Concentrations and inhalation risk assessment of short-chain polychlorinated paraffins in the urban air of Dalian, China.

The concentrations of short-chain polychlorinated paraffins (SCCPs) in the urban air of Dalian, China, were monitored from March to October 2010 and from September to October 2016 with active high-volume sampler. The total concentration of SCCPs (particulate phase + gas phase) ranged from 15.12 to 66.44 ng m, with an average of 30.26 ng m in 2010, and 65.30 to 91.00 ng m, with an average of 78.15 ng m in 2016. Hexa-chlorinated dodecane and hexa-chlorinated undecane are the predominant components in the gas phase, while octa-chlorinated undecane and hepta-chlorinated tridecane are dominant in the particulate phase. In 2010, 82.57-97.16% of the total SCCPs were found in the gas phase, except that in winter, where 63.11% of the total SCCPs were in the particulate phase; the air concentrations of SCCPs in gas phase were summer > autumn > spring > winter, which was positively correlated with the change of the average ambient temperature, while it was the contrary in particulate phase. In autumn, the gas phase and the total air concentration of SCCPs in 2016 were 2.57 times more than that in 2010, while the congener group patterns of SCCPs were similar. Spearman's rank correlation analysis between the concentrations of SCCPs with meteorological parameters was conducted. The gas-particle distribution was examined through the relationship of the logarithm of the gas-particle partition coefficient with that of the subcooled vapor pressure and the octanol-air partitioning coefficient of SCCPs. Results indicated that the absorption mechanisms contributed more to the partitioning process. The exposure risk of SCCPs was evaluated, which illustrated that the estimated exposure of SCCPs via the outdoor environment in Dalian did not exceed the health concern threshold of the European risk assessment.