Great Lakes Methodology for Predicting Fish Tissue Concentrations from Water Concentrations.

Mass transfer coefficients are estimated on the basis of empirical relationships

between organism wet weight, lipid content, and percentage of each prey item in

the diet. The model conservatively assumes that there is no loss of compound due

to metabolic transformation.

Information on the food chain of the management site is used to describe and

select typical organisms for use in the model.

Great Lakes Methodology for Predicting Fish Tissue

Concentrations from Water Concentrations.

The U.S. Environmental Protection Agency (EPA) has relied upon use of

steady-state bioconcentration factors (BCF) and bioaccumulation factors (BAF) to

relate water concentrations to the concentrations in fish tissue. A steady-state BCF

describes the ratio (L/kg) of a compound=s concentration in tissue to its

concentration in the surrounding water, when the organism is exposed in the

laboratory only through the water, by uptake through gill membranes or other

external body surfaces.

BCF = (g COC/kg wet wt tissue) = L/kg

(g COC / L water)

A steady state BAF describes the ratio (L/kg) the concentration of a substance

in tissue to its concentration in the surrounding water in situations where both the

organism and its food are exposed. BAF are typically based on field

measurements.

BAF = (g COC/kg wet wt tissue) = L/kg

(g COC / L water)

If lab or field measurements are unavailable, USEPA recommends that the

following methodology be used to derive BCFs and BAFs.

BCFs for organic compounds can be calculated from the octanol-water

partition coefficient, Kow, using the following relationship (Veith and Kosian

1983):

log BCF = 0.79 log Kow - 0.40

In the absence of a field measured BAF, USEPA recommends estimating

BAFs for organic compounds by multiplying the BCF by a factor which accounts

for the biomagnification of a pollutant through the food chain and lipid content of

the organism. As larger organisms, such as bluefish, consume other fish and

aquatic organisms, the concentration of some COCs are increased in the predator.

The factor which describes this biomagnification is called the food chain

multiplier (FCM). USEPA calculated FCMs that describe biomagnification

Appendix B Food Chain and Toxicity Models