Scientists find about a quarter of a million invisible microplastic particles in a liter of bottled water

The average liter of bottled water contains nearly a quarter of a million invisible pieces of such tiny nanoplastics, detected and categorized for the first time by a microscope using twin lasers.

Scientists have long thought there were a lot of these microscopic pieces of plastic, but until researchers at Columbia and Rutgers universities did their calculations, they never knew how many or what kind. Looking at five samples of each of three common brands of bottled water, researchers found particle levels ranged from 110,000 to 400,000 per liter, with an average of about 240,000, according to a study in Monday’s Proceedings of the National Academy of Sciences.

These are sub-micron sized particles. There are 25,400 microns – also called micrometers because it is one millionth of a meter – in one inch. A human hair is about 83 microns wide.

Previous studies have looked at slightly larger microplastics, which range from a visible 5 millimeters, less than a quarter of an inch, to one micron. About 10 to 100 times more nanoplastics than microplastics were found in bottled water, the study found.

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Much of the plastic appears to come from the bottle itself and the reverse osmosis membrane filter used to keep out other contaminants, said study lead author Naixin Qian, a physical chemist at Columbia. She would not disclose the three brands because researchers want more samples before choosing a brand and want to study more brands. However, she said they were regular and purchased from WalMart.

Researchers still can’t answer the big question: Are these nanoplastic pieces harmful to health?

“This is currently under review. We don’t know if it’s dangerous or how dangerous it is,” said study co-author Phoebe Stapleton, a toxicologist at Rutgers. “We know that they enter the tissues (of mammals, including humans) … and current research is looking at what they do in the cells.”

The International Bottled Water Association said in a statement: “There is currently both a lack of standardized (measurement) methods and scientific consensus on the potential health effects of nano- and microplastic particles. Therefore, media reports about these particles in drinking water do nothing more than unnecessarily scare consumers.

The American Chemistry Council, which represents plastics manufacturers, declined immediate comment.

The world is “sinking under the weight of plastic pollution, with more than 430 million tons of plastic produced annually” and microplastics found in the world’s oceans, food and drinking water, with some coming from clothing and cigarette filters, according to the United Nations Program for the environment. Efforts for a global plastics treaty continue after talks stalled in November.

All four co-authors interviewed said they reduced their use of bottled water after conducting the study.

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Wei Ming, the Columbia University physical chemist who pioneered the twin-laser microscope technology, said he has cut bottled water use in half. Stapleton said he now relies more on filtered water at home in New Jersey.

But study co-author Beizhan Yan, an environmental chemist at Columbia University who has increased tap water consumption, pointed out that the filters themselves could be a problem by introducing plastics.

“There’s just no winning,” Stapleton said.

Outside experts who praised the study agreed there was general concern about the dangers of fine plastic particles, but it was too early to say for sure.

“The danger of plastic itself is still an unanswered question. To me, the supplements are the most concerning,” said Duke University professor of medicine and director of the comparative oncology group Jason Sommarelli, who was not involved in the study. “We and others have shown that these nanoplastics can be internalized into cells, and we know that nanoplastics carry all kinds of chemical additives that can cause cellular stress, DNA damage, and alter metabolism or cell function.”

Sommarelli said his own as-yet-unpublished work has found more than 100 “known cancer-causing chemicals in these plastics.”

What’s troubling, said University of Toronto evolutionary biologist Zoe Diana, is that “small particles can show up in different organs and can pass through membranes they’re not meant to pass, like the blood-brain barrier.”

Diana, who was not part of the study, said the new tool used by the researchers makes this an exciting development in the study of plastics in the environment and the body.

About 15 years ago, Min invented a dual-laser microscope technology that identifies specific compounds by their chemical properties and how they resonate when exposed to lasers. Yang and Qian talked to him about using this technique to find and identify plastics that were too small for researchers using established methods.

Cara Lavender Lowe, an oceanographer at the Marine Education Association, said “the work could be an important advance in the detection of nanoplastics,” but said she would like to see other analytical chemists replicate the technique and results.

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

Hardesty is less concerned than others about nanoplastics in bottled water, noting that “I’m privileged to live in a place where I have access to ‘clean’ tap water and don’t have to buy drinking water in single-use containers.”

Yan said he’s starting to research other municipal water systems 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 suggest there may be less nanoplastics in tap water than bottled water.

Although it’s not known for human health, Yang said he has one recommendation for people who are concerned: Use reusable bottles instead of single-use plastics.

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