Air Pollution Relates to Airway Pathology in Wheezing Children

Rationale: Outdoor air pollution contributes to asthma development and exacerbations, yet its effects on airway pathology have not been defined in children. Objectives: To explore the possible link between air pollution and airway pathology, we retrospectively examined the relationship between environmental pollutants and pathological changes in bronchial biopsy specimens from children undergoing a clinically indicated bronchoscopy. Methods: Structural and inflammatory changes (basement membrane [BM] thickness, epithelial loss, eosinophils, neutrophils, macrophages, mast cells, and lymphocytes) were quantified in biopsy specimens by using immunohistochemistry. The association between exposure to particulate matter less than 10 μm in aerodynamic diameter (PM10), SO2 and NO2 and biopsy findings was evaluated by using a generalized additive model with Gamma family to allow for overdispersion, adjusted for atmospheric pressure, temperature, humidity, and wheezing. Results: Overall, 98 children were included (age 5.3 ± 2.9 yr; 53 with wheezing/45 without wheezing). BM thickness increased with prolonged exposure to PM10 (rate ratio [RR], 1.29; 95% confidence interval [CI], 1.09-1.52), particularly in children with wheezing. Prolonged exposure to PM10 was also associated with eosinophilic inflammation in children with wheezing (RR, 3.16; 95% CI, 1.35-7.39). Conversely, in children without wheezing, increased PM10 exposure was associated with a reduction of eosinophilic inflammation (RR, 0.12; 95% CI, 0.02-0.6) and neutrophilic inflammation (RR, 0.36; 95% CI, 0.14-0.89). Moreover, NO2 exposure was also linked to reductions in neutrophil infiltration (RR, 0.57; 95% CI, 0.34-0.93) and eosinophil infiltration (RR, 0.33; 95% CI, 0.14-0.77). Conclusions: Different patterns of association were observed in children with wheezing and in children without wheezing. In children without wheezing, exposure to PM10 and NO2 was linked to reduced eosinophilic and neutrophilic inflammation. Conversely, in children with wheezing, prolonged exposure to PM10 was associated with increased BM thickness and eosinophilic inflammation, suggesting that it might contribute to asthma development by promoting airway remodeling and inflammation.