Research Projects

Project at a Glance

Project Status: complete

Title: Respiratory effects of acid containing multicomponent pollutant atmospheres

Principal Investigator / Author(s): Mautz, William

Contractor: Air Pollution Health Effects Laboratory, Department of Community and Environmental Medicine, UC Irvine

Contract Number: A4-112-32

Research Program Area: Health & Exposure

Topic Areas: Acid Deposition, Health Effects of Air Pollution


The purpose of this study was to assess the possible adverse effects on the respiratory system of acid air pollutants inhaled in mixtures with other pollutant compounds commonly present in California urban air. A seven-component mixture of acid-forming oxidant pollutants representing the principal components of California urban air pollution was generated which was composed of 0.35 ppm ozone, 1.3 ppm nitrogen dioxide, 2.5 ppm sulfur dioxide, 1.1 mg/m3 manganese ferric and ammonium sulfite and 0.5 mg/m3 carbon soot at 85% relative humidity. Respiratory effects were compared to those produced by acid components (1 mg/m3 nitric acid + 0.5 mg/m3 sulfuric acid) and oxidant component 5 (0.35 ppm Cl3+1.3 ppm NO2) alone at 85% RH. The 03 and NO2 had time to react to form HNO3, nitrate radical (N03) and N2O5. HN03 formed in these reactions was measured at test exposure points. Laboratory rats were exposed four hours to the pollutant atmospheres and a variety of respiratory effects were examined among different sets of atmospheres including: 1) reflex changes in breathing pattern, 2) histopathological analysis of tissue damage to the lung and nasal epithelium, 3) particle clearance of the respiratory tract and 4) analysis of structural changes in pulmonary surfactant using infrared and ultraviolet spectroscopy, gas chromatography, and surface pressure measurements. At the concentrations tested, the acid components alone had no significant effects on the respiratory parameters examined. Mixtures containing 0.35 ppm ozone caused lung tissue damage, end-exposure breathing pattern changes, and pulmonary surfactant effects similar to effects of 0.35 ppm 03 alone. The mixture of 0.35 ppm O3 + 1.3 ppm NO2 resulted in an early-exposure breathing pattern change consistent with an upper airway irritant effect of HNO3 formed in reactions between the oxidants. No evidence of synergism between oxidants, 03 and NO2 or modifying effects of acids on 03 responses was found at these low concentrations in contrast to earlier studies using higher concentrations or exercise exposure. No significant effect on particle clearance of the seven-component atmosphere was observed although the trend of change was in the same direction as expected for an 03 effect. The chemical composition of pulmonary surfactant from rats exposed to 0.35 ppm 03 alone or in combination with 1.3 ppm NO2 was shown to change 24-48 hours after the exposure and methodology for isolating surfactant was shown to be critical for detecting the changes. The changes included shifts in the fatty acid composition and the formation of oxidized compounds in surfactant. The time course for the changes was consistent with the course of pulmonary inflammatory response to oxidant damage.


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