agency identify those contaminants that may 

have sufficient health and occurrence data to be placed on the “short list” for further evaluation 

in the Data Evaluation Phase (Appendix D summarizes the data for Phase 1). 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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8.A.1. Health Data Availability Assessment 

In making a regulatory determination for a contaminant, SDWA requires that the agency assess 

whether the contaminant “may have an adverse effect on the health of persons.” The agency 

relies on externally peer-reviewed health assessments to determine if, how, and at what level a 

contaminant “may have an adverse effect on the health of persons.” 

As part of the CCL 3 process, health effects data sources were compiled for each of the 116 

CCL 3 contaminants from one of the following EPA offices or other organizations: the agency's 

Integrated Risk Information System (IRIS), the agency’s Office of Water (OW), the agency's 

Office of Pesticide Programs (OPP), the National Academy of Sciences (NAS), the Agency for 

Toxic Substances and Disease Registry (ATSDR), World Health Organization (WHO)

[including Joint FAO/WHO Expert Committee on Food Additives (JECFA), Joint FAO/WHO 

Meeting on Pesticide Residues (JMPR), etc.], the California EPA’s Office of Environmental 

Health Hazard Assessment (OEHHA), Registry of Toxic Effects of Chemical Substances 

(RTECS), and/or supplemental data from a single study (USEPA, 2009c). The health data 

compiled in CCL 3 is useful to establish that the contaminant has an adverse health effect but 

since CCL 3 is a screening level process the agency is less stringent on the type of health data 

sources used in CCL 3 compared to RD 3. 

In the case of RD 3, the Health Data Availability Assessment is used to identify those among the 

116 CCL 3 contaminants that have an externally peer-reviewed health assessment either 

completed or in process from EPA and/or one of the designated non-EPA sources discussed 

below. 

8.A.1.a. Is a Health Assessment Available or In Process?

For contaminants in drinking water, an externally peer-reviewed health assessment prepared by 

EPA (i.e., either IRIS, OW, or OPP) generally addresses exposure, toxicokinetics, hazard 

identification, and dose-response for oral routes of exposure. For RD 3, certain non-EPA 

externally peer-reviewed health assessments (namely, from NAS, ATSDR, and WHO) were also 

considered for regulatory determinations if the health assessment used comparable methods, 

standards, and guidelines to an EPA health assessment. These non-EPA health assessments were 

recognized by the agency because of their standardized methods for characterizing health effects 

data, relevancy to drinking water exposures, and comparability to EPA methods. The designated 

health assessment data sources for RD 3 are explained further in Appendix B. 

A primary health effects data source was selected for each CCL 3 contaminant. A literature 

search was conducted to identify any CCL3 contaminant with a completed health assessment 

from a designated data source for RD 3 (IRIS, OW, OPP, NAS, ATSDR and WHO) since the 

publication of the Final CCL 3 Information Sheets in August 2009 (USEPA, 2009l). For those 

contaminants with no new health assessment, the health effects data source compiled during 

CCL 3 was used as the primary health effects data source for RD 3. In general, an externally 

peer-reviewed EPA health assessment was preferred over a designated non-EPA health 

assessment if both were available. 

If a suitable health assessment is available or in process from a designated data source, the 

contaminant proceeds to the Evaluation of Outcomes of the Health and Occurrence Data 

Availability Assessments (see section 8.A.2). For these contaminants, the potential health effects, 

the reference dose (RfD) or other non-cancer-health value, and/or cancer slope factor (CSF) from 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

20

each health assessment are compiled, as well as the date of the assessment. This information will 

be used if the contaminant moves to Phase 2. 

If a health assessment is not available or in process from one of the designated sources stated 

above, then the contaminant is not considered for this round of Regulatory Determination and the

contaminant is referred to the OGWDW Research Team to find potential avenues to fill health 

effects data gaps and/or develop a health assessment.

8.A.2. Occurrence Data Availability Assessment

The Occurrence Data Availability Assessment is used to identify contaminants that may have 

sufficient data and information to characterize known or likely occurrence in public water 

systems to address the second statutory criterion. EPA uses data from many sources to evaluate 

occurrence for contaminants considered for regulatory determinations (see Appendix C). When 

making a regulatory determination for a contaminant, the agency prefers to have nationally 

representative finished drinking water occurrence data, but non-national data may also be used

for RD 3. The steps for this assessment involve answering the following two questions 

(discussed in sections 8.A.2.a and 8.A.2.b): 

• Are nationally representative finished water occurrence data available?

• Are non-national finished water occurrence data available that show occurrence at levels 

of public health concern? 

In addition, the agency also identifies supplemental sources of information (e.g., ambient/source 

water occurrence, production/use, release, etc). 

8.A.2.a. Are Nationally Representative Finished Water Occurrence Data Available?

Nationally representative data are the primary source of the drinking water occurrence data used 

to evaluate whether or not a contaminant is “known to occur” in PWSs with a frequency and at 

levels of public health concern. If a contaminant has data available from at least one of the 

following data sources, which are administered or overseen by EPA, then it has nationally 

representative drinking water occurrence data: 

• Second Unregulated Contaminant Monitoring Regulation (UCMR2). 

• First Unregulated Contaminant Monitoring Regulation (UCMR1). 

• Unregulated Contaminant Monitoring (UCM) program. 

• National Inorganics and Radionuclides Survey (NIRS). 

These data sources are explained further in Appendix C. If nationally representative occurrence 

data are available, a contaminant proceeds to the Evaluation of Outcomes of Health and 

Occurrence Data Availability Assessments step. If a contaminant does not have national data, 

EPA evaluates whether pertinent non-national data are available in the next step (8.A.2.b). 

8.A.2.b. Are Non-National Finished Water Occurrence Data Available that Show 

Occurrence at Levels of Public Health Concern?

If nationally representative occurrence data are not available, EPA identifies and evaluates nonnational finished water data for consideration in the regulatory determination process. These data 

include: 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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• Finished water assessments by federal agencies (e.g., EPA and the United States 

Geological Survey (USGS)). These may be assessments that are geographically 

distributed across the nation but not intended to be statistically representative of the 

nation. 

• State-level finished water monitoring data. 

• Research performed by institutions and universities (e.g., scientific literature). 

Non-national data may be “sufficient” to evaluate the statutory criteria and support regulatory 

determination in some cases. It is difficult to determine that a contaminant is not occurring or not 

likely to occur based on non-national data because the data are limited in scope and the 

contaminant could be occurring in other parts of the country that have not been monitored. 

However, a compilation of non-national data sources can support a determination that there is a 

“substantial likelihood that the contaminant will occur in PWSs with a frequency and at levels of 

public health concern.” Therefore, a contaminant with non-national occurrence data is evaluated 

further to determine whether the contaminant is occurring at a level of public health concern. The 

purpose of this step is to not rule out any contaminants too early in the process that may have 

occurrence at levels of public health concern in finished water. 

In this phase, the agency assesses whether non-national finished water occurrence data show at 

least one detection in finished water at levels > 1⁄2 CCL 3 HRL5

 for the critical endpoint (see 

Appendix A for a description of how an HRL is derived). If a contaminant has non-national 

finished water occurrence data showing at least one detection > 1⁄2 CCL 3 HRL, the contaminant 

proceeds to the Evaluation of Outcomes of Health and Occurrence Data Availability Assessment

(section 8.A.3). If no national or non-national data are available, the contaminant is not 

considered for this round of Regulatory Determination and the contaminant is referred to the 

OGWDW Research Team to find potential avenues to fill occurrence data gaps. 

8.A.3. Evaluation of Outcomes of Health and Occurrence Data Availability 

Assessments 

After conducting the Health and Occurrence Data Availability Assessments, the agency 

identifies those contaminants that meet the following data availability criteria:

• An externally peer-reviewed health assessment from a designated source is available or in 

process. 

• A widely available analytical method for monitoring6 exists. 

 

5 For RD 3, the agency uses the CCL 3 HRL in this phase unless a completed peer-reviewed health assessment from 

a designated data source has been identified since the CCL 3 information sheets were published in 2009 (USEPA, 

2009l). Once the agency further evaluates the information in the most recent peer-reviewed health assessments 

identified in this phase, the agency may derive a draft HRL in phase 2, which may be different from the CCL 3 

HRL. The CCL 3 HRLs for the 116 contaminants can be found at: 

http://water.epa.gov/scitech/drinkingwater/dws/ccl/upload/Final-CCL-3-Contaminant-Information-Sheets.pdf. Note 

that HRLs are not final determinations about the level of a contaminant in drinking water that is necessary to protect 

any particular population (i.e., MCLG). 6 A widely available analytical method is a method employing technology that is commonly employed and in use at 

numerous drinking water laboratories. The CCL 3 microbes did not have a widely available analytical method for 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

22

• Either (a) national finished water occurrence data are available, or (b) non-national 

finished water occurrence data showing occurrence at levels > 1⁄2 CCL 3 HRL are 

available7. 

• If a contaminant meets all of these criteria, it is placed on the “short list” and proceeds to 

Phase 2, the Data Evaluation Phase. If any of these criteria are not met, no determination 

is made for these contaminants. In these cases, the agency identifies the information gaps 

that prevent these contaminants from moving forward. The contaminants may be 

considered for the next CCL. In some cases, if a contaminant does not meet the criteria 

for moving forward, it may proceed to Phase 2 for further evaluation as a member of a 

group of contaminants that meets all criteria. Contaminant groups are defined by the 

factors discussed in the DWS (section 6).

8.A.4. Outcome of Phase 1 for Regulatory Determination 3

After evaluating the 116 CCL 3 contaminants in Phase 1, the agency identified 35 of them for 

placement on the “short list” for continuation to Phase 2. Alongside the 35 short-listed CCL 3 

contaminants, EPA also identified two non-CCL 3 nitrosamines, n-nitroso-di-n-butylamine 

(NDBA) and n-nitrosomethylethylamine (NMEA) for inclusion in Phase 2. Although these two 

contaminants were not listed on CCL 3, they met the criteria described above for inclusion on the 

short list and the agency thought it advisable to evaluate them alongside other nitrosamines. The 

contaminants selected for evaluation in Phase 2 are listed in Exhibit 7. 

Exhibit 7: Contaminants to be Evaluated in Phase 2 of the Regulatory 

Determination Process

1,1,1,2-Tetrachloroethane1,3 Metolachlor oxanilic acid (OA)1,3

1,2,3-Trichloropropane1,3 Molinate1

1,3-Dinitrobenzene1 Molybdenum1

1,4-Dioxane2 Nitrobenzene1,3

Acephate2 N-Nitroso-di-n-butylamine (NDBA)1,3,5

Acetochlor1,3 N-Nitrosodiethylamine (NDEA)1,3

Acetochlor ethanesulfonic acid (ESA)1,3 N-Nitrosodimethylamine (NDMA)1,3

Acetochlor oxanilic acid (OA)1,3 N-Nitroso-di-n-propylamine (NDPA)1,3

 

monitoring and were not placed on the “short list” for Regulatory Determination 3 for this reason. 7 One exception to this criterion applies to contaminants monitored in the UCMR 1 Screening Survey (SS). As noted 

in section 5, the UCMR 1 SS is a statistically defined, national sample of PWSs. Because this survey only includes 

300 systems, the agency identified and compiled additional supplemental data to compliment the UCMR 1 SS data 

for contaminants that proceed to the Phase 2 evaluation for further evaluation on this basis.
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Alachlor ethanesulfonic acid (ESA)1,3 N-Nitrosodiphenylamine (NDPhA)3

Alachlor oxanilic acid (OA)1,3 N-Nitrosomethylethylamine (NMEA)1,3,5

Chlorate2 N-Nitrosopyrrolidine (NPYR)1,3

Cobalt1 Perfluorooctane sulfonic acid (PFOS)2

Dimethoate1 Perfluorooctanoic acid (PFOA)2

Disulfoton4 RDX1

Diuron4 Strontium1

Methyl bromide (Bromomethane)1 Terbufos2,3

Methyl tert-butyl ether1 Terbufos sulfone1,3

Metolachlor1,3 Vanadium1

Metolachlor ethanesulfonic acid (ESA)1,3

1 Has nationally representative finished water data and available or in process health 

assessment

2 Has other finished water data (occurrence at levels > 1⁄2 CCL 3 HRL) and an available 

or in-process health assessment

3 Component of a contaminant group and will be further evaluated in Phase 2

4 One exception to the criterion of having available nationally representative drinking 

water data applies to contaminants monitored in the UCMR 1 Screening Survey (SS). 

As noted in section 5, the UCMR 1 SS is a statistically defined, national sample of 300 

PWSs. Because this survey only includes 300 systems, the agency identified and 

compiled additional supplemental data to compliment the UCMR 1 SS data for these 

contaminants that proceed to Phase 2 for further evaluation. 

5

A non-CCL 3 contaminant that is part of the nitrosamine group. 

The remaining 81 CCL 3 contaminants did not advance and were not considered in RD 3 

because the agency lacked the following data/information sources that are necessary to evaluate 

the three SDWA criteria: (a) an IRIS, OPP, OW, NAS, ATSDR or WHO health assessment that 

can be used to fully characterize the critical health effect and derive a draft HRL and/or (b) 

national occurrence data to characterize occurrence in public water systems or non-national data 

showing at least one detection greater than 1⁄2 the CCL 3 HRL. Appendix D provides the full set 

of information used to arrive at this outcome. 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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8.B. Phase 2: Data Evaluation

The Regulatory Determination “short list” is a list of contaminants that have been identified in 

Phase 1 as having sufficient data to warrant expanded assessment. SDWA requires the agency to 

make determinations for at least five (5) of the contaminants on the CCL and to select for 

regulatory determination “contaminants that present the greatest public health concern,” 

including consideration of sensitive subpopulations (SDWA § 1412(b)(1)(B), (C)). The purpose 

of Phase 2 is to: 

(1) Evaluate the health and occurrence data for the “short list” contaminants more 

thoroughly. 

(2) Identify contaminants occurring with levels and frequencies of public health concern. 

(3) Identify contaminants that have no or low potential for public health concern. 

(4) Identify contaminants that have potential information or data gaps that may prevent 

them from moving to the next phase (Phase 3). 

The steps involved in the Data Evaluation Phase are described in the sections that follow. Note 

that the agency does not have a threshold for health or occurrence values that trigger whether or 

not a contaminant is of public health concern. There are a number of factors to consider in 

evaluating potential public health concern, some of which include the health effect(s), the 

potency of the contaminant, the concentrations at which the contaminant is occurring, how 

frequently the contaminant is found, the geographic distribution (national, regional, or local 

occurrence), other possible sources of exposure, potential impacts on sensitive populations or 

lifestages, etc. Given the many possible combinations of factors and the constantly evolving 

science, EPA believes it is best to analyze each contaminant and present the best available 

information that helps identify whether or not the occurrence of a contaminant is of public health 

concern (Appendix E summarizes the key data for Phase 2 evaluations). 

8.B.1. Phase 2--Step1: Collect and Evaluate Health Information and Derive a Draft HRL

In Phase 1, the agency identified available health assessments or health assessments that are in 

process from the designated sources. Using the health effects assessments compiled in Phase 1

(listed in Appendix D), a draft HRL is derived. In some cases, the health assessment or the HRL 

derived from the health assessment may need updating based on the following reasons: 

• Peer-reviewed publications have been identified through the literature after health 

assessment publication8

. 

• The health assessment was published prior to 1996 and does not follow current agency 

guidelines and standards.9

 

8

 The OW performs a literature search for studies published after the available health assessment (i.e., Phase 1) is

completed to determine if new information suggests a different outcome. The agency collects and evaluates any 

peer-reviewed publications identified through the literature search for their impact on the RfD and/or cancer 

assessment. In cases where the recent data indicates that a change to the existing RfD or cancer assessment is 

needed, an OW assessment may be prepared and independently peer-reviewed. 9 Contaminants that have quantitative cancer assessments conducted under the 1986 Guidelines for Carcinogen Risk 

Assessment (USEPA, 1986) would need to be updated using the more recent 2005 Guidelines for Carcinogen Risk 

Assessment (USEPA, 2005b), the Supplemental Guidance for Assessing Susceptibility from Early-life Exposures to 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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• The health assessment is from a non-EPA source (e.g., NAS, ATSDR and WHO) and 

may need to be updated to follow current agency guidelines and standards (see Appendix 

B). 

In other cases, the CCL 3 HRL is used as the draft HRL if the health assessment is from a 

designated source and does not need to be updated. 

EPA made Fall 2011 the cutoff point for completed health assessments for preliminary 

determinations for RD 3. If it was judged that an assessment could not be updated or completed 

by Fall 2011, the contaminant did not proceed to Phase 3. 

8.B.1.a. Derivation of the Draft HRL and Consideration of Sensitive Populations

HRLs are not final determinations about the level of a contaminant in drinking water that must 

not be exceeded to protect any particular population; they are derived prior to development of a 

complete exposure assessment. HRLs are risk-derived concentrations against which to evaluate 

the occurrence data to determine if contaminants occur at levels of potential public health 

concern. All adverse health effects (e.g., cancer, thyroid effects, reduced body weight etc.) are 

considered to be of equal importance when evaluating the occurrence above the draft HRL. The 

differences in health risk between the adverse health effects for each contaminant are reflected in 

the RfD or CSF and the HRL derivation methods. There are two general approaches to the 

derivation of an HRL. One approach is used for chemicals that cause cancer and exhibit a linear 

response to dose and the other applies to non-carcinogens and carcinogens evaluated using a 

non-linear approach. The derivation of HRLs for carcinogens and non-carcinogens are described 

in Appendix A. 

In evaluating contaminants for regulatory determination, Section 1412 (b)(1)(A)(i) of SDWA 

requires the agency to consider “among other factors of public health concern, the effect of such 

contaminants upon subgroups that comprise a meaningful portion of the general population (such 

as infants, children, pregnant women, the elderly, 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 compared to the general population.” If appropriate 

and if available, the agency quantitatively takes into account data from sensitive populations and 

lifestages when deriving HRLs for regulatory determinations in the following manner: 

(a.) For non-carcinogens, an HRL can be developed for a sensitive population if high quality 

data are available to associate exposure with the critical health endpoint in a specific group or 

during a specific period of sensitivity. Age-specific drinking water intake body weight ratio 

values from the Exposure Factors Handbook (USEPA, 2011d) can be used to reflect the 

period of exposure more accurately. The agency can also apply specific uncertainty factors 

(UFs) when deriving the RfD if toxicological data are lacking for a sensitive population. UFs 

are usually applied as integers of one, three, or ten. Two common UFs that can be applied to 

account for sensitive populations are: (1) variation in sensitivity among the members of the 

 

Carcinogens (USEPA, 2005c), and the Exposure Factors Handbook (USEPA, 2011d). These guidelines include new 

considerations for contaminants with a mutagenic mode of action and potential risks due to early childhood 

exposure (USEPA 2005b; 2005c). 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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human population (i.e., intraspecies variability) and (2) uncertainty associated with an 

incomplete database (Appendix A). 

(b.) For HRLs developed for carcinogens with a mutagenic mode of action (MOA), the 2005 

Cancer Guidelines require consideration related to increased risks due to early-life exposure. 

When chemical-specific data to quantify the increased risk are lacking, Age Dependent 

Adjustment Factors (ADAFs) are applied, with a 10-fold adjustment for early life exposures, 

a 3-fold adjustment for childhood/adolescent exposures, and no additional adjustment for 

exposures later in life. Age-specific drinking water intake body weight ratio values are also 

applied from the Exposure Factors Handbook (USEPA, 2011d). In cases where the data on 

the MOA are lacking, a default low-dose linear extrapolation approach without ADAFs is 

used (Appendix A). 

In addition to quantitatively addressing sensitive populations when deriving the HRL, the agency 

also performs a literature review of scientific data covering developmental and reproductive 

endpoints (e.g., fertility, embryo survival, developmental delays, birth defects, and endocrine 

effects) which is compiled and evaluated qualitatively. The sensitive populations identified for 

short list contaminants are listed in Appendix E and Appendix F. 

When the draft HRL has been established, it is used in the following steps to evaluate the 

occurrence information and identify contaminants of public health concern. 

8.B.2. Phase 2--Step 2: Gather and Evaluate Additional Occurrence Data Sources Relative 

to the Draft HRL

In this step, the agency compiles, analyzes, and evaluates the national or non-national occurrence 

information identified in Phase 1 against the draft HRL (developed as described in section 8.B.1) 

as well as the minimum reporting level (MRL). The agency also compiles additional occurrence 

data and information on monitoring in ambient or source water (relative to the draft HRL and 

also the detections at the minimum reporting limit), production, use, release to the environment, 

and persistence and mobility. This information will be used in steps 3 and 4 of Phase 2 (see 8.B.3 

and 8.B.4), and also in Phase 3 if a contaminant proceeds to that phase. 

8.B.3. Phase 2--Step 3: Identify Contaminants Occurring at Levels and Frequencies of 

Public Health Concern

In this step, the agency identifies contaminants occurring at levels and frequencies of public 

health concern that will proceed to Phase 3, the Regulatory Determination Assessment Phase. 

The candidate contaminants identified in this step are the highest priority for RD 3 and for the 

completion of their health assessments, if necessary. The agency considers the following 

information when identifying these contaminants:

• How many samples (# and %) have detections > draft HRL and 1⁄2 draft HRL in the 

national and non-national finished water occurrence data?

• How many systems (# and %) have detections > draft HRL and 1⁄2 draft HRL in the 

national and non-national finished water occurrence data?
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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• Is the contaminant associated with a contaminant group that is of public health concern 

and is being considered as part of the DWS (see factors considered for grouping under 

the DWS - section 6)?10

• Are there uncertainties or limitations with the data and/or analyses, such as the age of the 

dataset, limitation of the detection limit (i.e., MRL > draft HRL) and/or 

representativeness of the data (e.g., limited scope to a specific region) that may cause 

underestimation of occurrence in finished water at levels and frequency of public health 

concern?

8.B.4. Phase 2--Step 4: Identify Contaminants That Have No or Low Occurrence at Levels 

of Public Health Concern

After identifying contaminants in step 3 (8.B.3) that are occurring at levels and frequencies of 

public health concern, the agency evaluates the remaining contaminants on the short list to 

identify contaminants with no to low occurrence at levels of health concern that should proceed 

to Phase 3 for a potential negative determination. Because the primary goal of RD 3 is to focus 

on contaminants of public health concern and since the agency will likely make a decision “not 

to regulate” contaminants that have no to low occurrence at levels of public health concern, these 

contaminants are a lower priority for this effort. The agency considers the following information 

in selecting contaminants of no or low potential for public health concern to proceed to Phase 3: 

• Does the contaminant have national finished water data showing no or low # or % of 

detections > draft HRL11? 

• If a contaminant has other finished water data in addition to nationally representative 

finished water data, does it support no or low potential for occurrence in drinking water? 

• Does additional occurrence information of known quality support low or no occurrence 

or potential for occurrence in drinking water? For example, is the occurrence in 

ambient/source water at levels below the draft HRL? Are releases to the environment or 

use/production decreasing over time? 

• There are no critical information/data gaps after evaluating the available health or 

occurrence data. 

• The contaminant is not included or evaluated with a group of contaminants based on the 

factors defined by the DWS (e.g., cVOCs - see section 6). 

If a contaminant meets all or most of these factors and appears to have sufficient data to evaluate 

the statutory criteria for regulatory determination, the contaminant moves onto Phase 3. These 

contaminants have sufficient data for EPA to make a determination that they do not occur at 

levels and frequencies of public health concern in drinking water, including national finished 

water data. If any of these contaminants receive negative determinations as part of RD 3, they 

will be considered for the next round of the CCL if new data becomes available.

 

10 Carcinogenic Volatile Organic Compounds (including 1,2,3-trichloropropane) are being evaluated in a separate 

regulatory effort.

11 Note that non-national data tend to be limited in scope and EPA does not use them to support a determination that 

the contaminant is not or is not substantially likely to “occur in PWSs with a frequency and at levels of public health 

concern” and therefore a decision “not to regulate” (i.e., negative determination). 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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The remaining contaminants do not proceed to Phase 3 and are therefore not considered for this 

round of regulatory determination (i.e., “no determination” is made). They will be considered for 

the next CCL. The agency identifies the health, occurrence, and/or other data gaps that prevent 

these contaminants from moving forward and evaluates potential avenues to fill those gaps (e.g., 

inclusion in the next round of UCMR, developing an analytical method, conducting a health 

assessment). 

8.B.5. Outcome of Phase 2 for Regulatory Determination 3

After evaluating the 35 “short list” CCL 3 contaminants identified in 8.A.4 according to the steps 

in Phase 2, the agency determined that 10 CCL 3 contaminants (plus two non CCL 3 

contaminants, NDBA and NMEA)

12 should proceed to Phase 3, the Regulatory Determination 

Assessment Phase. The 10 CCL 3 contaminants, divided into two bins, are: 

“Occurring or Likely to Occur at Levels and Frequencies of Public Health Concern” 

• Chlorate. 

• N-Nitrosodimethylamine (NDMA). 

• N-Nitroso-di-n-propylamine (NDPA). 

• N-Nitrosodiethylamine (NDEA). 

• N-Nitrosopyrrolidine (NPYR). 

• Strontium. 

“Not Occurring or Likely to Occur at Levels and Frequencies of Public Health Concern”: 

• Dimethoate. 

• 1,3-Dinitrobenzene. 

• Terbufos. 

• Terbufos sulfone. 

As part of the DWS, 1,2,3-trichloropropane, 1,1,1,2-tetrachloroethane and nitrobenzene13 are 

being evaluated and considered for the Carcinogenic Volatile Organic Compounds (CVOCs) 

group rule under development. Because they are being addressed in a separate process, they were 

excluded from Phase 3 under RD 3.The remaining 22 contaminants did not proceed to Phase 3 

because of one or more of the following critical health, occurrence and/or other data gaps:Health:

• An updated health assessment is needed but was not completed by Fall 2011. 

• A health assessment was in process and was not completed by Fall 2011. 

 

12 NDBA and NMEA are being considered alongside four CCL 3 nitrosamines (NDEA, NDMA, NDPA, and NPYR) 

as part of the group approach under DWS. These compounds meet several factors for potential grouping, including 

similar health endpoints, a common analytical method, susceptibility to the same treatment technologies or 

approaches, and documented co-occurrence. A seventh nitrosamine, NDPhA, had no EPA analytical method suitable 

for monitoring so it did not move forward to Phase 3 and is not being evaluated alongside the others under the group 

approach.

13 Some of these contaminants were referred to the CVOC group after EPA’s February 2011 announcement about 

the CVOC group (see http://water.epa.gov/lawsregs/rulesregs/sdwa/dwstrategy/index.cfm).
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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• Critical health effects gap (e.g., lack of data to support quantification for the oral route of 

exposure). 

Occurrence:

• Lacks national occurrence data. 

• Insufficient non-national occurrence data to demonstrate occurrence at levels and 

frequencies of public health concern (although it may have some levels of public health 

concern). 

• Individual contaminant that is part of a group but lacks a widely available analytical 

method for occurrence monitoring. 

• Critical occurrence data gap (e.g., inconsistent results and/or trends in occurrence data, 

significant uncertainty in occurrence analyses and/or data). 

8.C. Phase 3: Regulatory Determination Assessment 

• The Regulatory Determination Assessment Phase involves a complete evaluation of the 

statutory criteria for each contaminant or group of contaminants that have passed Phase 2 

and have sufficient information and data for making a regulatory determination. In this 

phase, the agency evaluates the following statutory criteria:Statutory Criterion #1: 

Might the contaminant have an adverse effect on the health of persons? 

• Statutory Criterion #2: Is the contaminant known to occur or is there a substantial 

likelihood that the contaminant will occur in PWSs with a frequency and at levels of 

public health concern? 

• Statutory Criterion #3: In the sole judgment of the Administrator, does regulation of 

such contaminant present a meaningful opportunity for health risk reduction for persons 

served by PWSs? 

The following steps discuss the factors that the agency considers in evaluating each of these 

statutory criteria. Note that the third statutory criterion is the Administrator’s decision. 

8.C.1. Evaluation of Statutory Criterion #1 (Adverse Health Effect)

The contaminants for RD 3 are generally expected to meet statutory criterion #1 because their 

adverse health effects were analyzed as part of the determination to list them on the CCL 3. 

During the CCL 3 process, the critical health effect was identified and the level of potency (a 

value that indicates the lowest dose of a chemical that causes the adverse health effect) and 

severity (the relative impact of the adverse health effect) of the health effect was evaluated 

(USEPA, 2009g); therefore the answer to the health statutory criterion that the contaminant “may 

have an adverse effect on the health of persons” is typically “yes.” More importantly, the 

evaluation of the first statutory criterion includes the completion of any health assessment that 

needed to be updated and externally peer-reviewed, and the derivation of the final peer-reviewed 

HRL (Appendix A) to define the dose at which adverse health effects are likely to occur. The 

derivation of the final HRL takes into account many of the key elements that are considered 

when evaluating the first criterion, which include the mode of action, the critical health effect(s), 

the dose-response for critical health effect(s), impacts on sensitive population(s) or lifestages, the 

RfD, and/or the CSF. As noted earlier, the HRL is not a final determination about the level of a 

contaminant in drinking water that must not be exceeded to protect any particular population 

(i.e., a maximum contaminant level goal). The HRL is derived prior to development of a 

complete exposure assessment. The HRL is a risk-derived concentration against which EPA 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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compares the concentrations of a contaminant found in public water systems to determine if the 

levels are of potential public health concern. 

8.C.2. Evaluation of Statutory Criterion #2 (Known or Likely Occurrence in PWSs with a 

Frequency and Level of Concern)

The occurrence data for each contaminant are compared to the final peer-reviewed HRL to 

determine if the contaminant occurs at a frequency and levels of public health concern. The 

following factors, further refined from the previous phase and categorized by importance (i.e., 

primary versus additional), are considered when identifying contaminants or contaminant groups 

that are of public health concern: 

8.C.2.a. Factors of Primary Consideration

• How many samples (# and %) have detections > final HRL in the national and nonnational finished water occurrence data?

• How many systems (# and %) have detections > final HRL in the national and nonnational finished water occurrence data?

• Is the contaminant associated with a contaminant group that is of public health concern 

and is being considered as part of the DWS (see factors considered for grouping under 

the DWS - section 6)? 

• Is the geographic distribution of contaminant occurrence national, regional, or localized?

• In addition to the number of systems, what type of systems does the contaminant occur 

in? Does the contaminant occur in large or small systems? Does the contaminant occur in 

surface or ground water systems? 

• Are there significant uncertainties or limitations with the data and/or analyses, such as 

the age of the dataset, limitation of the analytical method (e.g., MRL > final HRL), or 

representativeness of the data (e.g., limited in scope to a specific region)?

8.C.2.b. Additional Factors of Consideration 

• How many samples (# and %) have detections > 1⁄2 final HRL14 in the national and nonnational finished water occurrence data?

• How many systems (# and %) have detections > 1⁄2 final HRL in the national and nonnational finished water occurrence data?

• How many samples (# and %) have detections > final HRL and 1⁄2 final HRL in the 

ambient/source water occurrence data?

• How many sites (# and %) have detections > final HRL and 1⁄2 final HRL in the 

ambient/source water occurrence data?

• Are production and use trends for the contaminant increasing or decreasing? 

• How many pounds are discharged annually to surface water and/or released to the 

environment? 

• Do the environmental fate and transport parameters indicate that the contaminant would 

persist and/or be mobile in water? 

 

14 Occurrence is also evaluated relative to 1⁄2 of the HRL as a more conservative estimate of the occurrence at or 

approaching levels of public health concern.
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• Is the contaminant introduced by water treatment processes (e.g., disinfection 

byproducts)? 

• Are there uncertainties or limitations with the data and/or analyses for these additional 

factors that should be considered? 

If a contaminant is known to occur or substantially likely to occur at a frequency and level of 

health concern in public water systems based on the factors listed above, then the agency 

answers “yes” to the second statutory criterion. Otherwise, the agency answers “no” to the 

second statutory criterion. 

An important consideration in this evaluation is the detection limit (DL) and/or the reporting 

level (RL), sometimes designated as a minimum reporting level (MRL), used in monitoring for 

drinking water contaminants. The DL is the minimum concentration of a contaminant in water 

that can be reliably differentiated from the signal arising from a blank (i.e., the contaminant can 

be determined to be present), although it typically is not possible to achieve reliable quantitation 

at the DL. The RL is a concentration at or above which results are reported by a laboratory or a 

study author, and is generally a concentration at which reliable quantitation is possible. The 

MRL is the minimum concentration that is required to be reported in a study. The MRL is 

usually set at a value that takes into account typical laboratory capabilities to detect and quantify 

a compound and the cost of increasingly precise measurements. If the HRL is equal to or greater 

than the MRL, any occurrence above the HRL can be reliably quantified and reported with 

confidence. If the HRL is less than the MRL, any reported concentration (commonly called a 

“detection”) is greater than the HRL. Occurrence at concentrations that exceed the HRL but are

below the MRL will go unreported. A variety of approaches can be used to estimate the 

occurrence below the MRL, including fitting an appropriate distribution model. 

In the case of carcinogens, if there is little to no occurrence at an MRL that is greater than an

HRL and the MRL is within the 10-4 to 10-6 risk range, the agency can make a decision for the 

second statutory criterion as long as this limitation is noted and other information/data are 

considered (e.g., contaminant manufacturing trends, trends in the amount released to the 

environment, occurrence in ambient water, etc.). 

8.C.3. Evaluation of Statutory Criterion #3 (Meaningful Opportunity)

In the end, it is up to the sole judgment of the Administrator to decide whether a drinking water 

regulation for a contaminant presents a meaningful opportunity for health risk reduction for 

persons served by public water systems. An explanation of the factors the Administrator 

considers is presented in Appendix G. 

8.C.4. Making a Regulatory Determination Decision

As noted earlier, the agency does not make a determination for those contaminants that do not 

have sufficient information to answer the three SDWA statutory criteria (Exhibit 8). 

If a contaminant has sufficient information and the agency answers “yes” to all three statutory 

criteria for a particular contaminant (Exhibit 8), then the agency makes a “positive” 
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determination that regulation is necessary. When the positive determination is finalized, the 

agency has 24 months to publish a proposed MCLG and NPDWR and 18 months to publish a 

final MCLG and promulgate a final NPDWR (SDWA section 1412(b)(1)(E))15. As noted 

previously, this regulatory determination process is distinct from the more detailed analyses 

needed to develop an NPDWR. Thus, a decision to regulate is the beginning of the agency's 

regulatory development process, not the end. 

If a contaminant has sufficient information and the agency answers “no” to any of the three 

statutory criteria, based on the available data, then the agency considers making a “negative” 

determination that an NPDWR is not necessary for that contaminant at that time. The agency 

may decide to develop a Health Advisory (HA), which provides non-regulatory concentration 

values for drinking water contaminants at which adverse health effects are not anticipated to 

occur over specific exposure durations (one-day, ten-days, several years, and a lifetime). HAs 

serve as informal technical guidance to assist federal, state, and local officials, and managers of 

public or community water systems (CWSs) in protecting public health when emergency spills 

or contamination situations occur. 

While a negative determination is considered a final agency action for this round of regulatory 

determination, the contaminant is considered in the next round of the CCL process and could be 

re-listed based on newly available health and/or occurrence information.

 

15 SDWA allows the agency to extend the promulgation date by 9 months.
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Exhibit 8: Regulatory Determination Outcomes

 

8.C.5. Outcome of the Regulatory Determination Assessment Phase for Regulatory

Determination 3

The summary sheets in Appendix F present the key data evaluated and the outcomes for statutory 

criteria 1 and 2. 

9. References Cited

Government Accountability Office (GAO). 2011. Safe Drinking Water Act: EPA Should 

Improve Implementation of Requirements on Whether to Regulate Additional 

Contaminants. Report to Congressional Requesters. GAO-11-254. May 2011. Available 

on the Internet at: http://www.gao.gov/products/GAO-11-254. 

National Academy of Sciences (NAS). 2001. Classifying Drinking Water Contaminants for 

Regulatory Considerations. Committee on Drinking Water Contaminants, Water Science 

and Technology Board, Board on Environmental Studies and Toxicology, National 

Research Council. 

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. Available on the Internet at: 

http://www.epa.gov/safewater/ndwac/pdfs/report_ccl_ndwac_07-06-04.pdf. 
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United States Environmental Protection Agency (USEPA). 1986. Guidelines for Carcinogen 

Risk Assessment. Federal Register. Vol. 51, No. 185. p. 33992, September 24, 1986. 

USEPA. 1997. Announcement of the Draft Drinking Water Contaminant Candidate List; Notice. 

Federal Register. Vol. 62, No. 193, p. 52194, October 6, 1997. Available on the Internet 

at: https://federalregister.gov/a/97-26433

USEPA. 1998. Announcement of the Drinking Water Contaminant Candidate List; Notice. 

Federal Register. Vol. 63, No. 40, p. 10273. March 2, 1998. Available on the Internet at: 

https://federalregister.gov/a/98-5313

USEPA. 1999a. Revisions to the Unregulated Contaminant Monitoring Regulation for Public 

Water Systems; Final Rule. Federal Register. Vol. 64, No. 180, p. 50556. September 17, 

1999. Available on the Internet at: https://federalregister.gov/a/99-23030

USEPA. 1999b. National Representative Sample of Small Water Systems: Statistical Design and 

State Plans for Unregulated Contaminant Monitoring. EPA 815-R-99-003. 

USEPA. 1999c. National Representative Sample of Small Public Water Systems: Statistical 

Design and State Plans for the Unregulated Contaminant Monitoring Regulation. Office 

of Water. EPA 815-R-99-003. August. 44 pp. 

USEPA. 2001. Statistical Design and Sample Selection for the Unregulated Contaminant 

Monitoring Regulation. EPA 815-R-01-004. 

USEPA. 2002. Announcement of Preliminary Regulatory Determinations for Priority 

Contaminants on the Drinking Water Contaminant Candidate List. Federal Register. Vol. 

67, No. 106, p. 38222, June 3, 2002. Available on the Internet at: 

https://federalregister.gov/a/02-13796

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. Available on the Internet at: https://federalregister.gov/a/03-18151

USEPA. 2004. Drinking Water Contaminant Candidate List 2; Notice. Federal Register. Vol. 69, 

No. 64, p. 17406, April 2, 2004. Available on the Internet at: 

https://federalregister.gov/a/04-7416

USEPA. 2005a. Drinking Water Contaminant Candidate List 2; Final Notice. Federal Register. 

Vol. 70, No. 36, p. 9071. February 24, 2005. Available on the Internet at:

https://federalregister.gov/a/05-3527

USEPA. 2005b. Guidelines for Carcinogen Risk Assessment. EPA 630-P-03-001B. March 2005. 

Available on the Internet at: http://www.epa.gov/ttn/atw/cancer_guidelines_final_3-25-

05.pdf. 

USEPA. 2005c. Supplemental Guidance for Assessing Susceptibility to Early-life Exposure to 

Carcinogens. EPA 630-R-03-003F. March 2005. Available on the Internet at: 

http://www.epa.gov/ttn/atw/childrens_supplement_final.pdf. 
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USEPA. 2007a. Drinking Water: Regulatory Determinations Regarding Contaminants on the 

Second Drinking Water Contaminant Candidate List—Preliminary Determinations. 

Federal Register. Vol. 72, No. 83, p. 24016, May 1, 2007. Available on the Internet at: 

https://federalregister.gov/a/E7-7539

USEPA. 2007b. Unregulated Contaminant Monitoring Regulation (UCMR) for Public Water 

Systems Revisions; Final Rule. Federal Register. Vol. 72, No. 2, p. 367. January 4, 2007. 

Available on the Internet at: https://federalregister.gov/a/E6-22123

USEPA. 2008a. Drinking Water: Regulatory Determinations Regarding Contaminants on the 

Second Drinking Water Contaminant Candidate List. Federal Register. Vol. 73, No. 147, 

p. 44251. July 30, 2008. Available on the Internet at: https://federalregister.gov/a/E8-

17463

USEPA. 2008b. Drinking Water: Preliminary Regulatory Determination on Perchlorate. Federal 

Register. Vol. 73, No. 198, p. 60262, October 10, 2008. Available on the Internet at: 

https://federalregister.gov/a/E8-24042

USEPA. 2008c. Drinking Water Contaminant Candidate List 3—Draft Notice. Federal Register. 

Vol. 73. No 35. p. 9628, February 21, 2008. Available on the Internet at: 

https://federalregister.gov/a/E8-3114

USEPA. 2008d. The Analysis of Occurrence Data from the First Unregulated Contaminant 

Monitoring Regulation (UCMR 1) in Support of Regulatory Determinations for the 

Second Drinking Water Contaminant Candidate List. EPA 815-R-08-012. June 2008. 

USEPA. 2009a. Drinking Water: Perchlorate Supplemental Request for Comments. Federal 

Register. Vol. 74, No. 159, p. 41883, August 19, 2009. Available on the Internet at: 

https://federalregister.gov/a/E9-19507

USEPA. 2009b. Drinking Water: Perchlorate Supplemental Request for Comments. Federal 

Register. Vol. 74, No. 183, p. 45841, September 23, 2009. Available on the Internet at: 

https://federalregister.gov/a/E9-22927 

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

815-R-09-006. August. 

USEPA. 2009d. Final Contaminant Candidate List 3 Microbes: Identifying the Universe, EPA 

815–R–09–004. August. 

USEPA. 2009e. Final Contaminant Candidate List 3 Chemicals: Screening to a PCCL. EPA 815-

R-09-007. August. 

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

815–R–09–005. Draft. August. 

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

CCL. EPA 815-R-09-008. August. 
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USEPA. 2009h. Final Contaminant Candidate List 3 Microbes: PCCL to CCL Process, EPA 

815–R–09–009. August. 

USEPA. 2009i. Summary of Nominations for the Third Contaminant Candidate List. EPA-815-

R-09-011. August. 

USEPA. 2009j. Final Comment Response Document for the Third Drinking Water Contaminant 

Candidate List 3 Categorized Public Comments. EPA 815-R-09-010. August. 

USEPA. 2009k. Drinking Water Contaminant Candidate List 3 – Final. Federal Register. Vol. 

74, No. 194, p. 51850. October 8, 2009. Available on the Internet at: 

https://federalregister.gov/a/E9-24287

USEPA. 2009l. Final CCL 3 Contaminant Information Sheets. EPA 815-R-09-012. August,.

USEPA. 2011a. Drinking Water: Regulatory Determination on Perchlorate. Federal Register. 

Vol. 76, No. 29, p. 7762, February 11, 2011. Available on the Internet at: 

https://federalregister.gov/a/2011-2603

USEPA. 2011b. Summary of Comments and Discussion, Preliminary Regulatory Determinations 

for the Third Contaminant Candidate List Stakeholder Meeting, June 16, 2011. 

USEPA. 2011c. Support for Regulatory Determination 3 Expert Reviews; October 26th and 27th 

2011. Meeting Summary. December 2011. 

USEPA. 2011d. Exposure Factors Handbook 2011 Edition (Final). U.S. Environmental 

Protection Agency, Washington, DC, EPA/600/R-09/052F. 

USEPA. 2013. Response to External Expert Review of the Regulatory Determination 3 Protocol: 

Expert Review Comments with EPA Responses. 
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Appendix A. Health Reference Levels

A Health Reference Level or HRL is a health benchmark that the agency uses in the Regulatory 

Determination process to assess occurrence information. HRLs are not final determinations about 

the level of a contaminant in drinking water that is necessary to protect any particular population

(i.e., MCLG). Rather, it is a benchmark against which EPA compares the concentrations of a 

contaminant found in public water systems to determine if it is present at levels of public health 

concern. 

The 1996 SDWA Amendments require special consideration of all sensitive populations and 

lifestages (e.g., infants, children, pregnant women, elderly, and individuals with a history of 

chronic illness) in the development of drinking water regulations. If appropriate and available, 

the agency takes into account data from sensitive populations and life stages when developing 

HRLs. The derivation of HRLs for carcinogens and non-carcinogens are shown below. 

Derivation of an HRL for Carcinogens 

For those contaminants considered to be likely or probable human carcinogens, a toxicity value 

that defines the quantitative relationship between dose and response (i.e., the cancer slope factor 

or CSF), is calculated and data on the mode of action (MOA) are evaluated. 

Unidentified Mode of Action 

In cases where the data on the mode of action are lacking, EPA typically uses a default 

low dose linear extrapolation to calculate a CSF. The unit risk is the estimated upperbound excess lifetime cancer risk from a continuous exposure to a chemical at a 

concentration of 0.001 mg/L (1 μg/L) in drinking water. The exposure estimate assumes 

an adult body weight of 70 kg and a 90th percentile adult drinking water intake of 2 

L/day.Unit Risk (μg/L)-1 = CSF x [(DWI x CW)/BW]

where:

CSF = The Cancer Slope Factor (mg/kg/day)-1

DWI = Drinking Water Intake for an adult, assumed to be 2 L/day (90th percentile)

CW = Unit risk concentration in drinking water of 0.001 mg/L (1 μg/L); 

BW = Body weight of an adult, assumed to be 70 kilograms (kg) 

The cancer HRL, which corresponds to an excess estimated lifetime cancer risk of one in a 

million (10-6), is calculated by dividing the population risk level by the unit risk: 

HRL (μg/L) = Risk Level of 10-6 ÷ Unit Risk (μg/L)-1 

Mutagenic Mode of Action 

If the chemical has a mutagenic mode of action, low dose linear extrapolation is used to 

calculate the CSF as described above. EPA’s 2005 Guidelines for Carcinogen Risk 

Assessment (USEPA, 2005b) require that the potential increased cancer risk due to earlylife exposure be taken into account for chemicals with a mutagenic mode of action. When 

chemical-specific data to quantify the increased risk are lacking, Age Dependent 

Adjustment Factors (ADAFs) are applied to estimate age-specific unit risks. The total 

age-adjusted unit risk is calculated as the sum of the unit risks for each of the three 

ADAF developmental groups (birth to < 2 yrs; 2 yrs to < 16 yrs; 16 yrs to 70 yrs). The 
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age-adjusted unit risks include a ten-fold adjustment for early life (birth to < 2 yrs) 

exposures, a three-fold adjustment for childhood/adolescent (2 yrs to < 16 yrs) exposures, 

and no additional adjustment for exposures later in life (16 yrs to 70 yrs), in conjunction 

with age-specific drinking water intake values derived from EPA’s 2011 Exposure 

Factors Handbook (USEPA, 2011a) and the fraction of a 70-year lifetime applicable to 

each age period. The total age-adjusted unit risk is the upper-bound excess lifetime 

cancer risk estimated to result from continuous postnatal exposure to a chemical at a 

concentration of 0.001 mg/L in drinking water.Age-Adjusted Unit Risk (μg/L)-1 = 

∑(CSF x ADAF x DWI/BWR x CW x F) 

where:

CSF = The Cancer Slope Factor (mg/kg/day)-1

ADAF = The Age Dependent Adjustment Factor for the age group: birth to twoyears (ADAF=10), two years to sixteen years (ADAF=3), and sixteen 

to seventy years (ADAF=1)

DWI/BWR = Drinking Water Intake Body Weight Ratio (DWI/BWR) expressed as 

liters per kg body weight for the age group (90th percentile, consumers 

only), in L/kg

CW = Unit risk concentration in drinking water of 0.001 mg/L (1 μg/L) 

F = The fraction of a 70-year lifetime applicable to the age period: 2/70 for 

birth to two years, 14/70 for two years to sixteen years, and 54/70 for 

sixteen years to seventy years)

The cancer HRL, which corresponds to an excess estimated lifetime cancer risk of one in a 

million (10-6), is calculated by dividing the population risk level by the unit risk: 

HRL (μg/L) = Risk Level of 10-6 ÷ Total Age-Specific Unit Risk (μg/L)-1NonLinear Mode of Action and Other Exceptions 

For carcinogens with an identified non-linear mode of action, the HRL is derived using the RfD 

approach, in the same manner as non-carcinogens, as described in the next section. For 

contaminants that are considered only “possible” human carcinogens (or “Group C,” per the 

agency’s 1986 Guidelines for Carcinogen Risk Assessment), the HRL is also generally derived 

using the RfD approach based on non-cancer effects, along with an additional safety factor of up 

to 10 to account for possible carcinogenicity.Derivation of an HRL for Non-carcinogens 

EPA generally calculates a reference dose (RfD) for those chemicals considered to be noncarcinogenic or not likely to be carcinogenic to humans. An RfD is an estimate of a daily oral 

exposure to the human population (including sensitive populations or life stages) that is likely to 

be without an appreciable risk of deleterious effects during a lifetime. The RfD can be derived 

from either a no-observed-adverse-effect level (NOAEL), a lowest-observed-adverse-effect level 

(LOAEL), or the 95% lower confidence bound on a benchmark dose (BMD), knows as a BMDL, 

with uncertainty factors applied to reflect limitations of the data used. In addition, if the critical 

health endpoint has high quality data associated with exposure for a specific developmental 

group or period of sensitivity, age-specific drinking water intake to body weight ratio values 

from the 2011 Exposure Factors Handbook may be included in deriving an HRL from the RfD 

(USEPA, 2011a). 
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The agency uses uncertainty factors (UFs) to address uncertainty resulting from incompleteness 

of the toxicological database (e.g., lacking sensitive population data). The individual UFs 

(usually applied as integers of one, three, or ten) are multiplied together and used to derive the 

RfD from experimental data. Individual UFs are intended to account for: 

(1) Variation in sensitivity among the members of the human population (i.e.,intraspecies 

variability). 

(2) Uncertainty in extrapolating animal data to humans (i.e., interspecies variability). 

(3) Uncertainty in extrapolating from data obtained in a study with less-than-lifetime

exposure to lifetime exposure (i.e., extrapolating from subchronic to chronic 

exposure). 

(4) Uncertainty in extrapolating from a LOAEL rather than from a NOAEL. 

(5) Uncertainty associated with an incomplete database.

Under the RfD approach, the HRL is calculated as follows:

HRL (mg/L) = [(RfD x BW)/DWI] x RSC 

where: 

RfD = Reference Dose

BW = Body Weight, assumed to be 70 kg for an adult and 10 kg for a child 

DWI = Drinking Water Intake, assumed to be 2 L/day (90th percentile) for an adult, and 1 

L/day (90th percentile) for a child

RSC = Relative Source Contribution, or the level of exposure believed to result from 

drinking water when compared to other sources (e.g., food, ambient air). In all

cases, a 20% RSC is used for HRL derivation because (1) HRLs are developed 

prior to a complete exposure assessment, and (2) 20% is the lowest and most 

conservative RSC used in the derivation of an MCLG for drinking water. 
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Appendix B. Health Assessment Data Sources for RD 3

EPA uses health assessments from several EPA and non-EPA designated sources to evaluate 

health effects for contaminants considered for RD 3. While EPA health assessments are 

preferred, non-EPA health assessments were also considered for RD 3, if the health assessment

used comparable methods, standards, and guidelines to an EPA health assessment. The following 

externally peer-reviewed health assessments sources comprise the drinking water health data 

used to support RD 3: 

EPA Health Assessments:

Integrated Risk Information System (IRIS):

(http://cfpub.epa.gov/ncea/iris/index.cfm?fuseaction=iris.showSubstanceList) 

EPA’s Integrated Risk Information System (IRIS) is a human health assessment program that 

compiles and evaluates information on health effects that may result from exposure to 

environmental contaminants. Through the IRIS Program, EPA provides the highest quality 

science-based human health assessments to support the agency’s regulatory activities. The IRIS 

database contains information on more than 550 chemical substances containing information on 

human health effects that may result from exposure to various substances in the environment. 

The IRIS database is prepared and maintained by EPA’s National Center for Environmental 

Assessment (NCEA) within the Office of Research and Development (ORD).

The heart of the IRIS database is its collection of searchable documents that describe the health 

effects of individual substances and that contain descriptive and quantitative information in the 

following categories: 

• Non-cancer effects: Oral reference doses and inhalation reference concentrations (RfDs 

and RfCs, respectively) for effects known or assumed to be produced through a nonlinear 

(possibly threshold) mode of action. In most instances, RfDs and RfCs are developed for 

the noncarcinogenic effects of substances. 

• Cancer effects: Descriptors that characterize the weight of evidence for human 

carcinogenicity, oral slope factors, and oral and inhalation unit risks for carcinogenic 

effects. Where a nonlinear mode of action is established, RfD and RfC values may be 

used. 

Office of Pesticide Program’s (OPP) REDs, IREDs and TREDs:

(http://iaspub.epa.gov/apex/pesticides/f?p=chemicalsearch:1) 

In 2008, EPA completed a review of older pesticides (those initially registered prior to 

November 1984) under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) to 

ensure that they met current scientific and regulatory standards. This process, called 

reregistration, enabled EPA to call in and review supporting scientific studies, complete human 

health and ecological risk assessments, and develop risk mitigation measures as needed using 

current science, transparency, and input from stakeholders and the public. EPA also reassessed 

existing tolerances (pesticide residue limits in food) to ensure that they met the safety standard 

established by the Food Quality Protection Act (FQPA) of 1996. EPA integrated reregistration 

and tolerance reassessment to most effectively accomplish the goals of both programs. When 

EPA completes its review of a pesticide for reregistration or tolerance reassessment, the agency 

issues a risk management decision document known as a RED, an IRED, or a TRED. EPA 
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publishes Notices of Availability in the Federal Register. 

• REDs (Reregistration Eligibility Decisions) 

When EPA completes the review and risk management decision for a pesticide that is 

subject to reregistration (that is, one initially registered before November 1984), the 

agency generally issues a Reregistration Eligibility Decision or RED document. The RED 

summarizes the risk assessment conclusions and outlines any risk reduction measures 

necessary for the pesticide to continue to be registered in the U.S. 

• IREDs (Interim Reregistration Eligibility Decisions)

EPA issues an IRED for a pesticide that is undergoing reregistration, requires a 

reregistration eligibility decision, and also needs a cumulative assessment as a result of 

FQPA because it is part of a group of pesticides that share a common mechanism of 

toxicity. The IRED, issued after EPA completes the individual pesticide’s aggregate risk 

assessment, may initiate risk reduction measures--for example, reducing risks to workers 

or eliminating uses that the registrant no longer wishes to maintain--to gain the benefits 

of these changes before the final RED can be issued, following the agency's consideration 

of cumulative risks. 

• TREDs (Reports on FQPA Tolerance Reassessment Progress and [Interim] Risk 

Management Decisions)

o A TRED may be issued as a document if no changes in the tolerances for a 

pesticide are required as a result of EPA’s review. If tolerance revisions are 

required, then the TRED may be issued as a Federal Register Notice. EPA issues 

a TRED for a pesticide that requires tolerance reassessment decisions, but does 

not require a reregistration eligibility decision at present because:The pesticide 

was initially registered after November 1, 1984, and by law is not included within 

the scope of the reregistration program. 

o EPA completed a RED for the pesticide before FQPA was enacted on August 3, 

1996. 

o The pesticide is not registered for use in the U.S. but tolerances are established 

that allow crops treated with the pesticide to be imported from other countries. 

Like IREDs, some TREDs will not become final until EPA considers the cumulative risks of all 

the pesticides in the cumulative group. 

Office of Water (OW) Assessments: 

(http://water.epa.gov/drink/standards/hascience.cfm) 

The agency performs a literature search for studies published after the available health

assessment (listed in Appendix D) is completed to determine if new information suggests a 

different outcome. The agency collects and evaluates any peer-reviewed publications identified 

through the literature search for their impact on the RfD and/or cancer assessment. In cases 

where the recent data indicates that a change to the existing RfD or cancer assessment is needed

and the contaminant is continuing to the Regulatory Determination Assessment Phase (Phase 3), 

the updated OW assessment, described in the Health Effects Support Document, is prepared and 

independently peer-reviewed. These documents address the exposure from drinking water and 
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other media, toxicokinetics, hazard identification, and dose-response assessment, and provide an 

overall characterization of risk from drinking water. For the contaminants with low or no 

occurrence, refer to the EPA health risk assessments online from OPP or IRIS for additional 

health effect information. 

Non-EPA Health Assessments: 

These non-EPA health assessments were recognized by the agency because of their standardized 

methods for characterizing health effects data, relevancy to drinking water exposures, and 

comparability to EPA methods. 

Agency for Toxic Substances & Disease Registry (ATSDR):

(http://www.atsdr.cdc.gov/az/a.html) 

By Congressional mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) 

produces “toxicological profiles” for hazardous substances found at National Priorities List 

(NPL) sites. These hazardous substances are ranked based on frequency of occurrence at NPL 

sites, toxicity, and potential for human exposure. Toxicological profiles are developed from a 

priority list of 275 substances. The ATSDR toxicological profile succinctly characterizes the 

toxicological and adverse health effects information for hazardous substances. Each peerreviewed profile identifies and reviews the key literature that describes a hazardous substance’s 

toxicological properties. Other pertinent literature is also presented, but is described in less detail 

than the key studies. 

ATSDR establishes oral minimal risk levels (MRLs) for non-neoplastic endpoints for acute (14 

days or less), intermediate (15-364 days), and chronic (365 days or more) exposure durations. 

MRLs for oral chronic exposure are similar to EPA’s RfDs. However, ATSDR and EPA use 

different approaches when the database is limited to subchronic studies and no adequate chronic 

study is available. ATSDR derives an intermediate duration MRL that protects against exposures 

up to 10% of a lifetime, and it does not incorporate an uncertainty factor to account for using a 

less-than-lifetime study. ATSDR does not perform quantitative cancer assessments or assign 

formal cancer classifications or descriptors.

The National Academies: (http://www.nationalacademies.org/) 

The United States National Academies comprises four organizations:

• National Academy of Sciences (NAS). 

• National Academy of Engineering (NAE). 

• Institute of Medicine (IOM). 

• National Research Council (NRC). 

The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, 

and National Research Council are private, nonprofit institutions that provide expert advice to 

decision makers and the public. 

EPA may commission the National Academies or use previously published reports to advise 

EPA on available scientific literature, public policy, health assessments, and exposure 

assessments. The reports from the National Academies are viewed as being valuable and credible 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

43

because of the institution’s reputation for providing independent, objective, and nonpartisan 

advice with high standards of scientific and technical quality. Checks and balances are applied at 

every step in the study process to protect the integrity of the reports and to maintain public 

confidence in them. 

World Health Organization (WHO):

(http://www.who.int/water_sanitation_health/dwq/chemicals/en/)

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

include facts sheets and comprehensive review documents for many individual chemicals. WHO 

derives guideline values for many of these chemicals. For each chemical contaminant or 

substance considered, a lead institution prepared a background document evaluating the risks for 

human health from exposure to the particular chemical in drinking water. Under the 

responsibility of the coordinators for a group of chemicals considered in the guidelines, the draft 

health criteria documents were submitted to a number of scientific institutions and selected 

experts for peer review. Comments were taken into consideration by the coordinators and authors 

before the documents were submitted for final evaluation by the experts meetings. A “final task 

force” meeting reviewed the health risk assessments and public and peer review comments and, 

where appropriate, decided upon guideline values. 

The guidelines are intended to be used as a basis for the development of national standards that, 

if properly implemented, will ensure the safety of drinking water supplies through the 

elimination, or reduction to a minimum concentration, of constituents of water that are known to 

be hazardous to health. WHO’s guideline value is a drinking water concentration that uses 

different default assumptions than EPA for estimating water concentration from doses, including 

a 60 kg adult body weight, daily water consumption of 2 L/day, and a default RSC for drinking 

water of 10% (unless data is available to derive an RSC). WHO develops one guideline value 

that is based on either cancer or non-cancer health effects. 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Appendix C. Data Sources for Occurrence

EPA uses data from several sources to evaluate occurrence and exposure for contaminants 

considered for regulatory determinations. The following sources comprised the national sources 

of drinking water occurrence data available to support determinations: 

• Second Unregulated Contaminant Monitoring Regulation (UCMR 2). 

• First Unregulated Contaminant Monitoring Regulation (UCMR 1). 

• Unregulated Contaminant Monitoring (UCM) program (Round 1 and 2). 

• National Inorganics and Radionuclides Survey (NIRS). 

All four are national assessments that were administered or overseen by EPA and contribute to 

EPA’s National Contaminant Occurrence Database (NCOD). EPA notes that NCOD was 

established in response to the SDWA mandate for a national drinking water contaminant 

occurrence database that would be integrated with the UCMR, CCL, and Regulatory 

Determination programs. The SDWA Amendments state that “a determination to regulate...shall 

be based on the best available public health information, including the occurrence data base 

established under section 300j-4(g) of this title.” 

In addition to these national sources of occurrence data, the agency also evaluates supplemental 

sources of information on occurrence in drinking water, occurrence in ambient and source water, 

and information on contaminant use and release. These are mostly national assessments by 

federal agencies such as EPA and the United States Geological Survey (USGS), but they also 

include regional- and state-level surveys and some research performed by private institutions. 

National Data Sources (National Drinking Water Data)

Unregulated Contaminant Monitoring Regulation (UCMR) Assessment Monitoring (AM): 

• Designed to provide nationally representative contaminant occurrence data. Conducted 

by all PWSs serving more than 10,000 people (a “census”), and a statistically designed 

national sample of 800 PWSs serving 10,000 or fewer people. 

• Includes all 50 states, four Territories, and Tribal lands. 

• Monitoring is conducted during a continuous 12-month period at each participating 

system, at a quarterly monitoring frequency for surface water systems and a twice-a-year 

monitoring frequency for ground water systems. At least one sample period must be 

during a specified vulnerable period. 

o UCMR1: Monitoring occurred during 2001-2003 and included 12 chemical 

contaminants. 

o UCMR 2: Monitoring occurred during 2008-2010 and included 10 chemical 

contaminants. 
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Unregulated Contaminant Monitoring Regulation: Screening Surveys (SS): 

• Monitoring for contaminants that require specialized analytical method technologies not 

in wide or common use.

o UCMR 1 Screening Survey monitoring was conducted by a statistically selected 

sample of 300 large and small PWSs. While the statistical design provided for 

national data, for relatively low occurrence contaminants there was concern that 

there was too much uncertainty in the results because of the small number of 

samples. Hence, these data were not used by themselves as a national data source.

Screening Survey monitoring was conducted for 13 chemicals for a 12-month 

period during 2001 and 2002, and for one microbe in 2003. 

o UCMR 2 Screening Survey design was modified to improve its scope. For UCMR 

2 monitoring included a census of all systems serving more than 100,000 

(approximately 400 PWSs--and the largest portion of the national population 

served by PWSs); and a statistically selected national sample of 320 PWSs 

serving 10,001 to 100,000 people, and 480 PWSs serving 10,000 or fewer people. 

Screening Survey monitoring was conducted for 15 contaminants for a 12-month 

period during 2008-2010.

Unregulated Contaminant Monitoring (UCM): 

Prior to the development of the UCMR, the unregulated contaminant monitoring (UCM) 

program required public water systems serving more than 500 people to monitor for specified 

contaminants, during two time periods. There was no requirement to report these data to EPA 

and individual states maintained these data in different forms and formats. Following a peerreviewed protocol, the most complete individual state data sets were assembled into a single 

“national cross-section” data set that is indicative of contaminant occurrence nationally.

• Round 1: The final database includes data on 62 contaminants. Data were collected from 

38 states, DC, and the Virgin Islands between 1988 and 1992. Application of the protocol 

resulted in a national cross-section with data from 24 states (22,000 PWSs).

• Round 2: The final database includes data on 48 contaminants. These data were collected 

from 35 states and primacy entities between 1993 and 1997. Application of the protocol 

resulted in a national cross-section with data from 20 states (27,000 PWSs).

National Inorganic and Radionuclide Survey (NIRS): 

NIRS provides data on the occurrence of a select set of radionuclides and inorganic chemicals. 

• It provides contaminant occurrence data from 989 community water systems (CWSs) 

served by ground water sources. 

• Each of these randomly selected PWSs was sampled a single time between 1984 and 

1986. Selection of the PWSs was designed so that the contaminant occurrence results 

from these PWSs would be representative of national occurrence of contaminants in 

ground water systems. 

• The data are from 49 states (there are no data from Hawaii), as well as Puerto Rico.
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Non-National Drinking Water Data Sources

Unregulated Contaminant Monitoring Regulation 1 Screening Survey: 

• As noted above, UCMR 1 Screening Survey monitoring was conducted by a national 

sample of 300 large and small PWSs. While the statistical design provided for national 

data, for relatively low occurrence contaminants there was concern that there was too 

much uncertainty in the results because of the small number of samples. Hence, these 

data were not used by themselves as a national data source. Monitoring was conducted 

for 13 chemicals for a 12-month period during 2001 and 2002, and for one microbe in 

2003.

o The scope of the UCMR 2 Screening Survey was expanded beyond that of 

UCMR 1 Screening Survey to the point that it could be considered a primary data 

source, as described above. 

Disinfection By-Product Information Collection Rule (DBP ICR): 

The DBP ICR required public water systems serving at least 100,000 people to monitor and 

collect data on disinfection byproducts (DBPs) from July 1997 to December 1998. The DBP data 

were collected from 296 water systems. The DBP ICR is national in scope, with monitoring sites 

geographically distributed across the country, but it is not intended to be statistically 

representative of the nation. 

Individual States’ Data

Six-Year Review Information Collection Request: 

The purpose of this ICR was to support the national contaminant occurrence and exposure 

assessments performed under the Six-Year Review process. EPA analyzes SDWA compliance 

monitoring data from public water supplies for contaminants with National Primary Drinking 

Water Regulations (NPDWRs). Data were obtained from compliance monitoring of public water 

systems. The data were used to construct a national cross-section that would be indicative of 

national contaminant occurrence. Data sets received from some states also included some limited 

information on unregulated contaminants that were useful for the Regulatory Determination 

Process.

• Six-Year 1 (2003): EPA reviewed 69 NPDWRs that were established prior to 1997. Data 

were obtained from 16 states (41,000 PWSs). Data from 1993 to 1997 were used in 

analyses.

• Six Year 2 (2010): EPA reviewed 71 NPDWRs. Data were obtained from 45 states plus 

Region 8 and Region 9 tribes (132,000 PWSs). Data collected from 1998-2005. Six of the 

states (California, Illinois, North Carolina, South Dakota, Ohio, and Texas) and the 

Region 9 tribes submitted PWS occurrence data for unregulated contaminants in addition 

to their data for regulated contaminants in response to the Second Six-Year Review ICR.

States –Websites: 

EPA was able to supplement the data on unregulated contaminants obtained during the Six Year 

2 process by downloading additional publicly available PWS monitoring data from state 

websites. Data were obtained from the Florida and Wisconsin state websites.
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Supplemental Drinking Water Data Sources

Community Water System Survey (CWSS): 

EPA periodically collects data on the financial and operating characteristics of a random sample 

of community water systems (CWSs) nationwide. All systems serving more than 500,000 people 

receive the survey and systems in this size category are asked questions about concentrations of 

unregulated contaminants in their raw and finished water. CWSS findings from 2000 and from 

2006 have been published. 

Consumer Confidence Reports (CCRs):

CCRs are annual water quality reports that CWSs are required to provide to their customers. 

These reports summarize information on water sources, detected contaminants, and system 

compliance with EPA drinking water standards. 

• CWSs with 15 or more connections or serving at least 25 year-round residents must 

prepare and distribute a CCR to all billing units or service connections every year. 

• CWSs serving 100,000 or more residents are also required to post their current CCRs on 

a publicly accessible Internet site. 

EPA reviewed CCRs published by the 26 systems that serve over 1 million customers for 

unregulated contaminant occurrence information. 

Pesticide Data Program (PDP): 

The goal of the Pesticide Data Program (PDP) Water Monitoring Survey is to collect monitoring 

data on pesticide residues. The PDP water monitoring survey began in 2001 when Congress 

allocated money to USDA’s Agricultural Marketing Service (AMS) for the purpose of providing 

these data. The PDP water survey is designed in consultation with EPA to provide data for 

agricultural use pesticides under evaluation, related to the Food Quality Protection Act (FQPA). 

The sampling frame is designed to provide coverage in regions of interest for at least two years 

to reflect the seasonal and climatic variability during growing seasons. PDP works with EPA and 

American Water Works Association (AWWA) to identify specific water treatment facilities

where monitoring data are needed. 

United States Geological Survey Pilot Monitoring Program (USGS PMP):

Initiated in 1999, PMP provides information on pesticide concentrations in drinking water. This 

study focused on small drinking water supply reservoirs in areas with high pesticide use to test 

and refine the sampling approach in areas where pesticides are probably present. Sampling sites 

represent a variety of geographic regions, as well as different cropping patterns. 

• These 12 sites were located in: California, Indiana, Ohio, Oklahoma, Louisiana, 

Missouri, South Carolina, South Dakota, New York, North Carolina, Pennsylvania, and 

Texas. 

• Samples were collected quarterly throughout the year and at weekly or biweekly intervals 

following the primary pesticide-application periods. 

• Water samples were collected from the raw-water intake and from the finished drinkingwater tap prior to entering the distribution system. At some sites, samples were also 

collected at the reservoir outflow.
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Environmental Working Group (EWG): 

EWG assembled a database of 20 million drinking water quality tests performed by water 

utilities since 2004. EWG obtained tap water testing data from state water offices, which had 

collected the results from the utilities as part of their primacy oversight and enforcement of state 

and federal water quality standards. The data came from approximately 48,000 PWSs in 45 states 

and the District of Columbia. Among the contaminants detected were 202 unregulated chemicals. 

Supplemental Ambient/Source Water Data Sources

USGS National Water Quality Assessment Program (NAWQA):

USGS instituted the National Water Quality Assessment program in 1991 to examine ambient 

water quality status and trends in the United States. 

• The program’s sampling approach is not statistically designed (does not involve random 

sampling). 

• Cycle 1 monitoring took place between 1991 and 2001. (Cycle 1 data were used in 

CCL 3; RD 3 supplemented these data with information from special USGS reports that 

may have also used some additional data from other programs or from the early years of 

NAWQA Cycle 2.)

• Data from over 6,400 surface water and 7,000 ground water sampling points (60% of the 

nation’s drinking water and water used for agriculture and industry). 

• Pesticides, nutrients, VOCs, trace elements, and radionuclides. 

• Special USGS reports included: 

o Source Water Survey (2001): A network of 25 ground water and 49 surface water 

sources of public drinking water supply in 25 states and Puerto Rico were 

sampled and analyzed for 100 emerging contaminants. 

o Ground Water Survey (2000): Water samples were collected from a network of 47 

ground water sites across 18 states. These samples were analyzed for 65 emerging 

contaminants. Site selection focused on a variety of geohydrologic areas 

suspected to be susceptible to contamination from either animal or human 

wastewaters and were in aquifers not necessarily used as a source of drinking 

water. The network consisted of 42 wells, 3 springs, and 2 sumps. 

o Stream Survey (1999-2000): Water samples were collected from a network of 139 

streams across 30 states during 1999 and 2000. Site selection focused on streams 

considered to be susceptible to contamination; selected sites represent a wide 

variety of hydrogeologic, climatic, and land-use settings across the United States. 

EPA Storage and Retrieval database (STORET): 

This EPA database contains raw biological, chemical, and physical data on surface and ground 

water collected by federal, state, and local agencies, Indian tribes, volunteer groups, academics, 

and others. Data contained in STORET are primarily for ambient water but they also include 

some drinking water data. 

USGS National Reconnaissance of Emerging Contaminants (NREC):

For CCL 3, the USGS provided EPA with data from various reconnaissance studies looking at 

the occurrence of emerging contaminants in surface waters and ground waters. The data 
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represent sites from over 30 states, and include analyses for over 124 contaminants. 

Production/Use/Release Data Sources

Chemical Update System/Inventory Update Rule (CUS IUR):

The IUR regulation under the Toxic Substances Control Act (TSCA) requires manufacturers and 

importers of certain chemical substances included on the TSCA Chemical Substance Inventory 

to report site and manufacturing information for chemicals manufactured (including imported) in 

amounts of 25,000 pounds or greater at a single site. Additional information on domestic 

processing and use must be reported for chemicals manufactured in amounts of 300,000 pounds 

or more at a single site. Prior to the 2003 amendments (i.e., reporting from 2002 or earlier), 

information was collected for only organic chemicals that were manufactured (including 

imported) in amounts of 10,000 pounds or more, and was limited to more basic manufacturing 

information such as production volume.

EPA Office of Pesticide Programs (OPP) Reregistration Documents: 

All pesticides sold or used in the United States must be registered by EPA. Because of advances 

in scientific knowledge, the law requires that pesticides which were first registered years ago be 

reregistered to ensure that they meet today’s more stringent standards. In evaluating pesticides 

for reregistration, EPA obtains and reviews various data and studies from pesticide producers, 

describing the human health and environmental effects of each pesticide. 

Office of Pesticide Programs Estimated Concentrations: 

EPA OPP used modeling to develop estimated concentrations for acute and chronic 

exposure scenarios involving surface water and ground water. The estimated 

concentrations were developed using the Pesticide Root Zone Model/Exposure Analysis 

Modeling System (PRZM/EXAMS) and Screening Concentrations in Ground Water 

(SCI-GROW) model. 

National Center for Food and Agricultural Policy (NCFAP): 

NCFAP is a private non-profit institution that maintained a national pesticide use database.

Annual pesticide use estimates for circa 1992 and 1997 are based on state level commercial 

agricultural usage patterns for 1990-1993 and 1995-1998, and state level crop acreage for 1992 

and 1997 (collected by USDA). The database contains estimates of pounds applied and acres 

treated in each state for 220 active ingredients and 87 crops. 

• The majority of chemicals monitored are herbicides, but it also contains fungicides and 

insecticides. 

• The database only includes applications of pesticides to cropland. It does not include nonbearing orchards or vineyards or governmental area-wide eradication programs. 

• The database is compiled from a wide variety of sources, thus there is no way to 

determine the accuracy of any of the estimates. When data for particular states and crops 

are unavailable, as they are in many cases, values are assigned on the basis of data from a 

nearby state.

USGS Pesticide Use Maps: 

USGS produces maps of pesticide use for compounds used in US crop production. USGS 

combines NCFAP state-based pesticide use coefficients for 87 crops with county-level crop 
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acreages obtained from the Census of Agriculture. The resulting maps show the distribution of 

average annual pesticide use. Map resolution is based at the county level.

Toxics Release Inventory (TRI):

Established in 1987, TRI requires facilities to report, to both EPA and the states, annual 

information on toxic chemical releases from facilities that meet certain reporting criteria.

• Not all facilities are required to report all releases. Facilities are required to report 

releases if they manufacture or process more than 25,000 pounds or use more than 10,000 

pounds. 

• Reporting requirements have changed over time (e.g., reporting thresholds have 

decreased); this creates the potential for misleading data trends over time. 

• TRI data are meant to reflect releases and should not be used to estimate general public 

exposure to a chemical. 
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Appendix D. Summary of Phase 1: Data Availability 

See attachment.

Appendix E. Summary of Phase 2 Data Evaluation See attachment.

Appendix F. Summary of Phase 3 Regulatory Determination 

Assessments 

See attachment.
EPA – OGWDW Protocol for Regulatory Determination 3 April 2014

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Appendix G. Evaluation of Statutory Criterion #3 Statutory Criterion #3 requires that in the sole judgment of the Administrator, regulation of a 

contaminant presents a meaningful opportunity for health risk reduction for persons served by 

PWSs. EPA evaluates the population exposed at the health level of concern along with several 

other factors to determine if regulation presents a meaningful opportunity for health risk 

reduction. The EPA Administrator may consider the following factors in evaluating statutory 

criterion #3: 

• Based on the occurrence information for statutory criterion #2 (and the potential number 

of systems impacted), what is the national population exposed or served by systems with 

levels > HRL and 1⁄2 HRL (provide actual and estimated # and %)? 

• What is the nature of the health effect(s) identified in statutory criterion #1 and are there 

sensitive populations that may be impacted (either qualitative or quantitative)? 

• For non-carcinogens, are there other sources of exposure that should be considered (i.e., 

what is the relative source contribution)? 

• What is the geographic distribution of occurrence (e.g., local, regional, national)? 

• Are there any uncertainties and/or limitations in the health and occurrence information or 

analyses that should be considered? 

• What other factors or other pieces of information should be considered that may have 

direct bearing on any decision to regulate the contaminant (e.g., treatment, analytical 

methods, etc.)? 

After evaluating these factors, if the Administrator determines that there is a meaningful 

opportunity to reduce risk by regulating the contaminant in drinking water, then the agency 

answers “yes” to the third statutory criterion.
April 2014 Page 1 of 3

CASRN Common Name Occurrence Data 

Type

Best Available Occurrence 

Data Source Primary Health Effects Data Source9 Health Assessment Status10 Place on Short List 

for Phase 2

96184 1,2,3-Trichloropropane1 National DW UCM IRIS (2009)11 Available Assessment Yes1

34256821 Acetochlor2 National DW UCMR1 (AM) OPP TRED (2006)11 Available Assessment Yes2

187022113 Acetochlor ethanesulfonic acid (ESA)2 National DW UCMR2 OPP TRED (2006) Available Parent Assessment Yes2

184992444 Acetochlor oxanilic acid (OA)2 National DW UCMR2 OPP TRED (2006) Available Parent Assessment Yes2

142363539 Alachlor ethanesulfonic acid (ESA)2 National DW UCMR2 OPP RED (1998) Available Parent Assessment Yes2

171262172 Alachlor oxanilic acid (OA)2 National DW UCMR2 OPP RED (1998) Available Parent Assessment Yes2

60515 Dimethoate National DW UCMR2 OPP IRED (2007) Available Assessment Yes

98953 Nitrobenzene1 National DW UCMR1 (AM) IRIS (2009) Available Assessment Yes1

62759 N-nitrosodimethylamine (NDMA)2 National DW UCMR2 Draft OW Health Assessment (2010)11 Available Assessment Yes2

56070167 Terbufos sulfone2 National DW UCMR2 OPP RED (2006) Available Parent Assessment Yes2

7440622 Vanadium National DW NIRS Draft ATSDR (2009)11 Assessment in Process (ATSDR) Yes

630206 1,1,1,2-Tetrachloroethane1 National DW UCM IRIS RfD (1987) Available Assessment Yes1

99650 1,3-Dinitrobenzene National DW UCMR2 IRIS RfD (1988) Available Assessment Yes

51218452 Metolachlor2 National DW UCM OPP RED (1995) Available Assessment Yes2

171118095 Metolachlor ethanesulfonic acid (ESA)2 National DW UCMR2 OPP RED (1995) Available Parent Assessment Yes2

152019733 Metolachlor oxanilic acid (OA)2 National DW UCMR2 OPP RED (1995) Available Parent Assessment Yes2

2212671 Molinate National DW UCMR1 (AM) IRIS (1988) Available Assessment Yes

7439987 Molybdenum National DW NIRS NAS (2001)/IRIS (1991) Available Assessment Yes

55185 N-Nitrosodiethylamine (NDEA)2 National DW UCMR2 IRIS (1987) Available Assessment Yes2

621647 N-Nitroso-di-n-propylamine (NDPA)2 National DW UCMR2 IRIS (1987) Available Assessment Yes2

930552 N-nitrosopyrrolidine (NPYR)2 National DW UCMR2 IRIS (1987) Available Assessment Yes2

74839 Methyl bromide (Bromomethane) National DW UCM OPP (2006)11 Available Assessment Yes

121824 RDX National DW UCMR2 IRIS (1988) Assessment in Process (IRIS) Yes

7440484 Cobalt National DW NIRS ATSDR (2004) Available Assessment Yes

1634044 Methyl tert-butyl ether (MTBE) National DW UCMR1 (AM) OEHHA(CA) (1999) Assessment in Process (IRIS) Yes

7440246 Strontium National DW NIRS IRIS (1992) Available Assessment Yes

75343 1,1-Dichloroethane1 National DW UCM OEHHA(CA) (2003) No Assessment No1

16655826 3-Hydroxycarbofuran3 National DW UCM OPP IRED (2006) [parent] No Assessment No3

74873 Chloromethane (Methyl chloride) National DW UCM RAISHE (1981) No Assessment No

7440564 Germanium National DW NIRS RTECS No Assessment No

74975 Halon 1011 (bromochloromethane) National DW UCM OW Health Advisory (1989) No Assessment No

103651 n-Propylbenzene National DW UCM RTECS No Assessment No

135988 sec-Butylbenzene National DW UCM RTECS No Assessment No

13494809 Tellurium National DW NIRS Supplemental Data (1988) No Assessment No

123911 1,4-Dioxane Non-National DW State data > 1/2HRL IRIS (2010)11 Available Assessment Yes

30560191 Acephate Non-National DW State data > 1/2HRL OPP RED (2006) Available Assessment Yes

107028 Acrolein Non-National DW State data IRIS (2003) Available Assessment No

741582 Bensulide Non-National DW State data OPP RED (2006) Available Assessment No

133062 Captan Non-National DW State data OPP RED (2004) Available Assessment No

14866683 Chlorate Non-National DW DBP ICR > 1/2HRL/DBP OPP RED (2006) Available Assessment Yes

141662 Dicrotophos Non-National DW State data OPP RED (2006) Available Assessment No

298044 Disulfoton4 Non-National DW UCMR1 (SS) & other OPP RED (2006) Available Assessment Yes4

330541 Diuron4 Non-National DW UCMR1 (SS) & other OPP RED (2003) Available Assessment Yes4

13194484 Ethoprop Non-National DW Supplemental OPP RED (2006) Available Assessment No

107211 Ethylene glycol Non-National DW State data IRIS (1987) Available Assessment No

96457 Ethylene thiourea (Maneb) Non-National DW Supplemental OPP RED (2005) Available Assessment No

22224926 Fenamiphos Non-National DW State data OPP IRED (2002) Available Assessment No

10265926 Methamidophos Non-National DW State data OPP RED (2006) Available Assessment No

301122 Oxydemeton-methyl Non-National DW Supplemental OPP RED (2006) Available Assessment No

CHEMICALS

Appendix D. Summary of Phase 1: Data Availability
April 2014 Page 2 of 3

CASRN Common Name Occurrence Data 

Type

Best Available Occurrence 

Data Source Primary Health Effects Data Source9 Health Assessment Status10 Place on Short List 

for Phase 2

CHEMICALS

Appendix D. Summary of Phase 1: Data Availability

42874033 Oxyfluorfen Non-National DW Supplemental OPP RED (2002) Available Assessment No

1763231 Perfluorooctane sulfonic acid (PFOS) Non-National DW Supplemental > 1/2HRL OW Provisional HA (2009) Assessment in Process (OW) Yes

335671 Perfluorooctanoic acid (PFOA) Non-National DW Supplemental > 1/2HRL OW Provisional HA (2009) Assessment in Process (OW) Yes

52645531 Permethrin Non-National DW State data OPP RED (2009) Available Assessment No

41198087 Profenofos Non-National DW Supplemental OPP RED (2006) Available Assessment No

107534963 Tebuconazole Non-National DW Supplemental OPP RED (2008) Available Assessment No

13071799 Terbufos2 Non-National DW UCMR1 (SS) & other OPP RED (2006) Available Assessment Yes2

78488 Tribufos Non-National DW Supplemental OPP RED (2006) Available Assessment No

50471448 Vinclozolin Non-National DW Supplemental OPP RED (2000) Available Assessment No

137304 Ziram Non-National DW State data OPP RED (2003) Available Assessment No

71363 1-Butanol Non-National DW State data IRIS (1988) Available Assessment No

319846 alpha-Hexachlorocyclohexane Non-National DW Supplemental IRIS (1987) Available Assessment No

100447 Benzyl chloride Non-National DW Supplemental IRIS (1989) Available Assessment No

50000 Formaldehyde Non-National DW DBP ICR IRIS (1990) Assessment in Process (IRIS) No

86306 N-Nitrosodiphenylamine (NDPhA)2,5 Non-National DW State data IRIS (1987) Available Assessment Yes2,5

57910 17alpha-estradiol7 Non-National DW Supplemental WHO (1999) No Assessment No7

75070 Acetaldehyde Non-National DW DBP ICR RTECS No Assessment No

64285069 Anatoxin-a Non-National DW Supplemental Supplemental Data (1981) No Assessment No

62533 Aniline Non-National DW State data RAISHE No Assessment No

25013165 Butylated hydroxyanisole Non-National DW Supplemental RTECS No Assessment No

143545908 Cylindrospermopsin Non-National DW Supplemental Supplemental Data (2006) No Assessment No

517099 equilenin7 Non-National DW Supplemental WHO (1999) No Assessment No7

474862 equilin7 Non-National DW Supplemental WHO (1999) No Assessment No7

114078 Erythromycin8 Non-National DW Supplemental WHO (2006) No Assessment No8

50282 Estradiol (17-beta estradiol) Non-National DW Supplemental OEHHA(CA) No Assessment No

50271 estriol7 Non-National DW Supplemental WHO (1999) No Assessment No7

53167 estrone7 Non-National DW Supplemental WHO (1999) No Assessment No7

57636 Ethinyl Estradiol (17-alpha ethynyl estradiol) Non-National DW Supplemental Supplemental Data (1981) No Assessment No

75456 HCFC-22 Non-National DW Supplemental RTECS No Assessment No

110543 Hexane Non-National DW State data RAISHE No Assessment No

72333 Mestranol Non-National DW Supplemental Supplemental Data (1981) No Assessment No

101043372 Microcystin-LR Non-National DW Supplemental Supplemental Data (2006) No Assessment No

68224 Norethindrone (19-Norethisterone) Non-National DW Supplemental Supplemental Data No Assessment No

106990 1,3-Butadiene1 Release TRI OEHHA(CA) (2000) No Assessment No1

109864 2-Methoxyethanol Release TRI RAISHE No Assessment No

107186 2-Propen-1-ol Release TRI IRIS (1986) Available Assessment No

101779 4,4'-Methylenedianiline Release TRI OEHHA(CA) (2001) No Assessment No

60355 Acetamide Release TRI OEHHA(CA) No Assessment No

110429624 Clethodim Use NCFAP OPP RED (2008) Available Assessment No

80159 Cumene hydroperoxide Release TRI RTECS No Assessment No

55290647 Dimethipin Release TRI OPP RED (2005) Available Assessment No

75218 Ethylene oxide Release TRI OEHHA(CA) (2000) No Assessment No

302012 Hydrazine Release TRI IRIS (1989) Available Assessment No

67561 Methanol Release TRI IRIS (1988) Assessment in Process (IRIS) No

55630 Nitroglycerin Release TRI RTECS Available Assessment No

872504 N-Methyl-2-pyrrolidone Release TRI WHO (2001) Available Assessment No

95534 o-Toluidine Release TRI OEHHA(CA) (1997) No Assessment No

75569 Oxirane, methyl- Release TRI OPP RED (2006) Available Assessment No

91225 Quinoline Release TRI IRIS (2001) Available Assessment No

112410238 Tebufenozide Use NCFAP OPP RED (1999) Available Assessment No
April 2014 Page 3 of 3

CASRN Common Name Occurrence Data 

Type

Best Available Occurrence 

Data Source Primary Health Effects Data Source9 Health Assessment Status10 Place on Short List 

for Phase 2

CHEMICALS

Appendix D. Summary of Phase 1: Data Availability

59669260 Thiodicarb Release TRI OPP RED (1998) Available Assessment No

23564058 Thiophanate-methyl Release TRI OPP RED (2004) Available Assessment No

26471625 Toluene diisocyanate Release TRI OEHHA(CA) (2000) No Assessment No

121448 Triethylamine Release TRI RTECS No Assessment No

76879 Triphenyltin hydroxide (TPTH) Release TRI OPP RED (1999) Available Assessment No

51796 Urethane Release TRI Supplemental Data (2005) No Assessment No

14797730 Perchlorate National DW UCMR1 (AM) IRIS (2005) Regulation Determinaton made in Feb 2011 No

Enterovirus5 National DW GWR EA Scientific Literature Available Assessment No5

Adenovirus5 Non-National DW Misc6 Scientific Literature Available Assessment No5,6

Caliciviruses5 Non-National DW Misc6 Scientific Literature Available Assessment No5,6

Legionella pneumophila5 Non-National DW Misc6 Scientific Literature Available Assessment No5,6

Mycobacterium avium5 Non-National DW Misc6 Scientific Literature Available Assessment No5,6

Naegleria fowleri 5 Non-National DW Misc6 Scientific Literature No Assessment No5,6

Campylobacter jejuni No Data Scientific Literature No Assessment No

Escherichia coli (0157) No Data Scientific Literature Available Assessment No

Helicobacter pylori No Data Scientific Literature Available Assessment No

Hepatitis A virus No Data Scientific Literature Available Assessment No

Salmonella enteric No Data Scientific Literature No Assessment No

Shigella sonnei No Data Scientific Literature No Assessment No

Have National DW Data (i.e. UCMR1(AM), UCMR2, UCM1/2, or NIRS) and No Health Assessment 

Have Non-National DW Data (e.g. UCMR1(SS), State Data, DBP-ICR, or supplemental DW and source water data such as PDP, PMP, NREC, and/or targeted surveys or localized state/federal monitoring 

studies) and Available or In Process Health Assessment 

Have Non-National DW Data (e.g. UCMR1(SS), State Data, DBP-ICR, or supplemental DW and source water data such as PDP, PMP, NREC, and/or targeted surveys or localized state/federal monitoring 

studies) and no Health Assessment

Do not have National or Non-National Finished Water Data

Not within scope of CCL RD3 since Regulatory Determination made in February 2011

5

Does not have a widely available analytical method for occurrence monitoring.

4

UCMR 1 SS is a statistically defined, national sample of PWSs. Because this survey only includes 300 systems, the Agency identified and compiled additional supplemental data to compliment the UCMR 1 SS data for 

these contaminants that proceed to the Phase 2 evaluation for further evaluation.

8

Health assessment did not use a standard US EPA methodology (i.e., antibiotic)

LEGEND

Have National DW Data (i.e. UCMR1(AM), UCMR2, UCM1/2, or NIRS) and Available or In Process Health Assessment 

6

Misc - The evaluation of the pathogens utilized miscellaneous reports from CDC and the scientific literature to try to characterize occurrence; see the CCL 3 support documents for details

7

Metabolite of 17-beta estradiol; no independent health assessment is available 

10The "Primary Health Effects Data Source" must have an externally peer-reviewed health assessment from designated EPA source (i.e., IRIS, OPP, or OW) to be considered an "Available Assessment" or an externally peerreviewed health assessment with an oral RfD/Cancer Slope Factor and comparable EPA methods from a designated non-EPA source (i.e., ATSDR, NAS, or WHO) to be considered an "Available Asessment." 

9

A literature search was conducted to determine if any health assessments had been completed from a designated EPA or non-EPA data sources since the publication of the Final CCL 3 Information Sheets in August 2009, if 

not, the health effects data sources compiled during CCL 3 were used as the "Primary Health Effects Data Source" for RD 3

11A designated EPA or non-EPA health assessment has been updated or completed since the publication of the Final CCL 3 Information Sheets (August 2009). 

PATHOGENS

3

Available parent (Carbofuran) assessment does not contain a chronic/subchronic RfD; all tolerances for the parent were cancelled in May 2009; therefore this compound does not proceed to Phase 2.

1

Component of cVOC contaminant group and is being evaluated in another regulatory process

2

Component of contaminant group and will be further evaluated in phase 2
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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Appendix E. Summary of Phase 2: Data Evaluation

Contaminant Profile Summary of Analyses, Results, and Status

(Note: the HRLs used in Phase 2 are draft values and are not final until Regulatory Determinations are complete) 

No. Contaminant/Background Health Effect Findings Initial Occurrence Findings Phase 2 Outcome & Rationale

1. 1,1,1,2-Tetrachloroethane

• CASRN = 630206

• Substance Key = 9105

• A halogenated alkane

• Used as a chemical 

intermediate

Production / Release Data

TRI-Release 2010

• Surface water = 0 lbs/yr (0 

states)

• Total = 3,565 lbs/yr (5 

states)

TRI-Release 2008

• Surface water = 0 lbs/yr (0 

states)

• Total = 2,904 lbs/yr (4 

states)

TRI-Release 2006

• Surface water = 0 lbs/yr (0 

states)

• Total = 4,358 lbs/yr (6 

states)

TRI-Release 2004

• Surface water = 36 lbs/yr (2 

Critical Health Endpoint

• Mineralization of the kidneys 

(male), hepatic clear cell change 

(female) (NTP, 1983)

• LOAEL = 89.3 mg/kg-day

• UF = 3,000

• RfD = 0.03 mg/kg-day

• Non-cancer HRL = 210 μg/L

Health Assessment Status

• IRIS (1987) 

• Possible human carcinogen, group 

C (1986 cancer guidelines)

• IRIS completed a comprehensive 

review of toxicological studies; a 

change to the RfD was not 

warranted (August 2006)

Sensitive Populations/Lifestages

• None identified

Analyzed using HRL of 210 μg/L

National Drinking Water Data 

NCOD/UCM Round 1 Finished Water (1988-1992)

• MRL unavailable (min detect = 0.06 μg/L)

• No detects >1⁄2HRL or >HRL 

• % samples w/ detects = 0.08% (43 of 56,734)

• % PWSs w/ detects = 0.18% (31 of 16,956)

• Median detect = 0.59 μg/L

• 99%ile detect = 8.28 μg/L

• Max detect = 9.2 μg/L

NCOD/UCM Round 2 Finished Water (1993-1997)

• MRL unavailable (min detect = 0.2 μg/L)

• No detects >1⁄2HRL or >HRL 

• % samples w/ detects = 0.07% (70 of 97,950)

• % PWSs w/ detects = 0.21% (51 of 24,127)

• Median detect = 0.5 μg/L

• 99%ile detect = 7.58 μg/L

• Max detect = 18.0 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1983-2009)

• No detects >1⁄2HRL or >HRL

• % systems w/ detects = 

Referred to CVOC for evaluation. 

After evaluation of group 

information, EPA will decide 

whether to include in CVOC group 

and evaluate for regulatory 

determination. 
Phase 2 of Protocol for Regulatory Determination 3 April 2014 2 of 84

states)

• Total = 12,088 lbs/yr (7 

states)

CUSIUR Production Data • >1M-10M lbs/yr (1998, 

2002)

Fate / Transport • Physical and chemical 

properties give contrary 

indications about expected 

mobility in water 

• Persistent in the 

environment (biodegrades 

sometimes/recalcitrant); 

BST is the highest category 

available to be awarded to a 

recalcitrant contaminant (CCL CIS) 

o CA: 0.15% (6 of 4,037) o FL: 3.70% (1 of 27) o IL: Not detected from 2 systems o NC: 0.52% (13 of 2,493) o OH: 0.04% (1 of 2,533) o R9 Tribes: Not detected from 285 systems o SD: Not detected from 281 systems o TX: Not detected from 5,660 systems o WI ’83-’99: Not detected from 1,929 systems o WI ’00-’09: Not detected from 1,120 systems 

Supplemental Drinking Water Data 

Recent CCRs from 26 CWSs that serve >1M (2006-2007)

• Not detected in 4 CWSs in NY

EWG (2004-2009)

• 18 PWSs from 11 states w/ detects, no detects >1⁄2HRL or >HRL

Supplemental Ambient/Source Water Data 

NAWQA Ambient Water (1992-2001)

• MRLs variable (0.03 - 0.2 μg/L) • No SW detects in 1,397 samples from 182 sites • No GW detects >1⁄2HRL or >HRL • % GW samples w/ detects = 0.09% (4 of 4,543) • % GW sites w/ detects = 0.10% (4 of 4,127) • Median detect = 0.0275 μg/L • 99%ile detect = 0.0644 μg/L • Max detect = 0.0644 μg/L

STORET • MRL unavailable (min detect = 0 μg/L

1

)

• Data from 19 states • No detects >1⁄2HRL or >HRL
Phase 2 of Protocol for Regulatory Determination 3 April 2014

3 of 84

• % GW samples w/ detects = 43.67% (1,135 of 2,599)

• % SW samples w/ detects = 39.46% (264 of 669)

• % GW sites w/ detects = 37.31% (400 of 1,072)

• % SW sites w/ detects = 14.18% (20 of 141)

• Median detect = 0 μg/L

• 90%ile detect = 0.5 μg/L

• Max detect = 42 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA Domestic Well Water Quality (1991-2004)

• Not detected in 2,268 samples 

NAWQA National Focused and Historic VOC Study (1985-2001)

• No detections at reporting level of 0.2 μg/L

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.015 - 0.2 μg/L

• No detects >1⁄2HRL or >HRL

• % samples w/ detects = 0.36% (3 of 832)

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• Not detected 

NAWQA Carbonate Aquifer Study (1993-2005)

• Not detected in 793 samples

USGS VOCs in Highway Runoff 

• Not detected

Occurrence summary and/or other information:

• Low percentage of detects in UCM1/2 as well as more recent state 

and ambient water data

2. 1,2,3-Trichloropropane

• CASRN = 96184

• Substance Key = 3817

Critical Health Endpoint

• Cancer (multi-site tumors) (NTP, 

1993)

Analyzed using HRL of 0.0004 μg/L

Referred to CVOC for evaluation. 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

4 of 84

• A halogenated alkane

• Chemical intermediate, also 

has been used as a paint 

and varnish remover, 

solvent, and degreasing 

agent

Production / Release Data

TRI-Release 2010

• Surface water = 369 lbs/yr 

(1 state)

• Total = 3,503 lbs/yr (3 

states)

TRI-Release 2008

• Surface water = 187 lbs/yr 

(1 state)

• Total = 1,557 lbs/yr (3 

states)

TRI-Release 2006

• Surface water = 416 lbs/yr 

(1 state)

• Total = 2,025 lbs/yr (3 

states)

TRI-Release 2004

• Surface water = 282 lbs/yr 

(1 state)

• Total = 9,053 lbs/yr (2 

states)

CUSIUR Production Data

• >10M-50M lbs/yr (1998)

• >1M-10M lbs/yr (2002)

• CSF = 30 (mg/kg-day)-1

• Cancer HRL = 0.0004 μg/L (with 

ADAF)

Non-Cancer Health Effect

• Increased absolute liver weight in 

male rats (NTP, 1993)

• UF = 300

• RfD = 0.004 mg/kg-day

• Non-cancer HRL = 30 μg/L

Health Assessment Status

• Updated since CCL3

o IRIS (2009)

Sensitive Populations/Lifestages

• Fetuses/infants/children

• Individuals with liver or kidney 

problems

National Drinking Water Data 

NCOD/UCM Round 1 Finished Water (1988-1992)

• MRL unavailable (min detect = 0.10 μg/L)

• All detects >1⁄2HRL and >HRL

• % samples w/ detects >HRL = 0.13% (76 of 57,205)

• % PWSs w/ detects >HRL = 0.25% (44 of 17,392)

• Median detect = 0.92 μg/L

• 99%ile detect = 90.1 μg/L

• Max detect = 112 μg/L

NCOD/UCM Round 2 Finished Water (1993-1997)

• MRL unavailable (min detect = 0.03 μg/L)

• All detects >1⁄2HRL and >HRL

• % samples w/ detects >HRL = 0.02% (23 of 97,955)

• % PWSs w/ detects >HRL = 0.08% (19 of 24,088)

• Median detect = 0.5 μg/L

• 99%ile detect = 2,347 μg/L

• Max detect = 3,000 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1983-2009)

• All detects >1⁄2HRL and >HRL

• % systems w/ detects >HRL = 

o CA: 3.99% (157 of 3,939)

o FL: 3.70% (1 of 27)

o IL: 66.67% (4 of 6)

o NC: 0.20% (5 of 2,493)

o OH: 0.04% (1 of 2,532)

o R9 Tribes: 0.72% (2 of 279)

o SD: 0.36% (1 of 281)

o TX: 0.09% (5 of 5,660)

o WI ’83-’99: 0.60% (11 of 1,826)

o WI ’00-’09: 0.09% (1 of 1,123)

After evaluation of group 

information, EPA will decide 

whether to include in CVOC group 

and evaluate for regulatory 

determination. 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

5 of 84

• 500k – <1 M lbs/yr (2006)

Fate / Transport

• Expected to be mobile in 

water and soil, based on 

physical and chemical 

properties

• Biodegradation is not 

expected to be significant. 

Expected to volatilize from 

surface water and from wet 

and dry soils.

Supplemental Drinking Water Data 

Recent CCRs from 26 CWSs that serve >1M (2006-2007)

• Detected in 1 CWS; max detect = 2.2 μg/L, >HRL

CWSS (2006)

• % PWSs w/ detects = 1.1% (1 of 94); max detect = 400 μg/L, >HRL

EWG (2004-2009) 

• At least 130 PWSs from 11 states w/ detects >HRL

NJDEP (1999-2004)

• Exceedances of health-based drinking water guidance value 

(presumably 0.005 μg/L):

o At 1.1% of private wells (30 of 2,640)

o At 4.2% of CWSs (11 of 260)

Supplemental Ambient/Source Water Data 

NAWQA Ambient Water (1992-2001)

• MRLs variable (most within 0.07 – 0.2 μg/L)

• All GW and SW detects >1⁄2HRL and >HRL

• % GW samples w/ detects >HRL = 1.06% (48 of 4,544)

• % SW samples w/ detects >HRL = 0.43% (6 of 1,397)

• % GW sites w/ detects >HRL = 0.97% (40 of 4,127)

• % SW sites w/ detects >HRL = 1.65% (3 of 182)

• Median detect = 0.4 μg/L

• 99%ile detect = 2.92 μg/L

• Max detect = 2.92 μg/L

STORET

• MRL unavailable (min detect = 0 μg/L1

)

• Data from 19 states

• All SW detects >1⁄2HRL and >HRL 

• % GW samples w/ detects = 57.26% (1,850 of 3,231)
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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• % GW samples w/ detects >1⁄2 HRL = 1.18% (38 of 3,231)

• % GW samples w/ detects >HRL = 1.18% (38 of 3,231)

• % SW samples w/ detects >HRL = 38.19% (241of 631)

• % GW sites w/ detects = 42.38% (448 of 1,057)

• % GW sites w/ detects >1⁄2 HRL = 3.31% (35 of 1,057)

• % GW sites w/ detects >HRL = 3.31% (35 of 1,057)

• % SW sites w/ detects >HRL = 14.93% (20 of 134)

• Median detect = 0 μg/L

• 90%ile detect = 0.2 μg/L

• Max detect = 10 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA National Focused and Historic VOC Study (1985-2001)

• MRL = 0.2 μg/L

• Random Survey (1999-2001): detected in 0.1% of CWSs (1 of 954); 

max conc. = 0.31 μg/L, >HRL

• Focused Survey (1999-2001): at 134 CWSs; max conc. = 0.09 μg/L, 

>HRL

• Historical Monitoring (1985-1995): At 264 urban wells, max conc. = 

1.1 μg/L (>HRL); at 1,729 rural wells; max conc. = 0.2 μg/L; >HRL

NAWQA Rural and Domestic Wells (1986-1999)

• MRL = 0.2 μg/L

• % samples w/ detects = 0.6% (10 of 1,615); max detect = 2.1 μg/L, 

>HRL

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.06 - 0.2 μg/L

• All detects >HRL

• % samples w/ detects >HRL = 1.20% (10 of 832)

Occurrence summary and/or other information:

• High degree of uncertainty in national data (UCM1/2); all detections 

are 250 times higher than HRL due to detection limit; likely more 

occurrence >HRL that is undetected

• Some recent state (e.g. CA) data indicate that it is potentially 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

7 of 84

occurring at “levels and frequencies of public health concern” with 

improved but varying analytical method/detection limits

• CA has large data set, most sensitive analytical method of state 

data and has 4% of systems with detections >HRL. Although 

improved, detection limit for CA is higher than HRL and CA likely 

has more occurrence >HRL that is undetected.

• Release to the environment has increased from 2004 to 2006 

although production has decreased from 1998 to 2002. 

• Being considered as part of the carcinogenic Volatile Organic 

Compounds (CVOCs) group regulatory effort. 

• On UCMR 3

3. 1,3-Dinitrobenzene

• CASRN = 99650

• Substance Key = 4045

• A nitrated aromatic 

compound

• Used as an industrial 

chemical

Production / Release Data

TRI-Release 2010

• Surface water = 0 lbs/yr (0 

states)

• Total = 10,595 lbs/yr (1 

state)

TRI-Release 2008

• Surface water = 2 lbs/yr (1 

state)

• Total = 19,858 lbs/yr (1 

state)

TRI-Release 2006

• Surface water = 0 lbs/yr (0 

states)

Critical Health Endpoint

• Increased spleen weight (Cody et 

al., 1981) 

• NOAEL = 0.4 mg/kg-day

• UF = 3,000

• RfD = 0.0001 mg/kg-day

• Non-cancer HRL = 0.7 μg/L 

Health Assessment Status

• Update not needed (no additional 

information) 

o IRIS (1988); completed a 

comprehensive review of 

toxicological studies; a change 

to the RfD was not warranted 

(May 2005)

o Not classifiable as to human 

carcinogenicity, group D (1986 

cancer guidelines)

o The ATSDR (1995) assessment 

is consistent

Sensitive Populations/Lifestages

• Individuals with genetic 

predisposition to 

methemoglobinemia and/or iron 

Analyzed using HRL of 0.7 μg/L

National Drinking Water Data

UCMR 2 Finished Water Assessment Monitoring (2008-2010)

• MRL = 0.8 μg/L

• Not detected in 32,017 samples from 4,137 PWSs

Supplementary Ambient/Source Water Data

STORET

• MRL unavailable (min detect = 0 μg/L1)

• Data from 2 states

• No GW detects in 48 samples from 17 sites

• No SW detects >1⁄2HRL or >HRL

• % SW samples w/ detects = 100% (95 of 95)

• % SW sites w/ detects = 100% (53 of 53)

• Median detect = 0.04 μg/L

• 90%ile detect = 0.31 μg/L

• Max detect = 0.33 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

Occurrence summary and/or additional information:

Proceeds to phase 3

Rationale: 

The contaminant has no or low 

potential of public health concern 

and does not have critical health or 

occurrence data gaps

Health:

Available health assessment; an 

update will not be needed

Occurrence:

No detections in national finished water

data 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

8 of 84

• Total = 17,745 lbs/yr (1 

state)

TRI-Release 2004

• Surface water = 2 lbs/yr (1 

state)

• Total = 528,962 lbs/yr (1 

state)

_______________________

Fate / Transport

• Expected to be moderately 

to highly mobile in water, 

based on physical and 

chemical properties

• Moderately persistent in the 

environment (biodegrades 

slowly with acclimation) 

(CCL CIS)

disorders, neonates, and those coexposed to other hemolytic agents

• Males having sperm production 

complications 

• No detections in recent national data (UCMR 2); minimal uncertainty 

because detection limit slightly higher than HRL

• Total releases and releases to surface water have decreased from 

2004 to 2006

4. 1,4-Dioxane

• CASRN = 123911

• Substance Key = 5539

• A cyclic aliphatic ether

• Commonly used as a 

solvent or solvent stabilizer 

in the manufacture and 

processing of paper, cotton, 

textile products, automotive 

coolant, cosmetics, and 

shampoos

• A disinfect byproduct

Production / Release Data

TRI-Release 2010

• Surface water = 23,007

Critical Health Endpoint

• Liver adenomas and carcinomas

(Kano et al., 2009)

• CSF = 0.10 (mg/kg-day)-1

• Cancer HRL = 0.4 μg/L

Non-Cancer Health Effect

• Liver and kidney toxicity (Kociba et 

al., 1974)

• NOAEL = 9.6 mg/kg-day

• UF = 300

• Chronic RfD = 0.03 mg/kg-day

• Non-cancer HRL = 210 μg/L

Health Assessment Status

• Updated since CCL3 

o IRIS (2010) 

Analyzed using HRL of 0.4 μg/L

Non-National Drinking Water Data 

State Drinking Water Data (2001-2007)

• % systems w/ detects =

o CA: 11.01% (24 of 218)

• % systems w/ detects >1⁄2HRL = 

o CA: 11.01% (24 of 218)

• % systems w/ detects >HRL = 

o CA: 10.55% (23 of 218)

Supplemental Drinking Water Data 

Recent CCRs from 26 CWSs that serve >1M (2007)

• Detected in 1 CWS; max detect = 3.0 μg/L, >HRL

Does not proceed to phase 3

Rationale: 

The contaminant has occurrence 

data gaps.

Health: 

Available health assessment

Occurrence:

Does not have national finished water 

data or sufficient non-national finished 

water data 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

9 of 84

lbs/yr (7 states)

• Total = 629,754 lbs/yr (16

states)

TRI-Release 2008

• Surface water = 41,014

lbs/yr (7 states)

• Total = 203,798 lbs/yr (20 

states)

TRI-Release 2006

• Surface water = 

49,035lbs/yr (8 states)

• Total = 316,133 lbs/yr (19 

states)

TRI-Release 2004

• Surface water = 89,521 

lbs/yr (7 states)

• Total = 821,067 lbs/yr (22 

states)

CUSIUR Production Data

• >1M-10M lbs/yr (1998, 

2002)

• 1 M – < 10 M lbs/yr (2006)

Fate / Transport

• Expected to be moderately 

to highly mobile in water, 

based on physical and 

chemical properties

• Moderately persistent in the 

environment (biodegrades 

slowly) (CCL CIS) 

• 

Sensitive Populations/Lifestages

• Individuals with compromised liver 

and kidney function

• Children 

CWSS (2006)

• % samples w/ detects = 68% (17 of 25); max detect = 2.2 μg/L, 

>HRL

EWG (2004-2009) 

• At least 14 PWSs from 3 states w/ detects >HRL

Occurrence summary and/or other information:

• CA has detections >HRL, but it is a limited data set with ~200 

systems

• On UCMR 3
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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5. Acephate

• CASRN = 30560191

• Substance Key = 31325

• Organic phosphoramide 

pesticide 

• Used as an insecticide 

Production / Release Data

OPP Estimated Environmental 

Concentrations

• Surface water chronic = 7.2

μg/L

• Ground water chronic = 0.02

μg/L 

TRI-Release 2010

• Surface water = 0 lbs/yr (0 

states)

• Total = 5,816 lbs/yr (2 

states)

TRI-Release 2008

• Surface water = 0 lbs/yr (0 

states)

• Total = 1,919 lbs/yr (3 

states)

TRI-Release 2006

• Surface water = 250 lbs/yr 

(1 state)

• Total = 25,608 lbs/yr (5 

states)

Critical Health Endpoint

• Brain Cholinesterase inhibition

(Chevron Chemical Company, 

1982)

• NOAEL = 0.12 mg/kg-day

• UF = 100

• RfD = 0.0012 mg/kg-day

• Non-cancer HRL = 8.4 μg/L

Health Assessment Status

• Possible human carcinogen, group 

C (1986 cancer guidelines)

• OPP RED (2006)

Sensitive Populations/Lifestages

• None identified

Analyzed using HRL of 8.4 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1998-2004)

• Max detect = 6 μg/L, >1⁄2HRL

• % systems w/ detects = 

o CA: 50.0% (2 of 4)

Does not proceed to phase 3

Rationale: 

The contaminant has occurrence 

data gaps.

Health: 

Available health assessment

Occurrence:

Does not have national finished water 

data or sufficient non-national finished 

water data 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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TRI-Release 2004

• Surface water = 0 lbs/yr (0 

states)

• Total = 20,789 lbs/yr (5 

states)

NCFAP Total Pesticide 

Application 1997

• 2.5M lbs/yr (35 states)

Pesticide Industry Sales and 

Usage Report

• 1999: 2M-3M lbs

• 2001: 2M-3M lbs

• 2005: 4M-6M lbs 

• 2007: 4M-6M lbs

RED 2006

• 4M-5M lbs of acephate

active ingredient used 

annually

Fate / Transport

• Expected to be highly 

mobile in soils (HSDB)

• Particulate acephate is 

removed by atmospheric 

deposition (HSDB)

• Not expected to volatilize 

from wet or dry soils 

(HSDB)

6. Acetochlor

• CASRN = 34256821

• Substance Key = 32393

• An acetanilide pesticide

Critical Health Endpoint

• Lung tumors (Brunsman, 2004)

• CSF = 0.0327 (mg/kg-day)-1

• Cancer HRL = 1 μg/L

Analyzed using HRL of 1 μg/L

National Drinking Water Data

Does not proceed to phase 3

Rationale: 

While acetochlor likely has no or 

low potential for public health 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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• Used as an herbicide for 

pre-emergence control of 

weeds

• Registered for use on field 

corn and popcorn. First 

registered in 1994

• Corn fields treated with 

acetochlor may later be 

rotated to grain sorghum 

(milo), soybeans, wheat, 

and tobacco, according to 

the currently registered use 

pattern

Production / Release Data

NCFAP Total Pesticide 

Application 1997

• 32,591,175 lbs/yr (35 

states)

Pesticide Industry Sales and 

Usage Report

• 1997: 31M-36M lbs

• 1999: 30M-35M lbs

• 2001: 30M-35M lbs

• 2005: 26M-31M lbs

• 2007: 28M – 33M lbs

Fate / Transport

• Expected to be moderately 

to highly mobile in soils 

(HSDB)

• Degrades faster in warmer 

and moister soils, primarily 

Non-Cancer Health Effect

• Histopathology (testes, kidney, and 

liver), increased alanine 

aminotransferase (ICI, Inc., 1988)

• NOAEL = 2 mg/kg-day

• UF = 100

• RfD = 0.02 mg/kg-day

• Non-cancer HRL = 140 μg/L

Health Assessment Status

• Updated since CCL3

o OPP TRED (2006)-cancer

• IRIS (1992) – Non-cancer

Sensitive Populations/Lifestages

• None identified

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 2 μg/L

• Not detected in 11,138 samples from 1,198 PWSs

UCMR 1 Finished Water Assessment Monitoring (2001-2003)

• MRL = 2 μg/L

• Not detected in 33,778 samples from 3,869 PWSs

Non-National Drinking Water Data

State Drinking Water Data (1999-2007)

• All detects >1⁄2HRL and >HRL

• % systems w/ detects >HRL = 

o IL: 0.11% (1 of 897)

o CA: Not detected from 279 systems

o OH: Not detected from 26 systems

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2006-2007)

• Not detected in 3 CWSs in NY

EWG (2004-2009)

• 2 PWSs from 2 states w/ detects >HRL

PDP Raw and Finished Water (2001-2009)

• Max detect in finished water = 0.357 μg/L, <1⁄2HRL

• Max detect in raw water = 0.669 μg/L, >1⁄2HRL

• % samples w/ detects = 4.25% (224 of 5,272); no detects >HRL 

PMP Raw Water (1999)

• No max detects >HRL in 323 samples

PMP Finished Water (1999)

concern based on national finished 

water data, it might be considered 

as a group along with other 

chloroacetanilides and/or their 

degradates in the future. And at this 

time, the Agency does not have a 

health assessment for the 

degradates (i.e., a health data gap).

Health: 

Health assessments for the degradates 

will not be completed by Fall 2011

Occurrence:

No detections for Acetochlor (parent) in 

national finished water data 
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through microbial activity • No max detects >HRL in 228 samples

Wisconsin GW Study (1999-2000)

• % monitoring wells w/ detects = 3.7% (1 of 27); avg. detect = 1.2 

μg/L, >HRL

Iowa Well Water Study (2006-2008)

• % samples w/ detects = 1% (1 of 469); no detects >1⁄2HRL or >HRL

Supplemental Ambient/Source Water Data 

NAWQA Ambient Water (1992-2001)

• MRLs variable (0.001 – 0.004 μg/L)

• No GW detects >1⁄2HRL or >HRL 

• % GW samples w/ detects = 0.31% (14 of 4,556)

• % SW samples w/ detects = 15.85% (1,950 of 12,306)

• % SW samples w/ detects >1⁄2HRL = 1.99% (245 of 12,306)

• % SW samples w/ detects >HRL = 1.40% (172 of 12,306)

• % GW sites w/ detects = 0.35% (14 of 4,023)

• % SW sites w/ detects = 17.53% (264 of 1,506)

• % SW sites w/ detects >1⁄2HRL = 5.05% (76 of 1,506)

• % SW sites w/ detects >HRL = 4.25% (64 of 1,506)

• Median detect = 0.032 μg/L

• 99%ile detect = 8.49 μg/L

• Max detect = 30.4 μg/L

STORET

• MRL unavailable (min detect = 0 μg/L1

)

• Data from 17 states

• % GW samples w/ detects = 0.93% (18 of 1,927)

• % GW samples w/ detects >1⁄2HRL = 0.36% (7 of 1,927)

• % GW samples w/ detects >HRL = 0.26% (5 of 1,927)

• % SW samples w/ detects = 20.20% (5,740 of 28,411)

• % SW samples w/ detects >1⁄2HRL = 4.78% (1,357 of 28,411)

• % SW samples w/ detects >HRL = 2.62% (744 of 28,411)
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• % GW sites w/ detects = 2.17% (9 of 415)

• % GW sites w/ detects >1⁄2HRL = 0.24% (1 of 415)

• % GW sites w/ detects >HRL = 0.24% (1 of 415)

• % SW sites w/ detects = 52.49% (833 of 1,587)

• % SW sites w/ detects >1⁄2HRL = 22.94% (364 of 1,587)

• % SW sites w/ detects >HRL = 15.88% (252 of 1,587)

• Median detect = 0.18 μg/L

• 90%ile detect = 1.4 μg/L

• Max detect = 117.80 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA Domestic Well Water Quality (1991-2004): 

• % samples w/ detects = 0.1% (2 of 2,046); no detects >1⁄2HRL or 

>HRL

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.002 - 0.003 μg/L

• No detects >1⁄2HRL or >HRL 

• % samples w/ detects = 0.25% (2 of 800)

NAWQA National Synthesis (1992-2001)

• MRL = 0.001 - 0.003 μg/L

• GW: no max detects >1⁄2HRL or >HRL

• SW: max detect from mixed land use sites (1.66 μg/L) and 

agricultural sites (10.6 μg/L) >HRL

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• Detects >HRL in Phase 1

o Phase 1 % GW detects = 0.5% (1 of 221); max detect = 0.037 

μg/L

o Phase 1 % SW detects = 12.3% (18 of 146); max detect = 4.32 

μg/L, >HRL

o Phase 2 % GW detects = 0.00% (0 of 51)

o Phase 2 % SWraw detects = 16.0% (14 of 90)

o Phase 2 % SWfinished detects = 11.0% (10 of 87)
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Acetochlor Registration Partnership (1995-2001)

• % wells w/ detects in GW study = 0.08% (14 of 175); max detect = 

4.35 μg/L, >HRL

• Max detect of 175 sites in SW study = 18.2 μg/L, >HRL

• Max annualized mean conc. of 175 sites in SW study = 1.43 μg/L, 

>HRL

CDC Fourth National Report (2003-2004)

• 95%iles <LOD in 2,501 urine samples

Occurrence summary and/or other information:

• No detections in recent national data (UCMR 2); Acetochlor (parent) 

is potentially not occurring at levels of public health concern

• Frequent detections in ambient water with some detections >HRL

• Acetochlor and other chloroacetanilides may be considered as a 

group

7. Acetochlor ethanesulfonic 

acid (ESA)

• CASRN = 187022113

• Substance Key = 79191

• An acetanilide pesticide 

degradate 

• See also parent compound

Production / Release Data

No data for production and 

release

Fate / Transport

• In water, acetochlor ESA 

mobility > acetochlor OA 

mobility > acetochlor 

mobility 

Critical Health Endpoint

• Parent (Acetochlor) is surrogate 

• Lung tumors (Brunsman, 2004)

• CSF = 0.0327 (mg/kg-day)-1

• Cancer HRL = 1 μg/L

Non-Cancer Health Effect

• Supplemental OPP data

• Decreased body weights, 

decreased body weight gains, and 

decreased food utilization (Lees 

2000)

• NOAEL = 230 mg/kg-day

• UF = 1,000

• RfD = 0.23 mg/kg-day

• Non-cancer HRL = 161 μg/L

Health Assessment Status

• Parent compound [OPP TRED 

2006]

Analyzed using HRL of 1 μg/L

National Drinking Water Data

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 1 μg/L

• All detects >HRL 

• % samples w/ detects >HRL = 0.02% (2 of 11,100)

• % PWSs w/ detects >HRL = 0.17% (2 of 1,198)

• Median detect = 1.15 μg/L

• 99%ile detect = 1.2 μg/L

• Max detect = 1.2 μg/L

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Not detected in 1 CWS in NY

Does not proceed to phase 3

Rationale: 

While acetochlor ESA has no or low 

detections based on national 

finished water data, there is no 

health assessment for the ESA 

degradate and it difficult to assess 

whether it is occurring at levels of 

concern. Also, acetochlor ESA 

might be considered as a group 

along with other chloroacetanilides 

and/or their degradates in the 

future. 

Health: 

Health assessment for Acetochlor ESA 

(degradate) will not be completed by 

Fall 2011
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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• Subject to microbial 

degradation, though more 

stable than parent 

compound 

Sensitive Populations/Lifestages

• None identified

PDP Raw and Finished Water (2001-2009)

• Max detect in finished water = 1.2 μg/L, >HRL

• Max detect in raw water = 1.9 μg/L, >HRL

• % samples w/ detects = 28.32% (1,260 of 4,449)

Wisconsin GW Study (1999-2000)

• Avg. detect in 27 monitoring wells = 2.9 μg/L, >HRL

• Avg. detect in 22 private drinking water wells = 1.8 μg/L, >HRL

Iowa Well Water Study (2006-2008)

• % samples w/ detects = 11% (53 of 472); max detect = 1.20 μg/L, 

>HRL

Supplemental Ambient/Source Water Data

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• Detects >HRL in Phase 1 

o Phase 1 % GW detects = 1.4% (1 of 73); max detect = 0.07 μg/L, 

no detects >1⁄2HRL or >HRL

o Phase 1 % SW detects = 41.0% (16 of 39); max detect = 1.42 

μg/L, >HRL

o Phase 2 % GWraw detects = 19.0% (6 of 32); max detect = 0.77 

μg/L, >1⁄2HRL

o Phase 2 % GWfinished detects = 19.0% (6 of 32); max detect = 0.8 

μg/L, >1⁄2HRL

o Phase 2 % SWraw detects = 25.0% (12 of 49); max detect = 0.40 

μg/L, no detects >1⁄2HRL or >HRL

o Phase 2 % SWfinished detects = 27.0% (13 of 48); max detect = 

0.31 μg/L, no detects >1⁄2HRL or >HRL

Acetochlor Registration Partnership (1999-2001)

• % wells w/ detects in GW study = 46.29% (81 of 175); max detect = 

20 μg/L, >HRL

• Max detect of 175 sites in SW study = 3.32 μg/L, >HRL

• Max annualized mean conc. of 175 sites in SW study = 1.01 μg/L, 

>HRL

Occurrence:

Two detections for Acetochlor ESA 

(degradate) in national finished water 

data 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

17 of 84

Occurrence summary and/or other information:

• Two detections in national data (UCMR 2); All detections for 

Acetochlor ESA in UCMR 2 are ≥ to parent (Acetochlor) HRL due to 

detection limit 

• Supplemental drinking water and ambient water data demonstrate 

some detections of Acetochlor ESA > parent (Acetochlor) HRL

8. Acetochlor oxanilic acid 

(OA)

• CASRN = 194992444

• Substance Key = 79193

• An acetanilide pesticide 

degradate 

• See also parent compound

Production / Release Data

No data for production and 

release

Fate / Transport

• In water, acetochlor ESA 

mobility > acetochlor OA 

mobility > acetochlor 

mobility 

• Subject to microbial 

degradation, though more 

stable than parent 

compound 

Critical Health Endpoint

• Parent (Acetochlor) is surrogate 

• Lung tumors (Brunsman, 2004)

• CSF = 0.0327 (mg/kg-day)-1

• Cancer HRL = 1 μg/L

Non-Cancer Health Effect

• Supplemental OPP data

• Decreased body weights, 

decreased body weight gains, and 

decreased food utilization (Williams 

2000)

• NOAEL = 230 mg/kg-day

• UF = 1,000

• RfD = 0.23 mg/kg-day

• Non-cancer HRL = 161 μg/L

Health Assessment Status

• Parent compound [OPP TRED 

2006]

Sensitive Populations/Lifestages

• None identified

Analyzed using HRL of 1 μg/L

National Drinking Water Data

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 2 μg/L

• Not detected in 11,100 samples from 1,198 PWSs

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Not detected in 1 CWS in NY

PDP Raw and Finished Water (2001-2009)

• Max detect in finished water = 1.3 μg/L, >HRL

• Max detect in raw water = 1.9 μg/L, >HRL

• % samples w/ detects = 24.09% (1,199 of 4,976)

Wisconsin GW Study (1999-2000)

• Avg. detect in 27 monitoring wells = 0.94 μg/L, >1⁄2HRL

• Avg. detect in 22 drinking water wells = 1.1 μg/L, >HRL

Iowa Well Water Study (2006-2008)

• % samples w/ detects = 1% (6 of 472); max detect = 0.150 μg/L, no 

detects >1⁄2HRL or >HRL

Supplemental Ambient/Source Water Data

Does not proceed to phase 3

Rationale: 

While acetochlor OA has no or low 

detections based on national 

finished water data, there is no 

health assessment for the OA 

degradate and it difficult to assess 

whether it is occurring at levels of 

concern. Also, acetochlor OA might 

be considered as a group along with 

other chloroacetanilides and/or their 

degradates in the future. 

Health: 

Health assessment for Acetochlor OA 

(degradate) will not be completed by 

Fall 2011

Occurrence:

No detections for Acetochlor OA 

(degradate) in national finished water 

data 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

18 of 84

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• Detects >HRL in Phase 1 

o Phase 1 % GW detects = 1.4% (1 of 73); max detect = 0.12 μg/L

o Phase 1 % SW detects = 38.5% (15 of 39); max detect = 1.74 

μg/L, >HRL

o Phase 2 % GWraw detects = 9.4% (3 of 32); max detect = 0.41 

μg/L 

o Phase 2 % GWfinished detects = 19% (6 of 32); max detect = 0.53 

μg/L

o Phase 2 % SWraw detects = 32% (16 of 49); max detect = 0.65 

μg/L

o Phase 2 % SWfinished detects = 25% (12 of 48); max detect = 0.40 

μg/L

Acetochlor Registration Partnership (1999-2001)

• % wells w/ detects in GW study = 14.86% (26 of 175); max detect = 

19.1 μg/L, >HRL

• Max detect of 175 sites in SW study = 6.34 μg/L, >HRL

• Max annualized mean conc. of 175 sites in SW study = 1.69 μg/L, 

>HRL

Occurrence summary and/or other information:

• No detections in national data (UCMR 2); All detections in UCMR 2 

are > parent (Acetochlor) HRL due to detection limit 

• Supplemental drinking water and ambient water data demonstrate 

some detections for Acetochlor OA > parent (Acetochlor) HRL 

9. Alachlor ethanesulfonic acid 

(ESA)

• CASRN = 142363539

• Substance Key = 71246

• An acetanilide pesticide 

degradate

Production / Release Data

TRI-Release 2010 (alachlor)

• Surface water = 9 lbs/yr (1 

Critical Health Endpoint

• Using parent (Alachlor) as a 

surrogate 

• CSF = 0.08 (mg/kg-day)-1

• Cancer HRL = 0.4 μg/L 

Non-Cancer Health Effect

• Supplemental OPP data

• Decreased body weight 

• Supplemental NOEL = 157 mg/kgday

• UF = 1,000

Analyzed using HRL of 0.4 μg/L

National Drinking Water Data

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 1 μg/L

• All detects >HRL 

• % samples w/ detects >HRL= 0.05% (5 of 11,099)

• % PWSs w/ detects >HRL= 0.25% (3 of 1,198)

• Median detect = 1.20 μg/L

• 99%ile detect = 1.30 μg/L

Does not proceed to phase 3

Rationale: 

While alachlor ESA has no or low 

detections based on national 

finished water data, there is no 

health assessment for the ESA 

degradate and it difficult to assess 

whether it is occurring at levels of 

concern. Also, alachlor ESA might 

be considered as a group along with 

other chloroacetanilides and/or their 

degradates in the future. 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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state)

• Total = 182 lbs/yr (2 states)

TRI-Release 2008 (alachlor)

• Surface water = 9 lbs/yr (1 

state)

• Total = 368 lbs/yr (2 states)

TRI-Release 2006 (alachlor)

• Surface water = 12 lbs/yr (1 

state)

• Total = 274 lbs/yr (1 state)

TRI-Release 2004 (alachlor)

• Surface water = 9 lbs/yr (1 

state)

• Total = 1,522 lbs/yr (3 

states)

NCFAP Total Pesticide 

Application 1997

• 15M lbs/yr (47 states) 

(alachlor)

Pesticide Industry Sales and 

Usage Report 

• 1987: 55M-60M lbs 

(alachlor)

• 1997: 13M-16M lbs 

(alachlor)

• 1999: 7M-10M lbs (alachlor)

• 2001: 6M-9M lbs (alachlor)

RED 1998

• 29.3M-44.6M lbs of alachlor 

active ingredient were used 

annually 1993-1995

• RfD = 0.16 mg/kg-day

• Non-cancer HRL = 1,100 μg/L

Health Assessment Status

• Parent compound [OPP RED 1998]

Sensitive Populations/Lifestages

• None identified

Alachlor, the parent compound, is 

already regulated with an MCL of 2 

μg/L

• Max detect = 1.30 μg/L

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Detected in 1 CWS; max detect = 0.58 μg/L, >HRL

CWSS (2006)

• Detected in 1 sample; max detect = 0.35 μg/L, >1⁄2HRL

PDP Raw and Finished Water (2001-2009)

• Max detect in finished water = 1.443 μg/L, >HRL

• Max detect in raw water = 1.037 μg/L, >HRL

• % samples w/ detects = 36.81% (1,708 of 4,640)

6-year Review – ICR [Alachlor parent] (1998-2005)

• % systems w/ detects of parent compound = 0.33% (of approx. 

37,000); max detect = 14 μg/L, >HRL

National Pesticide Survey (1988-1990)

• MRL = 0.50 μg/L

• Parent compound not detected in samples from 566 CWS wells and 

783 rural domestic wells

Iowa Well Water Study (2006-2008)

• % samples w/ detects = 27% (126 of 472); 75%ile and maximum 

detect >HRL

Wisconsin GW Study (1993)

• % samples w/ detects = 70.0% (205 of 293); max detect = 26.7 

μg/L, >HRL

Supplemental Ambient/Source Water Data

NAWQA Ambient Water [Alachlor parent] (1992-2001)

Health: 

Health assessment for Alachlor ESA 

(degradate) will not be completed by 

Fall 2011

Occurrence:

No detections for Alachlor ESA 

(degradate) in national finished water 

data
Phase 2 of Protocol for Regulatory Determination 3 April 2014

20 of 84

Fate / Transport

• Very mobile in soils; ten 

times more soluble than 

alachlor in water. 

• Subject to microbial 

degradation, though more 

stable than parent 

compound 

• MRLs variable (0.0012 – 0.003 μg/L)

• % sites w/ detects = 7.93% (568 of 7,166) 

• Max detect = 38.2 μg/L, >HRL

USGS Study in 12 Midwestern states (1991-1994)

• % samples w/ detects = 46% (of 153 wells); max detect = 8.6 μg/L, 

>HRL

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• Detects >HRL

o Phase 1 % GW detects = 34.5% (20 of 58); max detect = 0.64 

μg/L. >HRL

o Phase 1 % SW detects = 59.0% (23 of 39); max detect = 0.24 

μg/L 

o Phase 2 % GWraw detects = 77.0% (13 of 17); max detect = 0.68 

μg/L, >HRL

o Phase 2 % GWfinished detects = 77.0% (13 of 17) ; max detect = 

0.53 μg/L, >HRL

o Phase 2 % SWraw detects = 61% (30 of 49) ; max detect = 0.27 

μg/L

o Phase 2 % SWfinished detects = 59% (28 of 48) ; max detect = 0.37 

μg/L

Acetochlor Registration Partnership (1999-2001)

• % wells w/ detects in GW study = 43.43% (76 of 175)

• % samples w/ detects in SW study = 14%

Iowa Study (1995)

• % samples w/ detects = 65.0% (69 of 106); max detect = 14.8 μg/L, 

>HRL

Occurrence in the Lower Mississippi River (1991-1997)

• % samples w/ detects = 96% (154 of 160); median detect = 0.6 

μg/L, >HRL

Occurrence in Rivers & Reservoirs of Midwestern U.S. (1990-1993)

• Median detect in 76 reservoirs = 0.48 μg/L, >HRL

• Range of detects in Mississippi River mouth/headwaters = 0.2 – 1.5 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

21 of 84

μg/L 

Alachlor REDs - EPA OPP (1982-1996)

• 15 studies; all studies w/ detects >HRL

• Range of detects = 0.23 – 135 μg/L

• Range of max detects = 5.6 – 135 μg/L

CDC Fourth National Report (2003-2004)

• 95%iles <LOD for alachlor mercapturate in 1,942 urine samples 

Occurrence summary and/or other information:

• Five detections in national data (UCMR 2); All detections for 

Alachlor ESA in UCMR are >parent (Alachlor) HRL due to detection 

limit

• Supplemental drinking water and ambient water data demonstrate 

some detections of Alachlor ESA > parent HRL

10. Alachlor oxanilic acid (OA)

• CASRN = 171262172

• Substance Key = 79196

• An acetanilide pesticide 

degradate

Production / Release Data

TRI-Release 2010 (alachlor)

• Surface water = 9 lbs/yr (1 

state)

• Total = 182 lbs/yr (2 states)

TRI-Release 2008 (alachlor)

• Surface water = 9 lbs/yr (1 

state)

• Total = 368 lbs/yr (2 states)

TRI-Release 2006 (alachlor)

Critical Health Endpoint

• Using parent (Alachlor) as a 

surrogate 

• CSF = 0.08 (mg/kg-day)-1

• Cancer HRL = 0.4 μg/L 

Non-Cancer Health Effect

• Supplemental OPP data

• Decreased body weight 

• Supplemental NOEL = 157 mg/kgday

• UF = 1,000

• RfD = 0.16 mg/kg-day

• Non-cancer HRL = 1,100 μg/L

Health Assessment Status

• Parent compound [OPP RED 1998]

Sensitive Populations/Lifestages

Analyzed using HRL of 0.4 μg/L

National Drinking Water Data

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 2 μg/L 

• Not detected in 11,100 samples from 1,198 PWSs

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Not detected in 1 CWS

CWSS (2006)

• Not detected in 94 CWS

PDP Raw and Finished Water (2001-2009)

• Max detect in finished water = 0.4995 μg/L, >HRL

• Max detect in raw water = 0.102 μg/L, <1⁄2HRL

Does not proceed to phase 3

Rationale: 

While alachlor OA has no or low 

detections based on national 

finished water data, there is no 

health assessment for the OA 

degradate and it difficult to assess 

whether it is occurring at levels of 

concern. Also, alachlor OA might be 

considered as a group along with 

other chloroacetanilides and/or their

degradates in the future. 

Health: 

Health assessment for Alachlor OA 

(degradate) will not be completed by 

Fall 2011

Occurrence:

No detections for Alachlor OA 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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• Surface water = 12 lbs/yr (1 

state)

• Total = 274 lbs/yr (1 state)

TRI-Release 2004 (alachlor)

• Surface water = 9 lbs/yr (1 

state)

• Total = 1,522 lbs/yr (3 

states)

NCFAP Total Pesticide 

Application 1997

• 15M lbs/yr (47 states) 

(alachlor)

Pesticide Industry Sales and 

Usage Report

• 1987: 55M-60M lbs 

(alachlor)

• 1997: 13M-16M lbs 

(alachlor)

• 1999: 7M-10M lbs (alachlor)

• 2001: 6M-9M lbs (alachlor)

RED 1998

• 29.3M-44.6M lbs of alachlor 

active ingredient were used 

annually 1993-1995

Fate / Transport

• Expected to be less mobile 

than alachlor ESA 

• Subject to microbial 

degradation, though more 

stable than parent 

compound

• None identified

Alachlor, the parent compound, is 

already regulated with an MCL of 2 

μg/L

• % samples w/ detects = 21.44% (1,068 of 4,981)

6-year Review – ICR [Alachlor parent] (1998-2005)

• % systems w/ detects of parent compound = 0.33% (of approx. 

37,000); max detect = 14 μg/L, >HRL

National Pesticide Survey (1988-1990)

• MRL = 0.50 μg/L

• Parent compound not detected in samples from 566 CWS wells and 

783 rural domestic wells

Iowa Well Water Study (2006-2008)

• % samples w/ detects = 3% (14 of 472); 75%ile and max detects 

>HRL

Wisconsin GW Study (1993)

• % samples w/ parent compound detects = 4.0%; max detect = 6.91 

μg/L, >HRL

Supplemental Ambient/Source Water Data

NAWQA Ambient Water [Alachlor parent] (1992-2001)

• MRLs variable (0.0012 – 0.003 μg/L)

• % sites w/ detects = 7.93% (568 of 7,166) 

• Max detect = 38.2 μg/L, >HRL

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• Detects >HRL

o Phase 1 % GW detects = 5.5% (4 of 73); max detect = 1.23 μg/L, 

>HRL

o Phase 1 % SW detects = 41.0% (16 of 39); max detect = 0.13 

μg/L

o Phase 2 % GWraw detects = 25.0% (8 of 32); max detect = 0.84 

μg/L, >HRL

o Phase 2 % GWfinished detects = 28.0% (9 of 32); max detect = 

0.75 μg/L, >HRL

o Phase 2 % SWraw detects = 50% (24 of 49); max detect = 0.26 

(degradate) in national finished water 

data
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μg/L

o Phase 2 % SWfinished detects = 50% (24 of 48); max detect = 0.12 

μg/L 

Acetochlor Registration Partnership (1999-2001)

• % wells w/ detects in GW study = 9.14% (16 of 175)

• % samples w/ detects in SW study = 13%

Iowa Study (1995)

• % samples w/ parent compound detects = 7.5%; max detect = 0.6 

μg/L, >HRL

Occurrence in Lower Mississippi River (1991-1997)

• % samples w/ parent compound detects = 28% (76 of 271); max 

detect > 0.5 μg/L, >HRL

Occurrence in Rivers & Reservoirs of Midwestern U.S. (1990-1993)

• Parent compound detected in 76 reservoirs; median detect <0.05 

μg/L 

Alachlor REDs - EPA OPP (1982-1996)

• 15 studies; all studies w/ detects >HRL

• Range of detects = 0.23 – 135 μg/L

• Range of max detects = 5.6 – 135 μg/L

CDC Fourth National Report (2003-2004)

• 95%iles <LOD for alachlor mercapturate in 1,942 urine samples 

Occurrence summary and/or other information:

• No detections in national data (UCMR 2); All detections for Alachlor 

OA in UCMR are > parent (Alachlor) HRL due to detection limit 

• Supplemental drinking water and ambient water data demonstrate 

some detections for Alachlor OA > parent (Alachlor) HRL

11. Chlorate

• CASRN = 14866683

• Substance Key = 24376

• Chlorate and its salts are 

Critical Health Effects

• Thyroid effects (NTP, 2005)

• BMDL = 28 mg/L as sodium 

chlorate, or 0.9 mg/kg-day

Analyzed using HRL of 210 μg/L

Non-National Drinking Water Data 

Proceeds to phase 3

Rationale: 

The contaminant is of potential 

public health concern and does not 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

24 of 84

powerful oxidizers

• Chlorate compounds are 

used as herbicides and 

disinfectants for drinking 

water treatment

Production / Release Data

NCFAP Total Pesticide 

Application 1997

• 7,262,000 lbs/yr (16 states) 

(sodium chlorate)

RED 2006

• 2.8M lbs of sodium chlorate 

active ingredient are used 

annually

Fate / Transport

• Sodium chlorate highly 

soluble; chlorate ion mobile 

in water (RED)

• Sodium chlorate persists in 

the soil for 0.5 to 5 years 

(HSDB) 

• UF = 30 

• RfD = 0.03 mg/kg-day

• Non-cancer HRL = 210 μg/L

Health Assessment Status

• OPP RED (2006) used in draft OW 

Health Advisory (2011) [finalized in 

2013]

• Not likely to cause cancer at doses 

below those that alter thyroid 

hormone homeostasis

Sensitive Populations/Lifestages

• Individuals with anemia and 

possibly those with a glucose-6-

phosphate dehydrogenase 

deficiency

DBP ICR (1997-1998)

• MRL unavailable (min detect = 20 μg/L)

• % samples w/ detects = 86.68% (1,490 of 1,719) 

• % samples >1⁄2HRL = 51.08% (878 of 1,719)

• % samples >HRL = 19.31% (332 of 1,719)

• % systems w/ detects = 97.56% (80 of 82)

• Median detect = 120 μg/L

• 99% detect = 990.55 μg/L

• Max detect = 2,234 μg/L

State Drinking Water Data (2001-2007)

• Detects >HRL

• % systems w/ detects = 

o CA: 53.33% (24 of 45)

• % systems w/ detects >1⁄2HRL = 

o CA: 37.78% (17 of 45)

• % systems w/ detects >HRL = 

o CA: 22.22% (10 of 45)

Supplemental Drinking Water Data 

CWSS (2006)

• % PWS w/ detects = 3.19% (3 of 94); max detect = 51 μg/L, no 

detects >1⁄2HRL or >HRL

EWG (2004-2009)

• 10 PWSs in 6 states w/ detects >HRL

Occurrence summary and/or other information:

• DBP ICR is a non-national monitoring program of large systems

• DBP ICR data is also supplemented by recent state data 

demonstrating detections >HRL 

• Recent surveys (e.g. AWWA) indicate an increase in treatment 

practices that form chlorate (e.g. liquid hypochlorite, chlorine 

dioxide, ozone) under certain conditions

have critical health or occurrence 

data gaps

Health:

Available health assessment 

Occurrence:

Significant occurrence at levels of 

public health concern in non-national 

finished water data 
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• On UCMR 3

12. Cobalt

• CASRN = 7440484

• Substance Key = 18870

• A naturally-occurring 

element

• Commonly used in 

superalloys

Production / Release Data

TRI-Release 2010 (cobalt)

• Surface water = 2,957 lbs/yr 

(21 states)

• Total = 462,699 lbs/yr (37

states)

TRI-Release 2010 (cobalt

compounds)

• Surface water = 98,836

lbs/yr (31 states)

• Total = 5,143,016 lbs/yr (45

states)

TRI-Release 2008 (cobalt)

• Surface water = 2,599 lbs/yr 

(18 states)

• Total = 754,613 lbs/yr (38

states)

TRI-Release 2008 (cobalt

compounds)

• Surface water = 217,107

lbs/yr (30 states)

• Total = 6,288,524 lbs/yr (46

Critical Health Endpoint

• Blood effect - increased 

hemoglobin (human study) (Davis 

and Fields, 1958)

• LOAEL = 1 mg/kg-day

• UF = 100

• ATSDR MRL = 0.01 mg/kg-day

• Non-cancer HRL = 70 μg/L

Health Assessment Status

• ATSDR (2004)

• On the 2012 IRIS Agenda

Sensitive Populations/Lifestages

• Individuals who exhibit a 

polymorphism in the HLA-DP gene 

that makes them more susceptible 

to hard metal disease

• Individuals with ongoing respiratory 

illness (inhaled cobalt)

• Individuals with iron deficiency (oral 

exposure)

• Individuals with high alcohol 

consumption.

Analyzed using HRL of 70 μg/L

National Drinking Water Data

NIRS Finished Water [GW only] (1984-1986)

• MRL = 6 μg/L

• No detects >1⁄2HRL or HRL

• % PWSs w/ detects = 0.30% (3 of 989) 

• Median detect = 9.68 μg/L

• 99%ile detect = 10.63 μg/L

• Max detect = 10.65 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1996-2007)

• No detects >1⁄2HRL or HRL 

• % systems w/ detects = 

o CA: 14.93% (10 of 67)

o IL: 4.55% (1 of 22)

o OH: 12.00% (3 of 25)

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Cobalt-59 detected in 1 CWS; max detect = 9.4 μg/L, no detects 

>1⁄2HRL or >HRL

CWSS (2006)

• Not detected in 1 CWS

Does not proceed to phase 3

Rationale: 

The contaminant likely has no or 

low potential for public health 

concern, but has a health data gap

Health: 

Non-EPA health assessment will not 

be updated by Fall 2011

Occurrence:

No detections in national or nonnational finished water data at levels of 

public health concern based on the 

draft HRL.

 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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states)

TRI-Release 2006 (cobalt)

• Surface water = 760 lbs/yr 

(18 states)

• Total = 943,396 lbs/yr (37 

states)

TRI-Release 2006 (cobalt 

compounds) • Surface water = 172,263

lbs/yr (29 states)

• Total = 7,518,390 lbs/yr (45 

states)

TRI-Release 2004 (cobalt)

• Surface water = 1,277 lbs/yr 

(17 states)

• Total = 776,762 lbs/yr (38 

states)

TRI-Release 2004 (cobalt 

compounds) • Surface water = 86,563

lbs/yr (30 states)

• Total = 6,918,970 lbs/yr (46 

states)

Fate / Transport • Speciation and 

environmental fate and 

transport in water are 

influenced by the presence 

of organic ligands, 

concentration of anions, pH, 

Supplemental Ambient/Source Water Data

NAWQA Ambient Water (1992-2001)

• MRLs variable (most within 1-2 μg/L)

• No SW detects >HRL • % GW samples w/ detects = 26.38% (858 of 3,252) • % GW samples w/ detects >1⁄2HRL = 0.43% (14 of 3,252) • % GW samples w/ detects >HRL = 0.28% (9 of 3,252) • % SW samples w/ detects = 13.12% (312 of 2,378) • % SW samples w/ detects >1⁄2HRL = 0.08% (2 of 2,378) • % GW sites w/ detects = 24.62% (715 of 2,904) • % GW sites w/ detects >1⁄2HRL = 0.48% (14 of 2,904) • % GW sites w/ detects >HRL = 0.31% (9 of 2,904) • % SW sites w/ detects = 17.05% (67 of 393) • % SW sites w/ detects >1⁄2HRL = 0.25% (1 of 393) • Median detect = 0.22 μg/L • 99%ile detect = 50.18 μg/L • Max detect = 684.0 μg/L

STORET • MRL unavailable (min detect = 0 μg/L

1

)

• Data from 45 states • % GW samples w/ detects = 58.92% (2,123 of 3,603

)

• % GW samples w/ detects >1⁄2HRL = 13.07% (471 of 3,603)

• % GW samples w/ detects >HRL = 2.58% (93 of 3,603

)

• % SW samples w/ detects = 24.62% (22,697 of 92,176)

• % SW samples w/ detects >1⁄2HRL = 2.23% (2,053 of 92,176

)

• % SW samples w/ detects >HRL = 1.50% (1,382 of 92,176)

• % GW sites w/ detects = 62.01% (581 of 937)

• % GW sites w/ detects >1⁄2HRL = 14.73% (138 of 937

)

• % GW sites w/ detects >HRL = 4.06% (38 of 937)

• % SW sites w/ detects = 43.08% (7,261 of 16,855)

• % SW sites w/ detects >1⁄2HRL = 6.85% (1,155 of 16,855)

• % SW sites w/ detects >HRL = 4.93% (831 of 16,855)

• Median detect = 1.8 μg/L
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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and redox potential 

• Ionic cobalt compounds will 

not volatilize from water 

(HSDB, 2009)

• 90%ile detect = 39 μg/L

• Max detect = 245,800 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.01 μg/L– 1 μg/L

• No detects >1⁄2HRL or >HRL

• % samples w/ detects = 63.16% (396 of 627)

NAWQA Domestic Well Water Quality (1991-2004)

• MRL = 1 μg/L 

• % samples w/ detects in aquifer studies = 34.2% (537 of 1,572); no 

detects >1⁄2HRL or >HRL

• % samples w/ detects in agricultural land-use studies = 47.4% (37 

of 78); no detects >1⁄2HRL or >HRL

U.S. Glacial Aquifer Study (1991-2003)

• Max detect (95 μg/L) in 847 GW samples >HRL

CDC Fourth National Report (2003-2004)

• 95%ile concentration = 1.16 μg/L in 2,558 urine samples

Occurrence summary and/or other information:

• No detections >1⁄2 HRL or >HRL in national data (NIRS), or in nonnational drinking water data (CA)

• Some detections >HRL in ambient water data (STORET), 

(NAWQA)

• On UCMR 3

13. Dimethoate

• CASRN = 60515

• Substance Key = 2413

• An organophosphate 

• First registered in 1962

• Commonly used as an 

insecticide on field crops, 

(such as cotton), on orchard 

Critical Health Effect

• Cholinesterase inhibition (American 

Cyanamid Company, 1986)

• BMDL = 0.22 mg/kg-day

• UF = 100

• RfD = 0.0022 mg/kg-day

• Non-cancer HRL = 15.4 μg/L

Analyzed using HRL of 15.4 μg/L

National Drinking Water Data 

UCMR 2 Finished Water Assessment Monitoring (2008-2010)

• MRL = 0.7 μg/L

• Not detected in 32,013 samples from 4,138 PWSs

Proceeds to phase 3

Rationale: 

The contaminant has no or low 

potential for public health concern 

and does not have critical health or 

occurrence data gaps
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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crops, on vegetable crops, 

in forestry, and for 

residential purposes 

Production / Release Data

TRI-Release 2010

• Surface water = 5 lbs/yr (1 

state)

• Total = 8,442 lbs/yr (1 state)

TRI-Release 2008

• Surface water = 5 lbs/yr (1 

state)

• Total = 15,561 lbs/yr (2 

states)

TRI-Release 2006

• Surface water = 5 lbs/yr (1 

state)

• Total = 7,148 lbs/yr (2 

states)

TRI-Release 2004

• Surface water = 2,615 lbs/yr 

(2 states)

• Total = 31,480 lbs/yr (4 

states)

NCFAP Total Pesticide 

Application 1997

• 1,896,947 lbs/yr (43 states)

Pesticide Industry Sales and 

Usage Report

• 1999: 1M-2M lbs 

• 2001: 1M-2M lbs

Health Assessment Status

• OPP IRED (2007)

• Possible human carcinogen, group 

C (1986 cancer guidelines)

Sensitive Populations/Lifestages

• None identified

Non-National Drinking Water Data

State Drinking Water Data (1995-2007)

• No detects >HRL

• % systems w/ detects = 

o CA: 0.09% (2 of 2,153)

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2002-2007)

• Not detected in 1 CWS

PDP Raw and Finished Water (2001-2009)

• Max detect in finished water = 0.068 μg/L, <1⁄2HRL

• Max detect in raw water = 0.0088 μg/L, <1⁄2HRL

• % samples w/ detects = 0.05% (3 of 5,374); no detects >1⁄2HRL or 

>HRL 

PMP Raw Water (1999)

• % samples w/ detects = 1.3% (4 of 317); no detects >1⁄2HRL or 

>HRL

PMP Finished Water (1999)

• Not detected in any samples 

Supplemental Ambient/Source Water Data

STORET

• MRL unavailable (min detect = 0 μg/L1)

• Data from 7 states

• No detects >1⁄2HRL or >HRL

• % GW samples w/ detects = 1.04% (9 of 867)

• % SW samples w/ detects = 3.86% (171 of 4,432)

Health:

Available health assessment

Occurrence:

No detections in national finished water 

data 
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29 of 84

• 2005: <1M lbs

• 2007: <1M lbs

IRED 2008

• ~1.8M lbs used annually

Fate / Transport

• Expected to be very mobile 

in water, based on physical 

and chemical properties 

• Moderately persistent in the 

environment (biodegrades 

slowly with acclimation) 

(CCL CIS) 

• % GW sites w/ detects = 1.53% (9 of 587)

• % SW sites w/ detects = 15.64% (33 of 211)

• Median detect = 0 μg/L

• 90%ile detect = 0.16 μg/L

• Max detect = 0.44 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• No detects >HRL 

oPhase 1: Not detected in 221 GW samples 

oPhase 1 % samples w/ SW detects = 1.46% (2 of 146); detects 

<0.01 μg/L

oPhase 2: Not detected in 48 GW samples

CA DPR

• Max detect = 2.4 μg/L, no detects >1⁄2HRL or >HRL

Occurrence summary and/or other information:

• No detections in recent national data (UCMR 2)

• Total releases and releases to surface water have decreased from 

2004 to 2006

14. Disulfoton

• CASRN = 298044

• Substance Key = 6423

• An organophosphate 

pesticide

• Was used as an insecticide

• All remaining uses 

cancelled in 2009

Production / Release Data

OPP Estimated Environmental 

Concentrations

• Surface water chronic = 2.0-

Critical Health Endpoint

• Plasma, RBC, & brain 

cholinesterase inhibition

• NOAEL = 0.013 mg/kg-day

• UF = 100

• RfD = 0.00013 mg/kg-day

• Non-cancer HRL = 0.91 μg/L

Health Assessment Status

• OPP RED (2006)

• Evidence of noncarcinogenicity for 

humans, group E (1986 cancer 

guidelines)

Analyzed using HRL of 0.91 μg/L

Non-National Drinking Water Data 

UCMR 1 Finished Water Screening Survey (2001-2003)

• MRL = 0.5 μg/L

• Not detected in 2,300 samples from 295 PWSs

State Drinking Water Data (1995-2007)

• Not detected from systems in 2 states (CA and IL) 

Supplemental Drinking Water Data 

Does not proceed to phase 3

Rationale: 

The contaminant likely has no or 

low potential for public health 

concern, but has an occurrence 

data gap.

Health: 

Available health assessment

Occurrence:

The contaminant does not have 

national finished water data. While 

there are non-national finished water 

data showing no detections, there are 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

30 of 84

16.7 μg/L

• Ground water = 0.02 μg/L 

NCFAP Total Pesticide 

Application 1997

• 1,196,066 lbs/yr (32 states)

RED 2007

• ~1.2M lbs active ingredient 

used annually in the 1990s

Fate / Transport

• Expected to be of low to 

moderate mobility in water, 

based on physical and 

chemical properties 

• Moderately persistent in the 

environment (biodegrades 

slowly) (CCL CIS) 

Sensitive Populations/Lifestages

• None identified in humans

Recent CCRs from 26 CWSs that serve >1M (2002-2003)

• Not detected in 1 CWS

EWG (2004-2009) 

• Not detected in samples from 332 PWSs 

PDP Raw and Finished Water (2001-2009)

• Not detected in 5,871 samples

PMP Raw & Finished Water (1999)

• Not detected in any raw or finished samples

Supplemental Ambient/Source Water Data 

NAWQA Ambient Water (1992-2001)

• MRLs variable (most within 0.017-0.021 μg/L)

• No GW detects >1⁄2HRL or >HRL

• % GW samples w/ detects = 0.02% (1 of 6,080)

• % SW samples w/ detects = 0.17% (25 of 14,879)

• % SW samples w/ detects >1⁄2HRL = 0.02% (3 of 14,879)

• % SW samples w/ detects >HRL = 0.01% (2 of 14,879)

• % GW sites w/ detects = 0.02% (1 of 5,211)

• % SW sites w/ detects = 0.84% (16 of 1,907)

• % SW sites w/ detects >1⁄2HRL = 0.16% (3 of 1,907)

• % SW sites w/ detects >HRL = 0.10% (2 of 1,907)

• Median detect = 0.02 μg/L

• 99%ile detect = 3.81 μg/L

• Max detect = 3.81 μg/L

STORET

• MRL unavailable (min detect = 0 μg/L1

)

• Data from 17 states

• No GW detects >1⁄2HRL or >HRL

• No SW detects >HRL

• % GW samples w/ detects = 17.46% (33 of 189)

some detections of potential public 

health concern in ambient water data.
Phase 2 of Protocol for Regulatory Determination 3 April 2014

31 of 84

• % SW samples w/ detects = 5.28% (257 of 4,863)

• % SW samples w/ detects >1⁄2HRL = 0.02% (1 of 4,863)

• % GW sites w/ detects = 22.86% (32 of 140)

• % SW sites w/ detects = 21.73% (113 of 520)

• % SW sites w/ detects >1⁄2HRL = 0.19% (1 of 520)

• Median detect = 0 μg/L

• 90%ile detect = 0.133 μg/L

• Max detect = 0.56 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA Domestic Well Water Quality (1991-2004)

• MRL = 0.011 μg/L – 0.017 

• % samples w/ detects = 0.04% (1 of 2,539); no detects >1⁄2HRL or 

>HRL

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.01 μg/L– 0.02 μg/L

• Not detected in 647 samples

NAWQA National Synthesis (1992-2001)

• MRL = varies - maximum of 0.011 μg/L

• No detects in any GW samples

• SW samples: 2,013 samples from 83 agricultural sites; max detect 

= 3.340 μg/L, >HRL. 1,386 samples from 65 mixed land use sites; 

max detect = 0.826, >1⁄2HRL

Virginia Tech Monitoring

• Detects in 3 samples from 2 of 8 sites; detects >HRL

• Max detect = 6.11 μg/L, >HRL

Occurrence summary and/or other information:

• No detections in UCMR1 (SS), which is a statistically defined, 

national sample of 300 PWSs

• USGS ambient water study demonstrates some detections >HRL 

• Users voluntarily cancelled all product registrations but existing 

stocks can be used until June 2011
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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15. Diuron

• CASRN = 330541

• Substance Key = 6583

• A halogenated aromatic 

urea pesticide

• Used as an herbicide

• Approved for use on 33 

crops, including citrus, 

berries, asparagus and 

pineapple, plus other uses 

including as a mildewcide 

and preservative in paints 

and stains and as an 

algaecide in commercial fish 

production, residential 

ponds, and aquariums

Production / Release Data

TRI-Release 2010

• Surface water = 5 lbs/yr (1 

state)

• Total = 63,477 lbs/yr (6 

states)

TRI-Release 2008

• Surface water = 5 lbs/yr (1 

state)

• Total = 91,471 lbs/yr (7 

states)

TRI-Release 2006

• Surface water = 5 lbs/yr (1 

state)

Critical Health Endpoint

• Urinary bladder carcinomas

• CSF = 0.0191 (mg/kg-day)-1

• Cancer HRL = 1.8 μg/L

Non-Cancer Health Effects

• Hemolytic anemia (du Pont, 1964)

• LOAEL = 1.0 mg/kg-day

• UF = 300

• RfD = 0.003 mg/kg-day

• Non-cancer HRL = 21 μg/L

Health Assessment Status

• OPP RED (2003)

Sensitive Populations/Lifestages

• None identified

Analyzed using HRL of 1.8 μg/L

Non-National Drinking Water Data 

UCMR 1 Finished Water Screening Survey (2001-2003)

• MRL = 1 μg/L

• All detects (single detect) >HRL

• % PWSs w/ detects >HRL = 0.34% (1 of 293)

• Median detect = 2.1 μg/L

• 99%ile detect = 2.1 μg/L

• Max detect = 2.1 μg/L

State Drinking Water Data (1995-2007)

• % systems w/ detects = 

o CA: 1.82% (18 of 990)

o IL: Not detected from 1 system

• % systems w/ detects >1⁄2 HRL = 

o CA: 1.72% (17 of 990)

• % systems w/ detects >HRL = 

o CA: 1.52% (15 of 990)

Supplemental Drinking Water Data 

Recent CCRs from 26 CWSs that serve >1M (2006-2007)

• Not detected in 1 CWS

EWG (2004-2009)

• One PWS w/ detect >1⁄2HRL and >HRL = 4.9 μg/L 

• One PWS w/ detect >1⁄2HRL = 1.5 μg/L

PDP Raw and Finished Water (2002-2009)

• Max detect in finished water = 0.267 μg/L, <1⁄2HRL

Does not proceed to phase 3

Rationale: 

The contaminant likely has no or 

low potential for public health 

concern, but has an occurrence 

data gap.

Health: 

Available health assessment

Occurrence:

The contaminant does not have 

national finished water data. While 

there are non-national finished water 

showing no detections, there are some 

detections of potential public health 

concern in ambient water data.
Phase 2 of Protocol for Regulatory Determination 3 April 2014

33 of 84

• Total = 1,054 lbs/yr (7 

states)

TRI-Release 2004

• Surface water = 10 lbs/yr (2 

states)

• Total = 822 lbs/yr (6 states)

NCFAP Total Pesticide 

Application 1997 • 4,370,448 lbs/yr (39 states)

Pesticide Industry Sales and 

Usage Report • 1999: 2M-4M lbs • 2001: 3M-6M lbs • 2003: 4M-6M lbs • 2005: 4M-6M lbs • 2007: 2M-4M lbs

RED 2003 • ~9M-10M lbs of active 

ingredient used annually

CUSIUR Production Data • >1M-10M lbs/yr (1998)

Fate / Transport • Expected to be moderately 

to highly mobile in water, 

based on physical and 

chemical properties

• Persistent in the 

environment (biodegrades 

sometimes) (CCL CIS) 

• Max detect in raw water = 0.309 μg/L, <1⁄2HRL • % samples w/ detects = 9.89% (395 of 3,995); no detects >1⁄2HRL 

or >HRL

PMP Raw & Finished Water (1999) • No detect >1⁄2HRL or >HRL in 312 raw water samples and 224 

finished water samples

National Pesticide Survey (1988-1990)

• MRL = 0.32 μg/L • Not detected in 566 CWS wells and 783 rural domestic wells

Supplemental Ambient/Source Water Data 

NAWQA Ambient Water (1992-2001)

• MRLs variable (most are 0.002 μg/L) • % GW samples w/ detects = 3.33% (134 of 4,030) • % GW samples w/ detects >1⁄2HRL = 0.15% (6 of 4,030) • % GW samples w/ detects >HRL = 0.10% (4 of 4,030) • % SW samples w/ detects = 16.35% (906 of 5,541) • % SW samples w/ detects >1⁄2HRL = 1.79% (99 of 5,541) • % SW samples w/ detects >HRL = 1.05% (58 of 5,541) • % GW sites w/ detects = 3.36% (123 of 3,656) • % GW sites w/ detects >1⁄2HRL = 0.16% (6 of 3,656) • % GW sites w/ detects >HRL = 0.11% (4 of 3,656) • % SW sites w/ detects = 21.88% (196 of 896) • % SW sites w/ detects >1⁄2HRL = 3.24% (29 of 896) • % SW sites w/ detects >HRL = 1.67% (15 of 896) • Median detect = 0.09 μg/L • 99%ile detect = 8.4 μg/L • Max detect = 23.3 μg/L

STORET • MRL unavailable (min detect = 0 μg/L

1

)

• Data from 9 states
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• No SW detects >HRL

• % GW samples w/ detects = 4.63% (37 of 799)

• % GW samples w/ detects >1⁄2HRL = 0.25% (2 of 799)

• % GW samples w/ detects >HRL = 0.25% (2 of 799)

• % SW samples w/ detects = 77.11% (155 of 201)

• % SW samples w/ detects >1⁄2HRL = 1.00% (2 of 201)

• % GW sites w/ detects = 6.16% (31 of 503)

• % GW sites w/ detects >1⁄2HRL = 0.20% (1 of 503)

• % GW sites w/ detects >HRL = 0.20% (1 of 503)

• % SW sites w/ detects = 73.53% (50 of 68)

• % SW sites w/ detects >1⁄2HRL = 1.47% (1 of 68)

• Median detect = 0.03 μg/L

• 90%ile detect = 0.04 μg/L

• Max detect = 52 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA Domestic Well Water Quality (1991-2004)

• % samples w/ detects = 2.1% (38 of 1,772); detections did not 

exceed 2 μg/L (unknown if detections exceeded HRL)

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.0075 - 0.0793 μg/L

• No detects >1⁄2HRL or >HRL

• % samples w/ detects = 5.28% (31 of 587)

NAWQA National Synthesis (1992-2001)

• MRL = 0.060 μg/L

• GW: max detect (5.53 μg/L) from 3,445 mixed, urban and 

agricultural wells >HRL

• SW: max detect (14.0 μg/L) from 117 mixed, urban and agricultural 

setting >HRL

NAWQA 3 Study Units (1993-1998)

• MRL = 0.02 μg/L

• % samples w/ detects = 22% (185 of 858); no detects >HRL
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• No detects >1⁄2HRL or >HRL

oPhase 1: % GW detects = 3.3% (7 of 215); max detect = 0.166 

μg/L

oPhase 1: % SW detects = 30.3% (44 of 145); max detect = 0.44 

μg/L

oPhase 2: % GWraw detects = 6.6% (4 of 61); max detect = 0.113 

μg/L

oPhase 2: % GWfinished detects = 1.7% (1 of 59); max detect = 0.099 

μg/L

oPhase 2: % SWraw detects = 42% (38 of 90); max detect = 0.22 

μg/L

oPhase 2: % SWfinished detects = 24% (21 of 89); max detect = 0.18 

μg/L

South Florida Water Management (1998-2001)

• MRL = 0.2 - 0.4 μg/L

• % samples w/ detects = 4% (17 of 438); max detect = 1.2 μg/L, 

>1⁄2HRL

California Department of Pesticide Regulation (2000-2001)

• MRL = 0.05 μg/L

• San Joaquin River: 100% (54 samples), >HRL

• Sacramento River: max detect = 1.42 μg/L, >HRL

California Department of Pesticide Regulation SURF (2000)

• % samples w/ detects = 57.2% (350 of 612); 95%ile detect = 3.6 

μg/L, >HRL

Playa Lake, TX

• % samples w/ detects = 71% (from 32 lakes); mean = 2.7 μg/L, 

>HRL

Occurrence summary and/or other information:

• No detections in UCMR1 (SS), which is a statistically defined, 

national sample of 300 PWSs.

• State finished water data and USGS ambient water study 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

36 of 84

demonstrates some detections >HRL 

16. Methyl Bromide

• CASRN = 74839

• Substance Key = 2601

• A halogenated alkane

• Used as a fumigant 

fungicide

• Regulated under Montreal 

Protocol; phased out in 

2005 except for “critical use” 

and other exemptions

Production / Release Data

TRI-Release 2010

• Surface water = 1,254 lbs/yr 

(3 states)

• Total = 512,237 lbs/yr (16

states)

TRI-Release 2008

• Surface water = 71 lbs/yr (3 

states)

• Total = 489,628 lbs/yr (14 

states)

TRI-Release 2006

• Surface water = 361 lbs/yr 

(2 states)

• Total = 408,252 lbs/yr (16 

states)

TRI-Release 2004

• Surface water = 200 lbs/yr 

(3 states)

Critical Health Endpoint

• Decreased body weight, body 

weight gain, and food consumption

• NOAEL = 2.2 mg/kg-day

• UF = 100

• RfD = 0.020 mg/kg-day

• Non-cancer HRL = 140 μg/L

Health Assessment Status

• Updated since CCL3

o OPP RED (2006) 

• Not classifiable as to human 

carcinogenicity, group D (1986 

cancer guidelines)

Sensitive Populations/Lifestages

• Possibly the young and the elderly

Individuals with lung, kidney, or 

neurological diseases (ATSDR, 

1992)

Analyzed using HRL of 140 μg/L

National Drinking Water Data 

NCOD/UCM Round 1 Finished Water (1988-1992)

• MRL unavailable (min detect = 0.07 μg/L)

• No detects >1⁄2HRL or >HRL

• % samples w/ detects = 0.37% (255 of 68,424)

• % PWSs w/ detects = 0.77% (155 of 20,198)

• Median detect = 1.00 μg/L

• 99%ile detect = 32.92 μg/L

• Max detect = 43.00 μg/L

NCOD/UCM Round 2 Finished Water (1993-1997)

• MRL unavailable (min detect = 0.09 μg/L)

• No detects >1⁄2HRL or >HRL

• % samples w/ detects = 0.26% (235 of 90,731)

• % PWSs w/ detects = 0.75% (175 of 23,328)

• Median detect = 1.60 μg/L

• 99%ile detect = 25.06 μg/L

• Max detect = 38.10 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1983-2009)

• No detects >1⁄2HRL or >HRL 

• % systems w/ detects = 

o CA: 1.26% (51 of 4,041)

o FL: 3.70% (1 of 27)

o IL: Not detected from 2 systems

o NC: 0.88% (22 of 2,493)

o OH: 1.62% (41 of 2,531)

Does not proceed to phase 3

Rationale: 

The contaminant likely has low 

potential for public health concern 

and has a health data gap.

Health: 

Health Assessment will not be updated 

by Fall 2011

Occurrence:

The contaminant has national finished 

water data. While there are some 

detections at levels of public health 

concern, based on the draft HRL in the 

national finished water data, the data is 

from 1988-1997 and the contaminant 

was phased out for use in 2005. More 

recent non-national finished water and 

ambient/source water data show no or 

low detections at levels of public health 

concern, based on the draft HRL.
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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• Total = 552,208 lbs/yr (17 

states)

CUSIUR Production Data • >10M-50M lbs/yr (1998) • >1M-10M lbs/yr (2002)

Fate / Transport • Expected to be moderately 

to very mobile in water, 

based on physical and 

chemical properties

• Moderately persistent 

(biodegrades slowly) (CCL CIS) 

o R9 Tribes: 0.35% (1 of 286) o SD: Not detected from 281 systems o TX: 2.05% (116 of 5,660) o WI ’83-’99: 1.50% (29 of 1,929) o WI ’00-’09: 0.53% (6 of 1,123) 

Supplemental Drinking Water Data 

Recent CCRs from 26 CWSs that serve >1M (2006-2007)

• Detected in 1 of 5 CWSs; no detects >HRL

EWG (2004-2009)

• 141 PWSs from 23 states w/ detects; no detects >1⁄2HRL or >HRL

Supplemental Ambient/Source Water Data 

NAWQA Ambient Water (1992-2001)

• MRLs variable (0.1 - 0.26 μg/L) • No SW detects • No GW detects >1⁄2HRL or >HRL • % GW samples w/ detects = 0.07% (3 of 4,544) • % GW sites w/ detects = 0.07% (3 of 4,127) • Median detect = 0.1 μg/L • 99%ile detect = 0.49 μg/L • Max detect = 0.5 μg/L

STORET • MRL unavailable (min detect = 0 μg/L

1

)

• Data from 33 states • No GW detects >1⁄2HRL or >HRL • No SW detects >HRL • % GW samples w/ detects = 52.84% (4,590 of 8,687

)

• % SW samples w/ detects = 10.05% (1,087 of 1

0,816)

• % SW samples w/ detects >1⁄2HRL = 0.01% (1 of 10,816) 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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• % GW sites w/ detects = 32.43% (757 of 2,334)

• % SW sites w/ detects = 29.37% (309 of 1,052)

• % SW sites w/ detects >1⁄2HRL = 0.10% (1 of 1,052)

• Median detect = 0 μg/L

• 90%ile detect = 0.5 μg/L

• Max detect = 110 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA Domestic Well Water Quality (1991-2004)

• Not detected in 2,269 samples 

NAWQA National Focused and Historic VOC Study (1985-2001)

• Random Survey (1999-2001): detected in 0.21% of samples (2 of 

954) , at a maximum concentration of 6.4 μg/L; no detects >1⁄2HRL 

or >HRL

• Focused Survey (1999-2001): not detected above reporting limit of 

0.2 μg/L from 451 samples 

• Historical Monitoring (1985-1995): not detected in 335 urban wells; 

detected in 1 of 1,886 rural wells at conc. = 0.5 μg/L

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.074 - 0.26 μg/L

• Not detected in 832 samples

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• Not detected in 221 ground water samples or 147 surface water 

samples in Phase 1; not detected in 71 raw and 71 finished ground 

water samples in Phase 2

NAWQA Carbonate Aquifer Study (1993-2005)

• Not detected in 793 samples

USGS VOCs in Highway Runoff 

• Not detected

Occurrence summary and/or other information:
Phase 2 of Protocol for Regulatory Determination 3 April 2014

39 of 84

• No PWSs have detections > 1⁄2 draft HRL or HRL in UCM 1/2.

• National data is pre-1997 and the contaminant was phased out in 

2005, except for critical use

• No detections >1⁄2 draft HRL or HRL in non-national finished water

• No or low detections > draft HRL in ambient/source water

• On UCMR 3

17. Methyl tert-butyl ether

(MTBE)

• CASRN = 1634044

• Substance Key = 11918

• An aliphatic ether

• Until recently, was 

commonly used as an 

oxygenate and octane 

booster in gasoline

• Also used in the 

manufacture of isobutene 

and as an extraction solvent

Production / Release Data

TRI-Release 2010

• Surface water = 800 lbs/yr 

(6 states)

• Total = 1,471,221 lbs/yr (35

states)

TRI-Release 2008

• Surface water = 1,832 lbs/yr 

(6 states)

• Total = 351,774 lbs/yr (34

states)

TRI-Release 2006

• Surface water = 12,452 

Critical Health Endpoint

• Kidney adenomas/carcinomas

• CSF = 0.0018 (mg/kg-day)-1

• Cancer HRL = 19.4 μg/L

Non-Cancer Health Effects

• Decreased blood urea nitrogen 

levels in liver (Robinson et al., 

1990)

• LOAEL = 100 mg/kg-day

• UF = 300

• ATSDR MRL = 0.3 mg/kg-day

• Non-cancer HRL = 2,100 μg/L

Health Assessment Status

• 1999 OEHHA (CA) – Cancer

• 1996 ATSDR – Non-cancer

• On the 2012 IRIS Agenda

Sensitive Populations/Lifestages

• None identified

Analyzed using HRL of 19.4 μg/L

National Drinking Water Data 

UCMR 1 Finished Water Assessment Monitoring (2001-2003)

• MRL = 5 μg/L

• % samples w/ detects = 0.08% (26 of 33,768)

• % samples w/ detects >1⁄2HRL = 0.03% (11 of 33,768)

• % samples w/ detects >HRL = 0.01% (5 of 33,768)

• % PWSs w/ detects = 0.49% (19 of 3,871)

• % PWSs w/ detects >1⁄2HRL = 0.28% (11 of 3,871)

• % PWSs w/ detects >HRL = 0.13% (5 of 3,871)

• Median detect = 9.2 μg/L

• 99%ile detect = 48.8 μg/L

• Max detect = 49.0 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1991-2009)

• % systems w/ detects = 

o CA: 3.39% (150 of 4,419)

o FL: 22.58% (7 of 31)

o IL: 2.24% (26 of 1,161)

o OH: 0.46% (6 of 1,306)

o R9 Tribes: 0.46% (1 of 219)

o TX: 0.72% (41 of 5,660)

o WI ’91-’99: 1.97% (4 of 203)

o WI ’00-’09: 2.93% (27 of 920)

Does not proceed to phase 3

Rationale: 

The contaminant has no or low 

detections based on national 

finished water data but difficult to 

assess whether at public health 

concern due to health data gap.

Health: 

IRIS health assessment will not be 

completed by Fall 2011

Occurrence:

Low percentage of detections > draft 

HRL in national finished water data 

which indicates that it is potentially not 

occurring at levels of public health 

concern 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

40 of 84

lbs/yr (14 states)

• Total = 1,017,089 lbs/yr (41 

states)

TRI-Release 2004

• Surface water = 40,171 

lbs/yr (17 states)

• Total = 2,087,675 lbs/yr (42 

states)

CUSIUR Production Data • >1B lbs/yr (1998, 2002) • ≥ 1B lbs/yr (2006)

Fate / Transport • Expected to be moderately 

to highly mobile in water, 

based on physical and 

chemical properties

• Moderately persistent in the 

environment (biodegrades 

slowly) (CCL CIS) 

• % systems w/ detects >1⁄2HRL = o CA: 0.84% (37 of 4,419) o FL: 3.23% (1 of 31) o IL: 0.17% (2 of 1,161) o OH: Not detected from 1,306 systems o R9 Tribes: 0.46% (1 of 219) o TX: 0.11% (6 of 5,660) o WI ’91-’99: Not detected from 203 systems o WI ’00-’09: 0.43% (4 of 920) • % systems w/ detects >HRL = o CA: 0.43% (19 of 4,419) o FL: 3.23% (1 of 31) o IL: Not detected from 1,161 systems o OH: Not detected from 1,306 systems o R9 Tribes: Not detected from 219 systems o TX: 0.05% (3 of 5,660) o WI ’91-’99: Not detected from 203 systems o WI ’00-’09: 0.43% (4 of 920)

Supplemental Drinking Water Data 

Recent CCRs from 26 CWSs that serve >1M (2006-2007)

• Detected in 1 CWS; max detect = 7.7 μg/L, no detects >1⁄2HRL or 

>HRL

CWSS (2006) • % PWSs w/ detects = 1.06% (1 of 94) • % samples w/ detects = 35% (7 of 20); max detect = 5 μg/L, no 

detects >1⁄2HRL or >HRL

EWG (2004-2009)

• At least 35 PWSs from 14 states w/ detects >1⁄2HRL

Supplemental Ambient/Source Water Data 

NAWQA Ambient Water (1992-2001)
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41 of 84

• MRLs variable (most within 0.1 – 0.2 μg/L) • % GW samples w/ detects = 9.09% (422 of 4,645) • % GW samples w/ detects >1⁄2HRL = 1.83% (85 of 4,645) • % GW samples w/ detects >HRL = 1.74% (81 of 4,645) • % SW samples w/ detects = 46.22% (648 of 1,402) • % SW samples w/ detects >1⁄2HRL = 1.21% (17 of 1,402) • % SW samples w/ detects >HRL = 1.14% (16 of 1,402) • % GW sites w/ detects = 7.50% (311 of 4,146) • % GW sites w/ detects >1⁄2HRL = 0.82% (34 of 4,146) • % GW sites w/ detects >HRL = 0.75% (31 of 4,146) • % SW sites w/ detects = 62.09% (113 of 182) • % SW sites w/ detects >1⁄2HRL = 1.10% (2 of 182) • % SW sites w/ detects >HRL = 0.55% (1 of 182) • Median detect = 0.3 μg/L • 99%ile detect = 1,800 μg/L • Max detect = 23,000 μg/L

STORET • MRL unavailable (min detect = 0 μg/L

1

)

• Data from 18 states • % GW samples w/ detects = 46.21% (1,324 of 2,865

)

• % GW samples w/ detects >1⁄2HRL = 2.58% (74 of 2,865)

• % GW samples w/ detects >HRL = 2.06% (59 of 2,865)

• % SW samples w/ detects = 26.73% (472 of 1,766

)

• % SW samples w/ detects >1⁄2HRL = 0.57% (10 of 1,766)

• % SW samples w/ detects >HRL = 0.2

3% (4 of 1,766)

• % GW sites w/ detects = 37.62% (395 of 1,050)

• % GW sites w/ detects >1⁄2HRL = 

2.48% (26 of 1,050)

• % GW sites w/ detects >HRL = 1.81% (19 of 1,050)

• % SW sites w/ detects = 18.68% (65 of 348) • % SW sites w/ detects >1⁄2HRL = 2.59% (9 of 348) • % SW sites w/ detects >HRL = 1.15% (4 of 348) • Median detect = 0 μg/L • 90%ile detect = 2.55 μg/L • Max detect = 13,000 μg/L
Phase 2 of Protocol for Regulatory Determination 3 April 2014

42 of 84

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA National Focused and Historic VOC Study (1985-2001)

• Random Survey (1999-2001): detected in 8.7% of 934 samples; 

one detect >HRL

• Focused Survey (1999-2001): detected at 55.5% of 134 sites, max 

conc. in ground water >HRL

• Historical Monitoring (1985-1995): detected at 16.9% of 225 urban 

wells and 3.4% of 1,312 rural wells; max conc. = 10,000 μg/L, >HRL

USGS VOCs in Highway Runoff (1991-1995) 

• Detected in 3 of 3 stormwater studies, w/ reported max conc. of 8.7 

μg/L, no detects >1⁄2HRL or >HRL

USGS CWSs Drawing from Streams and Groundwater (2002-2005) 

• In Phase 1, no detects >1⁄2HRL or >HRL in 221 GW samples and 

147 SW samples (max conc. = 3.44 μg/L)

• In Phase 2, no detects >1⁄2HRL or >HRL in 71 GW samples and 95 

raw and 94 finished SW samples.

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.05 - 0.2 μg/L

• No detects >HRL

• % samples w/ detects = 13.82% (115 of 832)

• % samples w/ detects >1⁄2HRL = 0.12% (1 of 832)

NAWQA Domestic Well Water Quality (1991-2004)

• MRL = 0.08-0.2 μg/L

• % wells w/ detects = 4.3% (97 of 2,268); at least one detect >HRL

NAWQA Carbonate Aquifer Study (1993-2005)

• In 793 samples, max conc. = 51 μg/L, >HRL

CDC Fourth National Report (2003-2004)

• 95%iles <LOD in 1,307 blood samples
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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Occurrence summary and/or other information:

• Some detections > best available HRL in UCMR1 as well as 

supplemental state drinking water and USGS ambient water data

18. Metolachlor

• CASRN = 51218452

• Substance Key = 35270

• An acetanilide pesticide 

• A broad spectrum herbicide 

for general weed control. 

Initially registered in 1976 

for use on turf, it is now also 

registered for use on corn, 

cotton, peanuts, pod crops, 

potatoes, safflowers, 

sorghum, soybeans, stone 

fruits, tree nuts, nonbearing 

citrus, nonbearing grapes, 

cabbage, certain peppers, 

buffalo grass, guymon 

bermudagrass for seed 

production, nurseries, 

hedgerows/fencerows, and 

landscape plantings

Production / Release Data

NCFAP Total Pesticide 

Application 1997

• 67,336,211 lbs/yr (48 

states)

Pesticide Industry Sales and 

Usage Report: Metolachlor

• 1987: 45M-50M lbs

• 1997: 63M-69M lbs

• 1999: 26M-30M lbs

Critical Health Endpoint

• Decreased body weight gain

(Hazelette, 1989)

• NOEL = 9.7 mg/kg-day

• UF = 100

• RfD = 0.1 mg/kg-day

• Non-cancer HRL = 700 μg/L

Health Assessment Status

• OPP RED (1995)

• Possible human carcinogen, group 

C (1986 cancer guidelines)

Sensitive Populations/Lifestages

• None identified

Analyzed using HRL of 700 μg/L

National Drinking Water Data 

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 1 μg/L

• No detects >1⁄2HRL or >HRL 

• % samples w/ detects = 0.03% (3 of 11,137)

• % PWSs w/ detects = 0.25% (3 of 1,198)

• Median detect = 1.40 μg/L

• 99%ile detect = 2.71 μg/L

• Max detect = 2.73 μg/L

NCOD/UCM Round 2 Finished Water, 20-State Cross-Section (1993-

1997)

• MRLs variable (min detect = 0.01 μg/L)

• No detects >1⁄2HRL or >HRL 

• % samples w/ detects = 0.62% (211 of 34,112)

• % PWSs w/ detects = 0.89% (116 of 13,007)

• Median detect = 0.57 μg/L

• 99%ile detect = 7.1 μg/L

• Max detect = 13.8 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1984-2008)

• No detects >1⁄2HRL or >HRL 

• % systems w/ detects = 

o CA: 0.69% (15 of 2,172)

o FL: Not detected from 6 systems

o IL: 1.94% (17 of 875)

Does not proceed to phase 3

Rationale: 

While metolachlor has no or low 

potential for public health concern, 

based on national finished water 

data, it might be considered as a 

group along with other 

chloroacetanilides and/or their 

degradates in the future. And at this 

time, the Agency does not have a 

health assessment for the 

degradates (i.e., a health data gap). 

Health: 

Health assessments for the degradates 

will not be completed by Fall 2011

Occurrence:

Few detections for Metolachlor (parent) 

in national finished water data 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

44 of 84

• 2001: 15M-22M lbs

Pesticide Industry Sales and 

Usage Report: S-Metolachlor • 1999: 16M-19M lbs • 2001: 20M-24M lbs • 2003: 28M-33M lbs • 2005: 27M-32M lbs • 2007: 30M-35M lbs

RED 1995 • ~58.7M lbs active ingredient 

used annually between 

1987-1993

Fate / Transport • Moderately to very mobile in 

soil (RED)

• Subject to biodegradation 

and adsorption to 

suspended solids and 

sediment in water

o NC: 0.08% (2 of 2,477) o OH: 0.73% (6 of 821) o R9 Tribes: Not detected from 225 systems o SD: Not detected from 255 systems o TX: 1.78% (40 of 2,252) o WI ’83-’99: 0.77% (9 of 1,175) o WI ’00-’09: 0.77% (7 of 915)

Supplemental Drinking Water Data 

Recent CCRs from 26 CWSs that serve >1M (2006-2007)

• Not detected >1⁄2HRL or >HRL in 5 CWSs

CWSS (2000) • No detects >1⁄2HRL or >HRL

CWSS (2006) • % PWSs w/ detects = 3.19% (3 of 94); no detects >1⁄2HRL or >HRL

EWG (2004-2009)

• 115 PWSs from 20 states w/ detects; no detects >1⁄2HRL or >HRL

PDP Raw and Finished Water (2001-2009)

• Max detect in finished water = 2.031 μg/L, <1⁄2HRL • Max detect in raw water = 2.000 μg/L, <1⁄2HRL • % samples w/ detects = 42.17% (2.433 of 5,770); no detects

>1⁄2HRL or >HRL

PMP Raw & Finished Water (1999) • No max conc. >1⁄2HRL or >HRL 

Other studies w/ no detects >1⁄2HRL or >HRL • National Pesticide Survey (1988-1990) • Wisconsin GW Study (1999-2000)
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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Supplemental Ambient/Source Water Data 

NAWQA Ambient Water (1992-2001)

• MRLs variable (0.002 – 0.006 μg/L)

• No GW or SW detects >1⁄2HRL or >HRL

• % GW samples w/ detects = 12.28% (750 of 6,108)

• % SW samples w/ detects = 68.87% (10,767 of 15,634)

• % GW sites w/ detects = 11.44% (597 of 5,217)

• % SW sites w/ detects = 62.63% (1,220 of 1,984)

• Median detect = 0.03 μg/L

• 99%ile detect = 6.71 μg/L

• Max detect = 77.6 μg/L

STORET

• MRL unavailable (min detect = 0 μg/L1)

• Data from 27 states

• No detects >1⁄2HRL or >HRL 

• % GW samples w/ detects = 8.40% (260 of 3,094)

• % SW samples w/ detects = 37.03% (13,688 of 36,967)

• % GW sites w/ detects = 8.89% (84 of 945)

• % SW sites w/ detects = 58.99% (1,512 of 2,563)

• Minimum detect = 0.16 μg/L

• 90%ile detect = 1.37 μg/L

• Max detect = 133.20 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NREC Ambient Water

• MRL unavailable

• % SW sites w/ detects = 8.76%; no detects >1⁄2HRL or >HRL 

• % GW sites w/ detects = 1.23%; no detects >1⁄2HRL or >HRL

NAWQA National Synthesis (1992-2001)

• LT-MDL = 0.006 μg/L 

• No max. detects >1⁄2HRL or >HRL
Phase 2 of Protocol for Regulatory Determination 3 April 2014

46 of 84

NAWQA Domestic Well Water Quality (1991-2004)

• % samples w/ detects = 6.9% (174 of 2,540); no detects >1⁄2HRL or 

>HRL

NAWQA Carbonate Aquifer Study (1993-2005)

• % samples w/ detects = 14.9% (153 of 1,027); no detects >1⁄2HRL 

or >HRL

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.002 - 0.006 μg/L

• No detects >1⁄2HRL or >HRL

• % samples w/ detects = 8.62% (75 of 870)

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• No detects >1⁄2HRL or >HRL 

o Phase 1 % samples w/ GW detects = 10.9% (24 of 221); max 

detect = 3.58 μg/L

o Phase 1 % samples w/ SW detects = 51.4% (75 of 146); max 

detect = 2.93 μg/L

o Phase 2 % GWraw detects = 13.0% (8 of 64)

o Phase 2 % GWfinished detects = 11.0% (7 of 65)

o Phase 2 % SWraw detects = 59.0% (53 of 90)

o Phase 2 % SWfinished detects = 54.0% (47 of 87)

Pesticides in GW Database (1971-1991)

• % wells w/ detects = 0.96% (213 of 22,255); no detects >1⁄2HRL or 

>HRL

• % states w/ detects = 68.97% (20 of 29)

Acetochlor Registration Partnership (1995-2001)

• % wells w/ detects in GW study = 16.48% (30 of 182)

• % samples w/ detects in SW study = 53%

Iowa Well Water Study (2006-2008)

• % samples w/ detects = 1.92% (9 of 469); no detects >1⁄2HRL or 

>HRL

Iowa SDWA Compliance (1988-1995)
Phase 2 of Protocol for Regulatory Determination 3 April 2014

47 of 84

• % samples w/ detects = 16%; max detect = 9.4 μg/L, no detects 

>1⁄2HRL or >HRL

Other studies w/ no detects >1⁄2HRL or >HRL 

• Pesticides/Metabolites - Suffolk County, NY (1998)

• Metolachlor/Metabolites in Tile Drain & Stream Runoff - Canajoharie 

Creek Watershed (1997)

CDC Fourth National Report (2003-2004)

• 95%iles <LOD in 2,538 urine samples

Occurrence summary and/or other information:

• Few (3) detections, none >HRL in recent national data (UCMR 2); 

Metolachlor (parent) is potentially not occurring at levels of public 

health concern

• Frequent detections in ambient water with some detections >HRL

• Metolachlor and other chloroacetanilides may be considered as a 

group

19. Metolachlor ethanesulfonic 

acid (ESA)

• CASRN = 171118095

• Substance Key = 79218

• A degradate of metolachlor 

• See also parent compound

Production / Release Data

Not produced commercially

Fate / Transport

• Expected mobility in water: 

metolachlor ESA > 

metolachlor OA > 

metolachlor 

• May be very persistent in 

Critical Health Endpoint

• Parent (Metolachlor) is surrogate

• Decreased body weight gain

(Hazelette, 1989)

• NOEL = 9.7 mg/kg-day

• UF = 100

• RfD = 0.1 mg/kg-day

• Non-cancer HRL = 700 μg/L

Non-Cancer Health Effects

• OPP supplemental data

• No biologically significant effects

• NOEL ≥ 1,000 mg/kg-day

• Non-cancer HRL > 7,000 μg/L

Health Assessment Status

• Parent compound [OPP RED 1995]

Analyzed using HRL of 700 μg/L

National Drinking Water Data

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 1 μg/L

• No detects >1⁄2HRL or >HRL

• % samples w/ detects = 0.47% (52 of 11,100)

• % PWSs w/ detects = 1.59% (19 of 1,198)

• Median detect = 1.44 μg/L

• 99%ile detect = 3.63 μg/L

• Max detect = 3.95 μg/L

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Not detected >1⁄2HRL or >HRL in 1 CWS

Does not proceed to phase 3

Rationale: 

While metolachlor ESA has no or 

low detections based on national 

finished water data, there is no 

health assessment for the ESA 

degradate and it difficult to assess 

whether it is occurring at levels of 

concern. Also, metolachlor ESA 

might be considered as a group 

along with other chloroacetanilides 

and/or their degradates in the 

future. 

Health: 

Health assessment for Metolachlor 

ESA (degradate) will not be completed 

by Fall 2011
Phase 2 of Protocol for Regulatory Determination 3 April 2014

48 of 84

ground water Sensitive Populations/Lifestages

• None identified CWSS (2006)

• % PWSs w/ detects = 1.16% (1 of 86); no detects >1⁄2HRL or >HRL

PDP Raw and Finished Water (2001-2009)

• Max detect in finished water = 2.24 μg/L, <1⁄2HRL

• Max detect in raw water = 3.603 μg/L, <1⁄2HRL

• % samples w/ detects = 65.13% (3,192 of 4,901); no detects 

>1⁄2HRL or >HRL

Other studies w/ no detects >1⁄2HRL or >HRL

• Wisconsin GW Study (1999-2000)

Supplemental Ambient/Source Water Data

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• No detects >1⁄2HRL or >HRL

o Phase 1 % GW detects = 28.8% (21 of 73); max detect = 2.72 

μg/L

o Phase 1 % SW detects = 69.2% (27 of 39); max detect = 2.07 

μg/L

o Phase 2 % GWraw detects = 47.0% (15 of 32)

o Phase 2 % GWfinished detects = 41.0% (13 of 32) 

o Phase 2 % SWraw detects = 68.0% (33 of 49)

o Phase 2 % SWfinished detects = 59.0% (28 of 48)

Acetochlor Registration Partnership (1999-2001)

• % wells w/ detects in GW study = 58.24% (106 of 182)

• % samples w/ detects in SW study = 56%

Iowa Well Water Study (2006-2008)

• % samples w/ detects = 33.05% (156 of 472); no detects >1⁄2HRL or 

>HRL

Other studies w/ no detects >1⁄2HRL or >HRL

• Pesticides/Metabolites - Suffolk County, NY (1998)

Occurrence:

No detections for Metolachlor ESA 

(degradate) in national finished water 

data at levels of public health concern 

based on the draft HRL
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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• Metolachlor/Metabolites in Tile Drain & Stream Runoff - Canajoharie 

Creek Watershed (1997)

Occurrence summary and/or other information:

• No detections for Metolachlor ESA > parent (Metolachlor) HRL in 

national data (UCMR 2) as well as supplemental drinking water and 

ambient water data

20. Metolachlor oxanilic acid 

(OA)

• CASRN = 152019733

• Substance Key = 79220

• A degradate of metolachlor

• See also parent compound

Production / Release Data

Not produced commercially

Fate / Transport

• Expected mobility in water: 

metolachlor ESA > 

metolachlor OA > 

metolachlor 

• May be very persistent in 

ground water

Critical Health Endpoint

• Parent (Metolachlor) is surrogate

• Decreased body weight gain ( 

Hazelette, 1989)

• NOEL = 9.7 mg/kg-day

• UF = 100

• RfD = 0.1 mg/kg-day

• Non-cancer HRL = 700 μg/L

Non-Cancer Health Effects

• OPP supplemental data

• No biologically significant effects

• NOEL ≥ 1,000 mg/kg-day

• Non-cancer HRL > 7,000 μg/L

Health Assessment Status

• Parent compound [OPP RED 1995]

Sensitive Populations/Lifestages

• None identified

Analyzed using HRL of 700 μg/L

National Drinking Water Data

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 2 μg/L

• No detects >1⁄2HRL or >HRL 

• % samples w/ detects = 0.03% (3 of 11,100)

• % PWSs w/ detects = 0.08% (1 of 1,198)

• Median detect = 3.08 μg/L

• 99%ile detect = 3.53 μg/L

• Max detect = 3.54 μg/L

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Not detected >1⁄2HRL or >HRL in 1 CWS

CWSS (2006)

• % PWSs w/ detects = 1.16% (1 of 86); no detects >1⁄2HRL or >HRL 

PDP Raw and Finished Water (2001-2009)

• Max detect in finished water = 4.42 μg/L, <1⁄2HRL

• Max detect in raw water = 1.5 μg/L, <1⁄2HRL

• % samples w/ detects = 45.21% (2,251 of 4,979); no detects 

>1⁄2HRL or >HRL

Other studies w/ no detects >1⁄2HRL or >HRL

Does not proceed to phase 3

Rationale: 

While Metolachlor OA has no or low 

detections based on national 

finished water data, there is no 

health assessment for the OA 

degradate and it difficult to assess 

whether it is occurring at levels of 

concern. Also, metolachlor OA 

might be considered as a group 

along with other chloroacetanilides 

and/or their degradates in the 

future. 

Health: 

Health assessment for Metolachlor OA 

(degradate) will not be completed by 

Fall 2011

Occurrence:

No detections for Metolachlor OA 

(degradate) in national finished water 

data at levels of public health concern 

based on the draft HRL
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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• Wisconsin GW Study (1999-2000)

Supplemental Ambient/Source Water Data

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• No detects >1⁄2HRL or >HRL

o Phase 1 % GW detects = 15.1% (11 of 73); max detect = 2.96 

μg/L

o Phase 1 % SW detects = 66.7% (26 of 39); max detect = 1.47 

μg/L

o Phase 2 % GWraw detects = 38.0% (12 of 32)

o Phase 2 % GWfinished detects = 34.0% (11 of 32)

o Phase 2 % SWraw detects = 77.0% (38 of 49)

o Phase 2 % SWfinished detects = 59.0% (28 of 48)

Acetochlor Registration Partnership (1999-2001)

• % wells w/ detects in GW study = 34.62% (63 of 182)

• % samples w/ detects in SW study = 57%

Iowa Well Water Study (2006-2008)

• % samples w/ detects = 8.26% (39 of 472); no detects >1⁄2HRL or 

>HRL

Other studies w/ no detects >1⁄2HRL or >HRL

• Pesticides/Metabolites - Suffolk County, NY (1998)

• Metolachlor/Metabolites in Tile Drain & Stream Runoff - Canajoharie 

Creek Watershed (1997)

Occurrence summary and/or other information:

• No detections for Metolachlor OA > parent (Metolachlor) HRL in 

national data (UCMR 2) as well as supplemental drinking water and 

ambient water data

21. Molinate

• CASRN = 2212671

• Substance Key = 12912

• An azepine pesticide, used 

Critical Health Endpoint

• Reproductive toxicity

• NOEL = 0.2 mg/kg-day

• UF = 100

Analyzed using HRL of 14 μg/L

National Drinking Water Data 

Does not proceed to phase 3

Rationale: 

The contaminant likely has no or 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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as an herbicide

• Uses cancelled in 2004; 

phase-out scheduled to be 

complete in 2009

Production / Release Data

TRI-Release 2006

• Surface water = 4 lbs/yr (1 

state)

• Total = 799 lbs/yr (1 state)

TRI-Release 2004

• Surface water = 115 lbs/yr 

(1 state)

• Total = 2,089 lbs/yr (2 

states)

NCFAP Total Pesticide 

Application 1997

• 3,669,398 lbs/yr (6 states)

Fate / Transport

• Expected to be moderately 

mobile in water, based on 

physical and chemical 

properties

• Subject to biodegradation 

and volatilization 

• RfD = 0.002 mg/kg-day

• Non-cancer HRL = 14 μg/L

Health Assessment Status

• IRIS 1988 

• An OPP RED was in process but 

will not be completed due to 

cancellation of molinate

Sensitive Populations/Lifestages

• Fetuses

UCMR 1 Finished Water Assessment Monitoring (2001-2003)

• MRL = 0.9 μg/L

• No detects >1⁄2 HRL or >HRL

• % PWSs w/ detects = 0.03% (1 of 3,873)

• % samples w/ detects = 0.003% (1 of 33,799)

• Median detect = 5.7 μg/L

• 99%ile detect = 5.7 μg/L

• Max detect = 5.7 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1995-2007)

• No detects 1⁄2 HRL or >HRL

• % systems w/ detects = 

o CA: 0.13% (3 of 2,280) 

o IL: Not detected from 85 systems

o OH: Not detected from 24 systems

Supplemental Drinking Water Data 

Recent CCRs from 26 CWSs that serve >1M (2006-2007)

• Not detected in 3 CWSs in NY

EWG (2004-2009)

• 1 PWS in 1 state w/ detects; no detects >1⁄2HRL or >HRL

PDP Raw and Finished Water (2001-2009)

• Not detected in 3,270 samples

PMP Raw Water (1999)

• % samples w/ detects = 0.3% (1 of 333); max detect = 0.004 μg/L, 

no detects >1⁄2HRL or >HRL

low potential for public health 

concern

Health:

Available health assessment

Occurrence:

No detections in national or nonnational finished water data at levels of 

public health concern based on HRL
Phase 2 of Protocol for Regulatory Determination 3 April 2014

52 of 84

Supplemental Ambient/Source Water Data 

NAWQA Ambient Water (1992-2001)

• MRLs variable (most are 0.004 μg/L)

• No GW detects >1⁄2HRL or >HRL

• % GW samples w/ detects = 0.39% (24 of 6,080)

• % SW samples w/ detects = 5.38% (800 of 14,876)

• % SW samples w/ detects >1⁄2HRL = 0.30% (45 of 14,876)

• % SW samples w/ detects >HRL = 0.21% (31 of 14,876)

• % GW sites w/ detects = 0.46% (24 of 5,211)

• % SW sites w/ detects = 5.03% (96 of 1,907)

• % SW sites w/ detects >1⁄2HRL = 1.10% (21 of 1,907)

• % SW sites w/ detects >HRL = 0.68% (13 of 1,907)

• Median detect = 0.0372 μg/L

• 99%ile detect = 47.9 μg/L

• Max detect = 200 μg/L

STORET

• MRL unavailable (min detect = 0 μg/L1)

• Data from 13 states

• No GW detects in 33 samples from 14 sites

• % SW samples w/ detects = 30.18% (457 of 1,514)

• % SW samples w/ detects >1⁄2HRL = 1.59% (24 of 1,514)

• % SW samples w/ detects >HRL = 0.86% (13 of 1,514)

• % SW sites w/ detects = 31.47% (203 of 645)

• % SW sites w/ detects >1⁄2HRL = 3.41% (22 of 645)

• % SW sites w/ detects >HRL = 2.02% (13 of 645)

• Median detect = 0.05 μg/L

• 90%ile detect = 2.68 μg/L

• Max detect = 332.65 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

National Pesticide Survey (1988-1990)

• MRL = 0.18 μg/L

• Not detected in 566 CWS wells and 783 rural domestic wells
Phase 2 of Protocol for Regulatory Determination 3 April 2014

53 of 84

NAWQA Carbonate Aquifer Study (1993-2005)

• Not detected in 992 samples 

NAWQA Domestic Well Water Quality (1991-2004)

• % samples w/ detects = 0.1% (2 of 2,539); no detects >1⁄2HRL or 

>HRL

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.0008 - 0.004 μg/L

• No detects >1⁄2HRL or >HRL

• % samples w/ detects = 0.47% (3 of 635)

NAWQA National Synthesis (1992-2001)

• MRL = 0.001 μg/L

• GW: no max detects >1⁄2HRL or >HRL

• SW: max detect from agricultural sites (200 μg/L) >HRL; max detect 

from mixed land use sites (1.57 μg/L) no detects >1⁄2HRL or >HRL

Occurrence summary and/or other information:

• One detection, none >HRL in national finished water data 

(UCMR1) 

• Few detections in CA drinking water data, none >HRL

• Detections in ambient water data; some >HRL

• Uses cancelled in 2004; phase-out scheduled to be complete in 

2009

22. Molybdenum

• CASRN = 7439987

• Substance Key = 18825

• A naturally-occurring 

element 

• Commonly used form, 

Molybdenum trioxide, is 

used as a chemical reagent

Production / Release Data

Critical Health Endpoint(s)

• Gout-like symptoms and increased 

serum uric acid (Koval'skiy et al., 

1961 in IRIS 1991)

• LOAEL = 0.14 mg/kg-day

• UF = 30

• RfD = 0.005 mg/kg-day

• Non-cancer HRL = 35 μg/L

• Female reproductive effects 

(Fungwe et al., 1990 in IOM 2001)

Analyzed using HRLs of 35 μg/L and 200 μg/L

Analysis at HRL of 35 μg/L:

National Drinking Water Data

NIRS Finished Water [GW only] (1984-1986)

• MRL = 6 μg/L

• % PWSs w/ detects = 7.79% (77 of 989)

• % PWSs w/ detects >1⁄2HRL = 2.43% (24 of 989)

Does not proceed to phase 3

Rationale: 

The contaminant likely has no or 

low potential for public health 

concern, but has a health data gap.

Health: 

Health assessment will not be updated 

by Fall 2011

Occurrence:
Phase 2 of Protocol for Regulatory Determination 3 April 2014

54 of 84

TRI-Release 2010

• Surface water = 40,058

lbs/yr (15 states)

• Total = 1,416,893 lbs/yr (33

states)

TRI-Release 2008

• Surface water = 45,828

lbs/yr (16 states)

• Total = 1,495,177 lbs/yr (30

states)

TRI-Release 2006

• Surface water = 40,030 

lbs/yr (20 states)

• Total = 2,454,437 lbs/yr (36 

states)

TRI-Release 2004

• Surface water = 36,579 

lbs/yr (18 states)

• Total = 2,115,011 lbs/yr (36 

states)

Fate / Transport

• Ionic species expected to be 

mobile in most soils (HSDB)

• Persistent in the 

environment, though the 

form may change (CCL CIS) 

• NOAEL = 0.9 mg/kg-day

• UF = 30

• RfD eq. = 0.03 mg/kg-day 

• Non-cancer HRL = 200 μg/L

Health Assessment Status

• IRIS (1991)

• Not classifiable as to human 

carcinogenicity, group D (1986 

cancer guidelines)

• Updated since CCL3

o NAS (IOM 2001 pgs. 436-437)

Sensitive Populations/Lifestages

• People susceptible to gout

• % PWSs w/ detects >HRL = 0.61% (6 of 989)

• Median detect = 10 μg/L

• 99%ile detect = 106 μg/L

• Max detect = 181 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1995-2007)

• % systems w/ detects = 

o CA: 66.46% (107 of 161)

o IL: 17.23% (149 of 865)

o OH: 50.00% (13 of 26)

o WI ’00-’09: Not detected from 1 system

• % systems w/ detects >1⁄2HRL = 

o CA: 11.80% (19 of 161)

o IL: 13.99% (121 of 865)

o OH: 15.38% (4 of 26)

• % systems w/ detects >HRL = 

o CA: 3.73% (6 of 161)

o IL: 3.35% (29 of 865)

o OH: 7.69% (2 of 26)

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Detected in 2 CWSs; max detect in 1 CWS >HRL

CWSS (2006)

• % PWSs w/ detects = 6.90% (4 of 58); max detect = 203 μg/L, 

>HRL

EWG (2004-2009)

• At least 21 PWSs in 4 states w/ detects >HRL, and at least 22 

PWSs in 4 states w/ detects >1⁄2HRL

No detections in national or nonnational finished water data at levels of 

public health concern based on the 

draft HRL
Phase 2 of Protocol for Regulatory Determination 3 April 2014

55 of 84

Supplemental Ambient/Source Water Data

NAWQA Ambient Water (1992-2001)

• MRLs variable (most within 0.2 – 1 μg/L)

• % GW samples w/ detects = 55.57% (1,807 of 3,252)

• % GW samples w/ detects >1⁄2HRL = 3.78% (123 of 3,252)

• % GW samples w/ detects >HRL = 1.88% (61 of 3,252)

• % SW samples w/ detects = 47.14% (1,120 of 2,376)

• % SW samples w/ detects >1⁄2HRL = 2.78% (66 of 2,376)

• % SW samples w/ detects >HRL = 0.42% (10 of 2,376)

• % GW sites w/ detects = 56.51% (1,641 of 2,904)

• % GW sites w/ detects >1⁄2HRL = 4.03% (117 of 2,904)

• % GW sites w/ detects >HRL = 1.96% (57 of 2,904)

• % SW sites w/ detects = 60.56% (238 of 393)

• % SW sites w/ detects >1⁄2HRL = 4.33% (17 of 393)

• % SW sites w/ detects >HRL = 1.02% (4 of 393)

• Median detect = 3 μg/L

• 99%ile detect = 55.41 μg/L

• Max detect = 4,732.80 μg/L

STORET

• MRL unavailable (min detect = 0 μg/L1)

• Data from 37 states

• % GW samples w/ detects = 44.46% (987 of 2,220)

• % GW samples w/ detects >1⁄2HRL = 13.47% (299 of 2,220)

• % GW samples w/ detects >HRL = 10.63% (236 of 2,220)

• % SW samples w/ detects = 42.29% (26,511 of 62,686)

• % SW samples w/ detects >1⁄2HRL = 9.89% (6,200 of 62,686)

• % SW samples w/ detects >HRL = 3.85% (2,415 of 62,686)

• % GW sites w/ detects = 54.94% (384 of 699)

• % GW sites w/ detects >1⁄2HRL = 17.45% (122 of 699)

• % GW sites w/ detects >HRL = 16.17% (113 of 699)

• % SW sites w/ detects = 37.99% (5,754 of 15,145)
Phase 2 of Protocol for Regulatory Determination 3 April 2014

56 of 84

• % SW sites w/ detects >1⁄2HRL = 9.84% (1,491 of 15,145)

• % SW sites w/ detects >HRL = 4.27% (647 of 15,145)

• Median detect = 4 μg/L

• 90%ile detect = 33 μg/L

• Max detect = 75,000 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.06 - 1 μg/L

• % samples w/ detects = 77.23% (485 of 628)

• % samples w/ detects >1⁄2HRL = 2.23% (14 of 628)

• % samples w/ detects >HRL = 0.64% (4 of 628)

NAWQA Domestic Well Water Quality (1991-2004)

• 0.55% of wells exceeded 40 μg/L, >HRL

U.S. Glacial Aquifer Study (1991-2003)

• % samples w/ detects =71.8% (608 of 847)

• Max detect (304 μg/L) >HRL

Analysis at HRL of 200 μg/L:

National Drinking Water Data

NIRS Finished Water [GW only] (1984-1986)

• MRL = 6 μg/L

• No detects >HRL

• % PWSs w/ detects = 7.79% (77 of 989) 

• Median detect = 10 μg/L

• 99%ile detect = 106 μg/L

• Max detect = 181 μg/L

Non-National Drinking Water Data
Phase 2 of Protocol for Regulatory Determination 3 April 2014

57 of 84

State Drinking Water Data (1995-2007)

• No detects >HRL

• % systems w/ detects = 

o CA: 66.46% (107 of 161)

o IL: 17.23% (149 of 865)

o OH: 50.00% (13 of 26)

o WI ’00-’09: Not detected from 1 system

• % systems w/ detects >1⁄2HRL = 

o IL: 0.12% (1 of 865)

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Detected in 2 CWSs; max detect in 1 CWS >HRL

CWSS (2006)

• % PWSs w/ detects = 4.26% (4 of 94); max detect = 203 μg/L, 

>HRL

EWG (2004-2009)

• 1 PWSs w/ max detect of >1⁄2HRL

Supplemental Ambient/Source Water Data

NAWQA Ambient Water (1992-2001)

• MRLs variable (most within 0.2 – 1 μg/L)

• No SW detects >HRL

• % GW samples w/ detects = 55.57% (1,807 of 3,252)

• % GW samples w/ detects >1⁄2HRL = 0.28% (9 of 3,252)

• % GW samples w/ detects >HRL = 0.15% (5 of 3,252)

• % SW samples w/ detects = 47.14% (1,120 of 2,376)

• % SW samples w/ detects >1⁄2HRL = 0.04% (1 of 2,376)

• % GW sites w/ detects = 56.51% (1,641 of 2,904)

• % GW sites w/ detects >1⁄2HRL = 0.31% (9 of 2,904)
Phase 2 of Protocol for Regulatory Determination 3 April 2014

58 of 84

• % GW sites w/ detects >HRL = 0.17% (5 of 2,904)

• % SW sites w/ detects = 60.56% (238 of 393)

• % SW sites w/ detects >1⁄2HRL = 0.25% (1 of 393)

• Median detect = 3 μg/L

• 99%ile detect = 55.41 μg/L

• Max detect = 4,732.80 μg/L

STORET

• MRL unavailable (min detect = 0 μg/L1)

• Data from 32 states

• % GW samples w/ detects = 24.89% (388 of 1,559)

• % GW samples w/ detects >1⁄2HRL = 2.50% (39 of 1,559)

• % GW samples w/ detects >HRL = 2.37% (37 of 1,559)

• % SW samples w/ detects = 45.71% (18,231 of 39,884)

• % SW samples w/ detects >1⁄2HRL = 3.20% (1,276 of 39,884)

• % SW samples w/ detects >HRL = 2.85% (1,135 of 39,884)

• % GW sites w/ detects = 34.69% (170 of 490)

• % GW sites w/ detects >1⁄2HRL = 4.08% (20 of 490)

• % GW sites w/ detects >HRL = 3.67% (18 of 490)

• % SW sites w/ detects = 37.37% (3,854 of 10,313)

• % SW sites w/ detects >1⁄2HRL = 1.72% (177 of 10,313)

• % SW sites w/ detects >HRL = 1.09% (112 of 10,313)

• Median detect = 4 μg/L

• 90%ile detect = 44 μg/L

• Max detect = 75,000 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.06 - 1 μg/L

• No detects >1⁄2HRL or >HRL

• % samples w/ detects = 77.23% (485 of 628)

NAWQA Domestic Well Water Quality (1991-2004)

• 0.55% of wells exceeded 40 μg/L, but unknown if >HRL
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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U.S. Glacial Aquifer Study (1991-2003)

• Max detect (304 μg/L) in 847 GW samples >HRL

Occurrence summary and/or other information:

• No detections >HRL in national data (NIRS)

• On UCMR 3

23. Nitrobenzene

• CASRN = 98953

• Substance Key = 3998

• A synthetic aromatic nitro 

compound that occurs as an 

oily, flammable liquid

• Commonly used in the 

production of aniline; as a 

solvent in the manufacture 

of paints, shoe polishes, 

floor polishes, metal 

polishes, explosives, aniline 

dyes, pesticides, and drugs

(such as acetaminophen); 

and in its re-distilled form 

(oil of mirbane), as an 

inexpensive perfume for 

soaps

Production / Release Data

TRI-Release 2010

• Surface water = 175 lbs/yr 

(2 states)

• Total = 321,721 lbs/yr (16

states)

TRI-Release 2008

• Surface water = 189 lbs/yr 

Critical Health Endpoint

• Increased methemoglobin (NTP, 

1983)

• BMDL10 = 1.8 mg/kg-day

• UF = 1,000

• RfD = 0.002 mg/kg-day

• Non-cancer HRL = 14 μg/L

Health Assessment Status

• IRIS (2009)

• Likely to be carcinogenic to humans 

(2005 cancer guidelines) for all 

exposure routes (no cancer slope 

factor for oral route)

Sensitive Populations/Lifestages

• Neonates

• Persons prone to hereditary 

methemoglobinemia

• Persons with decreased glucose-6-

phosphate dehydrogenase activity

Analyzed using HRL of 14 μg/L

National Drinking Water Data

UCMR 1 Finished Water Assessment Monitoring (2001-2003)

• MRL = 10 μg/L

• All detects (both detects) >HRL

• % samples w/ detects >HRL = 0.01% (2 of 33,576)

• % PWSs w/ detects >HRL = 0.05% (2 of 3,861)

• Median detect = 60.8 μg/L

• 99%ile detect = 100 μg/L

• Max detect = 100 μg/L

UCMR 1 Finished Water Screening Survey (2001-2003)

• MRL = 0.5 μg/L

• Not detected in 2,306 samples from 295 PWSs

Non-National Drinking Water Data

State Drinking Water Data (1995-2007)

• No detects >1⁄2HRL or >HRL

• % systems w/ detects = 

o CA: 0.18% (1 of 546)

o IL: Not detected from 85 systems

o OH: Not detected from 1,134 systems

Supplemental Drinking Water Data

Referred to CVOC for evaluation. 

After evaluation of group 

information, EPA will decide 

whether to include in CVOC group 

and evaluate for regulatory 

determination. 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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(2 states)

• Total = 487,627 lbs/yr (14

states)

TRI-Release 2006

• Surface water = 42 lbs/yr (2 

states)

• Total = 579,017 (15 states)

TRI-Release 2004

• Surface water = 60 lbs/yr (1 

state)

• Total = 350,303 (14 states)

CUSIUR Production Data • >1B lbs/yr (1998, 2002) • ≥ 1B lbs/yr (2006)

Fate / Transport • Expected to be moderately 

to highly mobile in water, 

based on physical and 

chemical properties 

• Not persistent in the 

environment (biodegrades 

fast with acclimation) (CCL CIS) 

Recent CCRs from 26 CWSs that serve >1M (2002-2007)

• Not detected in 3 CWSs

EWG (2004-2009)

• 3 PWSs from 2 states w/ detects; no max detects >1⁄2HRL or >HRL

Supplemental Ambient/Source Water Data

STORET • MRL unavailable (min detect = 0 μg/L

1

)

• Data from 18 states • No SW detects >1⁄2HRL or >HRL • % GW samples w/ detects = 30.41% (350 of 1,151

)

• % GW samples w/ detects >1⁄2HRL = 2.17% (25 of 1,151

)

• % GW samples w/ detects >HRL = 0.09% (1 of 1,151)

• % SW samples w/ detects = 14.57% (95 of 652)

• % GW sites w/ detects = 40.82% (240 of 588)

• % GW sites w/ detects >1⁄2HRL = 3.91% (23 of 588)

• % GW sites w/ detects >HRL = 0.17% (1 of 588

)

• % SW sites w/ detects = 24.03% (62 of 258)

• Median detect = 0 μg/L • 90%ile detect = 0.24 μg/L • Max detect = 20 μg/L 1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

CDC Fourth National Report (2003-2004)

• 95%iles <LOD in 1,066 blood samples 

Occurrence summary and/or other information: • Few detections >HRL in national data (UCMR1) • No detections >HRL in state drinking water data and one >HRL in 

ambient water data
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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24. N-Nitrosodiethylamine 

(NDEA)

• CASRN = 55185

• Substance Key = 2243

• A nitrosamine 

• A suspected disinfection byproduct

• Used as an additive in 

gasoline and lubricants, and 

as an antioxidant and a 

stabilizer in plastics

Production / Release Data

TRI-Release 2010

• Surface water = 0 lbs/yr (0 

states)

• Total = 633 lbs/yr (1 state)

TRI-Release 2008

• Surface water = 0 lbs/yr (0 

states)

• Total = 650 lbs/yr (1 state)

TRI-Release 2006

• Surface water = 0 lbs/yr (0 

states)

• Total = 500 lbs/yr (1 state)

TRI-Release 2004

• Surface water = 0 lbs/yr (0 

states)

• Total = 1,000 lbs/yr (1 state)

Fate / Transport

Critical Health Endpoint

• Cancer (liver and esophagus) (Peto 

et al., 1991a,b)

• CSF = 30 (mg/kg-day)-1

• Cancer HRL = 0.0004 μg/L

(includes ADAFs and exposure 

factors)

Health Assessment Status

• Updated since CCL3

o Draft OW Health Advisory 

(2011)[finalized in 2013]

Sensitive Populations/Lifestages

• Fetuses/infants/children

• Consumers of alcoholic beverages

Analyzed using HRL of 0.0004 μg/L

National Drinking Water Data

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 0.005 μg/L

• All detects >HRL

• % samples w/ detects >HRL = 0.26% (46 of 18,038)

• %PWS w/ detects >HRL = 2.17% (26 of 1,198)

• Median detect = 0.007 μg/L

• 99%ile detect = 0.093 μg/L

• Max detect = 0.1 μg/L

Non-National Drinking Water Data

State Drinking Water Data (2001-2007)

• All detects >HRL

• % systems w/ detects >HRL = 

o CA: 7.14% (1 of 14)

Supplemental Ambient/Source Water Data

STORET (SW Only)

• MRL unavailable (min detect = ND)

• No SW detects in 3 samples from 3 sites in 3 states

Occurrence summary and/or other information:

• 2% of PWSs with detections in national data (UCMR2)

• Uncertainty in UCMR2 data; detection limit is 13 times higher than 

HRL; possible occurrence >HRL that is undetected

• One detection (>HRL) in CA drinking water data

• Included with NDMA in nitrosamine group

Proceeds to phase 3

Rationale: 

The contaminant is of potential 

public health concern, does not 

have critical health or occurrence 

data gaps, and is part of the 

nitrosamine group

Health:

Available health assessment

Occurrence:

Occurrence at levels of public health 

concern in national and non-national 

finished water data 
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• High mobility in soil (HSDB) 

• High volatility in water; 

subject to photodegradation 

(HSDB) 

25. N-nitrosodimethylamine 

(NDMA)

• CASRN = 62759

• Substance Key = 2446

• A nitrosamine and is a 

disinfection by-product

• Used as an industrial 

solvent, an anti-oxidant, 

and, formerly, in the 

production of rocket fuel

Production / Release Data

TRI-Release 2006

• Total = 0 lbs/yr (0 states)

TRI-Release 1998-1999

• Air emissions = 134 lbs (2 

states)

Fate / Transport

• Expected to be moderately 

mobile to very mobile in 

water, based on physical 

and chemical properties

• Subject to volatilization, 

photodegradation, and 

microbial degradation 

Critical Health Endpoint

• Cancer (liver) (Peto et al., 1991a,b)

• CSF = 21 (mg/kg-day)-1

• Cancer HRL = 0.0006 μg/L

(includes ADAFs and exposure 

factors)

Health Assessment Status

• Updated since CCL3

o Draft OW Health Advisory 

(2011)[finalized in 2013]

Sensitive Populations/Lifestages

• Fetuses/infants/children

• Consumers of alcoholic beverages

Analyzed using HRL of 0.0006 μg/L

National Drinking Water Data

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 0.002 μg/L

• All detects >HRL

• % samples w/ detects >HRL = 10.21% (1,841 of 18,040)

• % PWSs w/ detects >HRL = 27.05% (324 of 1,198)

• Median detect = 0.004 μg/L

• 99%ile detect = 0.06 μg/L

• Max detect = 0.63 μg/L

Non-National Drinking Water Data

State Drinking Water Data (2001-2007)

• All detects >HRL

• % systems w/ detects >HRL = 

o CA: 23.76% (24 of 101)

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2006-2007)

• Detected in 1 CWS

• Avg. annual detects = 0.0008 μg/L (2006) and 0.0014 μg/L (2007) 

>HRL

CWSS (2006)

Proceeds to phase 3

Rationale: 

The contaminant is of potential 

public health concern, does not 

have critical health or occurrence 

data gaps, and is part of the 

nitrosamine group

Health:

Available health assessment

Occurrence:

Significant occurrence at levels of 

public health concern in national and 

non-national finished water data
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(ATSDR) • % samples w/ detects = 22% (2 of 9); detects = 0.0014 μg/L, >HRL

EWG (2004-2009)

• 26 PWSs from 3 states w/ detects >HRL; all detects >HRL

Supplemental Ambient/Source Water Data

STORET

• MRL unavailable (min detect = 0 μg/L1

)

• Data from 14 states

• No GW detects >1⁄2HRL or >HRL

• % GW samples w/ detects = 32.44% (133 of 410)

• % SW samples w/ detects = 13.55% (68 of 502)

• % SW samples w/ detects >1⁄2HRL = 1.39% (7 of 502)

• % SW samples w/ detects >HRL = 1.39% (7 of 502)

• % GW sites w/ detects = 40.26% (122 of 303)

• % SW sites w/ detects = 24.71% (42 of 170)

• % SW sites w/ detects >1⁄2HRL = 2.35% (4 of 170)

• % SW sites w/ detects >HRL = 2.35% (4 of 170)

• Median detect = 0 μg/L

• 90%ile detect = 0 μg/L

• Max detect = 0.05 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

USGS VOCs in Highway Runoff

• Not detected

AwwaRF (early 2000s)

• % PWS w/ detects = 85.71% (18 of 21); median detect < 0.001 μg/L

Occurrence summary and/or other information:

• Significant occurrence >HRL; 27% of PWSs >HRL

• Uncertainty in national data (UCMR2); all detections are 3 times 

higher than HRL due to detection limit; likely more occurrence 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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>HRL that is undetected

• 24% of PWSs had detections >HRL in CA finished water data 

• Supplemental drinking water and ambient water data also 

demonstrate detections >HRL

• Included with other nitrosamines as a contaminant group

26. N-Nitrosodi-n-propylamine 

(NDPA)

• CASRN = 621647

• Substance Key = 8798

• A nitrosamine 

• A disinfection byproduct

Production / Release Data

TRI-Release 2010

• Surface water = 0 lbs/yr (0 

states)

• Total = 382 lbs/yr (2 states)

TRI-Release 2008

• Surface water = 0 lbs/yr (0 

states)

• Total = 423 lbs/yr (2 states)

TRI-Release 2006

• Surface water = 0 lbs/yr (0 

states)

• Total = 751 lbs/yr (2 states)

TRI-Release 2004

• Surface water = 0 lbs/yr (0 

states)

• Total = 506 lbs/yr (2 states)

Critical Health Endpoint

• Cancer (liver and esophagus) 

(Druckrey et al., 1967)

• CSF = 2 (mg/kg-day)-1

• Cancer HRL = 0.007 μg/L (includes 

ADAFs and exposure factors)

Health Assessment Status

• Updated since CCL3

o Draft OW Health Advisory 

(2011)[finalized in 2013]

Sensitive Populations/Lifestages

• Fetuses/infants/children

• Consumers of alcoholic beverages

Analyzed using HRL of 0.007 μg/L

National Drinking Water Data

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 0.007 μg/L

• Not detected in 18,049 samples from 1,198 systems

Non-National Drinking Water Data

State Drinking Water Data (1995-2007)

• CA: Not detected in 55 systems

• IL: Not detected in 1 system

Supplemental Drinking Water Data

EWG (2004-2009)

• 1 PWS in 1 state w/ detects >HRL

Supplemental Ambient/Source Water Data

STORET

• MRL unavailable (min detect = 0 μg/L1)

• Data from 20 states 

• % GW samples w/ detects = 32.62% (349 of 1,070)

• % GW samples w/ detects >1⁄2HRL = 1.40% (15 of 1,070)

Proceeds to phase 3

Rationale: 

The contaminant is part of the 

nitrosamine group and does not 

have critical health or occurrence 

data gaps

Health:

Available health assessment

Occurrence:

No detections in national and nonnational finished water data
Phase 2 of Protocol for Regulatory Determination 3 April 2014

65 of 84

Fate / Transport

• Moderate mobility in soil 

(HSDB) 

• Low/moderate volatility in 

water; subject to 

photodegradation (HSDB) 

• % GW samples w/ detects >HRL = 1.40% (15 of 1,070)

• % SW samples w/ detects = 11.79% (71 of 602)

• % SW samples w/ detects >1⁄2HRL = 1.66% (10 of 602)

• % SW samples w/ detects >HRL = 1.66% (10 of 602)

• % GW sites w/ detects = 45.61% (239 of 524)

• % GW sites w/ detects >1⁄2HRL = 2.48% (13 of 524)

• % GW sites w/ detects >HRL = 2.48% (13 of 524)

• % SW sites w/ detects = 21.17% (47 of 222)

• % SW sites w/ detects >1⁄2HRL = 4.05% (9 of 222)

• % SW sites w/ detects >HRL = 4.05% (9 of 222)

• Median detect = 0 μg/L

• 90%ile detect = 0 μg/L

• Max detect = 20 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

Occurrence summary and/or other information:

• Not detected in national data (UCMR2); detection limit = HRL

• Not detected in CA drinking water data

• Included with NDMA in nitrosamine group

27. N-Nitrosodiphenylamine 

(NDPhA)

• CASRN = 86306

• Substance Key = 3193

• A nitrosamine 

• A possible disinfection 

byproduct

• A chemical reagent that is 

commonly used as rubber 

and polymer additive

Production / Release Data

TRI-Release 2010

Critical Health Endpoint

• Cancer (bladder) (NCI 1979)

• CSF = 0.0049 (mg/kg-day)-1

• Cancer HRL = 7 μg/L

Health Assessment Status

• IRIS (1987)

• Probable human carcinogen, group 

B2 (1986 cancer guidelines)

Sensitive Populations/Lifestages

• Fetuses/infants/children

• Consumers of alcoholic beverages

• Individuals with bladder dysfunction

Analyzed using HRL of 7 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1995-2007)

• CA: Not detected in 441 samples from 53 systems

Supplemental Ambient/Source Water Data

STORET

• MRL unavailable (min detect = 0 μg/L1)

• Data from 24 states

• % GW samples w/ detects = 31.56% (355 of 1,125)

Does not proceed to phase 3

Rationale: 

Even though it is part of the 

nitrosamine group, there is no EPA 

approved analytical method for 

monitoring.

Health: 

Health Assessment will be updated by 

Fall 2011

Occurrence:

No detections in non-national finished 

water data; no existing EPA approved 

drinking water analytical method
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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• Surface water = 0 lbs/yr (0 

states)

• Total = 12 lbs/yr (1 state)

TRI-Release 2008

• Surface water = 0 lbs/yr (0 

states)

• Total = 20 lbs/yr (1 state)

TRI-Release 2006

• Surface water = 0 lbs/yr (0 

states)

• Total = 14 lbs/yr (2 states)

TRI-Release 2004

• Surface water = 0 lbs/yr (0 

states)

• Total = 14 lbs/yr (2 states)

CUSIUR Production Data

• 10K-500K lbs/yr (2002)

Fate / Transport

• Low mobility in soil (HSDB) 

• Moderate volatility in water; 

subject to photodegradation 

(HSDB) 

• % GW samples w/ detects >1⁄2HRL = 0.98% (11 of 1,125)

• % GW samples w/ detects >HRL = 0.98% (11 of 1,125)

• % SW samples w/ detects = 21.02% (378 of 1,798)

• % SW samples w/ detects >1⁄2HRL = 0.17% (3 of 1,798)

• % SW samples w/ detects >HRL = 0.17% (3 of 1,798)

• % GW sites w/ detects = 45.19% (244 of 540)

• % GW sites w/ detects >1⁄2HRL = 2.04% (11 of 540)

• % GW sites w/ detects >HRL = 2.04% (11 of 540)

• % SW sites w/ detects = 31.49% (177 of 562)

• % SW sites w/ detects >1⁄2HRL = 0.53% (3 of 562)

• % SW sites w/ detects >HRL = 0.53% (3 of 562)

• Median detect = 0 μg/L

• 90%ile detect = 0.04 μg/L

• Max detect = 480 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

Occurrence summary and/or other information:

• Limited drinking water data 

• Even though part of the nitrosamine group, there is no EPA 

approved analytical method for monitoring. 

28. N-nitrosopyrrolidine (NPYR)

• CASRN = 930552

• Substance Key = 10160

• A nitrosamine

• Used as a research 

chemical

• Suspected drinking water 

Critical Health Endpoint

• Cancer (liver) (Peto et al., 1984; 

Gray et al., 1991)

• CSF = 7 (mg/kg-day)-1

• Cancer HRL = 0.002 μg/L (includes 

ADAFs and exposure factors)

Analyzed using HRL of 0.002 μg/L

National Drinking Water Data

UCMR 2 Finished Water Screening Survey (2008-2010)

• MRL = 0.002 μg/L

Proceeds to phase 3

Rationale: 

The contaminant is part of the 

nitrosamine group and does not 

have critical health or occurrence 

data gaps 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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by-product

Production / Release Data

No data for production and 

release

Fate / Transport

• High mobility in soil (HSDB) 

• Low volatility in water; 

subject to photodegradation 

(HSDB) 

Health Assessment Status

• Updated since CCL3

o Draft OW Health Advisory 

(2011)[finalized in 2013]

Sensitive Populations/Lifestages

• Fetuses/infants/children 

Consumers of alcoholic beverages

• % samples w/ detects = 0.23% (41 of 18,043)

• % samples w/ detects >1⁄2HRL = 0.13% (23 of 18,043)

• % samples w/ detects >HRL = 0.03% (5 of 18,043)

• % PWSs w/ detects = 1.75% (21 of 1,198)

• % PWSs w/ detects >1⁄2HRL = 1.34% (16 of 1,198)

• % PWSs w/ detects >HRL = 0.25% (3 of 1,198)

• Median detect = 0.004 μg/L

• 99%ile detect = 0.021 μg/L

• Max detect = 0.024 μg/L

Non-National Drinking Water Data

State Drinking Water Data (2006-2007)

• CA: Not detected in 4 systems

Supplemental Drinking Water Data

EWG (2004-2009)

• 4 PWSs in 2 states w/ detects; one detect >HRL 

Supplemental Ambient/Source Water Data

STORET (SW Only)

• MRL unavailable (min detect = ND)

• No SW detects in 7 samples from 6 sites in 3 states

Occurrence summary and/or other information:

• Some PWSs with detections, few (3) >HRL in national data 

(UCMR2)

• Not detected in CA drinking water data

• Some detections, one >HRL in other supplementary data

• Included with NDMA in nitrosamine group

Health:

Available health assessment

Occurrence:

Few detections in national finished 

water data and one >HRL in 

supplementary data
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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29. Perfluorooctane sulfonic 

acid (PFOS)

• CASRN = 1763231

• Substance Key = 12176

• A perfluorooctylsulfonic and 

heptadecafluoro-1-

octanesulfonic acid

• Formerly used as a 

surfactant or emulsifier in 

fire-fighting foam, circuit 

board etching acids, alkaline 

cleaners, and floor polish, 

and as a pesticide active 

ingredient for insect bait 

traps

Production / Release Data

CUSIUR Production Data 

• 10K-500K lbs/yr (2002)

Fate / Transport

• Physical and chemical 

properties give contrary 

indications about expected 

mobility in water 

• Persistent in the 

environment (biodegrades 

sometimes/recalcitrant); 

BST is the highest category 

available to be awarded to a 

recalcitrant contaminant

(CCL CIS) 

Critical Health Endpoint

• Thyroid effects (increase in TSH; 

decrease in T3); decrease in HDL

(Seacat et al., 2002)

• NOAEL = 0.03 mg/kg-day

• UF = 30

• Non-cancer HRL = 0.2 μg/L 

Health Assessment Status

• Provisional HA (2009)

• OW Health Advisory in process

Sensitive Populations/Lifestages

• Not completely characterized

Analyzed using HRL of 0.2 μg/L

Supplemental Drinking Water Data

NJDEP (2006)

• MRL = 0.004 μg/L

• % sites w/ detects = 57% (13 of 23); max detect = 0.019 μg/L, no 

detects >1⁄2HRL or >HRL

Select Minnesota Municipal Wells (ca. 2004)

• % PWSs w/ detects = 16.2% (6 of 37)

• Range of detects = ND-1.4 μg/L; max detect >HRL

Select Minnesota Non-Community Wells (ca. 2004)

• Not detected in 22 PWSs

Select Minnesota Private Wells (ca. 2004)

• Not detected in 26 PWSs

Aggregate of Above Minnesota Wells (ca. 2004)

• % PWSs w/ detects = 7.1% (6 of 85); max detect = 1.4 μg/L, >HRL

Supplemental Ambient/Source Water Data

Tennessee River, AL (2000)

• MRL = 0.010 - 0.025 μg/L

• % samples w/ detects = 100% (40 of 40)

• Range of detects = <0.0168-0.144 μg/L; detects >1⁄2HRL 

Lake Erie and Lake Ontario (2003)

• MRL = 0.0007 μg/L

• % samples w/ detects = 100% (16 of 16)

• Range of detects = 0.011-0.121 μg/L; detects >1⁄2HRL

Upper Mississippi River Basin (2008)

Does not proceed to phase 3

Rationale: 

The contaminant has health and 

occurrence data gaps

Health: 

Health assessment will not be 

completed by Fall 2011

Occurrence:

Limited non-national finished water 

data available
Phase 2 of Protocol for Regulatory Determination 3 April 2014

69 of 84

• MRL = 0.001 μg/L

• % samples w/ detects = 97.1% (168 of 173); max detect = 0.287 

μg/L, >HRL

CDC Fourth National Report (2003-2004)

• 95%ile concentration = 54.6 μg/L in 2,094 serum samples

Occurrence summary and/or other information:

• Detections >HRL in supplemental drinking water data, however 

limited studies available

• On UCMR 3

30. Perfluorooctanoic acid 

(PFOA)

• CASRN = 335671

• Substance Key = 6614

• A perfluorinated aliphatic 

carboxylic acid 

• Used as an emulsifier and 

surfactant in fluoropolymers 

(such as Teflon), firefighting foams, cleaners, 

cosmetics, greases and 

lubricants, paints, polishes, 

adhesives, and 

photographic films

Production / Release Data

CUSIUR Production Data 

• 10K-500K lbs/yr (1998, 

2002)

• <500K lbs/yr (2006)

Critical Health Endpoint

• Increase in maternal liver weight at 

term (Lau et al., 2006)

• BMDL10 = 0.46 mg/kg-day

• UF = 30

• Non-cancer HRL = 0.4 μg/L

Health Assessment Status

• Provisional HA (2009)

• OW Health Advisory in process

Sensitive Populations/Lifestages

• Not completely characterized

Analyzed using HRL of 0.4 μg/L

Supplemental Drinking Water Data

NJDEP (2006)

• MRL = 0.004 μg/L

• % PWSs w/ detects = 78% (18 of 23)

• Range of detects = <0.0045-0.039 μg/L, no detects >1⁄2HRL or 

>HRL

Little Hocking, OH Water Distribution System (2006)

• Range of detects = 1.5-7.2 μg/L; detects >HRL

Little Hocking, OH Private Wells (2006)

• Range of detects = <0.01-14 μg/L; detects >HRL

Select Minnesota Municipal Wells (ca. 2004)

• % PWSs w/ detects = 16.2% (6 of 37)

• Range of detects = ND-0.9 μg/L; detects >HRL

Select Minnesota Non-Community Wells (ca. 2004)

• Not detected in 22 PWSs

Select Minnesota Private Wells (ca. 2004)

Does not proceed to phase 3

Rationale: 

The contaminant has a health and 

occurrence data gap

Health: 

Health assessment will not be 

completed by Fall 2011

Occurrence:

Limited non-national finished water 

data available
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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Fate / Transport • Physical and chemical 

properties give contrary 

indications about expected 

mobility in water 

• Persistent in the 

environment (biodegrades 

sometimes/recalcitrant); 

BST is the highest category 

available to be awarded to a 

recalcitrant contaminant (CCL CIS) 

• % PWSs w/ detects = 3.8% (1 of 26) • Range of detects = ND-0.67 μg/L; detects >HRL

Aggregate of Above Minnesota Wells (ca. 2004) • % PWSs w/ detects = 8.2% (7 of 85) • Range of detects = ND-0.9 μg/L; detects >HRL

Supplemental Ambient/Source Water Data

STORET • MRL unavailable (min detect = 0 μg/L

1

)

• Data from 1 state • % GW samples w/ detects = 82.05% (1,586 of 1,933

)

• % GW samples w/ detects >1⁄2HRL = 10.45% (202 of 1,933) • % GW samples w/ detects >HRL = 9.21% (178 of 1,933) • % SW samples w/ detects = 56.80% (259 of 456) • % SW samples w/ detects >1⁄2HRL = 21.05% (96 of 456) • % SW samples w/ detects >HRL = 17.98% (82 of 456) • % GW sites w/ detects = 97.29% (1,043 of 1,072) • % GW sites w/ detects >1⁄2HRL = 6.62% (71 of 1,072) • % GW sites w/ detects >HRL = 5.50% (59 of 1,072) • % SW sites w/ detects = 57.78% (78 of 135) • % SW sites w/ detects >1⁄2HRL = 25.19% (34 of 135) • % SW sites w/ detects >HRL = 20.74% (28 of 135) • Median detect = 0 μg/L • 90%ile detect = 1.796 μg/L • Max detect = 48,500 μg/L 1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

Tennessee River, AL (2000) • MRL = 0.025 μg/L • % samples w/ detects = 45% (18 of 40) • Range of detects = 0.14-0.598 μg/L; detects >HRL
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Lake Erie and Lake Ontario (2003)

• MRL = 0.013 μg/L

• % samples w/ detects = 100% (16 of 16)

• Range of detects = 0.015-0.070 μg/L, no detects >1⁄2HRL or >HRL 

Upper Mississippi River Basin (2008)

• MRL = 0.001 μg/L

• % samples w/ detects = 97.1% (168 of 173); max detect = 0.125 

μg/L, no detects >1⁄2HRL or >HRL

CDC Fourth National Report (2003-2004)

• 95%ile concentration = 9.80 μg/L in 2,094 serum samples

Occurrence summary and/or other information:

• Detections >HRL in supplemental drinking water data, however 

limited studies available

• On UCMR 3

Analyzed using HRL of 1.1 μg/L

Supplemental Drinking Water Data

NJDEP (2006)

• MRL = 0.004 μg/L

• % PWSs w/ detects = 78% (18 of 23)

• Range of detects = <0.0045-0.039 μg/L, No detects >1⁄2HRL or 

>HRL

Little Hocking, OH Water Distribution System (2006)

• Range of detects = 1.5-7.2 μg/L; detects >HRL

Little Hocking, OH Private Wells (2006)

• Range of detects = <0.01-14 μg/L; detects >HRL

Select Minnesota Municipal Wells (ca. 2004)
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• % PWSs w/ detects = 16.2% (6 of 37)

• Range of detects = ND-0.9 μg/L; No detects >HRL

Select Minnesota Non-Community Wells (ca. 2004)

• Not detected in 22 PWSs

Select Minnesota Private Wells (ca. 2004)

• % PWSs w/ detects = 3.8% (1 of 26)

• Range of detects = ND-0.67 μg/L; No detects >HRL

Aggregate of Above Minnesota Wells (ca. 2004)

• % PWSs w/ detects = 8.2% (7 of 85)

• Range of detects = ND-0.9 μg/L; No detects >HRL

Supplemental Ambient/Source Water Data

STORET

• MRL unavailable (min detect = 0 μg/L1)

• Data from 1 state

• % GW samples w/ detects = 82.05% (1,586 of 1,933)

• % GW samples w/ detects >1⁄2HRL = 8.85% (171 of 1,933)

• % GW samples w/ detects >HRL = 7.45% (144 of 1,933)

• % SW samples w/ detects = 56.80% (259 of 456)

• % SW samples w/ detects >1⁄2HRL = 15.79% (72 of 456)

• % SW samples w/ detects >HRL = 14.04% (64 of 456)

• % GW sites w/ detects = 97.29% (1,043 of 1,072)

• % GW sites w/ detects >1⁄2HRL = 5.22% (56 of 1,072)

• % GW sites w/ detects >HRL = 4.10% (44 of 1,072)

• % SW sites w/ detects = 57.78% (78 of 135)

• % SW sites w/ detects >1⁄2HRL = 20.74% (28 of 135)

• % SW sites w/ detects >HRL = 18.52% (25 of 135)

• Median detect = 0 μg/L

• 90%ile detect = 1.796 μg/L

• Max detect = 48,500 μg/L

1

A minimum value of zero may represent a detection that was entered 
Phase 2 of Protocol for Regulatory Determination 3 April 2014

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into the database as a non-numerical value (e.g., “Present”)

Tennessee River, AL (2000)

• MRL = 0.025 μg/L

• % samples w/ detects = 45% (18 of 40)

• Range of detects = <0.025-0.598 μg/L; No detects >HRL

Lake Erie and Lake Ontario (2003)

• MRL = 0.013 μg/L

• % samples w/ detects = 100% (16 of 16)

• Range of detects = 0.015-0.070 μg/L, No detects >1⁄2HRL or >HRL 

Upper Mississippi River Basin (2008)

• MRL = 0.001 μg/L

• % samples w/ detects = 97.1% (168 of 173); max detect = 0.125 

μg/L, no detects >1⁄2HRL or >HRL

CDC Fourth National Report (2003-2004)

• 95%ile concentration = 9.80 μg/L in 2,094 serum samples

Occurrence summary and/or other information:

• Detections >HRL in supplemental drinking water data, however 

limited studies available

• On UCMR 3

31. RDX (Hexahydro-1,3,5-

trinitro-1,3,5-triazine)

• CASRN = 121824

• Substance Key = 5404

• A nitrated triazine

• An explosive

• Has been used as a rat 

poison

Production / Release Data

Critical Health Endpoint

• Inflammation of the prostate (U.S. 

DOD, 1983)

• NOEL = 0.3 mg/kg-day

• UF = 100

• RfD = 0.003 mg/kg-day

• Non-cancer HRL = 21 μg/L

Health Assessment Status

• IRIS (1988)

• On the 2012 IRIS Agenda

• Possible human carcinogen, group 

Analyzed using HRL of 21 μg/L

National Drinking Water Data

UCMR 2 Finished Water Assessment Monitoring (2008-2010)

• MRL = 1 μg/L

• No detects >1⁄2HRL or >HRL

• % samples w/ detects = 0.01% (4 of 32,015)

• % PWSs w/ detects = 0.07% (3 of 4,137)

• Median detect = 1.065 μg/L

• 99%ile detect = 1.1 μg/L

• Max detect = 1.1 μg/L

Does not proceed to phase 3

Rationale: 

The contaminant has no or low 

potential of public health concern, 

but has a health data gap.

Health:

Health assessment will not be updated 

by Fall 2011

Occurrence:

Few detections in recent national 
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CUSIUR Production Data

• >500K-1M lbs/yr (1998)

• >1M-10M lbs/yr (2002)

Fate / Transport

• Expected to be moderately 

to highly mobile in water, 

based on physical and 

chemical properties

• Not expected to be 

persistent in the 

environment (biodegrades 

fast with acclimation) 

(CCL CIS) 

C (1986 cancer guidelines)

Sensitive Populations/Lifestages

• None identified

Non-National Drinking Water Data

State Drinking Water Data (2006)

• CA: Not detected from 1 system

Supplemental Ambient/Source Water Data

STORET (SW only)

• MRL unavailable (min detect = ND)

• No SW detects in 31 samples from 11 sites in 1 state

Occurrence summary and/or other information:

• Few detections in recent national data (UCMR 2); none >1⁄2 HRL 

• Production increased from 1998 to 2002

finished water data

32. Strontium

• CASRN = 7440246

• Substance Key = 18848

• A naturally-occurring 

element

• Commonly used as a 

faceplate glass additive, in 

pyrotechnics, in ferrite 

ceramic magnets, in master 

alloys, in pigments and 

fillers, and in electrolytic 

production of zinc

• Most applications use 

strontium carbonate as 

feedstock

Production / Release Data

No data for production and 

Critical Health Endpoint

• Effects on bone structure (replacing 

calcium in bone) (Marie et al., 

1985)

• BMDL10 = 328 mg/kg-day 

• UF = 1,000

• RfD = 0.3 mg/kg-day

• Period of sensitivity birth-18 yrs

• Non-cancer HRL = 1,500 μg/L

(includes exposure factors for 

period of sensitivity)

Health Assessment Status

• Updated since CCL3

o Draft OW health assessment 

(2011)[finalized 2013]

Analyzed using HRL of 1,500 μg/L

National Drinking Water Data

NIRS Finished Water [GW only] (1984-1986)

• MRL = 1 μg/L

• % PWSs w/ detects = 99.1% (980 of 989) 

• % PWSs w/ detects >1⁄2HRL = 14.26% (141 of 989)

• % PWSs w/ detects >HRL = 6.98% (69 of 989)

• Median detect = 178 μg/L

• 99%ile detect = 7,339 μg/L

• Max detect = 43,550 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1998-2005)

Proceeds to phase 3

Rationale: 

The contaminant is of potential 

public health concern and does not 

have critical health or occurrence 

data gaps

Health:

Available health assessment

Occurrence:

Significant occurrence at levels of 

public health concern in national and 

non-national finished water data
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release

Fate / Transport

• Expected to have low to 

moderate mobility in soils; 

mobility affected by salinity 

(ATSDR, HSDB) 

• Strontium released to air as 

strontium oxide will react to 

from strontium hydroxide 

and strontium ions (ATSDR) 

Sensitive Populations/Lifestages

• Growing children (especially those 

with low dietary calcium and vitamin 

D)

• Adults with kidney problems may 

be sensitive to impaired strontium 

excretion and retention

• Paget’s disease

• % systems w/ detects = 

o IL: 100% (19 of 19)

o OH: 93.75% (30 of 32)

o R9 Tribes: Not detected from 1 system

• % systems w/ detects >1⁄2HRL = 

o IL: 26.32% (5 of 19)

o OH: 31.25% (10 of 32)

• % systems w/ detects >HRL = 

o IL: 26.32% (5 of 19)

o OH: 21.88% (7 of 32)

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Detected in 2 CWSs from 1 state (NY); no detects >1⁄2HRL or >HRL

CWSS (2006)

• Detected in 1 sample; no detects >1⁄2HRL or >HRL

EWG (2004-2009)

• At least 16 PWSs from 4 states w/ detects >HRL

Supplemental Ambient/Source Water Data

STORET

• MRL unavailable (min detect = 0 μg/L1)

• Data from 33 states

• % GW samples w/ detects = 93.92% (2,179 of 2,320)

• % GW samples w/ detects >1⁄2HRL = 23.92% (555 of 2,320)

• % GW samples w/ detects >HRL = 13.88% (322 of 2,320)

• % SW samples w/ detects = 96.74% (39,780 of 41,121)

• % SW samples w/ detects >1⁄2HRL = 21.56% (8,866 of 41,121)

• % SW samples w/ detects >HRL = 7.71% (3,170 of 41,121)

• % GW sites w/ detects = 97.19% (865 of 890)

• % GW sites w/ detects >1⁄2HRL = 23.37% (208 of 890)
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• % GW sites w/ detects >HRL = 13.48% (120 of 890)

• % SW sites w/ detects = 99.06% (11,434 of 11,543)

• % SW sites w/ detects >1⁄2HRL = 11.55% (1,333 of 11,543)

• % SW sites w/ detects >HRL = 4.62% (533 of 11,543)

• Median detect = 270 μg/L

• 90%ile detect = 1,344.83 μg/L

• Max detect = 19,034,000 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

U.S. Glacial Aquifer Study (1991-2003)

• Max detect (9,120 μg/L) in 552 GW samples >HRL

NAWQA Carbonate Aquifer Study (1993-2005)

• Max detect (43,950 μg/L) >HRL

NAWQA Domestic Well Water Quality (1991-2004)

• 6.49% of wells exceeded 4,000 μg/L, >HRL

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.02 - 5 μg/L

• % samples w/ detects = 100.00% (503 of 503)

• % samples w/ detects >1⁄2HRL = 25.05% (126 of 503)

• % samples w/ detects >HRL = 12.13% (61 of 503) 

USGS Report (1991-2006)

• 2.2% of samples exceeded 4,000 μg/L, >HRL 

• Data from 446 wells in 16 states

Occurrence summary and/or other information:

• 7% of PWSs detections >HRL, 14% >1⁄2 HRL in national ground 

water data (NIRS)

• High percentage of detects in non-national drinking water data as 

well with a significant percentage >HRL and 1⁄2 HRL

• On UCMR 3
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33. Terbufos

• CASRN = 13071799

• Substance Key = 22585

• A phosphorodithioate 

pesticide

• Used as an insecticidenematicide to control a 

variety of insect pests. It 

was first registered in 1974 

to control insect pests on 

corn, sugar beets, and 

sorghum. Target pests 

include corn rootworms, 

wireworms, white grubs, 

billbugs, sugarbeet root 

maggots, cutworms, and 

nematodes

Production / Release Data

OPP Estimated Environmental 

Concentrations

• Surface water chronic = 1.3-

5.5 μg/L

• Ground water chronic = 4.8-

7.4 μg/L 

NCFAP Total Pesticide 

Application 1997

• 6,515,603 lbs/yr (37 states)

Pesticide Industry Sales and 

Usage Report

• 1999: 5M-7M lbs

• 2001: 3M-5M lbs

RED 2006

Critical Health Endpoint

• Plasma ChE inhibition & reduced 

body/organs weights & male fertility

• NOAEL = 0.005 mg/kg-day

• UF = 100

• RfD = 0.00005 mg/kg-day

• Non-cancer HRL = 0.35 μg/L

Health Assessment Status

• OPP RED (2006)

• Not classifiable as to human 

carcinogenicity, group D (1986 

cancer guidelines)

Sensitive Populations/Lifestages

• None identified

Analyzed using HRL of 0.35 μg/L

Non-National Drinking Water Data

UCMR 1 Finished Water Screening Survey (2001-2003)

• MRL = 0.5 μg/L

• Not detected in 2,301 samples from 295 PWSs

State Drinking Water Data (2002-2007)

• CA: Not detected in 191 samples from 23 systems

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (1997)

• Not detected in 1 CWS

PDP Raw and Finished Water (2001-2009)

• Not detected in 4,168 samples

PMP Raw & Finished Water (1999)

• Not detected in any raw or finished samples

Supplemental Ambient/Source Water Data

NAWQA Ambient Water (1992-2001)

• MRLs variable (most are 0.013 μg/L)

• No GW detects >1⁄2HRL or >HRL

• % GW samples w/ detects = 0.03% (2 of 6,080) 

• % SW samples w/ detects = 0.19% (28 of 14,480)

• % SW samples w/ detects >1⁄2HRL = 0.03% (4 of 14,480)

• % SW samples w/ detects >HRL = 0.01% (1 of 14,480)

• % GW sites w/ detects = 0.04% (2 of 5,211) 

• % SW sites w/ detects = 1.05% (20 of 1,907)

Proceeds to phase 3

Rationale: 

The contaminant has no or low 

occurrence at a level of public 

health concern, does not have 

critical health or occurrence data 

gaps and is included in a parentdegradate contaminant group

Health:

Available health assessment

Occurrence:

No detections in non-national finished 

water data
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• ~7.5M lbs of active 

ingredient used annually 

between 1987-1996

Fate / Transport • Expected to be of low to 

moderate mobility in water, 

based on physical and 

chemical properties 

• Moderately persistent in the 

environment (biodegrades 

slowly with acclimation) (CCL CIS) 

• % SW sites w/ detects >1⁄2HRL = 0.21% (4 of 1,907) • % SW sites w/ detects >HRL = 0.05% (1 of 1,907) • Median detect = 0.017 μg/L • 99%ile detect = 0.56 μg/L • Max detect = 0.56 μg/L

STORET • MRL unavailable (min detect = 0 μg/L

1

)

• Data from 17 states • No GW detects in 699 samples from 441 sites • % SW samples w/ detects: 7.84% (457 of 5,826

)

• % SW samples w/ detects >1⁄2HRL = 0.39% (23 of 5,826)

• % SW samples w/ detects >HRL = 0.0

3% (2 of 5,826)

• % SW sites w/ detects: 22.08% (138 of 625) 

• % SW sites w/ detects >1⁄2HRL = 2.24% (14 of 625)

• % SW sites w/ detects >HRL = 0.32% (2 of 625)

• Median detect = 0 μg/L • 90%ile detect = 0.01 μg/L • Max detect = 3.2 μg/L 1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA National Synthesis (1992-2001)

• MRL = 0.009 μg/L • GW: no max detects >1⁄2HRL or >HRL • SW: max detect from agricultural sites (0.56 μg/L) >HRL

USGS CWSs Drawing from Streams and Groundwater (2002-2005)

• Not detected

NAWQA Carbonate Aquifer Study (1993-2005)

• Not detected in 1,027 samples

NAWQA Domestic Well Water Quality (1991-2004)

• % samples w/ detects = 0.04% (1 of 2,539); no detects >1⁄2HRL or 

>HRL
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NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.006 - 0.013 μg/L

• Not detected in 898 samples

Terbufos REDs - EPA OPP

• 20 confirmed detections out of 4,563 GW samples taken in 13 

states

• Range of detects = 0.01 - 20 μg/L

Occurrence summary and/or other information:

• Not detected in UCMR1 (SS), which is a statistically defined, 

national sample of 300 PWSs; some uncertainty because the 

minimum reporting limit is 1.5 times higher than the HRL

• No detections in CA drinking water data and a few detections in 

ambient water data with one >HRL and a few >1⁄2 HRL 

• Included with Terbufos Sulfone (degradate) in contaminant group

34. Terbufos sulfone

• CASRN = 56070167

• Substance Key = 37071

• A degradate of terbufos 

• See also parent compound

Production / Release Data

Not produced commercially

Fate / Transport

• Expected to be moderately 

to highly mobile in water, 

based on physical and 

chemical properties. 

• Moderately persistent in the 

environment (biodegrades 

Critical Health Endpoint

• Parent compound (Terbufos)

• Plasma ChE inhibition & reduced 

body/organs weights & male fertility

• NOAEL = 0.005 mg/kg-day

• UF = 100

• RfD = 0.00005 mg/kg-day

• Non-cancer HRL = 0.35 μg/L

Health Assessment Status

• Parent compound [OPP RED 

(2006)]

• Parent compound [Not classifiable 

as to human carcinogenicity, group 

D (1986)]

Sensitive Populations/Lifestages

• None identified

Analyzed using HRL of 0.35 μg/L

National Drinking Water Data

UCMR 2 Finished Water Assessment Monitoring (2008-2010)

• MRL = 0.4 μg/L

• All detects >HRL 

• % samples w/ detects >HRL = 0.003% (1 of 32,012)

• % PWS w/ detects >HRL = 0.02% (1 of 4,138)

• Median detect = 0.42 μg/L

• 99%ile detect = 0.42 μg/L

• Max detect = 0.42 μg/L

Supplemental Drinking Water Data

PDP Raw and Finished Water (2001-2009)

Proceeds to phase 3

Rationale: 

The contaminant has no or low 

occurrence at a level of public 

health concern, does not have 

critical health or occurrence data 

gaps, and is included in a parentdegradate contaminant group

Health:

Available parent health assessment

Occurrence:

No detections in national finished water 

data and supplemental drinking water 

and ambient water data
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slowly with acclimation)

(CCL CIS) • Not detected in 4,101 samples

Supplemental Ambient/Source Water Data

Iowa Data

• Not detected in 13 wells

Occurrence summary and/or other information:

• Not detected in national data (UCMR2); minimal uncertainty 

because the detection limit is slightly higher than the HRL

• No detections in supplemental drinking water (Iowa) and ambient 

water data (PDP)

35. Vanadium

• CASRN = 7440622

• Substance Key = 18882

• A naturally-occurring 

element

• Commonly used as 

Vanadium pentoxide which 

is a chemical intermediate 

and a catalyst

Production / Release Data

TRI-Release 2010 (vanadium 

compounds)

• Surface water = 451,251 

lbs/yr (37 states)

• Total = 50,810,725 lbs/yr 

(48 states)

TRI-Release 2010 (vanadium 

except when contained in an 

alloy)

Critical Health Endpoint(s)

• Minor renal effects (Domingo et al., 

1985 in ATSDR 1992)

o NOAEL = 0.3 mg/kg-day

o UF = 100

o ATSDR MRL = 0.003 mg/kg-day

o Non-cancer HRL = 21 μg/L

• Blood pressure, body weight, and 

hematological effects (12 week 

human study) (Fawcett et al. 1997 

in Draft ATSDR 2009)

o NOAEL = 0.12 mg/kg-day

o UF = 10 

o ATSDR MRL = 0.01 mg/kg-day

o Non-cancer HRL = 70 μg/L

Health Assessment Status

• ATSDR (1992)

• Updated since CCL3

o Draft ATSDR (2009) [became 

final in 2012]

• On the 2012 IRIS Agenda

Analyzed using HRLs of 21 μg/L and 70 μg/L

Analysis at HRL of 21 μg/L:

National Drinking Water Data

NIRS Finished Water [GW only] (1984-1986)

• MRL = 3 μg/L

• % PWSs w/ detects = 14.76% (146 of 989)

• % PWSs w/ detects >1⁄2HRL =4.75% (47 of 989)

• % PWSs w/ detects >HRL = 1.72% (17 of 989)

• Median detect = 7.3 μg/L

• 99%ile detect = 45.1 μg/L

• Max detect = 70.4 μg/L

Non-National Drinking Water Data

State Drinking Water Data (1996-2007)

• % systems w/ detects = 

o CA: 67.61% (1,824 of 2,698)

o IL: Not detected from 17 systems

Does not proceed to phase 3

Rationale: 

The contaminant likely has no or 

low potential for public health 

concern, but has a health data gap.

Health: 

Non-EPA health assessment will not 

be updated by Fall 2011

Occurrence:

No detections > draft HRL in national 

finished water data but some in nonnational finished water and ambient 

water data at levels of potential public 

health concern based on the draft HRL
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81 of 84

• Surface water = 8,773 lbs/yr 

(6 states)

• Total = 2,341,137 lbs/yr (21

states)

TRI-Release 2008 (vanadium 

compounds)

• Surface water = 1,196,720

lbs/yr (39 states)

• Total = 42,805,369 lbs/yr 

(49 states)

TRI-Release 2008 (vanadium 

except when contained in an 

alloy)

• Surface water = 7,790 lbs/yr 

(5 states)

• Total = 2,264,849 lbs/yr (19

states)

TRI-Release 2006 (vanadium 

compounds)

• Surface water = 402,734 

lbs/yr (38 states)

• Total = 50,462,858 lbs/yr 

(47 states)

TRI-Release 2006 (vanadium 

except when contained in an 

alloy) 

• Surface water = 16,889 

lbs/yr (5 states)

• Total = 2,591,471 lbs/yr (21 

states)

TRI-Release 2004 (vanadium 

compounds)

• Surface water = 662,878

Sensitive Populations/Lifestages

• Individuals with compromised renal 

systems

o OH: Not detected from 23 systems

• % systems w/ detects >1⁄2HRL = 

o CA: 35.73% (964 of 2,698)

• % systems w/ detects >HRL = 

o CA: 17.90% (483 of 2,698)

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Detected in 1 CWS; no detects >1⁄2HRL or >HRL in 1 CWS

CWSS (2006)

• % samples w/ detects = 80% (4 of 5); no detects >1⁄2HRL or >HRL

EWG (2004-2009)

• 670 PWSs from 4 states w/ detects; at least 10 of these PWSs (all 

in one state) had detects >HRL

Supplemental Ambient/Source Water Data

STORET

• MRL unavailable (min detect = 0 μg/L1

) 

• Data from 44 states

• % GW samples w/ detects = 49.83% (2,069 of 4,152)

• % GW samples w/ detects >1⁄2HRL = 11.49% (477 of 4,152) 

• % GW samples w/ detects >HRL = 10.04% (417 of 4,152)

• % SW samples w/ detects = 49.21% (39,501 of 80,264)

• % SW samples w/ detects >1⁄2HRL = 7.57% (6,073 of 80,264)

• % SW samples w/ detects >HRL = 3.27% (2,625 of 80,264)

• % GW sites w/ detects = 75.27% (691 of 918)

• % GW sites w/ detects >1⁄2HRL = 32.57% (299 of 918)

• % GW sites w/ detects >HRL = 29.41% (270 of 918)

• % SW sites w/ detects = 48.82% (6,952 of 14,240)

• % SW sites w/ detects >1⁄2HRL = 14.04% (1,999 of 14,240)
Phase 2 of Protocol for Regulatory Determination 3 April 2014

82 of 84

lbs/yr (37 states)

• Total = 52,583,423 lbs/yr 

(48 states)

TRI-Release 2004 (vanadium 

except when contained in an 

alloy) • Surface water = 1,170 lbs/yr 

(6 states)

• Total = 1,600,795 lbs/yr (23 

states)

Fate / Transport • Commonly found as vanadyl 

ion (4+) or vanadate ion 

(5+) in water; vanadate is 

more mobile 

• Vanadyl and vanadate ions 

strongly bind to mineral and 

biogenic particulates in 

water; only 13% of 

vanadium in water is in 

solution (ATSDR, 2009) 

• % SW sites w/ detects >HRL = 7.11% (1,012 of 14,240)

• Median detect = 3.2 μg/L • 90%ile detect = 16 μg/L • Max detect = 86,000 μg/L 1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.02 μg/L– 5 μg/L • % samples w/ detects = 88.40% (404 of 457) • % samples >1⁄2HRL = 21.66% (99 of 457) • % samples w/ detects >HRL = 10.72% (49 of 457)

California GAMA Water Quality Monitoring (2002-2009)

• Detects >50 μg/L from 1.50% of wells (16 of 1,067), >HRL

U.S. Glacial Aquifer Study (1991-2003)

• % samples w/ detects = 62.3% (344 of 552) • Max detect (294 μg/L) >HRL

Analysis at HRL of 70 μg/L:

National Drinking Water Data

NIRS Finished Water [GW only] (1984-1986)

• MRL = 3 μg/L • No detects >HRL • % PWSs w/ detects = 14.76% (146 of 989) • % PWSs w/ detects >1⁄2HRL = 0.40% (4 of 989) • Median detect = 7.3 μg/L • 99%ile detect = 45.1 μg/L • Max detect = 70.4 μg/L

Non-National Drinking Water Data
Phase 2 of Protocol for Regulatory Determination 3 April 2014

83 of 84

State Drinking Water Data (1996-2007)

• % systems w/ detects = 

o CA: 67.61% (1,824 of 2,698)

o IL: Not detected from 17 systems

o OH: Not detected from 23 systems

• % systems w/ detects >1⁄2HRL = 

o CA: 7.52% (203 of 2,698)

• % systems w/ detects >HRL = 

o CA: 1.33% (36 of 2,698)

Supplemental Drinking Water Data

Recent CCRs from 26 CWSs that serve >1M (2007)

• Not detected >1⁄2HRL or >HRL in 1 CWS

CWSS (2006)

• % samples w/ detects = 80% (4 of 5); no detects >1⁄2HRL or >HRL

EWG (2004-2009)

• 670 PWSs from 4 states w/ detects; at least 4 of these PWSs had 

detects >HRL

Supplemental Ambient/Source Water Data

STORET

• MRL unavailable (min detect = 0 μg/L1

) 

• Data from 44 states

• % GW samples w/ detects = 49.83% (2,069 of 4,152)

• % GW samples w/ detects >1⁄2HRL = 9.06% (376 of 4,152)

• % GW samples w/ detects >HRL = 3.90% (162 of 4,152)

• % SW samples w/ detects = 49.21% (39,501 of 80,264)

• % SW samples w/ detects >1⁄2HRL = 2.07% (1,658 of 80,264)

• % SW samples w/ detects >HRL = 1.15% (924 of 80,264)

• % GW sites w/ detects = 75.27% (691 of 918)
Phase 2 of Protocol for Regulatory Determination 3 April 2014

84 of 84

• % GW sites w/ detects >1⁄2HRL = 27.23% (250 of 918)

• % GW sites w/ detects >HRL = 15.25% (140 of 918)

• % SW sites w/ detects = 48.82% (6,952 of 14,240)

• % SW sites w/ detects >1⁄2HRL = 4.75% (676 of 14,240)

• % SW sites w/ detects >HRL = 2.44% (348 of 14,240)

• Median detect = 3.2 μg/L

• 90%ile detect = 16 μg/L

• Max detect = 86,000 μg/L

1

A minimum value of zero may represent a detection that was entered 

into the database as a non-numerical value (e.g., “Present”)

NAWQA Quality of Public Supply Wells (1993-2007; Toccalino et al.)

• MRL = 0.02 μg/L– 5 μg/L

• % samples w/ detects = 88.40% (404 of 457)

• % samples >1⁄2HRL = 5.03% (23 of 457)

• % samples w/ detects >HRL = 0.44% (2 of 457)

California GAMA Water Quality Monitoring (2002-2009)

• Detects >50 μg/L from 1.50% of wells (16 of 1,067), >HRL

U.S. Glacial Aquifer Study (1991-2003)

• Max detect (294 μg/L) in 552 GW samples >HRL

Occurrence summary and/or other information:

• 4 detections >1⁄2 HRL but no detections >HRL in national data 

(NIRS)

• Some detections >HRL in non-national drinking water data (CA) 

and ambient water data (STORET)

• On UCMR 3
Appendix F - Summary of Phase 3 Reg Det Assessment for 1,2,3-Trichloropropane -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for 1,2,3-Trichloropropane

Background 

• Volatile, chlorinated organic compound

• Used as a chemical intermediate, paint and varnish remover, solvent, and degreasing agent 

• No natural sources

• Production: 0.5 million - 1 million lbs in 2002 (CUS)

-Down from >10 million - 50 million lbs in 1986

• Industrial releases to surface water: 187 lbs in 2008 (TRI)

-Down from 5,498 lbs in 2000 but up from 62 lbs reported in 1997

• Total industrial releases: 1,557 lbs in 2008 (TRI)

Evaluation of Statutory Criteria

Health

• IRIS Risk Assessment (2009) 

• Likely to be a carcinogenic to humans (2005 cancer guidelines), 

by a mutagenic mode of action 

• Critical Effect = Cancer

- Based on oral gavage multisite tumors study in mice (NTP, 

1993)

-Cancer Slope factor = 30 (mg/kg-day)-1

• HRL: 0.0004 μg/L (cancer with ADAF) 

• Non-cancer effects = Increased absolute liver weight 

-Based on 2-year bioassay in male rats (NTP, 1993)

-RfD = 0.004 mg/kg-day; BMDL = 1.1 mg/kg-day; UF = 300

Might the contaminant 

have an adverse effect on 

the health of persons?

Yes

Rationale: 

• Adverse effects (from 

animal studies) are cancer 

(pharynx/palate, tongue, 

forestomach, liver, uterus, 

harderian gland) and 

increased liver weight 

Occurrence

National Data:

• UCM Round 1 cross-section, 1988-1992 (min detect = 0.1 μg/L):

-Detections in 44 of 17k systems (0.25%)

-Detections in 76 of 57k samples (0.13%)

-Likely underestimation of occurrence at levels of health 

concern, since reporting levels exceeded HRL of 0.0004 μg/L by 

orders of magnitude

• UCM Round 2 cross-section, 1993-1997 (min detect = 0.03 μg/L; 

most common RL = 0.1 μg/L):

-Detections in 19 of 24k systems (0.08%)

-Detections in 23 of 98k samples (0.02%)

-Likely underestimation of occurrence at levels of health 

concern, since reporting levels exceeded HRL by orders of 

magnitude

Non-National Data:

• California, 1995-2007 (min detect = 0.001 μg/L)

-Detections in 157 of 3,939 systems (4.0%)

-Detections in 5k of 113k samples (4.4%)

• Florida, 2004-2007 (min detect = 1.9 μg/L)

-Detections in 1 of 27 systems (3.7%)

-Detections in 1 of 1,766 samples (0.1%)

Is the contaminant known 

to occur or is there a 

substantial likelihood that 

the contaminant will 

occur in PWSs with a 

frequency and at levels of 

public health concern?

Yes

Rationale: 

• Detected under UCM 

Rounds 1 and 2, with

reporting levels orders of 

magnitude higher than 

the HRL of 0.0004 μg/L. 

Recent monitoring 

suggests a continuing 

presence in water 
Appendix F - Summary of Phase 3 Reg Det Assessment for 1,2,3-Trichloropropane -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for 1,2,3-Trichloropropane

• Illinois, 1998-2004 (min detect = 250 μg/L)

-Detections in 4 of 6 systems (67%)

-Detections in 4 of 11 samples (36%)

• North Carolina, 1998-2005 (min detect = 0.57 μg/L)

-Detections in 5 of 2,493 systems (0.2%)

-Detections in 18 of 20k samples (0.09%)

• Ohio, 1998-2005 (min detect = 0.5 μg/L)

-Detections in 1 of 2,532 systems (0.04%)

-Detections in 1 of 9,283 samples (0.01%)

• Region 9 Tribes, 1998-2005 (min detect = 1.8 μg/L)

-Detections in 2 of 279 systems (0.7%)

-Detections in 3 of 1,113 samples (0.3%)

• South Dakota, 1990-2007 (min detect = 0.67 μg/L)

-Detections in 1 of 281 systems (0.4%)

-Detections in 1 of 1,110 samples (0.1%)

• Texas, 1998-2005 (min detect = 13 μg/L)

-Detections in 5 of 5,660 systems (0.1%)

-Detections in 7 of 36k samples (0.02%)

• Wisconsin, 1983-1999 (min detect = 0.1 μg/L)

-Detections in 11 of 1,826 systems (0.6%)

-Detections in 11 of 13k samples (0.08%)

• Wisconsin, 2000-2009 (min detect = 3.9 μg/L)

-Detections in 1 of 1,123 systems (0.1%)

-Detections in 1 of 6,462 samples (0.02%)

Other Relevant Information

• Some physical and chemical properties indicate mobility and

volatility in water and soil

-Estimated half-life in water is 38 days (PBT Profiler) 

-Persistent in the environment (biodegrades slowly with 

acclimation)

• Estimated national population exposed to 1,2,3-

trichloropropane at levels detected in UCM program 

-From UCM Round 1 cross-section: 17.8M (6.65%)

-From UCM Round 2 cross-section: 0.2M (0.06%)

-Likely underestimation of population served at levels of health 

concern, since reporting levels exceeded HRL by orders of 

magnitude

• Sensitive populations 

- Pregnant women/Fetuses/Infants/Children

- Individuals with liver or kidney problems

• Proposed for UCMR 3 monitoring 
Appendix F - Summary of Phase 3 Reg Det Assessment for 1,2,3-Trichloropropane -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for 1,2,3-Trichloropropane

Conclusion

The data suggest that 1,2,3-trichloropropane has adverse health effects (criterion 1) and 

occurs at levels and frequency of public health concern (criterion 2). The available information 

will be presented to the Administrator for determination of whether a drinking water 

regulation would present a meaningful opportunity to protect public health (criterion 3). EPA 

intends to consider whether to regulate of 1,2,3-trichloropropane as part of a group of 

carcinogenic volatile organic compounds (cVOCs).
Appendix F - Summary of Phase 3 Reg Det Assessment for 1,3-Dinitrobenzene -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for 1,3-Dinitrobenzene

Background 

• A nitrated aromatic compound 

• Used as an industrial chemical and in the production of other substances

• No natural sources

• >10 million - 50 million lbs produced in 1986 (only available year) (CUS)

• Total industrial releases: 19,858 lbs in 2008 (TRI)

• Industrial releases to surface water: 2 lbs in 2008 (TRI)

-Down from high of 816 lbs in 1997

Evaluation of Statutory Criteria

Health

• Update not needed (no additional information)

-IRIS (1988) & ATSDR (1995) are consistent

-Not classifiable as to human carcinogenicity, group D 

(1986 cancer guidelines) 

• Critical effect: increased spleen weight (Cody et al., 1981)

-Based on sub-chronic drinking water study in rats

-RfD = 0.0001 mg/kg-day; NOAEL = 0.4 mg/kg-day; UF = 

3000 

• HRL: 0.7 μg/L (non-cancer)

Might the contaminant have an 

adverse effect on the health of 

persons?

Yes

Rationale: 

Adverse effect is increased 

spleen weight (from animal 

studies) 

Occurrence

National Data 

• UCMR 2 Assessment Monitoring, 2008-2010 (MRL = 0.8

μg/L)

-No detections in 32,017 samples from 4,137 systems 

-Possible underestimation of occurrence at levels of 

health concern since MRL slightly higher than HRL of 0.7 

μg/L

Is the contaminant known to 

occur or is there a substantial 

likelihood that the contaminant 

will occur in PWSs with a 

frequency and at levels of 

public health concern?

No

Rationale: 

IN UCMR 2, no detections > MRL 

of 0.8 μg/L, which is slightly 

higher than HRl of 0.7 μg/L.

Other Relevant Information

• Expected to be moderately to highly mobile in water, 

based on physical and chemical properties

-Estimated half-life in water is 38 days (PBT profiler)

-Moderately persistent in the environment (biodegrades 

slowly with acclimation)

• Estimated national population exposed to concentrations 

= 0% for UCMR2 since no detects > HRL in 32,017 samples 

from 4,137 systems

• Sensitive Populations/Lifestages: 

-Individuals with a genetic predisposition to blood 

disorders and/or iron disorders

-Males having other sperm production complications 

could also have increased sensitivity

• Proposed for UCMR 3 monitoring
Appendix F - Summary of Phase 3 Reg Det Assessment for 1,3-Dinitrobenzene -- April 2014 Conclusion

The data suggest that 1,3-dinitrobenzene has adverse health effects (criterion 1) but does not 

occur at levels and frequency of public health concern (criterion 2). The available information 

will be presented to the Administrator for determination of whether a drinking water 

regulation would present a meaningful opportunity to protect public health (criterion 3).
Appendix F - Summary of Phase 3 Reg Det Assessment for Chlorate -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for Chlorate

Background 

• Inorganic chemical: ClO3

-

(+5 oxidation state of chlorine atom)

• Chlorate salts are used in pesticides

-Approximately 2.8 million lbs of sodium chlorate applied annually (OPP’s 2006 RED)

• No production data available from IUR program or industrial release data available from TRI

• Chlorate can form as a drinking water treatment by-product:

-During liquid hypochlorite storage

-Disinfection with chlorine dioxide

Evaluation of Statutory Criteria

Health

• OPP Risk Assessment (2006)

• Critical Effect: Increased thyroid gland follicular cell 

hypertrophy and mineralization

-Based on chronic study in rats (NTP, 2004) 

-RfD = 0.03 mg/kg-day; BMDL = 0.9 mg/kg-day ; UF = 30

• HRL: 210 μg/L (non-cancer) 

• Not likely to cause cancer at doses below those that alter 

thyroid hormone homeostasis 

Might the contaminant 

have an adverse effect on 

the health of persons?

Yes

Rationale: 

• Adverse effect (from 

animal studies) is thyroid 

gland follicular cell 

hypertrophy and 

mineralization 

Occurrence

Non-National Data:

• DBP ICR, July 1997-Dec 1998 (min detect = 20 μg/L):

-Detections > HRL of 210 μg/L at 34 of 82 systems (41%) using 

hypochlorite and/or chlorine dioxide 

-Plant Influent (Source Water): detections > HRL in 4 of 749 

samples (0.5%) at 4 of 106 systems (4%)

-Finished Water at Hypochlorite Systems: detections > HRL in 

42 of 298 samples (14%) at 22 of 59 systems (37%) 

-Finished Water at Chlorine Dioxide Systems: detections > HRL 

in 88 of 384 samples (23%) at 15 of 29 systems (52%)

-Chlorate levels are not highly variable throughout distribution 

system when chlorine dioxide is used

• State of California 2001-2007 (min detect = 0.01 μg/L)

-Detections > HRL in 10 of 45 systems (22%) 

Is the contaminant known 

to occur or is there a 

substantial likelihood that 

the contaminant will occur 

in PWSs with a frequency 

and at levels of public 

health concern?

Yes

Rationale: 

• Detections > HRL of 210 

μg/L in 41% of 82 systems

using hypochlorite and/or 

chlorine dioxide (DBP ICR)
Appendix F - Summary of Phase 3 Reg Det Assessment for Chlorate -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for Chlorate

Other Relevant Information

• Sensitive populations 

- Individuals with blood conditions such as anemia or those 

with kidney disease 

- Individuals with genetic diseases such as hereditary 

methemoglobinemia and glucose-6-phosphate dehydrogenase 

deficiency 

- Individuals who may be unusually sensitive to oxidants

• Population exposed to concentrations > HRL at DBP ICR

participating systems: 11.8M (28.4% of the population served by 

hypochlorite and chlorine dioxide systems included in the study) 

• Disinfection by-product

• EPA is reviewing recent surveys (AWWA, EPA-CWSS) that show 

substantial increases in the number of systems using disinfection 

practices associated with high levels of chlorate formation

• Proposed for UCMR 3 monitoring

Conclusion

The data suggest that chlorate has adverse health effects (criterion 1) and occurs at levels and 

frequency of public health concern (criterion 2). The available information will be presented to 

the Administrator to determine whether a drinking water regulation would present a 

meaningful opportunity to protect public health (criterion 3). 
Appendix F - Summary of Phase 3 Reg Det Assessment for Dimethoate -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for Dimethoate

Background 

• An organophosphate pesticide 

• Commonly used as an insecticide on field crops (e.g., wheat, alfalfa, corn, and cotton), 

orchard crops, vegetable crops, in forestry, and for residential purposes

• Usage estimated at 1.8 million lbs in 2008 (OPP)

-Up from 1986: >500,000 – 1 million lbs production/importation (CUS)

•Total industrial releases: 15,561 lbs in 2008 (TRI)

• No natural sources

Evaluation of Statutory Criteria

Health

• OPP Risk Assessment (2007)

-Possible human carcinogen, group C (1986 cancer guidelines)

•Critical effect: Brain cholinesterase inhibition 

-Based on 2-year chronic feeding study in rats

-Chronic oral RfD = 0.0022 mg/kg-day; BMDL = 0.22 mg/kg-day; 

UF = 100

•HRL: 15.4 μg/L (non-cancer)

Might the contaminant 

have an adverse effect on 

the health of persons?

Yes

Rationale: 

• Adverse effect (from 

animal studies) is brain 

cholinesterase inhibition 

• Possible human 

carcinogen

Occurrence

National Data

•UCMR 2 Assessment Monitoring, 2008-2010 (MRL = 0.7 μg/L)

-No detections > MRL or HRL of 15.4 μg/L in 32,013 samples 

from 4,138 systems

•USGS data, 2002-2005 (Hopple et al., 2009 and Kingsbury et al., 

2008) (reporting level = 0.0061 μg/L)

-Phase 1: No detections in 221 GW samples; 2 (1.4%) detections 

in 146 SW samples at 9 systems (max estimated at 0.009 μg/L); 

no detections > 1⁄2 HRL

-Phase 2: No detections in 48 raw & finished GW samples

Is the contaminant known 

to occur or is there a 

substantial likelihood that 

the contaminant will 

occur in PWSs with a 

frequency and at levels of 

public health concern?

No

Rationale: 

No detections in UCMR 2

at the HRL of 15.4 μg/L. 

Other Relevant 

Information 

• Sensitive Populations/Lifestages: None identified 

• Estimated national population exposed to concentrations = 0% 

for UCMR2 since no detects > HRL in 32,013 samples from 4,138 

systems

• Physical/chemical properties indicate very mobile in water 

• 36% partitions to water (modeled system of water, air, soil, and 

sediment) 

• Moderately persistent (biodegrades slowly with acclimation) 
Appendix F - Summary of Phase 3 Reg Det Assessment for Dimethoate -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for Dimethoate

Conclusion

The data suggest that dimethoate has adverse health effects (criterion 1) but does not occur at 

levels and frequency of public health concern (criterion 2). The available information will be 

presented to the Administrator to determine whether a drinking water regulation would 

present a meaningful opportunity to protect public health (criterion 3). 
Appendix F - Summary of Phase 3 Reg Det Assessment for NDEA -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for NDEA

Background 

• Organic nitrosamine compound, also known as N-nitrosodiethylamine

• Used as an additive in gasoline and in lubricants, as an antioxidant, and as a stabilizer in 

plastics

• Found in discharges of municipal wastewater

• Found in some food products (e.g., cured meats and fish, beer, smoked products)

• Can form in the body by nitrosation of dietary amines

• By-product from water treatment, particularly disinfection with chloramines

Evaluation of Statutory Criteria

Health

• OW Health Assessment (2011) – External peer review in process

• Likely to be a carcinogenic to humans (2005 cancer guidelines), 

by a mutagenic mode of action

• Critical Effect: Cancer

-Based on liver and esophageal tumors (Peto et al. 1991) 

-Cancer slope factor: 30 (mg/kg-day)

-1

• HRL: 0.0004 μg/L (cancer with ADAFs) 

Might the contaminant 

have an adverse effect on 

the health of persons?

Yes

Rationale: 

Cancer in multiple animals 

(monkeys, mice, rats, 

hamsters, guinea pigs, 

rabbits, dogs) and multiple 

tumor types (liver, kidney, 

lung, esophageal, nasal 

cavity, tracheal, bronchial 

and forestomach) 

Occurrence 

National Data

• UCMR 2 Screening Survey, 2008-2010 (MRL = 0.005 μg/L): 

-Detections > MRL in 46 of 18,038 samples (0.26%)

-Detections at 26 of 1,198 systems (2.17%)

-Likely underestimation of occurrence at levels of health 

concern, since MRL higher than HRL

Non-National Data

• State of California, 2001-2007 (min detect = 0.03 μg/L) 

-Detection > HRL in 1 of 106 samples (1%)

-Detection > HRL at 1 of 14 systems (7%)

Is the contaminant known 

to occur or is there a 

substantial likelihood that 

the contaminant will 

occur in PWSs with a 

frequency and at levels of 

public health concern?

Yes

Rationale: 

Detected in 2.17% of 

UCMR 2 systems at the 

MRL of 0.005 μg/L. 

Also consider as part of 

nitrosamine group.

Since MRL is 

approximately 12 times 

higher than HRL of 0.0004 

μg/L, occurrence at a level 

of health concern is likely 

higher.
Appendix F - Summary of Phase 3 Reg Det Assessment for NDEA -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for NDEA

Other Relevant 

Information • Sensitive Populations/Lifestages: 

-Newborns and infants 

-Heavy consumers of alcohol

• Processing changes since the 1970’s have resulted in: 

-Reduced nitrate and nitrite for curing meat and fish

-Addition of chemicals that inhibit nitrosamine formation

-Better temperature controls when drying high protein foods

• Levels of dietary nitrosamines have decreased

• Estimated national population exposed to NDEA concentrations 

above the UCMR 2 MRL (0.005 μg/L): 12.9M (7.1%). Population 

exposed to NDEA concentrations above the HRL is likely higher.

Conclusion

The data suggest that NDEA has adverse health effects (criterion 1) and occurs at levels and 

frequency of public health concern (criterion 2). The available information will be presented to 

the Administrator to determine whether a drinking water regulation would present a 

meaningful opportunity to protect public health (criterion 3). EPA also intends to consider 

whether appropriate to regulate NDEA as part of a nitrosamine group.
Appendix F - Summary of Phase 3 Reg Det Assessment for NDMA -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for NDMA

Background 

• Organic nitrosamine compound, also known as N-nitrosodimethylamine

• Has been used as an industrial solvent and in the production of liquid rocket fuel, 

antioxidants, and softeners for copolymers

• Unintended byproduct of manufacturing activities at facilities (e.g., tanneries, fish processing 

plants, foundries, and pesticide, dye, rubber, and tire manufacturing plants) 

• Found in discharges of municipal wastewater

• Found in some food products (e.g., cured meats and fish, beer, smoked products)

• Can form in the body by nitrosation of dietary amines

• By-product from water treatment, particularly disinfection with chloramines

Evaluation of Statutory Criteria

Health

• OW Health Assessment (2011) 

• Likely to be a carcinogenic to humans (2005 cancer guidelines), 

by a mutagenic mode of action 

• Critical Effect: Cancer

- Based on liver tumors (Peto et al. 1991) 

- Cancer slope factor: 21 (mg/kg-day)

-1

• HRL: 0.0006 μg/L (cancer with ADAFs)

Might the contaminant 

have an adverse effect on 

the health of persons?

Yes

Rationale: 

Cancer in multiple animals 

(rats, mice, hamsters, 

guinea pigs, rabbits) and 

multiple tumor types 

(liver, lung, kidney, nasal 

cavity, and bile duct) 

Occurrence 

National Data

• UCMR 2 Screening Survey, 2008-2010 (MRL = 0.002 μg/L): 

-Detections in 1,841 of 18,040 samples (10.21%)

-Detections at 324 of 1,198 systems (27.05%)

-Likely underestimation of occurrence at levels of health 

concern, since MRL is 3 times higher than HRL

Non-National Data

• State of California, 2001-2007 (min detect = 0.001 μg/L)

-Detections in 1,531 of 4,532 samples (34%)

-Detections at 24 of 101 systems (24%)

Is the contaminant known 

to occur or is there a 

substantial likelihood that 

the contaminant will 

occur in PWSs with a 

frequency and at levels of 

public health concern?

Yes

Rationale: 

Detected in 27% of 

UCMR 2 systems at the

MRL of 0.002 μg/L. 

Also consider as part of 

nitrosamine group.

Since MRL is 

approximately 3 times 

higher than HRL of 0.006 

μg/L, occurrence at a level 

of health concern is likely 

higher.
Appendix F - Summary of Phase 3 Reg Det Assessment for NDMA -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for NDMA

Other Relevant Information

• Sensitive Populations/Lifestages: 

-Newborns and infants 

-Heavy consumers of alcohol

• Processing changes since the 1970’s have resulted in: 

-Reduced nitrate and nitrite for curing meat and fish

-Addition of chemicals that inhibit nitrosamine formation

-Better temperature controls when drying high protein foods

• Levels of dietary nitrosamines have decreased

• NDMA is the predominant nitrosamine in drinking water 

(approximately 27% of systems)

• NDMA detected approximately 4 times more frequently in SW 

than GW in UCMR 2

-19% vs 6% in chlorinating SW/Mixed vs GW systems 

-81% vs 39% in chloraminating SW/Mixed vs GW systems

• Estimated national population exposed to NDMA 

concentrations above the UCMR 2 MRL (0.002 μg/L): 87.9M 

(41.5%). Population exposed to NDMA concentrations above 

the HRL is likely higher

• Generally higher detection rates and concentrations at 

maximum residence time location in distribution systems than 

at entry point

Conclusion

The data suggest that NDMA has adverse health effects (criterion 1) and occurs at levels and 

frequency of public health concern (criterion 2). The available information will be presented to 

the Administrator to determine whether a drinking water regulation would present a 

meaningful opportunity to protect public health (criterion 3). EPA also intends to consider

whether appropriate to regulate NDMA as part of a nitrosamine group. 
Appendix F - Summary of Phase 3 Reg Det Assessment for NDPA -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for NDPA

Background 

• Organic nitrosamine compound, also known as N-nitrosodipropylamine 

• Occurs as a contaminant in substituted dinitrotrifluralin herbicides 

• Found in discharges of municipal wastewater 

• Can form in the body by nitrosation of dietary amines

• By-product from water treatment, particularly disinfection with chloramines

Evaluation of Statutory Criteria

Health

• OW Health Assessment (2011) – External peer review in process

• Likely to be a carcinogenic to humans (2005 cancer guidelines), 

by a mutagenic mode of action 

• Critical Effect: Cancer 

-Based on liver tumors (Druckrey et al. 1967 ) 

-Cancer slope factor: 2 (mg/kg-day)

-1

• HRL: 0.007 μg/L (Cancer with ADAFs) 

Might the contaminant 

have an adverse effect on 

the health of persons?

Yes

Rationale: 

Cancer in multiple animals

(rats, mice) and multiple 

tumor types (liver, nasal 

cavity, esophagus, tongue, 

forestomach, and lung)

Occurrence

National Data

• UCMR 2 Screening Survey, 2008-2010 (MRL = 0.007 μg/L): 

-No detections > MRL or HRL of 0.007 μg/L in 18,049 samples 

from 1,198 systems

• STORET, ambient water records (min detect = 0.19 μg/L) 

-Detections > HRL in 22 of 1,142 samples (1.9%)

-Detections > HRL at 20 of 426 sites (4.7%) 

Non-National Data

• State of California 1995-2007

-No detections in 439 samples from 55 systems 

• State of Illinois, 2005 

-No detection in 1 sample from 1 system 

Is the contaminant known 

to occur or is there a 

substantial likelihood that 

the contaminant will 

occur in PWSs with a

frequency and at levels of 

public health concern?

While not detected at the 

HRL of 0.007 μg/L in 

UCMR 2, consider as part 

of nitrosamine group. 

Other Relevant 

Information • Sensitive Populations/Lifestages: 

-Newborns and infants

-Heavy consumers of alcohol

• Estimated national population exposed to concentrations = 0% 

for UCMR2 since no detects > HRL in 18,049 samples from 1,198 

systems

• Processing changes since the 1970’s have resulted in: 

-Reduced nitrate and nitrite for curing meat and fish

-Addition of chemicals that inhibit nitrosamine formation

-Better temperature controls when drying high protein foods

• Levels of dietary nitrosamines have decreased
Appendix F - Summary of Phase 3 Reg Det Assessment for NDPA -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for NDPA

Conclusion

The data suggest that NDPA has adverse health effects (criterion 1). The available information 

will be presented to the Administrator to determine whether a drinking water regulation 

would present a meaningful opportunity to protect public health (criterion 3). EPA also intends 

to consider whether appropriate to regulate NDPA as part of a nitrosamine group. 
Appendix F - Summary of Phase 3 Reg Det Assessment for NPYR -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for NPYR

Background 

• Organic nitrosamine compound, also known as N-nitrosopyrrolidine

• Has been found in tobacco smoke, processed meats, and spice premixes, air samples from 

rubber tire plants, and effluent water from chemical factories 

• Found in discharges of municipal waste water

• Can form in the body by nitrosation of dietary amines

• By-product from water treatment, particularly disinfection with chloramines

Evaluation of Statutory Criteria

Health

• OW Health Assessment (2011) – External peer review in process

• Likely to be a carcinogenic to humans (2005 cancer guidelines), 

by a mutagenic mode of action 

• Critical Effect: Cancer

- Based on liver tumors (Preussman et al., 1977) 

- Cancer slope factor: 2 (mg/kg-day)

-1

- HRL: 0.007 μg/L (cancer with ADAFs) 

Might the contaminant 

have an adverse effect 

on the health of 

persons?

Yes

Rationale: 

Liver tumors in multiple 

animals (rats, mice, 

hamsters)

Occurrence

National Data

• UCMR 2 Screening Survey, 2008-2010 (MRL = 0.002 μg/L): 

-Detections > HRL of 0.007 μg/L in 5 of 18,043 samples (0.03%)

-Detections > HRL at 3 of 1,198 systems (0.25%)

Non-National Data (min detect= N/A)

• State of California, 2006-2007

-No detections in 57 samples from 4 systems 

Is the contaminant 

known to occur or is 

there a substantial 

likelihood that the 

contaminant will occur 

in PWSs with a 

frequency and at levels 

of public health 

concern?

Yes

Rationale: 

Detected in 0.25% of 

UCMR 2 systems at the 

HRL of 0.007 μg/L . 

Also consider as part of 

nitrosamine group.

Other Relevant 

Information • Sensitive Populations/Lifestages: 

-Newborns and infants

-Heavy consumers of alcohol

-Males may be more sensitive than females

• Processing changes since the 1970’s have resulted in: 

-Reduced nitrate and nitrite for curing meat and fish

-Addition of chemicals that inhibit nitrosamine formation

-Better temperature controls when drying high protein foods

• Levels of dietary nitrosamines have decreased

• Estimated national population exposed to NPYR concentrations 
Appendix F - Summary of Phase 3 Reg Det Assessment for NPYR -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for NPYR

>HRL (from UCMR 2): 0.95M (0.56%)

Conclusion

The data suggest that NPYR has adverse health effects (criterion 1) and occurs at levels and 

frequency of public health concern (criterion 2). The available information will be presented 

to the Administrator to determine whether a drinking water regulation would present a 

meaningful opportunity to protect public health (criterion 3). EPA also intends to consider 

whether appropriate to regulate NPYR as part of a nitrosamine group.
Appendix F - Summary of Phase 3 Reg Det Assessment for RDX -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for RDX

Background 

• Organic compound, IUPAC name 1,3,5-trinitroperhydro-1,3,5-triazine

• Used as an explosive by the U.S. military (superseded TNT as the primarily used explosive) 

and for some civilian uses

• No natural sources

• Production: 1 million - <10 million lbs in 2006 (CUS)

• Industrial Releases: No data (TRI)

Evaluation of Statutory Criteria

Health

• IRIS Risk Assessment (1988) 

- IRIS updated assessment scheduled to be 

completed (2011)

- Possible human carcinogen, group C (1986 cancer 

guidelines) 

• Critical Effect = Inflammation of the prostate

-Based on 2-year rat feeding study (U.S. DOD, 1983)

-RfD = 0.003 mg/kg-day; NOAEL = 0.3 mg/kg-day; 

UF = 100

• HRL: 21 μg/L (non-cancer)

Might the contaminant have an 

adverse effect on the health of 

persons?

Yes

Rationale: 

• Adverse effect (from animal 

studies) is inflammation of the 

prostate

Occurrence

National Data

• UCMR 2 Assessment Monitoring, 2008-2010 (MRL = 

1 μg/L)

-No detections > HRL of 21 μg/L in 32,015 samples 

from 4,137 systems

Non-National Data

• California, 2006 (min detect = N/A)

-No detections in 1 sample at 1 system 

Is the contaminant known to occur 

or is there a substantial likelihood 

that the contaminant will occur in 

PWSs with a frequency and at levels 

of public health concern?

No

Rationale: 

• No detections above HRL of 21 μg/L

Other Relevant 

Information 

• Sensitive Populations/Lifestages: None identified 

• Estimated national population exposed to 

concentrations = 0% for UCMR2 since no detects > 

HRL in 32,015 samples from 4,137 systems

Conclusion

The data suggest that RDX has adverse health effects (criterion 1) but does not occur at levels 

and frequency of public health concern (criterion 2). The available information will be 

presented to the Administrator to determine whether a drinking water regulation would 

present a meaningful opportunity to protect public health (criterion 3).
Appendix F - Summary of Phase 3 Reg Det Assessment for Strontium -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for Strontium

Background 

• Inorganic chemical (element, atomic number 38 on periodic table)

• Occurs naturally. Enters water through contact with and weathering of rocks and soils, from 

atmospheric deposition, and from wastewater discharges

• Used in fertilizers, pyrotechnics, previously used in cathode-ray tube TVs; present in coal

• 11 strontium-containing compounds reported as produced/imported in 2006 (CUS)

-Strontium carbonate reported as produced/imported in the greatest quantity (10 million - <50 

million lbs) 

• Industrial releases: no TRI data

Evaluation of Statutory Criteria

Health

• OW Health Assessment (2011) – External peer review in 

process

-Not classifiable as to human carcinogenicity, group D (1986

cancer guidelines) 

• Critical Effect: decreased bone calcification

-Based on a 9-week oral study in male weanling rats (Marie et 

al., 1985)

-RfD = 0.3 mg/kg-day ; BMDL = 328 mg/kg-day ; UF = 1,000

• HRL: 1,463 μg/L (non-cancer); period of sensitivity birth-18yrs

Might the contaminant 

have an adverse effect on 

the health of persons?

Yes

Rationale: 

• Adverse effect (from 

animal studies) is 

decreased bone 

calcification

Occurrence

National Data:

• NIRS, 1984-1986, ground water systems only, one sample per 

system (MRL = 1 μg/L):

-Detections > HRL of 1,463 μg/L in 70 of 989 systems (7.1%)

Non-National Data: 

• Illinois, 1998-2005, both ground water and surface water 

systems (min detect = 71 μg/L):

-Detections > HRL of 1,463 μg/L in 5 of 19 systems (26%), 

including 1 of 3 SW systems (33%)

-Detections > HRL of 1,463 μg/L in 5 of 21 samples (24%), 

including 1 of 3 SW samples (33%)

• Ohio, 2000-2005, both ground water and surface water 

systems (min detect = 4 μg/L):

-Detections > HRL of 1,463 μg/L in 7 of 32 systems (22%), 

including 2 of 4 SW systems (50%)

-Detections > HRL of 1,463 μg/L in 18 of 77 samples (23%), 

including 8 of 20 SW samples (40%)

• Region 9 Tribes, 2003, ground water system only (min detect = 

N/A):

-No detections in 1 sample/system

• USGS data: 1993-2007 (Toccalino et al., 2010), ground water 

systems only, one sample per system (min detect = 5.61 μg/L)

-Detections > HRL of 1,463 μg/L in 62 of 503 systems (12%)

Is the contaminant known 

to occur or is there a 

substantial likelihood that 

the contaminant will occur 

in PWSs with a frequency 

and at levels of public 

health concern?

Yes

Rationale: 

•NIRS data indicate 

occurrence at levels > HRL 

of 1,463 μg/L in 7.1% of

ground water systems

• Also detected above HRL 

thresholds at surface water 

systems (based on limited 

sampling from Illinois and 

Ohio monitoring programs)
Appendix F - Summary of Phase 3 Reg Det Assessment for Strontium -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for Strontium

Other Relevant Information

• Mining in U.S. ceased in 1959. Annual imports of strontium 

minerals and compounds have steadily declined since 2001 to 

less than 10,000 metric tons

• Expected to have moderate or moderate-to-low mobility in 

soils (ATSDR, HSDB) 

• Ubiquitous at low levels in ground water (detected in 99% of 

NIRS systems at MRL of 1 μg/L)

• Sensitive Populations/Lifestages: 

- Growing children (especially those with low dietary calcium 

and vitamin D)

- Adult with renal problems may be sensitive to impaired 

strontium excretion and retention

- Padget’s disease

• Estimated national population exposed (from NIRS): 

-Exposed to concentrations > HRL of 1,463 μg/L: 10.7M (10.8%)

• Proposed for UCMR 3 monitoring 

Conclusion

The data suggest that strontium has adverse health effects (criterion 1) and occurs at levels 

and frequency of public health concern (criterion 2). The available information will be 

presented to the Administrator to determine whether a drinking water regulation would 

present a meaningful opportunity to protect public health (criterion 3). 
Appendix F - Summary of Phase 3 Reg Det Assessment for Terbufos -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for Terbufos

Background 

• Terbufos is an organophosphate compound

• Used as a pesticide, primarily on corn and sugar beets

-Approx. 7.5 million lbs used per year between 1987 and 1996 (OPP’s 2006 RED)

-8.7 million lbs applied in 37 states in 1992 and 6.5 million lbs applied in 37 states in 1997 

(NCFAP)

• Industrial releases: No TRI data available

• No natural source

Evaluation of Statutory Criteria

Health

• OPP Risk Assessment (2006) 

-Not classifiable as to human carcinogenicity, group D (1986

cancer guidelines) 

• Critical effect: Plasma cholinesterase inhibition 

-Based on cholinesterase inhibition from 28-day and 1-year 

studies in dogs

-RfD = 0.00005 mg/kg-day; NOAEL = 0.005 mg/kg-day; UF = 100

• HRL: 0.35 μg/L (non-cancer)

Might the contaminant 

have an adverse effect on 

the health of persons?

Yes

Rationale: 

Plasma cholinesterase 

inhibition (from animal 

studies) 

Occurrence

Non-National Data

• UCMR 1 screening survey: 2001-2003 (MRL = 0.5 μg/L): 

-No detections > MRL or HRL of 0.35 μg/L in 2,301 samples 

from 295 systems

• USGS data: 1993-2007 (Toccalino et al., 2010) (MRL = 0.006-

0.013 μg/L): 

-No detections in 898 samples/systems

• USGS data: 2002-2005 (Hopple et al., 2009 & Kingsbury et al., 

2008) (min detect = N/A): 

-Phase 1: No detections in 367 samples in 230 systems

-Phase 2: No detections in 48 raw and 48 finished water 

samples

• California, 2002-2007 (min detect = N/A):

-No detections in 191 samples from 23 systems 

Is the contaminant known 

to occur or is there a 

substantial likelihood that 

the contaminant will 

occur in PWSs with a 

frequency and at levels of 

public health concern?

No

Rationale: 

In UCMR 1, no detections 

> HRL of 0.35 μg/L.

Other Relevant 

Information • Limited soil mobility (HSDB)

• Sensitive Populations/Lifestages: None identified 

• Estimated national population exposed to concentrations = 0% 

for UCMR1 since no detects > HRL in 2,301 samples from 295 

systems
Appendix F - Summary of Phase 3 Reg Det Assessment for Terbufos -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for Terbufos

Conclusion

The data suggest that terbufos has adverse health effects (criterion 1) but does not occur at 

levels and frequency of public health concern (criterion 2). The available information will be 

presented to the Administrator to determine whether a drinking water regulation would 

present a meaningful opportunity to protect public health (criterion 3).
Appendix F - Summary of Phase 3 Reg Det Assessment for Terbufos Sulfone -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for Terbufos Sulfone

Background 

• Terbufos sulfone is a degradate of the pesticide terbufos (an organophosphate compound)

• Terbufos is used primarily on corn and sugar beets

-Approx. 7.5 million lbs used per year between 1987 and 1996 (OPP’s 2006 RED)

-8.7 million lbs applied in 37 states in 1992 and 6.5 million lbs applied in 37 states in 1997 

(NCFAP)

• Industrial releases: No TRI data available

• No natural source

Evaluation of Statutory Criteria

Health

• Data on terbufos sulfone health effects are inadequate; 

therefore the health effects assessment is based on data for 

the parent compound, terbufos

• OPP Risk Assessment for terbufos (2006)

-Not classifiable as to human carcinogenicity, group D (1986

cancer guidelines) 

• Critical effect: Plasma cholinesterase inhibition 

-Based on cholinesterase inhibition from 28-day and 1-year 

studies in dogs

-RfD = 0.00005 mg/kg-day; NOAEL = 0.005 mg/kg-day; UF = 100

• HRL: 0.35 μg/L (non-cancer)

Might the contaminant 

have an adverse effect on 

the health of persons?

Yes

Rationale: 

Plasma cholinesterase 

inhibition (from animal 

studies)

Occurrence

National Data

• UCMR 2 Assessment Monitoring, 2008-2010 (MRL= 0.4 μg/L): 

- Detection > HRL of 0.35 μg/L in 1 of 4,138 systems (0.02%)

- HRL is less than the MRL

Non-National Data

• Iowa (min-detect= N/A):

-No detections in 13 wells 

Is the contaminant known 

to occur or is there a 

substantial likelihood that 

the contaminant will 

occur in PWSs with a 

frequency and at levels of 

public health concern?

No

Rationale: 

In UCMR 2 survey, only a 

single detection > HRL of 

0.35 μg/L. 

Other Relevant 

Information • Expected to be more mobile in soil and more resistant to 

biodegradation than the parent compound, terbufos (OPP 

RED)

• Estimated national population exposed to concentrations > 

HRL (from UCMR 2): 44,600 (0.02%)

• Sensitive Populations/Lifestages: None identified 
Appendix F - Summary of Phase 3 Reg Det Assessment for Terbufos Sulfone -- April 2014

Summary of Phase 3 Regulatory Determination 

Assessment for Terbufos Sulfone

Conclusion

The data suggest that terbufos sulfone has adverse health effects (criterion 1) but does not 

occur at levels and frequency of public health concern (criterion 2). The available information 

will be presented to the Administrator to determine whether a drinking water regulation 

would present a meaningful opportunity to protect public health (criterion 3).