Loose fibers from functional clothing, discarded PET bottles or abandoned packaging: When such plastic materials enter the environment, they often persist there for a long time. UV radiation, precipitation and ozone cause them to become brittle—and over time, mechanical forces break them down into increasingly smaller particles. Swirled up by the wind, they are carried farther through the atmosphere. Until now, it was unclear how much microplastic ends up back in Swiss soil and water bodies through this process.