Welding generates complex metal aerosols, inhalation of which is thought to cause Parkinson's disease (PD)-like neurotoxicity, due to the presence of manganese (Mn) in the welding electrodes. As neurological disorders are generally progressive in nature, with latency between insult and appearance of clinical symptoms, a logical approach for workplace safety and health is to prevent adverse exposures. For welding, this can be achieved by minimizing welding fume (WF) generation rate and/or suitably modifying existing welding practices to reduce toxic exposures. Here, we show that by specifically modulating welding voltage, keeping current and shielding gas constant, the fume composition and neurotoxicological properties of WF can be significantly altered. Rats were exposed by whole-body inhalation to filtered air or WF particulates generated by gas-metal arc-stainless steel welding (GMA-SS; 40 mg/m3; 3h/d x 10d) either at 25V (standard/low; LVSS) or at 30V (high; HVSS) voltage. Both conditions produced good weld quality and similar particulate morphology, although aerosols from HVSS welding comprised of a larger fraction of ultrafine particulates that are characteristically considered to be more toxic than their fine counterparts. Exposure to particulates from LVSS welding caused neuroinflammation (increased Ccl2, Tnfa, Nos2; 1.5 - 3.9 fold; P<0.05) and decreased PD-related proteins (Th, Park5, Park7; 18 - 47%; P<0.05) in the dopaminergic brain areas, striatum and midbrain. Paradoxically, exposure to particulates from HVSS welding did not elicit any dopaminergic neurotoxicity. We determined that the lack of neurotoxicity may be a consequence of the reduced solubility of manganese in HVSS fumes. Our findings show promise for modified welding practices as a potential prevention strategy for Mn-related neurotoxicity during welding; however, it warrants additional investigations to determine if such modifications can be suitably adapted at the workplace to avert or reduce neurological risks.
Toxicology; Exposure-levels; Chemical-composition; Workers; Work-environment; Humans; Men; Women; Environmental-exposure; Environmental-hazards; Environmental-health; Metal-compounds; Metallic-compounds; Toxins; Biomarkers; Animals; Laboratory-animals; Welding; Welders; Metal-compounds; Metallic-compounds; Metal-dusts; Metal-fumes; Aerosols; Aerosol-particles; Manganese-compounds; Nervous-system-disorders; Nervous-system-function; Neurotoxicity; Preventive-medicine
The Toxicologist. Society of Toxicology 53rd Annual Meeting and ToxExpo, March 23-27, 2014, Phonex, Arizona