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.     

Kinetics of fuel particle weathering and 90Sr mobility in the Chernobyl 30-km exclusion zone

Weathering of fuel particles and the subsequent leaching of radionuclides causes 90Sr mobility in Chernobyl soils to increase with time after deposition. Studies of 90Sr speciation in soils collected in 1995 and 1996 from the Chernobyl 30-km exclusion zone have been used to calculate rates of fuel particles dissolution under natural environmental conditions. Results show that the velocity of fuel particle dissolution is primarily dependent on the physico-chemical characteristics of the particles and partially dependent on soil acidity. Compared to other areas, the fuel particle dissolution rate is significantly lower in the contaminated areas to the west of the Chernobyl reactor where deposited particles were presumably not oxidized prior to release. The data have been used to derive mathematical models that describe the rate of radionuclide leaching from fuel particles in the exclusion zone and changes in soil-to-plant transfer as a function of particle type and soil pH.     

Environmental radioactivity and dose evaluation in Taiwan after the Chernobyl accident

A substantial increase in fission product activity was observed in various environmental samples taken in Taiwan after the Chernobyl accident. The concentration of long-lived fission products in air above ground, precipitation, grass, vegetation and milk were monitored in the next 7 wk. The individual effective dose equivalent committed by the first year of exposure and intake following the accident were evaluated. Average individual doses for the population in Taiwan are estimated at 0.9 microSv due to global fallout from the Chernobyl accident. This value is lower than that reported in neighboring countries in the Far East and poses no increased health impact to the public in Taiwan.     

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.     

Retrospective evaluation of 131I deposition density and thyroid dose in Poland after the Chernobyl accident

The 131I deposition in Poland after the Chernobyl accident on 26 April 1986 was evaluated from the determined 129I deposition and the estimated 129I/131I ratio at the time of the arrival of fallout. Concentrations of 129I and 127I were determined by neutron activation analysis in uncultivated soils from 16 locations in Poland. Determination of 137Cs in soils was carried out by gamma spectrometry. The atomic ratio of 129I/131I at the time of fallout arrival was estimated using the 129I/131I ratio at the time of the accident, which, on the basis of the core inventory data, was assumed to be 22.8. It was estimated from the time of fallout arrival and from the weighed mean atomic ratio that the 129I/131I ratio for Poland was 32.8. The calculated 131I deposition ranged from 63.2 to 729 kBq m(-2). High deposition of 131I occurred in the locations with rainfall but occasionally also in locations without rainfall. Committed equivalent doses from 131I were evaluated for 5-y-old children, 10-y-old children, and adults using the computer model CLRP for the situations with and without countermeasures including iodine prophylaxis. The highest thyroid doses from inhalation and ingestion without countermeasures were 178 mSv, 120 mSv, and 45 mSv for 5-y-old children, 10-y-old children, and adults, respectively. The countermeasures reduced these doses by about 30%.     

Reduction of births in Italy after the Chernobyl accident

After the Chernobyl accident serious concern spread throughout Italy about the possible effects of the consequent exposure to radioactivity on fetuses. A reduction of births in the first three months of 1987, and particularly in February (7.2% reduction in the birth rate), was observed throughout Italy. In April-June 1987 a 4.8% increase in the number of births was observed. The magnitude of both phenomena varied in different areas of the country. The total number of births in the first six months of 1987 was very similar to the expected (264,241 versus 263,659). Induced abortions increased in Lombardia (northern Italy) in June (+1.6%) and July of 1986 (+3.4%) and in Campania (southern Italy) in June (+12.7%) and August (+4.3%). No increase in legal abortions was detected in Lazio (central Italy). Italian data suggest a voluntary decrease in the number of planned pregnancies and the termination of some of them in the first weeks after the accident as a consequence of postdisaster stress.     

Estimate of the dose due to 90Sr to the Austrian population after the Chernobyl accident

In order to estimate the contribution of 90Sr to the exposure of the Austrian population, the ratio of 90Sr to 137Cs in 126 food samples and nine drinking water samples was determined. From this and the average activity concentration of 137Cs in each type of food as obtained by the measurement of some 100,000 food samples after the Chernobyl accident, a good estimate of the average activity concentration of 90Sr in these food items could be obtained. Samples were investigated at various times after the accident to take into account possible changes with time in the 90Sr-activity concentration and its ratio to 137Cs. Also, pre-Chernobyl samples were measured to estimate the relative contribution of the reactor accident and the fallout of the atomic bomb testing to the intake of 90Sr. Assuming average food consumption, the intake of 90Sr for an adult person amounted to 168 Bq in the first year and 115 Bq in the second year after the accident, resulting in an effective dose equivalent of 5.9 muSv and 4.0 muSv, respectively. This is a minor fraction of the dose due to the ingestion of Cs isotopes, which amounted to 360 muSv in the first year and 97 muSv in the second year. For the one-year-old infant, a 90Sr intake of 96 Bq (10.5 muSv) in the first year and 65 Bq (7.1 muSv) in the second year is estimated. Approximately 50% of the intake in the first year and 70% of that in the second year are due to 90Sr from nuclear weapons testing.     

Radioactive waste management in the Chernobyl exclusion zone: 25 years since the Chernobyl nuclear power plant accident

Radioactive waste management is an important component of the Chernobyl Nuclear Power Plant accident mitigation and remediation activities in the so-called Chernobyl Exclusion Zone. This article describes the localization and characteristics of the radioactive waste present in the Chernobyl Exclusion Zone and summarizes the pathways and strategy for handling the radioactive waste-related problems in Ukraine and the Chernobyl Exclusion Zone and, in particular, the pathways and strategies stipulated by the National Radioactive Waste Management Program.     

137Cs uptake with cafeteria food after the Chernobyl accident.

After the Chernobyl accident, the activity concentrations of radiocesium were measured in both the meals served at the cafeteria of a research center and in the employees eating there. The time-dependent means of monthly 137Cs activities in meals and people show a similar distribution pattern with highest values between March and July 1987, i.e., only 1 y after the accident. In meals, the highest activities were found when the menu consisted of pork, milk, or milk products. The 50-y cumulative effective dose calculated from the whole-body measurements is 0.21 mSv for male and 0.15 mSv for female employees. Cafeteria food contributed only a small share to this exposure.     

Assessment of radiocesium incorporation in Austrians after the Chernobyl accident

Residents of Vienna, Austria were whole-body counted for radiocesium content due to fallout deposited after the Chernobyl accident. Data for a 2-y period were compared with prior estimates of radiocesium body burden based on food consumption. Our results suggest that the prior estimates be revised and the rejection limit be increased by a factor of 2 for contaminated food.     

Risk estimation of radioactive contamination after the Chernobyl accident using bioindicators.

After the Chernobyl nuclear accident, game meat and, in particular, sheep meat in the Republic of Croatia showed a high degree of radioactive contamination compared to large livestock. The activity concentrations of 131I, 134Cs, and 137Cs were measured in meat and internal organs (i.e., lung, liver, kidney, and heart) of game (e.g., venison, hare, and wild boar) and sheep that were used as biological indicators of radioactive contamination. In order to estimate the importance of game and sheep as a dietary source of radioactivity, the effective dose equivalent for the average and critical population (hunters and livestock raising families) were calculated. The data indicated that sheep meat represents greater risk for the human population, in case of a nuclear accident, than game meat. The share of meat from sheep (4.4%) prevailed over the share of meat from game (0.5%) when comparing the average intake of meat per inhabitant in Croatia. This result pointed to an increased risk for families who depend mostly on sheep meat in the case of a nuclear accident.     

Time trends of thyroid cancer incidence in Ukraine after the Chernobyl accident.

The rate of childhood thyroid cancer incidence observed in northern Ukraine during the period 1986-1998 is described as a function of time-since-exposure, age-at-exposure, and sex. Conclusions are drawn for the excess absolute risk per dose: after a minimal latency period of about three years it shows a linear increase with time-since-exposure for at least nine years. It is roughly constant in age-at-exposure, up to 15 years. For girls exposed very young it is about a factor 2 larger than for boys. For children exposed at age 16-18 this ratio increases to about 5. The thyroids of young children are not more sensitive to radiation dose than those of older ones in absolute risk in northern Ukraine in the currently used data set. As the background is increasing with age, a constant absolute risk gives a decreasing relative risk.     

Multi-fractal nature of radioactivity deposition on soil after the Chernobyl accident.

Fractal analysis is introduced in the field of environmental health physics. In particular, it is applied to the complex and inhomogeneous deposition pattern of radioactivity after the Chernobyl accident. The patchiness of 137Cs hot spots is quantified by a fractal dimension as low as 1. The problem of finding hot spots that might be of health concern is discussed.     

European stillbirth proportions before and after the Chernobyl accident

BACKGROUND: Numerous investigations have been carried out concerning the possible impact of the Chernobyl accident, in April 1986, on the prevalence of anomalies at birth and on perinatal mortality. The accident has contaminated Eastern Europe more heavily than Western Europe. If there was an effect of the radioactive contamination on perinatal mortality or stillbirth proportions one would expect to find it more pronounced in Eastern Europe as compared to Western Europe. We therefore studied long-term time trends in European stillbirth proportions. METHODS: Linear logistic regression was applied to model the time trends in stillbirth proportions. Dummy variables were used to account for effects that can be associated with certain years or locations. A synoptic logistic regression model is suggested for the western, central, and eastern parts of Europe. RESULTS: There is a marked differential effect in the long-term stillbirth time trends between Western Europe (Belgium, France, Great Britain, Iceland, Ireland, Luxembourg, Portugal, Spain), Central Europe (Austria, Denmark, Germany, Italy, Norway, Switzerland), and Eastern Europe represented by four countries (Greece, Hungary, Poland, Sweden). In contrast to the western and central European trends, the eastern European trend exhibits an absolute increase of the stillbirth proportion in 1986 as compared with 1985 and an apparent upward shift of the whole trend line from 1986 on. CONCLUSION: Our results are in contrast to those of many analyses of the health consequences of the Chernobyl accident and contradict the present radiobiological knowledge. As we are dealing with highly aggregated data, other causes or artefacts may explain the observed effects. Hence, the findings should be interpreted with caution and further independent evidence should be sought.     

Leukemia following the Chernobyl accident

The accident at the Chernobyl Nuclear Power Plant in Ukraine in 1986 led to a substantial increase of thyroid cancer among those exposed as children. The other cancer that is the most sensitive to the effects of ionizing radiation is leukemia, and this paper evaluates the evidence relating exposure to Chernobyl radioactivity and leukemia risk. Two types of objectives are identified, namely, scientific evidence and public health, and two approaches to addressing such objectives are discussed. Empirical studies in affected populations are summarized, and it is concluded that, possibly apart from Russian cleanup workers, no meaningful evidence of any statistical association between exposure and leukemia risk as yet exists. However, it is important to carry on with such studies to satisfy various public health objectives.     

Population health protection at territories contaminated after the Chernobyl accident

A concept of preserving population health at territories contaminated after the Chernobyl accident is proposed, which is based on the results of multifactorial evaluation of relationships and prognostic evaluations of the basic medical demographic parameters.     

Radiocesium concentration in migratory birds wintering in Spain after the Chernobyl accident

Levels of 137Cs and 134Cs resulting from the Chernobyl nuclear accident were studied in 195 birds that winter in two regions of Spain. Only five of the 12 species examined were contaminated. The average values for 137Cs vary between 1.6 and 41 Bq kg-1 fresh. In particular, the contamination for song-thrushes (Turdus philomelos) are compared between the regions of Extremadura and Valencia, 350 km east of Extremadura at the same latitude. The results show that the contamination of birds wintering in Spain decreases from east to west. The whole-body dose commitment for humans consuming these contaminated birds was calculated. The values are well below the established ICRP guideline.