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This contribution responds to the recent paper of Thun et al. (American Journal of Industrial Medicine 20:629-642, 1991) on an occupational standard for cadmium. The contribution of non-invasive in situ measurements of cadmium in liver and in kidney to the study of cadmium industrial toxicology is particularly reviewed. It is contended that clear scientific grounds do not exist for recommending cadmium in air occupational standard below 10 micrograms m-3, and that other arguments would need to be adduced to support a recommendation for a lower level. Last, a number of unanswered questions are identified and the need for further work is highlighted.

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).

The primary objective of this study was to evaluate the cadmium (Cd) levels measured in scalp hair as a potential predictive index of the body burden of Cd. In vivo measurements of kidney and liver Cd along with hair, blood, and urine Cd levels were obtained in 29 industrially-exposed workers and ten control subjects. The relationship of hair Cd levels to the Cd values for the kidney, liver, blood, and urine were tested using nonparametric analyses. In the control group no statistically significant correlations were found. In the Cd-exposed workers with more than one year of employment there were weak correlations (p approximately equal to 0.05); however, the relationships were not sufficiently quantitative for predicting the status of an individual worker. Furthermore, when workers with less than one year of exposure were included in the analysis, no significant correlations were obtained. Although this latter group of workers had low body burdens of Cd, exceptionally high Cd concentrations were found in their hair--an observation that was unexpected. It was concluded that hair Cd levels are not a good index of body burden of Cd in the industrially-exposed individual.