the past and future trends of heat stress based on wet bulb globe temperature index in outdoor environment of tehran city, iran

background: the workers who are working in the open and warm environments are at risk of health effects of climate and heat changes. it is expected that the risk is increase with global warming. this study aimed to investigate the changes of wet bulb globe temperature (wbgt) index in the past and to predict their trend of future changes in tehran, capital of iran. methods: the meteorological data recorded in tehran, iran during the statistical period between 1961 and 2009 were obtained from the iran meteorological organization and based on them, wbgt index was calculated and processed using man-kendall correlation test. results: the results of man-kendall correlation test showed that the trend of changes of annual mean wbgt during the statistical period under study (1961-2009) has been significantly increasing. in addition, the result of proposed predictive model estimated that an increase of about 1.55 degree in wbgt index will be seen over 40 years from 2009 to 2050 in tehran. conclusion: climate change in tehran has had an effect on person's exposure to heat stresses consistent with global warming.