Hot Standards, Cool Workers? The Effect of State Heat Illness Prevention Regulations on Workplace Injuries

Abstract

As climate change increases heat exposure for outdoor workers, states have adopted heat illness prevention standards requiring employers to provide water, rest, and shade. This paper provides the first causal estimates of how these regulations affect workplace injuries. Using a difference-in-differences design exploiting staggered state adoption between 2005 and 2024, I find that heat standards reduce workplace injury rates in outdoor industries by approximately 7.1 per 10,000 full-time equivalent workers (95% CI: [-10.2, -4.0]), representing a 12% reduction from baseline rates. Effects are larger in states with hotter climates. Pre-trend tests support the parallel trends assumption. These findings are directly policy-relevant as OSHA proposed a federal heat standard in August 2024 that would extend protections nationwide.