In vivo measurement of critical level of kidney cadmium: dose effect studies in cadmium smelter workers.

In vivo measurements of kidney and liver cadmium burdens were obtained in 82 industrially exposed workers and ten control subjects. Kidney cadmium levels ranged from 0.9 mg to 57 mg, and liver concentrations ranged from 0.8 ppm to 120 ppm for the industrial group. Comparison values for the control group were 0.4 mg to 11.8 mg for the kidney and 0.6 ppm to 7.9 ppm for the liver. A biphasic relationship between kidney Cd levels and liver Cd levels was observed. The kidney and liver Cd levels showed an increase until approximately a 40 ppm concentration was reached in the liver. Thereafter, the kidney levels decreased as the liver concentration continued to increase. The kidney cadmium level at which this change occurred was approximately 31 mg for the total kidney. Further estimates of the critical level, based on years of exposure and renal dysfunction (beta 2-microglobulin, proteinuria), yielded estimates of 31 mg to 42 mg cadmium (300-400 micrograms/gm for the renal cortex).