Tire Rubber Was 41% of the Microplastic in One Swedish Highway's Runoff

Rubber polymers linked to tires made up 41% of the microplastic measured in stormwater running off a Swedish highway, averaged across the samples in which those polymers could be quantified. Researchers at Chalmers University of Technology in Gothenburg measured 13 plastic and rubber polymers in runoff collected during rainfall events, and put total concentrations at 2.4 to 4,200 micrograms per liter, a spread of more than a thousandfold.

The authors say the measurements are meant to support work on ways to treat road runoff. Stormwater from built-up areas is an established route by which microplastic, tire wear in particular, reaches rivers and the sea. The study was published Oct. 27, 2026, in the open-access journal Microplastics and Nanoplastics.

Polyethylene and polypropylene were among the polymers found most often, along with two rubbers used in tires, styrene-butadiene rubber and polyisoprene. That pattern matches other studies of road runoff.

Microplastic concentrations tracked none of the simpler measures taken alongside them: no significant correlation appeared with total or volatile suspended solids, the standard gauge of how much solid matter water carries, or with metals.

Their method could not measure particles below 10 micrometers, and the authors say the tire-related concentrations may therefore be underestimates; they came out lower than in comparable studies. The paper calls for standardized sampling and preparation methods that can reliably measure smaller particles and hold up in complex environmental samples.

The work was funded by the Swedish Research Council (FORMAS), the Norwegian Public Road Administration and several Swedish foundations, and Chalmers paid for open-access publication. The authors credit the Swedish Road Administration for support at its Testsite E18 and for supplying weather and traffic data.