The hot summer of 2026 showed that water is a precious resource, both in sufficient quantity and of good quality. With climate change, dry spells and heavy precipitation increasingly alternate, which also impairs water quality. During dry periods, microplastics thus accumulate on roads, roofs and other sealed surfaces. During heavy rain, they are washed away all at once and enter streams, rivers and lakes via the sewer system, an effect that increases with more frequent extreme weather conditions. The largest source of microplastics is tyre wear. Today, 10'000 tonnes enter the environment every year, around 4000 tonnes of which enter Swiss waters. Since 2002, wastewater from heavily trafficked national and cantonal roads should therefore have been treated. In 2023, the Federal Council did present an action plan in the report «Reifenabrieb als grösste Quelle von Mikroplastik. Massnahmen zur Verminderung» (translation: «Tyre wear as the largest source of microplastics. Measures for reduction»), but according to the response to IP 25.3381, implementation of this requirement is enormously behind schedule: full implementation is not expected for approximately 50 years. Road rehabilitation measures related to drainage could halve the share of microplastics entering bodies of water.