Response of ciliated epithelium to ozone and sulfuric acid

The effects of ozone (O₃), sulfuric acid (H₂SO₄), and their interaction on ciliary activity were investigated. Following in vivo exposure to various concentrations of O₃ and H₂SO₄, ciliary activity of isolated tracheal ring cultures was microscopically determined under stroboscopic illumination. Assay of tracheal rings immediately after a 2-hr exposure to 880 μg H₂SO₄/m³ showed a significant decrease (P < 0.0001) in ciliary beating frequency from controls. Following 72 hr in vitro maintenance, there was still a significant depression (P < 0.01) in ciliary activity of treatment cultures. In vivo recovery studies indicated that ciliary activity had returned to the normal range 72 hr after exposure. Exposure to 196 μg O₃/m³ for 3 hr resulted in no significant difference from controls in ciliary activity. Experiments designed to investigate the effects of a sequential exposure to O₃ followed by H₂SO₄ indicated a significant decrease (P < 0.05) in the ciliary beating frequency of exposed animals which was less than that observed with H₂SO₄ alone. As indicated by the results of these studies, combined action experiments are extremely relevant in assessing the toxicity of environmental pollutants.