People exposed to heavy concentrations of secondhand smoke in confined spaces, such as bars and cars, experience impaired breathing and airway restriction within 20 minutes, 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 this week at the American College of Chest Physicians' annual meeting in Atlanta.

Data and conclusions presented at meetings should be considered preliminary until published in a peer-reviewed medical journal.