Oxidant Generation and Lung Injury after Particulate Air Pollutant Exposure Increase with the Concentrations of Associated Metals

Abstract

We tested the hypothesis that particulate air pollutants are associated with metals that have a capacity to transport electrons and that biologic activity of the particulates can correlate with the concentrations of these metals. The metals studied were titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper. Measurements included (1) oxidized products of deoxyribose catalyzed by particulates, (2) induction of a neutrophilic alveolitis after particulate instillation, (3) increments in airway reactivity after particulate instillation, and (4) mortality after exposures to both dusts and a microbial agent. Employing 10 different dusts of either natural or anthropogenic origin, in vitro generation of oxidized products of deoxyribose increased with ionizable concentrations of all metals, except for titanium, associated with the particles. After tracheal instillation of dust into rats, both the neutrophil influx and lavage protein increased with ionizable concentrations of these same metals. Changes in airway reactivity following instillation of dusts in rats also appeared to be associated with the ionizable concentrations of these metals. Similarly, mortality after injection of particles in mice with subsequent exposure to aerosolized Streptococcus zooeptdemicus reflected metal concentrations. We conclude that particulate air pollutants are associated with metals which have a capacity to catalyze electron transfer. An in vitro measure of oxidant production increased with ionizable concentrations of the metals. Indices of in vivo lung injury also corresponded to concentrations of these same metals.