Potential causal links of long-term PM 2.5 components exposure with diabetes incidence and mortality in the United States

There is limited evidence on the relationship of diabetes burden with fine particulate matter (PM2.5) and its components, which is not conducive to sustainable development in the context of rapid urbanization. To obtain relevant clues in the United States (US), we collected annual county-level diabetes incidence and mortality, concentrations of PM2.5 and five major components (including elemental carbon, organic carbon, sulfate, nitrate, and ammonium), temperature, and socioeconomic factors during 2008-2017. Through an integrating method of difference-in-differences approach and quantile G-computation, we observed that (i) long-term PM2.5 components mixture exposure was associated with diabetes mortality, but not incidence, with percent risk increase (IR %) of 3.58 % (95 %CI: 1.84 %, 5.36 %); (ii) among the five components of PM2.5, sulfate was estimated to have the largest weight (0.519); (iii) the effect of PM2.5 and its components mixture was higher when the summer mean temperature was 2 or 3 degrees below the 10-year average temperature; (iv) in counties with higher health insurance coverage, nitrate was the most important component (with the greatest weight of 0.829). Our findings suggest that long-term PM2.5 exposure is associated with increased diabetes mortality, and reducing sulfate and nitrate emission could effectively alleviate the burden of PM2.5-related diabetes mortality in the US.