While health appears to be the main reason for banning smoking outdoors, officials say fire safety and littering also play a role.
The number of cities and counties that bar smoking in outdoor areas - including parks, cafes, concert venues, stadiums and beaches - has soared from 30 in 1999 to at least 1,124 today, according to the American Non-smokers' Rights Foundation, an advocacy group that tracks local ordinances.
"What we're seeing is the trend is going from the inside out," says Cynthia Hallett, the foundation's executive director. She says many places that have indoor bans are expanding their restrictions, which include 47 beaches and 222 parks.
Last month alone:
-- Beverly Hills nixed lighting up in outdoor cafes.
-- Albuquerque banned smoking in parks and public venues, including the zoo and botanical garden.
-- Davis County, Utah, barred it from amusement parks, pools, public gardens, most parts of golf courses and even cemeteries.
"In some cases, (bans) are about fire safety," says Steven Feldman, spokesman for the Association of Zoos and Aquariums. The National Zoo in Washington, which had small fires linked to cigarette butts, banned smoking in December.
At least 81 zoos have gone smoke-free and 88 others have designated smoking areas, Feldman says. He says zoos have acted because many visitors are children.
The beach bans were motivated partly by litter concerns, Hallett says. Cigarettes are the top source of debris in global beach cleanups led by the Ocean Conservancy.
Albuquerque Mayor Martin Chávez says littering is a problem, but he pushed for an outdoor ban mostly for health reasons. "No amount of smoking is good for you," he says.
One in five American adults smoke cigarettes, according to government statistics.
Stanford University researchers found, in a study published in May, that people sitting within 2 feet of a single cigarette at an outdoor cafe could inhale as much secondhand smoke as in a smoky tavern.
The study is flawed, partly because people don't sit close enough outside to cause a health risk, says Audrey Silk, founder of Citizens Lobbying Against Smoker Harassment. If the problem is littering, she says, "enforce the litter laws."
What's driving outdoor bans, Silk says, is "public hate of anything smoking or smoker-related."
Philip Morris, the nation's largest cigarette maker, believes secondhand smoke poses indoor health risks but smoking should be permitted outside, says spokesman Bill Phelps. He says the only exception should be areas intended for kids.
Some proposed outdoor bans have been rejected, including one in Norman, Okla., last month. Others have passed but not quietly.
"There have been some very upset smokers," says Mayor Chávez. He retreated a bit this month by exempting golfers because municipal golf courses are not kid venues.
Albuquerque's outdoor ban, unlike some others, imposes no fines.