FRESHLY GENERATED STAINLESS-STEEL WELDING FUME INDUCES GREATER LUNG INFLAMMATION IN RATS AS COMPARED TO AGED FUME

It has been previously reported that both short- and long-lived reacti ve oxygen species (ROS) are present on the surface of freshly generate d fumes, The objective of this study was to determine if freshly forme d welding fume induces greater lung inflammation and injury in rats du e to the presence of reactive oxygen species than aged welding fume. F ume was collected during gas metal are welding using a stainless steel consumable electrode and found to be of respirable size with a mean d iameter of 0.77 mu m +/- 0.48. Male CD/VAF rats were dosed intratrache ally with the welding fume 30 min (fresh) and 1 and 7 days (aged) afte r fume collection at a dose of 1.0 mg/100 g b wt. Bronchoalveolar lava ge (BAL) was performed 24 h post-instillation. Lung injury and inflamm ation were assessed by measuring the concentration of neutrophils, alb umin, lactate dehydrogenase (LDH), and glucosaminidase (GLU) in the re covered BAL fluid. More neutrophils and enhanced GLU activity were obs erved for the 'fresh' group as compared to both 'aged' groups (P < 0.0 5). Slight, but not significant, elevations were seen in albumin conte nt and LDH activity for the 'fresh' group as compared to the 'aged' gr oups. No significant differences were observed for any of the paramete rs when fume aged for 1 and 7 days were compared. When the 'fresh' and 'aged' fumes (12.5, 25, and 50 mu g/ml) were suspended in dichloroflu orescin (15 mu M), a probe which becomes fluorescent when oxidized, th e concentration-dependent increases in fluorescence were greater for t he 'fresh' fume versus the 'aged' fumes. We have demonstrated that fre shly generated stainless steel welding fume induces greater lung infla mmation than 'aged' fume. This is likely due to a higher concentration of ROS on fresh fume surfaces. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.