WASHINGTON—It’s widely assumed that swapping cigarette puffing for vapor huffing is better for health—after all, electronic cigarettes that heat up and atomize a liquid concoction can skip all the hazards of combustion and smoke. But researchers are still scrambling to understand the health effects of e-cig use (aka vaping) and to track down the variable and undisclosed components of those vaporized mixtures. The most recent data hints at unexpected health effects unique to e-cig use.

After comparing genetic information swabbed from the noses of smokers, vapers, and non-users of both, researchers found that smoking suppresses the activity of 53 genes involved in the immune system. Vaping also suppressed those 53 immune genes—along with 305 others. The results were presented Friday at the annual conference of the American Association for the Advancement of Science in Washington.

Though research on the significance of that gene suppression is still ongoing, the initial results suggest that e-cig users may have compromised immune responses, making them potentially more vulnerable to infections and diseases.

“The gene expression changes we’re seeing are consistent with a modified immune response,” lead researcher Ilona Jaspers of the University of North Carolina at Chapel Hill told Ars. “Any time you change [the immune system], it's probably out of balance," she said, explaining that a hyper-immune response or a weak response is problematic. Whether the imbalance caused by e-cigs leads to boosted infection risks or other immune diseases, “we don’t know,” Jaspers added.

For the study, Jaspers and colleagues mined the noses of different groups of healthy people—around a dozen each of cigarette smokers, e-cigarette vapers, and people who didn’t use either. The researchers fit the volunteers into the three categories based on smoking “diaries” that they filled out for three weeks prior to nose-sampling. The researchers homed in on the schnoz because cellular and immune responses there can offer clues to those responses in the lungs, which are harder to sample, Jaspers noted.

Harvesting the genetic data from the participants, researchers looked at the activity of nearly 600 genes, all of which are related to controlling and mounting immune responses. Comparing smokers’ genetic information to that of non-users, the team found that the activity of 53 genes was dialed down in smokers collectively. Comparing e-cig users to smokers and non-users revealed the same dampened activity for those 53 genes but also 305 others—a total of 358 immune genes were muted in e-cig users’ noses.

In follow-up lab studies, Jaspers and colleagues tested e-cig liquid on immune cells from healthy volunteers. Specifically, the researchers collected immune cells, such as neutrophils and macrophages, that are responsible in part for swallowing up invading bacteria. When the cells were put into diluted solutions of different e-cigarette liquids, the cells weren’t as good at sucking in the microbes. The data, while preliminary, suggests that immune cells in e-cig users may be unable to prevent bacterial breaches, thus opening the gates to infection.

The researchers also looked at the gene-altering effects of different flavors of e-cigarettes on the cells in the delicate lining of the respiratory tract. The flavorings that seemed to have the most potent gene-altering effects were additives that taste like cinnamon—cinnamaldehyde—as well as butter flavors.

These flavorings are considered safe, Jaspers pointed out—but only for eating. The additives are categorized as generally recognized as safe (GRAS) for food and beverages, but they have never been tested for safety when inhaled, she adds. The point is driven home with one of the flavors, the butter-mimicking diacetyl. This flavor has been found in some e-cig flavorings, but it's known to cause bronchiolitis obliterans, a severe disease caused by scar tissue and inflammation built up deep in the lungs. The link was discovered years ago in food manufacturing, particularly microwave popcorn factory employees who developed “popcorn worker’s lung.”

A concerning factor in e-cig use is that it’s not well known what or how much flavor additives and components are in e-cigarette liquid, Jaspers said.

The concern was echoed by clinical pharmacologist Neal Benowitz of the University of California, San Francisco. “E-cigarettes are not one thing,” he said, noting that the devices, liquids, and flavorings vary widely. “We’re really in the beginning of understanding the toxicity.”