November 2009

The DOE Office of Emergency Management (OEM) has issued the following Emergency Management Update relating to the release of Revision 25 of the Chemical Mixture Methodology Workbook. Using the Emergency Management Issues Special Interest Group (EMI SIG) Listserv, OEM periodically sends updates related to emergency management topics of interest.

Previous issues of updates are available on the EMI SIG website and on the Subcommittee on Consequence Assessment and Protective Actions (SCAPA) webpage. Generally, in cases where the subject requires more than one page of discussion, the update includes a summary discussion and links are provided for more detail.

Release of Revision 25 of the Chemical Mixture Method (CMM) Workbook

The new Chemical Mixture Method (CMM) Microsoft Excel Workbook, Revision 25, has been released and is available to download from The new version of the CMM workbook features Health Code Numbers (HCNs) for all of the 3,373 chemicals in the Protective Action Criteria (PAC) Revision 25 data set, including the 23 new chemicals added in PAC Rev 25. All of the PAC data incorporated into the CMM Rev 25 are fully compatible with PAC Rev 25.

The CMM provides recommended default emergency exposure guidelines for mixtures of chemicals. The CMM makes extensive use of HCNs to examine the additive impact that each chemical component in a chemical mixture may have on specific target organs. The CMM is a more realistic predictor of potential human health impacts than can be obtained using the (1) non-conservative method of separately analyzing the consequences of each chemical component or the (2) overly-conservative method of adding the exposures from each chemical together regardless of the human organ targeted by the chemical. The CMM is recommended by SCAPA for potential use in emergency planning hazards assessments (EPHAs), safety analyses, and in emergency response situations.

A newly updated CMM User’s Guide is also available to download on the CMM webpage. The User’s Guide includes detailed information such as how to use the CMM workbook, how it operates, and suggestions on how to interpret its results. Additional technical information on the CMM and HCNs are also available on the website, as is contact information for submitting questions and requests to the CMM development team.