In the same way the smell of smoke from someone's hair, clothes, house, or car upsets the senses, the brain is affected by this invisible residue, recently labeled third-hand smoke, as well.
Loads of heavy metal (and we're not talkin' music!), carcinogens, hazardous chemicals, and radioactive materials cling onto people and their possessions. This invisible residue is a recipe for disaster because it can be easily ingested to cause damage.
Children are especially at risk. Parents might smoke while their children are away and out of the house, and they don't witness any visible damage in doing so. By playing in a space where someone has smoked, kids are exposed to third-hand smoke.
Be sure to visit the article, "A New Cigarette Hazard: 'Third-Hand Smoke,'" from the New York Times.