Jul 16, 2014 02:21 PM EDT By J Baulkman, UniversityHerald Reporter

Third hand smoke is just as deadly as first and second hand smoke, according to a recent study.

Researchers from the University of York found that tobacco smoke gases and particles deposited to surfaces and dust in the home are a potential cancer risk in non-smokers - particularly young children. Until now, the risks of this exposure known as 'third hand tobacco smoke' have been highly uncertain and not considered in public policy.

"The risks of tobacco exposure do not end when a cigarette is extinguished," Dr. Jacqueline Hamilton, lead investigator of the study, said in a statement. "Non-smokers, especially children, are also at risk through contact with surfaces and dust contaminated with residual smoke gases and particles, the so-called third hand smoke. This risk should not be overlooked and its impact should be included in future educational programs and tobacco-related public health policies."

For the study, the research team collected dust samples from private homes occupied by both smokers and non-smokers. They examined exposure to carcinogen N-nitrosamines and tobacco specific nitrosamines (TSNAs) in the dust samples. These are produced when nicotine deposits on indoor surfaces and then is released again to the gas phase or reacts with ozone, nitrous acid and other atmospheric oxidants. They are classified as carcinogenic for humans.

Using observations of house dust composition, they estimated the cancer risk by applying the most recent official toxicology information.

They found that for children aged one to six years old, the cancer risks exceeded the limit recommended by the U.S. 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.

"The TSNAs concentrations found in smoke-free homes would suggest that TSNAs formed in smoking environments can persist for extended periods, possibly due to partitioning to ambient particles, and subsequently be transported into non-smokers' homes from outside," researcher Noelia Ramirez said in a statement.

Each year 600,000 people die worldwide through passive inhalation of environmental tobacco smoke, also known as second hand smoke. As numerous countries have introduced smoking bans in public places, the home has become the main source of passive smoking exposure.

"Over 40 percent of children have at least one smoking parent and whereas there is a general public awareness about the harms of second hand smoke, there is little knowledge about the dangers of third hand smoke," Alastair Lewis said in a statement. "Carcinogenic materials can be passed from smokers to non-smokers during shared contact, for example between clothes and surfaces and also enter homes via airborne transport of cigarette smoke."

The findings were recently published in the journal Environment International.

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