Study Measures Microplastic Emissions from Mountain Biking for the First Time

Researchers at Bayreuth University have presented the first measurable evidence of microplastic emissions from off-road cycled mountain bike tyres. The paper, published in Science of The Total Environment, sheds new light on how alternative transport like bicycles is adding to environmental microplastic contamination. Although tire wear from motor vehicles is already documented to be a massive source of microplastics, what is potentially coming from other forms of non-motorized transport like mountain biking has not been explored before. Microplastics are man-made polymer particles smaller than 5 millimeters in size that are now widely found in air, water, soil, and even within living organisms.

Tire wear is one of the largest sources of microplastic contamination, as car tires release an estimated 11 grams of microplastic per 100 kilometers. German tire wear accounts for 57% of road traffic microplastic pollution and some 35% of national microplastic load. However, the contribution from bicycles, at times considered the green option, had not been quantified—until now. The Bayreuth research was conducted by the Chair of Sport Ecology and involved a team that included doctoral researcher Fabian Sommer. To quantify emissions of microplastics in the field, the researchers fitted nine mountain bikers with brand new tyres and asked them to ride through their normal routes with their activity tracked using GPS. The tyres were collected every so often and weighed to quantify the material lost through abrasion over time.

The findings indicated that mountain bike tires emitted around 3.5 grams of microplastic for every 100 kilometers.

Estimated yearly, this amounts to roughly 88 grams of microplastic per cyclist. While the figure itself is small, it is still one of direct microplastic emissions into the environment, particularly since mountain biking is generally done in forests, mountains, and other environmentally sensitive places. While this, the overall contribution of mountain biking to Germany's overall microplastic emissions is minimal—less than 1%—when compared on a national level. Interestingly, it was also discovered that tire wear was highest in the first 500 kilometers of usage. The peak abrasion can be attributed to initial break-in of factory residue and excess rubber structures such as fine rubber hairs on new tires. After passing this break-in point, the rate of abrasion would probably slow down, possibly by the wearing off of sharp edges on the tires that otherwise cause higher wear.

The findings of the research set cycling—i.e., mountain biking—in context to view it not just as a sport and recreational activity but also as an environmental research subject. Although emissions from cycles are significantly less polluting than emissions from motorized vehicles, having any detectable microplastic pollution is raising concerns about sustainability and the synergistic effect of fashionable leisure activities.

After the initial study, the researchers have expanded their work to cover abrasion testing of e-mountain bike tires, gravel bike tires, and road bike tires.

Future studies will continue to involve analysis of environmental samples from trail systems and ride sites to assess the extent of microplastic dispersion within ecosystems. This part of the research is conducted in collaboration with Prof. Dr. Christian Laforsch's research group at the Collaborative Research Center 1357 Microplastics, University of Bayreuth. The study adds to the wider literature on the microplastic cycle by determining previously unrecognized sources of contamination. While mountain biking has significantly fewer microplastic inputs into the environment than automobiles or trucks, the results are provoking more debate regarding sustainable product design and policy protection for controlling microplastic release from all, not just large, sources.

In general, the research is an improvement over microplastic studies, particularly regarding sustainable transportation. While mountain biking is a greener mode of transport compared to motorized ones, it is also contributing to the microplastic burden in ecosystems. The research further points towards ongoing surveillance and tire tread technology that would further minimize wear and impact on nature, but at no cost in terms of recreational bikers' performance desired.

Source & Credits

Study: "Microplastic emissions from mountain bike tires under real-world conditions" by Theresa Hübner et al., in Science of The Total Environment (2025). DOI: 10.1016/j.scitotenv.2025.178971
Performed by: University of Bayreuth, Chair of Sport Ecology