Cancer incidence in areas with elevated levels of natural radiation
by S.M.J. Mortazavi, M. Ghiassi-Nejad, P.A. Karam, T. Ikushima, A. Niroomand-Rad, J.R. Cameron
International Journal of Low Radiation (IJLR), Vol. 2, No. 1/2, 2006

Abstract: It has been reported that on reaching a certain level of cell damage the production of repair enzymes is triggered which decreases the chromosome aberrations. If this happens, prolonged exposure to high levels of natural radiation in areas with elevated levels of background radiation could decrease the frequency of chromosome aberrations. Recent epidemiological studies indicated that there is an increased risk of cancer in healthy individuals with high levels of chromosomal aberrations. Studies performed in Nordic countries as well as Italy, showed that increased levels of chromosome aberrations in lymphocytes can be used to predict cancer risk in humans. One may conclude that a dose of ionising radiation sufficient to produce a certain level of cell damage increases production of antioxidants and repair enzymes that decrease either the frequency of chromosome aberrations or the cancer risk. People in some areas of Ramsar, a city in northern Iran, receive an annual radiation dose from background radiation that is more than five times higher than the 20 mSv. Yr^-1 that is permitted for radiation workers. Inhabitants of Ramsar have lived for many generations in these high background areas. If an annual radiation dose of a few hundred mSv is detrimental to health, causing genetic abnormalities or an increased risk of cancer, it should be evident in these people. The absorbed dose rate in some high background radiation areas of Ramsar is approximately 55-200 times higher than that of the average global dose rate. It has been reported that 3–8% of all cancers are caused by current levels of ionising radiation. If this estimation were true, all the inhabitants of such an area with extraordinary elevated levels of natural radiation would have died of cancer. Our cytogenetic studies show no significant differences between people in the high background area compared to people in normal background areas. As there was no increased level of chromosome aberrations, it may be predicted that the cancer incidence is not higher than in the neighbouring areas with a normal background radiation level. Although there is not yet solid epidemiological information, most local physicians in Ramsar report anecdotally that there is no increase in the incidence rates of cancer or leukemia in their area. There are no data to indicate a significant increase of cancer incidence in other high background radiation areas (HBRAs). Furthermore, several studies show a significant decrease of cancer death rates in areas with high backgrounds. It can be concluded that prolonged exposure to high levels of natural radiation possibly triggers processes such as the production of antioxidants and repair enzymes, which decreases the frequency of chromosome aberrations and the cancer incidence rate.

Online publication date: Fri, 30-Sep-2005

The full text of this article is only available to individual subscribers or to users at subscribing institutions.

 
Existing subscribers:
Go to Inderscience Online Journals to access the Full Text of this article.

Pay per view:
If you are not a subscriber and you just want to read the full contents of this article, buy online access here.

Complimentary Subscribers, Editors or Members of the Editorial Board of the International Journal of Low Radiation (IJLR):
Login with your Inderscience username and password:

Username:        Password:          Forgotten your password?

Want to subscribe?
A subscription gives you complete access to all articles in the current issue, as well as to all articles in the previous three years (where applicable). See our Orders page to subscribe.

If you still need assistance, please email subs@inderscience.com