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.
For the people in the comments who either won’t or seemingly can’t read the article: The paint on the top of the caps is plastic-based and before they’re put on the bottle they’re stored in a big jumbled up pile where the paint chips off and coats the caps in tiny flakes. When the cap gets put on the bottle, the flakes on the bottom of the cap get washed off into your drink. Studies show that washing the caps first dramatically reduces the micro-plastic contamination.