Methods for predicting the rate constant for uptake of organic chemicals from water by fish.

Bioaccumulation is an important information requirement for chemicals risk assessment. The most widely used test guideline for measuring bioaccumulation in fish is the OECD 305 test guideline and, in the future, it is likely to include a dietary exposure method for substances that are difficult to test by the more usual aqueous exposure route. This new method results in a biomagnification factor (BMF), whereas for regulatory purposes a bioconcentration factor (BCF) is often required. Therefore, being able to estimate a BCF quantitatively from the data generated in the dietary study would meet an accepted regulatory need. The information generated by the dietary study includes the depuration rate constant. To use these data to estimate a BCF, an estimate of the rate constant for uptake from water is needed, allowing a kinetic BCF to be calculated. The present study considers and tests methods that are currently available for predicting uptake rate constants from water using a database of bioconcentration data. A number of methods were found to perform similarly when tested with substances with a log K(OW) range of approximately 3.5 to 8.2. The uncertainty in the estimated uptake rate constant was relatively large, however, even for the best performing methods.