Chewing gum releases microplastics into saliva, study finds

Chewing gum made from either synthetic polymers or tree-based resins sheds significant quantities of tiny plastic particles into saliva,  according to a study currently undergoing peer review that was presented Tuesday at a meeting of the American Chemical Society.

Researchers found that chewing gum, on average, releases over 600 particles of microplastics per gram, with the average stick of gum weighing between two and six grams, according to the study, in which researchers chewed 10 different types of leading gum brands and then sampled their saliva at various time points.

“We need to be aware that these gums are releasing plastics into our body,” said Sanjay Mohanty, study co-author, a professor at University of California Los Angeles.

Synthetic gum is made up of plastic polymers, a fact that most people are not aware of, said study lead author Lisa Lowe, a graduate student in Mohanty’s lab. It didn’t come as a shock to the researchers, then, that gum released microplastics.

The scientists were surprised, however, that “natural” gums that use plant resins as a base had similar levels of microplastics, which must be getting there somehow during the manufacturing process, they said.

The US Food and Drug Administration (FDA) has no standards for microplastics in food and has stated that “current scientific evidence does not demonstrate that levels of microplastics or nanoplastics detected in foods pose a risk to human health.”

However, some research has begun to hint at links between microplastics in the body and negative health outcomes. For example, a study published in March 2024 in The New England Journal of Medicine followed 312 patients who had fatty deposits, or plaques, removed from their carotid artery. Almost six in 10 had microplastics, and these people fared worse than those who did not: Over the next 34 months, they were 2.1 times more likely to experience stroke, heart attack, or die.

But the researchers of this study make no claims about health effects and don’t want to alarm anybody or single out gum unnecessarily, since microplastics are found in many foods, Mohanty said.

“Gum is safe to enjoy as it has been for more than 100 years,” a spokesperson for the National Confectioners Association said in an emailed statement. “Food safety is the number one priority for U.S. confectionery companies, and our member companies use only FDA-permitted ingredients.”

The 10 brands of gum in the study primarily released four different types of microplastics, including polyolefins, polyethylene terephthalate (PET), polyacrylamides, and polystyrenes. PET is commonly used to make plastic bottles and is the most common polymer found in the human brain, in the one landmark study on the topic. Polystyrene is used in packing peanuts and many other products.

The study only measured microplastics above 20 microns in size (a tiny fraction of a millimeter), meaning that there could be many more fibers that are not turning up, perhaps by a factor of 10, Mohanty said. The team hopes to look for even smaller particles in future work, he added.

The paper found that gums released most microplastics within the first few minutes of chewing, and release over 90% of the plastic particles within eight minutes.

The research suggests that chewing gum is likely to slowly release even more microplastics over time in the environment, making it important to properly dispose of it, Lowe said.

(Featured image by Thomas Watson via Unsplash+.)