Think glass is safer than plastic? It might contain more cancer-linked microplastics; study says

A recent study conducted by France’s food safety agency, ANSES, has challenged the common belief that glass bottles are a safer option for beverage packaging. The study revealed that drinks stored in glass bottles contain significantly higher levels of microplastics compared to those in plastic bottles or cans.

Image alt: Study reveals glass bottles may contain more microplastics than plastic.

On average, glass bottles containing soft drinks, lemonade, iced tea, and beer were found to have approximately 100 microplastic particles per liter. This is up to 50 times more than the levels found in plastic bottles or metal cans. Researchers initially hypothesized that plastic bottles would be the primary source of microplastic contamination, but the study's findings contradicted this expectation. The microplastics were found to originate primarily from the paint coating on the metal caps used to seal the bottles, highlighting a previously overlooked contamination pathway.

Unexpected High Levels of Microplastics in Glass Bottles

The ANSES study analyzed a variety of popular beverages, including soda, beer, lemonade, iced tea, water, and wine, packaged in different materials and sold across France. The results indicated that glass bottles contained an average of 100 microplastic particles per liter, whereas plastic bottles and cans had levels ranging from five to fifty times lower.

Among the beverages tested, beer bottles displayed some of the highest microplastic counts, averaging around 60 particles per liter. Water showed the lowest contamination levels, ranging from 1.6 to 4.5 particles per liter depending on the container. Wine, even when bottled in glass with caps, contained very few microplastics.

What is the Source of Plastic in Glass Bottles?

Image alt: Close-up of a glass bottle with metal cap.

Detailed analysis revealed that the microplastics found in glass-bottled drinks matched the shape, color, and polymer composition of the paint used on the metal caps. Friction and rubbing during storage and transport cause microscopic scratches on the caps, leading to the shedding of tiny plastic particles into the beverages. While invisible to the naked eye, these microplastics contaminate the drinks during bottling and storage. Tests indicated that cleaning the caps or improving storage conditions could reduce microplastic contamination, suggesting potential mitigation strategies for manufacturers.

Implications and Future Directions

While the study demonstrates higher microplastic contamination in glass bottles due to cap paint, the health risks associated with these levels remain uncertain due to a lack of toxicological reference data. The findings challenge the conventional wisdom that glass packaging is inherently safer or cleaner than plastic. Researchers recommend further investigation into the health impacts of microplastics and advocate for improvements in packaging materials and storage practices to minimize contamination. This study prompts regulatory bodies and manufacturers to reconsider the design and materials used in beverage packaging to ensure consumer safety.