High Background Radiation Areas Research Articles

Spatial analysis of radionuclide concentration in the high background radiation regions of Kerala, India.

Every creature on earth undergoes continuous exposure to natural background radiation. Hence, it is crucial to monitor systematically, the degree of radioactivity in the ecosystem and possible radiological health hazards. The present study attempt to investigate the dynamics of prominent radionuclides and various radiological parameters associated with terrestrial gamma radiations along the littoral regions of the Kollam district, a well-reported high background radiation area in India. The gamma radiation exposure rate along the coastal belt of Kollam was measured using a portable Micro-R-survey meter and associated radiological parameters have been calculated and compared with the global average values. The result indicates that the radiological parameters cross the safe limits recommended by the UNSCEAR 2000. A high value is found in the shoreline of Chavara, with a maximum absorbed dose rate of 11945.1nGyh-1. The monazite-enriched black sand widely distributed all along the coast, which contains natural radioisotopes such as 40K, 226Ra and 232Th, has greatly contributed to the increase in radiation levels in the regions.

Microbial consortium and impact of industrial mining on the Natural High Background Radiation Area (NHBRA), India – Characteristic role of primordial radionuclides in influencing the community structure and extremophiles pattern

The present investigation is the first of its kind which aims to study the characteristics of microbial consortium inhabiting one of the natural high background radiation areas of the world, Chavara Coast in Kerala, India. The composition of the microbial community and their structural changes were evaluated under the natural circumstances with exorbitant presence of radionuclides in the sediments and after the radionuclide's recession due to mining effects. For this purpose, the concentration of radionuclides, heavy metals, net radioactivity estimation via gross alpha and beta emitters and other physiochemical characteristics were assessed in the sediments throughout the estuarine stretch. According to the results, the radionuclides had a significant effect in shaping the community structure and composition, as confirmed by the bacterial heterogeneity achieved between the samples. The results indicate that high radioactivity in the background environment reduced the abundance and growth of normal microbial fauna and favoured only the growth of certain extremophiles belonging to families of Piscirickettsiacea, Rhodobacteriacea and Thermodesulfovibrionaceae, which were able to tolerate and adapt towards the ionizing radiation present in the environment. In contrast, communities from Comamondacea, Sphingomonadacea, Moraxellacea and Erythrobacteracea were present in the sediments collected from industrial outlet, reinforcing the potent role of radionuclides in governing the community pattern of microbes present in the natural environment. The study confirms the presence of these novel and unidentified bacterial communities and further opens the possibility of utilizing their usefulness in future prospects.

Uranium Isotope Characterization in Volcanic Deposits in a High Natural Background Radiation Area, Mamuju, Indonesia

Mamuju is an area of high natural radiation in Indonesia with high natural radiation levels (average 613 nSv h−1). Mamuju is anomalous due to its high average 238U and 232Th concentrations of 22,882 and 33,549 Bq kg−1, respectively, in laterite and rock. High natural radionuclide concentrations of 238U, 232Th, and 40K have also been reported in soil samples from several locations in Mamuju, including Botteng, Northern Botteng, Takandeang, Ahu, and Taan. High radiation levels are related to radioactive mineral occurrences in the Adang volcanic complex, comprised of phonolitoid and foiditoid lithologies. According to the International Atomic Energy Agency (IAEA), uranium deposits can be classified into several types, among them a volcanic-related deposits, which include three sub-types: stratabound, structure-bound, and volcano-sedimentary deposits. This study aims to characterize volcanic rock deposit sub-types in the Mamuju area based on uranium radioisotope measurements. The uranium isotopes were measured using a tandem quadrupole inductively coupled plasma mass spectrometer combined with chemical separation by extraction chromatography using UTEVA resin. The analytical results for the 234U/238U ratios are used to determine the formation characteristics of minerals in each deposit sub-type based on mineral formation age, post-formation processes, and disturbances that affected the formation processes. Based on geochronological calculations using 234U/238U mineralization age, the deposits in the Mamuju area are 0.914–1.11 million years old and are classified as recent mineralization. These data have important implications for tracing uranium source rocks in the Mamuju area and may explain the anomalously high radiation levels in the Mamuju area.

Radium deposition in human brain tissue: A Geant4-DNA Monte Carlo toolkit study

NASA has encouraged studies on 226Ra deposition in the human brain to investigate the effects of exposure to alpha particles with high linear energy transfer, which could mimic some of the exposure astronauts face during space travel. However, this approach was criticized, noting that radium is a bone-seeker and accumulates in the skull, which means that the radiation dose from alpha particles emitted by 226Ra would be heavily concentrated in areas close to cranial bones rather than uniformly distributed throughout the brain. In the high background radiation areas of Ramsar, Iran, extremely high levels of 226Ra in soil contribute to a large proportion of the inhabitants' radiation exposure. A prospective study on Ramsar residents with a calcium-rich diet was conducted to improve the dose uniformity due to 226Ra throughout the cerebral and cerebellar parenchyma. The study found that exposure of the human brain to alpha particles did not significantly affect working memory but was significantly associated with increased reaction times. This finding is crucial because astronauts on deep space missions may face similar cognitive impairments due to exposure to high charge and energy particles. The current study was aimed to evaluate the validity of the terrestrial model using the Geant4 Monte Carlo toolkit to simulate the interactions of alpha particles and representative cosmic ray particles, acknowledging that these radiation types are only a subset of the complete space radiation environment.

Micronucleus assay in the blood of residents in Mamuju, West Sulawesi, Indonesia, a high background radiation area

Micronucleus assay in the blood of residents in Mamuju, West Sulawesi, Indonesia, a high background radiation area

Seasonal 222Rn activity in spring water close to rare earth element and uranium mines in North Vietnam

Abstract222Rn is among the most important issues for radiation exposure in/near high background radiation areas such as near rare-earth-element (REE) and uranium mines in North Vietnam. Seasonal 222Rn activity concentration in spring water was determined by RAD-7, with average ranges of 1270 ± 60–66,400 ± 2630 Bq m−3, therein the highest value was a REE, and the lowest a uranium mine. The 222Rn activity concentration was higher in the dry season, which could be attributed to 222Rn leaching to spring waters from nearby mines, and lower in the rainy season due to dilution by rain water. The 222Rn annual effective doses were within permissible limits.

Generation of map on natural environmental background absorbed dose rate in India

A systematic mapping of natural absorbed dose rate was carried out to assess the existing exposure situation in India. The mammoth nationwide survey covered the entire terrestrial region of the country comprising of 45127 sampling grids (grid size 36 km2) with more than 100,000 data points. The data was processed using Geographic Information System. This study is based on established national and international approaches to provide linkage with conventional geochemical mapping of soil. Majority (93%) of the absorbed dose rate data was collected using handheld radiation survey meters and remaining were measured using environmental Thermo Luminescent Dosimeters. The mean absorbed dose rate of the entire country including several mineralized regions, was found to be 96 ± 21 nGy/h. The median, Geometric Mean and Geometric Standard Deviation values of absorbed dose rate were 94, 94 and 1.2 nGy/h, respectively. Among the High Background Radiation Areas of the country, absorbed dose rate varied from 700 to 9562 nGy/h in Karunagappally area of Kollam district, Kerala. The absorbed dose rate in the present nationwide study is comparable with the global database.

Functional analysis of polymorphism haplotypes of MGMT in residents of high background radiation area.

To investigate the distribution of polymorphisms and their frequent haplotypes in the regulatory region of MGMT in residents of high background radiation area (HBRA) and their impacts on transcriptional activity, we collected DNA samples from 83 healthy Chinese residents in HBRA and searched for genetic polymorphisms in the regulatory region of MGMT. Haplotypes were characterized by Haploview analysis. Transcriptional activities of different polymorphism haplotypes were detected by using a dual-luciferase reporter assay. Six genetic polymorphisms were identified within the regulatory region (1024 bp) of MGMT. Linkage disequilibrium (LD) patterns and haplotype profiles were analyzed using the identified genetic polymorphisms. These polymorphisms we found to be in high LD, with a D' of 0.928 (r2 = 0.581) for -808 T>C and -19 C>T, 0.928 (r2 = 0.581) for -797 G>A and -19 C>T in Han Chinese HBRA residents. Complete LD with a D' of 1.0 (r2 = 1.0) was observed between -808 T>C and -797 G>A. Haploview analysis revealed the existence of three polymorphism haplotypes in the core region of regulatory region of MGMT. Using serially truncated regulatory region of human MGMT luciferase reporter gene constructs, we found a 1002 bp (-637 nt to +365 nt) fragment in the MGMT gene was the core region. Dual-luciferase reporter assays showed that different polymorphism haplotypes bearing different variant alleles exhibit distinct transcriptional activities, especially the polymorphism haplotype carrying -19 T has the strongest transcriptional activity. In summary, the present study obtained genetic characteristics of the six polymorphisms in the regulatory region of the MGMT gene in HBRA residents, and the results suggest that different polymorphism haplotypes have significant effects on the transcriptional activity of the MGMT and that the -19 C>T polymorphism may be a functional variant involved in the transcriptional regulation of the MGMT gene.

234U/238U disequilibrium and 235U/238U ratios measured using MC-ICP-MS in natural high background radiation area soils to understand the fate of uranium

The Chhatrapur-Gopalpur coastal area in Odisha, India is a well-known natural high background radiation (HBRA) area due to the abundance of monazite (a thorium bearing radioactive mineral) in beach sands and soils. Recent studies on Chhatrapur-Gopalpur HBRA groundwater have reported high concentrations of uranium and its decay products. Therefore, the soils of the Chhatrapur-Gopalpur HBRA are reasonably suspected as the sources of these high uranium concentrations in groundwater. In this report, first the uranium concentrations in soil samples were measured using inductively coupled plasma mass spectrometry (ICP-MS) and they were found to range from 0.61 ± 0.01 to 38.59 ± 0.16 mg kg−１. Next, the 234U/238U and 235U/238U isotope ratios were measured to establish a baseline for the first time in Chhatrapur-Gopalpur HBRA soil. Multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) was used for measurement of these isotope ratios. The 235U/238U ratio was observed to be the normal terrestrial value. The 234U/238U activity ratio, was calculated to understand the secular equilibrium between 234U and 238U in soil and it varied from 0.959 to 1.070. To understand the dynamics of uranium in HBRA soil, physico-chemical characteristics of soil were correlated with uranium isotope ratios and this correlation of 234U/238U activity ratio indicated the leaching of 234U from Odisha HBRA soil.

Natural Radioactivity and Excess Lifetime Cancer Risk Associated With Soil in Kargi Area, Marsabit – Kenya

Purpose: The main aim of investigating activity concentrations together with distribution of radionuclides naturally in soil from Kargi was to evaluate radiological health hazard together with environmental radioactivity. Research shows radionuclides as one source of exposure due to radiation with detrimental effects health wise for populations found in areas considered high background radiation.
 Methodology: After collecting 117 soil samples from the area, analysis was done in order to measure their natural radioactivities due to 40K, 232Th and 226Ra radionuclides. Measurements method of gamma spectrometry employing a high purity germanium (HPGe) detector was employed basically to evaluate the radiological hazard of radioactivities. For 40K, 232Th and 226Ra, mean calculated activities were 353.19±110.07, 7.98±3.98 and 7.37±2.60 Bqkg-1 respectively. Mean values of absorbed and effective dose rates, external and internal hazard indices together with radium equivalent activity were 23.82±6.59 nGyh-1 and 0.14±0.04 mSvy-1, 0.12±0.03 and 0.14±0.04 and 45.90±12.65 Bqkg-1 respectively. Comparing with approved global values, the values were found to be below the given global limits.
 Findings: Evidence of involvement of metasomatic activity of the radioelements or fractionation during weathering is seen as calculations give a higher value Th/U. Excess cancer risk, calculated from the samples showed lower values as compared to global standard values hence minimal chance of getting cancer disease. The area is safe from cancer causing radionuclides.
 Unique Contribution to theory, Practice and Policy: It is recommended that High Background Radiation Area (HBRA) are healthy and good for human settlement.

The bacterial population inhabiting a top-ranking High Background Radiation Area: A first-time report

Aim: To study the soil bacterial population inhabiting the High Background Radiation Area (HBRA) of Chavara-Neendakara placer deposits, Kerala, India. Methodology: The study was performed by culture-dependant methods involving isolation and characterization of microbes through plate culturing and sequencing the 16S rDNA primed PCR amplicons. Results: Histochemical observations and molecular taxonomic studies through BLAST search, multiple sequence alignment of the sequences and SeaView phylogenetic analyses, resulted in identification of 35 bacterial species belonging to 22 genera. Shannon-Simpson diversity-predominance indices, revealed an over-riding presence of Firmicutes (~60%) in the HBRA soil. Interpretation: The results reveal for the first time, the composition, structure and dynamics of the bacterial population inhabiting an HBRA. Key words: Chavara-Neendakara placer deposit, Firmicutes, Gini-Simpson Index, High background radiation area, Shannon index

Dosimetric Study on Natural Background Ionizing Radiation and Impact Assessment on Public Health: A systematic Review in Nigeria

Environmental natural background ionizing radiation contamination and degradation is a global concern because of its negative effect on public health. Public health risk continues to be one of the environmental and public concerns in Nigeria. The emission of natural background ionizing radiation from the outer space, crust of the earth, food, and water and construction materials contributed a lot to the public environmental exposure. The populations’ exposure to background radiation emanated from terrestrial, cosmic, and internal radiation account for 82% which are out of control. Present work was aimed to carry out an investigational study of the natural background ionizing radiation levels, identify locations with high or low BIR and assess the health effect within Nigeria’s communities based on the available data extracted from the literatures and establish a baseline data of exposure rate, absorbed dose rate, annual effective dose equivalent, and excess life cancer risk from outdoor and indoor background radiation. This dosimetric study of natural background radiation in Nigeria is important to monitor the levels of radiation to which people are exposed directly or indirectly. Recently, several studies have been done in Nigeria and different values were reported based on indoor and outdoor background radiation doses. In this paper, a review and literature survey of natural background ionizing radiation was carried out. The data extracted based on indoor and outdoor revealed that Plateau, Oyo, River, Delta and Ondo, Sokoto, Kano and Niger have the highest value of dose rate compared to the world average value. The order of magnitude of the dose rate were Plateau > Oyo > Rive > Delta > Ondo and River > Plateau > Sokoto > Kano > Oyo > Ondo > Delta > Niger for Indoor and outdoor respectively. The highest outdoor & indoor annual effective doses were observed in OYO, Sokoto, Ondo, Delta, Akwanga, Plateau, and River. The results were comparatively greater than the world acceptable limit of 1.0 mSv/y. The order of magnitude of annual effective are OYO > Sokoto > Ondo > Niger Delta and Akwanga > Plateau > Delta > River for outdoor and indoor respectively. The regions with highest excess life cancer risks in Nigeria were observed in Oyo, Akwanga, Ondo, Plateau, River, Kaduna, Anambra, Port court, Abuja, Delta, Ibadan and Kano. Radiation cancer induction values obtained were remarkably high compared to world average value of 0.29×10-3. The amount of radiation absorbed by individual organs exposed to high natural background radiation areas were observed to be highest in tests organ, the order of magnitude were Tests > Bone marrow > Whole body > Lung > Ovaries > Kidney > Liver. But all the estimated mean values of organs doses were remarkably lower than that of world average value. Since the mean absorbed dose rate and annual effective dose in several areas is higher than 0.084µSv/h and 1.0 mSv/year for general public in many locations, long term exposure of the public to these radiations may lead to radiation induced health hazard such as erythema, skin cancer, genetic mutation and sterility.

High Environmental Radioactivity in Artisanal and Small-Scale Gold Mining in Eastern Democratic Republic of the Congo

The radioactivity associated with artisanal and small-scale gold mining activities (ASM) carried out along the Ulindi River, in the eastern Democratic Republic of the Congo, was evaluated by gamma-ray spectrometry and inductively coupled plasma–mass spectrometry of soil and sediment samples. The results revealed that activity concentrations of 238U (up to 3127 ± 98 Bq kg−1), 226Ra (up to 2710 ± 89 Bq kg−1) and 232Th (up to 2142 ± 162 Bq kg−1) were 71- to 89-fold higher than the worldwide average concentrations reported by UNSCEAR in soils. Primordial radionuclides are, thus, present in high concentrations in deposits of gold in that region and the average ambient effective radiation dose rate was determined at 8.4 mSv y−1 (range 0.5 to 40 mSv y−1). This area may be classified as a natural high background radiation area (HBRA). The radiation risk for artisanal miners and population members manipulating those geological materials were assessed through radiological parameters. such as the radium equivalent activity index (RaEq), outdoor gamma absorbed dose rate (ODRA), annual effective dose equivalent (AEDE), and excess lifetime cancer risk (ELCR). The mean values of these parameters were significantly elevated in comparison to the world average levels and indicated the existence of significant radiation risks for gold miners and members of the local population. A radiation safety policy seems needed to protect workers and the local population in this region.

The status of natural radioactivity in Nigerian environments.

Proper documentation of baseline radiation data of different environments is an important step toward adequate environmental monitoring, and it provides quick means to quantitatively check and determine possible radionuclide contamination by anthropogenic sources. Besides, such documentation is useful for decision making processes, assessment of dose rates to the public, epidemiological studies, and environmental regulations. This review summarizes the results of studies conducted on radioactivity in Nigerian environments. For most soil samples, the levels of radioactivity are well within the world averages of 33, 45, and 420Bqkg-1 for 226Ra, 232Th and 40K, respectively. Other soil samples from regions such as Abeokuta in the southwest, and Jos in the northcentral have been described as high background radiation areas with radioactivity values comparable with those obtained from known high background radiation areas such as the Odisha (formerly Orissa) coast in India (with values reported as 350, 2,825, and 180Bqkg-1 for 238U/226Ra, 232Th, and 40K, respectively). In some parts of Nigeria, surface and underground water sources used for drinking and other purposes also present elevated levels of 226Ra above the world range of 0.01 to 0.1Bql-1 and the tolerable levels recommended by the World Health Organization and U.S. Environmental Protection Agency. Corresponding radiation doses due to measured radioactivities from different environments were estimated and compared with those reported in similar studies around the world. More so, the human and environmental health hazards that might be associated with the reported radioactivity in different environmental settings are discussed. The present report is expected to support authorities in developing appropriate regulations to protect the public from radiation exposure arising from environmental radioactivity. The report also examines other areas of consideration for future studies to ensure adequate radiation monitoring in Nigeria.

Assessment of Threshold Dose of Thoron Inhalation and Its Biological Effects by Mimicking the Radiation Doses in Monazite Placer Deposits Corresponding to the Normal, Medium and Very High Natural Background Radiation Areas.

The dose contributed from thoron (220Rn) and its progeny has been neglected in the dose assessment because of its short half-life (t1/2 = 55.6s) and generally low concentrations. Recently, concentrations of 220Rn gas and its progeny were found to be pronounced in the traditional residential dwellings in China, on beaches of India and in other countries. Accordingly, we investigated the biological effects of thoron (220Rn) decay products in various mouse organs, succeeding inhalation of thoron gas in BALB/c mouse. We investigated the biological effects upon thoron inhalation on mouse organs with a focus on oxidative stress. These mice were divided into (4 random groups): sham inhalation, thoron inhalation for 1, 4 and 10days. Various tissues (lung, liver and kidney) were then collected after the time points and subjected to various biochemical analyses. Immediately after inhalation, mouse tissues were excised for gamma spectrometry and 72h post inhalation for biochemical assays. The gamma spectrometry counts and its subsequent calculation of the equivalent dose showed varied distribution in the lung, liver and kidney. Our results suggest that acute thoron inhalation showed a differential effect on the antioxidant function and exerted pathophysiological alterations via oxidative stress in organs at a higher dose. These findings suggested that thoron inhalation could alter the redox state in organs; however, its characteristics were dependent on the total redox system of the organs as well as the thoron concentration and inhalation time.

Study of certain congenital malformations due to low-level radiation exposures from high background radiation areas

The coastal regions of some states (Kerala, Tamil Nadu, Andhra Pradesh and Orissa) in India are known to have plenty of thorium-rich minerals, therefore possess high external gamma radiation fields, and are identified as Natural High Background Radiation Areas. There are concerns about congenital malformations due to the high background radiation prevailing in the region.Therefore, scientists find interest to study the possible biological effects of low-level exposures on the local populace who are living with generations under these extraordinary radiation fields. The present study is an attempt to find the correlation between the incidences of certain congenital malformations through a 1:3 matched case-control study. A total of 75 subjects (58 mental retardation cases and 17 Cleft lip/palate cases) along with 225 controls were selected for the investigations. Indoor and outdoor gamma dose rates were measured using a halogen-quenched GM tube-based survey meter, while the indoor inhalation dose rates were measured based on the radon and progeny measurements using the twin cup dosimeters equipped with LR-115 Type II solid-state nuclear track detectors. Conditional logistic regression analysis was used to find out the correlation between the radiation dose with congenital malformation. This study found an insignificant risk of cleft lip/palate (but not for mental retardation) from the exposures to natural high external gamma radiation fields in the study area. Therefore, the results of the investigation indicate no explicit risk of congenital malformations by the high background natural radiation prevailing in the region.

Thorium promotes lung, liver and kidney damage in BALB/c mouse via alterations in antioxidant systems

Thorium (232Th), long lived (14.05 billion years) most stable thorium isotope, is thrice naturally abundant than uranium. 232Th occurs as rocky deposits and black monazite sands on the earth's crust geographically distributed in coastal South India and other places globally. Monazite sand comprises of cerium and large quantities of radioactive thorium. The environmental hazard lies in monazite rich area being termed as High Background Radiation Area (HBRA). In this study, we mimicked the HBRA under controlled chamber conditions using thorium oxalate as a thorium source for BALB/c mice exposure. Furthermore, sequential radio-disintegration of 232 Th leads to thoron (220Rn), the noble gas and other daughter products/progeny predominantly via alpha decay/emissions. Such progeny tend to attach to aerosol and dust particles having potential inhalation hazard followed by alpha emissions and damages that we evaluated in mouse lung tissues post thoron inhalation. Secondly, along with the radio disintegration and alpha emission, high energy gamma is also generated that can travel to various distant organs through the systemic circulation, as significant findings of our study as damages to the liver and kidney. The mechanistic findings include the damages to the hematological, immunological and cellular antioxidant systems along with activation of canonical NF-κβ pathway via double stranded DNA damage.

Path Analysis : Public Health Impacts Overview in High Natural Background Radiation Area in Botteng, West Sulawesi of Indonesia

Introduction: The effect of ionizing radiation exposure in a human being is chromosome aberrations. Botteng has the highest annual radiation exposure rate in Indonesia, which is 6,15 ± 0,81 mSv/year. The people in Botteng were exposed to the low dose radiation, continuously. The purpose of this research is to describe the pathway radiation exposured to inhabitants and the cytogenetic response in the high natural background radiation area.Methods : This is a statistical research by cross-sectional. The population is 61 residents, who were chosen randomly from 9 different exposure rate areas. Path analysis model is used to determine the linearity relationship between internal and external radiation dose to the frequency of chromosomal aberrations in lymphocyte cells.Results: The results concluded that the external radiation dose rate is 5.49 mSv / year, the internal radiation dose rate is 10.34 mSv / year, the effective dose rate of lymphocyte cells is 1.92 mSv / year, and the mean of chromosome aberrations frequency is 0.00082 of approximately 14,695 metaphase cells observed. The result of the analysis showed that there was no significant correlation between the external dose and the chromosome aberrations frequency. There is a linear relationship between the internal dose and the chromosome aberrations frequency (f count = 6,634 and p-value 0,013 <0,05). The internal and external radiation dose simultaneously affects the effective dose (R2 = 0.901, p-value = 0,000> 0.05), The Internal and external radiation doses affect the chromosome aberrations frequency of peripheral blood lymphocytes only through effective doses (R2 = 0.093, p-value = 0.017> 0.05)Conclusion: this study provide an effective recommendation for further research as an effort to improve public health in areas with high natural background radiation.

The Effects of High Level Natural Radiation in Mamuju - Indonesia on the Immune System of Its Residents

The immune system is one of the most significant defenses against environmental insults including natural radiation. The purpose of this preliminary study was to assess the effects of high natural radiation to Mamuju residents, by focusing on immune-related blood cell counts (leukocytes, lymphocytes, monocytes, and granulocytes) and immunoglobulin E (IgE) level. The blood samples were collected from 18 adult residents in a high background radiation area (HBRA) while 18 residents in a normal background radiation area (NBRA) served as a control group. The blood components were measured by using the hematopoietic analyzer, and IgE immune biomarker was measured with ELISA (enzyme-linked immunosorbent assay) according to standard protocols. The data showed that the level of all blood cells, except for monocytes, of residents in HBRA was higher than that of NBRA. Statistical analysis revealed that there was no significant difference ( P >0.05) in the blood cell counts and IgE level in both groups and their values were within normal limits. The level of IgE in HBRA was significantly higher than the control area ( P ≤0.05), as its IgE level in males compared to females in both residents. The relationship between IgE level and age were negative in these residents. From this study, it was concluded that long-term exposure to high radiation may affect the immune system as one of radiation adaptive response.

Radiation exposure in a region with natural high background radiation originated from rare earth element deposits at Bat Xat district, Vietnam.

Surface deposits of rare earth element (REE) were identified in the Bat Xat district, Northern Vietnam. As the area is inhabited, an in-depth investigation was carried out to assess the radioactivity levels and to evaluate the radiation exposure and radiological risks for the population. Samples of REE ore, soils, water and several foods locally produced were collected and analyzed by gamma spectrometry for determination of 232Th, 226Ra, and 40K. Radon (222Rn and 220Rn) measurements were carried out in dwellings at the villages located near by the REE deposit area, and in Hanoi for comparison. Based on the measured radionuclide concentrations, several radiological parameters were calculated to evaluate the radiological risks for the population and to compare with worldwide values. Results indicate that the representative person of the most exposed group living near the REE deposits may receive a total annual effective dose as high as 37.9 ± 10.6mSv, i.e., approximately 16 times the world average dose of 2.4mSv y-1. Consequently, this area should be considered a high background radiation area. Exposure to external radiation and internal radiation from ingestion and inhalation of radionuclides were assessed separately. Radon inhalation contributed to approximately 70% of the total annual effective dose, with both radon isotopes contributing significantly, while the ingestion of local foods and water gave minor contributions to the total effective dose. Several measures were considered to improve the radiation safety and recommendations are given to relocate the most exposed members of the population.