Last year a report in The Lancet found higher rates of certain cancers among jet pilots and crew members. Now, the authors of that study report that this increased cancer risk is due to chromosome damage caused by excessive exposure to ionizing radiation from the sun.

The form of cancer found to be most increased among the flight crews is acute myeloid leukemia, which is very often fatal, with an average survival time of 3 to 4 years following diagnosis. Even in patients who experience complete remission, recurrence is common.

The disease develops rapidly, with symptoms including:

• Anemia

Immature leukemia cells continue to divide in the bone marrow, which leads to rapid death if left untreated. It affects granulocytes and monocytes, white blood cells that destroy bacteria and some parasites.

In the current report, researchers note that they found damage to chromosome 7 in 4 out of seven (57%) aircrew members with the cancer, in comparison with only 81 of 761 cases (11%) of the cancer among non-flight crew members.

The researchers conclude that "Our results indicate that deletions or loss of the long arm of chromosome 7 in myelodysplasia and acute myeloid leukemia could be an indicator of previous exposure to ionizing radiation."

This is not the first time that radiation exposure has been linked to leukemia. People in Japan, exposed to the nuclear bomb radiation have been found to have higher rates as well.

The Lancet, December 23, 2000; 356