Even the highest peaks are not immune to human pollution.

While the presence of microplastics has already been detected on Everest, in the Arctic or in the middle of the oceans, a study, published Tuesday, December 21, in the journal Nature Communications, shows that these pollutants can be transported between continents by winds. altitude. 

These residues of a few millimeters at most, resulting, for example, from deteriorating packaging or washing clothes, are of increasing concern to researchers. 

Their presence has even been highlighted near the summit of Everest, probably waste from the equipment of climbers who crowd every year on the roof of the world. 

Other studies have found them in the snow of the Alps or the Arctic and they have also been identified in rivers and the most remote parts of the oceans. 

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Studies had also measured them in the air in close proximity to the ground.

Researchers from the CNRS, the University of Grenoble Alpes 2 and the University of Strathclyde (Scotland) this time looked for them in "pure" air, at altitude above the clouds. 

Samples were taken at the Pic du Midi observatory, perched at 2,877 meters in the French Pyrenees, between June and October 2017, with a pump sucking 10,000 m3 of air per week. 

All of them contained microplastics.

In quantities without immediate risk to health but significant in a presumed preserved area, where "one can not easily attribute" this pollution to any local origin, write the researchers. 

Plastic "goes around in circles in a perpetual cycle"

To understand its origin, they calculated the trajectory of the different air masses sampled over the seven days preceding the samples. 

As a result, the pollutants originate in particular from the northwest of the African continent, passing over the Mediterranean, North America or the Atlantic Ocean. 

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These data confirm an intercontinental path, because the atmospheric zone studied, the free troposphere, acts as a "hyper-fast path" over very large distances for particles, explains Steve Allen, lead author of the study. 

For the researcher, it is the marine origin of a part of these particles which constitutes the most salient teaching of the study. 

"That plastic is being pulled from the ocean to such heights shows that there is no possible storage sink, it goes around in circles in a perpetual cycle. It shows that you can't just send plastic abroad, because it will come back to you "in another form. 

Especially since some of the particles analyzed, on the order of a micron, "are of a size that we can breathe," adds Deonie Allen, also author of the study. 

These results "show that it is indeed a global problem", adds the researcher. 

With AFP 

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