Involuntary Passive Smoking

Key Points

• Secondhand smoke contains 4000 different chemicals, of which more than 60 are carcinogenic.

• About one third of lung cancers occur in nonsmokers who live with a smoker or work in a smoky environment.

• Passive smoking is the third leading preventable cause of death, after alcohol and smoking itself.

• Passive smoking increases the risk of SIDS in infants and otitis media, cancer, and respiratory disease in older children, in direct proportion to smoke exposure.

Secondhand smoke, also called environmental tobacco smoke (ETS), is the combination of smoke emitted from the burning end of a cigarette, cigar, or pipe and the smoke exhaled by a smoker. Two thirds of the smoke from a burning cigarette never reaches a smoker's lungs, but instead goes directly into the air. Sidestream smoke is emitted into the air from a smoldering cigarette or cigar between puffs, and mainstream smoke is what the smoker inhales directly—the exhaled smoke also contributes to ETS. Although diluted by air before being inhaled, sidestream smoke contains greater concentrations of toxic substances than mainstream smoke because of a lower combustion temperature and lack of filtration through the cigarette.

The 2006 Report of the Surgeon General, The Health Consequences of Involuntary Exposure to Tobacco Smoke (USHHS, 2006), concludes the following:

1. Secondhand smoke causes premature death and disease in children and adults who do not smoke.

2. Children exposed to secondhand smoke are at increased risk for sudden infant death syndrome (SIDS), acute respiratory infections, ear problems, and more severe asthma. Smoking by parents causes respiratory symptoms and slows lung growth in their children.

3. Exposure of adults to secondhand smoke has immediate adverse effects on the cardiovascular system and causes coronary heart disease and lung cancer.

4. The scientific evidence indicates that there is no risk-free level of exposure to secondhand smoke.

5. Eliminating smoking in indoor spaces fully protects nonsmokers from exposure to secondhand smoke. Separating smokers from nonsmokers, cleaning the air, and ventilating buildings cannot eliminate exposures of nonsmokers to secondhand smoke.

Tobacco smoke contains more than 4000 different chemicals, at least 60 of which are known carcinogens (National Toxicology Program, 2005). The U.S. Environmental Protection Agency, (EPA) the National Toxicology Program, the U.S. Surgeon General, and the International Agency for Research on Cancer have determined that environmental tobacco smoke is a class A (known) human carcinogen, in the same class as asbestos, mustard gas, arsenic, and benzene. In addition to the 3000 lung cancer deaths a year in nonsmokers, almost 40,000 heart disease deaths each year are linked to secondhand smoke. Secondhand smoke exposure also causes chronic otitis media, cough, and lower respiratory illnesses in children, such as asthma, bronchitis, and pneumonia. It is estimated that tobacco smoke in the home and workplace could be responsible for the deaths of about 50,000 nonsmokers annually in the United States, making passive smoking the third leading preventable cause of death, after those from direct smoking and alcohol (Air Resources Board, 2005).

In a classic study, Hirayama (1981) was among the first scientists to demonstrate an increased risk of lung cancer in nonsmoking housewives exposed to the secondhand cigarette smoke of their husbands (see eFig. 50-2 online). Since then, many studies have shown an association between being married to a smoker and having an increased risk of lung cancer. Overall risk of lung cancer increases 20% to 30% in nonsmokers exposed to ETS in the home; combined home and work exposure further increases the risk (USD-HHS [Report of the Surgeon General], 2006).

A report from the California EPA's Air Resources Board is another well-researched review of the health effects of passive smoking. Their meta-analyses of the breast cancer risk indicate that the RR for breast cancer, particularly among premenopausal women, is between 1.68 and 2.20 (Air Resources Board, 2005; Miller et al., 2006). A 2009 Canadian task force report found a causal link between passive smoke exposure and breast cancer, especially in younger, premenopausal women, and a causal relationship between active smoking and breast cancer at all ages (Johnson et al., 2011).

It is estimated that the risk of MI is up to 70% greater for a woman whose husband smokes (Wells, 1994). Relative risk estimates from meta-analysis indicate a 25% to 30% increase in the risk for coronary heart disease in exposed nonsmok-ers; as with lung cancer, multiple sites of exposure increase the risk (USDHHS [Report of the Surgeon General], 2006). The cardiovascular effects of even brief exposure to secondhand smoke are often nearly as great as those of direct smoking, with platelet aggregation and arterial endothelial damage occurring within 30 minutes of exposure; furthermore, secondhand smoke induces oxidative stress and promotes vascular inflammation (Barnoya and Glantz, 2005). Exposure to secondhand smoke is associated with increased levels of inflammatory markers related to the development of atherosclerosis. People exposed have higher white blood cell counts and elevated CRP levels, oxidized LDL cholesterol, homocysteine, and fibrinogen. Even occasional exposure results in elevated levels. These increases are similar to those seen in active smokers.

Reports show that the health benefits of banning smoking in public places and the workplace include a reduction in heart attacks. Examination of community MI rates after implementation of strong smoke-free legislation found a pooled random-effects estimate of the rate of acute MI hos-pitalization 12 months later to be 0.83 (95% CI, 0.80-0.87), with growth of this benefit expected over time (Lightwood and Glantz, 2009). With similar findings, systematic review and meta-analysis of 10 locations with smoke-free legislation concluded that the acute MI risk decreased by 17% overall, with the greatest effect in younger individuals and nonsmok-ers (Meyers et al., 2009).

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