Arsenic is also used in many industrial processes and has previously been used as an agricultural pesticide. There are known around 40 different forms of arsenic. Arsenic trioxide, the best characterized form of arsenic, is an inorganic compound with a high toxicity level. Marine fish contains more than ten different chemical forms of arsenic, and the majority of these are organic compounds, which are non-toxic.
Inorganic arsenic compounds such as arsenic trioxide are carcinogenic and also affect our nervous system. In the marine environment, there are organic forms of arsenic that are water-soluble. The main compound in fish and other types of seafood is arsenobetaine, which is a non-toxic form of arsenic. Humans absorb arsenobetaine, but excrete it unchanged.
The most important sources of inorganic arsenic in our diet are rice and other grain products. A maximum limit has not yet been set for arsenic in food products, or for the tolerable weekly intake of arsenic. The previously stipulated values have been withdrawn by EFSA and JECFA, because there no lower exposure limit determined that can be declared to be absolutely safe.
Maximum content in fish feed
In fish feed, arsenic mainly occurs as arsenobetaine. The maximum content for total arsenic in fish feed is 10 milligrams per kilogram, regardless of the chemical form. The maximum content for arsenic in fish feed has not been exceeded in recent years. Both arsenobetaine and arsenolipids is probably absorbed by fish and not excreted to any significant extent. The transfer from the feed to the environment is therefore insignificant.