Inorganic arsenic

Inorganic arsenic is a group of arsenic compounds in which arsenic is combined with elements such as oxygen, chlorine, or sulfur, rather than forming the carbon-containing compounds classified as organic arsenic. Arsenic itself is a naturally occurring element found throughout the Earth's crust. The word “inorganic” identifies its chemical form, not whether its source is natural or industrial .¹

This distinction matters because arsenic compounds differ in toxicity. Inorganic arsenic is highly toxic, whereas common organic forms in seafood, such as arsenobetaine, are much less harmful. A measurement described simply as total arsenic combines different forms and therefore does not, by itself, establish how much inorganic arsenic is present. The chemical form is an essential part of interpreting an arsenic measurement .¹

Inorganic arsenic can enter drinking water from geological sources and can also reach foods through contaminated soil or water. Long-term exposure through drinking water and food can cause chronic poisoning, and inorganic arsenic is a recognized human carcinogen .²