Attenuation of acute lung injury by ozone inhalation--the effect of low level pre-exposure.

The attenuating influence of a pre-exposure of rats to a low concentration of ozone (O3) for 7 days on a subsequent O3 challenge was investigated. Effects of O3 were quantified by measuring indicators of lung permeability and inflammation in bronchoalveolar lavage fluid. The results suggest that pre-exposure to relatively low levels of O3 produces a diminished permeability response in lower airways of rats upon a following challenge with a higher level of O3. Extrapolated to human exposure situations, these data suggest that health effect evaluation of repeated exposure periods of enhanced O3 levels is rather complex and needs further investigation.