New study found microplastics in a place you wouldn't expect — but does it really matter?

San Francisco Chronicle​

25-06-2025

If you're trying to avoid microplastics, picking a glass bottle over a plastic one would seem like a sensible step. But a new study from researchers in France uncovered counterintuitive results showing higher concentrations of microplastics in beverages that came from glass bottles compared to other materials — including plastic.
The study, titled 'Microplastic contaminations in a set of beverages sold in France,' was conducted by researchers at French food safety agency ANSES and is published in the August edition of the peer-reviewed Journal of Food Composition and Analysis.
In it, researchers looked at microplastic concentrations in drinks like water, cola, tea, lemonade, beer and wine in different types of containers, including plastic and glass bottles and metal cans. With the exception of wine, researchers found the most microplastic content in beverages that came out of glass bottles.
So what's going on? How could there be more plastic in glass than plastic?
The culprit: The cap.
Though the bottles were made of glass, the caps were painted metal. Most paint is made of plastic. When scientists compared the color of the plastic particles in the liquid, it was the same color as the paint on the lid. That means bits of paint got scratched off the caps and went into the drinks. The study included close-up photos where you can see small scratches on the insides of the caps.
That also explains why they found comparatively fewer particles in wine: They were traditional glass bottles capped with corks, not metal lids.
The study was set up to examine the levels of microplastic content across different container materials, which is why the study phrases the highlighted results in that context ('Drinks in glass bottles more contaminated by microplastics').
But the conclusions indicate something more nuanced: There are multiple sources of microplastic contamination in what we eat and drink, and it's impossible to avoid them all, even if you're conscientious.
The findings are consistent with what microplastics researchers around the world have found in many other studies, said Tasha Stoiber, a senior scientist with environmental advocacy nonprofit the Environmental Working Group: 'It fits in with what we know, which is that microplastics are in a range of food and beverages.'
The study only looked at a handful of brands per category, and only six samples per brand, which all came from the same batch lot. If anything, experts who reviewed the study said, the findings are an indication that bottled beverage manufacturers should be examining their materials and processes and seeing whether simple steps like pre-cleaning the caps with air or liquid could meaningfully reduce microplastic concentrations.
The results don't mean that you should never drink a bottled beverage ever again, or that you need to scrutinize cap or bottle material. Microplastics are in just about everything we eat and drink, said Britta Baechler, the Director of Ocean Plastics Research for Ocean Conservancy. She co-authored a study published last year that found microplastics in every type of commonly consumed protein the researchers looked at, including seafood, chicken, steak, pork and plant-based protein. She called this study 'yet another reminder of how deeply embedded plastic is in our lives and our food system.'
In the grand scheme of microplastic consumption, fussing over what a bottle or cap of an individual drink is made of won't make a huge difference. Here's what experts say you can do to reduce your exposure:
Avoid heating up food in plastic. Heating plastic releases more particles into food, and faster. Nonstick coating is made of plastic, so opting to cook on stainless steel or cast iron is another smart step.
Avoid storing food in or eating food off of plastic. Glass, metal and ceramic are all better picks for your plates and storage containers.
Eat more whole, unprocessed food and drinks. Researchers found fewer microplastics in water than bottled lemonade, tea or cola. In Baechler's study on proteins, the ones with the fewest microplastics per gram were chicken breasts and pork chops; heavily processed products like breaded shrimp, fish sticks and chicken nuggets contained the highest concentrations.
Drink filtered or tap water from your home out of stainless or glass drinkware. Tap water has consistently been found to contain fewer microplastics than other sources, Baechler said.
Broadly speaking, despite the findings of this study, microplastics experts still say glass bottles are better than plastic ones. Glass itself does not — cannot — shed microplastics into what you drink. And glass bottles are much more recyclable than plastic. Many plastic bottles, even ones that make it into your recycling bin, wind up not being recycled.
'We're finding microplastics in everything,' said Amelia Meyer, a co-leader of the Plastics Working Group at Stanford University. 'You can only do so much. You have to drink water.'