We knew the snow and rain of the Pyrenees contaminated by microplastics. The “clean air” of the mountains is no longer an exception. A study published this Tuesday in the scientific journal Nature Communications, involving scientists from the CNRS, the Université Grenoble-Alpes and the University of Strathclyde (Scotland), confirms the presence of these tiny plastic particles (between one micrometer and five millimeters) generally invisible to the naked eye, at the top of the Pic du Midi, at an altitude of 2,877 meters. In particular polyethylene and polystyrene, used for packaging, as well as polyvinyl chloride, which is used for piping. A discovery all the more “Surprising in a place isolated from sources of pollution”, underlines the CNRS which helped to deepen knowledge on a still little-known object of study.
A pump is installed at the Pic du Midi observatory. The air was analyzed there over a period of four months, from June 23, 2017 to October 23, 2017. A microplastic every four cubic meters (or a microplastic in a small car) was detected. “Not much, admits Jeroen Sonke of the research team, but this still represents, on a global scale, 2,000 tonnes of microplastics at high altitudes where they generally vegetate for a week. ” Too little in any case to present a real risk to health, indicates the CNRS. The figure is to be compared to the 300,000 tonnes of small debris found in the oceans or in concentrations of microplastics in the air of our homes that are ten, a hundred, or even a thousand times higher.
Dust blown by the wind
This new study “Will allow better understand the life cycle of plastic on a global scale ”, emphasizes our interlocutor. And in particular where it comes from, based on mathematical models of the trajectories of air masses. “Many of these microplastics in the air of the Pyrenees find their origin in the oceans and the urban, agricultural or industrial fabric, whether regional or even international. Here, our results suggest that the microplastics of the Pic du Midi come from the Atlantic Ocean and the continents of Africa or North America ”, explains the research director at CNRS. The sea mist and the wind of a more or less strong speed raise the dust which is thus propelled into the atmosphere. This is how microplastics land in remote areas, at high altitude, at the Pic du Midi, in the poles and Mount Everest, which culminates at 8,849 meters. Air transport which is therefore both intercontinental and transoceanic. According to the study, the shortest distance traveled by microplastics is around 275 kilometers and the longest 10,000 kilometers.
Ultimately, the scientists hope to carry out new experiments in order to obtain even more precise data. And try to know, for example, from which gyre (the five zones of massive plastic accumulation, also called “plastic continents”) the microplastics come from. “We know that the North Pacific and North Atlantic oceans are the most polluted and, on the continent side, it is South East Asia and China, where there is little recycling”, recalls Jeroen Sonke. Moreover, given the current conclusions on the presence of microplastics at high altitude (the free troposphere), can we assume that the same is true in the stratosphere located just above? “We have not planned to look into it for the moment because it requires significant logistics, he admits. But if we search, we will certainly find some! “