Chromosomal changes seen in long-term airline pilots

NEW YORK (Reuters Health) - New research suggests that airline pilots with long-term flying experience may be exposed to higher than average levels of radiation, resulting in more chromosomal translocations than usually seen.

Further studies with longer follow-up and more subjects, however, will be needed to determine if these pilots are at increased risk for cancer, according to the report in the online issue of Occupational and Environmental Medicine.

Chromosomal translocations occur when a chromosome fragment breaks off and attaches to another. This can lead to a range of medical problems, such as leukemia, breast cancer, schizophrenia or muscular dystrophy, depending on were the fragments reattach.

"Airline pilots are exposed to cosmic ionizing radiation, but few flight crew studies have examined translocations in relation to flight experience," Dr. Lee C. Yong, from the National Institute for Occupational Safety and Health, Cincinnati, Ohio, and colleagues explain.

The research team therefore looked for chromosome translocations in the blood cells of 50 airline pilots and from 50 comparison subjects.

On average, chromosomal translocations were just as common in airline pilots as in the control subjects. However, among pilots, the frequency of translocations was directly related to flight years. For each 1-year increase in flight years, the likelihood of a translocation rose by 6 percent.

Relative to pilots in the lowest quartile of flight years, those in the highest quartile were 2.59-times more likely to have chromosomal translocations, the report indicates.

"Although the results of epidemiological studies on cancer risk among pilots have been inconsistent, many of these studies involved relatively short follow-up periods" with "relatively young" subjects so evaluation of radiation-associated cancers could not be performed, the investigators note.

SOURCE: Occupational and Environmental Medicine 11, 2008.