Serum levels of club cell secretory protein (Clara) and short- and long-term exposure to particulate air pollution in adolescents

Background: Studies in populations have shown that particulate air pollution is associated with changes in lung function in adolescents. Objective: We investigated the effect of short- and long-term exposure to particulate matter (PM10) on the pulmonary health of adolescents, using serum lung club cell secretory protein (Clara) (CC16) as a biomarker for respiratory epithelium integrity. Methods: We measured serum CC16 in 825 adolescents (57% girls, mean age: 15 years). Short-term and long-term exposure to ambient PM10 was estimated for each participant's home address using a kriging interpolation method. To explore the association between PM10 and serum CC16 we applied restricted cubic splines with 5 knots located at the 5th, 25th, 50th, 75th and 95th percentiles of the PM10, distribution. The explorative analyses showed a change in the slope of this association, after which a change-point analysis was performed. Results: After adjustment for potential covariates, the analysis showed strong associations between PM10 concentrations, averaged over the week preceding the clinical examination, and serum CC16 levels. Each 5 mu g/m(3) increase in mean PM10 concentration in the week before the clinical examination was associated with a substantial increase of 0.52 mu g/l (95% confidence interval: 0.31 to 0.73; p < 0.0001) in serum CC16 levels. The association appears nonlinear with a flattening out of the slope at mean week PM10 levels above 37 mu g/m(3). There was no evidence of an association between long-term exposure to PM10 and serum CC16 concentrations. Conclusions: Our findings suggest that short-term exposure to particulate air pollution may compromise the integrity of the lung epithelium and lead to increased epithelial barrier permeability in the lungs of adolescents, even at low concentrations.(C) 2014 Elsevier Ltd. All rights reserved.