According to a Science Daily news brief, a recent study—published in Proceedings of the National Academy of Sciences by a research team primarily from Columbia University—has used a new technique to count nanoplastic particles in bottled water for the first time. The technique, called “stimulated Raman scattering microscopy,” probes water samples with two simultaneous lasers that have been tuned to make targeted molecules resonate.
According to the study’s authors, the team’s technique, coinvented by Columbia University biophysicist Prof. Wei Min, found that an average liter of bottled water contained approximately 240,000 detectable plastic fragments. This, according to Science Daily, was “10 to 100 times greater than previous estimates.”
Scientists have shown that potable bottled water typically contains tens of thousands of tiny microplastic fragments (per bottle) and that microplastics break down further into smaller pieces known as nanoplastics (measuring one micrometer or less—1/70th of the width of a human hair). Little has been known, however, about what numbers, sizes, and types of the tinier nanoplastic particles are in bottled water.
That may be about to change.
"This opens a window where we can look into a world that was not exposed to us before,” Associate Professor Beizhan Yan, study coauthor and Columbia University environmental chemist, said in the Science Daily brief.
The team tested bottled water for seven common plastic particulates down to 100 nanometers in size, focusing on three popular bottled water brands sold in the US. Their findings ranged from 110,000 to 370,000 particles per liter, of which 90% were nanoplastics and 10% were microplastics. They were also able to distinguish between the seven types of plastic and determine their distinguishing shapes, a feat that could be helpful in future research.
Unsurprisingly, a plastic commonly found in the samples was the plastic used to make the water bottle, polyethylene terephthalate (PET). However, a type of nylon called polyamide, which is commonly used to purify water before bottling it, was found in greater quantities than PET.
Moreover, the seven targeted plastics only made up about 10% of the nanoparticles found in the samples, leaving 90% unidentified. This demonstrates "the complicated particle composition inside the seemingly simple water sample," the study authors wrote. “The common existence of natural organic matter certainly requires prudent distinguishment," they added.
What is next for the researchers? “There is a huge world of nanoplastics to be studied," said Min. He noted that the mass of nanoplastics is far less than the mass of microplastics, but "it's not size that matters. It's the numbers, because the smaller things are, the more easily they can get inside us." Indeed, compared with microplastics, nanoplastic particles can more readily make their way into body tissues—including lung tissues—with unknown, potentially serious health impacts.
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