A review of 22 studies on secondhand smoking concludes that nonsmokers exposed to high levels of tobacco smoke on the job double their risk of getting lung cancer, Reuters reported Jan. 31.

University of Illinois epidemiologist Leslie Stayner and colleagues based their conclusion on studies of workers exposed to high levels of tobacco smoke, defined using factors like the number of smokers in the workplace as well as actual exposure to smoke.

The review also found that nonsmokers exposed over long periods of time to lower levels of tobacco smoke had a 50-percent higher risk of developing lung cancer compared to other nonsmokers.

"We believe that our study provides the strongest evidence to date that smoking in the workplace does present a substantial risk to workers -- and particularly to workers who are working in highly exposed areas such as bar workers or restaurant workers," Stayner said.

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