A nationwide analysis of heat and workplace injuries in the United States.

Abstract

Background: Exposure to heat leads to physiological and cognitive impairments that increase the risk of workplace injuries. This study estimates the number and proportion of work injuries reported to the United States Occupational Safety and Health Administration (OSHA) that can be attributed to heat exposure. These estimates contribute to the calculation of the benefits of standards, policies, and programs that reduce workplace exposure to extreme heat.

Methods: We analyzed all 2023 injury cases reported to OSHA's Injury Tracking Application by establishments with 100 or more employees, primarily in high-hazard industries. Each injury was geocoded and matched with high-resolution weather data for the specific injury date. Using a case-crossover design, we compared heat index on each injury day (case) with matched non-injury control days for the same worker. Conditional logistic regression was applied separately for summer-only and year-round periods with a non-linear term for heat index to estimate the odds ratios for injury occurrence. We additionally examined heat-injury patterns by industry sectors and in states with/without workplace heat standards.

Results: The odds of work injury increased non-linearly with a rising heat index: the pooled national estimate showed a clear upward trend starting around 85°F and accelerating above 90°F. Our results were consistent across nearly all industry sectors, including those that are predominantly indoors. Using a heat index of 80°F as reference, odds ratios (OR) of injuries at or above 90°F, 100°F and 110°F were 1.03 (95% confidence intervals [CI]: 1.02, 1.04), 1.10 (1.07, 1.13), and 1.20 (1.13, 1.26), respectively. At a heat index of 110°F or higher, the odds increased by 22% in states without occupational heat rules (OR=1.22; 1.15,1.29) versus 9% in states with rules (OR=1.09; 0.84, 1.41), suggesting a protective effect, although confidence intervals overlapped. Overall, we estimate 1.18% (95% empirical CI: 0.92%, 1.45%) of all injuries were attributable to heat exposure on days exceeding a heat index of 70°F.

Conclusion: Heat exposure increases the overall risk of work injury, an effect consistent across nearly all major industries.