Chromosome aberrations in workers occupationally exposed to tritium.

This paper reports the findings of an historical chromosome analysis for unstable aberrations, undertaken on 34 nuclear workers with monitored exposure to tritium. The mean recorded ß-particle dose from tritium was 9.33 mGy (range 0.25-79.71 mGy) and the mean occupational dose from external, mainly γ-ray, irradiation was 1.94 mGy (range 0.00-7.71 mGy). The dicentric frequency of 1.91 ± 0.53 × 10-3 per cell was significantly raised, in comparison with that of 0.61 ± 0.30 × 10-3 per cell for a group of 66 comparable worker controls unexposed to occupational radiation. The frequency of total aberrations was also significantly higher in the tritium workers. Comparisons with in vitro studies indicate that at these dose levels an increase in aberration frequency is not expected. However, the available historical tritium dose records were produced for the purposes of radiological protection and based on a methodology that has since been updated, so tritium doses are subject to considerable uncertainty. It is therefore recommended that, if possible, tritium doses are reassessed using information on historical recording practices in combination with current dosimetry methodology, and that further chromosome studies are undertaken using modern FISH techniques to establish stable aberration frequencies, as these will provide information on a cumulative biological effect.

Risk of Lung Cancer Mortality in Nuclear Workers from Internal Exposure to Alpha Particle-emitting Radionuclides.

BACKGROUND: Carcinogenic risks of internal exposures to alpha-emitters (except radon) are poorly understood. Since exposure to alpha particles-particularly through inhalation-occurs in a range of settings, understanding consequent risks is a public health priority. We aimed to quantify dose-response relationships between lung dose from alpha-emitters and lung cancer in nuclear workers. METHODS: We conducted a case-control study, nested within Belgian, French, and UK cohorts of uranium and plutonium workers. Cases were workers who died from lung cancer; one to three controls were matched to each. Lung doses from alpha-emitters were assessed using bioassay data. We estimated excess odds ratio (OR) of lung cancer per gray (Gy) of lung dose. RESULTS: The study comprised 553 cases and 1,333 controls. Median positive total alpha lung dose was 2.42 mGy (mean: 8.13 mGy; maximum: 316 mGy); for plutonium the median was 1.27 mGy and for uranium 2.17 mGy. Excess OR/Gy (90% confidence interval)-adjusted for external radiation, socioeconomic status, and smoking-was 11 (2.6, 24) for total alpha dose, 50 (17, 106) for plutonium, and 5.3 (-1.9, 18) for uranium. CONCLUSIONS: We found strong evidence for associations between low doses from alpha-emitters and lung cancer risk. The excess OR/Gy was greater for plutonium than uranium, though confidence intervals overlap. Risk estimates were similar to those estimated previously in plutonium workers, and in uranium miners exposed to radon and its progeny. Expressed as risk/equivalent dose in sieverts (Sv), our estimates are somewhat larger than but consistent with those for atomic bomb survivors.See video abstract at, http://links.lww.com/EDE/B232.

Chromosome analysis in a case of a plutonium contaminated wound.

Chromosome analysis of peripheral blood lymphocytes was undertaken over a 10 year period following an intake of plutonium through a hand wound. Frequencies of cells with unstable complex aberrations remained high throughout this time, probably reflecting direct exposure of lymphocytes as they passed plutonium which had transferred to regional lymph nodes. Analysis at the final sampling time also revealed cells with stable aberrations at a much higher frequency relative to the number of unstable cells than expected from direct exposure, and is therefore most likely to be reflecting exposure to lymphocyte precursor cells from plutonium that has become deposited on bone surfaces.

Chromosome aberrations determined by sFISH and G-banding in lymphocytes from workers with internal deposits of plutonium.

PURPOSE: To examine the influence of α-particle radiation exposure from internally deposited plutonium on chromosome aberration frequencies in peripheral blood lymphocytes of workers from the Sellafield nuclear facility, UK. MATERIALS AND METHODS: Chromosome aberration data from historical single colour fluorescence in situ hybridization (sFISH) and Giemsa banding (G-banding) analyses, together with more recent sFISH results, were assessed using common aberration analysis criteria and revised radiation dosimetry. The combined sFISH group comprised 29 men with a mean internal red bone marrow dose of 21.0 mGy and a mean external γ-ray dose of 541 mGy. The G-banding group comprised 23 men with a mean internal red bone marrow dose of 23.0 mGy and a mean external γ-ray dose of 315 mGy. RESULTS: Observed translocation frequencies corresponded to expectations based on age and external γ-ray dose with no need to postulate a contribution from α-particle irradiation of the red bone marrow by internally deposited plutonium. Frequencies of stable cells with complex aberrations, including insertions, were similar to those in a group of controls and a group of workers with external radiation exposure only, who were studied concurrently. In a similar comparison there is some suggestion of an increase in cells with unstable complex aberrations and this may reflect recent direct exposure to circulating lymphocytes. CONCLUSIONS: Reference to in vitro dose response data for the induction of stable aberrant cells by α-particle irradiation indicates that the low red bone marrow α-particle radiation doses received by the Sellafield workers would not result in a discernible increase in translocations, thus supporting the in vivo findings. Therefore, the greater risk from occupational radiation exposure of the bone marrow resulting in viable chromosomally aberrant cells comes from, in general, much larger γ-ray exposure in comparison to α-particle exposure from plutonium.

FISH chromosome analysis of plutonium workers from the Sellafield nuclear facility.

Chromosome analysis using a single-color FISH technique to paint three pairs of chromosomes was undertaken on a group of 46 retired plutonium workers with assessed bone marrow doses >60 mSv, 34 of whom were categorized as having robust dosimetry and 12 for whom internal doses were considered less reliable. Comparisons were made with a group of 34 workers with negligible radiation exposure and a group of 34 workers with similar recorded external gamma-ray doses but negligible internal dose. The simple translocation frequency of 17.65 +/- 1.96 x 10(-3) per genome equivalent for the 34 plutonium workers with robust dosimetry was significantly increased in comparison with that of 10.06 +/- 1.16 x 10(-3) per genome equivalent for the unirradiated control group (P = <0.001) and that of 13.55 +/- 1.43 x 10(-3) per genome equivalent for the group with similar external gamma-ray exposure (P = 0.012). Thus, although in vitro studies have indicated that the majority of alpha-particle-irradiated cells suffer complex non-transmissible chromosome damage, in vivo a significant proportion survive with simple exchanges that can be passed on to descendant cells. In contrast, the three groups demonstrated no significant differences in stable complex aberrations. No evidence of an increase in dicentrics or unstable complex aberrations associated with plutonium exposure was observed, and it can therefore be assumed that there is little, if any, ongoing irradiation of mature lymphocytes. The translocation frequency of 12.08 +/- 1.92 x 10(-3) per genome equivalent for the group of 12 plutonium workers with less reliable internal dosimetry could adequately be accounted for by age and external dose and indicates that the internal bone marrow doses are likely to have been overestimated. Cytogenetic analysis can therefore make a valuable contribution to the validation of internal doses from plutonium deposition.