ARB Research Seminar

This page updated June 19, 2013

Research Findings on Particulate Matter Related Toxicity from the Southern California Particle Center and Supersite

Photo of John R. Froines

Photo of Costas Sioutas

John R. Froines, Ph.D., University of California, Los Angeles, and Costas Sioutas, Ph.D., University of Southern California

June 18, 2003
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Presentation: 1. 2.
Video: 1. 2.
Research Project


The Southern California Particle Center and Supersite (SCPCS) is one of five centers established by the U.S. EPA to address the scientific uncertainties associated with airborne particulate matter (PM) and related adverse health effects. The overall objective of the SCPCS is to identify and conduct high priority research to better understand the effects of PM and ensure protection of public health. The SCPCS emphasizes research on the following topics: 1) Studies emphasizing investigation of the biological mechanisms of PM effects in relation to PM physical and chemical characteristics, 2) studies of emission sources and adverse health effects, and 3) studies of the effects of varying spatial and temporal patterns of ambient PM and co-pollutants and resulting health effects (with particular emphasis on the role of atmospheric chemistry). This seminar will describe the results of research in these three areas undertaken by the Center. In particular, a focus will be on studies of the relative toxicity of ultrafine, fine, and coarse PM.

A fundamental hypothesis of this Center is that the adverse effects of airborne PM are due to the reactive organic compounds and metals adsorbed to the particulate core. Examples of the reactive compounds include quinones and their reduction products. Quinones express their toxicity through two reactions: electrophilic addition and oxidation-reduction (redox). The redox reaction generates toxic reactive oxygen species (ROS) through the reduction of oxygen. One equivalent of quinone can generate multiple equivalents of ROS and in this way overwhelm the protective effects of the antioxidant enzymes and other reducing agents. This hypothesis has led to a study that PM possesses unique chemical reactivity with biological systems that is more than the sum of the reactivity of its individual chemical components. We shall report on the development of in vitro assays that enable assessment of toxicity of PM in relation to particle size and composition.

The seminar will report on animal research conducted in close proximity to freeways, as well as human epidemiological and clinical studies, supported in part by ARB, that addresses the toxicity of PM. A question and answer period will follow each presentation.

Speaker Biography

Constantinos (Costas) Sioutas received his doctorate in Environmental Engineering from Harvard University, and is Associate Professor of Civil and Environmental Engineering at the University of Southern California. Dr. Sioutas has designed a variety of monitors for particulate matter (PM), including particle concentrators and monitors for coarse, fine, and ultrafine PM. He is the Deputy Director of the Southern California Particle Center and Supersite, and is also a member of the California's Air Quality Advisory Committee on Particulate Matter.

John R. Froines received his doctorate in Chemistry from Yale University, and has been a professor at the UCLA School of Public Health since 1981. Dr. Froines studies the health effects of particulate matter in the ambient environment and the biochemical mechanisms of the carcinogenicity of toxic air contaminants. Dr. Froines is the Director of the Southern California Particle Center and Supersite, and also chairs California's Scientific Review Panel (SRP) for toxic air contaminants.

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for the seminars please view the Main Seminars web page