Anti-tobacco advocates are using a new study to make the case for a smoking ban on bar and restaurant patios.

A researcher at Johns Hopkins University in Baltimore, Maryland found harmful levels of second-hand smoke in a survey of Montreal bar patios.

The study found that a single lit cigarette could create air quality levels comparable to a smoggy day in Los Angeles.

Professor Ryan Kennedy, who conducted the study, says the tests suggests second-hand smoke can be harmful outdoors, even on a windy day.

"Even if a patio is completely uncovered … smoking on a patio can generate very high concentrations of fine particles — those which penetrate deep into the lungs," Kennedy said.

However, the president of the Quebec bar-owners union, Peter Sergakis, says he doesn't believe the study's findings.

He says he plans to commission his own research.

Sergakis says his businesses have not recovered after smoking was banned inside restaurants and bars in Quebec in 2006.

"When they stopped smoking inside, we lost about 25 per cent of the business," he said. "Our clientele is smokers and drinkers."

Quebec to review Tobacco Act

The provincial Tobacco Act is expected to be studied later this month by members of the government committee on health and social services.

David Lefebvre, spokesman for the Quebec council on tobacco and health, says advocates are hoping the study will be taken into consideration.

"The current act risks the health of employees who work on restaurant and bar patios, while it protects the office workers," Lefebvre said in a statement.

Several provinces have already banned smoking on patios, including Newfoundland and Labrador, Nova Scotia, and Alberta.

With files from the Canadian Press