Deep underground mines in the tropics: Evaluation of the Heat Stress Risk

Heat stress indices are applied to assess risk of hyperthermia, but how well they correlate with core body temperature requires further investigation. This study was undertaken at three underground mines located in the tropical region of Australia to evaluate the effectiveness of systems implemented to protect workers from hyperthermia and to evaluate the observed heat strain against heat stress indices. Tympanic temperature, heart rate, hydration, Effective temperature (ET), Thermal Work Limit (TWL), Predictive Heat Strain (PHS), air velocity, wet bulb (WB), dry bulb and globe temperatures were measured. Findings included: • Two workers exceeded 38°C core temperature • Workers maintained their hydration status. • WB is a poor predictor of heat strain (R2=0.40). • ET and TWL demonstrated good correlations to observed heat strain (R2=0.60). • Predicted Heat Strain (PHS) provided the strongest correlation (R2=0.73). No single heat stress index is effective across the full range of work environment. The optimal approach is a cascaded risk management strategy; applying simple tools to low heat stress risk situations giving way to more sophisticated methods as the heat stress risk level increases