Arsenic occurs naturally in both organic (typically non-toxic) and inorganic forms. Inorganic arsenic is toxic and carcinogenic (cancer-causing). Arsenic is a naturally occurring element, found widely in the environment as an inorganic salt. Groundwater may flow through arsenic-containing bedrock or soil, contaminating drinking water drawn from wells. Past use of arsenic-containing pesticides and fertilizers may also contaminate fields where rice (which selectively absorbs arsenic) and apples are grown.^1,2

In addition to being naturally present in the environment, it has also been used for many years for industrial purposes, including pest control, animal antimicrobial treatment, wood preservation, petroleum refining, and in the mining/smelting industries. Most industrial uses of arsenic employ the more toxic inorganic forms. Release of arsenic through these processes can lead to increased inorganic arsenic in the atmosphere, in water, and in soil. Workers in industrial processes and communities near these industries may be exposed to arsenic from coal-fired power plants, hardening metal alloys, purifying industrial gases, and in the electronics industry in the form of gallium arsenide and arsine gas as components in semiconductor devices. Arsenic has been reported in imported folk or homeopathic remedies.³  

Although inorganic arsenic can cross the placenta, increasing the likelihood of exposure to the fetus, arsenic may be found, as noted above, in water and food. In addition to inorganic forms of arsenic, there are organic forms found in seafood (farm-raised and wild) that are generally
considered non-toxic.⁴