Uptake and elimination by fish of polydimethylsiloxanes (silicones) after dietary and aqueous exposure

Abstract

Although several polydimethylsiloxane oligomers are taken up by fish after dietary and aqueous exposure, they do not significantly accumulate, despite their high hydrophobicity compared to polychlorinated biphenyls. For both cyclic and linear oligomers with less than fourteen silicon units, this is probably due to short half life times. For all oligomers these were less than 4.5 days. Linear oligomers with more than fourteen silicon units were not detectable in fish, probably due to a lack of uptake. After dietary exposure the body burden of PDMS oligomers usually never exceeded the daily exposure dose. The biomagnification factors were less than 0.06, whereas for 2, 2’, 5, 5'‐tetrachlorobiphenyl 1.4 was found. After aqueous exposure, bioconcentration factors were all less than 1200 for PDMS oligomers, and 27,000 for the biphenyl. In addition it was found that the uptake rate constants of the silicon compounds from water by fish were comparable to those of other hydrophobic chemicals such as PCB's. Hence it was concluded that the relatively low bioconcentration and biomagnification factors of PDMS oligomers with less than fourteen silicon units must be explained by rapid elimination, rather than by slow uptake.