Heat rules for employers reduce work injuries by 15% to 27%: Study

September 30, 2025

California’s workplace heat standard, which requires access to water and shade and includes provisions for high heat and training, has resulted in fewer heat-related illnesses for several industry segments, according to the Workers’ Compensation Research Institute.

A WCRI study estimated that California’s heat standard, enacted in 2005 in a first in the country, resulted in a decline in work-related injuries on hot days for industries with “substantial exposure” to outside heat by 15% to 17% in construction, 24% to 27% in agriculture and 19% to 25% in transportation.

The heat standard had an effect that increased with outside temperatures, and the effect was strongest for temperatures above 95 degrees, according to the study, which used claims and climate data. Researchers also found that the heat standard had a larger impact on younger workers, described as those under 35.

The study, which examined pre-2005 claims data to current years, comes at a time when several states have or have proposed heat rules for workers and the federal Occupational Safety and Health Administration continues to work on a heat standard.