High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam
1
2
1.
EFN – Environmentalists For Nuclear Energy – www.ecolo.org / and Biology Division,
Kyoto University of Education, Kyoto 612-8522, Japan
2.
Department of Environmental Medicine, 601 Elmwood Ave Box HPH, Rochester, NY
14642, USA
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam
Abstract
Life evolved on Earth in radiation environment that was a few times more intense than today.
People in some areas around the world live in dwellings with radiation and radon levels as much as more than 200 times the global average. Inhabited areas with high levels of natural radiation are found in different areas around the world including Yangjiang, China; Kerala, India; Guarapari,
Brazil and Ramsar, Iran. Ramsar in northern Iran is among the world’s well-known areas with highest levels of natural radiation. Annual exposure levels in areas with elevated levels of natural radiation in Ramsar are up to 260 mGy y
-1 and average exposure rates are about 10 mGy y
-1 for a population of about 2000 residents. Due to the local geology, which includes high levels of radium in rocks, soils, and groundwater, Ramsar residents are also exposed to high levels of alpha activity in the form of ingested radium and radium decay progeny as well as very high radon levels (over
1000 MBq m
-3
) in their dwellings. In some cases, the inhabitants of these areas receive doses much higher than the current ICRP-60 dose limit of 20 mSv y
-1
. As the biological effects of low doses of radiation are not fully understood, the current radiation protection recommendations are based on the predictions of an assumption on the linear, no-threshold (LNT) relationship between radiation dose and the carcinogenic effects. Considering LNT, areas having such levels of natural radiation must be evacuated or at least require immediate remedial actions. Inhabitants of the high level natural radiation areas (HLNRAs) of Ramsar are largely unaware of natural radiation, radon, or its possible health effects, and the inhabitants have not encountered any harmful effects due to living in their paternal houses. In this regard, it is often difficult to ask the inhabitants of HLNRAs of
Ramsar to carry out remedial actions. Despite the fact that considering LNT and ALARA, public health in HLNRAs like Ramsar is best served by relocating the inhabitants, the residents’ health seems unaffected and relocation is upsetting to the residents. Based on the findings obtained by studies on the health effect of high levels of natural radiation in Ramsar, as well as other HLNRAs, no consistent detrimental effect has been detected so far. However, more research is needed to clarify if the regulatory authorities should set limiting regulations to protect the inhabitants against elevated levels of natural radiation.
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam
Introduction
Humans, animals and plants have been exposed to natural radiation since the creation of life. More than 3.5 billion years ago, when the living organisms appeared on the Earth, the level of natural radiation was about 3 times higher than its current level. Also in the early days of life, there may have been as many as 100 million natural reactors, such as found in Oklo, Gabon. It has been estimated that the dose rate around natural reactors was up to 47 Gy per minute (Jaworowski 1997).
It has been proposed that the mutation repair mechanism that exist today, reflect the response of early life to the high background radiation environment under which they evolved. Although background radiation presently accounts for 1-6% of background mutations, it has been estimated that high levels of background radiation in the early days of life, accounted for up to 33% of mutations to the first life forms (Karam and Leslie 1999). The annual per caput effective doses from natural and man-made sources for the world’s population is currently about 2.8 mSv. Nearly 85% of this dose (2.4 mSv) comes from natural background radiation (UNSCEAR 2000). Levels of natural radiation can vary greatly. Ramsar (Figure 1), a northern coastal city in Iran, has some areas with one of the highest levels of natural radiation studied so far. The effective dose equivalents in very high-level natural radiation areas (VHLNRAs) of Ramsar in particular in Talesh Mahalleh, are few times higher than the dose limits for radiation workers. Inhabitants who live in some houses in this area receive annual doses as high as 132 mSv from external terrestrial sources and the maximum credible annual radiation exposures were up to 260 mGy (Figure 2). External exposure rates from terrestrial gamma radiation in Iran and the annual background doses to the inhabitants of some areas around the world are summarized in Tables 1 and 2 respectively.
Origin of the high levels of natural radioactivity
Radioactivity in the high level natural radiation areas (HLNRAs) of Ramsar is due to
226
Ra and its decay products, which have been brought up to the earth’s surface by the water of hot springs.
There are at least 9 hot springs with different concentrations of radium in this city that visitors as well as residents use as spas. According to the results of the surveys performed by the Atomic
Energy Organization of Iran (AEOI), the radioactivity seems to be firstly due to the mineral water and secondly due to some travertine deposits having thorium content higher than that of uranium
(Sohrabi 1990).
As shown in Figure 3, igneous bedrocks have high concentrations of uranium. Although uranium is not soluble in anoxic ground water, it decays into radium-226, and radium is soluble in ground water. Dissolved radium is carried by groundwater to the surface, passing through pores and fractures in the rock. When underground water reaches the surface at hot spring locations, calcium carbonate precipitates out of solution and radium-226 substitutes for calcium (RaCo
3
). High concentrations of radium carbonate (white color, molecular weight 286.03) can be found in the residue of hot springs. In some cases the residents of the hot areas used the Ra-enriched rock from the hot springs as building materials to construct their houses. Due to levels of natural radiation in these areas, up to 200 times higher than normal background areas (Sohrabi 1997a), some radiation experts have suggested that dwellings having such high levels of natural radiation need urgent remedial actions (Sohrabi 1997b). In spite of this nearly all inhabitants still live in their unaltered paternal dwellings. Because of the expense of remedial actions and the long history of high background radiation levels, it is nearly impossible to ask the inhabitants to carry out remedial
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam actions. Furthermore, any detrimental effect caused by high levels of natural radiation in Ramsar has not been detected so far.
The Need for Radio-epidemiological Studies
As the biological effects of low doses of radiation are not fully understood, the current radiation protection recommendations are based on the predictions of an assumption on the linear, nothreshold (LNT) relationship between radiation dose and its carcinogenic effects. Considering the
LNT hypothesis as a scientific fact, there is a general belief that even low levels of radiation as well as exposures to natural sources are harmful. Among the greatest advantages of radioepidemiological studies in HLNRAs is the possibility of obtaining results from direct observation on human beings without extrapolating the effects of high doses of radiation to low dose region and from laboratory animals to humans (Wei 1997). These studies are of great importance when the study subjects have lived in the HLNRAs for many generations. It should be noted that at present there are no reliable radio-epidemiological data regarding the incidence of cancer in the inhabitants of HLNRAs of Ramsar. However, some of the local physicians strongly believe that the population living in these areas does not reveal increased solid cancer or leukemia incidence. As the majority of the inhabitants of Ramsar have lived there for many generations, an investigation to assess whether there is an apparent lack of radiation susceptibility among residents of the high level natural radiation areas was conducted.
Current Findings

Chromosome Aberrations . Preliminary results showed no significant difference even in the case of the inhabitants who lived in houses with extraordinarily elevated levels of natural radiation.

Dose-Effect Relationship
There is a great controversy about the dose-effect relationship in published reports on the frequency of chromosome aberrations induced by chronic exposure to elevated environmental levels of radiation. This controversy exists in studies of residents in areas with elevated levels of natural radiation as well as the residents of areas contaminated by nuclear accidents. Using chromosomal aberrations as the main endpoint, an experiment to assess the dose-effect relationship in the residents of high level natural radiation areas of Ramsar was carried out. A cytogenetical study was performed on 21 healthy inhabitants of the high level natural radiation areas and 14 residents of a nearby control area. Preliminary results showed no positive correlation between the frequency of chromosome aberrations and the cumulative dose of the inhabitants.

Hematological Alterations. It has been reported that in mice and rats total body exposure to moderate doses decreases the number of circulating erythrocytes, platelets, granulocytes, lymphocytes etc. However, data on hematopoieses as a result of exposure to very low doses of ionizing radiation are scarce (Lee et al.
2001). Hematological parameters such as counts of leukocytes (WBC), lymphocytes, monocytes, granulocytes, red blood cells (RBC), hemoglobin (Hb), hematocrit (Ht), MCV, MCH, MCHC, RDW, PLT, and MPV were studied in all of the individuals. The results of this study indicated that there was no any statistically significant alteration in hematological parameters of the inhabitants of
VHLNRAs of Ramsar compared to those of the neighboring control area.
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam

Immunological Changes. It is well known that high doses of ionizing radiation suppress the activity of the immune system. On the other hand, the low-level whole body irradiation
(WBI) can enhance the immunological response. To assess whether relatively high doses of natural radiation can alter humoral immune parameters, an experiment was conducted on the inhabitants of VHLNRAs of Ramsar, permanently living in houses with elevated levels of natural radiation. Immunological factors such as the concentration of serum immunoglobulins of IgA, IgG, IgM and C3, C4 components of the complement system in healthy donors from VHLNRAs and a neighboring NBRA were studied. Preliminary findings indicate that there is a slight increase in IgA and IgG levels of the inhabitants of
VHLNRAs compared to those of matched controls. IgM, C3, and C4 complements were in the normal range. In spite of the fact that the increase in IgA and IgG were not so marked to show probable enhanced immunological capability, it can be concluded that relatively high doses of natural radiation are not immunosuppressive. More research is needed to clarify the immunological alterations induced by different levels of natural radiation.
Adaptation to High Levels of Natural Radiation
When living organisms are exposed to a variety of DNA damaging stresses such as UV, alkylating or oxidizing agents and heat, adaptive responses are induced which render them resistant to the killing and mutagenic insults (Samson and Carins, 1977). This type of reduced radiation susceptibility after exposure to ionizing radiation was first reported by Olivieri et al.
(1984). Cultured human lymphocytes exposed to a low dose of ionizing radiation had fewer chromatid aberrations induced by a subsequent high dose, compared to lymphocytes not preexposed to a low dose. Since then, radioadaptive response has been demonstrated for several end-points including gene mutation (Sanderson and Morely 1986, Kelsey et al.
1991, Rigaud et al.
1993), cell killing (Joiner 1994) and neoplastic transformation (Azzam et al.
1994) other than cytogenetic damage such as chromosomal aberrations, micronuclei and sister chromatid exchanges (Ikushima 1987, Shadley and Wolff 1987, Sankaranarayanan et al.
1989, Sasaki
1995, Ryabchenko et al.
1998) in various types of cells in vitro and in vivo . Radioadaptive response has been observed not only in cultured human lymphocytes (Shadley and Wolff
1987, Sankaranarayanan et al.
1989, Ryabchenko et al.
1998, Wienck et al.
1986, Wolff et al.
1988, Shadley and Wienck 1989) but also in cultured mammalian cells (Ikushima 1987, Sasaki
1995), cultured animal lymphocytes (Flores et al.
1996), human embryonic cells (Ishii and
Watanabe et al.
1996), plant cells (Heindorff et al.
1987), mammalian cells in vivo (Wojcik and Tuschl 1990, Cai and Liu 1990, Yonezawa et al.
1990, Farooqi and Kesavan 1993, Liu et al.
1992) occupationally exposed persons (Barquinero et al.
1995, Gourabi and Mozdarani
1998), residents of areas contaminated by Chernobyl accident (Tedeschi et al.
1995, Padovani et al.
1995).
To assess the possible induction of adaptive response in the inhabitants of HLNRAs of
Ramsar, blood samples of the residents and a nearby control area were exposed to a challenge dose of 1.5 Gy (natural radiation was the adapting dose). Following exposure to the challenge dose, the number of chromosomal aberrations was determined and the results were averaged to determine the mean number of chromosomal aberrations per cell (reported as MCAPC).
Results of this study showed 56% fewer MCAPC (P<0.001) resulting from the challenge dose among HLNRAs residents compared to lymphocytes from residents of neighboring low
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam background areas (Ghiassi-nejad et al . 2002). These results are in keeping with those reported in laboratory studies.
We feel these results are intriguing because no overt conditioning dose was given to Ramsar residents; in this case, the “conditioning” dose was exposure to the natural background radiation in the Ramsar HBRA. It was generally believed that the presence of adaptive response does not mean that the low dose radiation is beneficial to living organisms (Sagan
1989, Wolff 1989). After publication of the preliminary results on the presence of adaptive response in the residents of HLNRAs of Ramsar (Mortazavi et al.
2001), some scientist believed that the induced adaptive response may have considerable implications in radiation protection. Pollycove and Feinendegen (2001) reported that Ramsar results suggest that chronic low dose radiation may not only reduce mortality from all causes and cancer mortality but may also be protective against accidental high dose radiation.
Worldwide Studies on HLNRAs
Epidemiological evidence has indicated that the natural radiation in HLNRAs is not harmful to residents. Furthermore, cancer mortality rate is significantly lower in the high background areas than in the control areas. A summary of current findings are discussed:
1.
Kerala, India
Some areas in India have high levels of natural radiation due to presence of monazite along with other heavy minerals such as ilmenite, rutile, zircun, garnet, etc. The monazite contains approximately 9% thorium and 0.3% uranium (Paul 1998). Over 140,000 inhabitants in Kerala, on the southwest coast of India, receive an annual average dose of 15-25 mGy (Kesavan 1997).
The average life span of the inhabitants of Kerala is 72 years while for all India it is only 54 years (Goraczko 2000 and its citations). A comprehensive study on the residents of HLNRAs of
Kerala showed no evidence that cancer incidence is consistently higher because of the levels of external gamma radiation exposure in the area (Nair et al. 1999). In another study the incidence of congenital malformations in the densely populated monazite bearing sands of Kerala, the stratification of newborns with malformations, stillbirths or twinning showed no correlation with the natural radiation levels in different areas. No significant differences were observed in any of the reproductive parameters between 26,151 newborns from HLNRAs and 10,654 from a
NLNRA (Jaikrishan et al . 1999).
2.
Yangjiang, China
A health survey study on the inhabitants of HLNRAs of Yangjiang, China was started in 1972.
In HLNRAs of Yangjiang county in China (annual doses are about 330 mR) it has been indicated that mortality from all cancers and those from leukemia, breast and lung were not higher than that of the control area (110 mR/y). Furthermore, it was shown that when samples of circulating lymphocytes taken from the inhabitants were tested in vitro for mitotic response to phytohemagglutinin (PHA) and the degree of unscheduled DNA synthesis (UDS), there were higher responsiveness and UDS rates in the HLNRA samples than in those from the control area
(Chen and Wei, 1991). It was found that in a HLNRA in China the cancer (non-leukemia) mortality was 14.6% lower than in NBRA, and the leukemia mortality among men was 15% lower and among women 60% lower. No difference in the frequency of various genetical
6

High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam diseases was observed between Chinese HLNRA and NBRA (Wei et al.
1990). To date, based on the data as: cancer mortality from 1,008,769 person-years in HBRA and 995,070 personyears in CA; hereditary diseases and congenial malformations from 13,425 subjects in HBRA and 13,087 subjects in CA; human chromosome aberrations, and immune function of the inhabitants, no detrimental effect associated with the high levels of natural radiation detected
(Zha et al.
1996). On the contrary the mortality due to all cancers in HLNRAs was generally lower than that in the control NBRA. However, the difference was not statistically significant
(Tao et al.
1999, 2000).
3.
Other HLNR or Radon Prone Areas
In the Unites States a negative correlation of normal background radiation with overall cancer death was observed. In Rocky Mountain states, where the level of natural radiation is 3.2 times higher than that in Gulf states, the age adjusted overall cancer death was 79% of that in Gulf states (Jagger 1998). Misasa town in Tottori prefecture, Japan, where radon spa has been operating for long time, consists of high radon background area with relatively large and stable population. A study on the cancer incidence showed no difference in the incidence of all-site cancers, while stomach cancer incidence seemed to decrease for both sexes and lung cancer incidence for males only seemed to increase in the elevated radon level area (Ye et al . 1998).
Later the same group conducted a case control study. The case consisted of 28 people who had died of lung cancer in the years 1976-96 and 36 controls were randomly selected from the residents in 1976, matched by sex and year of birth. This study could not detect the risk pattern of lung cancer, possibly associated with residential radon exposure (Sobue et al . 2000).
HLNRAs and the Current Controversies
Substantial evidence indicate that it may be incorrect to estimate the hazard of the low radiation doses and very low dose rates by straight extrapolation of the effects of much higher doses and dose rates higher by more than ten orders of magnitude, such as encountered by the survivors of nuclear attacks in Hiroshima and Nagasaki. Radio-epidemiological studies on the inhabitants of HLNRAs provide a unique opportunity to study effects of relatively high doses at low dose rates, such as experienced in the normal practice of radiological protection. Due to statistical considerations, these studies should rather be of long duration. In Ramsar, the population who live in the HLNRAs is estimated to be about 2000 persons. In this regard, to obtain statistically reliable results, only a longterm study can provide considerable number of person-years of observation. On the other hand there are published reports on the increased life span of A-bomb survivors (Mine et.al
, 1990) or the increased survival of laboratory animals exposed to low doses of ionizing radiation (Jaworowski,
1997). Therefore the life span of the inhabitants of VHLNRAs of Ramsar should be also studied as a part of the future long-term studies.
It is generally believed that the risk of low-dose radiation exposures has for a variety of reasons been highly politicized. This has led to a frequently exaggerated perception of the potential health effects, and to lasting public controversies (Kellerer 2000). Current radiation protection recommendations are based on the predictions of an assumption on linear, no-threshold dose-effect relationship (LNT). Using LNT and ALARA, public health is best served by relocating HLNRAs inhabitants. However, relocation is upsetting to the residents (Mortazavi et al.
in press). Beneficial effects and lack of detriment after irradiation with low levels of ionizing radiation, including a
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam prolonged exposure to high levels of natural radiation of the inhabitants of HLNRAs, are inconsistent with LNT. These unexpected observations contradict the linear no-threshold theory (for a review see Mortazavi et al.
1999). Similar health surveys should be performed in the HLNRAs of
Ramsar, where the annual doses are much higher than the Yangjiang County. 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. It can be claimed 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 (e.g. lifetime doses up to 18 Sv in VHLNRAs of Ramsar).
Conclusion
Using LNT and ALARA, public health is best served by relocating HLNRAs inhabitants. Several statistically significant epidemiological studies contradict the validity of LNT concept by showing hormetic effects in a form of risk decrements of cancer mortality and mortality from all causes in populations exposed to low-dose radiation. Populations in areas with high level natural radiation show no adverse health effects when compared to low-dose populations. Furthermore, relocation is upsetting to the residents and several studies of large populations indicate beneficial health effects of low doses of ionizing radiation. Preliminary findings on the biological effects of prolonged exposure to high levels of natural radiation in the inhabitants of VHLNRAs of Ramsar, showed no harmful health effects. It can be concluded that in HLNRAs the LNT model might be inappropriate to use as the basis for public health measures. However, more research is needed to clarify if the regulatory authorities should set limiting regulations to protect the inhabitants against elevated levels of natural radiation.
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam
Figure 1. Ramsar, a city in northern Iran has some inhabited areas with highest levels of natural radiation in the world. The city lies between the Elburz mountaints and the Caspian sea and has many attractions such as beaches, mountain and jungle for the toursists.
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam
Figure 2. High Background Radiation Areas Around the World. Numbers given are in mSv/year.
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).
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam
Figure 3. The origin of high levels of natural radioactivity in Ramsar.
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam
Table.1 External exposure rates from terrestrial gamma radiation in Iran.
Iran’s Important Radiological Data
Population in 1996 (10
6
)
Average absorbed dose rate in air (nGy h
-1
): Outdoors
Average aAbsorbed dose rate in air (nGy h -1 ): Indoors
Indoors/outdoors ratio
Source: Survey of natural radiation exposure, UNSCEAR 2000.
69.98
71
115
1.6
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High Levels of Natural Radiation in Ramsar, Iran SMJ Mortazavi & PA Karam
Table.2 Mean and maximum annual natural terrestrial radiation doses to the inhabitants of some areas around the world.
Country Area Approximate population
Absorbed Dose rate in air a
(nGy h
-1
)
Brazil Guarapari 73 000
Iran
India
China
Ramsar b
Mahallat
Kerala
Yangjiang
2 000
100 000
80 000
90-170 (street)
90-90 000 (beaches)
70-17 000
800-4000
200-4 000
370 (average) a includes cosmic and terrestrial radiation. b i t should be noted that the monazite sand beaches at Guarapari in Brazil have a higher dose rate, but these areas are uninhabited. Therefore it can be claimed that Ramsar has the highest level of natural radioactivity studied so far.
Source: UNSCEAR 2000.
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