Murine lung carcinogenesis following exposure to ambient ozone concentrations.

Inbred strain A/J mice, responsive to the chemical induction of pulmonary adenomas, were used to assess any of several roles that the photochemical air pollutant ozone might play in lung carcinogenesis. In separate experiments, animals were exposed to two concentrations of ozone (0.31 +/- 0.01 and 0.50 +/- 0.02 ppm) intermittently for a 6-month period, to evaluate the potential of ozone to act as either a pulmonary carcinogen, a tumor promoter, or an inhalant capable of increasing lung tumor yield when exposure was in conjunction with a pulmonary carcinogen, urethane. Statistical analyses of results indicated that ozone exposure at both concentrations caused an increase in lung tumor number relative to clean air controls, but that ozone was not an effective tumor promoter under the conditions of our protocol. When ozone exposure immediately preceded treatment with urethane (CAS: 51-79-6), animals were at increased risk for the development of lung adenomas.