Banning smoking in Irish-style pubs decreases air pollution by 93 percent, according to a study co-sponsored by the Harvard School of Public Health (HSPH).

Harvard researchers collaborated with scientists from the U.S. and Ireland to survey pubs in 15 countries around the world. Though researchers investigated pubs in 41 cities, including Beijing, Sydney, and Beirut, the study was originally conceived to evaluate the public health benefits of Ireland’s 2004 ban on smoking in public places.

According to the study, pubs in cities without smoking bans had significantly higher levels of fine-particle pollution.

The Environmental Protection Agency sets standards for outdoor, but not indoor, air quality; any levels above 301 micrograms per cubic meter are “hazardous.” The average level in smoking pubs was much higher at 340 micrograms per cubic meter.

The results “underscore the importance of smoke-free policies,” according to the study’s authors. HSPH Professor of the Practice of Public Health Gregory N. Connolly said that the study would probably have “strong implications for states and countries considering smoking bans.”

Currently, 11 states ban smoking in public places, and many more are now considering legislation. The Harvard study has already been cited by public health advocates in Minnesota, Colorado, Utah, France, and Australia.

According to Connolly, “the key is to use science to focus not on only on economic issues but on health issues as well.”

He said that workers at Irish pubs, many of whom have no health insurance, are at increased risk for respiratory problems and lung cancer.

K. Michael Cummings, chair of the Department of Health Behavior at Roswell Park Cancer Institute, also contributed to the study.

“I anticipate that this study will be added to the toolbox of public health advocates.” Cummings said.