Tehran University of Medical Sciences International Journal of Occupational Hygiene 2008-5109 3 2 2011 12 15 56 62 Mohammad Javad Golhosseini Department of Occupational Health, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Hossein Kakooei Department of Occupational Health, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Seyed Jamaleddin Shahtaheri Department of Occupational Health, School of Public Health, Institute for Environmental Research, Tehran, Iran Kamal Azam Department of Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Davood Panahi Department of Occupational Health, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran 2015 10 04 Occupational exposure to carbon monoxide (CO) of taxi drivers has seldom been evaluated in Iran. Accordingly, in-vehicle CO levels were evaluated during 6 months inside the taxis between May 2009 and October 2010. The CO concentrations of 36 personal samples were collected using a direct reading instrument equipped with electrochemical sensor. The arithmetic mean of the personal monitoring CO levels was 19.84 ± 4.24 ppm per day, with a range of 13.29-33.46 ppm. The observed concentrations of CO fell well lower than occupational standards. Exposures to CO during traffic flow in the evening were considerably higher than those measured in the morning. The weekdays, months and atmospheric environment had a significant effect on exposure to CO (p< 0.0001). The average CO level was 19.84 ± 4.24 ppm, which was higher than the outdoor CO levels (3.21 ppm). In conclusion, the penetration of outdoor CO pollution and engine combustion/exhaust infiltration constituted the main sources of the taxis drivers' personal exposure to CO. https://ijoh.tums.ac.ir/index.php/ijoh/article/view/35 https://ijoh.tums.ac.ir/index.php/ijoh/article/download/35/35