Estimation of heat stress in Tanzania by using ISO heat stress indices.

The aim of this study was to evaluate the usefulness of the ISO heat stress standards in estimating the heat stress and strain in workplaces in Tanzania. Another aim was to select and to develop simplified methods for measuring physiological parameters in developing countries. The methods were tested in four hot factories and at a construction site. It seems that in tropical working environments the climatic conditions for which the ISO 7933 standard is applicable are too narrow. For instance, the mean skin temperature was incorrectly estimated by ISO 7933. An approximate analysis of the working situation can nevertheless be carried out by assuming the mean skin temperature to be 34.5 degrees C. During the study, heat stress and strain were not as high as expected; deep body temperatures were usually lower than 38 degrees C, sweat rates lower than 400 g/h and heart rates below 100 beats/min for about 72% of the measuring time. This is due to the job rotation of the workers and the long rest periods, because the number of workers is large in the factories, and the weather was not at its hottest during the survey.