Uptake, distribution and elimination of monosodium methanearsonate following long term oral administration of the herbicide to sheep and goats

Abstract

The herbicide monosodium methanearsonate is used for weed control on many crops. These crops are a potential source of toxicity to herbivores. The rate and extent of accumulation and washout of As during daily oral administration of MSMA were evaluated in Iranian dairy sheep and goats. Subjects received 10 mg MSMA as As/kg body wt daily for 28 consecutive days. The total As concentration in blood and milk was measured during and after the period of MSMA administration while As in urine and feces was measured for 10 days following administration of the last dosage of MSMA. As was accumulated slowly during 28 days of MSMA administration and steady states were essentially complete in sheep after 20 days and in goats following 25 days of MSMA administration. Blood As concentration decreased rapidly after termination of MSMA administration. In both test animals, the half-lives of washout were smaller than accumulation. The concentration of As in the urine and feces of both species did not increase significantly over controls and animals were free of As relatively shortly after administration stopped. As from MSMA was mainly absorbed from gastrointestinal tract and was not significantly accumulated in the body. As was eliminated from body by way of urine and feces with urinary excretion being the most important route.