Long-term exposure to ambient fine particulate matter-bound polycyclic aromatic hydrocarbons and cancer mortality: A...

The association of ambient fine particulate matter (PM_2.5) exposure with cancer mortality was controversial, which may ascribe to the difference in PM_2.5 constituents. Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic constituents in PM_2.5, which are suspected to account for PM_2.5-induced cancer mortality but are yet to be investigated. We aimed to assess the association between long-term exposure to PM_2.5-bound PAHs and cancer mortality and estimate the attributable mortality. A difference-in-differences approach was used to investigate the causal effect of long-term exposure to PM_2.5-bound PAHs on cancer mortality. We divided Jiangsu province, China into 53 spatial units and summarized the annual number of cancer deaths in each spatial unit during 2016-2020. Annual population-weighted exposure to PM_2.5-bound PAHs of each spatial unit was assessed by an inverse distance weighting method. The association between PM_2.5-bound PAHs exposures and cancer mortality was evaluated by controlling spatial differences, temporal trends, PM_2.5 mass exposures, temperatures, and socioeconomic status. Records of 793,269 cancer deaths were identified among 84.7 million population. Each ln-unit increase of exposure to total benzo[a]pyrene equivalents (∑BaPeq), total carcinogenic PAHs (∑PAH7c), and total PAHs (∑PAHs) was significantly associated with a 3.21%, 3.48%, and 2.64% increased risk of cancer mortality, respectively; the risk increased monotonically at low-level exposures but attenuated or flattened afterward (all p for nonlinearity <0.05). Similar exposure-response associations were identified for specific PAHs except that the associations for both fluoranthene and benzo[a]anthracene were linear. We estimated that exposure to ∑BaPeq, ∑PAH7c, and ∑PAHs contributed to 5.73%, 8.73%, and 7.33% of cancer deaths, respectively. In conclusion, long-term exposure to PM_2.5-bound PAHs was associated with an increased risk of cancer mortality and contributed to substantial cancer deaths. Our findings highlight the importance to prevent deaths from cancer by reducing PM_2.5-bound PAHs exposures and the necessity to take into consideration specific constituents in particulate pollution management in future.