Glass Bottles Hold More Microplastics Than Plastic Ones

In a finding that turns popular assumptions on their head, a new study has revealed that drinks sold in glass bottles actually contain more microplastics than those packaged in plastic bottles or metal cans. The research, conducted by France’s food safety agency ANSES, was published last month in the Journal of Food Composition and Analysis. It offers fresh insight into the growing concern over microplastics infiltrating our everyday environment — from the air we breathe to the food and beverages we consume.

Tiny fragments of plastic, known as microplastics, have been detected virtually everywhere on the planet. They’ve been found in ocean water, rain, seafood, drinking water, and even human bloodstreams. While no direct link between microplastics and health problems has yet been proven, the topic is fast becoming a critical area of environmental and public health research.

Unexpected Results Behind the Bottle Cap

The ANSES-led study set out to measure the concentration of microplastics in various beverages sold in France, ranging from water and lemonade to beer and wine. To the researchers’ surprise, drinks sold in glass bottles were the most contaminated, containing an average of 100 microplastic particles per liter — far more than their plastic or metal-packaged counterparts, which showed five to 50 times lower levels.

Iseline Chaib, a Ph.D. student involved in the research, admitted the team had expected the opposite result. Initially puzzled, they soon discovered that the microplastic particles shared the same shape, color, and polymer composition as the paint on the exterior of the bottle caps sealing the glass containers.

Further investigation revealed microscopic scratches on the painted surfaces of the caps, likely caused by friction during storage and transport. These tiny abrasions were enough to release plastic fragments onto the bottle openings, eventually ending up in the drinks themselves.

How Different Drinks Compare

Not all drinks were equally affected. Interestingly, both still and sparkling waters contained relatively low levels of microplastics, ranging from 4.5 particles per liter in glass bottles to 1.6 in plastic bottles. Wine also performed well in the analysis, even when packaged in glass bottles with plastic-sealed caps — a discrepancy that remains unexplained for now, according to ANSES research director Guillaume Duflos.

Soft drinks showed higher contamination rates, with around 30 particles per liter, lemonade climbing to 40, and beer containing roughly 60 microplastics per liter in glass bottles. While these figures might sound alarming, the agency emphasized that no official safety threshold currently exists for microplastic consumption, making it difficult to assess the actual health risk.

An Easy Fix for an Invisible Problem

One promising takeaway from the research is that manufacturers could significantly reduce microplastic contamination with relatively simple adjustments to their production processes. The ANSES team tested a cleaning method that involved blowing bottle caps with air, followed by rinsing with water and alcohol, which succeeded in cutting microplastic levels by 60%.

This discovery offers a practical and affordable solution for beverage producers, especially those marketing their products as eco-friendly alternatives to plastic packaging. It also highlights the unintended consequences of assuming that glass is inherently safer or cleaner than plastic when it comes to packaging.

Microplastics Everywhere — And We’re Just Beginning to Measure

While this study focuses on bottled drinks, the issue of microplastics extends far beyond what’s in our glasses. A growing body of research has detected microplastics in human lungs, blood, and placentas. In 2022, a Dutch study made headlines after finding microplastics in the bloodstream of healthy volunteers for the first time, with half of the samples containing traces of PET plastic, commonly used in drink bottles.

As awareness grows, scientists worldwide are racing to determine how these particles might affect the human body and ecosystems at large. In the meantime, studies like this one serve as a sobering reminder that reducing plastic pollution isn’t always as straightforward as swapping one material for another.