Chewing Gum Could Release Microplastics Into Saliva, Study Finds

According to a new study currently undergoing peer review, chewing gum could be a source of ingested microplastics. Researchers found that chewing gum could release thousands of microplastic particles into saliva over time, increasing the chance of ingestion.

“Our goal is not to alarm anybody,” Sanjay Mohanty, principal investigator of the study and an engineering professor at the University of California, Los Angeles (UCLA), said in a statement. “Scientists don’t 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’s what we wanted to examine here.”

Scientists analyzed five brands of natural and five brands of synthetic chewing gums to determine potential for microplastic shedding. While synthetic chewing gums are made with rubbery, petroleum-based polymers, natural gum varieties rely on plant-based polymers for that chewable texture, with the polymers often coming from tree sap.

“Our initial hypothesis was that the synthetic gums would have a lot more microplastics because the base is a type of plastic,” said Lisa Lowe, a graduate student at UCLA who is presenting the research this week at the American Chemical Society spring meeting.

In one experiment in the study, each gum sample was chewed for 4 minutes, with saliva samples pulled every 30 seconds. After chewing, the person rinsed their mouth with water and that too became a sample. For another experiment, researchers collected saliva samples multiple times throughout a 20-minute timeframe and measured the microplastic amounts in each sample.

While researchers had expected to find more microplastic shedding from synthetic gums, both natural and synthetic products led to similar amounts of microplastics released into saliva, often within just 2 minutes of chewing the gum. Both natural and synthetic gums had the same polymers, most of which were polyolefins. As the American Chemical Society reported, this group of plastics contains plastic types such as polyethylene (PE) and polypropylene (PP).

The team found an average of 100 microplastics shed into saliva for each gram of gum. Some pieces of gum released up to 637 microplastics per gram. 

Based on the calculations of a gram of gum weighing between 2 and 6 grams, the researchers determined that a single stick of gum could release up to 3,000 microplastics, and for habitual gum-chewers, this could add up to 10,000 microplastics shed into saliva per year. 

As Reuters reported, humans ingest around 5 grams of microplastics per week, and the new research revealed that chewing gum could contribute to the amount of ingested plastic particles.

To minimize ingestion, the researchers recommended chewing one piece of gum for longer versus swapping in new sticks of gum more frequently, based on their findings that 94% of the collected microplastics were released within 8 minutes of chewing.

But the findings also revealed that people should avoid discarding gum into environments, where additional microplastics could be shed and the polymer-based gum itself could become a piece of pollution.

“The plastic released into saliva is a small fraction of the plastic that’s in the gum,” Mohanty said in a statement. “So, be mindful about the environment and don’t just throw it outside or stick it to a gum wall.”