Volatile methylsiloxane levels of settled dust in hair salons: Spatial and occupational exposure trends

Volatile methylsiloxanes (VMS) are prevalent ingredients of personal care products, including hair care products. Hair salons, in which these products are frequently used, exposes residents to significant VMS levels. Therefore, this study investigated seven different VMS compounds in the dust from 50 hair salons. The median total VMS concentration was 906 (6.19-64,200) μg·g^-1, primarily comprising dodecamethylcyclohexasiloxane (D6, 452 μg g^-1), followed by octamethylcyclotetrasiloxane (D4, 303 μg g^-1). Potential sources of cyclic VMS compounds are PCPs, while for linear VMS, they are laundry detergents, mainly used for towels in hair salons. Statistically significant spatial differences were observed between hair salons in different districts in the city, possibly influenced by socioeconomic factors, with hexamethylcyclotrisiloxane (D3), D4, and D6 showing the greatest variation among all the VMS compounds based on district. Winter and summer samples exhibited seasonal differences within the same district, with winter samples showing higher VMS concentrations owing to decreased ventilation. Ingestion exposure assessments revealed greater VMS exposure for hair salon workers in higher socioeconomic areas under normal case exposure conditions (normal ingestion rate with 8 h of exposure, up to 2.62 ng·day^-1 kg^-1), whereas worst-case exposure (higher ingestion rate with 12 h of exposure) was approximately 3.79 times higher. Hair salons were the most exposed to D6 in all the districts through dust ingestion. A comparison with other studies revealed lower exposure levels in the present study.