Unraveling radiation resistance strategies in two bacterial strains from the high background radiation area of Chavara-Neendakara: A comprehensive whole genome analysis.

This paper reports the results of gamma irradiation experiments and whole genome sequencing (WGS) performed on vegetative cells of two radiation resistant bacterial strains, Metabacillus halosaccharovorans (VITHBRA001) and Bacillus paralicheniformis (VITHBRA024) (D10 values 2.32 kGy and 1.42 kGy, respectively), inhabiting the top-ranking high background radiation area (HBRA) of Chavara-Neendakara placer deposit (Kerala, India). The present investigation has been carried out in the context that information on strategies of bacteria having mid-range resistance for gamma radiation is inadequate. WGS, annotation, COG and KEGG analyses and manual curation of genes helped us address the possible pathways involved in the major domains of radiation resistance, involving recombination repair, base excision repair, nucleotide excision repair and mismatch repair, and the antioxidant genes, which the candidate could activate to survive under ionizing radiation. Additionally, with the help of these data, we could compare the candidate strains with that of the extremely radiation resistant model bacterium Deinococccus radiodurans, so as to find the commonalities existing in their strategies of resistance on the one hand, and also the rationale behind the difference in D10, on the other. Genomic analysis of VITHBRA001 and VITHBRA024 has further helped us ascertain the difference in capability of radiation resistance between the two strains. Significantly, the genes such as uvsE (NER), frnE (protein protection), ppk1 and ppx (non-enzymatic metabolite production) and those for carotenoid biosynthesis, are endogenous to VITHBRA001, but absent in VITHBRA024, which could explain the former's better radiation resistance. Further, this is the first-time study performed on any bacterial population inhabiting an HBRA. This study also brings forward the two species whose radiation resistance has not been reported thus far, and add to the knowledge on radiation resistant capabilities of the phylum Firmicutes which are abundantly observed in extreme environment.

Radioactivity and elemental oxidation composition in soil from Yangjiang, a high background natural radiation area, China.

Soil is an important source and medium of radionuclides, and the content of radioactivity in soil is crucial for radiological impact evaluation. In this study, twenty soil samples in the high background natural radiation area of Yangjiang, China were collected and analyzed for 226Ra, 232Th, 40K and 137Cs concentrations in order to evaluate the radiological health risk in the area. Results showed that the average activity concentrations of 226Ra, 232Th and 40K are 66 Bq/kg, 109 Bq/kg and 211 Bq/kg, respectively. The calculated radiological parameters of radium equivalent activity (Raeq), absorbed dose rate (D), annual effective dose equivalent (AEDE), internal and external hazard indices (Hin and Hex) show a large variation at different sampling sites. Additionally, the elemental oxidation composition and 40K/K mass ratio in the soil were analyzed to further augment the background information of the high background radiation area in Yangjiang.

Investigation of natural and artificial radioactivity levels in travertines of the Cappadocia region in Turkey.

This study determined natural and artificial radionuclide concentrations to evaluate natural radioactivity and health risk levels of nine travertines in the Yaprakhisar and Balkayasi regions in Turkey. The samples coded B1-M, B2, B5, B7, B8, and B10 represent waste derived from the Yaprakhisar travertines, as well as samples T5-M, T12, and Z1 travertines derived from Balkayasi. The levels of natural and artificial radionuclide concentrations (232Th, 40K, and 137Cs) were measured using a high-purity germanium (HpGe) detector system. The travertine activity ranged from 2.09 to 12.07 Bq kg-1 for 232Th, 4.21 to 13.41 Bq kg-1 for 40K, and 0.42-3.26 Bq kg-1 for 137Cs. The results showed that the activity concentration values for 232Th, 40K, and 137Cs were coherent with the travertine analysis results in the UNSCEAR, 2000; 2008 publications. The values obtained were lower than the average values in the UNSEAR reports. The radiological hazard parameters calculated in this study were absorbed gamma dose rate (D), radium equivalent activity (Raeq), annual gonadal dose equivalent (AGDE), exposure dose (ER), total annual effective dose (AEDEtotal), excess lifetime cancer risk (ELCRtotal), gamma representative level (GRL), internal hazard index (Hin) and external hazard index (Hex).

Natural radionuclides and radiological risk assessment in the stream and river sediments of a high background natural radiation area Kanyakumari, India.

The Kanyakumari coast is known to be a high background natural radiation area due to the placer deposits of heavy minerals such as ilmenite, monazite, and rutile. The Kanyakumari river sediments that could be the source of the elevated amounts of natural radionuclides in the coastal sands have been studied in this paper. The activity concentrations of primordial radionuclides 226Ra, 232Th, and 40K were determined using high-purity germanium (HPGe) gamma-ray spectrometry. The mean activity concentrations of 226Ra, 232Th, and 40K were found to be 75 Bq kg-1, 565 Bq kg-1, and 360 Bq kg-1, respectively. The mean absorbed dose rate was 395 nGy h-1. Radiological hazard parameters were studied and compared with the world average values. The contribution of 232Th to the total dose rate was found to be higher than that of the two other radionuclides. The high mean ratio of 232Th/226Ra suggested an enrichment of 232Th and the occurrence of 226Ra leaching due to an oxidizing environment. Principal component analysis (PCA) was carried out for the radionuclides in order to discriminate the source of the sediments. This study provides new insights into the distribution of natural radionuclides in sediments of rivers and streams.

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.

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 11 945.1nGyh-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.

Annual gamma-ray background dose rates in dwellings of rural Tumkur.

The exposure to high levels of ionising radiation can cause severe health risks including cancer. The monitoring of background radiation is a primary task of nuclear scientists and researchers in the present day. The aim of the present work is to measure effective annual dose rate due to gamma-ray background radiation in dwellings of selected villages around Tumkur. It is very important to monitor background radiation in dwellings to safeguard from the harmful effects of gamma-ray background radiation. The dose rates in dwellings were measured using a German-made portable gamma dosemeter, Gamma-Scout. The measured annual dose rates were in the range of 1.103-2.824 mSv/y. From this survey, it was observed that the average annual dose rate for dwellings under study area with concrete ceiling and tiles floor are comparatively higher than the dwellings with griddle ceiling and stone floor.

Estimation of radiation dose due to thoron and progeny inhalation in high background natural radiation area of Odisha, India.

Results of the preliminary measurements of indoor radon, thoron and progeny concentrations showed very high values of thoron concentrations in the eastern coastal region of Odisha, India. Therefore, measurements of thoron and its progeny concentrations were extended to a larger number of houses in this area for the assessment of the radiation dose received by the public. The measured values of thoron concentrations were used for the calculation of annual effective doses. The estimated values of the annual effective dose due to thoron exposure were observed in the range of 0.2-14.7 mSv. The estimated radiation doses responsible for thoron exposure were observed considerably high in the region. The results obtained are compared with those obtained in other studies performed so far in the study area and a review of different studies involving different measurement techniques is presented in the paper. The results of this study support the preliminary studies showing high values of thoron levels in the study area.

Distribution of naturally occurring radionuclides and gamma dose rate assessment in the soils of high background natural radiation area Odisha, India.

A study on the activity concentration of primordial radionuclides 226Ra, 232Th and 40K was carried out on the surface soil samples collected from the coastal villages between Chhatrapur and Gopalpur regions of high background natural radiation area Odisha, India, using high purity germanium gamma spectroscopy. The mean activity concentrations of 226Ra, 232Th and 40K were found to be 231, 1692 and 250 Bq/kg, respectively. The total mean absorbed dose owing to the presence of 226Ra, 232Th and 40K was 1139 nGy/h. The mean annual effective dose was found to be 1397 µSv/y and higher than the UNSCEAR average value 70 µSv/y.

Monitoring of outdoor natural gamma absorbed dose rate in air in Hyderabad, Telangana, India.

The Indian Environmental Radiation Monitoring Network continuously monitors the outdoor natural gamma absorbed dose rate in air at different locations throughout India by employing Geiger-Mueller (GM) detector-based field-installed environmental radiation monitors (ERMs). Hyderabad, Telangana, India is known to have high natural background radiation levels due to the presence of high concentrations of primordial radionuclides in its granitic rocks. There are a total of 59 ERMs installed at various locations across Hyderabad. Long-term monitoring data of these locations are presented in this paper. The mean values of outdoor natural gamma absorbed dose rate in air at the monitoring locations were found to vary in the range of 104-258 nGy.h-1 with a mean of 193 ± 40 nGy.h-1. The mean annual effective dose due to outdoor natural gamma radiation was estimated to be 0.24 ± 0.05 mSv.y-1. Analysis of the long-term seasonal variation of outdoor natural gamma absorbed dose rate in air showed that the same was lowest during monsoons.

Hydrogen transfer reactions via organic radicals in gamma-irradiated chibaite.

Chibaite, a silica-framework structure with cage-like voids occupied by gaseous molecules, was found in marine sediments. Its formation age could be evaluated using electron spin resonance (ESR) if the radicals formed by natural radiation can be assumed to accumulate over time. To investigate whether hydrogen transfer reactions, where organic radicals withdraw hydrogen atoms from other molecules in adjacent cages, occur in chibaite and affect ESR dating, gamma-irradiated chibaite was measured by ESR. Methyl, ethyl, n-propyl, isopropyl, tert-butyl radicals and hydrogen atoms were created by gamma irradiation at 77 K. The amount of tert-butyl radicals increased around 240 K and the similar amount of the other organic radicals decreased simultaneously, implying that hydrogen transfer reactions occur between isobutane and the organic radicals in chibaite around 240 K and therefore would have no influence on ESR dating because the reactions are completed at the environmental temperature.

Geological control of terrestrial background radiation in Garhwal Himalaya, India.

Activity concentrations of 226Ra, 232Th, and 40K were measured in soil samples from several areas of Garhwal Himalaya, Northern India, by gamma-ray spectrometry. In this region, which extends around the Himalayan Main Central Thrust, a tectonic line that separates several geological provinces, background levels of natural terrestrial radiation were assessed. The maximum levels of radium, 285 Bq/kg and 136 Bq/kg, respectively, were found in the Budhakedar and Uttarkashi regions, exceeding the world average value of 35 Bq/kg. The mean radiation levels were found to be different between the areas, which reflects the geological diversity in the region. The overall absorbed dose rate owing to radionuclide presence in the Uttarkashi area ranged from 79 to 188 nGyh-1, with an average of 118 nGyh-1. That is more than UNSCEAR's world-populated weighted average value of 59 nGyh-1. The present investigation indicated that the absorbed dose rates are greater in Uttarkashi and Budhakedar than in other places. The multiple comparison analysis between geology and absorbed dose rate shows that the geology of Uttarkashi and Budhakedar are statistically similar. According to several hazard indices, terrestrial background radiation is not of radiological concern in the investigated region.

Background radiation and cancer risks: A major intellectual confrontation within the domain of radiation genetics with multiple converging biological disciplines.

This paper assesses the judgments of leading radiation geneticists and cancer risk assessment scientists from the mid-1950s to mid-1970s that background radiation has a significant effect on human genetic disease and cancer incidence. This assumption was adopted by the National Academy of Sciences (NAS) Biological Effects of Atomic Radiation (BEAR) I Genetics Panel for genetic diseases and subsequently applied to cancer risk assessment by other leading individuals/advisory groups (e.g., International Commission on Radiation Protection-ICRP). These recommendations assumed that a sizeable proportion of human mutations originated from background radiation due to cumulative exposure over prolonged reproductive periods and the linear nature of the dose-response. This paper shows that the assumption that background radiation is a significant cause of spontaneous mutation, genetic diseases, and cancer incidence is not supported by experimental and epidemiological findings, and discredits erroneous risk assessments that improperly influenced the recommendations of national and international advisory committees, risk assessment policies, and beliefs worldwide.

Car-borne survey and dose assessment from external radiation exposure in Bangka Island.

With a history of more than 200 years of tin mining, Bangka Island has brought along a byproduct of heavy minerals containing radionuclide elements. There are some concerns about this byproduct material contributing to natural radiation in the environment. In this study, a car-borne survey was conducted to accurately assess natural background radiation in Bangka Island. Indoor and outdoor ambient dose rates in 146 houses were also measured to assess the radiation dose from external exposure received by the public. Soil samples were collected and measured using a gamma spectroscopy system to evaluate the contributions of specific radionuclides to external terrestrial exposure. From 3790 measurement points during the car-borne survey, the highest ambient dose equivalent rate was 596 nSv h-1 measured in Muntok area, with a mean value of 101 nSv h-1 and a median value of 95 nSv h-1. The ambient dose equivalent rate distribution map showed a relatively higher value in the northern coastal area of the island, where the Pemali tin deposit is located. The annual effective dose received from external radiation in the 146 houses in Bangka Island ranged from 0.44 to 1.30 mSv year-1, with a median value of 0.66 mSv year-1. The soil contained a relatively high amount of thorium (232Th), which contributed 69% to external radiation exposure in Bangka Island.

Why Low-level Radiation Exposure Should Not Be Feared.

ABSTRACT: The purpose of this paper is to address the public fear that is usually associated with low-level radiation exposure situations. Its ultimate objective is to provide persuasive assurances to informed but skeptical members of the public that exposure situations involving low-level radiation are not to be feared. Unfortunately, just acquiescing to an unsupportive public fear of low-level radiation is not without consequences. It is causing severe disruptions to the benefits that harnessed radiation can produce for the well-being of all humanity. In this pursuit, the paper provides the scientific and epistemological basis needed for regulatory reform by reviewing the history in quantifying, understanding, modeling, and controlling radiation exposure, including some of the evolving contributions of the United Nations Scientific Committee on the Effects of Atomic Radiation, the International Commission on Radiological Protection, and the myriad of international and intergovernmental organizations establishing radiation safety standards. It also explores the various interpretations of the linear no-threshold model and the insights gained from radiation pathologists, radiation epidemiologists, radiation biologists, and radiation protectionists. Given that the linear no-threshold model is so deeply imbedded in current radiation exposure guidance, despite the lack of a solid scientific base on the actually proven radiation effects at low-doses, the paper suggests near-term ways to improve regulatory implementation and better serve the public by excluding and/or exempting trivial low-dose situations from the regulatory scope. Several examples are given where the unsubstantiated public fear of low-level radiation has resulted in crippling the beneficial effects that controlled radiation offers to a modern society.

Countrywide monitoring of absorbed dose rate in air due to outdoor natural gamma radiation in India.

The Indian Environmental Radiation Monitoring Network continuously monitors, throughout India, the absorbed dose rate in air due to outdoor natural gamma radiation, by using Geiger-Mueller detector-based standalone environmental radiation monitors. The network consists of 546 monitors spread across 91 monitoring locations distributed all over the country. In this paper, the countrywide long-term monitoring results are summarised. The measured mean dose rate of the monitoring locations followed a log-normal distribution and ranged from 50 to 535 nGy.h-1 with a median value of 91 nGy.h-1. Due to outdoor natural gamma radiation, the average annual effective dose was estimated to be 0.11 mSv.y-1.

Cold season dose rate contributions from gamma, radon, thoron or progeny in legacy mines with high natural background radiation.

In areas with high natural background radiation, underground cavities tend to have high levels of airborne radionuclides. Within mines, occupancy may involve significant exposure to airborne radionuclides like radon (222Rn), thoron (220Rn) and progeny. The Fen carbonatite complex in Norway has legacy mines going through bedrock with significantly elevated levels of uranium (238U) and especially thorium (232Th), and significant levels of their progeny 222Rn and 220Rn. There are also significantly elevated levels of gamma radiation in these mines. These mines are naturally chimney ventilated and release large volumes of air to the outdoors giving a large local outdoor impact. We placed alpha track detectors at several localities within these mines to measure airborne radionuclides and measured gamma radiation of bedrock at each locality. The bedrock within the mines shows levels up to 1900 Bq kg-1 for 238U, 12 000 Bq kg-1 for 232Th and gamma dose rates up to 11 µSv h-1. Maximum levels of airborne radionuclides were 45 000 Bq m-3 for 220Rn and 6900 Bq m-3 for 222Rn. In addition, we measured levels of thoron progeny (TnP). In order to estimate radiation dose contribution, TnP should be assessed rather than 220Rn, but deposition-based detectors may be biased by the airflow of mine-draft. We present dose rate contributions using UNSCEAR dose conversion factors, and correcting for airflow bias, finding a combined cold season dose rate within these mines of 17-24 µSv h-1. Interestingly, fractional dose rate contributions vary from 0.02 to 0.6 for gamma, 0.33 to 0.95 for radon and 0.1 to 0.25 for TnP.

Assessing the radiation contamination of large areas using advanced technologies.

Military, disaster management and in many cases civilian tasks include surveying of a given section of terrain that is likely to be contaminated with radioactive materials. Such a measurement series can form the basis for the complete recultivation and decontamination of large areas. This survey can take place after an emergency situation. This paper will use concrete surveys to illustrate the efficiency of new measurement technologies and developments. All these technologies aim to carry out radiation reconnaissance tasks as quickly and accurately as possible. Different hot spots were found during on-foot radiation reconnaissance. During in-situ measurements, a Bayesian-based isotope identifying algorithm was used and the measured data were validated with results from gamma spectroscopy in the laboratory. A rapid on-site quantitative analysis was also performed by evaluating the samples taken next to the hot spots. In addition to the measurement, the data were generated and stored in a standard N42 format ideal for data exchange. Many issues were solved like how the measurement data are associated with relevant additional information (e.g. time and coordinate), and how the measurement results can be shared with other partner organisations. Another important consideration was the preparation of the team conducting the measurement. The total cost of the survey was significantly reduced by the fact that the measurement was manageable by one technician and one expert. A quality assurance system had to be established to meet all relevant standards and strict documentation requirements. In addition to operating at high background radiation, these measurements presented additional challenges due to the low activity of hidden and mixed radioactive sources.

Recent review of natural and artificial background radiation dosimetry studies in Saudi Arabia.

This paper includes a review of the natural background radiation of the Kingdom of Saudi Arabia. The review deals with natural radioactivity measurements conducted in the past few decades in the Kingdom. The numerous research works reviewed refer to different materials soils processed building material, terrestrial (dwellings) and mining sites. For the measurements, different experimental techniques were adopted. The highest mean specific activity of 238U, 232Th and 40 K in soil samples was found to be 39.0, 25.6, and 343.0 Bq/kg, respectively. While the world average values are 33, 45 and 420 Bq/kg, respectively. For building materials, the highest mean values for 226Ra, 232Th and 40 K were 89, 106 and 773 Bq/kg, respectively. The mean indoor and outdoor dose rates were 455 µGy/y (Riyadh City) and 883 µGy/y (Al-Khamis City), respectively. For the mining sites the mean values for 238U, 226Ra, 228Ra, gross α and gross ß, were 0.12, 0.33, 21, 0.78 and 2.44 Bq/kg, respectively. Based on the available data it is concluded that most of the natural background radiation levels in the measured locations were within acceptable limits, while a few isolated locations showed elevated dose rates. This review suggests that new improved radiological survey methods be employed to cover the entire country, and that areas identified with comparably high dose rates be re-assessed, especially, in dwellings and mining sites.

Radiogeochemistry, mineralogy, lithology, radiogenic heat production, and health implication using airborne radiometric data of Ilesha and its surroundings.

The current study analyzed and interpreted airborne radiometric data from Ilesha's basement complex rock and its surroundings. At the surface, the concentrations of the most frequent primordial radionuclides notably K, elemental concentration of uranium eU, and elemental concentration of thorium eTh were measured. The weighted mean elemental and activity concentrations were 0.85%, 2.75 ppm, 10.22 ppm, and 267.54 Bq kg-1, 34.41 Bq kg-1, 41.51 Bq kg-1 for 40 K, 238U, and 232Th, respectively. The low concentration of 40 K was certainly due to the effects of weathering, kaolinization of granites, and pedogenesis activities. The abundance of uranium was ascribed to the availability of uranium minerals such as allanite, apatite, and sphene with accessories minerals, while that of thorium was due to minerals such as cheralite, thorite, uranothorite, thorianite, and uranothorianite with accessories minerals. The RPHR weighted mean 1.48 µWm-3 compared to the earth's crust mean between 0.8 and1.2 µWm-3 was higher due to significant presence of gneiss rocks in all the studied profiles. Radiological hazard, in particular, dose rates, external hazard index, internal hazard index, radium equivalent, annual gonadal dose, effective dose dispensed to various organs of the body were computed to determine the deleterious effects of rocks in the area. The weighted means of annual gonadal dose of 363.98 µSv y-1 and outdoor 0.91 × 10×3 and indoor 1.65 × 10-3 excessive life cancer risks were more than the global average 300 µSv y-1, 0.29 × 10-3 and 1.16 × 10-3. As a result, proper surveillance is required in the area in order to prevent epidemics occurrence in future.