Incidence of cancer among commercial airline pilots

Objectives-To describe the cancer pattern in a cohort of commercial pilots by follow up through the Icelandic Cancer Registry. Methods-This is a retrospective cohort study of 458 pilots with emphasis on subcohort working for an airline operating on international routes. A comp uterised file of the cohort was record linked to the Cancer Registry by mak ing use of personal identification numbers. Expected numbers of cancer case s were calculated on the basis of number of person-years and incidences of cancer at specific sites for men provided by the Cancer Registry. Numbers o f separate analyses were made according to different exposure variables. Results-The standardised incidence ratio (SIR) for all cancers was 0.97 (95 % confidence interval (95% CI) 0.62 to 1.46) in the total cohort and 1.16 ( 95% CI 0.70 to 1.81) among those operating on international routes. The SIR for malignant melanoma of the skin was 10.20, 95% CI 3.29 to 23.81 in the total cohort and 15.63, 95% CI 5.04 to 36.46 in the restricted cohort. Anal yses according to number of block-hours and radiation dose showed that mali gnant melanomas were found in the subgroups with highest exposure estimates , the SIRs were 13.04 and 28.57 respectively. The SIR was 25.00 for maligna nt melanoma among those who had been flying over five time zones, Conclusions-The study shows a high occurrence of malignant melanoma among p ilots. It is open to discussion what role exposure of cosmic radiation, num bers of block-hours flown, or lifestyle factors-such as possible excessive sunbathing-play in the aetiology of cancer among pilots. This calls for fur ther and more powerful studies. The excess of malignant melanoma among thos e flying over five time zones suggests that the importance of disturbance o f the circadian rhythm should be taken into consideration in future studies .