• Posted June 3, 2026

High-Puff Vapes Become More Toxic Over Time, Study Says

E-cigarettes that offer a lot of extra puffs might become more toxic the longer they are used, a new study says.

High-puff vapes can typically deliver into the thousands of inhalations before they run out, because they hold more e-liquid and are designed for extended use, researchers said.

But toxic chemicals called aldehydes start building up in the e-liquid as it is repeatedly exposed to vapor-producing heat, researchers reported May 28 in the journal ACS Omega.

“Our findings suggest that the fluid remaining in a heavily used device has a very different and measurably more toxic chemical profile than fresh e-liquid,” said senior researcher Prue Talbot, a professor of molecular cell and systems biology at the University of California-Riverside (UCR).

“Chemical levels varied across brands, but our overall findings show extended use of high-puff disposable vapes may lead to greater accumulation of harmful byproducts,” Talbot said in a news release.

For the study, researchers analyzed liquid from 77 discarded vape devices representing 20 different brands. Puff counts on the devices ranged from 300 to 6,000.

Specifically, the team looked for chemicals called aldehydes known to form when vape liquids are heated.

Researchers found that levels of several toxic aldehydes increased significantly after the devices were used, including methylglyoxal (MGO), glyoxal (GO), and formaldehyde.

“Formaldehyde is a recognized carcinogen,” said lead researcher Esther Omaiye, a postdoctoral scholar at UCR.

What’s more, these chemicals reached alarming levels in high-puff e-cigarettes, the study found.

To see whether these levels might harm users, researchers exposed human lung cells to MGO and another aldehyde called acetaldehyde.

MGO caused significant cell damage, proving 10 to 100 times more toxic than acetaldehyde, researchers reported.

“These are not trace amounts,” Omaiye said in the release. “When tested on human lung cells, these aldehydes caused measurable damage.”

People who vape should exercise caution with high-puff devices, particularly as they near the end of their e-liquid, researchers said.

“Until regulatory standards catch up and require testing across the full use cycle of a device, consumers have no way of knowing what they are actually inhaling late in a device’s life,“ Omaiye said.

“Puff count is not just a marketing figure," Talbot said. "It is a variable that directly affects chemical exposure and must be incorporated into safety assessments.” 

More information

The American Lung Association has more about what’s in an e-cigarette.

SOURCE: University of California-Riverside, news release, May 28, 2026