TOXICOLOGICAL PROFILE FOR CHROMIUM - Davidborowski.com

CHROMIUM 2192. HEALTH EFFECTSHuman variability in plasma reduction capacity can influence the ratio between blood and urinarychromium levels (Korallus 1986a, 1986b). In vitro experiments indicate that when chromium(VI) plasmalevels exceed the plasma reduction capacity (PRC), chromium(VI) enters erythrocytes, is reduced, andbinds to hemoglobin. The bond persists for the lifetime of the erythrocytes (120 days); therefore, a singledetermination allows a longitudinal evaluation of exposure for an extended period in the past. Lowchromium concentrations in erythrocytes indicate that the amount of chromium(VI) uptake did not exceedthe PRC. The capacity of human plasma to reduce chromium(VI) compounds to chromium(III)compounds varies, with slow and fast reducers recognized (Korallus 1986a, 1986b). It is not clear what isresponsible for individual differences in the PRC, although difference in magnitude of PRC appears tocorrelate with the levels of ascorbic acid in plasma. The relationship between blood and urine chromiumlevels and air chromium trioxide concentrations in slow and fast reducers at the end of a 5-day shift at adichromate plant is shown in Figure 2-5. This figure indicates that individuals who reduce chromium(VI)compounds slowly have much higher blood chromium levels, while fast reducers have higher urinarychromium levels.A significant correlation (r=0.71) was found between exposure levels and postshift, urinary chromium inworkers exposed to chromium(VI) as chromium trioxide in the chrome plating industry. The urinarychromium level of 5.2 µg/L reflects a time-weighted average exposure of 0.002 mg chromium(VI)/m 3 .This correlation was obtained by excluding workers with obvious skin contamination (Lindberg andVesterberg 1983a).Examination of end-of-shift chromium levels indicated a correlation between urinary chromium levelsand exposure to soluble chromium(VI) compounds, but not to insoluble chromates or chromium(III)compounds (Minoia and Cavalleri 1988; Mutti et al. 1985b). The relationship between workroom airconcentrations of water soluble chromium(VI) compounds and daily increases in urinary chromium (preexposurevalues subtracted from end-of-shift values) are shown in Figure 2-6. An increase in urinarychromium of 12.2 µg/g creatinine above pre-exposure values or a total concentration of 29.8 µg/gcreatinine (end-of-shift values) corresponded to an air concentration of 50 µg chromium(VI)/m 3 fromwelding fumes (Mutti et al. 1985b).Serum and urine concentrations of chromium were significantly elevated in a group of 73 tanneryworkers, compared to a group of 52 control subjects, at the end of the workweek on Friday and beforeexposure began on Monday. Serum and urine chromium levels did not correlate with length of