Cosmic Radiation and Airline Pilots: Exposure Pattern as a Function of Aircraft Type

Abstract

The project presented here has been carried out as part of an epidemiological project on Norwegian aircraft personnel, entitled 'Exposure to low level ionising radiation and incidence of cancer in airline pilots and crew'. The purpose of the main project is to determine if there may be a relationship between exposure to cosmic radiation at aircraft cruising altitudes and the incidence of cancer. The methodology used as basis for estimating the radiation exposures is presented. The information used as basis for the dose estimations comes from a variety of sources: the files at the Personnel Licensing Section and the Aviation Medical Section of Norwegian Aviation Administration, the route tables of Scandinavian Airlines System (SAS), large amounts of expert information contributed by members of the Pilot's Associations in Norway and a couple of non-Norwegian pilots and from other members of the staff of SAS and other airlines. The estimation for each pilot was based on individual information of annual block hours and an estimated dose rate for each type of aircraft. The latter was estimated as a weighted average of CARI-estimated doses on a selection of routes flown by the airplanes in the different time periods. The project includes all pilots that have been licensed in Norway since 1946. These pilots have been flying a large variety of different types of aircraft and routes. The cosmic radiation intensity is a function of altitude in the atmosphere and, less markedly, of geographical latitude and of the intensity of the radiation from the sun (quantified as the heliocentric potential). Different types of aircraft fly at different altitudes and are used for different purposes (passenger traffic, cargo, air photography, preparation of maps etc) and used on different routes. The end results of the project described in this article are radiation exposures per block hour for each type of aircraft, and for each individual year (the differences between years reflect the variation in intensity of the solar radiation, as well as variations in the route schedules of air companies). In the main project these results are subsequently combined with the number of block hours each year for each pilot to generate the individual radiation exposures per year and cumulative over the pilot's career. The end results of the calculations are dose rates per block hour (also referred to as flight hours) for Norwegian pilots employed by SAS, as a function of aircraft type and year. For planes used by the Scandinavian Airline System (SAS) the dose rate ranged from 0.07 µSv.h-1 (Twin Otter, 1975) to 4.3 µSv.h-1 (DC-10, 1975). For a given airplane more moderate, but still significant, differences over time were noticed, i.e. 2.5 µSv.h-1 (DC-10, 1980) and 4.3 µSv.h-1 (DC-10, 1975).