Heat Stress Is a Major Driver of India’s Kidney Disease Epidemic

An epidemic of CKDu — a designation that indicates the disease is not linked with known precursors like high blood pressure or diabetes — began to emerge more than 20 years ago among agricultural laborers in Central America and Sri Lanka and is now present in more than 35 countries, including India, where the disease is becoming increasingly common among outdoor workers in rural areas. The country lacks a national registry or database that tracks CKDu diagnoses. But according to an article in the Bulletin of the World Health Organization, unpublished estimates from rural Uddanam in Andhra Pradesh — a major farming region and a recognized hotspot for kidney disease — have suggested that CKDu could be affecting as much as between 40 and 60 percent of the population in that region.

CKDu’s link with global warming is a growing area of research. Experts warn that rising temperatures linked to climate change are increasing outdoor workers’ exposure to excessive heat, high humidity, and dehydration — factors that are linked with acute kidney injury, which diminishes the organs’ ability to filter waste products from blood. Left untreated, kidney injury can lead to a range of health complications — including pericarditis and pulmonary embolism — that can be fatal.

Doctors in Tamil Nadu are increasingly reporting kidney issues in men in their 30s and 40s who work long hours outdoors, mostly farming or working in sanitation or construction. The trend was highlighted last year, after the state health department, with Madras Medical College, offered urine dipstick tests to 5.7 million people. More than half of those with confirmed CKD had no history of diabetes or hypertension. 

Another study, from July, conducted among farming communities in Odisha, in eastern India, identified 14 percent of the total screened population with chronic kidney disease linked to frequent heat stress and dehydration. The study noted that prolonged exposure to high heat, combined with strenuous work that generates additional body heat and inadequate rehydration, have been increasingly linked, globally, to a heightened risk of kidney injury.

According to an earlier study, conducted in the salt pans of Tamil Nadu between 2017 and 2020, nearly 90 percent of workers toiled in temperatures that exceeded safe exposure limits set by international heat stress guidelines. Workers’ median water intake during an eight-hour shift was just one liter — a far cry from the recommended one liter an hour. In high temperatures, kidney experts say, workers can lose up to a liter of water per hour through sweating.

Researchers around the world continue to study other potential causes of CKDu, including the role of agricultural chemicals, exposure to heavy metals, and high levels of silica in drinking water. As Gouranga Santra, a professor of medicine at the Deben Mahata Government Medical College and Hospital in West Bengal, wrote in a letter published in the Journal of the Association of Physicians of India, results of studies from different locations have been inconsistent, and “combined effects may also be possible.” Still, he writes, “the common factors found [in different study locations] are heat and related dehydration.”

“Kidneys could perhaps be the canary in the coal mine that tell us the impact of climate change on human health,” says Vivekanand Jha, a professor of nephrology at Oxford University and the executive director of India’s George Institute for Global Health. 

Climate change has already raised global temperatures by nearly 1.5 degrees C above preindustrial levels, and temperatures are expected to continue rising in the near future. Heat waves in India have already become more frequent, intense, and longer lasting. The increase in heat has serious health, economic, and social consequences, especially for poorer countries. Outdoor workers who engage in strenuous physical activity and who lack adequate protections, including rest breaks and drinking water, are among the most vulnerable.

Vidhya Venugopal, a professor at the Sri Ramachandra Institute of Higher Education and Research, who has been studying the impact of heat exposure across 35 occupations, says that people who routinely work in hot conditions, such as salt pan workers, brick kiln workers, construction workers, or stone quarry workers, experience acute kidney injury daily, year after year. Kidney function decreases only gradually, but it can eventually culminate in CKD. 

Jason Glaser, the CEO of Washington, D.C.-based La Isla Network, an occupational health research organization focused on heat-related illnesses, and the lead author of several studies on the association between occupational heat stress and CKD in Central America, sees similar patterns in India and says that heat is most likely the main driver of CKDu.  

“I see the same Venn diagram of high environmental temperatures, very heavy work, and insufficient labor protections that put people’s health, and indeed their kidneys, at risk,” he says. “I think that until better study designs are carried out, academics will keep quibbling about other possible exposures being the primary drivers. [But] if you take the massive heat-stress component out of the occupational setting, you won’t see people in their early 30s, or even younger, with destroyed kidneys en masse.”

But heat alone isn’t the problem, Glaser stresses. Public health officials must also address the lack of proper workplace protections, including breaks for rest in the shade, access to drinking water, and safe, clean bathrooms — with no place to relieve themselves, women working in salt pans often avoid eating or drinking anything during work hours. They must also consider revising policies, like piece-rate payment schemes, that encourage people to keep working despite exhaustion and thirst. Glaser’s published research shows that when employers provide rest, shade, and hydration to agricultural workers at risk of CKDu, productivity goes up and employers see better returns on their investment. “Governments certainly would too,” he says. “State-funded health systems cannot afford dialysis.” 

India does not have universal health coverage, and most medical expenses fall on patients and their families, compounding the financial strain imposed when wage earners can no longer earn. While the government does offer free dialysis programs for poor patients — dialysis and kidney transplant are the only treatments for end-stage kidney disease — these services are limited and unable to meet the rising demand. 

CKDu is already a serious health issue, says Jha, and if left unaddressed it will be an even bigger public health crisis for those born in the next 20 to 30 years. Jha stresses the issue isn’t just disease, it’s also about inequity: The communities with the least access to health care are the ones most likely to suffer from CKDu. 

“It’s a vicious cycle,” she says. “From birth, they have limited access to basic services, which increases their risk of getting sick. Once they do, they often miss out on early diagnosis and preventive care, allowing the disease to progress faster. Without access to treatment, they face worse outcomes and develop kidney diseases at least a decade earlier than those in more privileged sections of society.” 

Addressing CKDu means not only improving detection and treatment but also focusing on prevention by providing workers with water, rest periods, and shade. “Water means hydrating yourself every hour,” says Venugopal. “Rest means taking a break every hour. Shade is also important. Even if workers are given five to ten minutes of rest in a cooler place each hour, with access to water, it would make a huge difference.”