Identified in a Nonsmoking Classroom: A New Avenue for Exposure to Third Hand Smoke
Researchers measuring air in an unoccupied, nonsmoking classroom found that almost 30% of the tiny particles in it were associated with residue of so-called thirdhand smoke, a finding that reveals a whole new route by which people can be exposed to smoke from tobacco products. Subsequent laboratory experiments performed using cigarette smoke confirmed the classroom findings, regarding the ability of third hand smoke (THS) residue to travel far from its original source. The findings may help inform non-smoking policies for public spaces. The negative health effects of secondhand smoke are well-known, yet THS - which humans encounter involuntarily through interactions with chemical residues left behind on clothing, furniture or other indoor surfaces, following smoking - has received little attention. Thus, the mechanisms of human THS exposure have remained poorly understood. Peter F. DeCarlo and colleagues measured aerosol composition inside a nonsmoking, unoccupied classroom that was well-ventilated (they also took measurements of air outside this classroom's building). They alternated measurements every four minutes using a valve switching system to test for the possible uptake of THS in aerosol particles. Overall, 29% of the indoor particulate matter humans could breathe was associated with the residue of THS in the non-smoking university classroom, they report. It was likely delivered through the ventilation system, their studies go on to suggest, following chemical analyses. In addition to helping inform non-smoking policies, the authors say these results can add to discussions on policies governing the use of electronic cigarettes, which they would expect to expose humans to THS similarly.