en Environmental Health, Sciences, and Engineering Environmental Health, Sciences, and Engineering پژوهشي Original Article <p><span style="font-family:times new roman;"><strong>Background: </strong><span style="font-size:14px;">Environmental gamma ray refers to the gamma radiation from terrestrial sources and building materials. In enclosed spaces radiation can become a health hazard leading to potential increase in the rates of lung cancer. The goal of this study is to assess the exposure to natural gamma radiation of children in the schools of Zanjan province.</span><br> <strong>Method:</strong><span style="font-size:14px;">The natural gamma radiation was assessed in 46 primary schools of Zanjan province. A total number of 75 classrooms were studied. The measurements were performed in classrooms and schoolyards using a Geiger&ndash;Muller detector (RDS-110). Alongside radiation measurements, all the data corresponding to the characteristics of each school building were collected.</span></span></p> <p><span style="font-family:times new roman;"><strong>Results:</strong> <span style="font-size:14px;">The results showed that the outdoor dose rate ranged from 82 to 106nSv h^-1 while gamma dose rate due to inside classrooms ranged from 106 to 137nSvh^-1. The findings represented that the highest indoor gamma dose rate belonged to the buildings of more than 30 years and metal frame and brick (<em>P</em><0.05).</span></span></p> <p><span style="font-family:times new roman;"><strong>Conclusion</strong></span><span style="font-family:times new roman;"><span style="font-size:14px;"><strong>: </strong>We concluded that the effective dose due to gamma radiation from terrestrial sources and building materials for students of primary schools in Zanjan province (0.83 mSv) was higher than worldwide average of the annual effective dose (0.48 mSv).</span></span></p> Natural gamma radiation, Primary schools, Effective dose 130 137 http://jhehp.zums.ac.ir/browse.php?a_code=A-10-70-2&slc_lang=en&sid=1 Mohammad Reze Mehrasbi : zmehr@zums.ac.ir 10031947532846009244 10031947532846009244 Yes Department of Environmental Engineering, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran. Faranak Saghatchi Saghatchif@zums.ac.ir 10031947532846009245 10031947532846009245 No Department of Radiology, School of Paramedical Sciences, Zanjan University of Medical Sciences, Zanjan, Iran. Zahra Khodaei zkhodaee58@yahoo.com 10031947532846009246 10031947532846009246 No Department of Environmental Engineering, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran. Jose Luis Gutierrez-Villanueva jose.luis.guti.villa@gmail.com 10031947532846009247 10031947532846009247 No Faculty of Medicine, Radon Group. University of Cantabria 39011 Santander (Spain). Koroosh Kamali drkamali@zums.ac.ir 10031947532846009248 10031947532846009248 No Department of Public Health, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran.