Phenylmethylsiloxanes in indoor dust from residential area of China: Source, occurrence, bioavailability and exposure assessment.

Phenylmethylsiloxanes, as modified products of dimethylsiloxanes, have been used in personal care products (PCPs) and household appliances, with indoor dust serving as one potential reservoir due to their particle-binding properties. This study measured six isomers of two phenylmethylsiloxanes (P3 and P4) in PCPs (<LOD-381 μg/g, df = 38-43 %, n = 58), indoor dust (<LOD-158 ng/g, df = 33-65 %, n = 103), and outdoor soil samples (<LOD-3.2 ng/g, df = 0-25 %, n = 20) from Chinese Cities. Overall, mean dust concentrations of ∑(P3 + P4) were highest in barbershops (176 ng/g), followed by bathrooms (49.5 ng/g), living rooms (13.3 ng/g), and bedrooms (5.4 ng/g) of residences. Dust phenylmethylsiloxanes had positive correlations with the number of PCPs in bathrooms (R = 0.95 for ∑P3, 0.82 for ∑P4) and electronic appliances (R = 0.86 for ∑P3, 0.84 for ∑P4) in living rooms, suggesting their important contribution to phenylmethylsiloxane emission. The mean concentration ratio of ∑(P3 + P4) to their major degradation product, i.e., PhMeSi(OH)2 , in dust was 2.4 times higher than that in soil, indicating stronger persistence of phenylmethylsiloxanes in indoor environment. Simulated experiments indicated bioavailabilities (1.1-8.2 %) of phenylmethylsiloxanes during dust ingestion lower than that (20.4 %) of their degradation product. Dermal absorption of PCPs dominated (>99 %) intakes of phenylmethylsiloxanes for adults, while dust ingestion/adsorption (0.19 ng/d) may play important roles for toddlers/infants with little usage of phenylmethylsiloxanes-containing PCPs. Additionally, total daily intakes of PhMeSi(OH)2 (0.30-0.84 ng/d) via ingestion and dermal absorption of dust were higher than P3 (0.06-0.31 ng/d) and P4 (0.02-0.09 ng/d), suggesting exposure risk of degradation product of phenylmethylsiloxanes deserving attention.