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Hot weather ‘significantly’ increases risk of on-the-job injury, researchers say

Photo: Xurzon/iStockphoto

Los Angeles — When temperatures rise, the risk of injuries and incidents on the job escalates “significantly,” according to a recently published working paper authored by researchers from the University of California, Los Angeles and Stanford University.

Looking at more than 11 million workers’ compensation claims in California between 2001 and 2018 and comparing them to “high-frequency” local weather data, the researchers found that injuries increased 6% to 9% on days when the temperature topped 90° F, compared with days when the thermometer read 50-69° F. When temps hit triple digits, the injury risk increased 10% to 15%.

“Heat affects your physiology,” the paper’s lead author R. Jisung Park, an assistant professor of public policy at UCLA, said in a university press release. “It affects your cognition. It affects your body’s ability to cope. It seems possible that what we’re observing in the data for these workers is that they’re more likely to make mistakes or errors in judgment.”

The researchers estimate the annual financial cost of heat-related injuries to be $750 million to $1.2 billion in California. That estimate includes health care expenses, lost wages and productivity, and disability claims.


Workers in the state’s lowest household income tier are around five times more likely to be affected by a heat-related injury or illness than those in the highest income tier. Low-income communities typically are in the hottest parts of California, the release notes.

According to the paper, the number of heat-related injuries has declined since 2005, when California became the first state to mandate heat illness prevention for outdoor workplaces when temperatures rise above 95° F.

The study was published in July as part of the Institute of Labor Economics’ Discussion Paper Series. Park testified about the results during a July 15 hearing before the House Select Committee on the Climate Crisis.

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