Tapio Rytömaa

The Estonian study of Chernobyl cleanup workers: II. Incidence of cancer and mortality.

A cohort of 4,742 men from Estonia who had participated in the cleanup activities in the Chernobyl area sometime between 1986 and 1991 and were followed through 1993 was analyzed with respect to the incidence of cancer and mortality. Incidence and mortality in the cleanup workers were assessed relative to national rates. No increases were found in all cancers (25 incident cases compared to 26.5 expected) or in leukemia (no cases observed, 1.0 expected). Incidence did not differ statistically significantly from expectation for any individual cancer site or type, though lung cancer and non-Hodgkins lymphoma both occurred slightly more often than expected. A total of 144 deaths were observed [standardized mortality ratio (SMR) = 0.98; 95% confidence interval (CI) = 0.82-1.14] during an average of 6.5 years of follow-up. Twenty-eight deaths (19.4%) were suicides (SMR = 1.52; 95% CI = 1.01-2.19). Exposure to ionizing radiation while at Chernobyl has not caused a detectable increase in the incidence of cancer among cleanup workers from Estonia. At least for the short follow-up period, diseases directly attributable to radiation appear to be of relatively minor importance when compared with the substantial excess of deaths due to suicide.

Radon and lung cancer in Finland.

A study with 291 cases and 495 controls on indoor radon and lung cancer incidence was conducted in a Finnish population residing in a high-exposure area. Relative risks of 1.8 and 1.5 for the incidence of lung cancer were observed for those exposed to concentrations of 95-185 Bq m(-3) and 186 Bq m(-3), respectively. The increase in risk was not statistically significant.

Fallout from Chernobyl and incidence of childhood leukaemia in Finland, 1976-92.

Abstract Objective: To assess effects of fallout from Chernobyl on incidence of childhood leukaemia in Finland. Design : Nationwide cohort study. External exposure measured for 455 Finnish municipalities with instruments driven 19 000 km throughout the country. Values specific to municipalities corrected for shielding due to houses and fallout from A bomb testing. Internal exposure estimated from whole body measurements on a random sample of 81 children. Mean effective dose for two years after incident calculated from these measurements. Data on childhood leukaemia obtained from Finnish cancer registry and verified through hospitals treating childhood cancers. Setting : Finland, one of the countries most heavily contaminated by the Chernobyl accident; the population was divided into fifths by exposure. Subjects : Children aged 0-14 years in 1976-92. Main outcome measures: Standardised incidence ratio of childhood leukaemia and relative excess risk of childhood leukaemia per mSv. From incidence data of Finnish cancer registry for 1976-85, expected numbers specific to sex and age group (0-4, 5-9, and 10-14 years) were calculated for each municipality for three periods (1976-85, 1986-8, and 1989-92) and pooled as exposure fifths. Dose response was estimated as regression slope of standardised incidence ratios on mean doses for fifths for each period. Results : Population weighted mean effective doses for first two years after the accident were 410 µSv for the whole country and 970 µSv for the population fifth with the highest dose. In all Finland the incidence of childhood leukaemia did not increase 1976-92. The relative excess risk 1989-92 was not significantly different from zero (7% per mSv; 95% confidence interval −27% to 41%). Conclusions: An important increase in childhood leukaemia can be excluded. Any effect is smaller than eight extra cases per million children per year in Finland. The results are consistent with the magnitude of effect expected.

Hereditary Minisatellite Mutations among the Offspring of Estonian Chernobyl Cleanup Workers

Abstract Kiuru, A., Auvinen, A., Luokkamäki, M., Makkonen, K., Veidebaum, T., Tekkel, M., Rahu, M., Hakulinen, T., Servomaa, K., Rytömaa, T. and Mustonen, R. Hereditary Minisatellite Mutations among the Offspring of Estonian Chernobyl Cleanup Workers. Radiat. Res. 159, 651–655 (2003). A single accidental event such as the fallout released from the Chernobyl reactor in 1986 can expose millions of people to non-natural environmental radiation. Ionizing radiation increases the frequency of germline mutations in experimental studies, but the genetic effects of radiation in humans remain largely undefined. To evaluate the hereditary effects of low radiation doses, we compared the minisatellite mutation rates of 155 children born to Estonian Chernobyl cleanup workers after the accident with those of their siblings born prior to it. All together, 94 de novo paternal minisatellite mutations were found at eight tested loci (52 and 42 mutants among children born after and before the accident, respectively). The minisatellite mutation rate was nonsignificantly increased among children born after the accident (0.042 compared to 0.036, OR 1.33, 95% CI 0.80–2.20). Furthermore, there was some indication of an increased mutation rate among offspring born after the accident to workers who had received doses of 20 cSv or above compared with their siblings born before the accident (OR 3.0, 95% CI 0.97–9.30). The mutation rate was not associated with the fathers age (OR 1.04, 95% CI 0.94–1.15) or the sex of the child (OR 0.95, 95% CI 0.50–1.79). Our results are consistent with both no effect of radiation on minisatellite mutations and a slight increase at dose levels exceeding 20 cSv.

Biodosimetry of Chernobyl cleanup workers from estonia and latvia using the glycophorin A in vivo somatic cell mutation assay

The reactor accident at Chernobyl in 1986 necessitated a massive environmental cleanup that involved over 600,000 workers from all 15 Republics of the former Soviet Union. To determine whether the whole-body radiation received by workers in the course of these decontamination activities resulted in a detectable biological response, over 1,500 blood samples were obtained from cleanup workers sent from two Baltic countries, Estonia and Latvia. Here we report the results of studies of biodosimetry using the glycophorin A (GPA) locus in vivo somatic cell mutation assay applied to 734 blood samples from these workers, to 51 control samples from unexposed Baltic populations and to 94 samples from historical U.S. controls. The data reveal inconsistent evidence that the protracted radiation exposures received by these workers resulted in a significant dose-associated increase in GPA locus mutations compared with the controls. Taken together, these data suggest that the average radiation exposure to these workers does not greatly exceed 10 cGy, the minimum levels at which radiation effects might be detectable by the assay. Although the protracted nature of the exposure may have reduced the efficiency of induction of GPA locus mutations, it is likely that the estimated physical doses for these cleanup worker populations (median reported dose 9.5 cGy) were too low to result in radiation damage to erythroid stem cells that can be detected reliably by this method.

Glycophorin A biodosimetry in Chernobyl cleanup workers from the Baltic countries.

The 1986 Chernobyl nuclear accident resulted in massive contamination of the area, necessitating evacuation of the population, extensive environmental cleanup of radioactive materials, and construction of a sarcophagus to isolate the reactor.1 These operations were accomplished by 500000 to 600000 workers from all 15 republics of the former Soviet Union. To characterise the exposure to radiation and the potential adverse health outcomes in these populations, we have undertaken a comprehensive cohort study in the Baltic countries using record linkage techniques. Here we report estimates of physical doses and biodosimetry data for 782 of these workers. We identified three populations of Chernobyl workers who were male residents of Estonia (4836), Latvia (5709), and Lithuania (5446) and who were sent to the Chernobyl area primarily in 1986 or 1987. Estimates of their physical doses …

The Estonian study of Chernobyl cleanup workers: I. Design and questionnaire data

Nearly 2% of the male population of Estonia aged 20-39 years were sent to Chernobyl to assist in the cleanup activities after the reactor accident. A cohort of 4,833 cleanup workers was assembled based on multiple and independent sources of information. Information obtained from 3,704 responses to a detailed questionnaire indicated that 63% of the workers were sent to Chernobyl in 1986; 54% were of Estonian and 35% of Russian ethnicity; 72% were married, and 1,164 of their 5,392 children were conceived after the Chernobyl disaster. The workers were less educated than their counterparts in the general population of Estonia, and only 8.5% had attended university. Based on doses entered in worker records, the mean dose was 11 cGy, with only 1.4% over 25 cGy. Nearly 85% of the workers were sent as part of military training activities, and more than half spent in excess of 3 months in the Chernobyl area. Thirty-six percent of the workers reported having worked within the immediate vicinity of the accident site; 11.5% worked on the roofs near the damaged reactor, clearing the highly radioactive debris. The most commonly performed task was the removal and burial of topsoil (55% of the workers). Potassium iodide was given to over 18% of the men. The study design also incorporates biological indicators of exposure based on the glycophorin A mutational assay of red blood cells and chromosome translocation analyses of lymphocytes; record linkage with national cancer registry and mortality registry files to determine cancer incidence and cause-specific mortality; thyroid screening examinations with ultrasound and fine-needle biopsy; and cryopreserved white blood cells and plasma for future molecular studies. Comprehensive studies of Chernobyl cleanup workers have potential to provide new information about cancer risks due to protracted exposures to ionizing radiation.

Cancer Incidence Among Finnish Nuclear Reactor Workers

Learning ObjectivesDiscuss why and how this study was carried out and the characteristics of the radiation to which nuclear reactor workers in Finland are exposed.Describe the findings, focusing on the relationship, if any, between cancer incidence and cumulative radiation exposure.Recognize the possible influence of other cancer risk factors on the findings of this study. Because of their well-documented exposures to repeated low doses of ionizing radiation, nuclear reactor workers offer an opportunity to assess cancer risk from low-dose radiation. A cohort of all 15,619 Finnish nuclear reactor workers was established through dose-monitoring records. A questionnaire survey revealed no substantial differences in consumption of tobacco or alcohol between different exposure groups nor between nuclear power company employees and contract workers. In the follow-up for cancer incidence, no clear excess in cancer incidence was observed overall, nor was any observed in any of the specific cancer types studied. There was little evidence for an association between cancer incidence and cumulative radiation dose, but the statistical power was limited. More precise estimates will be available from an international collaborative study of nuclear industry workers, including our cohort.