(Reuters Health) – In a long-term study of more than 300,000 workers in France, the U.S. and the U.K., those with many years of exposure to low doses of radiation had an increased risk of dying from leukemia.
Medical workers and even patients are also exposed to much more radiation than was common decades ago, the study authors point out, but it’s unclear what amount of low-level exposure raises cancer risk, they say.
“A lot of epidemiological or radiobiological studies have brought evidence that exposure to ionizing radiation can cause cancer and leukemia,” said lead author Dr. Klervi Leraud of the Radiobiology and Epidemiology Department at Fontenay-aux-Roses in Cedex, France.
Workers exposed to ionizing radiation who are later diagnosed with leukemia can already ask for financial compensation in the U.S., the U.K. or France, Leraud told Reuters Health by email.
Leukemia is a cancer of the tissues that make blood cells, and it’s known to be caused by exposure to high doses of radiation, like that released by the atomic bombs dropped on Japan in 1945. In the years following those bombings, leukemia cases increased among the survivors, the authors note in The Lancet Haematology. But such high doses are rare today.
For the new study, researchers considered 308,297 nuclear energy workers whose radiation exposures were monitored. All had worked for at least a year for the French Atomic Energy Commission or similar employers or for the Departments of Energy and Defense in the U.S., or were members of the National Registry for Radiation Workers in the U.K.
The workers were followed for an average of 27 years, with data on exposure and health status through the early- to mid-2000s, depending on their country. Researchers looked for deaths from leukemia or lymphoma, a cancer of the immune system that also involves blood cells.
About 22 percent of the workers had died by the end of follow-up. There were 531 deaths due to leukemia and 814 due to lymphoma.
In the U.S., the average person’s yearly exposure to ionizing radiation in 1982 was 0.5 mGy, but by 2006 it had risen to 3 mGy, largely due to medical exposures, Leraud and colleagues write.
In the new study, the researchers calculate that for each gray (1,000 mGy) of total radiation exposure, a worker’s risk of leukemia rose three-fold. The effect was greatest for chronic myeloid leukemia, with a 10.45-fold risk increase per gray.