Concentrations of nicotine and smoking-related volatile organic compounds spiked when moviegoers entered a well-ventilated, non-smoking theater in Mainz, Germany, exposing them to the equivalent of between one and 10 cigarettes' worth of secondhand smoke over one hour, according to a study published in the March 6 issue of Science Advances.
This "thirdhand" tobacco smoke residue carried on smokers' clothing and bodies resulted in especially high concentrations of smoking-related volatile organic compounds like toxic benzene and formaldehyde during late-night and R-rated films, when attendance drops but the proportion of adults climbs.
The results of this first study demonstrating real-time thirdhand smoke emissions in an indoor nonsmoking environment may apply broadly to other indoor environments and suggest that current non-smoking regulations may not be enough to minimize the thirdhand cigarette smoke that nonsmokers breathe.
"This real-world study clearly demonstrated considerable off-gassing of thirdhand smoke from people into a non-smoking environment," said Drew Gentner, an assistant professor of chemical and environmental engineering at Yale University and an author of the study. "Based on these results, it is our hope that the work will generate much-needed discussions about thirdhand smoke and that research and policy will continue to evolve from those discussions."
Decades of research have armed the scientific community with a solid understanding of harmful smoking health effects — no level of exposure is considered safe. But while regulations have decreased smoking in public, not everyone has stubbed out their cigarettes for good. Twenty-two percent of people worldwide still light up, with pollutants from tobacco smoke in the form of evaporated gases and dusts settling on surfaces and posing an insidious health threat, especially for infants and children.
While previous studies have shown that nicotine accumulates on clothing and demonstrated that volatile organic compounds linger in a smoker's home long after the smoke clears, none have illustrated how thirdhand smoke delivers these compounds to nonsmoking environments.
"People spend approximately 90% of their time indoors, and the atmospheric chemistry community has been increasingly directing their attention to understanding the chemical composition of indoor environments and the driving factors of indoor air quality in the present day," said Gentner. "My group is interested in understudied sources of air pollutants that are becoming increasingly important as successful policy has reduced emissions and human exposure to traditional sources of air pollutants, such as motor vehicles."
In order to observe firsthand how the chemicals in cigarette smoke quietly dissipate from smokers' bodies into a nonsmoking indoor atmosphere, Roger Sheu, a Ph.D. student at Yale University and the lead author on the study, and colleagues used mass spectrometry to measure tracers of tobacco smoke as guests took their seats prior to five G-rated and ten R-rated films. Since movie theaters are well-ventilated, regularly cleaned, and free from other sources of indoor emissions like cooking or candles, it was the perfect location.
"We had a really great set-up where we were conveniently sampling from the exhaust air duct right after the air left the theater, so we were able to measure the average chemical composition of the air in the theater without disturbing the occupants," said Gentner.
As adult audience members filed into the theater, readings of the key gas-phase tobacco smoke tracers 2,5-dimethylfuran, 2-methylfuran, and acetonitrile surged. And while the unsuspecting moviegoers laughed and gasped along with the onscreen drama, they also inhaled benzene, formaldehyde, and plenty of nicotine — by far the most abundant compound detected.
"We did not expect the off-gassing of chemicals from residual tobacco smoke on people to be such a prominent source of reactive chemicals into the room," said Gentner. "These results, along with past surface measurements of nicotine in non-smoking environments, indicate this is occurring frequently around us."
Even after the audience left the room, Gentner notes that contaminants would have remained on the theater's surfaces, some of which may react with other chemicals to further impact air quality and human health. While most chemicals the researchers measured are associated specifically with tobacco cigarettes, electronic cigarettes may have contributed emissions as well.
"Electronic cigarettes are not sources of most of the compounds we report here, and we did not observe enhancements in chemicals specifically concentrated in vaping emissions," said Gentner. "However, we identify thirdhand vaping as a key area for future research. For example, we did see a lot of nicotine, which is present in vaping products. So nicotine from e-cigarettes could have also been transported by people and off-gassed in the theater."
In addition to exploring the impact of thirdhand vaping, Sheu and colleagues hope to further test both secondhand and thirdhand smoke in a controlled environment, comparing different types and brands of tobacco. They emphasize that 2-methylfuran and 2,5-dimethylfuran may be used to determine the presence and age of thirdhand smoke contamination in future studies.