Environmental Occurrence of Polydimethylsiloxane

An extensive monitoring program was conducted to determine the occurrence of polydimethylsiloxane (PDMS) in environmental compartments impacted by consumer waste disposal practices. Eight wastewater treatment plants, representative of those found in North America, were monitored to determine PDMS removal during wastewater treatment. Surface waters, sediments, and sludge-amended soils impacted by wastewater treatment plant effluents and sludges were also monitored for a more complete assessment of the environmental fate of PDMS. Newly developed GPC−ICP and/or HPLC−ICP analytical techniques were used to provide insight into the environmental fate of PDMS and anticipated PDMS degradation products. PDMS was found to be highly removed during wastewater treat ment with effluent concentrations, in most cases, below the quantitation limit of the analytical technique (<5 μg/L). PDMS sludge concentrations ranged from 290 to 5155 mg/kg and varied as a function of influent concentration and sludge processing method. Sediment levels of <6 mg/kg were measured near the outfall of the wastewater treatment plants sampled. Measured sludge-amended agricultural soil concentrations ranged from <0.41 to 10.4 mg/kg and were lower than expected in most cases based on calculated PDMS loadings via historical sludge application. The lower than expected PDMS concentrations in sludge-amended soil combined with detection of dimethylsilane-1,1-diol, an expected PDMS breakdown product, suggest degradation of PDMS in the soil environment.