Plastic waste in the oceans and other bodies of water is an environmental problem that is currently being intensively researched. New reports are published nearly every month. Some publications have brought up tires, or particles from tire and road construction materials, as one of the largest sources of microplastics ending up in oceans and other bodies of water.
Tires use rubber rather than plastic. However, plastic and rubber are both polymers. When looking at micro-polymers instead of only plastics, wear particles from tire and road materials are one of the sources of micro-polymers ending up in the ocean.
Many publications include the dust created during tires’ contact with the road – i.e. wear particles from the tire and road surface – under microplastics. Roughly one half of the particles come from the tire and the other half from the road surface. Typically, most of these particles are fairly heavy and land on the roadside, compacting into the soil instead of being carried into a body of water. Some particles, however, are flushed off the road and its surroundings into ditches, sewage systems and, further, into bodies of water. A recent study in the vicinity of the river Seine concluded that some 18% of particles ended up in bodies of water and a further 2% were carried into estuaries (Unice, Weeber, Abramson et al., Characterizing export of land-based microplastics to the estuary, 2018).
When discussing microplastics ending up in the oceans, there are two types of sources: primary and secondary. Primary sources release microplastic particles directly into the oceans, whereas secondary sources release them as a result of the disintegration of larger plastic pieces. According to a report compiled by the EU, the largest group of primary sources consists of the small particles released from the washing waters of synthetic textiles, such as fleece clothing. Wear particles from tire and road materials are the second largest primary source. Together, these primary sources form 15–31% of the microplastics in the oceans, that is, less than one third.
Secondary sources include larger plastic items, such as bottles, bags and fishing nets that are ground into microplastics over time. These are estimated to form 69–81% of the sources of microplastics in the oceans, that is, at least two thirds. (European Parliament: Microplastics: sources, effects and solutions, 2018)
ADDITIONAL RESEARCH IS REQUIRED
A new emission standard called Euro 7 is under development with the purpose to reduce air pollution from new motor vehicles sold in the EU to meet the European Green Deal’s zero-pollution ambition. Euro 7 is expected to be implemented from 2025. The Euro 7 emission standards will be the first worldwide ones to move beyond regulating exhaust pipe emissions. The standards will set additional limits for particulate emissions from brakes and rules on wear particle emissions from tires.
Nokian Tyres is are actively following the studies on this topic and participates in external international studies ordered by ETRMA and other organizations. Reliable field and laboratory tests for understanding the nature, routes of entry, and harmful impacts of the particles are required because many of the current estimates are based on mathematical models and calculations.
To help build the scientific knowledge as well as develop practical solutions for reducing the levels of these particles found in the environment, the European Tyre and Rubber Manufacturers’ Association (ETRMA) launched the multi-sectorial TRWP Platform in July 2018. As a member of ETRMA, Nokian Tyres contributes to the work.
Nokian Tyres is also a full member of the European Tyre and Rim Technical Organisation (ETRTO) and participates in global standardization work. Currently ETRTO is contributing to the creation of tire abrasion test method development. Its target is to have a feasible tire abrasion rate test method with the following characteristics: repeatable, reproducible, cost efficient and practicable, representative of real driving environment, usable for regulation purpose and open to all worldwide.
Want to read more of tire and road wear? Here is a link to ETRMA's page on the subject.