The debate continues over whether secondhand smoke causes cancers of sites other than the lung.1 This may in part be due to the challenges in studying the risk from secondhand smoke where the exposure is common and the relative risk associated with exposure may be small.2 On the basis of the published evidence it is reasonable to state that there is at least the possibility of an association between secondhand smoke and the following cancers, but further research is required.
4.10.1 Head and neck cancers
Reviews published in the mid-2000s agreed that secondhand smoke is implicated in the development of several head and neck cancers, but differ in their assessment of the likelihood of causality. The California Environmental Protection Agency (2005) concludes that exposure to secondhand smoke is a cause of nasal sinus cancers in non-smoking adults.3 The Report of the US Surgeon General (2006) acknowledges an association between secondhand smoke exposure and a risk of nasal sinus cancer among non-smokers, but concludes that further studies are required to establish the link as causal.2 Several studies published after these reviews also suggested long-term exposure (over 15 years) to secondhand smoke is associated with an increased risk for upper aerodigestive tract cancers, which include cancers of the mouth, throat and larynx.4-6
A meta-analysis from 2021 supports a causal association between secondhand smoke exposure and oral cancer.7 Five studies were analysed, which included over 3,500 people exposed to secondhand smoke, and the same number unexposed. Those exposed to secondhand smoke had a 1.5-fold increased chance of getting oral cancer compared to unexposed people. In this study, people exposed to secondhand smoke for longer periods (10 to 15 years) had double the chance of oral cancer compared to those who were unexposed.7
Secondhand smoke may increase the risk of developing cancer of the nasal airways leading to the throat (nasopharyngeal cancer) in non-smokers,3 but more research is required before this association can be confirmed.1, 2
4.10.2 Breast cancer
An increase in published research since the late 1990s has seen the debate continue to evolve about the association between development of breast cancer and both active smoking and exposure to secondhand smoke. An association between tobacco smoke exposure and breast cancer is biologically plausible, as known or suspected human carcinogens in tobacco smoke and their resulting DNA adducts have been found in normal and cancerous breast tissue of exposed women. However, the epidemiological evidence has been mixed. The quality of data on secondhand smoke exposure has often been inadequate, with few studies collecting a lifetime history of exposure. This could lead to an underestimate of the risk of breast cancer from secondhand smoke.8
The major scientific reviews differ in their conclusions regarding the association between breast cancer and exposure to tobacco smoke. In 2004, the International Agency for Research on Cancer (IARC) found the evidence for an association between breast cancer and secondhand smoke was inconsistent, adding that ‘the lack of association of breast cancer with active smoking weighs heavily against the possibility that involuntary smoking increases the risk for breast cancer’.9 However, the latest update issued by the IARC in 2009 reported that there was limited evidence that active smoking causes breast cancer, but the evidence for an association with secondhand smoke remained inconclusive.4 In its 2005 review, the California Environmental Protection Agency concluded that the weight of evidence is consistent with there being a causal association between exposure to secondhand smoke and the development of breast cancer, particularly in premenopausal women aged under 50. In this group, the risk of developing breast cancer may be doubled.3 The Report of the US Surgeon General (2014) more cautiously states that ‘the evidence is suggestive but not sufficient to infer a causal relationship between exposure to secondhand tobacco smoke and breast cancer’.10
A review by the Canadian Expert Panel on Tobacco Smoke and Breast Cancer Risk (2009) concluded that active smoking causes breast cancer, and exposure to secondhand smoke causes breast cancer among younger, primarily premenopausal women who have never smoked. It noted that the risks associated with secondhand smoke appear to be similar to those associated with active smoking when secondhand smoke exposure is statistically controlled for, which is a phenomenon yet to be explained.8
The epidemiological and mechanistic relationship between tobacco smoke exposure and breast cancer is complex and not fully resolved. However because of the high incidence of breast cancer in the general female population, the Report of the US Surgeon General recommends that women be advised to avoid exposure to secondhand smoke.2
4.10.3 Cervical cancer
Limited research suggests that exposure to secondhand smoke may be associated with an increased risk of developing cancer of the cervix, but more research is required.1, 3
4.10.4 Cancers of the bladder and kidney
A number of studies have explored the relationship between secondhand smoke exposure and bladder cancer and these have yielded varying results. Overall, the evidence is inconclusive.1, 11, 12, 13, 14
The available evidence suggests a possible causal relationship between secondhand smoke exposure and kidney cancer exists, however more evidence is required.1
4.10.5 Childhood cancers
See Section 4.17.
Relevant news and research
For recent news items and research on this topic, click here. ( Last updated August 2021)
1. Lee PN, Thornton AJ, and Hamling JS. Epidemiological evidence on environmental tobacco smoke and cancers other than lung or breast. Regulatory Toxicology and Pharmacology, 2016; 80:134-63. Available from: https://www.ncbi.nlm.nih.gov/pubmed/27321059
2. US Department of Health and Human Services. The health consequences of involuntary exposure to tobacco smoke: a report of the Surgeon General. Atlanta, Georgia: US Department of Health and Human Services, Centers for Disease Control and Prevention, Coordinating Center for Health Promotion, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2006. Available from: http://www.cdc.gov/tobacco/data_statistics/sgr/sgr_2006/index.htm.
3. Office of Environmental Health Hazard Assessment and California Air Resources Board. Health effects of exposure to environmental tobacco smoke: final report, approved at the Panel's June 24, 2005 meeting. Sacramento: California Environmental Protection Agency, 2005. Available from: http://www.oehha.ca.gov/air/environmental_tobacco/2005etsfinal.html
4. Secretan B, Straif K, Baan R, Grosse Y, El Ghissassi F, et al. A review of human carcinogens--Part E: tobacco, areca nut, alcohol, coal smoke, and salted fish. Lancet Oncology, 2009; 10(11):1033-4. Available from: https://www.ncbi.nlm.nih.gov/pubmed/19891056
5. Lee YC, Boffetta P, Sturgis EM, Wei Q, Zhang ZF, et al. Involuntary smoking and head and neck cancer risk: pooled analysis in the International Head and Neck Cancer Epidemiology Consortium. Cancer Epidemiology, Biomarkers & Prevention, 2008; 17(8):1974-81. Available from: https://www.ncbi.nlm.nih.gov/pubmed/18708387
6. Lee YC, Marron M, Benhamou S, Bouchardy C, Ahrens W, et al. Active and involuntary tobacco smoking and upper aerodigestive tract cancer risks in a multicenter case-control study. Cancer Epidemiology, Biomarkers & Prevention, 2009; 18(12):3353-61. Available from: https://www.ncbi.nlm.nih.gov/pubmed/19959682
7. Mariano LC, Warnakulasuriya S, Straif K, and Monteiro L. Secondhand smoke exposure and oral cancer risk: a systematic review and meta-analysis. Tobacco Control, 2021. Available from: https://www.ncbi.nlm.nih.gov/pubmed/33903278
8. Johnson KC, Miller AB, Collishaw NE, Palmer JR, Hammond SK, et al. Active smoking and secondhand smoke increase breast cancer risk: the report of the Canadian Expert Panel on Tobacco Smoke and Breast Cancer Risk (2009). Tobacco Control, 2011; 20(1):e2. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21148114
9. International Agency for Research on Cancer Working Group on the Evaluation of Carcinogenic Risks to Humans. Tobacco smoke and involuntary smoking. IARC monographs on the evaluation of carcinogenic risks to humans, Vol. 83.Lyon, France: IARC, 2004. Available from: http://monographs.iarc.fr/ENG/Monographs/PDFs/index.php.
10. US Department of Health and Human Services. The health consequences of smoking - 50 years of progress. Atlanta, GA: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2014. Available from: https://www.ncbi.nlm.nih.gov/books/NBK179276/.
11. Bjerregaard B, Raaschou-Nielsen O, Sorensen M, Frederiksen K, Christensen J, et al. Tobacco smoke and bladder cancer in the European prospective investigation into cancer and nutrition. International Journal of Cancer, 2006; 119:2412-16. Available from: http://www.ncbi.nlm.nih.gov/pubmed/16894557
12. Jiang X, Yuan JM, Skipper PL, Tannenbaum SR, and Yu MC. Environmental tobacco smoke and bladder cancer risk in never smokers of Los Angeles County. Cancer Research, 2007; 67(15):7540-5. Available from: https://www.ncbi.nlm.nih.gov/pubmed/17671226
13. Tao L, Xiang YB, Wang R, Nelson HH, Gao YT, et al. Environmental tobacco smoke in relation to bladder cancer risk--the Shanghai bladder cancer study [corrected]. Cancer Epidemiology, Biomarkers & Prevention, 2010; 19(12):3087-95. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21056942
14. Van Hemelrijck MJ, Michaud DS, Connolly GN, and Kabir Z. Secondhand smoking, 4-aminobiphenyl, and bladder cancer: two meta-analyses. Cancer Epidemiology, Biomarkers & Prevention, 2009; 18(4):1312-20. Available from: https://www.ncbi.nlm.nih.gov/pubmed/19336562