WC Experts Say California Heat Study Creates Opportunities for Safety Improvements

Nancy Grover

Sarasota, FL (WorkersCompensation.com) – Workers in hotter conditions may be more prone to workplace accidents and injuries – even if their work is inside. A recent study out of California showed an association between higher temperatures and overall occupational injuries. Experts say the findings should spur employers to implement strategies to protect their workers.

“Sometimes research can make a big difference in identifying potential areas for improved workplace safety,” said Bill Zachry, board member of the California State Compensation Insurance Fund, former Senion Fellow at the Sedgwick Institute, and former GVP Risk Management for Safeway/Albertson’s. “This study gives us an increased opportunity to reduce the overall frequency of injuries.”


Researchers at UCLA and Stanford analyzed California workers’ compensation claims over an 18-year period and compared it to daily temperature data. The study was published by the Institute of Labor Economics.

While many organizations focus on heat-related safety measures for employees who work outside, this study showed many indoor workers are also at risk, especially those in the manufacturing, warehousing and wholesale industries.

“Hotter temperature increases workplace injuries significantly, causing approximately 20,000 injuries per year,” the researchers wrote. “The effects persist in both outdoor and indoor settings (e.g. manufacturing, warehousing), and for injury types ostensibly unrelated to temperature (e.g. falling from heights), consistent with cognitive or cost-related channels.”

The authors suggested heat can impair decision making, which could be the reason for an increase in injuries such as being hit by a moving vehicle or mishandling dangerous machinery.

Higher risks were seen for men vs. women, younger vs. older workers, and workers at the lower end of the income distribution. The increase in injuries affected “a wide range of body parts,” the study said, “suggesting that the mechanisms may not be limited to heat-illnesses such as heat stroke or heat syncope.”

Overall, the researchers saw an increase in workplace accidents and injuries of up to 9 percent when temperatures were in the 90s, and as much as 15 percent higher when temperatures were above 100 degrees.

The authors did note that there was a decline in the heat-sensitivity of injuries during the 18-year study period, “suggesting significant scope for adaption using existing technologies,” they said. The association between increased injury rates and higher temperatures was lower after 2005, when California implemented a heat illness prevention regulation targeted to outdoor workers. However, the connection persisted throughout the study years – through 2018.

“As we experience increased heat events it is useful to know the impact that these events may have on people and equipment so we can work to mitigate the negative impact on lives and property,” Zachry said. “The next step is educating the employers on prevention methods to help reduce their claims frequency and claims severity through heat exposure mitigation.”

Zachry suggests employing strategies such as:

  • Looking at warehousing and manufacturing in buildings which do not have air conditioning and using this study to determine if there may be a cost benefit for improving the workplace physical environment. Not limiting heat related reviews to only outside venues.
  • Educating the workforce that “energy” drinks are not necessarily the best solution for hydration.
  • Educating employers and workers to improve early identification and intervention of heat illnesses
  • Educating employers to improve their focus on safety when the temp goes above 90 (regardless of exposure)

The study can also serve as a reminder of the importance of hydration. Employers are encouraged to provide hydration stations and remind their employees to properly hydrate throughout the day.

“While many people know the importance of hydration, Harvard [researchers] also explain the substantial impact on human beings in a significantly important manner for functionality, as drinking enough water helps regulate body temperature, keeps joints lubricated, prevents infections, delivers nutrients to cells, and keeps organs functioning properly. Being well hydrated also improves sleep quality, cognition, and mood,” said Dr. Claire Muselman, VP at North American Risk Services. “If we are looking at the causes for injuries with heightened temperatures, this article presents reasonable information considering what dehydration does to the body mechanics and cognitive function of employees.”

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