A study by scientists at the University of California, Riverside shows ultrasonic cigarettes, or u-cigarettes, marketed as a less harmful alternative to traditional e-cigarettes, may pose significant health risks due to the presence of harmful metals in their liquids and aerosols. 

U-cigarettes have a “sonicator” that vibrates a liquid solution, usually containing nicotine, flavorings, and propylene glycol or vegetable glycerin, to produce microscopic droplets (aerosol). The technology uses high-frequency ultrasonic vibrations instead of heating coils used in traditional electronic cigarettes, or e-cigarettes. 

The study, published in Environmental Health Perspectives, quantified chemical elements and metals in various flavors of SURGE u-cigarettes, JUUL e-cigarettes, and other pod-style e-cigarettes.

“U-cigarettes claim to be less harmful than e-cigarettes,” said Esther Omaiye, a postdoctoral researcher in the Department of Molecular, Cell and Systems Biology and the paper’s first author. “Since this novel technology has limited evidence-based data, we were interested in investigating this claim to understand the chemistry and toxicology involved and the potential impact on user behavior.”

Using advanced analytical techniques, such as scanning electron microscopy and inductively coupled plasma optical emission spectroscopy, the study identified 16 elements in at least one fluid or aerosol sample. 

“We found u-cigarette fluids and aerosols generally had higher concentrations of metals compared to fourth-generation e-cigarettes,” Omaiye said. “Metals in u-cigarettes are not essential for the functioning of the device. However, they are usually present as unintended contaminants. Their presence is a health concern.”

The researchers found that the products they tested, including SURGE, contained silicon, while nickel was found in low concentrations across all fluids, except for the KWIT Stick, which showed levels of up to 66,050 micrograms per milliliter of e-fluid. Additionally, the researchers found SURGE u-cigarettes have copper and zinc in their fluids, with minimal transfer to aerosols.

“The most concerning results were the elevated levels of arsenic and selenium in SURGE products, both of which are listed on the FDA’s Harmful and Potentially Harmful Constituents List,” said senior author Prue Talbot, a professor of the graduate division. “Our study underscores the urgent need for regulations to limit arsenic and selenium in these products and calls for routine surveillance to identify rogue products with abnormally high metal levels.” 

According to Talbot and Omaiye, the data raises serious concerns about the long-term health risks associated with u-cigarette use, including potential cancer and neurotoxicity. They note that inhalation of high levels of these elements can have severe health consequences, including lung diseases such as silicosis and metal fume fever, organ damage, and cancer, particularly from carcinogens like nickel and arsenic. 

“Even metals like zinc and selenium, essential for life in small amounts, can become toxic at high levels, highlighting the potential danger of inhaling contaminated aerosols,” Omaiye said. “As fine particles or aerosols, these elements can bypass body defenses and reach deep into lung tissues. Users should stay informed about what is in their devices and exercise caution when evaluating claims about safety. For non-vapers, it is best not to start, but if they choose to, they must understand the risks involved.”

Talbot and Omaiye plan to build on their findings to deepen their understanding of emerging tobacco products and technologies, as well as their impact on public health. 

“Regardless of the vaping technology, inhalation of metals like arsenic, nickel, lead, or chromium is always hazardous—even at low concentrations over time,” Talbot said. “These metals are not filtered by the lungs the way they might be by the digestive system, making inhalation exposure particularly concerning.” 

Omaiye emphasized that researchers must continue conducting independent studies on vaping technologies to assess metal exposure risks, focusing on device design, materials, and long-term effects. 

“Stricter manufacturing regulations and accountability are needed to ensure the safety of device components and vaping liquids,” she said. “Medical professionals, regulatory agencies, and the public must stay informed and proactive as new vaping technologies emerge, recognizing that changes in components may not eliminate health risks.”

The research was supported by the National Institutes of Health, California’s Tobacco-Related Disease Research Program, and UC Riverside. Omaiye is a recipient of a UC President’s Dissertation Year Fellowship.

The title of the paper is “Quantification of 16 Metals in Fluids and Aerosols from Ultrasonic Pod-Style Cigarettes and Comparison to Electronic Cigarettes.”

 

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