Study Shows Long-Term Exposure to Low Doses of Radiation Increases Leukemia Risk

Workers exposed to long-term low doses of radiation have an increased risk of dying from leukemia, a new study reports.

The long-term study looked at radiation exposure in more than 300,000 workers in France, the U.S. and the U.K. The researchers say it is unclear what amount of low-level exposure raises cancer risk, but they note that many people are exposed to much more radiation than was common decades ago, Reuters reports.

Dr. Klervi Leraud of the Radiobiology and Epidemiology Department at Fontenay-aux-Roses in Cedex, France, lead author of the study, which appeared online in The Lancet Haematology in June, said, “A lot of epidemiological or radiobiological studies have brought evidence that exposure to ionizing radiation can cause cancer and leukemia.”

For this study, the researchers considered 308,297 nuclear energy workers whose radiation exposures were monitored. Every worker had worked for at least a year for the French Atomic Energy Commission or a similar employer 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., according to Reuters. The workers were followed for an average of 27 years, with data on radiation exposure and health status through the early- to mid-2000s, depending on their country. The researcher team examined the records for deaths from leukemia or lymphoma. About 22 percent of the workers had died by the end of follow-up, with 531 deaths due to leukemia and 814 due to lymphoma. The researchers found that as cumulative radiation exposure increased, so did the risk of dying from certain kinds of leukemia.

The workers, on average, had been exposed to a cumulative dose of 16 milligray (mGy) of radiation over the years of the study, or about one mGy per year. For comparison, a medical computed tomography (CT) scan of the lumbar spine exposes the patient to between one and two mGy, according to the Food and Drug Administration. In the U.S., the average 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, the authors say. For each gray (1,000 mGy) of total radiation exposure, a worker’s risk of leukemia rose three-fold, the researchers calculated. The effect was greatest for chronic myeloid leukemia, with a 10.45-fold risk increase per gray.

Dr. Maria Blettner of University Medical Center in Mainz, Germany said, “radiation safety standards in most—if not all—countries are very high.” Blettner said in an email to Reuters Health, “There is an occupational limit and if this limit is reached persons are not allowed to work in the areas with a potential exposure.” But, she added, we “know too little about what other factors play a role together with radiation to increase leukemia risk, and whether certain people are more sensitive to radiation exposure.” Currently, there is no test to determine which people are more “radio-sensitive” than others, Blettner said.

 

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