Despite slick marketing, u-cigarettes might be more dangerous than older vape models. Scientists found they release metals like arsenic and selenium—linked to cancer and lung disease—into users’ lungs.

A new study from scientists at the University of California, Riverside reveals that ultrasonic cigarettes, or u-cigarettes, could be far more dangerous than they appear. Marketed as a safer alternative to traditional e-cigarettes, these high-tech devices may actually expose users to harmful metals found in both the liquid and the vapor they produce.

U-cigarettes use a unique technology called a “sonicator” to generate aerosol. Instead of using heated coils like conventional e-cigarettes, they rely on high-frequency ultrasonic vibrations to transform a liquid mixture—typically containing nicotine, flavorings, and a base like propylene glycol or vegetable glycerin—into an inhalable mist.

Investigating U-Cigarette Chemistry and Safety

The study, published recently in Environmental Health Perspectives, analyzed chemical and metal content in multiple flavors of SURGE u-cigarettes, as well as popular brands of e-cigarettes like JUUL and similar pod-style devices.

“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 powerful tools like scanning electron microscopy and optical emission spectroscopy, the researchers detected 16 different elements in at least one fluid or vapor sample.

U-Cigarettes Found to Contain Higher Metal Levels

“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.

Arsenic and Selenium Levels Raise Alarms

“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.

Inhaled Metals Bypass Body Defenses

“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.”

A Call for Vigilance and Regulation

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.”