Researchers from the University of Athens, the Hellenic Cancer Society and the Harvard School of Public Health had 15 healthy study participants go inside a chamber meant to simulate a bar or car filled with secondhand smoke particulates for 20 minutes to see how their breathing was impaired.

In just that short amount of time, air flow through the participants’ airways was impeded.

“The observed short-term effects of secondhand smoke tell us that even a short exposure is indeed harmful for normal airways,” study researcher Dr. Panagiotis Behrakis, M.D., FCCP, of the University of Athens, said in a statement.

The new findings were presented at the annual meeting of the American College of Chest Physicians; because the study has yet to be published in a peer-reviewed journal, findings should be regarded as preliminary.

Similarly, a study published in 2007 in the American Journal of Public Healthshowed that cancer-causing NNK — a compound that comes from the smoke of cigarettes — builds up by 6 percent every hour in bar- and restaurant-workers who are exposed to secondhand smoke during their night shifts, TIME reported.

“We were somewhat surprised by the immediacy of the effect and the fact that we could measure the average hourly increase,” study researcher Michael Stark, principal investigator at the Mulmomah County Health Department in Oregon, told TIME.

Earlier this year, a study in theAmerican Journal of Public Healthshowed just how many lives secondhand smoke claims in the U.S. each year: 42,000, Livescience reported.

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