9NEWS HOLIDAY GUIDE
Five major airports allow smoking - Harsfield-Jackson in Atlanta, Washington Dulles, McCarran in Las Vegas, Denver International Airport and Salt Lake City International.
Researchers at the Centers for Disease Control and Prevention measured smoke levels inside and just outside the designated smoking areas and compared them to non-smoking airports.
Standing just outside a smoking area in an airport allowed for five-times the secondhand smoke exposure than if a passenger were in a completely smoke-free environment.
"We know that there's no risk-free level of secondhand smoke exposure and therefore, individuals who are inside these smoking room environments or even outside them are potentially susceptible to secondhand smoke exposure - which is problematic for workers as well as travelers, particularly children," Dr. Brian King with CDC's Office on Smoking and Health said.
More than 110 million passengers passed through the five airports in 2011.
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