Airline pilot cosmic radiation and circadian disruption exposure assessment from logbooks and company records

Abstract

Objectives: US commercial airline pilots, like all flight crew, are at increased risk for specific cancers, but the relation of these outcomes to specific air cabin exposures is unclear. Flight time or block (airborne plus taxi) time often substitutes for assessment of exposure to cosmic radiation. Our objectives were to develop methods to estimate exposures to cosmic radiation and circadian disruption for a study of chromosome aberrations in pilots and to describe workplace exposures for these pilots.

Methods: Exposures were estimated for cosmic ionizing radiation and circadian disruption between August 1963 and March 2003 for 83 male pilots from a major US airline. Estimates were based on 523 387 individual flight segments in company records and pilot logbooks as well as summary records of hours flown from other sources. Exposure was estimated by calculation or imputation for all but 0.02% of the individual flight segments' block time. Exposures were estimated from questionnaire data for a comparison group of 51 male university faculty.

Results: Pilots flew a median of 7126 flight segments and 14 959 block hours for 27.8 years. In the final study year, a hypothetical pilot incurred an estimated median effective dose of 1.92 mSv (absorbed dose, 0.85 mGy) from cosmic radiation and crossed 362 time zones. This study pilot was possibly exposed to a moderate or large solar particle event a median of 6 times or once every 3.7 years of work. Work at the study airline and military flying were the two highest sources of pilot exposure for all metrics. An index of work during the standard sleep interval (SSI travel) also suggested potential chronic sleep disturbance in some pilots. For study airline flights, median segment radiation doses, time zones crossed, and SSI travel increased markedly from the 1990s to 2003 (P(trend) < 0.0001). Dose metrics were moderately correlated with records-based duration metrics (Spearman's r = 0.61-0.69).

Conclusions: The methods developed provided an exposure profile of this group of US airline pilots, many of whom have been exposed to increasing cosmic radiation and circadian disruption from the 1990s through 2003. This assessment is likely to decrease exposure misclassification in health studies.

Figures

Fig. 1.

Components of cumulative effective galactic cosmic radiation dose for 83 pilots. The cumulative ED for 51 faculty (comparison group; recreational travel only) is included for comparison. Black boxes indicate interquartile range and lines indicate data range. Private flight is not shown since values were too low to visualize.

Fig. 2.

Cumulative total and particle absorbed galactic cosmic radiation doses for pilots. Black boxes indicate interquartile ranges and lines indicate data ranges.

Fig. 3.

Exposure metrics per pilot flight segment by type of flight and decade. Galactic cosmic radiation absorbed dose (in microGray), total ED (proton weighting factor = 2) and neutron ED (in microSieverts), SSI travel, and time zones crossed are presented. Black boxes indicate interquartile ranges and lines indicate 5th–95th percentiles of data. Metrics were calculated from individual segment data, which does not include commuter travel, pass travel, or summary flight hours. For SSI travel, segment data were only available from the study airline from 1992 to 2003. The 611 flight segments from the 1960s (0.1% of all flights) were incorporated into the 1970–1979 group since these flights represent four pilots and 99% of these segments were private flights.