Using an advanced microscopic technique, American researchers have detected 100,000 nanoplastic molecules per liter of water in plastic bottles. Because of their small size, these particles can enter the bloodstream, cells, and the brain, thus posing potential health risks. The study, recently published in the Proceedings of the National Academy of Sciences, raises concerns about the impact of these nanoparticles.
An Unknown Realm
Formed as plastics break down into increasingly small pieces, these particles are consumed by humans and other organisms, with unknown effects on health and ecosystems. Whereas macroplastics have been found in various organs, including the lungs and liver, the study marks a unique exploration into the world of nanoplastics.
Concerns about nanoplastic presence in humans intensified when a 2018 study revealed contamination signs in 93% of 259 examined bottles from nine countries.
The novelty of this research lies in its focus, using a refined spectrometry method, on the poorly understood world of nanoplastics, which derive from the decomposition of microplastics. For the first time, American researchers, including biophysicists and chemists, counted and identified these tiny particles in bottled water. On average, they found around 240,000 detectable plastic fragments per liter, which is 10-100 times more than previous estimates based on larger sizes.
Microplastics are defined as fragments ranging from 5 mm to 1 µm, whereas nanoplastics, particles < 1 µm, are measured in billionths of a meter.
In contrast to microplastics, nanoplastics are so small that they can traverse the intestines and lungs and move directly into the bloodstream, reaching organs such as the heart or brain or even the fetus via the placenta.
“This was previously an obscure, unexplored area. Toxicity studies could only speculate about what was in there,” said Beizhan Yan, PhD, coauthor of the study and environmental chemist at the Lamont–Doherty Earth Observatory of Columbia University, New York. “This study opens a window for us to observe a world we were not exposed to before.”
90% Nanoplastics Found
The new study employed a technique called stimulated Raman scattering microscopy, which was invented by study coauthor Wei Min, a biophysicist at Columbia. This method involves probing samples simultaneously with two lasers tuned to resonate specific molecules.
Researchers tested three bottled water brands that are popular in the United States, analyzing plastic particles up to 100 nm in size. They identified 110,000-370,000 plastic particles per liter. About 90% were nanoplastics — which are invisible by standard imaging techniques — and the rest were microplastics. The study also identified the seven plastics involved.
The most common is polyamide, a type of nylon, likely from plastic filters purportedly used to purify water before bottling. Next is polyethylene terephthalate, which is commonly used for water bottles and other food containers. Researchers also found other common plastics, including polystyrene, polyvinyl chloride, and methyl methacrylate, used in various industrial processes.
Not Size But Quantity
What’s more concerning is that the seven types of plastics accounted for only about 10% of all nanoparticles found in the samples. Researchers have no idea about the composition of the remaining 90%. If these are all nanoparticles, their number could reach tens of millions per liter, representing the complex composition of seemingly simple water samples, as noted by the authors.
Researchers now plan to expand beyond bottled water, exploring the vast realm of nanoplastics. They emphasize that, in terms of mass, nanoplastics are far smaller than microplastics, but “it’s not about size. It’s about the numbers as smaller things can easily penetrate us.”
The team aims to study tap water, which also contains microplastics but in much smaller proportions than bottled water.
This article was translated from the Medscape French edition.