As the research becomes more clear as to the effects of microplastics on the body, it’s understandable that people are becoming increasingly concerned about the quantity of tiny plastic particles that are gathering in their internal organs.

With microplastics discovered across the brain, the blood, the liver and the lungs, to name just a few vital organs, you might wonder how exactly these tiny bits of plastic actually get into the body.

You’d be forgiven for assuming – given the prevalence of microplastics in our oceans – that seafood was the main culprit, but actually microplastics are entering our bodies through not just consumption of foods and drinks containing it, but also through inhalation, and even through the skin.

With all this in mind, it’s understandable that regulators want to understand and limit the quantity of microplastics in our products, particularly those for consumption, given the long-term health and environmental implications.

Thus researchers for ANSES – French Agency for Food, Environmental and Occupational Health & Safety – have recently embarked on a thorough study of microplastics in bottled beverages. But their conclusions, published in the Journal of Food Composition and Analysis, has stopped many in their tracks, and for good reason.

That’s because, across all the tested drinks – including beer, water, wine, soda, iced tea, and more – microplastics were present, proving one of the many ways in which unsuspecting consumers are ingesting microplastics on a daily basis.

However, most shockingly was the fact that glass bottles were the main culprit, with approximately 100 particles of microplastics per liter – between five and fifty times the level found in cans and, fascinatingly, plastic bottles too.

This left the research team totally taken aback, as Iseline Chaïb explained in an ANSES statement:

“We were expecting the opposite result when we compared the level of microplastics in different drinks sold in France.”

However, there is good news for wine and water drinkers, with much lower levels of microplastic contamination when compared to other beverages, regardless of the container (though this was still higher in glass bottles).

Of course, the real question is why the contents of glass bottles are contaminated with microplastics at a significantly higher level than beverages bottled in a container actually made of plastic.

Well, with a little detective work, the scientists came to a hypothesis: the microplastics couldn’t come from the glass bottles themselves, nor were they present in the uncontaminated beverage before bottling. This left just one culprit: the caps.

A little testing proved that their theory was true. Not only were the microplastics usually similar in color to the paint on the caps, they noticed microscopic scratches on the caps too. To make their evidence conclusive, they conducted a final series of experiments, as Chaïb continued:

“We studied three scenarios. We cleaned the bottles and filled them with filtered water so that no microplastics could be detected, then we placed caps on the bottles without treating the caps, after blowing on the caps with an air bomb, or after blowing air and rinsing the caps with filtered water and alcohol.”

Their tests were clear: when bottle caps weren’t cleaned, per liter of water there were around 287 microplastic particle contaminants. With air blown on the caps before sealing, this rate dropped to 106 microplastic particles, with only 87 after the caps had been rinsed after blowing and before capping.

The conclusion? To protect the consumer, manufacturers need to make extra effort to ensure their caps are free from imperfections and contamination. Or the savvy consumer could just drink wine or water instead.

If you thought that was interesting, you might like to read about why we should be worried about the leak in the bottom of the ocean.