Resuspension of Road Dust
Are you allergic to road dust?
Particles from sources close, adjacent to or some distance from the roadway enter the atmosphere and once airborne, are removed from the atmosphere through processes such as deposition and gravitational settling, and descend onto the road surface. These particles become part of the road dust material and then can subsequently become resuspended by turbulence from passing vehicles or wind. Soil from verges parallel to the road is a common source of road dust and is likely to contain a number of heavy metals absorbed from traffic emissions. Road dust is a complex mixture of particles from a number of natural and anthropogenic sources which have been found to contain carcinogenic components and heavy metals from exhaust and non-exhaust processes, along with mould spores, animal dander, pollen and pollen fragments. Resuspended road dust has a significant impact on atmospheric particle concentrations. Research carried out inside a motorway tunnel in Hatfield, Hertfordshire, UK has estimated that resuspension of road dust contributes 27% to the total particle concentrations (For more information see Research). Issues have also been raised regarding the health issues associated with resuspension. Miguel et al. (1999) found road dust contained allergens from at least twenty different sources, and when dust was resuspended by passing traffic, lead to an increase in allergenicity of the resuspended particles in the atmosphere by 5-12%.
Factors which affect resuspension include:
- The weather - wet conditions decrease resuspension.
- Traffic density and the fraction of heavy goods vehicles passing over the surface: heavier vehicles create greater turbulence.
- Frequency of road sweeping: road sweeping can reduce road dust and decrease resuspension.
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