Summary
The EPA IRIS chemical assessment for methylmercury (CASRN 22967-92-6) provides the US federal oral reference dose for methylmercury exposure, anchored on developmental neurotoxicity observed in cohort studies (the Faroe Islands and Seychelles cohorts). The IRIS RfD for methylmercury is 0.1 µg/kg body weight per day. Methylmercury is the dominant species in seafood and is the species addressed in the FDA/EPA fish consumption advice. The IRIS file is currently in step 1 of EPA’s reassessment process; the operative RfD remains the value derived in the 2001 assessment.
| Parameter | Value |
|---|---|
| CASRN | 22967-92-6 |
| Oral RfD | 0.1 µg MeHg/kg b.w./day (1 × 10⁻⁴ mg/kg/day) |
| Critical study | Faroe Islands cohort (Grandjean et al.); Seychelles cohort considered |
| Critical effect | Developmental neurotoxicity in offspring exposed in utero through maternal seafood consumption |
| Last revised | 2001-07-27 |
| Reassessment status | In step 1 (draft scoping) at IRIS |
Provenance notes
This source page is created from the file EPA_IRIS_Methylmercury_ToxReview.pdf. The companion file EPA_IRIS_InorganicMercury_ToxReview.pdf (SHA 88ffb70e) appears to contain the same methylmercury content despite its filename suggesting inorganic mercury; the InorganicMercury filename is misleading. Both files appear to be downloads of the same EPA IRIS methylmercury chemical assessment summary; only the Methylmercury-named file is treated as the source of record here.
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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 | 4 sections added; narrative text revised |