WE'RE all aware of the dangers of second-hand smoke; only recently, a leading doctor said smoking should be banned in cars carrying children.
But could there be even greater worry? Could you suffer the effects of passive smoking from simply travelling in a smoker's car -even if they haven't lit up?
Is that nasty ash-tray tang that lingers on car-seat fabric, curtains in homes and the clothes of the nicotine addict strong enough to damage other people's health?
These questions were posed in an article by The Mail of London in a recent article on a research on the effect of cigarette smoke on children.
The Mail reported that according to some experts, thirdhand smoke, as it is known, is as dangerous to health as the fumes billowing directly from a pipe or cigarette, particularly for babies and children.
A recent report in the United States of America has warned that even if you don't smoke in front of your family, you might be putting them at risk of cancer or delaying the development of their brain, thanks to polluting their environment with a lingering chemical cloud.
The warning came from a paper produced in the respected journal, Paediatrics, earlier this year.
The study surveyed more than 1,500 households, learning that just 26.7 per cent of those that included a smoker had strict rules about not smoking in the home.
"The dangers of third-hand smoke are very real," explained the leader of the study, Professor Jonathan Winickoff, of Massachusetts General Hospital, Boston, United States of America.
"Toxic particles in cigarette smoke can remain on nearby surfaces long after the cigarette has been put out, meaning the sofa is potentially as problematic as the ashtray itself," Winickoff said.
Small children and babies are particularly susceptible because they crawl on the carpet and are likely to breathe in close proximity to smokers or even lick and suck clothing or items that smokers have touched.
Winickoff is also concerned about new mothers who smoke, saying, "When you're near your baby, even if you are not smoking, the child comes into contact with those toxins.
"And if you breastfeed, the toxins will transfer to your baby in the breast milk."
According to the National Toxicology Programme in the United States of America, tobacco smoke contains about 4,000 chemicals, including 250 poisonous gases and metals.
Such poisonous gases and metals in tobacco include butane (used in lighter fuel), arsenic, carbon monoxide, benzene, toluene (found in paint thinners), ammonia, chromium (used to make steel), cadmium (used to make batteries), lead and hydrogen cyanide (which is used in chemical weapons).
The smoke even contains polonium-210 - the highly radioactive carcinogen used to murder Russian spy, Alexander Litvinenko, in London in 2006.
Experts fear that these particles are carcinogenic and that some of the toxins may affect brain development in young children, who may be more affected than adults as their bodies and brains are still growing.
And these concerns are not confined to the Americans.
"Parents who smoke should be aware that when they cuddle or hold a child on their lap, they are exposing them to the smoke on their clothes," says Professor Ros Smyth, Head, Division of Child Health, University of Liverpool.
Smyth added, "They should be particularly aware if they have a child with a respiratory problem such as asthma."
It is a question of risk, says Professor Andrew Shennan of baby charity, Tommy's.
Shennan said, "You wouldn't go into a room full of asbestos, so would you go into a room full of other toxins?"
Earlier this year, two students in San Antonio, Texas, United States of America, won an award at the Intel International Science and Engineering Fair for an experiment on fruit fly larvae that had been exposed to foam saturated with tobacco smoke.
The pair observed a high number of mutations, which could influence scientific knowledge of the effect of environmental - or third-hand -smoke on humans.
Meanwhile, a San Diego study in 2004 discovered that in households where there was a smoker, although all smoking was done outside, children still had nicotine in strands of their hair and in their urine.
Mothers who smoked away from their children were found to have nearly as much nicotine on their hands as smokers who made no special effort.
This new research on third-hand smoke builds on previous studies into second-hand smoking, or passive smoking - inhaling someone else's cigarette smoke.
The original passive smoking studies began in the Seventies and although the initial findings linking passive smoking to disease were contested by the industry, it is now accepted that there is a clear link.
In 2004, the World Health Organisation (WHO) declared that scientific evidence unequivocally established that exposure to tobacco from passive smoking causes death, disease and disability.
It also found that the risk for lung cancer when a spouse smoked was 20 per cent for a woman and 30 per cent for a man. It is estimated heavy exposure to cigarette smoke at work pushes this to 50 per cent.
The danger with passive smoking is so-called 'side stream' smoke - this is full of the same toxins as the 'mainstream smoke' inhaled directly by the smoker from the filter end of the cigarette, but comes from the burning tip of the cigarette.
Indeed, fresh side-stream smoke is actually four times more toxic than mainstream smoke, according to research from the Centre for Tobacco Control Research and Education at the University of California, United States of America.
The report concluded, "Smokefree public places and workplaces are the only practical way to protect the public health from the toxins in side-stream smoke."
Further studies have shown that children who passively smoke as a result of living in households where there is a smoker are more likely to suffer from respiratory disease, asthma attacks, middle ear infections and cot death.
The increasing weight of the evidence about the dangers of passive smoking led many countries to consider smoking bans in enclosed public places, with Norway the first to go smoke-
free in 2004, Italy in 2005 and the United Kingdom in 2007. Doctors and health workers have already noted a corresponding fall in the number of hospital admissions for heart-related conditions.
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