In northern latitudes mineral dust is formed when cars use studded tires and roads are sanded to obtain more traction on the icy road surfaces. Mineral dust originates from both asphalt and anti-skid aggregates and the dust is deposited on the ground.
During late winter, especially when the surfaces of roads dry out, the dust rises into the air.
Urban dust can be hazardous to health and it lowers the quality of everyday life in cities. In order to protect people from the effects of airborne particles, new European limiting values for PM10 (thoracic particles <10 μm) concentrations in the air have been decided (European Council Directive 1999/30/EC). During springtime, dust episodes, the actual PM10 concentrations in Finnish cities are often clearly higher than the new limiting values. The European Union member states are allowed to exceed the prevailing limiting values in specified areas, if it can be shown that this is caused by the winter maintenance of roads.
The present study is an extension to studies of Kupiainen et al. (2001) and Räisänen et al. (2002). Kupiainen et al. (2001) found that anti-skid aggregate wears the pavement more than expected and named this phenomenon as the sandpaper effect. According to Räisänen et al. (2002) successive breakage of particles into smaller particles with more wearing surface can be minimized by using anti-skid aggregates with good resistance to fragmentation. The other important property, relevant to production of urban dust, is the particle size distribution of anti-skid aggregates (Räisänen et al. 2002).
In the present study, more emphasis has been put on the particle size distribution of anti-skid aggregates and new anti-skid materials have also been tested.
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