PM2.5 components mixture and atherosclerotic cardiovascular disease mortality: a national analysis of Medicare enrollees.

Fine particulate matter (PM2.5) exposure is adversely linked to atherosclerotic cardiovascular disease (ASCVD). However, most studies focused on PM2.5 mass rather than its chemical composition. PM2.5s individual chemical components can have distinct, cumulative, and potentially synergistic health impacts. We investigated the associations of PM2.5s composition and sources with ASCVD mortality, considering the combined associations and regional variations in the US. We used data from the Centers for Medicare and Medicaid Services, (65,838,403 person-years) from 2000 to 2016. We estimated PM2.5 exposure using machine-learning models and attributed components to five source categories. We used Poisson survival models to assess the associations with the source categories. Higher ASCVD mortality risk (RR [95% CI] per interquartile range increase) was associated with oil combustion (1.050[1.049;1.051]), industrial (1.054[1.052;1.056]), coal/biomass burning (1.064[1.062;1.067]), and traffic sources (1.044[1.042;1.046]). Comparing source-specific effects within each region, oil combustion effects were more pronounced in the East and Midwest, and coal/biomass burning effects were more pronounced in the West and Southwest. In conclusion, we found higher ASCVD mortality risk associated with PM2.5, with differential effects across sources and US regions. These associations persisted even after limiting our sample to ZIP code-years with PM2.5 <9 g/m3 - the National Ambient Air Quality Standards (NAAQS). This highlights the importance of consideration of local population characteristics and exposure patterns when assessing health risks associated with PM2.5.