The enigma of environmental organoarsenicals: Insights and implications

Abstract

Over 300 species of naturally occurring-organoarsenicals have been identified with the development of modern analytical techniques. Why there so many environmental organoarsenicals exist is a real enigma. Are they protective or harmful? Or are they simply by-products of existing pathways for non-arsenical compounds? Fundamental unanswered questions exist about their occurrence, prevalence and fate in the environment, metabolisms, toxicology and biological functions. This review focuses on possible answers. As a beginning, we classified them into two categories: water-soluble and lipid-soluble organoarsenicals (arsenolipids). Continual improvements in analytical techniques will lead to identification of additional organoarsenicals. In this review, we enumerate identified environmental organoarsenicals and speculate about their pathways of synthesis and degradation based on structural data and previous studies. Organoarsenicals are frequently considered to be nontoxic, yet trivalent methylarsenicals, synthetic aromatic arsenicals and some pentavalent arsenic-containing compounds have been shown to be highly toxic. The biological functions of some organoarsenicals have been defined. For example, arsenobetaine acts as an osmolyte, and membrane arsenolipids have a phosphate-sparing role under phosphate-limited conditions. However, the toxicological properties and biological functions of most organoarsenicals are largely unknown. The objective of this review is to summarize the toxicological and physiological properties and to provide novel insights into future studies.

Graphical abstract

Keywords:

• Arsenic;
• arsenolipids
• arsenic toxicity
• physiological functions of organoarsenicals
• water-soluble organoarsenicals

Handling Editors:

• Albert Juhasz and Lena Ma

Additional information

Funding

Our research was supported by the National Natural Science Foundation of China (42077289 and 41877422), grants GM136211 and GM055425 from the U.S. National Institutes of Health to BPR and BIO/MCB Grant 1817962 from the U.S. National Science Foundation to MY.