Methylmercury (MeHg) CASRN 22967-92-6 | IRIS

IRIS

Methylmercury (MeHg)

CASRN 22967-92-6 | DTXSID9024198

IRIS Summary (PDF) (44 pp, 258 K)
Status: Methylmercury (MeHg) is in step 1 at this time; see Quick Check.

Noncancer Assessment

Reference Dose for Oral Exposure (RfD) (PDF) (44 pp, 258 K) Last Updated: 07/27/2001

System	RfD (mg/kg-day)	Basis	PoD	Composite UF	Confidence
Nervous, Developmental	1 x 10 ^-4 (High end of BMDL05 range)	Developmental neuropsychological impairment	BMDL ₅ : 1.5 x 10^-3 mg/kg-day	10	High
Nervous, Developmental	1 x 10 ^-4 (Low end of BMDL05 range)	Developmental neuropsychological impairment	BMDL ₅ : 8.6 x 10^-4 mg/kg-day	10	High

Reference Concentration for Inhalation Exposure (RfC) (PDF) (44 pp, 258 K)
Not assessed under the IRIS Program.

Cancer Assessment

Weight of Evidence for Cancer (PDF) (44 pp, 258 K) Last Updated: 05/01/1995

WOE Characterization	Framework for WOE Characterization
C (Possible human carcinogen)	Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1986)

Basis:

Based on inadequate data in humans and limited evidence of carcinogenicity in animals. Male ICR and B6C3F1 mice exposed to methylmercuric chloride in the diet had an increased incidence of renal adenomas, adenocarcinomas and carcinomas. The tumors were observed at a single site and in a single species and single sex. The renal epithelial cell hyperplasia and tumors were observed only in the presence of profound nephrotoxicity and were suggested to be a consequence of reparative changes in the cells. Several nonpositive cancer bioassays were also reported. Although genotoxicity test data suggest that methylmercury is capable of producing chromosomal and nuclear damage, there are also nonpositive genotoxicity data.
This may be a synopsis of the full weight-of-evidence narrative.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure (PDF) (44 pp, 258 K)

Not assessed under the IRIS Program.

Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure (PDF) (44 pp, 258 K)

Not assessed under the IRIS Program.

Program Outlook Details

Public Assessment Materials	Date
Problem Formulation Materials/IRIS Assessment Plan	Apr-2019
Preliminary Assessment Materials/Systematic Review Protocol	May-2020
Public Comment	TBD
External Peer Review	TBD
Post Final Assessment	TBD

Note: Any future dates displayed in the table above should be considered estimates and are subject to change. Once the external peer review is complete, estimated dates for release of the final assessment will be published. For the latest information on the status of this assessment, please refer to the IRIS Program Outlook. To access assessment documents, meeting materials or other supporting documents related to this assessment, visit the Chemical Documents tab. For more information about the development process, visit the IRIS Process page.

May 2020: Systematic Review Protocol for the Methylmercury (MeHg) IRIS Assessment (Preliminary Assessment Materials) (Report)

Apr 2019: IRIS Assessment Plan for Methylmercury (Scoping and Problem Formulation Materials) (Report)

Jan 2001: IRIS Summary Update (2001) and EPA Guidelines for Methylmercury (2009 & 2010) (Other)

Oct 2000: Reference Dose for Methylmercury (External Review Draft, 2000) (Report)

Additional EPA toxicity information may be available by visiting the following sites:

Human Health Benchmarks for Pesticides (HHBP). This database provides human health benchmarks for pesticides that may be present in drinking water.
Office of Pesticide Programs Pesticide Chemical Search. This database provides links to health effects information and registration status for pesticides.
Chemistry Dashboard. This database provides information on chemical structures, experimental and predicted physicochemical, and toxicity data.

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

Quick Check

US EPA

IRIS