Tiny bits of plastic in bottled water: the study

Bottled water can contain hundreds of thousands of tiny pieces of plastic. Even up to a hundred times more than previously calculated. This is reported by a new study published in the journal 'Pnas'. Nanoplastics have 'come to the surface' thanks to a new microscopic technique that has highlighted this world of invisible fragments which – researchers warn – can pass into the blood, cells and brain.

In recent years, experts explain, concern about the impact of so-called microplastics has grown, also because their presence has been detected practically everywhere on Earth, from polar ice to soil, drinking water and food. These particles are consumed by humans and other creatures, with unknown potential effects on health and ecosystems. A major focus of the research was also bottled water, which has been shown to contain tens of thousands of identifiable fragments in each container. But now researchers have managed to go further, entering the little-known realm of nanoplastics, 'daughters' of microplastics that have degraded further. For the first time they counted and identified these tiny particles in bottled water and found that on average one liter contained about 240,000 detectable plastic fragments, numbers 10 to 100 times larger than previous estimates, based mainly on fragments of larger.

Nanoplastics are so small that, unlike microplastics, they can pass through the intestines and lungs directly into the bloodstream and travel from there to organs including the heart and brain. They can invade individual cells and cross the placenta to unborn babies. “This was just a dark, unexplored area before,” says study co-author Beizhan Yan, an environmental chemist at Columbia University's Lamont-Doherty Earth Observatory. The technique “opens a window with which we can look into a world that had not previously been exposed to us.” Global plastic production is approaching 400 million tons per year. More than 30 million tonnes are discharged into water or land every year, and many products made from plastic, including synthetic fabrics, release particles while still in use.

But most plastic doesn't break down into relatively benign substances; it simply divides and redivides into smaller and smaller particles of the same chemical composition. Beyond individual molecules, there is no theoretical limit to how small they can become. And if microplastics are defined as fragments ranging from 5 millimeters up to 1 micrometer (a human hair is about 70 micrometers wide), nanoplastics are particles smaller than 1 micrometer, they are measured in billionths of a meter. The new study uses a technique co-invented by one of the study's authors, Wei Min, a biophysicist at Columbia. The researchers tested three popular brands of bottled water sold in the United States (they declined to name which ones), analyzing plastic particles down to just 100 nanometers in size.

In detail they identified from 110,000 to 370,000 particles in each liter, 90% of which were nanoplastics; the rest microplastics. They also determined which of the 7 specific plastics detectable with the technique were and traced their shape, qualities that could be valuable in biomedical research. A common one was the Pet. This is not surprising, as this is what many water bottles are made of. However it has been outnumbered by polyamide, a type of nylon. Ironically, Beizhan Yan said, this likely stems from the plastic filters used to purify the water before it is bottled. Other common plastics researchers found: polystyrene, polyvinyl chloride, and polymethyl methacrylate, all used in various industrial processes.

A final note described as “a little disturbing” is that the 7 types of plastic searched for by the researchers represented only about 10% of all the nanoparticles found in the samples; experts have no idea what the rest is. If they were all nanoplastics, that would mean they could be as many as millions per liter. Researchers are now going beyond bottled water. “There is a huge world of nanoplastics to study,” notes Min. Among other things, the team plans to examine tap water, which has been shown to contain microplastics, albeit in much lower quantities than bottled water. And it is also working with environmental health experts to measure nanoplastics in various human tissues.