Estimation of Biological Effects of Tritium.

Nuclear fusion technology is expected to create new energy in the future. However, nuclear fusion requires a large amount of tritium as a fuel, leading to concern about the exposure of radiation workers to tritium beta radiation. Furthermore, countermeasures for tritium-polluted water produced in decommissioning of the reactor at Fukushima Daiichi Nuclear Power Station may potentially cause health problems in radiation workers. Although, internal exposure to tritium at a low dose/low dose rate can be assumed, biological effect of tritium exposure is not negligible, because tritiated water (HTO) intake to the body via the mouth/inhalation/skin would lead to homogeneous distribution throughout the whole body. Furthermore, organically-bound tritium (OBT) stays in the body as parts of the molecules that comprise living organisms resulting in long-term exposure, and the chemical form of tritium should be considered. To evaluate the biological effect of tritium, the effect should be compared with that of other radiation types. Many studies have examined the relative biological effectiveness (RBE) of tritium. Hence, we report the RBE, which was obtained with radiation carcinogenesis classified as a stochastic effect, and serves as a reference for cancer risk. We also introduce the outline of the tritium experiment and the principle of a recently developed animal experimental system using transgenic mouse to detect the biological influence of radiation exposure at a low dose/low dose rate.

[Assessment of Erythropoiesis Status in Roach (Rutilus rutilus) of the Radioactively Contaminated Techa River].

At present volumetric activity of ß-emitting radionuclides in water at various locations of the Techa River ranges from 5 to 40-Bq/L; a specific activity of ß-emitting radionuclides in the bottom sediments at various locations ranges 10 Ito 106 Bq/kg dry weight. A significant increase of the erythroblast content in blood as compared to that in the roach from the reference watercourse (the Miass River) was observed during spawning in the spring. Due to this fact the number of erythrocytes was equal to that in the control animals under chronic radiation exposure at the dose rates of 0.9 and 16 µGy/day, and was insufficient at the dose rate of 108 gGy/day. During summer feeding no changes in the indexes of erythropoiesis in roach were observed under chronic radiation exposure at the dose rate of 0.9 µGy/day; the number of erythrocytes in the peripheral blood declines when the dose rates are 16 and 108 µGy/day. When performing a regression analysis, we revealed a dose-rate-dependent decrease in the absolute number of erythrocytes, normocytes, polychromatocytes, dividing and non-dividing erythroid cells in the peripheral blood of roach from the Techa River and an increase of a relative number of normochromatophylic erythrocytes.

[Application of the EPR and FISH Methods to Dose Reconstruction for People Exposed in the Techa River Area].

Release of liquid radioactive waste into the Techa River from the Mayak Production Association during 1949-1956 resulted in a significant exposure of about 30000 people who lived in downstream settlements. The residents were exposed to internal and external radiation. The article discusses the capability of two methods that were used 50 years after the termination of radioactive discharges for the dose reconstruction, namely EPR measurements of tooth enamel, and FISH measurements of stable chromosome aberrations in circulating lymphocytes. The Main issue in the application of these methods for the dose reconstruction was local irradiation from strontium radioisotopes incorporated in teeth and bones. The EPR and FISH assays were supported by measurements of the 90Sr content in the skeleton and teeth in order to estimate and subtract internal doses from incorporated 89, 90Sr. The resulting dose estimates obtained from EPR and FISH mea- surements were found to be consistent The settlement-averaged values in the upper-Techa Region varied from 550-570 mGy to 130-160 mGy and showed a reduction with the distance from the release site. The EPR- and FISH-based dose estimates were in agreement with the doses calculated with the dosimetry system TRDS that uses data on radionuclide contamination of the Techa River floodplain and individual residential histories.

[Tritium in the Water System of the Techa River].

The aim of the paper is to study modern tritium levels in various sources of the drinking water supply in the settlements situated in the riverside zone of the Techa. Almost everywhere the water entering water-conduit wells from deep slits (100-180 m) contains averagely 2-3 times higher tritium concentrations than the water from less deep personal wells, slits and springs. Tritium levels in the drinking water supply decrease with the distance from the dam; while in wells, springs and personal wells they are constant all along the river. The observed phenomenon can be explained by the fact that the river bed of the Techa is situated at a break zone of the earth crust, where the contaminated deep water penetrates from the reservoirs of the "Mayak" enterprise situated in the upper part of the regulated river bed. Less deep water sources (personal wells, slits and springs) receive predominantly flood, atmospheric and subsoil waters and are not connected with the reservoirs.

[Apoptosis of Peripheral Blood Lymphocytes in the Members of the Techa River Cohort Chronically Exposed to Radiation].

The purpose of the present research was to estimate the intensity of the apoptotic death of lymphocytes during the period of carcinogenic effect realization in the residents of the Techa riverside villages. The investigation included analyses of the frequency of lymphocytes at the early and late stages of apoptosis and necrosis of peripheral blood lymphocytes using the method of FITC Annexin V, lymphocyte counts at the stage of DNA fragmentation using the TUNEL method, and the number of CD95(+)-lymphocytes. In the capacity of additional tests, loading tests involving in vitro irradiation at the dose of 1 Gy of a suspension of lymphocytes and incubations for 5 and 24 hours were used. Activation of the initial apoptotic and necrotic death of peripheral blood lymphocytes was revealed in the persons chronically exposed to low-intensity radiation within the range from 0.01 to 4.23 Gy. Exposed patients demonstrated a decrease in the number of CD95(+)-cells as compared to unexposed patients. The results of the cell death studies in the persons residing in the Techa riverside villages testify indirectly to the genomic instability of the peripheral blood lymphocytes.

[Ranking of radionuclides and pathways according to their contribution to the dose burden to the population resulting from NPP releases].

Approaches are described towards estimating the consequences of radioactive contamination of ecosystems by nuclear fuel cycle enterprises with the rationale for the optimal specification level for nuclear power plants (NPP) operating in the normal mode. Calculations are made based on the initial data of the IAEA project, INPRO ENV, dealing with the ranking of radionuclides escaping to the environment from the operating NPPs. Influence of various factors on rankings of radionuclides and pathways of public exposure is demon- strated. An important factor is the controlled radionuclide composition of atmospheric NPP releases. It has been found that variation in the dose coefficients for some radionuclides leads to significant changes not only in the ranking results but also in the estimates of total dose burdens. Invariability is shown of the estimation concerning the greatest contribution of the peroral route to the population dose of irradiation in the situation considered. A conclusion was drawn on the need of taking into consideration uncertainties of different factors when comparing effects on the environment from enterprises of conventional and innovative nuclear fuel cycles.

[Analysis of DNA damage/repair level in Rutilus rutilus L. from reservoirs of the Techa River cascade with different levels of radiactive pollution].

The Comet Assay and micronucleus assays have been used to evaluate the condition of the nuclear DNA in erythrocytes of peripheral blood of roach (Rutilus rutilus L.) from water-storage of low-level radioactive waste. The Rutilus rutilus L. from the Shershny reservoir, Chelyabinsk, was used as a control population. Radionuclide maintenance in water, sediments and roach in those reservoirs and Shershny reservoir was defined. The dose rate for Rutilus rutilus L. was calculated using program complex ERICA Assessment Tool 1.0 May 2009. Our investigation has shown that a chronic radiation of population (dose rate - 5.2 mGy/day and 19.5 mGy/day) leads to a significantly higher level of the DNA damage in erythrocytes of peripheral blood and increases the speed of nuclear DNA reparation after irradiation of erythrocytes in vitro. We suppose that it may be a result of the increased quantity of active form of oxygen in cells of the fish in water-storage of low-level radioactive waste.

Long-term investigation of environmental radioactivity levels and public health around the Qinshan Nuclear Power Plant, China.

To evaluate the impact of the Qinshan Nuclear Power Plant (Qinshan NPP) in normal operation on the surrounding environment and population, the radioactivity levels of drinking water and the ambient environment, as well as the residents' cancer incidence, were continuously monitored for a period of 9 years (2012-2020). All of the gross α and ß radioactivity concentrations in drinking water were less than the WHO recommended values (0.5 Bq/L for gross α and 1 Bq/L for gross ß). The results of ambient environment accumulated dose monitored by thermoluminescent dosimeters (TLDs) indicated that the ambient environment radioactive level around the Qinshan NPP is consistently at natural background radiation levels. The age-dependent annual effective doses due to the ingestion of tap water or exposure to the outdoor ambient environment are lower than the reference dose of 0.1 mSv/year. The corresponding excess risks are at relatively low levels. Thus, the consumption of drinking water and outdoor activities are not expected to give rise to any detectable adverse effects on the health of the public around the Qinshan NPP. For all cancers combined, the age-standardized incidence rate by the Chinese 2000 standard population of the inhabitants living around Qinshan NPP is consistent with that of Zhejiang Province as a whole. Based on current radiation risk estimates, radiation exposure is not a plausible explanation for any excess cancers observed in the vicinity of the Qinshan NPP.

Groundwater uranium and cancer incidence in South Carolina.

OBJECTIVE: This ecologic study tested the hypothesis that census tracts with elevated groundwater uranium and more frequent groundwater use have increased cancer incidence. METHODS: Data sources included: incident total, leukemia, prostate, breast, colorectal, lung, kidney, and bladder cancers (1996-2005, SC Central Cancer Registry); demographic and groundwater use (1990 US Census); and groundwater uranium concentrations (n = 4,600, from existing federal and state databases). Kriging was used to predict average uranium concentrations within tracts. The relationship between uranium and standardized cancer incidence ratios was modeled among tracts with substantial groundwater use via linear or semiparametric regression, with and without stratification by the proportion of African Americans in each area. RESULTS: A total of 134,685 cancer cases were evaluated. Tracts with ≥50% groundwater use and uranium concentrations in the upper quartile had increased risks for colorectal, breast, kidney, prostate, and total cancer compared to referent tracts. Some of these relationships were more likely to be observed among tracts populated primarily by African Americans. CONCLUSION: SC regions with elevated groundwater uranium and more groundwater use may have an increased incidence of certain cancers, although additional research is needed since the design precluded adjustment for race or other predictive factors at the individual level.

Radiocaesium accumulation capacity of epiphytic lichens and adjacent barks collected at the perimeter boundary site of the Fukushima Dai-ichi Nuclear Power Station.

We investigated the radiocaesium content of nine epiphytic foliose lichens species and the adjacent barks of Zelkova serrata (Ulmaceae, "Japanese elm") and Cerasus sp. (Rosaceae, "Cherry tree") at the boundary of the Fukushima Dai-ichi Nuclear Power Station six years after the accident in 2011. Caesium-137 activities per unit area (the 137Cs-inventory) were determined to compare radiocaesium retentions of lichens (65 specimens) and barks (44 specimens) under the same growth conditions. The 137Cs-inventory of lichens collected from Zelkova serrata and Cerasus sp. were respectively 7.9- and 3.8-times greater than the adjacent barks. Furthermore, we examined the radiocaesium distribution within these samples using autoradiography and on the surfaces with an electron probe micro analyzer (EPMA). Autoradiographic results showed strong local spotting and heterogeneous distributions of radioactivity in both the lichen and bark samples, although the intensities were lower in the barks. The electron microscopy analysis demonstrated that particulates with similar sizes and compositions were distributed on the surfaces of the samples. We therefore concluded that the lichens and barks could capture fine particles, including radiocaesium particles. In addition, radioactivity was distributed more towards the inwards of the lichen samples than the peripheries. This suggests that lichen can retain 137Cs that is chemically immobilised in particulates intracellularly, unlike bark.

Health effects of radon: a review of the literature.

PURPOSE: Radon is natural radioactive noble gas that can be found in soil, water, outdoor and indoor air. Exposure to radon accounts for more that 50% of the annual effective dose of natural radioactivity. The purpose of the current review is to summarize recent literature and evaluate the weight of evidence on the adverse health effects of radon. CONCLUSIONS: Radon is an established human lung carcinogen based on human epidemiological data supported by experimental evidence of mutagenesis studies in cell culture and laboratory animals. Extrapolation from cohort studies on miners suggested that radon is the second leading cause of lung cancer death after tobacco smoke. The majority of studies on the relationship between radon and other types of cancers showed weak or no association. Low levels of radon can be found in drinking water; however, radon released during water usage adds small quantities to indoor radon concentration. Studies showed that the risk of stomach cancer and other gastrointestinal malignancies from radon in drinking water is small. Studies of the genetic and cytogenetic effects of indoor radon yielded equivocal results; while radon exposure in miners induces gene mutations and chromosomal aberrations. Numerous in vitro cytogenetic studies demonstrated that radon induces different types of genetic and cytogenetic damage that is likely to play a role in radon lung carcinogenesis.

[Intergrated assessment of the radioecological state of the biota in Moscow water objects].

The paper presents the results of studying the regularities and distribution pattern of natural radionuclides (potassium-40, thorium-232), as well as the representatives of the uranium family (radium-226, polonium-210) and the technogenic isotope cesium-137 in different objects of the water ecosystem in the North-Western District of Moscow (bottom sediment, hydrobiota). Some radiation parameters of these objects (the total alpha- and beta-activities of the radionuclides, their specific effective activity are given. On the basis of the experimental findings, the authors have made an assessment of the radioecological situation in the water pool of the district examined.

Radon concentration in self-bottled mineral spring waters as a possible public health issue.

Since 2013, the Council Directive 2013/51/Euratom has been regulating the content of radioactive substances in water intended for human consumption. However, mineral waters are exempted from this regulation, including self-bottled springs waters, where higher radon concentration are expected. Therefore, a systematic survey has been conducted on all the 33 mineral spring waters of Lazio (a region of Central Italy) in order to assess if such waters, when self-bottled, may be of concern for public health. Waters have been sampled in two different ways to evaluate the impact of bottling on radon concentration. Water sampling was possible for 20 different spring waters, with 6 samples for each one. The results show that 2 (10%) of measured mineral spring waters returned radon concentrations higher than 100 Bq L-1, i.e., the parametric value established by the Council Directive. These results, if confirmed by other surveys involving a higher number of mineral spring waters, would suggest regulating also these waters, especially in countries like Italy for which: (i) mineral water consumption is significant; (ii) mineral concession owners generally allow the consumers to fill bottles and containers, intended for transport and subsequent consumption, directly from public fountains or from fountains within the plant; (iii) the consumers' habit of drinking self-bottled mineral water is widespread.

RADIATION DOSE TO MALDIVIANS VIA THE CONSUMPTION OF TUNA FISH CAUGHT FROM THE COASTAL WATERS OF INDIAN OCEAN.

Recognising the consumption of tuna fish as a major foodstuff in Maldivian diet, the presence of naturally occurring radionuclides in Yellowfin and Skipjack tuna are determined by using HPGe gamma-ray spectrometry to evaluate the health hazards to Maldivians. The samples were collected from different atolls of Maldives adjacent to the coastal waters of Indian Ocean. The activity concentrations (Bq kg-1) in Yellowfin tuna for 226Ra, 232Th and 40K are in the ranges of 4.2 ± 1.8-10.5 ± 1.1, 1.3 ± 0.3-3.2 ± 0.7 and 589 ± 29-697 ± 34, respectively while in Skipjack tuna the respective ranges are 3.9 ± 0.5-13.2 ± 1.1, 1.3 ± 0.3-2.7 ± 0.6 and 511 ± 28-681 ± 35. The committed effective dose (mean 263 µSv y-1) received by an individual due to the dietary intake of Yellowfin tuna falling below the UNSCEAR referenced global internal dose limit of 290 µSv y-1; while for Skipjack tuna, the estimated dose (mean 365 µSv y-1) exceeds the world average limiting value. The carcinogenic risk was found to be well below the ICRP referenced acceptable limit of 2.5 × 10-3. The present study indicates that the radiation dose to Maldivian via the consumption of Yellowfin tuna poses an insignificant threat to the public health. However, prolonged consumption of Skipjack tuna fish from the studied areas may pose a cumulative risk to the public health.

Radon concentration in hydrogeothermal deposit and spas of Boyacá, Colombia.

Inhaled radon and its progenies induce health concern due to high activity-concentration in selected thermal spas of Boyacá region. Hydrogeothermal water sources in a high risk seismic area, are studied to determine by water bubbling method radon concentration values; their occurrence is between few hundreds and 2000 Bq dm-3. Deposits, existing in this area, reach at the surface soil gas radon concentration up to 210 kBq m-3. Maintenance workers, health tourists and visitor's possible detrimental health effects, are discussed in relation to radon balneotherapy beneficial aspects.

Dose distribution measurements and calculations for Dounreay hot particles.

Discrete fragments of irradiated nuclear fuel have been discovered on the foreshore at the Dounreay nuclear site in Scotland, offshore on the seabed and at nearby beaches which have public access. The fragments contain mainly (137)Cs and (90)Sr/(90)Y and for particles recovered to date, (137)Cs activities are within the range of 10(3) to 10(8) Bq. The most active particles found at Sandside Beach contain approximately 3 x 10(5)Bq (137)Cs. Direct measurements of the spatial dose distributions from 37 fuel fragments were measured in detail for the first time using radiochromic dye film as part of a national evaluation of the associated potential radiological hazard. Monte Carlo code calculations of the doses are in good agreement with measurements, taking into account variations to be expected due to differences in shape and the increasing importance of self-absorption for the larger, more active fragments. Dose measurements provide little evidence for wide variations in the (137)Cs:(90)Sr/(90)Y ratio between fragments. Specific attention is given to the evaluation of skin dose, averaged over an area of 1 cm(2) at a depth of 0.07 mm, since this is of major radiological concern. There is no obvious dependence of skin dose on the site of origin of the fragments (foreshore, seabed or beaches) for a given (137)Cs activity level. A dose rate survey instrument (SmartION) was shown to provide a rapid and convenient method for skin dose assessment from fuel fragments in the (137)Cs activity range measured (2 x 10(5) to 2 x 10(7) Bq). A conversion factor multiplier of 240 can be applied to the open window SmartION scale reading to estimate the skin dose rate within +/-25%.

Ra-226 bioaccumulation and growth indices in fish.

PURPOSE: To determine the accumulated activity of Ra-226 in fathead minnows fed with environmentally relevant levels of Ra-226 for 5 months in water at 20 °C, and to evaluate the influence of this level of Ra-226 on the growth of fathead minnows. METHODS: Fathead minnows were fed with fish food containing 10-10,000 mBq/g Ra-226 for 5 months. At the end of the experiment, the fish were sacrificed, flash frozen in liquid nitrogen and kept at -20 °C. Longitudinal sections of 40 µm thickness were cut at the middle of the fish body using a cryostat. The activity of Ra-226 in each section was determined using autoradiography with a nuclear track detector CR-39. According to the weight and the width of the fish, the activity of Ra-226 in the whole fish body could be estimated. In addition, the length and the weight of the fish were measured and the condition factor was calculated to evaluate the growth and fitness of the fish. RESULTS: There is a positive but non-linear relationship between the accumulated activity of Ra-226 in fish body and the concentration of Ra-226 in fish food. The highest activity of Ra-226 accumulated in fish body was found from fish fed with 10,000 mBq/g Ra-226 food. This was calculated as 256.4 ± 49.1 mBq/g, p < 0.05, and the calculated dose rate was 6.2 ± 1.2 mGy/y. For fish fed with food containing lower concentration of Ra-226 (up to 1000 mBq/g), the bioaccumulation of Ra-226 in the body saturated. The Ra-226 concentration factor (CF) for fish was inversely proportional to the Ra-226 activity in food, and the highest CF value was 2.489, obtained from the lowest dietary Ra-226 activity (10 mBq/g). In addition, condition factors (K) of fish in all Ra-226-treated groups were significantly lower than those of the controls. CONCLUSION: The results show that the bioaccumulation of Ra-226 in fish is not simply related to the dietary Ra-226 activity, and has a saturation value when the dietary activity is low. In addition, the environmental level of Ra-226 in the fish food has a small adverse effect on the growth and fitness of fathead minnows.

Lung and stomach cancer associations with groundwater radon in North Carolina, USA.

Background: The risk of indoor air radon for lung cancer is well studied, but the risks of groundwater radon for both lung and stomach cancer are much less studied, and with mixed results. Methods: Geomasked and geocoded stomach and lung cancer cases in North Carolina from 1999 to 2009 were obtained from the North Carolina Central Cancer Registry. Models for the association with groundwater radon and multiple confounders were implemented at two scales: (i) an ecological model estimating cancer incidence rates at the census tract level; and (ii) a case-only logistic model estimating the odds that individual cancer cases are members of local cancer clusters. Results: For the lung cancer incidence rate model, groundwater radon is associated with an incidence rate ratio of 1.03 [95% confidence interval (CI) = 1.01, 1.06] for every 100 Bq/l increase in census tract averaged concentration. For the cluster membership models, groundwater radon exposure results in an odds ratio for lung cancer of 1.13 (95% CI = 1.04, 1.23) and for stomach cancer of 1.24 (95% CI = 1.03, 1.49), which means groundwater radon, after controlling for multiple confounders and spatial auto-correlation, increases the odds that lung and stomach cancer cases are members of their respective cancer clusters. Conclusion: Our study provides epidemiological evidence of a positive association between groundwater radon exposure and lung cancer incidence rates. The cluster membership model results find groundwater radon increases the odds that both lung and stomach cancer cases occur within their respective cancer clusters. The results corroborate previous biokinetic and mortality studies that groundwater radon is associated with increased risk for lung and stomach cancer.

Natural radioactivity levels and associated health hazards from the terrestrial ecosystem in Rosetta branch of the River Nile, Egypt.

Twenty soil and 25 sediment samples were collected from the banks and bottom of the River Nile in the surroundings of biggest cities located close to it. Natural radioactivity concentrations of 226Ra, 232Th and 40K have been evaluated for all samples by means of γ spectrometric analysis. The radioactivity levels of soil and sediment samples fall within the internationally recommended values. Nevertheless, high natural background radiation zones are detected in the Kafr El-Zayat region due to the presence of a fertilizer factory, and in the Rosetta region due to the presence of black sand deposits. The absorbed dose rate, the γ index and excess life time cancer risk are calculated. High values for some of the radiation health parameters are detected in the Kafr El-Zayat and Rosetta regions representing a serious problem to public health because the soil and sediment are used as constructing material for buildings. Furthermore, the isotope analysis of uranium for representative collected sediment samples via α spectrometry showed average specific activities of 18.7 ± 3.6, 0.087 ± 0.0038 and 18.6 ± 3.8 Bq kg-1 for 234U, 235U and 238U, respectively. In general, these values confirm the balance in the isotopic abundance of U isotopes.

[Correlation between the probability and dosage characteristics of safety in the processing of radioactive liquids].

The authors show it possible and expedient to use the probability characteristics for evaluation of the safe operation of radiation-dangerous plants. The calculated values of doses that might be following an accident at these plants fail to give an adequate account of reality since the doses are largely variates. To divide accidents into classes or levels, it is necessary to use the principle of non-excess of accident probability of the given class or level rather than the threshold principle of non-excess of doses.