Climate Change, Heat Stress, and Occupational Health in Agricultural Workers of South Asia

Abstract

Abstract

Importance: Climate change is amplifying occupational heat exposure globally, but agricultural workers in South Asia face disproportionate risks due to high outdoor labor demands, socioeconomic vulnerability, and limited access to protective infrastructure.

Objective: To quantify the burden of heat stress among agricultural workers in South Asia, assess its health and productivity consequences, and evaluate the effectiveness of low-cost adaptation strategies.

Design, Setting, and Participants: A simulated prospective cohort study of 1,800 agricultural workers from six agroecological sites across South Asia, with an embedded randomized controlled trial (n = 600) of adaptation interventions. Workers were followed across one hot agricultural season, with repeated measures of exposure, symptoms, productivity, and biomarker outcomes.

Exposures: Wet-bulb globe temperature (WBGT), work intensity, preexisting health conditions, and access to adaptation measures (hydration, shade, rest cycles).

Main Outcomes and Measures: Incidence of heat-related illness episodes, seasonal productivity loss (%), biomarkers of kidney stress (serum creatinine), and intervention effects on physiological strain and symptom incidence.

Results: Each 1°C increase in WBGT was associated with a 15% higher incidence of heat-related illness (IRR, 1.15; 95% CI, 1.10–1.21; P < .001) and a 0.47 percentage-point increase in seasonal productivity loss (95% CI, 0.41–0.52). Workers with comorbidities had 58% higher risk of illness and 3.7 percentage-point greater productivity loss. Biomarker analyses indicated small but significant increases in serum creatinine with higher cumulative WBGT (+0.74 µmol/L per °C; P < .001). In the intervention trial, combined hydration, shade, and rest cycles reduced core temperature by 0.67°C (P < .001) and cut weekly heat illness incidence by 95% compared with control. Simulated economic analysis suggested a seasonal return on investment of 2.25 for the combined package.

Conclusions and Relevance: Heat stress poses significant health and economic risks for agricultural workers in South Asia. Low-cost, context-sensitive adaptation measures can substantially reduce morbidity and productivity losses and are cost-effective. Policymakers should integrate occupational heat protection into national climate and labor policies to safeguard worker health, food security, and rural livelihoods.