People have known about the direct dangers of smoking since at least the 1960s. Only recently, however, has research confirmed that when you smoke in public, you put the health of others at risk. The dangers of secondhand smoking has been used to justify increasingly stringent restrictions on smoking in public places.

Types of Secondhand Smoke

Two types of secondhand smoke have been identified by the National Cancer Institute--sidestream smoke and mainstream smoke. Sidestream smoke is the smoke that is released from the burning end of a cigarette, and mainstream smoke is the smoke that is exhaled by the smoker. Both of these types of smoke contain not only tobacco smoke, but also residue from paper and chemicals used to treat the tobacco.

Incidence

Secondhand smoke can be measured in the environment by looking for trace chemicals found in tobacco smoke, such as nicotine. It can be measured in the blood, saliva and urine of a secondhand smoker by looking for cotinine, a chemical that is produced when the body breaks down nicotine. Nicotine and carbon monoxide have also been found in the bodies of secondhand smokers.

Health Risks

Secondhand smoke damages the bodies of secondhand smokers in the same ways that it damages the bodies of smokers, according to the U.S. Surgeon General, although to a lesser degree. Thousands of cases of lung cancer and tens of thousands of cases of heart disease are attributed to secondhand smoking every year. The American Lung Association reports that secondhand smoke also causes at least 150,000 respiratory infections in infants each year in the U.S.

Restrictions

The U.S. federal government has banned smoking on all domestic flights and most foreign-bound flights originating from the U.S. Smoking is also prohibited on interstate buses and most passenger trains, federal buildings, and on the premises of organizations that provide federally-funded services to children. State and local governments vary in their restrictions. Many prohibit smoking in all public places, including nightclubs and bars.

Dissent

Anti-smoking activists such as Stanton Glantz, Professor of Medicine at the University of California San Francisco, claim that even half an hour of exposure to secondhand smoke can significantly increase the risk of a heart attack. Dr. Michael Siegel, Professor of Community Health Services at the Boston University School of Public Health, disagrees. He claims that the effects of such short exposure are completely reversible and do not harden the arteries. He accuses extreme anti-smoking advocates of "stretching the truth."