Offering alarming new evidence of dangers of inhaling second-hand smoke, a new study shows that non-smoking employees absorb a potent carcinogen not considered safe at any level while working at places where they have to breath tobacco from customers and coworkers.

In the study to be published in August 2007 edition of the American Journal of Public Heath, researchers say they have found that the carcinogen, NNK, is found in the body only as a result of using tobacco or breathing second-hand smoke.

Researchers at the Multnomah County Health Department and Oregon Department of Human Services report that elevated levels of NNK showed up in the urine of non-smoking employees shortly after they encountered secondhand smoke during their shifts.

Moreover, levels of NNK, which is known to cause lung cancer, increased by six per cent for each hour of work.

This is the first study to show increases in NNK as a result of a brief workplace exposure, and that levels of this powerful carcinogen continue to increase the longer the person works in a place where smoking is permitted.

"NNK is a major cancer causing agent from tobacco products and workers should not have to be exposed to any dose of this very dangerous chemical," said Michael Stark of the Multnomah County Health Department and the study's lead author.

The study comes ahead of a week-long conference on implementing the international tobacco control treaty beginning in Bangkok, Thailand, beginning on June 30 and will give plenty of ammunition to the anti-smoking lobby to stress on quick implementation of the Framework Convention on Tobacco Control.