Tens of thousands of people die prematurely each year as a result of years spent breathing tobacco smoke in the air around them. Scientists say that non-smokers who live with a smoker have a 23 per cent increased risk of heart disease and a 26 per cent increased risk of lung cancer, even though they inhale only 1 per cent of the smoke.
It makes little difference whether the person you live with smokes ten or 60 cigarettes a day. The lethal dose is lower than has been realised and any extra exposure makes only a small difference.
The finding, by researchers from the Wolfson Institute for Preventive Medicine in London, is the most definitive evidence yet of the dangers of passive smoking and will add to the tobacco industry's woes. It suggests that the Government could cut heart disease deaths at a stroke by banning smoking in public places - an achievement that 20 years of cajoling about the nation's diet has failed to secure.
Tessa Jowell, minister for public health, said that the findings of the study, which was commissioned by the health department, made a "compelling case" for action. The Government is to publish a White Paper on tobacco control, expected next month.
"These are shocking figures, bearing in mind these are people who choose not to smoke ... We are considering action to promote more smoke-free public places. It is not fair that people have no choice but to endure cigarette smoke, especially in the light of its known harmful effects," Ms Jowell said.
Unprecedented security surrounded release of the research which is published in tomorrow's British Medical Journal. Its editor, Dr Richard Smith, said he feared the tobacco industry might seek an injunction preventing distribution of the journal because it would strengthen the hand of non-smokers who had contracted lung cancer and were considering legal action.
The researchers analysed 19 studies of heart disease involving 6,600 cases and 37 studies of lung cancer involving 4,600 cases. They say they were astonished by the results on heart disease which were not expected.
Dr Malcolm Law, one of the authors, said: "We had always thought the risks of smoking were proportional to the amount smoked. In the case of heart disease, they aren't. That is what is novel about this research."
The finding shows that a small exposure to tobacco has a large effect on heart disease. Although non-smokers breathe only 1 per cent of the smoke taken by smokers their risk of heart disease rises by almost one third of that of smokers (whose risk is increased by 80 per cent). The reason is, the researchers say, that the body's blood-clotting system is very sensitive to small amounts of smoke.
Lung cancer is 20-fold higher in smokers but the risk in this case is proportional to the amount smoked. Passive smokers suffer a 25 per cent increase in risk despite absorbing only one per cent of the smoke.
In health terms, the finding on heart disease is more important because, unlike lung cancer, it is common among non-smokers and any increase in risk translates into thousands of extra cases.
But in legal terms, the finding on lung cancer is more important because a non-smoker who lives with a smoker and develops lung cancer could have a case against a tobacco company. It would be much harder for a non-smoker to prove that heart disease was the direct result of living with a smoker.
The finding will require the tobacco industry to re-write advertisements such as that put out by Philip Morris which compared the risks of passive smoking to drinking a glass of milk or eating a biscuit.
An editorial in the BMJ dismisses the advertisement as "inane" and compares it to the industry's denials of the hazards of active smoking in past decades.
The British Medical Association said the research was the latest blow to the tobacco manufacturers in little more than a week.
A major UK cancer charity has announced plans to refuse funds to researchers who accept "tainted" tobacco money, airline attendants in the US have won a $300m (pounds 190m) settlement for the effects of passive smoking, new research published in the UK medical journal Thorax shows children of mothers who smoke suffer 70 per cent more respiratory illnesses and a report from the US Environmental Protection Agency in California linked passive smoking to cot death, heart disease and asthma.
Dr Bill O'Neill, science and research adviser to the BMA, said: "The new evidence has lessons for individual smokers who are exposing their loved ones to needless risk, as well as employers, pub and restaurant owners who all have a responsibility to eliminate tobacco smoke from public places.
"The tobacco industry must now stop its pathetic attempts to evade the evidence and accept that cigarettes not only harm and kill those who smoke them, they harm and kill non-smokers, too."
A spokesman for the Tobacco Manufacturers' Association said it would examine the study and take note of its findings.Reuse content