Movie theater study reveals the invisible effects of "thirdhand" cigarette smoke

Just being in a room with a smoker for one hour may be enough to expose you to the harmful effects of between one and 10 cigarettes' worth of second-hand smoke.

The revelations come from one of the first studies to look at exposure to "thirdhand" cigarette smoke — the miasma that smokers carry into environments where no one is smoking. The results suggest that avoiding people who are smoking is not enough to prevent exposure to the harmful combustion chemicals of cigarettes, and that new regulations for public spaces are needed.

In the new study, published in the journal Science Advances on Wednesday, researchers show that being around somebody who has smoked for an extended period of time may be as harmful as standing near someone who is smoking.

“These findings advance our understanding of the fate of chemicals from cigarette smoke and catalyzes, at least we hope, an important discussion about human exposure to thirdhand smoke off-gassing from people,” Drew Gentner, associate professor at Yale University, and an author on the study, says.

It is well-established that, during firsthand smoking (smoking the cigarette yourself) and secondhand smoking (being around someone who is smoking a cigarette), individuals are exposed to dangerous compounds that can damage the lungs — and even lead to lung cancer.

According to the CDC, secondhand smoke causes over 7,000 lung cancer deaths in non-smokers each year because they are inhaling the same substances as smokers.

But the new research suggests being inside a non-smoking room or smoke-free area alongside smokers may be enough to cause similar damage.

The health affects of thirdhand smoke are estimated to be five to 60 percent of the combined disease burden from secondhand smoke and thirdhand smoke exposure, the researchers say.

Nicotine's far-reaching effects

The study takes place in an unusual environment, but one with which we are all familiar: A movie theater. Movie theaters in the United States have been smoke free for decades.

But even in a non-smoking, well-ventilated movie theater where no one was actively smoking or had been smoking, the scientists found significant concentrations of nicotine and other smoke-related chemicals, including formaldehyde, benxene, and acrolein.

The reason? These toxic compounds had travelled in to the movie theater via the smokers' bodies, hair, and clothing. Once inside the theater, these compounds were released into the air, and rubbed into the fabrics of the seats, armrests, and other theater furniture. And they stuck around, long after the audience let out.

“These emission and air concentrations peak upon audience arrival and decrease over time, but not completely,” Gentner says.

“Even when the audiences left, in many cases, they left a persistent contamination observable the following days in the unoccupied theater," he says.

"The really surprising thing was the magnitude of this effect."

According to Gentner, the chemicals' sticking power stems from the fact they don't just stay in the air — instead, they may condense onto the room's surfaces. Some compounds stick around more than others, so there may be some variation among different to cigarette brands.

The results offer solid evidence why nicotine and other smoking-related chemicals have previously been found in non-smoking environments. The smokers themselves are the unwitting mules for these harmful substances.

“Even though the theater is a non-smoking facility, the transport of these compounds into the theater, via people, provides an explanation for why noticeable levels of nicotine have been found in non-smoking spaces in previous literature,” Genter says.

“If we look at some of our cleanest or supposedly cleanest environments, pediatric, neonatal care units', prior work has actually shown that they find nicotine on surfaces in some of those environments.”

Still, the sheer scale of the problem was a surprise, Gentner says. These data suggest that non-smokers who share smoke-free environments with those who do smoke are exposed to as many as 10 cigarettes-worth of secondhand smoke an hour.

“The really surprising thing was the magnitude of this effect and how it dramatically changed the composition of both the gasses and particles in the room, and left persistent contamination,” Gentner says.

It is impossible to say whether having more smokers in a room, and how recently they smoked, has an effect on the level of off-gassing in a non-smoking room, Gentner says.

“It's a subset of individuals that would be driving this effect,” he says.

No-smoking zone?

Back in the movie theater, the data reveal that you are most likely to be exposed to thirdhand smoke during late-night and R-rated films, likely driven by the higher number of people of legal smoking age who attend these films.

Concentration would increase in smaller and not well ventilated locations.

“The movie theater was a great case study location and not a particularly bad location for exposure to thirdhand smoke since it was a large well ventilated indoor environment,” Gentner says.

“But I think if we were to speculate... maybe a club or a bar, really a place where people are smoking immediately before entry. It gives them sort of a very large dose. And then obviously the more people you have doing this the larger the impact.”

“We want [smokers] to be aware that the chemicals from their cigarettes do not stay entirely outside."

Ultimately, the research suggests the regulations we have now may not be enough to minimize potential damage from smoking for nonsmokers. Restrictions like not allowing smoking within 25 feet of a building, may help combat the problem, Gentner says. More research could offer other solutions, he says. In the meantime, smokers themselves can be more aware of the hidden effects they have on others who don't share their habit.

“We want [smokers] to be aware that the chemicals from their cigarettes do not stay entirely outside,” Gentner says.

“They themselves remain a source of those chemicals when they go back inside, which may be particularly important in the presence of small children or sensitive populations.”

“It's our hope that the work will generate much needed discussions about thirdhand smoke and that the research and policy will continue to evolve from those discussions.”

Abstract: The contamination of indoor nonsmoking environments with thirdhand smoke (THS) is an important, poorly understood public health concern. Real-time THS off-gassing from smokers into a nonsmoking movie theater was observed with online and offline high-resolution mass spectrometry. Prominent emission events of THS tracers (e.g., 2,5-dimethylfuran, 2-methylfuran, and acetonitrile) and other tobacco-related volatile organic compounds (VOCs) coincided with the arrival of certain moviegoers and left residual contamination. These VOC emission events exposed occupants to the equivalent of 1 to 10 cigarettes of secondhand smoke, including multiple hazardous air pollutants (e.g., benzene and formaldehyde) at parts-per-billion concentrations. Nicotine and related intermediate-volatility nitrogen-containing compounds, which vaporized from clothes/bodies and recondensed onto aerosol, comprised 34% of observed functionalized organic aerosol abundance. Exposure to THS VOC emission events will be considerably enhanced in poorly ventilated or smaller spaces in contrast with a large, well-ventilated theater—amplifying concentrations and potential impacts on health and indoor chemistry.