EFFECT OF 0.3 AND 0.9 MU-M SULFURIC-ACID AEROSOLS ON TRACHEAL MUCOUS CLEARANCE IN BEAGLE DOGS

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Abstract
Tracheal mucous clearance was measured in 8 Beagle dogs after 1 h exposures to H2SO4 [a pollutant] mist with particle sizes of 0.3 .mu.m and 0.9 .mu.m mass median aerodynamic diameter (MMAD). The method used was to anesthetize the dogs with halothane, insert a fiberoptic bronchoscope into the trachea, turn off the anesthetic and then deposit a 10 .mu.l droplet containing approximately 50 .mu.Ci of [99mTc]macroaggregated albumin as the dog started to regain consciousness. .gamma.-Camera scintiphotos were taken every min for 25 min in awake dogs to measure velocities of the labeled material moving up the trachea. For the 1.0 mg/m3, 0.9 .mu.m MMAD exposures, tracheal mucous velocities were significantly depressed after 30 min (26% reduction, P = 0.05), 1 day (40%, P < 0.01) and even after 1 wk (30%, P = 0.05). Velocities had returned to the control range 5 wk after exposure. For the 0.5 mg/m3 exposures nonsignificant increases in clearance were seen after 30 min (35%) and 1 day (8%). After exposure (1 wk) there was a significant depression in clearance (34%, P < 0.01). There were no significant changes after exposures to 0.3 .mu.m MMAD aerosols at concentrations of 1.0 or 5.0 mg/m3.