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 3--Ecological Exposure Assessment, Effects Assessment, and Risk
Characterization ...................................................................................................49
Exposure Assessment ............................................................................................49
Step 1: Estimating the concentration of COCs in the dredged material ...........49
Step 2: Estimating exposure point concentrations (EPC).................................51
Step 3: Food chain modeling.............................................................................54
Use of Higher-Level Food Chain Models .............................................................59
Ecological Effects Assessment ..............................................................................61
Step 1: Identify information sources .................................................................61
Step 2: Summarize toxicological data...............................................................63
Step 3: Selecting and developing toxicity factors .............................................64
Gas Research Institute approach for developing toxicity factors .....................65
California EPA approach ..................................................................................66
EPA Region X approach ...................................................................................67
The use of toxicity models ................................................................................67
Risk Characterization ............................................................................................67
4--Human Health Risk Assessment .........................................................................72
Hazard Identification .............................................................................................73
Step 1: Consult USEPA resource documents ...................................................75
Step 2: Describing the receptors and exposure pathways.................................76
Direct exposure pathways. ................................................................................77
Indirect exposure pathways ...............................................................................79
Step 3: Quantify exposure.................................................................................82
Specifying the equation to calculate dose .........................................................83
Estimate exposure point concentrations (EPCs)...............................................84
Reviewing site-specific information for exposure factors ................................86
Reviewing USEPA Default Exposure Assumptions .............................................87
Toxicity Assessment..............................................................................................90
Step 1: Determine Toxicity Factors ..................................................................91
Step 2: Assemble Sources of Toxicity Information ..........................................91
Human Health Risk Characterization....................................................................91
5--Uncertainty Analysis ...........................................................................................95
Identify Likely Sources of Uncertainty..................................................................96
Identify Clearly All Significant Assumptions .......................................................97
Identify Range, Wherever Possible, the Distribution of Values a Parameter
May Take ........................................................................................................97
Test the Sensitivity of the Risk Assessment .........................................................97
References ..................................................................................................................99
Appendix A: Summary of Federal, State, and Regional Guidance ..........................A1
Appendix B: Food Chain and Toxicity Models ....................................................... B1
Appendix C: Information Sources ............................................................................ C1
Appendix D: Toxicological Profiles .........................................................................D1
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