Third-hand smoke is something few people know about, but it is a very real thing and it poses serious health risks, especially to children, according to a study published in the journal Pediatrics.

What is third-hand smoke?

It is not smoke curling up into the air from a burning cigarette. It is the unseen residue of contaminants carried aloft with tobacco smoke. They remain suspended in the air long after the cigarette has been put out and the second-hand smoke has disappeared.

The toxic volatile compounds stay scattered in the air while some harmful particles eventually start to cling to fabric on furniture and carpeting, clothing, and even to people’s hair. These toxic residues range from heavy metals to radioactive particles.

The National Toxicology Program says at least 250 toxic gases, metals and chemicals are present in third-hand smoke. These include hydrogen cyanide, an ingredient in chemical weapons; toluene, a chemical component of paint thinners; arsenic; chromium (which is used in steel production); lead; cadmium (used in battery manufacture) and carbon monoxide. Third-hand smoke also contains polonium-210, a radioactive material that has been used in espionage to murder people.

These hazardous materials become especially dangerous for kids and toddlers, said the researchers, because they play on these surfaces, crawl on it, and touch it with their hands which they eventually put into their mouths. Or the kids may hug their parents, touching the clothing and hair as they do so.

The researchers note that most people are aware of the dangers of second-hand smoke but know nothing about third-hand smoke.

Parents aware of the dangers of second-hand smoke may make it a rule not to smoke when children are around. But they might light up when the kids are not in the house or smoke inside the car. They do not realize that while the kids may not be directly exposed to second-hand smoke, but they do get into contact with all the toxic residues that no one ever sees.

In their survey that covered more than 1,500 respondents, the researchers found that 85% of smokers and 95% of non-smokers believed that children were harmed by direct exposure to second-hand smoke. However less than half (only 43%) of smokers and 65% of non-smokers thought that exposure to third-hand smoke was harmful.

Only about a quarter of respondents imposed no-smoking bans in their homes. If more people knew about the hazards of third-hand smoke, more of them might think of not allowing smoking in their homes — and cars.

Safety Tips:

* Consider quitting cigarettes very seriously.

* Do not allow kids to touch your clothing and hair if you have been smoking or have stayed in a room where people smoked.