As we all know, smokers continue to smell like smoke long after they drink their last cigarette. But it’s not just a scent; this “third-hand smoke” contains many of the harmful compounds in cigarette smoke and lingers on clothing, bodies and surfaces. We have now confirmed that smokers can take third-hand smoke with them into smoke-free environments.
An article in Science Advances this week reports that third-hand smoke has been found in a movie theater that has been smoke-free for 15 years. Each time a new audience poured into the cinema, chemist Roger Sheu and his colleagues discovered a sharp spike in tobacco-related pollutants. They estimated that the public was exposed to the equivalent of one to 10 cigarettes of secondhand smoke.
Regulations preventing indoor smoking have done a great job of limiting exposure to cigarette smoke, Sheu and his colleagues write, but third-hand smoke is a “major route of exposure” to the hazardous compounds found in tobacco. With global smoking rates still above 20 percent and public health experts agreeing that there is no safe level of exposure to tobacco smoke, it poses a “great risk to non-smokers,” they say.
Third-hand smoke occurs when the hazardous substances in tobacco settle on surfaces – including smokers’ clothes and bodies, as well as surfaces such as furniture – and then mix with dust or other particles. People are exposed to these chemicals by inhaling dust or vaporized gases or by touching the contaminated surfaces.
Third-hand smoke contamination has been found in smokers’ clothing, breath, and homes. But can it be taken in a smoke-free environment? Researchers had thought it likely, but Sheu and his colleagues wanted to gather evidence to confirm and see how bad the exposure was.
They chose a cinema in Mainz, Germany, which was well ventilated and monitored the tobacco-related substances in the air through multiple showings of a few different films. Smokers would have had to drink their cigarettes outside and then take a few minutes to enter the cinema, making third-hand smoke the only possible source of these compounds.
Bringing the outside in
Sheu and his colleagues found that the cinema had relatively high concentrations of 35 different compounds derived from tobacco smoke. These concentrations peaked when new audiences entered the cinema at the beginning of a showing. The spikes were much worse for adult-oriented action movies than for family movie screenings, suggesting that certain audience demographics were bringing in more third-hand smoke.
Over the course of each film, the third-hand smoke compounds started to decline, partly because these compounds tend to “degas” less over time, and partly because of the cinema’s ventilation. But there were more spikes towards the end of some films, when audiences left the theater — possibly caused by clothes shifting when people get up or people breathing slightly faster when they started moving again, Sheu and his colleagues suggest. People’s exposure to the pollutants would differ depending on where in the cinema they sat — for those sitting next to a smoker, exposure would have been relatively high.
Other public areas may have a much higher contamination rate. A large, well-ventilated movie theater could even be at the lower end of the exposure, while people in public transportation, classrooms and offices often depart from small spaces that aren’t necessarily well-ventilated. And for parents who smoke diligently outdoors, the likelihood of them taking pollutants indoors should be a concern.
It’s difficult to determine exactly how many health risks come from third-hand smoke, but previous research has shown that it contributes to anywhere from five to 60 percent of the total disease burden caused by combined exposure to secondhand smoke and third-hand smoke. smoke. Children are especially vulnerable.
Trying to figure out how bad exposure to third-hand smoke is will take a lot more work. Sheu and his team point to the need for more controlled research on exactly how smokers emit pollutants, answering questions such as how much comes out of their clothes compared to their bodies and how the contamination changes over time after they finish. are smoking. Work on vaping will also be important in understanding whether e-cigarettes can introduce a new and different kind of third-hand smoke.
scientific progress2020. DOI: 10.1126/sciaadv.aay4109 (About DOIs).