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Passing it on

Thanks to the public smoking ban, office parties are no longer the smoky affairs they used to be. But at parties in private homes, non-smokers are still exposed to other people's tobacco fumes. Sometimes Naomi (a non-smoker) wonders about those parties, and about how much second-hand smoke it takes to cause disease.

Then she reads the reports last month of a World Health Organisation (WHO) study which concludes that one death in 100 can be attributed to passive smoking, and asks herself: "Could that be me?"

Sadly, the research shows that it could. Other recent studies indicate that children who inhale second-hand smoke are more likely to have mental-health problems, and adults are more likely to have hearing loss.

With a smoking ban protecting people from passive smoking at work and on the town, doctors are concerned that we are being lulled into a false sense of security. Smokers still smoke at home -- and those who live with them, including children, are inhaling 1pc of their smoke. That fraction of smoke still raises cohabitants' risk of getting lung cancer or heart disease by up to a third.

The WHO report found that second-hand smoke caused 603,000 deaths worldwide in 2004 from heart disease, respiratory conditions and lung cancer. About 40pc of children, 35pc of women and 33pc of men were regularly exposed to second-hand smoke.

Global figures often seem far from our daily lives, but these are not. Lynn Mitchell is 53 and doesn't think she has long left. She has always despised the smell of tobacco and never smoked herself, but her parents, sister and husband were all smokers. She developed asthma as a child and breathlessness during exercise as a young woman, and had chronic obstructive pulmonary disease diagnosed 16 years ago. Doctors have linked this directly to continuous exposure to tobacco smoke.

Now in a wheelchair and with a life expectancy of months rather than years, she tells me between coughs that all she has left is a determination to warn others that the dangers of passive smoking are real. "I think the message goes over people's heads," she says.

If Lynn's case sounds extreme, it is less easy to dismiss after an assertion by the British Medical Association and other medical bodies that there is "no safe level of exposure to tobacco smoke".

This refers to research on the relationship of tobacco to heart disease and lung cancer. The bare facts are that, in adults, second-hand smoke increases the risk of lung cancer by 20-30pc and the risk of heart attack by 25-35pc. Unfortunately, these figures apply even if you are exposed to only a few wisps of smoke a day.

Professor John Britton, chairman of the tobacco advisory group for the Royal College of Physicians, explains that with lung cancer the risk is cumulative: the more smoke-filled breaths you take, the greater the risk -- but the risk applies from the first breath; and while some people can spend their lives exposed to smoke and not contract cancer, others develop it after very limited exposure.

With heart disease, the risk equation is different and the chances of getting it are disproportionately high for a passive smoker. A non-smoker regularly exposed to tobacco smoke is at the same risk as someone who smokes up to 10 cigarettes a day. Researchers believe that this is because blood platelet cells are extremely sensitive to tobacco smoke. Various studies have suggested that being exposed to tobacco smoke in the environment for 20 minutes a day has a similar damaging effect on platelets to smoking one or two cigarettes a day.

The risk of respiratory complaints generally increases according to the amount of smoke to which you have been exposed, and at what stage in your life (children's lungs are particularly vulnerable to infection and irritation).

"If you ask who should be worried about second-hand smoke, the answer is anyone who is exposed to it," says Professor Britton. So even if, like Naomi, you live with someone who makes cursory efforts to protect you, your health is being affected.

Cigarette smoke in the air is still harmful even if you cannot smell it, says Elin Roddy, an expert in respiratory diseases.

These messages may sound alarmist -- after all, we are exposed to exhaust fumes and other toxins every day. But the point is that our exposure to cigarette smoke usually occurs in confined spaces, unlike our exposure to general atmospheric pollution.

Non-smokers -- especially children, who breathe more rapidly than adults -- can receive particularly high doses of smoke in cars. There is evidence that just one cigarette, even with the car window open, creates a greater concentration of second-hand smoke than an evening in a smoky pub. A study by the Ontario Tobacco Research Unit indicated that the pollution created by one cigarette inside a car was 100 times greater than the accepted standard for fine-particle exposure as defined by the US Environmental Protection Agency.

Roddy, a consultant respiratory physician, sees the effects of second-hand smoke on his patients every day. For some, lung and airway disease is caused by second-hand smoke, and for many it causes flare-ups and deterioration.

"I've seen many lung cancer patients who have never smoked," he says, "and when you talk to them about their background, it's amazing how many have been regularly exposed to second-hand smoke."

About 10pc of people with lung cancer have never smoked.

What can passive smokers do to help themselves? The good news for those living with smokers is that the risk of contracting many smoking-related diseases diminishes rapidly once exposure ends permanently.

Campaigners put the emphasis on persuading smokers to give up, or leave the house to smoke. However, evidence suggests that nagging is not successful. Robert West, a professor of Health Psychology and Director of Tobacco Studies, says that smoking is driven more by addiction than by choice, and that any form of nicotine withdrawal, even after 90 minutes, causes tetchiness.

"A direct approach to a smoker isn't likely to be successful," he says. "You need to find a natural situation that brings up the subject of smoking -- say, someone in the house has a cough -- then suggest that you need to work out a solution together. If you can set rules together, it makes it easier when they have been violated. You can say: 'What can we do to get things back on track?'"

Suggesting nicotine gum or patches as a replacement for cigarettes can be useful, says Professor West, and may even help smokers to quit.

Ms Roddy's approach lifts blame from smokers but also puts responsibility gently on their shoulders. "I don't blame them, I blame nicotine addiction and the tobacco industry," she says. But smokers can plead partial knowledge of the effects of their smoking on others only for so long. "There is still a lack of awareness. But when there is information out there, smokers have an increasing responsibility to minimise their loved ones' exposure."