**5. Effects on human**

The biological activity of arsenic in the body covers a broad spectrum from toxic to therapeutic agent. Not to forget- Arsenic is a human carcinogen (IARC 2004). A number of studies show that arsenic is an essential element for humans. Other studies have attempted to show that arsenic has not been demonstrated to be essential to humans (Ohtake 2000).

The major routes of arsenic absorption in the general population are ingestion and inhalation. Meat, fish and poultry account for 80 % of dietary arsenic intake (Edmonds and Francesconi 1987). Arsenic is absorbed in the small intestine by an electrogenic process involving a proton gradient. The absorbed arsenic undergoes hepatic biomethylation. The products are less toxic but not completely innocuous. About 50 % of the ingested dose may be eliminated in the urine in 3-5 days. Metabolism of As involves reduction of As V to a trivalent state and subsequent oxidative methylation.
