Researchers Seek Remedies for Heat Stress Among Farmworkers

Tue Oct 28 2025 15:46:36 GMT+0200 (Eastern European Standard Time)

In Southern California's Imperial Valley, farmworkers work under extreme heat as researchers explore interventions to protect their health amidst the rising temperatures caused by climate change.

Farmworkers in the Imperial Valley begin their grueling days at dawn to avoid soaring temperatures. As the region faces increasingly extreme heat, researchers from San Diego State University are examining the health consequences and potential remedies for heat stress among these workers. Their studies hope to identify particular areas of concern and recommend solutions to ensure better conditions for farmworkers as climate challenges grow more severe.

In the summers, the sky is jet black when Raul Cruz arrives at this Imperial Valley sugarcane field to start his day. He chops, cleans and bundles the crop, taking heed as the sun rises. It’s hard work, but so is starting at 4 a.m., even though he knows it’s the safest thing when temperatures in this California desert frequently soar into the triple digits.

“We just have to because we need to beat the heat,” said Cruz, who’s worked here for 15 years. They finish work by 9 or 10 a.m. to avoid the risk of heat stroke, he added, but when the heat starts creeping up around 8 a.m., “mentally, it’s stressful.”

The hot climate that makes this Southern California region a farming powerhouse is also what makes it dangerous for farmworkers, who are increasingly vulnerable to rising temperatures due to greenhouse gas emissions from burning coal, oil, and natural gas. Researchers from San Diego State University are working to understand the health consequences of heat stress on farmworkers and where heat is most extreme in this rural landscape. They hope their findings can lead to a better understanding of rural heat islands, identify gaps in research, and help develop interventions that better protect them in the face of climate change.

“Workers could potentially be dying or having some serious issues,” said project leader Nicolas Lopez-Galvez, assistant professor in the School of Public Health at SDSU. “It’s better to start acting sooner.”

Since the start of the 20th century, California temperatures have increased almost 3°F (about 1.7°C), according to state and federal data. Warming has accelerated, and seven of the state’s last eight years through 2024 were the warmest on record. While all areas of the state have warmed, Southern California is heating up about twice as fast as Northern California.

Researchers are trying to understand how farmworkers’ heat stress might vary depending on the crops, the season, and the number of breaks they take.

Over the past two years, they’ve collected year-round data from some 300 farmworkers. Body sensors measure things like core body temperature and heart rate while they work. Elsewhere in the fields, environmental monitors measure the day’s temperature, humidity, wind speed, sun angle, and cloud cover, also known as the wet-bulb globe temperature, considered the best metric to understanding heat stress. Using satellite imagery along with historical and current wet-bulb globe temperature data, researchers are mapping areas of extreme heat, particularly in the Imperial and Coachella valleys.

They are learning that ground-level crops can expose workers to higher heat levels compared to tree crops, for example, but it also depends on their harvesting months. In summer, farmworkers who prepare fields for planting or help maintain irrigation systems are also more exposed.

Rural heat can vary based on things like tree cover, proximity to a body of water, and empty fields, which may be hotter. “It creates this island where people might be living or working that are higher in terms of heat stress compared to other places,” said Lopez-Galvez.

Through this research, the authors were able to recommend how frequently farmworkers should take rest breaks to protect themselves from heat stress, based on how often wet-bulb globe temperatures exceed safety thresholds across seasons and work shifts. While California has heat rules, they’re not strictly enforced, he added.

“We realized that farmworkers are not getting enough rest breaks, and also there are no clear policy guidelines in terms of heat-related rest breaks,” he said.

Lopez-Galvez said they plan to continue their research in California’s Central Valley and hope to expand it into Yuma, AZ and other parts of the Southwest.