Thirdhand smoke is made up of the pollutants that settle indoors when tobacco is smoked. The chemicals in thirdhand smoke include nicotine as well as cancer-causing substances such as formaldehyde, naphthalene and others.

Thirdhand smoke builds up on surfaces over time. It can become embedded in most soft surfaces such as clothing, furniture, drapes, bedding and carpets. It also settles as dust-like particles on hard surfaces such as walls, floors and in vehicles. Thirdhand smoke can remain for many months even after smoking has stopped.

Thirdhand smoke can't be eliminated by airing out rooms, opening windows, using fans or air conditioners, or confining smoking to only certain areas of a home. Traditional household cleaning often cannot effectively remove thirdhand smoke from many surfaces.

Thirdhand smoke poses a potential health hazard to nonsmokers — especially children. Substances in thirdhand smoke are known to be hazardous to health. People are exposed to the chemicals in thirdhand smoke when they touch contaminated surfaces or breathe in the gases that thirdhand smoke may release.

Infants and young children are at greater risk for exposure to thirdhand smoke than adults due to activities such as crawling and putting non-food items in their mouths. They also tend to spend more time indoors.

Research has clearly shown that secondhand smoke causes many health problems, including cancer, heart disease and respiratory illness. The effects from long-term exposure to the toxins in thirdhand smoke are not as well studied. But research has shown that indoor smoking raises the risk of exposure to harmful chemicals, and that ventilation and cleaning cannot adequately eliminate these hazards.

The only way to protect nonsmokers, especially young children, from the dangers of thirdhand smoke is to remove all forms of smoking from indoor areas, including inside vehicles.