“…The immediate effects of exposure to TS (43,45,86,88), 03 (12,20,46), Pb (5), and probably NO2 (31) are to decrease the viability of the pulmonary alveolar macrophage (PAM) population. Longer exposure periods usually result in an increased population of the PAMs in the lung (45,86,89), accompanied in some species by increased numbers of polymorphonuclear leukocytes (27,89). An exception to this rule is Pb exposure (or exhaust fumes containing lead sesquioxide); long-term exposure to these agents depletes the PAM population in the lung (4,5).…”