When parents smoke, they often open windows or fans to remove the smell of smoke, but experts have found that one threat to children’s health is not so easy to remove: third-hand smoke. This new term, refers to the invisible but toxic gases and particles that remain in the room for a long time even after secondhand smoke is removed, clinging to the smoker’s hair and clothes, as well as to chair cushions and blankets. These residues include heavy metals, carcinogens and even radioactive substances that children can come into contact with or swallow when they crawl or play on the floor. In a new study to explore the risks of these chemical exposures to infants and children, doctors at Boston Children’s Mass Hospital coined the term – third-hand smoke. The study is published in that month’s issue of the journal Pediatrics. ”Everyone knows secondhand smoke is harmful, but they don’t understand thirdhand smoke.” said the study’s leader, Jonathon Winewolf, an associate professor of pediatrics at Harvard Medical School. “When children are not home, parents may smoke in the house, or smoke in the car, or the child sits in the back of the car and they open the windows and smoke, thinking the child can’t inhale secondhand smoke.” Dr. Winiwolf said. “We need a term to describe this invisible poison.” Walk into an elevator with someone outside who has just finished a cigarette, or walk into a room where someone has just smoked, and all you’ll smell is third-hand smoke. “Your nose doesn’t lie,” he says, “these things are toxic, and your brain is telling you: ‘Run away.” The study surveyed 1,500 U.S. residents about their attitudes toward smoking . It found that most people, both smokers and nonsmokers, were aware that secondhand smoke is harmful to children. 95 percent of nonsmokers and 84 percent of smokers agreed that “inhaling the smell of their parents’ smoke is harmful to the health of infants and children.” However, very few people are aware of the dangers of thirdhand smoke. When asked if they agreed that “being in a room where you smoked yesterday is harmful to the health of babies and children. Only 65 percent of non-smokers and 43 percent of smokers agreed with that view. Dr. Vinewolf said the study found that the belief that secondhand smoke is harmful to children’s health cannot be strictly enforced by banning smoking in the home or car. On the other hand, the idea that third-hand smoke is harmful may strengthen the implementation of a home smoking ban. ”It requires us to promote a new and important health message.” He said, “We keep hearing respondents state ‘I turn on the fan and the smell of smoke is blown away.’ That means a lot of people know secondhand smoke is harmful and have found ways to remove it.” Dr. Philip Landrigan of the Center for Children’s Environmental Health at Mount Sinai School of Medicine in New York suggests that third-hand smoke is a new behavioral concept. ”The core message conveyed by this term is that simply closing the kitchen door to smoke does not protect children from it,” he said, “Third-hand smoke contains carcinogens that pose a cancer risk to anyone at any age who comes in contact with it.” Substances in third-hand smoke include: hydrogen cyanide used in the manufacture of chemical weapons, butane from light petroleum, toluene from paint thinner, arsenic, lead, carbon monoxide, and even the highly radioactive carcinogenic substance used in the 2006 murder of former Soviet spy Alexander Levinic. Eleven of these substances are highly carcinogenic.