Vehicles are a major contributor to polluting emissions which damage health and foster global warming. So too are the asphalt roads which they ride upon.
Asphalt is a petroleum-based product widely used to pave roads, sidewalks and parking lots. The roofs of buildings – both commercial and residential – are commonly asphalt based.
“Asphalt-related products emit substantial and diverse mixtures of organic compounds into the air, with a strong dependence on temperature and other environmental conditions,” related chemist Peeyush Khare. Both solar radiation and heat pry pollutants from asphalt.
“The total emission factor for asphalt rises with temperature. It doubles from 40°C to 60°C (typical in-use summertime temperatures) and increases by 70% on average per 20°C temperature steps across 60° to 140°C (i.e., storage and application temperatures). Further, emissions are highly sensitive to solar exposure,” reports environmentalist Drew Gentner. Solar radiation alone increases asphalt emissions by 20%.
Altogether, nearly 2/3rds of urban areas are asphalt. Paved surfaces and roofs respectively comprise 45% and 20% of outdoor surfaces in US cities.
Though a significant source of emissions which cause global warming, asphalt is not considered in climate models.
Peeyush Khare et al, “Asphalt-related emissions are a major missing nontraditional source of secondary organic aerosol precursors,” Science Advances (2 September 2020).
“Asphalt adds to air pollution, especially on hot, sunny days,” Phys.org (2 September 2020).