Bioconcentration and biotransformation of the nonionic surfactant octaethylene glycol monotridecyl ether 14C-C13EO8

Alcohol ethoxylates (AEs) are the most important nonionic surfactants used in household detergents. In this study, we investigated the bioconcentration behavior of C-14-labeled C13EO8 as a representative of AEs in fathead minnow (Pimephales promelas). The rate constants of uptake and elimination of the parent C-14-C13EO8 were 317 L/kg/d and 10.1/d, respectively. The parent compound-specific bioconcentration factor (BCF) was found to be 31.4 L/kg. In contrast, the steady-state ratio of the concentrations in fish and water (C-f,C-tot/C-w,C-tot)(ss) of total radioactivity was 224 L/kg. The thin layer chromatography chromatograms demonstrated that the C-14-C13EO8-derived radioactivity is incorporated into a large variety of chemical species. This, as well as the large discrepancy between the BCF and (C-f,C-tot/C-w,C-tot)(ss) are qualitative indicators of the extent of biotransformation. The first-order, one-compartment model of bioconcentration was extended to allow for quantification of the in vivo rate constant of biotransformation of C-14-C13EO8. The value obtained amounted to 10/d, and the model results indicated that biotransformation is the dominating contributor in the elimination of AEs. A comparison of C13EO8 to compounds of other classes of environmentally relevant contaminants highlights the importance of biotransformation as a process contributing to the reduction of the bioconcentration potential of these compounds.