[The retrospective cytogenetic dosimetry using the results of conventional chromosomal analysis in Chernobyl clean-up workers].

The paper presents the results of the cohortal biodosimetry carried out in 435 Chernobyl clean-up workers, who were surveyed with the conventional cytogenetic technique in terms from several days to 10 years after the end of their duties in the Chernobyl accident exclusive zone. An empirical model of the aberrant cell dynamics was utilized for the calculation of mean initial yields of dicentrics and centric rings in groups with different terms and duration of staying in the Chernobyl zone. Corresponding protracted irradiation doses estimated from aberration levels ranged from 79 to 670 mGy. The probabilistic distribution of the radiation doses was constructed by the applying the Bayesian analysis to initial individual chromosome exchange yields extrapolated to the exposure termination moment. This distribution was characterized by the mean dose about 460 mGy and maximum of probability density in the interval of 50-300 mGy. For the late somatic risk assessment in clean-up workers the probabilistic distribution of equivalentally-acute radiation doses was proposed; that had the mean value about 270 mGy, modal classes of 250-350 mGy and 99.8% of the probability density concentrated within the dose range from 0 to 1000 mGy.

[Long-term follow-up cytogenetic survey and biological dosimetry in persons evacuated from 30-km Chernobyl NPP zone]. / Rezul'taty dinamicheskogo tsitogeneticheskogo obsledovaniia i biologicheskoi dozimetrii u lits, évakuirovnnykh iz 30-kilometrovoi zony ChAES.

The paper presents the results of the follow-up cytogenetic survey and biological dosimetry carried out in inhabitants of Pripiat' town and nearby villages, who were departured from the Chernobyl NPP 30-km exclusive zone during first days after the Chernobyl catastrophe. The unstable chromosome aberration level in inhabitants were significantly increased above control in terms up to 1 year after evacuation and declined gardually during next 14 years. In early period the cytogenetic damage frequency in evacuees showed no dependence on gender. The chromosome type aberration level appeared to be lower in young persons comparing with adults. The dicentrics plus centric rings yield had a positive correlation with duration of staying at Chernobyl zone. The average doses of protracted exposure were calculated from the dicentrics and centric rings yields; the dose estimations appeared to be 1.4 times higher in persons evacuated 3-11 days after the accident than that of in persons with shorter departure time. Uing the Bayesian analysis the probabilistic distribution of biological doses was constructed for the studied evacuees group. This distribution was characterized by a mean dose of 360 mGy, the modal doses of 200-450 mGy and 80% of probability density within the dose range 0-1000 mGy, that seems to be sufficient for considering the increased risk of late somatic radiation effects for this cohort.

[Role of non-radiation factors in forming cytogenetic effects in evacuees from a 30-km zone of the Chernobyl Nuclear Power Plant]. / Rol' faktorov neradiatsionnoi prirody v formirovanii tsitogeneticheskykh éffektov u évakuantov iz 30-km zony Chernobil'skoi AES.

The time-effect relationship for chromatid type aberrations, chromosome type fragments, hyperploidy and polyploidy levels in peripheral blood lymphocytes were investigated in inhabitants of t. Pripiat' and nearby villages, who were departured from the Chernobyl NPP 30-km exclusive zone during first days after the Chernobyl catastrophe. The time-course changes of the mentioned cytogenetic indices in evacuees were displayed as a gradual decline of chromosomal rearrangements and genome abnormality frequencies from the statistically elevated level in the first 1-2 years after the accident to the subcontrol meanings at the end of the 14-years observation period. In early terms after exposure the frequency of chromatid exchanges in adult men and the polyploidy level in women aged 23-35 years were sufficiently increased comparing with other evacuee subgroups. Some peculiarities of the fragment aberration frequency dynamics were shown for persons with different terms of the departure from the Chernobyl zone. The role of the combination of mutagenic factors acted in the accidental situation at Chernobyl for inducing the elevated level of cytogenetic damage in evacuees is discussed.

[Time-effect relationship for unstable chromosome exchange levels in Chernobyl clean-up workers]. / Zavisimost' "vremia-effekt" dlia urovnia nestabil'nykh khromosomnykh obmenov u likvidatorov posledstvii avarii na Chernobyl'skoi AES.

The post-irradiation changes of dicentric and centric ring levels were studied in Chernobyl liquidators using the data of 507 individual chromosomal surveys of persons sampled at different time after their activities at Chernobyl NPP accident zone. The time-effect relationship within 0-10.5 years after exposure was displayed as exponential decline of the mean chromosome exchange frequency with average decay half-time 2.2 y. During 10.5-13 years after exposure the increasing and stabilization of chromosome exchange yield on the level 2-3-times higher than control was observed. In the first few months after irradiation the dicentric and centric ring frequency in liquidators had the clear reverse correlation with the duration of person's duties at the Chernobyl zone. The parameters of unstable chromosome exchange elimination were independent on the initially induced aberration yield, that resulted in earlier reaching the subcontrol level in persons who had more protracted duration of duties at the Chernobyl accident zone.

[The distribution of individual radiation doses in liquidators of Chernobyl accident using cytogenetic analysis]. / Otsenka raspredeleniia individual'nykh doz oblucheniia u likvidatorov posledstvii avarii na Chernobyl'skoi AEC po rezul'tatam tsitogennogo analiza.

The cytogenetic screening was carried out in 100 Chernobyl clean-up workers (liquidators) with registered doses during 1 year after exposure. The bayesian analysis has been applied for constructing the individual distribution of probability density for biological doses estimated from dicentric and centric ring yields in liquidators. The coincidence of the biological and registered dose has been found in 25% of cases; among the rest persons the documented doses exceeded the biological estimations in 25% of cases and the cytogenetic doses were higher than registered ones in 50% of cases. The total distribution of biological doses was constructed by pooling the individual data in 50 mGy dose intervals. The distribution obtained had the maximum at 300-350 mGy and contained 68% of probability density in the dose range 0-1000 mGy. The probabilistic approach in cohort biodosimetry showed the necessity of corrections in radiogenic risk assessment for Chernobyl liquidators. The advantages of bayesian technique for biodosimetrical treatment of cytogenetic data in conditions of small number of cells scored and low aberration yields induced by low dose irradiation were discussed.

[Level of chromosome aberrations in peripheral blood lymphocytes in evacuees from the 30-kilometer zone of the Chernobyl Atomic Energy Station and residents of radioactively-polluted territories in the long term after the Chernobyl accident]. / Uroven' aberratsii khromosom v limfotsitakh perifiericheskoi krovi u évakuantov iz 30-kilometrovoi zony ChAES i zhitelei radioaktivno zagriaznennykh territorii v otdalennye sroki posle Chernobyl'skoi avarii.

Eighteen Ukrainian evacuees from the Chernobyl exclusive zone, twenty one inhabitants of radioactively contaminated areas of Belarus and twelve control donors age-matched to the exposed persons were investigated 14-15 years after the Chernobyl accident for chromosomal aberration yields detected in blood lymphocytes by fluorescence in situ hybridisation technique. Unstable aberration yields measured in both Chernobyl cohorts were close to the background frequencies. Positive age-dependence trends in control donors were determined for the all type stable aberration levels. In evacuees the tendency for diminishing the difference between them and controls for stable aberration levels with persons' age increasing was found. The total stable chromosome exchange yields in evacuees 46-55 years old and inhabitants of areas with low contamination level didn't exceed the control values, but for younger evacuees and inhabitants of sufficiently contaminated regions the statistical increase above the age relevant background meanings was detected for this end-point. The advantages of using the FISH-detectable stable aberrations and particularly the total level of stable chromosome exchanges as the end-points for retrospective biological indication of past radiation exposure in Chernobyl cohorts were discussed.

[The dynamics of the cytogenetic effects in the peripheral blood lymphocytes of those who worked in the cleanup of the aftermath of the accident at Chernobyl Atomic Electric Power Station]. / Dinamika tsitogeneticheskikh éffektov v limfotsitakh perifericheskoi krovi likvidatorov posledstvii avarii na Chernobyl'skoi AES.

Dynamics of cytogenetic anomalies in liquidators of the Chernobyl accident has been studied. Dicentric and ring frequencies appeared to be the most informative criteria of radio-induced chromosome aberrations. The rate of cell elimination with dicentrics and rings was higher in liquidators exposed to more than 25 cGy of radiation that in those exposed to less than 25 cGy of radiation. The rate of elimination of chromatid-type aberrations and genomic mutations was very low in the group of liquidators exposed to higher dose of radiation.

[A cytogenetic examination of persons subjected to radiation exposure in certain regions of Ukraine]. / Tsitogeneticheskoe obsledovanie lits, podvergshikhsia radiatsionnomu vozdeistviiu v nekotorykh regionakh Ukrainy.

We have summarized the results of cytogenetic studies of peripheral blood lymphocytes conducted in the institutions of Kiev and Kharkov in persons irradiated after the accident of the Chernobyl NPP. The average level of chromosomal aberrations and the appearance of cytogenetic markers characteristic of their irradiation effect was higher in the examinees in comparison with the control. The increase in the number of aberrations in certain Kiev residents as well as the development of lymphogranulomatosis in some liquidators of the accident were detected. The increase in the frequency of chromosomal aberrations in liquidators of the accident was accompanied by the reduction in the level of reparative DNA synthesis of blood lymphocytes. The necessity to expand cytogenetic examination in persons that participated in the liquidation of the accident on the ChNPP and Kiev inhabitants is discussed.

[Cytogenetic study of peripheral blood lymphocytes in the occupational irradiation of medical radiologists]. / Tsitogeneticheskoe issledovanie limfotsitov perifericheskoi krovi pri professional'nom obluchenii meditsinskikh radiologov.

Cultures of the peripheral blood lymphocytes have been cytogenetically analyzed in 95 medical radiologists and 25 persons of the control group. The chromosome aberrations frequency in medical personnel was found to exceed the spontaneous level. The amount of the chromosome aberrations and of the chromosomal-type aberrations increased with the growth of the accumulated irradiation dose and the length of service.