Threshold Dose Rate Research Articles

RADIOLOGICAL EVALUATION OF THE CONCENTRATION AND IMPACT OF OIL AND GAS ACTIVITIES IN ERUEMUKOHWARIEN AREA OF SOUTHERN NIGERIA

The study was carried out in-situ using a Radalert 100 nuclear radiation monitor and a geographical positioning system (GPS). Five facilities were investigated at the rig site which included the rig site host community as well as the camp site for the oil workers at Ekapkamreh town. Ten 10 sampling locations were evaluated at a total of 60 study points. The values obtained range between 0.115±0.018 (µSv/hr) and 0.299±0.040 (µSv/hr) for the rig site environment, 0.111±0.006 (µSv/hr) and 0.337±0.031 (µSv/hr) for field logistic base (offices and workshops), 0.114±0.011 (µSv/hr) and 0.312±0.021 (µSv/hr) for components of the mud circulation section. Also, the radiological concentration of the Chemical Store ranged between 0.126±0.019 (µSv/hr) and 1.181±0.104 (µSv/hr), while the radiological values obtained from other facilities within the rig site ranged from 0.155±0.026 (µSv/hr) and 0.249±0.026 (µSv/hr). Radiation readings obtained for soil ranged from 0.149±0.05 (µSv/hr) to 0.219±0.025 (µSv/hr) and 0.114±0.039 (µSv/hr) to 0.219±0.051 (µSv/hr) respectively at the host community and camp site. Most of the results obtained showed that the general environment of the rig site is slightly above the permissible absorbed dose rate threshold of 0.15(µSv/hr) recommended by the United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in 2009. However, the exposure rates exceed the standard background level of 13µR/hr (coequal to 0.13µSv/hr). There is high tendency for the industry workers to be exposed to radiation with time.

220.6: Effective radiation dose and bone marrow radiation exposure as a result of radiological investigation in a cohort of multivisceral transplant patients

Introduction: A patient who experienced a rare form of leukaemia following multivisceral transplantation prompted an investigation of cumulative radiation exposure due to radiological investigations in a cohort of multivisceral transplant patients from our centre. In addition, bone marrow dosimetry was calculated in view of the high incidence of bone marrow suppression in this group of patients. Methods: Dose data for CT examinations was retrospectively collected using PACS. Effective doses for each phase of each scan were estimated using 2016 updated conversion coefficients. The total number of scans and total effective dose were calculated for each patient and the stochastic risks for general cancer risk of 4.1%/Sv and leukaemia risk of 0.63%/Sv stated by the International Commission on Radiological Protection (ICRP) were estimated. Bone marrow dose per Dose-Length-Product (DLP) conversion factors were created for each anatomical region using the ImPACT Calculator, which allowed total bone marrow doses to be estimated for each patient. Bone marrow dose rates were compared against the acute radiation dose rate threshold for reduced haematopoiesis of 0.25–0.5 Gy/year suggested by the ICRP. Results: Radiation doses were calculated for 80 patients undergoing multivisceral transplant procedures (+/- liver) at Addenbrooke’s Hospital, Cambridge UK between 1998 and 2018. The average age was 49 years (range 16 – 61). The majority of the radiation dose was incurred by CT scans – 1700 in total over an average of 4.4 years per patient (SD 2.6yrs). Mean number of scan phases per patient was 33.7 (SD 17.8). Maximum number of scan phases for one patient was 83. Mean effective dose was 291 mSv (SD 224 mSv), Maximum effective dose was 1057 mSv (4.3% general cancer risk, 1.1% Leukaemia risk). 5 patients received cumulative doses in excess of 800mSv and 2 exceeded 1Sv. The highest bone marrow dose was 0.66Gy, 0.4Gy/month. 74 patients exceeded the ICRP recommended limit of 0.02 Gy/month and 11 exceeded 0.25 Gy/year and 11 patients exceeded the monthly threshold for >120 days. Conclusions: Significant radiation exposure is experienced by this cohort of patients and the threshold dose rate for reduced haematopoiesis is often exceeded with significant potential implications for the development of cancer and bone marrow suppression.

Effects of 90Sr on Tree Swallow Nestlings Near Groundwater Contaminant Plumes.

Discharge of groundwater contaminant plumes has created elevated concentrations of Sr in some aquatic sediments at Chalk River Laboratories. Tree swallows (Tachycenita bicolor) feed and supply their nestlings almost exclusively with airborne insects that developed as larvae in aquatic sediments. To monitor the uptake and test for potential detriment due to Sr in a terrestrial animal, we measured the gross beta concentrations in the bone of 12-d-old tree swallow nestlings in areas having sediments with elevated levels of gross beta (Sr and Y) and in several control areas where sediment gross beta was primarily due to naturally occurring K. Nesting behavior and reproductive success of the tree swallows were similar regardless of the gross beta concentrations in sediments near their nest boxes. Radiation can damage DNA and cause micronuclei to form in cells, so we examined the frequency of micronuclei in erythrocytes of nestlings. The formation of micronuclei in the erythrocytes of the nestlings was also similar wherever nestlings were analyzed. The results revealed no significant increases even near sediments with the highest gross beta levels. At Perch Lake, where Chalk River Laboratories has a large area of Sr-contaminated sediments, the bones of 12-d-old nestlings contained gross beta concentrations as high as 29 Bq g. This would produce a skeletal dose rate of 9 μGy h, which is one-fourth of the threshold dose rate of 40 μGy h, above which detriment could occur. Failing to find any indication of detriment in the field study, we irradiated wild eggs in the lab and returned them to their nest for natural incubation, hatching, and feeding by the parents. There was an increase in formation of micronuclei following a dose of 3.2 Gy, and the other results were consistent with existing literature.

Impact of TID on latch up induced by pulsed irradiation in CMOS circuits

Latch up (LU), an inherent destructive phenomenon owning to P-N-P-N structure in bulk Complementary Metal-Oxide -Silicon (CMOS) circuits, is highly sensitive to pulsed irradiation. A criterion for LU is concluded, and the impact of total ionizing dose (TID) on LU criterion is discussed. In the progress of accumulating TID, generated oxide trapped charges and interface states enhance surface recombination in the base of the parasitic bipolar junction transistor (PBJT), leading to increase of the base recombination current; and the trapped charges in the shallow trench isolation (STI) can also increase leakage current. In spite of hindering effect of the base recombination in PBJTs to LU, the STI leakage current plays a dominant role to gain sensitivity of LU. Experimental results confirm the fact that TID can lower the dose rate threshold for LU. For instance, the threshold in the device with doses 150 krad(Si) is nearly 50% lower than that in the pristine device. Simulations in SPICE and Sentaurus are conducted, and the results agree with that of experiments.

Evidence of a Dose-Rate Threshold for Life Span Reduction of Dogs Exposed Lifelong to γ-Radiation.

Our return to a study on dogs exposed lifelong to cobalt-60 γ-radiation was prompted by a comment that data in dog studies have large statistical errors due to the small number of dogs. We located an earlier article on the same study that had a better mortality curve for the dogs in each dose-rate group. The median life span of the dogs in each group was tabulated, and the standard error of each was calculated. No statistically significant shortening of median life span was observed for the lowest dose-rate group at any reasonable significance level (P value: .005-.05), whereas for dogs with higher irradiation rates, life span shortening was statistically significant at highest reasonable significance level (P value: .005). The results were entered on a graph of life span versus dose rate, assuming a threshold dose–response model. The fitted line indicates that the dose-rate threshold for γ-radiation induced life span reduction is about 600 mGy per year, which is close to the value we found previously. Making allowance for the calculated standard errors, we conclude that this threshold is in the range from 300 to 1100 mGy per year. This evidence is relevant for emergency measures actions (evacuation of residents) and for nuclear waste management.

In situ oxidation and reduction of cerium dioxide nanoparticles studied by scanning transmission electron microscopy

Cerium dioxide nanocubes and truncated octahedra were reduced and oxidized in the scanning transmission electron microscope. The reduction process was stimulated by the electron beam and oxidation was supported by background gases in the microscope environment. High-angle annular dark field imaging is sensitive to local lattice distortions that arise as oxygen vacancies are created and cerium cations reduce enabling high spatial resolution characterization of this process with temporal resolution on the order of seconds. Such measurements enable us to differentiate and infer that the observed behavior between the nanocubes and truncated octahedra may be due to the difference in crystallographic termination of surfaces. In situ measurements taken with different partial pressures of oxygen reveal the cerium oxidation state and the dose rate threshold for the onset of beam reduction are influenced by the environment. Increasing oxygen partial pressure reduces the Ce3+ content and decreases susceptibility to electron beam driven reduction.

MTH1, an 8-oxo-2'-deoxyguanosine triphosphatase, and MYH, a DNA glycosylase, cooperate to inhibit mutations induced by chronic exposure to oxidative stress of ionising radiation.

Our previous results showed that in addition to the immediate interaction of ionising radiation with DNA (direct and indirect effect), low-dose and chronic low-dose rate of irradiation induce endogenous oxidative stress. During oxidative stress, free radicals react with DNA, nucleoside triphosphates (dNTPs), proteins and lipids, and modify their structures. The MYH and MTH1 genes play important roles in preventing mutations induced by 8-hydroxy-guanine, which is an oxidised product of guanine. In this study, we used short-hairpin RNA to permanently knockdown MYH and MTH1 proteins in human lymphoblastoid TK6 cells. Knockdown and wild-type cells were chronically exposed to low dose rates of γ-radiation (between 1.4 and 30 mGy/h). The cells were also subjected to acute doses delivered at a high-dose rate. Growth rate, extracellular 8-hydroxy-2'-deoxyguanosine, clonogenic cell survival and mutant frequencies were analysed in all cell types. A reduced level of cell growth and survival as well as increased mutant frequencies were observed in cells lacking both MYH and MTH1 proteins as compared to cells lacking only MYH and wild-type cells. To sum up, our results suggest that low-dose rates elevate oxidative stress. MTH1 together with MYH plays an important role in protection against mutations induced by modified dNTPs during chronic oxidative stress. In addition, we found no dose-rate effect at the level of mutations in the wild-type TK6 and MYH-KD cells. Our data interestingly indicate a dose-rate threshold for mutation induction in MTH1/MYH double knockdown cells.

In situ TEM study of electron-beam radiation induced boron diffusion and effects on phase and microstructure evolution in nanostructured CoFeB/SiO2 thin film

Using in situ transmission electron microscopy (TEM), we studied boron diffusion and segregation in CoFeB/SiO2 nanostructured thin film stacks. We also investigated how these phenomena affected the phase and microstructure of CoFeB thin films under electron beam irradiation at 300 kV. A unique phase transformation was observed in CoFeB thin films under high-dose electron irradiation, from a polycrystalline Co3Fe to a unilateral amorphous phase of Co3Fe and nanocrystalline FexCo23−xB6. The unilateral amorphization of the Co3Fe film showed an electron-dose-rate sensitivity with a threshold dose rate. Detailed in situ TEM studies revealed that the unilateral amorphization of the Co3Fe film arose from boron segregation at the bottom of the Co3Fe thin film induced by radiation-enhanced diffusion of boron atoms that were displaced by electron knock-on effects. The radiation-induced nanocrystallization of FexCo23−xB6 was also found to be dose-rate sensitive with a higher electron beam current leading to earlier nucleation and more rapid grain growth. The nanocrystallization of FexCo23−xB6 occurred preferentially at the CoFeB/SiO2 interface. Kinetic studies by in situ TEM revealed the surface crystallization and diffusion-controlled nucleation and grain growth mechanisms. The radiation-enhanced atomic diffusivity and high-concentration of radiation-induced point defects at the Co3Fe/SiO2 interface enhanced the local short-range ordering of Fe, Co, and B atoms, favoring nucleation and grain growth of FexCo23−xB6 at the interface.

Lower thresholds for lifetime health effects in mammals from high-LET radiation – Comparison with chronic low-LET radiation

Lower threshold dose rates and confidence limits are quantified for lifetime radiation effects in mammalian animals from internally deposited alpha-emitting radionuclides. Extensive datasets on effects from internal alpha-emitters are compiled from the International Radiobiological Archives. In total, the compiled database includes 257 records, which are analyzed by means of non-parametric order statistics. The generic lower threshold for alpha-emitters in mammalian animals (combined datasets) is 6.6·10−5 Gy day−1. Thresholds for individual alpha-emitting elements differ considerably: plutonium and americium - 2.0·10−5 Gy day−1; radium – 2.1·10−4 Gy day−1. Threshold for chronic low-LET radiation is previously estimated at 1·10−3 Gy day−1.For low exposures, the following values of alpha radiation weighting factor wR for internally deposited alpha-emitters in mammals are quantified: wR(α) = 15 as a generic value for the whole group of alpha-emitters; wR(Pu) = 50 for plutonium; wR(Am) = 50 for americium; wR(Ra) = 5 for radium. These values are proposed to serve as radiation weighting factors in calculations of equivalent doses to non-human biota.The lower threshold dose rate for long-lived mammals (dogs) is significantly lower than comparing with the threshold for short-lived mammals (mice): 2.7·10−5 Gy day−1, and 2.0·10−4 Gy day−1, respectively. The difference in thresholds is exactly reflecting the relationship between the natural longevity of these two species.Graded scale of severity in lifetime radiation effects in mammals is developed, based on compiled datasets. Being placed on the severity scale, the effects of internal alpha-emitters are situated in the zones of considerably lower dose rates than effects of the same severity caused by low-LET radiation. RBE values, calculated for effects of equal severity, are found to depend on the intensity of chronic exposure: different RBE values are characteristic for low, moderate, and high lifetime exposures (30, 70, and 13, respectively).The results of the study provide a basis for selecting correct values of radiation weighting factors in dose assessment to non-human biota.

On the spatial resolution limit of direct-write electron beam lithography

The mechanism for direct-write electron-beam lithography in insulating resists is introduced in this letter, and it is based on damage by the induced electric field in transmission electron microscope. Under this mechanism, the direct-write EBL is electron dose-rate dependent, and there is a dose-rate threshold, below which the lithographic process does not operate, regardless of the total electron dose. The spatial resolution is determined by the strength of the induced electric field. In theory, the highest spatial resolution should be set by the dimension of the electron beam, and thus the EBL should be able to create nanostructures at the atomic scale. So far, the best resolution obtained was in the direct write of conductive nanochannels in Li4Ti5O12, in which 1.5nm isolated features and a 1.0–1.5nm half-pitch array of nanochannels were achieved.

Dose-rate-dependent damage of cerium dioxide in the scanning transmission electron microscope

Beam damage caused by energetic electrons in the transmission electron microscope is a fundamental constraint limiting the collection of artifact-free information. Through understanding the influence of the electron beam, experimental routines may be adjusted to improve the data collection process. Investigations of CeO2 indicate that there is not a critical dose required for the accumulation of electron beam damage. Instead, measurements using annular dark field scanning transmission electron microscopy and electron energy loss spectroscopy demonstrate that the onset of measurable damage occurs when a critical dose rate is exceeded. The mechanism behind this phenomenon is that oxygen vacancies created by exposure to a 300keV electron beam are actively annihilated as the sample re-oxidizes in the microscope environment. As a result, only when the rate of vacancy creation exceeds the recovery rate will beam damage begin to accumulate. This observation suggests that dose-intensive experiments can be accomplished without disrupting the native structure of the sample when executed using dose rates below the appropriate threshold. Furthermore, the presence of an encapsulating carbonaceous layer inhibits processes that cause beam damage, markedly increasing the dose rate threshold for the accumulation of damage.

The linear no-threshold theory: Readers weigh in

The linear no-threshold theory: Readers weigh in

Control of Electron Beam-Induced Au Nanocrystal Growth Kinetics through Solution Chemistry.

Measurements of solution-phase crystal growth provide mechanistic information that is helpful in designing and synthesizing nanostructures. Here, we examine the model system of individual Au nanocrystal formation within a defined liquid geometry during electron beam irradiation of gold chloride solution, where radiolytically formed hydrated electrons reduce Au ions to solid Au. By selecting conditions that favor the growth of well-faceted Au nanoprisms, we measure growth rates of individual crystals. The volume of each crystal increases linearly with irradiation time at a rate unaffected by its shape or proximity to neighboring crystals, implying a growth process that is controlled by the arrival of atoms from solution. Furthermore, growth requires a threshold dose rate, suggesting competition between reduction and oxidation processes in the solution. Above this threshold, the growth rate follows a power law with dose rate. To explain the observed dose rate dependence, we demonstrate that a reaction-diffusion model is required that explicitly accounts for the species H(+) and Cl(-). The model highlights the necessity of considering all species present when interpreting kinetic data obtained from beam-induced processes, and suggest conditions under which growth rates can be controlled with higher precision.

Forecasting Radiation Effects on Wildlife in Japan After the Fukushima Nuclear Accident, Based on Limited Information of Post-Accident Early Stage in 2011

Abstract. Due to the 11 March 2011 Tohoku earthquake, massive radioactive materials were released from the Fukushima Daiichi Nuclear Power Plant (Fukushima NPP). It is crucial to predict the regional distribution and magnitude of the effects on wildlife by radioactive materials. However, during the post-accident early stage in 2011, limited information on large-scale pollution and prediction maps was open to public. Hence, this paper aimed to provide (1) the pollution map covering areas within 300 km from the Fukushima NPP where the radiation intensity exceeded 0.5 μSv/h, (2) pollution maps which predicted air dose for the next 30 years after the accident, and (3) maps of areas where wildlife might be affected by radioactive isotopes by the Fukushima nuclear accident. First, the relative contributions of 131I, 134Cs, and 137Cs were estimated from time series observation data. Second, a 30-year prediction of the pollution was calculated based on the isotope half-lives. Third, the chronic radiation effects on vertebrates were estimated using the threshold dose rate proposed by Sazykina et al. (2009). We examined the chronic radiation effects on morbidity, reproduction, and longevity. The results indicated that radioactive materials could have affected vertebrate morbidity within a 350 km2 area in early April 2011; the threshold level was the median result of Sazykina et al. (2009) with bootstrapping. Based on the prediction, a 15.5 km2 region will remain affected after 30 years. These areas should be monitored to confirm the effects of radioactivity on wildlife.

The Effect of Dose Rate on the Frequency of Specific-Locus Mutations Induced in Mouse Spermatogonia is Restricted to Larger Lesions; a Retrospective Analysis of Historical Data

A series of 19 large-scale germ-cell mutagenesis experiments conducted several decades ago led to the conclusion that low-LET radiation delivered to mouse spermatogonia at dose rates of 0.8 R/min and below induced only about one-third as many specific-locus mutations as did single, acute exposures at 24 R/min and above. A two-hit origin of the mutations was deemed unlikely in view of the then prevailing evidence for the small size of genetic lesions in spermatogonia. Instead, the dose-rate effect was hypothesized to be the result of a repair system that exists in spermatogonia, but not in more mature male reproductive cells. More recent genetic and molecular studies on the marker genes have identified the phenotypes associated with specific states of the mutant chromosomes, and it is now possible retrospectively to classify individual past mutations as "large lesions" or "other lesions". The mutation-frequency difference between high and low dose rates is restricted to the large lesion mutations, for which the dose-curve slopes differ by a factor exceeding 3.4. For other lesion mutations, there is essentially no difference between the slopes for protracted and acute irradiations; induced other lesions frequencies per unit dose remain similar for dose rates ranging over more than 7 orders of magnitude. For large lesions, these values rise sharply at dose rates >0.8 R/min, though they remain similar within the whole range of protracted doses, failing to provide evidence for a threshold dose rate. The downward bend at high doses that had been noted for X-ray-induced specific-locus mutations as a whole and ascribed to a positive correlation between spermatogonial death and mutation load is now found to be restricted to large lesion mutations. There is a marked difference between the mutation spectra (distributions among the seven loci) for large lesions and other lesions. Within each class, however, the spectra are similar for acute and protracted irradiation.

On the dose-rate threshold of beam damage in TEM

Electron beam damage in a CaF2–Al2O3–SiO2 glass is investigated using time-dependent Ca L23 and O K-edge electron energy-loss spectroscopy. It appears that there is a threshold dose rate, below which the damage involving the formation of O defects may not be detected, at any total dose. This suggests that the threshold phenomenon of dose rate may result from the competition of damage and recovery processes. The accumulation of damage can only occur when the damage rate is higher than the recovery rate. For surface sputtering process in TEM, the recovery rate is negligible. Therefore, there is no threshold dose rate for surface sputtering.

A 1.8-GHz radiofrequency radiation induces EGF receptor clustering and phosphorylation in cultured human amniotic (FL) cells

Purpose: Many studies have shown that exposure to radiofrequency radiation (RFR) could activate cellular signal transduction pathways. In the present research, we investigated the effects of exposure to a 1.8-GHz RFR at different intensities on epidermal growth factor (EGF) receptor clustering and phosphorylation in human amniotic (FL) cells.Materials and methods: Receptor clustering on cellular membrane surface was analyzed using immunofluorescence assessed by confocal microscopy, and phosphorylation of EGF receptors was measured by western blot technology. EGF treatment served as a positive control.Results: The results showed that, compared with sham exposure, exposure to RFR at specific absorption rate (SAR) of 0.5, 1.0, 2.0, or 4.0 W/kg for 15 min significantly induced EGF receptor clustering and enhanced phosphorylation on the tyrosine-1173 residue in FL cells, whereas exposure to a SAR 0.1 W/kg radiation for 15 min did not cause a significant effect.Conclusion: Based on the results of this experiment, we conclude that membrane receptors could be one of the main targets that RFR interacts with cells, and the dose-rate threshold, in the case of EGF receptors, is between SAR of 0.1 and 0.5 W/kg. The results indicate a sigmoid dependence of RFR effects on intensity.

Comparative analysis of doses to aquatic biota in water bodies impacted by radioactive contamination

Comparative analysis of doses to the reference species of freshwater biota was performed for the following water bodies in Russia or former USSR: Chernobyl NPPs cooling pond, Lakes Uruskul and Berdenish located in the Eastern Urals Radioactive Trace, Techa River, Yenisei River. It was concluded that the doses to biota were considerably different in the acute and chronic periods of radioactive contamination. The most vulnerable part of all considered aquatic ecosystems was benthic trophic chain. A numerical scale on the “dose rate – effects” relationships for fish was formulated. Threshold dose rates above which radiation effects can be expected in fish were evaluated to be the following: 1 mGy d−1 for appearance of the first morbidity effects in fish; 5 mGy d−1 for the first negative effects on reproduction system; 10 mGy d−1 for the first effects on life shortening of fish. The results of dose assessment to biota were compared with the scale “dose rate – effects” and the literature data on the radiobiological effects observed in the considered water bodies. It was shown that in the most contaminated water bodies the dose rates were high enough to cause the radiobiological effects in fish.

Mutation induction by inhaled radon progeny modeled at the tissue level

The observable responses of living systems to ionizing radiation depend on the level of biological organization studied. Understanding the relationships between the responses characteristic of the different levels of organization is of crucial importance. The main objective of the present study is to investigate how some cellular effects of radiation manifest at the tissue level by modeling mutation induction due to chronic exposure to inhaled radon progeny. For this purpose, a mathematical model of the bronchial epithelium was elaborated to quantify cell nucleus hits and cell doses. Mutagenesis was modeled considering endogenous as well as radiation-induced DNA damages and cell cycle shortening due to cell inactivation. The model parameters describing the cellular effects of radiation are obtained from experimental data. Cell nucleus hits, cell doses, and mutation induction were computed for the activity hot spots of the large bronchi at different exposures. Results demonstrate that the mutagenic effect of densely ionizing radiation is dominated by cell cycle shortening due to cell inactivation and not by DNA damages. This suggests that radiation burdens of non-progenitor cells play a significant role in mutagenesis in case of protracted exposures to densely ionizing radiation. Mutation rate as a function of dose rate exhibits a convex shape below a threshold. This threshold indicates the exhaustion of the tissue regeneration capacity of local progenitor cells. It is suggested that progenitor cell hyperplasia occurs beyond the threshold dose rate, giving a possible explanation of the inverse dose-rate effect observed in the epidemiology of lung cancer among uranium miners.

Elaboration on a radiological environmental impact assessment methodology for Northern environments

The present work encompasses some key aspects of a 3-year long research project (INTRANOR) where the main focus has been specifically on environmental assessments for radiation exposure through application of existing methodologies and their adaptation to quantify transfer, exposure and effects in Boreal/Arctic ecosystems. Non-parametric statistical methods have been applied in order to estimate the threshold dose rates above which radiation effects can be expected in vertebrate organisms. In addition, industrial areas contaminated by uranium mill tailings and radium production wastes, in the Komi Republic, Russia, were selected as suitable sites to study further the effects of exposure to radiation under boreal conditions. Dose–effect relationships have been established for a few natural populations inhabiting this area. Analyses of data have allowed benchmarks to be established below which no decrease in reproductive capacity could be observed. Other work performed within the project includes the collation of data in relation to naturally occurring radionuclides and application of existing methodologies to characterise background radiation exposures. These dose-rates may be a suitable means of contextualising the exposure attributable to enhanced dose-rates arising from human activities. Finally, combined action of ionizing radiation and low temperature has been analyzed and mathematically modelled.