Observations: SAP Friday September 14, 2012

September 14, 2012


Weight of the Evidence and Models


Weight of the Evidence


Weight of the evidence and the use of models were two very significant  topics addressed today.


From the onset, weight of the evidence and the requirements set forth the Data Quality Act could be on a collision course—all dependent upon how weight of the evidence is implemented.


If the weight of the evidence is implemented in a “Lazy Susan” manner, meaning that each reviewer tastes a morsel of data spun around a circular table and then opines on the merits of the information, such an approach is probably inconsistent with the DQA  because the end result could not be replicated.


We expected that the panel would have an extensive discussion of the weight of the evidence but the discussion only lasted for minutes.



Failure of the agency to follow its guidelines on weight of the evidence was addressed in the legal action Tozzi v EPA.  A companion action, Tozzi v HHS is where  the court ruled that the NTP  Report on Carcinogens was judicially reviewable.


In  its  pleadings in the EPA case,  CRE stated:


  1. Under the 1999 draft guidelines a substance may be classified in the highest cancer classification, “carcinogenic to humans”, based on a “weight of the evidence” approach. In contrast to the 1986 guidelines, which require that human cancer causation be demonstrated by reference to sufficient epidemiologic evidence alone before a substance is placed into the highest category, the 1999 draft guidelines permit such classifications to be based on insufficient epidemiological evidence in conjunction with animal and mode of action evidence.


  1. EPA has not published the 1999 draft guidelines in the Federal Register for public notice and comment and it has not published them as final.


In this instance EPA arbitrarily adopted an undefined weight of the evidence approach without notice and comment.


CRE recommends that the  panel revisit this matter.



Use of Models


Dr. Berenbaum stated that the literature dealing with bees is filled with worthless statistical studies. On the other hand, Dr. Fefferman had a deep appreciation for models and was pushing to have them play a very significant role in the SAP deliberations.


CRE notes the old saying that “ all models are inaccurate, some are useful”.


The panel did not address CREM, the Council for Regulatory Environmental Modeling chaired by EPA. CREM is an interagency group charged with assessing the reliability of models used for environmental risk assessments.


CRE has described the impact of the DQA on model development in a number of national  and international fora.


CRE recommends that the SAP solicit the input from CREM..

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