City pavement is a big source of air pollution

A new study published yesterday in Science Advances finds that asphalt pavement and roofing give off lots of gases that go on to form air pollutants. In summertime, asphalt in cities might contribute more to pollutants called secondary organic aerosols than cars and trucks.

This category of pollutants is challenging to understand. Not only do they come from myriad sources—asphalt is a big one, but paints and other products also release the precursor compounds to pollutants—but the chemical reactions that create these secondary compounds are also complex. While there’s been a lot of progress in understanding and reducing vehicle emissions, unraveling non-combustion pollutant pathways remains a major challenge. “If we want to solve our air quality problem, we’re going to need to expand our view to include less traditional sources,” says Allen Robinson, a civil engineer studying fine particulate matter at Carnegie Mellon University, who was not involved in the study.