Phosgene is a hazardous air toxic and a potential occupational health hazard. Studies were initiated to determine whether exposure to phosgene resulted in local pulmonary or systemic immune dysfunction. The effect of phosgene on lung natural killer (NK) activity was quantified at different times after exposure. Acute phosgene exposure resulted in a suppressed pulmonary NK activity on days 1, 2, and 4 after exposure; however, normal levels of biological activity were observed 7 days after exposure. The suppressed NK activity was not restored after removal of adherent cells. Pulmonary immunotoxicity was also observed after exposure at 0.5 ppm, while no adverse effects were observed at 0.1 ppm phosgene. Systemic immunotoxic effects were observed for NK activity in the spleen, but not in the peripheral blood. The report is the first of a systemic immunotoxic effect after exposure to phosgene. It is thus important in pulmonary immunotoxicology to evaluate systemic immune functions, since secondary effects -- distant to the original interaction -- may occur with potential serious consequences. (Copyright (c) 1989 Marcel Dekker, Inc.)