One Liter of Bottled Water May Contain 240,000 Tiny Plastic Fragments

Plastic pollution is a burgeoning environmental catastrophe. The hardy synthetic polymers that make up plastic allow it to linger for a while—with devastating consequences. The photos are heartbreaking: ghost nets strangling entangled marine wildlife; post-mortems of animal stomachs stuffed with plastic trash. But even more disastrous than the big stuff may be the invisible debris: microplastics and nanoplastics. Those pulverized bits are so tiny that they can infiltrate small spaces, including into our bodies and cells.

As much as experts are convinced that puny plastics are all around us, few methods to date have been able to directly detect them. Scientists suspect that the hardest to see are the most damaging of the lot: plastic fragments 100 nanometers in size or less, less than 1/100th the width of human hair. Now, a new study, published Monday in the Proceedings of the National Academy of Sciences, reports a plastics detection technique that can quickly identify the size and composition of miniscule particulates. The authors found that an average of 240,000 particles populate a liter of bottled water, a number greater than previously reported. The find illuminates the true presence of micro- and nanoplastics littering our homes and lives.

“This is really a breakthrough,” says Sherri Mason, director of sustainability at the Pennsylvania State University at Erie, the Behrend College, who wasn’t involved in the research. “If we can’t detect the particles, then we can’t study them. That’s why this study is so important.”

Every time we step on a synthetic carpet, rip open a plastic container, spin our tires when we drive on the road or do laundry, there’s a good chance we’re spewing out thousands of micro- and nanoplastic shavings unseen. “Plastic is much more like skin than we realize,” says Mason. “Like skin, it’s constantly flaking off.”

All that debris can slip into waterways, enter our lungs, and end up in our stomachs through our food and drinks.

The little that scientists know so far about the health hazards of micro- and nanoplastics is already enough to cause alarm. Lab-made nanoplastics can aggravate the immune system, tamper with the body’s metabolism and goad cells into self-destructing. In mice, nanoplastics raise the risk of Parkinson’s disease, disrupt fetal development and seep into the brain to wreak havoc there. But these early studies so far involve pristine polymers that are uniform in size and composition. The kinds of plastics that the real world is awash in are much more diverse, and their impact may be more complex.

Nanoplastics in particular have long eluded study because they’re so tiny; they don’t generate a strong signal when scientists try to probe them. To overcome this challenge, the new study uses a technique called stimulated Raman scattering microscopy. The method involves directing two lasers onto a sample of strewn micro- and nanoplastics. This double dose of light causes the atoms in the particles to resonate. By fingerprinting the energy signatures corresponding to the atomic vibrations, the researchers can identify the types of polymers present. Moreover, they can also work out the size and shape of fragments based on the tiny scattering of the light that hits the pieces.

The whole process, from the light measurement to the data analysis, is automated and takes about two hours per sample. That’s more than ten times faster than existing methods, says study author Wei Min, a chemist at Columbia University. He’s a co-inventor of the stimulated Raman scattering technique, which he first applied to sussing out lipids in tissues in 2008.

To test the new method’s ability to detect nanoparticles, the researchers turned to bottled water. A 2018 study led by Mason found that bottled water can contains some 10,000 plastic particulates per liter, though her team was only looking for bits 6.5 micrometers in size or bigger. With the new method, Min’s group found that every liter harbored at least ten times more flecks. The researchers detected anywhere between 110,000 and 370,000 particles in each liter. Moreover, 90 percent of the specks were nanoplastics, a previously missed category that earlier studies were unable to account for.

About 10 percent of the detected particles belonged to seven common plastics. The other 90 percent were unidentified polymers.

Interestingly, the researchers observed that the different kinds of plastics in bottled water came in different shapes, sizes and distributions, which were telling of their genesis, says first author and Columbia University chemist Naixin Qian. For example, polyethylene terephthalate (PET) often appeared as chunky micrometer-sized shards, likely sloughed off from the bottles themselves, which are frequently made out of PET. The smaller nanoplastics probably were shed into existence during the earliest stages of bottled water production and further disintegrated upon additional processing. The study authors also found polyamide and polystyrene plastics, predominantly as nanoparticles, which, ironically, are commonly used as membrane materials to filter water in treatment plants. “The nanoplastic picture is actually more diverse than what I had imagined,” Qian says.

The study’s results could one day be used to guide micro- and nanoplastic reduction strategies in water treatment.

For the first time, the new method cracks open the door to studying micro- and nanoplastics in the wild, not just in the idealized settings of the lab. The research team plans to use the technique to study the pollution footprint of laundromats, plastics in the air and tap water contamination. More urgently, the researchers want to kick-start toxicity studies to understand how nano-sized plastic affects biology at the cellular and genetic levels. The team is already inundated with hundreds of collaboration requests from research groups all around the world. “I’m actually holding them back,” says study author Beizhan Yan, an environmental chemist at Columbia University.

He adds that how much microplastics hurt people’s health “is still an open question.” Experts say that until scientists collect toxicity data, the government has less of an urgent mandate to regulate micro- and nanoplastics as it does for other contaminants.

To date, there is little federal oversight in the United States on microplastics, let alone on nanoplastics. A few states have implemented their own laws, the most notable example being California, which was the first to ban single-use plastic bags in 2014 and require microplastics testing for drinking water in 2022. Last year, the European Commission prohibited microplastics additives in consumer products to reduce the amount that would inadvertently leach into the environment. Estimates suggest that millions of tons of microplastic particles are already scattered around the Earth. Nanoplastics most certainly number a lot more.

Miniscule plastics are everywhere, wafting in the very air we breathe and raining down on Antarctica as snow. Techniques such as this one that make this invisible pollution visible will provide a crucial step for chipping away at the plastics problem.

Shi En Kim | | READ MORE

Shi En Kim is a Washington, D.C.-based freelance science journalist. Her work has appeared in National Geographic, Scientific American, the Atlantic, Popular Science and others. In 2021, she interned at Smithsonian magazine as an AAAS Mass Media Fellow.