^ijkm = 



RfDm 



(10) 



where: 

 Hijiun 



RfDm 



Hazard Index of a health effect from intake of chemical 

 m associated with fishery species i for human subpopula 

 tion j in area k (dimensionless) 



Reference Dose for chemical m (mg kg"^ day'^) 



and Eijicm is defined as above. RfDm values are given in IRIS (U.S. EPA 

 1987a). 



When all significant exposure routes and sources are taken into ac- 

 count, the estimated total exposure for all routes replaces Eijkm in the 

 numerator of Equation 10 and the resulting hazard index is compared 

 to a value of 1.0 to evaluate the chemical hazard (Stara et al. 1983; U.S. 

 EPA 1985b). Values of the hazard index for total exposure or of Hjjkm 

 that are above 1.0 indicate that the estimated exposure is potentially of 

 concern. Above 1.0, increasing values of either hazard index indicate 

 increasing hazard. However, the hazard index does not define a dose 

 response relationship, and its numerical value should not be regarded 

 as a direct estimate of risk. 



Because Hijkm as calculated by Equation 10 do not account for ex- 

 posures other than that from consumption of single fisheries species, 

 values of Hijicm substantially below 1.0 do not necessarily indicate a lack 

 of significant risk overall. Although species-specific hazard indices are 

 useful for evaluating whether contamination of any single species is of 

 concern, two problems remain: 



• How can hazards from mixed-species diets of fish and shellfish 

 be evaluated? 



• How should exposures from sources other than consumption 

 of contaminated fish and shellfish (either single-species or 

 mixed-species diets) be taken into account? 



To address the first question above, one approach would be to sum 

 Hijkm values across all species to obtain a hazard index, Hjkm, as- 

 sociated with the entire fishery. However, Hjkm could not be inter- 

 preted as representative of actual hazard to individuals, since the sum 

 of estimated exposures across species will not be the same as exposures 

 associated with the mixed-species diets of individuals (see above, 

 Exposure Assessment, Exposure Dose Determination, Mixed-Species 

 Diet). An alternative approach recommended here is to use the 

 average effective dose (Ejkm) for mixed-species diets to calculate a 

 hazard index. This hazard index for mixed-species diets still does not 

 account for exposures due to other sources. 



To address the second question above, the sum of exposures from all 

 sources should be compared to the RfD to evaluate total hazard. 

 Guidance on estimation of exposures due to other sources is available 

 in U.S. EPA (1986b,f). If exposure estimates for sources other than the 

 fishery are not available, then some relatively small fraction of the RfD 

 (e.g., 0.1) could be assigned to intake from consumption of fish and 



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