0141756 



..... : i 



1979). The cadmium metallothionein is thus maintained in the 

 kidneys. Cadmium then interferes with zinc in enzymes necessary 

 for reabsorption and catabolism of proteins, producing tubular 

 proteinuria. Development of proteinuria in humans takes a number 

 of years of chronic exposure (more than 10). High concentrations 

 of cadmium in kidneys of livestock fed cadmium in their diet 

 suggests that this condition will occur in domestic animals if the 

 exposure time is of sufficient duration. However, with the 

 possible exception of horses, it is unlikely that animals would be 

 maintained for such long periods, especially in large commercial 

 operations. 



Cadmium has been shown to decrease uptake of calcium by bone 

 in rats and chronic exposure via water and food in the presence of 

 a calcium deficient diet has been implicated in the development of 

 the Itai-Itai disease in humans. Osteoporosis has been observed 

 in horses and foals near a zinc smelter and has been attributed to 

 direct cadmium poisoning or "the result of a conditioned copper 

 deficiency associated with high intakes of zinc and cadmium" 

 (Gunson et al . 1982) . 



Studies of the effect of cadmium on the reproduction of 

 livestock strongly indicate a high incidence of abortions and 

 deformed offspring. A diet of 50 ppm cadmium succinate produced 

 dead and abnormal calves and lambs (Wright et al. 1977). Goats on 

 a diet of 75 ppm experienced 50 percent abortions, with no normal 

 young (Anke et al. 1970). 



The tendency of cadmium to accumulate in the kidney and liver 

 of livestock and the low rate of elimination from the body make 

 bioaccumulation of cadmium very important as a means of introduc- 

 ing this element into the human food chain. There is less danger, 

 however, from consumption of livestock muscle tissues which 

 accumulate very little cadmium (Table 12) . 



Available data strongly suggests carcinogenic effects of 

 cadmium on humans. Many studies involving subcutaneous injections 

 of cadmium chloride or other cadmium salts in rats have produced 

 sarcoma. Similar studies with oral ingestion of cadmium in rats 

 and mice did not suggest cadmium was carcinogenic in the doses 



155 



