When you drink bottled water, you're drinking lots and lots of plastic particles

New study finds most of the plastic comes from bottle itself, filtration

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The average litre of bottled water has nearly a quarter million pieces of ever-so-tiny nanoplastics, detected and categorized for the first time by a microscope using dual lasers.

Scientists long figured there were lots of these microscopic plastic pieces, but until researchers at Columbia and Rutgers universities did their calculations they never knew how many or what kind.

Looking at five samples each of three common bottled water brands, researchers found particle levels ranged from 110,000 to 400,000 per litre, averaging at around 240,000, according to a study in Monday's Proceedings of the National Academy of Sciences.

These are particles that are less than a micron in size. There are 25,400 microns — also called micrometres because it is a millionth of a metre — in an inch. A human hair is about 83 microns wide.

Previous studies have looked at slightly bigger microplastics that range from the visible five millimetres, less than a quarter of an inch, to one micron. About 10 to 100 times more nanoplastics than microplastics were discovered in bottled water, the study found.

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How plastic gets into bottled water

Much of the plastic seems to be coming from the bottle itself and the reverse osmosis membrane filter used to keep out other contaminants, said study lead author Naixin Qian, a Columbia physical chemist. She wouldn't reveal the three brands in question, because researchers want more samples before they single out a brand and want to study more brands. Still, she said they were common brands and bought at a Walmart.

What's disturbing, said University of Toronto evolutionary biologist Zoie Diana, is that "small particles can appear in different organs and may cross membranes that they aren't meant to cross, such as the blood-brain barrier."

Kara Lavender Law, an oceanographer at the U.S.-based Sea Education Association, said "the work can be an important advance in the detection of nanoplastics," but she said she'd like to see other analytical chemists replicate the technique and results.

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Denise Hardesty, an Australian government oceanographer who studies plastic waste, said context is needed. The total weight of the nanoplastic found is "roughly equivalent to the weight of a single penny in the volume of two Olympic-sized swimming pools."

Yan said he is starting to study other municipal water supplies in Boston, St. Louis, Los Angeles and elsewhere to see how much plastic is in their tap water. Previous studies looking for microplastics and some early tests indicate there may be less nanoplastic in tap water than bottled.

Even with unknowns about human health, Yan said he does have one recommendation for people who are worried: Use reusable bottles instead of single-use plastics.

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