FRIDAY, April 13, 2018 (HealthDay News) -- The flavor you choose for your e-cigarette liquid may determine how many toxins you inhale, new research suggests.
Those toxins -- called free radicals -- are linked to cancer, heart disease, inflammation and other diseases, the scientists said.
In the study, citrus and floral flavors tended to have higher levels of free radicals, while vanilla flavors produced lower levels.
"When [e-cigarettes] first came on the market, many people were saying they were harmless and that it was just water vapor," said lead researcher John Richie, a professor of public health sciences and pharmacology at Penn State College of Medicine.
"We know that's not true, but we also don't have the numbers on how dangerous e-cigarettes are," he added in a university news release. "But now we know that e-cigarettes do produce free radicals, and the amount is affected by the flavorants added."
Exactly how are these free radicals produced?
"E-cigarettes have a coil for heating the liquid that gets quite hot and may aid the production of free radicals," Richie said.
"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 bubble gum," he said.
In the study, Richie and his colleagues measured levels of free radicals produced by 50 flavors of a popular brand of e-cigarette, and compared them to flavorless e-liquid. About 43 percent of the flavors produced significantly higher levels of free radicals, while a few flavors produced lower levels.
The researchers then examined the individual chemicals in the flavors to identify which chemicals were associated with higher levels of free radicals. Similar flavors of e-cigarette liquids may contain different chemicals.
The team said it identified six flavor additives that significantly increased production of free radicals. These included linalool, dipentene and citral, which are often used to produce citrus or floral flavors, according to the researchers.
The researchers also found that ethyl vanillin -- often added for vanilla flavor -- decreased the production of free radicals by 42 percent.
Along with providing information for consumers, the findings could help policymakers create e-cigarette regulations, Richie said.
"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 [free] radical production and might make them safer," he said.
"E-cigarettes are regulated by the Center for Tobacco Products in the [U.S. Food and Drug Administration], and I think these results can be useful to help set guidelines in terms of regulating these products," Richie concluded.
The study appears in the May issue of the journal Free Radical Biology and Medicine.
The U.S. National Institute on Drug Abuse has more about e-cigarettes.