UNSCEAR Research Articles

Radiation Doses and Associated Risk From the Fukushima Nuclear Accident.

The magnitude of dose due to the Fukushima Daiichi Accident was estimated by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2013 report published in April 2014. Following this, the UNSCEAR white paper, which comprises a digest of new information for the 2013 Fukushima report, was published in October 2015. Another comprehensive report on radiation dose due to the accident is the International Atomic Energy Agency (IAEA) report on the Fukushima Daiichi Accident published in August 2015. Although the UNSCEAR and IAEA publications well summarize doses received by residents, they review only literature published before the end of December 2014 and the end of March 2015, respectively. However, some studies on dose estimation have been published since then. In addition, the UNSCEAR 2013 report states it was likely that some overestimation had been introduced generally by the methodology used by the Committee. For example, effects of decontamination were not considered in the lifetime external dose estimated. Decontamination is in progress for most living areas in Fukushima Prefecture, which could reduce long-term external dose to residents. This article mainly reviews recent English language articles that may add new information to the UNSCEAR and IAEA publications. Generally, recent articles suggest lower doses than those presented by the UNSCEAR 2013 report.

Residential Exposure to Natural Background Radiation and Risk of Childhood Acute Leukemia in France, 1990-2009.

Background:Exposures to high-dose ionizing radiation and high-dose rate ionizing radiation are established risk factors for childhood acute leukemia (AL). The risk of AL following exposure to lower doses due to natural background radiation (NBR) has yet to be conclusively determined.Methods:AL cases diagnosed over 1990–2009 (9,056 cases) were identified and their municipality of residence at diagnosis collected by the National Registry of Childhood Cancers. The Geocap study, which included the 2,763 cases in 2002–2007 and 30,000 population controls, was used for complementary analyses. NBR exposures were modeled on a fine scale (36,326 municipalities) based on measurement campaigns and geological data. The power to detect an association between AL and dose to the red bone marrow (RBM) fitting UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) predictions was 92%, 45% and 99% for exposure to natural gamma radiation, radon and total radiation, respectively.Results:AL risk, irrespective of subtype and age group, was not associated with the exposure of municipalities to radon or gamma radiation in terms of yearly exposure at age reached, cumulative exposure or RBM dose. There was no confounding effect of census-based socio-demographic indicators, or environmental factors (road traffic, high voltage power lines, vicinity of nuclear plants) related to AL in the Geocap study.Conclusions:Our findings do not support the hypothesis that residential exposure to NBR increases the risk of AL, despite the large size of the study, fine scale exposure estimates and wide range of exposures over France. However, our results at the time of diagnosis do not rule out a slight association with gamma radiation at the time of birth, which would be more in line with the recent findings in the UK and Switzerland.Citation:Demoury C, Marquant F, Ielsch G, Goujon S, Debayle C, Faure L, Coste A, Laurent O, Guillevic J, Laurier D, Hémon D, Clavel J. 2017. Residential exposure to natural background radiation and risk of childhood acute leukemia in France, 1990–2009. Environ Health Perspect 125:714–720; http://dx.doi.org/10.1289/EHP296

Environmental-Impact Assessment of Natural Radioactivity Around a Traditional Mining Area in Al-Ibedia, Sudan.

Recently, in the Sudan, traditional gold mining has been growing rapidly and has become a very attractive and popular economic activity. Mining activity is recognized as one of the sources of radioactivity contamination. Hence, the radioactivity concentration and radiological hazard due to exposure of radionuclides (226)Ra, (232)Th, and (40)K were evaluated. The measurements were performed using gamma-ray spectrometry with an NaI (Tl) detector. The results show that (226)Ra, (232)Th, and (40)K activity concentration ranged from 2.66 to 18.47, 9.20 to 51.87, and 0.17 to 419.77 Bq/kg with average values of 7.54 ± 4.91, 20.74 ± 11.29, and 111.87 ± 136.84 Bq/kg, respectively. In contrast, (222)Rn in soil, (222)Rn in air, and (226)Ra in vegetables along with radiation dose were computed and compared with the international recommended levels. Potential radiological effects to miners and the public due to (226)Ra, (232)Th, (40)K, and (222)Rn are insignificant. (226)Ra transferred to vegetables appears to be negligible compared with the allowable limit 1.0 mSv/year set by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The average value of the annual gonadal dose equivalent (AGDE) is lower than the global average of 300 µSv/year (UNSCEAR 2000). However, some locations exhibit values >300 µSv/year. To the best of our knowledge, so far there seems to be no data regarding radioactivity monitoring in traditional mining areas in the Sudan.

Detection of minor and trace elements in powdered milk

Passive gamma ray spectrometry and neutron capture prompt gamma activation analysis (PGAA) were used to investigate powdered cow's milk samples [termed optimal (1), optimal (2) and optimal (3)] collected from local markets in the city of Cairo, Egypt. Standard material with a total average activity of 0.830±0.2μCi and a certified reference material [IAEA (A-14)] were used to study the accuracy of a passive multi-gamma ray measurement method. Three powdered milk samples of the same geometry and volume were used in this analysis. The specific activity of 226Ra ranged from 24.5±2.1 to 114±1.2Bq/kg, 232Th from 8±1 to 14±1.2Bq/kg and 40K from 444±28 to 1826.1±3.1Bq/kg, all of which were higher than the activities corresponding to the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR) (50, 50 and 500Bq/kg for 226Ra, 232Th and 40K, respectively). The average dose rate at 1cm for 40K ranged from 8.21E−02±0.12 to 3.3E−1±0.22mSv/h/cm. We also showed that 208Tl81, 212Pb82 and 212Bi83 should be considered products of thorium. k0-PGAA was carried out using an integrated and calibrated prompt gamma ray system with a neutron flux of 106n/cm2 per second. The thermal to epithermal neutron flux ratio (f) and cadmium ratio were measured using a thin gold foil technique (ration=160). Different Cl concentrations were prepared as standards for k0-PGAA. The elemental concentrations of Na, Mg, Al, Ca, Mn, Fe, Cu, Ga, Zn, As, Se, Cs, Cd, In, Th and I were measured in the three powdered milk samples. The mean±standard deviation ranges of the elements were as follows: Na=1069±49–1583±53ppm, Mg=347±13.64–385±16.71ppm, Al=45±1.30–72±2.40ppm, Fe=5500±110–7123±130ppm, Zn=107±3–123±6ppm, Ca=4200±72–5483±81ppm, Mn=1269±69–1784±72ppm, Pr=1.7±0.02–2.6±0.07ppm, Ga=265±5–293±8ppm, Cu=57±0.5–64±0.9ppm, In=1000± 38.64–1574±41.34ppm, Cd=6.1±2.71–12.6±4.11ppm, I=53±0.09–62±1.18ppm, Cs=4±1.56–11±4.22ppm, As=26±0.66–29±0.89ppm, Se=126±4.8–144±5.7ppm, Th=47±1.0–78±6.0ppm.

History and Organizations for Radiological Protection.

International Commission on Radiological Protection (ICRP), an independent international organization established in 1925, develops, maintains, and elaborates radiological protection standards, legislation, and guidelines. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) provides scientific evidence. World Health Organization (WHO) and International Atomic Energy Agency (IAEA) utilise the ICRP recommendations to implement radiation protection in practice. Finally, radiation protection agencies in each country adopt the policies, and adapt them to each situation. In Korea, Nuclear Safety and Security Commission is the governmental body for nuclear safety regulation and Korea Institute of Nuclear Safety is a public organization for technical support and R&D in nuclear safety and radiation protection.

Comparative study of natural radiation exposure to the public in three uranium and oil regions of Cameroon

The objective of this work is to compare natural radiation exposure to the public in the uranium regions of Poli and Lolodorf and the oil region of Bakassi in Cameroon. From some reported studies on natural radiation exposure in Cameroon, the radiation risk was determined. Activity concentrations, external radiation, and the ingestion and inhalation dose of each of the above regions were compared with the world average value given by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). From the total dose, the radiation risk of each region was calculated and compared with the world average value. The specific case of indoor radon exposure was particularly considered. The radiation risk attributed to the indoor radon exposure was compared with the lung cancer rate in Cameroon as given by the International Agency for Research on Cancer (IARC). In conclusion, the local risks are elevated but not necessarily representative of the country as a whole.

Assessment of the Annual Additional Effective Doses amongst Minamisoma Children during the Second Year after the Fukushima Daiichi Nuclear Power Plant Disaster.

An assessment of the external and internal radiation exposure levels, which includes calculation of effective doses from chronic radiation exposure and assessment of long-term radiation-related health risks, has become mandatory for residents living near the nuclear power plant in Fukushima, Japan. Data for all primary and secondary children in Minamisoma who participated in both external and internal screening programs were employed to assess the annual additional effective dose acquired due to the Fukushima Daiichi nuclear power plant disaster. In total, 881 children took part in both internal and external radiation exposure screening programs between 1st April 2012 to 31st March 2013. The level of additional effective doses ranged from 0.025 to 3.49 mSv/year with the median of 0.70 mSv/year. While 99.7% of the children (n = 878) were not detected with internal contamination, 90.3% of the additional effective doses was the result of external radiation exposure. This finding is relatively consistent with the doses estimated by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The present study showed that the level of annual additional effective doses among children in Minamisoma has been low, even after the inter-individual differences were taken into account. The dose from internal radiation exposure was negligible presumably due to the success of contaminated food control.

Terrestrial Gamma Radiation Exposure in Bangka-Belitung Islands, Indonesia

Bangka-Belitung is known as tin producer and it geologically contains higher concentrations of natural radionuclides than most other areas. The aim of this study was to evaluate the level of terrestrial gamma radiation in Bangka-Belitung Islands. The external gamma radiation dose rate from terrestrial gamma-rays have been measured at one meter above the ground by means of a portable gamma spectrometer at 66 survey points. The terrestrial gamma dose rates in Bangka island range from 43.67 to 511.54 nGy h -1 with a mean of 183.45 nGy h -1 , while in Belitung island they range from 15.54 to 416.39 nGy h -1 with a mean of 132.60 nGy h-1. From this work, a strong correlation was found between dose rates found from in-situ radiation measurements and dose rates calculated theoretically from radioactivity contents of the soil at the same locations. Generally, Bangka-Belitung islands have higher outdoor natural gamma dose rates than the world average value of 0.058 μGy h -1 for the regions with normal background radiation specified by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Received: 27 August 2014; Revised: 05 March 2015; Accepted: 30 March 2015

Medical exposure assessment: the global approach of the United Nations Scientific Committee on the Effects of Atomic Radiation.

The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) was established in 1955 to systematically collect, evaluate, publish and share data on the global levels and effects of ionizing radiation from natural and artificial sources. Regular surveys have been conducted to determinate the frequencies of medical radiological procedure, the number of equipment and staffing and the level of global exposure using the health care level (HCL) extrapolation model. UNSCEAR surveys revealed a range of issues relating to participation, survey process, data quality and analysis. Thus, UNSCEAR developed an improvement strategy to address the existing deficiencies in data quality and collection. The major element of this strategy is the introduction of an on-line platform to facilitate the data collection and archiving process. It is anticipated that the number of countries participating in UNSCEAR's surveys will increase in the future, particularly from HCL II-IV countries.

A dynamic model to estimate the activity concentration and whole body dose rate of marine biota as consequences of a nuclear accident

This paper describes a dynamic compartment model (K-BIOTA-DYN-M) to assess the activity concentration and whole body dose rate of marine biota as a result of a nuclear accident. The model considers the transport of radioactivity between the marine biota through the food chain, and applies the first order kinetic model for the sedimentation of radionuclides from seawater onto sediment. A set of ordinary differential equations representing the model are simultaneously solved to calculate the activity concentration of the biota and the sediment, and subsequently the dose rates, given the seawater activity concentration. The model was applied to investigate the long-term effect of the Fukushima nuclear accident on the marine biota using 131I, 134Cs, and, 137Cs activity concentrations of seawater measured for up to about 2.5 years after the accident at two locations in the port of the Fukushima Daiichi Nuclear Power Station (FDNPS) which was the most highly contaminated area.The predicted results showed that the accumulated dose for 3 months after the accident was about 4–4.5Gy, indicating the possibility of occurrence of an acute radiation effect in the early phase after the Fukushima accident; however, the total dose rate for most organisms studied was usually below the UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation)’s bench mark level for chronic exposure except for the initial phase of the accident, suggesting a very limited radiological effect on the marine biota at the population level. The predicted Cs sediment activity by the first-order kinetic model for the sedimentation was in a good agreement with the measured activity concentration. By varying the ecological parameter values, the present model was able to predict the very scattered 137Cs activity concentrations of fishes measured in the port of FDNPS. Conclusively, the present dynamic model can be usefully applied to estimate the activity concentration and whole body dose rate of the marine biota as the consequence of a nuclear accident.

The communication of the radiation risk from CT in relation to its clinical benefit in the era of personalized medicine: part 1: the radiation risk from CT.

The theory of radiation carcinogenesis has been debated for decades. Most estimates of the radiation risks from CT have been based on extrapolations from the lifespan follow-up study of atomic bomb survivors and on follow-up studies after therapeutic radiation, using the linear no-threshold theory. Based on this, many population-based projections of induction of future cancers by CT have been published that should not be used to estimate the risk to an individual because of their large margin of error. This has changed recently with the publication of three large international cohort follow-up studies, which link observed cancers to CT scans received in childhood. A fourth ongoing multi-country study in Europe is expected to have enough statistical power to address the limitations of the prior studies. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) report released in 2013 specifically addresses variability in response of the pediatric population exposed to ionizing radiation. Most authorities now conclude that there is enough evidence to link future cancers to the radiation exposure from a single CT scan in childhood but that cancer risk estimates for individuals must be based on the specifics of exposure, age at exposure and absorbed dose to certain tissues. Generalizations are not appropriate, and the communication of the CT risk to individuals should be conducted within the framework of personalized medicine.

CLARIFYING THE PARADIGM ON RADIATION EFFECTS & SAFETY MANAGEMENT: UNSCEAR REPORT ON ATTRIBUTION OF EFFECTS AND INFERENCE OF RISKS

The aim of this paper is to describe a relatively recent international agreement on the widely debated concepts of: (i) attributing effects to low dose radiation exposure situations that have occurred in the past and, (ii) inferring radiation risk to situations that are planned to occur in the future. An important global consensus has been recently achieved on these fundamental issues at the level of the highest international intergovernmental body: the General Assembly of the United Nations. The General Assembly has welcomed with appreciation a scientific report on attributing health effects to radiation exposure and inferring risks that had been prepared the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) following a formal request by the General Assembly.

Radiological risk assessment of 238U, 232Th and 40K in Thailand coastal sediments at selected areas proposed for nuclear power plant sites

This paper reports on the distribution of three natural radionuclides 238U, 232Th and 40K in marine sediments along the Gulf of Thailand to establish baseline data for future environmental monitoring. Sediments were collected from five potential sites selected for nuclear and thermal power plants commission as well as heavy industry development. Concentration of uranium and thorium were determined using inductively coupled plasma mass spectrometry (ICP-MS) as well as activity of 238U series (226Ra), 232Th series (228Ac) and 40K by γ-spectroscopy. The radiation hazard parameters were calculated based on United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Variation in concentration of natural radionuclides at different sampling areas could be attributed to organic matter content and sediment particle size. The radiological health hazards to the people living nearby sampling areas and the people who handle the marine sediments are within limits recommended by UNSCEAR.

A high-resolution map of gamma dose rates in Cluj County, Romania using LiF:Mg,Cu,P detectors.

Outdoor gamma radiation measurements in Cluj County, Romania have been performed using solid-state thermoluminescent detectors in order to develop a high-resolution database for natural gamma dose rates. Integrated measurements have been carried out for an exposure time of minimum 3 weeks. According to European Union requirements, the territory has been divided into 69 grids of 10 × 10 km. The cells were monitored using LiF:Mg,Cu,P detectors. For two locations the results were 136 ± 7 and 150 ± 7 nGy h(-1), respectively. These results can be explained by the existent geological substrate. The values ranged from 56 ± 4 to 150 ± 7 nGy h(-1), with an average value of 91 ± 2 nGy h(-1), being in agreement with the 2008 United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) Report. A high-resolution map of gamma dose rates in Cluj County is presented for the first time.

Specific Activity and Radioactive Contour Maps of Natural (<sup>40</sup>K, <sup>226</sup>Ra and <sup>232</sup>Th) and Anthropogenic (<sup>137</sup>Cs) Radionuclides in Surface Soil Samples from Phang Nga Province, Thailand

The specific activity of the natural (40K, 226Ra and 232Th) and anthropogenic (137Cs) radionuclides have been studied and evaluated for 97 surface soil samples collected from 7 districts of Phang Nga province in the south of Thailand. High-purity germanium (HPGe) detector and gamma ray spectrometry analysis system were employed to measure and analyze the experimental results. It was found that, the ranges of specific activities of 40K, 226Ra, 232Th and 137Cs in surface soil samples are 251.50 – 15740.34, 15.21 – 791.42, 18.14 – 854.34 and < 0.33 – 16.91 Bq/kg with average values are 2886.77 ± 225.93, 165.71 ± 8.45, 160.36 ± 7.93 and 5.76 ± 2.49 Bq/kg, respectively. The results were also compared with some research data in national and global radioactivity measurement and evaluations. Furthermore, the radiological hazards of Phang Nga province were calculated through the radium equivalent activity (Raeq), the external hazard index (Hex), the gamma absorbed dose rate (D) and the annual effective dose rate (AEDout) and also compared with research data in the south of Thailand and the safety limits recommended values by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Moreover, the radioactive contour maps of the natural (40K, 226Ra and 232Th) and anthropogenic (137Cs) radionuclides have been also created for the investigated area.

The impact of the Fukushima nuclear accident on marine biota: Retrospective assessment of the first year and perspectives

An international study under the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) was performed to assess radiological impact of the nuclear accident at the Fukushima-Daiichi Nuclear Power Station (FDNPS) on the marine environment. This work constitutes the first international assessment of this type, drawing upon methodologies that incorporate the most up-to-date radioecological models and knowledge.To quantify the radiological impact on marine wildlife, a suite of state-of-the-art approaches to assess exposures to Fukushima derived radionuclides of marine biota, including predictive dynamic transfer modelling, was applied to a comprehensive dataset consisting of over 500 sediment, 6000 seawater and 5000 biota data points representative of the geographically relevant area during the first year after the accident. The dataset covers the period from May 2011 to August 2012. The method used to evaluate the ecological impact consists of comparing dose (rates) to which living species of interest are exposed during a defined period to critical effects values arising from the literature.The assessed doses follow a highly variable pattern and generally do not seem to indicate the potential for effects. A possible exception of a transient nature is the relatively contaminated area in the vicinity of the discharge point, where effects on sensitive endpoints in individual plants and animals might have occurred in the weeks directly following the accident. However, impacts on population integrity would have been unlikely due to the short duration and the limited space area of the initially high exposures. Our understanding of the biological impact of radiation on chronically exposed plants and animals continues to evolve, and still needs to be improved through future studies in the FDNPS marine environment.

Characterization of 222Rn and meteorological parameters in Uro houses at South Kordofan state

This study was carried out to assess and map indoor radon concentration and to estimate radiation dose in Uro town in Sudan's South Kordofan state. A portable radon meter (RRA-01M-03), equipped with simple sensors of meteorological parameters has been used for carrying out radon measurement. The annual absorbed dose from the corresponding measured radon concentration was calculated using dose rate conversion factors of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The corresponding annual effective dose and equivalent dose to the lungs were estimated. Measured activity concentrations of 222Rn, annual absorbed dose, annual effective dose and equivalent dose to the lungs were found in the range 20–4482 Bq/m3, 0.32–70.67 mSv/y, 0.76–169.61 mSv−y and 0.16 × 10−7 to 35,856 × 3.5856 × 10−11 mSv−y, with geometric mean 109.43 Bq/m3, 1.73, 4.16 and 1.1 × 10−7 mSv−y, respectively. Upon comparing the results with global data, it was found with the exception of six samples, the obtained values fall far below the action level of 200–600 Bq/m3 recommended by the International Commission on Radiological Protection. However, the geometric mean is higher than the reported average global indoor radon concentration. Meteorological parameters were measured and no correlation was noted between radon concentration and these parameters. The overall annual effective dose was higher than the UNSCEAR recommended reference dose level of 1.0 mSv−y.

Radiological Health Hazard Indices and Excess Life Time Cancer Risk of Oil Producing Communities in Nigeria

The γ radiation exposure due to radioactivity concentration of K, U and Th in soil samples from 250 different locations from 40 communities in the oil – producing region of Nigeria was carried out. The radioactivity concentrations of these radionuclides were used to determine the absorbed dose, annual effective dose equivalent, the health hazard indices and cancer risk using standard analytical methods. The range of values for the absorbed dose are 6.97 nGyh to 33.29 nGyh, annual effective dose equivalent Original Research Article British Journal of Medicine & Medical Research, 4(36): 5853-5865, 2014 5854 (outdoor) are 8.55 μSvy to 40.83 μSvy and (indoor) are 34.19 μSvy to 163.36 μSvy. The external hazard index ranges from 0.038 to 0.174 while the internal health hazard index is from 0.045 to 0.191. The cancer risk obtained for the communities ranges from 0.030 x 10 to 0.143 x 10. All these values are below the standard limits when compared to the world permissible United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR) values for such environment. This shows that the exploration and exportation of crude oil in Nigeria did not pose a radioactive health hazard to the oil producing communities.

Potential impacts of radon, terrestrial gamma and cosmic rays on childhood leukemia in France: a quantitative risk assessment

Previous epidemiological studies and quantitative risk assessments (QRA) have suggested that natural background radiation may be a cause of childhood leukemia. The present work uses a QRA approach to predict the excess risk of childhood leukemia in France related to three components of natural radiation: radon, cosmic rays and terrestrial gamma rays, using excess relative and absolute risk models proposed by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Both models were developed from the Life Span Study (LSS) of Japanese A-bomb survivors. Previous risk assessments were extended by considering uncertainties in radiation-related leukemia risk model parameters as part of this process, within a Bayesian framework. Estimated red bone marrow doses cumulated during childhood by the average French child due to radon, terrestrial gamma and cosmic rays are 4.4, 7.5 and 4.3 mSv, respectively. The excess fractions of cases (expressed as percentages) associated with these sources of natural radiation are 20 % [95 % credible interval (CI) 0-68 %] and 4 % (95 % CI 0-11 %) under the excess relative and excess absolute risk models, respectively. The large CIs, as well as the different point estimates obtained under these two models, highlight the uncertainties in predictions of radiation-related childhood leukemia risks. These results are only valid provided that models developed from the LSS can be transferred to the population of French children and to chronic natural radiation exposures, and must be considered in view of the currently limited knowledge concerning other potential risk factors for childhood leukemia. Last, they emphasize the need for further epidemiological investigations of the effects of natural radiation on childhood leukemia to reduce uncertainties and help refine radiation protection standards.

Risk of medical imaging

Risk of medical imaging