Thirty of America’s 50 largest cities are now covered by laws that prohibit smoking in all indoor areas of private workplaces, restaurants, and bars, according to a study from the Centers for Disease Control and Prevention (CDC). That's a sharp contrast to 2000, when only one of the 50 largest U.S. cities—San Jose, Calif.—was covered by such a law. As of Oct. 5, 2012, 16 of the 50 largest cities were covered by local comprehensive smoke-free laws, and 14 more were covered by state comprehensive smoke-free laws.

"Today, almost half of Americans are protected by state or local laws of this kind, compared to less than three percent in 2000," says the CDC. "Scientific studies have found that smoke-free laws reduce exposure to secondhand smoke, reduce smoking, and improve health, including reducing heart attacks."

While new local comprehensive smoke-free laws continue to be adopted in a number of cities and counties, last week North Dakota voters approved the first statewide comprehensive smoke-free law adopted since 2010.

"Communities have made tremendous progress eliminating smoking from worksites and public places in 60 percent of big cities in the United States. Smoke-free laws save lives and don’t hurt business," said CDC Director Thomas R. Frieden, M.D., M.P.H. "If we can protect workers and the public in the remaining 20 largest cities, 16 million people would be better protected from cancer and heart disease caused by secondhand smoke."

The study, "Comprehensive Smoke-Free Laws—50 Largest U.S. Cities, 2000 and 2012," published in this week’s Morbidity and Mortality Weekly Report, reported that 10 of the 20 cities without comprehensive smoke-free laws are located in the south. Additionally, 10 of the 20 cities without such laws are located in states that prohibit local smoking restrictions from being stronger than or different from state law.

"Hundreds of cities and counties have passed their own smoke-free laws, including many communities in the south," said Tim McAfee, M.D., M.P.H., director of CDC’s Office on Smoking and Health. "If we continue to progress as we have since 2000, all Americans could be protected from secondhand smoke exposure in workplaces and public places by 2020."

The 2006 Surgeon General’s Report concluded that there is no risk-free level of exposure to secondhand smoke. Secondhand smoke causes heart disease and lung cancer in nonsmoking adults and is a known cause of sudden infant death syndrome or SIDS, respiratory problems, ear infections, and asthma attacks in infants and children. Even brief exposure to secondhand smoke can trigger acute cardiac events, such as heart attack. Cigarette use kills an estimated 443,000 Americans each year, including 46,000 by heart disease and 3,400 by lung cancer among nonsmokers from exposure to secondhand smoke.

For an online version of this MMWR report, visit http://www.cdc.gov/mmwr.

For quitting assistance, call 1-800-QUIT-NOW (1-800-784-8669) or visit www.smokefree.gov. Information on quitting and preventing children from using tobacco is available at: www.BeTobaccoFree.gov.