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September 6, 2020 09:43 pm

Is Hot Asphalt Increasing Air Pollution?

"A new study suggests fresh asphalt is a significant, yet overlooked, source of air pollution," reports Science. "In fact, the material's contribution to one kind of particulate air pollution could rival or even exceed that of cars and trucks." UPI reports: And its emissions double as its temperature increases from 104 to 140 degrees Fahrenheit, researchers found. Sunlight plays a key role in these asphalt emissions, with even moderate levels of sunshine tripling the release of air pollutants, according to the study published Sept. 2 in the journal Science Advances... In-use pavement usually gets as hot as between 117 and 153 degrees Fahrenheit in the summer, while roofs can reach 167 degrees, the study authors said. As the major contributors to air pollution get cut back — for example, through cleaner vehicle emissions — passive pollution sources like these will have a growing influence on the air we breathe, said Peter DeCarlo, an associate professor and air pollution expert with Johns Hopkins University, in Baltimore. "In doing that reduction, we are discovering these new sources that are now playing a more prominent role in our air pollution issues," DeCarlo said.... Asphalt probably contributes most to air pollution when it's freshly laid, DeCarlo added. During the paving process, asphalt is heated to as much as 248 to 320 degrees Fahrenheit, the researchers said. "If you've ever been around people laying asphalt, you smell it. It's clear something is getting into the air when that happens," DeCarlo said. But asphalt likely continues to emit air pollutants even after it's aged, when sunlight bakes the material, he noted. Switching to concrete for paving would help reduce emissions, he said, but concrete is not an ideal paving material in all locales. Another possible solution might be the application of "cool pavement" technology, where colored sealants are applied to paved surfaces so they reflect more solar energy and become less likely to heat up, Gentner said. Emissions might also vary with different asphalt application methods and different formulations of the paving product, Gentner suggested.

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