An e-cigarette study led by the University of California, Riverside, highlights the need for regulation to protect public health.

Electronic cigarettes (ECs) contain nicotine, solvents and flavoring chemicals and are especially popular among young people.

In 2020, the U.S. Food and Drug Administration banned the use of refill-based flavored pods, but the ban did not extend to single-use flavored EC products, such as Puff EC. Unfortunately, the chemical composition and toxicity of the liquid in Puff EC is largely unknown.

Researchers at the University of California, Riverside and Portland State University have now examined 16 single-use Puff devices to determine their flavor chemicals, synthetic coolants and nicotine concentrations.

Synthetic cooling agents, such as WS-23, provide a cooling sensation.

Using gas chromatography and mass spectrometry, the team identified 126 flavor chemicals in Puff EC fluid and tested the chemicals for toxicity to human bronchial epithelial cells.

They report in the journal Chemical Research in Toxicology that the chemicals in single-use Puff EC are high in levels and are cytotoxic -- or toxic to living cells.

"Our data support the regulation of flavor chemicals and synthetic coolants in Puff EC to see their potentially harmful effects on health," said Esther Omaiye, a former graduate student in the Environmental Toxicology Graduate Program and first author of the research paper. . "The levels of nicotine, flavor chemicals and synthetic coolants in Puff EC exceed levels used in other consumer products, raising questions about the safety of Puff products."

Omaiye, who is now a postdoctoral researcher in Prue Talbot's lab, said one of the areas of regulatory concern related to EC is the continued development of novel chemicals in e-liquids.

"For years, we've been aware that EC design is evolving," said Talbot, a professor of cell biology who led the research team. “It wasn’t until recently that we realized that the chemicals used in EC fluids were also changing. These changes often make EC products more attractive to teens or try to circumvent FDA regulation—such as using synthetic nicotine instead of tobacco-derived nicotine to evade FDA regulation.”

According to Talbot, the synthetic coolant WS-23 developed for shaving cream is now contained in EC fluids, but there is little information on its inhalation toxicology.

"Our work shows that the concentrations of WS-23 used in Puff ECs are sufficient to have adverse health effects with long-term use," she said.

Other findings from the study are:

Puff EC contains much higher concentrations of synthetic coolants and flavor chemicals than JUUL EC.

Although the risk of inhalation remains unknown, EC manufacturers are increasing the use and concentration of synthetic coolants, which are attractive to younger users.

Talbot and Omaiye were joined by Wentai Luo, Kevin J. McWhirter and James F. Pankow of Portland State University in Oregon.

The research was funded by the National Institute of Environmental Health Sciences and the Center for Tobacco Products. Omaiye is supported by the UC President's Dissertation Annual Fellowship.

The title of the research paper is "Disposable puff bar electronic cigarettes: Chemical composition and toxicity of e-liquids and synthetic coolants."