Health. Glass bottles contain more microplastics... than plastic ones.

Drinks such as beer, soda, iced tea, wine, and water sold in glass bottles contain more microplastics than those in plastic bottles, a contamination likely due to the paint coating the metal caps, according to a study released Friday by ANSES.

Conducted as part of a thesis co-financed by the French National Agency for Food, Environmental and Occupational Health Safety and the Hauts-de-France region, this work was published in mid-May in the specialist journal Journal of Food Composition and Analysis .

"We expected the opposite result."

The aim of this research project was to "investigate the quantity of microplastics in different types of drinks sold in France and to examine the impact that different containers can have" on this microplastic content, explains Guillaume Duflos, research director at ANSES. "This is the first time this type of work has been carried out in France," he emphasizes.

The findings revealed an average of around one hundred microplastic particles per litre in glass bottles of cola, lemonade, iced tea and beer, contamination levels five to fifty times higher than those in plastic bottles or cans.

"We expected the opposite result," explains doctoral student Iseline Chaïb, who conducted this work at the ANSES food safety laboratory in Boulogne-sur-Mer (Pas-de-Calais). "We then noticed that in the glass, the particles emerging from the samples were of the same shape, color, and polymer composition—the same plastic—as the exterior paint on the caps that seal these glass bottles," she continues.

Painting of capsules called into question

In addition, the paint on the capsules "has tiny scratches, invisible to the naked eye, probably due to friction between the capsules when they are stored before use," the team of researchers noted, estimating that this "could release particles onto the surface of the capsules."

For water – mineral or natural – the quantity of microplastics was found to be "relatively low regardless of its container, with an average of 4.5 particles per liter in glass bottles and 1.6 particles in plastic bottles or cartons," explains ANSES.

Wine also contained few microplastics, including in glass bottles with corks, a variability whose origin "remains to be explored, except for those contained in capped glass bottles," says Guillaume Duflos. On the other hand, colas contained around thirty microplastic particles, lemonades around forty, and beers around 80.

Measures to be taken by manufacturers

In the absence of reference toxicological data, it is not possible to say whether or not the quantities of microplastics found present a risk to health, ANSES points out.

Manufacturers can easily take steps to significantly reduce the number of microplastic particles per liter from capsules, argues the agency, whose laboratory successfully tested a homemade cleaning method – blowing with air, then rinsing with filtered water and alcohol – which reduced it by 60%.

Changing the storage conditions of capsules "before use to avoid friction" or changing the composition of capsule paints could reduce the level of contamination of drinks by microplastics, argues ANSES.