Third-hand smoke may be a cancer danger

BERKELEY, Calif., Feb. 9 (UPI) -- Third-hand smoke, the residue from tobacco that clings to surfaces, reacts with an indoor air pollutant to produce carcinogens, U.S. researchers say.

Corresponding author Hugo Destaillats, a chemist at the Lawrence Berkeley National Laboratory in California, and colleagues report that in laboratory tests using cellulose as a model indoor material exposed to smoke, levels of newly formed tobacco-specific nitrosamines detected on cellulose surfaces were 10 times higher than those originally present in the sample following exposure for three hours to a "high but reasonable" concentration of nitrous acid.

Unvented gas appliances are the main source of nitrous acid indoors, while most vehicle engines emit some nitrous acid that can infiltrate the passenger compartments, the authors said.

"The burning of tobacco releases nicotine in the form of a vapor that adsorbs strongly onto indoor surfaces, such as walls, floors, carpeting, drapes and furniture. Nicotine can persist on those materials for days, weeks and even months," Destaillats said in a statement.

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

The findings are published in the Proceedings of the National Academy of Sciences.