CASRN 95-63-6

IRIS Toxicological Review of Trimethylbenzenes (Revised External Review Draft)

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In August 2013, EPA submitted a revised draft IRIS assessment of trimethylbenzenes to the agency's Science Advisory Board (SAB) and posted this draft on the IRIS website. EPA had previously released a draft of the assessment for public comment, held a public meeting about the draft, and then revised it based on the comments received. The SAB CAAC-Trimethylbenzenes panel will review this draft assessment. Details about the meeting dates, times, and location are available via the Federal Register Notice posted on March 25, 2014. The SAB provided information on how the public can participate in the external peer review meetings, as well as instructions about how to provide comments to the SAB in the notice. Additional information on the SAB review of trimethylbenzenes is on the SAB website.

Report Information: The Toxicological Review of Trimethylbenzenes was originally released for a 60-day public comment period on June 29, 2012. [Federal Register Notice Jun 29, 2012] EPA revised the toxicological review in response to the public comments received. EPA has released the revised external review draft trimethylbenzenes assessment and the SAB CAAC is conducting a peer review of the scientific basis supporting the assessment that will appear in the Integrated Risk Information System (IRIS) database. Information regarding the peer review can be found at the SAB review of trimethylbenzene website.


U.S. EPA. IRIS Toxicological Review of Trimethylbenzenes (Revised External Review Draft). U.S. Environmental Protection Agency, Washington, DC, EPA/635/R-13/171, 2013.


J. Allen Davis,  Ph:  513-569-7024,  Email:

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Trimethylbenzenes (TMB) are a mixture of three isomers: 1,2,3-, 1,2,4- and 1,3,5-TMB. TMBs are produced during petroleum refining, and 1,2,4-TMB makes up approximately 40% of a certain petroleum product (the C9 fraction) which is used as a component of gasoline. Because of this, vehicle emissions are a major source of TMBs. Other uses of TMBs include solvents in research and industry, dyestuff intermediate, paint thinner, and as a UV oxidation stabilizer for plastics.


Date Description
Feb 2012EPA hosted an interagency science consultation meeting on the review of the draft Toxicological Review of Trimethylbenzenes.
May 2012EPA sent an abbreviated version of the toxicological review containing only information on 1,2,3-trimethylbenzene for interagency science consultation at the recommendation of reviewers.
Jun 2012EPA released the external peer review draft of the trimethylbenzenes assessment for public review and comment. Additionally, the interagency science consultation draft, comments from reviewers, and EPA’s responses to selected major interagency comments were also released (see "related links"). [Federal Register Notice June 29, 2012]
Aug 2013EPA’s Science Advisory Board (SAB) announced a request for nominations for experts to augment the SAB Chemical Assessment Advisory Committee (CAAC) for the review of the EPA’s draft IRIS assessment for trimethylbenzenes. [Federal Register Notice Aug 28, 2013](3pp., 210KB, about PDF), and made available the revised external review draft assessment and draft charge to peer reviewers.
Jan 2014EPA’s SAB announced a 3-day public peer review meeting for the draft IRIS Toxicological Review of Trimethylbenzenes for Feb 18-20, 2014. [Federal Register Notice Jan 31, 2014]
Feb 2014To provide the public with additional time to prepare, EPA SAB staff office is rescheduling the February 18-20 meeting of the SAB Chemical Assessment Advisory Committee (CAAC). The EPA SAB staff office will announce a new date in the near future.
Mar 2014EPA's SAB Staff Office has announced two meetings for the SAB CAAC-Trimethylbenzenes panel for the review of the draft IRIS assessment of trimethylbenzenes. A public teleconference is scheduled for May 22, 2014. A face-to face panel meeting is scheduled for June 17-19, 2014 in Arlington, VA. [Federal Register Notice Mar 25, 2014]
Mar 2014EPA updated the peer review charge to include a question regarding EPA's assessment revisions and response to public comments.
May 2014EPA's SAB posted the agenda to the public teleconference meeting that will take place on May 22, 2014. See the SAB site for details.


EPA’s SAB will hold two meetings in May and June 2014 for the external peer review of the trimethylbenzenes IRIS assessment. Information on the peer review can be found at the SAB Trimethylbenzenes website. Following external peer review, the assessment will be revised taking into consideration the comments received. It will then undergo a final internal review by EPA, and other federal agencies and the Executive Office of the President. After completing this review it will be posted to the IRIS database.

Additional Information

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