Cancer incidence among Nordic airline cabin crew

Abstract

Airline cabin crew are occupationally exposed to cosmic radiation and jet lag with potential disruption of circadian rhythms. This study assesses the influence of work-related factors in cancer incidence of cabin crew members. A cohort of 8,507 female and 1,559 male airline cabin attendants from Finland, Iceland, Norway and Sweden was followed for cancer incidence for a mean follow-up time of 23.6 years through the national cancer registries. Standardized incidence ratios (SIRs) were defined as ratios of observed and expected numbers of cases. A case-control study nested in the cohort (excluding Norway) was conducted to assess the relation between the estimated cumulative cosmic radiation dose and cumulative number of flights crossing six time zones (indicator of circadian disruption) and cancer risk. Analysis of breast cancer was adjusted for parity and age at first live birth. Among female cabin crew, a significantly increased incidence was observed for breast cancer [SIR 1.50, 95% confidence interval (95% CI) 1.32-1.69], leukemia (1.89, 95% CI 1.03-3.17) and skin melanoma (1.85, 95% CI 1.41-2.38). Among men, significant excesses in skin melanoma (3.00, 95% CI 1.78-4.74), nonmelanoma skin cancer (2.47, 95% CI 1.18-4.53), Kaposi sarcoma (86.0, 95% CI 41.2-158) and alcohol-related cancers (combined SIR 3.12, 95% CI 1.95-4.72) were found. This large study with complete follow-up and comprehensive cancer incidence data shows an increased incidence of several cancers, but according to the case-control analysis, excesses appear not to be related to the cosmic radiation or circadian disruptions from crossing multiple time zones.Airline cabin crew are occupationally exposed to ionizing radiation with doses 2-6 mSv per year. 1 This is roughly twice the average annual dose from natural and medical sources received by the general population. Cosmic radiation in the common cruising altitudes (8,000-10,000 m) consists mainly of gamma and neutron radiation, with some heavy nuclei. In 1990, the International Commission on Radiological Protection recommended that in-flight radiation exposure to jet aircrew should be regarded as occupational exposure. 2 Of the radiation-related cancers, only breast cancer has shown increased incidence rates among airline personnel consistently in several studies. Out of the seven cohort studies of cabin crew, 3-9 all but one 6 indicate an increased incidence of breast cancer. However, the excess risks seem to be higher than can be explained by the low radiation doses received, 10 and several other factors may contribute to the observed excess.Cabin crew also work in shifts including work at night and are exposed to jet lags (a temporary condition after air travel across several time zones) dependent on time, distance and direction (east-west vs. north-south) of flight routes. Such exposures may contribute to circadian disruption, including suppression of the chronobiotic neurohormone melatonin, which has anticancer properties. [11][12][13] There is accumulated epidemiologic and biologic eviden...

Breast cancer incidence among female flight attendants: exposure–response analyses

“…In the only other relatively large study evaluating both exposures (17), breast cancer risk was not associated with cosmic radiation dose after adjusting for parity or with number of flights crossing ≥6 time zones after adjusting for parity and age at first birth. None of the previous studies report evaluating effect modification by parity (17-23).…”

“…Studies suggest that flight attendants have an increased incidence of breast cancer compared to the general population (1,2). However, the reason is unclear.…”

Numerical model for computation of effective and ambient dose equivalent at flight altitudes

“…An important feature of space weather is the assessment of aircrew exposure due to CR, specifically during GLEs. At present there is no evidence of any immediate threat on human health from SEPs, and the biological risk of radiation doses accumulated by aircrew is still a matter of scientific debate (Sigurdson & Ron 2004;Ballarini et al 2007;Hammer et al 2009;Pukkala et al 2012;Dos Santos Silva et al 2013). In addition, a recent survey of the exposure due to CRs demonstrated that none exceeded the recommended level of 6 mSv/y and the majority of aircrew received around 3 mSv/y (Bennett et al 2013a(Bennett et al , 2013b.…”

Loss of BMAL1 in ovarian steroidogenic cells results in implantation failure in female mice

“…ovary | circadian rhythm | fertility | steroidogenesis D isruption of circadian rhythms has been implicated in a variety of human health conditions, including cancer, diabetes, and infertility (1)(2)(3)(4)(5). Previous work has shown that the brain muscle arnt-like 1 (BMAL1) protein (also known as MOP3 or ARNTL), in a dimeric complex with the CLOCK protein, is an essential component of the "molecular clock" that controls circadian driven gene expression (6,7).…”