KATHMANDU: A new French study has found that drinks sold in glass bottles contain significantly more microplastics than those in plastic bottles or metal cans, challenging common assumptions about safer packaging choices.
Conducted by the French food safety agency ANSES, the research revealed that soft drinks, lemonade, iced tea, and beer sold in glass bottles contained an average of 100 microplastic particles per litre — five to 50 times more than those in plastic containers.
“We expected the opposite result,” said Iseline Chaib, a PhD student who led the study. Investigators traced the contamination not to the bottles themselves, but to the paint used on the outside of the caps sealing the glass bottles. The painted caps showed microscopic scratches, likely from friction during storage, which released plastic particles.
In contrast, bottled water — both still and sparkling — contained much fewer microplastics: 4.5 particles per litre in glass bottles and just 1.6 in plastic. Wine also had low levels, even when sealed with plastic-lined caps, though researchers said the reason for this remains unclear.
Soft drinks averaged around 30 microplastic particles per litre, lemonade 40, and beer 60 — far higher than water or wine. Despite these figures, the study notes that no standard yet exists for what constitutes a harmful level of microplastics in food or drink.
“This doesn’t necessarily mean there’s a health risk, but it highlights a previously overlooked source of contamination,” said Guillaume Duflos, ANSES research director.
The good news, researchers say, is that microplastic contamination from bottle caps can be drastically reduced. A cleaning method involving air-blowing and rinsing with water and alcohol reduced contamination by up to 60 percent.
The findings were published last month in the Journal of Food Composition and Analysis and are likely to fuel ongoing global debates about packaging, health, and sustainability.
Comment