Comprehensive exposure assessments from the viewpoint of health in a unique high natural background radiation area, Mamuju, Indonesia.

Mamuju is one of the regions in Indonesia which retains natural conditions but has relatively high exposure to natural radiation. The goals of the present study were to characterize exposure of the entire Mamuju region as a high natural background radiation area (HNBRA) and to assess the existing exposure as a means for radiation protection of the public and the environment. A cross-sectional study method was used with cluster sampling areas by measuring all parameters that contribute to external and internal radiation exposures. It was determined that Mamuju was a unique HNBRA with the annual effective dose between 17 and 115 mSv, with an average of 32 mSv. The lifetime cumulative dose calculation suggested that Mamuju residents could receive as much as 2.2 Sv on average which is much higher than the average dose of atomic bomb survivors for which risks of cancer and non-cancer diseases are demonstrated. The study results are new scientific data allowing better understanding of health effects related to chronic low-dose-rate radiation exposure and they can be used as the main input in a future epidemiology study.

Cytogenetic analysis of nuclear abnormalities in the erythrocytes of gecko lizards (Phyllopezus periosus) collected in a semi-arid region of northeast Brazil: Possible effects of natural background radioactivity.

High natural-background radioactivity levels occur in the semi-arid region of the State of Rio Grande do Norte, northeastern Brazil. We have studied the lizard Phyllopezus periosus, an endemic species of the Brazilian caatinga with saxicolous habitat, as a bioindicator of environmental quality. Specimens were collected in three areas, an environmental protection area and two areas recognized as having high natural background radiation, one of these being a mining area. Level of metals and gamma radiation emitters present in the water sources potentially used by the lizards were measured. The biological endpoints assessed were micronuclei and nuclear abnormalities in blood samples. Significant differences in background radioactivity levels were found among the assessed areas. Statistically significant differences in micronuclei and nuclear abnormality frequencies were seen, among the study areas and a relationship between radioactivity level and genetic damage was observed.

A review of studies of childhood cancer and natural background radiation.

PURPOSE: The projected existence and magnitude of carcinogenic effects of ionizing radiation at low doses and low-dose rates is perhaps the most important issue in radiation protection today. Studies of childhood cancer and natural background radiation have the potential to throw direct light on this question, into a dose range below a few tens of mSv. This paper describes the studies that have been undertaken and their context, discusses some problems that arise and summarizes the present position. CONCLUSIONS: Many such studies have been undertaken, but most were too small to have a realistic chance of detecting the small effects expected from such low doses, based on risk projections from higher exposures. Case-control or cohort studies are to be preferred methodologically to ecological studies but can be prone to problems of registration/participation bias. Interview-based studies of the requisite size would be prohibitively expensive and would undoubtedly also run into problems of participation bias. Register-based studies can be very large and are free of participation bias. However, they need to estimate the radiation exposure of study subjects using models rather than individual measurements in the homes of those concerned. At present, no firm conclusions can be drawn from the studies that have been published to date. Further data and perhaps pooled studies offer a way forward.

Chronic exposure of humans to high level natural background radiation leads to robust expression of protective stress response proteins.

Understanding exposures to low doses of ionizing radiation are relevant since most environmental, diagnostic radiology and occupational exposures lie in this region. However, the molecular mechanisms that drive cellular responses at these doses, and the subsequent health outcomes, remain unclear. A local monazite-rich high level natural radiation area (HLNRA) in the state of Kerala on the south-west coast of Indian subcontinent show radiation doses extending from ≤ 1 to ≥ 45 mGy/y and thus, serve as a model resource to understand low dose mechanisms directly on healthy humans. We performed quantitative discovery proteomics based on multiplexed isobaric tags (iTRAQ) coupled with LC-MS/MS on human peripheral blood mononuclear cells from HLNRA individuals. Several proteins involved in diverse biological processes such as DNA repair, RNA processing, chromatin modifications and cytoskeletal organization showed distinct expression in HLNRA individuals, suggestive of both recovery and adaptation to low dose radiation. In protein-protein interaction (PPI) networks, YWHAZ (14-3-3ζ) emerged as the top-most hub protein that may direct phosphorylation driven pro-survival cellular processes against radiation stress. PPI networks also identified an integral role for the cytoskeletal protein ACTB, signaling protein PRKACA; and the molecular chaperone HSPA8. The data will allow better integration of radiation biology and epidemiology for risk assessment [Data are available via ProteomeXchange with identifier PXD022380].

Lens opacity prevalence among the residents in high natural background radiation area in Yangjiang, China.

The aim of the study was to evaluate the risk and threshold doses of lens opacity among residents exposed to low-dose radiation. Residents aged ≥45 years were recruited from a high natural background radiation (HNBR) area in Yangjiang City and a control area selected from nearby Enping City. Lens opacities (LOPs) were classified according to the Lens Opacities Classification System (LOCS) III system. Face-to-face interviews were conducted to collect information on lifestyles, migration and medical history. Life-time cumulative doses were estimated using gender, age, occupancy factors and environmental radiation doses received indoors and outdoors. Logistic regression analyses were conducted to estimate the dose response and determine thresholds. In the HNBR area, among 479 study participants, 101 (21.1%), 245(51.1%) and 23 cases (4.8%), respectively, of cortical, nuclear and posterior subcapsular (PSC) LOPs were found. In the control area, those types of LOPs were identified among 58 cases (12.6%), 206 cases (51.2%) and 6 cases (1.3%) of 462 examinees, respectively. Cumulative eye lens dose was estimated to be 189.5 ± 36.5 mGy in the HNBR area. Logistic analyses gave odds ratios at 100 mGy of 1.26 [95% confidence interval (CI) 1.00-1.60], 0.81 (95% CI 0.64-1.01) and 1.73 (95% CI 1.05-2.85) for cortical, nuclear and PSC LOPs, respectively. For cortical LOPs, a logistic analysis with a threshold dose gave a threshold estimate of 140 mGy (90% CI 110-160 mGy). The results indicated that population exposed to life-time, low-dose-rate environmental radiation was at an elevated risk of cortical and PSC LOPs. A statistically significant threshold dose was obtained for cortical LOPs and no threshold dose for PSC LOPs.

Lung damage by thoron progenies versus possible damage redemption by lung stem cells: a perspective.

PURPOSE: Natural radiation is the major source of human exposure to ionizing radiation. About 52% of the total dose received from the high natural background radiations (HNBR) areas are due to inhalation dose from radon (222Rn)/thoron (220Rn) and their progenies. Hence, we reviewed the biological effects of 222Rn/220Rn and their progenies on lung tissue, and the possible role of lung stem cells in salvaging the damage caused by 222Rn/220Rn and their progenies. MATERIALS AND METHOD: We have extensively reviewed articles among several hits obtained in PubMed, Scopus, and Elsevier databases with keywords 'Radon/Thoron' OR Thoron progeny/Radon progeny OR 'Thoron/Radon inhalation and lungs', and proceed for further analysis. Also, databases related to oxidative damage to lung stem cells by radiation and the repair mechanisms involved by the lung stem cells were also included. RESULTS: Based on the existing epidemiological data on radon in residential buildings, we found that evidence exists on the association of radon induced lung carcinogenesis, but the data regarding the role of thoron induced lung damage is very limited and inconclusive. We also found that limited information has been provided based on ecological designs, leading to poor documentation of health statistics, in particular, organ-specific cancer rates. Finally, we tried to elucidate the possible mechanisms of lung injury induced by thoron inhalation and the probable role of lung stem cell toward the redemption of such oxidative damages. CONCLUSION: Existing epidemiological data on thoron inhalation and associated health outcomes are limited and inconclusive. Further, in vivo experiments, with respect to radon/thoron inhalation dose rate ranges corresponding to the HNBR areas will be helpful in understanding the cellular and molecular effects.

IL-2 and IL-2R gene polymorphisms and immune function in people residing in areas with high background radiation, Yangjiang, China.

PURPOSE: Long-term exposure to low dose radiation may trigger immune response and stimulate hormesis. Interleukin-2 (IL-2) and interleukin-2 receptor (IL-2R) play a crucial role in immune function. We aimed to explore the possible association of IL-2 and IL-2R gene polymorphisms with low dose radiation exposure, as well as the relationship with IL-2 gene expression in people residing in areas with a high background radiation in Yangjiang, China. MATERIALS AND METHODS: We recruited and assigned 54 native men residing in Yangxi County, Yangjiang city to the high natural background radiation (HNBR) group, and 53 native men residing in Hengpi County, Enping city to the control area (CA) group. All the participants wore a thermoluminescent dosimeter (TLD) for 90 days, and answered questionnaires. The serum levels of IL2, IL4, IL5, sIL2R, and tumor growth factor (TGF), and expression levels of IL2RA, IL2RB, IL2RG, and IL2 were also analyzed. Additionally, we tested 10 polymorphic loci associated with the IL-2 gene. RESULTS: The annual effective radiation doses in the HNBR and CA groups were 6.24 mSv y-1 and 1.95 mSv y-1, respectively. After adjusting for potential confounding factors, the serum levels of IL-2 and IL-5 were higher in the HNBR group than the CA group (p < .05), while the serum level of TGFß was lower in the HNBR group (p < .05). The IL-2 gene mRNA expression level was higher in the HNBR group than the CA group (p < .05). The IL-2RB rs76206423 AA allele showed significant variations in the HNBR group (p = .0381). CONCLUSIONS: Long-term exposure to low dose radiation may enhance immune function, and IL-2RB rs76206423 may be related to the expression of IL-2 by other coding variants. Moreover, our data provide a better understanding of the molecular mechanism of the immune response to low dose radiation.

The downfall of the linear non-threshold model. / El ocaso del modelo lineal sin umbral.

The linear non-threshold model (LNTM) is a theoretical dose-response function as a result of extrapolating the late effects of high-dose exposure to ionizing radiation to the low-dose range, but there is great uncertainty about its validity. The acceptance of LNTM as the dominant probabilistic model have survived to the present day and it is actually the cornerstone of current radiation protection policies. In the last decades, advances in molecular and evolutive biology, cancer immunology, and many epidemiological and animal studies have cast serious doubts about the reliability of the NLTM, as well as suggesting alternative models, like the hormetic theory. Considering the given evidences, a discussion between the involved scientific societies and the regulatory commissions is promtly required in order to to reach a redefiniton of theradiation protection basis, as it would be specially crucial in the medical field.

Premature chromosome condensation assay to study influence of high-level natural radiation on the initial DNA double strand break repair in human G0 lymphocytes.

The inherent capacity of individuals to efficiently repair ionizing radiation induced DNA double strand breaks (DSBs) may be inherited, however, it is influenced by several epigenetic and environmental factors. A pilot study tested whether chronic low dose natural radiation exposure influences the rejoining of initial DNA DSBs induced by a 2 Gy γ-irradiation in 22 individuals from high (>1.5 mGy/year) and normal (≤1.5 mGy/year) level natural radiation areas (H&NLNRA) of Kerala. Rejoining of DSBs (during 1 h at 37 °C, immediately after irradiation) was evaluated at the chromosome level in the presence and absence of wortmannin (a potent inhibitor of DSB repair in normal human cells) using a cell fusion-induced premature chromosome condensation (PCC) assay. The PCC assay quantitates DSBs in the form of excess chromosome fragments in human G0 lymphocytes without the requirement for cell division. A quantitative difference was observed in the early rejoining of DNA DSBs between individuals from HLNRA and NLNRA, with HLNRA individuals showing a higher (P = 0.05) mean initial repair ratio. The results indicate an influence of chronic low dose natural radiation on initial DNA DSB repair in inhabitants of HLNRA of the Kerala coast.

PROBLEMS OF RADIO SAFETY OF THE POPULATION OF THE ZAPORIZHZHIA REGION WHICH RELATES TO EXPOSURE TO BASIC SOURCES (by review of the literature). / PROBLEMY RADIATsIY̆NOÏ BEZPEKY NASELENNIa ZAPORIZ'KOÏ OBLASTI, IaKE ZAZNAIe OPROMINENNIa VID OSNOVNYKh DZhEREL (za ogliadom literatury).

The analysis of scientific literature is carried out in order to generalize the data of many years of research on radioe- cology of the environment of the population of the Zaporizhzhia region. The results of researches on the main sources of radioactive contamination of the territory, levels and structure of radiation doses of the population due to the natural radiation, diet, medical procedures, and the dose burden of the population are estimated. The main sources of radiation sources existing in the Zaporizhzhia region are considered, their characteristics are given, the rate of their influence on the environment and human is given. For this purpose a wide range of official literary sources and own researches were used.The Zaporizhzhia region is located in the south-eastern part of Ukraine and remarcable of the geomorphological structure, which is characterized by the presence of Ukrainian crystalline array enriched with minerals with an ele- vated level of natural radioactivity. This explains the large component of the radiation dose of the population due to the natural component. Total medieval efficiency of the population dosage of the Zaporizhzhia region at the expense of the natural component - 4,37 mSv, the main contribution to this dose is Radon-222 - 76 %. The level of radon-222 in the air of residential premises ranges from 37 to 112 Bq·m-3. Moreover, the percentage of exceeding the norm (100 Bq·m-3) is from 8% to 62%, depending on the administrative district. On average, 25 % of residential buildings in the region do not match the requirements of NRSU-97 regarding the content of radon in the air of the premises. Even more acute problem of the increased Radon radiation appears for the children's population. Due to the more stringent requirements of NRSU-97 regarding Radon content in the air of premises of preschool education- al institutions (PEI) (50 Bq·m-3), 99% of the premises of the PEI do not match the standards. Doses of children radi- ation because of Radon are higher than in adults and amounted to an average of 6.4 mSv per year with a spread of 4.3-9.7 mSv.The second place after Radon exposure to Zaporozhia region is a medical exposure. The analysis of patient dose loads in recent years suggests that the annual dose of irradiation of the population fluctuates in the range of 0.86-0.97 mSv·year-1, the average dose of irradiation is 0.9 mSv·year-1, which is almost 50 % more than the average Ukrainian rate and exceeds the average in the world twice.In the Zaporizhzhia region, the total annual radiation dose of the population due to the main sources of radiation is 5.0 mSv·year-1, with the main contribution of Radon-222 - 3.3 mSv and medical exposure - 0.9 mSv. Radon-222 in the air of the premises is the most important radiation factor for the population of Zaporizhzhia region, which creates an average risk level that is unacceptable for the population and requires careful regulatory control with the help of governmental and regional programs.

Reducing the ionizing radiation background does not significantly affect the evolution of Escherichia coli populations over 500 generations.

Over millennia, life has been exposed to ionizing radiation from cosmic rays and natural radioisotopes. Biological experiments in underground laboratories have recently demonstrated that the contemporary terrestrial radiation background impacts the physiology of living organisms, yet the evolutionary consequences of this biological stress have not been investigated. Explaining the mechanisms that give rise to the results of underground biological experiments remains difficult, and it has been speculated that hereditary mechanisms may be involved. Here, we have used evolution experiments in standard and very low-radiation backgrounds to demonstrate that environmental ionizing radiation does not significantly impact the evolutionary trajectories of E. coli bacterial populations in a 500 generations evolution experiment.

Effect of Heterogeneity in Background Incidence on Inference about the Solid-Cancer Radiation Dose Response in Atomic Bomb Survivors.

A recent analysis of solid cancer incidence in the Life Span Study of atomic bomb survivors (Hiroshima and Nagasaki, Japan) found evidence of a nonlinear, upwardly curving radiation dose response among males but not among females. Further analysis of this new and unexpected finding was necessary. We used two approaches to investigate this finding. In one approach, we excluded individual cancer sites or groups of sites from all solid cancers. In the other approach, we used joint analysis to allow for heterogeneity in background-rate parameters across groups of cancers with dissimilar trends in background rates. Exclusion of a few sites led to the disappearance of curvature among males in the remaining collection of solid cancers; some of these influential sites have unique features in their background age-specific incidence that are not captured by a background-rate model fit to all solid cancers combined. Exclusion of a few sites also led to an appearance of curvature among females. Misspecification of background rates can cause bias in inference about the shape of the dose response, so heterogeneity of background rates might explain at least part of the all solid cancer dose-response difference in curvature between males and females. We conclude that analysis based on all solid cancers as a single outcome is not the optimal method to assess radiation risk for solid cancer in the Life Span Study; joint analysis with suitable choices of cancer groups might be preferable by allowing for background-rate heterogeneity across sites while providing greater power to assess radiation risk than analyses of individual sites.

Long-term immune effects of high-level natural radiation on Yangjiang inhabitants in China.

Purpose: Low dose radiation was found to perturb immune function or inflammatory reactions, which required further study. This study aimed to evaluate the health effects following long-term low dose radiation by detecting levels of peripheral blood lymphocyte subsets and serum cytokines of residents living in the Yangjiang High Background Radiation Area (HBRA). Materials and methods: Flow cytometry was used to detect peripheral blood T lymphocytes and its subsets (CD4+ T, CD8+ T lymphocyte) in 100 healthy female residents selected from HBRA and a Control Area (CA), respectively. Thirty cytokines or receptors and CRP levels were measured using antibody arrays in the 40 subjects described above. Subjects were chosen based on an age and BMI match between the two groups. Cytokine expression levels were then verified using ELISA methods. Result: In comparison to CA, CD8+ T lymphocyte numbers were significantly increased with cumulative dose following adjustment to age and BMI. Of the 30 selected targets, 22 indexes were measurable and inflammatory cytokines such as IFN-γ, IL-α, MCP-1, sIL-6R, EGFR, and CRP levels were observed to be significantly up-regulated with cumulative doses. ELISA results confirmed the cytokine array results and found CRP, MCP-1, and sIL-6R levels are linear with cumulative dose following adjustment to age and BMI. Conclusion: Immune function was found to be affected in humans exposed to long-term low dose radiation. Specifically, we observed an increase in CD8+T lymphocyte numbers and an up-regulation of inflammatory biomarkers, including IFN-γ, MCP-1, sIL-6R, EGFR, CRP.

Risk assessment due to various terrestrial radionuclides concentrations scenarios.

PURPOSE: The purpose of this paper is to evaluate the morbidity excess cancer risk (ECR) due to internal and external exposure to three category levels of natural radionuclides in soil like 238U, 232Th and 40K. Although the exposure rate in soil is low but effect this radiation over time can lead to cancer risk and this risk can be calculated. MATERIALS AND METHODS: Natural activity concentration levels of 40K, 238U and 232Th in soil were selected from last reports in three concentration categories including: low, medium and high levels. The excess cancer risks of three concentration levels were calculated by means of RESidual-RADioactivity (RESRAD) code. RESULTS AND CONCLUSIONS: The calculated average morbidity ECR from 40K, 238U and 232Th in three concentration categories levels in soil were 1.40 × 10-4, 8.56 × 10-4 and 1.35 × 10-3, respectively. This calculation shows that the excess cancer risk value is the highest value in 100 years' time in all categories. Overall ECR from 40K radionuclide was maximal and the highest exposure pathways was through plant pathway; however, these pathway changes over 60 years to the drinking water pathway. The results of this study may be useful to risk assessment and for decision making for public health protection against high-level radiation.

ASSESSMENT OF TERRESTRIAL RADIATION BY DIRECT MEASUREMENT OF AMBIENT DOSE EQUIVALENT RATE OF BACKGROUND RADIATION.

Estimation of terrestrial external radiation is essential for assessment of public exposure to natural radiation. During national survey of natural radionuclide in soil in Iran, 979 soil samples were collected from different locations, in the same time ambient dose equivalent rate was measured by a scintillator detector. In this work, terrestrial radiation was estimated by direct measurement of ambient dose equivalent rate of background radiation. The response of dose measuring instrument to cosmic radiation at ground level was measured and other components were discussed and estimated. For verification, terrestrial radiation derived from this method was compared with those calculated from activity concentration of natural radionuclides in soil. The averages of ambient dose equivalent rate derived from activity concentration of by natural radionuclide in soil and from direct measurement are 55.07 and 62.57 nSv/h, respectively. The source of statistical and systematic uncertainties are introduced and discussed.

Reassessing Impacts of Extended Daily Exposure to Low Level Solar UV Radiation.

Currently, health agencies recommend that no sun-protection is required when the UV Index (UVI) is less than 3. We use high-quality data from spectroradiometers and model calculations to demonstrate that this simplification is seriously flawed, particularly for mid-latitude conditions. For days when the peak UVI is below the threshold for advising protection, the daily dose of sun-burning UV available frequently far exceeds the threshold for damage to fair skin. This may have important health consequences, as populations at mid latitudes include a significant proportion with fair skin that is susceptible to damage.

Evidence for Adaptive Response in a Molecular Epidemiological Study of the Inhabitants of a High Background-radiation Area of Yangjiang, China.

Our previous studies have shown that cancer mortality in high background-radiation areas of China was lower than that in a control area, indicating the possibility of an adaptive response in high background-radiation areas. Our aim is to determine the effect of low-dose radiation on the level of DNA oxidative damage, DNA damage repair, antioxidant capacity, and apoptosis in high background-radiation area and control area populations of Guangdong through a molecular epidemiological study in order to identify adaptive response. Blood samples were collected from male residents aged 50 to 59 y in a high background-radiation area (Yangjiang) and a control area (Enping), and activities of superoxide dismutase, glutathione, catalase, total antioxidant capacity, and expression of O6-methylguanine-DNA methyltransferase gene (MGMT), human 8-oxoguanine DNA N-glycosylase 1 gene (hOGG1), proapoptotic genes and antiapoptotic genes, oxidative-stress-related genes, as well as concentrations of 8-OHdG, TrxR, HSP27, and MT-COX2 were determined. The activities of antioxidative enzymes, relative mRNA expression level of DNA repair genes, antiapoptotic genes, oxidative-stress-related genes HSPB1 and MT-COX2, and the concentration of antioxidant index TrxR in the high background-radiation area population increased significantly compared to the control population (p < 0.05). The relative mRNA expression level of proapoptotic genes and the concentration of DNA oxidative damage index 8-OHdG were significantly lower in the high background-radiation area compared to those in the control area (p < 0.05). In conclusion, under long-term, natural, high background, ionizing radiation, DNA damage-repair capacity and antioxidant capacity of inhabitants in the high background-radiation area may be enhanced. Additionally, it could induce up regulation of cell-survival gene expression and down regulation of apoptotic gene expression. It might be speculated that enhanced antioxidant and DNA repair capacity and inhibition of apoptosis might play important roles in adaptive response of low-dose radiation in high background-radiation areas.

Effective Dose Calculation Program (EDCP) for the usage of NORM-added consumer product.

The aim of this study is to develop the Effective Dose Calculation Program (EDCP) for the usage of Naturally Occurring Radioactive Material (NORM) added consumer products. The EDCP was developed based on a database of effective dose conversion coefficient and the Matrix Laboratory (MATLAB) program to incorporate a Graphic User Interface (GUI) for ease of use. To validate EDCP, the effective dose calculated with EDCP by manually determining the source region by using the GUI and that by using the reference mathematical algorithm were compared for pillow, waist supporter, eye-patch and sleeping mattress. The results show that the annual effective dose calculated with EDCP was almost identical to that calculated using the reference mathematical algorithm in most of the assessment cases. With the assumption of the gamma energy of 1 MeV and activity of 1 MBq, the annual effective doses of pillow, waist supporter, sleeping mattress, and eye-patch determined using the reference algorithm were 3.444 mSv year-1, 2.770 mSv year-1, 4.629 mSv year-1, and 3.567 mSv year-1, respectively, while those calculated using EDCP were 3.561 mSv year-1, 2.630 mSv year-1, 4.740 mSv year-1, and 3.780 mSv year-1, respectively. The differences in the annual effective doses were less than 5%, despite the different calculation methods employed. The EDCP can therefore be effectively used for radiation protection management in the context of the usage of NORM-added consumer products. Additionally, EDCP can be used by members of the public through the GUI for various studies in the field of radiation protection, thus facilitating easy access to the program.

Frequency of chromosome aberrations among adult male individuals from high and normal level natural radiation areas of Kerala in the southwest coast of India.

Chromosome aberration analysis was carried out in peripheral blood lymphocytes of adult male individuals from normal level natural radiation areas (NLNRA, ≤1.5 mGy/year, N = 27) and high level natural radiation areas (HLNRA, >1.5mGy/year, N = 70) of Kerala coast in southwest India. The mean age of individuals from NLNRA and HLNRA was 40.9 ±â€¯9.4 and 43.7 ±â€¯12.4 years, respectively, with an overall mean of 42.9 ±â€¯11.6 (range: 18-80). Whole-blood cultures were set up and about 260 metaphases were scored per individual. The frequency of chromosome aberrations was calculated per 1000 cells. The overall basal frequency of unstable (dicentrics and rings), stable (translocations and inversions) and other (fragments and breaks) aberrations was 1.54 ±â€¯0.25, 4.1 ±â€¯0.40 and 6.66 ±â€¯0.51, respectively. Individuals of NLNRA and HLNRA had statistically similar frequency of unstable (2.11 ±â€¯0.64 v/s 1.39 ±â€¯0.26; RR = 0.66; 95% CI: 0.33-1.33), stable (4.60 ±â€¯0.94 v/s 3.97 ±â€¯0.44; RR = 0.86; 95% CI: 0.55-1.36) and other (7.85 ±â€¯1.23 v/s 6.36 ±â€¯0.56; RR = 0.81; 95% CI: 0.57-1.15) chromosome aberrations. Frequencies of unstable, stable and other chromosome aberrations did not show any dose response after stratification of HLNRA samples into three dose groups (1.51-5.0 mGy/year, 5.01-10 mGy/year and >10.0 mGy/year). Smokers showed an increase in other chromosome aberrations (P < 0.001), but smoking was not associated with unstable and stable aberrations. Alcohol consumption and tobacco chewing had no significant association with any type of chromosome aberrations. In conclusion, chronic low dose radiation prevailing in Kerala coast did not show any significant effect on the basal frequency of chromosome aberrations among the adult population.