Glass bottles contain microplastics originating from bottle caps, study finds

A new study has found that the lids of glass bottles sold in France can contribute to microplastic contamination in the beverages. The researchers determined that microplastics found in beverages had the same color and polymer size as the paint on the outer layer of the bottle caps.

The scientists recommend an additional step in beverage production to clean the bottle cap before lidding to limit the risk of microplastic contamination.

Published in the Journal of Food Composition and Analysis, the study investigates the level of microplastic contamination in different types of beverages, including bottled water, colas, tea, lemonade, beer, and wine, sold in France. 

Contaminated caps

The study’s results indicate that glass bottles were more contaminated with microplastics than most other packaging types. However, glass wine bottles were not as contaminated with microplastics as other types of beverages as the bottles are often closed with corks rather than plastic or metal caps. 

The researchers suggest that most of the microplastics found on the glass bottle lids come from the paint on the outer layer of the cap. They found some caps had scratches and abrasions that could have resulted in microplastic contamination. 

“It is likely that caps are stored in large quantities, increasing the possibility of abrasion and surface friction when capsules collide. This theory was supported by the discovery of scratches on their surface and pieces of capsules of the same color adsorbed inside of them,” say the researchers. 

Future-proofing glass

According to the researchers, the absence of standardized methods for microplastic analysis leads researchers to adopt different analytical strategies to understand the nanomaterial. 

To tackle the presence of microplastics in glass bottle caps, the scientists recommend that producers and retailers pre-clean capsules by blowing them out and rinsing them in water or ethanol. 

“Pre-cleaning new capsules has significantly reduced the number of microplastics per encapsulated bottle compared to untreated capsules. Cleaning seems essential and could significantly minimize contamination of the liquid in the bottle by paint particles present in the capsule,” conclude the researchers.