Cobalt-free studs could reduce airborne particles from winter tyres
Winter tyres with cobalt-free studs do significantly less damage to the roads, say scientists in Sweden.
The team from KTH Royal Institute of Technology, Sweden, compared studs containing cobalt with iron-nickel ones. They believe they can reduce airborne particles by 20% by making the swap.
The team say that hard-wearing cobalt, which is used for rock drilling tools, grinds and pulverises asphalt into ultra-fine particles that go deep into the body when inhaled.
Studs only need to be 20-30% harder than asphalt to make driving on ice safer, says Professor Ulf Olofsson at the Department of Engineering Design. 'But the studs on the market today are double the hardness of road material and nine times the hardness of glacial ice at -40°C. That’s overkill,' he says.
In the EU, non-exhaust vehicle emissions from tyre, road and brake wear are equivalent to exhaust emissions in terms of PM10 (particles with aerodynamic diameters smaller than 10µm), Olofsson says. But in the Nordic countries, non-exhaust PM10 emissions significantly exceed those from exhaust due to the frequent use of studded tyres.
The tyres also increase the costs of road maintenance, and Olofsson estimates that Swedish road surfaces have a lifespan of only half of German roads, a country which has banned studded tyres.
