Inhale at your own risk

In September 2018, the former commissioner of the Food and Drug Administration declared teenagers’ use of e-cigarettes had reached “an epidemic proportion of growth.” A survey later revealed that about a fourth of US high school students had vaped within the previous 30 days. How this surge in use arose, and what the health implications may be, are under scrutiny at Yale. The first essential step in this work is to understand what, precisely, is being vaped.

“Aside from the nicotine, there are a lot of flavors and sweeteners added to these e-liquids,” says Julie Zimmerman, a professor in the schools of engineering and environment. She and several colleagues recently studied eight flavor pods manufactured by Juul, the country’s most popular e-cigarette company to find out what was in the e-liquids.

Zimmerman found a critical problem: “Even if the companies disclose what’s in each vial, the liquids are not stable,” she says. “Different compounds are reacting with each other and forming new compounds—even as they’re stored on the shelf, as people carry them around.” The flavor compound vanillin, for instance, reacted with other ingredients to create acetals, which can irritate the lungs.

Lately, a mysterious lung disease, tentatively linked to vaping, has caused over 1,000 hospitalizations and more than 25 deaths. Zimmerman notes that informed policy needs to begin with basic knowledge: “We don’t even really know what’s in these flavor pods.” Even if we did, she adds, we don’t know if they’re safe for vaping. “These chemicals may have a well-known toxicological profile for ingestion. But we know nothing about when they’re breathed into lungs.”