Scientists find most microplastics in drinking water smaller than EU detection limits

Most microplastics found in bottled and tap water samples were smaller than 20 microns (μm), according to researchers who are urging the European Union to update its recommended detection limit to include these fine plastic particles.

Scientists tested 10 different bottled water brands and one tap water source in Toulouse, France with a new method to detect fine microplastics smaller than 20 μm, which to date have been omitted from many studies due to detection limitations, they say.

A recent March 2024 methodology decision from the European Union on measuring microplastics in drinking water limits it to larger particles “with a dimension between 20 μm and 5 mm”.

But the smaller microplastics are more likely to pass through the intestine into the blood and organs, the researchers wrote in the new study published in the journal PLOS Water.

“The idea of the paper was to prove that it's possible to analyse the very fine plastics and microplastics and try to show the European Union that it makes very little sense to set the detection limit at 20 microns,” said Oskar Hagelskjaer, CEO and founder of Microplastic Solution and first author of the study.

He told Euronews Health that the new study shows they can “analyse this fraction that's below 20 microns, which is the size range that has been deemed the most dangerous in terms of human health”.

The study found that the large majority were very fine microplastics with 98 per cent of those found in the samples under 20 μm, and 94 per cent less than 10 μm in diameter.

The key difference in their methodology was more sensitive instrumentation and quality control to make sure that the detection process did not contaminate the sample.

Bethanie Carney Almroth, a professor of ecotoxicology at the University of Gothenburg in Sweden, who was not involved in the study, told Euronews Health that the study’s methodology was “quite strong” as they looked at what could happen to the sample during processing as well as the accuracy of their measurements.

‘Pervasive problem’

The researchers found a wide range of microplastics in both bottled and tap water, with a range of 19 to 1,154 microplastic particles per litre.

The tap water in Toulouse contained 413 microplastic particles per litre, which was higher than eight of the 10 bottled water samples, though Hagelskjaer said it is dangerous to draw conclusions based on one tap water sample.

The results, however, indicate that “bottled water and treated surface water contain similar concentrations of [microplastics], while groundwater-sourced drinking water may be less contaminated,” the researchers wrote in the study.

The microplastic concentration resembled other sources of treated drinking water but was roughly 10 times higher than groundwater-sourced drinking water in Denmark, they added.

Hagelskjaer said this makes sense as groundwater seeps through soil and has “natural filtration” while the tap water in Toulouse is sourced mainly from the Garonne River and goes through a 10-step filtration process. He speculated that this process or the river may lead to microplastic contamination.

He added that one finding he found “very curious” was that while the bottled water samples were packaged in polyethylene terephthalate (PET) bottles, the PET content wasn’t the most prevalent plastic. This means the bottles might not be the largest culprit for the plastics in the water.

It’s unclear what these microplastics mean overall for human health, according to Carney Almroth.

“They're finding them everywhere they look. We know that we have them in our bodies,” she said, adding that “now there is evidence emerging showing a health impact of those exposures”.

“It's a very pervasive problem,” she added with “no place left on the planet that's not contaminated”.