Workplace Exposures May Mask Wildfire Smoke-Related Exposure Inequities and Mortality

Millions of outdoor workers cannot avoid wildfire smoke, likely leading to inequalities in exposure and health risk, but we lack a comprehensive understanding of how many outdoor workers are exposed to wildfire smoke in the United States (US). We first characterized work-related exposure to wildfire PM_2.5 for 3,108 contiguous US counties during 2006-2019 by integrating data on wildfire smoke-specific PM_2.5, workplace activities, and employment counts. We then compared the racial and ethnic composition of each county with the person-days exposed to ambient and work-related wildfire smoke to investigate whether certain racial and ethnic groups experience differential exposure to wildfire smoke at home and at work. Lastly, we replicated a previous analysis of ambient wildfire smoke impacts on all-cause mortality and stratified it by work-related exposure to understand differential mortality effects of ambient wildfire PM_2.5. Despite experiencing less ambient exposure to wildfire PM_2.5, counties with higher portions of non-Hispanic Black and Hispanic Americans experienced higher work-related exposures. We also find suggestive evidence that the effect of ambient smoke fine particulate matter (PM_2.5) concentrations on all-cause mortality may differ by workplace exposure. These findings suggest that workplace exposures should be considered in wildfire smoke-adaptation measures.