Silicone materials are used in a wide variety of consumer/industrial products and process aids. Disposal to wastewater treatment is the primary source of entry for silicones (primarily poly(dimethylsiloxane) or PDMS) in aquatic environments.However, limited information is available on the concentration ranges, distribution, and fate of silicone materials in surface sediments. In this study, PDMS was measured in the surface sediments of four marine and four freshwater areas heavily impactedby municipal wastewater discharge to illustrate worst-case situations for the United States. Concentrations of PDMS were measured in 12-14 samples from each study area. Measured dry weight concentrations of PDMS ranged from below detection(0.2μg·g{sup}-1) to 309μg·g{sup}-1. Low level concentrations (<0.6μg·g{sup}-1) that were measured in 25 of the sediments may have been natural silicon materials rather than PDMS. Generally, concentrations of PDMS were greatest in sediments fromdepositional areas near effluent outfalls. Mean concentrations of PDMS (ISE) ranged from 0.6±0.1 to 78±20μg·g{sup}-1 and were lowest in areas having advanced levels of wastewater treatment. Concentrations of PDMS in these "worstcase" sediments wereless than the "no observable effects concentration" (NOEC) established in laboratory studies using sediment-dwelling organisms.
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