A new study from France’s national food safety agency has revealed an unexpected finding in the fight against plastic pollution: beverages sold in glass bottles can contain significantly more microplastics than those in plastic bottles or cans. Microplastics are tiny plastic particles, typically smaller than 5 millimeters, that have become widespread in our environment, from the deepest oceans to the food we consume. While the direct health effects of ingesting these particles are still being researched, scientists are working to understand how and where they enter our food supply. This latest research, published in the Journal of Food Composition and Analysis, aimed to measure the number of microplastics in various drinks sold in France and determine how different types of packaging contribute to contamination.

Researchers at the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) were surprised by what they found: Across soft drinks, lemonades, iced teas, and beers, they discovered that beverages in glass bottles had the highest levels of contamination, with some containing five to 50 times more microplastics than their counterparts in plastic bottles or metal cans. For instance, beers contained an average of about 83 microplastic particles per liter. “We expected the opposite result,” Iseline Chaib, a Ph.D. student who conducted the research, told Agence France-Presse. The team noted that the contamination was not coming from the glass itself but from an entirely different source.

Upon closer inspection, the scientists identified the bottle caps as the primary culprit. They discovered that the microplastic particles found in the drinks were the same shape, color, and chemical makeup as the paint used on the outside of the metal caps. A polymer, which is the large, chain-like molecule that forms the basic structure of plastics and paints, was a match between the cap coating and the contaminating particles. The agency explained that friction between the caps during storage and transportation likely creates “tiny scratches, invisible to the naked eye,” which can “release particles onto the surface of the caps” that then fall into the drink when the bottle is sealed or opened.

While the findings may seem concerning, the study also offers a clear path forward for manufacturers. Researchers emphasized that there is currently no established reference level for what amount of microplastics might be toxic, so the immediate health risk remains unknown. Furthermore, not all drinks were equally affected; water and wine showed relatively low contamination levels, even in glass bottles. Most importantly, the agency tested a simple solution: cleaning the caps with a blast of air and then rinsing them with water and alcohol before bottling. This process successfully reduced plastic contamination by 60 percent, suggesting that a simple change in the production line could significantly decrease the number of microplastics in our beverages.

References

• Chaïb, I., Doyen, P., Merveillie, P., Dehaut, A., & Duflos, G. (2025). Microplastic contaminations in a set of beverages sold in France. Journal of Food Composition and Analysis, 144, 107719. https://doi.org/10.1016/j.jfca.2025.107719
• Frasquet, R. (2025, June 20). Glass bottles found to contain more microplastics than plastic bottles. Phys.Org; Phys.org. https://phys.org/news/2025-06-glass-bottles-microplastics-plastic.html