Secondhand Smoke

The smoke released into the air from tobacco products, called environmental tobacco smoke or secondhand smoke, has a major health impact. Of the estimated 480,000 smoking-related deaths in the United States, 53,000 have been attributed to secondhand smoke, making it the third leading cause of preventable death after active smoking and alcohol use. People who have never smoked, but who have been exposed to secondhand smoke have an increased risk of lung cancer and heart disease.

Secondhand smoke and lung disease

In addition to nicotine, tobacco smoke contains tar, carbon monoxide, hydrogen cyanide, phenols, ammonia, formaldehyde, benzene and nitrosamine. Among the 4,000 individual compounds that have been identified in tobacco smoke, 60 have been found to produce irreversible changes in normal cells and produce cancerous tumors.

Nonsmokers who are exposed to secondhand smoke absorb a less concentrated, but harmful dose of these chemicals just as smokers do. The greater the exposure to secondhand smoke, the greater the level of these harmful compounds in the body.

It is estimated that secondhand smoke causes about 3,000 lung cancer deaths each year. Moreover, children of smoking parents have significantly more respiratory tract infections than other children. Secondhand smoke can also cause asthma and increase the number of episodes and severity of asthma in children.

Secondhand smoke and heart disease

Secondhand smoke appears to be related to tobacco smoke-induced atherosclerosis, or the hardening or thickening of the arteries, which leads to cardiovascular disease. Smoking increases the thickness of the innermost part of the arteries by 50 percent, while exposure to environmental tobacco smoke is associated with an increase of 20 percent, similar to the increase in ex-smokers.

Approximately 50 percent of all coronary disease and stroke can be attributed to known risk factors like smoking. Exposure to environmental tobacco smoke may explain the risk in some individuals who have not smoked.

Recent studies show that passive smoking is also a risk factor for ischemic heart disease. Ischemic heart disease is a condition in which there is altered demand versus blood supply ratio to the heart. In other words, the heart muscle requires more blood supply (oxygen) for it to function than what is supplied through its narrowed arteries (atherosclerosis). Heart attack or injury to the heart muscle occurs when this mismatch exceeds a certain limit.

It is also suggested that secondhand smoking may be associated with injury to the lining of endothelial cells of the vessels supplying blood to the heart. This, along with atherosclerosis, worsens the situation and makes the individual more susceptible to a heart attack.

Studies assessing the velocity of blood in the vessels supplying the heart found that passive smoking substantially reduced the flow in healthy nonsmokers.

By Drew Edwards, MS; Mark S. Gold, MD
© 1999 University of Florida McKnight Brain Institute