Greening the Blacktop
Strategies for improving the environmental and health
performance of asphalt paving.
By Meg Calkins, ASLA
Conventional asphalt pavement, or asphalt concrete, is the most
commonly used site and road construction material, used on 90 percent
of new roads. It is inexpensive, flexible, easily placed without
formwork, relatively long lasting, and durable. In addition, a wide
range of surface finishes and overlays can be applied to fit any
design setting and extend the pavement’s life cycle without removing
the full paving section. However, asphalt pavement does pose some
environmental and human health risks: the most serious from the
asphalt binder during extraction and refining and, to a lesser degree,
during manufacture and placement.
The human health effects of asphalt binders from mixing,
heating, and placement stages are controversial, and there is much criticism of
research methods used to determine quantities of fumes and emissions.
Uncaptured emissions and fumes from heating asphalt binders can pose both mild
and severe health impacts during plant mixing and placement of asphalt
pavement, yet the degree of exposure and the severity of the impacts are still
Emissions of hazardous air pollutants (HAPs) from asphalt
processing and placement are also an environmental concern. However, the
asphalt industry has made efforts to reduce these emissions, and in 2002,
hot-mix asphalt (HMA) plants were removed from the Environmental Protection
Agency’s list of “major” sources of hazardous air pollutants to be regulated.
In addition to health impacts, an environmental impact of
hot-mix asphalt is the energy consumed in heating the asphalt binder and
aggregates and keeping them hot during transport and placement.
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