A new study found the chemical by-products of tobacco smoke cling to the air and surfaces of smokers' homes long after they've moved out, msnbc.com reported Dec. 16.

Researchers at San Diego State University led by psychology professor Georg Matt, Ph.D., analyzed the homes of 100 smokers and 50 nonsmokers for chemical smoking residue just before the residents completed a planned move. Two months later, they re-measured air and surface nicotine in the homes that had been rented or sold to nonsmokers, and checked the fingerprints of the new residents for nicotine.

They also analyzed urine samples of the youngest new inhabitants for cotinine, a nicotine metabolite.

Although the homes had been thoroughly cleaned, including painting and carpet replacement in many cases, nonsmokers living in the homes of former smokers had seven to eight times more nicotine on their fingertips than those who moved into nonsmoker homes, and urine cotinine levels were three to five times higher in their children.

Overall, air and surface nicotine was 30 to 150 times higher in the homes formerly occupied by smokers compared with homes formerly occupied by nonsmokers.

Smoke-related chemical residues, referred to as thirdhand smoke, “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.”

Such homes are “reservoirs of tobacco smoke pollutants,” creating a source for involuntary tobacco exposure to those who move into them, the authors said.

The study was published online Oct. 30 in the journal Tobacco Control.