Cohort study of occupational cosmic radiation dose and cancer mortality in German aircrew, 1960–2014

Abstract

ObjectivesTo determine cancer mortality compared with the general population and to examine dose-response relationships between cumulative occupational radiation dose and specific cancer outcomes in the German aircrew cohort.MethodsFor a cohort of 26 846 aircrew personnel, standardised mortality ratios (SMR) were calculated. Dose-response analyses were carried out using Poisson regression to assess dose-related cancer risks for the period 1960–2014. Exposure assessment comprises recently available dose register data for all cohort members and newly estimated retrospective cabin crew doses for 1960–2003.ResultsSMR for all-cause, specific cancer groups and most individual cancers were reduced in all aircrew groups. The only increases were seen for brain cancer in pilots (n=23, SMR 2.01, 95% CI 1.15 to 3.28) and for malignant melanoma (n=10, SMR 1.88, 95% CI 0.78 to 3.85). Breast cancer mortality among female cabin crew was similar to the general population (n=71, SMR 1.06, 95% CI 0.77 to 1.44). Overall median cumulative effective dose was 34.2 mSv (max: 116 mSv) for 1960–2014. No dose-response associations were seen in any of the models. For brain cancer, relative risks were elevated across dose categories. An indicative negative trend with increasing dose category was seen for large intestine cancer in female cabin crew (n=23).ConclusionsThere was no evidence for significant dose-response patterns for the considered cancer types. Interpretation of results remains difficult as cumulative dose is closely related to age. Future work should focus on investigating radiation jointly with other risk factors that may contribute to risks for specific cancers among aircrew.

Hazards at 10 000 m: studies of aircrew and their importance in understanding cancer risks from cosmic radiation and circadian disruption

“…These sources of error (termed ‘Berkson error’) generally lead to greater imprecision but do not bias point estimates if the group means are measured accurately. For many of the cohorts in which long-haul flights predominate, there are also very strong ( r >0.9) correlations of aircrew employment duration, night work (eg, as measured by travel during the standard sleep interval of 22:00–08:00), measures of circadian disruption (eg, number of time zones crossed) and cosmic radiation dose 2 5 6. This problem was previously noted by Schüz in the earlier commentary 1.…”

“…As noted for previous follow-up of the same cohort,1 3 4 large deficits in mortality for most causes were observed compared with the general population, in particular deficits of 16% to 73% for all-cause, all-cancer and lung cancer mortality, which suggests a continued strong healthy worker effect. Dreger and colleagues2 observed an excess of mortality from cancers of brain and colon and of melanoma of skin compared with the general population; however, positive associations were not seen between cosmic radiation and any studied outcome.…”

“…Six years ago, a commentary1 in this journal queried whether there is more yet to learn about cancer from studies of aircrew cohorts and outlined some possible avenues for research, including the assembly of large cohorts from individual employers, evaluation of cancer types that are not strongly related to reproductive and other behaviours, and measurement of circadian disruption exposure in addition to cosmic radiation. The publication by Dreger and colleagues2 in this issue offers an opportunity to assess progress in understanding cancer risk among aircrew. Dreger and colleagues2 report on cancer mortality in a nearly 27 000-person cohort of cockpit and cabin crew from a large German airline, extending follow-up by 10 years.…”

“…The publication by Dreger and colleagues2 in this issue offers an opportunity to assess progress in understanding cancer risk among aircrew. Dreger and colleagues2 report on cancer mortality in a nearly 27 000-person cohort of cockpit and cabin crew from a large German airline, extending follow-up by 10 years. In this study, they estimated cosmic radiation doses through linkage to a national dose registry (since 2003) and by conducting the more challenging retrospective assessment required to estimate doses for cabin crew before 2003.…”

“…Lower radiation weighting may also imply that aircrew may experience lower doses, and the studies may have lower power, than originally anticipated. Furthermore, the cumulative dose distribution in most aircrew cohorts is fairly narrow (eg, in the study by Dreger and colleagues2 the IQR was 13–52 mSv), which also affects study power.…”