Urinary excretion of chromium as an indicator of exposure to various chromium forms in MMA/SS welders

Increased levels of Cr discharged with urine after working shift, Cr-U (arithmetic mean 15.8 mu g/g creatinine), and Cr buildup during working shift, DeltaCr-U (arithmetic mean 3.8 mu g/g creatinine), were observed in 15 MMA/SS welders exposed during the working week to welding fumes containing Cr VI (33-56%) - mainly soluble (87%) and Cr III (44-67%) - mainly insoluble (72%). The highest correlation coefficients were obtained for DeltaCr-U vs. Cr total (r = 0.58), Cr VI (r = 0.56) and soluble Cr III in the air. Increased DeltaCr-U value for exposures at MAC Cr VI (16.8 mu g/g creatinine) was demonstrated in welders employed longer than 7 years and exposed to Cr VI below MAC level, which might suggest that the duration of employment affects that value within the low range of concentration of Cr VI in the air (< 0.03 mg/m3). Nevertheless, linear relationship between DeltaCr-U for exposures to Cr VI at MAC levels and duration of employment was not confirmed for wide range of air Cr VI (0.005-0.4 mg/m3). Similar DeltaCr-U values at MAC for Cr VI (6.4 and 6.6 mu g/g creatinine) were obtained for all welders, and those employed over 7 years, respectively, which may suggest that this parameter can be misleading.