Recent research reveals that beverages in glass bottles can contain more microplastics than those in plastic bottles, primarily due to paint flakes from metal bottle caps. While microplastics are found in many drinks regardless of packaging, the health impact remains unclear. Further studies are needed to understand the risks and develop safer packaging solutions.
Microplastics, tiny pieces of plastic ranging from about 5 millimeters down to one nanometer, have become a growing concern due to their presence in the environment and even inside the human body. Studies have detected microplastics in human blood, lungs, and brains, raising questions about their sources and potential health effects.
Microplastics are small plastic particles that can be as large as a Lego stud or as small as 100,000 times thinner than a human hair. They originate from the breakdown of larger plastic items or from manufactured microbeads used in products. These particles can enter the human body primarily through food and drink, but the extent of their health impact is still largely unknown.
A group of French scientists conducted a study in 2025 to measure microplastic content in various beverages, including water, beer, wine, soda, and lemonade. They also examined how packaging types—glass bottles, plastic bottles, cans, and large plastic jugs—affect microplastic levels.
For example, water in glass bottles contained nearly three times more microplastics than in plastic bottles, while lemonade in glass bottles had over 70 times more microplastics than in plastic bottles.
Since microplastics are plastic particles, it was puzzling why glass bottles would have more of them. The researchers collected microplastic particles from the glass bottled drinks and discovered that most particles matched the color and composition of the paint on the metal bottle caps.
They also observed scratches and tiny paint flakes on the caps, suggesting that caps might rub against each other during storage, causing paint to flake off into the drinks. This paint, which counts as plastic, is likely the main source of microplastics in glass bottled beverages.
Wine bottles typically use corks instead of painted metal caps, which explains why wine samples contained fewer microplastics.
The researchers tested methods to reduce microplastic shedding from caps, such as blowing air on the caps and rinsing them with water and ethanol. These methods lowered the number of microplastic particles in bottled water but did not eliminate them completely.
Currently, there is insufficient information to determine what levels of microplastic consumption are safe or harmful. The principle "the dose makes the poison" applies, but without clear data, it is difficult to assess risk.
While the discovery that glass bottles can shed more microplastics than plastic ones due to painted caps is surprising, it is not a reason to panic. The presence of microplastics in beverages is widespread, and more research is needed to understand their health effects and to develop safer packaging options.
For now, consumers can stay informed and support further scientific studies to clarify the risks and solutions related to microplastic contamination in food and drink.
Supporting ongoing research and encouraging manufacturers to reconsider packaging materials, especially the use of painted metal caps, could be important steps toward reducing microplastic exposure in the future.
