FACTORS GOVERNING THE MASS LOADING OF AEROSOLIZED CARBON-BLACK PARTICLES WITH ACID SULFATES, INHALATION EXPOSURE, AND ALVEOLAR MACROPHAGE PHAGOCYTIC FUNCTION

A flow-past nose-only inhalation system is described for the coexposur e of animals to carbon black aerosols (CBA) and sulfur dioxide (SO2) a t varying relative humidities (RH). The conversion of SO2 to sulfate ( SO42-) on the CBA, at a fixed aerosol concentration, was dependent on RH and SO2 concentration. The effect of the aerosol-gas mixture on alv eolar macrophage (AM) phagocytosis was assessed 3 days following nose- only exposure of mice for 4 h. Exposure to 10 mg/m(3) CBA alone at low RH (10%) and high RH (85%), to 10 ppm SO2 alone at both RH, and to th e mixture at low RH had no effect on AM phagocytosis. in contrast, AM phagocytosis was significantly suppressed Following coexposure at 85% RH, the only circumstance in which significant chemisorption of the ga s and oxidation to SO42- occurred. The results suggest that Fine carbo n particles are an effective vector for the delivery of toxic amounts of SO42- to the periphery of the lung under conditions of elevated RH.