Smoking bans are nothing if not controversial, at least as they're being proposed and implemented. But are they effective?

Study after study has shown that bartenders and other employees at places that have a ban on cigarettes show significant health improvements following implementation of the ban: respiratory problems decline both for smoking and non-smoking workers, and bartenders with asthma have shown reduced airway inflammation and improved quality of life.

Bans on smoking in public places also benefit public health generally: a CDC-sponsored study found that smoking bans reduce risk of heart disease and heart attack—that the incidence of heart attacks falls by up to 47 percent in areas with smoking bans in place.

Young people in particular seem to benefit from such bans: one study earlier this year found that children who live "where smoking is banned at workplaces, colleges and stores had 39 percent lower prevalence of cotinine in their blood -- an indicator of tobacco smoke exposure -- compared to children exposed to secondhand smoke," UPI reports.

As a reminder that home life is almost always the most powerful influence over a child's health, the benefit is lost if children go home to parents or other household members who smoke, but the notable difference between children exposed to different levels of secondhand smoke is nothing to sneeze at.

So where is smoking banned, exactly?

In 26 states, just barely a majority, there is a statewide ban on smoking in enclosed public places: Arizona, California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Iowa, Kansas, Maine, Maryland, Massachusetts, Michigan, Minnesota, Montana, Nebraska, New Jersey, New Mexico, New York, Ohio, Oregon, Rhode Island, Utah, Vermont, Washington, and Wisconsin.

Some of those list exemptions, such as for casinos or hotels allowing a percentage of smoking rooms. A few other states have similar bans but with specific exemptions for bars.

States with no statewide smoking ban at all in non-government spaces: Alabama, Alaska, Indiana, Kentucky, Mississippi, Missouri, Oklahoma, South Carolina, Texas, West Virginia, and Wyoming—and Oklahoma prohibits local governments from enacting laws stricter than the state's, meaning if you're sensitive to smoke, Oklahoma probably isn't the place for you.

The U.S. isn't the only one, of course; at least some states and countries on every continent have similar bans in effect.