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Potential neurotoxic responses in rats after pulmonary administration of welding fume with varying concentrations of manganese.
Neurotoxicology 2006 Dec; 27(6):1163
Questions persist regarding a possible causal association between neurological effects in welders and the presence of manganese (Mn) in welding fume. Here, our objective was to examine the potential neurotoxic effect of Mn in rats after pulmonary administration of different welding fumes. Three welding fumes were collected: gas metal arc-mild steel fume (GMA-MS); flux-cored arc hardsurfacing fume (FCA-HS); and manual metal arc hardsurfacing fume (MMA-HS). The amount of Mn in the FCAHS (2.0 mg Mn/gm total metal) and MMA-HS (1.8 mg Mn/gm total metal) fumes was -6x higher than in the GMAMS (0.32 mg Mn/gm total metal) fume. Male Sprague-Dawley rats were instilled intratracheally with 0.5 mg/rat of one of the welding particle samples once weekly for seven weeks. Control animals received saline using the same treatment regimen. Four days after the last treatment, the animals were sacrificed, and lungs and discrete brain regions were recovered for metal and toxicity analyses. Significant increases in Mn levels were observed in the lungs of the animals treated with FCA-HS and MMA-HS fumes compared to the GMA-MS group. Slight elevations in Mn levels were observed in the striatum and cortex of brains from animals treated with each of the welding fumes compared to control levels. Measurement of glial fibrillary acidic protein (GFAP) and neurotransmitter levels as well as Fluoro-Jade B (FJB) staining provided an assessment of neurotoxicity. No FJB staining was observed but slight, although not significant, increases in striatal GFAP were found in the welding fume groups compared to the controls. Also, an increase in striatal dopamine and its metabolite DOPAC were observed in some of the welding fume groups. These preliminary findings indicate that Mn that has deposited in the lungs of animals treated with welding fume may potentially reach specific brain regions. Questions still exist as to whether inhaled welding fumes induce neurotoxicity. Further study at more chronic time points is needed.
Welding-industry; Fumes; Animal-studies; Arc-welding; Metal-fumes; Metallic-fumes; Brain-matter; Welders; Neurotoxic-effects; Neurotoxicology; Neurotoxins
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Page last reviewed: May 5, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division