Sum-PAH Model

through the top predatory fish in the food chain, trophic level 4 (Thomann 1989).

Estimation of FCMs for organic contaminants with Kow greater than 6.5 is less

certain and for such compounds, the USEPA recommends using a FCM of 1 as a

default value.

For lipophilic organic chemicals, BCFs and BAFs are presumed to be directly

proportional to the percent lipid from one tissue to another, and BAF are

calculated as follows:

Wildlife BAF = (predicted BCF)(Ol/Fl)(FCM)

Human Health BAF = (predicted BCF)(FFl/F1)(FCM)

where

predicted BCF (L/kg) is estimated from the regression described above (not

to exceed 100,000)

Fl = average percent lipid of the organisms used to establish the

relationship between BCF and Kow

Ol = percent lipid content of the receptor

FFl = average percent lipid content for a fish fillet

FCM = appropriate food chain multiplier

Concentrations of metals in fish tissue can be estimated from established BAFs

by using a methodology recommended by the EPA (Stephan 1993). Established

BAFs for metals are based on measured BCFs and BAF and are not calculated

with FCM.

Fish tissue concentrations of both organic contaminants and metals are

calculated as:

CF = (CW)(BAF)

where

= concentration of contaminant in fish (g COC/kg wet wt)

= concentration of contaminant in water (g COC/L)

BAF = appropriate bioaccumulation factor (L/kg)

Sum-PAH Model

Polycyclic aromatic hydrocarbons (PAHs) can be biotransformed by aquatic

organisms to metabolites that exert toxic effects by more specific modes of action

than nonpolar narcosis. A concentration-response model has been developed

which predicts toxic effects of PAHs to benthic invertebrates (Swartz et al. 1995).

Appendix B Food Chain and Toxicity Models