- Glass bottles contain up to 50 times more microplastics than plastic bottles
- Beer bottles had the highest microplastic count, averaging 60 particles per litre
- Microplastics in glass bottles mainly originate from the paint on the caps sealing them
Glass bottles contain significantly more microplastics than plastic bottles, a study released by France's food safety agency, ANSES, has claimed, contradicting the longstanding assumptions. On average, the glass bottles of soft drinks, lemonade, iced tea and beer contained around 100 microplastic particles per litre, up to 50 times higher than in plastic or metal containers.
As per the findings published in the Journal of Food Composition and Analysis, the researchers initially expected the glass bottles to be comparatively safer than plastic bottles, but the results surprised them.
"We expected the opposite result," said PhD student Iseline Chaib, who led the research.
Caps were suspected to be the main source of contamination, as the majority of particles isolated in beverages were identical to the colour of caps and shared the composition of the outer paint.
"We then noticed that in the glass, the particles emerging from the samples were the same shape, colour and polymer composition, so therefore the same plastic as the paint on the outside of the caps that seal the glass bottles," Ms Chaib added.
Of all the bottles, the beer bottles had the highest microplastic count, with an average of 60 particles per litre, followed by lemonade with around 40 per cent. Flat and sparkling water showed relatively low levels of microplastics across all packaging types: about 4.5 particles per litre in glass bottles compared to 1.6 particles in plastic ones.
"The results show that glass containers were more contaminated than other packaging for all beverages except wine, because wine bottles were closed with cork stoppers rather than metal caps."
Guillaume Duflos, research director at ANSES, said the reason for this contradiction remains unclear at this stage. However, the agency tested a possible solution which could fix the problem.
"Blowing them out and rinsing them with water/ethanol/water significantly reduced the number of microplastics per encapsulated bottle, lowering it by approximately three, compared to untreated capsules," the study highlighted.
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Microplastic menace
The plastic production has grown from 1.5 million tonnes in the 1950s to 400.3 million tonnes in 2022. However, the increased manufacture of single-use plastics has also led to a rise in garbage found in terrestrial and aquatic habitats due to inefficient waste management.
Microplastics, the tiny pieces of plastic smaller than five millimetres, have been spotted, ranging from the Mariana Trench to Mount Everest. They are found in human brains, placentas, and the bellies of fish deep in the ocean.
