What is the impact of outdoor pollution on children's asthma?

Outdoor pollution is a complex mix of more than 200 air contaminants. Among these pollutants, ozone, nitrogen dioxide and fine particles may generate bronchial inflammation and hyperreactivity. The hypothesis that pollution contributes to the development of asthma in children is based on epidemiological, clinical and experimental data. Many risk factors during the in utero and postnatal period have been identified in the aetiology of childhood asthma. During pregnancy, outdoor pollution was identified as a causal factor of respiratory disease in neonatal cohort studies. Several epidemiological studies also demonstrate that outdoor pollution is a trigger of asthma exacerbations. This review aims to highlight the current knowledge on outdoor pollution and asthma.