Abstract
Trimellitic anhydride (TMA) and its precursor trimellitic acid (TMAc) are chemical intermediates widely used in the coatings and plastics industries. The production of an exposure atmosphere necessary for the development of an inhalation animal model to study the effects of TM A and TM Ac has been severely hampered because of the highly charged, hygroscopic, and poor packing characteristics of these two chemicals. Several attempts to conduct inhalation exposures using commercially available generators have been unsuccessful, particularly at the extremely low concentrations required (the TLV® of TMA is 40 µg/m3). The Model 3400 TSI fluidized bed aerosol generator contained a continuous feed bead-chain system that, with minor modifications, was capable of delivering consistent quantities of powder to the fluidized bed chamber until a buildup of the powder at the nozzles caused the generator to clog, thus failing to produce consistent and reproducible aerosols. The TSI fluidized bed aerosol generator was modified so that its chain delivery system transported the dust to a newly designed aerosolization unit. The new aerosolization unit drew air from an inlet, past the chain carrying the dust, and through an air jet. The concentrated aerosol was diluted in a 0.5 m3 mixing chamber and subsequently delivered by air jets to the mixing turrets of the inhalation chambers. Several inhalation studies, with concentrations as low as 10 µg/m3, were conducted successfully on TMA and TMAc with this system.