Health significance of pulmonary function responses to airborne irritants.

Abstract

Exposures to airborne irritants such as O/sub 3/, NO/sub 2/, SO/sub 2/ and H/sub 2/SO/sub 4/ can produce measurable changes in a variety of pulmonary functions such as respiratory mechanics, pulmonary gas exchange, mucociliary particle clearance, and airway permeability. The most commonly measured indices of pulmonary function are those obtained by analyzing flows and volumes during a maximal forced expiratory maneuver, because they can be obtained readily in both laboratory and field studies in humans. Other functional measures are essentially limited to laboratory studies on relatively small populations of humans, or on experimental animals. Interpretation of respiratory function changes in relation to exposures to airborne irritants is complicated by the large interindividual variability in baseline function and responsiveness, the superposition of both the transient effects of recent acute exposure and the cumulative effects of chronic exposure at any given measurement, and the inherent day-to-day variability of effort dependent indices. Each of several components may affect the same functions, but with different time scales and may affect different segments of the population of different degrees. The greatest uncertainties lie in the significance of transient and apparently reversible effects, and their contribution, if any, to permanent functional changes. Use of animal modelsmore » to study the role of transient changes in function on the development of permanent changes is illustrated in terms of the effects of H/sub 2/SO/sub 4/ on particle clearance function.« less