This summary table contains detailed information about research studies. Summary tables offer an informative look at the science behind many breast cancer guidelines and recommendations. However, they should be viewed with some caution. In order to read and interpret research tables successfully, it is 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 slightly 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 500 breast cancer cases and meta-analyses. 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 
Young et al. 
Ontario Women’s Diet and Health Study 
Exposure in home, at work or in social settings
Lissowska et al. 
Johnson et al. 
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. 
Nishino et al. 
Roddam et al. 
Premenopausal women:0.89 (0.64-1.25)
Yang et al. 
10 cohort studies
Pirie et al. 
8 cohort studies
17 case-control studies
Johnson et al. 
19 cohort and case-control studies
Miller et al. 
* Results were similar when pre- and postmenopausal women were examined separately.
† Results are for non-Hispanic white women in this study. Among 798 cases and 924 control women who were Hispanic or American Indian, there was an increased risk of breast cancer among pre- and peri-menopausal women with RR=2.3 (1.2-4.5), but not among postmenopausal women with RR=1.0 (0.6-1.8).
‡ Results are for hormone receptor-positive breast cancers. Results for hormone receptor-negative breast cancers were similar.
§ Increased risk of breast cancer was found only among case-control studies. All cohort study results showed no link between secondhand smoke exposure and breast cancer risk.
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