EPA/600/6-88/005Ca

DO NOT QUOTE OR CITE June 1994

External Review Draft

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 Group

Office of Health and Environmental Assessment

U.S. Environmental Protection Agency

Washington, D.C.

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.

Tables v

Figures vi

Foreword vii

Preface viii

Authors, Contributors, and Reviewers xi

I. INTRODUCTION 1

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

II. VOLUME II. PROPERTIES, SOURCES, ENVIRONMENTAL LEVELS,

AND BACKGROUND EXPOSURES 9

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

III. VOLUME III. SITE-SPECIFIC ASSESSMENT PROCEDURES 48

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

IV. RECOMMENDATIONS FOR FUTURE RESEARCH 98

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

I-1 Toxicity equivalency factors (TEF) for CDDs and CDFs 3

I-2. Dioxin-Like PCBs 4

I-3. Nomenclature for dioxin-like compounds 5

II-1. Possible number of positional CDD (or BDD) and

CDF (or BDF) congeners 10

II-2. CDD and CDF air emission estimates for West Germany, Austria,

United Kingdom, Netherlands, Switzerland, and the

United States 17

II-3. Current CDD and CDF multi-media emission estimates for the

United States 19

II-4. Summary of CDD/F levels in United States food (pg/g fresh weight) 27

II-5. Summary of CDD/F levels in environmental media and

food (whole weight basis) 28

II-6. Estimated TEQ background exposures in the United States 35

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 59

III-2. Exposure media concentrations estimated for the demonstration of

the stack emission source category 67

III-3. Lifetime Average Daily Doses, LADD, for the high end stack emission

demonstrations scenario (LADD in units of ng/kg-day) 68

III-4. Percent contribution of the different exposure pathways within each

exposure scenario 70

III-5. Summary of key tests of the fate, transport, and transfer models 82

IV-1. Analysis of air emission sources 99

II-1 Structure of Dioxins and Furans 9

II-2 Structure of dioxin-like PCBs 11

II-3 Estimated TEQ emissions to air from combustion sources in the

United States 22

II-4 Background environmental levels in TEQ 29

II-5 Background TEQ exposures for North America by pathway 37

II-6 Comparison of background TEQ exposures for North America,

Germany, and the Netherlands 38

III-1 Roadmap for assessing exposure and risk to dioxin-like

compounds 50

III-2 Diagram of the fate, transport, and transfer relationships

for the on-site source category 53

III-3 Diagram of the fate, transport, and transfer relationships

for the off-site source category 53

III-4 Diagram of the fate, transport, and transfer relationships

for the stack emission source category 54

III-5 Diagram of the fate, transport, and transfer relationships

for the effluent discharge source category 54

III-6 Results of sensitivity analysis of algorithms estimating

above and below ground vegetation, and beef fat

concentrations resulting from stack emissions 74

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. Callahan

Director

Exposure Assessment Group

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.

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.

Primary authors for Volume I include all authors listed below.

Primary authors of each chapter are listed below in alphabetical order.

Jerry Blancato Chapter 6

U.S. Environmental Protection Agency

Las Vegas, NV

Elizabeth Brown Chapter 4

Versar, Inc.

David Cleverly Chapter 3

U.S. Environmental Protection Agency

Washington, DC

Jeff Dawson Chapter 3

Versar, Inc.

Keith Drewes Chapter 4

Versar, Inc.

Carl D'Ruiz Chapter 3

Versar, Inc.

Robert J. Fares Chapter 4

Versar, Inc.

Geoffrey Huse Chapters 2, 4, 5

Versar, Inc.

Tim Leighton Chapters 3, 5

Versar, Inc.

Matthew Lorber Chapters 3, 4

U.S. Environmental Protection Agency

Washington, DC

Nica Mostaghim Chapter 4

Versar, Inc.

Linda Phillips Chapter 3, 4, 5

Versar, Inc.

John L. Schaum Chapter 1 - 5

U.S. Environmental Protection Agency

Washington, DC

Greg Schweer Chapter 2 - 5

Versar, Inc.

Primary authors of each chapter are listed below in alphabetical order.

David H. Cleverly Chapters 3, 7

U.S. Environmental Protection Agency

Washington, DC

Matthew Lorber Chapter 1-7

U.S. Environmental Protection Agency

Washington, DC

John L. Schaum Chapters 1, 2

U.S. Environmental Protection Agency

Washington, DC

Paul White Chapter 7

U.S. Environmental Protection Agency

Washington, DC

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:

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

In addition, the following experts outside of EPA have reviewed and/or contributed to this document:

Michael Bolger

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

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

Zephyr Consulting

Seattle, WA

George Lew

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

The following individuals within EPA have reviewed and/or contributed to this document: