Workers at New York City hookah bars are inhaling hazardous levels of second-hand smoke, according to a study released Monday.

NYU researchers, who tested 10 hookah-bar workers when their shifts ended, reported finding elevated levels of toxins as well as evidence of inflammation linked to lung and heart diseases.

“Hookah use is often exempt from clean indoor air laws that protect people from secondhand smoke. Ours is the first study that links poor hookah-bar quality to damaging effects in workers,” said Terry Gordon, an NYU professor of environmental medicine.