Effects of welding fumes of differing composition and solubility on free radical production and acute lung injury and inflammation in rats

The goals of this study were to examine acute lung damage and inflammation, as well as free radical production, caused by welding fumes of different chemical compositions and solubilities. The fumes were from a gas metal arc welding using a mild-steel (GMA-MS) or stainless-steel electrode (GMA-SS) and a manual metal arc welding using a stainless-steel electrode (MMA-SS), which was further separated into soluble and insoluble fractions. The MMA-SS was the only fume to contain soluble chromium. Free radical production was observed only in suspensions of MMA-SS fume under various conditions. Male Sprague-Dawley rats were intratracheally instilled with either a welding fume suspension at 2 mg/rat or a saline vehicle, and various parameters of inflammation and damage were measured at 3 h and days 1, 3, and 6. Only the MMA-SS treatment caused a continued increase in lung weight until day 6 and elevated lipid peroxidation at day 3. All of the fumes caused increases in macrophages and neutrophils obtained by lavage, but the increased cellularity was extended through day 6 following the MMA-SS treatment only. Only the MMA-SS treatment led to an increased recovery of eosinophils and damage to the alveolar-capillary barrier. While all of the fumes produced increases in cytotoxicity, the MMA-SS treatment caused the maximal response at day 3. These findings indicate that different welding fumes caused varied responses in the lungs of rats, correlated to their metal composition and ability to produce free radicals. Additionally, both the soluble and insoluble fractions of the MMA-SS fume were required to produce most effects, indicating that the responses are not dependent exclusively on the soluble metals.