Manganese (Mn) is a common metal in welding fume aerosols and suspected of inducing adverse neurological effects in exposed workers. Measurements of Mn in blood and urine have proven to be unreliable indicators of exposure. The goal of the current study was to determine if Mn accumulation in the nail (claw) can be used as a potential biomarker. To model this, male Sprague-Dawley rats were treated by intratracheal instillation (IT) with 2 mg/rat of shielded manual metal arc-hardsurfacing (MMA-HS; high Mn) or gas metal arc -mild steel (GMA-MS; low Mn) welding fumes once a week for 28 weeks. Vehicle controls received saline by IT. The percentage of Mn, relative to the other metals in the collected fume, was more than double (50.9 %) in the MMA-HS fume compared to GMA-MS (21.7 %). At 7 days after the last exposure, right lung lobes, specific brain regions, blood, and nails were harvested from each group. Mn levels were determined by inductively coupled plasma atomic emission spectroscopy. Significant elevations in lung Mn were observed following repeated exposure to MMA-HS and GMA-MS fumes for 28 weeks. Despite the difference in Mn composition of the two fumes, repeated exposure to equal mass doses of the fumes produced comparable Mn lung burden, suggesting a steady-state may have been achieved. Measurements of blood Mn were near or at the limit of detection and, as a consequence, variable. In contrast, Mn levels significantly increased in the nails, as well as in striatum and midbrain, potential targets of Mn neurotoxicity, for the MMA-HS group compared to the GMA-MS group and controls. Our results demonstrate nail Mn to be a potentially viable and sensitive biomarker for welding fume exposure. The ease with which nails can be harvested, transported, and stored makes them an attractive surrogate for monitoring exposures in occupational settings.
Biological-effects; Cell-biology; Cytology; Fumes; Laboratory-animals; Laboratory-testing; Molecular-biology; Neurophysiological-effects; Neurophysiology; Neurotoxic-effects; Quantitative-analysis; Risk-analysis; Statistical-analysis; Welders; Welding-industry; Workplace-monitoring; Exposure-assessment; Biomarkers; Animal-studies; Animals
The Toxicologist. Society of Toxicology 50th Annual Meeting and ToxExpo, Washington, DC, March 6-10, 2011