Effects of nitric acid vapor alone, and in combination with ozone, in exercising, healthy subjects as assessed by bronchoalveolar and proximal lavage. Final report

Nitric acid (HNO3) is the most prevalent acidic air pollutant in the western U.S. and has the potential to cause adverse respiratory effects through both acidification and oxidation reactions. In order to study this potential, we measured physiologic endpoints e.g., specific airway resistance (SRaw), bronchoalveolar and proximal airway lavage endpoints (e.g., total and differential cell counts, and concentrations of various proteins), and examined bronchial biopsies in a group of 10 healthy subjects who were exposed to 500 micrograms/cu m HNO3 vapor for 4 h during moderate exercise and underwent bronchoscopy 18 h later. In a second group of experiments, 15 healthy subjects were exposed to 500 micrograms/cu m HNO3 vapor plus either 0.2 ppm or 0.4 ppm ozone (O3) or to the appropriate concentration of O3 alone, to determine if HNO3 might enhance the toxicity of O3. Nitric acid gas caused no significant changes in either physiologic or inflammatory endpoints in comparison to the air exposures. In conclusion, the data gathered do not suggest that HNO3 vapor causes either proximal airway or distal lung injury, or that HNO3 potentiates the inflammatory response produced by O3 in healthy adults.