Very high background radiation areas of Ramsar, Iran: preliminary biological studies.
TL;DR: Inhabitants of high background radiation areas had about 56% the average number of induced chromosomal abnormalities of normal background radiation area inhabitants following this exposure, which suggests that adaptive response might be induced by chronic exposure to natural background radiation as opposed to acute exposure to higher levels of radiation in the laboratory.
Abstract: People in some areas of Ramsar, a city in northern Iran, receive an annual radiation absorbed dose from background radiation that is up to 260 mSv y−1, substantially higher than the 20 mSv y−1 that is permitted for radiation workers. Inhabitants of Ramsar have lived for many generations in these hig
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TL;DR: In this paper, the authors used histone H2AX phosphorylation on a serine four residues from the carboxyl terminus (producing gammaH2AX) as a sensitive marker for DNA double-strand breaks (DSBs).
Abstract: Histone H2AX phosphorylation on a serine four residues from the carboxyl terminus (producing gammaH2AX) is a sensitive marker for DNA double-strand breaks (DSBs). DSBs may lead to cancer but, paradoxically, are also used to kill cancer cells. Using gammaH2AX detection to determine the extent of DSB induction may help to detect precancerous cells, to stage cancers, to monitor the effectiveness of cancer therapies and to develop novel anticancer drugs.
1,349 citations
TL;DR: The carcinogenic risk induced by low doses of ionizing radiation is controversial and cannot be assessed with epidemiologic methods alone because at low doses the data are imprecise and often conflicting.
Abstract: The carcinogenic risk induced by low doses of ionizing radiation is controversial. It cannot be assessed with epidemiologic methods alone because at low doses the data are imprecise and often conflicting. Since the 1970s, the radiation protection community has estimated the risk of low doses by means of extrapolation from the risk assessed at high doses, generally by using the linear no-threshold (LNT) model.
The LNT relationship implies proportionality between dose and cancer risk. This approach is based on one set of data and two hypotheses: (a) The relationship between dose and DNA damage in vivo seems linear from 1 mGy to 100 Gy with use of H2AX foci as a marker for DNA double-strand breaks (DSBs)—however, this marker is not specific (1); (b) each DSB is hypothesized to have the same probability of inducing cell transformation, irrespective of the quantity of DSBs present simultaneously in the cell; and (c) each transformed cell is hypothesized to have the same probability of developing into an invasive cancer, irrespective of the dose delivered to the tissue. The advances during the past 2 decades in radiation biology, the understanding of carcinogenesis, and the discovery of defenses against carcinogenesis challenge the LNT model, which appears obsolete (2–6).
Life developed in a bath of ionizing radiation and solar ultraviolet radiation and created aerobic organisms requiring (a) defenses against the metabolically induced reactive oxygen species, (b) DNA repair, and (c) elimination of damaged cells. Several sets of data show the efficacy of these defenses to be much higher at low than at high doses and for fractionated or protracted irradiation than for acute irradiation.
The LNT model was introduced as a concept to facilitate radiation protection (7). But the use of this model led to the claim that even the smallest dose (one electron traversing a cell) may initiate carcinogenesis—for instance, from diagnostic x-ray sources (8,9). This claim is highly hypothetical and has resulted in medical, economic, and other societal harm.
The French Academies report (10) concluded that the LNT model and its use for assessing the risks associated with low doses are not based on scientific evidence. In contrast, the Biological Effects of Ionizing Radiation (BEIR) VII report (11) and that of the International Commission on Radiological Protection (ICRP) (12) recommended the use of the LNT model. We wish to update this debate by using recent radiation biologic and epidemiologic data.
483 citations
TL;DR: The possible contribution of studies of populations living in high natural background radiation (HNBR) areas (Guarapari, Brazil; Kerala, India; Ramsar, Iran; Yangjiang, China), including radon-prone areas, to low dose risk estimation is reviewed.
Abstract: Natural radiation is the major source of human exposure to ionising radiation, and its largest contributing component to effective dose arises from inhalation of 222Rn and its radioactive progeny. However, despite extensive knowledge of radiation risks gained through epidemiologic investigations and mechanistic considerations, the health effects of chronic low-level radiation exposure are still poorly understood. The present paper reviews the possible contribution of studies of populations living in high natural background radiation (HNBR) areas (Guarapari, Brazil; Kerala, India; Ramsar, Iran; Yangjiang, China), including radon-prone areas, to low dose risk estimation. Much of the direct information about risk related to HNBR comes from case–control studies of radon and lung cancer, which provide convincing evidence of an association between long-term protracted radiation exposures in the general population and disease incidence. The success of these studies is mainly due to the careful organ dose reconstruction (with relatively high doses to the lung), and to the fact that large-scale collaborative studies have been conducted to maximise the statistical power and to ensure the systematic collection of information on potential confounding factors. In contrast, studies in other (non-radon) HNBR areas have provided little information, relying mainly on ecological designs and very rough effective dose categorisations. Recent steps taken in China and India to establish cohorts for follow-up and to conduct nested case–control studies may provide useful information about risks in the future, provided that careful organ dose reconstruction is possible and information is collected on potential confounding factors.
245 citations
Cites background from "Very high background radiation area..."
...In preliminary studies, no significant differences were found between aberrations in lymphocytes of 21 subjects from the HNBR and 14 subjects from normal background areas in Iran [44, 45]....
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TL;DR: A photoluminescent uranium organic framework, whose photolUMinescence intensity can be accurately correlated with the exposure dose of X- or γ-radiations, allowing for precise and instant detection of ionizing radiations down to the level of 10-4 Gy, representing a significant improvement on the detection limit.
Abstract: Precise detection of low-dose X- and γ-radiations remains a challenge and is particularly important for studying biological effects under low-dose ionizing radiation, safety control in medical radiation treatment, survey of environmental radiation background, and monitoring cosmic radiations. We report here a photoluminescent uranium organic framework, whose photoluminescence intensity can be accurately correlated with the exposure dose of X- or γ-radiations. This allows for precise and instant detection of ionizing radiations down to the level of 10−4 Gy, representing a significant improvement on the detection limit of approximately two orders of magnitude, compared to other chemical dosimeters reported up to now. The electron paramagnetic resonance analysis suggests that with the exposure to radiations, the carbonyl double bonds break affording oxo-radicals that can be stabilized within the conjugated uranium oxalate-carboxylate sheet. This gives rise to a substantially enhanced equatorial bonding of the uranyl(VI) ions as elucidated by the single-crystal structure of the γ-ray irradiated material, and subsequently leads to a very effective photoluminescence quenching through phonon-assisted relaxation. The quenched sample can be easily recovered by heating, enabling recycled detection for multiple runs.
210 citations
TL;DR: Data show that the time delay between receipt of dose and cancer death increases with decreasing dose, which means that, with low level radiation, death from natural causes will often occur first, which implies an effective threshold.
Abstract: We present a wide variety of experimental data indicating that linear no-threshold theory (LNT) greatly exaggerates the cancer risk from low level radiation LNT is based on cancer initiating hits on DNA molecules, but many other factors affect the progression from DNA damage to a fatal tumor, such as availability of DNA repair enzymes, immune response, and cell suicide Data are presented to show that these are generally stimulated by low level radiation (LLR) and suppressed by high doses that serve as calibrations for LNT Since the great majority of cancers are caused by natural chemical processes, the protection against these provided by LLR may make LLR beneficial rather than harmful Genes turned on and turned off by LLR are often different from those affected by high doses Direct studies of cancer risk vs dose are reviewed: animal experiments generally indicate that LNT exaggerates the risk of low level radiation, and the same is true of most data on humans except possibly where dose rates are very high Data show that the time delay between receipt of dose and cancer death increases with decreasing dose, which means that, with low level radiation, death from natural causes will often occur first This implies an effective threshold Responses to this type of information by various official and prestigious groups charged with estimating cancer risks from radiation are reviewed
199 citations
References
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01 Jan 2000
TL;DR: This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices, in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation.
Abstract: NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Sixty-third Session, Supplement No. 46. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. Scientific Annexes Annex A. Medical radiation exposures Annex B. Exposures of the public and workers from various sources of radiation INTROdUCTION 1. In the course of the research and development for and the application of atomic energy and nuclear technologies, a number of radiation accidents have occurred. Some of these accidents have resulted in significant health effects and occasionally in fatal outcomes. The application of technologies that make use of radiation is increasingly widespread around the world. Millions of people have occupations related to the use of radiation, and hundreds of millions of individuals benefit from these uses. Facilities using intense radiation sources for energy production and for purposes such as radiotherapy, sterilization of products, preservation of foodstuffs and gamma radiography require special care in the design and operation of equipment to avoid radiation injury to workers or to the public. Experience has shown that such technology is generally used safely, but on occasion controls have been circumvented and serious radiation accidents have ensued. 2. Reviews of radiation exposures from accidents have been presented in previous UNSCEAR reports. The last report containing an exclusive chapter on exposures from accidents was the UNSCEAR 1993 Report [U6]. 3. This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices. Its conclusions are to be seen in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation. 4. The Committee's evaluations of public, occupational and medical diagnostic exposures are mostly concerned with chronic exposures of …
3,924 citations
TL;DR: The Gibbs free energies, enthalpies and entropies of 42 dissolved uranium species and 30 uranium-bearing solid phases have been critically evaluated from the literature and estimated when necessary for 25°C.
2,019 citations
"Very high background radiation area..." refers background in this paper
...Uranium is not dissolved because the groundwater is anoxic and uranium is insoluble in anoxic waters (Langmuir 1978; Grandstaff 1976)....
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TL;DR: The results indicate that the radioadaptive response may result from the induction of a novel, efficient DNA repair mechanism which leads to less residual damage, but not fromThe induction of protective functions that reduce the initial DNA damage.
Abstract: To verify the hypothesis that the induction of a novel, efficient repair mechanism for chromosomal DNA breaks may be involved in the radioadaptive response, the repair kinetics of DNA damage has been studied in cultured Chinese hamster V79 cells with single-cell gel electrophoresis. The cells were adapted by priming exposure with 5 cGy of γ-rays and 4-h incubation at 37°C. There were no indication of any difference in the initial yields of DNA double-strand breaks induced by challenging doses from non-adapted cells and from adapted cells. The rejoining of DNA double-strand breaks was monitored over 120 min after the adapted cells were challenged with 5 or 1.5 Gy, doses at the same level to those used in the cytogenetical adaptive response. The rate of DNA damage repair in adapted cells was higher than that in non-adapted cells, and the residual damage was less in adapted cells than in non-adapted cells. These results indicate that the radioadaptive response may result from the induction of a novel, efficient DNA repair mechanism which leads to less residual damage, but not from the induction of protective functions that reduce the initial DNA damage.
221 citations
"Very high background radiation area..." refers background in this paper
...The results of many studies indicate that when cells are exposed to low doses of stressing agents, they often become less sensitive to the harmful effects of a subsequent higher dose (Ikushima et al. 1996)....
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...Adaptation to radiation stress It is known that cellular damage from a small amount of ionizing radiation and a variety of DNA damaging agents, such as UV, alkylating or oxidizing agents, and heat, can induce repair responses (Ikushima et al. 1996; Ikushima and Mortazavi 2002)....
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...It is known that cellular damage from a small amount of ionizing radiation and a variety of DNA damaging agents, such as UV, alkylating or oxidizing agents, and heat, can induce repair responses (Ikushima et al. 1996; Ikushima and Mortazavi 2002)....
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TL;DR: The kinetics of uraninite dissolution in water may be summarized by the equation: R = (-d(uran)/dt) = 10/sup 20/./sup 25/ (SS) (RF)/sup -1/ (10/sup -3.38-10.8 NOC/) (a/sub..sigma..CO/sub 2//) (D.O.) (a sub H/sup +//) exp (-7045/T) day/sup 1/1/
Abstract: The kinetics of uraninite dissolution in water may be summarized by the equation: R = (-d(uran)/dt) = 10/sup 20/./sup 25/ (SS) (RF)/sup -1/ (10/sup -3.38-10.8 NOC/) (a/sub ..sigma..CO/sub 2//) (D.O.) (a/sub H/sup +//) exp (-7045/T) day/sup -1/ where R is the rate of the dissolution reaction, SS is the specific surface area (cm/sup 2/-gm/sup -1/), RF is an organic retardation factor, NOC is the mole fraction of nonuranium cations in the uraninite, D.O. is the dissolved oxygen content of the water (ppM), ..sigma..CO/sub 2/ is the total dissolved carbonate, and T is the absolute temperature. Application of these data may allow better understanding of factors influencing oxidation of uraninite and the resulting mobility of uranium in natural waters.
167 citations
"Very high background radiation area..." refers background in this paper
...Uranium is not dissolved because the groundwater is anoxic and uranium is insoluble in anoxic waters (Langmuir 1978; Grandstaff 1976)....
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