The debate continues over whether secondhand smoke causes cancers of some sites other than the lung. 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.
The most recent reviews agree that secondhand smoke is implicated in the development of nasal sinus cavity, but differ about the proven degree of causality. The California Environmental Protection Agency concludes that exposure to secondhand smoke is a cause of nasal sinus cancers in non-smoking adults.1 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
Secondhand smoke may increase the risk of developing cancer of the nasal airways leading to the throat (nasopharyngeal cancer) in non-smokers,1 but more research is required before this association can be confirmed.2
Limited evidence suggests that long-term exposure (more than 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.3–5
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 result in the contamination of the referent group, leading to an underestimate of the risks, should they exist.6
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'.7 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.3 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.1 The Report of the US Surgeon General (2006) more cautiously states that 'the evidence is suggestive but not sufficient to infer a causal relationship between second hand smoke and breast cancer'.2
The most recent 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.6
The epidemiological and mechanistic relationship between tobacco smoke exposure and breast cancer is complex and not fully resolved, and requires further research. 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
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
Recent studies report an increased incidence of bladder cancer in non-smoking adults exposed to secondhand smoke during childhood,9–11 and one study implicates exposure to tobacco carcinogens through breast milk and in utero exposure as a risk factor.12 Evidence for a link between adult exposure to secondhand smoke and bladder cancer is mixed and inconclusive.9–11,13 Of the two studies reporting an association, one found an association for women but not men,10 and another showed a stronger association for people possessing at-risk phenotypes of CYP1A2 and/or NAT2 (isoenzymes in activation and detoxification, respectively, of tobacco carcinogens).11 Further research is required before any of these associations can be confirmed.
See Section 4.9.9.
1. 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
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. Secretan B, Straif K, Baan R, Grosse Y, El Ghissassi F, Bouvard V, et al. A review of human carcinogens--Part E: tobacco, areca nut, alcohol, coal smoke, and salted fish. The Lancet Oncology 2009;10(11):1033–4. Available from: http://www.ncbi.nlm.nih.gov/pubmed/19891056
4. Lee Y, Boffetta P, Sturgis E, Wei Q, Zhang Z, Muscat J, 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: http://cebp.aacrjournals.org/cgi/content/full/17/8/1974
5. Lee Y, Marron M, Benhamou S, Bouchardy C, Ahrens W, Pohlabeln H, 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: http://cebp.aacrjournals.org/content/18/12/3353.long
6. Johnson K, Miller A, Collishaw N, Palmer J, Hammond S, Salmon A, 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;Jan 20(1):e2. Available from: http://tobaccocontrol.bmj.com/content/early/2010/10/27/tc.2010.035931.full
7. 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
8. US Department of Health and Human Services. The health consequences of involuntary smoking: a report of the Surgeon General. Rockville, Maryland: US Department of Health and Human Services, Public Health Service, Centers for Disease Control, Center for Health Promotion and Education, Office on Smoking and Health, 1986. Available from: http://www.cdc.gov/tobacco/data_statistics/sgr/previous_sgr.htm
9. Bjerregaard B, Raaschou-Nielsen O, Sorensen M, Frederiksen K, Christensen J and Tjonneland A. 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
10. Jiang X, Yuan J, Skipper P, Tannenbaum S and Yu M. Environmental tobacco smoke and bladder cancer risk in never smokers of Los Angeles County. Cancer Research 2007;67(15):7540–5. Available from: http://cancerres.aacrjournals.org/cgi/reprint/67/15/7540
11. Tao L, Xiang Y, Wang R, Nelson H, Gao Y, Chan K, et al. Tobacco smoke in relation to bladder cancer risk--the Shanghai bladder cancer study. Cancer Epidemiology, Biomarkers & Prevention 2010;19(12):3087–95. Available from: http://cebp.aacrjournals.org/content/19/12/3087.long
12. Hemminki K and Chen B. Parental lung cancer as a predictor of cancer risks in offspring: clues about multiple routes of harmful influence? International Journal of Cancer 2006;118:744–8. Available from: http://www.ncbi.nlm.nih.gov/pubmed/16094627
13. Van Hemelrijck M, Michaud D, Connolly G and Kabir Z. Secondhand smoking, 4-aminobiphenyl, and bladder cancer: two meta-analyses. Cancer Epidemiology Biomarkers & Prevention 2009;18(4):1312–20. Available from: http://cebp.aacrjournals.org/cgi/content/full/18/4/1312