Earth Protect Blog

By Christopher Flavelle

© The New York Times Co.

Extreme heat causes many times more workplace injuries than official records capture, and those injuries are concentrated among the poorest workers, new research suggests, the latest evidence of how climate change worsens inequality.

Hotter days don’t just mean more cases of heat stroke, but also injuries from falling, being struck by vehicles or mishandling machinery, the data show, leading to an additional 20,000 workplace injuries each year in California alone. The data suggest that heat increases workplace injuries by making it harder to concentrate.

“Most people still associate climate risk with sea-level rise, hurricanes and wildfires,” said R. Jisung Park, a professor of public policy at the University of California-Los Angeles and the lead author of the study. “Heat is only beginning to creep into the consciousness as something that is immediately damaging.” The findings follow recordbreaking heat waves across the Western United States and British Columbia in recent weeks. The new data, described in congressional testimony July 15, underlines how heat waves can hurt people in unexpected ways.

For example, extreme heat isn’t just a threat to outdoor workers, but also those who work indoors in places such as manufacturing plants and warehouses. Those injuries mean lost wages and higher medical bills for low-income workers across a huge range of industries, widening the pay gap as temperatures rise.

To understand the link between extreme heat and worker injuries, Park, along with his co-authors, Nora Pankratz and A. Patrick Behrer, obtained California workers’ compensation injury reports from 2001 through 2018 and built a database of more than 11 million injuries showing the date and ZIP code for each.

The authors combined those reports with the temperature highs for each day and place. They then looked to see whether the number of injuries increased on days with higher temperatures, and by how much.

That strategy offers a new way to estimate the number of heat-related injuries, rather than just relying on the cause of injury listed in workers’ compensation injury reports. Those reports showed an average of about 850 injuries per year that were officially classified as caused by extreme temperature, but the new data suggests that tally is far too low.

On days when the temperature was between 85 and 90 degrees Fahrenheit, the researchers found that the overall risk of workplace injuries, regardless of the official cause, was 5% to 7% higher than days when the temperatures were in the 60s. When the temperature tops 100 degrees, the overall risk of injuries was 10% to 15% greater.

That points to a high number of heat-related injuries that are listed in other categories. The researchers found that extreme heat is likely to have caused about 20,000 extra injuries a year. The lowest-paid 20% of workers suffer five times as many heat-related injuries as the highest-paid 20% of workers, the researchers found.

The findings also contain a sliver of good news.

The link between extreme heat and workplace injuries weakened after 2005, the researchers found. That’s also the year that California started requiring employers to take steps to protect workers from severe heat, such as providing water, shade and rest breaks for outdoor workers on days hotter than 95 degrees.