4.4 Measuring exposure to secondhand smoke

Unless otherwise noted, the following section is compiled from recent reviews published by the International Agency for Research on Cancer (2004),1 California Environmental Protection Agency (2005)2 and the Office of the US Surgeon General (2006).3

Indirect measures of secondhand smoke exposure can be obtained through questionnaires that ascertain the number of smokers and cigarettes smoked and, in some cases, the room size and distance from smokers. Direct measures include the measurement of concentration of atmospheric markers of secondhand smoke in the air and the levels of biomarkers in blood, urine, saliva, breast milk, amniotic fluid, hair, teeth or other bodily samples of non-smokers.4

The most commonly used biomarker is cotinine, a major metabolite of nicotine, which is specific to tobacco smoke. It is sensitive enough to distinguish between people not exposed to secondhand smoke and those exposed to low, moderate and high levels of secondhand smoke. As the half life of cotinine is about 20 hours in non-smokers, it can only reflect exposures in the preceding one or two days. Nicotine in hair can indicate exposure over a period of months. Measuring nicotine in children's milk teeth may determine cumulative exposure to secondhand smoke from infancy through childhood until the loss of the teeth, generally between ages six to eight years.4 Several other chemicals have been used as biomarkers, including 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), which is a metabolite of a tobacco-specific lung carcinogen, and protein and DNA adducts, which link secondhand smoke exposure directly to carcinogenic metabolites. Using biomarkers has several limitations. Measurement of one biomarker may not wholly reflect exposure to other components of secondhand smoke. There are variations in metabolism between individuals and within individuals, analytical constraints and limitations on the exposure timeframe that can be monitored.

Nicotine is the most widely studied atmospheric marker, as it is specific to tobacco smoke. Other markers include solanesol, 3-ethenylpyridine (3-EP), carbon monoxide, iso- and anteisoalkanes (C29-C34), polycyclic aromatic hydrocarbons (PAHs), fluorescing particulate matter, respirable suspended particles, and ultraviolet-absorbing particulate matter.

4.4.1 Exposure to secondhand smoke

Individual exposure to secondhand smoke is highly variable, depending on personal circumstances. Non-smokers who live and work in a smokefree environment and experience only brief exposure to smoke are likely to be exposed to less than 0.01 micrograms of secondhand smoke per cubic metre (24-hour time-weighted average nicotine air concentration). Conversely those exposed in the home and in vehicles may have an average exposure concentration of up to 7.4 micrograms per cubic metre, which is classified as high exposure by the California Environmental Protection Agency. Smokers' motor vehicles have much higher air nicotine concentrations than those generally measured in public or private indoor places.58 A national health survey published in 2010 estimated that 40% of US non-smokers aged three years and over had detectable amounts of cotinine in their blood, indicating exposure to secondhand smoke. Children were among those most likely to be exposed and the home was the major source of secondhand smoke exposure.9

Ventilation, air conditioning and heating systems alone do not reliably remove secondhand smoke from the indoor environment, and may instead distribute toxins throughout buildings. Providing separate areas where smoking is allowed also fails to eliminate exposure to secondhand smoke (see Section 15.3.1 for full discussion).

Secondhand smoke exposure in outdoor environments has recently begun to be investigated in a limited number of studies. Evidence indicates that outdoor secondhand smoke levels can be comparable to indoor concentrations under certain conditions, while smoking is taking place.1016 Secondhand smoke does not readily accumulate in outdoor environments, and it tends to disperse soon after smoking ceases.11,14 Outdoor concentrations of secondhand smoke are more variable than indoor concentrations, because they are more sensitive the proximity of smokers and to wind conditions, which are influenced by the extent of enclosure of a space.11,12,17 A study of outdoor areas of dining venues found that exposure to secondhand smoke increased when individuals were under an overhead cover, and as the number of nearby smokers increased.11 Currently there are no human biomarker studies directly measuring the level of exposure to secondhand smoke of people in outdoor areas, nor studies specifically examining the health effects of outdoor exposures. However, given the sensitivity of the cardiovascular system to acute exposure of secondhand smoke, the potential for harm cannot be ruled out at this stage, particularly under conditions where smokers congregate and ventilation is impeded (see sections 4.5 and 4.6).

4.4.2 Exposure to secondhand smoke from tobacco products other than cigarettes

Secondhand smoke from other types of tobacco products can differ from cigarette smoke. Cigars can be a larger source of carbon monoxide than cigarettes, but have lower emissions of fine particles and PAHs. However, because cigars are larger and have a longer smoking time than cigarettes, smoking a single cigar emits more particles and PAHs than smoking a single cigarette.

Waterpipes (also known as hookahs, narghile, shisha or hubble bubble) are generally smoked using charcoal as a burning agent, with smoking sessions typically lasting 30 minutes to an hour.1821 Research shows that a single person smoking a waterpipe for up to 30 minutes produces, on average, more fine particles than smoking a cigarette.22 A recent study showed that a one-hour waterpipe smoking session can produce secondhand smoke with four times the amount of volatile aldehydes and carcinogenic polycyclic aromatic hydrocarbons (PAHs) and 30 times the carbon monoxide than that produced by a single cigarette.23

Recent news and research

For recent news items and research on this topic, click here (Last updated October 2016  


1. 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

2. 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

3. 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

4. Llaquet H, Pichini S, Joya X, Papaseit E, Vall O, Klein J, et al. Biological matrices for the evaluation of exposure to environmental tobacco smoke during prenatal life and childhood. Analytical and Bioanalytical Chemistry 2009;396(1):379–99. Available from: http://www.springerlink.com/content/4960m70q40652246/fulltext.html

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9. Kaufmann R, Babb S, O'Halloran A, Asman K, Bishop E, Tynan M, et al. Vital signs: Nonsmokers' exposure to secondhand smoke—United States, 1999–2008. Morbidity and Mortality Weekly Report 2010;59(35):1141–6. Available from: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5935a4.htm?s_cid=mm5935a4_w

10. California Environmental Protection Agency. Air Resources Board. Office of Environmental Health Hazard Assessment. Proposed identification of Environmental Tobacco Smoke as a toxic air contaminant : as approved by the Scientific Review Panel on June 24, 2005. Part A: Exposure assessment. Sacramento, Calif: California EPA, 2005. Available from: ftp://ftp.arb.ca.gov/carbis/regact/ets2006/app3part%20a.pdf

11. Cameron M, Brennan E, Durkin S, Borland R, Travers MJ, Hyland A, et al. Secondhand smoke exposure (PM2.5) in outdoor dining areas and its correlates. Tobacco Control 2010;19(1):19–23. Available from: http://www.ncbi.nlm.nih.gov/pubmed/19850553

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13. Boffi R, Ruprecht A, Mazza R, Ketzel M and Invernizzi G. A day at the European Respiratory Society Congress: passive smoking influences both outdoor and indoor air quality. European Respiratory Journal 2006;27(4):862–3. Available from: http://www.ncbi.nlm.nih.gov/entrez/pubmend/16585096

14. Klepeis N, Ott W and Switzer P. Real-time measurement of outdoor tobacco smoke particles. Journal of the Air & Waste Management Association 2007;57(5):522–34. Available from: http://www.ashaust.org.au/pdfs/OutdoorSHS0705.pdf

15. Repace J. Measurements of outdoor air pollution from second hand smoke on the UMBC campus Bowie, MD: Repace Associates, Inc, 2005. Available from: http://www.repace.com/pdf/outdoorair.pdf

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17. Klepeis NE, Gabel EB, Ott WR and Switzer P. Outdoor air pollution in close proximity to a continuous point source. Atmospheric Environment 2010;43(20):3155–67. Available from: http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6VH3-4W1BVCD-2-1&_cdi=6055&_user=10&_pii=S1352231009003033&_orig=search&_coverDate=06%2F30%2F2009&_sk=999569979&view=c&wchp=dGLzVtz-zSkWb&md5=e7d35b20ef1c1a97220b2a5410d4adec&ie=/sdarticle.pdf

18. Maziak W, Rastam S, Ibrahim I, Ward KD, Shihadeh A and Eissenberg T. CO exposure, puff topography, and subjective effects in waterpipe tobacco smokers. Nicotine & Tobacco Research 2009;11(7):806–11. Available from: http://www.ncbi.nlm.nih.gov/pubmed/19420278

19. Shihadeh A, Azar S, Antonios C and Haddad A. Towards a topographical model of narghile water-pipe cafe smoking: a pilot study in a high socioeconomic status neighborhood of Beirut, Lebanon. Pharmacology, Biochemistry, and Behavior 2004;79(1):75–82. Available from: http://www.ncbi.nlm.nih.gov/entrez/pubmed/15388286

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22. Maziak W, Rastam S, Ibrahim I, Ward KD and Eissenberg T. Waterpipe-associated particulate matter emissions. Nicotine & Tobacco Research 2008;10(3):519–23. Available from: http://www.ncbi.nlm.nih.gov/pubmed/18324571

23. Daher N, Saleh R, Jaroudi E, Sheheitli H, Badr T, Sepetdjian E, et al. Comparison of carcinogen, carbon monoxide, and ultrafine particle emissions from narghile waterpipe and cigarette smoking: sidestream smoke measurements and assessment of second-hand smoke emission factors. Atmospheric Environment 2010;44(1):8–14. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20161525

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