What Is Third-Hand Smoke? Skin Exposure 'Mimics' The Impacts Of Actual Smoking

A team of researchers has found another means by which smoking may impact people's health. It's via third-hand smoke, which may induce skin diseases and even "mimic" the harmful impacts of actual smoking.

It is widely known that smoking is not good for health, and so is exposure to second-hand smoke. But perhaps not everyone is aware of third-hand smoke (THS).

THS is made up of the residual tobacco smoke pollutants that stay on dust and surfaces after smoking tobacco, the researchers explained in their paper, published in eBioMedicine. It may be "re-emitted into the gas phase; or react with oxidants and other compounds in the environment to yield secondary pollutants."

According to the researchers, there is a "general lack of knowledge" on the exact health impacts of exposure to THS on human health.

For their work, the researchers conducted a clinical investigation with 10 healthy, non-smoking subjects between 22 to 45 years old. During the three-hour trials, the subjects wore clothes that were either clean or laced with THS. And each hour, they exercised on a treadmill for about 15 minutes to induce sweating and "increase dermal uptake."

"The order of the exposures was randomized and separated by 20-30 days," the researchers noted. "Each participant received both exposures."

Plasma and urine samples were collected prior to the exposure as well as three and eight hours after, when they woke up the next morning and 22 hours after the exposure.

Indeed, the researchers found that those who were exposed to THS had elevated levels of "urinary biomarkers of oxidative damage to DNA, lipids and proteins." These even stayed elevated even after they were no longer exposed.

"We found exposure of human skin to THS initiates mechanisms of inflammatory skin disease, and elevates urinary biomarkers of oxidative harm, which could lead to other diseases, such as cancer, heart disease and atherosclerosis," one of the study authors, Shane Sakamaki-Ching, who graduated from the University of California-Riverside (UCR), said in the university news release.

The impacts are similar to or "mimics" the ones observed in actual cigarette smokers, the researchers said. And while the exposures during the study were brief, and thus were "unlikely" to cause skin disease, the markers that the researchers found were "associated with early-stage activation of contact dermatitis, psoriasis and other skin conditions."

Skin diseases such as allergic contact dermatitis and psoriasis have been linked to cigarette use, researchers said.

"These results demonstrate acute dermal THS exposure is not only harmful to humans, but also has the potential to initiate diseases," they wrote.

This sheds light on just how THS may impact people, perhaps even without knowing it.

"If you buy a used car previously owned by a smoker, you are putting yourself at some health risk. If you go to a casino that allows smoking, you are exposing your skin to THS," the study's corresponding author, Prue Talbot of UCR, said in the news release. "The same applies to staying in a hotel room that was previously occupied by a smoker."

As such, the results of the study may help doctors in diagnosing people who have a history of exposure to THS and also guide policies in limiting THS exposures.