The Chemical Mixture Methodology using Health Code Numbers
The Chemical Mixture Methodology (CMM) provides recommended default emergency exposure guidelines for mixtures of chemicals. The CMM makes extensive use of Health Code Numbers (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. To use the CMM, download the CMM workbook and carefully review the CMM user’s guide.
The latest version of the Chemical Mixture Methodology Workbook (“CMM Revision 25”; October, 2009) is available for use. This version includes HCNs for every chemical in PAC Rev 25 with the exception of ten biotoxins compounds that have been temporarily removed from the CMM workbook (a revision in the procedure for the development of HCNs for biotoxins is under consideration).
A User's Guide for the Chemical Mixture Methodology (“CMM Revision 25”; October, 2009) explains how to use this CMM workbook. This includes an explanation on how the CMM uses chemical concentration information, PAC data, and HCN values to compute hazard indices to support emergency preparedness decision making.
A summary technical description of the CMM and HCNs are provided in the CMM and HCN background information webpage.
The CMM Development Team
Rocky Petrocchi is the leader of the CMM development team. Dr's. Xiao-Ying Yu and Jayne-Anne Bond provide technical support. Donna Trott has developed HCNs for many hundreds of new chemicals in the CMM data set and has improved the HCN development process. Phil Bouslaugh has performed HCN reviews and updates for many of the chemicals that were first added to the CMM data set prior to 2001. Doug Craig is the original developer of the CMM and remains a creative force on the development team. Cliff Glantz addresses workbook usability issues and plays an active role in updating the CMM User’s Guide. Vern McDougall provides project management support for many CMM activities.
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Rocky Petrocchi |
Xiao-Ying Yu |
Jayne-Anne Bond |
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Donna Trott |
Philip Bouslaugh |
The CMM team's activities are guided by the TEEL Advisory Group (TAG). The TAG is chaired by Tom Tuccinardi. The TAG is sponsored by Jim Fairobent and Dave Freshwater from DOE/NA-41. Members include Cliff Glantz (SCAPA Chair), Doug Craig, Rocky Petrocchi, Po-Yung Lu, Xiao-Ying Yu, Jayne-Anne Bond, and Richard Thomas.
Updates to the CMM Data Set
CMM Revision 25 is up-to-date and compatible with PAC Rev 25. Prior to the release of CMM Rev 24, the CMM workbook was at least one revision or more behind the PAC data set. In other words, previous CMM workbooks provided HCNs for hundreds of fewer chemicals than were included in the then-current PAC data set. The present plan is for SCAPA to develop and publish a compatible revision of the CMM workbook within weeks of the publication of a new revision of the PAC data set. Based on past history, a major revision of the CMM workbook should be expected every year or so to accommodate the addition of new chemicals to the PAC data set and incorporate updates to HCNs.
Because of ongoing revisions to the HCNs and PAC data in the CMM, users of the CMM may wish to periodically review past CMM analyses for their key facilities or accident scenarios. In many cases, updated information will reduce over-conservatism in previous analyses. However, in some cases updated information may warrant more stringent emergency preparedness actions.
Need HCN's for a New Chemical?
Please complete and submit this form: Word format | PDF format
If a chemical of interest is not in the PAC or CMM data sets, please complete this form and e-mail it to the contacts listed at the bottom of the form. Requested chemicals will be added to a list that is prioritized for PAC and HCN development. Chemicals of critical importance can be given immediate attention.
Questioning an Existing HCN Value?
Please complete and submit this form: Word format | PDF format
If you have a problem with an existing HCN value (e.g., a HCN number is not given for a target organ you believe is impacted by the chemical), please document your concerns in this form and e-mail it to the contacts listed at the bottom of the form.
For Further Information...
For further inquiries about the CMM, please send an e-mail the PAC/TEEL Development Team.