Introductory remarks: Session on disease conditions predisposing afflicted individuals to the toxic effects of pollutants.

Earlier papers have dealt with the effect of genetic makeup and age on response to pollutants, particularly at cellular and enzyme levels; the gut has been considered and, in relation to a,antitrypsin deficiency, the lung. The next paper considers the lung as the portal of entry, and in the two following papers as the site of attack as well. For these introductory remarks I have selected several points of current or special interest. Seeing our lungs filter so much air the dose of any irritant or agent to which the lung is exposed may be greatly in excess of environmental concentration. The anatomical site at which a pollutant impinges is important; for the gaseous phase it is alveolar, for the particulate it may be alveolar or airway depending on particle size. In the alveoli it is mainly the macrophages that represent the respiratory defense mechanism, whereas in the airways it is mucociliary clearance. Mucus secretion, clearance, and bronchial muscle constriction each need to be assessed in relation to any irritant or pollutant. Our understanding of the nonrespiratory functions of lung, to use the current shorthand, is proceeding fast. In this connection I commend to you a recent series of monographs of which Dr. Claude Lenfant is Executive Editor which deals with a fast-growing field and, although it is invidious perhaps to choose any of the nine that have appeared to date, I would especially mention Volumes 1, 4 and 5 as particularly relevant to the topic of this meeting: Immunologic and Infectious Reactions in the Lung (1), Metabolic Functions of the Lung (2) and Respiratory Defense Mechanisms (3). In considering populations at risk, it is important