Second-hand smoke (SHS) has a dose-response relationship. This means that the more SHS you are exposed to, through your lungs, mucus membranes (eyes, mouth, nose) and skin, the more damage is done to your tissues. The bigger (and more chronic) the dose, the bigger the response.
Health Canada estimates that over 800 deaths per year are caused by exposure to SHS, but this is a conservative number based on studies of adult exposure in the workplace only. By far the biggest toll is coronary heart disease (25-30% increased risk), followed by lung cancer (20-30% increased risk). Chronic exposure to SHS also causes nasal sinus cancer, breast cancer in predominantly pre-menopausal women (68-120% increased risk), asthma and altered vascular properties (changes to arteries).
In children, exposure to SHS causes pre-term delivery, low birth weight and Sudden Infant Death Syndrome (SIDS). It also causes pneumonia and chronic bronchitis, asthma, middle ear infections, chronic cough, phlegm, wheezing and breathlessness.
There is also suggestive evidence that SHS is linked to stroke, cervical cancer, brain cancer and lymphomas in children, exacerbation of cystic fibrosis, adverse impact on cognition and behaviour, allergic sensitization and miscarriage.
Of the 4,000 chemicals identified in SHS, 69 of them are carcinogens (including benzene, cadmium, formaldehyde and toluene) and 250 are regulated toxins. In 1992 the U.S. Environmental Protection Agency (U.S. EPA) classified SHS as a “Group A” (known human) carcinogen. This classification placed SHS among the most toxic industrial and automotive air pollutants. In 2005 the California Air Resources Board (a sub-division of the California Environmental Protection Agency) formally declared SHS a “toxic air contaminant.” This unanimous decision was based on a rigorous 4 year scientific study that included public consultation and independent peer review.
There is no known safe level of exposure to SHS. Few issues have been subject to as many scientifically rigorous reviews as SHS, and the scientific consensus is that it is a carcinogen, all exposure is harmful and therefore involuntary exposure should be eliminated. This conclusion is shared by, among others:
- Health Canada
- U.S. Surgeon General
- U.S. Environmental Protection Agency (EPA)
- California EPA
- U.S. National Academy of Science
- International Agency for Research on Cancer
- U.S. National Institute for Occupational Safety and Health
- U.S. Occupational Safety and Health Administration
- U.S. National Cancer Institute
- U.S. National Toxicology Program
- Australian National Health and Medical Research Council
- British Scientific Committee on Tobacco and Health
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