Inclusion of short-term adaptation to thermal stresses in a heat load warning procedure

It is considered to be very probable that the frequency and intensity of heat waves will increase and that heat waves, such as the one experienced in Europe in 2003, will not remain an exception. Everything goes to suggest that human beings have adapted to their local climate. Extreme events such as heat waves, for example, can, however, cause considerable stress to the thermoregulative processes in the human organism. Heat load warning systems provide a possibility for reducing heat-induced morbidity and mortality. We are presenting a method that, apart from a thermophysiologically relevant evaluation of the environment, also takes into account short-term adaptation processes of human beings to the thermal environment. The forecast method differs from previously used methods in that it is based on a combination of absolute and relative thresholds and thus includes the local adaptation to the thermal conditions of the previous weeks. This is an attempt to give a quantitative description of the mainly qualitative statements in literature on acclimatisation. A further advantage of this method is that, due to the inclusion of relative, i.e. local, conditions, it can, in principle, be applied to all climates.