Abstract

Reactive oxygen species (ROS) produced by inhaled ambient particles may contribute to a variety of adverse health outcomes, and play a role in aerosol aging. ROS includes the hydroxyl radical, hydrogen peroxide and superoxide, and other species; some ROS assays may also be sensitive to organic hydroperoxides. Measuring ROS is growing in popularity by atmospheric chemists, driven largely by the question of what components of particles or types of particles are more likely to cause disease. There are a large number of ROS assays in use with no clear leader in terms of the most predictive of disease outcomes. To make mattes more complicated, ROS production is normally monitored in aqueous extraction solutions, the composition of which has a substantial effect on the outcome. Further, there is the matter of timescale; some ROS are presumably present in the particles initially while others are generated by the particles over timescales of hours or more. The talk will present results of recent field campaigns in California as well as laboratory results with a focus on the most active transition metals, iron, copper and manganese, and the strong role of biomass burning, where present, and their relative activity in three different ROS assays. These will be discussed in the context of the matrix of ROS assay approaches.