Large amounts of microplastics from worn road markings

The wear and tear of road markings is an important source of microplastic emissions. The amounts are difficult to calculate but are estimated to be at the same level as emissions from other significant and already-known sources. This is shown in a new study from VTI.

Microplastics is a collective term for small fragments of plastic and rubber up to five millimetres in size. They can be produced as microplastics, for example for scrubbing materials, or formed as a result of the wear or degradation of plastics. How microplastics affect health is largely unknown.

The single largest emission comes from the wear and tear of tyres. Other significant sources include antifouling paints, granules from artificial turf and the painting of buildings. The new report from VTI now shows that the wear and tear of road markings can create equally large amounts.

The estimate is based on survey responses from Sweden’s municipalities, sales statistics, an estimation of wear and tear, the length of the road network and calculations from previous studies. The estimated amount – 40-570 tonnes of microplastics per year – can be compared with 200-700 tonnes from antifouling paints, 100-300 tonnes from the painting of buildings and 500 tonnes from artificial turf.

A total of 223 out of 290 municipalities responded to the survey sent by the researchers, so there is a great deal of interest and commitment regarding this issue.

“At the same time, knowledge is unfortunately almost non-existent. Almost no one knows how much material is purchased for road markings or what the quality is like. In addition, few municipalities have a budget specifically for road markings,” says project manager Ida Järlskog.

“This makes our estimate uncertain. But regardless of whether it is 40 or 570 tonnes, we are talking about significant emissions.”

The wear and tear of road markings is mainly affected by winter road maintenance, the use of studded tyres and large traffic flows. The markings that wear out the most are those that cars and other vehicles pass over, such as centre lines when overtaking, pedestrian crossings and stop lines. There is so much wear to a pedestrian crossing that it normally needs to be maintained every year.

The wear and tear, and the amount of microplastics released, can be reduced through better maintenance, higher quality materials and through more care taken when the streets are ploughed (for snow) or swept clean. The researchers also open up a discussion as to how many road markings are actually needed.

“Maybe it’s possible to alter the design of pedestrian crossings so that cars don’t drive over the white fields? And perhaps it is possible to remove or reduce markings that primarily have a decorative function? Then, of course, it’s important to think about road safety, so that it is not affected,” says Ida Järlskog.

In a follow-up project, researchers hope to examine the most effective interventions that can form the basis for possible municipal action plans. In addition to the measures already mentioned, this may include, for example, requirements regarding the procurement of road markings. At present, there are no regulations on the quality of the material or how maintenance is carried out.

Text: Mikael Sönne

Translation: CBG

The report: Microplastic emissions from wear of road markings: overview and assessment for Swedish conditions (DIVA) External link.