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Spread and toxicity of PAH from tar asphalt roads

Up until the beginning of the 70s roads were mostly built using asphalt with coal tar as binder, so called tar asphalt. This tar asphalt remains under the wear layer in many roads both in Sweden and abroad and contains PAH which is both an environmental hazard and cancerogenic.

The question is how tar asphalt should be handled during maintenance of these old roads. It can either be reused in the roads on site or excavated and deposited at a landfill. These alternatives need to be weighed against each other.

The landfilling alternative involves production and transport of large quantities of asphalt and concomitant well understood environmental as well as fiscal costs. Conversely the environmental risks of retaining and reusing tar asphalt in the road system are relatively unknown. The purpose of this project is to create a basis for environmental risk assessments of reuse and retention of tar asphalt on site during road maintenance.

In the first study of this project we developed and tested a simple model for the bioavailability of PAHs from coal tar asphalt particles mixed in soil. Now, we are working on applying that model to predict ecotoxic effects by a weighted sum of bioavailable PAHs. Preliminary results published in a masters thesis by Luca Formenti, and an early release of an excel tool for applying the model to soil contaminated by coal tar asphalt particles are linked below.

Aquatic ecotoxicity of PAHs from tar asphalt roads - a masters thesis in pdf Pdf, 3.2 MB.