Effect of Temperature, Fuming Time, and Distance from Source on the Polycyclic Aromatic Compound (PAC) Content of Bitumen Fumes: Assessment Using a Laboratory Fuming Protocol in Combination with a Sensitive Method for Determining Relative Aggregate Levels of PACs in Complex Mixtures

Abstract

A laboratory fuming procedure was used in combination with a previously reported variation of the Ames Test (the Nitration Assay) to investigate the relationship between temperature, time at temperature, and distance from source, on the relative PAC content of fumes generated from paving bitumens. The test method, whose endpoint is mutagenic potency (Nitration Mutagenicity Index, NMI), takes advantage of large amplifications of Ames Test mutagenicity resulting from nitro-derivatization of PACs. NMIs were similar and quite low for fumes generated at 110°C, but increased exponentially up to 160°C. NMIs increased linearly with fuming time up to 40 min, after which they remained constant. With some initial fluctuation, they also remained constant with increasing distance of the condenser from the bitumen surface up to 100 cm. NMI increased with temperature at a faster rate than fume weight suggesting that the increases in NMI were related to both quantitative and qualitative changes in the PAC content of the fumes.

Key Words:

• bitumen
• bitumen fumes
• PAC
• temperature-dependence
• time and distance effects