The risk of heat exhaustion at a deep underground metalliferous mine in relation to body-mass index and predicted Vo2max

The risk of heat exhaustion at a deep underground metalliferous mine was assessed in relation to the body-mass index (BMI) and predicted maximal oxygen uptake ((V) over dot O(2)max) of miners, using case- control methodology. Sixty-five cases of acute heat exhaustion and 119 controls were studied. Heat exhaustion cases had a significantly higher BMI than controls (P=0.006). The odds ratios increased with BMI. For a BMI of 32.00-36.99, compared to a BMI of less than 27.00 the odds ratio was 3.63 (95% confidence interval, 1.42-9.36). (V) over dot O(2)max was not significantly lower in cases than controls. The odds ratios for heat exhaustion increased with decreasing (V) over dot O(2)max, but not significantly. The sample size provided 80% power of detecting an odds ratio of 2.5 or greater. Deep underground miners should be advised to maintain a BMI of 24-27. Selection of miners on the basis of BMI should not be used as an alternative to satisfactory engineering controls such as ventilation and refrigeration.