Worried about the increasing presence of microplastics in our environment? Here’s something else to think about: Scientists have found that chewing just one piece of gum can release hundreds to thousands of tiny plastic pieces into our saliva that are likely to be absorbed into our bodies when we swallow, according to unpublished research that will be presented at the American Chemical Society’s Spring 2025 meeting in San Diego.
While it’s true that there’s still more to learn about the health effects of microplastic exposure, ingestion of plastics is “probably not a good thing,” says Linda Kahn, PhD, MPH, an assistant professor of population health at the NYU Grossman School of Medicine in New York City.
“What we know about microplastics themselves leads us to believe that they could be associated with negative health outcomes,” says Dr. Kahn.
Study Subject Chewed Each Piece of Gum for 4 or 20 Minutes
To find out more about microplastics and chewing gum, scientists analyzed 10 popular chewing gum brands, five natural and five synthetic.
Chewing gums are made from a rubber base, sweetener, flavorings, and other ingredients. In general, natural gums use plant-based polymers (sometimes called bioplastics) and synthetic gums use petroleum-based polymers — in other words, gum contains plastic as an ingredient.
Researchers theorized that the synthetic gums would shed more microplastics, according to lead author Lisa Lowe, a PhD student who started the project as an undergraduate intern at UCLA.
For the first experiment, one volunteer chewed seven pieces of gum from each brand. The subject chewed each piece of gum for 4 minutes, producing samples of saliva every 30 seconds, then did a final mouth rinse with clean water, all of which got combined into a single sample.
In another experiment, the volunteer provided saliva samples periodically over 20 minutes of chewing gum, so researchers could look at the release rate of microplastics from each piece.
Key findings from the experiment included:
- Gum released an average of 100 microplastics per gram (g). Gum is usually between 2 and 6 g. For example, one piece of Extra brand gum weighs 2.5 g.
- Some types of gum released up to 637 microplastics per gram.
- Most of the microplastics detached from gum within the first 2 minutes of chewing. It wasn’t saliva that broke down the microplastics, but rather the act of chewing that made the pieces flake off.
- Surprisingly, both synthetic and natural gums released similar amounts of microplastics.
Researchers estimated that if the average person chewed 160 to 180 small sticks of gum per year, they would ingest around 30,000 pieces of microplastic.
How does microplastic exposure from chewing a piece of gum compare with exposure from plastic water bottles or plastic food storage containers? “This is hard to compare, because our study was limited by our analysis instruments,” says Lowe.
The technology researchers used could only identify microplastics 20 micrometers wide or larger — they couldn’t assess the smaller, nano-size plastics. That means their microplastic counts are likely underestimates, the study authors say.
Goodbye to Gum?
“I don’t think it is very critical that we don’t chew gum. There are so many places we are exposed to microplastics, and we can’t avoid them all. But I think it is important to be aware of this issue,” says Lowe.
If people want to continue to chew gum but limit their microplastic exposure, she suggests chewing one piece longer rather than popping in a new piece.
Because the research hasn’t been published yet, there are some unanswered questions, says Kahn. “If natural and synthetic gum both release microplastics, what is the source? The gum itself or the packaging?”
It would also be helpful to know if one type of gum is higher in microplastics, for example bubble gum or sugar-free gum, she says.
Kahn leans toward limiting gum. “It can’t hurt to be cautious,” she says. “If gum chewing is a source of microplastics, then it probably is not a great thing to do if you can avoid it, right?”