A new study from UCLA, says a single piece of chewing gum can release hundreds to thousands of microplastic particles into saliva, increasing the risk of ingestion and potential long-term health effects.
Published Apr 06, 2025 | 7:00 AM ⚊ Updated Apr 06, 2025 | 7:00 AM
Synopsis: Chewing gum may be an unexpected source of microplastics, according to a new study from UCLA. Researchers found that a single piece can release up to 3,000 plastic particles into saliva, with both synthetic and natural gums showing similar results. The health impact is still unclear, but scientists say more research is needed.
Plastic has become an unavoidable part of modern life, present in everything from household items to personal care products.
Everyday objects such as cutting boards, synthetic clothing and cleaning sponges shed microscopic plastic fragments known as microplastics, which can enter our bodies through inhalation, ingestion or skin contact.
Now, researchers have identified another unexpected source of microplastic exposure – chewing gum.
According to a recent study, a single piece of gum can release hundreds to thousands of microplastic particles into saliva, raising the risk of ingestion and possible long-term health effects.
“Our goal is not to alarm anybody,” said Sanjay Mohanty, the project’s Principal Investigator and an Engineering Professor at the University of California, Los Angeles (UCLA), in a statement.
“Scientists do not know if microplastics are unsafe to us or not. There are no human trials. But we know we are exposed to plastics in everyday life, and that is what we wanted to examine here.”
Although there is no conclusive evidence from human trials, animal studies and cell-based research suggest that microplastics could be harmful. While awaiting more definitive answers from the scientific community, individuals can take steps to reduce their exposure.
Scientists estimate that humans consume tens of thousands of microplastics – ranging between 1 micrometre and 5 millimetres in width – every year through food, drinks, plastic packaging, coatings, and manufacturing processes.
However, chewing gum as a source of microplastics has not been widely studied, despite its popularity around the world.
This led Mohanty and Lisa Lowe, a graduate student in his lab, to explore how many microplastics a person might ingest from chewing natural and synthetic gums.
Chewing gums are composed of a rubbery base, sweeteners, flavourings and other ingredients. Natural gum products use a plant-based polymer, such as chicle or other tree sap, to achieve the right chewiness, whereas others rely on synthetic rubber bases made from petroleum-based polymers.
“Our initial hypothesis was that the synthetic gums would have a lot more microplastics because the base is a type of plastic,” said Lowe, who began the project as an undergraduate intern at UCLA and presented the research.
The researchers tested five brands of synthetic gum and five brands of natural gum, all commercially available. In order to reduce variability due to individual chewing habits and saliva composition, they had all seven pieces from each brand chewed by the same person.
Inside the lab, this person chewed each piece for 4 minutes, providing saliva samples every 30 seconds, followed by a final mouth rinse with clean water. These were then combined into a single sample. In a separate test, saliva samples were collected over a 20-minute period to track the rate of microplastic release.
The number of microplastics present in each sample was then measured. Plastic particles were stained red and counted under a microscope, or analysed using Fourier-transform infrared spectroscopy, which also identified the polymer composition.
On average, Lowe recorded 100 microplastics released per gram of gum, with some pieces releasing up to 600 microplastics per gram. As a typical piece of gum weighs between 2 and 6 grams, a larger piece could release up to 3,000 plastic particles.
Assuming the average person chews 160 to 180 small sticks of gum per year, the study estimates that this could lead to the ingestion of around 30,000 microplastics annually. Given that people are already consuming tens of thousands of microplastics each year, chewing gum could significantly increase that number.
“Surprisingly, both synthetic and natural gums had similar amounts of microplastics released when we chewed them,” said Lowe. They also shared the same types of polymers: polyolefins, polyethylene terephthalates, polyacrylamides and polystyrenes. Among these, polyolefins – including polyethylene and polypropylene – were the most prevalent in both types of gum.
Most microplastics detached from the gum within the first 2 minutes of chewing. However, Mohanty noted that this was not due to enzymes in saliva breaking the plastic down. Instead, the abrasive motion of chewing was sufficient to make plastic particles flake off. After 8 minutes of chewing, 94 percent of the plastic particles collected during the tests had already been released.
To reduce potential exposure, Lowe suggests chewing one piece of gum for longer instead of frequently replacing it with a new one.
Due to the limitations of their equipment, the study only identified microplastics that were 20 micrometres wide or larger. Mohanty added that smaller particles likely went undetected and that further research is needed to assess the potential release of nano-sized plastics from chewing gum.
“The plastic released into saliva is a small fraction of the plastic that is in the gum,” Mohanty concluded. “So, be mindful about the environment and do not just throw it outside or stick it to a gum wall.”
(Edited by Dese Gowda)
