Environment and Breast Cancer: Science Review

Evidence From Humans
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Cancer incidence in California flight attendants (United States)
Reynolds, P., Cone, J., Layefsky, M., Goldberg, D. E., Hurley, S. Cancer Causes and Control. 2002. 13:4, 317-24.
Topic area
Electromagnetic fields - Environmental pollutant
Study Participants
Number of Cases
60 invasive, 12 in situ
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Association of Flight Attendants members residing in California in 1997; compared to general population and non-Hispanic whites.
Comment about participation selection
Person-years at risk was estimated from address in a single year. Eligible women are primarily young (born 1960 or later).
Exposure Investigated
Exposures investigated
Cosmic radiation, EMF, ozone, carbon monoxide, jet exhaust, schedule changes. Employment as a flight attendant in 1997; employment on international vs. domestic flights; length of employment; age at entry into employment as a flight attendant.
Statistical Analysis
Breast cancer outcome investigated
Primary breast cancer, invasive and in situ diagnosed in 1988-1995 and reported to California Cancer Registry
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
Not controlled.
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Description of major analysis
Standardized incidence ratio. Expected number of cancers based on California statewide sex and age-specific incidence in 1989-1993. Proportional incidence ratios calculated from case information only.
Strength of associations reported
PIR 1.36 (95% CI 1.04-1.75)
SIR flight attendants vs. all races = 1.42 (95% ci 1.09-1.83)
SIR flight attendants vs. non-Hispanic whites = 1.29 (0.99-1.66)
Incidence is more elevated for flight attendants on international flights, with 15 or more years of service, and younger at entry into work as a flight attendant. SIRs for these groups compared with non-Hispanic whites and all races range from 42% to 70% elevated and confidence intervals exclude one.
Results Comments
Actual risk is likely to fall between the estimate based on all races and the estimate based on non-Hispanic whites. Flight attendants are likely to have higher rates of reproductive risk factors related to breast cancer than the general population; however, effects of these factors may not be large enough to account for the observed elevated risk. Other large studies are under way.
Author address
California Department of Health Services, Environmental Health Investigations Branch, Oakland 94612, USA.