Monitoring of chromium and nickel in biological fluids of grinders grinding stainless steel

Abstract

Objective

Stainless steel (SS) welders usually spend some of their working time grinding, to finish and smoothen the welding groove. The aim of this study was to investigate possible relations between the concentrations of nickel (Ni) and chromium (Cr) in the work atmosphere generated by grinders grinding SS, and to compare the air levels to the levels of Cr and Ni in their biological fluids. Hereby, it might be possible to identify the contribution of grinding to the levels of Cr and Ni in biological fluids in SS welders. Also the airborne levels of Cr and Ni in SS grinders were compared to corresponding levels in SS welders.

Method/design

The subjects examined in this study were selected among SS grinders not performing welding. Nine grinders were monitored for 1 workweek, measuring Cr and Ni in air, blood and urine. They were questioned about their exposure to Cr and Ni during their working careers.

Results

Air levels of total Cr up to 95 μg/m³ and Ni levels up to 25 μg/m³ were measured. Chromium^VI (Cr^VI) was detectable only in five air samples; the levels in the remaining samples were below the detection limit. The levels of Cr in blood and urine were also low. The levels of Ni in urine were close to those for MMA and MIG/MAG SS welders. In spite of high levels of total Cr and Ni observed in air, the levels found in biological fluids were low. The Cr levels in more than 50% of the whole blood and red cell samples and about 1/3 of the Cr–plasma levels were below the detection limits. The mean blood levels for Cr were 0.43, 0.60 and 0.35 μg/l, in whole blood, plasma and red cells, respectively. The mean levels for Cr in the urine was 1.6, 1.4 and 1.4 μg/g creatinine for the first void, just before and just after work.

For Ni the mean blood levels were 0.87 μg/l in whole blood and 0.68 μg/l in plasma. The mean levels and ranges of Ni from the first void, just before and after work in urine were 3.79 μg/g creatinine, 3.39 and 4.56, respectively. The Cr concentrations found in whole blood, plasma and red cells were approximately the same as those found in the unexposed controls and among TIG SS welders, while the urinary levels were somewhat higher, but still lower than in the welders applying other welding techniques. The mean levels of Ni in the urine of grinders were higher than those of welders, except for SS welders welding the MIG/MAG-method.

Conclusion

SS Grinding seems not to contribute significantly to the uptake of Cr, which may be explained by the fact that most of Cr in the air is present in the metallic (0-valent) or trivalent form, and hardly any as Cr^VI, and therefore hardly being taken up in the airways. The grinders’ uptake of Ni seems to take place to the same extent as in SS welders.