Connecting the Oxidative Potential of Fractionated Particulate Matter With Chromophoric Substances

Particulate matter (PM) air pollution is recognized as a major cause of adverse health outcomes, yet much remains unknown about which fractions and compositions are the most harmful. Efforts in this direction can be improved by employing a cell-free approach, dithiothreitol (DTT) assay, the so-called oxidative potential (OP). Here, we provide a detailed examination of OP from fractionated PM by a combination extraction method of solvent and solid-phase extractions (SPE). We estimate that the average OP of water-soluble matter (WSM; 4.27 nmol/min/m(3)) is up to 1.2 times higher than methanol-soluble matter (3.66 nmol/min/m(3)) in most seasons apart from summer. Of these WSM, OP is distributed almost equally between hydrophobic and hydrophilic fractions. OP of PM is mainly related to transition metals (Cu: 12.1%, Mn: 2.5%); apart from these, more than 80% of the total OP remains unidentified. Identification of this unexplained OP by a novel approach, integrating the chromophore characteristics with parallel factor analysis, has shown that chromophore1 (C1) accounted for 98% of OP, although this factor only made a small contribution to the total fluorescence. Our paper highlights the importance of a holistic approach by evaluating the chemical structure-activity relationship between optical characteristics and OP. Information presented here draws a connection between light-absorbing organic aerosols and a possible toxicological mechanism on the basis of their optical properties.

Automated summary

This study examines the oxidative potential (OP) of particulate matter (PM) using a cell-free approach, the dithiothreitol (DTT) assay. The results suggest that water-soluble matter has a higher OP, mainly attributed to transition metals. A novel approach combining chromophore characteristics and parallel factor analysis identifies the major component of unexplained OP.