As we all know, smokers continue to smell of smoke long after they’ve finished their last cigarette. But it’s not just a smell; this “third-hand smoke” has many of the harmful substances in cigarette smoke, and it lingers on clothes, bodies, and surfaces. Now we’ve confirmed that smokers can bring third-hand smoke into smoke-free environments with them.

A paper in Science Advances this week reports finding third-hand smoke in a cinema that has been smoke-free for 15 years. Every time a new audience filed into the cinema, chemist Roger Sheu and his colleagues detected a sharp spike in tobacco-related pollutants. They estimate that the audiences were exposed to the equivalent of between one and 10 cigarettes’ worth of second-hand smoke.

Lingering contaminants

Regulations preventing indoor smoking have done a great job of limiting exposure to cigarette smoke, write Sheu and his colleagues, but third-hand smoke is a “major exposure pathway” to the hazardous substances found in tobacco. With worldwide smoking rates still above 20 percent and public health expert agreement that there is no safe level of exposure to tobacco smoke, this represents a “major risk for nonsmokers,” they say.