Wildfire smoke PM(2.5) and mortality in the contiguous United States

Despite the growing evidence on the health effects of wildfire smoke in the western U.S., the nationwide mortality risk and burden attributable to wildfire smoke fine particles (PM(2.5)) remain unclear. This study aims to investigate the association between wildfire smoke PM(2.5) and mortality from all causes, cardiovascular diseases, respiratory diseases, and mental disorders, and calculate the corresponding attributable mortality burden in all 3,108 counties in the contiguous U.S., 2006–2016. Monthly county-level mortality counts were collected from National Center for Health Statistics. Wildfire smoke PM(2.5) concentration was derived from a 10×10 km(2) resolution spatiotemporal model. Controlling for non-smoke PM(2.5), air temperature, and unmeasured spatial and temporal confounders, we found that a 1 μg/m(3) increase in smoke PM(2.5) was significantly associated with an increase of 0.14% (95% confidence interval [CI]: 0.11%, 0.17%) in all-cause mortality, 0.13% (95% CI: 0.08%, 0.18%) in cardiovascular mortality, 0.16% (95% CI: 0.07%, 0.25%) in respiratory mortality, and 1.08% (95% CI: 0.93%, 1.23%) in mental disorder mortality. Smoke PM(2.5) contributed to approximately 1,141 all-cause deaths/year (95% CI: 893, 1,388) in the contiguous U.S., of which over three-fourths were from cardiovascular, respiratory, and mental causes. We found a higher vulnerability among males than females, people aged 0 to 64 years than those ≥ 65 years, and racial/ethnic minorities than non-Hispanic White people. Mild droughts were found to enhance the association between smoke PM(2.5) and mortality. Our results indicate that wildfire smoke PM(2.5) harms both physical and mental health, which suggests the need for more effective wildfire mitigation strategies and public health responses in the U.S.