A study, published in late 2012, has found a "significantly elevated risk" for chronic lymphocytic leukaemia among workers that were involved in clean-up activities following the Chernobyl nuclear power plant accident in 1986. Based on studies of atomic bomb survivors, many experts did not previously consider this type of leukaemia to be associated with radiation exposure. However, some earlier studies on Chernobyl workers had suggested a possible link. The new research, published in Environmental Health Perspectives on 8 November 2012 (http://dx.doi.org/10.1289/ehp.1204996), provides stronger evidence for a link between CLL and radiation exposure.

The investigators, led by Dr. Lydia Zablotska (MD, PhD), followed 110,000 Ukrainian workers who participated in the cleanup after Chernobyl. New cases of leukaemia were tracked from 1986 through 2006, and were confirmed by a panel of expert haematologists. Researchers estimated the individual radiation doses to the bone marrow for the leukaemia patients and a comparison group similar to the patients in age and place of residence.

The research team estimated that 16% of all leukaemia cases in the worker population (15% for non-chronic lymphocytic leukaemia and 18% for chronic lymphocytic leukaemia), over a period of 20 years of medical follow-up, were attributable to radiation exposure from the accident.

"The genetic makeup of the Japanese population may have hidden any increased risk, because they are much less likely to develop this type of cancer anyway," Zablotska said. Chronic lymphocytic leukaemia accounts for only 3% of all cases of leukaemia in Japan — as opposed to about one-third of all leukaemia cases in the USA (16,000 in 2012) and 40% of all cases of leukaemia in Ukraine.