At least 5.31% of agricultural workers in Tamil Nadu have permanent kidney damage, according to a new study by Madras Medical College published in The Lancet. Alarmingly, half of these cases show no known causes such as diabetes, long-standing hypertension, family history, or underlying disease. Researchers suggest that prolonged heat exposure and dehydration could be driving this growing trend.
Chronic Kidney Disease of Unknown Cause (CKDu)
Chronic kidney disease (CKD) occurs when the kidneys gradually lose their ability to filter waste and excess fluids from the blood. The state government launched this study to assess both CKD and CKD of unknown cause (CKDu) among agricultural workers. Similar “hotspots” have been reported globally, often linked to occupational heat stress, agrochemical exposure, and environmental toxins.
Study Design and Key Findings
Conducted between August and December 2023, the study covered 125 villages across five agro-climatic zones, surveying 3,350 agricultural workers.
“We conducted kidney function tests in two phases – one in August and another in December,” explained Dr. N. Gopalakrishnan, senior nephrologist and lead author of the study, who also heads the state organ transplant network, Transtan.
In the first phase, 17.43% (584 participants) showed deterioration in kidney function. However, in the second phase, the prevalence dropped to 5.31%, suggesting that some workers experienced temporary kidney stress rather than permanent damage.
Heat Exposure Emerges as a Major Factor
Dr. Gopalakrishnan noted, “Many participants initially tested positive for poor renal function because their kidneys had suffered transient damage due to heat and dehydration. As temperatures dropped, their kidney function improved.”
He emphasized that these asymptomatic cases require close monitoring, as they remain at risk of developing chronic kidney disease.
Regional and Demographic Variations
As reported by TOI, the northeastern districts—including Chennai, Tiruvallur, and Kancheepuram—recorded the highest prevalence of kidney disease, followed by southern districts where heat stress levels were also high. Conversely, northwestern regions such as The Nilgiris, where daily temperatures are lower, showed the least prevalence.
Across all regions, kidney disease rates declined with falling temperatures in December, reinforcing the link between heat and renal stress. The study also found that men, older adults, and those with hypertension, anaemia, or long outdoor working hours faced a higher risk.
Other Factors Under Investigation
Interestingly, the study found no association between kidney disease and factors such as source of drinking water, snake bites, Covid-19 infection, or alcohol intake. However, Dr. R. Sakthirajan, senior nephrologist at Madras Medical College, cautioned that pesticides and water quality may still play a role.
“In districts like Namakkal, Salem, Dharmapuri, and Krishnagiri, temperatures were not as high as in the south, yet prevalence remained between 6.4% and 7.6%, suggesting that other environmental or occupational triggers may be involved,” he said.
Simple Preventive Measures Recommended
Dr. Gopalakrishnan advised farm workers to take practical precautions against heat-related kidney stress. “After every 45 minutes of outdoor work, take a break in the shade, drink sufficient water, and avoid holding urine for long periods,” he recommended.
Need for Continued Research
Both researchers stressed the urgent need for further studies to determine whether pesticide exposure and water contamination contribute to chronic kidney damage among Tamil Nadu’s agricultural workers. As Dr. Gopalakrishnan concluded, “We must identify all possible triggers to protect the health of those who feed the nation.”