Toxic metals in outdoor/indoor airborne PM2.5 in port city of Northern, China: Characteristics, sources, and personal exposure risk assessment

Outdoor and indoor PM2.5 samples were simultaneously collected over four seasons (2017–2018) in Caofeidian, China, and analyzed for 15 elements to investigate the characteristics, sources, and health risks of PM2.5-bound metals. Source-specific PM2.5-bound metals were analyzed using positive matrix factorization, combined with the conditional probability function and potential source contribution function model. The health risks were evaluated using the health risk assessment model, which included the exposure parameters of indoor and outdoor activities of Chinese residents. The annual median of PM2.5 concentrations (89.68 μg/m3) and total metals (2.67 μg/m3) from the outdoor samples significantly surpassed that of the indoor samples (51.56 μg/m3) and total metals (1.51 μg/m3) (P < 0.05). In addition, the indoor/outdoor concentration ratios indicated that most indoor metals mainly originated from outdoor emission sources. In the annual analysis of PM2.5-bound metal sources, this study identified five metal sources: coal combustion, resuspended dust, traffic emissions, fuel combustion sources, and industrial sources, among which industry sources (36.6%) contributed the most. The non-carcinogenic risks of metals for adults (2.81) and children (2.80) all exceed the acceptable non-carcinogenic risk level (1). The non-carcinogenic risk of Mn (1.46 for children, 1.48 for adults) was a key factor in the total non-carcinogenic risk. The total carcinogenic risk of metals for children (3.75 × 10-5) was above the acceptable level (1.0 × 10−6) but within the tolerant limit (1.0 × 10−4), and that for adults (1.48 × 10−4) was above the tolerant limit. The lifetime carcinogenic risk of Cr6+ had the highest proportion of the total carcinogenic risk for children (87.5%) and adults (87.8%). Our results revealed that both adults and children suffered carcinogenic and non-carcinogenic risks from the PM2.5-bound metals in Caofeidian. The corresponding emission control measures of metals in atmosphere should be considered.