Oxidative capacity of coarse and fine particles in different environments -

Abstract

Numerous epidemiological evidence indicates significant associations between exposure to particulate matter (PM) and increased risk of adverse health outcomes. Although the components of and the mechanism by which PM causes these health effects, is still unclear, and the majority of these studies state that they are due to cellular oxidative stress, caused by reactive oxygen species. Additionally, because the redox potential of PM is dependent on its composition, it is expected that variations in the sources affecting PM composition could cause a change in redox potential. This study focuses on determining the chemical and oxidative properties of size-segregated PM in different environments; urban background, roadside and dusty. Gravimetric analysis, high-resolution magnetic sector Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS), ion chromatography, NIOSH Thermal Optical Transmission method, Scanning Electron Microscope, Total Organic Carbon Analyzer, macrophage-based ROS (m-ROS) assay and Dithiothreitol (DTT) assay were used to assess the mass concentration, ionic, elemental and organic composition of coarse and fine PM and obtain the chemical mass closure and oxidative potential. Additionally, results will be used to deduce relationships and correlations between different PM components and the oxidative capacity. Considering the roadside site, particle mass levels were 1.3-2.6 times greater at than the urban background. A chemical mass closure showed that coarse PM was mostly composed of crustal material, contributing to 12-23percent of its mass across sites. In fine (PM₂.₅-₀.₂₅) and quasi-ultrafine (PM₀.₂₅), organic matter was dominant (46-56percent) at the roadside location, while secondary ions (SI, 54-68percent) were more abundant at the background site. Measured ROS-activity, on a per m³ of air volume basis, was 1.4-2.6 times greater at the roadside than background location, indicating that exposure to redox-active PM species may be greatest near the freeway