Page

3.5.5. Evaluation of Naturally Occurring CDD/CDFs by Examination of Sediment Core Data 3-92

3.5.6. Summary of Theories of CDD/CDF Emissions 3-94

3.6. COMBUSTION AND OTHER HIGH TEMPERATURE SOURCES 3-96

3.6.1. Municipal Solid Waste Incineration 3-97

3.6.2. Hazardous Waste Incineration 3-108

3.6.3. Medical Waste Incineration 3-110

3.6.4. Kraft Black Liquor Recovery Boilers 3-118

3.6.5. Sewage Sludge Incineration 3-119

3.6.6. Primary Nonferrous Metal Smelting/Refining 3-121

3.6.7. Secondary Nonferrous Metal Smelting/Refining 3-122

3.6.7.1 Secondary Aluminum Smelters and Refiners 3-122

3.6.7.2 Secondary Copper Smelters and Refiners 3-123

3.6.7.3 Secondary Lead Smelters and Refiners 3-124

3.6.8. Primary Ferrous Metal Smelting/Refining 3-126

3.6.9. Secondary Ferrous Metal Smelting/Refining 3-127

3.6.10. Scrap Electric Wire Recovery 3-128

3.6.11. Drum and Barrel Reclamation and Incineration 3-129

3.6.12. Tire Combustion 3-131

3.6.13. Motor Vehicle Fuel Combustion 3-132

3.6.14. Wood Burning at Residences 3-141

3.6.15. Industrial Wood-Burning Facilities 3-145

3.6.16. Wood Burned in Forest Fires 3-146

3.6.17. Coal Combustion 3-150

3.6.18. Combustion of Polychlorinated Biphenyls (PCBs) 3-151

3.6.19. Pyrolysis of Brominated Flame Retardants 3-152

3.6.20. Carbon Reactivation Furnaces 3-153

3.6.21. Cement Kilns 3-155

3.6.22. Additional Combustion and High Temperature Sources 3-164

3.7. RESERVOIR SOURCES 3-164

3.8. COMPARING SOURCE EMISSIONS TO DEPOSITION ESTIMATES 3-166

REFERENCES FOR CHAPTER 3 3-169

4. LEVELS OF CDD, CDF, AND PCB CONGENERS IN ENVIRONMENTAL

MEDIA AND FOOD 4-1

4.1. INTRODUCTION 4-1

4.2. CONCENTRATIONS IN SOIL 4-2

4.2.1. North American Data 4-2

4.2.2. European Data 4-4

4.2.3. Soil Summary 4-5

4.3. CONCENTRATIONS IN WATER 4-6

4.3.1. North American Data 4-6

4.3.2. European Data 4-7

4.3.3. Water Summary 4-7

4.4. CONCENTRATIONS IN SEDIMENT 4-8

Page

4.4.1. North American Data 4-8

4.4.2. European Data 4-11

4.4.3. Sediment Summary 4-13

4.5. CONCENTRATIONS IN FISH AND SHELLFISH 4-13

4.5.1. North American Data 4-14

4.5.2. European Data 4-18

4.5.3. Fish Summary 4-20

4.6. CONCENTRATIONS IN FOOD PRODUCTS 4-22

4.6.1. Migration of CDD/CDF from Paper Packaging Into Food 4-23

4.6.2. U.S. Food 4-25

4.6.3 European Food 4-38

4.6.4 Canadian Food 4-41

4.7. CONCENTRATIONS IN AIR 4-41

4.7.1. U.S. Data 4-44

4.7.2. European Data 4-45

4.7.3. Air Summary 4-47

4.8. TEMPORAL TRENDS 4-48

4.9. SUMMARY OF CDD/CDF LEVELS IN ENVIRONMENTAL MEDIA AND FOOD 4-50

4.10. MECHANISMS FOR ENTRY OF CDD/CDFS INTO THE FOOD CHAIN 4-57

REFERENCES FOR CHAPTER 4 4-60

5. BACKGROUND EXPOSURES TO CDD, CDF, AND PCB CONGENERS 5-1

5.1. INTRODUCTION 5-1

5.2. PREVIOUS ASSESSMENTS OF BACKGROUND EXPOSURES 5-1

5.3. UPDATED ASSESSMENT OF BACKGROUND EXPOSURES 5-8

5.3.1. North American Exposures 5-12

5.3.2. Comparison of Previous North American Studies to This Study 5-12

5.3.3. Comparison of Previous European Studies to this Study 5-15

5.4. ASSESSMENT OF BACKGROUND EXPOSURES ON THE BASIS OF BODY BURDEN DATA 5-18

5.4.1. Human Adipose Tissue and Blood Data 5-18

5.4.2. Dermal Exposure 5-27

5.5. HIGHLY EXPOSED POPULATIONS 5-28

5.5.1. Nursing Infants 5-29

5.5.2 Subsistence Fishers 5-33

5.5.3. Subsistence Farmers 5-34

REFERENCES FOR CHAPTER 5 5-35

6. PHARMACOKINETICS 6-1

6.1. INTRODUCTION 6-1

6.2. DAILY BACKGROUND LEVELS 6-2

6.2.1. Basis for Calculation 6-2

6.2.2. Daily Intakes 6-7

6.3. COMPARTMENTAL MODELING 6-14

6.3.1. Pharmacokinetic Model 6-14

 

Page

6.3.2. Model Utilization 6-17

6.3.3. Determining Liver Concentrations from Fat Levels 6-20

6.4. INTAKES THROUGH DAILY EXPOSURE 6-25

6.4.1. Determination of Daily Intake Dose from Exposure Concentrations 6-25

6.4.2. Dose Through Lactation 6-26

6.4.2.1. Concentration in the Milk 6-26

6.4.2.2. Dose to Infant 6-28

REFERENCES FOR CHAPTER 6 6-36

 

APPENDIX A: ENVIRONMENTAL CHEMISTRY A-1

APPENDIX B: ENVIRONMENTAL CONCENTRATIONS B-1

APPENDIX C: BIOAVAILABILITY OF DIOXINS C-1

Page

Table 1-1 Toxicity Equivalency Factors (TEF) for CDDs and CDFs 1-3

Table 1-2 Dioxin-Like PCBs 1-4

Table 1-3 Nomenclature for Dioxin-Like Compounds 1-5

Table 2-1 Possible Number of Positional CDD (or BDD) and CDF (or BDF)

Congeners 2-3

Table 2-2 Ranking Scheme for P-Chem Property Evaluation 2-6

Table 2-3 P-Chem Properties for the Dioxin-Like Congeners 2-8

Table 2-4 Vapor-to-Particle-Bound Ratio (V/P) for CDDs and CDFs in

Ambient Air: Monitoring Results & Modeling Estimates 2-23

Table 2-5 Rain Scavenging Ratios (W) and Percent Washout Due to

Particulates (%P) for CDDs and CDFs in Bloomington and

Indianapolis Ambient Air 2-25

Table 3-1 CDD and CDF Air Emission Estimates for West Germany,

Austria, United Kingdom, Netherlands, Switzerland,

and the United States 3-7

Table 3-2 Current CDD and CDF Emission Estimates for the United States 3-9

Table 3-3 Confidence Rating Scheme for U.S. Emission Estimates 3-13

Table 3-4 Summary of Bleached Chemical Pulp and Paper Mill Discharges

of 2,3,7,8-TCDD and 2,3,7,8-TCDF 3-17

Table 3-5 Quantity of Sewage Sludge Disposed Annually by Primary,

Secondary, or Advanced Treatment POTWs and Potential

Dioxin TEQ Releases 3-24

Table 3-6 Concentration Ranges of CDD/CDF Homologue Groups in

Chlorophenols^a (ppm) 3-27

Table 3-7 Summary of Specific Dioxin-Containing Wastes That Must Comply

with Land Disposal Retrictions 3-29

Table 3-8 CDD/CDF Concentrations in Chlorobenzenes (µg/kg) 3-32

Page

Table 3-9 CDD/CDF Levels (µg/kg) in Dioxazine Dyes and Pigments 3-36

Table 3-10 Chemicals Requiring TSCA Section 4 Testing Under the

Dioxin/Furan Rule 3-39

Table 3-11 Congeners and Limits of Quantitation (LOQ) for Which

Quantitation is Required Under the Dioxin/Furan Test Rule

and Pesticide Data Call-In 3-40

Table 3-12 Precursor Chemicals Subject to Reporting Requirements Under

TSCA Section 8(a) 3-41

Table 3-13 Results of Analytical Testing for Dioxins and Furans

in the Chemicals Tested To-Date Under Section 4

of the Dioxin/Furan Test Rule 3-42

Table 3-14 CDDs and CDFs in Chloranil and Carbazole Violet Samples

Analyzed Pursuant to the EPA Dioxin/Furan Test Rule 3-43

Table 3-15 Pesticides That Could Become Contaminated With Dioxins If

Synthesized Under Conditions Which Favor Dioxin Formation 3-46

Table 3-16 Pesticides That Are Suspected To Be Contaminated

With Dioxins 3-52

Table 3-17 Summary of Analytical Data Submitted to-Date in Response to

Pesticide Data Call-In 3-57

Table 3-18 Summary of Results for CDDs and CDFs in Technical

2,4-D Herbicides 3-58

Table 3-19 CDDs/CDFs in Petroleum Refinery Stack Gas from a Continuous

Regenerator Without Scrubber 3-60

Table 3-20 CDDs/CDFs in the Scrubber Wash Water from a Petroleum

Refinery Periodic/Cyclic Regenerator 3-61

Table 3-21 Concentration of CDDs/CDFs on Municipal Incinerator Fly Ash

at Varying Temperatures 3-70

Table 3-22 CDDs/CDFs Formed From the Thermolytic Reaction of 690 mg

Benzene + FeCl₃Silica Complex 3-76

Page

Table 3-23 De Novo Formation of CDDs/CDFs After Annealing Mg-Al

Silicate, 4% Charcoal, 7% Cl, 1% CuCl₂.2H₂O at 300° C 3-78

Table 3-24 De Novo Formation of Chlorinated Benzenes (CBzs),

Polychlorinated Naphthalenes (PCNs), and Polychlorinated

Biphenyls (PCBs) after Annealing Mg-Al Silicate, 4% Charcoal,

7% Cl, 1% CuCl₂.2H₂O 3-79

Table 3-25 CDDs/CDFs Formed from the Combustion of Vegetable Extracts

in the Presence of Chlorine Gas 3-86

Table 3-26 CDDs/CDFs Formed from the Combustion of Coal in the Presence

of NaCl, Cl₂, or Hydrochloric Acid 3-90

Table 3-27 Estimated Number of Operating MSWI Facilities in the United

States by Design Category and Type of Air Pollution Control

Device 3-101

Table 3-28 Estimated MSW Incineration Emission Factors (EF) and Annual

Emissions of Total CDD/CDFs 3-102

Table 3-29 Estimated Number and Type of Facilities and Quantities of

Medical Waste Generated Annually in the United States 3-112

Table 3-30 Medical Waste Incineration Facilities Operating in the

United States 3-113

Table 3-31 CDD/CDF Emission Factors for Controlled-Air Medical Waste

Incinerators Operating in the United States 3-115

Table 3-32 Estimated Annual Emission of Total CDD/CDFs (g/yr) from

Incineration of Medical Waste 3-116

Table 3-33 Descriptions and Results of Vehicle Emission Testing Studies

for CDDs and CDFs 3-134

Table 3-34 Average Concentrations (ppt) of TCDDs in Chimney Soot from

Residential Wood-Burning Stoves in the U.S. 3-143

Table 3-35 Concentrations of Total CDD/CDFs and Dioxin TEQ

(grams/dscm) Measured at the Stack of Portland Cement

Kilns Burning and Not Burning Hazardous Waste

As Supplemental Fuel 3-158

Page

Table 4-1 Background Data from the National Bioaccumulation

Study 4-15

Table 4-2 Summary of Dioxin/Furan Data Collected in the

California State Air Resources Board Study 4-29

Table 4-3 Summary of U.S. Food Data from NCASI Study 4-30

Table 4-4 Summary of Schecter et al. (1993) Data on U.S. Foods 4-31

Table 4-5 Summary of CDD/CDF Levels in U.S. Food (pg/g Fresh Weight) 4-37

Table 4-6 CDD/CDF Levels in German Food 4-39

Table 4-7 CDD/CDF Background Levels in Some European, Canadian,

and New Zealand Food 4-40

Table 4-8 Concentrations of Dioxins & Furans 4-42

Table 4-9 Maximum CDD/CDF Levels in Foods Collected in Canada

(pg/g fresh weight) as Reported by Birmingham et al. (1989) 4-43

Table 4-10 Estimated National Average Concentrations of Dioxins and

Furans from the 1982 and 1987 NHATS 4-51

Table 4-11 Summary of CDD/CDF Levels in Environmental Media and Food

(whole weight basis) 4-53

Table 4-12 CDD/CDF Congeners that Contribute the Highest Percentage

of TEQ to the Total TEQ for All Congeners Combined 4-54

Table 5-1 Predicted Average Daily Intake of 2,3,7,8-TCDD by the

General Population of the United States. 5-3

Table 5-2 Predicted Average Daily Intake of 2,3,7,8-TCDD from

Foods by the General Population of the United States. 5-5

Table 5-3 Daily Exposure to 2,3,7,8-TCDD and TEQ from Air, Soil,

Food, and Nonfood in The Netherlands 5-6

Table 5-4 Estimated Lifetime Average Daily Exposure of Canadians to

Dioxin TEQ 5-7

Table 5-5 Estimated Background Exposures in the United States. 5-9

Page

Table 5-6 Background Exposures via Consumption of German Food 5-11

Table 5-7 Comparison of Predicted Average Daily Intake of

2,3,7,8-TCDD and Total CDD/CDF TEQs 5-16

Table 5-8 NHATS Mean Adipose Tissue Data 5-20

Table 5-9 Human Adipose Tissue Data 5-21

Table 5-10 Mean Levels in Human Serum (ppt) 5-23

Table 5-11 CDD/CDF Levels in Human Blood from Various Countries 5-24

Table 5-12 Dioxin Levels in Human Adipose Tissues from Various

Countries 5-25

Table 6-1 Calculated Daily Intakes for 2,3,7,8-TCDD 6-9

Table 6-2 Half-life Calculations 6-13

Table 6-3 Model-Determined Daily Intakes 6-22

Page

Figure 3-1 Estimated TEQ Emissions to Air in the United States. 3-11

Figure 3-2 The Association Between Vapor Phase C1₂ and the

Formation of CDDs/CDFs 3-73

Figure 3-3 The de novo Synthesis of CDD/CDFs from Heating Carbon

Particulate at 300° C at Varying Retention Times 3-81

Figure 3-4 Relationship Between Temperature and the de novo Formation

of CDDsCDFs 3-82

Figure 4-1 Background Environmental Levels in TEQ 4-55

Figure 5-1 Background TEQ Exposure for North America by Pathway 5-13

Figure 5-2 Percent Contribution of Various Media to

2,3,7,8-TCDD Exposure in North America 5-14

Figure 5-3 Comparison of Background TEQ Exposures 5-17

Figure 6-1 Sample Calculation of Daily Intake for 2,3,7,8-TCDD 6-7

Figure 6-2 Model Estimates of Elimination of 2,3,7,8-TCDD from Fat 6-18

Figure 6-3 Accumulation of TCDD in Fat with 0.44 pg/kg/day dose -

Human 6-19

Figure 6-4 Accumulation of TCDD in Fat with 0.30 pg/kg/day dose -

Human 6-21

Figure 6-5 Combined Exposure Adipose Tissue Concentration 6-31

Figure 6-6 Background Exposure Adipose Tissue Concentration 6-32

Figure 6-7 Concentration After Lactational Exposure Only 6-33

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.

The purpose of this document is to present and evaluate information on the properties, sources, environmental levels and background exposures to dioxin-like compounds. It is the second in a three volume set addressing these compounds. The first volume provides an overall executive summary and the third volume presents methods for assessing site-specific assessments of exposure to these compounds. The three volume set serves as a final version of the 1988 draft document titled "Estimating Exposure to 2,3,7,8-TCDD." This effort represents a substantial expansion in scope to include all compounds that exhibit dioxin-like toxicity. 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 Numbers 68-D0-0101 and 68-D3-0013. Matthew Lorber of EAG served as the EPA Work Assignment Manager (as well as contributing author) providing overall direction and coordination of the production effort as well as technical assistance and guidance.

Primary and contributing 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 Fares Chapter 4

Versar, Inc.

Geoffrey Huse Chapters 2, 4, 5

Versar, Inc.

Gregory Kew Chapter 3

U.S. Environmental Protection Agency

Washington, DC

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 Chapters 3, 4, 5

Versar, Inc.

John L. Schaum Chapters 1 - 5

U.S. Environmental Protection Agency

Washington, DC

Greg Schweer Chapters 1 - 5

Versar, Inc.

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, Ph.D.

U.S. Food and Drug Administration

Washington, DC

James Falco, Ph.D.

Battelle, NW

Richland, WA

Heidelore Fiedler, Ph.D.

University of Bayreuth

Federal Republic of Germany

Charles Fredette

Connecticut Dept. of Environmental Protection

Hartford, CT

George Fries, Ph.D

United States Department of Agriculture

Beltsville Agricultural Research Center

Beltsville, MD

Laura Green, Ph.D., DABT

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 Rrsources Board

Sacramento, 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: