Street sweeping: A source to, or measure against, microplastic emissions

Published on November 14, 2023

Report studying the complicated relationship between if street sweepers contribute to or is a measure against microplastics. Especially seeing as the sweeping both is a effective way of collecting microplastics from road environments whilst also contributing to said microplastics due to the brushes often being made out of plastic brushes that get worn down.

Microplastics from road traffic are mainly caused by tyre wear, which is globally considered to be one of the largest sources of microplastics. Tyre wear particles have been shown to occur in all media (road surface, air, soil, stormwater, lakes and rivers and coastal sediments) and are dispersed both by runoff and by atmospheric transport. To reduce the dispersion and possible effects of road traffic microplastics emissions, measures can be taken to prevent the formation of particles and to prevent their dispersion through treatment measures. This study focuses on street cleaning as a method to reduce emissions, but as many street cleaning methods are based on the use of plastic brushes, cleaning as a source of microplastics has also been considered. The study was carried out in collaboration with the municipality of Karlstad and included a review of how street cleaning is carried out in Karlstad in relation to uptake and dispersion of microplastics. Furthermore, a comparison between two cleaning machines (elevator and vacuum) has been made and a monitoring of microplastic amounts on the road surface during different phases of spring sweeping has been carried out. In order to estimate the amount of plastic torn from the brushes, weighing of the brushes has been carried out. In order to gain knowledge about the work of more municipalities on street sweeping from a microplastic perspective, a questionnaire study was sent out to six municipalities in different parts of the country. The results show that both cleaning machines have the capacity to reduce the amount of microplastics on the road surface. However, during spring sweeping, the amount of polypropylene (the most common plastic in the brushes) on the road surface increases. The distribution of analysed plastics differs significantly between the road surface and the material collected by the machines. This is thought to be due to the fact that the machines mainly collect coarser fractions, while finer fractions remain on the road surface. Knowledge of, and thus consideration of, microplastics in relation to operational measures such as street cleaning is currently low among the municipalities surveyed, but awareness exists, as does the need for support in implementing possible measures. The present study shows a complex problem picture and represents a first step in understanding how street cleaning can be used as a measure, but also indicates that the wear of plastic brushes leads to a net emission of microplastics.