A new study from Yale University reveals that asphalt — the material used to construct roads and parking lots around the world — is a silent contributor to the air pollution that is harming both the environment and the people who live in it. The effect is at its worst on hot, sunny days, the study found, with the intense heat increasing the number of harmful particles the asphalt emits into the air.
According to the new study, pollution emitted by asphalt is ‘rarely’ factored into the figures when assessing air quality in major cities. This is unfortunate because this material contains hazardous pollutants that are slowly released back into the environment, particularly when the material is baking under a hot sun.
As the amount of air pollution resulting from combustion — such as from car engines — decreases, experts have noticed an increase in non-combustion air pollutants as contributing to organic compounds and secondary organic aerosols, more commonly called SOAs. These SOAs are a big source of an air pollutant called PM2.5, which refers to polluting particles measuring less than 2.5 micrometers across.
PM2.5 particles have a major negative impact on public health, underscoring the need for monitoring air quality and implementing steps to curb such pollutants. Tests involving asphalt heated to different temperatures found emission of various organic compounds, an issue that was worst at higher temperatures, but that was ultimately sustained long-term.
As well, the study found that temperature wasn’t the only factor increasing pollution emissions from asphalt — solar radiation likewise plays a major role. Ultimately, curbing this particular source of air pollution will require new, more environmentally-friendly alternatives to asphalt.