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LUNG INJURY CAUSED BY AMBIENT LEVELS OF OZONE
Citation:
Huang, T., L. Chang, F. Miller, AND J. Crapo. LUNG INJURY CAUSED BY AMBIENT LEVELS OF OZONE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-88/554 (NTIS PB91117606), 1988.
Description:
Exposures to low levels of 03 cause epithelial and interstitial injury in the proximal alveolar region. he sequential development of this lesion caused by a simulated ambient pattern of 03 was studied by exposing Fisher 344 rats to 0.06 ppm 03 overnight with an 8 hr daytime exposure having a slow increase to a peak of 0.25 ppm and.then gradually decreasing back to 0.06 ppm. nimals were studied using EM morphometric techniques after 7, 21 and 90 days exposure as well as post 90 days exposures. he early changes in 03 exposed animals included increases of volumes in type II epithelium (60%), type I epithelium (16%), cellular interstitium (52%), non-cell interstitium (33%), and in alveolar macrophages (180%). he response showed a biphasic reaction with the early injury subsiding after 21 days of 03 exposure. he animals exposed for 90 days showed a 28% increase in relative volume of type I and a 42% increase in type II epithelia. ild increase in interstitial volume could also still be detected at this time. uring the 42 days recovery period the changes in relative volume of epithelial cells subsided; however, an enhanced number (03) of type I cells with smaller average surface area (32%) persisted and did not show any trend back to normal. he relative volume of interstitial matrix remained slightly increased (12%) after recovery. hese data indicate that with long exposures a chronic alveolar epithelial and interstitial reaction occurs and that these reactions can only be partially reversed 42 days after the exposure is terminated.
