BackgroundDaily levels of ambient air pollution and pollen may affect lung function but have rarely been studied together. We investigated short-term exposure to pollen and air pollution in relation to lung function in school-age children from a French population-based birth cohort.MethodsThis study included 1063 children from the PARIS (Pollution and Asthma Risk: an Infant Study) cohort whose lung function and FeNO measurements were performed at age 8 years old. Exposure data were collected up to 4 days before testing. We estimated daily total pollen concentration, daily allergenic risk indices for nine pollen taxa, as well as daily concentrations of three air pollutants (particulate matter less than 10 µm (PM₁₀), nitrogen dioxide (NO₂), ozone (O₃)). Children with similar pollen and air pollution exposure were grouped using multidimensional longitudinal cluster analysis. Associations between clusters of pollen and air pollution exposure and respiratory indices (FEV₁, FVC, FeNO) were studied using multivariable linear and logistic regression models adjusted for potential confounders.ResultsFour clusters of exposure were identified: no pollen and low air pollution (Cluster 1), grass pollen (Cluster 2), PM₁₀(Cluster 3) and birch/plane-tree pollen with high total pollen count (Cluster 4). Compared with children in Cluster 1, children in Cluster 2 had significantly lower FEV₁and FVC levels, and children from Cluster 3 had higher FeNO levels. For FEV₁and FVC, the associations appeared stronger in children with current asthma. Additional analysis suggested a joint effect of grass pollen and air pollution on lung function.ConclusionDaily ambient chemical and biological air quality could adversely influence lung function in children.