They are invisible to our eyes, but every year millions of tons of microplastics, i.e. fragments smaller than five millimeters produced by human activities, enter the environment using the atmosphere as a real vector. According to a new analysis published in the journal Science, the planet’s rivers transported 263 thousand tons of microplastics into the oceans in just one year, a weight equivalent to 26 exact copies of the Eiffel Tower. But waterways are only one stage in a much larger cycle, which leads these wastes to travel for kilometers before falling back onto the planet in the form of rain or snow.
From water to sky
In fact, after arriving in the seas, these small particles are pushed up again by wave motion and winds. Once the water has evaporated, the plastic fragments remain suspended in the atmosphere like sea spray, ready to be transported very long distances and fall back to land through precipitation.
This is a phenomenon on which a recent study conducted in Switzerland has shed more light. Researchers monitored five different sites for a year, estimating that approximately 219 tons of microplastics are deposited annually across the country in areas below two thousand meters of altitude. Of these, 78 tonnes fall directly onto agricultural land, while another 10 end up in waterways.
Impressive numbers, which obviously vary based on the geographical area analyzed. According to research conducted by Janice Brahney, environmental biogeochemist at Utah State University, approximately one thousand tons of microplastics are deposited every year in protected areas of the western United States alone. “We are witnessing a constant increase in the quantity of plastic deposited – the expert explained to Wired -. All the samples subsequently analyzed contain increasingly greater concentrations of polymers”.
The data underestimated
As explained by Brahney, the real problem is that the current data represent an underestimated value compared to the real impact of the phenomenon. In fact, to date there is no standard method for measuring plastic in the air. Many of the tools used were not designed to collect microplastics, but different, denser and spherical particles. Plastics, on the other hand, have irregular shapes and lower densities, which make them difficult to identify. Then there are the problems caused by the wind, which can deflect the fragments away from the detection instrument, effectively leading to a lower count than the real one.
But how do these fragments end up in the sky? In addition to the mechanism powered by rivers and the sea, there are others on land that involve transport and agriculture. In urban areas, traffic in large centers moves road residues into the atmosphere due to the strong friction of tires with asphalt. Even activity in the fields contributes to this cycle: city purification plants concentrate microplastics in sewage sludge which is then used as fertilizer. When tractors move soil in windy conditions, particles are dispersed back into the air. According to analyses, most of the material collected consists of fibers from disintegrated clothing and tire residues.
From agricultural fields to blood vessels
The constant contamination of the environment has serious effects on the soil and marine fauna, even down to the very vegetables and fish we consume at the table. According to several scientific studies, plastic is capable of altering the structure of the soil and the cycle of nutrients, while the more microscopic nanoplastics are absorbed by the roots of plants together with water, ending up inside the internal tissues of vegetables and fruit such as carrots, lettuces and apples.
A similar process also occurs in aquatic ecosystems, where fish continuously absorb these substances, with the nanoparticles even reaching the animals’ brains, changing their behavior. Professor Juyong Brian Kim of Stanford Medicine began studying what happens when plastic enters the bloodstream in 2025, finding that micro- and nanoplastics can penetrate the cells lining blood vessels, causing major changes and contributing to faster progression of vascular disease.