Metal caps, frequently used on glass bottles, may be a ‘surprising’ source of microplastics, reveals a study by the French food safety agency (ANSES).
By analyzing the contents of glass, metal, cardboard, and plastic bottles, with beer, water, wine, soft drinks, tea, and lemonade, sold in stores in France, the researchers concluded that all of them contained microplastics. However, beverages in glass bottles contained the highest levels.
Expressing surprise at the results, the scientists say that microplastic contamination in glass bottles is likely due to the ink used on the metal caps used on these packages.
In an an article published in the Journal of Food Composition and Analysis, it is revealed that, on average, glass bottles of soda, lemonade, iced tea and beer contained 100 microplastics per liter, a value five to fifty times higher than the average quantities detected in plastic and metal bottles.
“We were expecting the opposite result when we compared the levels of microplastics in the different beverages sold in France,” confesses Iseline Chaïb, the study’s first author and a PhD student at ANSES.
Because there are no reference toxicological data, the authors say that it is not possible to know for sure whether the microplastic levels found actually represent a risk to human health.
Based on the results obtained, the scientists note that water was the beverage with the lowest levels of microplastics, regardless of the type of packaging, with an average of 4.5 particles per liter in glass bottles and 1.6 particles in plastic and cardboard bottles.
The team acknowledges that the reason for the variations in microplastic levels found across the various beverages analyzed remains unclear, except for beverages contained in glass bottles with metal caps.
The researchers say that the large amount of microscopic plastic particles in beverages in glass bottles “probably comes from the metal caps, and, more specifically, from the ink that covers them”.
The conclusion derives, above all, from the fact that most of the microplastics found in these beverages share the same color and composition as the ink on the caps. In addition, they say they have detected small scratches, invisible to the naked eye, on the caps, probably caused by friction, and they think that this may be the source of the microplastics that end up in the beverages.
