Vaping, which has long been promoted as a "healthier" alternative to smoking, may actually be more toxic than traditional cigarettes.
Researchers from the University of California, Davis, tested seven flavored e-cigarettes from three of the most popular brands and found that they release more toxic, cancer-causing metals than traditional cigarettes.
One of the disposable e-cigarettes studied released more lead during a day of use than nearly 20 packs of regular cigarettes.
The study's lead author, Mark Salazar, a doctoral candidate, said the levels were so high that "we thought our equipment was broken."
Scientists analyzed the metal content of seven types of wearable devices from ELF Bar, Flum Pebble, and Esco.
Using a device to activate e-cigarettes and heat their internal liquid, they generated between 500 and 1,500 puffs for each device.
After using the devices to simulate their use over a week, they were found to contain heavy metals such as nickel, lead and antimony.
These metals are used to manufacture the devices' heating coils, which turn the liquid into a vapor that is then inhaled. These metals leach from the devices into the e-cigarette liquid.
The vapor from three of the devices tested contained levels of lead and nickel above safe limits for cancer, while two of them had high levels of antimony - an element used in batteries and as a flame retardant.
Esco Bars were found to release four to thirteen times more lead in the first 200 puffs than a pack of 20 cigarettes. This amounts to an exposure to lead equivalent to smoking 19 cigarettes in a day.
Four devices sold by Esco contained levels of lead and nickel linked to respiratory diseases such as asthma and scarring of the lungs (pulmonary fibrosis).
The researchers stressed that although they only tested 3 of the 100 most popular vape brands, the results highlight serious health risks, especially for teenagers and young adults who use them most frequently.
All three heavy metals tested are considered probable carcinogens, meaning they can cause cancer. All have been linked to lung cancer, while lead has also been linked to kidney and brain cancer. Nickel has also been linked to cancer of the nose and sinuses.
Although e-cigarettes contain more heavy metals than traditional cigarettes, decades of research show that cigarettes are still more dangerous, because they contain about 7,000 carcinogenic substances, compared to the 2,000 found in vaping.
Cigarettes have also long been proven to cause lung cancer, while there is still no evidence of a direct link between vaping and the disease.
Brett Poulin, senior author of the study and professor in the Department of Environmental Toxicology at UC Davis, stated:
"Our study highlights the hidden dangers of these new and widespread e-cigarettes – with dangerous levels of neurotoxic lead and carcinogenic nickel and antimony – which indicates the need for urgent intervention and regulatory regulation."
"These risks are not only greater than other e-cigarettes, but in some cases are even greater than traditional cigarettes."
The study, published Wednesday in ACS Central Science, analyzed metals and metalloids – elements that have characteristics between metals and nonmetals.
Using a device to heat e-cigarettes, they produced between 500 and 1,500 puffs per device. The average user takes about 100 to 200 puffs per day.
The team found that vapors from three devices – ELF Bar Flavored, ELF Bar Clear and Esco Bar Flavored – exceeded the cancer risk limit for nickel.
Meanwhile, Flum Pebble Flavored and Esco Bar Flavored exceeded safety levels for antimony.
Also, Esco Bar Flavored and Esco Bar Clear released lead at levels that exceed the risk threshold for non-cancerous diseases, such as asthma and pulmonary fibrosis.
Mark Salazar, the study's first author and a doctoral candidate in Poulin's lab, said:
“We found that these wearable devices have toxins present from the start in the e-liquid, or that significantly leach from their ingredients in the liquid and end up in the vapor that is inhaled.”
According to the CDC, ELF was the most used brand by teenagers and young adults in 2023 and 2024.
Esco Bars sold about $82 million worth of products in the US in 2022.
No flavored e-cigarettes are legal for sale in the U.S., although the FDA has authorized some unflavored ones. However, both types are still available in stores and online.
According to data from Reuters, $2.4 billion in illegal vapes were sold in the US last year – a situation that experts consider particularly worrying, as these products are not controlled by any oversight agency.
About 6% of American adults – roughly 17 million people – use vapes, according to the most recent data from the CDC.
Also, about 6% of middle school students and 8% of high school students reported having used vaping at least once in the last 30 days.
Although e-cigarettes have been considered a safer alternative and an aid to quitting smoking, recent studies show that they may increase the risk of heart and lung damage.
In a case reported this month, a New Jersey man died from what is believed to be the first documented case of lung cancer caused by e-cigarettes.
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