Pollution characteristics of ambient PM_2.5-bound benzo[a]pyrene and its cancer risks in Beijing

The purpose of this study was to reveal the pollution characteristics of ambient PM_2.5-bound benzo[a]pyrene (B[a]P) in Beijing and to assess the lifetime cancer risk from respiratory pathway exposure. The average daily dose was evaluated by the annual concentrations of ambient PM_2.5-bound B[a]P, combined with Chinese human exposure factors and the age sensitivity factors. The 70-year lifetime cancer risks of different groups were assessed by the exposure assessment and stochastic analysis method recommended by California Environmental Protection Agency. The groups were divided by age and gender. The results showed that the ambient PM_2.5-bound B[a]P concentration during the cold season was 15.7 times greater than that during the warm season in Beijing. The annual average concentrations of PM_2.5-bound B[a]P in outdoors and indoors were 1.67 ng/m³ and 1.04 ng/m³, respectively, which exceeded the limit of Chinese National Ambient Air Quality Standard. The cancer risks of PM_2.5-bound B[a]P in males, females, and the general population were 9.085 × 10^-6, 8.050 × 10^-6, and 8.740 × 10^-6, respectively. The cancer risk constituent ratios of ambient PM_2.5-bound B[a]P in early life (≤16 years of age) for males, females, and the general population were 70.9%, 71.4%, and 71.3%, respectively. The males' cancer risk of PM_2.5-bound B[a]P in Beijing was higher than that of the females. The early life cancer risk exposure to PM_2.5-bound B[a]P should be paid more attention.