Secondhand smoke refers to tobacco smoke that is passively breathed in by people in the vicinity of a person who is smoking. Secondhand smoke is a mixture of the smoke from the tobacco product itself (termed sidestream smoke) and exhaled smoke from the smoker (known as mainstream smoke). When a nonsmoker inhales secondhand smoke, he or she is exposed to the same toxins and chemicals, including nicotine, as the smoker. Terms that have been used to refer to secondhand smoke are passive smoking, involuntary smoking, or environmental tobacco smoke (ETS).
Exposure of children to secondhand smoke also increases their health risks; and children are especially vulnerable to the effects of environmental tobacco smoke. About 35% of U.S. children live in homes where smoking occurs regularly. Research has shown that 50% to 75% of children in the U.S. have detectable levels of cotinine (the breakdown product of nicotine) in their blood, so even children who do not live with smokers may be at risk for adverse effects of secondhand smoke. Chemicals from tobacco smoke inhaled by a nursing mother are also known to reach breast milk.
Cigarettes are the most common sources of secondhand smoke, followed by cigars and pipe smoke. People can be exposed to environmental tobacco smoke anywhere - in their homes, in the workplace, and in recreational settings. At least 250 harmful chemicals have been identified in secondhand smoke, including at least 50 carcinogens (chemicals that are known to cause cancer). Just some of the dangerous chemicals present in secondhand smoke include vinyl chloride, cadmium, benzene, arsenic, and ethylene oxide. Secondhand smoke is known to cause cancer. It has been classified as a “known human carcinogen” by the U.S. Environmental Protection Agency (EPA). It is also associated with cardiovascular and respiratory diseases as well as other serious health conditions. We’ll take a look at some of these on the next few slides.
Passive smoking is an established risk factor for the development of lung cancer. Research has shown that nonsmokers who reside with a smoker have a 20% to 30% increase in risk for developing lung cancer when compared with nonsmokers who do not reside with a smoker.
Like cigarette smoking itself, secondhand smoke is a significant risk factor for the development of cardiovascular disease and heart attack. Breathing secondhand smoke for even a short time can have immediate adverse effects on the cardiovascular system, interfering with the normal functioning of the heart, blood, and vascular systems in ways that increase the risk of heart attack. Persons who already have heart disease are at especially high risk of suffering adverse affects from breathing secondhand smoke and should take special precautions to avoid even brief exposure.
Secondhand smoke contains many chemicals that can quickly irritate and damage the lining of the airways. Even brief exposure can trigger respiratory symptoms, including cough, chest congestion (phlegm), wheezing, breathlessness and decreased lung function. Brief exposure to secondhand smoke can also trigger an asthma attack in children with asthma. Babies exposed to secondhand smoke can also develop serious respiratory infections.
In addition to the risk of pneumonia and respiratory infections in babies exposed to secondhand smoke, passive smoke is known to increase the severity of asthma in children with this condition. Babies who are exposed to secondhand smoke are at an increased risk for sudden infant death syndrome (SIDS).
The question of whether or not passive smoking is associated with an increased risk of breast cancer is currently a source of both investigation and controversy. Breast cancer risk in active smokers is not known to be increased, yet some studies have found a possible link to breast cancer with exposure to passive smoke.
So, if you are a non-smoker, the safest way to avoid passive smoke is not to allow others to smoke in your home. This is particularly important if there are children in your home. On the other hand, if you are a smoker, obviously, quit smoking is the best way to protect your family and friends from secondhand smoke. A number of support systems, programs, and even prescription medications are available to help smokers break the habit.

