Third hand smoke - the sticky brown residue on smokers' walls and furniture - could be even MORE dangerous for children than passive smoking, warn experts
· Second-hand smoke reacts with indoor pollutants to create substance
· 'Noxious residue' sticks to items in the home, including children's toys
· When ingested substance sticks to DNA in a way which can lead to cancer
· Particularly dangerous for children - who are more vulnerable to its effects as they are small and at a developmental stage
· Discovered in research at Lawrence Berkeley National Laboratory
Third hand smoke that clings to walls and furniture could pose a more serious health threat to young children than passive smoking, a new study warns.
Researchers have found many of the 4,000 compounds in second hand smoke, which wafts through the air as a cigarette is smoked, can linger indoors long after a cigarette is stubbed out.
These substances can react with indoor pollutants such as ozone and nitrous acid, creating brand new compounds - some of which may be carcinogenic.
One residue - known as 'noxious residue' - remains on virtually all surfaces, including toys and other items toddlers may put in their mouths. The substance - called NNA - sticks to human DNA and can cause uncontrolled cell growth and the formation of cancerous tumours.
Dr Bo Hang, of the Lawrence Berkeley National Laboratory, found the residue NNA locks onto DNA to form what is known as a 'bulky adduct' - which is a piece of DNA bound to a cancer-causing chemical.
Other large compounds that attach to DNA tend to cause genetic mutations.
Dr Hang told an American Chemical Society meeting in Dallas: 'The best argument for instituting a ban on smoking indoors is actually third hand smoke.'
The biggest potential health risk is for babies and toddlers.
As they crawl and put their hands or toys in their mouths, they could touch, swallow or inhale compounds from third hand smoke.
Their small size and early developmental stage make them more vulnerable than adults to the effects of environmental hazards.
Although many public places prohibit smoking, Dr Hang said people can still smoke in most rental apartments and private residences, and smoking remains a huge public health issue.
So far, the best way to get rid of third hand smoke is by removing affected items, such as sofas and carpeting, as well as sealing and repainting walls, and sometimes even replacing contaminated wallboard.
Replacing furniture can be pricey, but Dr Hang said vacuuming and washing clothes, curtains and bedding can also help.
However, just as it took years to establish the cancer causing effects of first hand smoke, making the connection between third hand smoke or NNA and cancer could take a long time.
But early research into its nature, exposure and health effects is compelling enough a research consortium dedicated to investigating third-hand smoke was formed in California in 2010.
That helped fund Dr Hang's work on NNA induced DNA damage - which he said could eventually be used as biomarkers to identify people who have been exposed to third hand smoke.