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Background. Ozone (O3) and nitrogen dioxide (NO2) are two highly reactive compounds that have already been shown to be injurious to human health, and particularly to the centro-acinar region of the lungs. Several studies have demonstrated that measurement of lung-specific secretory proteins in serum, fir instance the 16 kDa Clara cell protein (CC16) and the surfactant-associated protein A (SP-A) might be useful to assess alterations of the lung epithelial barrier following acute exposure to O3. However, no study has so far examined whether chronic exposure to photo-oxidants such as O3 and NO2 induces the same effects in humans.
Methods. 312 healthy non-smoking adults from areas with different ambient levels of O3 and NO2 were enrolled on this study. 78 subjects were from Cuernavaca North in the suburbs of Mexico, 95 were from Mexico City (Mexico) and 139 subjects from Paris (France). Each participant was followed for 5 days. NO2 exposure levels were assessed by personal passive monitors. Ambient O3 levels were measured by local monitoring stations. Blood samples were taken on days 5, in the morning, in order to assess the integrity of the lung epithelial barrier. CC16 was measured on the whole population. SP-A assay was performed on the Mexican population only.
Findings. Levels of ambient O3were singnificantly higher in the two Mexican areas (mean, 80 μg/m³/h) compared to Paris (mean, 30 μg/m³/h). No difference was however observed between the ambient NO2 concentrations. CC16 concentration in serum was on average 50% lower in the Mexican subjects compared to the subjects from Paris and showed an inverse dose-effect relationship with ambient O3 levels. By contrast, a slight increase in serum SP-A levels was found in the Mexican subjects and was positively correlated with O3 levels. CC16 and SP-A did not differ between the two Mexican groups.
Conclusions. This study shows that chronic exposure to O3 is associated with a decrease of CC16 I serum. As no relationship was observed with the NO2 concentrations, we assumed that O3 was the main constituent responsible for the observed effects. These observations, very similar to those observed within smokers suggest that chronic exposure to O3 is associated with epithelial lung injury

Air Pollution --- Environmental Exposure --- Lung Diseases --- Epithelium