At least 23 states, the District of Columbia and Puerto Rico require most public places and workplaces, including restaurants and bars, to be smoke free, according to the National Conference of State Legislatures.
Another nine states ban smoking in workplaces but have various exemptions for restaurants or bars.
"We already have more than enough evidence why we should pass these smoke-free laws, but certainly this study should help push them along," said Danny McGoldick of the Campaign for Tobacco Free Kids.
