Executive Summary

Active smoking has been recognized as a major cause of disease and death for at least 40 years. But in the past 20 years a growing body of evidence has shown that exposure to environmental tobacco smoke (ETS)—in other words, second hand smoking—may also be a threat to health.

Scientists have documented the presence of some of the toxic and carcinogenic components of environmental tobacco smoke in the hair and body fluids of nonsmokers exposed to tobacco smoke, and an extensive database on the health effects of ETS now exists. Numerous epidemiological studies have examined the associations between ETS exposure and acute (short-term) and chronic (long-term) health effects. But debates still continue about the validity of the scientific methods used to establish causality for chronic diseases—lung cancer and cardiovascular disease, for example—reported in nonsmokers living or working with smokers. Study limitations and sometimes-equivocal results have led many observers to question whether the health risks that the studies have shown to be associated with environmental tobacco smoke are, indeed, real.

In this report the American Council on Science and Health (ACSH) evaluates the large body of evidence that exists regarding the health effects of ETS. ACSH's analysis yields the following conclusions:

• Irritation of the eyes, nose, and respiratory tract is the most common and firmly established adverse health effect associated with exposure to ETS.
• Exposed infants and children, in particular, are at increased risk of respiratory infections, middle-ear effusion (fluid inside the eardrum), and the exacerbation of asthma and other respiratory symptoms.
• Exposed adults are at increased risk for respiratory ailments; ETS may aggravate the symptoms of preexisting asthma and emphysema.
• Extensive epidemiological evidence indicates that ETS exposure is a weak risk factor in the development of lung cancer in nonsmokers regularly exposed to ETS in the workplace and/or at home.
• Epidemiological evidence also suggests that ETS is a weak risk factor for heart disease in nonsmoking spouses of smokers and in nonsmokers regularly exposed to ETS in the workplace and/or at home.
• Other reported links between ETS and chronic disease (breast cancer, cervical cancer, and leukemia, for example) have not been scientifically established and are not addressed in this report.

The scientific evidence that tobacco smoke in indoor environments is associated with acute and chronic respiratory illnesses, particularly in children, supports the adaptation of measures designed to reduce or prevent exposure to ETS. Such strategies may include increasing ventilation, eliminating the source of ETS by reducing active smoking, and limiting levels of exposure through indoor smoking restrictions. Prevention efforts should target highly exposed individuals (such as children and nonsmoking spouses of smokers, and workers in smoke-filled workplaces) and certain populations that are especially vulnerable to the risks of ETS.