Flying cancer evidence attacked

Experts do not know whether air crews are at risk

Direct "evidence" that cosmic radiation is to blame for leukaemia's developed by flight crews is flawed, say experts.

The study comes from the same team which produced controversial data last year which suggested flight crews were more likely to get acute myeloid leukaemia.

The possible link between damage to chromosome 7 and cosmic radiation is neither strengthened or weakened by the findings

Dr David Grant, Leukaemia Research Fund

This time they looked at the genetic structure of cells from seven flight crew who had developed either acute myeloid leukaemia, or myelodysplasia, an abnormality of the bone marrow which may lead eventually to leukaemia.

One theory suggests that, travelling high in the atmosphere, flight crews are exposed to greater levels of cosmic radiation, which then causes damage to the coded genetic information carried in the body's cells.

This damage could in theory trigger cancerous changes in cells.

The researchers, writing in the Lancet medical journal, say they found four out of seven had faults in exactly the same tiny area of genetic code.

At face value, the rate of this particular abnormality was much higher in this group than in a sample of 761 patients with these conditions from the general population.

Radiotherapy treatment

This area, called chromosome seven, has already been linked with cancers arising in patients who have received radiation therapy.

Dr Maryanne Gundestrup, who led the study at the National Clinic of Aviation Medicine in Copenhagen, said: "Our results indicate that deletions or loss of the long arm of chromosome seven in myelodysplasia and acute myeloid leukaemia could be an indicator of previous exposure to ionising radiation."

However, the tiny number of flightcrew involved, added to fact that some of these were so old that they must have stopped commercial flying at least a decade before, significantly weakens the research, suggest other experts.

If the root cause of a cancer is radiation exposure, it is very likely to emerge at least within a decade of exposure to the radiation, ruling out work-received radiation as a possible reason for their illness.

The Leukaemia Research Fund is already financing research into the importance of chromosome seven, and chromosome five, another piece of genetic code which scientists believe is crucial.

Dr David Grant, its scientific director, said: "The possible link between damage to chromosome 7 and cosmic radiation is neither strengthened or weakened by the findings.

"Acute myeloid leukaemia and myelodysplasia are predominantly diseases of older age.

"We note that three of Dr Gundestrup's seven patients were in their 60s or 70s when diagnosed. This is the age at which these diseases are most common.

"One of the other patients had no significant exposure to cosmic radiation."

Other studies have looked into possible links between regular long-haul flying and illness.

A British Airways sponsored study from 1999 showed no increased rate of acute myeloid leukaemia cases among its flight crew.