Environmental Context. Arsenic occurs in rock, fresh water and seawater. Organic arsenic compounds are found as natural constituents of many organisms and, because some, e.g. seafood, are consumed by humans, there is ongoing health interest in their arsenic content. Thio-arsenicals, a newly discovered group of arsenic compounds, may be integral to understanding the environmental behaviour of arsenic. This paper reviews recent research in arsenic environmental chemistry and discusses ideas intended to stimulate future research in this area.

Abstract. Recent results in the field of arsenic environmental and biological chemistry are presented, in particular the relevance of the discoveries to issues of human health are discussed.