Blood and urinary concentrations as estimators of cobalt exposure

Methods for determining low levels of cobalt in blood and urine within a normal range have been developed. Mineralizing by using small amounts of nitric acid, ion exchange separation, and electrothermal atomic absorption measurements are the techniques used. The normal content of cobalt is 8.5 nmol/L (range 1.7-20.4 nmol/L) in blood and 6.8 nmol/L (range 1.7-37.3 nmol/L) in urine in a nonoccupational cobalt-exposed group. After exposure, cobalt is excreted rapidly in urine. When exposure is relatively high, there is rapid continuous decrease in excretion for about 24 hr followed by a slower excretion phase. When exposure is low, the excretion of cobalt in urine is relatively constant but may be 4-10 times higher than in non-exposed persons. The slow excretion can continue at least 4 wk after exposure. Variations of cobalt concentrations in blood are smaller but follow the exposure. When blood and urine concentrations of cobalt were compared on a Friday afternoon, the correlation coefficient was 0.82. When the average exposure to cobalt for the whole week was compared with the cobalt concentration in urine, the correlation coefficient on Friday afternoon was 0.79 and on Monday morning 0.81. For blood, the correlation coefficient was 0.87 on Friday afternoon and 0.76 on Monday morning.