A new study released Monday by researchers at Duke University found that certain e-cigarette liquids contains extremely high levels of a chemical that has been banned as a synthetic food additive by the FDA since last year. The chemical, called pulegone, occurs naturally as an essential oil in plants including peppermint and pennyroyal, and was used in its synthetic form to add a minty flavor to things like candy and alcoholic drinks. But despite all the evidence that pulegone is carcinogenic and causes liver toxicity, researchers found the chemical is present in mint and menthol-flavored e-cig liquid at levels far above a safe threshold.

This study is the latest in a growing pile of proof to how little-regulated e-cigs and vapes are. To illustrate that, researchers compared pulegone levels in mint and menthol e-cig liquid to levels in menthol cigarettes. At all levels of daily consumption, pulegone exposure from vape pods are significantly higher than exposure from cigarettes, with rates ranging from 44 to 1,608 times higher.

The study had a few limitations: One is that the FDA’s ban on synthetic pulegone is based on animal consumption data. Another is that there’s no real data on toxicity from pulegone inhalation versus consumption in food or drinks. But researchers argue that levels of the chemical are so absurdly high in e-cig liquid that they may pose a serious health risk, and at the very least, the FDA needs to do something to address that risk.

“The argument we make in the paper is that there are health concerns with these mint- and menthol-flavored liquids, and until these health concerns are mitigated by the FDA, they shouldn’t be seen as alternatives [to cigarettes],” Sairam Jabba, a research associate at Duke University and first author on the study, told VICE. “At whatever rate of consumption we looked at, we found that pulegone levers were at a threshold that cause a potential health threat.”

Jabba said pulegone levels are so much lower in cigarettes because the tobacco industry has long known about the pulegone’s potentially carcinogenic qualities, and as a result, maintains minimal levels of the chemical in menthol cigarettes. Vape liquid could be escaping that same scrutiny because it’s impossible to know whether manufacturers are using the natural or synthetic form of the chemical, Jabba said, which only shows even more need for any kind of regulation.

Of course just last week, the Trump administration asked the FDA to consider cracking all the way down by taking all flavored e-cigarettes off the market. This directive comes during a terrifying and weird time for vaping: The country is in the midst of a rash of e-cig related illnesses and deaths, and also last week, the FDA accused JUUL Labs of breaking federal regulations by publicizing its product as a safer alternative to cigarettes.

According to the findings of this latest study, as well as growing evidence that vape manufacturing is full of rogue characters, the list of reasons to believe vaping is somehow safer than regular cigarettes is shrinking fast.