On the bio-accessibility of 14 elements in welding fumes

The bio-accessibility of 14 elements in welding fume particulate matter was investigated in 325 personal air samples collected during welding in two shipyards and one factory producing heavy machinery. The apparent solubility in a synthetic lung lining fluid (Hatch's solution) was used as proxy for the bio-accessibility. The Hatch solubility of the different elements was highly variable with a median < 1% for Al, Fe, Pb, Ti, between 4 and 6% for Co, Cr, Ni, V, W, between 13 and 27% for Cd, Cu, Mn, Zn, and 41% for Mo. For many elements, the solubility varied over a wide range of several tens of percent. The welding techniques used influenced the solubility of Co, Cr, Cu, Mn and V significantly. The plants investigated (i.e., the welded materials and used electrodes) had a significant influence on the solubility of Co, Cr, Cu, Mn, Mo, V and W. According to principal component analysis (PCA), the variation in solubility can be described by four components, which explain 69% of the variance. The first principal component mostly comprises elements that can predominantly occur as divalent cations, the second principal component elements often forming oxyanions. The principal components are independent of the absolute value of the Hatch solubility. The results of PCA indicate that the co-variation of Hatch solubility is mainly controlled by the most soluble compounds in contrast to the absolute value of apparent solubility, which is strongly influenced by the distribution of the elements between compounds with different equilibrium solubilities. The observed large variability and the significant differences between welding techniques and plants clearly show that the bio-accessibility cannot be obtained from the literature but has to be studied experimentally at each location of interest.

Biological monitoring of welders' exposure to chromium, molybdenum, tungsten and vanadium

BACKGROUND

Welders are exposed to a number of metallic elements during work. Bioaccessability, that is important for element uptake, has been little studied. This study addresses bioaccessability and uptake of chromium (Cr), molybdenum (Mo), tungsten (W) and vanadium (V) among welders.

METHODS

Bioaccessability of Cr, Mo, V and W was studied in airborne particulate matter collected by personal sampling of the workroom air among shipyard welders by using the lung lining fluid simulant Hatch solution. Associations between concentrations of Hatch soluble and non-soluble elements (Hatch_sol and Hatch_non-sol) and concentrations of the four elements in whole blood, serum, blood cells and urine were studied.

RESULTS

Air concentrations of the four elements were low. Only a small fraction of Cr, V and W was Hatch_sol, while similar amounts of Mo were Hatch_sol and Hatch_non-sol. Welders (N=70) had statistically significantly higher concentrations of all four elements in urine and serum when compared to referents (N=74). Highly statistically significant associations were observed between urinary W and Hatch_sol W (p<0.001) and serum V and Hatch_sol V (p<0.001), in particular when air samples collected the day before collection of biological samples were considered.

CONCLUSIONS

Associations between Hatch_sol elements in air and their biological concentrations were higher than when Hatch_non-sol concentrations were considered. Associations were generally higher when air samples collected the day before biological sampling were considered as compared to air samples collected two days before.

Biomarkers of iron status and trace elements in welders

Iron status was studied in 137 welders exposed to a geometric mean (GM) air concentration of 214 μg/m(3) (range 1-3230) of manganese (Mn), in 137 referents and in 34 former welders. The GM concentrations of S-ferritin were 119 (3-1498), 112 (9-1277) and 98 (12-989) μg/L (p=0.24) in the three groups, respectively. Also the GM concentrations of S-hepcidin were not significantly different between the groups (8.4 μg/L (2.8-117); 6.6 μg/L (1.8-100); 6.5 μg/L (1.2-22)) (p=0.22). Multiple linear regression analysis including all welders and referents showed an increase in the concentration of S-ferritin associated with having serum carbohydrate deficient transferrin (S-CDT) above the upper reference limit of ≥1.7%, indicating high alcohol consumption. Serum C-reactive protein was not associated with exposure as welders, but an association with S-ferritin was shown. The GM S-ferritin concentrations among all welders and referents with S-CDT≥1.7% were 157 μg/L (95% CI 113-218) as compared to 104 μg/L (95% CI 94-116) (p=0.02) in those with S-CDT<1.7%. The GM concentrations of Mn in biological fluids were higher in the welders as compared to the referents, while S-Fe, S-Co and B-Co were statistically significantly lower. This could suggest a competitive inhibition from Mn on the uptake of Fe and Co. Increasing concentrations of S-CDT was associated with higher S-Mn, S-Fe and B-Co in the multiple linear regression analysis. The association between S-CDT and S-Fe remained when all subjects with high S-CDT (≥1.7%) were excluded, suggesting increased uptake of Fe even at lower alcohol consumption.

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 (Hatch sol), while only 1.4% (<0.1-10.0%; N = 237) of the total Fe mass was Hatch sol. 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 Hatch sol Mn in the welding aerosol and B-Mn, S-Mn and U-Mn respectively. Pearson's correlation coefficient between mean Hatch sol 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 were observed in welders currently exposed to even less than 12 and 6 μg m (-3) Hatchsol Mn, respectively. When using the 95(th) percentile concentration among the referents as a cut-point, 70.0 and 64.5% of the most highly exposed welders exceeded this level with respect to B-Mn and U-Mn. The concentrations of B-Mn, S-Mn and U-Mn were all highly correlated in the welders, but not in the referents.

Air exposure assessment and biological monitoring of manganese and other major welding fume components in welders

In a cross-sectional study, 96 welders were compared with 96 control subjects. Also 27 former welders, all diagnosed as having manganism, were examined. Exposure to welding fumes was determined in the 96 welders, while the concentration of elements in whole blood and urine was determined in all subjects. The geometric mean (GM) concentrations of manganese (Mn) and iron in the workroom air were 97 microg m(-3) (range 3-4620 microg m(-3); n=188) and 894 microg m(-3) (range 106-20 300 microg m(-3); n=188), respectively. Thus the Mn concentration in the workroom air was on average 10.6% (GM) of that of the Fe concentration. No substantial difference was observed in the air Mn concentrations when welding mild steel as compared to welding stainless steel. The arithmetic mean (AM) concentration of Mn in whole blood (B-Mn) was about 25% higher in the welders compared to the controls (8.6 vs. 6.9 microg l(-1); p < 0.001), while the difference in the urinary Mn concentrations did not attain statistical significance. A Pearson's correlation coefficient of 0.31 (p < 0.01) was calculated between B-Mn and Mn in the workroom air that was collected the day before blood sampling. Although the exposure to welding fumes in the patients had ceased on average 5.8 years prior to the study (range 4 years-7 years), their AM B-Mn concentration was still higher than in referents of similar age (8.7 microg l(-1) vs. 7.0 microg l(-1)). However, their urinary concentrations of cobolt, iron and Mn were all statistically significantly lower.