Pulmonary function of guinea pigs exposed to freshly generated ultrafine zinc oxide with and without spike concentrations.

Exposure of guinea pigs 3 hr/day for 5 consecutive days to freshly formed ultrafine zinc oxide (ZnO) (count median diameter: 0.05 micron; geometric standard deviation: 2.0) at a concentration of 7 mg/m3 produced a gradual decrease in total lung capacity and vital capacity over the course of the exposure period. The carbon monoxide (CO) diffusing capacity (DLCO) was not affected until the fourth day, when it dropped abruptly to 30% below control levels. Wet-lung weight/body weight ratios and wet-lung/dry-lung weight ratios increased, indicating the presence of edema. Exposures to 2.7 mg/m3 ZnO, using the same 3 hr/day, 5 day time frame, did not alter any parameters measured. In 2 experiments a single high peak of ZnO (25-34 mg/m3) occurred. In one experiment exposure was stopped, but pulmonary function measurements were made as scheduled; in the other case, exposures to ZnO were continued. In both, lung volumes were decreased abruptly and to a greater extent than when peaks were absent. Continued exposure caused greater decrements in total lung capacity (TLC) and vital capacity (VC) as well as decrements in functional residual capacity (FRC) and residual volume (RV) than were observed when exposure was stopped. Peak exposures reduced DLCO to 45%-60% below control. These values rose to 25%-30% below control with or without continued exposure. Airway resistance increased and compliance decreased following peak exposures. When exposure was stopped, these changes were reversible; with continued exposure they still were different from control levels on the fifth day.(ABSTRACT TRUNCATED AT 250 WORDS)