Tehran University of Medical Sciences International Journal of Occupational Hygiene 2008-5109 6 3 2015 10 11 143 148 EN Roohalah Hajizadeh Department of Occupational Health Engineering, Faculty of Health, Tehran University of Medical Sciences, Tehran, Iran. Farideh Golbabaei Department of Occupational Health Engineering, School of Public Health, Tehran University of MedicalSciences, Tehran, Iran. Mohammad Reza Monazzam Associate Professor, Department of Occupational Health Engineering, School of PublicHealth, Tehran University of Medical Sciences, Tehran, Iran. Somayeh Farhang-Dehghan Department of Occupational Health Engineering, ,School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Esmail Ezadi-Navan Department of Occupational Health Engineering, Faculty of Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran. 2015 10 11 2015 10 11 Heat stress particularly  at  outdoor  workplaces in hot-dry    climates can  disrupt    the physical or mental functions and effect negatively on human performance. We aimed to study the effect of heat stress on productivity loss among workers of brick workshops in Qom Province – central Iran. This cross-sectional descriptive and analytic study was performed on 184 workers in 40 brick workshops. Environmental parameters including dry temperature, natural wet-bulb temperature, globe temperature, relative humidity and air velocity were measured at three times during work shift. WBGT (Wet Bulb Globe Temperature) heat stress index was calculated based on equation provided by Australian Bureau of Meteorology. Potential  labor productivity losses due  to  heat  stress  were  determined using  a  graph presented already. The total average of WBGT was 31.84±3.46°C. WBGT index according to different jobs  was  39.48±8.2°C, 29.86±2.79°C, 29.31±0.97°C and  28.69±1.89°C for working in  kiln,  material handling,  working  on  conveyor and  making  adobe,  respectively.  The  average  loss  productivity  in mentioned tasks was 93.57±16.54, 66.58±20.58, 65.53±15.26 and 48.27±13.04 respectively, with total average of productivity loss 68.48±16.35%. The statistically significant relationships were found between WBGT values and percentage of loss productivity in total and for all understudy jobs (p<0.001). Heat stress can lead to decrease in labor productivity at outdoor workplaces like brick industries. According to climate change in the future and gradual global warming, paying more attention to the occupational health issues in outdoor workplaces at dry and warm environment seems to be more important than before. https://ijoh.tums.ac.ir/index.php/ijoh/article/view/111 https://ijoh.tums.ac.ir/index.php/ijoh/article/download/111/111