With policymakers at the local, state, and federal levels debating heat safety standards, this study offers measurable evidence of how California’s 2005 heat standard impacted the frequency of injuries in occupations with substantial exposure to outdoor heat, like construction, agriculture, and transportation. The heat standard requires employers to provide water, shade, rest breaks, acclimatization plans, and emergency response protocols during excessive heat.

Previous WCRI research found that excessive heat not only causes heat-related illnesses such as heat exhaustion but also impairs judgment and perception, increasing the risk of accidents such as being struck by machinery. Heat-related illnesses are 11 to 18 times more frequent on days above 95°F compared with days between 75 and 80°F, yet they represent 20 to 25 percent of all injuries attributable to heat.

Impact of California’s Heat Standard on Workers’ Compensation Outcomes. Olesya Fomenko, Melissa McInerney, and Sebastian Negrusa. September 2025. WC-25-44.

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