Many cities and states in the U.S. have banned smoking in public places such as offices, restaurants and bars. The goal was to prevent non-smoker form being exposed to secondhand smoke -- which experts say can be as harmful as smoking itself. As Amy Katz reports, the bans have achieved that and more.

Smoking used to be allowed almost everywhere in the United States -- including offices, bars and restaurants. But after a number of studies reported on the dangers of secondhand smoke, thing began to change.

Secondhand smoke -- sometimes referred to as "passive smoke" -- is defined as cigarette, cigar, or pipe smoke that is inhaled unintentionally by nonsmokers. It may be harmful to their health, if they are exposed to it over a prolonged period of time.

So, some American cities and states instituted bans on smoking in public places. The bans have achieved their goals of reducing secondhand smoke.

They have also reduced smoking, according to Dr. Stanton Glantz of the Center for Tobacco Control Research. "When you make workplaces, public places, restaurants and bars smoke free, people smoke less, they sell fewer cigarettes."

Dr. Glantz also says workplace smoking bans alone have been shown to reduce cigarette consumption by 30 percent.

More than 2,000 American cities and counties now have some anti-smoking laws in effect.

In New York City, restaurants, bars and offices are all smoke-free. The number of smokers there dropped by a half-million people in four years.

In San Francisco, studies show that smoking bans have helped lower the lung cancer rate by six percent.

Many workplaces across the U.S. have smoking bans in effect.

David Spalding smoked for more than 20 years, but stopped when his employer -- health insurance company Blue Cross/Blue Shield of Minnesota -- banned smoking in and around its offices.

He says he would still be smoking if it were not for the company's strict "no smoking" policy. "I did not want to be driving off campus to have a cigarette in a car. It was that simple. And that was my catalyst."

Company vice president Dr. Marc Manley says Mr. Spalding is not alone. "When we started the policy about 18 percent of our employees smoked. And a year after the policy had been in place, the smoking rate was at 15 percent."

In many areas considering smoking bans, restaurant and bar owners have been the most vocal opponents, fearing that losing smokers would mean losing business. But studies in five states with smoking restrictions show no significant change in restaurant and bar revenue.

Some people, like Gretchen Morrison, are even banning smoking in their own homes. "It's not just the smell and the stench, it's for health reasons also."

Ms. Morrison says her self-imposed ban has forced her to cut back on her smoking -- which she hopes will lead her to quit.