Rats were exposed to either 1 to 20 mg/m3 of a respirable aerosol (0.8 to 1.3 μm mass median aerodynamic diameter) of ammonium persulfate for 7 days, 23.5 hr per day, or to filtered air. Rats inhaling 4 to 20 mg/m3 of ammonium persulfate lost body weight and had significantly increased lung wet weight, total lung protein, and total lung DNA levels, indicative of inflammation and/or edema. Tracheal mucus glycoprotein secretion rates tended to be higher in the exposed rats. A no observed-effect level was obtained at an aerosol concentration of 1 mg/mm3. In a single experiment, exposure of rats to gaseous hydrogen peroxide at a level equal to about 5 mg/m3 of ammonium persulfate in oxidizing equivalents in the presence of respirable ammonium sulfate particles did not elicit changes in any of the parameters evaluated. We conclude that the persulfate moiety, which probably occurs in small amounts in polluted air as an intermediate in the oxidation of sulfur dioxide (SO2) to sulfate, is a pneumotoxin.
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