Bronchoalveolar inflammation after exposure to diesel exhaust: comparison between unfiltered and particle trap filtered exhaust

Objectives-Air pollution particulates have been identified as having advers e effects on respiratory health. The present study was undertaken to furthe r clarify the effects of diesel exhaust on bronchoalveolar cells and solubl e components in normal healthy subjects. The study was also designed to eva luate whether a ceramic particle trap at the end of the tail pipe, from an idling engine, would reduce indices of airway inflammation. Methods-The study comprised three exposures in all 10 healthy never smoking subjects; air, diluted diesel exhaust, and diluted diesel exhaust filtered with a ceramic particle trap. The exposures were given for 1 hour in rando mised order about 3 weeks apart. The diesel exhaust exposure apperatus has previously been carefully developed and evaluated. Bronchoalveolar lavage w as performed 24 hours after exposures and the lavage fluids from the bronch ial and bronchoalveolar region were analysed for cells and soluble componen ts. Results-The particle trap reduced the mean steady state number of particles by 50%, but the concentrations of the other measured compounds were almost unchanged. It was found that diesel exhaust caused an increase in neutroph ils in airway lavage, together with an adverse influence on the phagocytosi s by alveolar macrophages in vitro. Furthermore, the diesel exhaust was fou nd to be able to induce a migration of alveolar macrophages into the airspa ces, together with reduction in CD3+CD25+ cells. (CD cluster of differentia tion) The use of the specific ceramic particle trap at the end of the tail pipe was not sufficient to completely abolish these effects when interactin g with the exhaust from an idling vehicle. Conclusions-The current study showed that exposure to diesel exhaust may in duce neutrophil and alveolar macrophage recruitment into the airways and su ppress alveolar macrophage function. The particle trap did not cause signif icant reduction of effects induced by diesel exhaust compared with unfilter ed diesel exhaust. Further studies are warranted to evaluate more efficient treatment devices to reduce adverse reactions exhaust in the airways. to d iesel exhaust in the airways.