Commercial jet aircrew may be at an increased risk for developing acute myeloid leukemia (AML) as a result of increased exposure to cosmic radiation, according to a study recently published in The Lancet.

Researchers have long known that chemotherapy and radiation therapy increase the risk of both myelodysplasia and AML; however, the results of this study indicate that cosmic radiation may be a risk factor as well. AML is a cancer of the bone marrow and blood that is characterized by the rapid, uncontrolled, abnormal growth of immature white blood cells in the bone marrow, which suppresses the formation and function of other blood cells. Myelodysplasia is a precursor condition that often develops into AML.

During this study, researchers studied the chromosomes of three groups of people with AML or myelodysplasia: seven aircrew members, 19 patients who developed AML after receiving radiation therapy and 761 unselected patients whose leukemia was unrelated to radiation therapy. The researchers found a deletion or loss of chromosome 7 in four of the seven aircrew members and eight of the 19 radiation patients. In comparison, they found the same abnormality in only 81 of the 761 unselected patients. The researchers concluded that the results indicate that the deletion or loss of chromosome 7 in myelodysplasia and AML could be an indicator of previous exposure to ionizing radiation.

The study was a follow-up study to one performed by the same group of researchers which showed that aircrew who had prolonged exposure to cosmic radiation were five times as likely to develop AML. While both studies indicate that cosmic radiation increases the risk of AML, that risk is relatively small. The average airline passenger is not exposed to flight hours comparable to those of aircrew.

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Larger studies will be needed to establish an association between cosmic radiation and the subsequent development of AML and myelodysplasia in aircrew. (The Lancet, Vol. 356, 2000)

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