Their new study looks at temperature increases in counties across the United States where crops grow. It also looks at different strategies the industry could adopt to protect workers’ health.
“Studies of climate change and agriculture have traditionally focused on crop yield projections, especially staple crops like corn and wheat,” says lead author Michelle Tigchelaar, a postdoctoral researcher at Stanford University who did the work while at the University of Washington. “This study asks what global warming means for the health of agricultural workers picking fruits and vegetables.”
The average picker now experiences 21 days each year when the daily heat index—a mix of air temperature and humidity—would exceed workplace safety standards.
Using projections from climate models, the study shows the number of unsafe days in crop-growing counties will jump to 39 days per season under 2 degrees Celsius (3.6 degrees Fahrenheit) warming, expected by 2050, and to 62 unsafe days under 4 degrees Celsius (7.2 degrees F) warming, 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 says.
The study also shows that heat waves, prolonged stretches of three or more of the hottest days for each county, will occur five times as often, on average, under 2 degrees Celsius of warming.
AGRICULTURAL WORKERS AT RISK
Roughly 1 million people officially work picking agricultural crops in the US. Researchers used the US Bureau of Labor Statistics job codes to determine their locations. The 20 counties that employ the most pickers are all in California, Washington, Oregon, and Florida. Experts estimate the actual number of agricultural workers in the US at more than 2 million.
These workers are already vulnerable to health risks. Agricultural workers tend to have lower incomes and less health coverage, a majority say they are not fluent in English, and many do not have legal work status in the US, meaning they are less likely to seek medical care. Farmworkers already report more kidney ailments and other conditions related to heat stress.
Tigchelaar began the study after a 2017 death in Washington state, when a blueberry picker died during a hot and smoky period. That prompted Tigchelaar, then a postdoctoral researcher, to think about how climate change particularly puts agricultural workers at risk.
“The people who are the most vulnerable are asked to take the highest risk so that we, as consumers, can eat a healthy, nutritious diet,” Tigchelaar says.
HOW TO PROTECT WORKERS
The authors also considered what steps might protect agricultural workers. The interdisciplinary team used an occupational health threshold value for heat stress that combines physical activity-generated heat with the external temperature and humidity.
They considered four adaptation strategies for workers:
- Work significantly less vigorously
- Take longer breaks
- Wear thinner and more breathable clothing
- Take breaks in a cooled shelter
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