Earlier studies have found increased breast cancer risk among female cabin crew. This has been suggested to reflect lifestyle factors (for example, age at first birth), other confounding factors (for example, age at menarche), or occupational factors such as exposure to cosmic radiation and circadian rhythm alterations due to repeated jet lag.
To assess the contribution of occupational versus lifestyle and other factors to breast cancer risk among cabin attendants in Finland.
A standardised self-administered questionnaire on demographic, occupational, and lifestyle factors was given to 1041 cabin attendants. A total of 27 breast cancer cases and 517 non-cases completed the questionnaire. Breast cancer diagnoses were confirmed through the Finnish Cancer Registry. Exposure to cosmic radiation was estimated based on self-reported flight history and timetables. A conditional logistic regression model was used for analysis.
In the univariate analysis, family history of breast cancer (OR = 2.67, 95% CI: 1.00 to 7.08) was the strongest determinant of breast cancer. Of occupational exposures, sleep rhythm disruptions (OR = 1.72, 95% CI: 0.70 to 4.27) were positively related and disruption of menstrual cycles (OR = 0.71, 95% CI: 0.26 to 1.96) negatively related to breast cancer. However, both associations were statistically non-significant. Cumulative radiation dose (OR = 0.99, 95% CI: 0.83 to 1.19) showed no effect on breast cancer.
Results suggest that breast cancer risk among Finnish cabin attendants is related to well established risk factors of breast cancer, such as family history of breast cancer. There was no clear evidence that the three occupational factors studied affected breast cancer risk among Finnish flight attendants.
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BACKGROUND: Cabin crews are exposed to cosmic radiation at work and this may increase their incidence of radiation-induced cancers. Former studies indicate an increased risk of breast cancer. METHODS: A retrospective cohort study was performed. The cohort was established from the files of the Civil Aviation Administration and included people with a valid licence as a cabin attendant between 1950 and 1994. The cohort was linked to the Cancer Registry of Norway. Observed number of cases was compared with expected, based on national rates. Breast cancer incidence was analysed, adjusting for individual fertility variables. RESULTS: A group of 3693 cabin attendants were followed over 72 804 person-years. Among the women, 38 cases of breast cancer were observed (standardized incidence ratio (SIR) = 1.1, 95% CI : 0.8-1.5). Among men excess risks were found for cancers in the upper respiratory and gastric tract (SIR = 6.0, 95% CI : 2.7-11.4) and cancer of the liver (two cases, SIR = 10.8, 95% CI : 1.3-39.2). For both sexes elevated risks were found for malignant melanoma and non-melanoma skin cancer; for men these were SIR = 2.9 (95% CI : 1.1-6.4) and SIR = 9.9 (95% CI : 4.5-18.8) respectively, while for women these were SIR = 1.7 (95% CI : 1.0-2.7) and SIR = 2.9 (95% CI : 1.0-6.9) respectively. For no cancer site was a significant decreased risk found. CONCLUSIONS: An increased risk of radiation-induced cancers was not observed. The excess risks of some other cancers are more probably explained by factors related to lifestyle.
Comment In: Int J Epidemiol. 2001 Aug;30(4):830-211511612
OBJECTIVE: To examine unusual exposure opportunities to flight crews from chemicals, cosmic radiation, and electric and magnetic fields. METHODS: This project evaluated the incidence of cancers of the breast and other sites among Association of Flight Attendants (AFA) members residing in California. AFA membership files were matched to California's statewide cancer registry to identify a total of 129 newly diagnosed invasive cancers among AFA members with California residential histories between 1988 and 1995. RESULTS: Compared to the general population, female breast cancer incidence was over 30% higher than expected, and malignant melanoma incidence was roughly twice that expected. Both of these are cancers that are associated with higher socioeconomic status and have been suggestively associated with various sources of radiation. CONCLUSIONS: Consistent with the results from Nordic studies of cabin crews and a recent meta-analysis of prior studies, these data suggest that follow-up investigations should focus on the potential relative contribution of workplace exposures and lifestyle characteristics to the higher rates of disease for these two cancers.
BACKGROUND: Aviation involves exposure to ionizing radiation of cosmic origin. The association between lesions of the ocular lens and ionizing radiation is well-known. OBJECTIVE: To investigate whether employment as a commercial airline pilot and the resulting exposure to cosmic radiation is associated with lens opacification. METHODS: This is a population-based case-control study of 445 men. Lens opacification was classified into 4 types using the World Health Organization simplified grading system. These 4 types, serving as cases, included 71 persons with nuclear cataracts, 102 with cortical lens opacification, 69 with central optical zone involvement, and 32 with posterior subcapsular lens opacification. Control subjects are those with a different type of lens opacification or without lens opacification. Exposure was assessed based on employment time as pilots, annual number of hours flown on each aircraft type, time tables, flight profiles, and individual cumulative radiation doses (in millisieverts) calculated by a software program. Odds ratios were calculated using logistic regression. RESULTS: The odds ratio for nuclear cataract risk among cases and controls was 3.02 (95% confidence interval, 1.44-6.35) for pilots compared with nonpilots, adjusted for age, smoking status, and sunbathing habits. The odds ratio for nuclear cataract associated with estimation of cumulative radiation dose (in millisieverts) to the age of 40 years was 1.06 (95% confidence interval, 1.02-1.10), adjusted for age, smoking status, and sunbathing habits. CONCLUSION: The association between the cosmic radiation exposure of pilots and the risk of nuclear cataracts, adjusted for age, smoking status, and sunbathing habits, indicates that cosmic radiation may be a causative factor in nuclear cataracts among commercial airline pilots.
Although physical monitoring of space radiation has been accomplished, we aim to measure exact DNA damage as caused by space radiation. If DNA damage is caused by space radiation, we can detect DNA damage dependent on the length of the space flight periods by using post-labeling methods. To detect DNA damage caused by space radiation, we placed fixed human cervical carcinoma (HeLa) cells in the Russian Mir space station for 40 days and in an American space shuttle for 9 days. After landing, we labeled space-radiation-induced DNA strand breaks by enzymatic incorporation of [3H]-dATP with terminal deoxyribo-nucleotidyl transferase (TdT). We detected DNA damage as many grains on fixed silver emulsion resulting from beta-rays emitted from 3H-atoms in the nuclei of the cells placed in the Mir-station (J/Mir mission, STS-89), but detected hardly any in the ground control sample. In the space shuttle samples (S/MM-8), the number of cells having many grains was lower than that in the J/Mir mission samples. These results suggest that DNA damage is caused by space radiation and that it is dependent on the length of the space flight.
OBJECTIVES: To describe the cancer pattern in a cohort of commercial pilots by follow up through the Icelandic Cancer Registry. METHODS: This is a retrospective cohort study of 458 pilots with emphasis on subcohort working for an airline operating on international routes. A computerised file of the cohort was record linked to the Cancer Registry by making use of personal identification numbers. Expected numbers of cancer cases were calculated on the basis of number of person-years and incidences of cancer at specific sites for men provided by the Cancer Registry. Numbers of separate analyses were made according to different exposure variables. RESULTS: The standardised incidence ratio (SIR) for all cancers was 0.97 (95% confidence interval (95% CI) 0.62 to 1.46) in the total cohort and 1.16 (95% CI 0.70 to 1.81) among those operating on international routes. The SIR for malignant melanoma of the skin was 10.20, 95% CI 3.29 to 23.81 in the total cohort and 15.63, 95% CI 5.04 to 36.46 in the restricted cohort. Analyses according to number of block-hours and radiation dose showed that malignant melanomas were found in the subgroups with highest exposure estimates, the SIRs were 13.04 and 28.57 respectively. The SIR was 25.00 for malignant melanoma among those who had been flying over five time zones. CONCLUSIONS: The study shows a high occurrence of malignant melanoma among pilots. It is open to discussion what role exposure of cosmic radiation, numbers of block-hours flown, or lifestyle factors--such as possible excessive sunbathing--play in the aetiology of cancer among pilots. This calls for further and more powerful studies. The excess of malignant melanoma among those flying over five time zones suggests that the importance of disturbance of the circadian rhythm should be taken into consideration in future studies.
Comment In: Occup Environ Med. 2000 Dec;57(12):84311221686
To assess whether occupational exposure among commercial airline cabin attendants are associated with risk of cancer.
Record linkage study.
Finland. SUBJECTS-1577 female and 187 male cabin attendants who had worked for the Finnish airline companies.
Standardised incidence ratio; expected number of cases based on national cancer incidences.
A significant excess of breast cancer (standardised incidence ratio 1.87 (95% confidence interval 1.15 to 2.23)) and bone cancer (15.10 (1.82 to 54.40)) was found among female workers. The risk of breast cancer was most prominent 15 years after recruitment. Risks of leukaemia (3.57 (0.43 to 12.9)) and skin melanoma (2.11 (0.43 to 6.15) were not significantly raised. Among men, one lymphoma and one Kaposi's sarcoma were found (expected number of cases 1.6).
Although the lifestyle of cabin attendants is different from that of the reference population--for example, in terms of social status and parity--concentration of the excess risks to primary sites sensitive to radiation suggests that ionising radiation during flights may add to the cancer risk of all flight personnel. Otherwise the lifestyle of cabin attendants did not seem to affect their risks of cancer. Estimates of the effect of reproductive risk factors only partly explained the increased risk of breast cancer. If present estimates of health hazards due to radiation are also valid for cosmic radiation, then the radiation doses of cabin attendants seem too small to account entirely for the observed excess risk.
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