Everybody has had the experience of walking into a smoke-filled room. The coughing and smarting of the eyes that can result is leading many people to ask whether this kind of ‘passive’ smoking may produce the same sort of serious diseases as those seen in smokers themselves. This possibility has been examined in a number of ways. The most obvious method was to look at the occurrence of smoking-related diseases in the husbands or wives of smokers. Studies of this kind were done in the early 1980s and some involved tens of thousands of people. All of these studies were brought together in 1986 by Professor Nicholas Wald and his colleagues in an influential paper published in the British Medical Journal. They added together the results of thirteen epidemiological studies and concluded that there was sufficient agreement between them to conclude that there was significant increased risk of lung cancer for someone married to a smoker. The average effect of a married man or woman smoking would be to increase the risk to the non-smoking partner by about 35 per cent. Much controversy remains, because others have suggested that there might have been biases in these studies. It has for example, been suggested that a non-smoker, when married to a smoker, it more likely to have been given the occasional cigarette during married life and that the explanation of the increased risk might lie in this. This possibility is difficult to reject.

Another approach comes from the laboratory; where work has been done to measure the products of smoking in the urine of non-smokers. These studies show only a few things with any certainty. Products of smoking are to be found in the urine of non-smokers who are married to smokers. Whether there is enough of them to be responsible for an increased risk of lung cancer is not proven.

This controversy is likely to continue and complete resolution is unlikely. We would agree with Sir Richard Doll’s view that ‘the one conclusion that can be drawn with certainty is that reached by the International Agency for Research on Cancer (in 1986): namely, that the presence of several known laboratory carcinogens in environmental smoke, combined with the knowledge that tobacco actively smoked causes lung cancer in humans must lead to the presumption that environmental smoke causes some risk of the disease.

It is worth setting this risk in perspective. A non-smoking woman has about one chance in 10,000 of getting lung cancer in any year. If she is married to a smoker her chance increases to about one and a half in 10,000 in each year. It might be argued that the consequences for her of her husband’s possible lung cancer, which might be as high as 20 in 10,000 in every year, is even worse than the risk to herself. She should try to stop him smoking, but rather more for his sake than for hers.

Risks to children in households where parents smoke are real. The Royal College of Physicians in its recent book Smoking and the Young reported that children who have smoking parents receive the same amount of nicotine as if they smoked 60-150 cigarettes each year. This is damaging: the children of parents who smoke arc shorter, have twice as much asthma, twice as many chest infections, have more time off school, get more chronic bronchitis and are more likely to die than the children of non-smokers.

There are many reasons, apart from the cancer risk, for not smoking in the home.

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