Secondhand smoke is smoke from burning tobacco products, such as cigarettes, cigars, or pipes.
Secondhand smoke also is smoke that has been exhaled, or breathed out, by the person smoking.
Tobacco smoke contains more than 7,000 chemicals, including hundreds that are toxic and about 70 that can cause cancer.
Secondhand Smoke Harms Children and Adults
There is no risk-free level of secondhand smoke exposure; even brief exposure can be harmful to health.1,2,6
Since 1964, approximately 2,500,000 nonsmokers have died from health problems caused by exposure to secondhand smoke.1
Health Effects in Children
In children, secondhand smoke causes the following:
Ear infections
More frequent and severe asthma attacks
Respiratory symptoms (for example, coughing, sneezing, and shortness of breath)
Respiratory infections (bronchitis and pneumonia)
A greater risk for sudden infant death syndrome (SIDS)
Health Effects in Adults
In adults who have never smoked, secondhand smoke can cause:
Heart disease
For nonsmokers, breathing secondhand smoke has immediate harmful effects on the heart and blood vessels.
It is estimated that secondhand smoke caused nearly 34,000 heart disease deaths each year during 2005–2009 among adult nonsmokers in the United States.
Lung cancer1,7
Secondhand smoke exposure caused more than 7,300 lung cancer deaths each year during 2005–2009 among adult nonsmokers in the United States.
Stroke1
Smokefree laws can reduce the risk for heart disease and lung cancer among nonsmokers.
Patterns of Secondhand Smoke Exposure
Exposure to secondhand smoke can be measured by testing saliva, urine, or blood to see if it contains cotinine.3 Cotinine is created when the body breaks down the nicotine found in tobacco smoke.
Secondhand Smoke Exposure Has Decreased in Recent Years
Measurements of cotinine show that exposure to secondhand smoke has steadily decreased in the United States over time.
During 1988–1991, almost 90 of every 100 (87.9%) nonsmokers had measurable levels of cotinine.7
During 2007–2008, about 40 of every 100 (40.1%) nonsmokers had measurable levels of cotinine.7
During 2011–2012, about 25 of every 100 (25.3%) nonsmokers had measurable levels of cotinine.8
The decrease in exposure to secondhand smoke is likely due to:8
The growing number of states and communities with laws that do not allow smoking in indoor areas of workplaces and public places, including restaurants, bars, and casinos
The growing number of households with voluntary smokefree home rules
Significant declines in cigarette smoking rates
The fact that smoking around nonsmokers has become much less socially acceptable
