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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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Summary
The harmfulness of tobacco smoking is related to the concentrations
of toxic chemicals in the smoke. Reducing the level of toxins
can reduce the risk of various diseases caused by smoking (1).
Toxin reduction policy should be firmly implemented and monitored
by means of legislation, as part of a wider strategy to reduce
smoking induced disease.
Constituents of tobacco smoke
Tobacco smoke contains thousands of different chemicals present as particles and gases. The particulate phase includes the addictive drug nicotine; tar, the sticky brown substance condensing out of tobacco and composed of many chemicals; benzene, and benzo(a)pyrene. The gas phase includes carbon monoxide (CO), the poisonous gas present in motor car exhausts; ammonia; dimethylnitrosamine; formaldehyde; hydrogen cyanide, and acrolein. Some of these have marked irritant properties and some 60, including benzo(a)pyrene and dimethyl-nitrosamine and mainly present in tar, have been shown to cause cancer when applied to living tissue.
Filter tip cigarettes yield less tar than plain cigarettes although some filter brands yield more CO. Most cigar and pipe tobacco smoke has a higher tar content than from cigarettes but because most life-long cigar and pipe smokers do not inhale, they take in less tar than an average cigarette smoker. Cigarette smokers who switch to pipes or cigars usually continue to inhale the smoke and so probably are no better and may be worse off (2). Herbal cigarettes and other non-tobacco cigarettes have no nicotine but produce tar and CO.
Lowering the tar levels of cigarettes has been shown to reduce significantly the incidence of lung cancer caused by smoking: but research suggests that the health advantages of switching to lower tar may be largely offset by the tendency of smokers to compensate for the reduction in nicotine (lower tar cigarettes also tend to be lower in nicotine) by smoking more or inhaling more deeply (3). There is no firm evidence that switching to lower tar cigarettes reduces coronary heart disease risk, though a number of governments are attempting to reduce CO yields in view of evidence which suggests that CO plays a role in causing heart disease in smokers. Nicotine levels have also been reduced in countries which have reduced tar levels, though below a certain nicotine level habitual cigarette smokers may smoke more cigarettes to compensate.
A low tar, low CO, but medium nicotine cigarette has therefore been suggested as the least dangerous product for those who continue to smoke.
In many industrialized countries, average tar levels have been reduced significantly since the 1950s, but in many developing countries, much higher emission levels are still common.
Policy
Lowering emission levels is important to try to reduce the risks of those who smoke and should form part of a comprehensive tobacco control policy. The reduction in risk will be small compared to the reduction achieved by smokers giving up their habit altogether and this area of tobacco policy should never be seen as anything but an interim measure to be taken while every effort is made to eliminate all use of tobacco.
The tobacco industry has used this aspect of tobacco control policy to try to justify continued tobacco advertising, maintaining that to reduce average tar yields, new brands will have to be introduced and that advertising will be needed to make the public aware of them. This is untrue: substantial changes can be made to existing brands simply by altering their yields. Publicizing the relative dangers of low tar and high tar cigarettes may result in smokers persuading themselves that so long as they smoke a low tar brand, they will be "safe".
Instead, the toxicity of existing brands should be progressively reduced. Upper limits should be set for tar and CO levels; these should be regularly reviewed and lowered. Legislation is essential for effective action in this, as in other areas of tobacco control. Differential tax rates favouring the lower-tar brands may also be considered, to speed up the lowering of average emission levels, a system used successfully in the UK in the 1970s.
Most important of all, the tobacco industry must never be permitted to determine the way emission policy is implemented, or be actively involved except to comply with legally enforced standards set by government.
Note well that lowering tar reduces the incidence of lung cancer. However, switching to lower tar cigarettes seems to have little effect on deaths due to coronary heart diseases and obstructive lung diseases. Furthermore, it should be mentioned that as cigarette smokers may smoke more cigarettes to compensate for the reduced nicotine level, the problem of passive smoking increases.
UICC Recommendation
WHO and UICC have suggested the goal of a market range of cigarettes between 5-15 mg of tar. The UICC recommends progressive eradication of high-tar brands from the market, starting with all brands over 25 mg; then 20 mg; then 15 mg (4). The EC has called for all 12 member states to set an upper limit of 15 mg of tar per cigarette, falling to 12 mg in 1995 (5).
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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