Press release 2016-03-29

Tire wear foremost source of microplastics

On behalf of the Swedish Environmental Protection Agency, IVL Swedish Environmental Research Institute has mapped the sources and pathways of microplastics. The main sources are tire and road wear particles (TRWP) produced during the interaction of a tire with the roadway surface, followed by rubber granulate from artificial turf infill. The percentages of the micro plastics from these sources that ends up in the marine environment are, however, very uncertain.

– The dissemination of microplastics in the oceans is of priority concern. The study is the most comprehensive survey of the sources and pathways of microplastics carried out in Sweden to date, and is an important basis for understanding how best to reduce the formation and release of these tiny particles, says Kerstin Magnusson, ecotoxicologist at IVL Swedish Environmental Research Institute.

In the report, researchers have ranked the sources of microplastic particles by size. The amount of microplastic particles emitted by traffic is estimated to 13 500 tonnes per year. Artificial turf ranks as the second largest source of emissions and is responsible for approximately 2300-3900 tonnes per year. Other sources include synthetic fibres from washing machine runoff, estimated at about 200-2200 tons per year, abrasion on boat hulls, approximately 500-1500 tonnes per year and industrial production and processing of plastics, 300-550 tons per year. Emissions from hygiene products containing microplastics are estimated to account for approximately 66 tonnes per year. The wide range of volumes show the uncertainty that still exists in the underlying data. 

– We know, for example, that road traffic generates huge amounts of microplastic particles but we do not know with certainty how far these particles spread, and how much ends up in the marine environment. The path to the sea for synthetic fibres is largely unimpeded as these are flushed out along with our grey water, and we are able to measure how much microdebris is removed in sewage treatment plants, says Kerstin Magnusson.

The microplastic particles present in the marine environment may have a variety of different origins. They may be fragments of larger debris, but may also consist of microplastic pellets used as raw material in the plastics industry and as ingredients in personal care products. The particles are transported to the ocean via sewage treatment plants, stormwater runoff, snow tipping and through airborne dissemination.

– Because these plastic particles break down extremely slowly, levels in the environment will inevitably increase as long as accumulation via wastewater treatment plants and other transportation routes continues. For this reason, it is vital to reduce the volumes of plastic particles in waste water emitted by households and industries, and that we gain a better understanding of other transportation routes, says Kerstin Magnusson.

Researchers point out that there are large gaps in our knowledge when it comes to many other sources that may contribute to the flow of microplastics into the ocean, including the potentially immense emission source constituted by waste management and littering that could not be quantified.

Microplastics are small particles of less than 5 millimetres in diameter. They may be ingested by plankton and filter feeders such as blue mussels .

See the report: Swedish sources and pathways for microplastics to the marine environment

For more information, please contact: Kerstin Magnusson, kerstin.magnusson@ivl.se, +46 (0)10-788 69 07 Mikael Olshammar, mikael.olshammar@ivl.se, +46 (0)10-788 65 08 Kerstin Åstrand, kerstin.astrand@naturvardsverket.se, +46 (0)10-698 15 49