Inorganic Arsenic: A Global Environmental Health Risk
Why are the Species of Arsenic Important?
Traditionally, most environmental or human health monitoring of arsenic has focused on the total concentration of all arsenic species; however, arsenic occurs in many forms, each with widely differing toxicity. The inorganic arsenic species As[III] and As[V] are by far the most toxic, and As[III] is about ten times more toxic than As[V] to mammals. Arsenate (As[V]) is the predominant form in most oxygenated waters. Two of the most common organoarsenic species are the methylated metabolites of inorganic arsenic, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), which are each at least 10-20 times less toxic than As[III]. Two other common organoarsenicals are arsenobetaine and arsenocholine, which are found in seafoods and seaweeds, and which are essentially non-toxic. Knowing the type and concentrations of arsenic species in a potential exposure source is crucial to understanding its potential toxicity.