Typical indoor concentrations and mass flow of cyclic volatile methylsiloxanes (cVMSs) in Dalian, China

Cyclic volatile methylsiloxaes (cVMSs), namely hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6), were studied for a typical indoor environment of male and female dormitories in the campus of Dalian Maritime University (DMU) in China. An empty, frit-fitted SPE cartridge was placed on top of an Isolute ENV + cartridge, sampling cVMSs in particulate and gas phases, respectively. The highest concentration of D3, D4, D5, and D6 was 190, 460, 37,000, and 670 ng m^-3, respectively. All cVMSs, especially D5, were higher in female dormitories than that in male dormitories. Emission rate from different sources of cVMSs in dormitories was calculated from a survey of the use of personal care products (PCPs) by students living in the dormitory during the sampling period. The mean emission rate (ER, mg·d^-1) of D4 and D5 in male dormitories was 0.12 ± 0.01 and 0.49 ± 0.03 mg d^-1, respectively, and that in female dormitories was 0.21 ± 0.05 and 46 ± 17 mg d^-1, respectively. Then, we modified an existing mass balance model to predict the indoor air levels of D4 and D5 in both male and female dormitories based on the usage of PCPs. There was a good agreement for D4 and D5 concentrations in female dormitories between modeled and measured concentrations with the ratio of predicted to measured values to be 1.5 and 1.2, respectively, which indicated that use of PCPs was the main source of cVMSs in university dormitories.