Generation of Bitumen Fumes Using Two Fume Generation Protocols and Comparison to Worker Industrial Hygiene Exposures

Abstract

This study had two fundamental goals. The first was to collect sufficient quantities of bitumen fumes used in both the roofing and paving industry in the United States to do detailed chemical and biological testing in preparation for a two-year animal skin painting study on select samples. These bitumen fumes need to be similar to the fumes to which workers in these industries are actually exposed. In this first phase, bitumen from four geographical regions of the United States were selected, which produced bitumen from four different major crude sources in roofing and four sources in paving. Each source was supplied to projects where workers were monitored for exposure. The industrial hygiene samples from workers were then tested for physical and chemical properties. These results were used to guide collection of fumes from each source using the vapor headspace of tanks containing each bitumen. Bitumen fumes were collected using the same protocol that the Fraunhofer Institute of Technology and Medicine employed in a recent animal inhalation study. The second goal of this study was to better understand previous studies conducted by NIOSH which generated fumes for mouse skin painting studies using a roofing bitumen in a laboratory fume generator. In the current study, bitumen fumes from the four roofing sources were generated using the NIOSH protocol and compared to fumes collected in the roofing work sites and taken from the tank headspace. One of the sources was selected to generate enough fumes for a chronic two-year animal skin painting study. Results from an array of physical, chemical and biological tests were used to characterize the subsequent fumes. Acceptance criteria were designed to match parameters that could be analyzed both on the workplace samples and the bitumen fumes collected from the tank and involved three basic categories: simulated distillation, fluorescence and gas chromatography/mass spectroscopy for polynuclear aromatic hydrocarbon analysis and extracted ion fingerprinting. Methods employed for the collection of these fumes were selected to optimize the capture of the most toxicologically relevant components. Distinctions between paving and roofing fume samples are outlined. Bitumen fumes from the paving sources produced from four different crude sources were quite similar to each other in a number of the tests performed. Bitumen fumes from the roofing sources also were very similar to each other. On the other hand, fumes generated using the NIOSH protocol show results that significantly differ from the corresponding worker exposures.