Does Passive Smoking Cause Cancer?

A study carried out by the International Agency for Research on Cancer (IARC) found that there was an estimated 16% increased risk of lung cancer among non-smoking spouses of smokers. For workplace exposure the estimated increase in risk was 17%. The study did not gain much significance due to small sample size. The study points towards a decreasing risk after cessation of exposure.

What is ETS?

Environmental tobacco smoke is the combination of two forms of smoke from burning tobacco products:

When a tobacco cigarette is smoked, about one-half of the smoke generated is side stream smoke. This form of smoke contains essentially all of the same carcinogenic (cancer-causing) and toxic agents that have been identified in the mainstream smoke inhaled by the smoker.

The exposure of nonsmokers to ETS is referred to as involuntary smoking, passive smoking, and secondhand smoke. Nonsmokers who are exposed to ETS absorb nicotine and other compounds just as smokers do. The greater the exposure to ETS, the greater the level of these harmful compounds in the body.

Although an involuntary smoker is exposed to less concentrated smoke than that inhaled by smokers, research has demonstrated that health risks can arise from inhaling this form of smoke.

Effects of passive smoking among children

Passive smoking is especially hazardous to children who have asthma. Exposure to smoke causes more severe asthma attacks, more emergency room visits, and more admissions to the hospital. These children are also less likely to outgrow their asthma.

The following conditions are worsened by passive smoking:

  • Pneumonia
  • Coughs or bronchitis
  • Laryngitis
  • Asthma attacks
  • Flu (influenza)
  • Ear infections
  • Middle ear fluid and blockage
  • Colds or upper respiratory infections
  • Sinus infections
  • Sore throats
  • Eye irritation
  • Crib deaths (SIDS)
  • School absenteeism caused by illness

A substantial body of evidence built up over the last forty years indicates that smoking tobacco is a major cause of illness and premature death. In recent years, several reports have also emphasized the exposure to environmental tobacco smoke (ETS) can cause lung cancer in people who have never smoked.

ETS Research

A recent review by National Institute for Occupational Safety and Health of the health effects of passive smoking in the workplace conducted indicates that ETS poses an increased risk of lung cancer and possibly heart disease in occupationally exposed workers. An extensive analysis of the health effects of ETS was released by the Environmental Protection Agency (EPA) in January 1993. Several studies, including those mentioned above, have found the following linkages:

  • ETS is responsible for approximately 3,000 lung cancer deaths each year.
  • ETS exposure causes more than 35,000 heart disease deaths each year.
  • ETS exposure results in 150,000 to 300,000 cases of bronchitis and pneumonia annually among young children up to 18 months of age.
  • ETS exposure in children irritates the upper respiratory tract and reduces lung function.
  • Between 200,000 and 1,000,000 asthmatic children are affected by ETS.


The risks estimated from secondhand smoke are based mostly on epidemiological studies. More than 100,000 deaths are attributed to smoking each year, while only 3,000 are blamed on ETS. In the case of heart disease, risk doubles or increases 100 percent while with ETS it only increases 30 percent. These numbers suggest that there are some risks involved with ETS, but it is substantially lower than those associated with smoking.

It is known that passive smoke can trigger asthma, allergies, and other respiratory problems in people sensitive to smoke.

Nothing is known about the lowest level of ETS exposure that renders someone safe. Ventilation can help remove some of the contaminants and erase odor, but pollutants still remain. As a result, even nonsmoking sections and other areas deemed “nonsmoking” do not offer complete protection.

Source: WHO, University of Michigan, Ohio State University