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Is the Presence of Asphalt in our Environment a Cause for Concern?


Scientists at Yale University in the USA have discovered that those surfaces on our footpaths, roads and playgrounds that are covered in asphalt can become a significant source of air pollution - on hot and sunny days.

And it is not just these road surfaces.  Asphalt is often used on the roofs of buildings too.


What is asphalt?

Asphalt, also known as bitumen, is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It can be found in natural deposits or it can be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.

Rolled asphalt concrete is the most common type of asphalt. It makes up more than 85% of the roads you drive on in the modern world. Its often an asphalt/concrete hybrid, with 5% asphalt and 95% aggregates mixed together.

There are more than 4,000 asphalt plants in the USA alone.


More about that Yale study

The researchers collected fresh asphalt and heated it to between 40 degrees C and 200 degrees C (that is 104 degrees F and 392 degrees F).  

They found that the hot asphalt emitted "substantial and diverse mixtures of organic compounds" which were small enough to be inhaled deep into human lungs.

They also found that the emissions double when the temperature increased from 40 degrees C to 60 degrees C (that is 104 degrees F to 140 degrees F) - which is the temperature asphalt can hit during a hot summer.

And it as not just the heat, sunshine had a dramatic impact too.

When the scientists exposed road asphalt to solar radiation, emissions jumped 300 percent.   Lead Researcher Peeyush Khare said: "That's important from the perspective of air quality, especially in hot, sunny summertime conditions."

The researchers suggested that during Southern California's summer temperatures, asphalt could produce more emissions than petrol and diesel vehicles combined.


Urban air pollution

Although the claims that the use of electric cars over gas and diesel cars will help to eradicate urban air pollution has great importance, the highways that such electric cars travel on will not.

This new research is just adding to the level of knowledge about the sources of air pollution.  

We have already written on the Perils of Living Close to a Busy Highway.  And since then, researchers from the University of Cambridge have confirmed that brake dust from vehicles is another major source of air pollution and could even be as dangerous as diesel fumes in terms of its effects on our health.


Will future forms of technology find a safer alternative to asphalt that will not rely on the oil industry?