DETROIT- Airline pilots who have flown for many years may be at risk of DNA damage from prolonged exposure to cosmic ionizing radiation, suggests a study published in the scientific journal Occupational and Environmental Medicine.

James D. Tucker, Ph.D., professor and chair of the Department of Biological Sciences in WSU\'s College of Liberal Arts and Sciences and a resident of Novi, Mich., was part of the 10-person team of investigators that compared the rate of chromosomal DNA abnormalities in blood samples of 83 airline pilots to 50 university faculty members from the same U.S. city.

The research team was led by principal investigator and project officer Lee C. Yong, Ph.D., of the National Institute for Occupational Safety and Health, and also included members of the National Cancer Institute, the American Cancer Society and Lawrence Livermore National Laboratory.

Cosmic ionizing radiation consists of energetic particles and rays that originate in space. Although cosmic radiation has been shown to cause genetic damage, the Earth\'s atmosphere protects people from most of those effects. "Airline pilots, however, spend a significant amount of their time flying at 35,000 feet, with three-quarters of the protective atmosphere beneath them," Tucker said. "We hypothesized this diminished protection would cause increased levels of chromosome damage."

The team investigated the number of times pairs of chromosomes had exchanged pieces, known as a translocation. Chromosome translocations are a reliable indicator of cumulative DNA damage associated with radiation exposure because they are not rapidly eliminated from the blood like other chromosome abnormalities. The research team found the chromosome translocation frequency of those who had flown the most was more than twice that of those who had flown the least, after taking age into account. The authors concluded that highly experienced flight pilots may be exposed to "biologically significant doses of ionizing radiation."

The study looked at damage specifically to white blood cells, which can cause leukemia and lymphoma. Since cosmic ionizing radiation hits all the cells in the body, however, exposure could be damaging to other cell types, raising the risk of other types of cancer as well. "People have examined chromosomes in tumors for a very long time now, and virtually every type of cancer cell has an increased number of chromosome translocations," Tucker said. "Some translocations result from cancer, while others actually cause cancer."

The next step in this line of research is to conduct epidemiological studies with longer follow-up of larger cohorts of pilots with a wide range of radiation exposure levels, so the relationship between ionizing radiation and cancer risk may be clarified.

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