Drinks packaged in glass bottles carry significantly higher levels of microplastics than those stored in plastic bottles, cans, or cartons, according to a new study by the French Agency for Food, Environmental and Occupational Health & Safety (ANSES).
Researchers found that beverages stored in glass containers with metal caps contained up to 100 plastic particles per liter, substantially more than those in other packaging formats.
The investigation, conducted at ANSES’s Food Safety Laboratory in Boulogne-sur-Mer, focused on popular drinks such as soda, iced tea, beer, water, and wine.
Researchers found that drinks such as cola and lemonade stored in capped glass bottles had microplastic levels five to 50 times higher than when the same types of drinks were stored in plastic bottles or aluminum cans.
The findings suggest that, in some cases, glass bottles contain more microplastics due to elements unrelated to the liquid itself.
“We expected the opposite result when we compared the amount of microplastics in different drinks sold in France,” said Iseline Chaïb, the doctoral researcher who led the study.
The team also measured contamination in bottled water and wine. These drinks showed relatively low microplastic content, with water in glass bottles containing an average of 4.5 particles per liter. In plastic bottles or cartons, the level dropped to 1.6. Wine, regardless of packaging, generally showed minimal contamination.
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The study points to the caps of glass bottles—specifically, the paint covering them—as the likely source of the particles. Analysis revealed that the microplastics found in the drinks closely matched the color and composition of the cap paint.
Under magnification, researchers observed micro-scratches on the painted surface of unused caps, likely caused by friction during storage or transport. These scratches may release plastic particles into the beverage when the bottle is sealed.
To confirm the link between cap paint and contamination, researchers carried out controlled cleaning tests. Bottles were filled with filtered water and sealed using caps treated in different ways: untouched, blown with compressed air, or blown and then rinsed with filtered water and alcohol.
The results were telling. Bottles sealed with untreated caps contained an average of 287 plastic particles per liter. That number fell to 106 when the caps were blown with air, and to 87 when rinsed after blowing.
While current data does not confirm whether these microplastic levels pose health risks, the study opens new avenues for industry response. Researchers recommend that manufacturers consider adjusting storage conditions to reduce cap friction or explore alternative paint materials to minimize particle shedding.
The findings underline a clear need to revisit assumptions about sustainable packaging. Despite their eco-friendly reputation, glass bottles contain more microplastics under certain conditions, raising questions about packaging safety and production practices.
