Sedigheh Basirjafari - Student of Medicine, Faculty of Medicine, Guilan University of Medical Sciences, Rasht, Iran
Saeideh Aghayari - Student of Medicine, Faculty of Medicine, Guilan University of Medical Sciences, Rasht, Iran
Seyed Mohammad Poorabas - Student of Medicine, Faculty of Medicine, Guilan University of Medical Sciences, Rasht, Iran
Hassan Moladoust - Biochemistry & Biophysics Dept., Faculty of Medicine, Guilan University of Medical Sciences, Rasht, Iran

Introduction Guilan is one of the provinces in North of Iran, with population of 2,480,874 and a total area of ​​14,042 square kilometers. This study assesses the outdoor natural gamma dose rates in the air of 49 cities in Guilan and calculates corresponding average annual effective dose. Materials and Methods A total of 260 different sample points measurements were carried out. The results include both terrestrial and cosmic ray components of gamma radiation level. Results The outdoor gamma dose rates range from 65 to 127 nSv h-1 with the mean of 94 ± 24 nSv h-1. Conclusion The average outdoor gamma dose rate for Guilan determined in this study is significantly higher in comparison with values reported by UNSCEAR 2000 from different countries with the mean of 59 nSv although in comparison with many provinces of Iran, it is lower.

Background Radiation, Guilan, Iran, Outdoor Dose Rate