Short-, medium- and long-chain chlorinated paraffins from indoor/outdoor air in Guanzhong Plain, China: Characteristics, distribution and human exposure risks

Research on the environment of long chain chlorinated paraffins (LCCPs) in the fine particulate matter (PM_2.5) and gas phase is still scarce, particularly in indoors. It limits the comprehensive investigation into the gas-particle partitioning behavior and health risk assessment of CPs. In this study, short-, medium- and long-chain chlorinated paraffins (SCCPs, MCCPs and LCCPs) of outdoor and indoor PM_2.5/gas phases were simultaneously studied in two rural villages in Guanzhong Plain of 2021. CPs were mainly accumulated in the gas phases, especially indoors. However, the indoor and outdoor distribution of CPs in PM_2.5 was affected by many factors, such as the sandstorm events, different fuel usage and living habits, etc. Moreover, the concentrations of MCCPs (from 0.7 to 16.1 ng/m³) in PM_2.5 were higher than SCCPs (from 0.3 to 5.6 ng/m³) and LCCPs (from 0.3 to 1.8 ng/m³). However, in gas phase, the concentrations of SCCPs were highest, then followed by MCCPs and LCCPs. The shorter carbon chain of SCCPs (C_10~11) and MCCPs (C₁₄) were the most abundant groups, while the higher carbon chain (C₂₉) dominated in the LCCPs. The lower chlorinated groups (Cl_5~6) were dominated for SCCPs, MCCPs and LCCPs. Principal component analysis (PCA) showed that there were no obviously different sources of the CPs in the two sampling sites. However, the CPs in gaseous phase and CPs in PM_2.5 displayed different sources. Human exposure risk assessment indicated that the CPs had no significant risks to different age groups basing on the inhalation. However, considering their persistence and bioaccumulation, CPs exposure should be monitored continually in this region.