External Exposure Dose Research Articles

Relationship between methylation of promoters of apoptosis genes in blood lymphocytes with the frequency of chromosomal aberrations and the dose of radiation

BACKGROUND: Impaired apoptosis can have serious consequences: the accumulation of mutant cells, the development of teratogenic effects and malignant neoplasms. In this regard, the study of the mechanisms of changes in the activity of apoptosis due to methylation under the influence of long-term irradiation is urgent.
 AIM: The study of the degree of methylation of gene promoters involved in the induction of apoptosis in the personnel of the Siberian Chemical Plant, exposed to long-term technogenic irradiation of ionizing radiation in the course of their professional activities.
 MATERIALS AND METHODS: The study was performed on peripheral blood samples of employees of the Siberian Chemical Plant, with a total dose of external exposure from 100 to 300 mSv. Chromosomal aberrations were detected by standard karyotyping of cultured blood lymphocytes. The degree of gene promoters methylation was determined using MethylScreen technology.
 RESULTS: The degree of gene methylation BIRC2, CASP3, CASP9, CIDEB, CRADD, DAPK1, DFFA, FADD, GADD45A, LTBR, TNFRSF21, TNFRSF25 ranges from 0.31 to 41.75%. A strong negative correlation was found between the degree of methylation of GADD45A (r = 0.7364, р = 0.009) with an increased frequency of aberrant cells, moderate negative correlation GADD45A (r = 0.6347, р = 0.035) with an increased frequency of dicentric chromosomes, moderate negative correlation CASP9 (r = 0.6606, р = 0.026), and strong negative correlation CIDEB (r = 0.7982, р = 0.003) with an increased frequency of chromatid fragments. A moderate negative correlation of the methylation degree of CASP9 (r = 0.6636, р = 0.026), and CIDEB (r = 0.6636, р = 0.026) with the total dose of external exposure was shown.
 CONCLUSIONS: The decrease in the level of apoptosis at doses of 100300 mSv can be explained by the achievement of the demethylation threshold for the promoters of the proapoptotic genes GADD45A, CASP9, CIDEB. This once again testifies in favor of the threshold model of the dependence of the radiation effect on the radiation dose.

The effect of exposure on cattle thyroid after the Fukushima Daiichi nuclear power plant accident

Nuclear plant accidents can be a risk for thyroid cancer due to iodine radioisotopes. Near the Fukushima Daiichi nuclear power plant, cattle were exposed to radiation after the accident occurred in May 2011. Here we estimated the total radiation exposure to cattle thyroid and its effects on thyroid function. Until October 2016, the estimated external exposure dose in Farm A was 1416 mGy, while internal exposure dose of 131I, 134Cs, and 137Cs were 85, 8.8, and 9.7 mGy in Farm A and 34, 0.2, and 0.3 mGy in Farm B, respectively. The exposed cattle had thyroid with relatively lower weight and lower level of stable iodine, which did not exhibit any pathological findings. Compared with the control, the plasma level of thyroid-stimulating hormone (TSH) was higher in Farm A cattle born before the accident, while the plasma thyroxine (T4) was higher in Farm A cattle born after the accident, suggesting that exposed cattle showed slight hyperactivation of the thyroid gland. In addition, Farm A cattle have higher level of cortisol, one of the anterior pituitary gland-derived hormones. However, we did not observe a causal relationship between the radiation exposure and cattle thyroid.

Effects of External Radiation Exposure Resulting From the Fukushima Daiichi Nuclear Power Plant Accident on the Health of Residents in the Evacuation Zones: the Fukushima Health Management Survey.

Associations have been reported between lifestyle-related diseases and evacuation after the Great East Japan Earthquake (GEJE). However, the relationship between lifestyle-related diseases and the effective radiation dose due to external exposure (EDEE) after the GEJE remains unclear. From among 72,869 residents of Fukushima Prefecture (31,982 men; 40,887 women) who underwent a comprehensive health check in fiscal year (FY) 2011, the data of 54,087 residents (22,599 men; 31,488 women) aged 16 to 84 years were analyzed. The EDEE data of 25,685 residents with incomplete results from the basic survey, performed to estimate the external radiation exposure dose, were supplemented using multiple imputation. The data were classified into three groups based on EDEE (0 to <1, 1 to <2, and ≥2 mSv groups and associations between the incidence of diseases and EDEE from FY2011 to FY2017 were examined using a Cox proportional hazards model, with FY2011 as the baseline. A higher EDEE was associated with a greater incidence of hypertension, diabetes mellitus, dyslipidemia, hyperuricemia, liver dysfunction, and polycythemia from FY2011 to FY2017 in the age- and sex-adjusted model. However, after further adjustment for evacuation status and lifestyle-related factors, the significant associations disappeared. No association was found between EDEE and other lifestyle-related diseases. EDEE was not directly associated with the incidence of lifestyle-related diseases after the GEJE. However, residents with higher external radiation doses in Fukushima Prefecture might suffer from lifestyle-related diseases related to evacuation and the resultant lifestyle changes.

Incidence risks for subtypes of heart diseases in a Russian cohort of Mayak Production Association nuclear workers.

Heart diseases are one of the main causes of death. The incidence risks were assessed for various types of heart diseases (HDs) in a cohort of Russian nuclear workers of the Mayak Production Association (PA) who had been chronically occupationally exposed to external gamma and/ or internal alpha radiation. The study cohort included all workers (22,377 individuals) who had been hired at the Mayak PA during 1948-1982 and followed up until 31 December 2018. The mean gamma-absorbed dose to the liver (standard deviation) was 0.43 (0.63) Gy, and the mean alpha-absorbed dose to the liver was 0.25 (1.19) Gy. Excess relative risk (ERR) per unit liver-absorbed dose (Gy) was calculated based on maximum likelihood. At the end of the follow-up, 559 chronic rheumatic heart disease (CRHD), 7722 ischemic heart disease (IHD) [including 2185 acute myocardial infarction (AMI) and 3976 angina pectoris (AP)], 4939 heart failure (HF), and 3689 cardiac arrhythmia and conduction disorder (CACD) cases were verified in the study cohort. Linear model fits of the gamma dose response for HDs were best once adjustments for non-radiation factors (sex, attained age, calendar period, smoking status and alcohol consumption) and alpha dose were included. ERR/Gy in males and females was 0.17 (95% confidence intervals: 0.10, 0.26) and 0.23 (0.09, 0.38) for IHD; 0.18 (0.09, 0.29) and 0.26 (0.08, 0.49) for AP; -0.01 (n/a, 0.1) and -0.01 (n/a, 0.27) for AMI; 0.27 (0.16, 0.40) and 0.27 (0.10, 0.49) for HF; 0.32 (0.19, 0.46) and 0.05 (-0.09, 0.22) for CACD; 0.73 (-0.02, 2.40) and -0.12 (-0.50, 0.69) for CRHD, respectively. Sensitivity analyses demonstrated the persistence of a significant dose-response regardless of exclusion/inclusion of adjustments for known potential non-radiation confounders (smoking, alcohol consumption, body mass index, hypertension, diabetes mellitus), and it was only the magnitude of the risk estimate that varied. The risks of HD incidence were not modified with sex (except for the CACD risk). This study provides evidence for a significant association of certain types of HDs with cumulative dose of occupational chronic external exposure to gamma radiation.

Physiologically based pharmacokinetic (PBPK) modeling of BDE-209 following oral exposure in Chinese population.

The wide usage of decabromodiphenyl ether (BDE-209) as additive brominated flame retardant has caused its widespread occurrence in the environment and high exposure risk in humans. Estimating its internal exposure dose and reconstruction of external exposure dose using physiologically based pharmacokinetic (PBPK) modelling approach is a key step in the risk assessment of BDE-209. However, the PBPK model for BDE-209 is currently unavailable. This study has established two oral permeability-limited PBPK models of BDE-209 without enterohepatic recirculation (EHR) (model 1) and with EHR (model 2) for Chinese population. Using the in vitro experiments, the average binding of BDE-209 to human plasma protein (99.64%±2.97%) was obtained. Moreover, blood sample analysis and systematic literature review were performed to obtain internal and external exposure data of BDE-209 used for model calibration and validation. The predictions of both models were within 2-fold of the observed, and a longer half-life of serum BDE-209 was observed in model 2 than model 1. Based on the models, a human biomonitoring guidance value (HBM-GV) of 93.61μg/g lw was derived for BDE-209, and there is no health risk found for Chinese population currently. This study provides new quantitative assessment tools for health risk assessment of BDE-209.

Radiation hazard assessments of natural radioactivity in clay-based cosmetic products in Malaysia

Natural sources such as clays, plant extracts, and raw materials containing naturally occurring radioactive material (NORM) have been used as ingredients for medicinal and cosmetic purposes since ancient times. Nowadays, a variety of commercially available cosmetics products used clay minerals containing NORMs as the main formulation, which poses unknown radiation risks to the consumer. In this study, 11 samples of clay-based cosmetic products were used to conduct dose assessments on members of the public for various usage scenarios to evaluate the external exposure dose. Gamma-ray spectroscopy was utilised to measure the activity concentrations of 238U, 232Th, and 40K in the sample. Meanwhile, doses to skin and other organs from these cosmetic products were modelled using Geant4 Monte Carlo simulations and the MIRD5 mathematical phantom, incorporating dose conversion factors (DCFs). The results revealed that the activity concentration for 238U, 232Th, and 40K ranged from 0.1 – 1.3, 0.06–15.6, and 0.22–6.9 Bq g−1, respectively, which were lower than the reference provided by the international regulation. The analysis for heavy metals showed that sample 9 contained a high amount of Cd, which gave an immediate alert to that particular product. Furthermore, the effective doses in the skin estimated in this study with the range of 2.7–240 μSv y−1, were significantly lower than the International Commission on Radiological Protection (ICRP) reference limit of 50 mSv per year for members of the general public. Based on the few μSv of effective dose exposure, it is sufficient to conclude that the dose from these products poses no radiological risk to the user. The addition of NORMs in cosmetic products should be done with caution because higher concentrations can raise the dose.

Вариация поглощенной дозы облучения дикого кабана, обитающего на территории радиоактивного загрязнения

The article presents the results of the assessment of the absorbed dose rate from incorporated radionuclides of 137Cs and 90Sr in the body of wild boar living in an area with different levels of radioactive contamination. The internal irradiation dose was evaluated for incorporated 137Cs in muscle and 90Sr in bone tissue of wild boar. During the assessment, it was assumed that radionuclides 137Cs uniformly distributed in the tissue and are in equilibrium conditions, and radionuclides are 90Sr concentrated in the bone tissue of the animal, during the year the concentration of radionuclides is assumed to be constant. In total, samples were obtained from 117 wild boar individuals, among which 87 animals were seized in the exclusion zone and 30 in the resettlement zone. From the animal carcass, spot samples of muscle tissue were taken according to 500 ± 50 g, the 137Cs content in the samples was determined for raw, natural mass. The activity of 90Sr in bone tissue was determined by radiochemical method. As a result of the studies, it was found that the average total exposure dose of wild boar seized in the exclusion zone is twice that of animals seized in the resettlement zone (p &lt; 0,05) and amounted to 653,6 ± 73,5 mGy/day for animals harvested in the exclusion zone and 328,8 ± 31,4 mGy/day for wild boar living in the zone resettlement. Analysis of the coefficients of variation showed that the maximum variation is observed among the values of the absorbed dose of radiation from the incorporated 137Cs in animals that were seized in the exclusion zone. The minimum variation rate occurs with respect to the external exposure dose in animals harvested in the resettlement zone. There is no significant difference (p &lt; 0,05) between the median absorbed dose of exposure of wild boars living in the exclusion zone and the resettlement zone. The result of our studies suggests that the density of contamination is not the main factor determining the formation of an animal’s radiation dose.

Statistical analysis of factors contributing to the formation of the external radiation dose

Objective . To determine factors contributing to the formation of the external radiation dose in individuals living in radionuclide-contaminated areas. Materials and methods . 25,503 residents from 289 settlements of the Gomel region were examined by the method of thermoluminescent dosimetry. Results . Some statistically significant differences between the doses in men and women were revealed. The study of age and sex groups found that the values of the external radiation dose in young men were 11% as high as those in women of the same age group. The values of the external radiation dose in elderly men were almost 10% as high as those in women of this group. The analysis of the type of activity of all the examined individuals has showed a large variation of external exposure dose values: on average, the external radiation dose is 32% as high in individuals who due to the nature of their practical activities stay outdoors for a long time as that in individuals who work in shielded premises and buildings. Conclusion . The factors contributing to the formation of the external exposure dose in individuals living in radionuclide-contaminated areas have been identified.

Analysis of the methodology for calculating the dose of external radiation exposure of the population

This work is devoted to the analysis of the methodology for calculating the dose of external radiation exposure to humans. In the course of the work, nuclear power facilities were investigated and the need for calculating radiation doses as a basis for ensuring radiation safety was determined. When solving the tasks, such research methods as system analysis, mathematical modelling, and calculation were used. The calculation of the functions of changes in internal radiation doses was carried out using the Matlab program. As a result of the work, the dependences of external radiation doses on time are obtained. The high processing speed and reliability of the data obtained allows the use of these methods in assessing the safe distance to nuclear power facilities for the living population. Also, the methods of calculating the dose of external radiation confirm their efficiency in the development of recommendations on radiation safety of the population.

Validation of a Model for Estimating Individual External Dose Based on Ambient Dose Equivalent and Life Patterns

Background: After the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, a model was developed to estimate the external exposure doses for residents who were expected to return to their homes after evacuation orders were lifted. However, the model’s accuracy and uncertainties in parameters used to estimate external doses have not been evaluated.Materials and Methods: The model estimates effective doses based on the integrated ambient dose equivalent (H*(10)) and life patterns, considering a dose reduction factor to estimate the indoor H*(10) and a conversion factor from H*(10) to the effective dose. Because personal dose equivalent (Hp(10)) has been reported to agree well with the effective dose after the FDNPS accident, this study validates the model’s accuracy by comparing the estimated effective doses with Hp(10). The Hp(10) and life pattern data were collected for 36 adult participants who lived or worked near the FDNPS in 2019.Results and Discussion: The estimated effective doses correlated significantly with Hp(10); however, the estimated effective doses were lower than Hp(10) for indoor sites. A comparison with the measured indoor H*(10) showed that the estimated indoor H*(10) was not underestimated. However, the Hp(10) to H*(10) ratio indoors, which corresponds to the practical conversion factor from H*(10) to the effective dose, was significantly larger than the same ratio outdoors, meaning that the conversion factor of 0.6 is not appropriate for indoors due to the changes in irradiation geometry and gamma spectra. This could have led to a lower effective dose than Hp(10).Conclusion: The estimated effective doses correlated significantly with Hp(10), demonstrating the model’s applicability for effective dose estimation. However, the lower value of the effective dose indoors could be because the conversion factor did not reflect the actual environment.

A new conceptional model for deriving average dermal absorption estimates from studies with multiple tested concentrations for non-dietary risk assessment of pesticides

Dermal absorption values are used to translate external dermal exposure into potential systemic exposure for non-dietary risk assessment of pesticides. While the Environmental Protection Agency of the United States of America (US EPA) derives a common dermal absorption factor for active substances covering all related products, the European Food Safety Authority (EFSA) requests specific product-based estimates for individual concentrations covering the intended use rates. The latter poses challenges, because it disconnects exposure dose from applied dose in absorption studies, which may not be suitable in scenarios where concentration is not relevant. We analyzed the EFSA dermal absorption database, collected 33 human in vitro studies from CropLife Europe (CLE) companies, where ≥3 in-use dilution concentrations were tested, and 15 dermal absorption triple pack datasets. This shows that absolute dermal absorption correlates with absolute applied dose on a decadic logarithm-scale, which is concordant with the toxicological axiom that risk is driven by exposure dose. This method is radically different from the current European approach focused on concentrations and offers new insights into the relationship of internal and external exposure doses when utilizing data from in vitro studies. A single average dermal absorption value can be simply derived from studies with multiple tested concentrations, by calculating the y-intercept of a linear model on a decadic logarithm scale while assuming a slope of 1. This simplifies risk assessment and frees resources to explore exposure refinements. It also serves as a basis to harmonize dermal absorption estimation globally for use in exposure-driven risk assessments.

External dose assessment of NORM added consumer products using Geant4 Monte Carlo simulations

Radioactive consumer products (RCP) are widely marketed for everyday use. The study herein was conducted on 21 commercially available RCP, including bio-glass discs, energy cards, scalar energy products, and anti-radiation stickers, all purposefully designed to contain naturally occurring radioactive material (NORM). This study investigates the dose influence of such consumer products which acts as external radiation sources that may be in contact with human body. The goal of this study is to assess the potential risk of using NORM-added consumer products, the presence of such products in the living environment unnecessarily exposing members of the public to radiation. A Pb-shielded high purity Ge (HPGe) spectrometer was used to perform the analysis of samples radioactivity levels. Simulations were performed using Geant4 Monte Carlo (GMC) simulations to estimate the equivalent organ doses and annual effective dose (AED) in the use of such products. The total activity in such radioactive consumer products ranges from 2.0 ± 0.1 to 7413 ± 576 Bq, 1.9 ± 0.8 to 1168 ± 131 Bq, and 21 ± 5–574 ± 103 Bq, for 232Th, 238U, and 4 K, respectively. It was found that RCP contains monazite, giving a relatively high concentration of uranium and thorium. The radiological risk posed by the use of such items as healthcare products is assessed, with the daily external exposure doses of particular concern. Dose assessments of the organ equivalent and average effective doses were performed by measuring the activity of 232Th, 238U, and 4 K using the aforementioned products for various exposure duration scenarios. Accordingly, sample A13 a bio-glass disc offered concentrations with mean percentages of 1.29 ± 0.003% and 0.043 ± 0.0003% for Th and U, respectively, giving rise to estimate the greatest annual effective dose exposure of 2.54 mSv among samples, considerably in excess of the public dose limit of 1 mSv y-1

Use of tourmaline-based healthcare products and associated radiation risks

Investigation is made of 23 commercially available tourmaline-based healthcare products containing naturally occurring radioactive material (the products including hot spa stones, face masks, waist supporter slimming belts, arm relief belts, socks, insoles, soaps, and combs) with negative ion health benefits claimed by the purveyors. Assessment is made of the radiological risk posed by the use of such products, external exposure dose being the particular focus. Gamma spectroscopy analysis and Geant4 Monte Carlo (GMC) simulations are used. Organ doses are obtained using male and female human phantoms, dose conversion factors (DCFs) being included. For 238U and 232tTh the tourmaline sock, code T20 was found to contain the greatest activity, at 2.4 ± 0.2 and 28.0 ± 1.3 Bq g ̶ 1 respectively; least was for the magnetic therapy face mask, code T02, at respective values 0.04 ± 0.01 and 0.1 ± 0.01 Bq g ̶ 1. Across all of the tourmaline products, the 4 K range was 0.16 ± 0.01–16.4 ± 1.1 Bq g ̶ 1. In terms of elemental concentration, sample T20 offered the greatest concentration, with mean percentages of 0.022 ± 0.001 and 0.78 ± 0.10, for Th and U, respectively. With the assumption of exposure for a period of 8 h per day, wearing the tourmaline sock product T20 would give rise to an annual effective dose of 0.64 mSv, less than the public annual dose limit of 1 mSv. Noting that the samples may give rise to greater doses, national screening programmes for activity are suggested in seeking to mitigate unnecessary radiation exposure.

Exposure of preschool-aged children to highly-concerned bisphenol analogues in Nanjing, East China

Bisphenol analogues (BPs) have already attracted wide concern owing to the environmental and health risks they pose. The exposure pathways and health risk of preschool-aged children to BPs, however, are still poorly understood. In this study, we choose population survey with 184 preschool-age children from a suburb of Nanjing, eastern China, further reveal the internal and external exposures concentrations, distribution profiles, potential sources and eventually assess health risk of preschool-age children to eight kinds of BPs. The results verify that the 95th percentile (P95) concentrations of Ʃ8BPs ranged from 0.27 to 41.6 ng/mL, with a median concentration of 7.83 ng/mL in the urine samples. BPA, and BPF were the predominant BPs in urine, accounting for 67.3%, and 18.0% of Ʃ8BPs. The urine-based estimated daily intake (EDI) of Ʃ8BPs was 187 ng/kg body weight/day. Similarly, BPA, and BPF were the main BPs in the environmental exposure sources, accounting for 80.8%, and 11.7% of the total BPs. Moreover, the total external exposure dose of Ʃ8BPs via the environmental sources was 68.1 ng/kg body weight/day, including BPA (56 ng/kg body weight/day), BPF (7.68 ng/kg body weight/day) and BPB (2.62 ng/kg body weight/day). The oral intake of drinking water and food (vegetables and rice) was the main exposure pathways of BPs in preschool-age children. Furthermore, the hazard quotient (HQ) of BPs have been evaluated and the results show no occurrence of high risk. Additionally, the urine-based EDI was significantly higher than the total external exposure dose, suggesting the existence of other pathways of BP exposure to be further explored. To the best of our knowledge, this is the first study to conduct both an internal and external exposure assessment of BPs.

Incidence risks for cerebrovascular diseases and types of stroke in a cohort of Mayak PA workers.

Incidence risks for cerebrovascular diseases (CeVD) and some types of stroke in a cohort of 22,377 Russian Mayak nuclear workers chronically exposed to ionising radiation and followed up until the end of 2018 are reported. Among total 9469 cases of CeVD, 2078 cases were strokes that included 262 hemorrhagic strokes (HS) and 1611 ischemic strokes (IS). Data evaluation was performed with categorical and dose-response analyses estimating the relative risk (RR) and excess relative risk (ERR) per unit cumulative liver absorbed dose of external gamma-ray or internal alpha-particle exposure based on a linear model utilizing the AMFIT module of the EPICURE software. CeVD incidence was found to be significantly associated with cumulative radiation dose: ERR/Gy was 0.37 (95% confidence interval (CI) 0.27, 0.47) in males and 0.47 (95% CI 0.31, 0.66) in females for external exposure, and 0.31 (95% CI 0.11, 0.59) in males and 0.32 (95% CI 0.11, 0.61) in females for internal exposure. When the model for the analysis of external radiation effect did not include an adjustment for alpha radiation dose (and vice versa), the radiogenic risk estimate increased notably both for males and for females. In contrast, exclusion from or inclusion in the model of additional adjustments for non-radiation factors did not notably change the risk estimates. ERR/Gy of external gamma dose for CeVD incidence significantly decreased with increasing attained age (males and females) and duration of employment (females). No significant associations of either stroke or its types with cumulative gamma-ray dose of external exposure or alpha-particle dose of internal exposure were found.

АНАЛИЗ РИСКА СМЕРТИ ОТ ЦЕРЕБРОВАСКУЛЯРНЫХ БОЛЕЗНЕЙ ЛИКВИДАТОРОВ ПОСЛЕДСТВИЙ АВАРИИ НА ЧАЭС, РАБОТНИКОВ АТОМНОЙ ПРОМЫШЛЕННОСТИ

Purpose: Assessment of the risk of death of the liquidators of the Chernobyl accident from cerebrovascular diseases. Material and methods: The risk of death of liquidators of the Chernobyl accident from cerebrovascular diseases (ICD 10: I60-I69.9) was estimated using the Industry Register of persons exposed to radiation as a result of the Chernobyl accident over a thirty-year period, with a verified dose of external exposure obtained by operating in the 30 km zone of the Chernobyl NPP. The study included men - 12,663 people, 1327 of them have a dose of occupational exposure. Rough relative risks of mortality from cerebrovascular diseases were evaluated for five dose groups based on internal control. At the second stage of the study, all data were stratified by age, dose load and Follow up period. Based on the obtained stratified data file, the Poisson regression procedure was carried out, for which the Epicure AMFIT module was used and the magnitude of the excess relative risk (ERR) of death from cerebrovascular diseases was calculated and the nature of the dose dependence of EI was investigated. A cohort epidemiological study of a group of liquidators of 1986-1990 was conducted over a thirty-year period, depending on the dose, both obtained during the liquidation of the consequences of the Chernobyl accident and during work with radioactive substances (RS) in the profession. Results: For the first time, direct estimates of the radiogenic risk of death from cerebrovascular diseases have been obtained. A risk decrease in this type of death per unit dose was shown for dose loads implemented during the liquidation of the consequences of the Chernobyl accident and professional doses too. Conclusion: Liquidators in the long-term after the work on eliminating the consequences of the accident need generally accepted medical care approaches aimed at preventing and treating such common diseases as cardiovascular diseases. The results can be used in the development of radiation safety regulation.

Риск заболевания нетоксическим зобом ликвидаторов последствий аварии на Чернобыльской АЭС, работников предприятий атомной промышленности

Estimates of radiation risk of non-toxic goiter (ICD 10: E04-E04.9) in Chernobyl liquidators were given from the information database of the Sectoral register of persons exposed to radiation as a result of the Chernobyl accident for 1989-2018. Used dosimetry information contained liquidators radiation doses were measured during their work inside the Chernobyl exclusion zone, and the employees’ occupational radiation dose. The study used information about men − 12663 people, of which 1327 workers have an occupational exposure dose. At the first stage, the excess relative risk per 1 Sv (ROR/Sv) of non-toxic goiter was estimated for four groups depending on age at the time of participation in work in the Chernobyl accident zone. At the second stage of the study, a Poisson process with an intensity parameter was chosen as a statistical model of morbidity. Based on the obtained individual non-stratified data, an analytical likelihood function for the Poisson process was built and the value of the excess relative risk (RRR) of the disease with nontoxic goi-ter was calculated. The nature of the dose dependence of the IOR was studied, for which the Amfit module of the Epicure statistical software package was used. A cohort study of liquidators 1986-1990 was carried out. for 1989-2018 depending on the dose of external exposure received during the liquidation of the consequences of the Chernobyl accident, and with the total dose received in the 30-km zone of the Chernobyl nuclear power plant with the dose during professional work. The values of the radiogenic risk of non-toxic goiter in liquidators of the consequences of the Cherno-byl accident are shown. A significant increase in the risk of IOR disease per dose unit for doses received during the liquidation of the consequences of the Chernobyl accident was not found. A significant increase in risk was noted when using total doses for its calculation only for liquidators in the age group of 50-59 years. The use of doses from various types of exposure in assessing the radiogenic risk of non-toxic goiter in liquidators of the consequences of the Chernobyl accident gives different values of the excess relative risk of developing this nosology. For a correct as-sessment of the radiation risk of non-toxic goiter, it is necessary to collect data on the doses of all types of exposure (occupational, emergency, medical and natural), and only the use of the total dose can give the true risk necessary to calculate the radiation safety standards.

Radiation dose for external exposure to gamma-ray using artificial neural network and MC simulation

Radiation dose for external exposure to gamma-ray using artificial neural network and MC simulation

Оценки неопределённостей доз внешнего и внутреннего облучения населения в загрязнённых областях РФ после аварии на ЧАЭС на основе инструментальных данных

The paper presents the results estimation of uncertainties in doses to the thyroid, from external and internal exposure to radiation following the Chernobyl accident. For the estimation the data-base of radiometry activities of Cs-134+137 in the body and I-131 to the thyroid in 1986 for 28,311 residents of Kaluga region and 16,470 residents of Bryansk region. Whole body radiation spectrome-try measurements made for 167,325 residents of Bryansk region from 1990 through 1994 were used. The computational model for reassessment of I-131 activities into individual exposure doses is an analytical relationship that describes the relative dynamics of radionuclide activities in a chain consisting “vegetation”, “milk”, “thyroid” and “inside the human body”, that is the chain of successive single-chamber models with time-constant transition rates between chambers and depending on the age of a person after single deposition of radionuclides on vegetation. The dy-namics of specific activities of I-131, Cs-134+137 in the vegetation chamber is calculated according to the agroclimatic model, with account of the dynamics of precipitation, the growth of forage and food vegetation biomass according to the data of the annual variation of average daily air tem-peratures in the surface layer of the atmosphere. The official methodology was used to calculate external exposure doses and reassess whole body radiation spectrometry measurements into in-ternal exposure doses. Based on the results of the studies, uncertainty estimates were obtained in terms of standard geometric deviations in the year of the accident – for individual, average in populated areas and integral dose estimates: (minimum/average/maximum) doses of internal thyroid and whole body exposure, respectively (1.1/2,0/3.0), (1.2/1.5/2.3) and (1.3/2.9/3.3); for doses since 1987, respectively (1.2/1.9/4.0), (1.2/1.9/2.1) and (1.4/5.2/8.2). The uncertainty of the calculation model for internal doses since 1987 is estimated at 2.1 times; the uncertainties estimated from the data of individual dosimetry of external and internal exposure of the population with the allocation of critical groups are equal to 1.5 and (1.9-2.2) times, respectively.

Consideration of the contribution of the natural background component during individual control of radiation doses to personnel

When ensuring radiation safety in the Russian Federation, there is a principle of separate independent assessment of doses from natural, medical, emergency and technogenic exposure. In practice, it is not always possible to comply with this principled approach. The established dose limits are related only to man-made radiation during normal operation of sources of ionizing radiation. However, during the formation of regional and federal databases on individual doses of personnel exposure, information is entered not on technogenic exposure, but on industrial exposure, that is, without subtracting the natural radiation background. The natural component of the individual dose at low radiation doses is quite significant. Failure to its subtraction leads to an overestimation of the individual dose of external exposure of personnel. Difficulties arise in the implementation of the subtraction of the natural radiation background: 1) in what cases it is necessary to subtract the background, 2) what value to choose for the subtracted background, 3) what method to measure the background, 4) at what stage of processing the measurement information to subtract the background. This article proposes a method for solving the problem of subtracting the natural background radiation from the values of individual doses of external exposure to personnel based on results of individual dosimetric control. Using the example of the city of St. Petersburg, the natural background radiation was measured by the thermoluminescent method of individual dosimetry at 50 control points for three consecutive years (2018-2020). To measure the natural background, we used individual thermoluminescent dosimeters of the same type as those used to measure individual equivalents of external radiation doses to personnel. The choice of using the thermoluminescent method as a predominant one for adjusting the average doses of external radiation from technogenic sources of ionizing radiation when subtracting the natural component of the dose has been substantiated. Comparison of official data on personnel exposure doses with the data obtained as a result of our own measurements is made. Recommendations are given on the use of the obtained values of the average natural radiation background in the formation of regional and federal databases on individual doses of personnel exposure.