Why are scientists warning about plastic exposure from everyday chewing gum?

Plastic is everywhere, and its tiny particles, known as microplastics, end up in many everyday products. Now, chewing gum may add to the list. A new study shows that chewing gum can release hundreds to thousands of microplastic particles per piece into saliva, which people could swallow.

Researchers presented their findings at the American Chemical Society's (ACS) Spring 2025 meeting. The meeting featured over 12,000 scientific presentations. While the researchers say they don’t yet know the effects of microplastics on health, they raise an important point about potential exposure.

What’s really in your gum?

Sanjay Mohanty, the project’s principal investigator and a professor at UCLA, stated that the goal of the study wasn’t to alarm anyone. “Scientists don’t know if microplastics are unsafe to us or not. There are no human trials,” Mohanty said. “But we know we are exposed to plastics in everyday life, and we wanted to examine that.”

Animal studies and studies with human cells have suggested that microplastics could be harmful. Experts recommend minimizing exposure until more data is available.

Scientists estimate that people consume tens of thousands of microplastics every year through food, drinks, plastic packaging, and other sources. While researchers have studied microplastics in food and packaging, they haven’t looked closely at chewing gum, even though it’s popular worldwide.

Mohanty and graduate student Lisa Lowe decided to test how much plastic people could ingest from chewing natural and synthetic gums. They tested five brands of synthetic gum and five brands of natural gum, all commercially available.

Gum contains a rubbery base, sweeteners, flavorings, and other ingredients. Natural gum uses plant-based polymers like chicle, a tree sap. Synthetic gums use petroleum-based rubber polymers.

Lowe, who began the project as an undergraduate intern, thought synthetic gum might release more microplastics because of its plastic base. But the study found that both synthetic and natural gums released similar amounts of microplastics.

How the study worked

To reduce differences in chewing patterns and saliva, one person chewed all the gum samples. Each piece was chewed for four minutes, and saliva samples were collected every 30 seconds. The person also rinsed their mouth with clean water at the end of each session. In a second test, researchers collected saliva samples over a 20-minute period to measure the release rate of microplastics.

Afterward, the researchers counted the microplastics using two methods: they stained plastic particles red and counted them under a microscope, and they also used Fourier-transform infrared spectroscopy to identify the chemical composition of the plastics. The study only counted particles larger than 20 micrometers due to technical limits. Smaller particles may have been present but went undetected.

The study showed that each piece of gum released, on average, 100 microplastic particles per gram of gum. Some pieces released as many as 600 microplastics per gram. A typical piece of gum weighs between 2 and 6 grams, so a large piece could release up to 3,000 microplastic particles. Researchers estimated that people who chew 160 to 180 pieces of gum each year could ingest around 30,000 microplastics from their gum alone.

Both synthetic and natural gums contained the same types of plastics. The most common polymers were polyolefins, including polyethylene and polypropylene. Other plastics present were polyethylene terephthalate, polyacrylamide, and polystyrene.

Most microplastics were released during the first two minutes of chewing. The act of chewing caused small pieces of plastic to flake off the gum, not because saliva enzymes broke down the gum. After about eight minutes of chewing, 94% of the microplastics had been released. This suggests that chewing itself is the main cause of plastic release.

To reduce exposure, Lowe recommends chewing a piece of gum for a longer time instead of switching to a new piece frequently. This could lower the number of microplastics released.

The study only measured microplastics larger than 20 micrometers. Smaller particles, such as nanoplastics, may have been present but went undetected. More research is needed to understand the full extent of microplastic release, especially for smaller particles.

The study also raised concerns about environmental pollution. Mohanty pointed out that the plastic released into saliva represents only a small fraction of the plastic in the gum. Improper disposal of gum—whether stuck to surfaces or thrown on the ground—also contributes to plastic pollution.

The study is still under peer review. While researchers wait for more answers on the health effects of microplastics, they suggest people reduce their exposure where possible. This includes being mindful of chewing gum habits and disposing of used gum properly.

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