CMTA questions health risk assessments

By CMTA Staff

Capitol Update, Oct. 6, 2006

CMTA will hold a meeting on October 17th at 10:00 am at its offices, 980 Ninth Street, Suite 2200, Sacramento, for those interested in the way California agencies treat mode-of-action data in conducting health risk assessments.  (See the background discussion below for more details on the issue.)
CMTA’s goal is to engage the Office of Environmental Health Hazard Assessment (OEHHA) in a process that will incorporate mode-of-action data in its risk assessments.  Such an outcome could have a significant impact on, for example, Proposition 65, the Toxic Air Contaminant program, the development of Public Health Goals for water contaminants, and permissible exposure levels for workers.  The preliminary strategy is to form an advisory group to organize and conduct a conference on the science behind this issue.  Joan Denton, Director of OEHHA, has already committed to working with the advisory group and to participating in the conference.  She has designated Lauren Zeise to serve on the advisory group. 

On the other hand, CMTA needs to determine whether industry supports this approach, and if so, who will serve on the advisory group and participate in the conference.  If you are interested and would like to attend this first meeting on Oct. 17th, please RSVP to Mike Rogge or 916-498-3313.

In recent years, new approaches to investigating the reasons for carcinogenic response have greatly advanced the understanding of why, how, and where tumors form.  Apart from simply identifying whether a substance may, or may not, cause cancer in animals or humans, scientists are increasingly able to narrow their understanding of the substance’s mode of action.  Some examples include the types of cells in which tumors form, the metabolites of a substance that may, or may not, be having a toxic effect, as well as numerous other nuances of the potential effects of a substance.
In instances where tumor effects from exposure to a particular substance are not seen in humans or rats, but are seen in mice bred specifically for susceptibility to tumor formation, new mode-of-action data can help determine if the location and nature of tumor development in mice is similar, or different, to the cell types, metabolism, and other aspects seen in rats or humans.  If the nature of the tumors seen in mice is not relevant to metabolic processes or cell types found in humans, the mode-of-action data may help to show that a finding of tumors in mice cannot be correlated to a potential human effect, and the occurrence of mouse tumors should not be used as a predictor of potential human effects.

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