The New York Times ran an excellent article discussing the problem of Third Hand Smoke:

3rd Hand Smoke is the term being used to describe the invisible yet toxic brew of gases and particles clinging to smokers’ hair and clothing, not to mention cushions and carpeting, that lingers long after second-hand smoke has cleared from a room. Among the substances in third-hand smoke are hydrogen cyanide, used in chemical weapons; butane, which is used in lighter fluid; toluene, found in paint thinners; arsenic; lead; carbon monoxide; and even polonium-210, the highly radioactive carcinogen that was used to murder former Russian spy Alexander V. Litvinenko in 2006. Eleven of the compounds are highly carcinogenic.

Dr. Philip Landrigan, a pediatrician who heads the Children’s Environmental Health Center at Mount Sinai School of Medicine in New York, said “There are carcinogens in this third-hand smoke, and they are a cancer risk for anybody of any age who comes into contact with them.”