Advanced imaging reveals bottled water nanoplastics

Whereas microplastics are defined as fragments ranging from 5mmdown to 1μm, nanoplastics are classified as particles below 1μm and are measured in nanometres (billionths of a metre). The presence of these tiny particles in virtually every environment on Earth and all aspects of food chains has only recently been confirmed, with the effects on human health largely unknown.

Using stimulated Raman scattering microscopy - which was co-developed by Columbia biophysicist and study co-author Wei Min - the team probed water samples with two simultaneous lasers tuned to make specific molecules resonate. Targeting seven common plastics, the researchers created a data-driven algorithm to interpret the results.

“Previously this was just a dark area, uncharted. Toxicity studies were just guessing what’s in there,” said study co-author Beizhan Yan, an environmental chemist at Columbia University. “This opens a window where we can look into a world that was not exposed to us before.”

The team tested three popular brands of bottled water sold in the United States, analysing plastic particles down to just 100 nanometres in size. Each litre was found to contain between 110,000 to 370,000 plastic particles, 90 per cent of which were nanoplastics, with the rest comprising microplastics. The work is published in the Proceedings of the National Academy of Sciences