All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
Exposure to secondhand smoke increases breast cancer risk in nonsmokers by 24%
Last reviewed: 02.07.2025
A recent meta-analysis of published epidemiological studies found that exposure to second-hand smoke significantly increases the risk of breast cancer in non-smoking women. The study was published in the British Journal of Cancer.
Breast cancer is the most commonly diagnosed malignancy in women, accounting for about 15% of all cancer deaths in women. In 2020, there were about 2.3 million new cases of breast cancer. Breast cancer accounts for one-third of all cancer diagnoses in women under 50.
In addition to non-modifiable risk factors such as age and genetic mutations, breast cancer is also associated with various modifiable risk factors, including smoking, alcohol consumption, physical inactivity, weight gain after menopause, and the use of contraceptives or hormonal therapy.
The researchers conducted a comprehensive literature search across multiple electronic databases using an innovative methodology combining umbrella reviews and traditional reviews. Ultimately, 73 original studies (case-control or cohort studies) published in English from 1984 to 2022 that examined the association between second-hand smoke exposure and breast cancer risk in non-smoking women were identified. Of these, 63 studies were included in the meta-analysis and 10 were excluded due to duplication of data. These studies included more than 35,000 breast cancer cases.
A meta-analysis found that non-smoking women exposed to second-hand smoke had a 24% increased risk of developing breast cancer. The risk was significantly higher in case-control studies compared with cohort studies.
A significantly increased risk of breast cancer was observed in women exposed to second-hand smoke at home, at home and work, and in unspecified settings. Further subdividing the data showed that non-smoking women exposed to second-hand smoke from a partner had a 16% increased risk of developing breast cancer. In addition, the risk of breast cancer increased by 5% in women exposed to second-hand smoke as children.
Dose-response analysis showed that the risk of breast cancer increased linearly with increasing duration, intensity, and pack-years of exposure to second-hand smoke. Specifically, for women exposed to second-hand smoke for more than 40 years, the risk increased by 30%.
The study identified second-hand smoke exposure as a strong risk factor for breast cancer in non-smoking women. This puts it on par with other significant modifiable risk factors such as alcohol consumption, which increases risk by 23%.
The findings of this meta-analysis highlight the need to promote smoke-free environments, particularly at home and in other private settings, and to raise public awareness of the health risks associated with exposure to second-hand smoke.