Scientists warn of new risk from cigarettes – third-hand smoke

Published on Monday 8 February 2010 21:40

NICOTINE residue on clothing, furniture and wallpaper can react with a common indoor pollutant to generate dangerous cancer chemicals, scientists claim.

The findings raise concerns about "third-hand smoke", the name given to nicotine residues that cling to surfaces for months.

They are also said to raise doubts about the safety of "e-cigarettes" – battery-powered devices which provide a nicotine "hit" without the risk of cancer.

Experiments at Lawrence Berkeley National Laboratory in California showed that nicotine combines with nitrous acid in the air to produce highly carcinogenic chemicals called tobacco-specific nitrosamines (TSNAs).

Nitrous acid is a common indoor pollutant chiefly generated by unvented gas appliances.

In the tests, contaminating cellulose surfaces with nicotine and exposing them to "high but reasonable" amounts of nitrous acid boosted levels of newly formed TSNAs ten-fold.

Substantial concentrations of TSNAs were also found on the inside surfaces of a lorry belonging to a heavy smoker.

Dr Hugo Destaillats, one of the Lawrence Berkeley researchers whose findings are reported in the journal Proceedings of the National Academy of Sciences, said: "The burning of tobacco releases nicotine in the form of a vapour that adsorbs strongly on to indoor surfaces, such as walls, floors, carpeting, drapes and furniture. Nicotine can persist on those materials for days, weeks and even months.

"Our study shows that when this residual nicotine reacts with ambient nitrous acid, it forms carcinogenic tobacco-specific nitrosamines or TSNAs."

Although nicotine in itself is highly toxic, other chemicals released by burning tobacco are generally believed to pose the greatest health hazard from smoking.

Dr Kamlesh Asotra, from the University of California's Tobacco-Related Disease Research Programme, which funded the research, said: "These results may be just the tip of the iceberg."

Smoking outdoors is not the answer to the problem, according to the researchers.

Co-author Dr Lara Gundel, another member of the Lawrence Berkeley team, said: "Nicotine residues will stick to a smoker's skin and clothing. Those residues follow a smoker back inside and get spread everywhere."

She added: "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."

The scientists said the findings also raised a question mark over the safety of "e-cigarettes".

The devices work by vaporising nicotine inside the tube of a plastic cigarette which can then be inhaled.

Since no tobacco is burned, e-cigarettes are not covered by smoking bans and are considered safe.

The researchers are now looking into the development of biomarkers to track exposure to TSNAs, and conducting further work on nicotine and nitrous acid reactions.