It’s not just the location of the recent microplastics that’s remarkable. It’s how the plastics got there: Researchers believe the microplastics must have been lofted there from faraway places, coating even high-altitude places devoid of humans with little bits of pollution. The team’s research was published on Tuesday in Nature Communications.
“We found plastic is now in the pollution superhighway that is the free troposphere. That’s the air mass above the clouds. Its low humidity and fast winds means long distance travel,” Steve Allen, an environmental scientist at the University of Strathclyde in Glasgow and lead author of the paper, said in an email. “We showed that these small plastic particles are moving transcontinental and transatlantic.”
The team found the microplastics at the Pic du Midi Observatory, which sits at nearly 10,000 feet (3,050 meters) in elevation in the French Pyrenees. For four months, the researchers sucked up air from Earth’s troposphere that was floating by, and filtered any larger bits (meaning, basically, anything that wasn’t air). They calculated that there was about one microplastic particle for every 141 cubic feet (4 cubic meters) of air. They then used a laser microscope to figure out what kind of plastic was ending up at the top of the Pyrenees. Most of the pieces they identified were either polystyrene or polyethylene polymers from packaging.
“They travel exactly like aerosols and in the same way, they go everywhere,” Allen said, referring to tiny particles like volcanic ash, sea salt, and air pollution that get swept up in the atmosphere. “Our study showed that plastic left the sea and wound up traveling in high altitude air, travelling up there for up to a week. This means that plastics might never find a final resting place. No matter where they land, they can get picked up and transported thousands of kilometers, then do it again.”
The team wrote that source areas for the plastic included Europe, North Africa, the Mediterranean Sea, and the Atlantic Ocean. Some particles could even come from as far away as the U.S. and Canada. While the levels of microplastic the team detected aren’t hazardous, they highlight the reach of human pollution.
When you factor in how slowly plastic breaks down, it paints a pretty bleak portrait for Earth’s future. Even long after humankind is gone from the Earth, perhaps we’ll leave our mark in the thin film of microplastics that coats the planet.
Correction: A previous version of this article incorrectly identified the mountain range on which the microplastics were detected as the French Alps. The microplastics were detected in the French Pyrenees mountains. We regret the error.