Improved method for estimating bioconcentration/bioaccumulation factor from octanol/water partition coefficient

A compound's bioconcenuation factor (BCF) is the most commonly used indicat or of its tendency to accumulate in aquatic organisms from the surrounding medium. Because it is expensive to measure. the BCF is generally estimated from the octanol/water partition coefficient (K-ow), but currently used reg ression equations were developed from small data sets that do not adequatel y represent the wide range of chemical substances now subject to review. To develop an improved method, we collected BCF data in a file that contained information on measured BCFs and other key experimental details For 694 ch emicals. Log BCF was then regressed against log K-ow and chemicals with sig nificant deviations from the line of best fit were analyzed by chemical str ucture. The resulting algorithm classifies a substance as either nonionic o r ionic, the latter group including carboxylic acids, sulfonic acids and th eir salts, and quaternary N compounds. Log BCF for nonionics is estimated f rom log K-ow and a series of correction factors if applicable; different eq uations apply for log K-ow 1.0 to 7.0 and >7.0. For ionics, chemicals are c ategorized by log K-ow and a log BCF in the range 0.5 to 1.75 is assigned. Organometallics, nonionics with long alkyl chains, and aromatic azo compoun ds receive special treatment. The correlation coefficient (r(2) = 0.73) and mean error (0.48) for log BCF (n = 694) indicate that the new method is a significantly better fit to existing data than other methods.