Research Projects

Project at a Glance

Project Status: complete

Title: Acid air pollutant mixtures: respiratory system responses and effects of exercise

Principal Investigator / Author(s): Mautz, William J

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

Contract Number: A6-148-33

Research Program Area: Health & Exposure

Topic Areas: Acid Deposition, Health Effects of Air Pollution


A toxicology study was performed to evaluate the effects on respiratory system of inhalation of airborne acids and ozone. Rats were exposed to 0, alone and in combination with a mixture of nitric acid (HN03) and sulfuric acid (H2SC4). Exposures were also performed with hydroxy methane sulfonic acid (HMSA) alone and in combination with 0.Test atmospheres at two concentration levels were generated into stainless steel exposure chambers and healthy rats were exposed four hours nose-only at rest or while walking on a treadmill at 10 m/min and 30% grade. This exercise level increased metabolic rate by a factor of about 1.5 over resting rates. Target concentrations for the lower concentration levels were 0.2 ppm OS, 0.5 mg/m3 HNO, 0.25 mg/m3 H, SO, and 0.25 mg/m3 HMSA and for the higher concentration levels were 0.4 ppm O, 1.0 mg/m3 HNO, 0.5 mg/m3 H, SO and 0.5 mg/m3 HMSA. In each exposure a matched group of rats exposed to purified air served as controls. The evaluation of respiratory effects consisted of (1) measures of respiratory irritancy including breath frequency, tidal volume, minute ventilation, oxygen consumption, ventilation equivalent for 02, and rectal temperature: (2) analyses of tissue injury to the lung and nasal epithelium; and (3) biochemical analyses of pulmonary surfactant (PS) including Fourier transform infrared spectrometry (FTIR) and ultraviolet spectrometry (W) of PS, gas chromatographic analysis of fatty acid composition of PS, and total protein content of lung lavage fluid. Exposure to 0.4 ppm 0, at rest induced changes in breathing pattern and metabolic rate indicative of pulmonary irritation, induced lung parenchymal tissue injury, and changed the fatty acid composition of PS. Exposure to 0.2 ppm 0, at rest did not result in significant effects on irritancy, tissue injury, or PS chemistry. Exercise exposure enhanced the effects of 0, on irritancy and tissue injury. Resting exposure to 0.5 mg/m3 HMSA alone had mild irritant effects but did not result in tissue injury or changes in PS chemistry. Addition of HNO, + H, SO, or HMSA to 0, in resting exposures altered some pulmonary function measures of irritancy but tissue injury effects were similar to those observed from exposure to 0, alone- Exposure to the 0, + HNO, + H2S0, combination gave evidence by FTIR for formation of some new compounds which are as yet unidentified. Exercise exposure to 0, + HNO, + H, SO, at the higher concentration level reduced the post-exposure breathing pattern responses and lung tissue injury observed for exercise exposure to 0, alone possibly as a result of the influence of HNO, on exercise breathing pattern and dose distribution. Exercise exposure to 0, + HMSA at the higher concentration level produced nasal epithelial injury that was not observed in 0, alone or in resting exposures to 0, + HMSA. The results of this investigation showed that the respiratory effects of single four-hour exposures at rest and exercise to ozone and mixtures were dominated by the effects of 0. While the presence of acids in some instances significantly modified the effects of 0, at the concentration tested, there was not a clear pattern of consistent interactions between these air pollutants. Such interactions may require higher concentrations or long term repeated exposures to be observed and understood.


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