Abstract

Global warming will unquestionably increase the impact of heat on individuals. The increasing prevalence of this environmental health risk requires the improvement of exposure assessment linked to meteorological data. Reliable assessments of heat stress and heat strain will help to reveal the size of the problem and design appropriate interventions at individual, workplace and societal level. However, it is common that air temperature is widely used as a single parameter in epidemiological studies on the effect of health. The evaluation of occupational heat stress requires measurement of four thermal climate factors (air temperature, humidity, air velocity and heat radiation); available weather station data may serve this purpose. However, the use of meteorological data for such assessment is limited because weather stations do not traditionally and directly measure some important climate factors, e.g. solar radiation. In addition, local workplace environmental conditions such as local heat sources, physical workload related metabolic heat production within the human body, and clothing properties, all affect the exchange of heat between the body and the environment. A robust occupational heat stress and heat strain index should properly address all these factors. This article reviews and highlights a number of selected indices, indicating their strengths and weaknesses in relation to meteorological data, local workplace environments, body heat production and the use of protective clothing. These heat stress and heat strain indices include Wet Bulb Globe Temperature, Discomfort Index, Predicted Heat Strain index, and Universal Thermal Climate Index. Relevant preventive strategies for alleviating heat strain are proposed.