Extreme heat turns work deadly » Yale Climate Connections

India’s sugarcane fields have always been hot and grueling places to work, but extreme heat related to climate change has made them even more dangerous. One afternoon in May 2025, temperatures rose past 42 degrees C (107.6 F), and Suvarna Yadav, fearing she might lose her job if she took a break, pushed herself to keep working past the point of exhaustion. She fainted, landing hard on her right hand.

The pain was excruciating, but she wrapped her wrist in a wet cloth and kept working for another two hours. She felt stabbing pain that shot through her wrist every time she lifted another 30-kilogram tray of sugarcane.

“I didn’t even realize when my wrist fractured,” she said. That evening, a doctor told her she needed a plaster cast and rest, but earning a living took priority. “If I had gone to work with a plaster, I’d have lost my job,” she said. She soldiered on into the fields every morning and lifted heavy loads all day long. Then in the evening, she would apply balm to her wrist and wrap it with an elastic bandage.

“Extreme heat made everything worse,” Yadav said, adding that almost everyone she knows in her village in western India has gotten injured at work during peak heat. In the sugarcane nurseries, where workers feed cane into machines, extreme heat causes workers to lose focus, and several have lost fingers or thumbs in accidents. Yadav, with “only” a broken wrist, said: “I’ve been lucky in the past, but extreme heat is taking away my chances of getting luckier.”

Extreme heat is causing more work-related injuries worldwide, doctors and scientists say. Experts who have conducted large studies in many countries link rising temperatures to more dehydration, fatigue, spasms, and, in extreme cases, heatstroke. Over 2.4 billion workers are exposed to excessive heat globally, resulting in 22.85 million occupational injuries and 18,970 fatalities each year. Experts warn that these figures almost certainly underestimate the true problem since heat-related injuries in many countries often go unreported, while other injuries are not attributed to heat, further masking the toll. Researchers say stronger safeguards are urgently needed, especially in countries that lack strong rules on workplace safety.

“Thermal discomfort can lead to carelessness, lack of alertness, loss of concentration, disorientation, and reduced vigilance,” said Alessandro Marinaccio, research director and director of the epidemiology unit at the Italian National Institute for Insurance against Accidents at Work. These changes, he added, make even routine tasks more dangerous.

Marinaccio noted that prolonged heat exposure can slow worker reaction times, impair judgment, and hurt coordination. This can increase the chances of slips, falls, or mishandling equipment. Heat can also create practical challenges that are easy to miss, such as “sweaty palms, fogged-up safety glasses,” and other disruptions that can lead to injury.

Around the world, studies show extreme heat boosts the chances of injuries both indoors and outdoors, impairing worker coordination, reaction time, and judgment.

Heat waves at work

In the United States, scientists reviewed every injury reported to the Occupational Safety and Health Administration’s Injury Tracking Application in 2023 by workplaces with more than 100 employees, matching each incident with local weather conditions. Using data from 845,000 work-related injuries, the researchers showed that injuries start becoming more likely as the heat index, which combines the effects of heat and humidity, exceeds 85°F. Chances of injury jump sharply, 20% or more, when the heat index reaches 110°F. Humidity hinders the body’s ability to cool itself, so it is an important consideration for injury risk.

In Italy, extreme heat was linked to over 25,000 workplace injuries from 2014 to 2019, with productivity decreasing by 6.5% for each 1 °C increase between 19.6°C and 31.8°C during heavy physical work. Compensation costs surpassed €292 million ($340 million).

In South Korea, scientists found that severe injuries could increase by over 15% from the 2050s to the 2090s. Similar results have emerged from Australia. And a Chinese study found that a 1°C rise in hourly ambient temperature was associated with a 1% increase in injury risk, even after adjusting for other environmental factors.

In Illinois, an analysis of hospital data found a higher occurrence of work-related injuries on days when temperatures exceed 76°F during summer months, particularly among younger workers aged 16-19.

“While much of the current research focuses on extreme heat and traumatic work-related injuries, less attention is given to acclimatization of new workers and those returning from an extended period of leave,” said Brett Shannon, study co-author, physician, and visiting research assistant professor in environmental and occupational health sciences at the University of Illinois Chicago.

Steps to reduce heat-related injuries

From both his clinical experience and research, Shannon believes workplaces require stronger safeguards.

“We need to improve workers’ ability to recognize the signs of heat-related illness and mandate systems to identify when a worker is suffering from heat-related illness, allowing them to seek assistance if isolated, to prevent injuries,” he said.

On acclimatization days, when temperatures rise above 76°F, and workers’ bodies are still adjusting to the heat, Shannon and his colleagues observed significant increases in open wounds and injuries caused by contact with or being struck by objects. On days with extreme heat, there were also rises in traumatic brain injuries, cuts or piercing injuries, and transport-related injuries.

Misconceptions about heat risk abound. For instance, Shannon said, many believe temperature alone determines danger.

In reality, “temperature is only part of the heat index. We also need to consider humidity, the amount of moisture in the air.”

Another widespread assumption is that younger workers are at less risk. In fact, he said, research shows that “heat-related deaths commonly occur on a worker’s very first day on the job or during a worker’s first week.”

To reduce heat-related injuries, experts say, the first step is to make workers and their employers aware of the risks. Many injuries can be prevented with relatively low-cost measures, such as providing workers with water, rest breaks in shady or cool places, and protective gear like cooling garments or ventilated jackets, Marinaccio said. Rescheduling the most demanding tasks to the cooler parts of the day is also an effective approach.

Marinaccio said governments also need to understand which groups face the greatest danger so policymakers can craft targeted injury-prevention measures. One tool that is needed, he said, is an early-warning system that identifies where and when workers face the greatest risk. The Italian Worklimate project is one example: a nationwide surveillance system that issues heat alerts, maps high-risk regions, and highlights vulnerable worker groups. Such systems, Marinaccio added, should be considered “a priority in light of climate change scenarios.”

The unequal burden

Across the world, the workers most exposed to rising temperatures often have the fewest protections.

As Shannon pointed out, “Most countries do not have a standard related to heat that sets exposure limits, acclimatization protocols, or safety programs.”

Also, informal workers face additional challenges. Many are paid by the piece, not by the hour. Shannon noted that this practice discourages preventive measures such as hydration, taking breaks, and reporting injuries or illnesses. As a result, heat-related injuries often go untreated or unrecorded.

In India’s cane fields, extreme heat caused 64-year-old farmer Jyotiram Yadav to collapse. When he regained consciousness nearly 12 hours later, doctors at the hospital told him he had suffered a heat-triggered heart attack.

“I was lucky my wife was nearby,” he said.

Just months later, he felt a familiar wave of dizziness while working at a sugarcane seedling nursery.

“I took a rest for a few minutes, drank some salt-sugar water, and started working again,” he said.

His story is becoming more common in his village, where farmers often report dizziness, headaches, and persistent body pain during the hottest weeks.

“Every summer, you will see many farmers often visiting a doctor, either with complaints of dizziness or getting a pain-relief injection,” he said.

Despite working in the field for over five decades, he says he’s injuring himself more frequently as temperatures have shot up. Even routine tasks like gripping a sickle, lifting bundles, and cutting grass for fodder have become riskier. In the past five years, he has slipped or cut himself several times because he struggles to focus in the heat.

“I can handle any farming equipment even in my sleep,” he said. “But in extreme heat, it’s becoming difficult to work. … I take a five-minute break every hour now, otherwise one mistake can lead to a major accident.”

His wife, Chabutai Yadav, also a farmer, often stops working when temperatures become unbearable. “You keep sweating the whole time, and it becomes hard to hold the farming equipment,” she said. “Cuts and slips are getting more common now.”