The average liter of bottled water contains almost a quarter of a million invisible pieces of tiny nanoplastics, which are detected and categorized for the first time by a microscope using dual lasers.
Scientists long thought there were many 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 each of three common brands of bottled water, researchers found that particle levels ranged from 110,000 to 400,000 per liter, averaging around 240,000 according to a study in Monday’s Proceedings of the National Academy of Sciences.
These are particles smaller than a micron in size. There are 25,400 microns – also called micrometers because they are one millionth of a meter – in an inch. A human hair is approximately 83 microns wide.
Previous studies have looked at slightly larger microplastics that range from the visible 5 millimeters, less than a quarter of an inch, down to one micron. The research shows that approximately 10 to 100 times more nanoplastics than microplastics have been discovered in bottled water.
Much of the plastic appears to come from the bottle itself and from the reverse osmosis membrane filter used to keep out other contaminants, said lead study author Naixin Qian, a physical chemist from Columbia. She does not want to reveal the three brands because researchers want more samples before choosing a brand and want to study more brands. Still, she said they were common and purchased at a WalMart.
Researchers still cannot answer the big question: are those pieces of nanoplastic harmful to health?
“That is currently being investigated. We don’t know if it’s dangerous or how dangerous,” said co-author Phoebe Stapleton, a toxicologist at Rutgers. “We do know that they get into the tissues (of mammals, including humans)… and current research is looking at what they do inside the cells.”
The International Bottled Water Association said in a statement: “There is currently both a lack of standardized (measurement) methods and no scientific consensus on the potential health effects of nano- and microplastic particles. That is why media reports about these particles in drinking water do nothing other than unnecessarily frighten consumers.”
The American Chemistry Council, which represents plastics makers, declined to immediately comment.
The world is “drowning 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, some of which comes from clothing and cigarette filters, said the United States. Environment Program of the Nations. Efforts for a global plastics treaty continue after talks stalled in November.
All four co-authors interviewed said they had started cutting back on bottled water use after conducting the study.
Wei Min, the Columbia physical chemist who pioneered dual laser microscope technology, said he has cut his bottled water use in half. Stapleton said she now relies more on filtered water at home in New Jersey.
But study co-author Beizhan Yan, a Columbia environmental chemist who increased his tap water use, pointed out that filters themselves can be a problem with the introduction of plastics.
“There’s just no winning,” Stapleton said.
Outside experts, who praised the research, agreed that there is a general unease about the dangers of fine plastic particles, but it is too early to say for sure.
“The danger of the plastics themselves is still an unanswered question. To me, the additives are the most concerning,” said Jason Somarelli, professor of medicine and comparative oncology group at Duke University, who was not part of the study. “We and others have shown that these nanoplastics can be internalized into cells and we know that nanoplastics contain a variety of chemical additives that can cause cell stress and DNA damage and alter metabolism or cell function.”
Somarelli said his own unpublished work has found more than 100 “known cancer-causing chemicals in these plastics.”
What’s troubling, says evolutionary biologist Zoie Diana of the University of Toronto, is that “small particles can appear in different organs and cross membranes that are not meant to cross, such as the blood-brain barrier.”
Diana, who was not part of the study, said the new tool researchers used makes this an exciting development in the study of plastics in the environment and the body.
About 15 years ago, Min invented dual laser microscope technology that identifies specific compounds based on their chemical properties and how they resonate when exposed to the lasers. Yan and Qian talked to him about using that technique to find and identify plastics that were too small for researchers using established methods.
Kara Lavender Law, an oceanographer at the Sea Education Association, said that “the work could be an important step forward in the detection of nanoplastics,” but she 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 is needed. The total weight of the nanoplastic found is “approximately equal 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 am privileged to live in a place where I have access to ‘clean’ tap water and do not have to purchase drinking water in single-use containers.”
Yan said he will survey other municipal water supplies in Boston, St. Louis, Los Angeles and elsewhere to see how much plastic is in their tap water. Previous studies on microplastics and some early tests indicate that there may be less nanoplastic in tap water than in bottles.
Despite the uncertainty about human health, Yan said he does have one recommendation for people who are concerned: use reusable bottles instead of single-use plastics.
___
Read more about AP’s climate coverage at http://www.apnews.com/climate-and-environment
___
Follow Seth Borenstein on X, formerly known as Twitter, at @borenbears
___
The Associated Press’ climate and environmental reporting receives support from several private foundations. View more about AP’s climate initiative here. The AP is solely responsible for all content.