According to the U.S. researchers concentrations of secondhand tobacco smoke inhaled in restaurants and bars that allow smoking are exceptionally high and hazardous.

The study said that a report by the Oklahoma Tobacco Research Center found the average particulate level measured in restaurant smoking rooms was beyond the hazardous extreme based on levels established by the U.S. Environmental Protection Agency. The levels in bars were higher.

Lead investigator Dr. Heather Basara, an industrial hygienist, said tobacco smoke levels were evaluated based on measurements of particulates smaller than 2.5 microns, which come primarily from tobacco smoke.

Restaurants with no smoking averaged 26 micrograms per cubic meter whereas levels averaged 380 micrograms per cubic meter of air in the restaurant smoking rooms tested, and 655 micrograms per cubic meter in the bars.

The EPA scale ranks outdoor levels of particulate pollution as unhealthy at 66-150, very unhealthy at 151-250 and hazardous at higher concentrations such as the levels found in the Oklahoma restaurant smoking rooms and bars tested for the report.

Basara said in a statement," These levels are exceptionally high and not healthy for the employees and patrons exposed to particles found in secondhand smoke." (With Input from Agencies)