performance loss among workers due to heat stress in high-temperature workplaces

background: heat stress is one of the harmful factors present in many workplaces. it can lead to performance loss and low functionality of the labor force. therefore, the aim of this study was to evaluate exposure to heat stress and its consequent performance loss among workers functioning in indoor high-temperature workplaces. materials and methods: this descriptive, analytical study was conducted on indoor high-temperature occupations in spring 2014. this study was conducted on 15 bakeries, 11 restaurants and kitchens, and 2 industries with heating processes in gonabad city, iran. in total, 1450 individuals worked on the investigated sites and were exposed to thermal stress. the inclusion criterion for this study was working in an environment that included a heating process and the exclusion criterion was unwillingness to participate in the study. heat stress was measured based on wet-bulb globe temperature(wbgt) and the iso 7243standard. the graph of performance loss versus thermal stress proposed by kjellstrom et al. was used to determine the performance loss caused by thermal stress.all individuals and managers were informed of the aims of the project and were assured of the confidentiality of the data. statistical analyses were performed using spss software. results: the mean exposure to heat stress in barbari, sangak, and lavash (three types of bread) bakeries were 29.73, 27.89, and 29.43 °c, with a mean performance loss of 65%, 23%, and 64%, respectively. in some cases, the performance loss in lavash bakeries was as high as 98%. the mean exposure to heat stress in refractory brick and porcelain manufacturing industries were 32.04 ºc and 32.35 °c, leading to a concomitant performance loss of 89% and 92%, respectively. the mean wbgt in the kitchens was 31.88, which could lead to a performance loss of 80%. conclusions: in addition to a host of diseases and complications caused by heat stress, extreme heat in the workplace can significantly reduce the performance of the labor force, and consequently,their production. through appropriate planning and control of heat stress in the workplace, not only are many diseases prevented, but also the performance and efficiency of workers are greatly improved.