Occupational Heat Exposure and Heat-Related Illness in Construction Workers: Trajectories, Worker Subgroup Differences, and Workplace Intervention Effectiveness

Occupational heat exposure represents one of the most consequential climate-change-related occupational health challenges globally, with substantial burden in South Asian construction sectors where high ambient temperatures, heavy physical work, large migrant workforces, and limited regulatory enforcement intersect. We conducted a 120-day summer audit (March-July 2024) of 486 construction workers across 12 work sites with structured heat exposure monitoring (wet-bulb globe temperature, WBGT) and heat-related illness (HRI) surveillance. Worker role distribution included masons (28.4%), helpers (24.3%), roof/facade workers (14.0%), iron-binders (12.8%), and concrete workers (9.9%). Daily ambient temperature ranged 28-50 °C with estimated WBGT 24-46 °C. Daily HRI incidence rose exponentially with WBGT, with rates 30-50× higher at WBGT ≥36 °C compared with <28 °C. Heavy work intensity and migrant worker status compounded WBGT-driven risk. Strongest predictors of moderate-severe HRI included WBGT ≥34, heavy work, migrant status, limited acclimatisation, inadequate hydration, pre-existing chronic disease, and elderly age. Workplace heat-protection programmes, structured work-rest cycles with shade/water provision, and supervisor training were strongly protective. The findings support continued investment in heat action plans, workplace regulation enforcement, structured intervention, and acclimatisation programmes for migrant workers.