| | GUIDELINES FOR EXPOSURE ASSESSMENT |
| | 0,63 | | MB |
| | 176 | | stron |
| | 6048 | | ID | UNITED STATES ENVIRONMENTAL PROTECTION AGENCY |
| | 1998 | | rok |
| | TABLE OF CONTENTS |
| | 1. INTRODUCTION . 13 |
| | 1.1. Intended Audience . 13 |
| | 1.2. Purpose and Scope of the Guidelines . 14 |
| | 1.3. Organization of the Guidelines . 15 |
| | 2. GENERAL CONCEPTS IN EXPOSURE ASSESSMENT 16 |
| | 2.1. Concepts of Exposure, Intake, Uptake, and Dose . 18 |
| | 2.1.1. Exposure . 19 |
| | 2.1.2. Applied Dose and Potential Dose 20 |
| | 2.1.3. Internal Dose 22 |
| | 2.1.4. Exposure and Dose Relationships 23 |
| | 2.1.4.1. Calculating Potential Dose for Intake Processes . 25 |
| | 2.1.4.2. Calculating Internal Dose for Uptake Processes . 30 |
| | 2.1.4.3. Calculating Internal Dose for Intake Processes . 35 |
| | 2.1.5. Summary of Exposure and Dose Terms With Example Units 36 |
| | 2.2. Approaches to Quantification of Exposure 39 |
| | 2.2.1. Measurement of Exposure at the Point-of-Contact . 40 |
| | 2.2.2. Estimates of Exposure from Scenario Evaluation . 41 |
| | 2.2.3. Exposure Estimation by Reconstruction of Internal Dose 43 |
| | 2.3. Relationships of Exposure and Dose to Risk . 44 |
| | 2.3.1. Individual Risk . 45 |
| | 2.3.2. Population Risk . 49 |
| | 2.3.3. Risk Descriptors 52 |
| | 3. PLANNING AN EXPOSURE ASSESSMENT . 54 |
| | 3.1. Purpose of the Exposure Assessment . 55 |
| | 3.1.1. Using Exposure Assessments in Risk Assessment . 55 |
| | 3.1.2. Using Exposure Assessments for Status and Trends 58 |
| | 3.1.3. Using Exposure Assessments in Epidemiologic Studies 58 |
| | 3.2. Scope of the Assessment . 59 |
| | 3.3. Level of Detail of the Assessment . 60 |
| | 3.4. Determining the Approach for the Exposure Assessment . 60 |
| | 3.5. Establishing the Exposure Assessment Plan . 62 |
| | 3.5.1. Planning an Exposure Assessment as Part of a Risk Assessment 62 |
| | 3.5.2. Establishing the Sampling Strategy . 64 |
| | 3.5.2.1. Data Quality Objectives 65 |
| | 3.5.2.2. Sampling Plan 66 |
| | 3.5.2.3. Quality Assurance Samples . 69 |
| | 3.5.2.4. Background Level . 70 |
| | 3.5.2.5. Quality Assurance and Quality Control 70 |
| | 3.5.2.6. Quality Assurance and Quality Control for |
| | Previously Generated Data . 71 |
| | 3.5.2.7. Selection and Validation of Analytical Methods . 71 |
| | 3.5.3. Establishing the Modeling Strategy 72 |
| | 3.5.3.1. Setting the Modeling Study Objectives 72 |
| | 3.5.3.2. Characterization and Model Selection . 72 |
| | 3.5.3.3. Obtaining and Installing the Computer Code . 74 |
| | 3.5.3.4. Calibrating and Running the Model 75 |
| | 3.5.3.5. Model Validation 75 |
| | 3.5.4. Planning an Exposure Assessment to Assess Past Exposures 76 |
| | 4. GATHERING AND DEVELOPING DATA FOR EXPOSURE ASSESSMENTS 78 |
| | 4.1. Measurement Data for Point-of-Contact Assessments . 78 |
| | 4.2. Obtaining Chemical Concentration Information . 79 |
| | 4.2.1. Concentration Measurements in Environmental Media 85 |
| | 4.2.2. Use of Models for Concentration Estimation 87 |
| | 4.2.3. Selection of Models for Environmental Concentrations 88 |
| | 4.3. Estimating Duration of Contact . 89 |
| | 4.3.1. Observation and Survey Data 90 |
| | 4.3.2. Developing Other Estimates of Duration of Contact 92 |
| | 4.4. Obtaining Data on Body Burden or Biomarkers . 93 |
| | 4.5. Obtaining Data for Pharmacokinetic Relationships . 94 |
| | 4.6. Obtaining Data on Intake and Uptake . 95 |
| | 5. USING DATA TO DETERMINE OR ESTIMATE EXPOSURE AND DOSE 96 |
| | 5.1. Use of Data in Making Inferences for Exposure Assessments 96 |
| | 5.1.1. Relevance of Data for the Intended Exposure Assessment 97 |
| | 5.1.2. Adequacy of Data for the Intended Assessment . 98 |
| | 5.1.2.1. Evaluation of Analytical Methods . 99 |
| | 5.1.2.2. Evaluation of Analytical Data Reports 99 |
| | 5.1.2.2.1. Evaluation of Censored Data Sets 100 |
| | 5.1.2.2.2. Blanks and Recovery 103 |
| | 5.1.3. Combining Measurement Data Sets from Various Studies . 104 |
| | 5.1.4. Combining Measurement Data and Modeling Results 104 |
| | 5.2. Dealing with Data Gaps 105 |
| | 5.3. Calculating Exposure and Dose 107 |
| | 5.3.1. Short-Term Versus Long-Term Data for Population Exposures . 107 |
| | 5.3.2. Using Point-of-Contact Data to Calculate Exposure and Dose . 108 |
| | 5.3.3. The Role of Exposure Scenarios in Exposure Assessment . 109 |
| | 5.3.3.1. Scenarios as a Means to Quantify Exposure and Dose 111 |
| | 5.3.3.2. Exposure Scenarios and Exposure Estimators as Input to Risk Descriptors . 113 |
| | 5.3.3.3. Exposure Scenarios as a Tool for Option Evaluation . 113 |
| | 5.3.4. General Methods for Estimating Exposure and Dose 114 |
| | 5.3.4.1. Preliminary Evaluation and Bounding Estimates . 115 |
| | 5.3.4.2. Refining the Estimates of Exposure and Dose . 117 |
| | 5.3.5. Using Estimates for Developing Descriptors 119 |
| | 5.3.5.1. Individual Exposure, Dose, and Risk 119 |
| | 5.3.5.2. Population Exposure, Dose, and Risk . 129 |
| | 6. ASSESSING UNCERTAINTY 134 |
| | 6.1. Role of Uncertainty Analysis in Exposure Assessment . 134 |
| | 6.2. Types of Uncertainty 136 |
| | 6.2.1. Scenario Uncertainty 137 |
| | 6.2.2. Parameter Uncertainty . 138 |
| | 6.2.3. Model Uncertainty 142 |
| | 6.3. Variability Within a Population Versus Uncertainty in the Estimate . 144 |
| | 7. PRESENTING THE RESULTS OF THE EXPOSURE ASSESSMENT 146 |
| | 7.1. Communicating the Results of the Assessment 146 |
| | 7.1.1. Exposure Characterization . 146 |
| | 7.1.2. Risk Characterization 148 |
| | 7.1.2.1. Integration of Hazard Identification, Dose-Response, and Exposure Assessments . 149 |
| | 7.1.2.2. Quality of the Assessment and Degree of Confidence 150 |
| | 7.1.2.3. Descriptors of Risk . 151 |
| | 7.1.2.4. Communicating Results of a Risk Assessment to the Risk Manager 151 |
| | 7.1.3. Establishing the Communication Strategy . 152 |
| | 7.2. Format for Exposure Assessment Reports . 153 |
| | 7.3. Reviewing Exposure Assessments 153 |
| | 8. GLOSSARY OF TERMS . 157 |
| | 9. REFERENCES 166 |