In the pilot study, researchers from the University of California, Los Angeles (UCLA) found that a single piece of chewing gum can release an average of 100 microplastics per 1 g, with some samples releasing up to 600 microplastics per 1 g. Given that typical gum pieces weigh between 2 and 6 g, this translated to a potential exposure of up to 3,000 plastic particles per piece.
The study's timing analysis revealed that most microplastics (94%) detached within the first 8 minutes of chewing, with significant release occurring in the initial 2 minutes. The researchers attributed this to mechanical abrasion rather than enzymatic breakdown.
"Surprisingly, both synthetic and natural gums had similar amounts of microplastics released when we chewed them," said lead study author Lisa Lowe.
The researchers tested five brands of synthetic gums and five brands of natural gums, all of which were commercially available. To control for variables in chewing patterns and salivary composition, seven pieces from each brand were chewed by a single participant.
Each piece was chewed for 4 minutes, with saliva samples collected at 30-second intervals followed by a final mouth rinse with clean water. A separate experiment collected saliva periodically over 20 minutes to assess the release rate of microplastics.
Laboratory analysis employed two techniques:
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Red staining and microscopic counting
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Fourier-transform infrared spectroscopy to determine polymer composition.
The study identified several polymer types in both synthetic and natural gums: polyolefins, polyethylene terephthalates, polyacrylamides, and polystyrenes. Polyolefins, which include polyethylene and polypropylene, were the most abundant polymers detected.
If the average person chews 160 to 180 small sticks of gum annually, the researchers estimated that this could result in the ingestion of approximately 30,000 microplastics per year—potentially doubling the estimated tens of thousands of microplastics humans consume annually through other sources.
"Our goal is not to alarm anybody," emphasized co–study author Sanjay Mohanty, PhD, Associate Professor of Civil and Environmental Engineering at UCLA. "Scientists don't know if microplastics are unsafe to us or not. There are no human trials, [b]ut we know we are exposed to plastics in everyday life, and that's what we wanted to examine here," he added.
The study was limited to identifying microplastics 20 μm or larger as a result of instrumental constraints. "It's likely smaller plastic particles were not detected in saliva," Dr. Mohanty noted, indicating that additional research is needed to assess potential release of nano-sized plastics from chewing gum.
The research was conducted with approval from UCLA's Internal Review Board and funded by UCLA, the University of Hawaii Maximizing Access to Research Careers program (supported by the National Institutes of Health), and the California Protection Council.
Lowe suggested that to reduce potential exposure to microplastics from gum, individuals might consider "chew[ing] one piece longer instead of popping in a new one."
Dr. Mohanty also emphasized proper disposal: "The plastic released into saliva is a small fraction of the plastic that's in the gum. So, be mindful about the environment and don't just throw it outside or stick it to a gum wall," he concluded.