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Does short-term exposure to elevated levels of natural gamma radiation in Ramsar cause oxidative stress?
Smj Mortazavi1, A Niroomand-Rad2, P Roshan-Shomal3
1Department of Medical Physics and Medical Engineering, Shiraz, Iran ; Ionizing and Non-ionizing Radiation Protection Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.
Background:
Ramsar, a city in northern Iran, has areas with some of the highest recorded levels of natural radiation among inhabited areas measured on the earth.
Aims:
To determine whether short-term exposure to extremely high levels of natural radiation induce oxidative stress.
Materials And Methods:
In this study, 53 Wistar rats were randomly divided into five groups of 10-12 animals. Animals in the 1(st) group were kept for 7 days in an outdoor area with normal background radiation while the 2(nd) , 3(rd) , 4(th) and 5(th) groups were kept in four different outdoor areas with naturally elevated levels of gamma radiation in Ramsar. A calibrated RDS-110 survey meter, mounted on a tripod approximately 1 m above the ground, was used to measure exposure rate at each location. On days 7 and 9 blood sampling was performed to assess the serum levels of catalase (CAT) and malondialdehyde (MDA). On day 8, all animals were exposed to a lethal dose of 8 Gy gamma radiations emitted by a Theratron Phoenix (Theratronics, Canada) Cobalt-60 (55 cGy/min) at Radiotherapy Department of Razi Hospital in Rasht, Iran.
Results:
Findings obtained in this study indicate that high levels of natural radiation cannot induce oxidative stress. CAT and MDA levels in almost all groups were not significantly different (P = 0.69 and P = 0.05, respectively). After exposure to the lethal dose, CAT and MDA levels in all groups were not significantly different (P = 0.054 and P = 0.163, respectively).
Conclusions:
These findings indicate that short-term exposure to extremely high levels of natural radiation (up to 196 times higher than the normal background) does not induce oxidative stress.
