THURSDAY, April 21 (HealthDay News) -- Smoking bans in workplaces, restaurants and bars across the United States are now in place in half the states, and all such venues across the country could be smoke-free by 2020, government researchers reported Thursday.

Indoor areas of worksites, restaurants and bars are major sources of secondhand smoke, and approximately 88 million nonsmoking Americans 3 and older are still exposed to it each year, said the researchers at the U.S. Centers for Disease Control and Prevention.

In a detailed report using 10 years of data on state smoking restrictions from the CDCs State Tobacco Activities Tracking and Evaluation System database, the researchers found that:

• 25 states and the District of Columbia have enacted comprehensive smoke-free laws in workplaces, restaurants and bars. The move began with Delaware in 2002, New York in 2003, Massachusetts in 2004, and Rhode Island and Washington in 2005. In 2006 and 2007, Arizona, Colorado, D.C., Hawaii, New Jersey, Minnesota, New Mexico and Ohio enacted laws; Illinois, Iowa, Kansas, Maryland, Maine, Michigan, Montana, Nebraska, Oregon, South Dakota, Utah, Vermont and Wisconsin acted in 2008- 2010.
• Ten states have laws that ban smoking in at least one or two of the three venues.
• Eight states have less-restrictive smoking laws, which allow smoking in designated areas or in areas with separate ventilation.
• Seven states still have no smoking restrictions for any of the three venues: Indiana, Kentucky, Mississippi, South Carolina, Texas, West Virginia and Wyoming.

The study appears in the April 22 issue of the CDC's Morbidity and Mortality Weekly Report.

"Eliminating smoking from worksites, restaurants and bars is a low-cost, high-impact strategy that will protect nonsmokers and allow them to live healthier, longer, more productive lives while lowering health care costs associated with secondhand smoke," CDC director Dr. Thomas R. Frieden said in an agency news release. "While there has been a lot of progress over the past decade, far too many Americans continue to be exposed to secondhand smoke at their workplaces, increasing their risk of cancer and heart attacks."

"Secondhand smoke is responsible for 46,000 heart disease deaths and 3,400 lung cancer deaths among nonsmokers each year," Ursula Bauer, director of CDC's National Center for Chronic Disease Prevention and Health Promotion, added in the news release. "Completely prohibiting smoking in all public places and workplaces is the only way to fully protect nonsmokers from secondhand smoke exposure."

The 2010 Surgeon General's report reiterated that any exposure to tobacco smoke -- including secondhand smoke -- can cause damage to the body's organs and DNA, the CDC news release said.

More information

The U.S. Environmental Protection Agency has more about the health effects of secondhand smoke.