In the last couple of years, electronic cigarette use has exceeded that of traditional cigarettes among teenagers. And now, a new study shows how e-cigs aren’t necessarily great for lung health either: not only is nicotine damaging for the lungs in any form, but even exposure to vapor from e-cigs that don’t contain nicotine may have deleterious effects.

E-cig use among middle and high school students tripled between 2013 and 2014, according to new data from the Centers for Disease Control and Prevention and the U.S. Food and Drug Administration. That’s two million high school students and nearly half a million middle school students across the country. "In today’s rapidly evolving tobacco marketplace, the surge in youth use of novel products like e-cigarettes forces us to confront the reality that the progress we have made in reducing youth cigarette smoking rates is being threatened," the FDA’s Mitch Zeller said in a statement last month.

Cigarette smoke causes the breakdown of lung endothelial cells – the ones that make up the lining of the paired organ – which can lead to various lung injuries and inflammation. The addictive chemical nicotine is just one of hundreds of components in cigarette smoke and researchers are still trying to figure out which of these are causing the injurious loss of lung cell integrity.

Indiana University’s Kelly Schweitzer and colleagues wanted to see if nicotine alone is enough to alter the cellular matrix that supports the shape and function of lung cells. They exposed mice, as well as cells from mice and humans, to cigarette smoke extract and to two kinds of e-cig solution: one containing nicotine, the other being nicotine-free. Nicotine’s harmful effects depend on the dose, they found, and result in loss of lung endothelial barrier function, acute lung inflammation and decreased lung endothelial cell proliferation. The team observed these effects in cigarette smoke and in e-cig solutions containing nicotine.

Importantly, the nicotine-free e-cig solutions also contained substances that harmed lung cells. For instance, acrolein targets molecules that hold the lung endothelial cells together.

"The increased use of inhaled nicotine via e-cigarettes, especially among the youth, prompts increased research into the effects on health. This research reports that components found in commercially available e-cigarette solutions and vapors generated by heating them may cause lung inflammation," study co-author Irina Petrache of IU says in a news release. "The effects described characterize short-term effects of e-cig exposures. Whereas studies of long-term effects await further investigations, these results caution that e-cigarette inhalation may be associated with adverse effects on lung health."

The findings were published in the American Journal of Physiology – Lung Cellular and Molecular Physiology this month.

[Via American Physiological Society]