INHALATION OF ACID COATED CARBON-BLACK PARTICLES IMPAIRS ALVEOLAR MACROPHAGE PHAGOCYTOSIS

A flow-past nose-only inhalation system was used for the co-exposure o f mice to carbon black aerosols (CBA) and sulfur dioxide (SO2) at vary ing relative humidities (RH). The conversion of SO2 to sulfate (SO4-2) on the CBA, at a fixed aerosol concentration, was dependent on RH and SO2 concentration. The effect of the aerosol-gas mixture on alveolar macrophage (AM) phagocytosis was assessed three days following exposur e for 4 h. Exposure to 10 mg/m(3) CBA alone at low RH (10%) and high R H (85%), to 10 ppm SO2 alone at both RH, and to the mixture at low RH had no effect on AM phagocytosis. In contrast, AM phagocytosis was sig nificantly suppressed following co-exposure at 85% RH, the only circum stance in which significant chemisorption of the gas by the aerosol an d oxidation to SO4-2 occurred. The results suggest that fine carbon pa rticles can be an effective vector for the delivery of toxic amounts o f SO4-2 to the periphery of the lung.