E-cigarettes can rapidly drive toxic metals deep into the lungs, where they can damage tissue, according to a new study providing detailed evidence on the risks of vaping.
Even short-term exposure can result in measurable accumulation of toxic metals in lung tissue, increasing the risk of chronic lung problems, cancer, cardiovascular disease, and other conditions.
This study was published last month (April 2026). Analytical and bioanalytical chemistryfor the first time used a special method to break down e-cigarette vapor, separate its components and accurately measure toxic metals. For the first time, researchers have detected chemical evidence that certain metal-based compounds (organometallics) that are easily absorbed by the lungs travel in e-cigarette aerosols.
The findings come after the FDA announced yesterday the approval of fruit-flavored e-cigarettes, including mango and blueberry, for adult smokers. The change in policy comes after months of appeals from the e-cigarette industry to President Donald Trump.
“Taken together, these findings provide new evidence that e-cigarettes deliver toxic components to the lungs, disrupting iron homeostasis (the normal balance) and posing risks to lung and systemic health,” the authors wrote.
Dr. Pamela Ring points out that exposure to toxic metals can come not only from liquids, but also from metals in heating devices. This suggests that regulation of e-cigarettes should include the entire device, similar to the definition of “e-cigarette” in California, she says.
“Studies like this are important because tobacco companies are aggressively promoting e-cigarettes as ‘harm reduction’ to distract from the fact that the majority of their profits still come from tobacco and that they are actually growing new nicotine markets rather than transforming them,” said Lin, professor of medicine and director of the UCSF Center for Tobacco Control Research and Education. “This study contributes to the growing body of evidence that e-cigarettes themselves carry significant health risks.”
Laura Crotty-Alexander, Ph.D., professor and associate chair of the Department of Medicine at the University of California, San Diego, agreed, saying, “These findings will help us understand exactly why e-cigarettes cause lung damage and increase cancer risk. Identifying the accumulation of inhaled metals in lung tissue is an important clue and helps explain the ‘how’ behind e-cigarette-related diseases.” ”
Rapid increase in e-cigarette use raises public health concerns
In the United States, youth and adolescents use e-cigarettes more than any other tobacco product. More than 100 million people, including at least 15 million children, use e-cigarettes because of the industry’s product design, aggressive marketing, widespread access to vulnerable populations, and limited regulatory oversight around the world.
Although the industry promotes e-cigarettes as a safe alternative to traditional smoking, research shows that children, adolescents, and young adults who use e-cigarettes are approximately three times more likely to start smoking cigarettes than non-users. In last year’s review, carcinogenic They conclude that nicotine e-cigarettes are likely carcinogenic and may increase the risk of oral and lung cancer. Additionally, recent research indicates that widely promoted sweet, minty, and fruity flavors may increase the risk of nicotine use and addiction.
The new study builds on new research showing that vapors expose people to toxic and carcinogenic metals. A 2020 study found that e-cigarette users had levels of metals and metalloids (elements such as arsenic) that were similar to or higher than cigarette users and higher than cigar users.
In another study from Johns Hopkins University, researchers found that nickel, chromium, and lead were present in multiple types of devices. Toxic metals were detected in all samples.
Complex aerosol, not just nicotine
E-cigarettes, most of which contain nicotine, heat a liquid into an aerosol that the user inhales. However, both liquids and aerosols are chemically complex mixtures. They contain many substances other than nicotine, which itself is harmful and highly addictive.
These include toxic metals, air pollutants, fragrance chemicals, and cancer-related compounds from device hardware or e-liquid ingredients. The researchers say that when the high temperatures of the heating element (device coil) combine with chemicals in the liquid, new metal-containing compounds can be formed.
Breathing in toxic metals and other pollutants can cause inflammation and interfere with lung and immune system development, leading to long-term breathing problems and illness. Some metals, such as zinc and copper, are essential in small amounts but harmful in large amounts.
“Whether these metals detected in the lungs remain confined to the respiratory system or enter the circulation and accumulate in distant organs remains a question and requires further investigation,” the researchers wrote. “This potential redistribution extends the potential health effects of e-cigarettes beyond local lung injury.”
Researchers analyzed e-liquid, aerosol and lung tissue from mice exposed to nicotine vapor for 30 minutes twice a day for four days. They selected a strain of laboratory mice that reacts strongly to cigarette smoke, causing lung inflammation and airway changes similar to those of human smokers.
The team then used a combination of chemical tests and spatial imaging to track how and where the metal traveled from the device to the lungs. They detected multiple metals in both liquids and aerosols, including nickel, lead, copper, aluminum, tin, arsenic, and trace amounts of mercury.
Increased exposure increased metal accumulation, with different metals gathering in different areas. For example, lead, nickel, and tin were concentrated in the upper lung regions, while zinc was more common in the lower lung regions.
Studies have shown that even short exposures caused measurable metal accumulation. Rather than being spread evenly, the metal collects in patchy, localized deposits. Over time, this buildup can increase the risk of lung damage, chronic disease, and impaired healing.
“Concerningly, we observed measurable changes in metal concentrations in (lung) tissues after just a few puffs, indicating that even short exposures are sufficient to alter metal levels,” the researchers wrote.
The researchers said the exposure pattern suggests that inhaled metals may persist in lung tissue rather than disappear immediately. Nickel levels increased significantly, as did copper, lead, and tin.
- Nickel rose from about 77 nanograms per gram (ng/g) in unexposed lung tissue to 368 after 8 puffs and 242 after 32 puffs.
- Copper and lead were spiked at high levels, with peak amounts increasing more than 3-fold for copper and 25-fold for lead compared to controls.
- Tin also rose rapidly, reaching levels approximately 15 times higher than controls at the highest exposure.
Because there are no specific regulatory limits for the metals found in e-cigarettes, the researchers could only compare their results to safety standards for inhalation from other areas, such as workplace air or pharmaceuticals. This gap exists not because the metals are safe, but because inhalation data are limited, the researchers say.
When compared to the pharmaceutical limit values for inhaled drugs (i.e. USP 232), several metals were found to be well above values considered safe. Copper and tin also exceeded the recommended limits, as follows:
- Arsenic was about 480 times more
- Approximately 250 times that of nickel
- Approximately 60 times more than chromium
- Approximately 180 times more than mercury
- Lead is approximately 17x
“Although the USP 232 limit was developed for pharmaceutical inhalation products rather than e-cigarettes, it is a conservative, health-based benchmark for inhalation exposure,” the authors wrote. “The fact that several of the metals listed here exceed these limits reinforces concerns of metal contamination in the e-cig liquids tested and the lack of comparable product-specific standards for e-cig emissions.”
At the same time, exposure to e-cigarettes significantly lowered iron levels in the lungs, causing researchers to express concern. Iron supports cellular oxygen transport, immune function, and energy production. Iron deficiency is associated with serious lung diseases such as chronic pulmonary obstructive disease (COPD), cystic fibrosis, and acute respiratory distress syndrome.
Researchers suggest that this drop may reflect subtle changes or redistribution of iron in the body. Or it may be due to a change in the way the iron is processed, rather than a simple loss.
Taken together, the combination of decreased iron, localized accumulation of lead, and increases in other metals and metalloids (such as nickel, copper, tin, and arsenic) is “of particular concern,” the researchers say.
“These risks are further exacerbated by the high prevalence of e-cigarette use among adolescents, who may be more susceptible to the effects of toxic substances during critical developmental periods,” the researchers wrote.
Research limitations and next steps
The researchers conducted the experiment over a four-day period in a mouse model, so the study does not measure long-term disease outcomes in humans. Exposure patterns may also vary depending on the device, liquid, and user behavior, the researchers noted.
Still, Crotty-Alexander suggests the study likely underestimates real-world exposure and risk.
“First, this experiment was performed on mice that only breathe through their noses, which means that many of the metal particles are filtered out before they reach the lungs,” she said. “Second, whereas most people who smoke e-cigarettes do so repeatedly throughout the day and every day, the mice were only exposed once.”
Increased usage and regulatory gaps
Unlike cigarettes, e-cigarette devices and liquids vary widely and often lack quality control, using materials with unknown health risks and limited oversight.
There are no specific restrictions on metals in e-cigarette liquids or vapors, so users can unknowingly expose themselves to dangerous levels.. Agencies such as the FDA and the World Health Organization (WHO) focus on nicotine and labeling.
Researchers are calling for stricter standards for device materials, mandatory testing for metal emissions, and human studies on adolescents, especially during critical developmental years when they are most susceptible to toxic effects. They also encourage studies comparing devices, long-term exposure, different e-liquids, and whether metals diffuse beyond the lungs.
“Given the widespread use of disposable e-cigarettes among adolescents, there is an urgent need for regulatory oversight of device materials and mandatory metal testing,” the authors write.
reference
McGrath J, Royle O, Thorpe A, et al. Analytical investigation of metal distribution from e-cigarette aerosol to lung deposition using multiplatform mass spectrometry. Analytical and bioanalytical chemistry. Published online 2026: 1-15. doi:10.1007/s00216-026-06487-1
