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Tobacco and Cancer Programme International Union Against Cancer 3, Rue du Conseil-Général, 1205 Geneva, Switzerland Tel: (4122) 809 1830, Fax: (4122) 809 1810 E-mail: tobacco-control@globalink.org | Tobacco and Cancer Programme |
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Breathing other people's smoke is called passive, involuntary or second-hand smoking. The non-smoker breathes "sidestream" smoke from the burning tip of the cigarette and "mainstream" smoke that has been inhaled and then exhaled by the smoker. Smokers are also exposed to sidestream smoke from their own and others' cigarettes. Many people spend much of their lives indoors and tobacco smoke can make a significant, measurable contribution to the level of indoor air pollution (1).
What's in the smoke?
Tobacco smoke is highly complex and contains thousands of chemicals which are released into the air as particles and gases. Many potentially toxic gases are present in higher concentrations in sidestream smoke than in mainstream smoke and nearly 85% of the smoke in a room results from sidestream smoke (2). The particulate phase includes tar (itself composed of many chemicals), nicotine, benzene and benzo(a)pyrene. The gas phase includes carbon monoxide, ammonia, dimethylnitrosamine, formaldehyde, hydrogen cyanide and acrolein. Some of these have marked irritant properties and some 60 are known or suspected carcinogens (cancer causing substances), including benzo(a)pyrene and dimethylnitrosamine.
How does this affect the passive smoker?
A recent report of the Environment Protection Agency (USA) concludes that exposure to second-hand cigarette smoke causes lung cancer in adults and is responsible for thousands of lung cancer deaths each year, thus meeting the criteria for classification as a group A carcinogen. The report also confirms that second-hand smoke exposes young children to a significantly greater risk of respiratory disease, including asthma.
As well as causing annoyance by making hair and clothes smell unpleasant, involuntary smoke exposure can cause symptoms such as eye irritation, headache, cough, sore throat, dizziness and nausea and produces small but measurable changes in the air passages in the lungs of otherwise healthy adults. Adults with asthma experience a significant and substantial decline in lung function when exposed to sidestream smoke for one hour (3). People with allergies and other respiratory and heart ailments may be more seriously affected.
The effects of long-term exposure
In March 1988, the United Kingdom Government's Independent Scientific Committee on Smoking and Health (ISCSH) published its fourth report, dealing in particular with passive smoking (4). The Committee scrutinized epidemiological studies on the effects of passive smoking and found that the overall findings were consistent with an increased risk of lung cancer in non-smokers in the range of 10-30%. This means that, if the risk of lung cancer in non-smokers is, say, 10 per 100,000, the risk in an exposed group would be 11 to 13 per 100,000 per year. This means that several hundred of the 40,000 deaths from lung cancer in the UK each year may be caused by passive smoking.
When this risk is compared to other risks, it is found that the lifelong risk from passive smoking is more than 100 times higher than the estimated effect of 20 years' exposure to chrysotile asbestos normally found in asbestos-containing buildings (5).
What is important is that (a) large numbers of people are involved; (b) some of them are at a greater risk than the general population due to pre-existing cardiac or respiratory conditions and/or prolonged exposure in homes or at the workplace; and (c) there is no "safe" level of exposure to carcinogens.
Recent studies have found an increased risk of diseases other than lung cancer in passive smokers. A prospective cohort study (6) carried out on a general population in the west of Scotland found that mortality from all causes was higher in passive smokers than in a control group of non-smokers, as were all causes of death related to smoking, including mortality from lung cancer and ischaemic heart disease. When passive smokers were divided into high and low exposure groups on the basis of the amount smoked by their cohabitees, those highly exposed had higher rates of symptoms and death. Similarly, as with other studies, it was found that amounts of cotinine, a derivative of nicotine, in non-smokers exposed to others' smoke were similar to the amounts found in light smokers.
Are young children at risk?
Infants of parents who smoke are more likely to be admitted to hospital for bronchitis and pneumonia in the first year of life. Chronic cough and phlegm are also more frequent among children of parents who smoke. "By enhancing the frequency or severity of childhood respiratory illnesses, (passive smoking) could contribute to the development of respiratory disease in adult life among non-smokers" (4). There is also evidence for an association between exposure to passive smoking and low birth weight.
Should non-smokers be protected?
Experts have concluded that, given public health initiatives to minimize or eliminate involuntary public exposure to other environmental pollutants with less carcinogenic potency than several of the substances in tobacco smoke, similar efforts to prevent involuntary exposure to tobacco smoke are necessary. In the USA, some 40 states restrict smoking in public places and workplace smoking policies have increased dramatically in the 1980s. According to a survey carried out by the Bureau of National Affairs in 1986, 36% of the responding organizations currently had a smoking policy, 2% were to implement one during 1986 and another 21% had such a policy under consideration (7).
Recommended reading: Passive Smoking, a Health Hazard, written for the general public by a medical journalist under the direction of a committee comprising distinguished doctors and representatives from a wide range of health and medical bodies (8).
UICC Recommendation
The International Union Against Cancer believes that the health risks to non-smokers (of passive smoking) provide added argument for the reduction of smoking in the community, and non-smoking should be regarded as the norm in enclosed areas frequented by the public or employees, special provision being made for smokers, rather than vice versa. The UICC recommends that all governments adopt policies to protect the rights of non-smokers and establish in law the right to smoke-free common environments, including the workplace.
Acknowledgement
This Tobacco Control Fact Sheet is based on Fact Sheets produced by Action on Smoking and Health (ASH), United Kingdom.
References:
March 1993
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Tobacco and Cancer Programme International Union Against Cancer 3, Rue du Conseil-Général, 1205 Geneva, Switzerland Tel: (4122) 809 1830, Fax: (4122) 809 1810 E-mail: tobacco-control@globalink.org | Tobacco and Cancer Programme |
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