Letter to the Editor: On the Radiation-Leukemia Dose-Response Relationship among Recovery Workers after the Chernobyl Accident

Abstract

This letter to the Editor continues the topic of the Chernobyl accident and probable overestimation of its consequences started in the journal Dose-Response (Jaworowski 2010; Jargin 2011) within a broader perspective: the dose-response relationship after low-dose low-rate exposures to ionizing radiation. UNSCEAR (2000) Report concluded that no increased risk of leukemia related to ionizing radiation has been found among recovery operation workers (liquidators) after the Chernobyl accident. According to the UNSCEAR (2008) Report, recent studies suggest an increase in the incidence of leukemia among the liquidators; however, limitations of those studies include low statistical power, uncertainties in dose reconstructions, and internal inconsistencies that suggest potential biases and confounding factors; evidence of the leukemia incidence increase among liquidators thus being “far from conclusive”. An association between a radiation exposure and leukemia incidence among liquidators was reported recently (Ivanov et al. 2012; Zablotska et al. 2013). Participation rates were higher among “cases” than among controls (Zablotska et al. 2013), a phenomenon noticed also by other researchers (Cardis et al. 2005; Kesminiene et al. 2008), being probably caused by higher motivation of the cases. The patients knowing their doses were probably on average more interested in further medical examinations if a dose estimate had been relatively high. In the health care system of the former Soviet Union, thoroughness of an examination sometimes depended on a patient’s initiative. In other words, individuals with higher dose estimates were probably given on average more attention, and cared more about their health themselves. “The dose-dependent participation of self-reported pre-screening cases” was pointed out by Zablotska et al. (2011), which probably can occur in Chernobyl-related research of different kind. Therefore, a probability of discovering a disease without specific local symptoms such as leukemia must be higher in people with higher dose estimates. Therefore, one of the reasons why no statistically significant radiation risks were observed for chronic lymphatic leukemia (CLL) by Ivanov et al. (2012) seems to be clear: this leukemia type is often accompanied by lymphadenopathy therefore probably remaining less frequently undiagnosed in the general population.