Size-dependent distribution and inhalation exposure characteristics of particle-bound chlorinated paraffins in indoor air in Guangzhou, China

Chlorinated paraffins (CPs) are now attracting special concerns worldwide as one type of new persistent toxic substances as classified by the Stockholm Convention. CPs are extensively applied in household goods and indoor decoration materials, but information on their occurrence and exposure risk in such environments is still very scarce. In this study, the current concentrations, particle size distributions, and inhalation exposure characteristics and risk of CPs were investigated in regard to indoor air particulate matter. Both short chain (SCCPs) and medium chain CPs (MCCPs) were determined in all size-fractioned particle samples with a range of 6.20-17.8 and 5.98-40.5 ng m−3, respectively. MCCPs were more abundant than SCCPs. Size distributions revealed that individual homologs, SCCPs, and MCCPs exhibited a similar unimodal distribution peaking in the fine particles with a diameter of 0.56-1.0 μm. The relative abundance of longer-chain or more heavily chlorinated homologs tend to gradually increase with particle size shift from coarse to fine mode. Vapor pressure may be a critical factor governing the size-dependent distribution of CPs. Deposition of particulate CPs in the human respiratory tract is also size-dependent. The contributions of fine particles to the regional depositions of CPs in the human respiratory tract increase with increasing carbon chain length or chlorine content. Based on the size-dependent distributions of CPs, inhalation exposure assessment from the ICRP model indicated no significant health risk due to CPs in current indoor environments.