tamination (e.g., laboratory-derived BCFs). Spatial characterization is 

 important for identifying areas of high contamination resulting from 

 heterogeneous transport and deposition of contaminants. Temporal 

 characterization is important for defining time-dependent changes b 

 contaminant concentrations that may mitigate future exposure and 

 risk. 



Predictions of spatial trends in chemical residues may also aid m 

 identifying and controlling sources of pollutants. For example, when 

 data on sources, sediments, and tissues are available, modeling of 

 chemical transport and transformation processes may help to link the 

 patterns of chemical contaminants observed in the environment with 

 specific individual sources. Information on differential degradation of 

 contaminants and compositional relationships for complex mixtures 

 can be used to support the model analysis (e.g.,'calibration and valida- 

 tion). Finally, modeling of contaminant releases in combination with 

 chemical residues in fisheries may aid in evaluating alternative source 

 controls or remedial actions for waste sites. The results of modeling 

 can indicate the level of source control or remedial action needed to 

 achieve a desired level of environmental quality. 



In the exposure assessment guidelines, U.S. EPA (1986b) describes 

 general approaches for characterizing sources, exposure pathways, 

 and environmental fate of chemicals. Analysis of chemical transport 

 and fate is a major endeavor, which cannot be addressed in detail here. 

 For additional information, the interested reader should consult Cal- 

 lahan et al. (1979), Burns et al. (1981), Jensen et al. (1982), Mills et al. 

 (1983), Games (1983), Connor (1984b), Thomann and Connolly 

 (1984), Onishi (1985a,b), U.S. EPA (1986b), Pastorok (1986), and 

 references therein. 



The second stage of the exposure assessment, analysis of exposed 

 populations, includes the following steps: 



• Identify potentially exposed human populations and map loca- 

 tions of fisheries harvest areas 



• Characterize potentially exposed populations 



- Subpopulations by age, sex, and ethnic composition 



- Population abundance by subpopulation 



• Analyze population activities 



- Harvest trip frequency 



- Seasonal and diel patterns of harvest trips 



- Time per harvest trip 



- General activity (e.g., clamming, crabbing, fishing) 



• Analyze catch/consumption patterns by total exposed popula- 

 tion and subpopulation 



- -Proportion of successful trips 



- Catch by numbers and weight according to species 



- Time since last meal of locally harvested organisms 



- Number of consumers sharing catch 



- Parts of organisms eaten 



- Method of food preparation (e.g., raw, broiled, baked) 



Analysis of Exposed 

 Populations 



53 



