Second-Hand Smoke Profile


IARC Monograph Vol. 83, 1992 (Group 1)
IARC Monograph Vol. 100E, 2012 (Group 1)

Second-Hand Smoke Profile

General Information

Second-hand smoke (SHS) is a mixture of tobacco smoke and ambient air.[1] SHS may be produced by cigarettes or other smoking devices, and is a combination of mainstream smoke (exhaled by the smoker) and sidestream smoke (emitted by the burning end of the tobacco product).[1,2] Approximately two thirds of the smoke from a burning cigarette enters the surrounding environment and may be inhaled by people in the area.[3] SHS may also be referred to as environmental tobacco smoke, involuntary smoking, or passive smoking.[1]

SHS comprises more than 4,000 chemicals emitted from burning tobacco, of which at least 250 are known to be carcinogenic or toxic.[2] Some chemicals found in SHS include arsenic, benzene, beryllium, cadmium, chromium, ethylene oxide, nickel, and vinyl chloride.[4] Compared to the smoke that is inhaled by smokers, SHS has over two times the amount of nicotine and tar, and five times the amount of carbon monoxide.[3]

The primary route of exposure to SHS is inhalation.[1,2] The complexity of SHS mixtures leads to difficulties in assessing exposure.[2] As surrogate measures of SHS exposure, research and public health studies typically monitor levels of nicotine, carbon monoxide, benzene, and respirable particulates suspended in air, or biomarkers such as levels of nicotine metabolites in saliva, blood or urine.[2,5]

SHS is classified by the International Agency for Research on Cancer (IARC) as Group 1, carcinogenic to humans,[1] with a well-established link to lung cancer.[1,2] An IARC review of Group 1 agents in 2012 reaffirmed this classification and included larynx and pharynx as “tumour sites for which there is limited evidence.” [6]

Other adverse health effects associated with exposure to SHS include eye, nose and throat irritation, dizziness, and nausea.[3] Children exposed to SHS may experience chronic respiratory illness, impaired lung function, and middle ear infection.[3] SHS can aggravate allergies or asthma symptoms, and long-term exposure has been linked to heart disease.[1,3] Health Canada estimates that over 1,000 non-smokers die in Canada each year as a result of SHS exposure.[3]

Regulations and Guidelines

In Canada, regulations governing environmental or occupational protection from SHS are administered by federal, provincial, and municipal governments.[5] Federal regulations apply to federal lands and corporations, as well as federally regulated areas (i.e., transportation, communications, and banking). Provincial regulations can ban or restrict smoking in workplaces or public places, whereas municipalities have the authority to introduce additional restrictions within their geographic boundaries.

Federal legislation

RegulationDescriptionYear (Ref.)
Non-Smokers’ Health ActRegulates smoking in federal workplaces and on common carriers;
amends Hazardous Products Act’s cigarette advertising regulations

Provincial/Territorial legislation

ProvinceLegislationYear (Ref.)
ABTobacco and Smoking Reduction Act2013[8,9]
BCTobacco and Vapour Products Control Act
Motor Vehicle Amendment Act
Bill 14: Tobacco Control Amendment Act
MBThe Smoking and Vapour Products Control Act
The Highway Traffic Act

The Non-Smokers Health Protection
Amendment Act (E-Cigarettes)
NBSmoke-free Places Act2015[16]
NLSmoke-free Environment Act2016[17]
NSSmoke-free Places Act2002[18]
NTTobacco Control and Vapour Products Act
Occupational Health and Safety Regulations, Section 81
Environmental Tobacco Smoke Work Site
(Under the Safety Act)
NUTobacco Control Act
Tobacco Control Regulations
Environmental Tobacco Smoke Work Site
(Under the Safety Act)
ONSmoke-free Ontario Act2016[25]
PESmoke-free Places Act2015[26]
QCTobacco Act2015[27]
SKThe Tobacco Control Act
The Occupational Health and Safety Regulations
(Under the Occupational Health and Safety Act)
YTSmoke-Free Places Act2009[30]

Legislation to ban smoking is mostly consistent across provincial and territorial jurisdictions. Smoking is prohibited in nearly all enclosed public places and places of employment in all provinces.[31] However, not all First Nations territories have applied such bans to their communities.[32] The majority of provincial legislation no longer permits smoking in separate designated smoking rooms or areas (DSRs/DSAs), although group living, long-term care facilities, and designated smoking hotel rooms are common exceptions.[31] Amendments to provincial smoking legislation ban smoking in vehicles when children are present.[31] Depending on the province, the maximum age for “children” ranges between 16 and 19, inclusive.[31] Legislation does not cover smoking in private homes.[33] Some provinces prescribe additional areas where smoking is prohibited, including school grounds and outdoor patios.[31] Other provinces continue to permit smoking on outdoor patios, with restrictions relating to the percentage of the patio that is enclosed.[31] Most recent amendments have incorporated restrictions on use of e-cigarettes and other smoking devices in public places and workplaces.[31]

Many municipalities have passed more restrictive bylaws to provide additional protection from SHS. Examples of municipal bylaws include smoking bans on outdoor patios and in public outdoor areas such as playgrounds and parks, hotel rooms, and private vehicles. Bylaws may also include buffer zones around entranceways, air intakes, and windows.[34]

Environmental Exposures Overview

Non-occupational exposures to SHS can occur in a variety of indoor and outdoor, private and public settings.

Survey results from CTUMS for exposure to SHS show little difference between 2009 and 2012; approximately 34% of respondents in both years indicated that they were exposed to second-hand smoke at least once a week.[35,36] However, daily exposure to second-hand smoke declined from 18% in 2012 to 21% in 2009.[35,36]

The most common reported sites of exposure in 2009 were building entrances (54%), followed by sidewalks or parks (53%), inside vehicles (20%), and at the workplace (20%).[35] In 2012, the most common reported sites of exposure were sidewalks or parks (54%), followed by building entrances (51%), at the workplace (21%), and inside vehicles (18%).[36]

Occupational Exposures Overview

The most important route of occupational exposure to SHS is inhalation.

CAREX Canada estimates that approximately 418,000 Canadian workers, or 2% of all Canadian workers, are exposed to SHS at work. The group of workers with the largest number of exposed individuals is trades, transport, and equipment operators. This group also has the highest rates of exposure, with an estimated 9% of workers being exposed. Other occupation groups with SHS exposure are sales and service, primary industry, and management.

According to the Burden of Occupational Cancer in Canada project, occupational exposure to SHS leads to approximately 130 lung cancers and possibly 20 suspected laryngeal cancers and 35 suspected pharyngeal cancers each year in Canada, based on past exposures (1961-2001).[37,38] This amounts to 0.6% of all lung cancers, 1.6% of all laryngeal cancers, and 2.4% of all pharyngeal cancers diagnosed annually. These estimates are focused on non-smokers due to difficulties in separating the impact of personal smoking and SHS exposure on cancer risk. Most SHS-related lung cancers occur among workers in the manufacturing and trade industries. Work-related SHS exposure resulted in approximately $129 million in costs for newly diagnosed lung cancer cases in 2011.[38]

For detailed estimates of exposure to SHS, see the occupational exposures tab.


1. International Agency for Research on Cancer (IARC). Monograph summary, Volume 83 (2002)
2. National Toxicology Program (NTP). 15th Report on Carcinogens: Tobacco Related Exposures (2021)
4. National Cancer Institute. Secondhand Smoke and Cancer (2018)
5. Physicians for a Smoke-Free Canada. Background on Protection from Second-Hand Smoke in Canada (2007) (PDF)
6. International Agency for Research on Cancer (IARC). Monograph summary, Volume 100 Part E (2009)
7. Government of Canada. Non-Smokers’ Health Act (2006)
8. The Canadian Legal Information Institute (CanLII). Tobacco and Smoking Reduction Act, SA 2005, c T-3.8. (2005)
9. Government of Alberta. Tobacco Reduction Act (2008)
10. The Canadian Legal Information Institute (CanLII). Northwest Territories. Bill 16: Tobacco Control Act (2007) (PDF)
13. Canadian Legal Information Institute. The Smoking and Vapour Products Control Act (2021)
16. The Canadian Legal Information Institute (CanLII). New Brunswick. Smoke-free Places Act, RSNB 2011, c 222 (2011, 2015)
17. The Canadian Legal Information Institute (CanLII). Newfoundland. Smoke-free Environment Act, 2005, SNL 2005, c S-16.2(2005, 2016)
18. The Canadian Legal Information Institute (CanLII). Nova Scotia. Smoke-free Places Act, SNS 2002, c 12 (2002, 2014)
19. The Canadian Legal Information Institute (CanLII). Northwest Territories Tobacco and Vapor Products Control Act, SNWT 2019, c 31 (2019)
22. The Canadian Legal Information Institute (CanLII). Nunavut. Tobacco Control Act, SNu 2003, c 13 (2003, 2013)
23. The Canadian Legal Information Institute (CanLII). Nunavut. Tobacco Control Regulations, Nu Reg 011-2007 (2007)
24. Workers Safety Compensation Commission (WSCC). Nunavut. Safety Act – Environmental Tobacco Smoke Work Site Regulations (2003)
25. Government of Ontario. Ontario. Smoke-Free Ontario Act (1994, 2016)
26. The Canadian Legal Information Institute (CanLII). Prince Edward Island. Smoke-Free Places Act (2002, 2015) (PDF)
27. The Canadian Legal Information Institute (CanLII). Quebec.Tobacco Control Act, CQLR c L-6.2 (1998, 2015)
28. Government of Saskatchewan. Saskatchewan. The Tobacco Control Act (2001, 2015) (PDF)
30. The Canadian Legal Information Institute (CanLII). Yukon. Smoke-free Places Act (2008, 2009)
32. Physicians for a Smoke-Free Canada. Towards effective tobacco control in First Nations and Inuit Communities (2007) (PDF)
33. Smoke-Free Housing Canada. Overview
37. Labrèche F, Kim J, Song C, Pahwa M, Calvin BG, Arrandale VH, McLeod CB, Peters CE, Lavoué J, Davies HW, Nicol AM. “The current burden of cancer attributable to occupational exposures in Canada.” Prev Med 2019;122:128-39.
38. Occupational Cancer Research Centre. Burden of Occupational Cancer (2017)


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As a national organization, our work extends across borders into many Indigenous lands throughout Canada. We gratefully acknowledge that our host institution, the University of British Columbia Point Grey campus, is located on the traditional, ancestral and unceded territories of the xʷməθkʷəy̓əm (Musqueam) people.