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High levels of genetic change in rodents of Chernobyl.

Base-pair substitution rates for the mitochondrial cytochrome beta gene of free-living, native populations of voles collected next to reactor 4 at Chernobyl, Ukraine, were estimated by two independent methods to be in excess of 10(-4) nucleotides per site per generation. These estimates are hundreds of times greater than those typically found in mitochondria of vertebrates, suggesting that the environment resulting from this nuclear power plant disaster is having a measurable genetic impact on the organisms of that region. Despite these DNA changes, vole populations thrive and reproduce in the radioactive regions around the Chernobyl reactor.

Animals↗

Childhood leukaemia in Europe after Chernobyl: 5 year follow-up.

The European Childhood Leukaemia - Lymphoma Incidence Study (ECLIS) is designed to address concerns about a possible increase in the risk of cancer in Europe following the nuclear accident in Chernobyle in 1986. This paper reports results of surveillance of childhood leukaemia in cancer registry populations from 1980 up to the end of 1991. There was a slight increase in the incidence of childhood leukaemia in Europe during this period, but the overall geographical pattern of change bears no relation to estimated exposure to radiation resulting from the accident. We conclude that at this stage of follow-up any changes in incidence consequent upon the Chernobyl accident remain undetectable against the usual background rates. Our results are consistent with current estimates of the leukaemogenic risk of radiation exposure, which, outside the immediate vicinity of the accident, was small.

Child↗

Molecular analysis of new subtypes of ELE/RET rearrangements, their reciprocal transcripts and breakpoints in papillary thyroid carcinomas of children after Chernobyl.

A high prevalence of RET rearrangements is found in papillary thyroid carcinomas (PTC) of children from Belarus after the Chernobyl reactor accident. The ELE/RET rearrangement (PTC3) is prevailing. Aberrant types of ELE/RET rearrangement have been found with a truncated ELE1 gene: As compared with the common form (PTC3r1) one aberrant type is shorter by one 144 bp exon (PTC3r2) (three cases); in the second atypic form (PTC3r3) the ELE1 part is 18 bp shorter than in PTC3r1. In agreement with the observation that the oncogenic RET is generated by a paracentric inversion at chromosome 10, we found not only ELE/RET, but also RET/ELE transcripts in these tumors. Sequencing of the breakpoint regions at the genomic DNA level revealed DNA modifications that might be relevant for illegitimate recombination after DNA doublestrand breaks. The high prevalence of ELE/RET rearrangements and various subtypes appears to be typical for radiation-induced thyroid carcinomas of children after the Chernobyl reactor accident.

Artificial Gene Fusion↗

Distribution of radionuclides in the environment in northern Italy after the Chernobyl accident.

Soon after the Chernobyl nuclear accident, the air-pumping stations in Pavia (northern Italy) were alerted. In a few days, a rapid increase in radionuclide concentration in air particulates was observed. Consequently, an environmental radioactivity monitoring programme was started in which several matrices such as soil, grass, vegetables and cows' milk were subjected to direct gamma-ray spectrometry. The radioactivity distribution and its variation with time is presented, discussed and compared with other available data. Detection limits, precision and accuracy are also reported, and depth profiles in soils for 137Cs are presented and correlated with soil quality parameters. A survey of environmental radioactivity in soil, in a search for residual Chernobyl fallout, was carried out and a map of the 137Cs distribution over a large area in northern Italy is presented and discussed.

Accidents↗

Behaviour of long-lived Chernobyl radionuclides in a soil-water system.

Field and laboratory experiments have been used to study the behaviour of long-lived radionuclides in the zone affected by the Chernobyl accident. Speciation of 90Sr and 137Cs in soils and bottom sediments was determined. The principal distinction of the Chernobyl fallout was that it contained a relatively small proportion of exchangeable forms because a considerable fraction of the radionuclides was incorporated as part of the insoluble fuel particles. Disintegration of fuel particles in soils and bottom sediments results in transition of non-exchangeable forms into exchangeable forms. Radionuclide species have different pathways and rates of migration in soils and bottom sediments. Migration of each chemical form was described by a convective-dispersive equation taking into account transformation processes of radionuclide species in soils or bottom sediments. Adsorption of 90Sr and 137Cs in the environment is controlled by the cation-exchange capacity and the selectivity of the solid phase (i.e., soil, bottom sediments and suspended matter) and the cationic composition of the liquid phase (i.e., soil solution, surface run-off and river or lake water). The corresponding parameters for the processes were obtained.

Accidents↗

Post-Chernobyl thyroid carcinoma in children.

The dramatic increase in childhood thyroid carcinoma observed in Belarus and Ukraine as early as 4 years after the Chernobyl nuclear accident, is well recognized as being a consequence of exposure to radioactive iodine fallout. Uncertainties persist concerning the contamination and the dosimetric data. Thyroid nodule, cervical lymph nodes or systematic ultrasound thyroid screening in exposed children led to the diagnosis. The carcinomas affected younger subjects, were less influenced by gender, and were more aggressive at clinical and histological presentation than in the case with naturally occurring carcinoma. Total thyroidectomy and radioiodine treatment remain the treatment of choice. The prognosis is good but further studies are needed to evaluate the prognosis of children presenting with pulmonary metastasis. The project of the Newly Independent States Chernobyl Tissue Bank will facilitate molecular genetic research into this important public health issue. Nevertheless, clinicians must keep in mind the simplicity and the effectiveness of iodine prophylaxis.

Adolescent↗

Prostatic intraepithelial neoplasia and apoptosis in benign prostatic hyperplasia before and after the Chernobyl accident in Ukraine.

The prevalence of prostatic intraepithelial neoplasia (PIN) in men who underwent surgery for benign prostatic hyperplasia (BPH) before and after the Chernobyl nuclear accident was studied. BPH samples were obtained by adenomectomy from 45 patients operated in 1984 before the accident (Group I), and 47 patients from the low contaminated Kiev City (Group II) and 76 from high contaminated area (Group III) operated between 1996 and 1998. Their BPH samples were examined histologically and immunohistochemically. The incidences of prostatic intraepithelial neoplasia (PIN) and high grade PIN (HGPIN) were 15.5 and 11.1% in Group I, 29.8 and 14.9% in Grpoup II, and 35. 5 and 19.7% in Group III. The difference between the incidences of PIN in Group I and III is significant (p<0.02). There was increased apoptosis in areas of PIN in Group II and III as compared to Group I (p<0.001). Since apoptosis has been shown to be associated with ionizing radiation and it is now found to be associated with PIN in patients diagnosed after the Chernobyl nuclear accident, this suggests that long-term low dose internal ionizing radiation potentially may cause prostate cancer.

Apoptosis↗

Gene rearrangement and Chernobyl related thyroid cancers.

The increase in thyroid carcinoma post-Chernobyl has been largely confined to a specific subtype of papillary carcinoma (solid/follicular). This subtype is observed predominantly in children under 10 in unirradiated populations, but maintains a high frequency in those aged 10-15 from those areas exposed to fallout from the Chernobyl accident. The aim of this study was to link morphology with molecular biology. We examined 106 papillary carcinomas from children under the age of 15 at operation. All were examined for rearrangements of the RET oncogene by reverse transcription polymerase chain reaction (RT-PCR); a subset of these cases were also examined for mutations of the three ras oncogenes, exon 10 of the thyroid stimulating hormone receptor, associated more usually with a follicular rather than papillary morphology, and exons 5, 6, 7 and 8 of the p53 gene, commonly involved in undifferentiated thyroid carcinoma. Rearrangements of the REToncogene were found in 44% of papillary carcinomas in which we studied fresh material; none of the tumours examined showed mutation in any of the other genes. The two rearrangements resulting from inversion of part of chromosome 10 (PTC1 and PTC3) accounted for the majority of RET rearrangements identified, with PTC1 being associated with papillary carcinomas of the classic and diffuse sclerosing variants and PTC3 with the solid/follicular variant.

Adolescent↗

Retrospectively evaluated finding of larger thyroid volume in east Slovakian adolescents in 1987 than in 1992. Effect of Chernobyl?

Previously published data on thyroid volume in 207 boys and 220 girls aged 15-16 years obtained in January 1987 (which happened to be just by chance 8 months after nuclear accident in Chernobyl) in Kosice (located 700 km from Chernobyl) were compared with recently obtained data (January 1992) from 85 boys and 129 girls of the same age and in the same place. It was found that in 1987 the average thyroid volume in a group of both sexes was 3.4 ml higher than in 1992 (p < 0.001), while the respective difference in girls only was 4.2 ml (p < 0.001). No differences in the urinary excretion of iodine were found. Though it cannot be retrospectively proven, it is hypothesized that the increased thyroid volume in 1987 might result from some delayed changes due to irradiation thyroiditis. The data are considered to deserve further attention.

Accidents↗

[Exposure of the fetoplacental unit, breast milk and cow's milk to radionuclides 1 year after Chernobyl].

Placenta, umbilical cord with membranes, amniotic fluid, foetal blood (from the umbilical vein), maternal urine and breast milk were examined for the non-natural radioisotopes 131iodine, 103ruthenium, 134caesium, 137caesium originating mainly from the nuclear power plant accident in Chernobyl compared with 40potassium existent in the natural environment. Apart from amniotic fluid, all samples contained considerable traces of caesium-radioisotopes. 131iodine and 103ruthenium could not be identified at the time of our survey due to their short half-life. The radioisotope load of placenta was found to be increased tenfold compared to studies before the Chernobyl catastrophe. Breast milk radioisotope load was found to be lower than that in cow's milk in a corresponding geographical region in the same period of time.

Accidents↗

Case control study of neuroblastoma in west-Germany after the Chernobyl accident.

BACKGROUND: To explore possible causes of a 1988 incidence peak of infant neuroblastoma in west German regions which were contaminated with more than 6000 Bq/m2 Cs137 from the Chernobyl accident. The primary working hypothesis was that parents of the diseased children had been contaminated by an excessive intake of locally produced food, especially mushrooms or deer. DESIGN: Case control study with 1:2 (cases:controls) matching. Data were collected from the children's parents by questionnaires and telephone interviews. SETTING: Nation-wide study (former FRG) based on the German Childhood Cancer Registry. SUBJECTS: Cases born in 1988 and reported with a neuroblastoma to the registry until March 1992. Population-based healthy controls, matched for age, sex and residence at time of diagnosis. RESULTS: The working hypothesis could not be confirmed by the study, because the parents of cases tended to eat less locally grown food than the parents of controls (RR = 0.63, 95% CI:0.20-1.97). Possible influence factors which previously have been described to be associated with neuroblastoma incidence could not be confirmed by the study. Parental exposure to herbicides and pesticides was associated with the occurrence of neuroblastoma (RR = 4.2, 95% CI:1.4-12.9). Neuroblastoma stage distribution in the contaminated regions was shifted towards lower stages as compared to the less contaminated regions and previous age cohorts. CONCLUSIONS: The study does not show additional evidence that the observed increase in neuroblastoma incidence might have been caused by exposure to fallout from the Chernobyl accident. The observed shift towards lower clinical stages may rather indicate increased diagnostic awareness. The association between neuroblastoma and parental exposure with herbicides and pesticides resulted from an extensive exploratory data analysis and needs to be confirmed in further studies.

Child, Preschool↗

Health status and internal radiocontamination assessment in children exposed to the fallout of the Chernobyl accident.

The Chernobyl fallout caused release of radioisotope contaminants in a very large area that includes Belarus, the Ukraine, and the Russian Federation. In this study, the authors monitored the health status and level of internal contamination in 422 children who resided in the aforementioned areas and who were < or = 10 y of age at the time of the accident. The children came to Italy for a 1-mo period between 1991 and 1992. During this time, the children underwent pediatric checkups and biochemical, immunological, and thyroid analyses. All children underwent whole-body counter measurements, and urine radiotoxicological analysis was performed for 224 of them. The 24 children evacuated from Pripiat, a village very close to the Chernobyl reactor site, were selected for cytogenetic analysis. All of these children continue to have a detectable internal contamination of caesium radioisotopes. This condition is likely the result of ground and foodstuff contamination in the various areas. The children did not evidence overt pathologies related to ionizing radiation. However, minor alterations in immunological and thyroid parameters were observed in the group of the evacuated children. Traditional cytogenetic dosimetry was not possible, but the occurrence of acentric fragments was observed-indicating a persistent effect of continuous exposure to low doses of radiation.

Adolescent↗

Physical dosimetry and biological indicators of carcinogenic risk in a cohort of persons exposed to unhealthy ecological factors following the Chernobyl Nuclear Power Plant accident.

The April 1986 Chernobyl Nuclear Power Plant accident caused ecological changes in the Ovruch State forests in the Zhytomir oblast in the Ukraine. The highest radioactivity existed in moss, followed by the pine-forest substrate and soil. During 1984-1985, the pine needles were primarily surface contaminated, whereas during 1986-1988, they were contaminated secondarily. Radioactivity in air was highest (1.07+/-0.185 Bq/l) during dry and sunny weather and when trees were felled; the lowest levels (0.196+/-0.044 Bq/l) occurred during periods of stable snow coverage. Between 1987 and 1989 (i.e., after the Chernobyl accident), the caesium levels in forestry employees exceeded by 13.9-fold the average levels found in the Ukrainian Polessje population. Ovruch forest guards and woodcutters had the highest effective equivalent doses of radiation, and they therefore exhibited the highest carcinogenic risk.

Air Pollutants, Radioactive↗

Radiation effects in lymphocytes of children living in a Chernobyl contaminated region of Belarus.

PURPOSE: To investigate cytogenetic and mutational effects in lymphocytes from individuals chronically exposed to radiation from the Chernobyl catastrophe. MATERIALS AND METHODS: Nine years after the Chernobyl accident (1986), peripheral blood lymphocytes from 20 Kalinkovichi children (age 10-15) and 10 Minsk children (age 10-17) were analysed for genetic damage by several assays. Radiation damage in exposed children was investigated in descendants of progenitor cells that were irradiated during a short period immediately after the accident. In the time-span between the accident and blood sampling the cells were also irradiated chronically by internal radiation originating from ingested radionuclides and, to a smaller extent, by external radiation from radionuclides. The parameters measured in whole blood smears were the frequency of micronucleated mononucleated lymphocytes and binucleated lymphocytes with nucleoplasmic bridges and associated micronuclei. Cultures of cytokinesis-blocked lymphocytes were used to analyse mononuclear and binuclear cells for the presence of micronuclei, also cell killing effects. A colony assay was used to study induction of recessive mutations in the HPRT gene. RESULTS: The analysis of whole-blood smears indicated a doubling of the frequency of micronuclei per 100 mononuclear lymphocytes in exposed children compared with unirradiated children. Small numbers of binucleated lymphocytes with nucleoplasmic bridges and associated micronuclei were found in blood smears from exposed children. Analysis of cytokinesis-blocked cultures indicated in mononuclear cells of exposed children a statistically significant increase in the frequency of micronuclei. When the same parameters were studied in binucleated cells there was no difference between exposed and unexposed children. Results of the dye-exclusion assay showed a four-fold increase in the percentage of dead cells between exposed and unexposed children. There was no evidence for induction of HPRT mutations in exposed children. CONCLUSION: These results indicate that the frequently advocated procedure of simply analysing micronuclei in cytokinesis-blocked binucleated lymphocytes can result in an underestimate of genetic damage induced by radiation accidents. Biodosimetric studies should therefore employ a battery of assays for the detection of several types of genetic damage in different generations of lymphocytes.

Adolescent↗

A preliminary assessment of the consequences for inhabitants of the UK of the Chernobyl accident.

The accident with the nuclear power reactor at Chernobyl in the USSR resulted in the release of substantial quantities of radioactive material and subsequent increases in radioactivity in the environment in many countries. In this paper the situation in the UK is considered and, from the preliminary monitoring measurements, the major routes of exposure of the population are identified and quantified. For the most part exposures in the UK are within variations in levels of natural background radiation to be found in Europe. An exception is the dose likely to have been received by the thyroids of young people in the north of the UK. From reported measurements of I-131 in milk it is predicted that thyroid doses up to 10-20 times the annual doses received from 'normal' natural background radiation might have affected young children drinking fresh cows' milk. The ways in which this component of exposure could have been reduced and the criteria that govern decisions as to whether or not to implement counter-measures are discussed. The importance of I-131 in milk as a route of exposure of the population to radioactivity is a feature that the Chernobyl accident has in common with the Windscale accident in the UK in 1957, and underlines the importance of milk-producing regions in relation to reactor-sitting policy.

Accidents↗

Environmental impact of the Chernobyl accident: mutagenesis in bank voles from Sweden.

An investigation was carried out in Sweden aimed at studying the possible genetic effects of the Chernobyl fallout on wild small mammals. The bank voles (Clethrionomys glareolus Schreb.) were obtained from three differently contaminated areas in Sweden and, for control, in an area with negligible contamination by fallout. Radionuclide determinations to assess the content of 137Cs and mutagenicity tests (bone marrow micronucleus test and sperm abnormality assay) were performed. The results obtained showed a positive correlation between the increase of micronucleated polychromatic erythrocytes (MPCE/1000 PCE) and both 137Cs content in muscle and in soil contamination. The estimated doses absorbed by the animals were far lower than those required for the same effect in laboratory experiments. An explanation of this discrepancy between dose and measured biological effect is not available, yet similar results have been repeatedly reported after the Chernobyl accident and should be a matter for further discussion. An increased frequency of micronucleated cells might occur at minimal dose gradients, and the micronucleus test appears to be a valid tool to show such effects.

Accidents↗

Radiobiological evaluation of immigrants from the vicinity of Chernobyl.

Eighty individuals (55 adults and 25 children) who were residents of four cities (Kiev, Mozyr, Gomel and Bobrujsk) located 100-200 km from Chernobyl at the time of the accident in 1986 were tested after immigrating to the US from 1989-1991. A whole-body counter was employed to quantitate radiocesium content. In addition, two biological measures of radiation effects, namely, chromosomal integrity using the micronucleus assay and somatic mutation analysis of erythrocytes at the glycophorin A (GPA) locus, were applied to this group. Radiocesium activity in the body ranged from 0 to 56.8 Bq/kg with a mean and standard deviation of 5.0 +/- 8.2 and a median value of 2.0 Bq/kg. Mean radiocesium content by groups was highest in adult males (9.0 +/- 11.7; range 0.21-56.8 Bq/kg) followed by adult females (3.3 +/- 4.5; range 0-21.3 Bq/kg), male children (3.0 +/- 5.7; range 0-20.2 Bq/kg) and lowest in female children (1.6 +/- 3.5; range 0-12.7 Bq/kg). Individuals with the highest radiocesium content in each group belonged to one family that lived in Mozyr (100 km from Chernobyl) until emigrating in 1989. The frequency of lymphocyte micronuclei and erythrocyte GPA allele-loss (O/N) somatic mutations were both significantly correlated with radiocesium content (r=0.57, p=0.002; r=0.75, p=0.002, respectively). The micronucleus frequency also correlated with the estimated internal absorbed dose from radiocesium in a subset of 20 immigrants for whom this calculation was possible (r=0.71, p=0.0005). Altogether, the biomonitoring data indicate that some subjects had radiation doses sufficient to produce gene and chromosomal mutations in blood cells, although these effects cannot be attributed solely to radiocesium exposure.

Adolescent↗

Retrospective biodosimetry of Chernobyl clean-up workers using chromosome painting and conventional chromosome analysis.

Blood samples of 52 Chernobyl clean-up workers were analysed by fluorescence in situ hybridization (FISH) using whole-chromosome painting probes for chromosomes 1, 4 and 12, simultaneously with a pancentromeric probe and by conventional chromosome analysis, for radiation-induced symmetrical translocations and dicentrics in T-lymphocytes. Based on FISH measurements of translocations, individual biodosimetry estimates between 0.32 and 1.0 Gy were obtained from 18 cases. Pooled data for the total group of 52 workers provided a collective biodosimetry estimate of 0.23 Gy. For a group of 34 workers with documented doses, the mean dose estimate of 0.25 Gy compared well with the mean documented dose of 0.26 Gy. However, no correlation between individual translocation frequencies (FG) and documented doses could be found. A statistical analysis of the expected dose-response suggests exposures to higher doses than documented for a substantial fraction of workers with ascribed doses < 0.2 Sv. For subjects working repeatedly at the reactor site between 1986 and 1995 the mean translocation frequency was significantly higher than for those working only in 1986. A comparison of dicentric frequencies obtained by conventional scoring and by FISH measurements showed no significant difference, although only two of 52 cases revealed significantly higher yields than the mean control level. Based on conventionally scored dicentric frequencies, a collective biodosimetry estimate of 0.23 Gy could be derived only of the group of persons working at Chernobyl exclusively in 1986 for which a documented average dose of 0.19 Gy was reported.

Adult↗