Welders in this study were selected from a vehicle manufacturer; control subjects were from a nearby food factory. Airborne manganese levels in the breathing zones of welders and controls were 1.45 ± SD1.08 mg/m 3 and 0.11 ± 0.07 μg/m 3 , respectively. Serum levels of manganese and iron in welders were 4.3-fold and 1.9-fold, respectively, higher than those of controls. Blood lead concentrations in welders increased 2.5-fold, whereas serum zinc levels decreased 1.2-fold, in comparison with controls. Linear regression revealed the lack of associations between blood levels of five metals and welder's age. Furthermore, welders had erythrocytic superoxide dismutase activity and serum malondialdehyde levels 24% less and 78% higher, respectively, than those of controls. These findings suggest that occupational exposure to welding fumes among welders disturbs the homeostasis of trace elements in systemic circulation and induces oxidative stress.The welding fume generated during the welding process possesses at least 13 metals, including manganese (Mn), beryllium (Be), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), mercury (Hg), molybdenum (Mo), nickel (Ni), zinc (Zn), antimony (Sb), and vanadium (V). 1 Welders are known to be at risk, particularly for chronic exposure to airborne manganese, which is one of the major coating materials in welding products (eg, bars and wires). [2][3][4][5][6] A recent study even suggests that exposure to manganese during welding may be a risk factor for the etiology of Parkinson's disease among the career welders. 7 Although limited studies have documented airborne manganese levels during welding, the question as to how low-level, long-term exposure to manganese or welding fume may affect blood levels of trace metals is unanswered. However, altered systemic homeostasis of iron and manganese is known to be associated with neurodegenerative disorders. 8 Manganese-induced neurological lesions are reportedly located in the globus pallidus and striatum of the basal ganglia. The pallidus and striatum display a marked decrease in myelinated nerve fibers, accompanied by depletion of striatal dopamine. [11][12][13][14] The mechanism whereby manganese induces neurodegenerative damage remains elusive. Nonetheless, several recent reports have suggested that manganese neurotoxicity may be associated with its interaction with other essential trace elements, including iron, 10,13,15,16 zinc, 17 copper, 17 and aluminum. 13,15,18 Particularly regarding manganese-induced neurotoxicity, studies have shown that chronic exposure to manganese appears to be associated with altered iron concentrations in blood as well as in the cerebrospinal fluid, presumably the result of Mn-Fe interaction at certain [Fe-S]-containing proteins, which regulate the homeostasis of iron. 10,16,[19][20][21] The excess accumulation of iron in neurons may consequently produce cellular oxidative stress, leading to neuronal damage.Superoxide dismutase (SOD), a cytoplasmic enzyme, catalyzes the react...

This study was performed to determine airborne manganese levels during welding practice and to establish the relationship between long-term, low-level exposure to manganese and altered serum concentrations of manganese, iron, and proteins associated with iron metabolism in career welders. Ninety-seven welders (average age of 36 years) who have engaged in electric arc weld in a vehicle manufacturer were recruited as the exposed group. Welders worked 7-8 h per day with employment duration of 1-33 years. Control subjects consisted of 91 employees (average age of 35 years) in the same factory but not in the welding profession. Ambient manganese levels in welders' breathing zone were the highest inside the vehicle (1.5 ± 0.7 mg/m 3 ), and the lowest in the center of the workshop (0.2 ± 0.05 mg/m 3 ). Since the filter size was 0.8 μm, it is possible that these values may be likely an underestimation of the true manganese levels. Serum levels of manganese and iron in welders were about three-fold (p < 0.01) and 1.2-fold (p < 0.01), respectively, higher than those of controls. Serum concentrations of ferritin and transferrin were increased among welders, while serum transferrin receptor levels were significantly decreased in comparison to controls. Linear regression analyses revealed a lack of association between serum levels of manganese and iron. However, serum concentrations of iron and ferritin were positively associated with years of welder experience (p < 0.05). Moreover, serum transferrin receptor levels were inversely associated with serum manganese concentrations (p < 0.05). These findings suggest that exposure to welding fume among welders disturbs serum homeostasis of manganese, iron, and the proteins associated with iron metabolism. Serum manganese may serve as a reasonable biomarker for assessment of recent exposure to airborne manganese.