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RELATIVE TOXICITY OF SIZE-FRACTIONATED PARTICULATE MATTER OBTAINED AT DIFFERENT DISTANCES FROM A HIGHWAY
Citation:
CHO, S. H., J. R. LEHMANN, Q. T. KRANTZ, J. K. MCGEE, M. J. DANIELS, D. L. DOERFLER, AND M. I. GILMOUR. RELATIVE TOXICITY OF SIZE-FRACTIONATED PARTICULATE MATTER OBTAINED AT DIFFERENT DISTANCES FROM A HIGHWAY. Presented at American Association for Aerosol Research Annual Meeting, Reno, NV, September 24 - 28, 2007.
Impact/Purpose:
research presentation
Description:
Epidemiological studies have reported an association between proximity to highway traffic and increased respiratory symptoms. This study was initiated to determine the contribution of ambient particulate matter (PM) to these observed effects. Ambient PM was collected for 2 weeks using a three-stage (ultrafine: < 0.1 µm; fine: 0.1-2.5 µm; and coarse: 2.5-10 µm) high-volume impactor at two different locations: 20 m (Near-Road: NR) and 300 m (Far-Road: FR) from an interstate highway in Raleigh, NC. Collected samples were sonicated in methanol, and resulting PM suspensions concentrated by evaporation, diluted in physiological sterile saline and analyzed by ICP-AES. Female CD-1 mice were intratracheally instilled with saline, 25 or 100 μg of each size fraction, then assessed for airway reactivity to methacholine and markers of lung injury and inflammation at 4 and 18 hours post-instillation. In both the NR and FR samples, fine particles comprised approximately 55 % of total PM mass while coarse and ultrafine contributed 30 % and 15 %, respectively. Total PM mass was 18 % more in NR than FR. Higher concentration of certain elements [Ba, Ca, Cr, Cu, Fe, Pb, Sb, SiO2, Ti, Zn (> 50%); Al, Mn, Sr (> 30%)] was measured in NR than FR suggesting potential for increased toxicity of NR PM. Pulmonary endpoints (neutrophils, IL-6, MIP-2, TNF-α, methacholine reactivity) showed that coarse PM was associated with the greatest effects, which were independent of collection distance from the highway. By comparison, fine and ultrafine PM-exposed animals and saline-control animals exhibited minimal adverse effects. These results support previous work, which has shown that on a mass basis, coarse ambient PM produces greater inflammatory responses than fine and ultrafine ambient PM, and in this instance distance from production source did not significantly enhance pulmonary toxicity.