Most people are probably familiar with the concept of second-hand cigarette smoke. Standing in the general vicinity of someone who is smoking can lead to unhealthy or even fatal tobacco exposure. Now scientists are warning of the dangers of third-hand smoking, showing even smoke-free locations may not be entirely safe.
The experience of sitting next to a heavy smoker and inhaling the stink from their clothes is common, but you may consider it more an annoyance than a health concern. However, Dr Drew Gentner and colleagues at Yale thought it better to check. They measured the concentrations of tobacco-related volatile organic compounds (VOCs) in a non-smoking cinema as patrons, both smoking and non-smoking, came and went.
In Science Advances they report: “These VOC emission events exposed occupants to the equivalent of 1-10 cigarettes of secondhand smoke, including multiple hazardous air pollutants (eg. benzene and formaldehyde) at parts-per-billion concentrations.” Nicotine was by far the most common molecule. Moreover, they add, that's not the worst of it. The movie theater, in this case, was large and well-ventilated. Conditions could be considerably worse in tighter situations.
The authors are not the first to consider third-hand smoke's dangers. They note previous studies that have shown its effects on cultured cells and live mice. As you might imagine, none of these are good. Similarly, smoker's homes have been found to contain a lot of VOCs even when they are not currently smoking.
The circumstances Gentner investigated, however, are relevant to far more people, and hadn't previously been examined.
The study was done in Germany, where smoking in cinemas has been banned for 15 years, easily long enough to remove any legacy of people lighting up inside. The venue's air intakes were far away from potential sources of smoke, yet 35 different VOCs associated with tobacco were detected over a four-day period. Concentrations peaked at the start of films as patrons arrived, carrying their smoke particles with them. The type of film made a difference, with those that appealed to children and their parents having smaller VOC spikes than horror movies.
Identifying the problem is one thing, addressing it another. There would be serious social and civil liberties consequences if people are banned from certain indoor locations because they carry tobacco on their clothes, not to mention the difficulties of enforcement.
Discouraging teenagers smoking early in life would certainly help, even if only in the long term. Earlier this week a study in Addiction measured the impact on teenagers of being close to tobacco outlets. Its finding that proximity did not affect whether someone smoked, but did increase the number of cigarettes consumed by smokers, suggests limiting outlet locations might help.