Summary
This 2021 review by David J. Thomas (US EPA, Experimental Toxicokinetics and Toxicodynamics Branch) synthesizes 30 years of research on the biological methylation of inorganic arsenic to mono- and dimethylated arsenic species (MMA and DMA) in mammals. The review covers the AS3MT methyltransferase enzyme that catalyzes arsenic biomethylation, the toxicokinetic and toxicodynamic implications of methylation (long debated as detoxification versus toxification of arsenic), inter-individual variation in methylation efficiency, and the relationship between methylation patterns and disease risk (particularly cancer and cardiovascular outcomes). The methylation chemistry is foundational for understanding why arsenic exposure-disease relationships vary across populations and why biomarker-based exposure assessment for inorganic arsenic must distinguish methylated species from inorganic precursors.
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Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 3 sections added; narrative text revised |