Hot
roads and roofs send harmful pollution into the air
 |
| Charlestown normally tries to discourage new asphalt - except when it benefits a friend or political crony. This is "Faith's Folly," a largely unused bike path in Ninigret Park laid at the behest of Faith LaBossiere, one of the founders of the Charlestown Citizens Alliance (CCA Party). It's a 1.3 mile stretch of asphalt. When Faith proposed the project, she told the Town Council it would only cost $7,000 but in the end, it has cost the town $267,000 plus the interest we pay on the bond money. The existing town Parks and Recreation Commission opposed the project. The CCA-controlled Town Council threw them off the Commission and replaced them with CCA Party loyalists in a move described in a Westerly Sun editorial as "Trumpian." (Photo by Will Collette) |
We
all know cars and trucks spew pollution into the air—but it turns out what's
underneath their tires do as well.
Asphalt—a
petroleum product used on roads and roofs—is a significant source of harmful
chemicals that end up contributing to ozone and particulate matter pollution,
according to a study published in Science Advances.
The
researchers found the emissions from asphalt are highest on hot, sunny days.
While producing asphalt is a known source of pollutants such particulate
matter, sulfur dioxide, nitrogen oxides, carbon monoxide, and volatile organic
compounds, the asphalt industry has said pollution from applied asphalt is
negligible.
The
findings are important as most states and cities have tackled combustion
sources of air pollution—such as cars and power plants—but have neglected to
take asphalt emissions into account.
"Asphalt
at typical application and in-use temperatures emits a complex mixture of
organic compounds that span a wide volatility range," the authors wrote.
The
researchers took samples of fresh asphalt and heated them to different
temperatures (from 104 degrees Fahrenheit to 392 degrees Fahrenheit), finding
that, as the asphalt heated up, emissions rose. Emissions doubled when
temperatures increased from 104 F to 140 F.
From
140 F to 284 F, emissions increased about 70 percent for every 20-degree jump.
In
addition, when road asphalt was exposed to solar radiation, which mimics
sunlight, emissions increased 300 percent. "That's important from the
perspective of air quality, especially in hot, sunny summertime
conditions," said Peeyush Khare, a researcher and graduate student at Yale
University and lead author of the study, in a statement.
Asphalt
releases organic compounds that are precursors to secondary organic aerosols,
which contribute to particulate matter pollution (PM2.5). PM2.5 consists of
toxic airborne particles much tinier than the width of a human hair, and is
linked to a variety of health impacts including respiratory and heart problems,
birth impacts and altered brain development for children.
Such
emissions are important because asphalt is so widespread—cities' total surface
areas are, on average, 45 percent paved.
The U.S. alone uses about 27 million metric tons of liquid asphalt each year,
according to a recent report.
Khare
and colleagues estimated in Los Angeles, for example, asphalt's potential to
emit secondary organic aerosols is comparable to vehicles.
Drew
Gentner, as associate professor of chemical and environmental engineering at
Yale University, said that asphalt is just one source of secondary aerosols in
cities, as personal care and cleaning products are other common sources.
Asphalt
is "another important non-combustion source of emissions that contributes
to secondary organic aerosols production, among a class of sources that
scientists in the field are actively working to constrain better," Gentner
said in a statement.
See
the full study here.
