Pilots' radiation exposure may damage genes

Airline pilots' exposure to radiation because of the long periods they spend at high altitudes may raise their odds of developing genetic abnormalities that could contribute to cancer, a new study suggests.

A number of studies have looked at whether airline crews are at increased risk of various cancers because of frequent exposure to cosmic radiation - radiation that is mostly blocked by the earth's atmosphere but exists at higher levels at high altitudes. Those studies have come to conflicting results, however.

This latest study, published in the journal Occupational and Environmental Medicine, looked at whether airline pilots tend to have a higher rate of genetic abnormalities known as chromosome translocations. These genetic alterations naturally become more common as people age, but they also arise from exposure to radiation, which can lead to cancerous changes in body cells.

Researchers led by Lee C. Yong, of the National Institute for Occupational Safety and Health, analysed blood samples from 89 airline pilots and a comparison group of 50 university professors of the same age.

They found that, overall, chromosome translocations were not more common among the pilots. However, when they focused on the pilot group alone, they found that the frequency of chromosome alterations increased along with the pilots' flight experience.

For every 10-year increase in flight experience, the rate of chromosome translocations increased by 81 per cent. The link persisted even when the researchers factored in the pilots' ages.

"Our data suggest that pilots with long-term flying experience may be exposed to biologically significant doses of ionising radiation," Dr Yong's team writes.

Long-range studies, the researchers conclude, are now needed to establish whether this translates into higher cancer risks.