Abstract
The urinary elimination of the metabolites of arsenic has been followed up as a function of time in volunteers who ingested a single oral dose of arsenic (500 μg As) either as sodium arsenite (Asi), monomethylarsonate (MMA), or cacodylate (DMA). The excretion rate increased in the order Asi < DMA < MMA. After 4 days, the amount of arsenic excreted in urine represents 46, 78, and 75% of the ingested dose in the case of Asi, MMA and DMA, respectively. With regard to the in vivo biotransformations, it is concluded that DMA is excreted unchanged; MMA is slightly (13%) methylated into DMA while roughly 75% of the arsenic excreted after ingestion of Asi is methylated arsenic (about 1/3 as MMA and about 2/3 as DMA).