Microplastics from road traffic

VTI has been commissioned by the Swedish government to develop and disseminate knowledge of microplastic emissions from road traffic. VTI will also identify and evaluate potentially effective policy instruments and measures in order to limit emissions. The assignment runs from 1 January 2018 to 1 June 2021.

Microplastic is a concept that has a widespread use. But the definition is not unambiguous. Our assignment includes, for example, rubber particles, as tyres are made of rubber. We also do not limit ourselves to microparticles, but study both smaller and larger particles. The latter can, by various types of influence, be broken down into microparticles.

About the assignment on the government's website (in Swedish) External link.

Summary of results

Scientific reports

Andersson-Sköld, Y. et al. 2020. Microplastics from Tyre and Road Wear: a Literature Review. External link.

Andersson-Sköld, Y. et al. 2020. Dispersion and Fate Models for Microplastics from Tyre and Road Wear: State of the art and Possibilities (in Swedish, summary in English). External link.

Scientific articles

Järlskog, I., et al., 2020. Occurrence of Tire and Bitumen Wear Microplastics on Urban Streets and in Sweepsand and Washwater. External link.

Järlskog, I., et al., 2021. Traffic-related Microplastic Particles, Metals, and Organic Pollutants in an Urban Area under Reconstruction. External link.

Popular science articles

Road surface technology, 2020. Microplastics Detection: a Review of the Research Literature. Issue: 6; Page: 12-16. External link.

Sub-projects

Within the framework of the assignment, several sub-projects have started gradually and some run partly in parallel. The sub-project that was the first to be reported is the compilation of knowledge about microplastic particles from tyre and road wear. See further below.

The following sub-projects for compilation and development of new knowledge are included in the government assignment:

The purpose of the knowledge compilation was to increase our own knowledge in the field, get a good picture of the overall knowledge and to identify knowledge gaps for further research. The report has been published in both Swedish and English.

See link above to the report Microplastics from Tyre and Road Wear: a Literature Review.

Contact: Yvonne Andersson Sköld

The purpose of the sub-project is to get a better (more accurate) estimate of how much microplastic is worn from tyres in Sweden. In order to perform calculations of tyre wear, VTI has, in cooperation with students at KTH (Royal Institute of Technology) and with the support of the tyre industry, collected information on tyre wear from a tyre recycling center and tyre repair shops. Measurements and literary data are combined with detailed vehicle and traffic statistics to calculate microplastic emissions.

Contact: Mats Gustafsson

The purpose of the sub-project is to identify, characterize and quantify the road system's microplastics as close to the source as possible, so that microplastic particles from the road system can be more easily identified and quantified when found in other parts of the downstream water system. This includes mapping seasonal variations and the difference between urban and rural roads.

The aim is also that the sampling of road-related microplastic particles also contributes to the development of sample preparation and analysis methods, see sub-project below.

Contact: Mats Gustafsson

The purpose of the sub-project is to identify possible analysis methods for microparticles from tyres with respect to number, mass, size distribution, shape and chemical composition. We also produce clean particles from tyres as reference materials for analyzes that focus on the chemical composition.

To be able to analyze field samples, development of a method that can separate the tyre microparticles from other particles is required. Such a sample preparation method is produced in collaboration between University of Gothenburg, Chalmers University of Technology and VTI. The sub-project is also partly financed by Formas for doctoral student Ida Järlskog.

Several analytical methods have been tested and evaluated in collaboration with the University of Gothenburg. In addition, one analytical method has been developed together with a company in Switzerland, Particle Vision GmbH.

Contact: Yvonne Andersson Sköld and Ida Järlskog

The purpose of the sub-project is to characterize the microplastics generated during tyre wear and to make comparisons between different tyre types. In VTI's road simulator, tyres are worn against an asphalt and a cement concrete surface and the resulting wear particles are collected both behind the tyres, as deposition on aluminum foils and on filters in the air. The collected particles are used for analysis development and are characterized physically as well as chemically to constitute reference material for collected field samples. At the same time, the tyre wear is compared between a selection of commonly used summer tyres, unstudded and studded winter tyres.

Contact: Mats Gustafsson

The purpose of the sub-project was to examine potential toxicity of leachates from various road marking products and to examine what chemical substances could potentially leach from different road markings into aquatic environments. The sub-project includes laboratory attempts with leaching tests, toxicity studies and chemical analyses which are performed in collaboration with the Department of Environmental Science at Stockholm University.

Road marking particles were leached in deionized water and the toxicity of the leachates on algae and bacteria were studied. The leachates were also analyzed in relation to content of organic substances and metals.

Contact: Mikael Johannesson

The purpose of the sub-project was to gain knowledge on the possibility of modelling microplastics dispersion and fate in nature. Microplastic particles from tyre and road wear are spread from the road to soil, water and air and are also transported within and between these environmental compartments. Therefore, it is important to quantify these flows and describe how far the microplastics are transported and where they end up. The project consists of a literature review which describes existing microplastics dispersion and fate modelling studies and which models are possible to use and most suited for studying this. See link above to the report Dispersion and Fate Models for Microplastics from Tyre and Road Wear: state of the art and Possibilities (in Swedish, summary in English).

Contact: Nina Svensson

The purpose of the sub-project is to identify possible policy instruments and measures that in a cost-effective way can reduce emission and dispersion of, as well as, exposure to microplastics from road traffic. Knowledge and experience derived from other sub-projects will partly support this sub-project. A preliminary compilation of policy instruments and measures is included as a chapter in the knowledge compilation on microplastic from tyre and road wear.

Contact for this project and also project manager for the entire government assignment is Mikael Johannesson.

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