Secondhand Smoke (SHS) Facts
Secondhand smoke is a mixture of gases and fine particles that includes—
- Smoke from a burning cigarette, cigar, or pipe tip,1
- Smoke that has been exhaled or breathed out by the person or people smoking, and1
- More than 7,000 chemicals, including hundreds that are toxic and about 70 that can cause cancer.2
Most exposure to secondhand smoke occurs in homes and workplaces. Secondhand smoke exposure also continues to occur in public places such as restaurants, bars, and casinos and in private vehicles.3
Health Effects: Children
In children, secondhand smoke causes the following:3
- Ear infections
- More frequent and severe asthma attacks
- Respiratory symptoms (e.g., coughing, sneezing, shortness of breath)
- Respiratory infections (i.e., bronchitis, pneumonia)
- A greater risk for sudden infant death syndrome (SIDS)
In children aged 18 months or younger, secondhand smoke exposure is responsible for—
- an estimated 150,000–300,000 new cases of bronchitis and pneumonia annually, and
- approximately 7,500–15,000 hospitalizations annually in the United States.4
Health Effects: Adults
In adults who have never smoked, secondhand smoke can cause heart disease and/or lung cancer.3
- For nonsmokers, breathing secondhand smoke has immediate harmful effects on the cardiovascular system that can increase the risk for heart attack. People who already have heart disease are at especially high risk.3,5
- Nonsmokers who are exposed to secondhand smoke at home or work increase their heart disease risk by 25–30%.3
- Secondhand smoke exposure causes an estimated 46,000 heart disease deaths annually among adult nonsmokers in the United States.6
- Nonsmokers who are exposed to secondhand smoke at home or work increase their lung cancer risk by 20–30%.3
- Secondhand smoke exposure causes an estimated 3,400 lung cancer deaths annually among adult nonsmokers in the United States.6
There is no risk-free level of contact with secondhand smoke; even brief exposure can be harmful to health.3
Estimates of Secondhand Smoke Exposure
When a nonsmoker breathes in secondhand smoke, the body begins to metabolize or break down the nicotine that was in the smoke. During this process, a nicotine byproduct called cotinine is created. Exposure to nicotine and secondhand smoke can be measured by testing saliva, urine, or blood for the presence of cotinine.3
Secondhand Smoke Exposure Has Decreased in Recent Years
- Measurements of cotinine have shown how exposure to secondhand smoke has steadily decreased in the United States over time.3,7
- During 1988–1991, approximately 87.9% of nonsmokers had measurable levels of cotinine.
- During 1999–2000, approximately 52.5% of nonsmokers had measurable levels of cotinine.
- During 2007–2008, approximately 40.1% of nonsmokers had measurable levels of cotinine.
- The decrease in exposure to secondhand smoke over the last 20 years is due to the growing number of laws that ban smoking in workplaces and public places, the increase in the number of households with smoke-free home rules, and the decreases in adult and youth smoking rates.8,9
Many in the United States Continue to be Exposed to Secondhand Smoke7
- An estimated 88 million nonsmokers in the United States were exposed to secondhand smoke in 2007–2008.
- Children are at particular risk for exposure to secondhand smoke: 53.6% of young children (aged 3–11 years) were exposed to secondhand smoke in 2007–2008.
- While only 5.4% of adult nonsmokers in the United States lived with someone who smoked inside their home, 18.2% of children (aged 3–11 years) lived with someone who smoked inside their home in 2007–2008.
Disparities in Secondhand Smoke Exposure
Racial and Ethnic Groups
- Although declines in cotinine levels have occurred in all racial and ethnic groups, cotinine levels have consistently been found to be higher in non-Hispanic black Americans than in non-Hispanic white Americans and Mexican Americans.7,8,9 In 2007–2008:
- 55.9% of non-Hispanic blacks were exposed to secondhand smoke.
- 40.1% of non-Hispanic whites were exposed to secondhand smoke.
- 28.5% of Mexican Americans were exposed to secondhand smoke.
- Secondhand smoke exposure tends to be high for persons with low incomes: 60.5% of persons living below the poverty level in the United States were exposed to secondhand smoke in 2007–2008.7
- Occupational disparities in secondhand smoke exposure decreased over the past two decades, but substantial differences in exposure among workers remain. African-American male workers, construction workers, and blue collar workers and service workers are among some of the groups who continue to experience particularly high levels of secondhand smoke exposure relative to other workers.10
Eliminating smoking in indoor spaces is the only way to fully protect nonsmokers from secondhand smoke exposure. Separating smokers from nonsmokers, cleaning the air, and ventilating buildings does not eliminate secondhand smoke exposure.3
- National Toxicology Program.
Report on Carcinogens, Twelfth Edition .
Research Triangle Park (NC): U.S. Department of Health and Human Sciences, National Institute of Environmental Health Sciences, National Toxicology Program, 2011 [accessed 2012 Mar 1].
- U.S. Department of Health and Human Services. A Report of the Surgeon General: How Tobacco Smoke Causes Disease: What It Means to You. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2010 [accessed 2011 Mar 11].
- U.S. Department of Health and Human Services. The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General. Atlanta: U.S. 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 [accessed 2011 Mar 11].
- United States Environmental Protection Agency. Respiratory Health Effects of Passive Smoking: Lung Cancer and Other Disorders . . Washington: U.S. Environmental Protection Agency, Office of Research and Development, Office of Health and Environmental Assessment, 1992 [accessed 2011 Mar 11].
- Institute of Medicine. Secondhand Smoke Exposure and Cardiovascular Effects: Making Sense of the Evidence . Washington: National Academy of Sciences, Institute of Medicine, 2009 [accessed 2011 Mar 11].
- Centers for Disease Control and Prevention. Smoking-Attributable Mortality, Years of Potential Life Lost, and Productivity Losses—United States, 2000–2004. Morbidity and Mortality Weekly Report 2008;57(45):1226–8 [accessed 2011 Mar 11].
- Centers for Disease Control and Prevention. Vital Signs: Nonsmokers' Exposure to Secondhand Smoke—United States, 1999–2008. Morbidity and Mortality Weekly Report 2010;59(35):1141–6 [accessed 2011 Mar 11].
- Pirkle JL, Bernert JT, Caudill SP, Sosnoff CS, Pechacek TF. Trends in the Exposure of Nonsmokers in the U.S. Population to Secondhand Smoke: 1988–2002 . Environmental Health Perspectives 2006;114(6):853–8 [accessed 2011 Mar 11].
- Centers for Disease Control and Prevention. Fourth National Report on Human Exposure to Environmental Chemicals . Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Environmental Health, 2009 [accessed 2011 Mar 11].
- Arheart KL, Lee DJ, Dietz NA, Wilkinson JD, Clark III JD, LeBlanc WG, Serdar B, Fleming LE. Declining Trends in Serum Cotinine Levels in U.S. Worker Groups: The Power of Policy. Journal of Occupational and Environmental Medicine 2008;50(1):57–63 [cited 2011 Mar 11].
For Further Information
Centers for Disease Control and Prevention
National Center for Chronic Disease Prevention and Health Promotion
Office on Smoking and Health
Media Inquiries: Contact CDC's Office on Smoking and Health press line at 770-488-5493.
File Formats: All viewers, players, and plug-ins used on this site can be downloaded from the file formats page. (For example: Adobe Acrobat Reader for pdf files, Windows Media Player for audio and video files, PowerPoint Viewer for presentation slides, etc.)
Get email updates
To receive email updates about Smoking & Tobacco Use, enter your email address:
- CDC/Office on Smoking and Health
4770 Buford Highway
Atlanta, Georgia 30341-3717
TTY: (888) 232-6348