Two Articles Based on TERESA Research Published
Two articles based on research conducted under EPRI’s Toxicological Evaluation of Realistic Emissions of Source Aerosols (TERESA) study have been published in the journal Inhalation Toxicology. 

• P.A. Ruiz, J.E. Lawrence, J.M. Wolfson, S.T. Ferguson, T. Gupta, C.-M. Kang, and P. Koutrakis.  “Development and evaluation of a photochemical chamber to examine the toxicity of coal-fired power plant emissions.”  Inhalation Toxicology 19 (8): 597-606 2007.  When investigating the toxicity of individual particle sources, it is important to consider the contribution of both primary and secondary particles.  The authors present the design of a new photochemical chamber that can be used to form secondary sulfuric acid particles from diluted coal-fired power plant emissions.  The chamber is a relatively small, well-mixed flow reactor that can fit in a mobile reaction laboratory.  It produces high concentrations of hydroxyl radical (OH) from the photolysis of ozone (O3) in the presence of water vapor.  A pilot chamber was tested in the laboratory, using mixtures of NO and SO2 in air, at concentrations approximately 100 times lower than those in power plant stack emissions.  This chamber was able to oxidize about 20% of the SO2, thereby producing 1350 μg m−3 of H2SO4 particles.  Further tests showed that increasing O3 concentrations and residence time increased the H2SO4 production.  A field chamber was built subsequently and used in a toxicological study.  Diluted coal-fired power plant emissions were introduced in the chamber.  Over 19 days of exposure, the chamber, on average, converted 17% of the supplied SO2 emissions and produced an average of 350 μg m−3 of H2SO4 particles.  Particle losses were determined for the pilot chamber, using artificial particles whose size ranged from 50 to 1000 nm.  The determined losses ranged from 21% to 42%, with no trend between the amount of particle loss and particle size.  Losses for the field chamber, estimated using model calculations, were found to be similar to those of the pilot chamber.
• P.A. Ruiz, T. Gupta, C.-M. Kang, J.E. Lawrence, S.T. Ferguson, J.M. Wolfson, A.C. Rohr, and P. Koutrakis.  “Development of an exposure system for the toxicological evaluation of particles derived from coal-fired power plants.”  Inhalation Toxicology 19 (8): 607-619 2007.  To investigate the toxicity of particles originating from coal-fired power plants, it is necessary to consider the effects of both primary particles and secondary components formed in the air through atmospheric reactions.  The authors describe a new exposure system that can be used to expose animals to both directly emitted particles and secondary particles.  The system consists of three main components.  The first is a sampling system to continuously collect and dilute power plant stack emissions.  The second is a reaction laboratory that contains reaction chambers to simulate atmospheric reactions.  The following atmospheric reactions were simulated:  (1) the oxidation of sulfur dioxide to form sulfuric acid, (2) the neutralization of sulfuric acid by ammonia, and (3) the reaction of α-pinene with ozone to form secondary organic aerosol.  Using these chambers with the diluted emissions, different typical atmospheric scenarios can be simulated.  The final component is a mobile toxicology laboratory where animals are exposed to the resulting test aerosols.  The authors report the characteristics of the test aerosol exposures obtained at a coal-fired electric power plant.  Particle exposures were characterized for concentrations of mass, elements, elemental carbon, organic species, inorganic ions, strong acidity, particle number, and size distributions.  Mass concentrations ranged from a few micrograms per cubic meter for a scenario of primary emissions only, to about 250 μg m−3 for the most complex scenario.  The authors show that the different scenarios produced a large variation in the composition of the test aerosol, thus potentially changing the toxicity of the emissions.

For more information, contact Annette Rohr, (650) 855-2765, arohr@epri.com.