In 1994, the National Institute for Occupational Safety and Health (NIOSH) entered into an interagency agreement with the Federal Highway Administration to investigate possible health effects associated with exposure to crumb-rubber modified asphalts. Previously researchers attempted to analyse polycyclic aromatic hydrocarbons (PAHs) in asphalt fumes using chromatographic techniques. However, asphalt fumes contain numerous alkyl-substituted PAHs and polycyclic aromatic compounds (PACs) containing heteroatoms of nitrogen, oxygen, and sulfur. Because many of these compounds co-elute, the resulting data were ambiguous. Furthermore, many researchers believe that some of the observed health effects were due to exposure to all of the PACs. For these reasons, NIOSH Method 5800 was devised for monitoring PACs as a chemical class in asphalt fumes. Asphalt fume samples were collected on a PTFE filter backed by an XAD-2 sorbent tube, extracted with hexane, and prepared to isolate the PACs from the polar and aliphatic compounds. The PACs were analysed using a flow injection technique and two f1uorescence detectors. The first detector (wavelength settings: 254-nm excitation, 370-nm emission) was more sensitive to 2- to 4-ring PACs. The second detector (wavelength settings: 254-nm excitation, 400-nm emission) was more sensitive to 4- and higher-ring PACs. The limit of detection (LOD) and limit of quantitation (LOQ) for PACs monitored at 370-nm emission were 0.01 and 0.03 ug/sample, respectively. The LOD and LOQ for PACs monitored at 400-nm emission were 0.02 and 0.07 ug/sample, respectively. Sampling media fortified with select PAHs indicated recoveries for 2- and 3-ring PAHs were between 60 and 91%, while recoveries for 4- to 6-ring PAHs were between 83 and 108%. Sampling media fortified with a PAC mixture gave average recoveries of 90 and 95% for total PACs monintored at the two emission wavelengths of 370 and 400-nm, respectively. This method was selective, specific, and sensitive for monitoring PACs as a chemical class. This method was used to make relative comparisons of asphalt fume exposures at seven paving sites. The results were used to determine if the addition of crumb-rubber modifier resulted in more hazardous exposures, that is, an increase in total PACs. In addition, the method was used to evaluate engineering controls developed for paving machines and is currently being used to re-evaluate these controls now that they are used extensively on highway-class paving machines.
Tijdschrift voor Toegepaste Arbowetenschap. Exposure Assessment in a Changing Environment, June 16-18, Utrecht, The Netherlands