An anonymous reader quotes a report from the Washington Post: People are swallowing hundreds of thousands of microscopic pieces of plastic each time they drink a liter of bottled water, scientists have shown -- a revelation that could have profound implications for human health. A new paper released Monday in the Proceedings of the National Academy of Sciences found about 240,000 particles in the average liter of bottled water, most of which were "nanoplastics" -- particles measuring less than one micrometer (less than one-seventieth the width of a human hair). [...]

The typical methods for finding microplastics can't be easily applied to finding even smaller particles, but Min co-invented a method that involves aiming two lasers at a sample and observing the resonance of different molecules. Using machine learning, the group was able to identify seven types of plastic molecules in a sample of three types of bottled water. [...] The new study found pieces of PET (polyethylene terephthalate), which is what most plastic water bottles are made of, and polyamide, a type of plastic that is present in water filters. The researchers hypothesized that this means plastic is getting into the water both from the bottle and from the filtration process.

Researchers don't yet know how dangerous tiny plastics are for human health. In a large review published in 2019, the World Health Organization said there wasn't enough firm evidence linking microplastics in water to human health, but described an urgent need for further research. In theory, nanoplastics are small enough to make it into a person's blood, liver and brain. And nanoplastics are likely to appear in much larger quantities than microplastics -- in the new research, 90 percent of the plastic particles found in the sample were nanoplastics, and only 10 percent were larger microplastics. Finding a connection between microplastics and health problems in humans is complicated -- there are thousands of types of plastics, and over 10,000 chemicals used to manufacture them. But at a certain point, [...] policymakers and the public need to prepare for the possibility that the tiny plastics in the air we breathe, the water we drink and the clothes we wear have serious and dangerous effects. "You still have a lot of people that, because of marketing, are convinced that bottled water is better," said Sherri Mason, a professor and director of sustainability at Penn State Behrend in Erie. "But this is what you're drinking in addition to that H2O."