Example 14: Risk to Flounder

The appropriate method to assess risk to flounder is to compare a measured effect level for body burden

of PCBs in flounder to the calculated flounder body burden. As indicated earlier, the selected toxicity

factor is 0.76 ug PCB/g wet weight. This is less than the 3.3 ug PCB /g body tissue concentration

calculated for winter flounder in this example. Therefore, the assessment shows that there is potential for

risk to the selected receptor, winter flounder. At this point, the risk assessor and risk mangers can:

Accept the initial conclusion and employ risk management activities.

Employ more complex fate and transport models and perhaps a more complex food chain

model and recalculate risk.

The conclusion of risk from the initial estimates has various sources of uncertainty including:

Uncertainty concerning the actual foraging area of a flounder

Uncertainty concerning the BSAF C the assessment used the recommended BSAF of 3

which may be overly conservative. A more sophisticated food chain model may give a

more realistic estimate of body burden.

Uncertainty associated with possible interspecies differences between the experimental

organism, Fundulus heteroclitus, and the flounder.

All the models used in the assessment are linear. Therefore, a simple sensitivity analysis

can be performed using the ranges of various parameters.

Note that this estimate of potential risk applies to PCB exposures. The risk from the other COCs at this

hypothetical site (PAHs and mercury) should be estimated as well. Also the risk characterization is iterative.

At this point, the risk assessor may want to implement more sophisticated estimates of sediment

concentrations using data intensive modeling. The assessor may also use a more sophisticated food chain

model (e.g., Appendix B).

Chapter 3 Ecological Exposure Assessment