Influence of collection region and site type on the composition of paved road dust

Abstract

Exposures to particulate matter (PM) re-suspended by traffic from paved roads are ubiquitous, but little is known about the variability in composition of paved road dust (PRD). This knowledge gap hinders estimates of exposure to PM components near roadways. Respirable fractions of PRD collected from multiple U.S. regions and site types were analyzed to explore chemical composition and variability. Fifty samples were collected from streets, traffic arterials, street canyons, freeways, and industrial sites in six urban regions in the southwestern, Southern California, northeastern, and southeastern U.S. regions and five rural sites. Samples were sieved, aerosolized, and size-classified into fine (PM2.5) and coarse (PM10-2.5) fractions. Analyses included metals and other elements, organic and elemental carbon, inorganic ions, endotoxin and glucan. Crustal elements, organic carbon, and reactive metals comprised the PRD mass with smaller fractions of elemental carbon and inorganic ions. Proportions of many inorganic components were strongly correlated between particle sizes, but fine and coarse organic carbon poorly correlated. Composition varied both among and within regions and site types, with evidence that chemical signatures varied more systematically by region than by site type. Local sources strongly influenced some samples. Samples from large urban areas had greater contents of reactive metals, but these comprised less than 0.2 % of the mass. Near-feedlot samples had high levels of endotoxin. The results provide insight into the variability of PRD composition, differences between re-suspended PRD and regional airborne PM, and improved source signatures for estimates of exposure to different PM components near roadways.