0141754 



The rapid excretion of arsenic from the system in sublethal 

 doses prevents any large bioaccumulat ion of arsenic in livestock. 

 Selby (1974) recommended a 14 day market withholding time for a 

 single dose of arsenic and a 6 week period for multiple arsenic 

 exposure. These authors suggested that arsenic intoxicated cattle 

 "...usually will represent a minimal hazard to man as a food 

 source . " 



Although epidemiological studies have implicated arsenic as a 

 carcinogen in humans, no literature was found indicating similar 

 implications in domestic livestock. The average elapsed time from 

 the beginning of skin treatments with arsenic compounds (Fowler's 

 solution) to the development of ephi thel iomatous growth in humans 

 has averaged 18 years (NRC 1977). It is thus likely that similar 

 occurrences in livestock would not have sufficient time to 

 develop, and possible metabolic differences such as exhibited by 

 rats, may produce a different syndrome. 



6.1.2 Cadmium toxicology 



Uptake of cadmium by domestic livestock is generally re- 

 stricted to ingestion via contaminated food supplies or soil. 

 Natural inhalation of cadmium at levels necessary to produce 

 toxicosis in livestock is poorly documented. Cadmium poisoning 

 through inhalation has been limited to human subjects, usually 

 associated with industrial exposure. Cadmium contamination of 

 livestock food sources may occur from airborne fallout, which 

 accumulates on or in forage, or from excessive levels in forage 

 grown on contaminated soils. Two of the major sources of cadmium 

 contamination are from the land disposal of sewage sludge high in 

 heavy metals and from mining and smelting operations. It is 

 likely that most instances of cadmium poisoning in domestic 

 livestock (ruminants and horses) are the result of the ingestion 

 of contaminated feed. 



Absorption of cadmium is apparently not controlled by a 

 homeostatic mechanism and therefore accumulation of cadmium in the 

 body will occur regardless of the existing body burden or level of 

 intake (NRC 1980). Absorption through the gastrointestinal tract 



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