A TECHNIQUE TO EXPOSE ANIMALS TO CONCENTRATED FINE AMBIENT AEROSOLS

This paper presents the development and evaluation of an ambient parti cle concentrator for conducting animal inhalation exposure studies. Th e system utilizes the principle of virtual impactors to concentrate am bient particles in the size range 0.1-2.5 mu m (aerodynamic diameter; d(p)) by drawing them through a series of three virtual impactors. Eac h impactor contains the majority of ambient fine mass (d(p) < 2.5 mu m aerodynamic diameter) in a bleed flow (minor flow) that is 20% of the total flow entering the virtual impactor. The virtual impactors have been characterized using indoor air samples as test aerosols. Fine mas s and sulfate concentrations at the outlet of the concentrating system were compared to the ambient fine mass and sulfate levels, which were determined using Harvard-Marple impactors. In each of the stages, par ticle concentration was increased by a factor of approximately 3. Thus , an overall concentration factor of about 25-30 was achieved. The mai n goal of this study was to demonstrate the feasibility of conducting animal exposures using the newly developed ambient fine particle conce ntrator.