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
Multiple approaches can be used to measure secondhand smoke exposure. These include measuring tobacco smoke constituents or metabolites in the environment or in biological samples, and measuring smoking behaviours through self-report or observation.
Biological measures, or biomarkers, are metabolites of tobacco constituents that are found in blood, urine, saliva, breast milk, amniotic fluid, hair, teeth or other body products.4 The most commonly used biomarker is cotinine, a major metabolite of nicotine. 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, cotinine reflects exposure to tobacco smoke in the preceding one or two days. In contrast, nicotine found in hair can indicate exposure over a period of months. Measuring nicotine in children’s milk teeth may be used to assess 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) (a metabolite of NNK, a tobacco-specific lung carcinogen), and protein and DNA adducts. These biomarkers link secondhand smoke exposure directly to carcinogenic metabolites.
Using biomarkers has several limitations. Measurement of one biomarker may not reflect exposure to other components of secondhand smoke. There are also variations in metabolism of tobacco smoke constituents between individuals and within individuals, as well as analytical constraints and limitations on the exposure timeframe that can be monitored.
Environmental measures focus on assessing atmospheric markers of secondhand smoke in the air, or the concentration of markers on surfaces in the case of thirdhand smoke. Nicotine is the most widely studied atmospheric marker, because 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.
Self-reported measures typically involve questionnaires to gather information from participants on their own smoking or those around them. These questionnaires may also include information on the indoor spaces or outdoor conditions where cigarettes are smoked in order to estimate the degree of secondhand smoke exposure. Observational approaches involve inspecting the environment under study and documenting the presence or frequency of smoking.
Studies exploring secondhand smoke exposure using a combination of biomarkers, environmental measures and self-reported measures have demonstrated that biomarker and environmental measurements are correlated with increased self-reported exposure.
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.5-8
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 completely 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. In outdoor environments secondhand smoke tends to disperse and concentrations vary depending on the proximity of smokers, physical attributes of the space (including partial enclosures) and wind conditions.9-12 Under certain conditions, outdoor secondhand smoke concentrations can be comparable to indoor concentrations.9, 10, 13-17 A study of outdoor dining areas found that exposure to secondhand smoke increased when individuals were under an overhead cover, and as the number of nearby smokers increased.9 There is also evidence that where smokers congregate, such as at the perimeter of smokefree areas, high concentration of secondhand smoke can be detected.18
Currently there is limited evidence regarding the level of exposure to secondhand smoke of people in outdoor areas and the health effects of outdoor exposure. However, given the sensitivity of the cardiovascular system to acute exposure of secondhand smoke, there is likely to be health harm, particularly under conditions where smokers congregate and ventilation is impeded (see sections 4.5 and 4.6).
Relevant news and research
For recent news items and research on this topic, click here.(Last updated March 2020)
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, 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
5. Jones MR, Navas-Acien A, Yuan J, and Breysse PN. Secondhand tobacco smoke concentrations in motor vehicles. Tobacco Control, 2009; 18(5):399–404. Available from: http://tobaccocontrol.bmj.com/content/18/5/399.long
6. Edwards R, Wilson N, and Pierse N. Highly hazardous air quality associated with smoking in cars: New Zealand pilot study. The New Zealand Medical Journal, 2006; 119(1244):2294. Available from: http://www.nzma.org.nz/journal/119-1244/2294/
7. Sendzik T, Fong G, Travers M, and Hyland A. An experimental investigation of tobacco smoke pollution in cars Nicotine and Tobacco Research, 2009; 11(6):627–34. Available from: http://ntr.oxfordjournals.org/content/11/6/627.full
8. Rees VW and Connolly GN. Measuring air quality to protect children from secondhand smoke in cars. American Journal of Preventive Medicine, 2006; 31(5):363–8. Available from: http://www.ncbi.nlm.nih.gov/pubmed/17046406
9. Cameron M, Brennan E, Durkin S, Borland R, Travers MJ, 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
10. Brennan E, Cameron M, Warne C, Durkin S, Borland R, et al. Secondhand smoke drift: Examining the influence of indoor smoking bans on indoor and outdoor air quality at pubs and bars. Nicotine & Tobacco Research, 2010; 12(3):271–7. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20097839
11. 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/article/pii/S1352231009003033
12. Vardavas CI, Karabela M, Agaku IT, Matsunaga Y, Myridakis A, et al. Secondhand smoke exposure within semi-open air cafes and tobacco specific 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (nnal) concentrations among nonsmoking employees. International Journal of Occupational Medicine and Environmental Health, 2014. Available from: http://www.ncbi.nlm.nih.gov/pubmed/25218107
13. 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 a.pdf
14. 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
15. 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
16. 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
17. Wilson N, Edwards R, and Parry R. A persisting secondhand smoke hazard in urban public places: Results from fine particulate (pm2.5) air sampling. The New Zealand Medical Journal, 2011; 124(1330). Available from: http://www.nzma.org.nz/journal/abstract.php?id=4564
18. Cho H, Lee K, Hwang Y, Richardson P, Bratset H, et al. Outdoor tobacco smoke exposure at the perimeter of a tobacco-free university. Journal of the Air Waste Management Association, 2014; 64(8):863 – 6. Available from: http://www.ncbi.nlm.nih.gov/pubmed/25185388