A new study by the Centers for Disease Control and Prevention (CDC) found that some of the country's busiest airports still allow indoor smoking and expose travelers and workers to the harmful effects of secondhand smoke, the L.A. Times reported Nov. 19.

The study focused on the nation's 29 largest airports, which accounted for “approximately 70% of total passenger boardings in the United States in 2009,” according to the study.

Between July and Sept. 2010, CDC researchers collected information on local smoking regulations and airport policies on indoor and outdoor smoking at all 29 airports, and then cross-referenced it with information from other sources, including communications with airport staff. The results were compared with a similar 2002 study of 31 large airports, also performed by the CDC.

Although 76 percent of airports now ban smoking indoors compared with 42 percent of airports in 2002, the seven remaining holdouts include three of the five airports with the most travellers: Hartsfield-Jackson Atlanta International, Dallas/Fort Worth International, and Denver International.

Second-hand smoke, the researchers wrote, “causes an estimated 46,000 heart disease deaths and 3,400 lung cancer deaths among U.S. nonsmoking adults annually.” In an editorial note, they said that closed and ventilated indoor smoking rooms do not eliminate exposure to secondhand smoke, and that no level of exposure to secondhand smoke is safe, according to the the 2006 Surgeon General's report.

The authors also wrote that no airport completely bans smoking on its property, and that outdoor smoking areas were not risk-free for non-smokers. They referred to a California study showing that “nicotine concentrations adjacent to outdoor smoking areas at airports can be as high as those in some smokers' homes.”

The study appeared in the CDC's Morbidity and Mortality Weekly Report on November 19, 2010.