Heat spares no one, but some bodies have nowhere to hide.
About half the world's population now faces consequences of intense heat events, with worker productivity dropping 2-3% per degree above 20°C and kidney injury becoming endemic among agricultural laborers. Women workers face compounded risks due to limited toilet access, reduced water intake, and post-work domestic labor in hot spaces, plus physiological differences in heat dissipation and thermoregulation.
- About half the world's population now faces consequences of frequent, intense heat events
- Worker productivity drops 2-3% for every degree Celsius above 20°C
- Nearly half of sugarcane workers in Guatemala showed signs of reduced kidney function
- Suvarna Dange developed a kidney stone after a single workday in 39°C heat with minimal water access
- Chingu Yadav, after 30+ years of farm work, suffered kidney and heart damage from persistent dehydration and had to quit
Extreme heat from climate change is causing widespread kidney and cardiovascular damage in outdoor workers globally, with dehydration during labor triggering acute health crises even in single work shifts.
Suvarna Dange felt the first warning sign on an April afternoon in 2026, working the sugarcane fields near Kolhapur in western India. The temperature had climbed past 39 degrees Celsius—over 102 degrees Fahrenheit—and after a long shift with minimal breaks and little water, a sharp pain seized her abdomen. By evening, back in her cement-block home, she was vomiting. A doctor's scan the next morning revealed a kidney stone, a hard mineral deposit that forms when urine becomes too concentrated. The physician explained that her working conditions—ten hours in the field from morning to evening, with just one short break and scarce access to water—had almost certainly contributed to the stone. He prescribed medication and advised her to drink more. She returned to work the same day.
"No matter how hot it gets, we keep working," Dange said.
Her story is no longer exceptional. According to a 2025 report from the World Health Organization and the World Meteorological Organization, roughly half the world's population now faces the health consequences of more frequent and more intense heat waves. For outdoor workers—particularly those in agriculture, construction, and manual labor—the toll is becoming measurable and severe. Worker productivity declines by 2 to 3 percent for every degree Celsius above 20 degrees. But the damage goes deeper than lost hours. Heat exposure triggers dehydration, which in turn damages kidneys, strains the heart, and disrupts the nervous system in ways that can be permanent.
A 2025 study of sugarcane workers in Guatemala found that nearly half showed signs of reduced kidney function linked directly to heat exposure and dehydration during work. Jaime Butler-Dawson, an epidemiologist at the Colorado School of Public Health who led the research, explained the mechanism: when the body is under heat stress during heavy labor, blood is redirected toward the skin to cool down, reducing circulation to internal organs including the kidneys. Dehydration makes this worse by lowering overall blood volume. The kidneys may not receive enough oxygen, and the filtering structures become stressed. Some workers developed acute kidney injury within a single shift. "These effects occur even when dehydration is relatively mild," Butler-Dawson said, "indicating that heat strain is a critical driver of kidney injury." The damage accumulates—small stresses each hot day, incomplete recovery each night, building toward long-term dysfunction.
The risk is not distributed equally. Women workers face compounded dangers. Many drink less water because they have limited or no access to toilets during work hours. After their shifts end, they return home to cook, clean, and care for children and family members, often in hot, poorly ventilated spaces. Physiologically, women may differ from men in sweating rates, body composition, and hormonal regulation—all factors that influence how the body dissipates heat. A study of more than 1,400 Indian outdoor workers found they were 2.5 times more likely to experience high heat stress under humid conditions. Behdin Nowrouzi-Kia, an occupational therapist at the University of Toronto, reviewed 17 studies across North and Central America and Asia and found consistent evidence that heat exposure impairs construction workers' health, particularly through dehydration and heat-related illness.
The cardiovascular consequences can be sudden and severe. As the body loses fluids through sweat, blood becomes more concentrated, raising the risk of clots. Electrolytes fall out of balance, disrupting the electrical signals that regulate heartbeat and risking dangerous arrhythmias. The heart must work harder to maintain circulation. For people with underlying heart conditions, dehydration significantly raises the risk of heart attack or stroke. Chingu Yadav, a 53-year-old farmworker in India, experienced this firsthand. One evening she grew restless; the next morning she was hospitalized. Doctors told her that persistent dehydration had damaged both her kidneys and her heart. She quit farm work after a similar episode the following year, but the harm was done. Now she feels constantly weak, struggles with routine tasks, and worries about losing her balance when she walks. For more than three decades, she had worked up to ten hours a day in the fields. "I never paid attention to how dehydration was affecting my health all these years," she said. "Earlier, I could work the entire day and not feel this tired. Now, even an hour in the heat feels scary."
A month after her initial kidney stone diagnosis, Dange's pain returned, more severe than before. Her doctor advised her to avoid working in extreme heat. She is taking medication again but does not know how much longer she can continue working. Researchers tracking Latino farmworkers in North Carolina documented how dehydration worsens throughout the workday: nearly half showed signs of dehydration before work began, but by day's end, all of them did. Limited access to clean water, few breaks, and harsh conditions made it nearly impossible to stay hydrated.
The World Health Organization and World Meteorological Organization have called for governments, employers, and health authorities to develop occupational heat-health policies tailored to local conditions and focused on vulnerable populations—middle-aged and older workers, those with chronic health conditions. The recommendations include technical innovations and expanded research. Experts emphasize that protection requires more than individual effort. Nowrouzi-Kia stressed that "improved access to drinking water and scheduled rest breaks are foundational." Butler-Dawson went further: "Protecting health with increasing and more frequent extreme temperatures requires redesigning work policies and practices to match new environmental realities, rather than asking bodies to endure unsafe conditions."
Back in Kolhapur, Dange continues to work in the fields even during heat waves. She takes breaks when she can and tries to stay hydrated. "People think they are used to working in the heat," she said. "But heat spares no one."
Notable Quotes
These effects occur even when dehydration is relatively mild, indicating that heat strain is a critical driver of kidney injury.— Jaime Butler-Dawson, epidemiologist, Colorado School of Public Health
Protecting health with increasing and more frequent extreme temperatures requires redesigning work policies and practices to match new environmental realities, rather than asking bodies to endure unsafe conditions.— Jaime Butler-Dawson
The Hearth Conversation Another angle on the story
Why does dehydration specifically damage the kidneys so quickly? It seems like something the body should be able to handle.
The kidneys are filters that need constant blood flow to work. When you're dehydrated and your body is redirecting blood to cool your skin, the kidneys don't get enough oxygen. It's like asking a filter to work with half the water pressure it needs. Even mild dehydration can stress them in a single shift.
And the heart damage—is that reversible, or are these workers looking at permanent disability?
Chingu Yadav worked in the fields for thirty years and now can barely walk without fear of falling. The damage appears to accumulate. Some of it may be reversible with rest and proper hydration, but for workers who can't stop working, the strain just keeps building. She had to quit entirely.
It sounds like the real problem isn't the heat itself, but that workers have no choice about when or how long they work in it.
Exactly. A doctor can tell Dange to avoid extreme heat, but her job doesn't give her that option. She needs the income. The WHO report essentially says the solution isn't asking workers to toughen up—it's redesigning how work happens when temperatures are this high.
Are there places where that's actually being done?
The source doesn't say. The recommendations are there, but implementation is another question. For now, workers like Dange are managing on their own—taking breaks when they can, carrying water, hoping it's enough.
What about women specifically? You mentioned they face different risks.
Women often have no access to toilets during work, so they drink less water to avoid needing to go. Then they go home and work again in hot kitchens. Their bodies also dissipate heat differently than men's. It's a compounding problem—biology plus working conditions plus a second shift at home.