Lymphocytic bronchiolitis after lung transplantation is associated with daily changes in air pollution

Acute rejection represents a major problem after organ transplantation, being a recognized risk for chronic rejection and mortality. Recently, it became clear that lymphocytic bronchiolitis (LB, B-grade acute rejection) is more important than previously thought, as it predisposes to chronic rejection. We aimed to verify whether daily fluctuations of air pollution, measured as particulate matter (PM) are related to histologically proven A-grade rejection and/or LB and bronchoalveolar lavage (BAL) fluid cellularity after lung transplantation. We fitted a mixed model to examine the association between daily variations in PM(10) and A-grade rejection/LB on 1276 bronchoscopic biopsies (397 patients, 416 transplantations) taken between 2001 and 2011. A difference of 10 μg/m(3) in PM(10) 3 days before diagnosis of LB was associated with an OR of 1.15 (95% CI 1.04-1.27; p = 0.0044) but not with A-grade rejection (OR = 1.05; 95% CI 0.95-1.15; p = 0.32). Variations in PM(10) at lag day 3 correlated with neutrophils (p = 0.013), lymphocytes (p = 0.0031) and total cell count (p = 0.024) in BAL. Importantly, we only found an effect of PM10 on LB in patients not taking azithromycin. LB predisposed to chronic rejection (p < 0.0001). The risk for LB after lung transplantation increased with temporal changes in particulate air pollution, and this was associated with BAL neutrophilia and lymphocytosis. Azithromycin was protective against this PM effect.