QSARs of bioconcentration - validity assessment of log Pow / log BCF correlations
Abstract
The bioconcentration factor (BCF) is an important parameter for the assessment of chemical substances in ecosystems. Chemical legislation does not request any experimental determination of bioconcentration potential in the basic tier, but relies on extrapolations from the compounds-1-octanol/water partition coefficient (log PsubOW) assuming a positive correlation between log PsubOW and log BCF. Substances with log PsubOW between 3 and 6 are classified highly accumulating; no substantial bioconcentration is assumed for compounds having log PsubOW smaller than 3 or bigger than 6. Basically, this assessment scheme represents the application of quantitative structure- activity relationships (QSARs) for legislative purposes. Considering that bioaccumulation is an equilibrium distribution between an organism, e.g. fish, and the surrounding water phase it seems reasonable that the BCF is estimated from other partition coefficients, namely log PsubOW. This concept is supported by numerous publ ications reporting linear log PsubOW/BCF correlations. To test the validity of the postulated log PsubOW/log BCF correlations, published BCF values were validated and compared with the respective calculated log PsubOW values generally revealing increasing BCF values with increasing log PsubOW. For compounds having log PsubOW bigger than 6 a gradual decrease of the BCF is found. The significance of the correlation however is not as high as could be assumed from the results found in the literature.
