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Independent Peer Review 
Reference Dose Document on Resorcinol 

What:  Independent Peer Review for the RfD on Resorcinol
March 18-19, 2003  
University of Cincinnati , Kingsgate Conference Center , Cincinnati , OH  

An independent panel of expert scientists met in Cincinnati to provide a comprehensive overall review of a risk assessment on the development of a reference dose (RfD) for resorcinol. AMEC Earth and Environmental, Inc. wrote the assessment for the sponsor, Beazer East, Inc.  Beazer East, Inc. was formerly known as Koppers Company, Inc. prior to 1988. Koppers Company Inc. owned and operated a facility that manufactured resorcinol.   

This review meeting followed a standard TERA process, beginning with a close examination of the supporting documentation and important references by the panel prior to the meeting. At the meeting, the authors of the assessment briefly presented their work. The panel then systematically discussed the assessment, starting with a discussion of the qualitative weight of evidence, followed by a discussion of the quantitative aspects of the assessment.

The panel reached consensus that clearly enough data exists on resorcinol to develop a RfD; however more of that data needs to be included in the document in order to support the RfD and allow the reader to independently evaluate its appropriateness.  

The panel reached unanimous consensus that sufficient human data exists to reach the hazard identification conclusion that resorcinol has the potential for thyroid effects in humans, but there are insufficient data to draw conclusions regarding the dose response for thyroid effects in humans.  However the panel also concluded that there was insufficient information presented in the document to identify other potential target organs in humans.   

After an in-depth, point-by-point discussion of the potential critical effects identified by the animal studies, the panel unanimously concluded that the weight-of-evidence points to thyroid effects as the critical effect for resorcinol.  There is a plausible mode of action, the data demonstrate a level of consistency and there are good reasons for not seeing effects in the animal studies that did not demonstrate thyroid effects.  Based on discussions regarding the animal studies, the panel concluded that mortality, CNS effects, organ weight changes, developmental/reproductive effects, and contact dermatitis were not critical effects for the development of an oral RfD.  The panel noted that methemoglobinemia could potentially be a critical effect, but there are no data to estimate a dose response.  

In conclusion, the panel reached unanimous consensus that thyroid effects are to be considered the critical effect.  The Cooksey and Seffner studies are to be considered as co-critical studies, supporting a point-of departure of 10 mg/kg-day.  Using the composite uncertainty factor of 100-300, as discussed above, the resulting RfD for resorcinol proposed by the panel ranges from 0.03 to 0.1 mg/kg-day.   

The panel unanimously agreed that it should review a revised document, which incorporates the conclusions of the panel and provides additional narrative support in response to the panelís recommendations before the panel would approve this RfD for inclusion on ITER.


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