E-cigarettes have become increasingly popular over the last two decades, especially among young people. These sleek, deliciously flavored smoking devices are often marketed as a safer alternative to conventional cigarettes, but alarming new research challenges that assumption.

In a study published June 25 in the journal ACS Central Science, researchers tested three popular disposable vape brands for hazardous metals and metalloids such as lead, chromium, antimony, and nickel. Inhaling these toxins can increase the risk of cancer, respiratory disease, and nerve damage. The findings show that e-cigarettes emit dangerously high levels of toxic metals—orders of magnitude higher than levels emitted by traditional cigarettes and other e-cigarettes. One brand released more lead during a day’s use than nearly 20 packs of cigarettes. Given the widespread underage use of vapes, the findings underscore an urgent need for regulatory action, the researchers conclude.

“Our study highlights the hidden risk of these new and popular disposable electronic cigarettes—with hazardous levels of neurotoxic lead and carcinogenic nickel and antimony—which stresses the need for urgency in enforcement,” co-author Brett Poulin, an assistant professor of environmental toxicology at the University of California, Davis, said in a statement. “These risks are not just worse than other e-cigarettes but worse in some cases than traditional cigarettes.”

The Food and Drug Administration (FDA) has cracked down on brands selling flavored, disposable vapes in the U.S. due to concerns about youth access, health risks, and unauthorized sales. Despite issuing warning letters to popular brands, slapping retailers with civil penalties, and blocking e-cigarette imports from other countries such as China, the agency has failed to keep these devices out of the U.S. market.

In the past few years, sales of disposable vapes have overtaken sales of older, refillable vapes. According to the FDA’s Annual National Youth Tobacco Survey for 2025, disposable e-cigarettes are the most commonly used tobacco product among young people. The survey found that 5.9% of middle and high school students (1.63 million) reported current use of e-cigarettes, and of those students, 55.6% use disposable vapes.

Previous studies have investigated the elemental composition of refillable e-cigarettes, but few have looked into these newer devices. To fill that gap, Poulin and his colleagues analyzed the metals and metalloids inside seven disposable vapes made by three brands, including flavored and unflavored liquids. They selected the brands based on popularity and purchased the e-cigarettes from online vendors based in the U.S. All the devices they tested contained nicotine except one, which allowed the researchers to test if nicotine influences the metal concentrations of e-liquids (commonly known as “vape juice”).

The key components of any vape are a battery, e-liquid (commonly known as “vape juice” or “e-juice), and a heating coil. When the user presses a button on the device or—in some cases—simply inhales, the battery heats the coil and turns the e-liquid into an aerosol. These metal components can leach into the e-liquid and thus work their way into the lungs.

The researchers tested the metal concentrations of unused e-liquids and aerosols, using a special instrument to activate the e-cigarettes and generate between 500 and 1,500 puffs per device. They found that “these disposable devices have toxins already present in the e-liquid, or they’re leaching quite extensively from their components into e-liquids and ultimately transferred to the smoke,” lead author Mark Salazar, a PhD candidate in Poulin’s lab, said in the statement.

Some unused e-liquids contained high levels of antimony, a toxic metalloid. Heating coils leached nickel into the e-liquid, while leaded bronze alloy components in some devices leached nickel and lead. The vapors of some devices contained surprisingly high metal levels, including antimony and lead. Interestingly, the metal concentrations of the aerosols increased as the number of puffs increased, suggesting that exposure worsens as the device ages.

Overall, the researchers determined that disposable e-cigarette users are exposed to markedly higher levels of toxic metals and metalloids than those who use refillable vapes, which may lead to increased health risks. Three of the tested vapes produced vapors that contained nickel levels that exceeded cancer risk thresholds, and two emitted potentially cancerous amounts of antimony. Four devices had nickel and lead emissions that surpassed risk thresholds for illnesses besides cancer, such as neurological damage and respiratory disease.

Of the nearly 100 disposable e-cigarette brands available in the U.S., this study tested only three. Despite regulatory efforts, these devices remain wildly popular among adolescents. The researchers hope that their work inspires others to investigate the health risks associated with disposable e-cigarettes, as it would appear they won’t be going away anytime soon.