Chewing gum can shed hundreds of microplastics into your mouth

Researchers have found yet another potential contributor to the increasing amount of microplastics found in our bodies: gum. According to a pilot study presented during the American Chemical Society’s spring meeting, a single piece of chewing gum is liable to release hundreds of polymer particles into our mouths. And while a portion of them are likely ingested by the chewer, improperly tossing your gum can also add to the environment’s microplastic problem.

Experts previously estimated humans eat tens of thousands of microplastic particles ranging between 1 micrometer- and 5 millimeters-wide each year. Much of that comes from plastic packaging and coatings, as well as miniscule polymers that rub off onto food and into drinks. But while a single stick of gum may be small, the average gum consumer chews 160–180 sticks per year. Recently, a team led by  at the University of California, Los Angeles (UCLA) engineering professor Sanjay Mohanty wondered how much microplastic might come from the habit.

To gain an initial understanding of the situation, they asked a single volunteer to test 10 brands of commercially available gum—five with synthetic additives and five with only natural ingredients. While future studies may employ many more participants, the researchers focused on a single person to limit the variations on chewing patterns and saliva.

The volunteer then proceeded to chew. A lot.

Seven pieces of each gum brand were chomped in succession by the participant for four minutes at time. Researchers then collected saliva samples every 30 seconds, along with a sample taken after rinsing their mouth with clean water. These were then all combined into a single, larger sample. In a second round, the person produced saliva samples at various intervals over 20 minutes to see how much microplastic was contained in a single stick of each gum. From there, the microplastics were counted after staining them red, as well analyzed for composition using Fourier-transform infrared spectroscopy.

“Our initial hypothesis was that the synthetic gums would have a lot more microplastics because the base is a type of plastic,” Lisa Lowe, the study’s co-collaborator and a graduate student in Mohanty’s lab, explained in a statement. (Yes, certain types of synthetic gum contain petroleum-based polymers.)

But if you think switching to an all-natural brand is better for you, think again.

“Surprisingly, both synthetic and natural gums had similar amounts of microplastics released when we chewed them,” Lowe added.

Most of the study’s gum shed the majority of its microplastics during the first couple minutes of chewing. But while saliva collects a lot of that, the team discovered it’s actually your teeth that are mostly responsible for dislodging the particles. About 94 percent of the plastic counted was shed by the eighth minute. Knowing this, Lowe recommends chewing one piece of gum as long as possible before moving on to the next stick.

The final tallies indicate chewers can expect an average of at least 100 microplastics per gram of gum, although that number can increase up to 600 particles per gram. Extrapolating this further, a 2–6 gram piece of gum may release as many as 3,000 microplastics. Multiply that by the average amount of gum chewed annually, that you could be looking at around 30,000 microplastics ingested each year. And given that experts believe people already annually eat tens of thousands of particles, this means regular gum chewers could be receiving a large influx of unwanted polymers thanks to their favorite brands.

Unfortunately, the total amount of microplastics from gum is likely much larger. Given the team’s available equipment, counting was limited to particles measuring at least 20-micrometers-wide—and many microplastics are much smaller than that.

“Our goal is not to alarm anybody,” said Mohanty. “But we know we are exposed to plastics in everyday life, and that’s what we wanted to examine here.”

But if you are going to continue chewing, the researchers also took the time to remind everyone to properly dispose of their well-masticated gum.

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

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