Background: Cockpit crews receive cosmic radiation during flight operations. The increasing total accumulated dose over the years might be expected to cause increased frequency of radiation-induced cancer. The rate should increase with number of flight hours per year, number of years of flying, and higher flight altitude. If the cumulative radiation exposure during flights is of concern, we would expect an increased cancer risk to be present among those crew members flying jets.
Methods: Cockpit-crew medical records (pilots and flight engineers) from 1946 onwards, holding information on the individual, flight hours, aircraft type, and date of commercial certification and decertification, were linked to the population-based Danish Cancer Registry, the central population registry, and the National Death Index.
Findings: Altogether 3877 cockpit crew members could be traced for follow-up, accruing 61095 person-years at risk in 3790 men and 661 in 87 women. The total number of cancers observed was 169 whereas 153.1 were expected (standardised incidence ratio 1.1 [95% CI 0.94-1.28]). Significantly increased risks of acute myeloid leukaemia (5.1 [1.03-14.91]), skin cancer, excluding melanoma (3.0 [2.12-4.23]), and total cancer (1.2 [1.00-1.53]) were observed among Danish male jet cockpit crew members flying more than 5000 h. Increased risk of malignant melanoma irrespective of aircraft type was also found among those flying more than 5000 h.
Interpretation: Both malignant melanoma and skin cancer were found in excess in cockpit crew members with a long flying history, probably attributable to sun exposure during leisure time at holiday destinations. We cannot confirm previously reported increased risk of brain and rectal cancers in pilots. The study shows that male cockpit crew members in jets flying more than 5000 h have significantly increased frequency of acute myeloid leukaemia.