Airway inflammatory response following exposure to 100% RME biodiesel in healthy subjects

Background Over 6 million die prematurely each year as a result of air pollution. As climate change takes center stage in political and scientific debates, alternative and renewable carbon-neutral fuels, such as biodiesel, receive increasing attention. It is anticipated that biofuels are less harmful to human health than fossil petrodiesel exhaust. We have demonstrated that exposure to pure rapeseed methyl ester (RME100) biodiesel or RME/diesel blend (30:70%) exhaust results in cardiovascular impairments, similar to those of petrodiesel exhaust inhalation. Aim To evaluate whether inhalation of 100% RME biodiesel exhaust results in an acute airway inflammatory response in healthy subjects. Methods Fifteen healthy volunteers were exposed to filtered air and RME100 exhaust (159 µg/m 3 ) for 1h during intermittent exercise, in a randomised double-blind crossover study. Bronchoscopy with sampling of endobronchial mucosal biopsies was performed six hours post-exposure. Biopsies were fixed in acetone, and embedded in glycolmetachrylate (GMA) for immunohistochemical analysis. Results Analyses of submucosal cell counts in the bronchial biopsies demonstrated an increase in neutrophils, eosinophils as well as expression of CD68 (p=0.006, p=0.038 and p=0.013 respectively) after RME100 as compared to the air exposure. Furthermore, the CD4/CD8 ratio was lower post-RME100 exposure in comparison with filtered air. Conclusion Exposure to exhaust from a diesel engine running on 100% RME biodiesel does not only cause acute cardiovascular effects, as recently shown, but also an airway inflammatory response. Before biofuels are more widely introduced, it is of importance to identify the potential adverse health effects.