ABSTRACT
Arsenic in environment exists in different inorganic forms depending on their valence states. It is the type of As species that determines the bioavailability and toxicity of As. Arsenic toxicity is dependent on the chemical species of As as well as whether it is inorganic or organic. Arsenic serves as an active ingredient of various herbicides, insecticides, rodenticides, wood preservatives, animal feeds, dyes, and semiconductors. There are more than 200 arsenic-containing minerals formed in the high-temperature environment of earth’s crust. Arsenic also enters the biosphere and can be transferred through the food chain. Microorganisms adapted to function in As rich environments can achieve the As resistance by oxidizing uncharged As ions to As on the cell surface to avoid the passive uptake of As by aquaglycerolporins. Methylation of environmental As by conversion to soluble and gaseous methylated species is a detoxifying process that contributes to the global cycling of As.
