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Study: Asphalt adds to harmful air pollution on hot, sunny days

Study: Asphalt adds to harmful air pollution on hot, sunny days
Posted at 10:36 AM, Sep 10, 2020

Hot weather can increase the risk of natural disasters like droughts and wildfires, now, there is evidence extreme heat can increase harmful chemicals in the air.

A study published recently in Science Advances looked at asphalt under different temperature conditions.

“A main finding is that asphalt-related products emit substantial and diverse mixtures of organic compounds into the air, with a strong dependence on temperature and other environmental conditions,” says Peeyush Khare, a Yale chemical and environmental engineer and the lead author of the study, in a statement.

The researchers took real-world samples of fresh road asphalt and put them in a controlled furnace with purified air. They heated the samples to temperatures between 104 and 392 degrees Fahrenheit, and measured the chemical components in the air.

Total emissions nearly doubled when temperatures went from 104 to 140 degrees. At 104 degrees, 94 percent of the emissions measured were hydrocarbons.

The group also exposed the asphalt samples to replicated solar heat, including UVA and UVB wavelengths, and found the rate of emission of potentially harmful chemicals increased. Showing that not only heat, but also solar radiation contributed to asphalt producing air pollution.

Paved surfaces and roofs make up approximately 45% and 20% of surfaces in U.S. cities, respectively.

Asphalt can be quite a bit hotter than the air around it, getting about 40 to 60 degrees warmer than the recorded air temperature.

The researchers concluded that while policies and regulations have been put in place about car emissions and other forms of air pollution, asphalt should not be overlooked as a contributor.

“It's another important non-combustion source of emissions that contributes to SOA (secondary organic aerosol) production, among a class of sources that scientists in the field are actively working to constrain better,” Drew Gentner, associate professor of chemical & environmental engineering, said.