This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. However, to get the most out of the tables, it’s important to understand some key concepts. Learn how to read a research table.
Introduction: Most large prospective cohort studies have found no link between breathing secondhand smoke (breathing the smoke from other people's cigarettes, also called passive smoking) and breast cancer.
However, findings from some case-control studies have shown a small increased risk of breast cancer, especially among premenopausal women.
More research is needed to draw solid conclusions about a possible link between secondhand smoke and breast cancer risk.
Learn more about secondhand smoke and breast cancer risk.
Find a summary of research studies on smoking and risk of breast cancer.
Learn about the strengths and weaknesses of different types of studies.
See how this risk factor compares with other risk factors for breast cancer.
Study selection criteria: Prospective cohort studies and case-control studies with at least 900 breast cancer cases and meta-analyses of cohort and nested case-control studies. Table note: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk.
Study Population(number of participants)
Secondhand Smoke Exposure
Relative Risk of Breast Cancer in Women Exposed to Secondhand Smoke Compared to Women Not Exposed to Secondhand Smoke, RR (95% CI)
Prospective cohort studies
Exposure in childhood or at home or at work
Nurses' Health Study 
Exposure in home or at work
Million Women Study 
Exposure in home
California Teachers Study 
Women’s Health Initiative Observational Study 
Black Women's Health Study 
National Institute of Environmental Health Sciences Sister Study 
Young et al. 
Ontario Women’s Diet and Health Study 
Exposure in home, at work or in social settings
Premenopausal women:1.61 (0.74-3.52)
Postmenopausal women:1.03 (0.69-1.55)
Lissowska et al. 
Johnson et al. 
Postmenopausal women:1.1 (0.6-1.8)
Slattery et al. 
Exposure in home, at work or outside of home
Premenopausal women:1.2 (0.6-2.7)‡
Postmenopausal women:1.0 (0.6-1.7)‡
Shrubsole et al. 
Macacu et al. 
11 cohort and nested case-control studies
Yang et al. 
10 cohort studies
Pirie et al. 
8 cohort studies
* Results were similar when pre- and postmenopausal women were examined separately.
† Results were similar when childhood and adult exposure to secondhand smoke were examined separately.
‡ Results are for non-Hispanic white women in this study.
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