Integrated Exposure Analysis. The integrated exposure analysis 

 results in an estimate of ingested dose by species. The ingested 

 dose is calculated for specific segnnents of the hunnan population 

 (for example, a certain age group along a certain stretch of river). 



For a given segment of the exposed population, the ingested dose 

 is calculated as shown below: 



Ingested dose = concentration of a chemical in the 

 edible portion of an organism x a 

 number representing the relative 

 amount of chemical absorbed by the 

 digestive system ^ by the average 

 body weight of all individuals in the 

 population segment. 



In the risk characterization stage, the preceding steps are brought 

 together to estimate the probability and extent of adverse effects 

 associated with consumption of contaminated fish or shellfish from 

 a given water body. Numerical estimates of risk can be presented 

 on an individual basis. Risk to an individual is expressed as a 

 probability (for example, a one in 1 0,000 increased lifetime chance 

 of getting cancer or other effects). Risk to a population is expressed 

 as the excess number of cancers or other adverse effects produced 

 within the specific population over one generation. 



The results of risk assessment may be presented in both tabular 

 and graphic format. All risk estimates should be interpreted as 

 plausible-upper-limit values for the stated assumptions and expo- 

 sure conditions, in keeping with EPA's national guidelines for risk 

 assessment (EPA 1986). Risk estimates for a given area and 

 aquatic food species vary with consumption rates, and consump- 

 tion rates vary greatly among individuals. Therefore, graphs show- 

 ing plausible-upper-limit risks versus consumption rates are 

 recommended as the primary means of presenting results. Using 

 the tables to compare the pattern shown on the graphs with 

 personal consumption rates of various fish and shellfish, con- 

 sumers can determine any extra risk to which they might be 

 exposed. 



Risk assessment results should include a summary of assumptions 

 and an uncertainty analysis. The summary should note general 

 assumptions inherent in all health risk assessments, and specific 

 assumptions adopted for the risk analysis in question. 



By using EPA's 1986 policy for risk assessments and estimating 

 the plausible-upper-limit to risk, it is highly unlikely that risk will be 

 underestimated. The "upper bound estimate" of the risk is not likely 

 to be exceeded. The actual risk is likely to be below this level, and 

 may be close to zero in some instances. Therefore, the estimate 

 provides a consistent basis for relative risk comparisons 



Risk Characterization 



D7 



