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

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Abstract
Alcohol ethoxylates (AEs) are the most important nonionic surfactants used in household detergents. In this study, we investigated the bioconcentration behavior of 14C‐labeled C13EO8 as a representative of AEs in fathead minnow (Pimephales promelas). The rate constants of uptake and elimination of the parent 14C‐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 (Cf,tot/Cw,tot)ss of total radioactivity was 224 L/kg. The thin layer chromatography chromatograms demonstrated that the 14C‐C13EO8‐derived radioactivity is incorporated into a large variety of chemical species. This, as well as the large discrepancy between the BCF and (Cf,tot/Cw,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 14C‐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.