Background Radiation Areas of Ramsar, Iran
M. Javad Mortazavi
Biology Division, Kyoto University of Education, Kyoto 612-8522, Japan
Ionizing and Non-ionizing Radiation Protection Research Center
Shiraz University Of Medical Sciences,
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Humans, animals and plants have been exposed to natural radiation since the creation of life. Interestingly, life evolved in a radiation field that was much more intense than today. The annual effective radiation dose from natural and man-made sources for the world's population is about 3 mSv, which includes exposure to alpha radiation from radon and its progeny nuclides. Nearly 80% of this dose (2.4 mSv) comes from natural background radiation, although levels of natural radiation can vary greatly. Ramsar, a northern coastal city in Iran, has areas with some of the highest levels of natural radiation measured to date. The effective dose equivalents in very high background radiation areas (VHBRAs) of Ramsar in particular in Talesh Mahalleh, are a few times higher than the ICRP-recommended radiation dose limits for radiation workers.
Figure 1. High Background Radiation Areas Around the World. According to UNSCEAR 2000 report, Ramsar, in northern Iran has some inhabited areas with the highest known natural radiation levels in the world. Figure adapted from Health Research Foundation, Kyoto, Japan with permission
Inhabitants who live in some houses in this area receive annual doses as high as 132 mSv from external terrestrial sources. The radioactivity of the high background radiation areas (HBRAs) of Ramsar is due to Ra-226 and its decay products, which have been brought to the surface by the waters of hot springs. There are more than 9 hot springs with different concentrations of radium in Ramsar that are used as spas by both tourists and residents.
According to the results of the surveys performed to date the radioactivity seems primarily to be due to the radium dissolved in mineral water and secondarily to travertine deposits having elevated levels of thorium combined with lesser concentrations of uranium (Sohrabi 1990). Due to extraordinary levels of natural radiation in these areas, in some cases 55-200 times higher than normal background areas, some experts have suggested that dwellings having such high levels of natural radiation need urgent remedial actions (Sohrabi 1997). In spite of this, many inhabitants still live in their unaltered paternal dwellings.
The preliminary results of cytogenetical, immunological and hematological studies on the residents of high background radiation areas of Ramsar have been previously reported (Mortazavi et al. 2001, Ghiassi-Nejad et al. 2002 and Mortazavi et al. in press), suggesting that exposure to high levels of natural background radiation can induce radioadaptive response in human cells. Lymphocytes of Ramsar residents when subjected to 1.5 Gy of gamma rays showed fewer induced chromosome aberrations compared to residents in a nearby control area whose lymphocytes were subjected to the same radiation dose. Despite the fact that in in vitro experiments lymphocytes of some individuals show a synergistic effect after pretreatment with a low dose(Mortazavi et al. 2000), none of the residents of high background radiation areas showed such a response.
Figure 4. A scientist is measuring the dose rate around these HOT oranges!
Based on results obtained in studies on high background radiation areas of Ramsar, high levels of natural radiation may have some bio-positive effects such as enhancing radiation-resistance. More research is needed to assess if these bio-positive effects have any implication in radiation protection (Mortazavi et al. 2001). The risk from exposure to low-dose radiation has been highly politicized for a variety of reasons. This has led to a frequently exaggerated perception of the potential health effects, and to lasting public controversies.
Figure 5. A group of scientists from Korea, Japan, India and USA are visiting HBRAs of Ramsar.
Current radiation protection recommendations are based on the predictions of an assumption on linear, no-threshold dose-effect relationship (LNT).Beneficial effects and lack of detriment after irradiation with low levels of ionizing radiation, including a prolonged exposure to high levels of natural radiation of the inhabitants of HBRAs, are inconsistent with LNT (Mortazavi et al. 1999).
Our preliminary results suggest that prolonged exposure to very high levels of natural radiation could lead to the induction of radiation resistance among exposed individuals, which has interesting implications for many aspects of radiation protection policy.
Figure 6. Experts are measuring dose rates in different points of an inhabited area.
The phenomenon of radioresistance in living organisms has long been a matter of interest for scientists. Experiments on Drosophila nebulosa collected in the woods of a high background radiation area in Brazil indicated the addition of some genes caused the radioresistance found in these flies compared to flies collected from adjacent control woods. In humans it is also possible that genetic alterations have occurred over the span of many generations to induce the radioresistance noted in our study. More research is needed to clarify the mechanisms that make individuals radioresistant.
Figure 7.a. Two survey meters show the dose rates of 142 and 143 micro Gy/h on the wall of the bedroom of one dwelling.
Figure 7.b. The surveymeter shows the dose rate on the bed.
There are many other areas with high levels of background radiation around the world, and epidemiological studies have indicated that natural radiation in these areas is not harmful for the inhabitants. Results obtained in our study are consistent with the hypothesis that a threshold possibly separates the health effects of natural radiation from the harm of large doses. This threshold seems to be much higher than the greatest level of natural radiation.
Radon levels in some dwellings of Ramsar are up to 3700 Bq/m3 (over 100 pCi/L). The people and their ancestors exposed to abnormally high radiation levels over many generations. If a radiation dose of a few hundred mSv per year is detrimental to health causing genetic abnormalities or an increased risk of cancer, it should be evident in these people. Ramsar was divided into eight health districts and a health center provided primary health services in each health district. Indoor radon concentration levels were previously measured in each dwelling by the Iranian Nuclear Regulatory Authority experts. The overall cancer mortality, lung cancer mortality and neonatal death rate of different districts in the years from 2000 to 2001 were collected. The radon prone houses were located in a district named Ramak. Our study showed that the highest lung cancer mortality rate was in Galesh Mahaleeh, where the radon levels were normal. On the other hand, the lowest lung cancer mortality rate was in Ramak, where the highest concentrations of radon in the dwellings were found.
Figure 8. The highest lung cancer mortality rate was in Galesh Mahaleeh, where the radon levels were normal. On the other hand, the lowest lung cancer mortality rate was in Ramak, where the highest concentrations of radon in the dwellings were found.
Figure 9. Different tumor markers and their associted cancers
Recently, as no excess cancer rate was reported in these areas by epidemiological studies, we studied the tumor markers in the inhabitants of these areas to shed some light on the impact of high levels of background radiation on cancer induction. The level of background gamma radiation as well as indoor radon was determined using RDS-110 and CR dosimeters. Thirty five individuals from a high background radiation area (HBRA) and 35 individuals from a normal background radiation area (NBRA) were randomly selected to participate in the study. Commercial ELISA kits (sandwich type ELISA tests) were used to measure the serum levels of PSA, CA15.3, CA125, Cyfra21-1, CEA, CA19.9, AFP and Tag72 tumor markers. This study showed that among the eight biomarkers investigated, the means of PSA, CA15.3, CA125, CA19.9 and AFP concentrations between the HBRAs and NBRAs were not significantly different. However, Cyfra21, CEA and Tag72 in HBRA group revealed statistically significant increases compared to those of NBRA group (P<0.05). Furthermore, a statistically significant correlation between the external gamma dose as well as indoor radon level and the concentration of CEA (P<0.001), Cyfra-21(P<0.001) and TAG 72 (P<0.001 and 0.01 respectively) biomarkers were observed. We concluded that chronic exposure to high background radiation induces significant alterations in Cyfra21, CEA and Tag72 levels. We believe that studies with other relevant tumor markers might overcome the limitations of epidemiological studies on cancer incidence in high background radiation areas.
S Taeb, SMJ Mortazavi, A Ghaderi, H Mozdarani, MR Kardan, SAR Mortazavi, A Soleimani, I Nikokar, M Haghani, A Soofi. Alterations of PSA, CA15.3, CA125, Cyfra21-1, CEA, CA19.9, AFP and Tag72 tumor markers in human blood serum due to long term exposure to high levels of natural background radiation in Ramsar, Iran. International Journal of Radiation Research. in press.
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1. Ghiassi-nejad, M; Mortazavi, SMJ; Cameron, JR; Niroomand-rad, A; Karam, PA; Very High Background Radiation Areas of Ramsar, Iran: Preliminary Biological Studies. Health Physics, 82(1): 87-93, 2002.
2. Mortazavi SMJ, M. Ghiassi-Nejad and M. Rezaiean. Cancer risk due to exposure to high levels of natural radon in the inhabitants of Ramsar, Iran in: High Levels of Natural Radiation and Radon Areas: Radiation Dose and Health Effects, T. Sugahara, M. Morishima, M. Sohrabi, Y Sasaki, I. Hayata, and S. Akiba Eds, pp. 436-437, Elsevier, Amsterdam, 2005.
3. Mortazavi, S.M.J., Karam, P.A. Apparent lack of radiation susceptibility among residents of the high background radiation area in Ramsar, Iran: can we relax our standards? (2005) Radioactivity in the Environment, 7 (C), pp. 1141-1147.
4. Mortazavi, S.M.J., Shabestani-Monfared, A., Ghiassi-Nejad, M., Mozdarani, H. Radioadaptive responses induced in lymphocytes of the inhabitants in Ramsar, Iran (2005) International Congress Series, 1276, pp. 201-203.
5. Mortazavi SMJ, Mozdarani H. Is it time to shed some light on the black box of health policies regarding the inhabitants of the high background radiation areas of Ramsar? Iranian Journal of Radiation Research. 2012;10(3-4):111-6.
6. Mortazavi SMJ, Niroomand-Rad A, Mozdarani H, Roshan-Shomal P, Razavi-Toosi SMT, Zarghani H. Short-term exposure to high levels of natural external gamma radiation does not induce survival adaptive response. Iranian Journal of Radiation Research. 2012;10(3-4):165-70.
8. S. Taeb1, S.M.J. Mortazavi, A. Ghaderi, H. Mozdarani, MR Kardan, A. Soleimani, S.A.R. Mortazavi, M Haghani, A. Soofi. Alterations of PSA, CA15.3, CA125, Cyfra21-1, CEA, CA19.9, AFP and Tag72 tumor markers in human blood serum due to long term exposure to high levels of natural background radiation in Ramsar, Iran. International Journal of Radiation Research. in press.
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