Vaping continues to be the leading form of nicotine use among youth, according to the latest Kentucky Incentives for Prevention survey. It shows vaping among 10th graders in Kentucky has increased by almost 6% in five years, from 11.4% in 2016 to 17% in 2021.Nationwide among youth, nearly 9 in 10 used flavored e-cigarettes, according to the Centers for Disease Control and Prevention. But what's actually in vape juices?E-juice usually contains nicotine, flavorings and other chemicals, according to the American Lung Association. It says that, additionally, when e-liquid heats up, more toxic chemicals are formed. However, experts we spoke with say sometimes, it's hard to tell just exactly how many chemicals are going into the body. Assistant professor Alex Carll is a researcher with the UofL Christina Lee Brown Envirome Institute. In 2022, UoL received a $3.6 million grant from the National Institutes of Health and the Food and Drug Administration to study how different flavoring chemicals impact the body, specifically the heart. "We're testing those and comparing their ability to promote disruptions in the heart's rhythm, called cardiac arrhythmias, as well as determining how the flavors themselves change, the way the brain regulates the heart because the arrhythmias and how the brain regulates the heart are very closely intertwined," said Carll. Now, it may sound like a simple choice between a flavor like Razz Ice or Banana Ice, but it may not be, according to Carll. "Something like that is going to have upwards of 15 to 30 different flavors and chemicals within it," he said. He says if a flavor has the term "ice" in the name, it typically has a cooling agent, like menthol. "But those cooling effects cause sort of nervous system responses that may interact with nicotine effects on the nervous system and the heart to promote cardiac arrhythmias, and so that's some of the data we have been demonstrating of late," he said. The director of the Kentucky Poison Control Center, Ashely Webb, says there are other issues with flavoring agents."Those agents were tested for safety when they're ingested or consumed," she said. "They haven't been tested for safety in the lungs. And so we have seen some severe lung disease in adolescents, especially as a result of inhaling things like diacetyl," said Webb. Diacetyl is a chemical with a buttery smell that was previously used to flavor microwave popcorn, according to the American Lung Association. It's also found in many e-cigarette flavors. The American Lung Association says it can cause scarring of the tiny air sacs in the lungs, resulting in the thickening and narrowing of the airways. In the past decade, nicotine salts have emerged, too. It's a type of e-liquid found in pod-style e-cigarettes, which can provide a higher amount of nicotine, according to the CDC. Webb says because nicotine salts are less harsh than regular tobacco, it becomes more attractive to people. "Especially when you start adding flavoring agents to it, it makes it more attractive," she said. "So, you know, as far as the chemical compounds that are in there, we still know that there's fewer chemicals, but that doesn't make them safer. There's still cancer-causing agents. And because it's less harsh chemical, they can inhale it more deeply into their lungs. And again, that's where the jury's still out. What does that look like in 20 or 30 years."Carll adds there is still a lot unknown about long-term effects because of the constantly changing market of e-cigarette products. "And, if you don't have a consistent sort of baseline, then we're not necessarily going to be seeing consistent effects over time," he said. Carll says the UofL study is funded through 2027.