San Diego State University researchers have found that pollutants released from cigarette smoke may linger longer within a home than previously thought, holding a presence long after the smoker has moved out. 

Georg E. Matt, study leader and a professor of psychology at San Diego State University, along with a team of researchers, has discovered that cigarette smoke pollutants can attach to home surfaces and slip into crevices for long periods of time after the smoker has already moved out. Then, when non-smokers move in, they could potentially absorb these toxic chemicals. 

"These oily, sticky droplets hang around for months after a smoker has left," said Matt. "While there was considerably less in homes once an active smoker moved out, there was still 10 to 20 percent of what was found while the smoker still lived there."

These pollutants have been dubbed "thirdhand smoke," and despite the fact that the home has been vacant for months and even cleaned after a smoker has left, the thirdhand smoke remains and can affect a new non-smoking occupant. 

Researchers came to this conclusion after studying the homes of 100 smokers and 50 non-smokers who were planning to move out. Nicotine levels were used as a "marker" for any other chemical residues that come from tobacco smoke. Chemicals on the walls, ceilings, floors and other surfaces were measured as well as the air. They even searched for nicotine on the residents' fingertips in all 150 homes as well as a nicotine breakdown product, cotinine, within urine samples of children.

Twenty-five non-smokers then moved into homes that were previously owned by smokers, and researchers again checked nicotine/chemical residues throughout the homes, on fingertips and in urine. After careful measurements, researchers concluded that nicotine levels in the air throughout the homes, which were vacant for two months after the smokers moved out, were 35 to 98 times as high "as they were in non-smoker homes." As far as surfaces go, nicotine levels were 30 to 150 times as high in the former smokers' homes compared to the homes of non-smokers. 

When testing for nicotine on fingertips, non-smokers who moved into the homes of smokers had nicotine levels seven to eight times higher than those who stayed in non-smoking homes. Children's urine contained nicotine levels three to five times higher than those in non-smoking homes.

"Above a certain threshold level, you can smell it," said Matt. "And if you can smell it, that means you're inhaling these compounds and they're going into your lungs. So smelling is a good indicator though it's not a super sensitive one."

Researchers advise those who live in a previous smokers' home to keep surfaces as clean as possible, and to keep children's hands clean. 

This study was published in the journal Tobacco Control.