Reviewing site-specific information for exposure factors

Example 16: Body Burdens in Winter Flounder

As indicated earlier, the risk assessor has identified a population in the area potentially exposed to PCBs

from flounders in a commercial catch. The proposed disposal site will influence a fraction of this flounder

catch. As described earlier, a tissue concentration of total PCBs can be calculated for flounder, based on

measured sediment concentrations and observed biota-to-sediment concentration factors. These

calculations resulted in a wet weight tissue concentration of 3.3 ug total PCB/g flounder tissue for

flounders foraging over the disposal site. This is the EPC for total PCBs in the human health risk

assessment.

Reviewing site-specific information for exposure factors

Wherever possible, exposure factors should be developed from site-specific

information. For example, local knowledge of subsistence fishermen may provide a

site-specific ingestion rate and exposure frequency. If this information is

unavailable, USEPA has provided data from key studies on exposure parameters

(USEPA/ORD 1995). It is recommended that the risk assessor use those data that

best represent the individual and population behaviors and descriptions for the

disposal site. For some exposure parameters, default values are recommended. Any

default assumptions that are used may under- or overestimate exposure parameters,

adding uncertainty to the overall analysis.

One method for obtaining site-specific information is to use surveys of the local

population or creel census data from state fisheries departments or local universities,

with review and analysis of the generally accepted survey techniques for the

consumption of fish and shellfish.

The USEPA (1992b) does not provide a default value for the fraction of the

seafood diet obtained from the management site. Therefore, it will be necessary to

estimate this value from site-specific information, fishery statistics, and knowledge

of the species in question.

The USEPA does not provide guidance regarding differential consumption of

various organs such as muscle, fish skin, fish liver, or other organs, nor is there

guidance on other considerations such as food preparation. All of these factors will

contribute to the accuracy of the risk estimates and uncertainty in those estimates.

Site-specific information may provide insights into local cultural eating habits. In

the absence of site-specific information, an assumption may be made for the

consumption of finfish: that people consume fish fillets, not the entire fish.

Fraction ingested (FI) for recreational/subsistence scenario. For recreational

fishes, in lieu of any site-specific catch statistics, or local information, it should be

conservatively assumed that all of the fish consumed by this group is caught within

the area influenced by the disposal site. This will represent the most conservative

case; although it is likely to be reflective of recreational or subsistence fishermen.

Thus, the FI for the recreational/subsistence fishermen would be 1.

Chapter 4 Human Health Risk Assessment