As bans spread across nation, some experts question evidence of harm from outdoor smoking

ATLANTA – The front lines of the “No Smoking” battle have moved outdoors.

City parks, public beaches, college campuses and other outdoor venues across the country are putting up signs telling smokers they can’t light up. Outdoor smoking bans have nearly doubled in the last five years, with the tally now at nearly 2,600 and more in the works.

But some experts question the main rationale for the bans. They say there’s not good medical evidence that cigarette smoke outdoors can harm the health of children and other passers-by. There are hundreds of studies linking indoor secondhand smoke to health problems like heart disease. But there’s been little research on outdoor smoking.