We often learn about the harmful effects of secondhand smoke or smoking directly — but rarely do we hear about what’s known as “thirdhand smoke” (THS), exhaled smoke that makes its way onto surfaces in our homes, cars, or even workplaces. Getting a whiff of a friend’s jacket reeking of that stale cigarette smell could be just as bad for you as inhaling someone’s cigarette smoke, drifting over from outside the bar, research has shown.

Now, new research investigates how thirdhand smoke can impact our bodies long-term, finding that it can contribute to the development of Type 2 diabetes. In the study, published in PLOS ONE, the researchers found that exposure to thirdhand smoke resulted in insulin resistance — a condition in which the body is able to produce insulin, but doesn’t use it properly. Insulin resistance is a precursor to Type 2 diabetes because glucose begins to build up in the blood.

Thirdhand smoke is often more subtle than secondhand smoke, making it more difficult to avoid — creeping into our clothes after a night out, or even into non-smoking hotel rooms. “Thirdhand smoke is the accumulation of secondhand smoke on environmental surfaces,” the authors write in the abstract. “THS is found on the clothing and hair of smokers as well as on surfaces in homes and cars of smokers. Exposure occurs by ingestion, inhalation and dermal absorption.” They go on to note that children are often at a higher risk of being exposed to thirdhand smoke because “they crawl on the floor, touch parents’ clothing/hair and household objects.”

In the study, the researchers exposed mice cages to secondhand smoke using a smoking machine. During the secondhand smoking, the cages were not filled with mice; but afterwards, a group of mice were introduced into them. A second group of mice, the control group, were not exposed to thirdhand smoke. The mice of the first group were either given a standard diet, or a “Western diet” — the typical high-fat diet of your average American. It turned out that mice exposed to thirdhand smoke who were also fed a Western diet had more oxidative stress and insulin resistance, but gained less weight than the control group, as smoking cigarettes curbs appetites.

This isn’t the first study to measure the potential damage of thirdhand smoke; a 2013 study found that THS could lead to DNA damage, among other health issues. But it might spur doctors to educate patients about the dangers of not only regular smoking — but also the smoking traces left in the environment.

“If confirmed in humans, our study could greatly impact how people view exposure to environmental tobacco toxins,” Manuela Martins-Green, a professor of cell biology and neuroscience at UC Riverside and lead author of the study, said in the press release. “Children and the elderly are especially vulnerable to THS and its impact on health. Because infants frequently crawl on carpets and touch objects exposed to exhaled smoke, they are at high risk for THS exposure. The elderly are at high risk simply because older organs are more susceptible to disease.”

Source: Adhami N, Starck S, Flores C, Green M. A Health Threat to Bystanders Living in the Homes of Smokers: How Smoke Toxins Deposited on Surfaces Can Cause Insulin Resistance. PLOS ONE, 2016.