Biomarkers of manganese exposure in Bay Bridge welders.
Gwiazda-R; Roels-HA; Park-R; Bowler-R; Lucchini-R; Smith-D
Toxicologist 2006 Mar; 90(1):38-39
Occupational exposure to manganese (Mn) is associated with emotional disturbances and subtle motor dysfunction. Identification of biomarkers of exposure and effect are critical for the detection of individuals at risk from elevated occupational and environmental Mn exposures. We investigated potential biomarkers of exposure in welders exposed in the construction of a section of Bay Bridge across the San Francisco Bay. Welders working in confined spaces in cofferdams were exposed to fumes with high Mn content (mean:0.209 mg/m3) for an average duration of 15 months, usually without respiratory protection. Cumulative inhaled Mn was calculated based on the amount of time each worker spent using different welding devices and the mean air Mn concentration near each device. Blood manganese concentrations (mean 9.57 ug/L, range: 5.13-14.15 ug/L, n=42) were significantly correlated with cumulative inhaled Mn (p<0.01), but plasma and urine Mn were not. No association was found between blood Mn concentration and average air Mn levels. Because Mn in plasma was relatively invariant at 0.58 +/- 0.13 ug/L over the whole range of blood Mn concentrations, the fraction of Mn in plasma was inversely correlated with blood Mn and ranged between 9 and 2.5% of whole blood Mn. In an animal study conducted to evaluate biomarkers of exposure, the concentration of Mn in plasma in Sprague-Dawley rats exposed i.p. 3 times/wk to MnCl2 for 15 weeks was also invariant over the same range of whole blood Mn concentrations observed in the welders. However, the fraction of Mn in rat plasma varied from 20 to 50% of total blood Mn content, indicating a larger plasma Mn binding capacity in rats' blood than in human blood. These results indicate that in the case of inhalation exposure to the respirable aerosol fraction (more than 90% in welding fumes) blood Mn concentration is a more suitable biomarker of cumulative Mn exposure, than plasma or urine Mn concentration.
Manganese-compounds; Biomarkers; Welding; Welders; Occupational-exposure; Environmental-exposure; Construction; Construction-industry; Construction-workers; Fumes; Fumigants; Exposure-levels; Exposure-assessment
The Toxicologist. Society of Toxicology 45th Annual Meeting and ToxExpo, March 5-9, 2006, San Diego, California