Introduction Rising temperature with consequent heat stress is likely to subject millions of workers exerting outdoors at risk of heat-related illnesses and adverse renal health outcomes. Need for such research evidence is urgently needed to address this issue especially in the changing climate scenario.

Objective To investigate the relationship between occupational heat stress, physiological indicators of heat strain, and associated renal health outcomes among brick workers in South India.

Methods We conducted a cross-sectional survey with 327 brick workers during the summer of 2017 & 2018. We collected Wet Bulb Globe Temperatures (WBGT°C), pre-and post-shift Core Body Temperature(CBT), Urine Specific Gravity(USG), and post-shift Sweat rate(SwR), and serum creatinine/uric acid for calculating eGFR (estimated Glomerular Filtration Rate), a kidney function indicator.

Results Workers were exposed to an average WBGT of 27.7°C±2.2 with more than 51% of measurements above the ACGIH-Threshold Limit Value (TLV). 69% of the workers reported heat-strain symptoms such as excessive sweating, exhaustion, and headaches. The workers exposed to above TLV-WBGT had 1.8-fold higher risk of dehydration (Adjusted Odds Ratio (AOR):1.8; 95%CI: 1.0–3.0, p=0.03), rise in CBT (AOR=2.2, CI: 1.0–4.7, p=0.02) and measured heat-related symptoms (AOR=2.5, 95%CI: 1.5–4.2, p=0.0001). Heat-exposed workers had CBT>1°C (14%), SwR>1lit/hr (24%), and USG>1.020 (35%). The prevalence of low eGFR ( ; 95%CI: 1.6–4.2) compared to workers exposed to WBGT below TLV.

Conclusion The preliminary study results only give a clue to the impacts of occupational heat stress on renal health. To have conclusive results, further epidemiological investigations are warranted with stratification for various personal and exposure factors that determine the disease etiology. With or without evidence, the drive for precautionary protective labor policies/welfare measures does not diminish for better occupational health outcomes.