US chemists conducted an experiment suggesting the toxicity of road asphalt. Under the effect of the sun, but also of water, the hydrocarbons present in the asphalt can escape. This would then be a threat to the environment, but also to road users.

As everyone knows, road traffic is one of the most important sources of pollution. However, the nature of the roads could also be one! A team of US chemists have studied the risks posed by asphalt and their results were published in the journal Environmental Science & Technology.

Remember that asphalt is a mixture of aggregates and bitumen, a hydrocarbon binder. However, this binder is obtained from crude oil residues recovered from the distillation process. Thanks to its agglomerating power, bitumen is therefore an ideal choice for building roads. However, chemists cite risks for the environment and human health.

More specifically, the researchers point the finger at polycyclic aromatic hydrocarbons. However, science has long known that these compounds are both carcinogenic and bad for the environment. The study directors therefore sought to understand the impact of roads already constructed by measuring the potential emanations of pollutants.

The chemists’ experiment consisted of placing a piece of asphalt on a sheet of glass before submerging it all in water and irradiating it using a solar simulator. The same experiment was carried out on a control piece of asphalt not exposed to solar radiation. The last step was to scan the water to study the chemical reaction that caused the compounds to be released.

The results show that solar radiation induces a process of polymer photodegradation. In other words, hydrocarbons are diffused in a massive way in the presence of water and sun. However, the quantity of water-soluble hydrocarbons from the leak was twenty-five times greater on the side of the piece of asphalt irradiated by the solar simulator! In conclusion, chemists believe that various weather patterns can generate fairly significant toxic leaks. However, the researchers say the scope of these leaks and the large-scale consequences will be the subject of further research.