Occupational Heat Stress Burden and Worker Productivity in Nigeria’s Cement Manufacturing Sector: An Empirical Assessment

Heat stress in cement manufacturing represents both an occupational health hazard and a significant economic productivity risk in Nigeria's industrial sector, particularly given projected increases in ambient temperature under current climate projections. This empirical analytical study assessed occupational heat stress exposure, physiological heat strain indicators, and productivity outcomes among workers in cement manufacturing plants in North West and North Central Nigeria, with fieldwork conducted in Sokoto, Katsina, and Niger States. Three hundred workers from kiln operations, raw material processing, and packing departments were recruited alongside 100 administrative controls. Environmental heat stress was measured using WBGT meters; physiological strain was assessed through tympanic temperature, heart rate, and dehydration biomarkers. Productivity was estimated using time-and-motion analysis and self-reported performance scores. Mean WBGT in kiln areas was 35.8 degrees Celsius, far exceeding the 25 degrees Celsius ISO recommendation for heavy work. Physiological heat strain was detected in 61.3 percent of kiln workers. Productivity analysis showed an average 22.7 percent output decline during peak heat exposure periods. Dehydration, as assessed by urinary specific gravity, was prevalent in 74 percent of production workers. Regression modeling demonstrated that every 1-degree Celsius increase in WBGT was associated with a 3.4 percent productivity decline. The study recommends engineering thermal controls in kiln departments, mandatory hydration protocols, acclimatization schedules, and integration of heat stress monitoring into cement plant occupational health programs. Keywords: heat stress, cement manufacturing, productivity, worker health, North West Nigeria.