What is Secondhand Smoke?

Secondhand smoke is a mixture of the smoke given off by the burning end of a cigarette, pipe, or cigar, and the smoke exhaled by smokers. Secondhand smoke is also called environmental tobacco smoke (ETS) and exposure to secondhand smoke is sometimes called involuntary or passive smoking. Secondhand smoke contains more that 4,000 substances, several of which are known to cause cancer in humans or animals.

* EPA has concluded that exposure to secondhand smoke can cause lung cancer in adults who do not smoke. EPA estimates that exposure to secondhand smoke causes approximately 3,000 lung cancer deaths per year in nonsmokers.
* Exposure to secondhand smoke has also been shown in a number of studies to increase the risk of heart disease.

Serious Health Risks to Children

Children are particularly vulnerable to the effects of secondhand smoke because they are still developing physically, have higher breathing rates than adults, and have little control over their indoor environments. Children exposed to high doses of secondhand smoke, such as those whose mothers smoke, run the greatest relative risk of experiencing damaging health effects.
bar chart on health effects

* Exposure to secondhand smoke can cause asthma in children who have not previously exhibited symptoms.
* Exposure to secondhand smoke increases the risk for Sudden Infant Death Syndrome.
* Infants and children younger than 6 who are regularly exposed to secondhand smoke are at increased risk of lower respiratory track infections, such as pneumonia and bronchitis.
* Children who regularly breathe secondhand smoke are at increased risk for middle ear infections.

Health Risks to Children with Asthma

* Asthma is the most common chronic childhood disease affecting 1 in 13 school aged children on average.
* Exposure to secondhand smoke can cause new cases of asthma in children who have not previously shown symptoms.
* Exposure to secondhand smoke can trigger asthma attacks and make asthma symptoms more severe.

The Science Behind the Risks

1. Surgeon General Warning: Secondhand Smoke Puts Children At Risk

On June 27th, 2006, the Surgeon General released a major new report on involuntary exposure to secondhand smoke, concluding that secondhand smoke causes disease and death in children and nonsmoking adults. The report finds a causal relationship between secondhand smoke exposure and Sudden Infant Death Syndrome (SIDS), and declares that the home is becoming the predominant location for exposure of children and adults to secondhand smoke.

* Get more information on "The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General" at

2. The National Survey on Environmental Management of Asthma and Children’s Exposure to Environmental Tobacco Smoke (NSEMA/CEE) (U.S. Environmental Protection Agency, 2004)

Key findings:

* 11% of children aged 6 years and under are exposed to ETS in their homes on a regular basis (4 or more days per week) compared to 20% in the 1998 National Health Interview Survey (NHIS).
* Parents are responsible for 90% of children’s exposure to ETS.
* Exposure to ETS is higher and asthma prevalence is more likely in households with low income and low education levels.
* Children with asthma have as much exposure to ETS as children without asthma.

Fact Sheet: National Survey on Environmental Management of Asthma and Children’s Exposure to Environmental Tobacco Smoke (PDF, 2 pp., 89 K, about PDF)

3. Respiratory Health Effects of Passive Smoking (Also Known as Exposure to Secondhand Smoke or Environmental Tobacco Smoke - ETS) (U.S. Environmental Protection Agency, 1992)

Key findings:

In adults:

* ETS is a human lung carcinogen, responsible for approximately 3,000 lung cancer deaths annually in U.S. nonsmokers. ETS has been classified as a Group A carcinogen under EPA's carcinogen assessment guidelines. This classification is reserved for those compounds or mixtures which have been shown to cause cancer in humans, based on studies in human populations.

In children:

* ETS exposure increases the risk of lower respiratory tract infections such as bronchitis and pneumonia. EPA estimates that between 150,000 and 300,000 of these cases annually in infants and young children up to 18 months of age are attributable to exposure to ETS. Of these, between 7,500 and 15,000 will result in hospitalization.
* ETS exposure increases the prevalence of fluid in the middle ear, a sign of chronic middle ear disease.
* ETS exposure in children irritates the upper respiratory tract and is associated with a small but significant reduction in lung function.
* ETS exposure increases the frequency of episodes and severity of symptoms in asthmatic children. The report estimates that 200,000 to 1,000,000 asthmatic children have their condition worsened by exposure to environmental tobacco smoke.
* ETS exposure is a risk factor for new cases of asthma in children who have not previously displayed symptoms.

View the full report: U.S. Environmental Protection Agency, Office of Research and Development, Office of Health and Environmental Assessment, Washington, DC, EPA/600/6-90/006F, December, 1992 (PDF, 525 pp., 4 M, about PDF) View a fact sheet summarizing this report:

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