Fresh asphalt is a major source of hazardous particles, laboratory study suggests
The greatest amount of semivolatile organic compounds escaped when the pavement was heated to 140°C, the temperature of road-paving, the team reports in Science Advances. Emissions fell as the asphalt cooled, but remained constant and significant at 60°C, a typical temperature for asphalt in Los Angeles during the summer, for the duration of the 3-day experiment. This suggests that asphalt could be a long-lasting source of pollution, Gentner says.
Sunshine was also important. Even moderate light caused a large increase in emissions regardless of temperature, although the reason is not clear. For road asphalt, emissions increased as much as 300% in moderate light. These emissions react to form tiny particles suspended in air, called aerosols, that are harmful when inhaled, and the results suggest asphalt contributes even more to this kind of air pollution in hot, sunny weather, Gentner says.
The researchers estimated the annual emissions from new paving and roofing in parts of Southern California. They calculate that molecules released from asphalt could lead to between 1000 and 2500 tons of particulate air pollution—compared with just 900 to 1400 tons from gasoline and diesel vehicles. (Both sources pale in comparison to volatile chemical products, such as pesticides, coatings, adhesives, cleaning agents, and personal care products, which together contribute 4500 to 9500 tons of particulate pollution per year.)
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