Policies that restrict smoking within a set distance of a building may need to be extended Jan Enkelmann/Getty Images

You can breathe in harmful chemicals from tobacco use even in non-smoking venues because they are carried on smokers’ bodies and clothes.

Third-hand smoke – the residue from cigarette fumes that sticks to surfaces and then wafts back into the air – has previously been found indoors in places where smoking is allowed.

To find out if third-hand smoke also pollutes non-smoking venues, Drew Gentner at Yale University and his colleagues monitored the air quality in a non-smoking cinema in Germany for four days, after first flushing it with clean air. Smoking is banned inside cinemas and other public places in Germany.


They observed spikes of tobacco chemicals in the air just after audiences arrived, which decreased over time but didn’t go away completely. The polluting substances were probably brought in on the bodies and clothes of people who had recently smoked cigarettes or been near smokers, says Gentner.

They observed larger spikes during movies rated for those aged 16 and above, most likely because the audiences were older and had greater tobacco exposure than those attending movies suitable for younger people, says Gentner.

The amount of tobacco chemicals that people watching the films aimed at older teens and adults were exposed to per hour was equivalent to that inhaled while sitting directly next to someone as they smoke up to 10 cigarettes.

Health impacts

The researchers detected a total of 35 tobacco chemicals in the cinema, including known hazards such as benzene, formaldehyde and acrolein. We still don’t know the long-term health impacts of breathing in third-hand smoke, but most public health experts agree that there is no safe level of tobacco smoke exposure, says Gentner.

The findings suggest that policies designed to protect non-smokers from second-hand smoke, like banning people from smoking within set distances of buildings, may need to be extended to protect people from third-hand smoke as well, says Gentner.

Moreover, parents who smoke outside their homes to avoid exposing their children to harmful tobacco chemicals should be aware that “the chemicals from their cigarettes do not stay entirely outside”, Gentner says, and parents “remain a source of those chemicals when they go back inside”.

Read more: Every 50 cigarettes smoked cause one DNA mutation per lung cell

He and his colleagues are hoping to measure the extent of third-hand smoke contamination in other indoor environments, as well as third-hand vapour from e-cigarettes.

Journal reference: Science Advances, DOI: 10.1126/sciadv.aay4109

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