Some disposable e-cigarettes release more lead in one day than 20 packs of conventional tobacco.

Mark Salazar, a PhD candidate in the lab of Brett Poulin, assistant professor in the Department of Environmental Toxicology at UC Davis, first saw a disposable vape cartridge while visiting a friend. These are self-contained devices containing a battery, e-liquid, and a heating element. Salazar was curious: What exactly was his friend smoking? He took the cartridge to the UC Davis lab and analyzed its vapor for metal concentrations.

"When I first saw the lead concentrations , they were so high that I thought our instrument was broken. That motivated us to investigate these disposables further," Salazar explains.

Under their seemingly harmless appearance, with attractive colors, flavors, and shapes, some disposable e-cigarettes and vaping pods release higher amounts of toxic metals than older e-cigarettes and traditional tobacco, according to this study from the University of California, Davis. Specifically, one of the disposable e-cigarettes studied released more lead during a day of use than nearly 20 packs of traditional tobacco .

The study, published Wednesday in the journal ACS Central Science, suggests that while most disposable e-cigarettes are illegal in the United States, they remain widely available. Most disposable e-cigarette users are teenagers or young adults, who are also highly susceptible to lead exposure. In fact, inhaling certain metals can increase the risk of cancer , respiratory diseases, and nerve damage.

"Our study highlights the hidden risks of these popular new disposable e-cigarettes—with dangerous levels of neurotoxic lead and carcinogenic nickel and antimony—underscoring the need for urgent regulatory enforcement," said lead author Brett Poulin. "These risks are not only worse than those of other e-cigarettes, but also, in some cases, those of traditional cigarettes," he warned.

Scientists analyzed the metals and metalloids present in seven types of disposable devices from three of the most popular brands. Using an instrument to activate the disposable e-cigarettes and heat the liquid inside, they generated between 500 and 1,500 puffs for each device . The result was that some devices emitted surprisingly high concentrations of elements in the vapor, including antimony and lead. Furthermore, the levels of chromium, nickel, and antimony increased as the number of puffs increased.

Most of the disposable e-cigarettes tested released significantly higher amounts of metals and metalloids into the vapor than older rechargeable vaporizers.

The scientists then disassembled the devices to trace the sources of the metals. "We found that these disposable devices have toxins already present in the e-liquid, or that they largely leach from their components into the e-liquids and ultimately transfer into the smoke," Salazar says.

Leaded bronze alloy components in some devices released nickel and lead into the vaping liquid. Nickel was also released from heating elements , and antimony was found at elevated levels in unused vaping liquids, factors that increase the risk of cancer.

The researchers also assessed the health risks to people who used them daily. The fumes from three of the devices contained levels of nickel, and two devices had antimony levels that exceeded cancer risk limits. Fumes from four of the devices emitted nickel and lead, exceeding risk thresholds for pathologies other than cancer, such as neurological damage and respiratory diseases.

Although the researchers tested only three of the nearly 100 brands of disposable e-cigarettes on the market, they believe the results of this initial work are already concerning given the popularity of disposable e-cigarettes, especially among teens.

In this regard, the market is ahead of science. Few studies are available on the newest devices, leaving consumers and regulators largely uninformed. The paper underscores the need to enforce regulations on illegal e-cigarettes, while continuing research to reveal the magnitude of the problem and its implications for public health.