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PubMed1996

Internal exposure from the ingestion of foods contaminated by 137Cs after the Chernobyl accident. Report 1. General model: ingestion doses and countermeasure effectiveness for the adults of Rovno Oblast of Ukraine.

The Chernobyl accident, which occurred in April 1986, resulted in the atmospheric release of about 70--100 PBq of 137Cs. This paper examines the doses to the adult population of the northern part of Rovno Oblast, Ukraine, from ingestion of 137Cs. Fallout of 137Cs in these regions was lower than in other regions of Ukraine. However, the transfer of 137Cs from soil to milk in the region considered is high (up to 20 Bq L-1 per kBq m-2) and results in the predominance of internal doses compared to those from external exposure. Numerous measurements of 137Cs soil deposition, 137Cs milk contamination, and 137Cs body burden have been made in the area and form the basis of a general model of internal exposure from the ingestion of foods contaminated by 137Cs. This paper has two main purposes. The first is to develop the general phenomenological description of the process leading to internal exposure from the ingestion of 137Cs contaminated foods in the situation where different countermeasures are realized. The second is to apply the model for the adult population of the northern part of the Rovno Oblast (first report) for the limited time period of up to six years after the accident. The doses actually received by the adults are estimated to be four to eight times smaller than the doses calculated for the situation without countermeasures.

Adult↗
PubMed1996

Countermeasures for radiocesium in animal products in Norway after the Chernobyl accident--techniques, effectiveness, and costs.

Nine years after the reactor accident in Chernobyl contamination by radiocesium is still a significant problem in sheep and reindeer production in Norway. To reduce the impact of the accident, effective countermeasures had to be developed and implemented. The levels of radiocesium in meat were reduced by a combination of countermeasures such as special feeding, use of cesium binders (bentonite and Prussian blue), and changing of slaughtering time. The countermeasures were labor intensive and expensive. Costs per averted dose per person-Sv were calculated to range from NOK 1,000 to 100,000 (7 NOK = $1 U.S.), with the use of cesium binders being the least expensive and condemnation of meat the most costly. Dietary advice, which did not include any compensation costs, had a cost of NOK 40 per person-Sv. Apart from the rejection of meat in 1986, countermeasures were deemed to be justified on a cost-benefit basis (less than NOK 600,000 per person-Sv).

Animals↗
PubMed1996

Summary of the BIOMOVS A4 scenario: testing models of the air-pasture-cow milk pathway using Chernobyl fallout data.

A unique opportunity to test dose assessment models arose after the Chernobyl reactor accident. During the passage of the contaminated plume, concentrations of 131I and 137Cs in air, pasture, and cow's milk were collected at various sites in the northern hemisphere. Afterwards, contaminated pasture and milk samples were analyzed over time. Under the auspices of the Biospheric Model Validation Study (BIOMOVS), data from 13 sites for 131I and 10 sites for 137Cs were used to test model predictions for the air-pasture-cow milk pathway. Calculations were submitted for 23 models, 10 of which were quasi-steady state. The others were time-dependent. Daily predictions and predictions of time-integrated concentrations of 131I and 137Cs in pasture grass and milk for six months post-accident were calculated and compared with observed data. Testing against data from several locations over time for several steps in the air-to-milk pathway resulted in a better understanding of important processes and how they should be modeled. This model testing exercise showed both the strengths and weaknesses of the models and revealed the importance of testing all parts of dose assessment models whenever possible.

Air Pollutants, Radioactive↗
PubMed1996

The feasibility of using 129I to reconstruct 131I deposition from the Chernobyl reactor accident.

Radioiodine released to the atmosphere from the accident at the Chernobyl nuclear power station in the spring of 1986 resulted in large-scale thyroid-gland exposure of populations in Ukraine, Belarus, and Russia. Because of the short half life of 131I (8.04 d), adequate data on the intensities and patterns of iodine deposition were not collected, especially in the regions where the incidence of childhood-thyroid cancer is now increasing. Results are presented from a feasibility study that show that accelerator-mass-spectrometry measurements of 129I (half life 16 x 106 y) in soil can be used to reconstruct 131I-deposition density and thus help in the thyroid-dosimetry effort that is now urgently needed to support epidemiologic studies of childhood-thyroid cancer in the affected regions.

Cesium Radioisotopes↗
PubMed1996

Long term radiocesium contamination of fruit trees following the Chernobyl accident.

Radiocesium contamination from the Chernobyl accident of fruits and leaves from various fruit trees was systematically studied from 1990 to 1995 on two agricultural experimentation farms in Northern Greece. The results are discussed in the framework of a previously published model describing the long-term radiocesium contamination mechanism of deciduous fruit trees after a nuclear accident. The results of the present work qualitatively verify the model predictions.

Cesium Radioisotopes↗
PubMed1997

An analysis of time-dependence for Chernobyl fallout in Italy.

We present here an analysis of the airborne radioactivity measured in Italy after the Chernobyl accident. We provide some quality assurance, isolate suspicious data, and devise a mathematical model to aid in interpreting time-dependent fallout data. The model consists of an interpolating function whose parameters can be related to 1) the arrival time of the radioactive cloud; 2) the time of the maximum radioactive concentration; and 3) the decay-rate of airborne radioactivity as the pollutant cloud passes. Multiple arrivals of the radioactive cloud in a given site can also be considered. The parametrization can be used to estimate concentrations of 137Cs using measurements of (131)I, 103Ru, or 132Te. The interpolating function is fitted to the data collected in several Italian Provinces. We feel this model is an useful tool for interpreting time-dependent fallout data.

Cesium Radioisotopes↗
PubMed1997

Reconstruction of doses and deposition in the western trace from the Chernobyl accident.

A model is presented for the explosive cloud of particulates that produced the western trace of high radioactive ground contamination in the Chernobyl accident on 26 April 1986. The model was developed to reproduce measured dose rates and nuclide contamination and to relate estimated doses to observed changes in: (1) infrared emission from the foliage and (2) morphological and histological structures of individual pines. Dominant factors involved in ground contamination were initial cloud shape, particle size distribution, and rate of particle fallout. At time of formation, the cloud was assumed to be parabolical and to contain a homogeneous distribution of spherically shaped fuel particulates having a log-normal size distribution. The particulates were dispersed by steady winds and diffusion that produced a straight line deposition path. The analysis indicates that two clouds, denoted by Cloud I and Cloud II, were involved. Fallout from the former dominated the far field region and fallout from latter the region near the reactor. At formation they had a full width at half maximum of 1800 m and 500 m, respectively. For wind velocities of 5-10 m s(-1) the particulates' radial distribution at formation had a standard deviation and mode of 1.8 microm and 0.5 microm, respectively. This distribution corresponds to a release of 390 GJ in the runaway explosion. The clouds' height and mass are not uniquely determined but are coupled together. For an initial height of 3,600 m, Cloud I contained about 400 kg fuel. For Cloud II the values were, respectively, 1,500 m and 850 kg. Loss of activities from the clouds is found to be small. Values are obtained for the rate of radionuclide migration from the deposit. Various types of biological damage to pines, as reported in the literature, are shown to be mainly due to ionizing radiation from the deposit by Cloud II. A formula is presented for the particulate size distribution in the trace area.

Air Pollution, Radioactive↗
PubMed1997

Survey of the 137Cs contamination in Belgium by in-situ gamma spectrometry, a decade after the Chernobyl accident.

The residual radiocesium concentration, nearly 10 y after the Chernobyl accident, is measured at different sites on the Belgian territory by means of in-situ gamma-spectrometry. A possible link between the rainfall at the beginning of May 1986 and the actual cesium concentration is investigated. The radiological impact of this contamination, even in the most affected regions in the Ardennes, is very small (<6 microSv y(-1)).

Belgium↗
PubMed1998

Cancer incidence among liquidators of the Chernobyl accident: solid tumors, 1986-1995.

The paper considers information about cancer incidence (solid tumors) among liquidators of the Chernobyl accident, which occurred in April 1986. The information was accumulated in the Russian National Medical and Dosimetric Registry (RNMDR) in the period from 1986 to early 1996. The RNMDR contains individual dosimetric and annual check-up data on liquidators resident in Russia. This paper presents results for male liquidators who had no oncological diseases before arrival to the 30-km zone and for whom the following information was available: confirmed dose of external radiation, birth date, date of arrival to the 30-km zone, time spent in the 30-km zone, and results of medical check-ups. The number of liquidators under study is 114,504, i.e., about 68% of all those registered in the RNMDR. The average dose of the studied cohort is 108 mGy; the average age at first arrival to the 30-km zone is 34.3 y; the total number of person-y is 797,781. The cohort of liquidators is briefly characterized. Cancer incidence in liquidators is compared to that of the population of Russia as a whole by calculating standardized incidence ratio (SIR). The values of SIR with 95% confidence intervals for all solid tumors and malignant neoplasms of the digestive system were 1.23 (1.15; 1.31) and 1.11 (1.01; 1.24), respectively. Assessment of radiation risks for the same classes of diseases has revealed a statistically significant increase in cancer incidence with external radiation dose. This study also shows that statistically significant excesses in the incidence of malignant neoplasms of the respiratory system have not been observed.

Adolescent↗
PubMed1999

Chernobyl accident: reconstruction of thyroid dose for inhabitants of the Republic of Belarus.

The Chernobyl accident in April 1986 resulted in widespread contamination of the environment with radioactive materials, including (131)I and other radioiodines. This environmental contamination led to substantial radiation doses in the thyroids of many inhabitants of the Republic of Belarus. The reconstruction of thyroid doses received by Belarussians is based primarily on exposure rates measured against the neck of more than 200,000 people in the more contaminated territories; these measurements were carried out within a few weeks after the accident and before the decay of (131)I to negligible levels. Preliminary estimates of thyroid dose have been divided into 3 classes: Class 1 ("measured" doses), Class 2 (doses "derived by affinity"), and Class 3 ("empirically-derived" doses). Class 1 doses are estimated directly from the measured thyroidal (131)I content of the person considered, plus information on lifestyle and dietary habits. Such estimates are available for about 130,000 individuals from the contaminated areas of the Gomel and Mogilev Oblasts and from the city of Minsk. Maximum individual doses are estimated to range up to about 60 Gy. For every village with a sufficient number of residents with Class 1 doses, individual thyroid dose distributions are determined for several age groups and levels of milk consumption. These data are used to derive Class 2 thyroid dose estimates for unmeasured inhabitants of these villages. For any village where the number of residents with Class 1 thyroid doses is small or equal to zero, individual thyroid doses of Class 3 are derived from the relationship obtained between the mean adult thyroid dose and the deposition density of (131)I or 137Cs in villages with Class 2 thyroid doses presenting characteristics similar to those of the village considered. In order to improve the reliability of the Class 3 thyroid doses, an extensive program of measurement of (129)I in soils is envisaged.

Adolescent↗
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

Chernobyl-derived radiocesium in heather honey and its dependence on deposition patterns.

Gamma-ray spectra were measured from Scottish heather honey samples gathered from hive locations with associated airborne gamma-ray survey data. The honeys all contained radiocesium, with activity concentrations ranging from 43-680 Bq kg(-1) 137Cs, and 134Cs/137Cs ratios consistent with Chernobyl deposition. Activity concentrations in honey were highly correlated with ground deposition within 2.5 km of the hive location over two successive years. Both isotope ratios and the quantitative relationships between environmental and food levels suggest that weapons testing fallout is significantly less available than recent deposition. The implications for design of future monitoring programs and radiological consequences are discussed. The whole-body retention of 137Cs in honey ingested by a volunteer was consistent with the ICRP's metabolic model for cesium.

Air Pollutants, Radioactive↗
PubMed2000

Relationship between the 137Cs whole-body counting results and soil and food contamination in farms near Chernobyl.

We measured the radioactivity in the soil and child food samples from farms near Mogilev (56-270 GBq km(-2) 137Cs), Gomel (36-810 GBq km(-2) 137Cs), and Klincy (59-270 GBq km(-2) 137Cs), who had whole-body 137Cs counting results measured as part of a health examination in the Chernobyl Sasakawa Health and Medical Cooperation Project. Soil contamination on the family farm seems to be the main source of human contamination because most of the people in the area live on small farms and they and their domestic animals eat crops from the farms. A clear correlation was found between the children's whole-body 137Cs counting results and the radioactivity in their food (correlation coefficient: 0.76; confidence level of correlation: 3.2 x 10(-9)). There were also significant correlations between the whole-body 137Cs counting results and both the radioactivity of the soil samples (correlation coefficient: 0.22; confidence level of correlation: 0.0107) and the average contamination level of their current residence (correlation coefficient: 0.20; confidence level of correlation: 0.0174).

Cesium Radioisotopes↗
PubMed2000

Radiation-epidemiological analysis of incidence of non-cancer diseases among the Chernobyl liquidators.

The work is concerned with assessment of radiation risks for non-cancer disease among the Chernobyl liquidators from 1986 to 1996. As of 1 January 1999, the Russian National Medical and Dosimetric Registry contains medical and dosimetric data for 174,000 liquidators. The cohort of 68,309 liquidators for whom best verified medical data are available is discussed. The dose dependency of incidence of non-cancer diseases was estimated by the cohort method and using the software package Epicure. For some classes of non-cancer diseases among liquidators, statistically significant estimates of radiation risk were derived for the first time. The highest excess relative risk per 1 Gy was found for cerebrovascular diseases; ERR Gy(-1)=1.17 at the 95% confidence interval (0.45; 1.88).

Adolescent↗
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

Age- and sex-specific relative thyroid radiation exposure to 131I in Ukraine after the Chernobyl accident.

The age- and sex-dependence of the 131I induced count rates is determined for the measurements performed in Ukraine after the Chernobyl accident on the thyroids of over 60,000 persons. For this, the individual measurements are scaled in such a way that the mean values over age and sex on one side and the mean values over measurement series on the other side are normalized to one. The resulting distribution of all scaled measurements is roughly log-normal. Half of them lie within a factor 1.6 of the median. 131I induced count rates have a minimum at birth year 1986, about half the value of adults. The maximum count rates with about 30% above adults are reached for males around age 16 y. The count rates are up to about 40% (at age 14-17 y) higher for males than for females. The results are within statistical uncertainties independent of the geographical area and the urban or rural nature of the settlements. Starting from the relative count rates, the age- and sex-dependence is calculated for the thyroid activities 1 mo after the accident for the integrated activities and for the doses. The dose of young children is a factor of about 6.5 higher than that of adults. Uncertainties are estimated throughout.

Adolescent↗
PubMed2001

Mortality among the Chernobyl emergency workers: estimation of radiation risks (preliminary analysis).

This paper presents results of the analysis of mortality among Chernobyl accident emergency workers who are resident in Russia. The analysis is based on information for the cohort of emergency workers (males) from six regions of Russia including 65,905 persons with documented external doses in the range 0.005-03 Sv. These data were gathered during the period 1991 to 1998 and cover a total of 426,304 follow-up person-y. In this period, 4,995 deaths occurred in the cohort under study. The mortality analysis was performed for four groups of causes of death (ICD-9 codes): (1) malignant neoplasms (140-239); (2) cardiovascular diseases (390-459); (3) injuries, poisoning and violent deaths, (800-999); and (4) the remainder (other than the above). The standardized mortality rate for groups 1, 3, and 4 is less than unity and varies from 0.6 to 0.9. For group 2 (death from cardiovascular diseases) the standardized mortality rate conforms with the control within 95% confidence intervals. The control was the mortality rate (males) for the corresponding ages in Russia in general and the internal control, the spontaneous mortality among emergency workers, derived from the equation of the observed and expected number of cases in the followed up cohort. Dose response of mortality was studied. Statistically significant radiation risks were obtained for mortality from malignant neoplasms (515 cases) and cardiovascular diseases (1,728 cases). The values of the excess relative risk per unit dose (ERR Sv(-1)) for malignant neoplasms and cardiovascular diseases are estimated as 2.11 (1.31, 2.92 95% CI) and 0.54 (0.18,0.91 95% CI) (for external control), 2.04 (0.45, 4.31 95% CI) and 0.79 (0.07, 1.64 95% CI) (for internal control), respectively. The risk of death from all noncancer causes is close to zero and not statistically significant.

Dose-Response Relationship, Radiation↗