A University of California, Riverside-led study has found that heavily used high-puff electronic cigarettes may contain higher levels of harmful chemicals than fresh e-cigarettes, raising concerns about potential health risks for users.
E-cigarettes, also called ECs or vapes, are sold with an advertised puff count — roughly how many inhalations the device is designed to deliver before it is depleted. A high-puff EC is one rated for many puffs, typically in the thousands. Because they hold more e-liquid and are designed for extended use, users can vape on a single device for days or weeks.
The researchers analyzed liquid from popular disposable vape devices collected from users and discarded products in Southern California. They compared the leftover liquid in used devices with fresh, unused versions of the same brands and flavors to see how the chemical makeup changed over time.
The study, published in ACS Omega, focused on chemicals known as aldehydes, which form when vape liquids are heated.
When e-liquid is aerosolized or heated to produce vapor, the solvents and flavor chemicals undergo thermal degradation and chemical breakdown. Aldehydes are a well-documented class of by-products from that process. Some, like formaldehyde, are already recognized as harmful constituents.
The researchers wanted to know whether prolonged use of a device, with more puffs and more heating cycles, would cause these compounds to accumulate in the remaining fluid over time. They found several toxic aldehydes, including methylglyoxal (MGO), glyoxal (GO), and formaldehyde, increased significantly after the devices were used.
“Several aldehydes we measured are known toxicants,” said Esther Omaiye, a postdoctoral scholar in the Department of Molecular, Cell and Systems Biology at UCR and the paper’s first author. “Formaldehyde is a recognized carcinogen. MGO and GO, for example, reached milligrams-per-milliliter concentrations in some of the vaped fluids we analyzed. These are not trace amounts. When tested on human lung cells, these aldehydes caused measurable damage.”
The researchers were concerned that a person using a high-puff device toward the end of its life might inhale significantly more of these compounds than someone using a fresh device. To better understand the health impact, they exposed human lung cells to MGO and acetaldehyde. MGO caused significant cell damage, disrupted normal cell structure, interfered with energy production, and increased oxidative stress, a process linked to inflammation and disease. The study found MGO was 10 to 100 times more toxic than acetaldehyde.
“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 Prue Talbot, a professor of the graduate division at UCR and Omaiye’s advisor. “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.”
Electronic cigarettes have been widely used in the United States since about 2007, and newer disposable devices are designed to deliver thousands of puffs before disposal.
“Our study highlights the need for greater attention to how prolonged device use affects chemical exposure,” Omaiye said.
Talbot and Omaiye advise vapers to exercise caution with high-puff devices, particularly as the devices approach the end of their life.
“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.
The researchers said the message is clear for researchers and regulators.
“Puff count is not just a marketing figure; it is a variable that directly affects chemical exposure and must be incorporated into safety assessments,” Talbot said.
Talbot and Omaiye were joined in the study by Man Wong at UCR; and Wentai Luo and Kevin J. McWhirter at Portland State University in Oregon.
The research was supported by grants from the National Institutes of Health, the Food and Drug Administration Center for Tobacco Products, and California’s Tobacco-Related Disease Research Program.
The title of the paper is “Methylglyoxal and Glyoxal in High-Puff Disposable Electronic Cigarette Liquids: Unexpected Accumulation and Enhanced Cytotoxicity.”
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