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Children exposed to chronic contamination after the Chernobyl accident: cytogenetic and radiotoxicological analyses.

In this study, we describe cytogenetic studies of lymphocytes obtained from children who were exposed after the Chernobyl accident to low doses of ionizing radiation. We sought to determine possible chromosomal damage relative to internal contamination, as measured by whole-body counter and urine radiotoxicological analyses. The study was performed during a 1-mo period on the peripheral blood of children hosted in Italy, but who resided in contaminated regions of the Russian Federation and Belarus. We used conventional cytogenetics to detect chromosomal aberrations. In some cases, we also used "chromosome painting" to look for stable aberrations. There were more acentric fragments in subjects than in controls; a few chromosome and chromatid breaks werefound in the subjects, but this finding did not differ significantly between subjects and controls.

Body Burden↗

Chernobyl, four years on.

It is still too soon to make a full assessment of the Chernobyl disaster, but one should be begun, and practical inferences, with particular reference to the prevention of radiation-induced cancers, may be drawn.

Accidents, Occupational↗

Observation of fallout in Hiroshima caused by the reactor accident at Chernobyl.

Fallout from the reactor accident at Chernobyl has been surveyed at Hiroshima. gamma-rays from samples of aerosol, rain water and tap water were measured using low-background gamma-ray spectrometers and concentrations of activities were followed. Almost all of the nuclides detected in Europe were observed in Hiroshima. In addition to dominant volatile fission products of 131I, 132Te-132I and 103Ru, long-lived fission products 137Cs, 106Ru-106Rh, 125Sb and activities produced through the (n, gamma) process in the reactor such as 134Cs, 136Cs and 110mAg were observed in relatively high concentrations.

Accidents↗

131I dose to the human fetal thyroid in the Zagreb district, Yugoslavia, from the Chernobyl accident.

The 131I activity was measured in 30 human fetal thyroids in Zagreb district after the Chernobyl accident. A model of radioiodine metabolism in the mother and human fetus which takes into account the age dependence of the uptake and retention of radioiodine in the fetal thyroid was developed. Having assessed that the total intake by the average mother was about 1330 Bq, a good correlation between calculated and measured fetal thyroid activities was found (r = 0.77, P less than 0.001). The fetal thyroid dose reached the maximum of 0.43 micro Gy/Bq intake at about the fifth month of gestation. It was concluded that the risk of having a child with a harmful trait due to 131I absorbed by the mother was negligible.

Accidents↗

The dependence of skin lesions on the depth-dose distribution from beta-irradiation of people in the Chernobyl nuclear power plant accident.

A detailed study was made of the conditions of exposure of 56 victims of the Chernobyl accident who suffered radiation lesions in the skin. The most typical conditions were experimentally reconstructed in order to investigate the specific characteristics of the distribution of doses to the skin according to depth for different exposure conditions. The absorbed doses at depths of 7 mg cm-2 and 150 mg cm-2 were calculated on the basis of measurements with multilayer skin dosemeters. The patients were classified into four groups. Dosimetric characteristics for each group were compared with the clinical pictures to establish the critical factors in the occurrence of lesions. It was demonstrated that the depth-dose distribution of beta-radiation to the skin is of great influence not only for the early effects of radiation but also for the later effects. Radiation lesions in the skin led to death if the area of the lesions exceeded about 50% of the total body surface, and if the doses to the skin were about 200-300 Gy at 7 mg cm-2 and more than about 30 Gy at 150 mg cm-2.

Accidents↗

'Rogue' cells observed in children exposed to radiation from the Chernobyl accident.

Eight 'rogue' lymphocyte metaphases containing a large number of aberrant chromosomes were noted during a survey of chromosomal damage in 328 Belarussian children. The study population comprised children of families living in territory contaminated by radiation from the Chernobyl accident. The majority of the sample had been evacuated within 1 week from very heavily polluted territory to areas that had received much less fallout. Two hundred cells were scored per subject and one rogue cell was found in a child exposed in utero; one in a child conceived after the accident and six in the postnatally exposed group. The possibility that the damage was due to exposure to radio-iodine concentrated in the thyroid gland, or to radiation from incorporated 'hot particles' of an alpha or beta/gamma emitter is discussed. It is concluded that the damage to these cells is unlikely to have been caused by radiation.

Accidents↗

Late T cell deficiency in victims of the Chernobyl radiation accident: possible mechanisms of induction.

T cell number, serum concentrations of thymic hormones and anti-epithelial autoantibodies were studied in people affected at Chernobyl NPP. Group 1 took part in the clearing-up operation and had no clinical manifestations of acute radiation sickness. Group 2 worked at the NPP during the accident; they survived acute radiation sickness (degree I-II, subgroup 2a; degree III-IV, subgroup 2b). The total doses of external radiation were 0.1-0.5 Gy in group 1, up to 4 Gy in subgroup 2a and up to 9 Gy in subgroup 2b. Total T cell number, serum thymic activity and alpha 1-thymosin concentration were decreased in all groups of affected persons. CD8+ cell number decreased only in group 1; CD4+ cell number in subgroup 2b. A decrease in thymic hormone level was most prominent in subgroup 2b. The titres of anti-epithelial antibodies were increased in all groups of affected persons independently of radiation dose. The titres were higher in patients with subnormal levels of alpha 1-thymosin. It has been proposed that radiation alters the function of thymic epithelial cells by direct action and/or through indirect mechanisms including participation of autoantibodies. The observed complex of alterations is similar to that in the normal process of immunological ageing.

Accidents↗

Chromosome painting in highly irradiated Chernobyl victims: a follow-up study to evaluate the stability of symmetrical translocations and the influence of clonal aberrations for retrospective dose estimation.

Follow-up fluorescence in situ hybridization (FISH) measurements of symmetrical translocations were performed in peripheral blood lymphocytes from 12 highly irradiated victims of the Chernobyl nuclear power plant accident biannually, between September 1991 and July 1994, to investigate the persistence of these aberration type with time post-exposure. Translocations were determined using biotin-labelled painting DNA probes for human chromosomes 1, 4 and 12 and a digoxigenin-labelled alpha-satellite pancentromeric DNA probe. In 11 of 12 cases the translocation frequencies remained fairly constant during the observation period, which allows to generate comparable dose estimates on the various sampling times. In one case (no. 9) the existence of a cell clone containing the consistent chromosome rearrangement t(1;13) (q25;q14) was identified using FISH in rehybridized slides with a digoxigenin-labelled painting DNA probe for chromosome 13 and a separate G-banding analysis. To obtain reliable dose estimates, total translocation frequency has to be corrected for the high contribution (16.5-23.5%) of this clonal translocation.

Accidents↗

Chromosome translocations in thyroid tissues from Belarussian children exposed to radioiodine from the Chernobyl accident, measured by FISH-painting.

Chromosome painting of chromosomes 1, 4 and 12 was performed on metaphase preparations of cultured thyroid cells to analyse the frequency of radiation-induced stable chromosome translocations in papillary thyroid carcinomas from 40 Belarussian children exposed to radioiodine from the Chernobyl accident, and from 31 reference case. As expected, we found the highest translocation frequencies in secondary thyroid tumours after radiotherapy, but there were also high frequencies in tumour tissues as well as in non-tumourous tissues from childhood papillary carcinoma samples from Belarus. Among the Belarussian tumours the cases from the Gomel region exhibited the highest frequency of translocations and five cases lie within the range of frequencies observed in secondary thyroid tumours after radiotherapy. The findings support the assumption that radiation was the principal cause of the tumours in Belarus, but they indicate also that only a minority of the Belarus cases, which have developed papillary carcinomas, were exposed to very high doses of radioiodine.

Adolescent↗

Micronuclei in lymphocytes of children from the vicinity of Chernobyl before and after 131I therapy for thyroid cancer.

The present study addresses the monitoring of children from the Belorussian and Ukrainian Republics exposed to the fall-out of the Chernobyl accident. Micronucleus analysis has been performed on 56 children from different areas. The micronucleus frequencies in individuals as well as in regional groups were comparable with controls, except for three donors. Such results had to be expected, taking into account that at least 7 years have passed since the accident. Most of the children whose micronucleus frequencies were determined are suffering from thyroid cancer and were treated by radioiodine (131I) therapy. We studied the effect of in vitro exposure with 131I on micronucleus induction and that proliferative ability of lymphocytes. The present investigation indicates that micronuclei can be usefully employed to detect individual exposures to the incorporated radionuclide within several days after the intake of the radionuclide in a dose range of around 65-390 mGy (effective dose).

Adolescent↗

Living with rattlesnakes: Chernobyl and Dounreay.

After the Three Mile Island nuclear plant accident in 1979, a local Pennsylvania resident told The New York Times 'You live with that plant over there for years and years and don't think much about it. But it's like living with a rattlesnake. Sooner or later it's going to bite you. You just don't know when.' As we enter the twenty-first century, many communities find themselves living with rattlesnakes--one at least of which has already bitten. This article considers the official responses to Chernobyl in the first decade after the accident and compares them to the statements surrounding the sudden 1998 decision to decommission the nuclear reprocessing plant at Dounreay in Scotland.

Explosions↗

Short rotation coppice as alternative land use for Chernobyl-contaminated areas of Belarus.

Field experiments were conducted in the Chernobyl-affected area to assess if short rotation coppice (SRC) for energy production is a feasible alternative for contaminated land. Four willow clones were planted on sandy and peaty soil and the radiocaesium (137Cs) and radiostrontium (90Sr) transfer factors (TF) and yield relevant parameters were recorded during four growing seasons. The 137Cs and 90Sr soil-to-willow wood TF on sandy soil (second growing season) were on average 1.40+/-1.06 x 10(-3) m2 kg(-1) and 130+/-74 x 10(-3) m2 kg(-1), respectively. The 137Cs TF recorded for the peaty soil (fourth growing season or end of the first rotation cycle) was on average 5.17+/-1.59 x 10(-3) m2 kg(-1). The 90Sr-TF was on average 2.61+/-0.44 x 10(-3) m2 kg(-1). No significant differences between clones for the 137Cs and 90Sr-TF were observed. Given the high TFs and the high deposition levels, Belarus exemption levels for fuel wood were highly exceeded. The annual average biomass production for one rotation cycle on the peaty soil ranged from 7.8 to 16.0 t ha(-1) y(-1) for one of the clones, comparable with average annual yield figures obtained for western Europe. On the sandy soils, first-year yields were 0.25 t ha(-1) y(-1). These soils are not suitable for SRC production and should better be dedicated to pine forests or drought-resistant grasses.

Cesium Radioisotopes↗

Total body potassium measurement--the effect of fallout from Chernobyl.

As a result of fallout from the nuclear accident at Chernobyl in April 1986, the caesium radioisotopes, 134Cs and 137Cs, have been detected in man. A minor consequence of this is that total body potassium (TBK) measurements obtained from the whole body activity of 40K, a naturally occurring radioisotope of potassium, can be overestimated because of gamma spectrum overlap between 134Cs and 40K. Whole-body activities for 134Cs and 40K were measured in 18 healthy adults (13 M, 5 F) in June/July, 1986, using a whole-body counter with NaI crystal scintillation detectors. Studies using anthropometric phantoms containing known activities of the two radionuclides, allowed the contribution of 134Cs to the '40K activity' in the human subjects to be assessed. The group mean 134Cs level was 172 Bq, resulting in an average overestimate in TBK of 2.8%. It is recommended that when TBK measurements are being undertaken and 134Cs contamination is suspected, then 134Cs levels should be measured and their effect corrected for.

Accidents↗

Strategy for population protection and area rehabilitation in Russia in the remote period after the Chernobyl accident.

The report presents the history of the development of criteria for radiation and social protection of the Russian population residing in the areas contaminated with radionuclides after the Chernobyl accident, in the remote time periods after the accident. The tendencies for reduction of standards with time are shown, and their causes are analysed. It is noted that the optimization principle was not applied in the explicit form for population protection. The current radiation situation in the contaminated areas of Russia is described, and the future situation is forecast. Main pathways of external and internal population exposure are described. Modern possibilities for reduction of the population exposure dose are discussed. The authors propose promising criteria and methods for population protection and rehabilitation of contaminated areas in Russia.

Health Physics↗

Dynamics of thyroid cancer incidence in Russia following the Chernobyl accident.

This paper presents an analysis of thyroid cancer incidence in the territories of Russia most contaminated after the Chernobyl accident. In the work, data on incidence in the Bryansk, Kaluga, Orel and Tula regions (5298000 persons) are used. Altogether, 2599 cases of thyroid cancer are considered from 1982 to 1995. Of them, 143 cases were among the population who were children and adolescents at the time of the accident in 1986. The work uses the approach based on comparison of distributions of thyroid cancer cases by age at diagnosis and age at exposure. It has been shown that since 1991 the age structure of the incidence has changed significantly with a growing proportion of cases among children and adolescents. The change in the structure occurred due to the radiation factor, specifically as a result of exposure of thyroid to incorporated 131I. It has been shown that the standardised incidence ratio (SIR) of thyroid cancer among children who were 0-4 years at exposure in 1991-6 was 6 to 10 times higher than among adults. On the average, SIR for children and adolescents at the time of exposure is about three times higher than in adults.

Adolescent↗

Iodine nutrition and the risk from radioactive iodine: a workshop report in the chernobyl long-term follow-up study.

The major fallout of radionuclides from the nuclear power station accident at Chernobyl on 26 April, 1986, occurred in regions of Ukraine and Belarus that are believed to be moderately deficient in dietary iodine. On 17 November, 2000, in conjunction with the Ukraine-Belarus-USA study of developing thyroid disease in a cohort of individuals exposed as children, a workshop was held to review what is known about iodine nutrition in the region, how this might influence the risk of thyroid tumor formation from radioiodine, and whether and how iodine nutrition should be monitored in this long-term project. This report is a summary of the workshop proceedings. Although no precise information about iodine intake in 1986 was found, the prevalence of mild goiter in the region's children suggested iodine deficiency and urinary iodine measurements begun in 1990 indicated that mild to moderate deficiency existed. Increased thyroid iodine uptake and increased thyroid size in 1986 resulting from iodine deficiency would have had counteracting influence on the thyroid radiation dose and knowledge of these parameters is required for dose reconstruction. More problematic is the possible role of iodine deficiency in the years following the accident. Theoretically, the resulting increase in thyroid cellular activity might increase the risk of tumorigenesis but experimental or clinical evidence supporting this hypothesis is meager or absent. Despite this limitation it was considered important to monitor iodine nutrition in the cohort subjects in relation to their place of residence and over time. Methods to accomplish this were discussed.

Goiter↗

Expression of receptor-type tyrosine kinase, Axl, and its ligand, Gas6, in pediatric thyroid carcinomas around chernobyl.

Protein-tyrosine kinases (PTKs) play a crucial role in regulating thyroid cell growth and differentiation. It is known that PTKs are activated by ionizing radiation, but the critical pathways through ionizing radiation-induced malignant transformation are not well defined. The Axl protein is a member of a new family of receptor tyrosine kinases, which the ligand, Gas6, a protein S-related molecule, has recently been identified. We previously clarified the expression of Axl and mitogenic action of Gas6 in thyroid carcinoma cells. To investigate the involvement of Gas6-Axl signaling in pediatric thyroid carcinoma further, we examined tissues obtained from 17 patients with thyroid papillary carcinomas from Gomel, Belarus, by immunohistochemistry and in situ hybridization. Axl and Gas6 were overexpressed in 76.5% and 70.6 % of cases, respectively. Solid component and invasive front tended to overexppress Gas6 and Axl in papillary carcinomas. Eighty-five percent of Axl positive cases coexpressed Gas6. In situ hybridization also confirmed the presence of axl mRNA in thyroid carcinoma tissues. These findings suggest that Axl and Gas6 expression might be involved in childhood thyroid tumorigenesis around Chernobyl.

Child↗