Researchers demonstrate health risks posed by 'third hand' tobacco smoke

Research led by the University of York has highlighted the potential cancer risk in non-smokers - particularly young children - of tobacco smoke gases and particles deposited to surfaces and dust in the home.

Until now, the risks of this exposure known as 'third hand tobacco smoke' have been highly uncertain and not considered in public policy.

However, a new study published in the journal Environment International, has estimated for the first time the potential cancer risk by age group through non-dietary ingestion and dermal exposure to third hand smoke. The results indicate potentially severe long-term consequences, particularly to children.

The research was carried out by York's Wolfson Atmospheric Chemistry Laboratories, the National Centre for Atmospheric Science, and the Chromatography and Environmental Applications research group at the Universitat Rovira i Virgili, Spain.

The study, which was supported by the UK Natural Environment Research Council (NERC) and the General Research Directorate of the Government of Catalonia, also demonstrates for the first time the widespread presence of tobacco related carcinogens in house dust, even in 'smoke-free' environments.

Scientists collected dust samples from private homes occupied by both smokers and non-smokers. Using observations of house dust composition, they estimated the cancer risk by applying the most recent official toxicology information.

What is thirdhand smoke, and why is it a concern?

Thirdhand smoke is generally considered to be residual nicotine and other chemicals left on a variety of indoor surfaces by tobacco smoke. This residue is thought to react with common indoor pollutants to create a toxic mix. This toxic mix of thirdhand smoke contains cancer-causing substances, posing a potential health hazard to nonsmokers who are exposed to it, especially children.

Studies show that thirdhand smoke clings to hair, skin, clothes, furniture, drapes, walls, bedding, carpets, dust, vehicles and other surfaces, even long after smoking has stopped. Infants, children and nonsmoking adults may be at risk of tobacco-related health problems when they inhale, ingest or touch substances containing thirdhand smoke. Thirdhand smoke is a relatively new concept, and researchers are still studying its possible dangers.

Thirdhand smoke residue builds up on surfaces over time and resists normal cleaning. 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. In contrast, secondhand smoke is the smoke and other airborne products that come from being close to burning tobacco products, such as cigarettes.

They found that for children aged one to six years old, the cancer risks exceeded the limit recommended by the US Environmental Protection Agency (EPA) in three quarters of smokers' homes and two thirds of non-smokers' homes. The maximum risk predicted from the third hand smoke levels in a smoker occupied home equated to one extra cancer case per one thousand population exposed.