Tehran University of Medical Sciences International Journal of Occupational Hygiene 2008-5109 9 1 2017 05 23 26 32 EN PARVIN NASSIRI Professor, Department of Occupational Health, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. MOHAMMADREZA MONAZZAM Professor, Department of Occupational Health, School of Public Health and Center for Air Pollution Research (CAPR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran FARIDEH GOLBABAEI Professor, Department of Occupational Health, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. ALIAKBAR SHAMSIPOUR Associate Professor, Department of Physical Geography, School of Geography, University of Tehran, Tehran, Iran. GHOLAMHEIDAR TEIMORI School of Health, Torbat Heydariyeh University of Medical Sciences, Torbat Heydariyeh, Iran HOSSEIN ARABALIBEIK Research Center for Science and Technology in Medicine (RCSTIM), Tehran University of Medical, Tehran, Iran. ALI REZA MORTEZAPOUR Department of Occupational Health Engineering, School of Public Health, Student Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran. MEHDI ASGHARI PhD Student of Occupational Health, Department of Occupational Health, School of Public Health and Center for Air Pollution Research (CAPR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran. 2017 03 04 2017 05 22 Working in hot environments is one of the common hazards in the workplaces, which can cause heat-related illnesses, affect workers’ health and increase a risk of occupational injuries and accidents. The aim of this study was to assess and compare thermal comfort indices of humidex, Discomfort Index (DI), and ET with physiological responses in the open-pit mines in Tehran Province, Iran. This cross-sectional study was conducted in summer 2016 on 175 male workers in 12 construction materials mines in Tehran Province, Iran. Environmental and physiological parameters were measured simultaneously at three periods and thermal indices were determined as well. In this study, correlation coefficients of indices at different times of day were analyzed. Data were analyzed using SPSS 18 software and Pearson correlation.  There was high correlation between thermal comfort indices with each other. All three indices used in this study had an appropriate relationship with core body temperature. Oral temperature had a greater correlation coefficient with thermal indices compared to the tympanic membrane temperature and skin temperature. Humidex had a high correlation coefficient with environmental parameters and physiological responses. The Humidex index is more valid than ET and DI indices. Humidex, among the studied indices, despite being simple, lack of need for sophisticated equipment to measure, low cost and easy interpretation can be used in open-pit mining. https://ijoh.tums.ac.ir/index.php/ijoh/article/view/255 https://ijoh.tums.ac.ir/index.php/ijoh/article/download/255/333