Effects of ambient inhaled ozone on vocal fold mucosa in bonnet monkeys

Deleterious effects of ambient ozone (O₃) on the nasal and lower airways is well documented. However, no investigations have considered possible effects on vocal fold mucosa. To this end, six macaque monkeys were exposed to 0.64 ppm O₃ for 8 h/day for a total of 7 days. Three monkeys were killed 12 h postexposure, and the other three at 7 days postexposure. Larynges were excised and subjected to histological staining and morphometric analyses. Results revealed increases in the thickness of epithelial tissue in the 12 h group. In the 7 day group, differences in both epithelial and lamina propria thicknesses were noted. Additional changes consistent with an initial inflammatory response, with associated disruption in glands and vessels, followed by some evidence of healing, were also noted. Implications of the data for the larynx and voice quality in humans exposed to similar and other environmental toxins are discussed.