Cancer incidence in Republic of Bulgaria aircrew, 1964-1994.

BACKGROUND: This study includes all cases of cancer among Republic of Bulgaria Air Force and civil aviation aircrew. Cancer incidence, Standardized Incidence Ratios (SIRs) and 95% confidential intervals were calculated for the pilots, using data about cancer incidence in the same age groups of the male population of the Republic of Bulgaria for the same period of time, taken from the National Cancer Register. RESULTS: The results show a considerable difference in the structure of cancer among males in Bulgaria, as compared to male pilots (r<0.0001). While cancer of the respiratory system has the greatest incidence among the civil population, cancer of the bladder has the greatest incidence among pilots, followed by testicular and skin cancer. For the period under consideration there is a lower risk of malignant diseases in pilots as compared to the rest of the population. There is a higher risk of testicular cancer only in civil aviation pilots. For Air Force aircrew there is a 10-fold higher risk of bladder cancer as compared to the rest of the population. CONCLUSION: We established an interdependence between age and cancer incidence, cancer incidence being higher among pilots in the age group from 20-40 yr. For the remaining age groups, cancer incidence among the civil population is approximately 2.5 times higher. Of the pilots with cancer, 73.53% returned to a flying career after an average of 7 mo treatment.