10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Oxidative Potential of Ambient Aerosols: First Measurement over Santiago Metropolitan Area
Carolona Molina, Vishal Verma, Victor Vargas, LEIVA G. MANUEL A., Facultad de Ciencias, Universidad de Chile
Abstract Number: 53 Working Group: Aerosols and Health - Connecting the Dots
Abstract In Chile, almost 90% of the population lives in polluted urban areas, such as Santiago Metropolitan Area (SMA, 33.5ºS, 70.5ºW), the capital of Chile. In SMA, the levels of PM often exceed national air quality standards and guidelines of the World Health Organization. The exceedance of limit values for both PM10 and PM2.5 occurs mainly due to urban expansion, domestic heating, growth of diesel vehicles fleet, and industrial activity. The particular geographic and meteorological conditions in SMA have additional effects on air quality. The population of SMA (7 millions inhabitants) are exposed to high levels of air pollution.
It is shown that PM produces adverse effects on human health, even at low concentrations. Although the mechanisms of PM related health effects are not well understood, the most accepted hypothesis considers the PM-induce inflammatory processes by promotion of oxidative stress; as a result of over-generating reactive oxygen species (ROS) and radical species that exceed the available antioxidant defenses producing cell damage. Therefore, the oxidative potential of PM (defined as a measure of the capacity of PM to oxidize target molecules and generating ROS or other reactive species) is a good indicator of its toxicity. Despite its importance, the oxidative potential of PM has not yet been studied over SMA, as per our knowledge.
In the present work, a dithiothreitol (DTT) assay was used to measure the ROS-generation potential of water-soluble PM2.5 and PM10 of 30 ambient PM samples. The results obtained show that even when the mass proportion of PM2.5 over PM10 is around 60%, the proportion in OP is 80%; indicating that the highest loss activity of DTT is contributed mainly by the fine fraction of the PM in SMA. The comparison of OP values with other cities in the world shows that the OP of SMA ambient PM is at upper end of the typical range observed for ambient PM. Finally, these preliminary results show the importance of systematically measuring the OP of PM in SMA; and even more in other polluted cities of Chile where the PM mass concentrations exceed even SMA.
Acknowledgments. One of the authors (MALG) acknowledges the support of Chilean National Commission for Scientific and Technological Research CONICYT/FONDECYT 2016 grant no. 1160617. The authors declare no financial relationships with any organizations that might have an interest in the submitted work; no other relationships or activities that could appear to have influenced the submitted work.