The goals of this study were to examine the roles of the soluble (Sol) and insoluble (Insol) fractions of a stainless steel welding fume (Tot) collected during manual metal arc welding in the development of rat lung damage and inflammation and correlate those effects with free radical production and metal composition. Welding fume fractions were separated by incubation in saline followed by centrifugation and filtration. Metal composition analysis by energy dispersive spectroscopy revealed both Cr and Mn in the Sol fraction. Using electron spin resonance, the generation of radicals from Cr(VI) was observed, with the highest signal from Tot, an intermediate signal from Sol, and a low signal from Insol. To examine the effects of the fumes on lung damage and inflammation, male Sprague-Dawley rats were intratracheally instilled with Tot at 2 mg/rat, or the equivalent volume of Sol, Insol, or the vehicle (saline). On days 1, 3, and 6, the right lung was assayed for lipid peroxidation (LPO) products while the left lobes were subjected to bronchoalveolar lavage (BAL). LPO was elevated in the lungs following Tot treatment, with most of the effect attributed to the Insol fraction. All fractions caused increases in BAL cell number, including elevated macrophage recovery. However, the Tot and Insol fractions caused increased PMN numbers at days 1 and 3, while the Tot and Sol fractions led to increased eosinophils at day 1. The changes in left lung weight were additive (Sol + Insol = Tot) on day 6, while albumin, total protein, and LDH activity in the first BAL fraction were all additive at day 3. These findings indicate that the ability of the fume to produce free radicals and much of the damage observed in the lungs of rats after Tot treatment depends on both the Sol and Insol fractions of the fume. However, PMN recruitment and LPO were due mainly to the insoluble particulates while eosinophil recruitment was due to the soluble components, most likely soluble metals.
The Toxicologist. Society of Toxicology 42nd Annual Meeting and ToxExpo, Cutting-Edge Science, Networking, New Perspectives, March 9-13, 2003, Salt Lake City, Utah