A recent study published in The Lancet highlights the significant risks posed by rising temperatures on the kidney health of agricultural workers in Tamil Nadu. The research, conducted between August and December 2023, reveals that prolonged exposure to heat, coupled with dehydration and extended outdoor work hours, is contributing to a worrying increase in kidney disease among farm laborers.
The Chronic Kidney Disease of unknown etiology (CKDu) AGRI study surveyed 3,350 agricultural workers across five agro-climatic zones in Tamil Nadu, including the North-East, North-West, Western, Cauvery Delta, and Southern regions. Researchers employed a stratified multi-stage cluster sampling method to gather data regarding occupational health and environmental exposures.
Findings indicate a notable seasonal fluctuation in kidney function. In August, one of the hottest months in Tamil Nadu, 17.4% of participants exhibited an estimated glomerular filtration rate (eGFR) below 60 mL/min/1.73 m2. By December, most participants showed a return to normal kidney function. “These were asymptomatic, sub-clinical episodes of acute kidney injury,” stated R. Sakthirajan, a senior assistant professor at the Institute of Nephrology, Madras Medical College. “The variation reflects physiological stress rather than measurement error.”
The research team noted that such transient injuries are related to repeated heat and dehydration stress during agricultural labor, a pattern observed in similar studies in Central America and Sri Lanka.
Overall, the study reported a chronic kidney disease prevalence of 5.31%, with nearly half of the cases classified as CKDu, which is not linked to diabetes, hypertension, or heart disease. The prevalence was notably higher in the North-East (7.68%) and Southern regions (6.4%) compared to the North-West (2.16%).
Utilizing the Universal Thermal Climate Index (UTCI) to measure heat exposure, researchers found workers experienced temperatures exceeding 38°C for over four hours daily, indicating “very strong heat stress” in the North-East and Southern zones during August.
Those diagnosed with CKD typically spent an average of 36.18 hours outdoors weekly, while those with CKDu averaged 38.07 hours. Additional risk factors included older age (above 53.5 years), male gender, hypertension, anemia, a history of renal stones, smokeless tobacco use, and long hours of outdoor work. Interestingly, factors such as access to potable water, snake bites, COVID-19 infections, and alcohol consumption showed no correlation with CKD prevalence.
Education levels also affected CKD rates, with a prevalence of 7.9% among individuals without formal education compared to 2.5% among graduates. The prevalence of diabetes (13.4%) and hypertension (30.6%) among participants aligned with national averages, yet two-thirds of those with hypertension and 40% of those with diabetes were newly diagnosed during the study, indicating a significant lack of awareness regarding these conditions.
The study”s findings align with global CKDu “hotspots” previously identified among agricultural workers in Central America, particularly in regions like El Salvador, Nicaragua, Mexico, and Panama, where heat and dehydration are suspected contributors to the disease.
To mitigate these risks, Gopalakrishnan Natarajan, a co-author and member secretary of TRANSTAN, emphasized the importance of simple preventive measures. “Adopting the Water-Rest-Shade protocol, which involves consuming approximately 750 mL of cool water every hour and taking 10-15 minute rest breaks each hour, can help protect workers from heat stress.” They also suggested flexible working hours to avoid peak heat and the inclusion of kidney function monitoring in routine occupational health assessments.
On a policy level, researchers noted the absence of heat-specific labor standards in India, advocating for the integration of heat-stress thresholds and kidney health monitoring into workplace safety regulations.
Despite only 1.6% of participants reporting symptoms such as swelling, nocturia was the most common complaint, affecting 12.9% of respondents. “The silent nature of CKD means that symptom-based diagnosis often overlooks many cases,” remarked Sudharshini Subramaniam, an associate professor at the Institute of Community Medicine. The authors recommend annual serum creatinine and urine albumin-creatinine testing for agricultural workers through existing primary health programs. They propose training village health nurses and multipurpose health workers to identify high-risk groups, such as men over 50, those with anemia, tobacco users, and individuals exposed to prolonged heat.
Expanding access to education and implementing tobacco cessation measures may also help reduce the risk of CKD among this vulnerable population. As Tamil Nadu faces increasingly hotter summers, the study underscores the urgent need for kidney health to be integrated into India”s climate and labor policies.
