On November 8, 2012 a study entitled “Radiation and Risks of Chronic Lymphocytic and Other Leukemias among Chernobyl Cleanup Workers,” was released examining the risks of leukemia, specifically, the most common type, chronic lymphocytic leukemia (CLL), in Chernobyl cleanup workers exposed to protracted low dose radiation (1). The findings of this study, which examined 110,645 Ukrainian cleanup workers between 1986-2006, demonstrated that exposure to low doses of radiation from post-Chernobyl clean-up caused a significant increase in the risk of leukemia. This study was significant because while the risks of high levels of exposure are well known, the risks of low doses have been more controversial. This is crucial because during the Chernobyl disaster approximately 500,000 people were registered as emergency and recovery workers, receiving low, continuous doses.
The Ukrainian male workers examined were between the ages of 20-60 years during cleanup activities in 1986-1990 following the Chernobyl nuclear power plant accident, were registered in the Chernobyl State Registry of Ukraine (SRU)before 1992, who resided in Kyiv City or in any one of five study oblasts (areas similar to a state or province: Cherkasy, Chernihiv, Dnipropetrovsk, Kharkiv and Kyiv) at the time of registration. Of those 110,645 a total of 162 cases of leukemia were found. This was found by examining cancer registries, conducting expert hematologic (blood) review and case ascertainment coupled with radiation dose estimates. For all leukemia cases a significant positive association existed with continuous radiation dosage.
The proportion of chronic lymphocytic leukemia cases in the study (roughly 58% of all leukemia cases) was higher than the 40% figure reported by most population based cancer registries and the 44% of all diagnosed leukemia ca-ses among males. The cancer registries were estimated to be missing as much as 38% of all of the chronic lymphocytic leukemia cases.
This study confirmed and strengthened previous studies which showed significant associations between protracted radiation exposure at low doses and leukemia incidence. Increased risks of leukemia, although not statistically significant, were also reported from a study of Chernobyl cleanup workers from Belarus, Russia and Baltic countries. Additionally, the results indicate that radiation risk estimates are elevated for both chronic and non-chronic lymphocytic leukemia (CLL and non-CLL). However, examining CLL is crucial given that this is the most prevalent form of leukemia and incidents of CLL are expected to rise when the population ages. Generally, studies had looked at high doses of radiation and it has been assumed that protraction of radiation dose results in a reduction of adverse biological effects; however this study has demonstrated quite the opposite.
This study was published in Environmental Health Perspectives (2012; doi:10.1289/ehp.1204996): http://www.nirs.org/radiation/radhealth/ehp1204996chernobylhealth.pdf