Dangerously hot days for crop pickers in the United States will double over the next three decades because of climate change, a new study warns.
"Studies of climate change and agriculture have traditionally focused on crop yield projections, especially staple crops like corn and wheat," lead author Michelle Tigchelaar, a postdoctoral researcher at Stanford University who conducted the study while at the University of Washington.
"This study asks what global warming means for the health of agricultural workers picking fruits and vegetables," Tigchelaar said in a UW news release.
Currently, the average crop picker faces 21 days each year when the daily heat index -- a mix of air temperature and humidity -- exceeds workplace safety standards. Those unsafe days will nearly double by 2050 and triple by the close of the century, the study shows.
Using climate model projections, the researchers predicted 39 unsafe days per season in crop-growing counties with 2 degrees Celsius, or 3.6 degrees Fahrenheit, warming, which is expected by 2050.
The total will be 62 unsafe days under 4 degrees Celsius, or 7.2 degrees Fahrenheit, warming, which is expected by 2100.
"I was surprised by the scale of the change -- seeing a doubling of unsafe days by mid-century, then a tripling by 2100. And we think that's a low estimate," Tigchelaar said.
The researchers also found that heat waves will occur five times as often, on average, with 2 degrees C of warming.
Officially, about 1 million people are employed in picking agricultural crops in the United States. All 20 counties that employ the most pickers are in California, Washington, Oregon and Florida. The actual number of agricultural workers in the United States is estimated to be more than 2 million, according to background notes with the study.
"The climate science community has long been pointing to the global south, the developing countries, as places that will be disproportionately affected by climate change," said study co-author David Battisti, a professor of atmospheric sciences at UW.
"This shows that you don't have to go to the global south to find people who will get hurt with even modest amounts of global warming -- you just have to look in our own backyard," he added.
The findings were published online recently in the journal Environmental Research Letters.
The U.S. Global Change Research Program has more on climate change and human health.
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