Mortality burden of outdoor occupational heat exposure in the United States

Abstract Background Outdoor workers are particularly vulnerable to the adverse impacts of heat, but many studies focus on heat exposure in residential settings only. This leads to a limited understanding of the full mortality burden due to occupational heat exposures. Here, we aimed to improve estimates of the total, short-term mortality burden attributable to outdoor occupational heat exposure in the United States (US). Methods We developed a panel data set for 3,108 US counties during 2010-2019 by linking all-cause mortality among the working age population, derived from CDC WONDER, with the prevalence of workers exposed to outdoor occupational heat, which integrates data on wet bulb globe temperature, workplace activities, and employment counts. We developed a quasi-Poisson regression model adjusted for ambient temperature, total precipitation, and county and state-year fixed effects to estimate short-term excess deaths attributable to outdoor occupational heat exposure. Findings Nationwide, approximately 3.8% (95% CI: 2.5-5.8%) of all workers were annually exposed to dangerous wet-bulb globe temperatures. This outdoor occupational heat exposure resulted in approximately 9,800 (3,100-17,000) annual excess deaths in the working age population. An estimated 62% of excess deaths occurred in the most socially vulnerable counties despite accounting for 25% of workers. Interpretation The mortality burden of occupational heat exposure is likely far larger than 39 officially reported annual deaths that the Bureau of Labor Statistics reports for this time period. The workplace should be an explicit focus of heat policies, advocacy, and adaptation measures. Funding US Centers for Disease Control and Prevention/National Institute for Occupational Safety and Health.