Thirdhand smoke wafting off moviegoers hurts air quality in theaters

The pollution is released from tobacco residue on people’s bodies and clothing

movie theater

Audience members who have been around cigarette smoke can contaminate the air of nonsmoking movie theaters with tobacco residue left on their bodies and clothing, a new study finds.

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“Nonsmoking” doesn’t necessarily mean smoke-free.

A new experiment monitoring airborne contaminants inside a nonsmoking theater indicates that hazardous cigarette fumes wafting off moviegoers can degrade air quality. Those pollutants include the carcinogen benzene (SN: 4/26/13) and toxic aldehydes, such as acrolein, formaldehyde and acetaldehyde (SN: 7/27/16).

Such thirdhand smoke, released from tobacco residue on people’s skin, hair and clothing, is an important public health concern, researchers report online March 4 in Science Advances. But it’s not yet clear whether the exposure levels seen in this experiment are enough to cause serious health problems, or how much people can protect themselves from thirdhand smoke in public (SN: 11/10/14). 

The experiment took place in a well-ventilated, nonsmoking theater in Mainz, Germany, which showed four to five films per day. Over four days, the researchers used a mass spectrometer to take a chemical inventory of pollutants exiting the theater’s ceiling vents. 

These measurements revealed that concentrations of tobacco-related compounds in the theater spiked when new crowds entered — especially for R-rated flicks and late showings, perhaps because audience members were more likely to have been smoking or hanging around smokers before arrival. Previous research has found traces of thirdhand smoke in supposedly nonsmoking areas, but this is the first study to catch people in the act of transferring the pollution.

To judge the severity of this pollution, environmental engineer Drew Gentner of Yale University and colleagues compared observed levels of thirdhand smoke components to the amounts of those chemicals that would have been emitted if someone were smoking inside the theater. 

During R-rated films, audiences were exposed to one to 10 cigarettes’ worth of various hazardous compounds per hour — though the exact amount that each audience member might inhale would depend on their position relative to the folks emitting pollutants. On average, audiences were exposed to eight cigarettes’ worth of benzene and four cigarettes’ worth of acetaldehyde per hour. Those differences in exposure levels arise because some chemicals detach from people’s clothes and bodies more easily than others. 

“This is clearly showing that we’re getting another exposure to tobacco smoke chemicals in places where we just don’t expect them,” says Peter DeCarlo, an air quality scientist at Johns Hopkins University not involved in the work. “The next step is really understanding what that means in terms of health,” he says. The relative risk for each person will depend on their moviegoing habits and the air pollution they encounter elsewhere in daily life. 

Even if thirdhand smoke does pose a significant risk to moviegoers, theaters aren’t likely to ban smokers or their friends and family from buying tickets. 

Rather, the findings of this experiment may inform how smokers behave at home — where thirdhand smoke is expected to be more potent, due to more confined spaces and poorer ventilation, says Hugo Destaillats, an environmental chemist the Lawrence Berkeley National Laboratory in California not involved in the study. People might think twice about smoking in the house, even when no one else is around, if they’re aware of the risks that smoke poses even after a cigarette is stubbed out. 

Previously the staff writer for physical sciences at Science News, Maria Temming is the assistant managing editor at Science News Explores. She has bachelor's degrees in physics and English, and a master's in science writing.

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