Should you sit on a cigarette smoker’s couch or let your toddler crawl on it?

The dangers of secondhand smoke exposure (breathing in smoke from cigarettes) have been documented for years, with federal health officials saying it contributes to about 41,000 deaths among nonsmoking adults and 450 deaths in infants a year.

But what about the thirdhand effect – smoke that gets on surfaces such as on clothing and hair and finds its way inside homes and cars?

Would you want, for example, your toddler crawling around on a couch contaminated with thirdhand smoke? Maybe not.

Researchers at the University of California at Riverside say they have found that thirdhand exposure (in a mouse model) has significant molecular effects on the liver and affects stress hormones of the brain as early as one month after exposure – and it worsens with time.

According to the scientists, exposure to thirdhand smoke for two months resulted in further molecular damage to the liver and at four to six months, caused even more damage. They found additional stress hormones in the brains of the mice at two months, four months and six months, which eventually caused immune fatigue in the mice.

Manuela Martins-Green, who led the research, said thirdhand smoke “is a stealth toxin, a silent killer. Contaminants can be absorbed through the skin and through breathing. Although our research was not done on humans, people should be aware that hotel rooms, cars and homes that were occupied by smokers are very likely to be contaminated with THS.”

This story was originally published September 14, 2017 at 7:24 PM with the headline "Should you sit on a cigarette smoker’s couch or let your toddler crawl on it?."