The results of a small study indicate that third-hand smoke (THS)—the incinerated particles of smoke that settle on clothing and other surfaces—could elevate biomarkers associated with inflammation. These findings mirror changes noted in cigarette smokers, the authors say.
The University of California, Riverside researchers note that THS can remain on indoor surfaces for months or years, causing potentially harmful exposure to both smokers and non-smokers. The study was published in The Lancet’s ebiomedicine.
“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,” said researcher Shane Sakamaki-Ching, PhD, in a press release.
They studied 10 healthy non-smokers between 22 and 45 years of age, who were asked to wear clothing exposed to third-hand smoke for three hours. Every hour, the volunteers exercised on a treadmill for 15 minutes, so that additional THS particles were absorbed through the skin via perspiration.
After analyzing blood and urine samples, the researchers found elevated biomarkers relating to DNA oxidative damage, as well as changes in blood protein levels. These changes persisted for up to 22 hours. A similar analysis of the same volunteers wearing clean clothing and following the same protocol did not identify any changes in these samples.
"Our third-hand smoke exposures were brief, did not cause skin irritation, and were unlikely to induce skin disease, nevertheless markers associated with early-stage activation of contact dermatitis, psoriasis, and other skin conditions were elevated," the researchers wrote.
Dr. Sakamaki-Ching added that the research underscores the idea that dermal exposure to THS could lead to molecular initiation of inflammation-induced skin diseases.
Further studies are planned.
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