Gender-related difference in sweat loss and its impact on exposure limits to heat stress

Abstract The aim of this study was to evaluate the validity of the recently proposed predicted heat strain (PHS) model with respect to gender, particularly in relation to the estimation of admissible exposure durations for work in hot environments. Two experiments addressing the effects of the climatic conditions inside vehicles during summer with altogether 96 females and 114 males were analysed. Each subject was exposed for 2 h to a typical summer climate. Highly significant gender-related differences were found for the observed sweat rates. When adjusting the sweat rate to anthropometric measures the differences remained statistically significant, even if females and males were matched for body surface area or surface-to-mass ratio. There is much evidence in the literature that gender-related differences in sweat loss diminish once they are adjusted to anthropometric variables or to physical fitness. However, thermal indices like the PHS model rely on absolute values of the physiological response to heat stress. Therefore, a systematic overestimation of the sweat loss for women could imply an underestimation of body heat storage and core temperature accordingly. A possible approach to revised limit values in the PHS model could be to reduce the values of the maximum sweat rate for women. Relevance to industry Work in hot environments is still present at many industrial workplaces, particulary in underdeveloped countries. International standards provide exposure limits for the prevention of heat disorders. The results of this study indicate that these limits should be revised with respect to gender-related differences in sweat loss.