Microplastics in Bottled Water at Least 10 Times Worse Than Once Thought

Pure, natural spring water, just as nature intended. Well, not exactly.

Bottled water has long been marketed as a safer alternative to what comes out of the tap—if it doesn’t come straight from a mountain spring, it’s at least purified and chemical free. But a new study by scientists at Columbia University and Rutgers University demonstrates that bottled water may be far worse when it comes to microscopic plastic pollutants capable of passing into the bloodstream.

For years scientists have raised the alarm over the global spread of microplastics, which form when plastics break down into increasingly smaller fragments. The particles, which range in size from five millimeters (1/4 of an inch) down to 1 micrometer (1 millionth of a meter, or 1/25,000th of an inch) have been found at the top of Mount Everest and at the bottom of the deepest ocean trenches, with unknown impacts on human and ecosystem health. Previous studies have found that a liter of bottled water can contain tens of thousands of identifiable (at least through a microscope) plastic particles. But those studies stopped at the 1 micrometer threshold, largely because of technological limitations.

This week’s study, published Jan. 8 in the journal Proceedings of the National Academy of Sciences, uses a newly developed laser technology to find even smaller fragments, upping the number of plastic particles in bottled water by a factor of 10, and in some cases, more than a 100. Using this new technology, which was invented by Columbia biophysicist and study coauthor Wei Min, the authors detected an average 240,000 plastic fragments per liter of bottled water.

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Approximately 90% of the particles were considered nanoplastics, which, as the name implies, are smaller than 1 micrometer. Unlike microplastics, nanoplastics are capable of passing through the intestine and lungs into the bloodstream. From there they can lodge in the heart muscle and other organs, pass the blood-brain barrier into the brain, and even into the bodies of unborn infants by crossing the placenta.  

Not surprisingly, one of the most common nanoplastic types in the three popular brands of bottled water tested (the scientists did not name the brands) was polyethylene terephthalate, or PET, which is the plastic most commonly used in the bottled drinks industry. Most likely the minute particles abrade into the water when the bottle is squeezed, or when the top is repeatedly screwed on or off. Another common plastic type found in the bottled water samples was nylon. Study co-author Beizhan Yan, a geochemistry research professor at Columbia’s Lamont-Doherty Earth Observatory (LDEO), suggests that such particles may in fact come from filters designed to purify the water.

Read More: There’s Almost No Research on the Health Impact of Plastic Chemicals in the Global South

So far, there is little research that shows what, exactly, nanoplastics do once they enter the bloodstream. But there is copious evidence that chemicals used in plastic production are deleterious for human health and mammalian reproduction. Even if the nanoplastics themselves are not harmful, they can serve as carriers for dangerous chemicals used in plastic production, such as bisphenols, phthalates, dioxins, organic contaminants, and heavy metals that are harmful in high doses, increasing the risk of cancer and impacting key organs such as the kidneys, the liver, the heart, reproduction and the nervous system. They can also accumulate through the food chain.

“There is a huge world of nanoplastics to be studied,” says Min. Even if nanoplastics make up 90% of the number of plastic particles found in bottled water, they make up far less in mass, he says. In this case that fact provides little comfort: “It’s not size that matters. It’s the numbers, because the smaller things are, the more easily they can get inside us.”