Passive smoke

Passive smoking is the inhalation of smoke, called second-hand smoke (SHS), or environmental tobacco smoke (ETS), by persons other than the intended "active" smoker. It occurs when tobacco smoke permeates any environment, causing its inhalation by people within that environment. Exposure to second-hand tobacco smoke causes disease, disability, and death. The health risks of second-hand smoke are a matter of scientific consensus. These risks have been a major motivation for smoke-free laws in workplaces and indoor public places, including restaurants, bars and night clubs, as well as some open public spaces.

Concerns around second-hand smoke have played a central role in the debate over the harms and regulation of tobacco products. Since the early 1970s, the tobacco industry has viewed public concern over second-hand smoke as a serious threat to its business interests. Harm to bystanders was perceived as a motivator for stricter regulation of tobacco products. Despite the industry's awareness of the harms of second-hand smoke as early as the 1980s, the tobacco industry coordinated a scientific controversy with the aim of forestalling regulation of their products.

Second-hand smoke causes many of the same diseases as direct smoking, including cardiovascular diseases, lung cancer, and respiratory diseases. These diseases include:

Epidemiological studies show that non-smokers exposed to second-hand smoke are at risk for many of the health problems associated with direct smoking. Most of the research has come from studies of nonsmokers who are married to a smoker. Those conclusions are also backed up by further studies of workplace exposure to smoke.

In 1992, a review estimated that second-hand smoke exposure was responsible for 35,000 to 40,000 deaths per year in the United States in the early 1980s. The absolute risk increase of heart disease due to ETS was 2.2%, while the attributable risk percent was 23%. A 1997 meta-analysis found that second-hand smoke exposure increased the risk of heart disease by a quarter, and two 1999 meta-analyses reached similar conclusions.

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