Cigarette smoking has long been linked to an increased risk of cancer in smokers and people exposed to cigarette fumes. Now, researchers are studying the effects of so-called third-hand smoke.
"Third-hand smoke is the accumulation of second-hand smoke on the environmental surfaces,” said Manuela Martins-Green, a cell biologist at the University of California, Riverside. “So, as the smoke is coming out of the ends of the cigarettes, it's then depositing on the sofas, the carpets, the clothing, the hair … all the surfaces … even if it's wood. And it's not just accumulating in the homes, [but] in the cars as well."
Young children are at particular risk for contact with third-hand smoke, Martins-Green said, as they crawl along the carpet and put their hands in their mouths.
And it's not a threat just in homes and cars, she added. Those toxic fumes can spread throughout a building via ventilation systems.
Martins-Green and her colleagues discovered that cigarette residues are easily absorbed into the body.
"And those chemicals are actually absorbed through the skin very rapidly,” Martins-Green said. “So they go in circulation and they go all over the body, and that's one thing you don't want."
Smoke and mice
Researchers studied the effects of third-hand smoke on mice, using smoke machines in the enclosures to simulate second-hand smoke.
They found the first signs of a health problem in the animals' livers, an increase in lipids or fats seen in people with pre-diabetes. They then measured the amount of glucose or blood sugar in the mice, and found that it, too, was elevated, as were levels of insulin, a hormone used by the body to convert glucose into energy.
Through exposure to the toxic chemicals in third-hand smoke, the mice had developed insulin resistance, a precursor to type 2 diabetes. The findings are published in the journal PLoS One.
Martins-Green said the process can start in childhood, and doctors are now seeing teenagers with elevated blood sugar.
"A very relevant aspect of our science … is that when you feed these mice high-fat diets like the teenagers and young adults eat, you know, these hamburgers and tacos and all these things laden with fat, that we find that the effects of the third-hand smoke make the situation — the disease situation — worse," she said.
Martins-Green is now leading an effort to look for a link between third-hand smoke and liver damage.