Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 53 5 2015 05 15 287 292 EN Ramin Mehrdad Center for Research on Occupational Diseases, Tehran University of Medical Sciences, Tehran, Iran. Sara Aghdaei Center for Research on Occupational Diseases, Tehran University of Medical Sciences, Tehran, Iran. Gholamreza Pouryaghoub Center for Research on Occupational Diseases, Tehran University of Medical Sciences, Tehran, Iran. 2015 10 11 Exposure to air pollutants, steel dust or other occupational and environmental hazards as oxidative stress have adverse effects on subway workers' health. Oxidative stress generates an excessive amount of reactive oxygen species (ROS) and Oxygen Free Radicals during their work time in the tunnels. Once DNA is repaired, Urinary 8-hydroxy-deoxyguanosine (8-OHdG) is excreted in the urine. Therefore, urinary level of 8-OHdG can reflect the extent of oxidative DNA damage. The aim of this study was to document the oxidative stress caused by exposure to these hazards by measuring 8-OHdG in workers urine. We collected urine samples of 81 male subway workers after their working shift. The concentration of urinary 8-OHdG was measured by ELISA method. We used linear regression analysis to compare the level of urinary 8-OHdG as a biomarker of oxidative stress between workers in tunnels and other staff. The mean concentration of urinary 8-OHdG for workers in the tunnel was 58.05 (SD=28.83) ng/mg creatinine and for another staff was 54.16 (SD =26.98) ng/mg creatinine.  After adjustment for age, smoking, driving and a second job in a linear regression model, the concentration of 8-OHdG for the exposed group was significantly higher than unexposed group (P=0.038). These findings confirm that the concentration of urinary 8-OHdG for workers who work in tunnels was significantly higher than the other staff. Additional investigations should be performed to understand that which ones of occupational exposures are more important to cause oxidative stress. https://acta.tums.ac.ir/index.php/acta/article/view/4890 https://acta.tums.ac.ir/index.php/acta/article/download/4890/4478