Scientists at Columbia University developed a laser-based imaging technique that can identify individual plastic particles down to 100 nanometres, and applied it to three popular US bottled-water brands.
They found an average of about 240,000 plastic particles per litre (range roughly 110,000 to 370,000), about 90% of which were nanoplastics too small to be counted by earlier methods. Polyamide (nylon), probably from filters used to purify the water, and PET from the bottles themselves were the most common polymers.
The study matters because nanoplastics are small enough to pass through the gut and lungs into blood and cells, and this was the first time they were counted in a common drink.
Only three brands were tested, and a subsequent letter in the same journal stressed the need for careful checks on clean samples, so that plastic from the lab itself is not counted by mistake. Quote as 'one study found'.