Just 20 minutes of breathing secondhand smoke in confined spaces, such as bars and cars, can cause impaired breathing and airway restriction, according to a small new study.

"Bars and cars are places where high concentrations of fine particles usually occur because of smoking," said Dr. Panagiotis Behrakis, of the University of Athens, in Greece, in a news release from the American College of Chest Physicians. "Nonsmokers are then forced to inhale extreme amounts of particulates directly into their lungs. The observed short-term effects of secondhand smoke tell us that even a short exposure is indeed harmful for normal airways."

In conducting the study, researchers from the University of Athens, the Hellenic Cancer Society in Greece and the Harvard School of Public Health exposed 15 healthy people to high concentrations of secondhand smoke for 20 minutes. The participants were exposed to the smoke in a chamber to mimic exposure to secondhand smoke in confined spaces.

During the exposure, the researchers assessed the participants' total respiratory impedance, resistance and reactance. They found the effects of short-term exposure to concentrated secondhand smoke are immediate and significant.

The study was presented Monday at the American College of Chest Physicians' annual meeting in Atlanta.

The information presented at scientific meetings should be considered preliminary until published in a peer-reviewed medical journal.