The bioavailability of manganese in welders in relation to its solubility in welding fumes

Blood and urine samples for determination of manganese (Mn) and iron (Fe) concentrations were collected in a cross-sectional study of 137 currently exposed welders, 137 referents and 34 former welders. Aerosol samples for measurements of personal air exposure to Mn and Fe were also collected. The aerosol samples were assessed for their solubility using a simulated lung lining fluid (Hatch solution). On average 13.8% of the total Mn mass (range 1–49%; N = 237) was soluble (Hatchsol), while only 1.4% (<0.1–10.0%; N = 237) of the total Fe mass was Hatchsol. The welders had statistically significantly higher geometric mean concentrations of Mn in whole blood (B-Mn 12.8 vs. 8.0 μg L−1), serum (S-Mn 1.04 vs. 0.77 μg L−1) and urine (U-Mn 0.36 vs. 0.07 μg g−1 cr.) than the referents. Statistically significant univariate correlations were observed between exposure to Hatchsol Mn in the welding aerosol and B-Mn, S-Mn and U-Mn respectively. Pearson's correlation coefficient between mean Hatchsol Mn of two days preceding the collection of biological samples and U-Mn was 0.46 (p < 0.001). The duration of employment as a welder in years was also associated with B-Mn and S-Mn, but not with U-Mn. Statistically significantly higher U-Mn and B-Mn...