Tyre wear particles (TWP) are a source to both air-borne particles and microplastic pollution of soil, water and sediments. The total wear of tyres in Europe has been estimated to 1.3 million tonnes/year, making it one of the largest sources to microplastics. The tyre rubber mix consists of about 40 60% synthetic and/or natural rubber, depending on tyre type. The rest is reinforcing fillers (30 35 %), plasticizers (15 %), vulcanization agents (2 5 %) and other additives (5 10 %). Winter tyres need to have softer rubber mixes than summer tyres to maintain friction at low temperatures, when rubber gets stiffer. Therefore, winter tyres normally contain a higher share of natural rubber than summer tyres.

Except being an important source for general microplastics, defined as polymer containing particles smaller than 5 mm, tyre wear also contributes to airborne particles (e.g. Fussel et al., 2022). Since non-exhaust particles from tyres, brakes and road surface are not yet regulated, their emissions increase with increasing traffic amounts. Also, increasing emissions of tyre and road wear particles are promoted by vehicles continuously getting heavier as a result of trends (e.g. SUV:s) and vehicle propulsion developments (electrification).

Information about tyre wear emissions and how their size and physico-chemical characteristics are affected by material properties and use is scarse, but highly relevant for future mitigation. In this paper, results from the Horizon Europe project Nº 955387 Low particle Emissions and lOw Noise Tyres (LEON-T) are presented. In the project particle emissions from six sets of tyres (summer, all-season and winter) run in a road simulator have been investigated, characterized, and analysed in relation to tyre properties. Data from similar tests of summer and winter tyres in a governmental assignment (GA) at VTI are also presented.