In a new study, researchers found that people can carry hazardous compounds from cigarette smoke that cling to their bodies and clothes and then release them into non-smoking environments.
The compounds can then expose people nearby to cigarettes’ adverse effects.
The research was conducted by a team at Yale University and elsewhere.
For the last decade, third-hand smoke has been described as the residual contamination from cigarette smoking that adheres to walls and other surfaces in places where smoking has previously occurred.
For example, hotels and rental car companies have implemented smoking restrictions to limit this contaminating odor from their rooms and cars.
The new study shows for the first time that humans can bring large quantities of this third-hand smoke into indoor, non-smoking environments.
The research suggests that even if someone is in a room where no one has smoked, that person could still face exposure to many of the hazardous chemical compounds that make up cigarette smoke, depending on who else had entered the room or previously visited it.
In the study, the team brought highly sensitive analytical instrumentation into a movie theater to track thousands of compounds, present as either gases or particles, over the course of a week.
A diverse range of volatile organic compounds found in tobacco smoke spiked dramatically when certain audiences arrived for the movies.
These increases were minor for G-rated movies, while audiences for R-rated movies—which included moviegoers more likely to smoke or to be exposed to smoke—consistently released much larger quantities of these compounds into the theater.
The relative proportions of these emitted compounds confirmed that they were from slightly aged cigarette smoke.
The amount of these hazardous and reactive gases wasn’t trivial.
The gas emissions matched exposure to 1-10 cigarettes of secondhand smoke in a one-hour period.
These emissions and air concentrations peaked upon audience arrival and decreased over time, but not completely, even when the audiences left.
In many cases, the movie-goers left persistent contamination observable the following days in the unoccupied theater.
The researchers say that’s because the chemicals don’t remain entirely in the air, but also adsorb onto various surfaces and furnishings, just as it does with third-hand smoke contamination in places where smoking has occurred.
The researchers also found a predominance of nitrogen-containing compounds from cigarettes, which would have migrated from people to other indoor surfaces.
These results on the human transport of third-hand smoke now help to explain why previous studies had found notable quantities of nicotine on surfaces in numerous non-smoking environments.
The researchers emphasize that avoiding movie theaters is not the solution to avoiding third-hand smoke.
In fact, the theater used for the study is modern, large, and well-ventilated, which reduced the effect of the emissions on concentrations of hazardous compounds in the room.
In less well-ventilated spaces—such as public transit, bars, offices, and homes—similar third-hand smoke emissions would likely result in considerably higher concentrations of many of these compounds.
One author of the study is Drew Gentner, associate professor of chemical & environmental engineering at Yale University.
The study is published in Science Advances.
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