Cigarettes may be dangerous long after the smoke has cleared and fears are today growing over the threat of ‘third hand smoke’.

The problem, says Hugo Destaillats, is that nicotine in tobacco smoke sticks to walls, floors, ceilings, anything it touches basically. In tests at the of the Lawrence Berkeley National Lab in the United States, Destaillats and his colleagues showed that this residue reacts with nitrous acid to form seriously carcinogenic compounds.

“Our study shows that when this residual nicotine reacts with ambient nitrous acid it forms carcinogenic tobacco-specific nitrosamines or TSNAs,” says Destaillats, of Berkeley Lab (press release). “TSNAs are among the most broadly acting and potent carcinogens present in unburned tobacco and tobacco smoke.”

In tests on a smoker’s truck the team found “substantial” amounts of cancer-causing TSNAs. Then in experiments designed to model indoor tobacco smoking they found that these TSNAs were produced in high quantities when residue-laden surfaces are exposed to nitrous acid, which is produced by equipment such as gas cookers.

Third-hand smoke, they write in Proceedings of the National Academy of Sciences USA, “represents an unappreciated health hazard”.

And don’t think you can get away with smoking outside either.

“Smoking outside is better than smoking indoors but nicotine residues will stick to a smoker’s skin and clothing,” says study author Lara Gundel (press release). “Those residues follow a smoker back inside and get spread everywhere.

“The biggest risk is to young children. Dermal uptake of the nicotine through a child’s skin is likely to occur when the smoker returns and if nitrous acid is in the air, which it usually is, then TSNAs will be formed.”

Are any smokers out there actually going to quit as a result of this finding though?

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