What do human brains, placentas and dolphin breath have in common? Signs of plastic pollution in the form of tiny particles known as microplastics.
The ocean is also polluted with plastic, and the issue may be even more extensive than previously thought. A study published Wednesday in the journal Nature estimates the volume of nanoplastics, which are even smaller than microplastics and invisible to the naked eye, to be at least 27 million metric tons in North Atlantic seas — more than the weight of all wild land mammals.
“I’ve analyzed plastic in Swedish lakes, in urban and very remote air, but this was different,” said Dusan Materic, head of a microplastics and nanoplastics research group at the Helmholtz Center for Environmental Research in Germany and one of the lead authors of the analysis. “It’s a missing part of the plastics story that we are answering here.”
Nanoplastics are microscopic fragments smaller than one micrometer — roughly the size of small bacteria.
“People were concerned about nanoplastics in ocean water, but they didn’t have the technology to see what they really looked like,” said Tengfei Luo, an engineering professor at the University of Notre Dame who was not involved in the new study. Last year, Dr. Luo was an author of a separate study in the journal Science Advances that was the first to successfully find nanoplastics in ocean water and show what they looked like.
“We all expected nanoplastics, the surprising part is the amount of it,” said Sophie ten Hietbrink, a doctoral student at Stockholm University in Sweden and a lead author of the study. She spent four weeks on a boat expedition collecting samples of water across nearly 3,500 nautical miles of coastlines and open ocean near Europe, led by Helge Niemann, a professor at Utrecht University and a scientist at the Royal Netherlands Institute for Sea Research.
The vials of water were first dried in an evaporation chamber, leaving only a salty residue, which was then heated. At higher temperatures, fragments of plastic burned and released their stinky, signature molecules. The researchers used mass spectrometry to identify the compounds and measure signals associated with different types of plastic.
“Burning plastic is smelly to us, but also releases a fingerprint detectable by mass spectrometer,” Dr. Materic said. “We needed to be absolutely confident that what we saw was a nanoplastic signal and not something else.”
Plastic pollution tends to float near the surface and build up in large, rotating ocean currents known as gyres. The researchers found nanoplastics were more concentrated by coastlines and near the water’s surface, but they detected the pollutant as far down as 4,500 meters.
The study found an average concentration of nanoplastics near coastlines of 25 milligrams per cubic meter of water — about the weight of a single large bird feather.
Nanoplastics are tiny enough that they can easily infiltrate the bodies of living creatures, Dr. Luo said. For fish and other animals that live in the ocean, that means constant exposure that builds up over time.
“I don’t think humans will be able to stop using plastics any time soon, but it’s important to have better management of plastic waste,” Dr. Luo said.
In August, representatives of more than 100 countries will gather in Geneva for the final meeting of the United Nations’ effort to tackle global plastic pollution.
Sachi Kitaijma Mulkey covers climate and the environment for The Times.
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