Microplastics in Glass Bottles—And What Companies are Doing About Them

In the world of sustainable packaging, glass bottles have long been considered the gold standard—durable, inert, and endlessly recyclable. But a surprising new study by France’s food safety agency ANSES has turned that assumption on its head.

According to the research, glass bottles may contain more microplastics than plastic bottles or aluminum cans, largely due to the painted metal caps used to seal them.

Surprising Findings from ANSES

The ANSES study analyzed 56 beverages—including soda, lemonade, iced tea, beer, wine, and water—packaged in various formats such as glass, plastic, cartons, and cans. The results were startling:

• Glass bottles averaged around 100 microplastic particles per liter, with certain drinks like beer reaching up to 133 particles/L.
• Plastic bottles had significantly lower counts, averaging around 1.6 particles/L in water.
• Aluminum cans also showed relatively low contamination.
• Interestingly, wine in glass bottles had among the lowest microplastic levels, likely because it is typically sealed with a natural cork rather than a metal cap.

Chart: Average Microplastic Contamination by Bottle Type (Particles/L)

The Culprit: Painted Metal Caps

The contamination was not caused by the glass itself, which remains inert. Instead, the source of microplastics was traced to the paint on the exterior of metal bottle caps. These paints, often polyester-based, degrade due to friction during transport and handling. Tiny, colored plastic flakes end up inside the sealed beverages, contaminating them before they even reach the consumer.

Are There Health Risks?

While there is no established toxicological threshold for microplastics in beverages, the presence of hundreds of particles per liter raises important questions. Long-term health impacts are still under study, but concerns include inflammation, cellular stress, and possible hormone disruption.

Organizations such as the World Health Organization (WHO) and the European Food Safety Authority (EFSA) are currently investigating the implications of chronic microplastic exposure.

What Companies Are Doing to Solve the Problem

Some forward-thinking beverage companies and bottlers are already taking action in light of the findings:

1. Cap Cleaning Protocols: Several companies are adopting pre-treatment protocols including air-blowing and rinsing metal caps with alcohol and water, which the ANSES study showed could reduce contamination by up to 60%.
2. Alternative Sealing Methods: Wineries have long used natural corks, and now some beverage companies are exploring plastic-free composite corks or aluminum caps without plastic linings.
3. Reformulating Paints: Cap manufacturers are testing low-shed and biodegradable paints to prevent microplastic flakes during handling.
4. Material Swaps: A few startups and sustainability-focused brands are switching to glass stoppers or ceramic caps, eliminating plastic and paint altogether.
5. Consumer Transparency: Brands have started labeling packaging to disclose the materials used, helping consumers make informed decisions.

Moving Toward a Cleaner Future

The discovery of microplastic contamination in glass bottles is a wake-up call. While glass remains a strong choice for sustainability, it’s no longer immune from scrutiny. Companies now face the dual challenge of maintaining the eco-cred of glass packaging while mitigating a newly discovered risk to public health.

As studies continue and regulations catch up, consumers can expect to see safer, cleaner, and more transparent packaging practices. Until then, checking the cap might be just as important as checking the label.

Ensuring Safety At Home

To further reduce your exposure to microplastics—whether they come from bottle caps, pipes, or household plumbing—an at-home water filtration system can be a smart investment. 

High-quality filters, like those available from iFilters, are designed to remove microscopic contaminants before they ever reach your glass, giving you cleaner, safer water straight from the tap. With the right system in place, you can enjoy peace of mind knowing your drinking water is protected from more than just the visible threats.