this post was submitted on 23 Jun 2025
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The researchers found an average of around 100 microplastic particles per liter in glass bottles of soft drinks, lemonade, iced tea and beer. That was five to 50 times higher than the rate detected in plastic bottles or metal cans.

"We expected the opposite result," Ph.D. student Iseline Chaib, who conducted the research, told AFP.

"We then noticed that in the glass, the particles emerging from the samples were the same shape, color and polymer composition—so therefore the same plastic—as the paint on the outside of the caps that seal the glass bottles," she said.

The paint on the caps also had "tiny scratches, invisible to the naked eye, probably due to friction between the caps when there were stored," the agency said in a statement.

This could then "release particles onto the surface of the caps," it added.

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[–] Bosht@lemmy.world 26 points 1 day ago (13 children)

Man on the surface this reeks of inside payoffs. I guess the technicality is plastic caps on glass bottles?? Which seems weird and nothing I've ever seen. Unless they're referencing the seal on the inside of some metal caps on glass bottles? Either way, seems suspect. I'd assume that overall drinking from glass is safer, as with plastic on any timeline you're dealing with the plastic breaking down and leaching chemicals and micro plastics into the liquid, which wouldn't be an issue with glass.

[–] Cawifre@lemmy.world 13 points 1 day ago

The paint itself on the outside of the bottle cap. The ultra thin layer of (apparently polymer a.k.a. plastic) paint that make the cap not just metal colored.

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[–] Ledivin@lemmy.world 11 points 1 day ago (1 children)

...do plastic bottles not have caps? I'm confused.

[–] baronvonj@lemmy.world 10 points 1 day ago (7 children)

their caps are fully plastic, not painted metal. The non-screwtop metal caps need to be bent to release their grip on the bottle. That scrapes the paint off the metal cap.

[–] Damage@feddit.it 11 points 1 day ago

it's more likely that paint is scratched off by other caps, idk about metal caps but plastic ones are usually handled in bags, thrown into a cap feeder that aligns them and loads them into the capper. I expect metal caps to go through a similar process, and all that movement is bound to scratch it and send particles everywhere.

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[–] Evil_Shrubbery@lemm.ee 8 points 1 day ago* (last edited 1 day ago)

Ok, great find, we can simply switch the caps & solve the problem.
(The corps will do that, right??)

But I wander with such tests ... could there be any significant detection issues?

Did they have the proper equipment and processes? A methodological limitation to particle size maybe?
Coz some researches find higher concentrations than 100.

[–] DarkCloud@lemmy.world 6 points 1 day ago

But the plastic bottle can still create a lot more, surely.

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