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

Abstract

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.