Wildfire smoke PM2.5and mortality in the contiguous United States

Abstract

AbstractDespite 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 (PM2.5) remain unclear. This study aims to investigate the association between wildfire smoke PM2.5and 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 PM2.5concentration was derived from a 10×10 km2resolution spatiotemporal model. Controlling for non-smoke PM2.5, air temperature, and unmeasured spatial and temporal confounders, we found that a 1 μg/m3increase in smoke PM2.5was 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 PM2.5contributed 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 PM2.5and mortality. Our results indicate that wildfire smoke PM2.5harms both physical and mental health, which suggests the need for more effective wildfire mitigation strategies and public health responses in the U.S.Significance StatementWildfires activities have significantly increased in the United States in recent decades. Smoke pollutants emitted by wildfires, particularly PM2.5, can bring adverse health effects. However, the nationwide wildfire smoke PM2.5-related mortality risk and burden remain unclear. Utilizing wildfire smoke PM2.5and mortality data in the contiguous U.S. from 2006 to 2016, we found significant associations between smoke PM2.5and increased mortality risks from all causes, cardiovascular diseases, respiratory diseases, and mental disorders. Each year, smoke PM2.5contributed to an estimated over one thousand deaths in the U.S., indicating a great number of indirect deaths brought by wildfires that official tolls could not capture. This study demonstrates the detrimental effects of wildfire smoke PM2.5on both physical and mental health and calls for more effective wildfire prevention and mitigation policies in the U.S.