Exposure to “third-hand smoke” – residue left on carpets, clothing, and furniture – appears to increase the risk of liver damage and diabetes in mice.
Cigarette smoke residue causes a cocktail of poison to build up on surfaces and clothing. It is believed that such toxins resist removal by industrial detergents.
To investigate the potential health risks of third-party smoke, Manuela Martins-Green of the University of California, Riverside, and her team exposed curtains, upholstery, and carpets to amounts of smoke similar to those used by the U.S. Environmental Protection Agency on smokers’ homes.
They then exposed cage mice to segments of these substances for up to six months and took brain, liver and blood samples at various intervals.
After one month, these mice saw an increase in inflammatory molecules in their blood and liver by about 50 percent compared to control mice that were not exposed to the substances.
Two months later, the team found increased cell damage in the rodents’ liver and brain. After four months, the cortisol level had increased by 45 percent compared to the controls. High levels of cortisol have been linked to weight gain and a weakened immune system.
After four months, mice exposed to the smoky substances increased their fasting blood sugar and insulin levels by 30 percent – both measures increased the risk of diabetes in mice. These values were even higher after six months.
First second Third
As always, it is difficult to apply the results to humans. The results are meaningful, biologically plausible, and important, says Taylor Hays of the Mayo Clinic in Rochester, Minnesota, but the effects on humans have yet to be studied. “It’s important to note that one-time or occasional exposure won’t have any measurable impact on humans,” he says.
Martins-Green believes that third-hand smoke is just as dangerous as first-hand and second-hand smoke. She warns parents not to assume that only smoking in their child’s absence or only smoking outdoors will protect their children from the harmful effects of smoke. “Cotton shirts are a terrible sink,” she says. “A parent goes outside to smoke, but then crawls into bed and reads a book to their child.”
Children are particularly vulnerable to third-hand smoke because they breathe faster than adults and are in closer contact with household surfaces, says Jonathan Winickoff of Massachusetts General Hospital, whose team coined the term “third-hand smoke”. He says their effective doses can be 20 times higher than that of adults. “
One thing that Hays, Winickoff, and Martins-Green all agree on is that third-hand smoke is difficult to banish. “To get rid of it in the wall boards, you have to get rid of the wall boards,” says Winickoff.
Journal reference: Clinical science, DOI: 10.1042 / CS20171053
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