Popular electronic cigarette (e-cigarette) products sold in the U.S. were contaminated with bacterial and fungal toxins, according to new research from Harvard T.H. Chan School of Public Health.

The study, which examined 75 popular e-cigarette products — both single-use cartridges and refillable e-liquids — found that 27 percent contained traces of endotoxin, a microbial agent found on gram-negative bacteria, and that 81 percent contained traces of glucan, which is found in the cell walls of most fungi. Exposure to these microbial toxins has been associated with myriad health problems in humans, including asthma, reduced lung function, and inflammation.

“Airborne gram-negative bacterial endotoxin and fungal-derived glucans have been shown to cause acute and chronic respiratory effects in occupational and environmental settings,” said David Christiani, Elkan Blout Professor of Environmental Genetics and senior author of the study. “Finding these toxins in e-cigarette products adds to the growing concerns about the potential for adverse respiratory effects in users.”

Read more at Harvard Gazette