Microplastics—tiny plastic particles, often less than a millimeter in size—fall across rural areas of Switzerland, adding over 200 tons annually to the land and water. These particles come from a variety of sources, including loose fibers from synthetic clothing, discarded plastic bottles, and packaging materials. Once in the environment, these plastics can persist for a long time, breaking down slowly due to factors like UV radiation, rain, and ozone. Wind can carry these microplastics over long distances, but until now, it was unclear how much of this plastic returns to Swiss soil and water. A new study by researchers at Empa, in collaboration with Eawag and Agroscope, has now systematically measured this for the first time. Supported by the Federal Office for the Environment (FOEN), the study found that approximately 219 metric tons of microplastics settle in Switzerland each year in areas below 2,000 meters in elevation. About 78 tons end up on agricultural land, and around 10 tons directly into water bodies. To gather this data, the researchers collected samples over an entire year at five locations across Switzerland, including urban Zurich and rural areas like Dübendorf, Magadino, Payerne, and Mount Chaumont in the Jura Mountains. They measured both wet and dry deposition—particles removed from the air by rain or snow, and those that fall due to gravity. The microplastics analyzed ranged in size from 20 to 215 micrometers, roughly the width of a human hair. In Zurich, the researchers found an average of 881 microplastic particles per square meter per day, more than double the levels found at the other rural sites. This is expected due to the city's higher population density, traffic, and use of plastic products. However, the team led by Empa researcher Christoph Hüglin was surprised to find that microplastic levels in rural areas were relatively similar, suggesting that these tiny plastics are not just an urban issue but also reach less populated regions. To ensure accurate results, the researchers used a specialized particle laboratory and a method called imaging infrared microspectroscopy, which allowed them to automatically scan filter samples and identify plastic particles by type. The most common plastics found were polyethylene terephthalate (PET, 31%), polyethylene (PE, 26%), and polypropylene (PP, 21%). These plastics are commonly used in packaging, films, and textiles, with PET also found in polyester clothing. While the study could not pinpoint the exact sources of each particle, it suggests that textiles may be a significant contributor to atmospheric microplastic pollution. Tire wear, which is also classified as microplastics, was studied separately. Microplastics return to the Earth's surface through two main processes: either by being washed out by rain or snow, or by settling during dry weather. In Switzerland, dry deposition accounts for about 60% of the mass of microplastics reaching the ground. While atmospheric input into water bodies is estimated at around 10 metric tons annually, inputs from treated wastewater are much lower, at about 5 metric tons. Compared to all airborne particles, including dust and soot, microplastics make up only a tiny fraction—between 0.02% and 0.12%. Despite their small proportion, the constant accumulation of these particles over time can lead to significant environmental buildup. While the long-term effects of microplastics on ecosystems and human health remain unclear, the study highlights the widespread presence of plastics in the environment. As Hüglin notes, while plastic is a valuable material, it is important to reduce littering, use it only when necessary, and work to close material cycles to minimize environmental impact.