The current national ambient air quality standards for PM<sub>2.5</sub> are based on particulate mass. Although epidemiological research conducted in the last few decades have associated PM mass with both respiratory and cardiovascular diseases, the heterogeneous and inconsistent nature of these associations suggests that not all components of PM are equally toxic. The capability of ambient particles to generate reactive oxygen species (ROS), conveniently called the ROS activity or the oxidative potential is proposed as a better metric for relating the PM pollution with health effects, and several recent epidemiological and clinical investigations also corroborate this hypothesis.<br/>In this talk, I would present our work on the measurement of oxidative potential of ambient PM from different geographical locations of the United States, i.e. western, southeastern and midwest US. The core objective of this work was to identify the components of ambient PM and their emission sources, which are most responsible for inducing the ROS generation. The role of organic compounds in the ROS activity of PM was assessed by their removal using thermodenuder and solid phase extraction technique, while the contribution of metals was quantified by chelation technique. A class of water-soluble organic compounds characterized by their strong hydrophobicity known as humic-like substances or HULIS, and transition metals particularly Fe, Cu and Mn were identified as the major species driving the ROS generation mechanism in ambient particles. However, our work shows that there are strong synergistic and antagonistic interactions among the HULIS components and transition metals. Limited source apportionment results revealed that biomass burning and secondary organic aerosol formation are the largest contributors to the ROS activity in southeastern United States. Further studies in this direction should help to develop the useful insights on the origin of PM toxicity leading to a better assessment of the human health effects of ambient particulate pollution.

Oxidative properties of ambient particulate matter: An assessment of the relative contributions from various aerosol components and their emission sources

254th National Meeting (2017)

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