Disposable vapes may be delivering more toxic metals than a pack of cigarettes.
A new study from the University of California, Davis (UC Davis), found that popular single-use e-cigarettes emit high levels of heavy metals such as lead (Pb), with some above established health risk thresholds.
The paper was published in ACS Central Science.
What’s in disposable vapes?
Disposable e-cigarettes are now the most widely used vaping products among teens and young adults in the US. They’re cheap, flavored and easy to buy, even though most aren’t approved for sale by the US Food and Drug Administration. Sales have overtaken older refillable models, but enforcement hasn’t kept up – and neither has the science.
Earlier studies on refillable e-cigarettes showed that heating elements can leach metals such as nickel (Ni) and chromium (Cr) into the vapor. Inhaling these metals is linked to cancer, respiratory illness and neurological harm. These risks are greater for young people, who are more sensitive to toxic exposures.
Disposable vapes are newer and less studied. They are sealed single-use devices, and little is known about what metals end up in the vapor, how they get there or what that means for health.
The new study came about when first author Mark Salazar, a PhD candidate at UC Davis, noticed a friend using a disposable vape. Curious, he brought the pod back to the lab and ran a test to see what was in the vapor.
“When I first saw the lead concentrations, they were so high I thought our instrument was broken,” said Salazar. “That sparked us into looking further into these disposables.”
Tracking heavy metals in e-cigarettes over time
Salazar and the team tested seven devices across three popular disposable vape brands: ELF Bar, Flum Pebble and Esco Bar. Tests included flavored, unflavored and 0% nicotine devices. Each device was tested from new to end-of-life, up to 1500 simulated puffs, to track how metal concentrations changed over time. They also checked the chemical form of certain metals, which affects how toxic they are once inhaled.
All three brands released significant levels of Ni, Cr, antimony (Sb) and Pb. The concentrations often increased the more the devices were used.
“Heating coil elements [Cr and Ni] likely leached into e-liquids and aerosols from coil degradation during use, increasing up to 1000-fold in concentration over the device life,” the authors said.
Pb and Ni in Esco Bar devices were traced to internal parts made from leaded bronze, a copper alloy with high Pb content. Sb was found in several devices but didn’t match any known internal component.
Some of the highest Pb levels – up to 175,000 µg per kg – came from Esco Bar e-liquids, equating to more Pb than in the smoke from 20 packs of cigarettes.
Compared to older refillable e-cigarettes, these devices released up to 100 times more metals, with Esco Bars showing elevated Pb and Ni even before use, suggesting users are exposed from the very first puff.
“We 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,” said Salazar.
The researchers also analyzed the oxidation states of metals in the vapor. All Cr was present as Cr(III), a less harmful form, while Sb appeared partly as Sb(III), its carcinogenic form.
Salazar and the team used published toxicity thresholds and metal concentrations in the aerosol to estimate cancer and noncancer risks for daily users.
Ni and Sb raised cancer risks above accepted limits. Pb and Ni levels exceeded safety thresholds for respiratory and neurological effects by up to nine times.
Disposable vapes and public health
One major concern is how these products are made. The use of leaded bronze, a metal not suitable for consumer health products, shows a lack of basic manufacturing oversight. With ~100 disposable brands currently on the market, most of them untested, regulators are far behind.
“Our study highlights the hidden risk of these new and popular disposable electronic cigarettes – with hazardous levels of neurotoxic Pb and carcinogenic Ni and Sb – which stresses the need for urgency in enforcement,” said corresponding author Dr. Brett Poulin, an assistant professor at UC Davis.
“These risks are not just worse than other e-cigarettes but worse in some cases than traditional cigarettes,” Poulin added.
This study looked at just three brands, but they’re among the most widely used in the US. Broader studies are needed, and the team emphasizes that future work should include more brands and explore how flavors, nicotine levels, shelf life and storage affect metal release. Lab studies and animal models will also be needed to track long-term effects, including whether non-toxic Cr could convert into its carcinogenic form once inhaled into the lungs.
Reference: Salazar MR, Saini L, Nguyen TB, et al. Elevated toxic element emissions from popular disposable e-cigarettes: sources, life cycle, and health risks. ACS Cent Sci. 2025. doi: 10.1021/acscentsci.5c00641
This article is a rework of a press release issued by the University of California – Davis. Material has been edited for length and content.
