'Third-hand smoke' which forms when second-hand smoke reacts with indoor air, damages DNA and sticks to it in a way that could potentially cause cancer.

Their talk was one of more than 10,000 presentations at the 247th National Meeting & Exposition of the American Chemical Society (ACS), taking place here through Thursday.

Bo Hang, Ph.D., who presented the research, said that although the idea of third-hand smoke made its debut in research circles just a few years ago in 2009, evidence already strongly suggests it could threaten human health.

'The best argument for instituting a ban on smoking indoors is actually third-hand smoke' said Hang Expart.

Researchers have found that many of the more than 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. Based on studies led by Hugo Destaillats, also at LBNL, these substances can go on to react with indoor pollutants such as ozone and nitrous acid, creating brand-new compounds, some of which may be carcinogenic.

One of those compounds goes by the acronym NNA. Hang’s research has shown that NNA, a tobacco-specific nitrosamine, locks onto DNA to form a bulky adduct as well as other adducts, in lab test tubes. Other large compounds that attach to DNA tend to cause genetic mutations. NNA also breaks the DNA about as often as a related compound called NNK, which is a well-studied byproduct of nicotine and a known potent carcinogen. This kind of DNA damage can lead to uncontrolled cell growth and the formation of cancerous tumors.

The biggest potential health risk is for babies and toddlers, he noted. 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, Hang noted that people can still smoke in most rental apartments and private residences — and smoking remains a huge public health issue. In 2011, nearly 44 million American adults reported smoking cigarettes, which ranks as the leading cause of preventable death in this country. And 34 million people smoke every day, according to data from the Centers for Disease Control & Prevention.