# Regulatory Determinati on 3 S uppor t D ocumentOffic e of Water (4607M)
EPA 815-R-15-014 December 2015OW – OGW DW Re gulatory Determination 3 Support Document

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### Disclaimer

T his document is designed to provide technical background information for the Environmental Protectio n A gency’s (EPA’s) third R eg ulatory D etermination (RD 3) for drinking water contaminants under Safe Drinking Water Act (SDWA) provisions, based on EPA’s th ird Contaminant Candidate List ( CCL 3 ).
This document is not a regulation itself, and it does not substitute for the SDWA or
EPA ’s regulations. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.OW

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### Executive Summary

This document provides background information to support the U.S. Environmental Protection Agency’s ( EPA ’s ) third Regulatory D etermination (RD 3) for drinking water contaminants under the Safe Drinking Water Act (SDWA) provisions, based on the third
C ontaminant Candidate List ( CCL 3). The regulatory determinations are presented formally in the Federal Register . This report itself does not constitute a regulation or a formal determination

. This regulatory support document consists of an introductory chapter on the CCL 3 and RD 3 process (Chapter 1), a chapter on data sources used to evaluate contaminants (Chapter 2), and three chapters (C hapters 3 , 4 and 5 ) devoted to the four contaminants receiving a final regulatory determination under RD 3: 1,3-dinitrobenzene, dimethoate, t erbufos , and terbufos sulfone. (Terbufos and terbufos sulfone are discussed together in one chapter.)
EPA evaluates contaminants for regulatory determination based on three statutory

cr iteria . Regulation with a n ational p rimary drinking w ater r egulation (NPDWR) is warranted if:
(a) the contaminant may have an adverse effect on the health of persons;

(b) the contaminant is known to occur or there is substantial likelihood that the contaminant will occur in public water s ystems ( PWS s) with a frequency and at levels of public health concern; and
(c) in the sole judgment of the Administrator, regulation of such contaminant presents a meaningful opportunity for health risk reduction for persons served by PWS s. In evaluating contaminants against these criteria, EPA gathered data and inf ormation on health effects and occurrence in public water systems, as well as physical and chemical properties, environmental fate and transport, formation (as applicable, e.g., in the case of disinfection by- products), and occurrence in ambient water. EPA also evaluated the availability of analytical methods and treatment technologies. The availability of treatment technologies is not taken into consideration when deciding whether regulation is warranted, but suitable technologies must be developed and available by the time a n NPDWR is promulgated.

EPA has determined that four contaminants (dimethoate, 1,3-dinitrobenzene, terbufos, and terbufos sulfone) do not satisfy all three criteria and do not warrant regulation at this time. Those decisions are presented formally in the Federal Register.
Chapters 3 , 4 and 5 of this document present and summarize the information and data gathered and used to evaluate the four contaminants receiving a final negative determination at this time

. Since EPA understands that members of the public with varied concerns might be more interested in certain contaminants and less interested in others, the document is designed in such a way that individual chapters are more or less self -contained and can be distributed separately

. Additional documents produced to support the RD 3 process include a n occurrence report based on data from the second Unregulated Contaminant Monitoring Rule ( UCMR 2 ) occurrence report and an RD 3 Protocol document that explains how the CCL 3 contaminants were evaluated and contaminants were selected for inclusion in RD 3.OW

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### Contents

Dis claimer ........................................................................................................................................ i Executive Summary

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C ontents

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Chapter 1: Introduction .............................................................................................. 1-1 Chapter 2: Evaluation of Health and Occurrence Data ............................................. 2-1 Chapter 3: Dimethoate ............................................................................................... 3-1 Chapter 4: 1,3-Dinitrobenzene................................................................................... 4-1 Chapter 5: Terbufos and Terbufos Sulfone ............................................................... 5-1OW – OGW DW Re gulatory Determination 3 Support Document

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# Chapter 1: Introduction

A chapter from:

Regulatory Determination 3 Support Document

EPA Report 815 -R-14- 003OW – OGW DW Re gulatory Determination 3 Support Document

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### Contents

C hapter 1: Introduction ................................................................................................................ 1-7
1.1 Purpose and Scope ........................................................................................................... 1-7
1.2 Ba ckground on the CCL and Regulatory Determinations ............................................... 1-7
1.2.1 Statutory Requirements for CCL and Regulatory Determinations .......... 1-7
1.2.2 The First Contaminant Candidate List (CCL 1) ....................................... 1-8
1.2.3 The First Regulatory Determination (RD 1) for CCL 1 ........................... 1-9
1.2.4 The Second Contaminant Candidate List (CCL 2) .................................. 1-9
1.2.5 The Second Regulatory Determination (RD 2) for CCL 2 ...................... 1-9
1.2.6 NDWAC Recommendations .................................................................. 1-10
1.3 The CCL Classification Process and the Third Contaminant Candidate List (CCL 3) . 1-10
1.4 Summary of the Approach Used to Identify and Evaluate Contaminants for Regulatory Determination 3 ............................................................................................................. 1-12 1.5 Summary of Regulatory Determination 3 ...................................................................... 1-15
1.6 References ...................................................................................................................... 1-15OW – OGW DW Re gulatory Determination 3 Support Document

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### Exhibits

E xhibit 1-1: General Overview of the Approach Used to Establish CCL 3 .............................. 1-11 Exhibit 1-2: General Overview of the Approach Used to Evaluate CCL 3 Contaminants for
R egulatory Determination 3 ...................................................................................... 1-13OW – OGW DW Re gulatory Determination 3 Support Document

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### Abbreviations

ATSDR Agency for Toxic Substances and Disease Registry

CCL Contaminant Candidate List

CCL 1 First Contaminant Candidate List

CCL 2 Second Contaminant Candidate List

CCL 3 Third Contaminant Candidate List
CCLCP Work Group Work Group on the Contaminant Candidate List Classification
Process
CFR Code of Federal Regulations

DDE 2,2

- bis(p

- chlorophenyl)ethylene

EPA Environmental Protection Agency

EPTC S

- ethyl dipropylthiocarbamate

FR Federal Register

HRL Health Reference Level

IRIS Integrated Risk Information System

MCL Maximum Contaminant Level

MCLG Maximum Contaminant Level Goal

NAS National Academ y of Science s NCOD National Contaminant Occurrence Database

NDWAC National Drinking Water Advisory Council

NPDWR National Primary Drinking Water Regulation

NRC National Research Council

OGWDW Office of Ground Water and Drinking Water

OPP Office of Pesticide Programs

OW Office of Water
PCCL Preliminary Contaminant Candidate List

P CCL 3 PCCL for t he Third Candidate Contaminant List

PWS Public Water System

RD 1 First Regulatory Determination

RD 2 Second Regulatory Determination

RD 3 Third Regulatory Determination

RED Reregistration Eligibility Decisions

SAB Science Advisory Board

SDWA Safe Drinking Water Act

UCMR 2 Second Unregulated Contaminant Monitoring Regulation

USEPA United States Environmental Protection Agency

WHO World Health OrganizationOW – OGW DW Re gulatory Determination 3 Support Document

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### Chapter 1: Introduction

1.1 Purpose and Scope
The 1996 Safe Drinking Water Act (SDWA) Amendments (section 1412(b)(1)) direct EPA to publish a list of currently unregulated contaminants that may pose risks for drinking water (referred to as the Contaminant Candidate List, or CCL) every five years and to make determinations on whether or not to regulate at least five contaminants from the CCL with a national primary drinking water regulation (NPDWR)

. This document serves to support EPA’s third Regulatory D etermination (RD 3), based on an evaluation of contaminants on the third Contaminant Candidate List ( CCL 3). This regulatory determination support document provides:

• A summary of the statutory requirements

, previous activities related to t he CCL and regulatory determinations, and the approach used to select and evaluate CCL 3 contaminants for RD 3,

• Background information on the data sources used to evaluate physical and chemical properties, use and environmental release, environmental fate, and occurrence and

expos ure for CCL 3 contaminants, and

• Detailed i nformation and data on the physical and chemical properties, use and environmental release, environmental fate, potential health effects, occurrence and

expos ure estimates and a summary of t he regulatory determination s made by the

agency for each of the four CCL 3 contaminant candidates receiving a final regulatory determination at this time

.

The four regulatory determination candidates discussed in this document are : 1,3-dinitrobenzene, d imethoate, t erbufos, and terbufos sulfone. Additional detail on the process used to evaluate CCL 3 contaminants can be found in the Protocol for the Regulatory
Determination 3 (USEPA, 2014a ).
EPA understands that members of the public with varied concerns might be more interested in certain contaminants and less interested in others, therefore the document is designed in such a way that individual chapters are more or less self-contained and can be distributed separately.



### 1.2 Background on the CCL and Regulatory Determinations

1.2.1 Statutory Requirements for CCL and Regulatory Determinations
The statutory requirements for the CCL and regulatory determinations can be found in SDWA Section 1412(b)(1). Th e 1996 SDWA Amendments require EPA to publish the CCL every five years. The CCL is a list of contaminants that are not subject to any proposed or promulgated NPDWRs, are known or anticipated to occur in PWSs, and may require regulation under SDWA to protec t public health

. SDWA requires consultation with the scientific community, including EPA’s Science Advisory Board (SAB) ; opportunity for public comments; and consideration of the National Contaminant Occurrence Database (NCOD), established under section 1445(g) of the Act. The 1996 SDWA Amendments also direct EPA to determine whether

or not to regulate at least five contaminants from the CCL every five years. There are threeOW – OGW DW Re gulatory Determination 3 Support Document

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1-8 criteria to be considered in making a regulatory determination. A decision to regul ate is warranted if :

(a) the contaminant may have an adverse effect on the health of persons;

(b) the contaminant is known to occur or there is substantial likelihood that the contaminant will occur in PWS s with a frequency and at levels of public health concern; and
(c) in the sole judgment of the Administrator, regulation of such contaminant presents a meaningful opportunity for health risk reduction for persons served by PWS s.

If EPA determines that all three of these statutory criteria are met , it makes a preliminary positive regulatory determination that a n NPDWR 1 is needed . Following a comment response period, if a final po sitive regulatory determination is made t he a gency has 24 months to publ ish a proposed Maximum Contaminant Level Goal 2 ( MCLG ) and an NPDWR. 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 The agency may determine that there is no need for a regulation when a contaminant fails to meet one or more of the criteria. A decision not to regulate is considered a final agency action and is subject to judicial review. The agency can choose to publish a Health Advisory (a non-regulatory action) or other guidance for any contaminant on the CCL, independent of the regulatory determination.

1 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 for public water systems for a specific contaminant or group of contaminants.

2 The MCLG is the "m aximum 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." (CFR 141.2)

3 The statute authorizes a nine month extension of this promulgation date. 1.2.2 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 National D rinking Water Advisory Council (NDWAC) on the process that should be used to identify contaminants for inclusion on CCL 1. For chemical contaminants, the agency developed screening and evaluation criteria based on recommendations from NDWAC. For microbiolo gical contaminants, NDWAC recommended that the agency seek external expertise to identify and select potential waterborne pathogens. As a result, the agency convened a n 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.
With the short time frame required, t he first CCL was largely based on expert knowledge and the evaluation of readily available information. EPA did obtain benefi cial input from the NDWAC, the scientific community, and the public through stakeholder meetings and the public comments received on the draft CCL 1 published on October 6, 1997 (62 FR 52193 ; USEPA,OW – OGW DW Re gulatory Determination 3 Support Document

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1-9 1997 ). EPA published the final CCL 1, which contained 50 chemical and 10 microbiological contaminants, on March 2, 1998 (63 FR 10273; USEPA, 1998 ). A more detailed discussion of how EPA developed CCL 1 can be found in the 1997 and the 1998 Federal Register notices (62 FR 52193; USEPA 1997 and 63 FR 10273; USEPA 1998 ).

1.2.3 The First Regulatory Determination (RD 1) for CCL 1
EPA published its preliminary regulatory determinations for a subset of contaminants listed on CCL 1 on June 3, 2002 (67 FR 38222; USEPA, 2002 ). The a gency published its final regulatory determinations on July 18, 2003 (68 FR 42898; USEPA, 2003 ). EPA identified nine contaminants from the 60 contaminants listed on CCL 1 that had sufficient data and information available to make regulatory determinations. The nine contaminan ts were Acanthamoeba , aldrin, dieldrin, hexachlorobutadiene, manganese, metribuzin, naphthalene, sodium, and sulfate. The

agency determined that an NPDWR was not necessary for any of these nine contaminants. The agency did, however, issue guidance on Acanthamoeba and health advisories for manganese , sodium, and sulfate.

The decision

- making process that EPA used to make its regulatory determinations for CCL 1 was based on substantial expert input and recommendations from different groups including stakeholders, the National Research Council (NRC), and NDWAC. In June 2002, EPA consulted with the SAB Drinking Water Committee and requested its review and comment on whether the protocol EPA developed, based on the NDWAC recommendations, was consistently applied and appropriately documented. SAB provided verbal feedback regarding the use of the NRC and NDWAC recommendations in EPA’ s decision criteria for making its regulatory determinations. SAB recommended that the a gency provide a transparent and clear explanation of the process for making regulatory determinations. The a gency took SAB’s recommendation into consideration and further explained the regulatory determination evaluation process in the 2003 Federal Register notice (68 FR 42898; USEPA, 2003 ) an d in the supporting documentation.

1.2.4 The Second Contaminant Candidate List (CCL 2)
After completing CCL 1, the agency realized the need to develop an enhanced, more robust approach to evaluating the risk of potential drinking water contaminants for future CCLs. The agency requested assistance from the NRC for guidance on an approach to develop a more rigorous and expansive approach for the CCL. The NRC’s evaluation, and other assessments leading to an enhanced process, overlapped with the deadline requirements to produce CCL 2. Hence, while EPA developed the more rigorous process, CCL 2 was based on the process used for CCL 1, and reflected the changes related to RD 1 . The CCL 2 carried forward the 51 chemical and microbial contaminants remaining on CCL 1 af ter RD 1. The agency published its draft CCL 2 Federal Register notice on April 2, 2004 (69 FR 17406; USEPA, 2004) and the final
CCL 2 Federal Register notice on February 24, 2005 (70 FR 9071; USEPA, 2005 ).

1.2.5 The Second Regulatory Determination (RD 2) for C CL 2

The agency published its preliminary regulatory determinations for c ontaminants listed on the CCL 2 Federal Register notice on May 1, 2007 (72 FR 24106; USEPA, 2007 ). In the May 1, 2007 notice, EPA made preliminary determinations for 11 of the 51 contaminants listed on the
CCL 2. These contaminants were: boron, the dacthal mono- and di-acid degradates, 1,1- dichloro-2,2- bis(p

- chlorophenyl)ethylene (DDE), 1,3 -dichloropropene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, s- ethyl dipropylthiocarbamate (EPTC ), fonofos, terbacil, and 1,1,2,2- tetrachloroethane. The agency determined that an NPDWR was not necessary for any ofOW – OGW DW Re gulatory Determination 3 Support Document

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1-10 these 11 contaminants. EPA finalized those regulatory determinations on CCL 2 on July 30, 2008 (73 FR 44251; USEPA, 2008a ).

1.2.6 NDWAC Recommen dations
In March 2000, EPA convened a Working Group under NDWAC to help develop an approach for making regulatory determinations. The Working Group developed a protocol for analyzing and presenting the available scientific data and recommended methods to i dentify and document the rationale supporting a regulatory determination decision. The NDWAC Working Group report was presented to and accepted by the entire NDWAC in July 2000.
The Working Group developed separate but similar protocols for microorganisms and chemicals. The approach for chemicals was based on an assessment of the impact of acute, chronic, and lifetime exposures, as well as a risk assessment that includes evaluation of occurrence, fate, and dose-response. The NDWAC protocol for chemicals pro vided a semi

quantitative, systematic approach for addressing each of the three Regulatory Determination criteria. EPA utilized NDWAC suggestions for Regulatory Determinations 1, 2, and 3. The RD 3 process was formalized in a Protocol document that was rev iewed by an expert panel in October, 2011, and revised in response to reviewer suggestions (USEPA, 2014a).



### 1.3 The CCL Classification Process and the Third Contaminant Candidate List (CCL 3)

As noted, after CCL 1 t he a gency realized the need to develop an enhanced approach to evaluating the risk of potential drinking water contaminants based on occurrence in drinking water and adverse health effects – both demonstrated and potential – for future CCLs. The

agency requested assistance from the NRC for guidance on methods and processes to identify and narrow a universe of potential contaminants into a smaller, more focused list of contaminants in drinking water for the future CCLs. The NRC recommended a multi- step process including using prototype classification algorithms that evaluate 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 contami nant. The NRC described two health effect s attributes, severity and potency, and three occurrence attributes: prevale nce, magnitude, and persistence/ mobility.
The details of the NRC recommendation are available in the report entitled “Classifying Drinking Water Contaminants for Regulatory Considerations ” (N RC , 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 conta minants.

With the NRC recommendations in hand, the Office of Water turned to the NDWAC to provide advice on whether to pursue the stepped approach recommended in the NRC report and to work out how this could be implemented. The NDWAC formed a subcommittee, the Work Group on the Contaminant Candidate List Classification Process (CCLCP Work Group), to provide advice to the NDWAC.
Based on the deliberations of the CCLCP Work Group, NDWAC released a report in June 2004 that found merit in the NRC recommendations, but noted that the EPA may need several CCL cycles to fully develop and implement the NRC recommended approach. 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 we re available at th e time. The NDWAC al so recognized that the agency would be developing a new and powerful tool that could be refinedOW – OGW DW Re gulatory Determination 3 Support Document

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1-11 and improved in successive efforts; therefore the a gency 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 CCL 3, which includes the following key steps:

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

(2) A screening process that uses readily available information on health effects and occurrence in water to narrow the universe of contaminants to a Preliminary CCL (PCCL) ; a nd

(3) A structured classification process that “scores” and ranks contaminants, to develop a CCL from the PCCL , involving prototype classification models as tools, coupled with expert review and assessment.

Exhibit 1-1 illustrates the three

- step process used to evaluate contaminants for CCL 3.

Exhibit 1-1 : General Overview of the Approach Used to E stablish CCL 3

Classification Tools

Evaluation

Expert Review

Universe

PCCL

Proposed CCL Surveillance and
Nomination STEP 1

Identify the

Universe

STEP 2

Screen
to a PCCL

STEP 3

Select the CCL

Final CCLOW – OGW DW Re gulatory Determination 3 Support Document

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1-12 To populate the CCL 3 Universe of c hemicals

, an extensive preliminary list of substances was compiled fro m a wide variety of data sources that met specific criteria

. The preliminary list

was refined by removing chemicals with a n existing NPDWR

, substances that are considered mixture s of chemicals , an d “non- chemically defined” entries

. The resultant CCL 3 Universe included approximately 6,000 chemicals (see USEPA, 2009a for further details on the CCL 3 Universe process)

. The Universe of chemicals was 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. As the result of this screening process, 561 chemical contaminants were selected to move on to the Preliminary CCL
3 (P CCL 3 ) from the approximately 6,000 chemicals in the CCL 3 Universe (see USEPA, 2009b for details on the screening process)

. To select contaminants for the CCL 3 from among the 561 P CCL 3 contaminants , EP A used classification models as a support tool to handle larger, more complex assortments of data in a consistent and reproducible manner. T he classification models were trained based on past expert decisions for a sample of chemicals

. To enable numerical scoring of the contaminants, using complex data, a scaling system was developed for four attributes: severity, potency, magnitude, and prevalence (see USEPA, 2009c for details). Contaminants were scored for each of these attributes, and the scores were run through three calibrated models. T he EPA Evaluation Team made several post

- model refinements to compile the draft list of CCL 3 contaminants. EPA also put out a special call for nominations to the CCL 3 (USEPA, 2009d), held expert panel consultations, consulted with the SAB, and accepted public comments (USEPA, 2009e). The draft CCL 3 was published on February 21, 2008 (73 FR 9628; USEPA, 2008b), and the final
CCL 3 was published on October 8, 2009 (74 FR 51850; USEPA, 2009f). The final CCL 3 consists of 104 chemicals or chemical groups, and 12 microbiological contaminants

. 

### 1.4 Summary of the Approach Used to Identify and Evaluate Contaminants for Regulatory Determination 3

Exhibit 1-2 provides a brief overview of the process EPA used to identify which CCL 3 contaminants should be considered for regulatory determinations . The exhibit also summarizes the SDWA statutory criteria EPA applies when making the regu latory determinations. Details about the process of evaluating CCL 3 contaminants for regulatory determination are found in the Protocol for the Regulatory Determination 3 (USEPA, 2014a ). A brief summary is provided in the following paragraphs.OW – OGW DW Re gulatory Determination 3 Support Document

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1-13 Exhibit 1-2: General Overview of the Approach Used to Evaluate CCL 3 Contaminants for Regulatory Determination 3

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? CCL3

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

In decidi ng which CCL 3 contaminants should be considered for RD 3 , the agency considered whether sufficient information and/or data were available to characterize contaminants’ potential health effects and the known/likely occurrence in and exposure from drinking water. For health effects, EPA considered whether an a gency -approved health risk

assessment 4 was available to identify any potential adverse health effect(s) and derive a Health Reference Level (HRL), an estimated concentration threshold below which adverse health effects are considered unlikely to occur ( for a th reshold toxicant), or below which adverse effects have a defined low probability of occurrence ( for a non-threshold toxicant , such as a carcinogen ). For occurrence, the agency considered whether available information and data provided a representative pict ure of known and/or likely occurrence in PWS s. If sufficient information and data were available to characterize adverse human health effects and known/likely occurrence in
PWS s, the agency identified the contaminant as potentially suitable for regulatory

4 Sources of health assessments used to evaluate CCL 3 contaminants for RD 3 eligibility included the agency’s Integrated Risk Information System (IRIS), the agency’s Office of Pesticide Programs (OPP) Reregistration Eligibility Decisions (REDs), the agency ’s Office of Water (OW), the National Academy of Sciences (NAS), the World Health Organization (WHO), and the Agency for Toxic Substances and Disease Registry (ATSDR).OW – OGW DW Re gulatory Determination 3 Support Document

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1-14 determinations. EPA also gathered information on the availability and adequacy of analytical methods (for monitoring) and treatment technologies . The availability of treatment technologies is not taken into consideration when deciding whether regulation is warranted, but suitable technologies must be developed and available by the time a n NPDWR is promulgated

. I n cases where EPA chose a contaminant as suitable for regulatory determination, the agency considered the following in evaluating each of the three s tatutory criteria ( see section 1.2.1).

(1) First statutory criterion: Is the contaminant likely to cause an adverse effect on the health of persons?

The a gency evaluated the best available, peer

- reviewed assessments and studies to characterize the human health effects that may result from exposure to the contaminant when found in drinking water. Based on this characterization, the agency estimated a n HRL for each contaminant. Section 2.3 of this document provides more detailed information about the approach used to evaluate and analyze the health information.

(2) Second statutory criterion - Is the contaminant known to occur, or is there a substantial likelihood that the contaminant will occur, in PWS s at a frequency and level of public health concern?

To evaluate known occurrence in PWSs, the agency compiled, screened, and analyzed data from several occurrence data sets to develop representative occurrence estimates for public drinking water systems. EPA used the HRL estimates for each contaminant as a benchmark against which to conduct an initial evaluation or screening of the occurrence data. For each contaminant EPA estimated , when possible, the number of PWSs (and the population served by these PWSs) with detections greater than one- half the HRL (> 1⁄2 HRL) and greater than the HRL (> HRL). To further evaluate the likelihood of a contaminant occur ring in drinking water, the agency considered information on the use and release of the contaminant into the environment and supplemental information on occurrence in water (e.g. ambient water quality data, special studies performed by other agencies, organizations, and/or entities). Section 2. 4 provides more details on the approach used to analyze the occurrence information/data.

(3) Third statutory criterion - In the sole judgment of the Administrator, does regulation of the contaminant present a meaningful opportunity for health risk reduction for persons served by PWS s?

EPA evaluated a number of additional factors to determine whether regul ation presents a meaningful opportunity for health risk reduction among persons served by PWSs, including: the total estimated population served by systems contamina ted at levels of health concern; the estimated contribution of drinking water exposure to total exposure (considering alternative routes of exposure such as food, air, soil, etc.) ; and the existence of sensitive subpopulations that might be at special risk.
If EPA determines that all three of these statutory criteria are met , it makes a preliminary positive regulatory determination that a n NPDWR is needed . Following a comment response period and a final positive regulatory determination, t he agency has 24 months to publ ish a proposed MCLG and an NPDWR. After the proposal, the a gency has 18 months to publish a final MCLG and promulgate a final NPDWR. It should be noted that this regulatoryOW – OGW DW Re gulatory Determination 3 Support Document

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1-15 determination process is distinct from the more detailed analyses needed to support the develop ment of the NPDWR itself . Thus, a decision to regulate is the beginning of the agency regulatory development process, not the end.
If the answer to any of the three statutory criteria is negative based on the available data

, then the agency makes a determination that an NPDWR is not necessary for that contaminan t at that time . A decision not to regulate is considered a final agency action and is subject to judicial review. The agency can choose to publish a Health Advisory (a non-regulatory action) or other guidance for any contaminant on the CCL, independent of the regulatory determination. If EPA has insufficient information/data to evaluate a contaminant according to the statutory criteria, it will not make a decision until such data become available.
For more detail on the regulatory determinations process, se e the Protocol for the Regulatory Determination 3 (USEPA, 2014a ).



### 1.5 Summary of Regulatory Determination 3

EPA identified five CCL 3 contaminants (1,3-dinitrobenzene, dimethoate, strontium, terbufos, and terbufos sulfone ) as suitable for regulatory determinations based on the available data and information on adverse health effects , known and likely occurrence in PWS s, and other factors

. After evaluating the se contaminants against the three SDWA criteria, the agency ma de a preliminary positive determ ination (determination to regulate with an NPDWR) for one contaminant, s trontium, and a preliminary negative determination (determination not to regulate) for the remaining four (dimethoate, 1,3-dinitrobenzene, terbufos, and terbufos sulfone) (79 FR 62715-62750; USEPA 2014b).
After reviewing public comments and considering additional data, EPA is making a final determination to not regulate dimethoate, 1,3-dinitrobenzene, terbufos, and terbufos sulfone. The Agency is postponing a final decision on strontium, pending the outcome of several investigations in progress. The formal determination for dimethoate, 1,3-dinitrobenzene, terbufos, and terbufos sulfone, along with a statement about the status of strontium and responses to all public comments received, can be found in the Federal Register notice which this support document accompanies. Additional information about the regulatory determination process and the information evaluated for each contaminant can be found in support documents developed for RD 3, which include, in addition to this support document: Occurrence Data from the Second Unregulated Contaminant Monitoring Regulation (UCMR 2) (which presents background information and findings from the UCMR 2 national drinking water surv ey) (USEPA, 2015), and the Protocol for the Regulatory Determination 3 (which documents the procedure used to select
RD 3 contaminants) (USEPA, 2014a).



### 1.6 References

National Research Council (N RC ). 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 Academies Press.
United States Environmental Protection Agency ( USEPA ). 1997. Announcement of the Draft Drinking Water Contaminant Candidate List; Notice. Federal Register. Vol. 62, No. 193, p. 52193. October 6, 1997.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 1, Introduction

1-16 USEPA. 1998. Announcement of the Drinking Water Contaminant Candidate List; Notice. Federal Register. Vol. 63, No. 40, p. 10273. March 2, 1998.

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.
USEPA. 2003. Announcement of Regulatory Determinations for Priority Contaminants on the Drinking Water Contaminant Candidate List. Federal Register. Vol. 68, No. 138, p. 42898. July 18, 2003.

USEPA. 2004. Drinking Water Contaminant Candidate List 2; Notice. Federal Register. Vol. 69, No. 64, p. 17406, April 2, 2004.

USEPA. 2005. Notice— Drinking Water Contaminant Candidate List 2; Final Notice. Federal Register. Vol. 70, No. 36, p. 9071, February 24, 2005.
USEPA. 2007. Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water Contaminant Candidate List— Preliminary Determinations; Proposed Rule. Federal Register. Vol. 72, No. 83, p. 24016, May 1, 2007.
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.
USEPA. 2008b. Drinking Water Contaminant Candidate List 3— Draft Notice. Federal Register. Vol, 73. No 35. p. 9628, February 21, 2008.

USEPA. 2009a. Final C ontaminant Candidate List 3 Chemicals: Identifying the Universe. EPA 815-R-09-006. August 2009.
USEPA. 2009b. Final Contaminant Candidate List 3 Chemicals: Screening to a PCCL. EPA 815- R-09-007. August 2009.

USEPA. 2009c. Final Contaminant Candidate List 3 Chemicals: Classification of PCCL to the CCL. EPA 815-R-09-008. August 2009.
USEPA. 2009d. Summary of Nominations for the Third Contaminant Candidate List. EPA-815- R-09-011. August 2009.
USEPA. 2009e. Final Comment Response Document for the Third Drinking Water Contaminant Candidate List 3 Categorized Public Comments. EPA 815-R-09-010. August 2009.
USEPA. 2009f. Drinking Water Contaminant Candidate List 3–Final. Federal Register. Vol. 74, No. 194, p. 51850, October 8, 2009.
USEPA. 2014a. Protocol for the Regulatory Determinations 3. Including Appendices A- F. EPA

815-R-14-005. April 2014.
USEPA 2014b. Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water Contaminant Candidate List. Federal Register. Vol. 79, No. 202, pp. 62715-62750
USEPA. 2015. Occurrence Data from the Second Unregulated Contaminant Monitoring Regulation (UCMR 2). Including Appendices A- C. EPA -815-R-15-013. December 2015.OW – OGW DW Re gulatory Determination 3 Support Document

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# Chapter 2:

Evaluation of Health and Occurrence Data

A chapter from:

Regulatory Determination 3 Support Document

EPA Report 815 -R- 15

- 014

December 2015OW – OGW DW Re gulatory Determination 3 Support Document

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2-2OW – OGW DW Re gulatory Determination 3 Support Document

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### Contents

C ontents ....................................................................................................................................... 2-3 Exhibits ........................................................................................................................................ 2-4 Abbreviations ............................................................................................................................... 2-5 Chapter 2: E v aluation of Health and Occurrence Data ................................................................ 2-9
2.1 Evaluation of Contaminant Background, Chemical, and Physical Properties ................. 2-9
2.2 Evaluation of Contamination Sources and Environmental Fate ...................................... 2-9
2.3 Evaluation of Adverse Health Effects ............................................................................ 2-13
2.3.1 Use of Carcinogenicity Data for the Derivation of a Health Reference Level .. 2-13
2.3.2 Use of Non

- carcinogenic Health Effects Data for Derivation of an HRL ......... 2-14
2.3.3 Sources of Data/Information for Health Effects ................................................ 2-15
2.4 Evaluation of Contaminant Occurrence and Exposure .................................................. 2-16
2.4.1 General Considerations ...................................................................................... 2-16
2.4.2 Occurrence in Ambient Water ........................................................................... 2-18
2.4.3 Occurrence in Drinking Water
– Primary Data Sources .................................... 2-21
2.4.4 Occurrence in Drinking Water
– Secondary Data Sources ................................ 2-30 2.5 Evaluation of Analytical and Treatment Methods ......................................................... 2-35
2.5.1 Evaluation of Analytical Methods ..................................................................... 2-35
2.5.2 Evaluation of Treatment Technologies .............................................................. 2-36
2.6 References ...................................................................................................................... 2-36OW – OGW DW Re gulatory Determination 3 Support Document

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2-4 

### Exhibits

Exhibit 2- 1: Chemical Volume Ranges Used in CUS

- IUR Reporting of National Production Volumes ............................................................................................................. 2-10 Exhibit 2- 2 : Sources and Dates of Health Effects Assessments ................................................ 2-16 Exhibit 2- 3 : Primary Sources of Drinking Water Occurrence Data Used to Evaluate RD 3 Contaminants Receiving a Final Regulatory Determination at This Time ........ 2-22 Exhibit 2-4: Cross-section States for UCM Round 1 and Round 2 ........................................... 2-28OW – OGW DW Re gulatory Determination 3 Support Document

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2-5 

### Abbreviations

ADAFs Age Dependent Adjustment Factors

AMWA Association of Metropolitan Water Agencies AQUA Automated Quantitative Usage Analysis

AWWA American Water Works Association

AwwaRF American Water Works Association Research Foundation

ATSDR U.S. Agency for Toxic Substances and Disease Registry

BMD B enchmark D ose
BMDL B enchmark D ose Lower Bound

BW Body Weight

CCL Contaminant Candidate List

CCL 3 Third Contaminant Candidate List

CCR Consumer Confidence Reports

CDR Chemical Data Reporting

CSF Cancer Slope Factor

CUS Chemical Update System

CW Unit Risk C oncentration in Drinking W ater
CWS Community Water System

CWSS Community Water System Survey

DBP Disinfection Byproducts

DBP ICR Disinfection Byproducts Information Collection Rule

DL Detection Limit

DOE Department of Energy

DWI Drinking Water Intake

EPA Environmental Protection Agency

EPCRA Emergency Planning and Community Right

- to

- Know
EWG Environmental Working Group

EXAMS Exposure Analysis Modeling System

FIFRA Federal Insecticide Fungicide and Rodenticide Act

FR Federal Register

HBSL Health Based Screening L evel

HSDB Hazardous Substances Data Bank

HRL Health Reference Level

IOC Inorganic Compound

IRED Interim Reregistration Eligibility Decisions

IRIS Integrated Risk Information System

IUR Inventory Update Reporting

LCMRL Lowest Concentration Minimum Reporting Level

LOAEL Lowest

- Observed

- Adverse

- Effect Level

MCL Maximum Contaminant Levels

MCLG Maximum Contaminant Level GoalOW – OGW DW Re gulatory Determination 3 Support Document

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2-6 mg/kg

- day Milligram per kilogram per day

MDL Method Detection Limit

MRL Minimum Reporting Level

MTBE Methyl T ertiary B utyl E ther NAWQA National Water Quality Assessment

NAS National Academy of Sciences

NCFAP National Center for Food and Agricultural Policy

NCOD National Drinking Water Contaminant Occurrence Database

NIRS National Inorganics and Radionuclides Survey

NOAEL No

- Observed

- Adverse

- Effect Level

NPDWR National Primary Drinking Water Regulation

NPS National Pesticide Survey

NRC National Research Council

NREC National Reconnaissance of Emerging Contaminants

OGWDW Office of Ground Water and Drinking Water

OPP Office of Pesticide Programs

OW Office of Water

PBT Persistence, Bioaccumulation, and Toxicity

PDP Pesticide Data Program

PMP Pilot Monitoring Program

PRZM Pesticide Root Zone Model

PWS Public Water System QA Quality Assurance

RAIS Risk Assessment Information System

RD 3 Third Regulatory Determination

RED Reregistration Eligibility Decisions

RfD Reference Dose

RSC Relative Source Contribution

SCI

- GROW Screening Concentration In GROund Water

SDWA Safe Drinking Water Act

SOC Synthetic Organic Compound

STORET EPA’s Storage and Retrieval
TRED Tolerance Reassessment Progress and Risk Management Decisions

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 AgricultureOW – OGW DW Re gulatory Determination 3 Support Document

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2-7 USEPA United States Environmental Protection Agency

USGS United States Geological Survey

USNLM U.S. National Library of Medicine

VOC Volatile Organic Compound

WHO World Health OrganizationOW – OGW DW Re gulatory Determination 3 Support Document

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2-8OW – OGW DW Re gulatory Determination 3 Support Document

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### Chapter 2: Evaluation of Health and Occurrence Data

This report provides background information to support the Environmental Protection
A gency’s (EPA’s) third R egulatory D etermination (RD 3) for drinking water contaminants based on the third Contaminant Candidate List (CCL 3). This process is conducted under provisions of the Safe Drinking Water Act (SDWA). Chapter 2 provides a general overview of the sources of data used to evaluate contaminants under CCL 3 and RD 3. It inc ludes, where available, information about the quality of the data. For more information about the CCL 3 and RD 3 processes, see Chapter 1 of this report and the RD 3 Protocol document (USEPA, 2014 ). For detailed findings on individual contaminants receivin g a final regulatory determination under RD 3 at this time , and a summary of EPA’s regulatory determination for each contaminant, see
C hapters 3, 4 and 5 of this document.
The outline of this chapter mirrors the organization of the contaminant- specific chapters that follow. Section 2.1 identifies the sources used to evaluate contaminant background information and chemical and physical properties. Section 2.2 covers sources of contamination and environmental fate. Section 2.3 describes the process of evalua ting health effects information, the use of carcinogenic and non- carcinogenic health effects data for the derivation of a health reference level ( HRL ), and the sources of information used for health effects evaluations. Section 2.4 describes the primary an d supplemental sources of ambient and drinking

water occurrence information used to evaluate contaminant occurrence and exposure. Section 2.5 describes the process used to evaluate analytical methods and treatment technologies.



### 2.1 Evaluation of Contaminant Background, Chemical, and Physical Properties

EPA consulted a number of standard sources to evaluate contaminant background and properties. These sources include the U.S. National Library of Medicine ’s (USNLM) Hazardous Substances Data Bank (HSDB)

, Toxici ty Profiles from the U.S. Agency for Toxic Substances and Disease Registry (ATSDR) , USNLM’s ChemIDplus website, reports about pesticides prepared by EPA’s Office of Pesticide Programs (OPP), chemical

- specific parameters from the Department of Energy’s (DOE ) Risk Assessment Information System (RAIS) , and standard chemistry reference books . To fill some information gaps , primary literature was consulted as well , with preference give to peer -reviewed sources.



### 2.2 Evaluation of Contamination Sources and Environmental Fate

Information about non-anthropogenic sources of contamination and the environmental fate of contaminants was assembled from the range of secondary sources and primary literature described in Section 2.1. When possible, environmental fate write -ups include estimates of partitioning and half-lives in various media from EPA’s Persistence, Bioaccumulation, and Toxicity ( PBT ) Profiler . Descriptions of special topics of concern such as formation through chemical reactions in environmental media and formation as disinfection byproducts (DBP) in water were prepared by consulting the primary peer

- reviewed literature and reports by government agencies and other authoritative organizations.

Q uantitative data on anthropogenic sources, including data on production, use, and industrial releases, comes from specific primary sources and data compilations. The most important of these are profiled in the following paragraphs.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 2, Evaluation of Data

2-10 Chemical Update System (CUS) – Inventory Update Reporting (IUR) Program
The Toxic Substances Control Act (TSCA) requires EPA to compile, keep current, and publish a Chemical Substance Inventory , a list of chemical substance s that are manufactured or processed in the United States. Following the promulgation of the 1986 Inventory Update Reporting (IUR) rule, chemical manufacturers (including importers) were required to report to EPA every four years the identity of and basic manufacturing information for organic chemical substances manufactured (including imported) in quantities of 10,000 pounds or more annually

at individual sites. Modifications of the IUR rule in 2003 and 2005 expanded the range of chemicals and plant sites reporting, expanded the type of data reported, raised the production volume threshold tha t tr iggers reporting from 10,000 pounds to 25,000 pounds, and made certain further adjustments. In 2011 the Agency issued the Chemical Data Reporting (CDR) Rule , which replaced the IUR Rule and established a somewhat modified program (USEPA, 2012a ).
Data on production volumes submitted under IUR are housed in the Chemical Update System (CUS). EPA makes certain non -confidential information available to the public. This includes aggregated national total annual production volumes for chemicals based on reports
fi led every four years from 1986 to 2006. As a result of the changes in minimum thresholds and other program modifications, the results from 2006 might not be directly comparable to results from earlier years. The first reporting year under the new CDR Rule is 2012; these data were not available at the time of writing

. In making total annual national production volumes for chemicals from 1986 through 2006 available to the public, the agency assigned production volumes to bins. E ight production and importation volume ranges were used . The ranges used for 2006 data differ slightly from those used for 1986-2002 data

. Exhibit 2-1 shows the productio n volume categories used for 1986-2002 data and for 2006 data. If no reports were filed for a chemical in a particular year, the chemical is flagged as having “no reports.”

Exhibit 2-1 : Chemical Volume Rang es Used in CUS

- IUR Reporting of National Production Volumes

1986

- 2002 2006 10,000 pounds

- 500,000 pounds <500,000 pounds
>500,000

- 1 million pounds 500,000 to <1 million pounds

>1 million

- 10 million pounds 1 million to <10 million pounds

>10 million

- 50 million pounds 10 million to <50 million pounds

>50 million

- 100 million pounds 50 million to <100 million pounds

>100 million

- 500 million pounds 100 million to <500 million pounds

> 500 million

- 1 billion pounds 500 million to <1 billion pounds Over 1 billion pounds 1 billion pounds or greater Sources: USEPA, 2008 a ; USEPA, 2012 b.

Several factors should be considered when interpreting production ranges assigned to chemicals. Site -specific production volumes less than 10,000 pounds (25,000 pounds in 2006) were not reported and thus are not included in the totals. Production volume ranges for 2006 are similar but not identical to production volume ranges for earlier reporting years. Other program changes, noted in previous paragraphs, affected reporting in 2006. Furthermore, the data provideOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 2, Evaluation of Data

2-11 a snapshot of production (including importation) every four years, and do not capture fluctuation from year to year.
Toxics Release Inventory (TRI)

EPA established the Toxics Release Inv entory (TRI) in 1987 in response to Section 313 of the Emergency Planning and Community Right- to

- Know Act (EPCRA). EPCRA section 313 requires facilities to report to both EPA and the states annual information on toxic chemical releases from facilities that meet reporting criteria. EPCRA section 313 also requires EPA to make this information available to the public through a computer database. The database is accessible through EPA’s TRI Explorer. In 1990 Congress passed the Pollution Prevention Act, which required that additional data on waste management and source reduction activities be reported under TRI. The TRI database details not only the types and quantities of toxic chemicals released to the air, water, and land by facilities, but also provides information on the quantities of chemicals sent to other facilities for further management (USEPA, 2002a; USEPA, 2003a ).
Facilities are required to report releases and other waste management activities related to TRI chemicals if they manufacture, process, or otherwise use more than established threshold quantities of these chemicals. Currently, for most chemicals the thresholds are 25,000 pounds for manufacturing and processing and 10,000 pounds for use. Both the number and type of facilities required to report has increased over time so that in 2002 over 24,000 industrial and Federal facilities submitted in excess of 93,000 reports on toxic releases. In 2000, special thresholds were added for persistent bioaccumulative toxic chemicals, for example dioxin and dioxin- like compounds (USEPA, 2002a ). Today, TRI includes information on releases of nearly 670 chemicals.
Although TRI can provide a general idea of release trends, it is far from exhaustive and has limitations. For example, small facilities (those with f ewer than 10 full- time employees and those that do not exceed certain manufacture and use limits) are not required to report releases. In addition, the reporting threshold for the manufacturing and processing of TRI chemicals changed between 1987 and 1989, dropping from 75,000 pounds per year in 1987 to 50,000 in 1988 to the current 25,000 in 1989; this creates the potential for misleading data trends over time (USEPA, 1996a ). Finally, TRI data are meant to reflect “ releases ” and should not be used to estim ate general public exposure to a chemical (USEPA, 2002a ).
Pesticide Usage Estimates from EPA ’s Office of Pesticide Programs (OPP) Reregistration
Documents

OPP sometimes presents estimations of annual U.S. usage of individual pesticides in its pesticide reregistration documents (e.g., Reregistration Eligibility Decisions (REDs), Interim Reregistration Eligibility Decisions (IREDs), Tolerance Reassessment Progress and Risk Management Decisions (TREDs). Many details of pesticide production and use are considered confidential business information and are not publically released. OPP relies on an Automated Quantitative Usage Analysis (AQUA) program to automatically extract info rmation about individual pesticides from relevant agency databases and calculate estimated total annual usage, among other figures (e.g., estimates of application rate, number of applications, and amount of crops treated). The estimate of total usage repre sents an approximate maximum annual value: “The likely maximum is calculated using statistical procedures that set a usage level below which actual usage is expected to fall 95% of the time” (USEPA, 2000a ). The values generated by AQUA are reviewed, modified as necessary based on additional information not contained in the electronic databases, and validated by comparison to other sources within and outside theOW

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2

- 12 agency . The AQUA methodology has been revised and refined over time since it was introduced in 19 93 (USEPA, 2000 a ).
EPA Pesticide Industry Sales and Usage Report

EPA’s OPP periodically issues Pesticides Industry Sales and Usage reports. The reports provide contemporary and historical information on U.S. pesticide production, imports, exports, usage, and sales, particularly with respect to dollar values and quantities of active ingredient. The most recent report presents data from the years 2000 and 2001 (USEPA, 2004).
The data presented in EPA’s Pesticid e Industry Sales and Usage reports represent “the best available information from the public domain and proprietary sources” (USEPA, 2004). Publicly available data come from OPP’s Pesticide Data Center, and from a variety of other sources, including nation al data from the United States Department of Agriculture (USDA). Proprietary data sources include widely used commercial data compilations produced by “well

known organizations” (USEPA, 2004).
Certain considerations apply when using or interpreting data pr esented in the Pesticide Industry Sales and Usage reports. OPP cautions that “ t he numbers in the report represent approximate values rather than precise values with known statistical properties ” (USEPA, 2004). In addition, OPP notes: “We caution the reader not to infer too much from changes in the amount of pesticides used from year to year. Changes in the amount of pesticides used are not necessarily correlated to changes in the level of pest control or changes in the human health or environmental risks as sociated with pesticide use” (USEPA, 2004).
National Center for Food and Agricultural Policy (NCFAP) Pesticide Use Database
The National Center for Food and Agricultural Policy (NCFAP), a private non

- profit institution, has assembled a national Pesticide U se Database. NCFAP annual pesticide use estimates for circa 1992 and circa 1997 are based on s tate

- level commercial agriculture usage patterns for the periods 1990

- 1993 and 1995

- 1998, and s tate

- level crop acreage for 1992 and 1997. The database contains es timates of pounds applied and acres treated in each state for 220 active ingredients and 87 crops. The majority of the chemicals monitored are herbicides, but the database also follows significant numbers of fungicides and insecticides (NCFAP, 2000).

The N CFAP data are estimates and have several limitations. First, the database only includes applications of pesticides to cropland (foliar, soil, and in furrow applications). Non

cropland applications, such as uses for homes, greenhouses, livestock, ornamental s, or golf

courses are not included. The database does not include non

- bearing orchards or vineyards, or governmental Area

- wide Eradication programs. Second, in interpreting the NCFAP database, it should be noted that records are compiled from a wide varie ty of sources. NCFAP states that there is no way to determine the accuracy of any of the estimates in the database, adding that some are based on surveys of farmers, while others are expert opinions from knowledgeable extension service specialists. (As not ed, the details of pesticide manufacture, sales, and use are confidential business information.) When data for particular s tates and crops are unavailable, as they are in many cases, values are assigned on the basis of data from a nearby s tate (NCFAP,
2000 ).
United States Geological Survey (USGS) Pesticide Use Maps

The United States Geological Survey ( USGS , 201 5 ) produce s maps of annual pesticide use for several hundred compounds used in United States crop production. The pesticide use maps show the average annual pesticide use intensity expressed as average weight (in pounds) ofOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 2, Evaluation of Data

2-13 a pesticide applied to each square mile of agricultural land in a county. The USGS maps are created using data from proprietary surveys of farm operations, USDA Census of Agriculture, the County Agricultural Production Survey, and other sources.
USGS used two methods to estimate pesticide usage, since pesticide usage information was not available in some districts. “EPest

- High” estimates were generated by projecting usage estimates for such districts based on usage in neighboring districts. “EPest- Low” estimates were generated by assuming no usage in such districts.
USGS notes that the maps are suitable for making national, regional, and watershed assessments of annual pesticide use , but that reliability of estimates generally decreases with scale (USGS, 2015 ).



### 2.3 Evaluation of Adverse Health Effects

Section 1412(b)(1)(A)(i) of the SDWA requires the EPA to determine whether each contaminant considered for regulatory determination may h ave an adverse effect on public health. This section describes the overall process the agency used to evaluate health effects, hazard and dose-response information, and the approach for deriving the health reference level ( HRL ) for the contaminants under consideration for RD 3 . HRLs are not final determinations about the level of a contaminant in drinking water that is necessary to protect any particular population and are derived prior to the 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. In evaluating contaminants for regulatory determination, Section 1412 (b)(1)(C) of SDWA also 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 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.
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 noncarcinogens and carcinogens evaluated using a non

- linear approach ; both are described in the following sections. If a contaminant has both a cancer HRL and a non- cancer HRL, generally the lower (more conservative) one is used in decision-making. For more information on the calculation and use of HRLs, see C hapter s 3, 4 and 5.

2.3.1 Use of Carcinogenicity Data for the Derivation of a Health Reference Level
Although none of the CCL 3 contaminants with cancer

- based HRLs were ultimately selected for preliminary or final regulatory determination under RD 3, a brief summary of the methodology for carcinogens is included here for completeness.

For those contaminants considered to be “ likely ” or “probable” human carcinogens, EPA evaluate s data on the mode of action of the chemical to determine the appropriate method of low dose extrapolation. When the data do not suggest the use of a n alternate extrapolation method,
EPA uses linear low dose extrapolation to calculate a toxicity value that defines the relationship between dose and response (i.e., cancer slope factor or CSF). Linear low dose extrapolation involves the assumption that every dose, no matter how small, is associated with some risk, and that the risk of adverse effects from a low dose is proportionate with the size of the dose. TheOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 2, Evaluation of Data

2-14 CSF is combined with an adult body weight of 70 kg and the 90 th percentile adult drinking water intake of 2 L/day to calculate the unit risk

, the estimated upper- bound excess lifetime cancer risk from a continuous exposure to a chemical at a concentration of 0.001 mg/L in drinking water.

Unit Risk (μg/L) -1 = CSF x [( DWI x CW)/BW]

where:

CSF = 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 for an adult, assumed to be 70 kilograms (kg)

The cancer HRL is the concentration of a contaminant in drinking water corresponding to an

excess estimated lifetime cancer risk of one

- in -a- million (1x 10 -6 ), calculated as follows:

HRL (μg/L) = Risk Level of 10

- 6 ÷ Unit Risk (μg/L) -1

If the chemical has a mutagenic mode of action , the U.S. EPA’s 2005 Guidelines for Carcinogen Risk Assessment (USEPA, 2005a ) requires that the potential increased cancer risk due to early -life exposure be taken into account. When chemical -specific data to quantify the increased risk are lacking, Age Dependent Adjustment Factors (ADAFs) are applied , in conjunction with age- specific drinking water intake values from the U.S. EPA’s Exposure Factors Handbook (USEPA, 2011) to estimate age -adjusted unit risks.
The critical endpoints for each of the four cont aminants receiving a final regulatory determination under RD 3 at this time were non -carcinogenic, so none of the four were evaluated using a cancer

- based HRL. Cancer

- based HRLs were used to evaluate numerous CCL 3 contaminants as part of the RD 3 process, as described in the RD 3 Protocol document (USEPA, 2014).

2.3.2 Use of Non- carcinogenic Health Effects Data for Derivation of an HRL
EPA generally calculates a reference dose (RfD) for those chemicals considered to be

non- carcinogenic, “not likely” to be carcinogenic to humans or a “possible” carcinogen ( Class C

, in EPA’s former cancer classification system ). An RfD is an estimate of a daily oral exposure to the human population (including sensitive populations or lifestages) 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), known 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 Exposure Factors Handbook (USEPA, 2011) may be included in deriving an HRL from the RfD.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 2, Evaluation of Data

2-15 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:

• the variation in sensitivity among the members of the human population (i.e., intraspecies variability);

• the uncertainty in extrapolating animal data to humans (i.e., interspecies variability);

• the 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);

• the uncertainty in extrapolating from a LOAEL rather than from a NOAEL; and/or

• the uncertainty associated with an incomplete database.

For each of the contaminants receiving a final regulatory determination under RD 3 at this time , EPA derived an HRL using the RfD approach as follows:

HRL (mg/L) = [(RfD x BW)/DWI] x RSC

Where:

RfD = Reference Dose (mg/kg

- day)

BW = Body Weight for an adult, assumed to be 70 kilograms (kg); for a child, assumed to be 10 kg

DWI = Drinking Water Intake for an adult, assumed to be 2 L/day (90th percentile); for child, assumed to be 1L/day (90 th percentile)

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 most conservative RSC used in the derivation of a maximum contaminant level goal ( MCLG ) for drinking water.

Further informatio n about these contaminants can be found in Chapters 3, 4 and 5

. 2.3.3 Sources of Data/Information for Health Effects

EPA use s the best available peer

- reviewed data and analyses in evaluating adverse health effects. Peer

- reviewed health

- risk assessments for CCL 3 chemicals considered for regulatory determinations are available from the agency’s Integrated Risk Information System (IRIS) Program, the agency’s OPP , the National Academy of Sciences (NAS), the ATSDR, and the World Health Organization (WHO). For a non-EPA health assessment (i.e., NAS, ATSDR, WHO) to be considered for regulatory determinations, the health assessment must use comparable methods, standards, and guidelines to an EPA health assessment. (See the RD 3 Protocol document (USEPA, 2014) for more detailed information on sources consulted.)OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 2, Evaluation of Data

2-16 Exhibit 2-2 summarizes the sources of the health assessment data for each chemical receiving a final regulatory determination under RD 3 at this time

. One of the contaminants receiving a regulatory determination had p eer

- reviewed health effects assessments available from
EPA ’s own IRIS Program

. 1 The remaining three had peer

- reviewed health effects assessments available from EPA OPP ’s RED s. 2

Exhibit 2-2: Sources and Dates of Health Effects Assessments

Chemical IRIS Date OPP RED Date

Dimethoate

--- --- X 2007 1,3

- Dinitrobenzene 1 X 1988

--- --- Terbufos

--- --- X 2006 Terbufos Sulfone 2

--- --- X 2006

1 The agency also reviewed a non

- EPA source (ATSDR, 1995) for 1,3

- dinitrobenzene

to corroborate the IRIS assessment.

2 The OPP RED for the parent compound (terbufos) was used.

The agency perform s a literature search for studies published after the available health effects assessment s to determine if new information suggests a different outcome. The agency collect s and evaluate s 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 indicated that a change to the existing RfD or cancer assessment was needed, an upda ted Office of Water ( OW )

assessment is prepared and independently peer- reviewed

. All quantitative cancer assessments conducted under the Guidelines for Carcinogen Risk Assessment (USEPA, 1986) were updated using the Guidelines for Carcinogen Risk Assessment (USEPA, 2005a), the Supplemental Guidance for Assessing Susceptibility from Early-life Exposures to Carcinogens (USEPA, 2005b), and the Exposure Factors Handbook (USEPA, 2011). These guidelines include new considerations for contaminants with a mutagenic mode of action and potential risks due to early childhood exposure.



### 2.4 Evaluation of Contaminant Occurrence and Exposure

2.4.1 General Considerations
Detection and reporting thresholds
Several types of concentration thresholds are important in the study of chemic al contaminants in drinking water. This section clarifies some of the terminology used in this report.

1 IRIS is an electronic EPA data base ( www.epa.gov/iris/index.html ) containing peer

- reviewed information on human health effects that may result from exposure to various chemicals in the environment. These chemical files contain descriptive and quantitative information on hazard identification and dose response, RfDs for chronic noncarcinogenic health effects, and slope factors and unit risks for carcinogenic effects.

2 OPP is required under the Federal Insecticide Fungicide and Rodenticide Act (FIFRA) to review all pesticides registered prior to 1984 and determine whether to reregister them for continued use. The results of the reregistration analysis are included in the REDs. Copies of the REDs are located at the following Web site: http://www. epa.gov/oppsrrd1/reregistration/status.htm

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2-17 Typically, an analytical method allows for low- level detection of a chemical in water at concentrations that cannot be quantified with accuracy. Thus th ere is a distinction between the detection limit (the threshold at or above which the presence or absence of a compound can be distinguished with a specified degree of confidence) and the quantitation level (a somewhat higher threshold, at or above which the concentration of a compound can be measured with a specified degree of precision and/or accuracy). Both of these thresholds can vary from method to method, contaminant to contaminant, laboratory to laboratory, and even from technician to technician, based on method limitations, chemical properties, technician skill, and the quality of analytical instrumentation. Published analytical methods specify the standards of precision and accuracy that define accep table laboratory performance, and often estimate “normal” or expected detection limits. In practice, the limits vary.

The reporting level is the threshold at or above which a contaminant’s presence or concentration is officially quantitated. Reporting levels may be established by the laboratory or by those who design and carry out a study. The requirements for precision and accuracy that are included in a published analytical method help to dictate where laboratories establish a reporting level for a partic ular analyte.
In the absence of an otherwise established reporting level, laboratories generally report results as low as can be reliably measured, i.e., at the quantitation level. Sometimes the terms “quantitation level” and “reporting level” are used int erchangeably in the laboratory context.

In a well

- designed occurrence study, the investigator will establish a reporting level in advance of data collection, based on analytical method(s) chosen, laboratory capabilities, and other considerations. Setting a reporting level is a balancing act: A reporting level set too high will result in the under -reporting of contaminants that are present, while a reporting level set too low may run into data quality problems

-- e.g., some of the participating laboratories m ay be unable to reliably quantify results at the low threshold. In the case of many of EPA’s nation- wide drinking water studies, the selected reporting level is known officially as the Minimum Reporting Level (MRL). The MRL for each contaminant in each stu dy is set at a level that EPA believes can be achieved with specified confidence by a broad spectrum of certified laboratories across the nation.
In some cases, an investigator may establish a “common reporting level,” a high, uniform reporting threshold f or multiple contaminants that facilitates inter -contaminant comparison. A common reporting level may be applied retrospectively. Some studies report results at low contaminant-specific thresholds and also at a high common reporting level. Longitudinal stud ies and data compilations sometimes select a high retrospective reporting level to facilitate comparison of results from older data collection efforts with results from newer efforts that employed more advanced analytical techniques with lower quantitation limits.
Knowing the reporting level(s) associated with a study or data set can help with interpretation of the results. For instance, k nowing that the reporting level is lower than a health

based threshold provides assurance that all exceedances of the th reshold were captured in the study results. Also, knowledge of reporting levels can help a reader to determine whether data from two studies are directly comparable. Compilations of data from multiple sources must be interpreted with caution if reporting l evels are not documented, as they may have varied widely.
To facilitate interpretation of occurrence results in the contaminant

- specific chapters that follow, reporting levels are provided whenever they are available. In many cases reporting levels

are no t known, and this too is documented. In some cases, the lowest reported concentrationOW

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- 18 values can give a rough idea of what the reporting threshold(s) might have been. ( Generally , the reporting level could not have been higher than the lowest reported conce ntration. If a sufficiently large number of detections are reported, the lowest reported concentration is probably a good approximation of the reporting level. )

In occurrence studies, the word detection is frequently used as shorthand for a sampling result that exceeds a given reporting level, and non

- detection for a result that does not exceed the reporting level. Thus

, even a sample that exhibits measurements that exceed the laboratory detection limit could, in the context of a particular study or data co mpilation, be considered a

non

- detection.
Rounding

In reporting quantitative occurrence findings, EPA is sensitive to the issue of precision (i.e., the desirability of presenting numbers with the right number of significant digits , if it can be determined )

, and the challenge of presenting findings in a uniform format

. EPA draws data from a wide variety of sources, some of which are better

- documented than others

, and calculate s other values internally . EPA follow s the following guidelines in this support doc ument

. When presenting results obtained from published studies or other sources , EPA reports the numbers exactly as given in the source, or retains the level of precision given in the source. ( A ll water concentration values are converted to micrograms per liter.)
When calculating new values, EPA follows different procedures for percentages and concentration values. With limited exceptions, c alculated percentages are presented to two decimal places. Calculated concentration values (e.g., median and 99 th

- perc entile concentrations)

are rounded, if necessary, to have the same number of decimal places as the (actual , reported ) minimum and maximum values, or whichever of the two has more decimal places

. 2.4.2 Occurrence in Ambient Water

Th is section describ e s the most i mportant sources EPA consulted to evaluate the occurrence of CCL 3 contaminants in U.S. ambient water (e.g., aquifers, rivers, lakes)

. USGS National Water Quality Assessment (NAWQA)

– Ambient Water Analysis
The USGS instituted the National Water Quality A ssessment (NAWQA) program in 1991 to examine ambient water quality status and trends in the United States. The NAWQA program is designed to apply nationally consistent methods to provide a consistent basis for comparisons among study basins across the coun try and over time. These occurrence assessments serve to facilitate interpretation of natural and anthropogenic factors affecting national water quality. For more detailed information on the NAWQA program design and implementation, please refer to Leahy an d Thompson (1994)

, Hamilton et al. (2004) , and NRC (2002)

. The NAWQA program conducts monitoring and water quality assessments in significant watersheds and aquifers referred to as “study units.” The program ’ s sampling approach is not “statistically” desig ned (i.e., it does not involve random site selection ), but it provides a representative view of the nation ’ s waters in its coverage and scope. Together, the 51 study units monitored between 1991 and 2001 include the aquifers and watersheds that supply more than 60% of the nation ’ s drinking water and water used for agriculture and industry. The NAWQA program monitors the occurrence of chemicals such as pesticides, nutrients, volatile organic compounds ( VOCs ) , trace elements, and radionuclides, and the condition of aquatic habitats andOW

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- 19 fish, insects, and algal communities (NRC, 2002; Hamilton et al. , 2004). NAWQA has collected data from over 6,400 surface water and 7,000 ground water sampling points. (The NAWQ A Data Warehouse can be reached via a link from the following W eb site: http://water.usgs.gov/nawqa/data.html ).
Monitoring of study units occurs in stages. Between 1991 and 2001, approximately one

third of the study units at a time were studied intensively for a period of three to five years, alternating with a period of less intensive research and monitoring that lasted between five and

seven years. Thus, all participating study units rotated through in tensive assessment in a ten

- year cycle (Leahy and Thompson, 1994). The first ten

- year cycle was designated Cycle 1. Summary reports are available for the 51 study units that underwent intensive monitoring in Cycle 1 (USGS, 2001). Cycle 2 monitoring , 2002 t o 2012, proceed ed with 42 study units (Hamilton et al. , 2004). Other adjustments were made during the course of Cycle 2. Partial analyses of Cycle 2 data are available.
EPA Analysis of NAWQA Cycle 1 Monitoring Results
Whereas the NAWQA program often uses the most representative data for particular site s to calculate summary statistics for particular interpretive reports , EPA, with the cooperation of USGS, has performed a summary analysis of all Cycle 1 water monitoring data from all study units (1991

- 2001) for many CCL 3 contaminants

. The surface water data consist of stream samples; all surface water data were included in the EPA summary analysis. For ground water, all well data were used; as with the USGS National Pes ticide Synthesis Project , data from springs and artificial drains were excluded. For each contaminant, EPA calculated detection frequencies simply as the percentage of samples and the percentage of sites with at least one detection. (A detection is an anal ytical result equal to or greater than the reporting limit.) EPA used USGS data without any censoring or weighting. From samples with detect ion s a number of descriptive statistics were also calculated, including the minimum, median, 90 th percentile, 99 th percentile, and maximum concentrations. In addition to summarizing the number of samples/sites with detections, the number and percentage of sites with detections greater than the HRL and the 1⁄2 HRL was also included. Note that reporting limits for some co ntaminants varied over time during the NAWQA program. Because reporting limits varied, the minimum concentration reported as a detection can sometimes be lower than the highest reporting limit.
USGS issues many special reports that are summarized for indiv idual contaminant discussions. There can be some overlap in data used in USGS reports. USGS may use only selected data for some reports (i.e., related to specific land use), whereas EPA used all data for a national overview of ambient occurrence. Selected special USGS programs are noted in following paragraphs

. USGS Analysis: National Synthesis Assessments
Through a series of National Synthesis efforts, the USGS NAWQA program is preparing comprehensive analyses of data on topics of particular concern. These National Synthesis

assessments aggregate NAWQA contaminant occurrence and water quality parameter data from individual study units and other sources to provide a national overview.OW

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- 20 Pesticide National Synthesis Pro ject
The NAWQA Pesticide National Synthes is Project is a national

- scale assessment of the occurrence and behavior of pesticides in streams and ground water of the United States and the potential for pesticides to adversely affect drinking

- water supplies or aquatic ecosystems.

Results from the mos t recent Pesticide National Synthesis analysis, based on complete Cycle 1 (1992

- 2001) data from NAWQA study units, are posted on the NAWQA Pesticide National Synthesis Web site (Gilliom et al. , 2007). Data for surface water and ground water are presented s eparately, and results in each category are subdivided by land use category. Land use categories include agricultural, urban, mixed (deeper aquifers of regional extent in the case of ground water), and undeveloped. The Pesticide National Synthesis analysis is a first step toward the USGS goals of describing the occurrence of pesticides in relation to different land use and land management patterns, and developing a deeper understanding of the relationship between spatial occurrence of contaminants and their fate, transport, persistence, and mobility characteristics.
The surface water summary data presented in the Pesticide National Synthesis (Gilliom et al. , 2007) only includes stream data. Sampling data from a single one

- year period, generally the year with the most complete data, were used to represent each stream site. Sites with few data or significant gaps were excluded from the analysis. NAWQA stream sites were sampled repeatedly throughout the year to capture and characterize seasonal and hydrologic va riability.
Ground water data reported in the Pesticide National Synthesis only include samples from wells; data from springs and agricultural tile drains were not included. In the National Synthesis analysis (Gilliom et al. , 2007), USGS uses a single samp le to represent each well, generally the earliest sample with complete data for the full suite of analytes.
Over the course of Cycle 1 (1992

- 2001), some NAWQA analytical methods were improved or changed. Hence, detection thresholds varied over time for som e compounds ( Gilliom et al. , 2007).
VOC National Synthesis : Ran dom and Focused VOC Surveys
The VOC National Synthesis began in 1994. The most comprehensive VOC National Synthesis reports to date are one random survey and one focused survey funded cooperat ively by the American Water Works Association Research Foundation ( AwwaRF ) and carried out by USGS in collaboration with the Metropolitan Water District of Southern California and the Oregon Health & Science University. The random survey (Grady, 2003) targ eted surface and ground waters used as source water by community water systems ( CWSs )

. Samples were taken from the source waters of 954 CWSs in 1999 and 2000. The random survey was designed to be nationally representative of CWS source water. In the focused survey (Delzer and Ivahnenko, 2003), 451 samples were taken from source waters serving 134 CWSs between 1999 and 2001. These surface and ground waters were chosen because they were suspected or known to contain Methly Tertiary Butyl Ether ( MTBE )

. T he focused survey was designed to provide insight into temporal variability and anthropogenic factors associated with VOC occurrence. Details of the monitoring plan for these two studies, including detection limits, are provided by Ivahnenko et al. (2001). Separately, AwwaRF also published the results of this monitoring effort (AwwaRF, 2003).OW

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- 21 VOC National Synthesis : Compilation of Historical VOC Monitoring Data
Additional products of the VOC National Synthesis include a compilation of historical VOC monitor ing data from multiple studies (Squillace et al. , 1999). The data, collected from 2,948 wells between 1985 and 1995 by local, state, and federal agencies, were reviewed to ensure they met data quality criteria. Most of the data were from early study unit m onitoring. The samples represent both urban and rural areas, and both drinking water and non

- drinking water wells. A full analysis of 10 years of study unit monitoring data has not yet been performed by the VOC National Synthesis.
Storage and Retrieval (ST ORET) Data Warehouse

EPA’s Storage and Retrieval ( STORET ) Data Warehouse is a collaborative database that contains raw biological, chemical, and physical data from surface and ground water sampling conducted by federal, state and local agencies, Indian t ri bes, volunteer groups, academics, and others. A wide variety of data relating to water quality from all 50 states as well as multiple territories and jurisdictions of the United States are represented in this data system . These are primarily ambient water data, but in some cases they are finished drinking water data

. Users began populating the STORET Data Warehouse in 1999. Most data are post

- 1999, but some earlier sampling is included.
STORET data have quality limitations. T he extent of national coverage a nd data completeness varies from parameter to parameter. Some (though not all) sample results are accompanied by information on sample location (latitude, longitude, state, county, Hydrologic Unit Code and a brief site identification), sample date, the med ium sampled (e.g., water, sediment, fish tissue), and the name of the organization that sponsored the monitoring. In addition, there can be information on why the data were gathered; sampling and analytical methods used; the laboratory used to analyze the samples; the quality control checks used when sampling, handling the samples, and analyzing the data; and the personnel responsible for the data. T here are few restrictions on submission of data based on analytical methods, quality assurance ( QA ) practices , etc. For more general STORET data information, please refer to: http://www.epa.gov/storet/index.html

. EPA reviewed STORET g round water data from wells and surface water data from lakes, rivers/streams, and reservoirs (USEPA, 2012 c )

. The STORET Data Warehouse also included Public Water System (PWS) data from three states ( Indiana, Missouri, and Ohio) ; EPA reviewed these as well (USEPA, 2012 c )

. 2.4.3 Occurrence in Drinking Water

– Primary Data Sources
The majo r or primary sources of the drinking water occurrence data used to support the RD 3 process , including selection and evaluation of RD 3 contaminants, were the following:

• the First Unregulated Contaminant Monitoring Regulation (UCMR 1 )

• the Second Unregulated Contaminant Monitoring Regulation (UCMR 2 )

• Rounds 1 and 2 of the Unregulated Contaminant Monitoring (UCM) program

• the Disinfection Byproducts Information Collection Rule ( DBP ICR)

• the National Inorganic s and Radionuclide s Survey (NIRS)

All five of these sources are national assessments that were administered or overseen by
EPA. UCMR 1, UCMR 2, and NIRS are designed to be statistically representative of nation alOW – OGW DW Re gulatory Determination 3 Support Document

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2-22 contaminant occurrence in public drinking water systems. (NIRS, which does not in clude surface water systems

, is designed to be statistically representative of national contaminant occurrence in ground water systems

. ) The UCM program and the DBP ICR are national in scope but we re not designed to be statistically representative of natio n al contaminant occurrence (see further discussion in the sub-sections of the report that follow). In the case of UCM, the agency has developed a peer

- reviewed cross

- section

- based approach to elicit national estimates from the data.

S everal CCL 3 contamina nts are currently being monitored under the third Unregulated Contaminant Monitoring Rule ( UCMR 3 ) (77 FR 26072 ; USEPA, 2012d). With d ata becoming available after 2015, UCMR 3 could support future rounds of Contaminant Candidate List ( CCL ) regulatory determinations and off

- cycle decision -making.

Exhibit 2-3 indicates which RD 3 contaminants have data from which of the primary sources. Note that none o f the four cont aminants receiving a final regulatory determination under
RD 3 at this time have data from UCMR 1 Assessment Monitoring, UCMR 2 Screening Survey, UCM Rounds 1 or 2 , DBP ICR , or NIRS. Data from these sources were used to evaluate CCL 3 contaminants as part of the RD 3 development process, as described in the RD 3 Protocol document (USEPA, 2014). The full list of primary occurrence data sources that were important for the development of RD 3 are included here for completeness.

Exhibit 2-3: Primary Sources of Drinking Water Occurrence Data Used to Evaluate RD 3 Contaminants Receiving a Final Regulatory Determination at T his Time

. UCMR 1 1 UCMR 2 1 UCM 1..

ContaminantList 1AssessmentMonitoringList 2ScreeningSurveyList 1AssessmentMonitoringList 2ScreeningSurveyRound 1CrossSectionRound 2CrossSectionDBP ICR1NIRS1

Dimethoate X
1,3

- Dinitrobenzene X

Terbufos X

Terbufos sulfone X

1 Data from UCM R 1 Assessment Monitoring, UCMR 2 Screening Survey, UCM , DBP ICR , and NIRS were used to assess CCL 3 contaminant occurrence in the RD 3 development process, but none of the contaminants receiving a final regulatory determination under RD 3 at this time have data from these sources

. They are covered in this chapter for completeness. See the RD 3 Protocol document (USEPA, 201 4 ) for detaile d information on the RD 3 development
process.

B asic occurrence values calculated for contaminants from primary data sources as part of the RD 3 process include direct counts of the number and percent of systems, and population served by systems, with at least one analytical detection above a given concentration threshold. EPA considered this to be a straightforward and accurate way to present these data for the regulatory determination process.
Where the data from the primary sources permit, national extrapolations are made to estimate the number of systems and the population in various size and source categories exposed to a given level of contamination. The extrapolations are made using figures from the 4 th editionOW

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- 23 of the Baseline Handbook (USEPA, 2003 b ) or other authoritative sources on national PWS characteristics and populations served (including census figures from primary occurrence sources themselves)

. The analytical approach that is used to evaluate the contaminant occurrence data was previously developed for other EPA Office of Ground Water and Drinking Water (OGWDW) national occurrence studies, including the first Six

- Year Review of National Primary Drinking Water Regulations (USEPA, 2003 c ), UCMR 1 (USEPA, 2008b ), and previous rounds of the

regu latory determination process (USEPA, 2002 b ; USEPA, 2008c )

. In each case, the data analysis process and presentation have been peer

- reviewed and subject to public and stakeholder review and comment.
Robust data from the UCMR program can support a more invol ved statistical analysis (Stage 2 analysis) to assess and estimate the annual mean concentrations at systems, for comparisons with HRLs. Th e Stage 2 approach , also peer

- reviewed

, is presented in the reports Occurrence Estimation Methodology and Occurrence Findings for Six

- Year Review of National Primary Drinking Water Regulations (USEPA, 2003 c ) and The Analysis of Regulated Contaminant Occurrence Data from Public Water Systems in Support of the Second Six

- Year Review of National Primary Drinking Water Regul ations (USEPA, 200 9 b )

. This advanced occurrence analysis was not deemed necessary for the four RD 3 contaminants with UCMR 1 and/or UCMR 2 data, since all four are receiving final negative determinations.

The following sections provide a brief summary of primary data sources and the approach used to estimate contaminant occurrence in each case

. References are provided to other reports that present additional detail. R eaders are referred to later chapters of this document and

to companion support documents for contaminant

- specific results . In the case of UCMR 1, UCM, and NIRS, readers are referred to support documents from earlier CCL and Regulatory Determination efforts for study details.
First Unregulated Contaminant Monitoring Regulation (UCMR 1)

In 1999, EPA developed the UCMR program in coordination with the CCL and the National Drinking Water Contaminant Occurrence Database (NCOD) to provide national occurrence information on unregulated contaminants (64 FR 50556 ; USEPA, 1999 a ; 65 FR
11372 ; USEPA, 2000 b ; 66 FR 2273 ; USEPA, 2001 a ). The UCMR is currently EPA’s primary authority for collecting monitoring data on the occurrence of unregulated contaminants in PWSs

. UCMR 1 data were available for one RD 3 contaminant , namely terbufos.
EPA designed the UC MR 1 data collection with three parts (or tiers) for monitoring

, primarily based on the availability of analytical methods and related analytical laboratory capability

. C ontaminants for which well

- established lab oratory methods were available were scheduled to undergo full UCMR 1 List 1 Assessment Monitoring. C ontaminants whose laboratory methods were newly developed and less widely available were placed on List 2; these were scheduled for a “Screening Survey” at a smaller group of systems. The purpose of the Screening Survey wa s to develop a preliminary assessment of national occurrence for contaminants of concern that may be difficult to monitor at the larger scale of Assessment Monitoring

. List 3 monitoring (“Pr e

- Screen Testing”) was intended to address contaminants with analytical methods that are in an early stage of development ; the analyses would be limited to a few special laboratories. The expectation was that Pre

- Screen Testing would only involve a limited number of systems determined to be most vulnerable to the targeted contaminants. EPAOW

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- 24 did not implement Pre

- Screen Testing under UCMR 1 due to the lack of suitable candidate methods

. EPA required all large 3 PWSs, plus a statistically representative nationa l sample of 800 small 4 PWSs

, to conduct Assessment Monitoring of List 1 contaminants

. 5 Approximately one

third of the participating small systems were scheduled to monitor for the List 1 contaminants during each calendar year from 2001 through 2003. Large systems could conduct one year of monitoring anytime during the 2001

- 2003 UCMR 1 period. EPA specified a quarterly monitoring schedule for surface water systems and a twice per year, six

- month

- interval monitoring schedule for ground water systems. Mo nitoring wa s scheduled so that one sampling

event occurred during the most vulnerable season for the water system. 6 The objective of the

peer

- reviewed UCMR 1 sampling approach for small systems was to collect contaminant occurrence data from a statistical ly selected, nationally representative sample of small systems. The small system sample was stratified and population

- weighted, and included some other sampling adjustments such as ensuring the selection of at least two systems from each s tate

. With

contam inant monitoring data from all large PWSs and a nationally representative sample of small PWSs, the UCMR 1 List 1 Assessment Monitoring program provides a contaminant occurrence data set suitable for national drinking water estimates.

In total, 372,086 sa mple results have been collected under the UCMR 1 List 1 Assessment Monitoring program at 3,0 90 large systems and 797 small systems. Approximately 33, 8 00 samples were collected for each contaminant. The UCMR 1 List 1 Monitoring program included systems from all 50 s tates , the District of Columbia, four U.S. t erritories , and tribal lands in five EPA Regions.

UCMR 1 Screening Survey sampling for List 2 contaminants was conducted at 300 systems (120 large and 180 small PWSs) statistically selected from the pool of systems required to conduct Assessment Monitoring. While the statistical design of the UCMR 1 Screening Survey provided national data, the small number of systems sampled left concerns about the relative uncertainty of the findings. For the RD 3 p rocess , supplemental data were identified and compiled to augment the UCMR 1 Screening Survey data. Terbufos was a UCMR 1 Screening Survey analyte

. A total of 29,765 sample results have been collected under the UC MR 1 List 2 Screening Survey from the participating large and small systems. Approximately 2, 300 samples were collected for each contaminant. The UCMR 1 List 2 Screening Survey included systems from 48

s tates , two U.S. t erritories , and t ribal lands in one EPA Region.

See USEPA (2001 b ) and USEPA ( 2008b ) for more information on UCMR 1 study design and data analysis.

3 Systems serving more than 10,000 people.

4 Systems serving 10,000 people or fewer.

5 Large and small systems that purchase 100% of their water supply were not required to participate in the
UCMR 1 Assessment Mo nitoring or the UCMR 1 Screening Survey.

6 The most vulnerable season is the season of greatest likelihood of contaminant occurrence, generally in the months of late spring and early summer, which are characterized by high volumes of surface water runoff a nd ground water recharge.OW

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- 25 EPA analyzed the UCMR 1 List 1 Assessment Monitoring and List 2 Screening Survey data to generate the following occurrence and exposure summary statistics for CCL 3 contaminants :

• the total number of systems and the total population served by these systems,

• the number and percentage of systems with detections, the 90 th and 99 th percentile concentration s from samples with detections, and the minim um, median , and maximum concentration s from samples with detections

,

• the number and percentage of systems with at least one detect ed concentration greater than the 1⁄2 HRL and at least one detect ed concentration greater than the HRL (or in some cases greater than or equal to the MRL ) , and

• the number of people and percentage of the population served by systems with at least one detect ed concentrat ion greater than the 1⁄2 HRL and greater than the HRL (or in some cases greater than or equal to the MRL).

The UCMR 1 summary occurrence statistics are presented in later chapters of this document and in USEPA ( 2008b )

. Note that in some cases, an H RL analysis was not performed because the H RL was low er than the M RL. EPA set the MRL for UCMR 1 contaminants based on the c apability of analytical methods, taking into consideration the relative magnitude of MRLs and health

- based thresholds to the extent possible

. In the case of VOCs, the MRL was determined by multiplying by 10 either the published minimum detection limit or 0 .5 μ g/L, whichever was greater. For other contaminants, the MRL was determined by multiplying by 10 the least sensitive method ’ s minimum detection limit, or, when available, multiplying by 5 the least sensitive method ’ s estimated detection limit (USEPA, 20 00 c ). MRLs were set approximately an order of magnitude higher than detection limits to ensure consistency, accuracy, and reproducibility of results.
Second Unregulated Contaminant Monitoring Regulation (UCMR 2)
UCMR 2 monitoring, designed to provide nationally representative contaminant occurrence data, was conducted from 2008 t hrough 2010. Similar in design to UCMR 1, UCMR 2 require d surface water systems to monitor quarterly and ground water systems to monitor twice

per year. M onitoring is scheduled so that one sampling event is during the most vulnerable season for the water system. As with UCMR 1, t here were multiple tiers of monitoring: Assessment Monitoring for contaminants with commonly used analytical meth od technologies, and Screening Survey monitoring for contaminants that require specialized analytical method technologies not in wide or common use. ( A gain , t here was no Pre

- Screen Testing.)

One difference between the UCMR 1 and UCMR 2 is that the UCMR 2 S creening Survey consists of a larger sample of PWSs , as described in following paragraphs

, and therefore provides monitoring data statistically robust enough to support national contaminant occurrence estimates. See USEPA (2005 c ), USEPA (2007)

, and USEPA ( 201 5 ) for more information on the UCMR 2 program, including study design and data analysis.

For UCMR 2, a ll large PWSs (serving more than 10,000 people), plus a statistically representative national sample of 800 small PWSs (serving 10,000 people or fewer), were required to conduct Assessment Monitoring during a 12

- month period between January 2008 and Decemb er 2010. UCMR 2 List 1 Assessment Monitoring o ccurrence data are available for three
RD 3 contaminants: 1,3

- dinitrobenzene, dimethoate, and terbufos sulfone

.OW

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- 26 For the UCMR 2 Screening Survey, monitoring was required by all PWSs serving more than 100,000 peo ple (approximately 400 PWSs , serving a large pro portion of the national population) , 320 representative PWSs serving 10,001

- 100,000 people, and 480 representative PWSs serving 10,000 people or fewer, during a 12

- month period between January 2008 and Decemb er 2010. With approximately 1,200 systems participating in the Screening Survey, sufficient data were generated to provide a confident national estimate of contaminant occurrence and population exposure. In UCMR 2, the 1,200 PWSs, provided more than 11,000 to 18,000 analyses (depending on the sampling design for the different contaminants). Multiple CCL 3 contaminants have UCMR 2 List 2 Screening Survey o ccurrence data

. The UCMR 2 occurrence analyses used to support RD 3 decision

- making are based on data co llected through June 2011 and released in July 2011

. A relatively small amount of additional data were received and added to the UCMR 2 data set after June 2011. The UCMR 2 data set was not considered “final” until December 2011. T hrough the end of June 2011, data had been received from 99.96% of systems (4,618 out of 4,620) that were expected to submit UCMR 2 data. (The two systems that had not submitted their data by the end of June 2011 were only scheduled to participate in Assessment Monitoring, not t he Screening Survey.)
EPA analyzed the UCMR 2 List 1 Assessment Monitoring and List 2 Screening Survey data to generate the following occurrence and exposure summary statistics for CCL 3 contaminants :

• the total number of systems and the total population s erved by these systems,

• the number and percentage of systems with detections, the 90 th and 99 th percentile concentration s from samples with detections, and the minimum, median, and maximum concentration s from samples with detections,

• the number and percent age of systems with at least one detect ed concentration greater than the 1⁄2 HRL and at least one detect ed concentration greater than the HRL (or in some cases greater than or equal to the MRL ) , and

• the number of people and percentage of the population serv ed by systems with at least one detect ed concentrat ion greater than the 1⁄2 HRL and greater than the HRL (or in some cases greater than or equal to the MRL).

The UCMR 2 summary occurrence statistics used to support RD 3 decision

- making for pertinent contaminants are presented in Chapters 3, 4, and 5 of this document and in Occurrence Data from the Second Unregulated Contaminant Monitoring Regulation (UCMR 2) (USEPA,
201 5 )

. Analysis of the complete set of UCMR 2 occurrence results is fou nd in the UCMR 2 Support Document (USEPA, 201 5 ).
Unregulated Contaminant Monitoring (UCM) Program Rounds 1 and 2
In 1987, EPA initiated the UCM program to fulfill a 1986 SDWA Amendment requirement to monitor for specified unregulated contaminants

. The UCM required PWS s serving more than 500 people to conduct the monitoring. The intent of the monitoring was to gather information on the occurrence of select contaminants in drinking water for future regulatory decision

- making purposes.
EPA implemented the UCM program in two phases or rounds. The first round of UCM monitoring generally extended from 1988 to 1992 and is referred to as UCM Round 1OW

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- 27 monitoring. The second round of UCM monitoring generally extended from 1993 to 1997 and is referred to as UCM Round 2 monitoring.

UCM Round 1 monitoring initially involved 34 required VOCs , 14 VOCs to be monitored at states’ discretion, and two synthetic organic compounds (SOCs). Monitoring for unregulated compounds was to be conducted alongside monitoring for r egulated compounds (52 FR 25720 ; USEPA, 1987). The final database for this round of monitoring included 62 regulated and unregulated contaminants ( USEPA, 2001c ). UCM Round 2 involved monitori ng for 20
VOCs from the earlier required list and 14 VOCs from the earlier discretionary list , plus 13 SOCs and sulfate . The final database for this round of monitoring included 48 unregulated contaminants ( USEPA, 2001 c ). There was no requirement that the monitoring da ta be rep o rted to EPA and individual states maintained the data in different forms and formats. In the context of various initiatives and information collection requests, many states voluntarily submitted the UCM data to EPA. EPA worked to assemble the sta te data into a composite data set that would support national occurrence estimates.

The UCM Round 1 database contains contaminant occurrence data from 38 s tates, Washington, D

. C

. , and the U.S. Virgin Islands. The UCM Round 2 database contains data from
3 5 s tates and several t ribes. However, some s tate data sets were incomplete; hence national occurrence estimates based on raw (unedited) UCM Round 1 or Round 2 data could be skewed to low

- occurrence or high

- occurrence settings (e.g., some s tates only reported detections). In addition, certain types of land use and geologic/hydrologic settings could be over

- or under

represented. To address potential biases in the data (including those due to incompleteness and lack of representativeness)

, EPA developed nationa l cross

- sections from the UCM Round 1 and Round 2 s tate data using an approach similar to that used for EPA ’ s 1999 Chemical Monitoring Reform (USEPA, 1999 b ), the first Six

- Year Review (USEPA, 2003 c ) , and the first round of Regulatory Determinations (USEPA, 2002 b )

. This national cross

- section approach for occurrence analyses was supported by scientific peer reviewers and stakeholders. Using t his approach , EPA constructed national cross

- sections using 24 of the 38 s tates from the UCM Round 1 database and 20 of the 34 s tates from the UCM Round 2 data base. The support document The Analysis of Occurrence Data from the Unregulated Contaminant Monitoring (UCM) Program and National Inorganics and Radionuclides Survey (NIRS) in Support of Regulatory Determin ations for the Second Drinking Water Contaminant Candidate List (USEPA, 2008d ) provides a description of how the national cross

- sections for the Round 1 and Round 2 data sets were developed and utilized for making regulatory determination s

. Since UCM Round 1 and Round 2 data represent different time periods and include occurrence data from different s tates, EPA developed separate national cross

- sections for each data set. The UCM Round 1 national cross

- section

, consist ing of data from 24 s tates, includes

ap proximately 3.3 million records from approximately 22,000 unique PWSs. The UCM Round 2 national cross

- section

, consist ing of data from 20 s tates, includes approximately 3.7 million records from slightly more than 27,000 unique PWSs. The UCM Round 1 and 2 national cross

sections represent significantly large samples of national occurrence data. Within each cross

section, the actual number of systems and analytical records for each contaminant varies.

EPA constructed the national cross

- sections in a way that provides a balance and range of

s tates with varying pollution potential indicators, a wide range of geologic and hydrologic conditions, and a very large sample of monitoring data points. While EPA recognizes that some limitations exist, the agency believe s that the national cross

- sections do provide a reasonable estimate of the overall distribution and the central tendency of contaminant occurrence across theOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 2, Evaluation of Data

2-28 United States. For more information on the development of national cross- sections, refer to
USEPA (1999b), USEPA (2002b), and USEPA (2003c ). See Exhibit 2-4 for a listing of s tates in each national cross -section.

Exhibit 2-4: Cross

- section States for UCM Round 1 and Round 2

UCM Round 1 – 24

- State Cross -Section

. UCM Round 2 – 20

- State Cross -Section

.

Alabama Minnesota* Alaska* New Hampshire

Alaska* Montana Arkansas New Mexico*

Arizona New Jersey Colorado North Carolina*

California New Mexico* Kentucky* North Dakota

Florida North Carolina* Maine Ohio*

Georgia Ohio* Maryland* Oklahoma

Hawaii South Dakota Massachusetts Oregon

Illinois Tennessee Michigan Rhode Island

Indiana Utah Minnesota* Texas

Iowa Washington* Missouri Washington*

Kentucky* West Virginia

Maryland* Wyoming

* S tates in both Round 1 and Round 2 Cross

- sections

EPA ana lyzed the UCM Round 1 and 2 National Cross- Section data to generate the following initial occurrence and exposure summary statistics for CCL 3 contaminants :

• the total number of systems and the total population served by these systems,

• the number and percentage of systems with detections, the 90 th and 99 th percentile concentration s from samples with detections, and the minimum, median , and maximum concentration s from samples with detections

,

• the number and percentage of systems with at least one observed detection that has a concentration greater than the 1⁄2 HRL and greater than the HRL (o r in some cases greater than or equal to the MRL), andOW

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- 29 • the number of people and percentage of the population served by systems with at least one detection that has a concentration greater than the 1⁄2 HRL and greater than the HRL (or in some cases greater t han or equal to the MRL).

The UCM R ound 1 and Round 2 summary occurrence statistics for pertinent contaminants are presented in USEPA (2001 c )

, USEPA (2002 b ) , and USEPA ( 2008d )

. Disinfection Byproducts Information Collection Rule ( DBP ICR)

The DBP ICR (61 FR 24353 ; USEPA, 1996 b ) required PWS s serving at least 100,000 people to monitor and collect data on DBPs over an 18

- month period from July 1997 to December 1998. The DBP data were collected from 296 very large water systems (that is, systems serving a population of more than 100,000) , including both surface water systems and ground water systems

. These very large systems provide d extensive information on the occurrence of DBPs and on water treatment methods. The DBP ICR data were collected as part of a national research project to support development of national drinking water standards. EPA

use d the data to identify national and regional patterns . The data were not intended to support conclusions about individual systems or treatment plants.
DBP ICR monitoring was conducted on a “per plant” basis; most participating systems had more than one water treatment plant. Plants using chlorine dioxide were required t o monitor on a monthly basis . These plants sampled at anywhere betw een one and four different locations in the distribution system. Sampling points generally represented the point of entry into the distribution system, a point of maximum residence time, or a point of average residence time. Plants monitoring hypochlorite were required to gather samples on a quarterly basis

. M onitor ing was conducted at one point in the distribution system, generally the point of entry into the distribution system.

A dditional details on the data collection process for the DBP ICR, along with an independent analysis of the data, can be found in a report sponsored by the Microbial/Disinfection Products Council (McGuire et al. , 2002). DBP ICR o ccurrence data are availabl e for several CCL 3 contaminant s

. EPA analyzed the DBP ICR data to generate the following occurrence and exposure summary statistics for CCL 3 contaminants :

• the total number of systems and the total population served by these systems,

• the number and percentage of systems with detections, the 90 th and 99 th percentile concentration s from samples with detections, and the minimum, median , and maximum concentration s from samples with detections

,

• the number and the percentage of systems with at least one co ncentration greater than the 1⁄2 HRL and greater than the HRL,

• the number of people and percentage of the population served by systems with at least one concentration greater than the 1⁄2 HRL and greater than the HRL.
In additional to developing system

- level r esults, EPA also analyzed findings at the level of the individual treatment plant.

W hile the DBP ICR only includes 296 systems, this was a census of the largest systems in the nation, serv ing over half of the nation’s population served by PWS s

. I t has pre viously beenOW

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- 30 vetted for use in regulatory development, and can be used in the regulatory determination

process. National Inorganics and Radionuclides Survey (NIRS)

In the mid

- 1980 ’ s, EPA implemented NIRS to provide a statistically representative sample of the national occurrence of inorganic contaminants in CWSs served by ground water. The survey is stratified based on system size (population served by the system). Most of the NIRS data are from smaller systems (92 percent from systems serving 3,300 person s or fewer).
The NIRS database includes 36 radionuclides and inorganic compounds (IOCs)

. NIRS provides contaminant occurrence data from 989 ground water CWSs in 49 state s (all except Hawaii) as well as Puerto Rico . S urface water systems were not included in the study, in part because IOCs tend to occur more frequently and at higher concentrations in ground water than in surface water. Each of the 989 randomly selected CWSs was sampled once between 1984 and 1986.
EPA analyzed the NIRS data to generate the following occurrence and exposure summary statistics for CCL 3 contaminants :

• the total number of systems and the total population served by these systems,

• the number and percentage of systems with detections, the 90 th and 99 th percentile concentration s from samples with detections, and the minimum, median , and maximum concentration s from samples with detections

,

• the number and the percentage of systems with at least one concentration greater than the 1⁄2 HRL and greater than the HRL,

• the number of people a nd percentage of the population served by systems with at least one concentration greater than the 1⁄2 HRL and greater than the HRL.
Because the NIRS data were collected in a randomly designed sample survey, the summary statistics are representative of natio nal occurrence in ground water CWSs. Information about NIRS monitoring and data analysis is available in Longtin (1988) and USEPA ( 2008c ).
One limitation of the NIRS is a lack of occurrence data for surface water systems. To provide perspe ctive on the occ urrence of the inorganic compounds in surface water systems relative to ground water systems EPA also reviewed various supplemental data sources.

2.4.4 Occurrence in Drinking Water

– Secondary Data Sources

The agency evaluated many sources of supplemental drin king water occurrence information (including information on occurrence in “source” or “raw” water, e.g., at the wellhead in ground water systems) to augment the primary drinking water occurrence data, to evaluate the likelihood of contaminant occurrence, and/or to more fully characterize a contaminant ’ s presence in the environment. These data sources are generally narrower in geographic scope than the primary drinking water data sources.
This section provides brief descriptions of many of the supplemental drinking water information/data sources cited in contaminant data discussions in this document and in companion support documents

.OW

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- 31 State Monitoring Data

Since there is no national database that receives and stores all relevant data regarding the

occurre nce of regulated or unregulated contaminants in public drinking water systems, EPA conducted a voluntary data call

- in from the states, territories, and tribes to obtain regulated contaminant occurrence data in support of national occurrence assessments con ducted for the second Six

- Year Review. EPA worked with the states and primacy agencies to receive the states’ and agencies’ complete records of compliance monitoring data (public drinking water system regulated contaminant occurrence data) for specified co ntaminants for 1998 through 2005. Using these data, EPA established a high quality national contaminant occurrence database consisting of data from 47 states/primacy agencies (45 states plus Region 8 and Region 9 tribes) for the regulated contaminants requ ested . For more details on the Six

- Year Review Information Collection Request Dataset, refer to USEPA (2009a).

Six states and the Region 9 t ribes submitted PWS occurrence data for unregulated contaminants in addition to their data for regulated contaminants

. EPA was able to supplement these data on unregulated contaminants by downloading additional publicly available monitoring data from state W eb sites (specifically, from Florida and Wisconsin)

. The result was a collection of unregulated contaminant monitoring data from nine states (eight states and one tribal entity; this support document uses the term “state” for SDWA primacy entities for convenience) . The nine data sets vary in the range of monitoring dates (in some cases e xtending beyond the 1998

- 2005 period of interest for Six

- Year Review), the number of contaminants monitored

, the number of systems reporting monitoring, and the number of samples taken. The number of systems varies widely in completeness of coverage relati ve to all the PWSs in the state. Hence, these data are used only to augment and compliment the national drinking water data and to assess any unique occurrence that may suggest a need for further review.
2000 Community Water System Survey ( 2000 CWSS)

The 2 000 Community Water System Survey (CWSS) (USEPA, 2002 c ; USEPA, 2002 d ) gathered data on the financial and operating characteristics of a random sample of CWS s nationwide. In addition, the Survey asked all CWS s serv ing more than 500,000 people (a total of
83 systems) to provide monitoring results for five regulated compounds (arsenic, atrazine, 2,4

- D, simazine, and glyphosate) and four unregulated compounds (radon , MTBE, metolachlor, and boron) , including results from raw water (i.e., before treatment) at eac h intake and from finished

water (i.e., following treatment) at each treatment plant. EPA received completed questionnaires from 58 of the 83 systems. N ot all systems answered every question. Note that because reported results are incomplete, they are only illustrative

, not statistically representative , and are only used as supplemental information

. 2006 Community Water System Survey ( 2006 CWSS)

The 2006 CWSS (USEPA, 2009 b ) gathered data on the financial and operating characteristics of a random sample of C WSs nationwide. All systems serving more than 500,000 people (94 systems in 2006) were included in the sample , and systems in that size category were asked questions about concentrations of unregulated contaminants in their raw and finished

water. Not all systems responded to the survey and, of the systems that responded to the survey,

n ot all systems answered every question. EPA supplemented the data set by gathering additional information about contaminant occurrence at the systems in this size category f rom publicly available sources (e.g., consumer confidence reports). Note that because reported results areOW

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- 32 incomplete, they are only illustrative

, not statistically representative, and are only used as supplemental information.
Water Systems’ Consumer Conf idence 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; they may also include general educational material. Under the CCR Rule (40 CFR Subpart O), 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. System s 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. N ote that because reported results are incomplete, they are more illustrative than statistically representative, and are only used as supplemental information.
United States Department of Agriculture (USDA) Pesticide Data Program (PDP)

The USDA Pesticide Da ta Program ( PDP ) has developed a national pesticide residue database. PDP was initiated in 1991 to collect data on pesticide residues in food with sampling conducted on a statistically defensible representation of pesticide residuals in the United States
f

ood supply (USDA, 2007). Sampling and testing are conducted on fruits and vegetables, select grains, milk, and (as of 2001) drinking water.
The PDP drinking water sampling program was initiated at CWSs in New York and California in 2001. Since then the dri nking water sampling program has expanded, though a somewhat changing mix of states is sampled each year. At one time or another, CWSs in 27 states and Washington, D.C.

, have contributed raw and/or finished water data to the program (USDA, 2011). 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 w ater treatment facilities to be monitor ed . EPA review s the PDP data on the occurrence of select contaminants in untreated and treated water. The CWSs selected for sampling tend to be small

and medium

- sized systems (primarily CWSs serving under 50,000), sy stems served by surface water, and systems located in regions of heavy agriculture. Sampling of untreated water in addition to treated wa ter began in 2004 (USDA, 2004).
USGS Pilot Monitoring Program (PMP)

In 1999, the Pilot Monitoring Program ( PMP ) was ini tiated by USGS and EPA to provide information on pesticide concentrations in drinking water. This study particularly focused on small drinking

- water supply reservoirs in areas with high pesticide use to test the sampling approach in areas where pesticides are probably present (Blomquist et al. , 2001). Sampling sites represent a variety of geographic regions, as well as different cropping patterns. The ideal site candidates were mostly small reservoirs located in high pesticide

- use areas, with a high runoff potential. Twelve water

- supply reservoirs, considered vulnerable to pesticide contamination, were selected from the list of candidates. These 12 sites were located in California, Indiana, Ohio, Oklahoma, Louisiana, Missouri, South Carolina, South Dakota, N ew 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

-OW

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- 33 water intake and from the finished drinking

- water tap prior to entering the distribution system. At some sites, samples were also collected at the reservoir outflow.
USGS NAWQA

– Source Water and Drinking Water Studies
Organic Compounds in Source Water of Selected Community Wa ter Systems ( Hopple et al.
, 2009 and Kingsbury et al.
, 2008)
As part of the NAWQA program, Hopple et al. (2009) and Kingsbury et al. (2008) conducted studies to characterize anthropogenic organic compounds in waters used as source waters for PWSs in the Un ited States. Hopple et al. (2009) focused on ground water and Kingsbury et al. (2008) focused on surface water. In Phase 1 of the studies, geographically diverse source water samples were collected between October 2002 and July 2005 from 9 CWSs served by s treams and from 12 aquifers. In Phase 2, USGS collected source and finished water samples at a subset of sites between June 2004 and September 2005.
Water Quality in Public

- Supply Wells (Toccalino et al., 2010)
A study by Toccalino et al. (2010), conducte d as part of the NAWQA Program, provides information about the occurrence of regulated and unregulated contaminants in the environment. Water samples were collected from s ource water ( in this case, untreated groundwater ) from 932 public

- supply wells located in parts of 40 NAWQA Study Units in 41 states. Each well was sampled once between 1993 and 2007. Six water

- quality properties and 215 chemical contaminants (58 regulated and 157 unregulated in drinking water) were anal yzed. Whenever possible, contaminant concentrations were compared to human

- health benchmarks: Maximum Contaminant Levels (MCLs) for 58 EPA

- regulated contaminants and health based screening levels (HBSLs) for 96 unregulated contaminants. The public wells sa mpled in this study represented 629 unique PWSs. The 629 PWSs with one or more wells sampled in this study represent about 0.5% of the approximately 140,000 groundwater

- supplied PWSs but nearly 25% of the population served by groundwater PWSs in the United States.
Water Quality in Domestic Wells ( DeSimone
, 2009)
As part of the NAWQA Program, USGS also conducted an assessment of the quality of water from domestic wells across the United States (DeSimone, 2009). The program analyzed the concentrations of majo r ions, trace elements, nutrients, radon, and organic compounds (pesticides and VOCs) at approximately 2,100 domestic wells (private drinking water wells) across 48 states, covering 30 regional aquifers. Water samples were collected between 1991 and 2004 f rom domestic wells (private wells used for household drinking water). In addition, USGS summarized data from wells sampled for NAWQA agricultural land

- use assessment studies to provide an indication of the potential effects of agricultural land

- use practic es on the ground water in the aquifers studied.
Water Quality in Carbonate Aquifers ( Lindsey et al.
, 2008)
A study by Lindsey et al. (2008), conducted as part of the NAWQA Program, provided an assessment of the water quality in carbonate aquifers in the Un ited States. Analytical results from ground water samples from 865 wells and 177 springs from 14 NAWQA study units (in 20 states) formed the basis of this study. The study analyzed samples collected between 1993 to 2005 for major ions, radon, nutrients, pe sticides and VOCs. The 12 aquifer systems selected for this study represent a wide range of climate, land

- use types, and degrees of confinement. The water use associated with the sampling sites used in this study fell into four categories: domesticOW

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- 34 water u se, public water use, “unused” (e.g., monitoring well or an abandoned domestic well), and other (e.g., aquaculture, commercial, dewatering, industrial cooling, etc.).
USGS National Reconnaissance of Emerging Contaminants (NREC)

For CCL 3

, USGS provided EP A with data from various reconnaissance studies looking at the occurrence of emerging contaminants in surface waters and ground waters . The data represent sites from over 30 states, and include analyses for over 124 contaminants.
National Pesticide Survey (NPS)
In 1990, EPA completed a national survey of pesticides in the source water of drinking water wells. The purpose of the National Pesticide Survey (NPS) was to determine the national occurrence frequencies and concentrations of select pesticides in the nation ’ s drinking water wells, and to improve EPA ’ s understanding of how pesticide occurrence in ground water correlates with patterns of pesticide usage and ground water vulnerability. The survey included approximately 1,300 CWS wells and rural domestic wells. Sampling was conducted between 1988 and 1990. The survey targeted areas representing a variety of pesticide usage levels and ground water vulnerability. The survey was designed to provide a statistically reliable estimate of pesticide occurrence in the nation ’ s drinking water wells. It was not designed to provide statistically valid results at the state or local level. Wells were sampled for 101 pesticides, 25 pesticide degradates, and nitrate (USEPA, 1990).

OPP Estimated Concentrations

EPA’s OPP use s modeling to develop estimated drinking water and environmental concentrations for acute and chronic pesticide exposure scenarios involving surface and/or ground water (USEPA, 2010a ). The Screening Concentration In GROund Water (SCI

- GROW) model estimates exposure values in vulnerable ground water using the pesticide’s environmental fate properties, maximum application rate, and available water monitoring data. These estimates are “conservative or high

- end exposure values

, ” and thus should not be used for r egional or national exposure estimates (USEPA, 2010b ). The Pesticide Root Zone Model (PRZM) models pesticide migration in soil. The PRZM model can be used in tandem with the Exposure Analysis Modeling System (EXAMS) to generate improve d exposure estimates. The EXAMS model examines the fate, transport, and exposure of pesticides in surface water (USEPA, 2010c ).
Environmental Working Group (EWG) Drinking Water Data base

In December 2009, t he Environmental Working Group ( EWG ) released its “National Drinking Wat er Database

, ” which includes data on both regulated and unregulated drinking

water contaminants collected between 2004 and 2009 from 45 states and the District of Columbia (EWG, 2009)

. ( In 2005, EWG had assembled a drinking water compilation covering an earlier time period; this older compilation is no longer posted by EWG on its W eb site .) EWG states that its 2009 database includes results on 315 contaminants from approximately 48,000
PW S s; data were obtained primarily from state water offices

. Upon assembly of the database, EWG reviewed the data for inconsistencies, potential outliers and other errors . It invited AWWA and the Association of Metropolitan Water Agencies ( AMWA ) to review t he data and/or have their constituents, the PWSs, review the data. S ome corrections apparently were made since the public release of the data in December of 2009 . The data analyzed in this document were downloaded on January 10, 2010. The information presented by EWG on its Web site does not include complete data for assessment; it consists of summary reports. These data were used by EPA as supplementary information , and wereOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 2, Evaluation of Data

2-35 reviewed particularly to assess if there were any unique findings that would warrant additional review.
The EWG online data include counts, by state, of the number of systems that had detections of each contaminant and the population served by those systems , as well as counts (when available) of the number of systems wi th exceedances of contaminant-specific thresholds and the associated population served. EWG established the thresholds by surveying health- based and legal limits established by state and federal agencies and selecting the most conservative one for each con taminant . Note that although EWG does provide some data on contaminant concentration

, the presentation of the concentration data is not complete. Specifically, EWG only provides concentration data (study- wide average and range of daily average detected concentrations) from t he ten water systems with the highest average detected concentrations of each contaminant. Hence, the data are not sufficient to estimate the magnitude of occurrence.



### 2.5 Evaluation of Analytical and Treatment Methods

2.5.1 Evaluation of Analytic al Methods
EPA has evaluated the availability of analytical methods for CCL 3 contaminants. In the case of a positive regulatory determination, EPA needs to ensure that laboratories have the capacity to measure the newly regulated contaminant with confidence at concentrations of concern (generally a health -based threshold) by the time the regulation goes into effect.
The Method Sensitivity Ratio (MSR) provides a measure of analytical method performance relative to the HRL for each contaminant. To determine the MSR, a reporting level is needed for each contaminant. Reporting levels can be estimated from detection limits or may be available in more recent EPA analytical methods as the Lowest Concentration Minimum Reporting Level (LCMRL). The “gold standard” fo r reporting levels is the MRL, which is determined by EPA from raw LCMRL data from multiple laboratories. The following quantities

are also sometimes used in MSR calculations:



## • Method Detection Limit (MDL)
– The MDL is determined over a single day and includes

an iteration step to optimize the MDL. MDLs are published in EPA analytical methods.



## • Detection Limit (DL)
– The DL is determined over a three

- day period and does not include an iteration step to optimize the DL. DL s are published in EPA analytical methods where the MDL procedure has not been used. Since DLs are determined over a three -day period and their calculation does not include the iterative optimization step, DLs are typically not as low as MDLs

.



## • 5xMDL or 5xD L
– A 5x multiplier is applied to the MDL or DL as a surrogate for the reporting level based on an MDL or a DL.



## • LCMRL – T he LCMRL is a single -laboratory reporting level for selected EPA analytical methods . It is determined via a statistical model for futur e analyte recovery using the method. The LCRML is o nly used for MSR calculation in cases where the analytical method has been recently developed and an MRL was not derived for use in EPA’s
UCMR program;



## • MRL
– The MRL is the r eporting level used for nationa l application in EPA’s UCMR

program . For UCMR 1 analytes , the MRL was established by EPA in light of anticipated laboratory capability. For UCMR 2 and UCMR 3 analytes, the MRL has been determined via a statistical model from multiple sets of single

- laborat ory LCMRL data

.OW

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- 36 The MRL is preferred as the reporting level of the best quality, followed by the LCMRL , and then 5xMDL and 5xDL. A favorable MSR is one that is greater than ten. That is, it is preferable that the concentration at which data can be reliably reported be at least 10 times lower than the
HRL ; this provides a margin of safety for uncertainty in the HRL and/or meth od performance (see USEPA, 2009 c ).

2.5.2 Evaluation of Treatment Technologies
The availability of treatment technologies is not a fa ctor EPA considers when making a regulatory determination. However, suitable treatment technologies must be made available before a NPDWR can be promulgated.

EPA conducted a preliminary review of the literature to investigate which treatment technologies have been investigated for their applicability to particular CCL 3 contaminant s. The review included both peer

- reviewed literature and “grey” literature. It was not necessarily exhaustive. It was conducted in 2009 and has not been sy stematically updated since that time.
For most contaminants EPA made some preliminary judgments, within the limits of the information available, about which treatment modalities appear to be the most promising.
A range of traditional and experimental trea tment modalities were considered in the literature reviewed. When applicable, modification of disinfection practices, pretreatment of DBP precursors, and other measures to prevent the formation of DBPs were included in the discussion of treatment technolog ies.



### 2.6 References
Agency for Toxic Substances and Disease Registry (ATSDR). 1995. Toxicological Profile for 1,3

- Dinitrobenzene and 1,3,5

- Trinitrobenzene (1,3

- DNB and 1,3,5

- TNB)

. Available on the Internet at: http://www.atsdr.cdc.gov/toxprofiles/tp74.pdf . Accessed October 16,
2012.

American Water Works Association Research Foundation (AwwaRF). 2003. Occurrence of MTBE and VOCs in Drinking Water Sources of the United States.
Blomquist, J.D., J.M. Denis, J.L. Cowles, J.A. Hetrick, R.D. Jones, and N.B. Birchfield. 2001. Pesticides in Selected Water

- Supply Reservoirs and Finished Drinking Water, 1999

- 2000: Summary of Results from a Pilot Monitoring Survey . U.S. Geological Survey Open

- File Report 01

- 456. 65 pp. Available on the Internet at: http://md.water.usgs.gov/nawqa/OFR_01

- 456.pdf

. Delzer, G.C. and T. Ivahnenko. 2003. Occurrence and Temporal Variability of Methyl te rt

- Butyl Ether (MTBE) and Other Volatile Organic Compounds in Select Sources of Drinking Water: Results of the Focused Survey. U.S. Geological Survey Water

- Resources Investigations Report 02

- 4084

. 65 p p. Available on the Internet at: http://sd.water.usgs.gov/nawqa/pubs/wrir/wrir02_4084.pdf

. DeSimone, L.A. 2009. Quality of W ater from D omestic W ells in P rincipal A quifers of the United States, 1991

- 2004 . U. S. Geological Survey Scientific Investigations Report 2008

- 5227

. 139 p p . Available on the Internet at : http://pubs.usgs.gov/sir/2008/5227/

. Environmental Working Group ( EWG ) . 2009. National Drinking Water Database. Available on the Internet at: http://www.ewg.org/tap

- water/home

. Accessed December 16, 2009.OW

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2

- 37 Gilliom, R.J., J.E. Barbash, C.G. Crawford, P.A. Hamilton, J.D. Martin, N. Nakagaki, L.H. Nowell, J.C. Scott, P.E. Stackelberg, G.P. Thelin, and D.M. Wolock. 2007. The Quality of Our Nation’s Waters

- Pesticides in the Nation’s Streams and Ground Water, 1992

– 2001 . Appen dix 7. Statistical summaries of water

- quality data. U.S. Geological Survey Circular 1291

. 172 p p. Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/pubs/circ1291/appendix7/

. Grady, S.J. 2003. A National Survey of Methyl tert

- Butyl Ether and Other Volatile Organic Compounds in Drinking

- Water Sources: Results of the Random Survey. U.S. Geological Survey Water

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.OW

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- 1995. Environmental Science and Technology

. 33( 23):4176

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. USDA. 2011. Pesticide Data Program, Annual Summary, Calendar Year 2009 . May 2011. Available on the Internet at: http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5091055

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. Vol. 51, No. 185. p. 33992, September
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XXX , p. 25720 , July 8

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to

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. Availabl e on the Internet at: http://www.epa.gov/tri/tridata/tri96/pdr/chap3.pdf

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. Monitoring Requirements for Public Drinking Water Supplies. Federal Register

. Vol. 61, No. 94, p. 24353, May 14, 1996.

USEPA. 1999 a . Revisions to the Unregulated Contaminant Monitoring Regulation for Public Water Systems; Final Rule. Federal Register . Vol

. 64, No

. 80, p. 50556, September 17, 1999.

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. A Review of Contaminant Occurrence in Pub lic Water Systems . EPA

- 816

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- Related Information in Pesticide Risk Assessment and Risk Management. August 21, 2000. Office of Pesticide Programs. Available on the Internet

at: www.epa.gov/oppbead1/use

- related.pdf.

USEPA. 2000 b . Unregulated Contaminant Monitoring Regulation for Public Water Systems: Analytical Methods for Perchlorate and Acetochlor; Announcement of Laboratory Approval and Performance Testing (PT) Program for the Analysis of Perchlorate; Final Rule and Proposed Rule. Federal Register . Vol

. 42, No. 65, p. 11372, March 2, 2000.

USEPA. 2000 c

. Unregulated Contaminant Monitoring Regulation Analytical Methods and Quality Control Manual

. EPA 815

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- 006.OW

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- 39 USEPA. 2001 a . Unregulated Contaminant Monitoring Regulation for Public Water Systems; Analytical Methods for List 2 Contaminants; Clarifications to the Unregulated Contaminant Monitoring Regulation. Federal Register . Vol. 66, No. 8, p. 2273, January 11, 2001.

USEPA. 2 001 b

. Reference Guide for the Unregulated Contaminant Monitoring Regulation

. Office of Water. EPA 815

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- 01

- 023. 65 pp. Available on the Internet at: http://www.epa.gov/ogwdw/ucmr/ucmr1/pdfs/guidance_ucmr1_ref_guide.pdf

. USEPA. 2001 c

. Occurrence of Unregula ted Contaminants in Public Water Systems: An Initial
Assessment . EPA 815

- P

- 00

- 001. May , 2001

. USEPA. 2002 a

. The Toxics Release Inventory (TRI) and Factors to Consider When Using TRI
Data. EPA 260

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- 017. November. Available on the Internet at: http://www .epa.gov/tri/triprogram/FactorsToConPDF.pdf

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. Analysis of National Occurrence of the 1998 Contaminant Candidate List (CCL) Regulatory Determination Priority Contaminants in Public Water Systems. May 2002.
EPA

- 815

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. EPA 815

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. USEPA. 2002 d

. Community Water System Survey 2000. Volume II: Detailed Tables and Survey Methodology

. EPA 815

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- 005B. December. Available on the Internet at: http://www.epa.gov/safewater/consumer/pdf/cwss_2000_volume_ii.pdf

. USEPA. 2003 a

. How are the Toxics Release Inventory Data Used? EPA 260

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- 002

- 004. May. Available on the Inter net at: http://www.epa.gov/tri/guide_docs/pdf/2003/2003_datausepaper.pdf

. USEPA. 2003b. Drinking Water Baseline Handbook, Fourth Edition (Draft) . September 4, 2003.

USEPA. 2003 c

. Occurrence Estimation Methodology and Occurrence Findings for Six

- Year Review of National Primary Drinking Water Regulations . EPA Report 815

- R

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- 006, Office of Water.

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. Biological and Economic Analysis Division, Office of Pesticide Programs. Available on the Internet

at: http://www.epa.gov/oppbead1/pestsales/index.htm

. USEPA. 2005a. Guidelines for Carcinogen Risk Assessment. EPA 630

- P

- 03

- 001B. March. Available on the Internet at: http://www.epa.gov/ttn/atw/cancer_guidelines_final_3

- 25

- 05.pdf

. USEPA. 2005b. Supplemental Guidance for Assessing Susceptibility to Early

- life Exposure to Carcinogens. EPA 630

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- 03

- 003F. March. Available on the Internet at: http://www.epa.gov/ttn/atw/childrens_supplement_final.pdf

. USEPA. 2005 c . Unregulated Contaminant Monitoring Regulation (UCMR) for Public Water Systems Revisions; Proposed Rule. Federal Register . Vol. 70, N o. 161, p. 49093, August 22, 2005.
USEPA. 2007. Unregulated Contaminant Monitoring Regulation (UCMR) for Publi c Water Systems Revisions. Federal Register. Vol. 72, No. 2, p. 367, January 4, 2007.OW

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- 40 USEPA. 2008 a . 2006 IUR Public Data Background Document. December 2008. Available on the Internet at: http://www.epa.gov/iur/pubs/iurdbbackground.pdf

USEPA. 2008b

. The An alysis 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

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. USEPA. 2008c . Drinking Water: Reg ulatory Determinations Regarding Contaminants on the Second Drinking Water Contaminant Candidate List. Federal Register. Vol. 73, No. 147, p. 44251. July 30, 2008.

USEPA. 2008d

. The Analysis of Occurrence Data from the Unregulated Contaminant Monitoring (U CM) Program and National Inorganics and Radionuclides Survey (NIRS) in Support of Regulatory Determinations for the Second Drinking Water Contaminant Candidate List

. EPA 815

- R

- 0 8

- 0 12

. June

. USEPA. 2009 a

. The Analysis of Regulated Contaminant Occurrence Data from Public Water Systems in Support of the Second Six

- Year Review of National Primary Drinking Water Regulations. EPA

- 815

- B

- 09

- 006. October 2009.

USEPA. 2009 b

. Community Water System Survey 2006

. Draft 3.5. EPA 815

- R

- 09

- 001.

USEPA. 2009 c

. Final Contaminant Candidate List 3 Chemicals: Classification of the PCCL to
CCL. Office of Water. EPA 815

- R

- 09

- 008.

USEPA. 2010a . Water Exposure Models Used by the Office of Pesticide Programs. Available on the Intern et at: http://www.epa.gov/oppefed1/models/water/models4.htm

. USEPA. 2010b . SCI

- GROW Description. Available on the Internet at: http://www.epa.gov/oppefed1/models/water/scigrow_description.htm

. USEPA. 2010c . Water Models. Available on the Internet at: http://www.epa.gov/oppefed1/models/water/index.htm#scigrow

. USEPA. 2011. Exposure Factors Handbook 2011 Edition (Final). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R

- 09/052F.

USEPA. 2012 a

. Chemical Data Repo rting/Inventory Update Reporting : Basic Information. Available on the Internet at: http://www.epa.gov/iur/pubs/guidance/basic.html

. Last updated August 23, 2012

. USEPA, 2012 b . Non

- confidential IUR Production Volume Information. Available on the
Internet at: http://www.epa.gov/iur/tools/data/2002

- vol.html. Last updated February 09,
2012.

USEPA. 2012 c . Storage and Retrieval (STORET) Data Warehouse. Available on the Internet at: http://www.epa.gov /storet/index.html. Data Warehouse consulted March 2012.

USEPA. 2012 d . Revisions to the Unregulated Contaminant Monitoring Regulation (UCMR 3) for Public Water Systems. Federal Register . Vol 77. No. 85, p. 26072, May 2, 2012.

USEPA, 2014 . Protocol for the Regulatory Determinations 3. Including Appendices A

- F. EPA

815

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- 14

- 005. April 2014

. USEPA. 201 5 . Occurrence Data from the Second Unregulated Contaminant Monitoring Regulation (UCMR 2). Including Appendices A

- C. EPA

- 815

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- 013

. Decembe r 2015.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 2, Evaluation of Data

2-41 United States Geological Survey (USGS). 2001. “Summary publications from 51 NAWQA study units sampled in 1991-2001.” Avai lable on the Internet at: http://water.usgs.gov/nawqa/nawqasum/

. Accessed May 24, 2004. Last updated May 19,
2004.
United States Geological Survey (USGS). 2015 . Pesticide National Synthesis Project, Annual Pesticide Use Maps, 2002 -2012. Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/usage/maps/index.php . Accessed September 24, 2015.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 2, Evaluation of Data

2-42OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-1 

# Chapter 3: Dimethoate

A chapter from:

Regulatory Determination 3 Support Document

EPA Report 815 -R- 15

- 014

December 2015OW

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– Chapter 3, Dimethoate

3

- 2OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-3 

### Contents

Contents ...........................................................................................................................................3 Exhibits ................................ ............................................................................................................4 Abbreviations ................................ ...................................................................................................5
3.1 Contaminant Background , Chemical and Physical Properties ............................................7 3.2 Sources and Environmental Fate .........................................................................................8
3.2.1 Production, Use, and Release...................................................................................8
3.2.2 Environmental Fate ................................................................................................12
3.3 Health Effects .....................................................................................................................13
3.4 Occurrence .........................................................................................................................14
3.4.1 Occurrence in Ambient Water ...............................................................................14
3.4.2 Occurrence in Drinking Water ...............................................................................17 3.5 Technology Assessment .....................................................................................................23 3.5.1 Analytical Methods ................................................................................................23
3.5.2 Treatment Technologies .........................................................................................23
3.6 Regulatory Determination ..................................................................................................24
3.6.1 Making Regulatory Determinations for Chemicals on the CCL ...........................24
3.6.2 Health Effects (Criterion #1) .................................................................................25
3.6.3 Occurrence in Public Water Systems (Criterion #2) ..............................................26
3.6.4 Risk Reduction (Criterion #3) ................................................................................27
3.6.5 Final Regulatory Determination Decision .............................................................28
3.7 References ..........................................................................................................................28OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-4 

### Exhibits

Exhibit 3- 1: Chemical Structure of Dimethoate ..............................................................................8 Exhibit 3- 2 : Physical and Chemical Properties of Dimethoate .......................................................8 Exhibit 3-3: Annual Production and Importation of Dimethoate in the United States (pounds) .....9 Exhibit 3-4: Environmental Releases (in pounds) of Dimethoate in the United States, 1997-
2010................................................................................................ ....................................10 Exhibit 3- 5 : Summary of Total Releases and Total Surface Water Discharges of Dimethoate, 2002, 2004, 2006, 2008, and 2010 .....................................................................................11 Exhibit 3-6: Estimated Annual Agricultural Use of Dimethoate, c. 2012 .....................................12 Exhibit 3- 7 : Dimethoate STORET Data – Summary of Detected Concentrations ........................15 Exhibit 3- 8 : Dimethoate STORET Data
– Summary of Samples ..................................................15 Exhibit 3- 9 : Dimethoate STORET Data
– Summary of Sites .......................................................16 Exhibit 3- 1 0: Dimethoate STORET Data
– Summary of States ....................................................16 Exhibit 3-11 : Dimethoate State Drinking Wate r Occurrence Data
– Summary of Detected Concentrations ...................................................................................................................19 Exhibit 3- 1 2: Dimethoate State Drinking Water Occurrence Data
– Summary of Samples .........19 Exhibit 3- 1 3: Dimethoate State Drinking Water Occurrence Data
– Summary of Systems .........19 Exhibit 3-14: Summary of Dimethoate PDP Data, 2001-2009 ......................................................20 Exhibit 3-15: Dimethoate Data from Source Water (Hopple et al., 2009 and Kingsbury et al., 2008) – Summary of Detections from Phase 1 ..................................................................22 Exhibit 3-16: Dimethoate Data from Source Water (Hopple et al., 2009) – Summary of Detections from Phase 2 – Ground Water .........................................................................22 Exhibit 3- 1 7: Method Sensitivity Ratio (MSR) for Dimethoate ....................................................23OW

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– Chapter 3, Dimethoate

3

- 5 

### Abbreviations

a.i. Active Ingredient

AMWA Association of Metropolitan Water Agencies

AWWA American Water Works Association

BMD Benchmark Dose

BMDL Benchmark Dose Level

CARC Cancer Assessment Review Committee

CAS Chemical Abstracts Service

CCL Contaminant Candidate List

CCL 3 Third Contaminant Candidate List

CCR Consumer Confidence Report
ChE Cholinesterase

CDPR California Department of Pesticide Regulation

CFR Code of Federal Regulations

CUS Chemical Update System

CWS Community Water System

CWSS Community Water System Survey

DL Detection Limit

EDSP Endocrine Disruptor Screening Program

EDWC Estimated Drinking Water Concentration

EPA Environmental Protection Agency

EPCRA Emergency Planning and Community Right

- to

- Know Act

EWG Environmental Working Group

FIFRA Federal Insecticide, Fungicide, and Rodenticide Act FQPA Food Quality Protection Act

FR Federal Register

GAC Granular Activated Carbon

GC Gas Chromatography

HS DB Hazardous Substance Data Bank

HRL Health Reference Level

ICR Information Collection Request

IRED Interim Reregistration Eligibility Decision

IUR Inventory Update Reporting

LCMRL Lowest Concentration Minimum Reporting Level

MCL Maximum Contaminant Level

MCLG Maximum Contaminant Level Goal

MRL Minimum Reporting L evel

MS Mass Spectrometry

MSR Method Sensitivity Ratio

N/A Not Applicable NAWQA National Water

- Quality AssessmentOW

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– Chapter 3, Dimethoate

3

- 6 NCFAP National Center for Food and Agricultural Policy

NPDWR National Primary Drinking Water Regulation

NTNCWS Non

- Transient Non

- Community Water System

OPP Office of Pesticide Programs

OPPTS Office of Prevention, Pesticides and Toxic Substances

PBT Persistence, Bioaccumulation, and Toxicity

PDP Pesticide Data Program

PMP Pilot Monitoring Program

PWS Public Water System QA Quality Assurance

RAIS Risk Assessment Information System

RD 3 Third Regulatory Determination

RED Reregistration Eligibility Decision

RfD Reference Dose

RSC Relative Source Contribution

RSD Relative Standard Deviation

SAP Scientific Advisory Panel

SCI

- GROW Screening Concentrations in Ground Water

SDWA Safe Drinking Water Act

SPE Solid Phase Extraction

STORET Storage and Retrieval

TRI Toxics Release Inventory

TSCA Toxic Substances Control Act

UCM Unregulated Contaminant Monitoring

UCMR 1 First Unregulated Contaminant Monitoring Regulation

UCMR 2 Second Unregulated Contaminant Monitoring Regulation

UF Uncertainty Factor

USDA United States Department of Agriculture

USEPA United States Environmental Protection Agency

USGS United States Geological Survey

UV UltravioletOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-7 

### Chapter 3: Dimethoate

The Environmental Protection Agency ( EPA ) has evaluated dimethoate for possible regulation as a drinki ng water contaminant . Dimethoate was listed on the agency’s third Contaminant Candidate List (CCL 3) and was considered for regulation as part of the third
R egulatory Determination (RD 3) under the Safe Drinking Water Act (SDWA) provisions. On October 20, 2014, EPA issued a preliminary determination not to regulate dimethoate (79 FR 62715). A final determination not to regulate dimethoate is issued in the Federal Register notice which this support document accompanies.

Information on the CCL 3 /RD 3 process is fo und in Chapter 1. Background on data sources used to evaluate CCL 3 /RD 3 chemicals is found in Chapter 2. This chapter presents information and analysis specific to dimethoate , including background information on the contaminant, information on sources and environmental fate, an analysis of health effects, an analysis of occurrence in ambient and drinking water, and information about the availability of analytical methods and treatment technologies. A summary of EPA's decision regarding dimethoate under RD 3 appears at the end of this chapter. (The decision is presented formally in the associated Federal Register notice).



### 3.1 Contaminant Background, Chemical and Physical Properties

Dimethoate is an organophosphate pesticide, commonly used as an insecticide on fi eld crops (e .g ., wheat, alfalfa, corn, and cotton), orchard crops, and vegetable crops, and in forestry. Synonyms for dimethoate include dimethogen, dimeton, dimevur, and c ygon (HSDB, 2009, USEPA, 2007b ). Dimethoate was first registered for use as a pestic ide in 1962 (USEPA, 2007b ).
EPA’s Office of Pesticide Programs (OPP) released a Revised Interim Reregistration Eligibility Decision (IRED) for dimethoate in 2007 (USEPA, 2007b). Dimethoate is included in EPA's Office of Prevention, Pesticides and Toxic Substances (OPPTS) April 2009 list of 67 chemicals ( Pesticide Active Ingredients and Pesticide Inerts ) selected for Tier I screening within the Endocrine Disruptor Screening Prog ram (EDSP) . EDSP consists of a two- tiered screening and testing process: Through Tier 1, EPA hopes to identify chemicals that have the potential to interact with the endocrine system. Through Tier 2, EPA will determine the endocrine- related effects caused by each chemical and obtain information about effects at various doses.

Exhibit 3-1 presents the structural formula for dimethoate. P hysical and chemic al properties and other reference information are listed in Exhibit 3-2

.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-8 Exhibit 3-1 : Chemical Structure of Dimethoate

Source: ChemIDPlus/National Library of Medicine

E xhibit 3-2 : Physical and Chemical Properties of Dimethoate

Property Data

Chemical Abstracts Service (CAS) Registry Number 60

- 51 -5

EPA Pesticide Chemical Code Not applicable

Chemical Formula C 5 H 12 NO 3 PS 2 Molecular Weight 229.26 g/mol (RAIS, 2009; HSDB, 20 09 ; ChemIDPlus, 2009)
Color/Physical State White crystalline solid (HSDB, 2010)

Boiling Point 361 deg C (HSDB, 20 09 )

Melting Point 52

- 52.5 deg C (HSDB, 2010)

Density 1.277 g/mL at 27 deg C (HSDB, 20 09 )
Freundlich Adsorption Coefficient 1,080 ( μ g/g)(L/ μ g) 1/n (Speth and Miltner, 1990)

Vapor Pressure 8.25E

- 06 mm Hg (RAIS, 2009; ChemIDPlus, 2009)
Henry’s Law Constant 2.40E

- 10 atm

- m 3 /mol (HSDB, 20 09 ; ChemIDPlus, 2009)

Log K ow 0.78 (dimensionless) (RAIS, 2009; HSDB, 20 09 ; ChemIDPlus, 2009)

K oc 5.2

- 50 L/kg ( HSDB, 2010 )

Solubility in Water 25,000 mg/L (RAIS, 2009; ChemIDPlus, 2009)

Other Solvents Readily soluble in most organic solvents (HSDB, 2010)

Conversion Factors (at 25 deg C, 1 atm) --

Note: “

-- ” indicates that no information was found.



### 3.2 Sourc es and Environmental Fate

3.2.1 Production , Use , and Release

Production data for dimethoate are available from EPA’s Inventory Update Reporting (IUR) program, and industrial release data are available from EPA’s Toxics Release Inventory (TRI). Information on the application of dimethoate as a pesticide is available from several

sources.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-9 Chemical Update System (CUS) – Inventory Update Reporting (IUR) Program
EPA collects information on chemicals manufactured in or imported into the United States from the Toxic Substances Control Act (TSCA) Chemical Substance Inventory. The IUR regulation requires manufacturers and importers of 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. Note that, 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. As a result of changes in minimum thresholds and other program modifications, the results from 2006 might not be directly comparable to results from earlier years (USEPA, 2010a).
The Chemical Update System – Inventory Update Reporting (CUS-IUR) assigns one of eight production and importation volume ranges for each chemical included in the inventory. The ranges used for the 2006 reports differ slightly from those used in the 1986 through 2002 reports. Exhibit 3-3 presents the production and importation of dimethoate in the United States from 1986 to 1990. (Note that no data were reported for 1994, 1998, 2002, or 2006.) Production and importation of dimethoate in the United S tates was between 500,000 and 1 million pounds in both 1986 and 1990.

Exhibit 3-3 : Annual Production and Importation of Dimethoate in the United States (pounds)

. . . Chemical Inventory Update Reporting Cycle

. . .

. 1986 1990 1994 1998 2002 2006
Range of Production / Importa t ion

Volume > 500,000 – 1 million pounds > 500,000 – 1 million pounds No Reports No Reports No Reports No Reports

T

oxics Release Inventory (TRI)

EPA establishe d TRI in 1987 in response to Section 313 of the Emergency Planning and Community Right

- to

- Know Act (EPCRA). EPCRA Section 313 requires the reporting of annual information on toxic chemical releases from facilities that meet specific criteria. Th is reported information is maintained in a database accessible through TRI Explorer (USEPA, 2012b).
Although TRI can provide a general idea of release trends, it has limitations. 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 of a chemical or use more than 10,000 pounds

per year . Reporting requirements have changed over time (e.g., reporting thresholds have decreased) ; this creates the potential for misleading data trends over time (USEPA, 1996). TRI data are meant to reflect releases and sh ould not be used to estimate general public expo sure to a chemical (USEPA, 200 4a ).OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-10 TRI data for dimethoate from the years 1997 through 2010 are summarized in Exhibit 3-4 (USEPA, 2012b ). Total on- and off- site r eported releases fluctuated between tens of pounds and tens of thousands of pounds during the reporting period, with the majority of these reported releases occurring during single years. Reported on- site air emissions were less than 60 pounds from 1997 to 2005. From 2006 to 2010, air emissions remained at several thousand pounds, with the highest reported emissions of over 15,000 pounds in 2008. Releases via underground injection were zero during all years of the reporting period, except in 2004 when reported releases exceeded 28,000 pounds. Reported on- site releases to surface water and land also generally followed this pattern, peaking at nearly 20,000 pounds released to land in 1998 and over 2,000 pounds released to surface water in 2004.

Exhibit 3-4 : Environmental Releases (in pounds) of Dimethoate in the United States, 1997

- 2010

Year

. . On -Site Releases

. Off -Site Releases Total On

- & Off -Site Releases

. Air Emissions Surface Water Discharges Underground Injection Releases to Land . .

1997 26 0 0 0 0 26

1998 57 5 0 19,975 69 20,106

1999 51 5 0 0 177 233

2000 36 255 0 0 0 291

2001 27 5 0 0 620 652

2002 22 5 0 0 0 27

2003 15 5 0 0 0 20

2004 11 2,615 28,795 29 29 31,480

2005 18 5 0 1,208 17 1,248

2006 6,407 5 0 736 0 7,148

2007 10,419 5 0 1,002 96 11,522

2008 15,549 5 0 5 2 15,561

2009 7,510 5 0 5 2,212 9,732

2010 8,437 5 0 0 0 8,442

Exhibit 3-5 presents the total releases, total surface water discharges, and the count of states reporting releases for the years 2002, 2004, 2006, 2008, and 2010 (U SEPA, 2012b) . Three

s tates reported releases of dimethoate in 2002. Four s tates reported releases of dimethoate in 2004. Two states reported releases of dimethoate in 2006 and 2008. One state reported releases of dimethoate in 2010. The number of states reporting surface water discharges of dimethoate ranged from one to two for the years included in Exhibit 3-5 . (For the purposes of TRI, “state” counts include the District of Columbia and United States territories in addition to the 50 states.)OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-11 Exhibit 3-5 : Summary of Total Releases and Total Surface Water Discharges of Dimethoate, 2002, 2004, 2006
, 2008, and 20 10

Year Total Releases (pounds) Count of States with Releases Total Surface Water Discharges

(pounds) Count of States with Surface Water

Discharges

2002 27 3 5 1

2004 31,480 4 2,615 2

2006 7,148 2 5 1

2008 15,561 2 5 1

2010 8,442 1 5 1

E

PA Office of Pesticide Programs (OPP) Reregistra tion Program

EPA has estimated that the total annual average domestic use of dimethoate (no time frame specified) is approximately 1.8 million pounds (USEPA, 2007b).
EPA Pesticide Industry Sales and Usage Report
EPA’s most recent Pesticide Industry Sales and Usage report s indicate that the amount of dimethoate active ingredient (a.i.) used in the United States was between 1 and 2 million pounds in 1999 and 2001, and less than 1 million pounds in 2005 and 2007 (USEPA, 2004b ; USEPA,
2011 ).
National Center for Food and Agricultural Policy (NCFAP) Pesticide Use Database

The National Center for Food and Agricultural Policy ( NCFAP ) maintains a national Pesticide Use Database, primarily for herbicides. Pesticide use estimates are based on state

- level commercial agriculture usage patterns and state

- level crop acreage. For 1992, NCFAP lists uses of dimethoate on 37 crops totaling approximately 2.6 million pounds a.i. per year in 4 6 states

. NCFAP lists uses of dimethoate on 33 crops totaling approximately 1.9 million pounds a.i. per year in 43 states in 1997 (NCFAP, 2003).
United States Geological Survey (USGS) Pesticide Use Maps

The United States Geological Survey ( USGS ) produces maps of annual pesticide use for several hundred compounds used in United States crop production. The pesticide use maps show the average annual pesticide use intensity expressed as average weight (in pounds) of a pesticide applied to each square mile of agricultural land in a county. The USGS maps a re created using data from proprietary surveys of farm operations, USDA Census of Agriculture, the County Agricultural Production Survey, and other sources.

Exhibit 3-6 (USGS, 20 15) shows the geographic distribution of average annual dimethoate use in the United States circa 20 12. A breakdown of use by crop is also included. USGS used two methods to estimate dimethoate usage, since pesticide usage information was not available in some districts. At left, the “EPest

- High” estimates were generated by projectingusage estimates for such districts based on usage in neighboring districts. At right, the “EPestLow” estimates were generated by assuming no usage in such districts. Estimated a nnual usage is variable but has generally declined over the years, and was somewhere in the range of 0. 8 – 3 million pounds in 2012. The map s indicate that dimethoate use is distributed fairly widely in the East, Midwest , Great Plains, and West

.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-12 Exhibit 3-6 : Estimated Annual Agricultural Use of Dimethoate, c. 20 12

Source: USGS, 20 15

3.2.2 Environmental Fate
Dimethoate is considered highly mobile and relatively non-persistent in the environment (USEPA, 2007b ). Modeling indicates that if dimethoate is released to the atmosphere it will exist in both the vapor and particulate phases. In the vapor phase, dimethoate will undergo oxidation reactions in the atmosphere with photochemically produced hydroxyl radicals. The half- life is estimated to be 5 hours based on structural estimation (H SD B, 2010). Dimethoate does not adsorb ultraviolet (UV) light and is not expected to undergo direct photolysis. Particulate

- phase dim ethoate can also be removed from the atmosphere by wet and dry deposition (H SD B, 2010).

The K oc value of 5.2-50 L/kg indicates that dimethoate is not likely to bind to soil and will be mobile in soils (HSDB, 2010). One study found that between 72 and 100 percent of dimethoate leached from sand y loam columns ( US EPA, 2007b ). The Henry’s Law Constant of
2.40E-10 at m-m 3 /mol indicates that volatilization from soil is likely to be a slow process. Half

lives of between 2 and 122 days validate this assumption (H SD B, 2010). Evaporation may be a significant loss mechanism from soil , and one study found dimethoate losses from soil were proportional to water losses. Dimethoate is also susceptible to hydrolysis and was found to have a half -life of 3.7 days at a pH of 9 (H SD B, 2010); however, hydrolysis half-lives of 68 and 156 days were observed in sterile buffer solutions at pH 7 and 5, respectively (USEPA, 2007b). Biodegradation may also be a significant process as one study found 77% degradation in soilOW

– O G W DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3

- 13 after two week s when an autoclaved sample of the same soil only experienced 18 to 20 % degradation (H SD B, 2010).

Based on a K oc of 5.2

- 50 L/kg and a Henry’s Law Constant of 2.40E

- 10 at m

- m 3 /mol

, d imethoate appears to be very mobile in water. It is not likely to volatilize from water or attach to particles (H SD B, 2010). Hydrolysis can be a loss pathway for dimethoate with the process being slow at low pH and becoming rapid at higher pH. Half

- lives for hydrolysis of dimethoate have been reporte d to be 156 days and 4.4 days in sterile buffer solutions at pH 5 and 9

res p ectively (H SD B, 2010). Biodegradation occurs slowly for dimethoate and is dependent on temperature. Half

- lives between 171 and 219 days were found at 6 deg C and between 29 and 43 days at 22 deg C (H SD B, 2010).
EPA developed the Persistence, Bioaccumulation, and Toxicity (PBT) Profiler to serve as a screening tool for estimating the percentage of a contaminant that is predicted to partition to water, air, soil, and sediment in a fo ur

- compartment system. PBT Profiler (2009) modeling predicts that 36% of dimethoate will partit ion to water, 6 4% to soil, 0% to air, and 0% to sediment. PBT Profiler (2009) modeling also projects biodegradation half

- lives in various media.
For dimethoate

, projected half

- lives are approximately 15 days in water, 30 days in soil, 0.2 days in air, and 140 days in sediment. Note that the PBT Profiler, as a screening tool, provides estimated values only and “not . . . definitive PBT determinations” (PBT Profiler , 2009).



### 3.3 Health Effects

Dimethoate is rapidly metabolized in mammals. Dimethoate affect s the proper function of the nervous system by inhibiting cholinesterase (ChE), an important enzyme involved in neurotransmission. ChE inhibition is mediated by the primary toxic metabolite of dimethoate, which is omethoate

. ChE inhibition is the most sensitive endpoint described in numerous studies with adult and juvenile animals, involving oral, dermal, or inhalation exposure to dimethoate or omethoate (USEPA, 200 7b ).
Dimethoate causes equivocal hemolymphoreticular tumors in male B6C3F1 mice and a weak response for combined spleen (hemangioma and hemangiosarcoma), skin (hemangiosarcoma), and lymph (angioma and angiosarcoma) tumors in male Wistar rats (USEPA, 1990; U SEPA, 200 7b ). Dimethoate is also positive in some mutagenic assays. The database for dimethoate includes a 3

- generation reproductive study in mice, developmental (teratology) studies in rats and rabbits, and a neurodevelopmental toxicity study (USEPA, 1990 ; USEPA, 200 7b ).

As discussed in the 2007 EPA OPP Reregistration Eligibility Decision (RED) assessment, EPA’s Cancer Assessment Review Committee (CARC) classified dimethoate as a Group C carcinogen (a possible human carcinogen) in 1991, with concurrence f rom the Federal Insecticide, Fungicide, and Rodenticide Act ( FIFRA ) Scientific Advisory Panel (SAP) on the agency’s clas sification in 1992

. The Group C finding was based on equivocal hemolymphoreticular tumors in the mouse study, and on the fact that the r at carcinogenicity study showed a weak effect of combined spleen (hemangioma and hemangiosarcoma), skin (hemangiosarcoma), and lymph (angioma and angiosarcoma) tumors tha t lacked a dose

- response effect

. The 2007, OPP established an acute reference dose ( R fD ) of 0.013 mg/kg for dimethoate

, based on a benchmark dose level ( BMDL 10 ) of 1.3 mg/kg for inhibition of brain ChE following a single oral dose administered to rats on postnatal day 11, using a 100

- fold unc ertainty factorOW

– O G W DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3

- 14 (USEPA, 200 7b )

. The 2007 OPP ass essment established a chronic oral RfD for dimethoate of 0.0022 mg/kg

- day based on a 2

- year feeding study in rats with inhibition of brain ChE as the critical effect (American Cyanamid Company, 1986). The RfD was derived using the benchmark dose ( BMD ) method and based on the lower 95% confidence limit (BMDL) of 0.22 mg/kg

- day, with application of a net uncertainty factor ( UF ) of 100 (i.e., x 10 f or intraspecies variability and x10 for interspecies variability). EPA ’s OPP did not apply any uncertainty fa ctor for database deficiencies, nor apply a Food Quality Protection Act ( FQPA ) factor, indicating that the database for dimethoate was considered to be complete

. EPA calculated a non

- cancer health reference level ( HRL ) of 15.4 μg/L for dimethoate using the RfD of 0.0022 mg/kg

- day for a 70 kg adult ingesting 2 L of drinking water per day and a relative source contributio n ( RSC ) of 20%. The chronic RfD and subsequent HRL of 15.4 μg/L for dimethoate are considered to be protective of any potential cancer risk or acute ChE effects (USEPA, 1990; USEPA, 200 7b ).
The critical effect of ChE inhibition is a more sensitive endpoint compared to the reproductive and developmental endpoints (USEPA, 200 7b ); therefore no sensitive populations were identified or characteriz ed. The OPP RED presents more detailed information about the potential health effects for dimethoate (USEPA, 200 7b ).



### 3.4 Occurrence
This section presents data on the occurrence of dimethoate in ambient water and drinking water in the United States. As describ ed in Section 3 .3 , a n HRL of 15 .4 μg/L was calculated for dimethoate based on non

- carcinogenic effects. This HRL represents the concentration of the contaminant in drinking water that is likely to be present without an appreciable risk of deleterious effects during a lifetime. Occurrence data from various sources presented in the following sections are analyzed with respect to the HRL and the 1⁄2 HRL. When possible, estimates of the population exposed at concentrations above the HRL and the 1⁄2 HRL are presented

. For additional background info rmation about many of the data sources used to evaluate occurrence, please refer to Chapter 2.

3.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant occurrence in ambient water provides informat ion on the potential for contaminants to adversely affect drinking water supplies. Dimethoate was not included in USGS National Water

- Quality Assessment (NAWQA) Cycle 1 monitoring (1992

- 2001). However, dimethoate data are available from EPA’s Storage and R etrieval (STORET) Data Warehouse and from two monitoring stud ies in California

. Storage and Retrieval (STORET) Data Warehouse

EPA’s STORET Data Warehouse is a collaborative database that contains raw biological, chemical, and physical data from surface and ground water sampling conducted by federal, state and local agencies, Indian t ribes, volunteer groups, academics, and others. A wide variety of data relating to water quality from all 50 states as well as multiple territories and jurisdictions of the Unit ed States are represented in this data system . These are primarily ambient water data, but in some cases they are finished drinking water data

. Users began populating the STORET Data Warehouse in 1999. Most data are post

- 1999, but some earlier sampling is included.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-15 STORET data have quality limitations. T he extent of national coverage and data completeness varies from parameter to parameter. There are no restrictions on submission of data based on analytical methods, quality assurance ( QA ) practices, etc. For more general STORET data information, please refer to: http://www.epa.gov/storet/index.html

. EPA reviewed STORET g round water data from wells and surface water data from lakes, rivers/streams, and reservoirs (USEPA, 20 12c). The STORET Data Warehouse also included public w ater s ystem (PWS) data from three state s (Indiana, Missouri, and Ohio) ; EPA reviewed these as well (USEPA, 20 12c). (For more data gathered by state drinking water programs, see the discussion of state monitoring data in section 3.4.2.)
The results of the STORET analysis are presented in Exhibit 3-7 through Exhibit 3-10

. These STORET data represent dimethoate samples collected between 1989 and 2009. Of 798 sites (211 surface water and 587 ground water) analyzed for dimethoate , 42 (5.26%) had detections. These sites all represent ground water and surface water; no PWS data were reported for this contaminant. Detected concentrations ranged from 0 μg/L t o 0.44 μg/L, with none greater than either the 1⁄2 HRL or the HRL. Minimum detected concentratio ns are reported in Exhibit 3-7 ; these minimum values may be indicative of reporting levels used. No Indiana, Missouri, or Ohio PWS data were available for this contaminant.

Exhibit 3-7 : Dimethoate STORET Data – Summary of Detected Concentrations

Source Water Type

. Concentration Value of Detections (μg/L)

. .

. Minimum 1 Median 90 th Percentile Maximum

Ground Water 0 0 0.088 0.44

Surface Water 0 0 0.161 0.268

Total 0 0 0.161 0.44

PWS 2 N/A N/A N/A N/A N/A = not applicable (no detections in this category).

1 A minimum value of zero may represent a detection that was entered into the database as a non

- numerical value (e.g., “Present”).

2 It could not be determined from the data in STORET whether the PWS facilities were served by ground water or surface water.

Exhibit 3-8 : Dimethoate STORET Data – Summary of Samples

Source Water Type Total Number of Samples Samples with D etections . Samples with D etections > 1⁄2 HRL (7.7 μg/L) . Samples with D etections > HRL (15 .4 μg/L) .

. . Number Percent Number Percent Number Percent

Ground Water 867 9 1.04% 0 0% 0 0%

Surface Water 4,432 171 3.86% 0 0% 0 0%

Total 5,299 180 3.40% 0 0% 0 0%

PWS 1 0 0 0% 0 0% 0 0%

1 It could not be determined from the data in STORET whether the PWS facilities were served by ground water or surface water.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-16 Exhibit 3-9 : Dimethoate STORET Data – Summary of Sites

Source Water Type Total Number of Sites Sites with D etections . Sites with D etections > 1⁄2 HRL (7. 7 μg/L) . Sites with D etections > HRL ( 15 .4 μg/L) .

. . Number Percent Number Percent Number Percent

Ground Water 587 9 1.53% 0 0% 0 0%

Surface Water 211 33 15.64% 0 0% 0 0%

Total 798 42 5.26% 0 0% 0 0%

PWS 1 0 0 0% 0 0% 0 0%

1 It could not be determined from the data in STORET whether the PWS facilities were served by ground water or surface water.

E xhibit 3- 10 : Dimethoate STORET Data – Summary of States

Source Water Type Total Number of

States States with D etections . States with D etections > 1⁄2 HRL (7. 7 μg/L) . States with D etections > HRL ( 15 .4 μg/L) .

. . Number Percent Number Percent Number Percent

Ground Water 3 2 66.67% 0 0% 0 0%

Surface Water 5 2 40.00% 0 0% 0 0%

Total 1 7 4 57.14% 0 0% 0 0%

PWS 2 0 0 0% 0 0% 0 0%

1 The number of states with ground water data plus the number of states with surface water data may not equal the “Total” number of states providing data because some states provided both ground water and surface water data.

2 It could not be determined from the data in STORET whether the PWS facilities were served by ground water or surface water.

A dditional Ambient Water Studies
The California Department of Pesticide Regulation (CDPR) undertook a multiyear surface water monitoring study. The highest concentration of dimethoate, 2.4 μg/L , was detected in the San Joaquin River basin (USEPA, 2007b). This detection did not exceed the 1⁄2 HRL or the
HRL

.

A team of researchers from EPA’s National Exposure Research Laboratory investigated the magnitude and temporal variability of trace levels of agricultural pesticides in alpine lakes in the Sierra Nevada mountains. Samples were collected weekly at one lake and at 4

- week intervals at other three lakes, from mid -June to mid-October of 2003. Of 4 1 pesticides and pesticide transformation products monitored, only eight were detected (Bradford et al., 2010). The study’s supporting information indicates that dimethoate was among the chemicals monitored and not detected. It should be noted that dimethoate was observed to have poor recovery (16±3% at 1 ng/L and no recovery at 100 pg/L) associated with the solid phase extraction (SPE)- based analytical method that was used in the study, and consequently the study authors were unable to calculate a method d etection limit for dimethoate. The poor recovery was attributed to poor partitioning to the SPE rather than overloading of the SPE (Momplaisir, et al. 2010). Due to the poor recovery, the non-detection results for dimethoate are not conclusive.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-17 3.4.2 Occurrence in Drinking Water

The agency reviewed a number of data sources for information on contaminant occurrence in drinking water. Data and information on dimethoate from the following sources are available and are summarized in this section:

• EPA’s Second Unregulated Contaminant Monitoring Regulation (UCMR 2).

• State drinking water monitoring programs

.

• Consumer Confidence Reports (CCRs) from PWSs

.

• United States Department of Agriculture (USDA) Pesticide Data Program (PDP)

.

• USGS Pilot Monitoring Program (PMP)

.

• USGS NAWQA Source Water and Drinking Water Studies

.

• Estimated concentrations in environme ntal media generated by EPA OPP modeling.

• Environmental Working Group (EWG) Drinking Water Database.
Note that there may be some overlap, as sources with different purpos es and audiences may have reported the same underlying data.
Reviewed sources that contain no information on dimethoate occurrence included, among others, EPA’s First Unregulated Contaminant Monitoring Regulation (UCMR 1), Rounds 1 and
2 of EPA’s Unregulated Contaminant Monitoring (UCM) program, and EPA’s Community Water System Survey (CWSS)

. Primary Data Sources
Second Unregulated Contaminant Monitoring Regulation (UCMR 2), 2008-2010
UCMR 2 monitoring, designed to provide nationally represen tative contaminant occurrence data, was conducted from 2008 to 2010. UCMR 2 required surface water systems to monitor quarterly and ground water systems to monitor twice per year. There were two tiers of monitoring: Assessment Monitoring for contaminants with commonly used analytical method technologies, and Screening Survey monitoring for contaminants that require specialized analytical method technologies not in wide or common use.

All very large PWSs (serving more than 100,000 people) and large PWSs (se rving 10,001-100,00 0 people), plus a statistically representative national sample of 800 small PWSs (serving 10,000 people or fewer), were required to conduct Assessment Monitoring during a 12- month period between January 2008 and December 2010. For the Screening Survey, monitoring

was required by all very large PWSs, 320 representative large PWSs, and 480 representative small PWSs, during a 12-month period between January 2008 and December 2010. See USEPA (2007a), USEPA (2010b), and USEPA (2015) for more i nformation on the UCMR 2 program, including study design and data analysis.

Dimethoate was monitored under the UCMR 2 Assessment Monitoring. The minimum reporting level (MRL) used for dimethoate in this study was 0.7 μg/L

. The design of UCMR 2 permits estimat ion of nat ional occurrence . To calculate national extrapolations, the percent of systems (or population served) estimated to exceed a specifiedOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-18 threshold is multiplied by the total number of systems (or population served) in the nation. (Note that b ecause a ll large and very large systems were required to conduct UCMR 2 Assessment Monitoring, survey census figures are used in those size categories

. ) See Chapter 2 for additional information on national extrapolations.
As of July 2011, a total of 32,013 dimethoate samples have been collected from 4,138 systems. There have not been any detections of dimethoate from the systems that sampled under
UCMR 2 , and thus no exceedances of the HRL or the 1⁄2 HRL

. The fact that there have not been any detections of d imethoate from systems sampled under UCMR 2 suggests that nation- wide occurrence of th is compound is likely to be low or negligible.
Supplemental Data Sources

State Monitoring Data , 199 5-2007
Because there is no national database that receives and stores all relevant data regarding the occurrence of regulated contaminants in public drinking water systems, EPA conducted a voluntary data call

- in from the states, territories, and tribes to obtain regulated contaminant occurrence data in support of national oc currence assessments conducted for the second Six

- Year Review. For more details on the Six- Year Review -Information Collection Request (ICR) Dataset, refer to USEPA (2009a ).

A few states also submitted PWS occurrence data for unregulated contaminants. EPA was able to supplement these data on unregulated contaminants by downloading additional publicly available monitoring data from state W eb sites. The result was a collection of unregulated contaminant monitoring data from nine states, representing those sta tes with varying degrees of completeness.
Drinking water occurrence data for dimethoate were submitted from the State of California. Dimethoate results from 48% of community water systems ( CWSs ) and 35% of nontransient non- community water systems ( NTNCWSs ) in California were included in the data set. Results are presented in Exhibit 3-12 through Exhibit 3-13

. Since dimethoate data from California represent only a small portion of all PWSs in the state, the exhibits do not include estimates of population served. Precise information about methods u sed and reporting levels is not available for the state data . Minimum detected concentrations are reported in Exhibit 3-11 ; these minimum values may be indicative of reporting levels used.

An analysis of the California data set indicates that dimethoate was detected in two (0.01%) of 21,571 drinking water samples. These d etections occurred in two (0.09%) of the 2,153 systems reporting data. Detected concentrations ranged from 1 μg/L to 2 μg/L ; all we re less than the 1⁄2 HRL and the HRL.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-19 Exhibit 3- 11 : Dimethoate State Drinking Water Occurrence Data – Summary of Detected Concentrations

State (Date Range) Source Water Type . . Concentration Value of Detections (μg/L)

. .

. . Minimum Median 90 th Percentile 99 th Percentile Maximum

Ground Water 1 1.5 1.9 1.99 2

California (1995

- 2007) Surface Water N/A N/A N/A N/A N/A

Unknown N/A N/A N/A N/A N/A

Total 1 1.5 1.9 1.99 2

N /A = not applicable ( no detections in this category ).

Exhibit 3- 12 : Dimethoate State Drinking Water Occurrence Data – Summary of Sample s

State (Date Range) Source Water Type Total Number of Samples Samples with Detections . Samples with Detections > 1⁄2 HRL ( 7. 7 μg/L) . Samples with Detections > HRL (15 .4 μg/L) .

. . . Number Percent Number Percent Number Percent

Ground Water 13,719 2 0.01% 0 0% 0 0%

California (1995

- 2007) Surface Water 7,838 0 0% 0 0% 0 0%

Unknown 14 0 0% 0 0% 0 0%

Total 21,571 2 0.01% 0 0% 0 0%

E xhibit 3- 13 : Dimethoate State Drinking Water Occurrence Data – Summary of System s

State (Date Range) Source Water Type Total Number of Systems Systems with Detections . Systems with Detections > 1⁄2 HRL ( 7. 7 μg/L ) . Systems with Detections > HRL (15 .4 μg/L) .

. . . Number Percent Number Percent Number Percent

Ground Water 1,786 2 0.11% 0 0% 0 0%

California (1995

- 2007) Surface Water 356 0 0% 0 0% 0 0%

Unknown 11 0 0% 0 0% 0 0%

Total 2,153 2 0.09% 0 0% 0 0%

Wa ter Systems’ Consumer Confidence Report s (CCR s ), 1998-2007
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 stan dards; they may also include general educational material. Under the CCR Rule (40 CFR Subpart O), 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. Systems serving 100,000 or more residents areOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-20 also required to post their current CCRs on a publicly accessible Internet site. EPA reviewed CCRs published by the 26 systems that serve over one million customers for unregulated contaminant occurrence information. Data on dimethoate were available from CCRs prepared by a single CWS in New York, New York. Reporting levels were not specified in this CCR.
New York City included data on dimethoate in its 1998 through 2007 CCRs. Samples were collected fr om one or more of the city’s three distribution systems (two supplied by surface water and one supplied by treated ground water). Dimethoate was not detected in any year. The number of samples was not reported.
United States Department of Agriculture (USDA ) Pesticide Data Program (PDP), 2001-2009
The USDA PDP maintains a national pesticide residue database. PDP was initiated in 1991 to collect data on pesticide residues in food with sampling conducted on a statistically defensible representation of pesticide residuals in the United States food supply (USDA, 2011 ). Sampling and testing are conducted on fruits and vegetables, select grains, milk, and (as of 2001) drinking water.
The PDP drinking water sampling program was initiated at CWSs in New York and California in 2001. Since then the drinking water sampling program has expanded, though a somewhat changing mix of states is sampled each year. At one time or another, CWSs in 27 states and Washington, D.C. have contributed raw and/or finished water data to the program (USDA, 2011). The CWSs selected for sampling tend to be small - and medium- sized systems (primarily CWSs serving under 50,000), systems served by surface water, and systems located in regions of heavy agriculture. Sampling of raw water i n addition to finished water began in 2004 (USDA, 2004).

Dimethoate was included in th e USDA PDP ( see Exhibit 3-14 ) (USDA, 2012) . It was detected in three of 5,374 total samples (0. 05%) collected between 2001 and 2009 , with limits of detection ranging from 0.0053 to 0.063 μg/L

. Within that set, it was detected in two (0.05 %) of 3,555 finished samples collected. Th e three detection s (0.009, 0.008, and 0.068 μg/L ) did not exceed the 1⁄2 HRL or the HRL. Note that temporal trends cannot be evaluated based on these data since, with the exception of 2002 and 2003, samples were not collected from the same sites and states in consecutive years.

Exhibit 3- 14 : Summary of Dimethoate PDP Data, 2001

- 200 9

Year Finished / Raw Total Number of Samples Number of Detections Percent of Detections Minimum Value of Detections (μg/L) Maximum Value of Detections (μg/L)

2001 Finished 283 0 0% N /A N /A

2002 Finished 659 0 0% N /A N /A

2003 Finished 793 0 0% N /A N /A

2004 Finished 239 0 0% N /A N /A

. Raw 239 1 1 0.4% 0. 00 88 0. 00 88

2005 Finished 230 0 0% N /A N /A

. Raw 232 0 0% N /A N /AOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-21 Year Finished / Raw Total Number of Samples Number of Detections Percent of Detections Minimum Value of Detections (μg/L) Maximum Value of Detections (μg/L)

2006 Finished 368 0 0% N /A N /A

. Raw 369 0 0% N /A N /A

2007 Finished 368 0 0% N /A N /A

. Raw 364 0 0% N /A N /A

2008 Finished 309 0 0% N /A N /A

. Raw 309 0 0% N /A N /A

2009 Finished 306 2 0.7% 0.0075 0.068

. Raw 306 0 0% N /A N /A N/A = not applicable (no detections in this category).

1 Only one distinct detected concentration was reported.

U

SGS Pilot Monitoring Program (PMP), 1999
In 1999, a PMP was initiated by USGS and EPA to provide information on pesticide concentrations in drinking water. This study focused on small drinking water supply reservoirs in

areas with high pesticide use in order to test the sampling approach in areas where pesticides are probably present (Blomquist et al

. , 2001). Sampling sites represent a variety of geographic regions, as well as different cropping patterns. The ideal site candida tes were mostly small reservoirs located in high pesticide-use areas with a high runoff potential. Twelve water-supply reservoirs considered vulnerable to pesticide contamination were selected from the list of candidates. These 12 sites were located in Cal ifornia, 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 pesticid e- application periods. Water samples were collected from the raw

water intake and from the finished drink ing water tap prior to entering the distribution system. At some sites, samples were also collected at the reservoir outflow.
Dimethoate was an analyte in the PMP . At a method reporting level of 0.005 μg/L

, dimethoate was detected in four (1.3%) of the 317 samples taken from raw water sites, with a maximum concentration of 0.022 μg/L , less than the 1⁄2 HRL and the HRL. Dimethoate was not detected in any of the 221 samples taken from finished water sites (Blomquist et al. , 2001).
USGS National Water Quality Assessment (NAWQA) Source Water and Drinking Water Studies
Organic Compounds in Source Water of Selected Community Water Systems (Hopple et al., 2009 and Kingsbury et al., 2008), 2002-2005
As part of the NAWQA program, Hopple et al. (2009) and Kingsbury et al. (2008) conducted studies to characterize anthropogenic organic compounds in U.S. waters used as

source waters for PWSs. Hopple et al

. (2009) focused on ground water and Kingsbury et al. (2008) focused on surface water. In Phase 1 of the studies ( Exhibit 3-15 ), geographically diverse source water samples were collected between O ctober 2002 and July 2005 from nine CWSs served by streams and from 221 CWS wells that withdraw from 12 aquifers. D imethoate was not detected in any of the 221 ground water samples and was detected in two (1.4%) of 146 surfaceOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-22 water samples at levels less than 0.01 μg/L , which is less than the 1⁄2 HRL and the HRL. In Phase 2 of the studies, USGS collected source and finished water samples at a subset of sites between June 2004 and September 2005. In this ph ase, 48 raw and 48 finished ground water samples were analyzed for dimethoate; it was not detected in any of these samples (Hopple et al. , 2009). Dimethoate was not included in the surface water portion of Phase 2 (Kingsbury et al. , 2008). Phase 2 results are presented in Exhibit 3-16 . The reporting level for dimethoate was 0.0061 μg/L in both phases, for both ground and surface water samples.

Exhibit 3- 15 : Dimethoate Data from Source Water (Hopple et al. , 2009 and Kingsbury et al., 2008) – Summary of Detections from Phase 1

. . Ground Water

. . Surface Water

.

Number of Samples Percent of Detections : All Percent of Detections :

> 0.01 μg/L Maximum Concentration (μg/L) Number of Samples Percent of Detections : All Percent of Detections :

> 0.01 μg/L Maximum Concentration (μg/L)

221 0% 0% N /A 146 1.4% 0% 0.009 N/A = not applicable (no detections in this category).

E xhibit 3- 16 : Dimethoate Data from Source Water (Hopple et al. , 2009) – Summary of Detections from Phase 2 – Ground Water

Number of Samples

. Percent of Detections

. Maximum Concentration (μg/L)

.
Raw Water Finished Water Raw Water Finished Water Raw Water Finished Water

48 48 0% 0% N /A N /A N/A = not applicable (no detections in this category).

O PP Estimated Concentrations
EPA’s OPP used modeling to develop estimated drinking water concentrations (EDWCs) for acute and chronic dimethoate exposure scenarios involving ground water (USEPA, 2007b ).The EDWCs were developed using the Screening Concentrations in Ground Water (SCIGROW) model. In ground water, the EDWC value for dimethoate was 0.04 μg/L for both acute and chronic exposures. This value is less than the 1⁄2 HRL and the HRL

. Environmental Working Group (EWG) Drinking Water Database, 2004-2009

In December 2009, EWG released its “National Drinking Water Database

, ” which includes data on occurrenc e of drinking water contaminants (regulated and unregulated) collected between 2004 and 2009 from 45 states and the District of Columbia (EWG, 2009). The 2009 EWG database includes results from approximately 48,000 water systems; data were obtained pri marily from state water offices.
EWG reviewed the data for inconsistencies, potential outliers, and other errors. It also invited the American Water Works Association (AWWA) and the Association of Metropolitan Water Agencies (AMWA) to review the data and/or ha ve their constituents, the PWSs, review the data. Some corrections apparently were made since the public release of the data in December , 2009. The data analyzed by EPA were downloaded on December 29 , 2010. EPA’sOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-23 analysis is based solely on the data made publicly available by EWG on its W eb site. Reporting levels are not specified in EWG’s database.

As of November 10, 2010, a total of 1,153 systems reported having tested for dimethoate between 2004 and 2009. No detections of dimethoate were found.



### 3.5 Technology Assessment

3.5.1 Analytical Methods
EPA has developed one analytical method for the analysis of dimethoate in drinking

water:

• EPA Method 527, Revision 1.0, Determination of Selected Pesticides and Flame Retardants in Drinking Water by Solid Phase Extraction and Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS), has a Detection Limit (DL) of 0.025 μg/L. The Lowest Concentration Minimum Reporting Level (LCMRL) is 0.36 μ g/L. Recoveries range from 78 to 114%, with Relative Standard Deviations (RSDs) of 2.6 to 7.1% (USEPA, 2005).
Although not listed in EPA Method 527, the MRL for dimethoate is 0.7 μg/L. This value

serve d as a national benchmark for labo ratories that participat ed in UCMR 2 using EPA Method 527 (72 FR 367; USEPA, 2007a ). The MRL for dimethoate was determined by EPA using data generated from EPA Method 527.
An estimated reporting level for the method (calculated as the MRL) was compared to the HRL for dimethoate to determine whether the available analytical method is capable of reliable quantitation at concentrations of estimated toxicological concern (see Exhibit 3-17 ). The Method Sensitivity Ratio (MSR) is calculated from the following equation:
MSR = HRL (μ g/L ) / MRL (μ g/L )

A favorable MS R is one that is greater than t en . That is, it is prefer able that the HRL be at least ten times above the concentration at which data can be reliably reported; this provides a margin of safety for uncertainty in the HRL and/or method performance (see USEPA, 2009b).

Exhibit 3- 17 : Method Sensitivity Ratio (MSR) for Dimethoate

Method MRL (μg/L) HRL ( μ g/L) MSR

527 0.7 15.4 22

T he MSR is greater than ten; hence, the available analytical method is capable of reliable quantitation at least ten times below the HRL.

3.5.2 Treatment Technologies
The availability of treatment technologies is not a factor EPA considers when making a regulatory determination. However, suitable treatment technologies must be made available before a n ational p rimary d rin king w ater regulation (NPDWR) can be promulgated.
A preliminary review of the literature reveals that the following treatment technologies have been investigated empirically for their applicability to this contaminant:OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-24 • Granular activated carbon (GAC)

.

• Pow dered activated carbon

.

• Conventional (coagulation, flocculation, sedimentation, filtration).

• Chlorine.

• Ozone.

• UV light (including photocatalysis).

• Riverbank filtration

.

• Nanofiltration

.

• Reverse osmosis

.

• Ultrafiltration

.

• Softening.

• Advanced oxidation processes (combinations of two or more oxidants including UV/peroxide, ozone/peroxide).

• Air stripping

.

• Ion exchange

. Based on percentage -removal values reported in the reviewed literature, the most promising options appear to be advanced oxidation processes, ozone, reverse osmosis, and chlorine.
Please note that the literature review was not exhaustive, and findings from the reviewed studies might not be directly comparable. A full assessment of treatment technology applicability will require a more detail ed review and analysis of the literature, and possibly additional research.



### 3.6 Regulatory Determination

3.6.1 Making Regulatory Determinations for Chemicals on the CCL
The statutory requirements for the CCL and regulatory determinations can be found in SDWA Section 1412(b)(1). The 1996 SDWA Amendments require EPA to publish the CCL every five years. The CCL is a list of contaminants that are not subject to any proposed or promulgated NPDWRs, are known or anticipated to occur in PWSs, and may require regulation under SDWA to protect public health. The 1996 SDWA Amendments also direct EPA to determine whether or not to regulate at least five contaminants from the CCL every five years. There are three criteria to be considered in making a regulatory determination. A dec ision to regulate is warranted if :

(a) the contaminant may have an adverse effect on the health of persons;

(b) the contaminant is known to occur or there is substantial likelihood that the contaminant will occur in PWS s with a frequency and at levels of public health concern; andOW

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- 25 (c) in the sole judgment of the Administrator, regulation of such contaminant presents a meaningful opportunity for health risk reduction for persons served by PWS s.

If EPA determines that all three of these statutory criteri a are met , it makes a preliminary positive regulatory determination that a n NPDWR 1 is needed . Following a comment response period and a final positive regulatory determination, t he a gency has 24 months to publ ish a proposed Maximum Contaminant Level Goal 2 (MCLG) and an NPDWR. After the proposal, the

a gency has 18 months to publish a final MCLG and promulgate a final NPDWR (SDWA section 1412(b)(1)(E)). 3 The agency may determine that there is no need for a regulation when a contaminant fails to meet one or mo re of the criteria. A decision not to regulate is considered a final agency action and is subject to judicial review. The agency can choose to publish a Health Advisory (a non

- regulatory action) or other guidance for any contaminant on the CCL, independent of the regulatory determination. Refer to section 1.4 for a summary of the approach used to identify and evaluate contaminants for RD 3. The following section summarizes the RD 3 decision for dimethoate.

3.6.2 Health Effects (Criterion #1)

The first criterion asks if the contaminant may have an adverse effect on the health of

persons. Since all chemicals have adverse effects at some level of exposure, the challenge is to identify a n HRL, a dose below which adverse health effects are considered unlikely to occur (threshold toxicant), or below which adverse effects have a defined low probability of occurrence (non

- threshold toxicant). The key elements that must be considered in evaluating the first criterion are the mode of action, the critical effect(s), the dose

- response for critical effect(s), the RfD for threshold effects, and the slope factor for non

- threshold effects.
A full description of the health effects associated with exposure to dimethoate is presented in section 3. 3 of this document.

Health Criterion Data
Dimethoate is rapidly metabolized in mammals. Dimethoate affects the proper function of the nervous system by inhibiting ChE, an important enzyme involved in neurotransmission. ChE inhibition is mediated by the primary toxic metabolite of dimethoate, which is omethoate. ChE inhibition is the most sensitive endpoint described in numerous studies with adult and juvenile animals, involving oral, dermal, or inhalation exposures to dimethoate or omethoate (USEPA, 200 7b ). Dimethoate causes equivocal hemolymp horeticular tumors in male B6C3F1 mice and a weak response for combined spleen (hemangioma and hemangiosarcoma), skin (hemangiosarcoma), and lymph (angioma and angiosarcoma) tumors in male Wistar rats (USEPA, 1990; USEPA, 200 7b ). Dimethoate is also positiv e in some mutagenic assays.

1 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 for public water systems for a specific contaminant or group of contaminant s.

2 The MCLG is the "maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, and which allows an adequate margin of safety. Maximum contaminant level goals are non

- enforceable health goals." (CFR 141.2)

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

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- 26 A chronic study based on inhibition of brain ChE in rats (American Cyanamid Company, 1986) was identified as the critical study for establishing a chronic oral RfD of 0.0022 mg/kg

day (USEPA, 200 7b ). The RfD was derived using the BMD method . It is based on the lower 95% confidence limit (BMDL) of 0.22 mg/kg

- day, with a net UF of 100 for intraspecies and interspecies variability. EPA calculated a non

- cancer HRL of 15.4 μg/L for dimethoate using the RfD of 0.0022 mg/kg

- day for a 70 kg adult ingesting 2 L of drinking water per day and a RSC of 20%. The chronic RfD and subsequent HRL of 15.4 μg/L for dimethoate are considered to be protective of any potential cancer risk or acute ChE effects (USEPA, 1990; USEPA, 200 7b ).

The USEPA’s CARC classified dimethoate as a Group C carcinogen (a possible human carcinogen) in 1991, with concurrence from the FIFRA SAP on the agency’s classification in 1992. The Group C finding was based on equivocal hemolymphoreticular tumors in the mouse study and on the fact that the rat carcinogenicity study showed a weak effect of combined spleen (hemangioma and hemangiosarcoma), skin (hemangiosarcoma), and lymph (angioma and angiosarcoma) tumors that lacked a dose

- response effect.

Health Criterion Conclusio n Toxicological data from animal studies indicate that dimethoate is a ChE inhibitor . Data on cholinesterase inhibition in rats support the development of an HRL of 15.4 μg/L for human exposure via drinking water. Based on these considerations, EPA conclud es that dimethoate meets the SDWA statutory criterion #1 for regulatory determination ; it may have an adverse effect on the health of persons.

3.6.3 Occurrence in Public Water Systems (Criterion #2)

The second criterion asks if the contaminant is known to occur or if there is a substantial likelihood that the contaminant will occur in PWSs with a frequency and at levels of public health concern. In order to address this question, EPA consulted a variety of information sources, including data from the UCMR 2 Scree ning Survey, a nationally representative survey of PWSs conducted from 2008 to 2010. EPA examined the total number of systems that reported detections of dimethoate, as well as those that reported concentrations of dimethoate above the HRL of 15.4 μg/L.

Av ailable monitoring data, including data that may shed light on regional and national occurrence, are presented in section 3. 4. Additional information on production, use, and fate is found in section 3. 2.

Occurrence Criterion Data
The primary occurrence dat a for dimethoate are recent (2008

- 2010) nationally

representative drinking water monitoring data generated through EPA’s UCMR 2. Dimethoate was not detected in any of the 32,013 UCMR 2 samples collected by 4,138 PWSs at levels greater than the 1⁄2 HRL (7.7 μ g/L), the HRL (15.4 μg/L), or the MRL (0.7 μg/L).
The State of California reported results from testing 24,571 finished drinking water samples from 2,153 PWSs; dimethoate was detected in two samples from two different PWSs. The detected concentrations (1 μ g/L and 2 μg/L) were less than the 1⁄2 HRL and the HRL. The USDA PDP monitored for dimethoate in finished water from 2001 to 2009 and found only two detections in 3,555 samples; both detected concentrations were less than the 1⁄2 HRL and the HRL. The USGS PMP monitored for dimethoate in finished water in 1999 and found no detections greater than 1⁄2 the HRL or the HRL in any of the 221 samples.OW

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– Chapter 3, Dimethoate

3

- 27 Dimethoate occurrence data for ambient water are consistent with those for finished drinking water. The USGS PMP also m onitored for dimethoate in ambient water in 1999 and found no detections greater than the 1⁄2 HRL or the HRL in any of the 317 samples. Mixed source and finished water data were gathered in a two

- phase USGS study conducted between 2002 and 2005 by Hopple et al. (2009) and Kingsbury et al. (2008). There were no detections in the 221 Phase 1 groundwater samples. Only two detections were reported from 146 Phase 1 surface water samples at nine PWSs. The highest concentration detected was 0.009 μg/L, which is less than the 1⁄2 HRL and the HRL. In Phase 2, there were no detections of dimethoate from 48 raw and finished water groundwater samples. There were no Phase 2 surface water results for dimethoate. Ambient water data in STORET included no measured results above 0.44 μg/L in 5,299 samples from 798 sites. Ambient water data reported by the California Department of Pesticide Regulation included no measured results above 2.4 μg/L.

Occurrence Criterion Conclusion
Dimethoate was not detected in any of the 32,013 UCMR 2 samples collected by 4,138 PWSs at levels greater than the 1⁄2 HRL (7.7 μg/L), the HRL (15.4 μg/L), or the MRL (0.7 μg/L). Additional data from states, USDA, and USGS confirm that dimethoate occurrence at levels of public health concern is rare. Based on th ese considerations, EPA concludes that dimethoate does not meet the SDWA statutory criterion #2 for regulatory determination; it does not occur with a frequency and at levels of public health concern in public water.

3.6.4 Risk Reduction (Criterion #3)

The third criterion asks if, in the sole judgment of the Administrator, regulation presents a meaningful opportunity for health risk reduction for persons served by PWSs

. In evaluating this criterion, EPA looked at several factors.
EPA calculated the total exposed population and the population exposed to levels above the HRL. Estimates of the populations exposed and the levels to which they are exposed were derived from the monitoring results. These estimates are included in section 3. 4 and summarized in the “Expose d Population Estimates” section.
In evaluating the third criterion, EPA also considered effects on potentially sensitive populations, including the fetus, infants, and children. Sensitive population considerations are discussed in the following “Sensitive Populations” section.
Exposed Population Estimates
The estimated population exposed to dimethoate at levels of public health concern is 0%; it was not found to occur at levels above the HRL (or the 1⁄2 HRL) in 4,138 PWSs and 32,013 samples from the UCMR 2 monitoring. In addition, other supplementary sources of finished water and ambient water data indicate that the occurrence of dimethoate in PWSs is likely to be low to non

- existent.
Sensitive Populations
EPA also evaluated whether information is available regarding the potential health effects on children a nd other sensitive populations. The database for dimethoate includes a 3

- generation reproductive study in mice, developmental (teratology) studies in rats and rabbits, and a neurodevelopmental toxicity study (USEPA, 1990, 200 7b ). The critical effect of ChE inhibition is a more sensitive endpoint compared to the reproductive and developmental endpoints (USEPA, 200 7b ); therefore no sensitive populations were identified or characterized. The OPPOW

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– Chapter 3, Dimethoate

3

- 28 RED (USEPA, 200 7b ) presents more detailed information about the p otential health effects and sensitive populations for dimethoate.

Risk Criterion Conclusion

Based on the estimated exposed population, including sensitive subpopulations , EPA has determined that dimethoate does not meet the SDWA statutory criterion #3 fo r regulatory determination; regulation of dimethoate does not present a meaningful opportunity health risk reduction for persons served by PWSs.

3.6.5 Final Regulatory Determination Decision

As stated in section 3.6.1 , a positive finding for all three criteria is required in order to make a determination to regulate a contaminant. EPA has made a final determination under RD 3 that dimethoate does not meet all three criteria.
Dimethoate has the potential to cause adverse health effects, including cholinesterase inhibition. However, dimethoate does not appear to occur in PWS s with a frequency and at levels of public health concern. Dimethoate was not detected in any of the 32,013 UCMR 2 samples collected by 4,138 PWSs at levels greater than the 1⁄2 HRL (7.7 μg/L), t he HRL (15.4 μg/L), or the MRL (0.7 μg/L). Due to the relatively small number of people likely exposed to dimethoate through drinking water, EPA concludes that regulation of dimethoate does not represent a meaningful opportunity for health risk reduction f or persons served by PWS s

. Additional information about the final regulatory determination can be found in the Federal Register n otice.



### 3.7 References
American Cyanamid Company. 1986. MRID No. 00164177, 40545501. (as cited in USEPA,
2008 ).
Blomquist, J.D., J.M. Denis, J.L. Cowles, J.A. Hetrick, R.D. Jones, and N.B. Birchfield. 2001. Pesticides in Selected Water

- Supply Reservoirs and Finished Drinking Water, 1999

- 2000: Summary of Results from a Pilot Monitoring Survey . U.S. Geological Survey Open

- File Report 01

- 456. 65 pp. Available on the Internet at: http://md.water.usgs.gov/nawqa/OFR_01

- 456.pdf

. Bradford, D.F, E.M. Heithmar, N.G. Tallent

- Halsell, G.

- M. Momplaisir, C.G. Rosal, K.E

. Varner, M.S. Nash, and L.A. Riddick. 2010. Temporal Patterns and Sources of Atmospherically Deposited Pesticides in Alpine Lakes of the Sierra Nevada, California,
USA. Environmental Science & Technology . 44: 4609

– 4614.

ChemIDPlus. 2009. Available on the Internet at: http://chem.sis.nlm.nih.gov/chemidplus/

. Accessed August 10, 2009.
Environmental Working Group (EWG). 2009. National Drinking Water Database. Available on the Internet at: http://www.ewg.org/tap

- water/home . Accessed December 29, 2010.
Hopple, J.A., G.C. Delzer, and J.A. Kingsbury. 2009. Anthropogenic O rganic C ompounds in
S ource W ater of S elected C ommunity W ater S ystems that U se G roundwater , 2002

- 05

. U.S. Geological Survey Scientific Investigations Report 2009

- 5200

. 74 p p. Available on the Internet at: http://pubs.usgs.gov/sir/2009/5200/pdf/sir2009

- 5200.pdf

.OW

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3

- 29 Hazardous Substances Data Bank (HSDB). 2009. Available on the Internet at: http://toxnet.nlm.nih.gov/cgi

- bin/sis/htmlgen?HSDB . Accessed August 10, 2009.

HSDB. 2010. Available on the Intern et at: http://toxnet.nlm.nih.gov/cgi

- bin/sis/htmlgen?HSDB

. Accessed September 2010.
Kingsbury, J.A., G.C. Delzer, and J.A. Hopple. 2008. Anthropogenic O rganic C ompounds in
S ource W ater of N ine C ommunity W ater S ystems that W ithdraw from S treams, 2002

- 05

. U.S. Geological Survey Scientific Investigations Report 2008

- 5208

. 66 p p. Available on the Internet at: http://pubs.usg s.gov/sir/2008/5208/pdf/sir2008

- 5208.pdf

. Momplaisir, G.

- M., C.G. Rosal, E.M. Heithmar, K.E. Varner, L.A. Riddick, D.F. Bradford, N.G. Tallent

- Halsell. 2010. Development of a solid phase extraction method for agricultural pesticides in large

- volume water s amples. Talanta , 81: 1380

– 1386
National Center for Food and Agricultural Policy (NCFAP). 2003. National Pesticide Use Database. Available on the Internet at: http://www.ncfap.org/pesticideuse.html

. Per sistence, Bioaccumulation, and Toxicity ( PBT ) Profiler. 2009. Available on the Internet at: http://www.pbtprofiler.net/ . Accessed August 10, 2009.
Risk Assessment Information System (RAIS). 2009. Available on th e Internet at: http://rais.ornl.gov/ . Accessed August 10, 2009.
Speth, T. and R. Miltner. 1990. Technical note: GAC adsorption capacities for SOCs. Journal of the American Water Works Association . 82 ( 2 ) :72.

U nited States Department of Agriculture (U SDA ) . 2004. USDA Pesticide Data Program Water Monitoring Survey Overview . 11 March 2004. Available on the Internet at: http://www.am s.usda.gov/AMSv1.0/getfile?dDocName=PDPWATOVIEW

. USDA. 2011. Pesticide Data Program, Annual Summary, Calendar Year 2009 . May 2011. Available on the Internet at: http://www.ams .usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5091055

. USDA. 2012. PDP

- Databases and Annual Summaries. Available on the Internet at: http://www.ams.usda.gov/AMSv1.0/ams.fetchTemplateData.do?template=TemplateG&to pNav=&leftNav=ScienceandLaboratories&page=PDPDownloadData/Reports&descriptio n=Downloa d+PDP+Data/Reports&acct=pestcddataprg . Accessed February 15, 2012.
United States Environmental Protection Agency (USEPA). 1990. IRIS Summary for Dimethoate. Available on the internet at: http://www.epa.gov/ncea/iris/subst/0044.htm .

USEPA. 1996. 1996 Toxic s Release Inventory: Public Data Release Report . Chapter 3: Year

- to

Year Comparison of Toxics Release Inventory Data. Available on the Internet at: http://www.epa.gov/tri/tridata/tri96/pdr/ chap3.pdf

. USEPA. 2004 a

. The Toxics Release Inventory (TRI) and Factors to Consider When Using TRI
Data. Available on the Internet at: http://www.epa.gov/tri/triprogram/FactorsT oConPDF.pdf . File created June 14 , 2004. Accessed February 22, 2011.

USEPA. 2004b. Pesticides Industry Sales and Usage 2000 and 2001 Market Estimates

. Available on the Internet at: http://www.epa.gov/opp00001/pestsales/01pestsales/market_estimates2001.pdf

.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 3, Dimethoate

3-30 USEPA. 2005. Method 527. Determination of Selected Pesticides and Flame Retardants in Drink ing Water by Solid Phase Extraction and Capillary Column Gas Chromatography/Mass Spectrometry (GS/MS). Revision 1.0. Technical Support Center, Office of Ground Water and Drinking Water. EPA 815-R-05-005.

USEPA. 2007a. Unregulated Contaminant Monitoring Regulation (UCMR) for Public Water Systems Revisions. Federal Register. Vol. 72, No. 2, p. 367, January 4, 2007.

USEPA. 2007b. Revised Interim Reregistration Decision for Dimethoate . Available on the
Internet at: http://www.epa.gov/pesticides/reregistration/REDs/dimethoate_ired_revised.pdf

. USEPA. 2009a. The Analysis of Regulated Contaminant Occurrence Data from Public Water Systems in Support of the Second Six- Year Review of National Primary Drinking Water Regulations . EPA -815-B-09-006. October 2009.

USEPA. 2009b. Final Contaminant Candidate List 3 Chemicals: Classification of the PCCL to
CCL. Office of Water. EPA 815 -R-09-008.
USEPA. 2009c. Drinking Water Contaminan t Candidate List 3 –Final. Federal Register . Vol. 74, No. 194, p. 51850, October 8, 2009.

USEPA. 2010a. Non-confidential IUR Production Volume Information . Available on the Internet

at: http://www.epa.gov/iur/tools/data/2002-vol.html

. USEPA. 2010b. Data Management and Analytical Plan for the Second Unregulated Contaminant Monitoring Regulation (UCMR 2) Data. June 2010 Draft Report Submitted
to EPA.

USEPA. 2011. Pesticide Industry Sales and Usage: 2006 and 2007 Market Estimates . Biological and Economic Analysis Division, Office of Pesticide Programs. Available on the Internet

at: http://www.epa.gov/opp00001/pestsales/

. USEPA. 2012a. Che mical Data Reporting/Inventory Update Reporting : Basic Information. http://www.epa.gov/iur/pubs/guidance/basic.html . Last updated August 23, 2012.
USEPA. 2012b. TRI Explorer: Trends. Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm

. USEPA. 2012c . Storage and Retrieval (STORET) Data Warehouse. Available on the Internet at: http://www.epa.gov/storet/index.html . Data Warehouse consulted March 2012.

USEPA. 2015. Occurrence Data from the Second Unregulated Contaminant Monitoring Regulation (UCMR 2). Including Appendices A-C. EP A 815-R-15-013. December 2015.

U nited States Geological Survey (U SGS ). 2015 . Pesticide National Synthesis Project, Annual Pesticide Use Maps , 1992-2012. Available on the Internet at: http://water.usgs.gov/nawqa/pnsp/usage/maps/index.php

. Accessed September 24, 2015.OW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-1 

# Chapter 4: 1,3-Dinitrobenzene

A chapter from:

Regulatory Determination 3 Support Document

EPA Report 815 -R- 15

- 014

December 2015OW

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- 2OW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-3 

### Contents

Contents .......................................................................................................................................... 3 Exhibits ................................ ........................................................................................................... 4 Abbreviations ................................ .................................................................................................. 5
4.1 Contaminant Background , Chemical and Physical Properties ............................................7 4.2 Sources and Environmental Fate .........................................................................................8
4.2.1 Production, Use, and Release...................................................................................8
4.2.2 Environmental Fate ................................................................................................10
4.3 Health Effects .....................................................................................................................11
4.4 Occurrence .........................................................................................................................13
4.4.1 Occurren ce in Ambient Water ...............................................................................13
4.4.2 Occurrence in Drinking Water ...............................................................................15 4.5 Technology Assessment .....................................................................................................16 4.5.1 Analytical Methods ................................................................................................16
4.5.2 Treatment Technologies .........................................................................................17
4.6 Regulatory Determination ..................................................................................................17
4.6.1 Making Regulatory Determinations for Chemicals on the CCL ...........................17
4.6.2 Health Effects (Criterion #1) .................................................................................18
4.6.3 Occurrence in Public Water Systems (Criterion #2) ..............................................19
4.6.4 Risk Reduction (Criterion #3) ................................................................................20
4.6.5 Final Regulatory Determination Decision .............................................................21
4.7 References ..........................................................................................................................21OW – OGW DW Re gulatory Determination 3 Support Document

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4-4 

### Exhibits

Exhibit 4-1: Chemical Structure of 1,3-Dinitrobenzene ................................................................. 7 Exhibit 4- 2 : Physical and Chemical Properties of 1,3 -Dinitrobenzene .......................................... 8 Exhibit 4-3: Annual Production and Importation of 1,3-Dinitrobenzene in the United States (pounds) .......................................................................................................................................... 9 Exhibit 4-4: Environmental Releases (in pounds) of 1,3-Dinitrobenzene in the United States, 1997-2010 ..................................................................................................................................... 10 Exhibit 4- 5 : Summary of Total Releases and Total Surface Water Discharges of 1,3

- Dinitrobenzene, 2002, 2004, 2006, 2008, and 2010 ..................................................................... 10 Exhibit 4-6 : 1,3- Dinitrobenzene STORET Data
– Summary of Detected Concentrations

.......... 14 Exhibit 4-7 : 1,3- Dinitrobenzene STORET Data
– Summary of Samples

.................................... 14 Exhibit 4-8 : 1,3- Dinitrobenzene STORET Data
– Summary of Sites

.......................................... 15 Exhibit 4-9 : 1,3- Dinitrobenzene STORET Data
– Summary of States

........................................ 15 Exhibit 4-10: Method Sensitivity Ratio (MSR) for 1,3-Dinitrobenzene ...................................... 17OW

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– Ch apter 4, 1,3

- Dinitrobenzene

4

- 5 

### Abbreviations

ATSDR Agency for Toxic Substances and Disease Registry

ATSDR MRL ATSDR Minimum Risk Level

CAS Chemical Abstracts Service

CCL Contaminant Candidate List

CCL 3 Third Contaminant Candidate List

CCR Consumer Confidence Report

CFR Code of Federal Regulations

CWSS Community Water System Survey

DL Detection Limit

EPA Environmental Protection Agency

EPCRA Emergency Planning and Community Right

- to

- Know Act

FR Federal Register

GAC Granular Activated Carbon

GC Gas Chromatography

HSDB Hazardous Substances Data Bank

HRL Health Reference Level

IRIS Integrated Risk Information System

IUR Inventory Update Reporting

LOAEL Lowest Observed Adverse Effect Level

LCMRL Lowest Concentration Minimum Reporting Level

MCL Maximum Contaminant Level

MCLG Maximum Contaminant Level Goal

MRL Minimum Reporting Level

MS Mass Spectrometry

MSR Method Sensitivity Ratio NAWQA National Water

- Quality Assessment

NDWAC National Drinking Water Advisory Council

NOAEL No Observed Adverse Effect Level

NPDWR National Primary Drinking Water Regulation

PBT Persistence, Bioaccumulation, and Toxicity

PWS Public Water System QA Quality Assurance

RAIS Risk Assessment Information System

RD 3 Third Regulatory Determination

RfD Reference Dose

RSC Relative Source Contribution

RSD Relative Standard Deviation

SDWA Safe Drinking Water Act

STORET Storage and Retrieval

TRI Toxics Release Inventory

TSCA Toxic Substances Control ActOW

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– Ch apter 4, 1,3

- Dinitrobenzene

4

- 6 UCM Unregulated Contaminant Monitoring

UCMR 1 First Unregulated Contaminant Monitoring

UCMR 2 Second Unregulated Contaminant Monitoring

UF Uncertainty Factor

USEPA United States Environmental Protection Agency

USGS United States Geological Survey

UV UltravioletOW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-7 

### Chapter 4: 1,3

- Dinitrobenzene

The Environmental Protection Agency (EPA) has evaluated 1,3-dinitrobenzene for possible regulation as a drinking water contaminant. 1,3-Dinitrobenzene was listed on the agency’s third Contaminant Candidate List (CCL 3) and was considered for regulation as part of the third R egulatory Determination (RD 3) under the Safe Drinking Water Act (SDWA) provisions. On October 20, 2014, EPA issued a preliminary determination not to regulate 1,3- dinitrobenzene (79 FR 62715 ). A final determination not to regulate 1,3-dinitrobenzene is issued in the Federal Register notice which this support document accompanies.

Informat ion on the CCL 3 /RD 3 process is found in Chapter 1. Background on data sources used to evaluate CCL 3 /RD 3 chemicals is found in Chapter 2. This chapter presents information and analysis specific to 1,3-dinitrobenzene, including background information on the contaminant, information on sources and environmental fate , an analysis of health effects, an analysis of occurrence in ambient and drinking water, and information about the availability of analytical methods and treatment technologies. A summary of EP A's decision regarding 1,3- dinitrobenzene under RD 3 appears at the end of this chapter. (The decision is presented formally in the associated Federal Register notice).



### 4.1 Contaminant Background, Chemical and Physical Properties

1,3- Dinitrobenzene is a nitr o aromatic compound that is used as an industrial chemical and in the production of munitions and other substances. Synonyms for 1,3-dinitrobenzene include m-dinitrobenzene, binitrobenzene, and 1,3-dinitrobenzol (HSDB, 2009).

Exhibit 4-1 presents the structural formula for 1,3-dinitrobenzene. P hysical and chemical properties and other reference i nformation are listed in Exhibit 4-2

.

Exhibit 4-1 : Chemical Structure of 1,3

- Dinitrobenzene

Source: ChemIDPlus/National Library of MedicineOW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-8 Exhibit 4-2 : Physical and Chemical Properties of 1,3

- Dinitrobenzene

Property Data

Chemical Abstracts Service (CAS) Registry Number 99

- 65 -0

EPA Pesticide Chemical Code Not applicable

Chemical Formula C 6 H 4 N 2 O 4 Molecular Weight 168.11 g/mol ( RAIS, 2009; HSDB, 2009; ChemIDPlus, 2009 )
Color/Physical State Pale white or yellow, crystalline solid (HSDB, 2010)
Boiling Point 302.8 deg C ( HSDB, 2009 )
Melting Point 89

- 90 deg C (HSDB, 2010)
Density 1.575 at 18 deg C/4 deg C (HSDB, 2010)
Freundlich Adsorption Coefficient 1,080 ( μ g/g)(L/ μ g) 1/n (Speth and Miltner, 1990)
Vapor Pressure 0.0002 mm Hg at 25 deg C ( HSDB, 2012 )
Henry’s Law Constant 4.9E

- 08 atm -m 3 /mol ( HSDB, 2009; ChemIDPlus , 2009 )
Log K ow 1.49 (dimensionless) ( RAIS, 2009; HSDB, 2009; ChemIDPlus, 2009 )

K oc 150 L/kg ( HSDB, 2010 )
Solubility in Water 533 mg/L ( RAIS, 2009; HSDB, 2009; ChemIDPlus, 2009 )

Other Solvents Very soluble in acetone and ethanol; soluble in ether (HSDB, 2010)

. 1 ppm (v/v) = 0.145 mg/m 3
Conversion Factors (at 25 deg C, 1 atm) 1 mg/m 3 = 6.88 ppm (v/v)

. (calculated)
Note: “-- ” indicates that no information was found.



### 4.2 Sourc es and Environmental Fate

4.2.1 Production , Use , and Release
As noted above, 1,3-dinitrobenzene is a nitro aromatic compound that is used as an industrial chemical and in the production of munitions and other substances. There are no known natural sources of 1,3-dinitrobenzene.

Production data for 1,3- dinitrobenzene are available from EPA’s Inventory Update
Re porting (IUR) program, and industrial release data are available from EPA’s Toxics Release Inventory (TRI), as described below.
Chemical Update System (CUS) – Inventory Update Reporting (IUR) Program

EPA collects information on chemicals manufactured in or imported into the United States from the Toxic Substances Control Act (TSCA) Chemical Substance Inventory. The IUR regulation requires manufacturers and importers of 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. Note that, 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 limite d to more basic manufacturing information such as production volume. Because of changes in minimum thresholds and other program modifications, the results from 2006 might not be directly comparable to results from earlier years (USEPA, 2010a ).OW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-9 The Chemical Update System – Inventory Update Reporting ( CUS

- IUR ) assigns one of eight production and importation volume ranges for each chemical included in the inventory. The ranges used for the 2006 reports differ slightly from those used in the 1986 through 2002 reports. Exhibit 4-3 presents the production and importation of 1,3-dinitrobenzene in the United States for 1986. (No data were reported for any other years.) Production and importation of 1,3- dinitrobenzene in the United States was between 10 and 50 million pounds in 1986.

Exhibit 4-3 : Annual Production and Importation of 1,3

- Dinitrobenzene in the United States (pounds)

. . . Chemical Inventory Update Reporting Cycle

. . .

. 1986 1990 1994 1998 2002 2006 Range of Production / Importation

Volume > 10 million – 50 million

pounds No Reports No Reports No Reports No Reports No Reports

T

oxics Release Inventory (TRI)
EPA established TRI in 1987 in response to Section 313 of the Emergency Planning and Community Right- to

- Know Act (EPCRA). EPCRA Section 313 requires the reporting of annual information on toxic chemical releases from facilities that meet specific criteria. This reported information is maintained in a database accessible through TRI Explorer ( USEPA, 2012a ).
Although TRI can provide a general idea of release trends, it has limitations. 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 of a chemical or use more than 10,000 pounds

per year . Reporting requirements have changed over time (e.g., reporting thresholds have decreased); this creates the potential for misleading data trends over time (USEPA, 1996). TRI data are meant to reflect releases and should not be used to estimate general public exposure to a chemical (USEPA, 2004 ).

TRI data for 1,3-dinitrobenzene from the years 1997 through 2010 are summarized in Exhibit 4-4 (USEPA, 2012a ). Total on- and off- site reported releases for most years ranged from hundreds of pounds to tens of thousands of pounds, though total rep orted releases for 2004 were greater than 500,000 pounds ( primarily as off

- site releases). Reported on- site releases to air and surface water were both in the range of hundreds of pounds from 1997-2002, after which reported air emissions increased to thousands and tens of thousands of pounds, and reported surface water releases decreased to below 15 pounds. Releases to land ranged from zero pounds to thousands of pounds. There were no reported releases by underground injection over the reporting period.OW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-10 Exhibit 4-4 : Environmental Releases (in pounds) of 1,3

- Dinitrobenzene in the United States, 1997

- 20 10

Year

. . On -Site Releases

. Off -Site Releases Total On

- & Off -Site Releases

. Air Emissions Surface Water Discharges Underground Injection Releases to Land . .

1997 421 816 0 451 0 1,688

1998 383 517 0 516 0 1,416

1999 385 442 0 49 100 976

2000 355 466 0 134 0 955

2001 316 412 0 0 0 728

2002 296 438 0 3,774 0 4,508

2003 63 0 0 229 0 292

2004 4,149 2 0 161 524,650 528,962

2005 13,698 8 0 123 1 13,830

2006 8,834 0 0 156 8,755 17,745

2007 7,350 0 0 7,310 0 14,660

2008 19,202 2 0 654 0 19,858

2009 8,815 13 0 575 0 9,403

2010 8,792 0 0 94 1,709 10,595

E xhibit 4-5 presents the total releases, total surface water discharges, and the count of states report ing releases for the years 2002, 2004, 2006, 2008, and 2010 (USEPA, 2012a). One state reported relea ses of 1,3-dinitrobenzene in 2002, 2004, 2006, 2008, and 2010. The number of states reporting surface water discharges of 1,3-dinitrobenzene ranged from none to one for the years included in Exhibit 4-5

.

Exhibit 4-5 : Summary of Total Releases and Total Surface Water Discharges of 1,3

- Dinitrobenzene
, 2002, 2004, 2006
, 2008, and 20 10

Year Total Releases (pounds) Count of States with Releases Total Surface Water Discharges

(pounds) Count of States with Surface Water

Discharges

2002 4,508 1 438 1

2004 528,962 1 2 1

2006 17,745 1 0 0

2008 19,858 1 2 1

2010 10

, 595 1 0 0

4.2.2 Environmental Fate
A vapor pressure of 0.0002 mm Hg at 25 deg C indicates that 1,3-dinitrobenzene will likely be in the vapor phase if it is released to the atmosphere. Vapor

- phase 1,3-dinitrobenzene undergoes oxidative reactions in the atmosphere. Its degradation by hydroxy l radicals is estimated to have a half -life of 526 days (HDSB, 2010). It is known to absorb light greater thanOW

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– Ch apter 4, 1,3

- Dinitrobenzene

4

- 11 290 nm and therefore may be susceptible to direct photolysis reactions, but the reaction rates for those reactions are unknown

. The K oc value of 150 L/kg implies that 1,3

- dinitrobenzene is expected to have moderate mobility and not strongly a d sorb to soil. It is known, however, to bind strongly to clay. Therefore it is expected to be less mobile in soils with high clay content over those with high organic content (HDSB, 2010). The relatively low Henry’s Law Constant of 4.9E

- 08 atm

- m 3 /mol indicates that 1,3

- dinitrobenzene is unlikely to volatilize from soil. Biodegradation can occur slowly. A half

- life of more than 64 days was measured in a silt loa m inoculums at 25 deg C (HDSB, 2010).

Based on a Henry’s Law Constant of 4.9E

- 08 atm

- m 3 /mol, volatilization is not expected to be a major loss pathway in water (HSDB, 2010) . A K oc of 150 L/kg (HSDB, 2010) suggest s that 1,3

- dinitrobenzene will not bind to suspended solids or sediments and will be mobile in

water

. 1,3

- Dinitrobenzene has been found to degrade in acclimated river water with a half

- life of 1 day, but did not degrade in unacclimated river water (HDSB, 2010). It is not expected to undergo hydroly sis because it does not have structural groups which are typically susceptible to hydrolysis.
EPA developed the Persistence, Bioaccumulation, and Toxicity (PBT) Profiler to serve as a screening tool for estimating the percentage of a contaminant that is p redicted to partition to water, air, soil, and sediment in a four

- compartment system. PBT Profiler (2009) modeling predicts that 34 % of 1,3

- dinitrobenzene will partition to water, 65% to soil, 1% to air, and 0% to sediment. PBT Profiler (2009) modeling als o projects biodegradation half

- lives in various media.
For 1,3

- dinitrobenzene , projected half

- lives are approximately 38 days in water, 75 days in soil, 540 days in air, and 340 days in sediment. Note that the PBT Profiler, as a screening tool, provides es timated values only and “not . . . definitive PBT determinations” (PBT Profiler, 2009).



### 4.3 Health Effects

1,3

- Dinitrobenzene is absorbed from the gastrointestinal tract of humans and animals. In
F

- 344 rats, the highest levels of radio

- labeled 1,3

- dinitrobenzene were found in the liver, kidney, and sciatic nerve after administration of radio

- labeled compound (USEPA, 1988). 1,3

- Dinitrobenzene appears to be highly metabolized through full or partial reduction of the nitro

groups to amine function al groups, and in some cases, via hydroxylation of the benzene ring. In one study in rabbits, the major metabolites in the urine were 2,4

- diaminophenol and 3

- nitroaniline (Hajjar et al., 1992). Some of the metabolites of 1,3

- dinitrobenzene are excreted as glucuronide or sulfate conjugates. The urine is the major route of excretion, and unabsorbed material is found in the feces.

1,3

- Dinitrobenzene has demonstrated adverse health effects in many rodent and occupational studies. Occupational studies indicate that humans are more sensitive to the effects of 1,3

- dinitrobenzene than are rodents because of lower methemoglobin reductase activity in some humans, especially neonates (ATSDR, 1995; US EPA, 1988), when compared to rodents (Linder et al., 1986, 1988). Met hemoglobinemia, hemolytic anemia, and cyanosis are seen in workers who experience an acute reaction to 1,3

- dinitrobenzene (Hajjar et al., 1992).

The lethal dose of 1,3

- dinitrobenzene was estimated to be between 5 and 50 mg/kg (Linder et al., 1986, 1988). Primary adverse biological effects from exposure to 1,3

- dinitrobenzene are on red blood cells, spleen, and testes. In a drinking water study, groups of 20 Carworth Farm rats of each sex were exposed to 0, 3, 8, or 20 mg/L 1,3

- dinitrobenzene for 16OW

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– Ch apter 4, 1,3

- Dinitrobenzene

4

- 12 weeks (C ody et al., 1981; USEPA, 1988). Hematocrit, hemoglobin levels, and white cell counts were measured on selected males in each group at 5, 10, and 14 weeks after the study commencement. Body weight, food and water consumption were recorded throughout the

exp eriment. At study termination, body and organ weights were measured, and all major tissues were examined histopathologically.

At t he 20 mg/L dose, 1,3

- dinitrobenzene decreased body weight gain in females, decreased hemoglobin concentrations and caused tes ticular atrophy in males, and was associated with splenic enlargement and hemosiderin deposits in both sexes of rats. Significantly increased spleen weights were also observed in both sexes of rats treated with 8 mg/L 1,3

- dinitrobenzene.
No treatment

- relat ed effects were identified at 3 mg/L 1,3

- dinitrobenzene. Cody et al. (1981) reported that the 3 mg/L concentration no observed adverse effect level ( NOAEL ) corresponded to a mean daily 1,3

- dinitrobenzene dose of 0.40 mg/kg in male rats.
Cody et al. (1981) identified signs of neurotoxicity in the same study. Rats treated with 3 and 8 mg/L 1,3

- dinitrobenzene showed significantly increased running wheel activity in running wheel studies, and non

- significant increases in recorded movement activity on a platfor m in activity platform count studies. There was no dose

- response reported for these observations. Hajjar et al. (1992) later expressed concern about whether these effects were test compound

related. In another component of the Cody et al. (1981) study, the length of the period of sodium hexobarbital

- induced sleep time was significantly decreased at concentrations of 50 mg/L or higher for females, and at 100 mg/L or higher for males. This was interpreted by the authors to suggest induction of hexobarbital

- me tabolizing enzymes by 1,3

- dinitrobenzene in microsomes of metabolically active cells primarily in the liver.
There have been many animal studies o n the testicular effects (i.e., sperm morphology, motility, and fertility) of 1,3

- dinitrobenzene, as discussed in Hajjar et al. (1992). Sertoli cells appear to be the target for the effects of 1,3

- dinitrobenzene on sperm, and older animals appear to be more sensitive than younger ones. There is currently no multigenerational animal study available for 1,3

- dinitrob enzene, and no data available from studies of 1,3

- dinitrobenzene developmental toxicity (Hajjar et al., 1992).

1,3

- Dinitrobenzene is mutagenic in several strains of S. typhimurium , both with and without activation. There are currently no long

- term studies of the tumorigenic effects of 1,3

- dinitrobenzene. The EPA Integrated Risk Information System (IRIS) assessment of the carcinogenicity of 1,3

- dinitrobenzene currently classifies it in Group D (not classifiabl e as to human carcinogenicity) (USEPA, 19 88 )

. Th e reference dose (RfD) for 1,3

- dinitrobenzene is 0.0001 mg/kg

- day (USEPA, 1988; Cody et al., 1981), and was derived from a NOAEL of 0.4 mg/kg

- day in a subchronic oral study in rats where increased spleen weight was identified as the critical effect (Cody e t al., 1981). An uncertainty factor (UF) of 3,000 was applied in the RfD derivation (10 for intraspecies differences, 10 for interspecies differences, 10 for extrapolating from a subchronic to a chronic duration, and 3 for the lack of chronic, developmenta l, and multigenerational reproductive toxicity studies). The EPA calculated a non

- cancer Health Reference Level (HRL) of 0.7 μg/L for 1,3

- dinitrobenzene using the oral RfD of 0.0001 mg/kg

- day for a 70 kg adult ingesting 2 L of drinking water per day, with the application of a 20% relative source contribution (RSC)

. The current EPA oral RfD value is supported by a more recent 1,3

- dinitrobenzene assessment conducted by the Agency for Toxic Substances and Disease Registry (ATSDR) (ATSDR, 1995) . An oral interme diate duration ATSDR minimal risk level (MRL) of 0.0005OW

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– Ch apter 4, 1,3

- Dinitrobenzene

4

- 13 mg/kg

- day for splenic hemosiderosis in male rats was established using a lowest observed adverse effect level ( LOAEL ) of 0.54 mg/kg

- day ( animals were dosed by gavage 5 days/week for 12 weeks, and the LOAEL of 0.75 mg/kg

- day was normalized for a 7

- day/week exposure ) and a net UF of 1,000 (intraspecies variability and interspecies variability, LOAEL to NOAEL). In the same study, adverse testicular effects were also observed at doses ≥1.5 mg/kg

- day and

a ltered spermatogenesis was noted at ≥3 mg/kg

- day (Linder et al., 1986) . The observed testicular effects were at higher doses compared to the splenic hemosiderosis and therefore considered secondary

. Based on EPA ass umptions and a net UF of 3,000 (10 for in traspecies variability, 10 for interspecies variability, 10 for the use of a LOAEL in place of a NOAEL and 3 for subchronic to chronic) applied to the LOAEL of 0.54 mg/kg

- day, the resultant HRL value of 1 μg/L supports the HRL value of 0.7 μg/L derived fro m the IRIS RfD (ATSDR, 1995). The IRIS assessment (USEPA, 19 88 ) presents more detailed information about the potential health effects for 1,3

- dinitrobenzene.
Individuals with a genetic predisposition to methemoglobinemia and/or hemosiderosis, neonates and those co

- exposed to other hemolytic agents, could be sensitive to 1,3

- dinitrobenzene exposure . Males having sperm production complications could also have increased sensitivity to 1,3

- dinitrobenzene exposure.



### 4.4 Occurrence

This section presents data on the o ccurrence of 1,3

- dinitr obenzene in ambient water and drinking water in the United States. As described in Section 4. 3

, a n HRL of 0.7 μg/L was calculated for 1,3

- dinitrobenzene based on non

- carcinogenic effects. An HRL represents the concentration of a contaminant in drinking water that is likely to be present without an appreciable risk of deleterious effects during a lifetime. Occurrence data from various sources presented below are analyzed with respect to the HRL and 1⁄2 the HRL. When possible, estimat es of the population exposed at concentrations above the HRL and 1⁄2 the HRL are presented

. For additional background information about many of the data sources used to evaluate occurrence, please refer to Chapter 2.

4.4.1 Occurrence in Ambient Water

Lakes, rivers , and aquifers are the ambient sources of most drinking water. Contaminant occurrence in ambient water provides information on the potential for contaminants to adversely affect drinking water supplies. 1,3

- Dinitrobenzene was not included in United States Geological Survey (USGS) National Water

- Quality Assessment (NAWQA) Cycle 1 monitoring (1992

- 2001). However, 1,3

- dinitrobenzene data are available from EPA’s Storage and Retrieval (STORET) Data Warehouse

. Storage and Retrieval (STORET) Data Warehouse

EPA’s STORET Data Warehouse is a collaborative database that contains raw biological, chemical, and physical data from surface and ground water sampling conducted by federal, state and local agencies, Indian t ribes, volunteer groups, academics, and others. A wi de variety of data relating to water quality from all 50 states as well as multiple territories and jurisdictions of the United States are represented in this data system. These are primarily ambient water data, but in some cases they are finished drinking water data. Users began populating the STORET Data Warehouse in 1999. Most data are post

- 1999, but some earlier sampling is included.
STORET data have quality limitations. The extent of national coverage and data completeness varies from parameter to para meter. There are no restrictions on submission of dataOW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-14 based on analytical methods, quality assurance (QA) practices, etc. For more general STORET data information, please refer to: http://www.epa.gov/storet/index.html

. EPA reviewed STORET ground water data from wells and surface water data from lakes, rivers/streams, and reservoirs (USEPA, 20 12b) . The STORET Data Warehouse also included public w ater s ystem (PWS) data from three state s (Indiana, Missouri, and Ohio); EPA reviewed these as well (USEPA, 20 12b).
The results of the STORET analysis for 1,3-dinitrobenzene are presented in Exhibit 4-6 through Exhibit 4-9 . Of the 70 sites (53 surface water and 17 ground water), 53 (75.71 %) reported detections of 1,3-dinitrobenzene. All detections were at surface water sites. Detected concentrations ranged from 0 to 0.33 μg/L. No 1,3-dinitrobenzene detections exceeded 1⁄2 the HRL or the HRL. Minimum detected concentrations are reported in Exhibit 4-6 ; these minimum values may be indicative of reporting levels used. (A minimum value of zero, on the other hand, could represent a detection that was entered into the database as a non

- numerical value (e.g., “Present”)

. No Indiana, Missouri, or Ohio PWS data were available for this contaminant.

Exhibit 4-6 : 1,3 -D initrobenzene STORET Data – Summary of Detected Concentrations

Source Water Type

. Concentration Value of Detections (μg/L)

. .

. Minimum Median 90 th Percentile Maximum

Ground Water N/A N/A N/A N/A

Surface Water 0 1 0.04 0.31 0.33

Total 0 1 0.04 0.31 0.33

PWS 2 N/A N/A N/A N/A N/A = not applicable (no detections in this category).

1 A minimum value of zero may represent a detection that was entered into the database as a non

- numerical value (e.g., “Present”).

2 It could not be determined from the data in STORET whether the public water supply facilities were served by ground water or surface water.

E xhibit 4-7 : 1,3

- Dinitrobenzene STORET Data – Summary of Samples

Source Water Type Total Number of Samples Samples with Detections . Samples with Detections > 1⁄2 HRL ( 0.35 μg/L) . Samples with Detections > HRL ( 0.7 μg/L) .

. . Number Percent Number Percent Number Percent

Ground Water 48 0 0% 0 0% 0 0%

Surface Water 95 95 100% 0 0% 0 0%

Total 143 95 66.43% 0 0% 0 0%

PWS 1 0 0 0% 0 0% 0 0%

1 It could not be determined from the data in STORET whether the public water supply facilities were served by ground water or surface water.OW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-15 Exhibit 4-8 : 1,3

- Dinitrobenzene STORET Data – Summary of Sites

Source Water Type Total Number of Sites Sites with Detections

. Sites with Detections

> 1⁄2 HRL ( 0.35 μg/L) . Sites with Detections

> HRL ( 0.7 μg/L) .

. . Number Percent Number Percent Number Percent

Ground Water 17 0 0% 0 0% 0 0%

Surface Water 53 53 100% 0 0% 0 0%

Total 70 53 75.71% 0 0% 0 0%

PWS 1 0 0 0% 0 0% 0 0%

1 It could not be determined from the data in STORET whether the public water supply facilities were served by ground water or surface water.

E xhibit 4-9 : 1,3

- Dinitrobenzene STORET Data – Summary of States

Source Water Type Total Number of States States with Detections . States with Detections > 1⁄2 HRL ( 0.35 μg/L) . S tates with Detections > HRL (0.7 μg/L) .

. . Number Percent Number Percent Number Percent

Ground Water 1 0 0% 0 0% 0 0%

Surface Water 1 1 100% 0 0% 0 0%

Total 1 2 1 50.00% 0 0% 0 0%

PWS 2 0 0 0% 0 0% 0 0%

1 The number of states with ground water data plus the number of states with surface water data may not equal the “Total” number of states providing data because some states provided both ground water and surface water data.

2 It could not be determined from the data in STORET whether the public water supply facilities were served by ground water or surface water.

4.4.2 Occurrence in Drinking Water

The agency reviewed a number of data sources for information on contaminant occurrence in drinking water. Data and information on 1,3-dinitrobenzene from the following source are available and are summarized in this section:

• EPA’s Second Unregulated Contaminant Monitoring Regulation (UCMR 2).

Reviewed sources that contain no information on 1,3- dinitrobenzene occurrence included, among others, EPA’s First Unregulated Contaminant Monitoring Regulation (UCMR 1), Rounds 1 and 2 of EPA’s Unregulated Contaminant Monitorin g (UCM) Program

, State drinking water monitoring programs, EPA’s Community Water System Survey (CWSS) , and Consumer Confidence Reports (CCRs) from PWSs

. Primary Data Sources
Second Unregulated Contaminant Monitoring Regulation (UCMR 2), 2008-2010

UCMR 2 mo nitoring, designed to provide nationally representative contaminant occurrence data, was conducted from 2008 to 2010. UCMR 2 required surface water systems to monitor quarterly and ground water systems to monitor twice per year. There were two tiers of monitoring: Assessment Monitoring for contaminants with commonly used analytical method technologies, and Screening Survey monitoring for contaminants that require specialized analytical method technologies not in wide or common use.OW

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– Ch apter 4, 1,3

- Dinitrobenzene

4

- 16 All very large PWSs (ser ving more than 100,000 people) and large PWSs (serving 10,001

- 10 0 ,000 people), plus a statistically representative national sample of 800 small PWSs (serving 10,000 people or fewer), were required to conduct Assessment Monitoring during a 12

- month period b etween January 2008 and December 2010. For the Screening Survey, monitoring

was required by all very large PWSs, 320 representative large PWSs, and 480 representative small PWSs, during a 12

- month period between January 2008 and December 2010. See USEPA (2 007)

, USEPA (2010 b ) , and USEPA (2015) for more information on the UCMR 2 program, including study design and data analysis.

1,3

- Dinitrobenzene was monitored under the UCMR 2 Assessment Monitoring. The Minimum Reporting Level (MRL) used for 1,3

- dinitrobenzene in this study was 0.8 μg/L , which is slightly greater than the HRL

. The design of UCMR 2 permits estimat ion of nat ional occurrence . To calculate national extrapolations, the percent of systems (or population served) estimated to exceed a specified threshold is multiplied by the total number of systems (or population served) in the nation. (Note that because a ll large and very large systems were required to conduct UCMR 2 Assessment Monitoring, survey census figures are used in those size categories )

. See Chapter 2 for additional information on national extrapolations.
As of July 201 1 , a total of 32

, 0 17 1,3

- dinitrobenzene samples have been collected from
4

, 137 systems. There have not been any detections of 1,3

- dinitrobenzene from the syste ms that sampled under UCMR 2

. The fact that there have not been any detections of 1,3

- dinitrobenzene from systems sampled under UCMR 2 suggests that nation

- wide occurrence of th is compound is likely to be low or negligible.



### 4.5 Technology Assessment

4.5.1 Analytical Methods
EPA has developed one analytical method for the analysis of 1,3

- dinitrobenzene in drinking water:

• EPA Method 529, Revision 1.0, Determination of Explosives and Related Compounds in Drinking Water by Solid Phase Extraction and Capillary Column Gas Chromatography/ Mass Spectrometry (GC/MS) , has Detection Limits (DLs) that range from 0.003 to 0.076 μg/L. The Lowest Concentration Minimum Reporting Levels (LCMRLs), although not included in EPA Method 529, range from 0.17 to 1.27 μg/L. Recoveries range f rom 77.6 to 128%, with Relative Standard Deviations (RSDs) of 1.0 to 11% (USEPA, 2002)

. Although not listed in EPA Method 529 , the MRL for 1,3

- dinitrobenzene is 0.8 μg/L. This value serve s as a national benchmark for laboratories that participat ed in UCMR 2 using EPA Method 529 ( 72 FR 367; USEPA, 2007 )

. The MRL for 1,3

- dinitrobenzene was determined by EPA using data generated from EPA Method 529.
An estimated reporting level (calculated as MRL) was compared to the HRL for 1,3

- dinitrobenzene in order to dete rmine whether the available analytical method is capable of reliable quantitation at concentrations of estimated toxicological concern (see Exhibit 4

- 10 ). The Method Sensitivity Ratio (MSR) is calculated from the following equation:
MSR = HRL (μ g/L ) / MRL (μ g/L )OW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-17 A favorable MSR is one that is greater than ten . That is, it is preferable that the HRL be at least ten times above the concentration at which data can be reliably reported; this provides a margin of safety for uncertainty in the HRL and/or method performance (see USEPA, 2009a).

Exhibit 4- 10 : Method Sensitivity Ratio (MSR) for 1,3

- Dinitrobenzene

Method MRL (μg/L) HRL (μg/L) MSR

529 0.8 0.7 0.875

T he MSR is less than ten; hence, the available analytical method is not capable of reliable quantitation at le ast ten times below the HRL.

4.5.2 Treatment Technologies
The availability of treatment technologies is not a factor EPA considers when making a regulatory determination. However, suitable treatment technologies must be made available before a National Primary Drinking Water Regulation (NPDWR) can be promulgated.
A preliminary review of the literature reveals that the following treatment technologies have been investigated empirically for their applicability to this contaminant:

• Granular activated carbon (GAC)

.

• Ultraviolet (UV) irradiation (in cluding photocatalysis).

• Advanced oxidation processes (a combination of two oxidants such as ozone/UV, ozone/peroxide, possibly with the addition of iron).

• Biologically active filtration

. Based on percentage -removal values reported in the reviewed literatu re, the most promising options appear to be GAC and advanced oxidation processes, especially Fenton’s reagent (iron/peroxide/UV).
Please note that the literature review was not exhaustive, and findings from the reviewed studies might not be directly comparable. A full assessment of treatment technology applicability will require a more detailed review and analysis of the literature, and possibly additional research.



### 4.6 Regulatory Determination

4.6.1 Making Regulatory Determinations for Chemicals on the CCL

The stat utory requirements for the CCL and regulatory determinations can be found in SDWA Section 1412(b)(1). The 1996 SDWA Amendments require EPA to publish the CCL every five years. The CCL is a list of contaminants that are not subject to any proposed or promulgated NPDWRs, are known or anticipated to occur in PWSs, and may require regulation under SDWA to protect public health. The 1996 SDWA Amendments also direct EPA to determine whether or not to regulate at least five contaminants from the CCL every five yea rs. There are three criteria to be considered in making a regulatory determination. A decision to regulate is warranted if :

(a) the contaminant may have an adverse effect on the health of persons;OW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-18 (b) the contaminant is known to occur or there is substantial likelihood that the contaminant will occur in PWS s with a frequency and at levels of public health concern; and
(c) in the sole judgment of the Administrator, regulation of such contaminant presents a meaningful opportunity for health risk reduction for persons served by PWS s.

If EPA determines that all three of these statutory criteria are met , it makes a preliminary positive regulatory determination that a n NPDWR 1 is needed . Following a comment response period and a final positive regulator y determination, t he agency has 24 months to publ ish a proposed Maximum Contaminant Level Goal 2 (MCLG) and an NPDWR. 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 The agency may determine that there is no need for a regulation when a contaminant fails to meet one or more of the criteria. A decision not to regulate is considered a final agency action and is subject to judicial review. The agency can choose to publish a Health Advisory (a non-regulatory action) or other guidance for any contaminant on the CCL, independent of the regulatory determination. Refer to section 1.4 for a summary of the approach used to identify and evaluate contaminants for RD 3. The following section summarizes the RD 3 decision for 1,3-dinitrobenzene.

4.6.2 Health Effects (Criterion #1)
The first criterion asks if the contaminant may have an adverse effect on the health of

persons. Because all chemicals have adverse effects at some level of exposure, the ch allenge is to identify a n HRL, a dose below which adverse health effects are considered unlikely to occur (threshold toxicant), or below which adverse effects have a defined low probability of occurrence (non-threshold toxicant). The key elements that must be considered in evaluating the first criterion are the mode of action, the critical effect(s), the dose

- response for critical effect(s), the RfD for threshold effects, and the slope factor for non- threshold effects.
A full description of the health effec ts associated with exposure to 1,3-dinitrobenzene is presented in Section 4.3 of this document.

Health Criterion Data
1,3-Dinitrobenzene is absorbed from the gastrointestinal tract of humans and animals. 1,3-Dinitrobenzene appears to be highly metabolized through full or partial reduction of the nitro - groups to amine functional groups, and in some cases, via hydroxylation of the benzene ring. Primary adverse biological effects from exposure to 1,3-dinitrobenzene are on red blood cells, spleen, and testes. There have been many animal studies of the testicular effects (i.e., sperm morphology, motility, and fertility) of 1,3-dinitrobenzene (Hajjar et al., 1992). Sertoli cells appear to be the target for the effects of 1,3 -dinitrobenzene on sperm, and older ani mals appear

1 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 for public water systems for a specific contaminant or group of contaminant s.

2 The MCLG is the "maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, and which allows an adequate margin of safety. Maximum contaminant level goals are non

- enforceable health goals." (CFR 141.2)

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

– O G W DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4

- 19 to be more sensitive than younger ones. There is currently no multigenerational animal study available for 1,3

- dinitrobenzene, and no data available from studies of 1,3

- dinitrobenzene developmental toxicity (Hajjar et al., 1992 ). Individuals w ith a genetic predisposition to methemoglobinemia and/or hemosiderosis, neonates

, and those co

- exposed to other hemolytic agents, could be sensitive to exposure to 1,3

- dinitrobenzene. Males having sperm production complications could also have increased se nsitivity to 1,3

- dinitrobenzene exposure.
A subchronic oral study based on increased spleen weight in rats was identified as the critical study for establishing an oral RfD of 0.0001 mg/kg

- day (USEPA, 1988; Cody et al., 1981). The RfD was derived by using a NOAEL of 0.4 mg/kg

- day, with a net UF of 3,000 (10 for intraspecies differences, 10 for interspecies differences, 10 for extrapolating from a subchronic to a chronic duration, and 3 for the lack of chronic, developmental, and multigenerational reproduct ive toxicity studies). EPA calculated a non

- cancer HRL of 0.7 μg/L for 1,3

- dinitrobenzene using the oral RfD of 0.0001 mg/kg

- day for a 70 kg adult ingesting 2 L of drinking water per day and a RSC of 20%. The current EPA oral RfD value is supported by a

re cent 1,3

- dinitrobenzene assessment (ATSDR, 1995), in which an oral intermediate duration ATSDR minimal risk level (MRL) of 0.0005 mg/kg

- day for splenic hemosiderosis in male rats was established using a LOAEL of 0.54 mg/kg

- day and a net UF of 1,000 (10 for intraspecies variability, 10 for interspecies variability, and 10 for LOAEL to NOAEL). Based on EPA assumptions and a net UF of 3,000 (10 for intraspecies variability, 10 for interspecies variability, 10 for the use of a LOAEL in place of a NOAEL, and 3 f or subchronic to chronic) applied to the LOAEL of 0.54 mg/kg

- day, the resultant HRL value of 1 μg/L supports the HRL value of 0.7 μg/L.

1,3

- Dinitrobenzene is mutagenic in several strains of S. typhimurium , both with and without activation. There are curren tly no long

- term studies of the tumorigenic effects of 1,3

- dinitrobenzene. The EPA IRIS assessment of the carcinogenicity of 1,3

- dinitrobenzene currently places the chemical in Group D (not classifiable as to human carcinogenicity) (USEPA, 19 88 ).

Health Criterion Conclusion
Toxicological data from animal studies indicate that red blood cells, spleen, and testes are targets of 1,3

- dinitrobenzene toxicity. Data on increased spleen weight in rats support the development of an HRL of 0.7 μg/L for human exposu re via drinking water. Based on these considerations, EPA concludes that 1,3

- dinitrobenzene meets the SDWA statutory criterion #1 for regulatory determination; it may have an adverse effect on the health of persons.

4.6.3 Occurrence in Public Water Systems (Crit erion #2)

The second criterion asks if the contaminant is known to occur or if there is a substantial likelihood that the contaminant will occur in PWSs with a frequency and at levels of public health concern. In order to address this question, EPA consult ed a variety of information sources, including data from the UCMR 2 Screening Survey, a nationally representative survey of PWSs conducted from 2008 to 2010. EPA examined the total number of systems that reported detections of 1,3

- dinitrobenzene, as well a s those that reported concentrations of 1,3

- dinitrobenzene above the HRL of 0.7 μg/L.
Available monitoring data, including dat a that may shed light on regional and national occurrence, are presented in Section 4. 4 , and are summarized below. Additional info rmation on production, use, and fate is found in Section 4. 2

.OW

– O G W DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4

- 20 Occurrence Criterion Data
The primary occurrence data for 1,3

- dinitrobenzene are recent (2008

- 2010) nationally

representative drinking water monitoring data generated through EPA’s UCMR 2. UCMR 2 is the only dataset with finished water data for this contaminant. UCMR 2 collected 32,017 samples from 4,137 PWSs. 1,3

- Dinitrobenzene was not detected in any sample above the MRL (0.8 μg/L), which is only slightly higher than the HRL (0.7 μg/L).
Finding s from the available ambient water data for 1,3

- dinitrobenzene are consistent with the results in finished water. Ambient water data in STORET included no measured results above 0.33 μg/L in 143 samples from 70 sites. It should be noted that some occurrenc e above the HRL may have gone undetected since reporting levels are not documented.

Occurrence Criterion Conclusion

1,3

- Dinitrobenzene was not detected in any of the 32,017 UCMR 2 samples collected by 4,137 PWSs using an MRL of 0.8 μg/L, which is only slig htly higher than the HRL (0.7 μg/L). Limited ambient water data confirm that 1,3

- dinitrobenzene occurrence does not appear to be common at levels of public health concern. Based on these considerations, EPA concludes that 1,3

- dinitrobenzene does not meet t he SDWA statutory criterion #2 for regulatory determination; it does not occur with a frequency and at levels of public health concern in public water.

4.6.4 Risk Reduction (Criterion #3)
The third criterion asks if, in the sole judgment of the Administrator, re gulation presents a meaningful opportunity for health risk reduction for persons served by PWSs

. In evaluating this criterion, EPA looked at several factors.
EPA calculated the total exposed population and the population exposed to levels above the HRL. Es timates of the populations exposed and the levels to which they are exposed were derived from the monitoring results. These estimates are included in Section 4. 4 and summarized in the “Exposed Population Estimates” section below.
In evaluating the third criterion, EPA also considered effects on potentially sensitive populations, including the fetus, infants, and children. Sensitive population considerations are discussed in the “Sensitive Populations” section, below.
Exposed Population Estimates

The est imated population exposed to 1,3

- dinitrobenzene at or above the MRL is 0%; it was not found to occur in finished drinking water at levels ≥ MRL (0.8 μg/L), which is only slightly higher than the HRL (0.7 μg/L), in 32,017 samples and 4,137 PWSs from the UCM R 2 monitoring.
Sensitive Populations
EPA also evaluated whether information is available regarding the potential health effects on children and other sensitive populations. Individuals with a genetic predisposition to methemoglobinemia ( the estimated prevalence in the general population is 1%

, or 1 per 100) and/or hemosiderosis, neonates, and those co

- exposed to other hemolytic agents, could be more sensitive to exposure to 1,3

- dinitrobenzene (Jaffe and Hultquist, 1989; ATSDR, 1995). Males ha ving sperm production complications could also have increased sensitivity to 1,3

- dinitrobenzene exposure (Hajjar et al., 1992). There is currently no multigenerational animal study available for 1,3

- dinitrobenzene, and no data available from studies of 1,3

- dinitrobenzene developmental toxicity (Hajjar et al., 1992). However, the RfD incorporated an UF for thisOW

– O G W DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4

- 21 database deficiency. The IRIS assessment (USEPA, 19 88 ) presents more detailed information about the potential health effects and sensitive population s for 1,3

- dinitrobenzene.

Risk Criterion Conclusion
Based on the estimated exposed population, including sensitive subpopulations, EPA has determined that 1,3

- dinitrobenzene does not meet the SDWA statutory criterion #3 for regulatory determination; regul ation of 1,3

- dinitrobenzene does not present a meaningful opportunity for health risk reduction for persons served by PWSs.

4.6.5 Final Regulatory Determination Decision
As stated in the “Criteria for Regulatory Determination” section above, a positive finding
f

or all three criteria is required in order to make a determination to regulate a contaminant. EPA has made a final determination under RD 3 that 1,3

- dinitrobenzene does not meet all three criteria.

1,3

- Dinitrobenzene has the potential to cause adverse hea lth effects, including effects in red blood cells, spleen, and testes. However, 1,3

- dinitrobenzene does not appear to occur in
PWSs with a frequency and at levels of public health concern. 1,3

- Dinitrobenzene was not detected in any of the 32,017 UCMR 2 sam ples collected by 4,137 PWSs using an MRL of 0.8 μg/L, which is only slightly higher than the HRL (0.7 μg/L). Due to the relatively small number of people likely exposed to 1,3

- dinitrobenzene through drinking water, EPA concludes that regulation of 1,3

- din itrobenzene does not represent a meaningful opportunity for health risk reduction for persons served by PWS s

. Additional information about the final regulatory determination can be found in the associated Federal Register n otice.



### 4.7 References

Agency for Tox ic Substances and Disease Registry (ATSDR). 1995. Toxicological Profile: 1,3

- dinitrobenzene and 1,3,5

- trinitrobenzene. Agency for Toxic Substances and Disease Registry, Public Health Service, U.S. Department of Health and Human Services. Available on the I nternet at: http://www.atsdr.cdc.gov/toxprofiles/tp.asp?id=842&tid=164 .

ChemIDPlus. 2009. Available on the Internet at: http://chem.sis.nlm.nih.gov/chemidplus/

. Accessed August 10, 2009.
Cody, T.E., S. Witherup, L. Hastings, et al. 1981. 1,3

- Dinitrobenzene: Toxic effects in vivo and in vitro. J. Toxicol. Environ. Health 7: 829

- 847.
Hajjar, N.P., M. Brower, P.A. Turck, et al. 1992. 1,3

- Dinitrobenzene (DNB). Drinking Water Health Advisory: Munitions. L ewis Publishers, Ann Arbor, MI. pp. 49

- 86. HSDB. 2010. Available on the Internet at: http://toxnet.nlm.nih.gov/cgi

- bin/sis/htmlgen?HSDB

. Accessed September, 2010.

Hazardous Substances Data B ank (HSDB). 2009. Available on the Internet at: http://toxnet.nlm.nih.gov/cgi

- bin/sis/htmlgen?HSDB . Accessed August 10, 2009.

HSDB

. 2010 . Available on the Internet at: http://toxnet.nlm.nih.gov/cgi

- bin/sis/htmlgen?HSDB

. Accessed September, 2010.

HSDB. 2012. Available on the Internet at: http://toxnet.nlm.nih. gov/cgi

- bin/sis/htmlgen?HSDB

. Accessed November, 2012.OW

– O G W DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4

- 22 Jaffe, E.R. and D. E. Hultquist. 1989. Cytochrome b 5 reductase deficiency and enzymopenic hereditary methemoglobinemia. In: Metabolic Basis of Inherited Disease. Scriver, C., Beaudet, A.L., Sly, W.S., and D. Valle, eds. New York: McGraw Hill Information Services Co. pp.2267

- 2280.

Linder, R.E., R.A. Hess, and L.F. Strader. 1986. Testicular toxicity and infertility in male rats treated with 1,3

- dinitrobenzene. J. Toxicol. Environ. Health 19:477

- 489 (as ci ted in Hajjar et al., 1992).
Linder, R.E., R.A. Hess, S.D. Perreault, et al. 1988. Acute effects and long

- term sequelae of 1,3

- dinitrobenzene on male reproduction in the rat. J. Androl. 9:326

- 327.
Persistence, Bioaccumulation, and Toxicity ( PBT ) Profiler. 2009. Available on the Internet at: http://www.pbtprofiler.net/ . Accessed August 10, 2009.
Risk Assessment Information System (RAIS). 2009. Available on the Internet at: http://rais.ornl.gov/ . Accessed August 10, 2009.
Speth, T. and R Miltner. 1990. Technical note: GAC adsorption capacities for SOCs. Journal of the A merican W ater W orks A ssociation . 82 ( 2 ) :72.
United States Environmental Protection Agency (USEPA). 1988. IRIS Summary: m

Dinitrobenzene. National Center for Environmental Assessment. Available at http://www.epa.gov/ncea/iris/subst/0318.htm.

U SEPA. 1996. 1996 Toxics Release Inventory: Public Data Release Report . Chapter 3: Year

- to

Year Comparison of Toxi cs Release Inventory Data. Available on the Internet at: http://www.epa.gov/tri/tridata/tri96/pdr/chap3.pdf

. USEPA. 2002. Method 529. Determination of Explosives and Related Compounds in D rinking Water by Solid Phase Extraction and Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS) . Revision 1.0. EPA/600/R

- 05/052. National Exposure Research Laboratory, Office of Research and Development.

USEPA. 200 4

. The Toxics Release Inventory (TRI) and Factors to Consider When Using TRI
Data. Available on the Internet at: http://www.epa.gov/tri/triprogram/FactorsToConPDF.pdf. File created June 1 4 , 2004. Accessed February 22, 2011.
USEPA. 2007. Unregulated Contaminant Monitoring Regulation (UCMR) for Public Water Systems Revisions. Federal Register. Vol. 72, No. 2, p. 367, January 4, 2007.

USEPA. 2009 a

. Final Contaminant Candidate List 3 Chemical s: Classification of the PCCL to
CCL . Office of Water. EPA 815

- R

- 09

- 008.

USEPA. 2009 b . Drinking Water Contaminant Candidate List 3

– Final. Federal Register . Vol. 74, No. 194, p. 51850, October 8, 2009.

USEPA. 2010a. Non

- confidential IUR Production Volume Information . Available on the Internet

at: http://www.epa.gov/iur/tools/data/2002

- vol.html

. USEPA. 2010 b

. Data Management and Analytical Plan for the Second Unregulated Contaminant Monitoring Regulation (UCMR 2) Data. June 2010 Draft Report Submitted
to EPA.

USEPA. 2012 a . TRI Explorer: Trends. Available on the Internet at: http://www.epa.gov/triexplorer/trends.htm

.OW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-23 USEPA. 2012b. Storag e and Retrieval (STORET) Data Warehouse. Available on the Internet at: http://www.epa.gov/storet/index.html. Data Warehouse consulted March 2012.

USEPA. 2015. Occurrence Data from the Second Unregulated Contaminant Monitoring Regulation (UCMR 2). Including Appendices A -C. EPA 815-R-15-013. December 2015.OW – OGW DW Re gulatory Determination 3 Support Document

– Ch apter 4, 1,3

- Dinitrobenzene

4-24OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-1 

# Chapter 5: Terbufos and Terbufos Sulfone

A chapter from:

Regulatory Determination 3 Support Document

EPA Report 815 -R- 15

- 014

December 2015OW

– O G W DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5

- 2OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-3 

### Contents

C ontents ...........................................................................................................................................3 Exhibits ................................ ............................................................................................................4 Abbreviations ................................ ...................................................................................................5 5.1 Contaminant Background, Chemical and Physical Properties ............................................7 5.2 Sources and Environmental Fate .........................................................................................9
5.2.1 Production, Use, and Release...................................................................................9
5.2.2 Environmental Fate ................................................................................................10
5.3 Health Effects .....................................................................................................................12 5.4 Occurrence .........................................................................................................................15 5.4.1 Occurrence in Ambient Water ...............................................................................15 5.4.2 Occurrence in Drinking Water ...............................................................................20 5.5 Technology Assessment .....................................................................................................30 5.5.1 Analytical Methods ................................................................................................30
5.5.2 Treatment Technologies .........................................................................................31 5.6 Regulatory Determination ..................................................................................................32 5.6.1 Making Regulatory Determinations for Chemicals on the CCL ...........................32
5.6.2 Health Effects (Criterion #1 ) .................................................................................33 5.6.3 Occurrence in Public Water Systems (Criterion #2) ..............................................34 5.6.4 Risk Reduction (Criterion #3) ................................................................................36
5.6.5 Final Regulatory Determination Decision .............................................................36 5.7 References ..........................................................................................................................37OW – OGW DW Re gulatory Determination 3 Support Document

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### Exhibits

Exhibit 5-1: Chemical Structure of Terbufos...................................................................................8 Exhibit 5-2: Chemical Structure of Terbufos Sulfone .....................................................................8 Exhibit 5- 3 : Physi cal and Chemical Properties of Terbufos and Terbufos Sulfone ........................8 Exhibit 5-4: Estimated Annual Agricultural Use of Terbufos, c. 2012 .........................................10 Exhibit 5-5: EPA Summary Analysis of Terbufos Data from NAWQA Study Units, 1992- 2001 – Summary of Detected Concentrations ...................................................................16 Exhibit 5-6: EPA Summary Analysis of Terbufos Data from NAWQA Study Units, 1992-
2001 – Summary of Samples .............................................................................................16 Exhibit 5-7: EPA Summary Analysis of Terbufos Data from NAWQA Study Units, 1992-
2001 – Summary of Sites ...................................................................................................16 Exhibit 5-8: USGS National Synthesis Summary of NAWQA Monitoring of Terbufos in Streams, 1992-2001 ...........................................................................................................18 Exhibit 5- 9 : USGS National Synthesis Summary of NAWQA Monitoring of T erbufos in Ground Water, 1992-2001 .................................................................................................18 Exhibit 5-10: Terbufos STORET Data – Summary of Detected Concentrations ..........................19 Exhibit 5-11: Ter bufos STORET Data
– Summary of Samples ....................................................19 Exhibit 5-12: Terbufos STORET Data – Summary of Sites ..........................................................20 Exhibit 5-13: Terbufos STORET D ata – Summary of States ........................................................20 Exhibit 5-14: Terbufos Sulfone Occurrence Data from UCMR 2 Assessment Monitoring – Summary of Detected Concentrations ...............................................................................22 Exhibit 5-15: Terbufos Sulfone National Occurrence Measures Based on UCMR 2 Assessment Monitoring Data
– Summary of Samples ......................................................23 Exhibit 5-16: Terbufos Sulfone National Occurren ce Measures Based on UCMR 2 Assessment Monitoring Data – Summary of System and Population Served Data – All Detections ....................................................................................................................23 Exhibit 5-17: Terbufos Sulfone National Occurrence Measures Based on UCMR 2 Assessment Monitoring Data – Summary of System and Population Served Data – Detections > 1⁄2 HRL ..........................................................................................................24 Exhibit 5-18: Terbufos Sulfone National Occurrence Measures Based on UCMR 2
Assessment Mon itoring Data – Summary of System and Population Served Data – Detections > HRL ..............................................................................................................25 Exhibit 5-19: Method Sensitivity Ratio (MSR) for Terbufos and Terbufos Sulfone ....................31OW

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- 5 

### Abbreviations

a.i. Active Ingredient

AMWA Association of Metropolitan Water Agencies

AWWA American Water Works Association

BW B ody W eight

CAS Chemical Abstracts Service

CCL Contaminant Candidate List

CCL 3 Third Contaminant Candidate List

CCR Consumer Confidence Report

CFR Code of Federal Regulations
ChE C holinesterase

CHO Chinese Hamster Ovary

CWS Community Water System

CWSS Community Water System Survey

DL Detection Limit

DNA D eoxyribonucleic A cid

EEC Estimated Environm ental Concentration

EPA Environmental Protection Agency

EWG Environmental Working Group

FR Federal Register

GC Gas Chromatography

HSDB Hazardous Substances Data Bank

HRL Health Reference Level

ICR Information Collection Request

IRED Interim Reregistration Eligibility Decision

IUR Inventory Update Reporting

LCMRL Lowest Concentration Minimum Reporting Level

LD 50 50% Lethal Dose

LOAEL Lowest Observed Adverse Effect Level

LT

- MDL Long

- Term Method Detection Level

MCL Maximum Contamina nt Level

MCLG Maximum Contaminant Level Goal

MDL Method Detection Limit

MRL Minimum Reporting Level

MS Mass Spectrometry

MSR Method Sensitivity Ratio

N/A Not Applicable NAWQA National Water

- Quality Assessment

NCFAP National Center for Food and Agricultural Policy

ND Not Detected

NOAEL No Observed Adverse Effect Level

NPDWR National Primary Drinking Water RegulationOW – OGW DW Re gulatory Determination 3 Support Document

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5-6 NPS National Pesticide Survey

NTNCWS Non

- Transient Non

- Community Water Systems

OPP Office of Pesticide Programs

PBT Persistence, Bioaccumulation, and Toxicity

PDP Pesticide Data Program

PMP Pilot Monitoring Program

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

PWS Public Water System QA Quality Assurance

RAIS Risk Assessment Inform ation System

RD 3 Third Regulatory Determination

RED Reregistration Eligibility Decision

RfD Reference Dose

RSC Relative Source Contribution

RSD Relative Standard Deviation

SCI

- GROW Screening Concentrations in Ground Water

SDWA Safe Drinking Water Act

SDWIS Safe Drinking Water Information System

STORET Storage and Retrieval

TRI Toxics Release Inventory

TSC Technical Support Center

UCM Unregulated Contaminant Monitoring

UCMR 1 First Unregulated Contaminant Monitoring Regulation

UC MR 2 Second Unregulated Contaminant Monitoring Regulation

UF Uncertainty Factor

USDA United States Department of Agriculture

USEPA United States Environmental Protection Agency

USGS United States Geological Survey

UV Ultraviolet

VOC Volatile O rganic CompoundOW – OGW DW Re gulatory Determination 3 Support Document

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5-7 

### Chapter 5: Terbufos and Terbufos Sulfone

The Environmental Protection Agency (EPA) has evaluated terbufos and terbufos sulfone for possible regulation as drinki ng water contaminant s. Terbufos and terbufos sulfone we re listed on the agency’s third Contaminant Candidate List (CCL 3) and we re considered for regulation as part of the third R egulatory D etermination (RD 3) under the Safe Drinking Water Act (SDWA) provisions. On October 20, 2014, EPA issued a preliminary determination not to regulate terbu fos and terbufos sulfone (79 FR 62715). A final determination not to regulate terbufos and terbufos sulfone is issued in the Federal Register notice which this support document accompanies

. Information on the CCL 3 /RD 3 process is found in Chapter 1 . Backg round on data sources used to evaluate CCL 3 /RD 3 chemicals is found in Chapter 2. This chapter presents information and analysis specific to terbufos and terbufos sulfone, including background information on the contaminants, information on sources and en vironmental fate, an analysis of health effects, an analysis of occurrence in ambient and drinking water, and information about the availability of analytical methods and treatment technologies. A summary of EPA's decision regarding terbufos and terbufos sulfone under RD 3 appears at the end of this chapter. (The decision is presented formally in the associated Federal Register notice).



### 5.1 Contaminant Background, Chemical and Physical Properties

Terbufos is a phosphorodithioate pesticide and is used as an inse cticide and nematicide to control a variety of pests. Synonyms for terbufos include S- tert -b utylthiomethyl O and O- diethyl phosphorodithioate (HSDB, 2009). Synonyms for terbufos sulfone include phosphorodithioic acid S

- (((1,1

- dimethylethyl) sulfonyl) methyl) O and O- diethyl ester (HSDB, 2009).
Terbufos 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 (USEPA, 2001a ). EPA’s Office of Pesticide Programs (OPP) released an Interim Reregistration Eligibility Decision (IRED) for terbufos in September of 2001 (USEPA, 2001a), and a Reregistration Eligibility Decision (RED) in July of 2006 (USEPA, 2006).

Terbufo s sulfone is a phosphorodithioate pesticide degradate of terbufos. The degradate

may co -occur in the environment with the parent compound.

Exhibit 5-1 and Exhibit 5-2 present the chemical structure s of te rbufos and terbufos sulfone , respectively

. Physical and chemical properties and other referenc e information are listed
in Exhibit 5-3

.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-8 Exhibit 5-1 : Chemical Structure of Terbufos

Source: ChemIDPlus/National Library of Medicine

E xhibit 5-2 : Chemical Structure of Terbufos Sulfone

Source: ChemIDPlus/National Library of Medicine

E xhibit 5-3 : Physical and Chemical Properties of Terbufos and Terbufos Sulfone

Property Information

.

. Terbufos Terbufos Sulfone
Chemical Abstracts Service (CAS) Registry Number 13071

- 79 -9 56070

- 16 -7

EPA Pesticide Chemical Code Not applicable Not applicable Chemical Formula C 9 H 21 O 2 PS 3 C 9 H 21 O 4 PS 3 Molecular Weight 288.4 g/mol (RAIS, 2009; HSDB, 2009; ChemIDPlus, 2009) 320.43 g/mol (ChemIDPlus, 2009)

Color/Physical State Clear, slightly brown liquid (HSDB, 2010) -- Boiling Point 332 deg C (RAIS, 2009)

-- Melting Point

- 29 deg C (HSDB, 2010)

-- Density 1.105 g/mL (HSDB, 2009)

-- Freundlich Adsorption Coefficient 4,420 ( μ g/g)(L/ μ g) 1/n (Speth et al., 2001) 0.4 – 2.93 (USEPA, 2006)

Vapor Pressure 3.2E

- 04 mm Hg (RAIS, 2009; HSDB, 2009; ChemIDPlus, 2009) 7.8 8E

- 06 mm Hg (ChemIDPlus, 2009)OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-9 Property Information

.

. Terbufos Terbufos Sulfone Henry’s Law Constant 2.4E

- 05 atm

- m 3 /mol (ChemIDPlus, 2009) 2.21E

- 08 atm

- m 3 /mol (ChemIDPlus, 2009) Log K ow 4.48 (dimensionless) (Speth et al., 2001 ; HSDB, 2010 ) 2.48 (dimensionless) (ChemIDPlus, 2009)
K oc 979 L/kg (RAIS, 2009; Speth et al., 2001) 500

- 5,000 L/kg (HSDB, 2010) 27.41 L/kg (RAIS, 2009)

Solubility in Water 5.07 mg/L (RAIS, 2009; HSDB, 2009; ChemIDPlus, 2009) 408 mg/L (ChemIDPlus, 2009)

Other Solvents Readily soluble in most organic solvents: aromatic hydroca rbons, chlorinated hydrocarbons, alcohols, acetone (HSDB, 2010) --

Conversion Factors (at 25 deg C, 1 atm) -- --

Note: “-- ” indicates that no information was found.



### 5.2 Sourc es and Environmental Fate

5.2.1 Production , Use , and Release
Terbufos is a phosphorodithi oate pesticide and is used as an insecticide and nematicide to control a variety of pests. Information on the application of terbufos as a pesticide is available from several sources, described below.
Production data from EPA’s Inventory Update Reporting (IUR) program are not available for terbufos . No industrial release data for terbufos are available from EPA’s Toxics Release Inventory (TRI). (The list of chemicals for which TRI reporting is required has never included terbufos (USEPA, 2010a)).
As a pest icide degradate, terbufos sulfone is neither produced nor used commercial ly

. Its formation is discussed under “Enviro nmental Fate,” below (Section 5.2.2).
EPA Office of Pesticide Programs (OPP) Reregistra tion Program

D ata available to EPA suggest that appr oximately 7.5 million pounds of terbufos active ingredient (a.i.) were used annually between 1987 and 1996 (USEPA, 2006).
EPA Pesticide Industry Sales and Usage Report

EPA’s most recent Pesticide Industry Sales and Usage report states that between 5 and 7 million pounds of terbufos a.i. were used in 1999 and between 3 and 5 million pounds of a.i. were used in 2001 (USEPA, 2004).
National Center for Food and Agricultural Policy (NCFAP) Pesticide Use Database
National Center for Food and Agricultural Policy ( NCFAP ) maintains a national Pesticide Use Database, primarily for herbicides. Pesticide use estimates are based on state

- level commercial agriculture usage patterns and state

- level crop acreage. NCFAP list ed uses of terbufos on four crops totaling approxim ately 8.7 million pounds a.i. per year in 37 states in 1992. In 1997, NCFAP list ed uses of terbufos on four crops totaling approximately 6.5 million pounds a.i. per year in 37 states (NCFAP, 2003).OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-10 United States Geological Survey (USGS) Pesticide Use Maps

The United States Geological Survey ( USGS ) produces maps of annual pesticide use for several hundred compounds used in United States crop production. The pesticide use maps show the average annual pesticide use intensity expressed as average weight (in po unds) of a pesticide applied to each square mile of agricultural land in a county. The USGS maps a re created using data from proprietary surveys of farm operations, USDA Census of Agriculture, the County Agricultural Production Survey, and other sources.

Exhibit 5-4 (USGS, 20 15) shows the geographic distribution of estimated average annual terbufos use in the United States circa 20 12. A breakdown of use by crop is also included. USGS used two methods to estimate dimethoate usage, since pesticide usage information was not available in some districts. At left, the “EPest

- High” estimates were generated by projectingusage estimates for such districts based on usage in neighboring districts. At right, the “EPestLow” estimates were gene rated by assuming no usage in such districts. Estimated a nnual usage has declined over the years, and was somewhere in the range of roughly 0.5 – 2 million pounds in 2012. The map s indicate that terbufos use is heaviest in the Midwest but also common in th e other parts of the country.

Exhibit 5-4 : Estimated Annual Agricultural Use of Terbufos, c. 201 2

Source: USGS, 20 15

5.2.2 Environmental Fate
A vapor pressure of 3.2E- 4 mm Hg at 20 -25 deg C suggests that te rbufos will be present only as a vapor in the atmosphere (HSDB, 2010). Terbufos can degrade in the atmosphere byOW

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5

- 11 reaction with photochemically produced hydroxyl radicals. The half

- life for reaction with hydroxyl radicals is estimated at 1.6 hours based on structural estimation methods (HSDB, 2010). Terbufos does not contain functional groups that are expected to absorb light at wavelengths >290 nm, and would not be expected to be susceptible to direct photolysis by sunlight in air (HSDB, 2010). Terbufos is known to undergo direct photolysis in water, but no data are available on its photolysis in air.

K oc values of 500

- 5,000 L/kg suggests that terbufos is likely to be slightly mobile in soils (HSDB, 2010). A Freundlich adsorption coefficient of between 0.4 a nd 2.93 suggests that terbufos sulfone is more mobile than the parent compound in soil (USEPA, 2006).
A Henry’s Law Constant of 2.4E

- 05 atm

- m 3 /mol and a vapor pressure of 3.20E

- 04 mm Hg suggest that volatilization of terbufos will be a significant loss me chanism from both wet and dry soils (HSDB, 2010)

. The corresponding values for terbufos sulfone are much smaller, suggesting that volatilization will be a less significant loss mechanism from both wet and dry soils

. Terbufos has a half

- life in soil of 11 t o 17 days with biodegradation and hydrolysis being the primary loss mechanisms (HSDB, 2010). Biological degradation has an estimated half

- life of between 14 and 40 days (USEPA, 2006). The half

- life for abiotic hydrolysis is estimated at 12.3 to 13.7 days a t typical environmental pH values of 5, 7

, and 9 (USEPA, 2006). Terbufos sulfone is more resistant to biological degradation with an estimated half

- life of 96 days (USEPA, 2006). One study found the half

- life of terbufos in a silty clay loam soil was betwe en 11 and 12 days. The half

- life of terbufos sulfone in the same fields was between 19 and 39 days (HSDB, 2010).

Based on a K oc range of 500

- 5,000 L/kg

, terbufos appears to be only slightly mobile in

water and will bind to sediments or suspended particles

. A Henry’s Law Constant of 2.4E

- 05

atm

- m 3 /mol for terbufos suggests that volatilization from water will be a significant loss mechanism. Half

- lives of terbufos in water have been calculated to be 2.8 days for a model stream and 26 days for a model lake (HS DB, 2010). Terbufos was found to biologically degrade with a half

- life of 3 days at pH 8.8 and 20 deg C (HSDB, 2010). Terbufos may also degrade in the presence of sunlight with a half

- life of approximately an hour (HSDB, 2010). Based on a K oc of 27.41 L/kg and a Henry’s Law Constant of 2.21E

- 08 at m

- m 3 /mol , terbufos sulfone appears to be very mobile in water. A log K ow of 2.48 and a water solubility of 408 mg/L suggest that terbufos sulfone is moderately mobile in water.
The empirical data indicate, in summ ary, that toxic residues of terbufos and degradates are highly mobile and persistent in the environment, with terbufos sulfone being more mobile and substantially more persistent than terbufos (USEPA, 2006).
EPA developed the Persistence, Bioaccumulation, and Toxicity (PBT) Profiler to serve as a screening tool for estimating the percentage of a contaminant that is predicted to partition to water, air, soil, and sediment in a four

- compartment system. PBT Profiler (2009) modeling predicts that 14% of terbufo s will partition to water, 76% to soil, 0% to air, and 10% to sediment. PBT Profiler (2009) modeling also projects biodegradation half

- lives in various media. For terbufos , projected half

- lives are approximately 38 days in water, 75 days in soil, 0.067 day s in air, and 340 days in sediment. Note that the PBT Profiler, as a screening tool, provides estimated values only and “not . . . definitive PBT determinations” (PBT Profiler, 2009).

A biodegradation half

- life of 38 days (PBT Profiler, 2009) indicate s tha t terbufos is moderately persistent in water

. EPA’s PBT Profiler (2009) predicts that 21 % of terbufos sulfone will partition to water 79% to soil, 0% to air, and 0% to sediment

. Projected half

- lives for terbufos sulfone are identicalOW

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– Chapter 5, Terbufos and Terbufos Sulfone

5

- 12 to the predicted half

- lives for the parent compound, or approximately 38 days in water, 75 days in soil, 0.067 days in air, and 340 days in sediment . Note that the PBT Profiler, as a screening tool, provides estimated values only and “not . . . definitive PBT determinations” (P BT Profiler, 2009).

A s with the parent compound, a biodegradation half

- life of 38 days (PBT Profiler, 2009) indicate s that terbufos sulfone is moderately persistent in water

. 

### 5.3 Health Effects

Terbufos has been found to be readily absorbed, with about 83% o f the radioactive label from a dose of terbufos (0.8 mg/kg) recovered in the urine within 168 hours . T he majority (80%) is excreted within 48 hours and only 3.5% of the dose is recovered in the feces (North, 1973). Terbufos was found to be widely distribut ed throughout the tissues, with the highest concentrations of radioactivity in the liver 6 hours after dosing, and in the kidney 12 hours after dosing (North, 1973). The majority of terbufos excreted in the urine was represented by metabolites not containi ng phosphorus (i.e., methane, ( t

- butylsulfinyl) (methylsulfinyl); terbufoxon sulfone; sulfoxide, ( t

- butylsulfonyl) methyl methyl; sulfone, t

- butyl (methyl

- sulfonyl) methyl; and sulfoxide, t

- butyl (methyl

- sulfonyl) methyl), while the majority excreted in th e feces contained phosphorus (i.e., terbufoxon, terbufoxon sulfoxide, terbufos sulfoxide, and terbufos sulfone). The proposed metabolic pathway for terbufos consists of sulfoxidation and desulfuration of terbufos, followed by hydrolysis of the thiolophosph orus bond, enzymatic S

methylation, and then additional S

- oxidation to final metabolites sulfone, t

- butyl (methyl

sulfonyl) methyl and sulfoxide, ( t

- butylsulfonyl) methyl methyl (Cheng, 1992). Cheng (1992) did not find any sex differential in the absorptio n or metabolic fate of terbufos in Sprague

Dawley rats. Although there have been no pharmacokinetic studies identified for the terbufos degradate, terbufos sulfone, systemic effects indicate that the compound is absorbed.

There are limited data available for terbufos, terbufos sulfoxide, or terbufos sulfone in humans. In animals the acute oral toxicity of terbufos varies with sex, species, and duration of exposure. Median lethal dose (LD 50 ) values of 3.5 to 9.2 mg/kg in mice, 1.4 to 9.0 mg/kg in rats, and 4.5 to 6.3 mg/kg in dogs hav e been reported . Clinical signs of cholinergic toxicity were noted, and included tremors, salivation, exophthalmos, prostration, decreased activity, chromodacryorrhoea, diuresis, piloerection, ataxia, urogenital staining, nasal discharge, anorexia, and labored breathing. Death has been noted to occur from within minutes to up to one week later after exposure (USEPA, 2003). An acute no observed adverse effect level ( NOAEL ) of 0.15 mg/kg

- day, based on plasma cholinesterase (ChE) in hibition and clinical signs, was identified in an oral neurotoxicit y study in rats . Acute neurotoxicity tests did not find any macroscopic or microscopic changes, even though there were treatment

- related abnormalities in the functional observational batter y test related to cholinergic toxicity (Mandella, 1998).

In a 14

- day study conducted in male dogs, terbufos was administered daily via gelatin capsule at doses of 2.5 or 250 μg/kg body weight (bw) per day (Bailey, 1988). Clinical signs and statistically si gnificantly inhibited ChE activity (plasma, erythrocyte, and brain, ranging from 37% (brain) to 79% (erythrocyte) inhibition) were noted at the 250 μg/kg bw per day dose of terbufos. ChE activity (plasma and brain) also was significantly reduced with the 2 .5 μg/kg bw per day dose (ranging from 42% (brain) to 25% (plasma) inhibition); this study lacked a
NOAEL.
In the same study (Bailey, 1988)

, the effects of terbufos sulfone were also evaluated using doses of 15, 62.5, 250, or 1000 μg/kg bw per day. Three o f the dogs administered terbufosOW

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– Chapter 5, Terbufos and Terbufos Sulfone

5

- 13 sulfone died during the course of the study after developing clinical signs of toxicity (i.e., tremor, languid behavior, prostration, ataxia, emesis, salivation, dyspnea, cold

- to

- the

- touch, squint eye, meiosis, no feces, an increase in soft feces, prolapsed rectum, and sanguineous

- appearing material in the cage). Plasma ChE activity was statistically significantly inhibited by terbufos sulfone at all time

- points: by 67

– 77% at the highest dose of 1000 μg/kg bw per day; by 39

– 56% at 250 μg/kg bw per day; and by 24

– 37% at 62.5 μg/kg bw per day. At the lowest dose (15 μg/kg bw per day), statistically significant inhibition of plasma ChE activity (of 20%) was seen only on day 8, but not on day 15, and thus was not clearly related to treatment. Statistically significant decreases in erythrocyte ChE activity were observed only at the highest dose, where inhibition, ranging from 57% to 93%, was noted at all time

- points. Inhibition of brain ChE activity was found at the two higher dose s (statistically significant only at the highest dose, by 62%). Cerebellar ChE activity was inhibited by 23% (not statistically significant) at 250 μg/kg bw per day, and by 46% (not statistically significant) at the highest dose (1000 μg/kg bw per day). Gr oss necropsy found treatment

- related lesions in the 1,000 μg/kg bw per day group only (Bailey, 1988).
ChE inhibition is the critical effect for short term terbufos exposures. This critical effect has been evaluated in a 14

- day feeding study in rats (Fisch er, 1978), a 28

- day oral toxicity study in dogs (Shellenberger, 1984) and a 29

- day capsule study in dogs (Shellenberger, 1987). Depending on the dose tested and duration, these studies also observed death, reduced food consumption, reduced body weights, re duced relative organ weights (liver and kidneys), and clinical signs.

The terbufos database for animal studies with 85

- day to lifetime durations is extensive

. Ch E inhibition was noted in a 30

- day feeding study in dogs (Morici, 1972), a 31

- day feeding study in rats (Morici, 1972), 85

- day feeding study in rats (Mandella, 1999), a 3

- month feeding study in rats (Daly and Knezevich, 1979), a 6

- month feeding study in dogs (Morgareidge, 1973),
a 1

- year oral toxicity study in dogs (Shellenberger and Billups, 1986), a 1

- year feeding study in rats (Daly, 1987), and a 2

- year feeding study in rats (Rapp, 1974). The critical dose for ChE inhibition was identified as a NOAEL of 0.005 mg/kg

- day from a 28

- day oral study in dogs (Shellenberger, 1984), and a one year oral stu dy in dogs (Shellenberger and Billups, 1986). There are no subchronic or chronic studies available which describe the effects of the degradate, terbufos sulfone.
There are data on reproductive and developmental effects for terbufos but not for its degradat e, terbufos sulfone. In a two

- generation reproductive study in rats, terbufos administered in the diet beginning 63 days prior to F 0 mating, at concentrations of 0, 0.5, 1.0, or 2.5 mg/kg diet (equivalent to daily intakes of 0.035 to 0.22 mg/kg

- day in the F 0 generation, and 0.04 to 0.24 mg/kg

- day in the F 1 generation), caused a decrease in male fertility, the number of pregnant females, pup viability, and pup body weight in the highest dose group (Schroeder, 1989). The only non

- ChE effect observed in the pa rental animals was a decrease in body weight during lactation in the 2.5 mg/kg food dose group. ChE activity was decreased in F 0 and F 1 adults, even with the lowest dose tested. The NOAEL identified in this study for reproductive effects and offspring toxi city was 1.0 mg/kg in the diet (equivalent to 0.07 mg/kg

- day in males, and approximately 0.09 mg/kg

- day in females) (Schroeder, 1989). In a 3

- generation reproductive study conducted by Smith and Kasner (1972)

, terbufos administered via the diet at doses of 0, 0.25, or 1 ppm (equivalent to 0, 0.0125, or 0.05 mg/kg

- day) to rats during this 6

- month study period resulted in a reported Lowest Observed Adverse Effect Level ( LOAEL ) of 0.05 mg/kg

day, based on an increased percentage of litters with dead offspring in each of the 3 generations, as compared to controls. The NOAEL for this study was 0.0125 mg/kg

- day.OW

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– Chapter 5, Terbufos and Terbufos Sulfone

5

- 14 Developmental studies with terbufos in rats and rabbits did not find any treatment

- related effects (USEPA, 2003), although the rat studies were potentiall y flawed. The rabbit study by Hoberman (1988a, 1988b) appears to be well conducted. In this study, the NOAEL of 0.25 mg/kg

- day for terbufos was the same for maternal toxicity and fetal toxicity. Maternal toxicity was based on increased number of does with soft or liquid feces, maternal body weight loss during gestational days 16 to 20, occurrence of reddened areas in the fundic region of the stomach at necropsy, and one abortion at the highest dose. Fetal toxicity was based on decreased fetal body weight an d an increase in the incidence of does with any resorption sites at the next highest dose.
Terbufos has been found to be negative in the majority of mutagen i city tests, both in vivo animal studies (chromosomal aberrations in rats) and in vitro studies (i.e ., reverse mutation in Salmonella typhimurium , point mutations and chromosomal aberrations in Chinese hamster ovary (CHO) cells, and unscheduled d eoxyribonucleic a cid ( DNA ) synthesis in primary male rat hepatocytes) (USEPA, 2003). However, a dominant letha l mutation test in rats had inconclusive results (MacKenzie, 1986), and a mitotic gene conversion test in yeast was positive with technical

- grade terbufos, with or without metabolic activation, and weakly positive with commercial

- grade terbufos, without me tabolic activation (Gentile et al., 1982). Genotoxicity studies of the degradate, terbufos sulfone are lacking.
There has been no evidence that terbufos is carcinogenic in either mice administered doses of 0.45 to 1.8 mg/kg terbufos via gavage for 18 month s (Silverman et al., 1986), or in rats fed 0.0125 to 0.1 mg/kg

- day terbufos for 2 years (Rapp, 1974). EPA (USEPA, 1988) determined that the data were not adequate to make a determination regarding the potential carcinogenicity of terbufos and classified it in Group D, not classifiable as to human carcinogenicity, following the a gency’s 1986 cancer guidelines (USEPA, 1986) . There are no long

- term animal studies of terbufos sulfone.

The 2006 EPA OPP RED identifies the reference dose ( RfD ) for terbufos as 0.0 0005 mg/kg

- day, derived from the NOAEL of 0.005 mg/kg

- day for Ch E inhibition in the 28

- day

- and
1

- year dog studies by Shellenberger (1984) and Shellenberger and Billups (1986), respectively, with application of a 100

- fold uncertainty factor (UF) (10 for in terspecies variability and 10 for intraspecies variability ) (USEPA, 2006)

. EPA calculated a non

- cancer health reference l evel ( HRL ) of 0.35 μg/L for terbufos using the RfD of 0.00005 mg/kg

- day for a 70 kg adult ingesting 2 L of drinking water per day and a relative source contribution ( RSC ) of 20%.
Lacking subchronic or chronic studies, the OPP did not develop an RfD for terbufos sulfone in the RED (USEPA, 2006). Bailey (1988) conducted a 14

- day study of both terbufos and its sulfone degradate in dogs. The NOAEL based on ChE activity for terbufos sulfone was greater than the LOAEL of 2.5 mg/kg

- day for the same endpoint following 14

- day dosing with the parent compound terbufos. This suggests that the terbufos sulfone degradate is less toxic than its parent, and that the use of the terbufos HRL of 0.35 μg/L for the degradate, terbufos sulfone, is reasonable

. The USEPA concluded in 2003 and in 2006 that the existing toxicity database for terbufos is sufficient to evaluate its potential hazards to the general p opulation, and adequate to characterize its potential hazards to fetuses, infants, and children. Developmental studies with terbufos in rats and rabbits did not find any develo pmental effects (USEPA, 2003) and n o sensitive populations were identified or ch aracterized. There are no data on reproductive and developmental effects for terbufos sulfone. The OPP RED (USEPA, 2006) presents more detailed information about the health effects for terbufos and terbufos sulfone.OW

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5

- 15 

### 5.4 Occurrence

This section presents data o n the occurrence of terbufos and terbufos sulfone in ambient water and drinking water in the United States. As described in S ection 5

. 3 , a n HRL of 0.35 μg/L was calculated for terbufos based on non

- carcinogenic effects, and the same value was adopted as th e HRL for terbufos sulfone. This HRL represents the concentration of the contaminant in drinking water that is likely to be present without an appreciable risk of deleterious effects during a lifetime. Occurrence data from various sources presented below a re analyzed with respect to the HRL and 1⁄2 the HRL. When possible, estimates of the population exposed at concentrations above the HRL and 1⁄2 the HRL are presented

. For additional background information about many of the data sources used to evaluate

occurre nce, please refer to Chapter 2.

5.4.1 Occurrence in Ambient Water
Lakes, rivers, and aquifers are the ambient sources of most drinking water. Contaminant occurrence in ambient water provides information for the potential for contaminants to adversely affect drin king water supplies. Occurrence data for terbufos in ambient water are available from the USGS National Water

- Quality Assessment (NAWQA) program and from EPA’s Storage and Retrieval (STORET) database. Terbufos sulfone was not included in NAWQA Cycle 1 moni toring (1992

- 2001), and no terbufos sulfone data are available from EPA’s STORET Data Warehouse

. Limited information pertaining to the occurrence of the two contaminants is available in relation to a published study by EPA’s National Exposure Research Labo ratory

. United States Geological Survey (USGS) National Water

- Quality Assessment (NAWQA) Ambient Water Analys e s USGS instituted the NAWQA program in 1991 to examine ambient water quality status and trends in the United States. The NAWQA program generates h igh quality contaminant occurrence and other water quality parameter data for significant watersheds and aquifers across the nation. The program is designed to apply nationally consistent methods to provide a uniform basis for contaminant occurrence compar isons and assessments among study basins across the country and over time. The occurrence assessments can also serve to facilitate interpretation of natural and anthropogenic factors affecting national water quality. For more detailed information on NAWQA program design and implementation, refer to Leahy and Thompson (1994) and Hamilton et al. (2004).
EPA Analysis of NAWQA Cycle 1 Monitoring Results, 1992

- 2001
With the cooperation of USGS, EPA performed a summary analysis of all Cycle 1 water monitoring dat a from all study units (1992

- 2001). EPA’s analysis of the NAWQA data is a simple, non

- parametric occurrence analysis that provides summary statistics to chara cterize contaminant occurrence.
All surface water data from sampled streams were included in the E PA summary analysis. The ground water analysis relied on well data and excluded data from springs and drains. EPA calculated detection frequencies as the percentage of samples and the percentage of sites with at least one detection, without any censoring o r weighting. (A detection is an analytical result equal to or greater than the reporting level.) EPA calculated other descriptive statistics as well, including the minimum, median, 95 th percentile, 99 th percentile, and maximum concentrations (based only on samples with detections). Reporting levels varied over time during the NAWQA program. In most cases

, the reporting level for t erbufos was 0.01 3 μg/L

. Therefore,OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-16 in some cases the minimum concentration reported as a detection could be lower than the highes t reporting level.
The results of the EPA analysis of terbufos are presented in Exhibit 5-5 through Exhibit
5-7 . (As noted above, terbufos sulfone was not a NAWQA analyte. ) Overall, terbufos was detected in 0.14% of samples and at 0.31% of sites. The median concentration based on detections from all sites is 0.02 μg/L. The 99 th percentile concentration based on detections from all sites is 0.56 μg/L. Of the 20,960 samples from 7,118 sites, one (0.005%) sam ple from one (0.01%) site had a detected concentration of terbufos that was greater than the terbufos HRL

.

Exhibit 5-5 : EPA Summary Analysis of Terbufos Data from NAWQA Study Units, 1992

- 2001 – Summary of Detected Concentrations

Source Water Type

. Concentration Values of Detections, μ g/L

. . .

. Minimum Median 90 th Percen tile 99 th Percen tile Maximum

Ground Water 0.008 0.01 0.01 2 0.01 2 0.01 2

Surface Water 0.002 1 0.02 0.23 0.56 0.56

All S ites 0.002 1 0.0 2 0.21 0.56 0.56

E xhibit 5-6 : EPA Summary Analysis of Terbufos Data from NAWQA Study Units, 1992

- 2001 – Summary of Samples

Source Water Type Total Number of Samples Samples with Detections . Samples with De tections > 1⁄2 HRL (0.175 μg/L) . Samples with Detections > HRL (0.35 μg/L) .

. . Number Percent Number Percent Number Percent

Ground Water 6,080 2 0.03% 0 0% 0 0%

Surface Water 14,880 28 0.19% 4 0.03% 1 0.01%

All S ites 20,960 30 0.14% 4 0.02% 1 0.005%

E xhibit 5-7 : EPA Summary Analysis of Terbufos Data from NAWQA Study Units, 1992

- 2001 – Summary of Sites

Source Water Type Total Number of Sites Sites with Detections . Sites with Detections > 1⁄2 HRL (0.175 μ g/L) . Sites with Detections > HRL (0.35 μg/L) .

. . Number Percent Number Percent Number Percent

Ground Water 5,211 2 0.04% 0 0% 0 0%

Surface Water 1,907 20 1.05% 4 0.21% 1 0.05%

All Sites 7,118 22 0.31% 4 0.06% 1 0.01%

NA WQA Pesticide National Synt hesis Project , 1992-2001
Through a series of National Synthesis efforts, the USGS NAWQA program is preparing comprehensive analyses of data on topics of particular concern. These National Synthesis

assessments aggregate NAWQA contaminant occurrence and wat er quality parameter data from individual study units and other sources to provide a national overview. The NAWQA Pesticide National Synthesis Project is a national

- scale assessment of the occurrence and behavior ofOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-17 pesticides in streams and ground water of the United States and the potential for pesticides to adversely affect drinking water supplies or aquatic ecosystems.
Results from the most recent Pesticide National Synthesis analysis, based on complete Cycle 1 (1992-2001) data from NAWQA study units, are posted on the NAWQA Pesticide National Synthesis W eb site (Gilliom et al., 2007). Data for surface water and ground water are presented separately, and results in each category are subdivided by land use category. Land use categories include agricultura l, urban, mixed (deeper aquifers of regional extent in the case of ground water), and undeveloped. The Pesticide National Synthesis analysis is a first step toward the USGS goals of describing the occurrence of pesticides in relation to different land use and land management patterns, and developing a deeper understanding of the relationship between spatial occurrence of contaminants and their fate, transport, persistence, and mobility characteristics.
The surface water summary data presented in the Pestici de National Synthesis (Gilliom et al., 2007) only includes stream data. Sampling data from a single one-year period, generally the year with the most complete data, were used to represent each stream site. Sites with few data or significant gaps were excluded from the analysis. NAWQA stream sites were sampled repeatedly throughout the year to capture and characterize seasonal and hydrologic variability. Ground water data reported in the Pesticide National Synthesis only include samples from wells; data from springs and agricultural tile drains were not included. In the National Synthesis analysis (Gilliom et al., 2007), USGS uses a single sample to represent each well, generally the earliest sample with complete data for the full suite of analytes.

Over the course of Cycle 1 (1992-2001), some NAWQA analytical methods were improved or changed. Hence, detection thresholds varied over time for some compounds. USGS used the maximum Long

- Term Method Detection Level (LT

- MDL) for each analyte as a uniform reporting threshold. 1 The maximum LT

- MDL for terbufos was 0.009 μg/L (Gilliom et al., 2007). Terbufos was an analyte in the Pesticide National Synthesis Project , but terbufos sulfone was not.
In NAWQA stream samples ( Exhibit 5-8 ), terbufos was found at frequencies ranging from 0% of samples in undeveloped and urban areas to 0.05% of samples in agricultural settings, and 0.27% of samples in mixed land use settings. The 95 th percentile concentrations were less than the maximum LT

- MDL in all l and use settings. The highest surface water concentration of
0.560 μg/L , which is greater than the terbufos HRL , was detected at an agricultural site.

1 The LT

- MDL, developed by USGS, is a censoring level for analytical methods. Details are at: https://bqs.usgs.gov/ltmdl/calculation.html

.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-18 Exhibit 5-8 : USGS National Synthesis Summary of NAWQA Monitoring of Terbufos in Streams, 1992

- 2001

Land Use Type Number of Sites Number of Samples Detection Frequency (Samples) . Concentration Values (of detections, in μg/L)

.

. . . . Median 95 th Percentile Maximum
Agricultural 83 2,004 0.05% N D N D 0.56 0

M ixed 65 1,386 0.27% N D N D 0.03 1

Undeveloped 8 144 0% N D N D N D

Urban 30 811 0% N D N D N D ND = not detected (concentration is less than the maximum LT

- MDL and is expected to be less than any higher percentile concentration shown in the table)

.

I n NAWQA gr ound water samples ( Exhibit 5-9 ), terbufos was found at frequencies ranging from 0% of samples in undeveloped and agricultural areas to 0.04% of samples in mixed land use settings, and 0.12% of samples in urban areas. The 95 th percentile concentrations were less than the maximum LT

- MDL in all land use settings. The highest ground water concentration of 0.012 μg/L was detected at an urban site. No maximum detected concentrations of ground water exceeded the terbufos HRL.

Exhibit 5-9 : USGS National Synthesis Summary of NAWQA Monitoring of Terbufos in Ground Water, 1992

- 2001

Land Use Type Number of Wells Detection Frequency . Concentration Values (of detections, in μg/L)

.

. . . Median 95 th Percentile Maximum
Agricultural 1,405 0% N D N D N D

Mixed 2,729 0.04% N D N D 0.008

Undeveloped 34 0% N D N D N D

Urban 856 0.12% N D N D 0.01 2 ND = not detected (concentration is less than the maximum LT

- MDL and is expected to be less than any higher
pe rcentile concentration shown in the table)

.

S torage and Retrieval (STORET) Data Warehouse

EPA’s STORET Data Warehouse is a collaborative database that contains raw biological, chemical, and physical data from surface and ground water sampling conducted by federal, state

, and local agencies, Indian tribes, volunteer groups, academics, and others. A wide variety of data relating to water quality from all 50 states as well as multiple territories and jurisdictions of the United States are represented in this data system. These are primarily ambient water data, but in some cases they are finished drinking water data . Users began populating the STORET Data Warehouse in 1999. Most data are post-1999, but some earlier sampling is included.
STORET data have quality limitations. T he extent of national coverage and data completeness varies from parameter to parameter. There are no restrictions on submission of data based on analytical methods, quality assurance ( QA ) practices, etc. For more general STORET data informa tion, please refer to: http://www.epa.gov/storet/index.html

.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-19 EPA reviewed STORET g round water data from wells and surface water data from lakes, rivers/streams, and reservoirs (USEPA, 20 12). The STORET D ata Warehouse also included public w ater s ystem (PWS) data from three state s (Indiana, Missouri, and Ohio) ; EPA reviewed these as well (USEPA, 20 12). (For more data gathered by state drinking water programs, see the discussion of state monitoring data in S ection 5.4.2 , below.)
The results of the STORET analysis for terbufos are presented in Exhibit 5-10 through Exhibit 5-13

. (The STORET database does not contain any information on terbufos sulfone .) These STORET data represent terbufos samples collected between 1982 and 2010. Fewer records are available in the early years. Of 1,066 (625 surface water and 441 ground water) sites that submitted data, 138 (12.95% ) surface water sites reported detections of terbufos, with 14 (1.31 %) sites reporting a detection greater than 1⁄2 the terbufos HRL and 2 (0.19%) sites reporting a detection greater than the terbufos HRL

. All detections were at surface water sites. Detected concentrations ran ged from 0 μg/L to 3.2 μg/L. The maximum concentration of 3.2 μg/L was greater than the HRL. Minimum detected concentratio ns are reported in Exhibit 5-10 ; these minimum values may be indicative of reporting levels used. (A minimum value of zero, on the other hand, could represent a detection that was entered into the database as a non

- numerical value (e.g., “Present”) ). No Missouri or Ohio PWS data were available for this contaminant.

Exhibit 5- 10 : Terbufos STORET Data – Summary of Detected Concentrations

Source Water Type

. Concentration Value of Detections (μg/L)

. .

. Minimum Median 90 th Percentile Maximum

Ground Water N/A N/A N/A N/A

Surface Water 0 1 0 0.01 3.2

Total 0 1 0 0.0 1 3.2

PWS ( IN ) 2 0 0 0 0
N/A = not applicable ( no detections in this category ).

1 A minimum value of zero may represent a detection that was entered into the database as a non

- numerical value (e.g., “Present”).

2 It could not be determined from the data in STORET whether the Indiana PWS facilities were served by ground water or surface water.

E xhibit 5- 11 : Terbufos STORET Data – Summary of Samples

Source Water Type Total Number of Samples Samples with D etec tions . Samples with Detections > 1⁄2 HRL (0.175 μg/L) . Samples with Detections > HRL (0.35 μg/L) .

. . Number Percent Number Percent Number Percent

Ground Water 699 0 0% 0 0% 0 0%

Surface Water 5,826 457 7.84% 23 0.39% 2 0.03%

Total 6,525 457 7.00% 23 0.35% 2 0.03%

PWS ( IN ) 1 21 21 100% 0 0% 0 0%

1 It could not be determined from the data in STORET whether the Indiana PWS facilities were served by ground water or surface water.OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-20 Exhibit 5- 12 : Terbufos ST ORET Data – Summary of Sites

Source Water Type Total Number of Sites Sites with D etections . Sites with Detections > 1⁄2 HRL (0.175 μg/L) . Sites with D etections > HRL (0.35 μg/L) .

. . Number Percent Number Percent Number Percent

Ground Water 441 0 0% 0 0% 0 0%

Surface Water 625 138 22.08% 14 2.24% 2 0.32%

Total 1,066 138 12.95% 14 1.31% 2 0.19%

PWS ( IN ) 1 6 6 100% 0 0% 0 0%

1 It could not be determined from the data in STORET whether the Indiana PWS facilities were served by ground water or surface wat er.

E xhibit 5- 13 : Terbufos STORET Data – Summary of States

Source Water Type Total Number of

States States with D etections . States with D etections > 1⁄2 HRL (0.175 μg/L) . Stat es with D etections > HRL (0.35 μg/L) .

. . Number Percent Number Percent Number Percent

Ground Water 3 0 0% 0 0% 0 0%

Surface Water 17 11 64.71% 3 17.65% 2 11.76%

Total 1 17 11 64.71% 3 17.65% 2 11.76%

PWS ( IN ) 2 1 1 100% 0 0% 0 0%

1 The number of states with ground water data plus the number of states with surface water data may not equal the “Total” number of states providing data because some states provided both ground water and surface water data.

2 It could not be determined from the data in STORET whether the Indiana PWS facil ities were served by ground water or surface water.

5.4.2 Occurrence in Drinking Water

The agency reviewed a number of data sources for information on contaminant occurrence in drinking water. Data and information on terbufos and/or terbufos sulfone from the fo llowing sources are available and are summarized in this section :

• EPA’s First Unregulated Contaminant Monitoring Regulation (UCMR 1).

• EPA’s Second Unregulated Contaminant Monitoring Regulation (UCMR 2).

• State drinking water monitoring programs

.

• Consumer Confidence Reports (CCRs) from PWSs

.

• United States Department of Agriculture (USDA) Pesticide Data Program (PDP)

.

• USGS Pilot Monitoring Program (PMP)

.

• USGS NAWQA Source Water and Drinking Water Studies

.

• National Pesticide Survey (NPS)

.

• Monitoring i nformatio n reviewed by the OPP r eregistration p rogram

.

• Estimated concentrations in environmental media generated by EPA OPP modeling.

• Environmental Working Group (EWG) Drinking Water Database.
Note that there may be some overlap, as sources with different purposes and audiences may have reported the same underlying data.OW

– O G W DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5

- 21 Reviewed sources that contain no information on terbufos or terbufos sulfone occurrence included, among others, Rounds 1 and 2 of EPA’s Unregulated Contaminant Monitoring (UCM)

program, and EPA’s C ommunity Water System Survey (CWSS)

. Primary Data Sources
First Unregulated Contaminant Monitoring Regulation (UCMR 1) , 2001

- 2003
UCMR 1 required the collection of data to support nationally representative estimates of contaminant occurrence in PWSs. UCMR 1 monitoring occurred primarily from 2001 to 2003 and required surface water systems to monitor quarterly and ground water systems to monitor twice per year. There were two tiers of monitoring: Assessment Monitoring for contaminants with commonly used anal ytical method technologies, and Screening Survey monitoring for contaminants that require specialized analytical method technologies not in wide or common use.
All large PWSs serving more than 10,000 people, plus a statistically representative national sa mple of 800 small PWSs (serving 10,000 people or fewer) were required to conduct UCMR 1 Assessment Monitoring. For the UCMR 1 Screening Survey, EPA required monitoring by a representative sample of 120 large and 180 small PWSs. Monitoring by each PWS was

r equired during a 12

- month period between January 2001 and December 2003. Due to the small sample size, contaminant occurrence estimates based on data from UCMR 1 Screening Survey are statistically less robust than those based on data from the UCMR 1 Assess ment Monitoring. (For more details on all aspects of UCMR 1, refer to USEPA, 2008.)

A total of 2

, 301 terbufos samples were collected under the UCMR 1 Screening Survey Monitoring from 295 systems (178 small systems and 117 large systems) . There were no dete ctions of terbufos from any of the small or large systems that sampled under UCMR 1. The minimum reporting level (MRL) for terbufos was 0.5 μg/L. Terbufos sulfone was not an analyte
in UCMR 1.

The design of UCMR 1 permits estimat ion of nat ional occurrence

. To calculate national extrapolations, the percent of systems (or population served) estimated to exceed a specified threshold is multiplied by the total number of systems (or population served) in the nation. See Chapter 2 for additional information on na tional extrapolations. Since no detections of terbufos were observed among 2,301 samples from 295 systems in the UCMR 1 Screening Survey sample, terbufos occurrence in the nation’s small and large systems is likely to be negligible.
Second Unregulated Con taminant Monitoring Regulation (UCMR 2), 2008

- 2010
UCMR 2 monitoring, designed to provide nationally representative contaminant occurrence data, was conducted from 2008 to 2010. UCMR 2 require d surface water systems to monitor quarterly and ground water sy stems to monitor twice per year. There were two tiers of monitoring: Assessment Monitoring for contaminants with commonly used analytical method technologies, and Screening Survey monitoring for contaminants that require specialized analytical method techn ologies not in wide or common use.

All very large PWSs (serving more than 100,000 people) and large PWSs (serving 10,00 1

- 100,00 0 people), plus a statistically representative national sample of 800 small PWSs (serving 10,000 people or fewer), were required to conduct Assessment Monitoring during a 12

- month period between January 2008 and December 2010. For the Screening Survey, monitoring

was required by all very large PWSs, 320 representative large PWSs, and 480 representative small PWSs, during a 12

- month period between January 2008 and December 2010. See USEPAOW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-22 (2007), USEPA (2010b), and USEPA (2015) for more information on the UCMR 2 program, including study design and data analysis.

Terbufos sulfone was monitored under the UCMR 2 Assessment Monitoring, and terbufos was not. Monitoring results for terbufos sulfone from the UCMR 2 Assessment Monitoring ( as of July 2011) are presented in Exhibit 5-14 through Exhibit 5-18 . The MRL used for terbufos sulfone in this study was 0.4 μg/L , which is slightly greater than the terbufos sulfone
HRL (0.35 μg/L ).

The design of UCMR 2 permits estimat ion of nat ional occurrence . To calculate national extrapolations, the percent of systems (or population served) estimated to exceed a specified threshold is multiplied by the total number of systems (or population served) in the nation. (Note that because a ll large and very large systems were required to conduct UCMR 2 Assessment Monitoring, survey census figures are used in th ose size categories

. ) See Chapter 2 for additional information on national extrapolations. The results of this national extrapolation are presented in Exhibit 5-16 through Exhibit 5-18

. As of July 2011 , a total of 32,012 samples have been collected from 4,138 systems. Of these systems , one reported a detection of 0.42 μg/L, which is slightly greater than the terbufos sulfone HRL . T hese findings suggest that an estimated one PWS serving 44,600 people nation ally ha s a detection of terbufos sulfone greater than the terbufos sulfone HRL. That population of 44,600 represents approximately 0.02% of the national population served by
PWSs.

Exhibit 5- 14 : Terbufos Sul fone Occurrence Data from UCMR 2 Assessment Monitoring – Summary of Detected Concentrations

Total Number of Samples . . Concentration Value of Detections (μg/L)

. .

. Minimum Median 90 th
Percentile 99 th Percentile Maximum

. . . Small Systems (serving ≤ 1 0,000 people)

. . Ground Water N/A N/A N/A N/A N/A

Surface Water N/A N/A N/A N/A N/A
All Small Systems N/A N/A N/A N/A N/A

. . . Large Systems (serving 10,001 - 100,000 people)

-- CENSUS

. . Ground Water 0.42 0.42 0.42 0.42 0.42

Surface Water N/A N/A N/A N/A N/A
All Large Systems 0.42 0.42 0.42 0.42 0.42

. . . Very Large Systems (serving > 100,000 people)

-- CENSUS

. . Ground Water N/A N/A N/A N/A N/A

Surface Water N/A N/A N/A N/A N/A
All Very Large Systems N/A N/A N/A N/A N/A

. . . All Systems

. . All Water Systems 0.42 0.42 0.42 0.42 0.42

N/A = not applicable ( no detections in this category ).OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-23 Exhibit 5- 15 : Terbufos Sulfone National Occurrence Measures Based on UCMR 2 Assessment Monitoring Data – Summary of Samples

Source Water Type Total Number of Samples Samples with Detections . Samples with Detections > 1⁄2 HRL (0. 175 μg/L) . Samples with Detections > HRL ( 0.35 μg/L) .

. . Number Percent Number Percent Number Percent

. . . . Small Systems (s erving ≤ 10,000 people)

. . . Ground Water 2,328 0 0.00% 0 0.00% 0 0.00%

Surface Water 920 0 0.00% 0 0.00% 0 0.00%
All Small Systems 3,248 0 0.00% 0 0.00% 0 0.00%

. . . . Large Systems (serving 10,001 - 100,000 people)

-- CENSUS

. . . Ground Water 11, 680 1 0.01% 1 0.01% 1 0.01%

Surface Water 10,301 0 0.00% 0 0.00% 0 0.00% All Large Systems 21,981 1 0.005% 1 0.005% 1 0.005%

. . . . Very Large Systems (serving > 100,000 people)

-- CENSUS

. . . Ground Water 2,013 0 0.00% 0 0.00% 0 0.00%

Surface Water 4,770 0 0.00% 0 0.00% 0 0.00%

All Very Large Systems 6,783 0 0.00% 0 0.00% 0 0.00%

. . . . All Systems

. . . All Water Systems 32,012 1 0.003% 1 0.003% 1 0.003%

E xhibit 5- 16 : Terbufos Sulfone National Occurrence Measures Based on UCMR 2 Assessment Monitoring Data – Summary of System and Population Served Data – All Detections

Source Water Type UCMR 2 Sample

. Number (and Percent) of Detections in the UCMR 2 Sample . National Inventory

. National Estimat e 1 of the Number (and Percent) of Detections .

. Systems Population Systems Population Systems Population Systems Population

. . . . Small Systems (serving ≤ 10,000 people)

. . . .

Ground Water 618 1,790,743 0 (0%) 0 (0%) 57,818 37,685,557 0 (0%) 0 (0%)

Surface Water 182 878,262 0 (0%) 0 (0%) 3,866 8,928,745 0 (0%) 0 (0%)

All Small Systems 800 2,669,004 0 (0%) 0 (0%) 61,684 46,614,302 0 (0%) 0 (0%)

. . . . Large Systems (serving 10,001 - 100,000 people) – CENSUS

. . . .

Ground Water 1,374 34,828,693 1 (0.07%) 44,600 (0.13%) 1,37 4 34,828,693 1 (0.07%) 44,600 (0.13%)

Surface Water 1,56 6 49,720

, 870 0 (0%) 0 ( 0%) 1,56 6 49,720

, 870 0 (0%) 0 (0%)

All Large Systems 2,94 0 84,549
, 563 1 (0.03%) 44,600 (0.05%) 2,94 0 84,549 ,5 63 1 (0.03%) 44,600 (0.05%)OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-24 Source Water Type

. UCMR 2 Sample

. Number (and Percent) of Detections in the UCMR 2 Sample . National Inventory

. National Estimat e 1 of the Number (and Percent) of Detections .

Systems Population Systems Population Systems Population Systems Population

. . . . Very Large Systems (serving > 100,000 people) – CENSUS

. . . .

Ground Water 63 17,269,919 0 (0%) 0 (0%) 63 17,269,919 0 (0%) 0 (0%)

Surface Water 335 124,711,765 0 (0%) 0 (0%) 335 124,711,765 0 (0%) 0 (0%)

All Very Large Systems 398 141,981,684 0 (0%) 0 (0%) 398 141,981,684 0 (0%) 0 (0%)

. . . . All Systems

. . . .

All Water Systems 4,138 229,200
, 252 1 (0.02%) 44,600 (0.02%) 65,02 2 273,145
, 549 1 (0.002%) (0.02%) 44,600

1 National estimates for the small systems are extrapolations

, generated by multiplying the UCMR 2 national statistical sample findings of system/population percentages and national system/population inventory numbers for PWSs developed from EPA’s Safe Drinking Water Information System ( SDWIS ) , the CWSS, and UCMR (see Chapter 2 for discussion)

. National estimates for the large and very large systems are based directly on the UCMR 2 r esults

, since this was a census, i.e., all large and very large systems were required to conduct UCMR 2 Assessment Monitoring

. Due to rounding, some calculations may appear to be slightly off.

E xhibit 5- 17 : Terbufos Sulfone National Occurrence Measures Based on UCMR 2 Assessment Monitoring Data – Summary of System and Population Served Data – Detections > 1⁄2 HRL

. Source Water Type UCMR 2 Sample

. Number (and Percent) of Detections > 1/2 HRL (0.175 μg/L) in the UCMR 2 Sample . National Inventory

. National Estimate 1 of the Number (and Percent) of Detections > 1/2 HRL (0.175 μg/L) .

Systems Population Systems Population Systems Population Systems Population

. . . . Small Systems (serving ≤ 10,000 people)

. . . .

Ground Water 618 1,790,743 0 (0%) 0 (0%) 57,818 37,685,557 0 (0%) 0 (0%)

Surface Water 182 878,262 0 (0%) 0 (0%) 3,866 8,928,745 0 (0%) 0 (0%)

All Small Systems 800 2,669,004 0 (0%) 0 (0%) 61,684 46,614,302 0 (0%) 0 (0%)

. . . . Large Systems (serving 10,001 - 100,000 people) – CENSUS

. . . .

Ground Water 1,374 34,828,693 1 (0.07%) 44,600 (0.13%) 1,37 4 34,828,693 1 (0.07%) 44,600 (0.13%)

Surface Water 1,56 6 49,720

, 870 0 (0%) 0 (0%) 1,56 6 49,720

, 870 0 (0%) 0 (0%)

All Large Sys tems 2,94 0 84,549
, 563 1 (0.03%) 44,600 (0.05%) 2,94 0 84,549 ,5 63 1 (0.03%) 44,600 (0.05%)OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-25 . Source Water Type UCMR 2 Sample

. Number (and Percent) of Detections > 1/2 HRL (0.175 μg/L) in the UCMR 2 Sample . National Inventory

. National Estimate 1 of the Number (and Percent) of Detections > 1/2 HRL (0.175 μg/L) .

Systems Population Systems Population Systems Population Systems Population

. . . . Very Large Systems (serving > 100,000 people)

-- CENSUS

. . . .

Ground Water 63 17,269,919 0 (0%) 0 (0%) 63 17,269,919 0 (0%) 0 (0%)

Surface Water 335 124,711,765 0 (0%) 0 (0%) 335 124,711,765 0 (0%) 0 (0%)

All Very Large Systems 398 141,981,684 0 (0%) 0 (0%) 398 141,981,684 0 (0%) 0 (0%)

. . . . All Systems

. . . .

All Water Systems 4,138 229,200
, 252 1 (0.02%) 44,600 (0.02%) 65,02 2 273,145
, 549 1 (0.002%) (0.02%) 44,600

1 National estimates for the small systems are extrapolations

, generated by multiplying the UCMR 2 national statistical sample findings of system/population percentages and national system/population inventory numbers for PWSs developed from EPA’s SDWIS, the CWSS, and UCMR (see Chapter 2 for discussion)

. National estimates for the large and very large systems are based directly on the UCMR 2 results

, since this was a census, i.e., all large and very large systems were required to co nduct UCMR 2 Assessment Monitoring

. Due to rounding, some calculations may appear to be slightly off.

E xhibit 5- 18 : Terbufos Sulfone National Occurrence Measures Based on UCMR 2 Assessment Monitoring Data – Summary of System and Population Served Data – Detections > HRL

Source Water Type UCMR 2 Sample

. Number (and Percent) of Detections > HRL (0.35 μg/L) in the UCMR 2 Sample . National Inventory

. National Estimate 1 of the Number (and Percent) of Detections > HRL (0.35 μg/L) .

. Systems Population Systems Population Systems Population Systems Population

. . . . Small Systems (serving ≤ 10,000 people)

. . . .

Ground Water 618 1,790,743 0 (0%) 0 (0%) 57,818 37,685,557 0 (0%) 0 (0%)

Surface Water 182 878,262 0 (0%) 0 (0%) 3,866 8,928,745 0 (0%) 0 (0%)

All Small Systems 800 2,669,004 0 (0%) 0 (0%) 61,684 46,614,302 0 (0%) 0 (0%)

. . . . Large Systems (serving 10,001 - 100,000 people)

-- CENSUS

. . . .

Ground Water 1,374 34,828,693 1 (0.07%) 44,600 (0.13%) 1,37 4 34,828,693 1 (0.07%) 44,600 (0.13%)

Surface Water 1,56 6 49,720

, 870 0 (0%) 0 (0%) 1,56 6 49,720

, 870 0 (0%) 0 (0%)

All Large Systems 2,94 0 84,549
, 563 1 (0.03%) 44,600 (0.05%) 2,94 0 84,549 ,5 63 1 (0.03%) 44,600 (0.05%)OW – OGW DW Re gulatory Determination 3 Support Document

– Chapter 5, Terbufos and Terbufos Sulfone

5-26 . Source Water Type UCMR 2 Sample

. Number (and Percent) of Detections > HRL (0.35 μg/L) in the UCMR 2 Sample . National Inventory

. National Estimate 1 of the Number (and Percent) of Detections > HRL (0.35 μg/L) .

Systems Population Systems Population Systems Population Systems Population

. . . . Very Large Systems (serving > 100,000 people)

-- CENSUS

. . . .

Ground Water 63 17,269,919 0 (0%) 0 (0%) 63 17,269,919 0 (0%) 0 (0%)

Surface Water 335 124,711,765 0 (0%) 0 (0%) 335 124,711,765 0 (0%) 0 (0%)

All Very Large Systems 398 141,981,684 0 (0%) 0 (0%) 398 141,981,684 0 (0%) 0 (0%)

. . . . All Systems

. . . .

All Water Systems 4,138 229,200
, 252 1 (0.02%) 44,600 (0.02%) 65,02 2 273,145
, 549 1 (0.002%) 44,600 (0.02%)

1 National estimates for the small systems are extrapolations

, generated by multiplying the UCMR 2 national statistical sample findings of system/population percentages and national system/population inventory numbers for PWSs developed from EPA’s SDWIS, the CWSS, and UCMR (see Chapter 2 for discussion)

. National esti mates for the large and very large systems are based directly on the UCMR 2 results

, since this was a census, i.e., all large and very large systems were required to conduct UCMR 2 Assessment Monitoring

. Due to rounding, some calculations may appear to be slightly off.

Supplemental Data Sources

State Monitoring Data , 2002 -2007

Since there is no national database that receives and stores all relevant data regarding the occurrence of regulated contaminants in public drinking water systems, EPA conducted a voluntary data call

- in from the states, territories, and tribes to obtain regulated contaminant occurrence data in support of national occurrence assessments conducted for the second Six- Year Review. For more details on the Six- Year Review - Information Col lection Request ( ICR ) Dataset, refer to USEPA (2009a ).

A few states also submitted PWS occurrence data for unregulated contaminants. EPA was able to supplement these data on unregulated contaminants by downloading additional publicly available monitoring data from state W eb sites. The result was a collection of UCM data from nine states, representing those states with varying degrees of completeness.
Drinking water occurrence data for terbufos were submitted by the State of California. Terbufos results from 0.7% of community water systems ( CWSs ) and 0.07% of non- transient

non- community water systems ( NTNCWSs ) were included in data submitted from California. Precise information about methods used and reporting levels is not available.

An analysis of th os e data indicates that terbufos was not detected in any of the 191 drinking water samples collected from 23 systems between 2002 and 2007

. No data on terbufos sulfone were reported

. Water Systems’ Consumer Confidence Report s (CCR s), 1997

CCRs are an nual 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; they may also include generalOW

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- 27 educational material. Under the CCR Rule (40 CFR Subpart O), CWSs with 15 or more connections or serving at least 25 year

- round residents mu st prepare and distribute a CCR to all billing units or service connections every year. Systems 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 sys tems that serve over one million customers for unregulated contaminant occurrence information. Data on terbufos were available only from the CCR for New York City. Reporting levels were not specified in this CCR

. New York City included data on terbufos in its 1997 CCR. The city is served by 2 distribution systems supplied by surface water from 19 reservoirs and 3 controlled lakes, and 1 distribution system supplied by treated ground water. A total of 22 terbufos samples were taken at one surface water syste m, 10 samples at the other surface water system, and 22 at the ground water system that year. There were no detections of terbufos

. United States Department of Agriculture (USDA) Pesticide Data Program (PDP) , 2001

- 2009
The USDA PDP maintains a national pe sticide residue database. PDP was initiated in 1991 to collect data on pesticide residues in food with sampling conducted on a statistically defensible representation of pesticide residuals in the United States food supply (USDA, 20 11 ). Sampling and testin g are conducted on fruits and vegetables, select grains, milk, and (as of 2001) drinking water.
The PDP drinking water sampling program was initiated at CWSs in New York and California in 2001. Since then the drinking water sampling program has expanded, t hough a somewhat changing mix of states is sampled each year. At one time or another, CWSs in 27 states and Washington, D.C.

, have contributed raw and/or finished water data to the program (USDA, 2011). The CWSs selected for sampling tend to be small

- and medium

- sized systems (primarily CWSs serving under 50,000), systems served by surface water, and systems located in regions of heavy agriculture. Sampling of raw water in addition to finished water began in 2004 (USDA, 2004).

Terbufos and terbufos sulfone were included in the USDA PDP (USDA, 2012) . Neither contaminant was detected in any of the 4,168 total terbufos samples ( including 2,597 finished samples )

, or 4,101 total terbufos sulfone samples ( including 2,923 finished samples )

, collected between 2001 an d 2009 . The number of samples each year ranged from 134 to 612 for terbufos and from 238 to 794 for terbufos sulfone

. Terbufos ha d limits of detection ranging from 0.00 52

to 0.1 00 μg/L . Terb ufos sulfone ha d limits of detection ranging from 0.00 4 5 to 0.0 1 8 μg/L

. Note that temporal trends cannot be evaluated based on these data since, with the exception of 2002 and 2003, samples were not collected from the same sites and states in consecutive years.
United States Geological Survey (USGS) Pilot Monitoring Pr ogram (PMP) , 1999
In 1999, PMP was initiated by USGS and EPA to provide information on pesticide concentrations in drinking water. This study focused on small drinking water supply reservoirs in areas with high pesticide use in order to test the sampling a pproach in areas where pesticides are probably present (Blomquist et al

. , 2001). Sampling sites represent a variety of geographic regions, as well as different cropping patterns. The ideal site candidates were mostly small reservoirs located in high pestic ide

- use areas, with a high runoff potential. Twelve water

- supply reservoirs, considered vulnerable to pesticide contamination, were selected from the list of candidates. These 12 sites were located in California, Indiana, Ohio, Oklahoma, Louisiana, Missour i, South Carolina, South Dakota, New York, North Carolina, Pennsylvania, and Texas.OW

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- 28 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 drinking water tap prior to entering the distribution system. At some sites, samples were also collected at the reservoir outflow.
Terbufos was an analyte in the PMP. At a method reporting level of 0.013 μg/L , terbufos was not detected in any of the raw or finished water sites from the 12 sites sampled (Blomquist et al., 2001).

The PMP did not include t erbufos sulfone as an analyte but did include the related metabolite terbufos

- O

- analogue sulfone. At a repor ting method level of 0.016 μg/L , t erbufos

- O

analogue sulfone was not detected in any of the 317 raw water samples but was detected in two (0.9%) of the 221 finished water samples. The highest concentration detected was 0.016 μg/L

, which is less than the te rbufos HRL

. United States Geological Survey (USGS) National Water Quality Assessment (NAWQA) Source Water and Drinking Water Studies
Organic Compounds in Source Water of Selected Community Water Systems (Hopple et al., 2009 and Kingsbury et al., 2008), 20 02

- 2005
Hopple et al. (2009) and Kingsbury et al. (2008) conducted studies

, as part of the NAWQA program, to characterize anthropogenic organic compounds in U

. S

. waters used as source waters for PWSs. Hopple et al. (2009) focused on ground water and Kingsb ury et al. (2008) focused on surface water. In Phase 1 of the studies, geographically diverse source water samples were collected between October 2002 and July 2005 from nine CWSs served by streams and from 221 CWS wells that withdraw from 12 aquifers. In Phase 2 of the studies, USGS collected source and finished water samples at a subset of sites between June 2004 and September 2005. In Phase 1 of the studies, terbufos was not detected in 221 ground water samples or 146 surface water samples. In Phase 2 of the studies, a total of 48 raw and 48 finished ground water samples were analyzed for terbufos. It was not detected in any ground water samples. Terbufos was not included in the surface water portion of Phase 2 (Hopple et al., 2009; Kingsbury et al., 2008 ). The reporting level for terbufos was 0.0 17 μg/L, and was the same for both phases and for ground and surface water samples.
Water Quality in Public

- Supply Wells ( Toccalino et al.
, 2010) , 1993

- 2007
As a part of the NAWQA program, water samples were colle cted from source (untreated) ground water from 932 public

- supply wells located in parts of 40 NAWQA Study Units in 41 states (Toccalino et al., 2010). Each well was sampled once between 1993 and 2007. The public wells sampled in this study represented 629 unique PWSs, representing 0.5% of the approximately 140,000 ground

- water

- supplied PWSs, but nearly 25% of the population served by ground water

- PWSs in the United States. A total of 898 samples from these wells were analyzed for terbufos. Terbufos was not detected in any of the 898 samples collected. Reporting limits used for terbufos in this study ranged from 0.006 μg/L to 0.01 3 μg/L.
Water Quality in Domestic Wells ( DeSimone
, 2009) , 1991

- 2004
USGS conducted a recent assessment of the quality of water fro m domestic wells across the United States using NAWQA data (DeSimone, 2009). The program included the analysis of major ions, trace elements, nutrients, radon, and organic compounds (pesticides and volatile organic compounds ( VOCs ) ) at approximately 2,100 domestic wells (private drinking water wells) across 48 states, covering 30 regional aquifers, between 1991 and 2004. In addition,OW

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- 29 USGS summarized data from wells sampled for NAWQA agricultural land

- use assessment studies to provide an indication of the po tential effects of agricultural land

- use practices on the ground water in the aquifers studied. Reporting thresholds varied ; thresholds of both 0.00 9 μ g/L and 0.01 3 μ g/L are listed

. Terbufos was detected in one (0.04%) of the 2,539 samples from aquifer and agricultural land

- use studies , at an unspecified concentration that was less than 0.01 μg/L, and therefore also less than the terbufos HRL and 1⁄2 the terbufos HRL

. Water Quality in Carbonate Aquifers ( Lindsey et al.
, 2008) , 1993

- 2005
As part of the NAWQA p rogram, Lindsey et al. (2008) conducted an assessment of the

wate r quality in carbonate aquifers, which account for 22% of the ground water pumped by the country’s PWSs

. From 1993 to 2005, the study analyzed 1,042 wells and springs across 12 aquifer system s and 20 states for major ions, radon, nutrients, pesticides, and VOCs. Terbufos was not detected in any of 1,027 samples. Reporting levels were not given

. National Pesticide Survey (NPS) , 1988

- 1990
In 1990, EPA completed a national survey of pesticides a nd pesticide degradates in drinking water wells. The purpose of the NPS was to determine the national occurrence frequencies and concentrations of select pesticides in the nation’s drinking water wells, and to improve EPA’s understanding of how pesticide o ccurrence in ground water correlates with patterns of pesticide usage and ground water vulnerability. The survey included 566 CWS wells and 783 rural domestic wells. Sampling was conducted between 1988 and 1990. The survey targeted areas representing a var iety of pesticide usage levels and ground water vulnerability. The survey was designed to provide a statistically reliable estimate of pesticide occurrence in the nation’s drinking water wells. It was not designed to provide statistically valid results at the state or local level. Wells were sampled for 101 pesticides, 25 pesticide degradates, and nitrate (USEPA, 1990).
Terbufos was included as an analyte, but could not be quantified or reliably detected with the analytical techniques available (USEPA, 1990 ). Terbufos sulfone was not included in the study.
Monitoring Information Reviewed by the OPP Reregistra tion Program

EPA OPP gathered monitoring information from various sources in the RED for terbufos ( USEPA

, 2006)

. Reviewed d ata on terbufos in ground wa ter came from the registrant, USGS NAWQA, EPA’s Pesticides in Ground W ater Database, and several states within the major use

areas. There were 20 confirmed detections of terbufos , plus another seven questionable or unconfirmed detections, out of 4,563 grou nd water samples taken in 13 states. Concentrations of terbufos detected in the ground water studies ranged from 0.01 μg/L to a maximum concentration of 20.0 μg/L , which is greater than the terbufos HRL and 1⁄2 the HRL . In Iowa, 13 wells were also sampled fo r terbufos sulfone; it was not detected in any samples

. Reporting levels are not provided in the RED (USEPA, 2006)

. OPP Estimated Concentrations
EPA’s OPP used modeling to develop estimated environmental concentrations (EECs) for acute and chronic exposu re scenarios for terbufos and its degradates (terbufos sulfone and terbufos sulfoxide), in aggregate, in surface water and ground water (USEPA, 2006). The EECs were developed using the Pesticide Root Zone Model/Exposure Analysis Modeling System (PRZM/EXAMS ) and Screening Concentrations in Ground Water (SCI

- GROW) model.OW

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- 30 For acute and chronic exposure, the EEC values for terbufos and its degradates, in aggregate, range from 4.8 to 7.4 μg/L in ground water. In surface water, EEC values for terbufos and its de gradates, in aggregate, range from 5.4 to 13.3 μg/L and from 1.3 to 5.5 μg/L for acute and chronic exposures, respectively.
Environmental Working Group (EWG) Drinking Water Database, 2004

- 2009

In December 2009, EWG released its “National Drinking Water Dat abase

, ” which includes data on occurrence of drinking water contaminants (regulated and unregulated) collected between 2004 and 2009 from 45 states and the District of Columbia (EWG, 2009) . The 2009 EWG database includes results from approximately 48,000 w ater systems; data were obtained pri marily from state water offices.
EWG reviewed the data for inconsistencies, potential outliers

, and other errors

. It also invited the American Water Works Association (AWWA) and the Association of Metropolitan Water Agen cies (AMWA) to review the data and/or have their constituents, the PWSs, review the data. S ome corrections apparently were made since the public release of the data in December

, 2009. The data analyzed by EPA were downloaded on December 29 , 2010. EPA’s

ana lysis is based solely on the data made publicly available by EWG on its W eb site. Reporting levels are n ot specified in EWG’s database.

As of November 1 0 , 2010, a total of 195 systems reported having tested for terbufos between 2004 and 2009. No detections of terbufos were found.



### 5.5 Technology Assessment

5.5.1 Analytical Methods
EPA has developed three analytical methods for the analysis of terbufos in drinking

water :

• EPA Method 507, Revision 2.1, Determination of Nitrogen

- and Phosphorus

Containing Pesticides in W ater by Gas Chromatography with a Nitrogen

- Phosphorus Detector, has a Method Detection Limit (MDL) of 0.054 μ g/L. The method lists

r ecoveries rang ing from 77 to 97%, with Relative Standard Deviations (RSDs) of 4 to 7%. However, personnel from EPA’s Technic al Support Center (TSC) have indicated that terbufos is not stable by this method (USEPA, 1995a)

.

• EPA Method 525.2, Revision 2.0, Determination of Organic Compounds in Drinking Water by Liquid

- Solid Extraction and Capillary Column Gas Chromatography/Mass
S

pectrometry, has MDLs that range from 0.077 to 0.15 μ g/L. The method lists recoveries ranging from 90 to 123%, with RSDs of 4.2 to 11%. However, personnel from EPA’s TSC have indicated that terbufos is not stable by this method (USEPA, 1995b)

.

• EPA Method 5 26, Revision 1.0, Determination of Selected Semivolatile Organic Compounds in Drinking Water by Solid Phase Extraction and Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS) , has MDLs that range from 0.017 to
0.05 μ g/L. Recoveries range from 80. 2 to 128%, with RSDs of 1.6 to 4.6% (USEPA, 2000)

. EPA has developed one analytical method for the analysis of terbufos sulfone in drinking

water :OW – OGW DW Re gulatory Determination 3 Support Document

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5-31 • EPA Method 527, Revision 1.0, Determination of Selected Pesticides and Flame Retardants in Drinking Water by Solid Phase Extraction and Capillary Column Gas Chromatography/Mass Spectrometry (GC/MS), has a Detection Limit (DL) of 0.041 μg/L. The Lowest Concentration Minimum Reporting Level (LCMRL) is 0.27 μg/L. The method lists recoveries ranging from 87.3 to 111%, with RSDs of 1.6 to 11%. However, personnel from EPA’s TSC have indicated that there are stability problems with terbufos sulfone via this method (USEPA, 2005).
Although not included in any analytical methods, the MRL for terbufos is 0.5 μg/L. This valu e serve d as a national benchmark for laboratories that participated in UCMR 1 using EPA Method 526 (66 FR 2273; USEPA, 2001b). The MRL of 0.5 μg/L for use of EPA Method 526 was obtained from precision and accuracy measurements made during method development. The MRL of 0.5 μg/L was also verified by second laboratory validation (66 FR 2273; USEPA, 2001b). Note that the MRLs established for UCMR 1 were defined and calculated differently from those MRLs used in subsequent rounds of UCMR.
Although not included in any analytical methods, the MRL for terbufos sulfone is 0.4 μg/L. This value serves as a national benchmark for laboratories participating in UCMR 2 using EPA Method 527 (72 FR 367; USEPA, 2007). The MRL of 0.4 μg/L was determined by EPA using data gen erated from EPA Method 527.
An estimated reporting level for the method (calculated as the MRL) was compared to the
HRL s for terbufos and terbufos sulfone to determine whether the available analytical method s

are capable of reliable quantitation at concen trations of estimated toxicological concern (see Exhibit 5-19 ). The Method Sensitivity Ratio (MSR) is calculated from the following equation:

MSR = HRL (μg/L) / MR L (μg/L)

A favorable MSR is one that is greater than 10. That is, i t is preferable that the HRL be at least 10 times above the concentration at which data can be reliably reported; this provides a margin of safety for uncertainty in the HRL and/or method performance (see USEPA, 2009b).

Exhibit 5- 19 : Method Sensitivity Ratio (MSR) for Terbufos and Terbufos Sulfone

Contaminant Name Method M RL ( μ g/L) HRL ( μ g/L) MSR

Terbufos 526 0.5 0.35 0.7

Terbufos Sulfone 527 0.4 0.35 0.88

B oth of the MSRs are less than 10 ; hence, the available analytical method s are not capable of r eliable quantitation at least 10 times below the HRL.

5.5.2 Treatment Technologies
The availability of treatment technologies is not a factor EPA considers when making a regulatory determination. However, suitable treatment technologies must be made available before a National Primary Drinking Water Regulation (NPDWR) can be promulgated.OW – OGW DW Re gulatory Determination 3 Support Document

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5-32 A preliminary review of the literature reveals that the following treatment technologies have been investigated empirically for their applicability to terbufos:

• Ultraviolet (UV) irradiation (photocatalysis with titanium dioxide)

.

• Chlorine.

• Conventional treatment.
Based on percentage -removal values reported in the reviewed literature, the most promising option appears to be UV irradi ation (photocatalysis with titanium dioxide ).

The preliminary review of the literature revealed no information about the applicability of treatment technologies to terbufos sulfone.
Please note that the literature review was not exhaustive, and findings f rom the reviewed studies might not be directly comparable. A full assessment of treatment technology applicability will require a more detailed review and analysis of the literature, and possibly additional research.



### 5.6 Regulatory Determination

5.6.1 Making Regulatory Determinations for Chemicals on the CCL
The statutory requirements for the CCL and regulatory determinations can be found in SDWA Section 1412(b)(1). The 1996 SDWA Amendments require EPA to publish the CCL every five years. The CCL is a list of contami nants that are not subject to any proposed or promulgated NPDWRs, are known or anticipated to occur in PWSs, and may require regulation under SDWA to protect public health. The 1996 SDWA Amendments also direct EPA to determine whether or not to regulate at least five contaminants from the CCL every five years. There are three criteria to be considered in making a regulatory determination. A decision to regulate is warranted if :

(a) the contaminant may have an adverse effect on the health of persons;

(b) t he contaminant is known to occur or there is substantial likelihood that the contaminant will occur in PWS s with a frequency and at levels of public health concern; and
(c) in the sole judgment of the Administrator, regulation of such contaminant presents a meaningful opportunity for health risk reduction for persons served by PWS s.

If EPA determines that all three of these statutory criteria are met , it makes a preliminary positive regulatory determination that a n NPDWR 2 is needed . Following a comment r esponse period and a final positive regulatory determination, t he agency has 24 months to publ ish a proposed Maximum Contaminant Level Goal 3 (MCLG) and an NPDWR. After the proposal, the

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 for public water systems for a specific contaminant or group of contaminants.

3 The MCLG is the "maximum level of a contaminant in drinking water at which no known or anticipate dOW

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- 33 a gency has 18 months to publish a final MCLG and promulgate a final NP DWR (SDWA section 1412(b)(1)(E)). 4 The agency may determine that there is no need for a regulation when a contaminant fails to meet one or more of the criteria. A decision not to regulate is considered a final agency action and is subject to judicial revie w. The agency can choose to publish a Health Advisory (a non

- regulatory action) or other guidance for any contaminant on the CCL, independent of the regulatory determination. Refer to section 1.4 for a summary of the approach used to identify and evaluate contaminants for RD 3. The following section summarizes the RD 3 decision for terbufos and terbufos sulfone

. 5.6.2 Health Effects (Criterion #1)
The first criterion asks if the contaminant may have an adverse effect on the health of

persons. Since all chemicals have adverse effects at some level of exposure, the challenge is to identify a HRL, a dose below which adverse health effects are considered unlikely to occur (threshold toxicant), or below which adverse effects have a defined low probability of occurrence (non

- threshold toxicant). The key elements that must be considered in evaluating the first criterion are the mode of action, the critical effect(s), the dose

- response for critical effect(s), the RfD for threshold effects, and the slope factor for non

- thre shold effects.
A full description of the health effects associated with exposure to terbufos and terbufos sulfone is presented in Section 5

. 3 of this document.

Health Criterion Data
Terbufos has been found to be readily absorbed. The proposed metabolic pat hway for terbufos consists of sulfoxidation and desulfuration of terbufos, followed by hydrolysis of the thiolophosphorus bond, enzymatic S

- methylation, and then additional S

- oxidation to final metabolites sulfone, t

- butyl (methyl

- sulfonyl) methyl and sulf oxide, ( t

- butylsulfonyl) methyl methyl (Cheng, 1992). Although there have been no pharmacokinetic studies identified for terbufos sulfone, systemic effects indicate that the compound is absorbed. There are limited data available on terbufos and terbufos su lfone in humans. Clinical signs of cholinergic toxicity were noted in animal studies, and included tremors, salivation, exophthalmos, prostration, decreased activity, chromodacryorrhoea, diuresis, piloerection, ataxia, urogenital staining, nasal discharge, anorexia, and labored breathing from oral exposure to terbufos. Animal studies have reported ChE inhibition as the critical effect for subchronic and chronic exposures to terbufos. There are no subchronic or chronic studies available which describe the ef fects of terbufos sulfone.
EPA concluded in 2003 and in 2006 that the existing toxicity database for terbufos is sufficient to evaluate its potential hazards to the general population, and adequate to characterize its potential hazards to fetuses, infants , and children. Developmental studies of terbufos in rats and rabbits did not find any developmental effects (USEPA, 2003) and no sensitive populations were identified or characterized. A two

- generation reproductive study in rats reported that terbufos cau sed a decrease in male fertility, the number of pregnant females, pup viability, and pup body weight in the highest dose group (Schroeder, 1989). There are no data on reproductive and developmental effects of terbufos sulfone. Terbufos has been found to be negative in the majority of mutagenicity tests, both in vivo animal studies (chromosomal aberrations in rats) and in vitro studies (i.e., reverse mutation in Salmonella typhimurium , point mutations and

adverse effect on the health of persons would occur, and which allows an adequate margin of safety. Maximum contaminant level goals are non

- enforceable health goals." (CFR 141.2)

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

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- 34 chromosomal aberrations in CHO cells, and unscheduled DNA synthesis in primary male rat hepatocytes) (USEPA, 2003). Genotoxicity studies of terbufos sulfone are lacking.
Dog studies, by Shellenberger (1984) and Shellenberger and Billups (1986), on ChE inhibition were identified as the critical studies for es tablishing the RfD of 0.00005 mg/kg

- day for terbufos. The RfD was derived from a NOAEL of 0.005 mg/kg

- day and a net UF of 100 for interspecies and intraspecies variability (USEPA, 2006). EPA calculated a non

- cancer HRL of 0.35 μg/L for terbufos using the R fD of 0.00005 mg/kg

- day for a 70 kg adult ingesting 2 L of drinking water per day and a RSC of 20%. Lacking subchronic or chronic studies, the OPP RED did not develop an RfD for terbufos sulfone (USEPA, 2006). Bailey (1988) conducted a 14

- day study of both terbufos and terbufos sulfone in dogs. Data from the study suggests that terbufos sulfone is less toxic than its parent, and that the use of the terbufos HRL of 0.35 μg/L for terbufos sulfone is reasonable

. There has been no evidence that terbufos is car cinogenic in either mice (Silverman et al., 1986) or in rats (Rapp, 1974). EPA (USEPA, 1988) determined that the data were not adequate to make a determination regarding the potential carcinogenicity of terbufos and placed it in Group D (not classifiable a s to human carcinogenicity), following the agency’s 1986 cancer guidelines (USEPA, 1986). There are no long

- term animal studies of terbufos sulfone carcinogen i city.

Health Criterion Conclusion
Toxicological data from animal studies indicate that terbufos exposure is associated with ChE inhibition and reproductive effects. Data on ChE inhibition in dogs support the development of an HRL of 0.35 μg/L for human exposure to terbufos via drinking water. The l imited data on terbufos sulfone toxicity suggest that it is less toxic than its parent , making an HRL of 0.35 μg/L for terbufos sulfone protective of human health. Based on these considerations, EPA concludes that terbufos and terbufos sulfone meet the SDWA statutory criterion #1 for regulatory determination ; they may have an adverse effect on the health of persons.

5.6.3 Occurrence in Public Water Systems (Criterion #2)

The second criterion asks if the contaminant is known to occur or if there is a substantial likelihood that the contaminant will occur in PWSs wit h a frequency and at levels of public health concern. In order to address this question, EPA consulted a variety of information sources, including data from the UCMR 1 Screening Survey and the UCMR 2 Assessment Monitoring

, national survey s of PWSs conducte d from 2001 to 2003 and from 2008 to 2010 , respectively

. EPA examined the total number of systems that reported detections of terbufos and terbufos sulfone, as well as those that reported concentrations of terbufos and terbufos sulfone above their respecti ve HRLs (both 0.35 μg/L).
Available monitoring data, including data that may shed light on regional and national occurrence, are presented in Section 5

. 4 , and are summarized below. Additional information on production, use, and fate is found in Section 5

. 2

. Occurrence Criterion Data
The primary occurrence data for terbufos are from the UCMR 1 screening survey (2001

- 2003). The UCMR 1 screening survey collected 2,301 finished water samples from 295 PWSs. Terbufos was not detected at levels at or above the MRL (0.5 μg/L), which is slightly higher than the HRL (0.35 μg/L).OW

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- 35 The primary occurrence data for terbufos sulfone are nationally

- representative finished water monitoring data generated through EPA’s UCMR 2 (2008

- 2010). UCMR 2 collected 32,012 finished wate r samples from 4,138 PWSs. Terbufos sulfone was detected in only one sample, at a concentration of 0.42 μg/L. The MRL was 0.4 μg/L, which is slightly higher than the HRL (0.35 μg/L).

Finished water data for terbufos and terbufos sulfone from California, I owa, USDA, and USGS are consistent with the UCMR 1 and UCMR 2 data. The State of California reported no detections of terbufos in 191 samples from 23 PWSs. The State of Iowa reported no detections of terbufos sulfone from 13 wells. The USDA PDP monitored f or terbufos (2,597 samples) and terbufos sulfone (2,923 samples) in finished water from 2001 to 2009 and reported no detections. The USGS PMP monitored for terbufos in finished water in 1999 and reported no detections.
Terbufos and (very limited) terbufos sulfone occurrence data for ambient water from EPA, STORET, and several USGS programs or studies are consistent with those for finished water. The USGS NAWQA Program (1992

- 2001) reported no groundwater detections above 1⁄2 the HRL (0.175 μg/L) or the HRL (0 .35 μg/L) for terbufos in 20,960 samples at 7,118 sites. NAWQA reported surface water detections for terbufos in 28 of 14,480 samples (0.19%) at 20 of 1,907 sites (1.05%). Of the 28 surface water detections for terbufos, only four samples (0.03%) at four s ites (0.21%) were above 1⁄2 the HRL and only one sample (0.01%) at one site (0.05%) was above the HRL (Gilliom et al., 2007). The NAWQA Carbonate Aquifer Study (1993

- 2005; Lindsey et al., 2008) and the NAWQA Domestic Well Water Quality Study (1991

- 2004; DeSi mone, 2009) reported no detections for terbufos above 1⁄2 the HRL or the HRL in 1,027 and 2,539 samples, respectively. Ambient water data from a two phase USGS study conducted between 2002 and 2005 by Hopple et al. (2009) and Kingsbury et al. (2008) reported no terbufos detections in the 221 Phase 1 groundwater samples or the 146 Phase 1 surface water samples. In Phase 2, there were no detections of terbufos from 48 raw and 48 finished groundwater samples. (Terbufos was not included as an analyte in the Phase 2 surface water study.) Ambient water data from a USGS study conducted between 1993 and 2007 by Toccalino et al. (2010)

, reported no terbufos detections in 898 groundwater samples. Terbufos ambient data reported in the EPA
OPP’s RED for t erbufos included 20 detections in 4,563 groundwater samples from 13 s tates. The detected concentrations ranged from 0.01 to 20 μg/L, a range that extends both above and below 1⁄2 the HRL (0.175 μg/L) and the HRL (0.35 μg/L). The USGS PMP monitored for terbufos in ambient wat er in 1999 and reported no detections. Terbufos ambient data are reported in STORET from 17 s tates. No groundwater detections were reported in 699 samples at 441 sites. STORET reported surface water detections in 457 of 5,826 samples (7.84%) at 138 of 625 sites (22.1%). Of the 457 surface water detections, only 23 samples (0.39%) at 14 sites (2.24%) were above 1⁄2 the HRL and only two samples (0.03%) at two sites (0.32%) were above the HRL.

Occurrence Criterion Conclusion
Terbufos was not detected in any of t he 2,301 UCMR 1 samples collected by 295 PWSs, using an MRL of 0.5 μg/L, which is slightly higher than the HRL (0.35 μg/L). Terbufos sulfone was detected in only one out of 32,012 UCMR 2 samples from 4,138 PWSs, using an MRL of 0.4 μg/L, which was slightly higher than the HRL (0.35 μg/L). The detected terbufos sulfone concentration was 0.42 μg/L.

Based on these considerations, EPA concludes that terbufos and terbufos sulfone do not meet the SDWA statutory criterion #2 for regulatory determination; they do n ot occur with a frequency and at levels of public health concern in PWS s.OW

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- 36 5.6.4 Risk Reduction (Criterion #3)
The third criterion asks if, in the sole judgment of the Administrator, regulation presents a meaningful opportunity for health risk reduction for perso ns served by PWS s. In evaluating this criterion, EPA looked at several factors.
EPA calculated the total exposed population and the population exposed to levels above the HRL. Estimates of the populations exposed and the levels to which they are exposed we re derived from the monitoring results. These estimates are included in Section 5

. 4 and summarized in the “Exposed Population Estimates” section below.
In evaluating the third criterion, EPA also considered effects on potentially sensitive populations, inc luding the fetus, infants, and children. Sensitive population considerations are discussed in the “Sensitive Populations” section, below.
Exposed Population Estimates
The estimated population exposed to terbufos at or above the MRL is 0%; the compound

wa s not found to occur in finished water at levels greater than or equal to the MRL (0.4 μg/L), which is slightly higher than the HRL (0.35 μg/L), in 2,301 samples from 295 PWSs in
UCMR 1.
The estimated population exposed to terbufos sulfone at a level of p ublic health concern is 44,600 (0.02% of the population served by PWSs); there was only one detection greater than the HRL in 4,138 PWSs (1 of 32,012 samples in UCMR 2).
Sensitive Populations
EPA also evaluated whether information is available regarding th e potential health effects on children and other sensitive populations. Developmental studies with terbufos in rats and rabbits did not find any developmental effects (USEPA, 2003). There are no data on reproductive and developmental effects for terbufos s ulfone. No sensitive populations were identified or characterized. The OPP RED (USEPA, 2006) presents more detailed information about the potential health effects and sensitive populations for terbufos and terbufos sulfone

. Risk Criterion Conclusion

Base d on the estimated exposed populations, including sensitive subpopulations, EPA has determined that terbufos and terbufos sulfone do not meet the SDWA statutory criterion #3 for regulatory determination; regulation of neither terbufos nor terbufos sulfone presents a meaningful opportunity for health risk reduction for persons served by PWSs.

5.6.5 Final Regulatory Determination Decision
As stated in the “Criteria for Regulatory Determination” section above, a positive finding for all three criteria is required i n order to make a determination to regulate a contaminant. EPA has made a final determination under RD 3 that terbufos and terbufos sulfone do not meet all three criteria.
Terbufos has the potential to cause adverse health effects, including ChE inhibitio n and reproductive effects. The limited toxicity studies for terbufos sulfone suggest that it is less toxic than the parent compound. Neither terbufos n or terbufos sulfone appear to occur in PWS s with a frequency and at levels of public health concern. Ter bufos was not detected in any of the 2,301 UCMR 1 samples collected by 295 PWSs, using an MRL of 0.5 μg/L, which is slightly higher than the HRL (0.35 μg/L). Terbufos sulfone was detected in only one out of 32,012 UCMR 2OW

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5

- 37 samples from 4,138 PWSs, using an M RL of 0.4 μg/L, which was slightly higher than the HRL (0.35 μg/L). The detected terbufos sulfone concentration was 0.42 μg/L. Due to the relatively small number of people likely exposed to terbufos and terbufos sulfone through drinking water, EPA conclude s that regulation of terbufos or terbufos sulfone does not represent a meaningful opportunity for health risk reduction for persons served by PWS s

. Additional information about the final regulatory determination can be found in the associated Federal Regi ster n otice.



### 5.7 References

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