UC Irvine

The objective of this study was to evaluate the toxicity of inhaled diesel engine–generated fine carbon particles, when an acid mixture of the type found in California's air was also present. Rats were exposed nose–only for 5 hours per day for 5 consecutive days. The target concentrations of the pollutants in the three atmospheres studied were: (a) 0.5 mg/m3 diesel exhaust soot, (b) 0.35 mg/m3 nitric acid + 0.15 mg/m3 sulfuric acid, and (c) 0.5 mg/m3 diesel exhaust soot + 0.35 mg/m3 nitric acid + 0.15 mg/m3 sulfuric acid. Control rats were exposed using the same schedule to purified air. The evaluation of potential toxic effects in exposed rats included: (a) measurement of respiratory tract clearance of insoluble tracer particles; (b) histopathologic examination of respiratory tract tissues, including autoradiographic measures of cell turnover as an index of cell killing; and (c) measurement of functional effects on pulmonary alveolar macrophages. Biological effects were observed for each of the atmospheres studied. None of the atmospheres produced significant lung cell damage, but retained soot deposits were seen in the lung after exposure to atmospheres that contained soot. Although the diesel soot + acids atmosphere did not alter early or late clearance of tracer particles, this atmosphere – and the other two atmospheres studied – depressed pulmonary macrophage functions. This interference with macrophage functions may have significant implications to human health. © 1991, Mary Ann Liebert, Inc. All rights reserved.