Nonsmoking bar and restaurant workers had detectable levels of a known carcinogen in their bodies after working just one shift in a smoke-filled environment, Reuters reported June 29.

Researchers who studied a group of workers in Oregon found that they were more likely to have detectable levels of NNK, a toxin linked to lung cancer, in their bodies than those who worked in nonsmoking environments. Researchers compared workers at 52 establishments where smoking was allowed to 32 bars and restaurants where indoor smoking was banned. Workers gave urine samples before and after working shifts of at least four hours.

"NNK is only found in the body as a result of either smoking or breathing other people's smoke," researcher Michael Stark of the Multnomah County Health Department in Portland. "As a group, four out of five of the nonsmokers who worked in a smoking environment had some detectable level of this deadly chemical in their body, and as a group, for every hour that they worked, that level increased by 6 percent."

The study appears online in the American Journal of Public Health.