Glass bottles worse? Study finds 50 times more microplastics than plastic

Drinks including water or soda sold in glass bottles contain significantly more microplastics than those in plastic bottles, according to a surprising study released by France's food safety agency, ANSES, on Friday.

Tiny, mostly invisible pieces of plastic, known as microplastics, have been detected across the world — in the air we breathe, the food we eat, and even within human bodies. While no direct evidence yet confirms that this plastic presence is harmful to human health, an emerging field of research is focused on understanding its scale and potential impact.

Guillaume Duflos, research director at ANSES, told AFP that the team aimed to “investigate the quantity of microplastics in different types of drinks sold in France and examine the impact different containers can have.”

The researchers found an average of around 100 microplastic particles per litre in glass bottles of soft drinks, lemonade and iced tea — five to 50 times higher than the levels found in plastic bottles or metal cans.

“We expected the opposite result,” said PhD student Iseline Chaib, who conducted the research.

Chaib said they later realised the particles in the glass bottles matched the shape, colour, and polymer composition of the paint on the outside of the caps sealing the bottles.

The paint showed “tiny scratches, invisible to the naked eye, probably due to friction between the caps when stored,” ANSES said. These scratches likely released microplastic particles that fell into the bottles.

When it came to bottled water — both flat and sparkling — the amount of microplastic was relatively low in all containers: 4.5 particles per litre in glass bottles compared to 1.6 particles in plastic.

Wine also contained very few microplastics, even in glass bottles with painted caps. Duflos said the reason behind this difference "remains to be explained."

Among soft beverages, contamination levels varied:

ANSES noted that there is no established reference level for what constitutes a toxic amount of microplastics in drinks, so it is not currently possible to determine if these levels pose a health risk.

However, the agency suggested that drink manufacturers can easily reduce contamination. One cleaning method tested — blowing the caps with air followed by rinsing with water and alcohol — reduced microplastic presence by up to 60%.

The full study by ANSES was published last month in the Journal of Food Composition and Analysis.