Indoor Air Cyclic Volatile Methyl Siloxanes In A University Campus:Monitoring And Heath Risk Assessment

In this work, four kinds of cyclic volatile methyl siloxanes (cVMS) are chosen for the study:D3 (hexamethylcyclotrisiloxane), D4 (octamethylcyclotetrasiloxane), D5 (decamethylcyclopentasiloxane) and D6 (dodecamethylcyclohexasiloxane). A low flow air sampler is independently researched and developed, which can not only state synchronization acquisition particles and gaseous cVMS samples. Through the elution efficiency, sampling efficiency and recovery, flow rate attenuation and other technical indicators to evaluate the improved method, improve the cyclic siloxane laboratory quality control system. Indoor air samples are collected from Dalian Maritime University (DMU) using this sampler from June to July.2014. Home, male/female dormitories, lab/offices were studied. The levels, compositions and sources of cVMSs were studied, and human health risk of D5 was assessed by US EPA health risk assessment model.The method evaluation results show that the 1 ml of D3～D6 for SPE elution recoveries are between 83-129%, for ENV+are between 83-126%,> 80% of D3～D6 can be eluted by 1 ml of n-hexane. The sampling efficiencies are between 84-109%. Quantity in ENV+is more than 400 time higher than ENV+backup, less than 2% of the target is absorped by backup, the backup content can be ignored. In the sampling time for 24 hours, smaller velocity variation, frit showing a little effect on the accumulation of flow rate for the particles.Particle phase samples, in addition to the D3, total 25 samples in indoor particle phase did not detected, detectable rate for D4, D5, D6 is 20%,48% and 4%, respectively, and levels in particle phase is lower, an order of magnitude lower than the detection limit. Gaseous phase samples, D3, D4, D5 and D6 detection rate is 100%, the average total siloxane concentration (∑cVMS) is ranging 0.29-78.4. D5 is predorminant in all cVMS, accounted for 89.00% of total cVMS concentration. ∑cVMS in Female dorms is the highest,27～80 times higher than other sites.By analyzing the characteristic ratio and using list, indicating the use of personal care products and cosmetics was an important source of cVMS in indoor especially in female dormitories. Electrical/electronic devices were likely another important source of emissions of cVMSs in indoor. Correlation analysis shows that the D3 and D4, D5 and D6 correlation reached 1% significant level (r=0.70,0.92); The D3 and D5, D3 and D6 were negative correlation (r=0.18.0.12).Non cancer risk evaluation for D5 showed that the hazard quotient (HQ) was 2.14E-04～4.31E-02 for the five indoor environments, indicating that D5 in these study areas had no appreciable adverse non-cancer health risks for the exposed population. But the contribution of particle phase in inhalation exposure is only 0.03%.