A huge amount of research is currently underway examining the broad health effects of e-cigarettes, which are frequently suggested to be safer than regular cigarettes. A new study from researchers at Pennsylvania State University has examined the specific chemicals used to flavor e-cigarette liquids and found that different flavorants can significantly alter the levels of free radicals in the resulting vapor.

Previous research has revealed that e-cigarette vapor does contain free radical chemicals, albeit at much lower levels than is found in traditional cigarette smoke. In the hopes of helping develop safer guidelines, this new study set out to examine whether different flavoring chemicals added to e-cigarette liquids produce more, or less, free radicals.

"E-cigarettes have a coil for heating the liquid that gets quite hot and may aid the production of free radicals," says John Richie, one of the Penn State researchers working on the study. "It's important to look at the effect of flavors on these free radical levels because e-cigarettes come in hundreds of flavors, many of which are marketed toward kids, like bubblegum."

The study measured the presence of free radicals found in vapor produced by 49 popular e-cigarette flavoring agents, compared to a flavorless e-liquid used as a baseline control. The flavorless control liquid was a generic combination of glycerol and propylene glycerol – the standard base for many flavored e-cigarette liquids. It was found that 43 percent of the flavors were seen to increase the production of free radicals in the e-cigarette vapor, with linalool, dipentene, and citral, used to add citrus or floral characteristics to the vapor, three of the highest free-radical-producing flavorants.

Perhaps the most interesting finding in the study was the discovery that some flavorants actually inhibited the production of free radicals. This meant the addition of these chemicals to the control liquid resulted in less free radical production than the control liquid by itself. Ethyl vanillin, producing vanilla tasting notes, was found to be the strongest free radical inhibitor, decreasing production of the toxins by an impressive 42 percent.

"We found that many of these flavorings increase free radicals, but a few decreased them, as well, which raises the possibility that maybe there are things you can add to these liquids that could reduce radical production and might make them safer," says Richie.

This promising research suggests certain flavorants could be incorporated into e-cigarette liquids to reduce potential harm to the consumer. More research needs to be done to better understand the levels of toxins produced by vaping different chemicals but this is an important step towards clearer guidelines that establish safe regulations around e-cigarettes.

The research was published in the journal Free Radical Biology and Medicine.