Glass bottles contain more microplastics than plastic containers

For years, people have chosen glass bottles for their beverages, believing them to be safer and more environmentally friendly than plastic. The clink of glass often feels more trustworthy than the crinkle of plastic.

But a new study has revealed something unexpected: drinks stored in glass bottles may contain more microplastics than those in plastic or metal containers.

This finding flips our assumptions about packaging safety and highlights a surprising source of contamination, bottle caps.

Researchers from ANSES examined various beverages sold in France. They analyzed water, colas, lemonades, iced tea, wine, and beer. The results challenge the common belief that glass is always the cleaner, safer option.

Guillaume Duflos of ANSES said the goal was to investigate the quantity of microplastics in different types of drinks sold in France and examine the impact different containers can have.

Glass bottles leak microplastics

Glass bottles were the worst offenders, with an average of 100 microplastic particles per liter. Plastic bottles and cans held far fewer – ranging between 2 and 30 particles per liter depending on the drink.

“We expected the opposite result,” said Iseline Chaib, who led the research.

The team identified the source: paint from the caps on glass bottles. Using Fourier Transform Infrared Spectroscopy (FTIR), they matched particles found in the drinks to the same polymer and color as cap coatings.

Further experiments confirmed that cap paint flakes off during storage. The scratches are too small to see, but they shed particles that enter the liquid when sealed.

Beer bottles among the most contaminated

Among beverages, beer was the most contaminated with microplastics – especially when sold in small glass bottles. On average, beer contained 82.9 particles per liter, but small glass bottles reached 133.7 particles per liter.

Lemonades also had high contamination: 111.6 particles per liter in glass, compared to just 1.5 in plastic. Colas followed a similar pattern, showing 103.4 in glass versus 2.1 in plastic.

Iced teas in glass averaged 86.3 particles per liter. Plastic containers had just 2.2 particles. In every case except wine, glass led to higher contamination.

Water and wine still relatively safe

Water fared the best. Across all types, it averaged 2.9 particles per liter. Glass bottles held slightly more (4.5), while plastic bottles had less (1.6).

Wine remained a mystery. Even in glass bottles, contamination was low. That’s because wine bottles often use corks, not painted caps. Brick-packaged wine had the highest wine-related levels: up to 30 particles per liter.

Cleaning bottle caps cuts microplastics

Researchers wanted to see if they could stop microplastics from getting into drinks. So, they looked at the caps.

The team took clean bottles and sealed them with new caps. Then they measured how many microplastics ended up inside. With no cleaning, the number was high – about 287 particles in just one liter of water.

The experts blew air through the caps to shake off loose paint. That helped as count dropped to 105 particles per liter.

Next, the researchers went one step further. They rinsed the caps with water and ethanol before sealing. This dropped the number even more – to just 86 particles per liter.

That’s nearly a 70 percent drop. No complicated machines or big changes – just air and a rinse. Manufacturers could start doing this right now and make their drinks cleaner.

More polyester, more trouble

The study also revealed that polyester was the most common polymer in microplastics. This was especially true for glass-stored drinks, reinforcing the cap-paint link.

Across all beverages stored in glass bottles, most microplastics were fragments (not fibers), and ranged in size from 30 to 500 micrometers.

While the study confirms their presence, it doesn’t prove harm. No standard exists yet for a “safe” level of microplastics in food or drink.

“There is no reference level for a potentially toxic amount of microplastics,” noted the study authors. Until toxicology research catches up, consumers remain in the dark about long-term health effects.

Glass bottles have their own risks

The findings challenge how we think about glass packaging. Though glass avoids chemical leaching from plastics, it can introduce more microplastics due to its metal caps.

Cleaning those caps can cut contamination. But even then, some particles remain. This study, published in the Journal of Food Composition and Analysis, is the first of its kind in France.

The message is clear: packaging choices matter – and sometimes the “greener” option comes with its own set of invisible risks.

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