Just because the smoke has cleared the air doesn't mean the dangers of tobacco smoke don't linger. Third-hand smoke — the gunk that settles on floors, furniture, draperies, and even kids' toys — has the potential to damage DNA in a way that increases the risk of cancer. The sticky, tarry residue is especially dangerous for infants and toddlers who typically spend a lot of time on floors, putting everything they can into their mouths. This stuff isn't good for family pets, either.

The dangers of third-hand smoke were discussed as a presentation at the 247th National Meeting & Exposition of the American Chemical Society (ACS) in Dallas, Texas, in March 2014. Dr. Bo Hang, of the Lawrence Berkeley National Laboratory (LBNL), made the presentation. The LBNL is a part of the US Department of Energy housed on the grounds of the University of California, Berkeley.

Hang considers third-hand smoke to be alarming enough that he describes it as "the best argument for instituting a ban on smoking indoors." More than 4,000 chemical compounds are present in tobacco smoke, many of which linger for hours after visible evidence of the smoke is gone. Furthermore, some of these chemicals interact with common household pollutants to form entirely new chemical compounds, some of which are expected to be carcinogenic.

When tobacco smoke and its solid residue are touched, swallowed, or inhaled, they react with DNA in a detrimental fashion. One chemical compound — a nitrosamine known as NNA — attaches itself to DNA to form an adduct (a cancer-causing chemical bound to DNA). The NNA breaks the DNA strand in a way that promotes uncontrolled cellular growth, which marks the formation of a potentially cancerous tumor. The NNA effect on DNA is similar to a compound called NNK, which is a well documented potent cancer-causing agent. Other chemical compounds cause various gene mutations.

This genetic activity makes infants and toddlers especially vulnerable since their bodies are undergoing rapid growth and development on the cellular level. Their rapid rate of cellular growth, compounded with the time they spend on the floor, puts them at greater risk than older members of the family.

Non-smoking families often face exposure when moving into a previously occupied residence. Third-hand smoke may linger if a previous occupant smoked.

For best protection against third-hand exposure, Hang recommends replacing any furnishings that may be contaminated, including carpeting and upholstered furniture. Walls may need to be sealed and repainted and, in cases of extreme contamination, wallboards may need to be replaced. Frequent vacuuming of the floors and draperies helps minimize routine exposure as does frequent washing of clothing and bedding.

Source: "Major 'third-hand smoke' compound causes DNA damage -- and potentially cancer." ACS. American Chemical Society. Mar 16, 2014. Web. Mar 27, 2014.