Large quantities of microplastics are found in wastewater from roads. It comes from the abrasion of car and lorry tyres, polymers and bitumen contained in asphalt, shoe soles and road markings. Particularly during heavy rainfall, plastic particles are often washed off the road not only into the sewage system, but also onto fields and into bodies of water. On roads with little traffic, road wastewater is not always discharged via the sewage system into a road wastewater treatment plant (abbreviated in German to SABA), but is instead discharged unfiltered into the nearest body of water or seeps into the subsoil.
Researchers at Empa have taken a closer look at the abrasion material of tyres: micro-rubber. They have calculated that between 1988 and 2018, around 200,000 metric tons of micro-rubber could have accumulated in the environment in Switzerland. According to these calculations, about three-quarters remain in a five-m-etre-wide strip to the left and right of the road, 5 percent end up in the soil beyond the strip and 20 percent in water bodies
(source: “Rubber in the Environment”, Empa, 2019).
In a study by the Fraunhofer Institute UMSICHT, the researchers identified tyre abrasion as the biggest cause of microplastics in the environment in Germany. The abrasion of asphalt takes third place, shoe soles seventh and road markings ninth place.
(Source: “Plastics in the Environment: Micro- and macroplastics”, Fraunhofer Institute UMSICHT, 2018).