Inflammation in induced sputum after aluminium oxide exposure: an experimental chamber study

Introduction Workers in aluminium production are exposed to a complex mixture of particles and gases potentially harmful to the airways, among them aluminium oxide (Al 2 O 3 ). With the use of an exposure chamber, we aimed to examine the effects of short-term controlled exposure to Al 2 O 3 on lung function and inflammatory markers in healthy volunteers. Methods 15 men (age 19–31) were exposed in random order to clean air or Al 2 O 3 particles (3.8–4.0 mg/m 3 ) for 2 h including 30 min exercise (stationary bike, 75 W). The permissible exposure level (PEL) for Al 2 O 3 by Occupational Safety and Health Administration, USA, is 5 mg/m 3 time weighted average (TWA). Sham and particle exposures were separated by at least 2 weeks. Spirometry was carried out, and induced sputum and blood samples were collected 48 h before and 4 and 24 h after exposure. Results Levels of sputum neutrophils (mean (±SEM)) was increased 24 h post-Al 2 O 3 vs pre-Al 2 O 3 exposure (43% (4) vs 31% (4), p=0.01) and the protein level of interleukin (IL)-8 had a 4.8 (0.9)-fold change increase 24 h after exposure (p 2 O 3 exposure, gene signatures in sputum were significantly increased related to several pathways. Conclusions The present study suggests that controlled exposure to Al 2 O 3 particles at levels below PEL (TWA) induces airway inflammation in healthy humans marked by elevated neutrophils and elevated IL-8. In addition, increased expression of genes associated with several biological processes was observed in sputum. Interestingly, inhaled Al 2 O 3 -induced effects were localised to the airways and not systemic.