Passive smoking and the risk to health
By Dr Walter Chin
May 20, 2001
Over 50 years ago, the British Medical Journal published a landmark study by Doll and Hill from which the authors concluded that cigarette smoking was an important factor in causing lung cancer. Since then, the role of smoking has been strongly substantiated as a cause of the lung cancer epidemic, and extensive research has shown that smoking also affects virtually every organ system in the body.
The statistics on tobacco still remain appalling. About 1.1 billion people smoke cigarettes, 80 per cent of whom live mainly in developing countries. Each day, 82,000 to 99,000 young people throughout the world start smoking. Tobacco is responsible for the deaths of four million people a year worldwide (one in ten adult deaths), and that number could rise to ten million annually by the year 2030 (one in six deaths) if the present smoking trend continues.
Tobacco smoke contains a range of 4,000 different gases and particles. The major gases include carbon monoxide, hydrogen cyanide, ammonia, nitrogen oxides, and nitrosamines - the latter are known to be carcinogenic. Particulates include nicotine, benzene, and a variety of known carcinogens, including benzo(a)pyrene, tars, and polinium-210. Mainstream tobacco smoke, which is the smoke inhaled in high concentration by smokers as they draw on a cigarette, amounts to about 15 per cent of the smoke produced by a cigarette. The remainder, usually called sidestream smoke, is inhaled by smokers and non-smokers in a concentration that varies with the size, and thus the dilution effect of the room, and the number of persons smoking within it. The concentration of most of the constituents of smoke is much higher in sidestream smoke than in mainstream smoke. Three of the substances produced from tobacco smoking are particularly important. Nicotine is the substance that causes addiction to tobacco. Tar produces chronic irritation of the respiratory system, and in addition, has a direct cancer-causing action. Carbon monoxide competes with oxygen in the blood stream, and thus interferes with oxygenation of tissues. In the long term, persistently high levels of carbon monoxide in the blood - which occur in smokers - lead to hardening of the arteries, which in turn greatly increases the risk of coronary thrombosis.
The Environmental Protection Agency in the USA has classified environmental tobacco smoke as a class A carcinogen along with asbestos, benzene, and radon gas. The agency has also documented causal associations between exposure to environmental tobacco smoke and lower respiratory tract infections such as pneumonia and bronchitis, middle ear disease, and exacerbations of asthma in children.
The California Environmental Protection Agency has also confirmed the findings of the EPA and concluded that passive smoking is a cause of heart disease mortality, acute and chronic heart disease morbidity, retardation of foetal growth, and induction of asthma in children.
Active tobacco smoking is extremely harmful and represents the greatest identifiable preventable cause of ill health. The main harmful effects of smoking are respiratory diseases (lung cancer, bronchitis, and emphysema) and cardiovascular diseases (coronary artery disease and peripheral vascular disease). A substantial proportion of cancer in the mouth, pharynx, larynx, oesophagus, kidney, and bladder is also attributable to tobacco. Smoking is also implicated in a chronic form of leukaemia and may also cause cancer of the stomach, colon and rectum. Smoking causes about 30 per cent of all cancer deaths in the world. Active smoking accounts for thousands of premature deaths annually. Half of all smokers can expect to die, on average, eight years earlier than their non-smoking contemporaries, from smoking-related diseases. Taking up smoking while very young substantially increases the risk of getting these diseases.
Passive smoking causes the same detrimental health effects as active smoking. Passive smoking, also called involuntary or second-hand smoking, occurs when environmental tobacco smoke is breathed in. The term passive smoking first appeared in the literature in 1974, when a group at St Thomas's Hospital in London reported in the Lancet that exposure to ambient tobacco smoke in homes was associated with increased respiratory disease in children. The emerging evidence of the risks to health through passive smoking has initiated new bases for public health action against smoking. This has occurred because, if smoking is a risk not only to an individual's own health but poses an avoidable risk to others, then smoking can no longer be regarded as simply a private matter.
Maternal smoking during pregnancy has major effects on the foetus. The risks of stillbirth, miscarriage, and death soon after delivery are increased by 30 per cent, and the risk of prematurity is doubled. On average, the birthweight of babies born to mothers who smoke during pregnancy is 200 g lower, and they may have impaired mental development, and an increased rate of congenital abnormalities.
In later childhood, there is strong evidence of an increased risk of asthma, middle ear infections, and sore throats in children whose parents smoke. Children whose mothers smoke more than ten cigarettes a day are twice as likely to have asthma as those with non-smoking mothers, and attacks may be more severe and frequent. And as these children grow older, they also show evidence of impaired lung function. And second hand smoke can also provoke allergies, such as hay fever.
In adults the risk of wheezing, bronchitis symptoms, and asthma increases with exposure to smoke, and with increasing intensity of exposure, and lung function is worse. A considerable body of data suggests that the risk of ischaemic heart disease is increased by exposure to environmental tobacco smoke. A study has shown that regular exposure to second hand smoke nearly doubles the risk of coronary artery disease. Passive smoking is believed to cause heart damage in much the same way as active smoking, by causing damage to the lining of the coronary arteries, lowering the high density lipoprotein (good) cholesterol, and increasing the viscosity of the blood. There is also evidence to suggest that many lung cancer deaths could be attributed to environmental tobacco smoke.
The importance of passive smoking is that passive smokers are the "innocent victims" of tobacco smoke. This is particularly worrying when those affected are children, who as a consequence may not achieve their full physical and intellectual potential, and yet have no choice in the matter. Passive smoking raises the issue of personal freedom, both for smokers who feel that they should be able to choose to smoke if they wish, and for non-smokers who feel that they have a right to breathe air which is safe and unpolluted, whether at home, the workplace, or in public areas and buildings.
With so much scientific evidence about the dangers of passive smoking available, it is not surprising that in 1998, the British Medical Associa-tion called for legislation or regulations to ban smoking in public places to protect people from the dangers of passive smoking.
There is urgent need for this kind of legislation in Guyana. The objective of this legislation should be a total ban on smoking in all public places. Smoking, if it occurs at all, should only be permitted in physically separate and independently ventilated areas.
The intention would be to give non-smokers maximum protection from tobacco smoke.