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PubMed1999

Chernobyl post-accident management: the ETHOS project.

ETHOS is a pilot research project supported by the radiation protection research program of the European Commission (DG XII). The project provides an alternative approach to the rehabilitation of living conditions in the contaminated territories of the CIS in the post-accident context of Chernobyl. Initiated at the beginning of 1996, this 3-y project is currently being implemented in the Republic of Belarus. The ETHOS project involves an interdisciplinary team of European researchers from the following institutions: the Centre d'etude sur l'Evaluation de la Protection dans le domaine Nucleaire CEPN (radiological protection, economics), the Institute National d'Agronomie de Paris-Grignon INAPG (agronomy, nature & life management), the Compiegne University of Technology (technological and industrial safety, social trust), and the Mutadis Research Group (sociology, social risk management), which is in charge of the scientific co-ordination of the project. The Belarussian partners in the ETHOS project include the Ministry of Emergencies of Belarus as well as the various local authorities involved with the implementation site. The ETHOS project relies on a strong involvement of the local population in the rehabilitation process. Its main goal is to create conditions for the inhabitants of the contaminated territories to reconstruct their overall quality of life. This reconstruction deals with all the day-to-day aspects that have been affected or threatened by the contamination. The project aims at creating a dynamic process whereby acceptable living conditions can be rebuilt. Radiological security is developed in the ETHOS project as part of a general improvement in the quality of life. The approach does not dissociate the social and the technical dimensions of post-accident management. This is so as to avoid radiological risk assessment and management being reduced purely to a problem for scientific experts, from which local people are excluded, and to take into consideration the problems of acceptability of decisions and the distrust of the population towards experts. These cannot be solved merely by a better communication strategy. This paper presents the main features of the methodological approach of the ETHOS project. It also explains how it is being implemented in the village of Olmany in the district of Stolyn (Brest region) in Belarus since March 1996, as well as its initial achievements.

Animals↗
PubMed1999

Long-term follow-up of the 137Cs body burden of individuals after the Chernobyl accident--a means for the determination of biological half-lives.

Since 1986, the year of the Chernobyl accident, 137Cs body burdens of members of a Bavarian reference group have been measured monthly. These time series were individually analyzed with respect to the long-term component T1 of the biological half-life of 137Cs, assuming a continuous 137Cs intake, which is based on reference data for the food consumption in the Federal Republic of Germany. In 13 individual cases, T1 was additionally deduced after single ingestion of 137Cs. The resulting T1 deduced from continuous and from single intake agreed within about 20%. Using the results of 64 cases, it is shown that there is a dependency of T1 with sex for adults. T1 for children and adults are also significantly different. When combining all data for children, adult females and adult males, significant correlations of T1 with age, 40K and body mass can be found. Since body mass, for example, is a parameter very simple to measure, the given correlations are useful for practical purposes.

Adolescent↗
PubMed1999

Derivation of working levels for radionuclides in animal feedstuffs for use following a nuclear accident.

Maximum permitted levels of radiocesium in marketed animal feedstuffs have been specified by the European Commission for use in the event of a future nuclear accident. However, more specific guidance is required for use under UK conditions. Using information on typical animal diets, relative activity concentrations in feedstuffs and feed-to-product transfer, practical working levels have been derived for (134,137)Cs and 90Sr in animal feedstuffs and drinking water; application of these levels should ensure that activity concentrations in milk, meat, or eggs do not exceed the relevant Council Food Intervention Level. Despite the complexity of some animal diets, only one or two feedstuffs typically contribute 5% or more to intakes of activity. The working levels for radiocesium in these feedstuffs ranged from a factor of 20 higher than the maximum permitted levels to a factor of around 20 lower. In most cases, the maximum permitted levels are unnecessarily cautious. Working levels for 90Sr in feedstuffs are generally higher than those for radiocesium, except for feedstuffs for dairy cattle and laying hens. Factors affecting the practicability and effectiveness of changes in diet as a countermeasure to reduce activity concentrations in animal products were also considered within this study.

Animal Feed↗
PubMed2000

Internal exposure from the ingestion of foods contaminated by 137Cs after the Chernobyl accident--report 2. Ingestion doses of the rural population of Ukraine up to 12 y after the accident (1986-1997).

Doses from the ingestion of 134Cs and 137Cs during 12 y following the Chernobyl accident have been estimated for approximately 3 million persons living in rural areas of the Zhitomir, Rivne, and Kyiv Oblasts of northern Ukraine. This assessment is based upon an extensive monitoring campaign that provided measurements of 137Cs in more than 120,000 samples of milk and in more than 100,000 persons; such measurements were made in approximately 4,500 locations. Two approaches were used for the dose assessment. In the first approach a so-called reference dose is estimated for each settlement on the basis of measured 137Cs concentration in milk, determination of the milk equivalent of diet, and consumption rates; a further assumption is that a high fraction of the food consumed is produced locally. The reference dose is used as the official dose estimate, which is the basis for any decision on possible financial compensation and economic privileges. In a second step, the so-called real age-dependent dose is estimated from the results of whole body counter measurements and the kinetics of radiocesium in the human body. Real doses above 0.5, 5, and 50 mSv were received by about 40%, 10%, and 0.2%, respectively, of the considered population. With the exception of 1986, for which the monitoring results were limited, the real individual doses derived from whole-body counting are consistently lower than the reference doses. However, this difference declined from a factor of 3-4 in 1987-1989 to a factor of approximately 1.5 in the mid 1990's. The difference between reference and real doses is attributed to the effectiveness of countermeasures implemented after the accident. The effectiveness of these countermeasures decreased with time due to increasing economic problems in Ukraine. The collective reference and real doses of the rural population due to the intake of 134Cs and 137Cs are estimated to be 13,300 and 5,300 person-Sv, respectively. Thus, about 8,000 person-Sv is estimated to have been averted by countermeasures.

Age Factors↗
PubMed2001

Statistical data evaluation in mobile gamma spectrometry: an optimization of on-line search strategies in the scenario of lost point sources.

There is a potential risk that hazardous radioactive sources could enter the environment, e.g., via satellite debris, smuggled radioactive goods, or lost metal scrap. From a radiation protection point of view there is a need for rapid and reliable methods for locating and identifying sources. The methods could also be used to locate hot spots after radioactive fallout. Carborne and airborne gamma spectrometry systems are suitable for the task. This work focuses on a situation where the radionuclide to search for is known, which is not an unlikely scenario. The possibility that the source is located near a road can be high, and thus motivating a carborne spectrometer system. The main object is to optimize on-line statistical methods in order to achieve a high probability for locating the point source and still have reasonably few false alarms caused by variations in the natural background radiation. Data were obtained from a carborne 3-L NaI(Tl) detector and two point sources located at various distances from the road. The nuclides used were 137Cs and 131I. Spectra were measured stationary on the road. From these measurements we have reconstructed counts in spectral windows applicable to different speed and sampling times; the time 3 s and speeds 32 and 54 km h(-1) are used in this work. The maximum distance a source can be located from the road and still be detected is estimated with four different statistical analysis methods. This distance is called the critical distance, CD. The method is applied on gross counts in the full energy peak spectral window. For each method alarm levels have been calculated from background data obtained in Scania (Skåne), in the south of Sweden. The results show large differences in CD. With the best approach, the two sources could be detected from about 180 m (137Cs, 6 GBq) and 170 m (131I, 4.5 GBq).

Automobiles↗
PubMed2002

A consistent radionuclide vector after the Chernobyl accident.

The radionuclide vector in the release plume from the destroyed unit 4 of the Chernobyl Nuclear Power Plant was assessed. Emphasis was laid on radionuclides relevant for the internal dose, including those with short half-lives, and on the radionuclide vector in the 30-km zone where practically no data in air or foodstuff are available. An evaluation of data was performed by comparing core analysis data and actual measurements of air filters and deposition data. The derived nuclide vector is consistent with most measurements and core analysis data. The ratios of the various radionuclides with regard to the guide isotope 137Cs vary both with direction of release and with increasing distance from the power plant. The variation and its causes are discussed, and a credible, consistent model for the vector at arbitrary distances from the nuclear power plant, in particular with regard to non-volatile radionuclides, is given. In that way the observed large discrepancies of the radionuclide vector determined by Russian and Ukrainian researchers, and those measured in Central and Northern European are explained by the fact that 90Sr, 95Zr, 140Ba, and 144Ce, which showed a much higher ratio to 137Cs close to the reactor than at 1,000 km distance, were attached to particle sizes of 8 microm and thus quicker deposited than the volatile radionuclides which were attached to 1 microm particulates on average. Also, the 131I to 137Cs ratio changes with distance by almost one order of magnitude which is explained by the higher deposition velocity of iodine.

Air Pollutants, Radioactive↗
PubMed2002

Reconstruction of the inhalation dose in the 30-km zone after the Chernobyl accident.

Due to lack of measurements of activity concentrations in air, the assessment of the inhalation dose of the population evacuated from the 30-km zone after the Chernobyl accident is not possible from continuous filter measurements. Since the evaluation of the inhalation dose in each settlement of the zone is of great interest for epidemiological purposes, an approach was chosen that utilizes the available data on ground deposition of 137Cs, a recently performed best estimate of the radionuclide vector and its spatial distribution as well as the radionuclide dependent deposition velocity. The derived inhalation dose values in the 30-km zone range between 3 mSv to 150 mSv effective dose for adults depending on the distance to the reactor site and the day of evacuation. For 1-y-old infants the values range between 10 to 700 mSv. In Chernobyl town, an effective inhalation dose of 25 mSv until evacuation day was assessed. Thyroid doses due to inhalation ranged from 0.02 to 1 Sv for adults, for 1-y-old infants from 0.02 to 6 Sv. The inhalation dose in each settlement of the 30-km zone is approximately 8-13 times higher than the external exposure in each settlement if evacuation of the settlement occurred at an early stage. For settlements with evacuation at a later stage (day 10 or later) the inhalation dose was about 50-70% higher than the external dose. The dominant contribution to the effective inhalation dose comes from 131I (about 40%) and tellurium and rubidium isotopes (about 20-30%). Despite high zirconium and cerium ground depositions, zirconium and cerium isotopes contribute rather little to the inhalation dose which is mainly due to the great particle sizes to which they are attached. The relative contribution of short-lived radionuclides is, despite higher activities than at greater distances, less than 5%.

Air Pollutants, Radioactive↗
PubMed2002

Reconstruction of the ingestion doses received by the population evacuated from the settlements in the 30-km zone around the Chernobyl reactor.

As a consequence of the Chernobyl accident, about 50,000 people were evacuated from the settlements in the 30-km zone around the reactor in the period 3-11 d after the accident. As no countermeasures were implemented in the early phase, people continued to consume milk and some leafy vegetables. In this paper, average effective ingestion doses are modeled for evacuees. Input data for the assessment are the 137Cs activity per unit area, the ratios of the radionuclides relative to 137Cs, the mean day of evacuation, and intake rates for milk and green vegetables. The transfer of radionuclides from deposition to humans is estimated by modeling radionuclide interception by vegetation, weathering, and the time-dependent transfer of radionuclides to milk taking into account site-specific agricultural practices. Depending on the evacuation day and site, the estimated ingestion doses for the settlements are in the range of 20 to 1,300 mSv and 3 to 180 mSv for infants and adults, respectively. 131I is by far the most important isotope, the ingestion dose due to 133I is more than one order of magnitude lower. The most exposed organ is the thyroid, inducing more than 80% and 50% of the ingestion dose for infants and adults. The ingestion doses are compared to the doses due to inhalation and external exposure. The internal dose exceeds the external by a factor of about 2-10 for adults and 2-40 for 1-y-old infants depending on site and evacuation day. The thyroid doses assessed for the evacuees are consistent with results achieved in studies performed in areas outside the 30-km zone.

Adult↗
PubMed2002

Chernobyl accident: retrospective and prospective estimates of external dose of the population of Ukraine.

Following the Chernobyl accident many activities were conducted in Ukraine in order to define the radiological impact. Considered here are gamma spectrometric analyses of soil-depth-profile samples taken in the years 1988-1999, gamma spectrometric measurements of radionuclide concentration in soil samples taken in 1986, and measurements of external gamma-exposure rate in air. These data are analyzed in this paper to derive a "reference" radionuclide composition and an attenuation function for the time-dependent rate of external gamma exposure that changes due to the migration of radiocesium into the soil column. An attenuation function for cesium is derived that consists of two exponential functions with half lives of 1.5 and 50 y. The dependencies of attenuation on direction and distance from the Chernobyl Nuclear Power Plant are also demonstrated. On the basis of these analyses the average individual and collective external gamma doses for the population of Ukraine are derived for 1986, 1986-2000, and 1986-2055. For the 1.4 million persons living in rural areas with 137Cs contamination of >37 kBq m(-2), the collective effective dose from external exposure is estimated to be 7,500 person-Sv by the end of 2000. A critical group of 22,500 persons who received individual doses of >20 mSv is identified for consideration of increased social and medical attention.

Adolescent↗
PubMed2003

Evaluation of radioactive exposure from 137Cs in contaminated areas of Northern Ukraine.

The paper gives averages of 137Cs deposition densities in soils from three areas in Northern Ukraine measured 12 to 15 y following the Chernobyl accident: in an area near Narodici (75 km west of the Chernobyl nuclear power plant in the so-called zone II) heavily contaminated by the Chernobyl fall-out and in areas around Korosten and Zhitomir showing contamination levels to be much lower. The three areas exhibited very different 137Cs deposition densities of 2.2 MBq m(-2), 400 kBq m(-2), and 5 kBq m(-2), respectively. During a 1-y observation, measurements of the 137Cs transfer in the food chain to humans and 137Cs whole body contents dependent on the 137Cs daily intake were carried out under realistic conditions of the rural inhabitants who lived in settlements within zone II. Detailed investigations of components of the daily diet showed that the high 137Cs contamination levels found in soils of zone II do not affect in any way low 137Cs concentrations of all important agricultural products harvested and consumed by villagers. With regard to consumption habits of the population of zone II, mushrooms and wild berries were found to contribute more than 95% of the 137Cs daily intake to the 137Cs whole body content of about 12 kBq (with maximum values up to 760 kBq) measured in a group of inhabitants of zone II during a period from July 1998 to July 1999. The median of the annual dose of these inhabitants from external and internal exposures was 1.2 mSv y(-1) with a geometric standard deviation of 2.6. Excluding extreme habits, the geometric mean of the total exposure was 1.0 mSv y(-1) with a geometric standard deviation of 1.3.

Adolescent↗
PubMed2004

Dose reconstruction by EPR spectroscopy of tooth enamel: application to the population of Zaborie village exposed to high radioactive contamination after the Chernobyl accident.

Individual irradiation doses were determined by electron paramagnetic resonance spectroscopy of the tooth enamel of the inhabitants of Zaborie, the most contaminated inhabited settlement not evacuated after the Chernobyl accident. Dose determination was performed using a specially developed automatic spectrum processing procedure. Spectrum processing was carried out in different operating modes, and average results were taken in order to reduce the contribution of uncertainty in dose determination caused by spectrum processing. The absorbed doses determined in enamel were corrected to take into account the contribution of natural background radiation and to determine the individual excess dose due to radioactive contamination of the territory. Individual excess doses are compared to calculated individualized doses to teeth, estimated using the local radioactive contamination levels, dose rates, and information concerning individual behavior. The individual excess doses measured by electron paramagnetic resonance spectroscopy and the calculated individualized doses are fully independent. Mean square variation between results of two methods was found to be 34 mGy, which is consistent with error estimation for both methods. This result can validate both the methodology of signal processing presented here when using electron paramagnetic resonance dosimetry of tooth enamel for low doses and the methodology of individualized dose calculation.

Algorithms↗
PubMed2004

Application of NCRP air screening factors for evaluating both routine and episodic radionuclide releases to the atmosphere.

Two separate methods were used to identify the most important historic airborne releases of radionuclides at the Idaho National Engineering and Environmental Laboratory (INEEL) with regard to potential human health impact. Both routine and episodic releases were evaluated. Although not specifically intended for an initial screening or ranking evaluation, particularly for episodic releases, the National Council on Radiation Protection and Measurements (NCRP) screening method was shown to be a valid method for providing a measure of the relative importance of both routine and episodic radionuclide releases, based on comparisons with the Radiological Safety Analysis Code (RSAC). For the work at the INEEL, a relative ranking procedure was used to identify the most important releases because a screening criterion (e.g., dose or risk value) against which the potential health impacts of the releases could be measured was not established. In addition, a precedent for a screening-level evaluation of episodic releases is lacking at this time. As a result, a ranking procedure was considered necessary because it was not clear that the NCRP method would provide screening-level dose estimates for episodic releases that could be defensibly compared to a screening criterion. To evaluate the NCRP method at the INEEL, routine operational releases were evaluated and ranked separately from episodic, or acute, releases because different assumptions and approaches were required to assess their potential importance. Based on comparisons with the RSAC method, the NCRP method may slightly underpredict the ingestion dose for episodic releases; however, using the NCRP screening method to identify the relative importance of release events, radionuclides, years, and facilities was shown to be valid and defensible for both routine and episodic releases. Because of the NCRP method's simplicity and relative ease of application, it provides a cost-effective and scientifically defensible way to make decisions and set priorities about decisions and directions in risk assessment.

Air Movements↗
PubMed1999

Pathomorphology of thyroid gland lesions associated with radiation exposure: the Chernobyl experience and review of the literature.

The common sources of ionizing radiation exposure to the thyroid gland in humans are accidental environmental exposure and medical, therapeutic, or diagnostic irradiation. Radiation often induces notable histologic changes in the thyroid tissue and is a well-established risk factor for benign and malignant thyroid tumors. In this paper, we review the acute and chronic histologic changes in the thyroid gland subjected to irradiation, and characterize benign thyroid nodules and malignant tumors arising after exposure, with particular emphasis on thyroid lesions in the population exposed to ionizing radiation as a result of the Chernobyl nuclear accident.

Acute Disease↗
PubMed2006

Unexpected additional increase in the incidence of thyroid cancer among a recent birth cohort in Switzerland.

Data collected by the Swiss Cancer Registries Network (ASRT/VSKR) have been used to analyse trends in thyroid cancer during the last available 20 years, to make within-country geographical comparisons for current incidence rates. Age-standardized (European population) incidence rates per 100,000 for all morphologies combined ranges from 1.62 to 2.99 among males and from 2.13 to 8.09 among females in Switzerland. Regression analyses for both sexes combined detected an increase in time for papillary cases and a decrease for other types. Age-period-cohort analyses revealed that the youngest cohorts of men and women born after 1940 had an increased risk of all types of thyroid cancer while the cohort of people born between 1920 and 1939 were at increased risk of the papillary subtype. Assuming a higher sensitivity to ionizing radiation among the youngest people, a Chernobyl effect cannot be definitively excluded and continuous study of this topic should be encouraged.

Adenocarcinoma↗
PubMed2005

Method for estimating ingestion doses to the public near the Savannah River site following an accidental atmospheric release.

At the Savannah River Site, emergency response computer models are used to estimate dose following releases of radioactive materials to the environment. Downwind air and ground concentrations and their associated doses from inhalation and ground shine pathways are estimated. The emergency response model (PUFF-PLUME) uses real-time data to track either instantaneous (puff) or continuous (plume) releases. A site-specific ingestion dose model was developed for use with PUFF-PLUME that includes the following ingestion dose pathways pertinent to the surrounding Savannah River Site area: milk, beef, water, and fish. The model is simplistic and can be used with existing code output.

Air Pollutants, Radioactive↗
PubMed2006

Measurement of 129 I and 137 Cs in soils from Belarus and reconstruction of 131I deposition from the Chernobyl accident.

I and Cs have been measured in a large number of soil samples collected throughout the country of Belarus to support efforts for thyroid-dose reconstruction following the Chernobyl accident. Samples of soil consisting of multiple 30-cm-deep cores per site were sampled following a selection process to ensure sites were undisturbed and representative. Samples were measured by accelerator mass spectrometry (AMS) for I, gamma spectrometry for Cs, and gas chromatography (GC) for total iodine. Results show that both I and Cs are retained firmly in the top approximately 15 to 20 cm of the soil. Our results also suggest that the correlation between I and Cs deposition across the country of Belarus is poor; hence, I is a better surrogate for I than is Cs. It was also noted that total iodine concentrations in topsoil from Belarus are low compared with other regions of the world where radiogenic thyroid cancer has been studied.

Cesium Radioisotopes↗