abs

Exposure and Human Health Reassessment of 2,3,7,8-

8,87

Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds -

702

stron

Part I: Estimating Exposure to Dioxin-Like Compounds - Volume

2: Properties, Environmental Levels, and Background Exposures

5920

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

2004

rok

CONTENTS

1 INTRODUCTION 1-1

1.1 BACKGROUND 1-1

1.2 DESCRIPTION OF DIOXIN-LIKE COMPOUNDS 1-2

1.3 TOXICITY EQUIVALENCY FACTORS 1-4

1.4 OVERALL COMMENTS ON THE USE OF VOLUME IV OF THE DIOXIN EXPOSURE

DOCUMENT 1-8

1.5 EXECUTIVE SUMMARY OF VOLUME III 1-11

REFERENCES FOR CHAPTER 1 1-45

2 ESTIMATING EXPOSURES AND RISKS 2-1

2.1 INTRODUCTION 2-1

2.2 EXPOSURE EQUATION 2-2

2.3 CANCER AND NON-CANCER RISK ASSESSMENT 2-4

2.3.1 Background Exposure Dose and Body Burden 2-6

2.3.2 The Increment Over Background Concept for Non-Cancer Risk Assessment 2-13

2.3.3 Traditional Agency Cancer Risk Assessment Procedures 2-15

2.3.4 Interpretation of Cancer and Non-Cancer Risk Assessment Results for Dioxin 2-18

2.4 THE TOXIC EQUIVALENCY PROCEDURE 2-19

2.5 PROCEDURE FOR ESTIMATING EXPOSURE 2-20

2.6 STRATEGY FOR DEVISING EXPOSURE SCENARIOS 2-22

2.7 EXPOSURE PATHWAYS AND PARAMETERS 2-26

2.7.1 Soil Related Exposures 2-26

2.7.1.1 Soil Ingestion 2-26

2.7.1.2 Soil Dermal Contact 2-28

2.7.2 Vapor and Dust Inhalation 2-30

2.7.3 Water Ingestion 2-32

2.7.4 Ingestion of Terrestrial Food Products 2-32

2.7.4.1 Derivation of the Contact Fractions for Beef, Milk, Chicken, Eggs, Vegetables, and Fruits 2-

2.7.4.2 Beef Ingestion 2-37

2.7.4.3 Dairy Ingestion 2-37

2.7.4.4 Chicken Ingestion 2-38

2.7.4.5 Egg Ingestion 2-38

2.7.4.6 Vegetable and Fruit Ingestion 2-38

2.7.5 Fish Ingestion 2-39

REFERENCES FOR CHAPTER 2 2-41

3 EVALUATING ATMOSPHERIC RELEASES OF DIOXIN-LIKE COMPOUNDS FROM

COMBUSTION SOURCES 3-1

3.1 INTRODUCTION 3-1

3.2 ESTIMATING THE EMISSIONS OF DIOXIN-LIKE COMPOUNDS FROM ANTHROPOGENIC

COMBUSTION SOURCES 3-2

3.2.1 A Strategy for Generating Emission Factors 3-4

3.2.2 Use of Homologue and Congener-Specific Profiles to Estimate Emission Factors 3-7

3.2.2.1Using Congener Profiles to Convert Total CDD/F 3-8

3.2.2.2 Estimating Congener-Specific Emissions when no Congener Profiles are Available 3-8

3.2.3 Estimation of Emissions of Dioxin-Like Compounds from the Hypothetical Incinerator 3-9

3.2.4 Estimation of the Vapor Phase/Particle Phase Partitioning of Emissions of Dioxin-Like

Compounds 3-10

3.2.4.1 Vapor Phase/Particulate Phase Inferences from Stack Measurements 3-10

3.2.4.2 Discussion of Vapor/Particle Ratios Derived from Stack Testing Methods 3-13

3.2.4.3 Vapor/Particle Partitioning of CDD/Fs from Ambient Air Sampling 3-16

3.2.4.4 Discussion of the Vapor/Particle Partitioning in Ambient Air Sampling Studies 3-23

3.2.4.5 Junge-Pankow Model of Particle/Gas Distribution in Ambient Air 3-23

3.2.4.6 Modeling the Vapor/Particle (V/P) Distribution of CDD/Fs . 3-26

3.2.4.7 Comparison of Measured and Modeled Vapor/Particle Distributions for CDD/Fs 3-29

3.2.4.8 Discussion of Monitored and Modeled Results for CDD/Fs . 3-31

3.2.4.9 Discussion of Vapor/Particle Partitioning 3-33

3.2.5 Estimation of the Concentration of Dioxin-Like Compounds in Incineration Ash 3-34

3.3 AIR DISPERSION/DEPOSITION MODELING OF THE STACK GAS EMISSIONS OF DIOXIN-

LIKE COMPOUNDS 3-36

3.3.1 Basic Physical Principles Used to Estimate Atmospheric Dispersion/Deposition of Stack

Emissions 3-37

3.3.2 Estimation of Dry Surface Deposition Flux 3-39

3.3.3 Estimation of the Particle Size Distribution in the Stack Emissions . . 3-42

3.3.4 Estimation of Wet Deposition Flux 3-44

3.3.5 Using ISCST3 to Model Emissions of Particles and Vapors 3-46

3.4 RESULTS OF THE AIR DISPERSION MODELING OF CONGENERSPECIFIC EMISSIONS

FROM THE HYPOTHETICAL ORGANIC WASTE INCINERATOR 3-47

3.5 REVIEW OF PROCEDURES FOR ESTIMATING SITE-SPECIFIC IMPACTS FROM A STACK

EMISSION SOURCE 3-50

REFERENCES FOR CHAPTER 3 3-52

4 ESTIMATING EXPOSURE MEDIA CONCENTRATIONS 4-1

4.1 INTRODUCTION 4-1

4.2 BACKGROUND FOR SOLUTION ALGORITHMS 4-1

4.3 ALGORITHMS FOR THE SOIL CONTAMINATION SOURCE CATEGORY 4-7

4.3.1 Surface Water and Sediment Contamination 4-8

4.3.2 Exposure Site Soil Concentrations 4-23

4.3.3 Vapor- and Particle-Phase Air Concentrations 4-31

4.3.4 Biota Concentrations 4-41

4.3.4.1 Fish Concentrations 4-41

4.3.4.2 Vegetation Concentrations 4-49

4.3.4.3 Beef and Milk Concentrations 4-69

4.3.4.4 Chicken and Egg Concentrations 4-78

4.3.5 Specific Cases of Soil Contamination 4-84

4.3.5.1 Landfills Receiving Ash from Municipal Waste Incinerators 4-85

4.3.5.2 Land Application of Sludge from Pulp and Paper Mills 4-92

4.3.5.3 Sites Studied in the National Dioxin Study 4-95

4.4 ALGORITHMS FOR THE STACK EMISSION SOURCE CATEGORY 4-97

4.4.1 Steady-State Soil Concentrations 4-99

4.4.2 Surface Water Impacts 4-100

4.5 ALGORITHMS FOR THE EFFLUENT DISCHARGE SOURCE CATEGORY 4-106

4.5.1 The Simple Dilution Model 4-108

REFERENCES FOR CHAPTER 4 4-116

5 DEMONSTRATION OF METHODOLOGY 5-1

5.1 INTRODUCTION 5-1

5.2 STRATEGIES FOR DEVISING EXPOSURE SCENARIOS 5-2

5.3 EXAMPLE EXPOSURE SCENARIOS 5-8

5.4 EXAMPLE COMPOUNDS 5-12

5.5 SOURCE TERMS 5-13

5.6 RESULTS 5-19

5.6.1 Observations Concerning Exposure Media Concentrations 5-20

5.6.2 Observations Concerning LADD Exposure Estimates 5-27

5.7 HEALTH RISK DEMONSTRATIONS 5-30

REFERENCES FOR CHAPTER 5 5-34

6 USER CONSIDERATIONS 6-1

6.1 INTRODUCTION 6-1

6.2 CATEGORIZATION OF METHODOLOGY PARAMETERS 6-1

6.3 SENSITIVITY ANALYSIS 6-7

6.3.1 Limitations of the Sensitivity Analysis Exercises 6-7

6.3.2 Methodology Description and Parameter Assignments 6-10

6.3.3 Results 6-23

6.3.3.1 Estimation of Vapor-Phase and Particle-phase Air Concentrations Distant from a Site of Soil

Contamination 6-23

6.3.3.2 Estimation of Soil Erosion Impacts to Nearby Sites of Exposure 6-25

6.3.3.3 Estimation of Soil Erosion Impacts to Nearby Surface Water Bodies 6-27

6.3.3.4 Vapor-Phase Transfers and Particle-Phase Depositions to Above Ground Vegetation 6-29

6.3.3.5 Estimation of Below Ground Vegetation Concentrations 6-33

6.3.3.6 Beef Fat Concentration Estimation in the Soil Contamination and Stack Emission Source

Categories 6-34

6.3.3.7 Impact of Distance from the Stack Emission Source on Concentrations in Soil, Vegetables,

and Beef Fat 6-37

6.3.3.8 Water and Fish Concentrations Resulting from Effluent Discharges 6-38

6.3.3.9 Water and Fish Concentrations Resulting from Stack Emissions 6-39

6.3.4 Key Trends from the Sensitivity Analysis Testing 6-40

6.4 MASS BALANCE CONSIDERATIONS 6-42

REFERENCES FOR CHAPTER 6 6-48

7 MODEL COMPARISONS AND MODEL VALIDATIONS 7-1

7.1 INTRODUCTION 7-1

7.2 MODEL COMPARISON EXERCISES 7-3

7.2.1 Evaluation of Alternative Air-to-Leaf Modeling Approaches 7-3

7.2.1.1 The Field Data 7-4

7.2.1.2 Model Descriptions and Application to the Field Data 7-4

7.2.1.3 Results and Discussion of the Air-to-Leaf Model Comparison Exercise 7-9

7.2.1.4 Literature Comparisons of Air-to-Plant Modeling Approaches 7-14

7.2.2 An Alternate Modeling Approach for Estimating Water Concentrations Given a Steady Input

Load from Overland Sources 7-16

7.2.3 Estimating Fish Tissue Concentrations Based on Water Column Concentrations Rather than

Bottom Sediment Concentrations 7-19

7.2.4 Other Modeling Approaches and Considerations for Air Concentrations Resulting from Soil

Volatilization 7-24

7.2.5 Alternate Models for Estimating Plant Concentrations from Soil Concentrations 7-37

7.2.6 Alternate Modeling Approaches for Estimating Beef and Milk Concentrations 7-40

7.2.7 An Alternate Approach to Vapor/Particle Partitioning in the Air 7-49

7.3 MODEL VALIDATION EXERCISES 7-54

7.3.1 The Impact of Dioxin Soil Contamination to Nearby Soils 7-54

7.3.2 Soil Concentrations and Concurrent Concentrations in Bottom Sediments and Fish 7-57