Radiation and the Risk of Chronic Lymphocytic and Other Leukemias among Chornobyl Cleanup Workers

Department of Epidemiology and Biostatistics, School of Medicine, University of California San Francisco, San Francisco, California, USA.
Environmental Health Perspectives (Impact Factor: 7.98). 01/2013; 121(1):59-65. DOI: 10.1289/ehp.1204996
Source: PubMed


BACKGROUND: Risks of most types of leukemia from exposure to acute high doses of ionizing radiation are well known, but risks associated with protracted exposures, as well as associations between radiation and chronic lymphocytic leukemia (CLL), are not clear.

OBJECTIVES: We estimated relative risks of CLL and non-CLL from protracted exposures to low-dose ionizing radiation.

METHODS: A nested case-control study was conducted in a cohort of 110,645 Ukrainian cleanup workers of the 1986 Chornobyl nuclear power plant accident. Cases of incident leukemia diagnosed in 1986-2006 were confirmed by a panel of expert hematologists/hematopathologists. Controls were matched to cases on place of residence and year of birth. We estimated individual bone marrow radiation doses by the Realistic Analytical Dose Reconstruction with Uncertainty Estimation (RADRUE) method. We then used a conditional logistic regression model to estimate excess relative risk of leukemia per gray (ERR/Gy) of radiation dose.

RESULTS: We found a significant linear dose response for all leukemia [137 cases, ERR/Gy = 1.26 (95% CI: 0.03, 3.58]. There were nonsignificant positive dose responses for both CLL and non-CLL (ERR/Gy = 0.76 and 1.87, respectively). In our primary analysis excluding 20 cases with direct in-person interviews < 2 years from start of chemotherapy with an anomalous finding of ERR/Gy = -0.47 (95% CI: < -0.47, 1.02), the ERR/Gy for the remaining 117 cases was 2.38 (95% CI: 0.49, 5.87). For CLL, the ERR/Gy was 2.58 (95% CI: 0.02, 8.43), and for non-CLL, ERR/Gy was 2.21 (95% CI: 0.05, 7.61). Altogether, 16% of leukemia cases (18% of CLL, 15% of non-CLL) were attributed to radiation exposure.

CONCLUSIONS: Exposure to low doses and to low dose-rates of radiation from post-Chornobyl cleanup work was associated with a significant increase in risk of leukemia, which was statistically consistent with estimates for the Japanese atomic bomb survivors. Based on the primary analysis, we conclude that CLL and non-CLL are both radiosensitive.

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    • "While a recent pooled analysis of nuclear power industry workers from 15 countries found little evidence for an association between low doses of external ionizing radiation, primarily γ-ray dose, and CLL mortality (Vrijheid et al., 2008), recent studies of incident CLL among Chornobyl cleanup workers reported increased risks in relation to bone marrow doses of γ-radiation (Kesminiene et al., 2008; Romanenko et al., 2008). Twenty-year follow up of Chornobyl cleanup workers from Ukraine provided evidence of significantly increased risks of CLL due to protracted gamma radiation exposures (ERR/Gy ¼2.93, 95% CI: 0.07, 9.64, p¼ 0.041) (Zablotska et al., 2013), as did a fifty-five year follow up of the A-bomb survivors (Hsu et al., 2013). Richardson et al. (2009) reported elevated risk of NHL mortality associated with whole-body radiation dose in both a cohort of male nuclear workers and in the A-bomb survivors with γ-ray doses lagged by 5 and 10 years. "
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    ABSTRACT: Uranium workers are chronically exposed to low levels of radon decay products (RDP) and gamma (γ) radiation. Risks of leukemia from acute and high doses of γ-radiation are well-characterized, but risks from lower doses and dose-rates and from RDP exposures are controversial. Few studies have evaluated risks of other hematologic cancers in uranium workers. The purpose of this study was to analyze radiation-related risks of hematologic cancers in the cohort of Eldorado uranium miners and processors first employed in 1932–1980 in relation to cumulative RDP exposures and γ-ray doses. The average cumulative RDP exposure was 100.2 working level months and the average cumulative whole-body γ-radiation dose was 52.2 millisievert. We identified 101 deaths and 160 cases of hematologic cancers in the cohort. Overall, male workers had lower mortality and cancer incidence rates for all outcomes compared with the general Canadian male population, a likely healthy worker effect. No statistically significant association between RDP exposure or γ-ray doses, or a combination of both, and mortality or incidence of any hematologic cancer was found. We observed consistent but non-statistically significant increases in risks of chronic lymphocytic leukemia (CLL) and Hodgkin lymphoma (HL) incidence and non-Hodgkin lymphoma (NHL) mortality with increasing γ-ray doses. These findings are consistent with recent studies of increased risks of CLL and NHL incidence after γ-radiation exposure. Further research is necessary to understand risks of other hematologic cancers from low-dose exposures to γ-radiation.
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    • "Considering the above arguments and dose comparisons , reliability of conclusions about " a significant increase in the risk of leukemia with radiation dose based on the entire study sample " (Zablotska et al. 2013) appear to be questionable. "

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    • "The epidemiological cohort studies on CVD and radiation exposure have used data from those exposed through radiation therapy [1] [2] [3] [4] [5] [6], occupational or environmental exposures [1, 6–14] and the Japanese atomic bombs [15] [16] [17] [18] [19]. In most of the radiotherapy studies, where exposures are local rather than total body, the rate of myocardial infarction did not noticeably increase at doses less than 1.5 Gy. "
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