Epidemiological studies have shown an increased incidence of respiratory illness in welders. Stainless steel (SS) welding fumes have been shown to have a greater effect on alveolar macrophage (AM) function than mild steel (MS) fumes. The objective of this study was to evaluate the effects of different welding fumes on the clearance of a bacterial pathogen from the lungs. Fumes were collected during flux-cored manual metal arc (MMA) and gas metal arc (GMA) welding using either S8 or MS consumable electrodes. The fume composition was: 1) GMA.sS: 52.3% Fe, 22.2% Cr, 18.3% Mn, 4.9% Ni, 2.3% Si; 2) GMA-MS: 89.2% Fe, 8.2% Mn, 2.6% Si; 3) MMA-SS.: 22.3% K, 19.4% Fe, 13.1 % Cr, 12.6% Si, 8.2% Ca, 8.0% Mn, 17.4% other. CDNAF rats were dosed intratracheally with saline (control) or the welding samples at a dose of J.O mg/100 g b wt. At 1 and 35 days postinstillation, 5000 Listeria monocytogenes were intratracheally instilled into the treated animals. Five days after intratracheal exposure to L. monocytogenes, the lungs and spleen were removed, homogenized, and cultured quantitatively on Brain Heart Infusion agar at 370 C. Colony forming units (CFUs) were counted after an overnight incubation. After a 1 day fume treatment, all three we1ding samples caused a significant decrease (p<O.OS) in the 5-day clearance of L. monocytogenes from the lungs as compared to control. At 35 days post-instillation, the MMA-SS and OMA-SS samples significantly increased (p<O_OS) L. monocytogenes clearance from the lungs as compared to the GMA-MS and control groups. No significant differences were seen among the treatment groups in the number of bacteria cultured from the spleen.We have demonstrated that subchronic exposure to SS fumes may have a greater effect on the pulmonary clearance of L. monocytogenes as compared to MS fumes. This is most likely due to differences in fume composition and the greater effect of S8 fumes on AM function.
The Toxicologist. Society of Toxicology 38th Annual Meeting, March 14-18, 1999, New Orleans, Louisiana