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June 1994External Review Draft
ESTIMATING EXPOSURE TO DIOXIN-LIKE COMPOUNDS
VOLUME I: Executive Summary |
NOTICE
THIS DOCUMENT IS A PRELIMINARY DRAFT. It has not been formally released by the U.S.
Environmental Protection Agency and should not at this stage be construed to represent
Agency policy. It is being circulated for comment on its technical accuracy and policy
implications. Exposure Assessment GroupOffice of Health and Environmental AssessmentU.S. Environmental Protection Agency
Washington, D.C. |
DISCLAIMER
This document is an external draft for review purposes only and does not constitute
U.S. Environmental Protection Agency policy. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use. |
CONTENTS OVERVIEW Part I |
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CONTENTS Part I |
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I: |
INTRODUCTION |
1 |
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- I.1. BACKGROUND 1
- I.2. TOXICITY EQUIVALENCY FACTORS 2
- I.3. OVERALL COMMENTS ON THE USE OF THE DIOXIN EXPOSURE DOCUMENT 6
- REFERENCES FOR INTRODUCTION 8
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II: |
PROPERTIES, SOURCES, ENVIRONMENTAL LEVELS, AND BACKGROUND EXPOSURES |
9 |
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- II.1. CHEMICAL STRUCTURES AND PROPERTIES 9
- II.2. SOURCES 12
- II.2.1. Theories of Formation During Combustion 12
- II.2.2. Estimates of Annual Releases of Dioxin-Like Compounds 14
- II.3. OCCURRENCE AND BACKGROUND EXPOSURES 25
- II.3.1. United States Food Data 26
- II.3.2. Summary of Media Levels 26
- II.3.3. Conclusions for Mechanisms of Impact to Food Chain 30
- II.4. TEMPORAL TRENDS 33
- II.5. BACKGROUND EXPOSURE LEVELS 34
- II.6. HIGHLY EXPOSED POPULATIONS 40
- REFERENCES FOR VOLUME II 43
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III: |
SITE-SPECIFIC ASSESSMENT PROCEDURES |
48 |
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- III.1. EXPOSURE EQUATION 48
- III.2. PROCEDURE FOR ESTIMATING EXPOSURE 49
- III.3. ESTIMATING EXPOSURE MEDIA CONCENTRATIONS 51
III.3.1. Overview of Fate, Transport, and Transfer Algorithms of the Methodology 52
- III.4. DEMONSTRATION OF METHODOLOGY 64
III.4.1. Results from the Demonstration of the Stack Emission Source Category 66
- III.5. USER CONSIDERATIONS 71
- III.5.1. Categorization of Methodology Parameters 71
- III.5.2. Sensitivity Analysis 73
- III.5.3. Mass Balance Considerations for Soil Contamination 79
- III.6. UNCERTAINTY 79
- REFERENCES FOR VOLUME III 94
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IV: |
RECOMMENDATIONS FOR FUTURE RESEARCH |
98 |
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- IV.1. SOURCES, FORMATION, CONTROLS AND MONITORING 98
- IV.2. ENVIRONMENTAL FATE, TRANSPORT AND BIOACCUMULATION 102
- IV.3. CHEMICAL/PHYSICAL PROPERTIES 106
- IV.4. EXPOSURE 107
- IV.5 PHARMACOKINETICS 109
- IV.6. COPLANAR PCBS 109
- IV.7. NON-CHLORINE HALOGENATED FORMS OF DIBENZODIOXINS/FURANS AND COPLANAR
BIPHENYLS 110
- IV.8. GLOBAL IMPACTS 111
- REFERENCES FOR RECOMMENDATIONS SECTION 112
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V |
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TABLES |
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TABLES |
I |
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Table I-1 |
Toxicity equivalency factors (TEF) for CDDs and CDFs |
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Table I-2 |
Dioxin-Like PCBs |
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Table I-3 |
Nomenclature for dioxin-like compounds |
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TABLES |
II |
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Table II-1. |
Possible number of positional CDD (or BDD) and CDF (or BDF) congeners |
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Table II-2 |
CDD and CDF air emission estimates for West Germany, Austria, United Kingdom, Netherlands, Switzerland,
and the United States |
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Table II-3 |
Current CDD and CDF multi-media emission estimates for the United States |
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Table II-4 |
Summary of CDD/F levels in United States food (pg/g fresh weight) |
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Table II-5 |
Summary of CDD/F levels in environmental media and food (whole weight basis) |
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Table II-6 |
Estimated TEQ background exposures in the United States |
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TABLES |
III |
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Table III-1 |
Percent distribution of CDDs and CDFs between vapor-phase (V) and particulate-phase (P) as interpreted by
various stack sampling methods, ambient air monitoring, and ambient air theoretical partitioning |
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Table III-2 |
Exposure media concentrations estimated for the demonstration of the stack emission source category |
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Table III-3 |
Lifetime Average Daily Doses, LADD, for the high end stack
emission demonstrations scenario (LADD in units
of ng/kg-day) |
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Table III-4 |
Percent contribution of the different exposure pathways within
each exposure scenario |
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Table III-5 |
Summary of key tests of the fate, transport, and transfer models |
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TABLES |
IV |
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Table IV-1 |
Analysis of air emission sources |
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VI |
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FIGURES |
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FIGURES |
II |
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Figure II-1 |
Structure of Dioxins and Furans |
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Figure II-2 |
Structure of dioxin-like PCBs |
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Figure II-3 |
Estimated TEQ emissions to air from combustion sources in the United States |
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Figure II-4 |
Background environmental levels in TEQ |
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Figure II-5 |
Background TEQ exposures for North America by pathway |
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Figure II-6 |
Comparison of background TEQ exposures for North America, Germany, and the Netherlands |
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FIGURES |
III |
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Figure III-1 |
Roadmap for assessing exposure and risk to dioxin-like compounds |
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Figure III-2 |
Diagram of the fate, transport, and transfer relationships for the on-site source category |
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Figure III-3 |
Diagram of the fate, transport, and transfer relationships for the off-site source category |
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Figure III-4 |
Diagram of the fate, transport, and transfer relationships for the stack emission source category |
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Figure III-5 |
Diagram of the fate, transport, and transfer relationships for the effluent discharge source category |
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Figure III-6 |
Results of sensitivity analysis of algorithms estimating above and below ground vegetation, and beef fat
concentrations resulting from stack emissions |
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VII: |
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FOREWORD |
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The Exposure Assessment Group (EAG) within the Office of Health and Environmental
Assessment of EPA's Office of Research and Development has three main functions:
(1) to
conduct exposure assessments,
(2) to review assessments and related documents, and
(3) to
develop guidelines for exposure assessments.
The activities under each of these functions
are supported by and respond to the needs of the various EPA program offices. In relation
to the third function, EAG sponsors projects aimed at developing or refining techniques
used in exposure assessments.This document is the first of a three-volume set addressing exposure to dioxin related
compounds. The purpose of this document is to provide an Executive Summary of Volumes II
and III. Volume II describes the properties, sources, environmental levels and background
exposures to dioxin-like Compounds. Volume III presents methods for assessing
site-specific assessments of exposure to these compounds.
The document is intended to be
used as a companion to the health reassessment of dioxin-like compounds that the Agency is
publishing concurrently. It is hoped that these documents will improve the accuracy and
validity of risk assessments involving this important family of compounds. Michael A. CallahanDirector
Exposure Assessment Group |
VIII: |
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PREFACE |
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In April 1991, the U.S. Environmental Protection Agency (EPA) announced that it would
conduct a scientific reassessment of the health risks of exposure to
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and chemically similar compounds
collectively known as dioxin.
The EPA has undertaken this task in response to emerging
scientific knowledge of the biological, human health, and environmental effects of dioxin.
Significant advances have occurred in the scientific understanding of mechanisms of dioxin
toxicity, of the carcinogenic and other adverse health effects of dioxin in people, of the
pathways to human exposure, and of the toxic effects of dioxin to the environment.
In 1985 and 1988, the Agency prepared assessments of the human health risks from
environmental exposures to dioxin. Also, in 1988, a draft exposure document was prepared
that presented procedures for conducting site-specific exposure assessments to dioxin-like
compounds. These assessments were reviewed by the Agency's Science Advisory Board (SAB).
At the time of the 1988 assessments, there was general agreement within the scientific
community that there could be a substantial improvement over the existing approach to
analyzing dose response, but there was no consensus as to a more biologically defensible
methodology. The Agency was asked to explore the development of such a method. The current
reassessment activities are in response to this request.The scientific reassessment of dioxin consists of five activities:
1. Update and revision of the health assessment document for dioxin.
2. Laboratory research in support of the dose-response model.
3. Development of a biologically based dose-response model for dioxin.
4. Update and revision of the dioxin exposure assessment document.
5. Research to characterize ecological risks in aquatic ecosystems.
The first four activities have resulted in two draft documents (the health assessment
document and exposure document) for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related
compounds. These companion documents, which form the basis for the Agency's reassessment
of dioxin, have been used in the development of the risk characterization chapter that
follows the health assessment. The process for developing these documents consisted of
three phases which are outlined in later paragraphs.
The fifth activity, which is in progress at EPA's Environmental Research Laboratory in
Duluth, Minnesota, involves characterizing ecological risks in aquatic ecosystems from
exposure to dioxins. Research efforts are focused on the study of organisms in aquatic
food webs to identify the effects of dioxin exposure that are likely to result in
significant population impacts.
A report titled, Interim Report on Data and Methods for
the Assessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) Risks to Aquatic Organisms
and Associated Wildlife (EPA/600/R-93/055), was published in April 1993. This report
will serve as a background document for assessing dioxin-related ecological risks.
Ultimately, these data will support the development of aquatic life criteria which will
aid in the implementation of the Clean Water Act.
The EPA had endeavored to make each phase of the current reassessment of dioxin an open
and participatory effort. On November 15, 1991, and April 28, 1992, public meetings were
held to inform the public of the Agency's plans and activities for the reassessment, to
hear and receive public comments and reviews of the proposed plans, and to receive any
current, scientifically relevant information.In the Fall of 1992, the Agency convened two peer-review workshops to review draft
documents related to EPA's scientific reassessment of the health effects of dioxin.
The
first workshop was held September 10 and 11, 1992, to review a draft exposure assessment
titled, Estimating Exposures to Dioxin-Like Compounds. The second workshop was held
September 22-25, 1992, to review eight chapters of a future draft Health Assessment
Document for 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and Related Compounds.
Peer-reviewers were also asked to identify issues to be incorporated into the risk
characterization, which was under development.In the Fall of 1993, a third peer-review workshop was held on September 7 and 8, 1993,
to review a draft of the revised and expanded Epidemiology and Human Data Chapter, which
also would be part of the future health assessment document.
The revised chapter provided
an evaluation of the scientific quality and strength of the epidemiology data in the
evaluation of toxic health effects, both cancer and noncancer, from exposure to dioxin,
with an emphasis on the specific congener, 2,3,7,8-TCDD.As mentioned previously, completion of the health assessment and exposure documents
involves three phases:
Phase 1 involved drafting state-of-the-science chapters and a
dose-response model for the health assessment document, expanding the exposure document to
address dioxin related compounds, and conducting peer review workshops by panels of
experts. This phase has been completed.
Phase 2, preparation of the risk characterization, began during the September 1992
workshops with discussions by the peer-review panels and formulation of points to be
carried forward into the risk characterization. Following the September 1993 workshop,
this work was completed and was incorporated as Chapter 9 of the draft health assessment
document. This phase has been completed.
Phase 3 is currently underway. It includes making External Review Drafts of both the
health assessment document and the exposure document available for public review and
comment.
Following the public comment period, the Agency's Science Advisory Board (SAB) will
review the draft documents in public session. Assuming that public and SAB comments are
positive, the draft documents will be revised, and final documents will be issued.
Estimating Exposures to Dioxin-Like Compounds has been prepared by the Exposure
Assessment Group of the Office of Health and Environmental Assessment, Office of Research
and Development, which is responsible for the report's scientific accuracy and
conclusions. A comprehensive search of the scientific literature for this document varies
somewhat by chapter but is, in general, complete through January 1994. |
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IX: |
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AUTHORS, CONTRIBUTORS, AND REVIEWERS |
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The Exposure Assessment Group (EAG) within EPA's Office of Health and Environmental
Assessment was responsible for the preparation of this document. General support was
provided by Versar Inc. under EPA Contract Number 68-D0-0101.
Dr. William Farland, as
overall Director of the Dioxin Reassessment, provided policy guidance and technical
comments. Matthew Lorber of EAG served as EPA task manager (as well as contributing
author) providing overall direction and coordination of the production effort. |
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AUTHORS FOR VOLUME I |
Primary authors for Volume I include all authors listed below. |
Primary authors of each chapter are listed below in alphabetical order. |
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AUTHORS FOR VOLUME II |
Name |
Chapters |
Company |
Carl D'Ruiz |
03 |
Versar, Inc. |
David Cleverly |
03 |
U.S. Environmental Protection Agency Washington, DC |
Elizabeth Brown |
04 |
Versar, Inc. |
Geoffrey Huse |
05 |
Versar, Inc. |
Geoffrey Huse |
02 |
Versar, Inc. |
Geoffrey Huse |
04 |
Versar, Inc. |
Greg Schweer |
05 |
Versar, Inc. |
Greg Schweer |
02 |
Versar, Inc. |
Jeff Dawson |
03 |
Versar, Inc. |
Jerry Blancato |
06 |
U.S. Environmental Protection Agency Las Vegas, NV |
John L. Schaum |
05 |
U.S. Environmental Protection Agency Washington, DC |
John L. Schaum |
01 |
U.S. Environmental Protection Agency Washington, DC |
Keith Drewes |
04 |
Versar, Inc. |
Linda Phillips |
03 |
Versar, Inc. |
Linda Phillips |
05 |
Versar, Inc. |
Linda Phillips |
04 |
Versar, Inc. |
Matthew Lorber |
04 |
U.S. Environmental Protection Agency Washington, DC |
Matthew Lorber |
03 |
U.S. Environmental Protection Agency Washington, DC |
Nica Mostaghim |
04 |
Versar, Inc. |
Robert J. Fares |
04 |
Versar, Inc. |
Tim Leighton |
03 |
Versar, Inc. |
Tim Leighton |
05 |
Versar, Inc. |
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AUTHORS FOR VOLUME III |
Primary authors of each chapter are listed below in alphabetical order. |
Name |
Chapters |
Company |
David H. Cleverly |
03 |
U.S. Environmental Protection Agency Washington, DC |
David H. Cleverly |
07 |
U.S. Environmental Protection Agency Washington, DC |
John L. Schaum |
02 |
U.S. Environmental Protection Agency Washington, DC |
John L. Schaum |
01 |
U.S. Environmental Protection Agency Washington, DC |
Matthew Lorber |
07 |
U.S. Environmental Protection Agency Washington, DC |
Matthew Lorber |
01 |
U.S. Environmental Protection Agency Washington, DC |
Paul White |
07 |
U.S. Environmental Protection Agency Washington, DC |
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CONTRIBUTORS AND REVIEWERS |
An earlier draft of this exposure document was reviewed by the Science Advisory Board
in 1988. A revised draft was issued in August 1992 and was reviewed by a panel of experts
at a peer-review workshop held September 10 and 11, 1992. Members of the Peer Review Panel
for this workshop were as follows: |
Name |
Qualifications |
Company |
M. Judith Charles |
Ph.D |
University of North Carolina Chapel Hill, NC |
Dennis Paustenbach |
Ph.D |
ChemRisk - A McLaren/Hart Group Alameda, CA |
Ray Clement |
Ph.D |
Ontario Ministry of the Environment Quebec, Canada |
Richard Dennison |
Ph.D |
Environmental Defense Fund Washington, DC |
Richard Reitz |
Ph.D |
Dow Chemical Midland, MI |
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In addition, the following experts outside of EPA have reviewed and/or contributed to
this document: |
Name |
Qualifications |
Company |
Michael Bolger |
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US Food and Drug Administration Washington, DC |
James Falco |
Ph.D |
Battelle Northwest Richland, WA |
Heidelore Fiedler |
Ph.D |
University of Bayreuth Federal Republic of Germany |
Charles Fredette |
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Connecticut Department of Environmental Protection Hartford, CT |
George Fries |
Ph.D |
United States Department of Agriculture Beltsville Agricultural Research Center Beltsville, MD |
Laura Green |
Ph.D, D.A.B.T |
Cambridge Environmental, Inc. Cambridge, MA |
Dale Hattis |
Ph.D |
Clark University Worcester, MA |
Steven Hinton |
Ph.D., P.E. |
National Council of the Paper Industry for Air and Stream Improvement Tufts University Medford, MA |
Kay Jones |
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Zephyr Consulting Seattle, WA |
George Lew |
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California Air Resources Board Sacremento, CA |
Thomas E. McKone |
Ph.D |
Lawrence Livermore National Laboratory Livermore, CA |
Derek Muir |
Ph.D |
Freshwater Institute Department of Fisheries and Oceans Winnipeg, MB, Canada |
Marvin Norcross |
Ph.D |
Food Safety Inspection Service, USDA Washington, DC |
Vlado Ozvacic |
Ph.D |
Ministry of the Environment Toronto, ON, Canada |
Thomas Parkerton |
Ph.D |
Manhattan College Riverdale, NY |
Christopher Rappe |
Ph.D |
University of Umea Institute of Environmental Chemistry Umea, Sweden |
Curtis C. Travis |
Ph.D |
Oak Ridge National Laboratory Oak Ridge, TN |
Thomas O. Tiernan |
Ph.D |
Wright State University Dayton, OH |
Thomas Umbreit |
Ph.D |
Agency for Toxic Substances and Disease Registry Atlanta, GA |
G.R. Barrie Webster |
Ph.D |
University of Manitoba Winnipeg, Canada |
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The following individuals within EPA have reviewed and/or contributed to this document: |
OFFICE |
REVIEWERS/CONTRIBUTORS |
Office of Research and
Development |
- Frank Black
- Brian Gullett
- Joel McCrady
- Philip Cook
- Donna Schwede
- Bill Petersen
- James Kilgroe
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Office of Air and Radiation |
- Pam Brodowicz
- George Streit
- Thomas
Lahre
- Anne Pope
- Phil Lorang
- Walter Stevenson
- Dennis Pagano
- Jim Crowder
- Dallas Safriet
- Joe Somers
- Joseph Wood
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Office of Pollution, Pesticides
and Toxic Substances |
- Joe Cotruvo
- Steven Funk
- Pat Jennings
- Leonard Keifer
- Robert Lipnick
- Tom Murray
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Office of Water |
- Ryan Childs
- Mark Morris
- Edward Ohanian
- Al Rubin
- Maria Gomez Taylor
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Office of General Counsel |
Chuck Elkins |
Office of Policy, Planning and
Evaluation |
Dwain Winters |
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