This article discusses the impact of microplastics on air pollution. Due to their small size, microplastics are easily carried by winds over long distances.

For her research the biogeochemist Janice Brahney had collected dust deposited in a desert area in the Western United States, so to study how phosphorus is transported in the air in these remote places and how it might affects the ecosystems.

The samples she collected contained more than just soil particles. When she examined them under a microscope, she found a significant amount of plastic particles. There were fibres, spheres, and fragments of various colours. 

The area Brahney was studying was a remote region in the high deserts of the Uintas in Utah and Rocky Mountain National Park, where human activity was almost non-existent. Brahney's detailed investigation concluded that microplastics were being transported into the atmosphere and then deposited on the ground through snow, rain, or even dust-laden winds.

When Brahney began her studies in the western part of the United States, there were studies conducted in urban areas like Paris, but there were no publications demonstrating that these particles could travel through the planet's atmosphere. Brahney invited an atmospheric scientist from Cornell University, Natalie Mahowald, who was shocked by the idea that they could travel such long distances.

Mahowald noticed that when she saw the microplastics, they had a unique shape that posed new challenges. "Microplastic fibres can be 1 micron wide and 200 µm long; they don't look like spheres, which are much easier to study. They have a peculiar shape," she said.

This model suggested that 84% of the plastic Brahney found came from roads. As vehicles move, their tires wear down and release plastic particles into the air, which then travel through the air current. These tire wear and brake pad dust generate new microplastics in the air, while other significant sources come from oceans and agricultural fields.

According to Brahney and Mahowald, most of the world's oceans are, in fact, sources of atmospheric plastic. This finding has emerged in the last three years, but studies suggest that this pollution has been circulating around the world for decades. Mahowald believes that microplastics in the atmosphere potentially influence cloud formation. These particles form ice clouds that affect climate and weather. If the high level of these microplastics in the air contributes to the formation of these clouds, then they may be contributing to global warming.

Laura Revell, an environmental physicist from the University of Canterbury, states that atmospheric microplastics can cool or warm the planet depending on the altitude they are located in the atmosphere.

The temperature in the atmosphere varies with different altitudes, and this variation affects the optical properties of microplastics and the amount of radiation they absorb or reflect. Revell's study shows that if microplastics are found near the boundary layer, the most affected level of the troposphere by Earth's surface activity, they may have a cooling effect. However, if they are found above the boundary layer, they may impact greenhouse gases.