Cyclic siloxanes in indoor environments from hair salons in Hanoi, Vietnam: Emission sources, spatial distribution, and implications for human exposure

In this study, three typical cyclic siloxanes (CSis) were found in hair care products, indoor dust and indoor air samples at hair salons in Hanoi, Vietnam. The total concentrations of CSis in three kinds of hair care products ranged from 8.77 to 515 μg g−1. The mean and median concentrations of CSis in dust samples collected at hair salons were 671 and 654 μg g−1, respectively. The total concentrations of CSis in indoor air samples collected at the hair salons ranged from 415 to 2610 ng m−3 (mean: 1030; median: 849 ng m−3, respectively). Among three cyclic siloxanes mentioned in this study, decamethylcyclopentasiloxane (D5) was found at the highest level in all categories of samples. D5 had also a strong correlation between indoor dust and indoor air from hair salons (the coefficient of determination (R2): 0.852); meanwhile dodecamethylcyclohexasiloxane (D6) and octamethylcyclotetrasiloxane (D4) had good correlations (R2 = 0.618 and 0.585, respectively). This result indicates that hair care products are main emission source of cyclic siloxanes in indoor environments at the hair salons. The average exposure doses to total SCis through both of dust ingestion and inhalation were estimated to be 103 and 79.5 ng kg-bw−1 day−1 for women and men, respectively. These levels were higher than those reported for some Asian countries. This is among the most comprehensive investigations on the emission sources and distributions of cyclic siloxanes in indoor dust and indoor air at hair salons in Vietnam.