Monitoring the mechanical degradation of rubber finds significant application in today’s industry, for example in automotive components or industrial seals [1,2]. Since radioisotopes enable simple and precise detection while requiring only small substance amounts [3,4], they are ideal tools for this investigation. We present the successful radiolabelling of ethylene-propylene-diene terpolymer (EPDM) rubber with gaseous ruthenium(VIII) oxide (RuO4). We investigated the influence of the time the rubber was exposed to the measured activity found in the rubber. This can be seen in figure 1, where the y-axis is the normalized activity and the x-axis is the exposure time. The uptake of the radioactivity increases up to a certain point, where the rubber seems to be saturated and therefore then appears to be constant. Further investigations on the radioactive uptake are ongoing, as well as the visualization of the spacial distribution of the activity inside the rubber with autoradiographic methods. [1] Zellhofer M et al 2022 Tribol Lett 70 55 [2] Stamenkovic D et al 2014 Tribol Ind 36 9-16 [3] Sterba J 2018 J Radioanal Nucl Chem 316 753-759 [4] Steinhauser G et al 2013 Environ Sci Pollut Res Int 20 2527-2534