Insufficient information is available to establish environmental standards or guidelines for pollutants comprising acid precipitation so as to avoid adverse effects on lung function in normal subjects and patients with pulmonary disease. Overly lax standards could lead to adverse health effects while too stringent standards could result in wasteful expenditures by government and the private sector. We propose to investigate sulfuric acid aerosols in combination with nitrogen dioxide at realistic ambient concentrations in both healthy and asthmatic subjects. We have constructed an environmental chamber that can accurately deliver particulate and gaseous pollutants of known concentrations for up to 48 hours. The objective of our study is to evaluate the short- term respiratory and clinical effects and to identify mechanisms and markers of injury during exposure to constituents of acidic pollution. Our protocols will emphasize repetitive exposures and development of exposure-response relationships. Alterations in lung function will be detected by pulmonary function tests that have sufficient sensitivity to detect changes in lung function before symptoms occur. In normal subjects, mechanisms of injury will be studied by bronchoalveolar lavage performed after the exposure. We will examine effector cell populations and sub- populations in the lavage assessed by flow cytometry, cell surface markers, potential for cytokine production, and functional responses important in defense against microorganisms. Alterations in mucin structure following pollutant exposure will be assessed. The relationship between pollutant exposure and enhanced susceptibility to infection will be evaluated by inactivation of virus and surface expression of viral antigens by lavaged alveolar macrophages. In asthmatics, airway reactivity testing will be performed after pollutant exposure. Bronchial challenge with carbachol will be utilized to detect subclinical actions of pollutants. If bronchoconstriction is observed in asthmatics following pollutant inhalation, we will examine mechanisms by pretreatment using either inhaled or oral blocking agents and antagonists. Data obtained from these studies should permit a better assessment of adverse health effect from inhalation of ambient air pollutants as well as an understanding of their mechanisms of toxicity.