0141752 



6.0 APPENDIX 

 6.1 Toxicology Mechanisms of Metals for Livestock 



6.1.1 Arsenic toxicology 



Arsenic is second only to lead for heavy metal poisoning of 

 domestic livestock (Sahli 1982, Buck et al. 1976). Arsenic 

 intoxication can occur through inhalation or ingestion of arsenic 

 bearing compounds. The trivalent forms of arsenic are generally 

 more toxic than are pentavalent forms (Franke and Moxon 1936) and 

 inorganic compounds are generally more toxic than organic forms 

 (Savchuck et al . 1960). The most common means of arsenic poison- 

 ing is through ingestion of contaminated food and the most 

 affected livestock are cattle, sheep, and horses (Sahli 1982, 

 Selby et al. 1977). Arsenic poisoning in livestock by inhalation 

 of arsenic compounds is not well documented. 



Absorption of arsenic is dependent upon the means of exposure 

 (inhalation or ingestion), the form of arsenic, the species of 

 animal, and the condition of the animal. Soluble forms such as 

 sodium arsenite are readily absorbed by all body surfaces but less 

 soluble forms such as arsenic trioxide are not as well absorbed 

 and are partially eliminated by excretion in the feces (Buck et 

 al. 1976). Less than 10 percent of the usually soluble forms 

 appear in the feces (NRC 1980). Absorbed arsenic is transported 

 via the blood to most body tissues. In peracute, acute, or 

 subacute poisoning, arsenic tends to accumulate in the liver and 

 kidneys, with levels of 2 to 100 ppm (wet weight) found in these 

 organs in dying animals. High levels have also been observed in 

 skin tissues, hair, and spleen. Absorbed arsenic compounds are 

 generally excreted via urine, with lesser amounts in milk and 

 feces (Peoples 1964, Lakso and Peoples 1975, Shar iatpanahi and 

 Anderson 1984a). Bennett and Schwartz (1971) found that a 

 considerable portion of arsenic from lead arsenate fed to sheep 

 was excreted in feces within 3 to 7 days. Phenylarsonic compounds 

 are generally excreted rapidly by the urinary system in domestic 

 animals, with 50 to 75 percent excreted within one day and the 



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