Methyl siloxanes in barbershops and residence indoor dust and the implication for human exposures

Methyl siloxanes (MSs) have been widely added as emollients or solvents in various personal care products (PCPs) such as soap, shampoo and hair conditioner. A considerable percentage of MSs are released into the atmosphere directly from the use of PCPs in indoor environments. Indoor dust is a major reservoir of MSs, due to their particle-binding affinity. Dust ingestion could be one exposure pathway for special populations (hairdressers, for example). Though the toxicity of MSs is known, there is no information regarding the occurrence of MSs in barbershop dusts and the exposure of hairdressers through indoor dust ingestion. In the present study, the levels of three cyclic siloxanes (D4–D6) and 13 linear siloxanes (L4–L16) were measured in indoor dust samples collected from barbershops, and some other microenvironment including bathhouses, dormitories and households for comparison. The concentrations of ∑ MSs in barbershop dusts were one to two orders of magnitude higher than those from the other three indoor microenvironments. The daily intakes of ∑ MSs through indoor dust ingestion were estimated using the model of worst-case exposure (95th percentile concentration) and high dust ingestion, For the hairdressers in workplaces (barbershops), the exposure rates were 14.3 ng/kg-bw/day, and for the general population, college students and toddlers (1–3 yr), the corresponding exposure rates in living spaces were 3.43, 2.00 and 222 ng/kg-bw/day, respectively. Such high exposure levels of MSs through dust ingestion indicate that we should not overlook the potential health risks for occupational groups and toddlers.