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Questions for the Panel on Anticipated Residues Methodology

Scientific Advisory Panel (SAP) June 1997 Meeting

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) has completed its review of the Office of Pesticide Programs (OPP) policy for determination of anticipated residues of pesticides in foods for use in chronic dietary exposure assessments. The review was conducted in an open meeting held in Arlington, Virginia, on June 3, 1997. The meeting was chaired by Dr. Ernest E. McConnell. Other Panel Members present were: Dr. Janice E. Chambers (Mississippi State University); Dr. Richard Fenske (University of Washington); Dr. Robert Herrick (Harvard University); Dr. Paul Kuznesof (U S Food and Drug Administration; Dr. Harihara M. Mehendale (Northeast Louisiana University); Dr. Richard Parry, Jr. ( U S Department of Agriculture); Dr. Stephen Saunders (Frito-Lay Corporation); Dr. Edward Stein (U.S. Department of Labor); Dr. Donald Wauchope (U.S. Department of Agriculture); Dr. Willis Wheeler (Wheeler Associates).

Public Notice of the meeting was published in the Federal Register on April 22, 1997.

Oral statements were received from:
Dr. Douglas Baugher, Orius Associates, Inc.
Dr. Leslie Bray, Novartis Crop Protection, Inc.
Dr. Edward Day, Jr., Dow Elanco
Dr. Michele Loftus, TAS, Inc.
Dr. Janet Ollinger, American Crop Protection Association

Written statements were received from:
American Crop Protection Association


1. Please comment on the overall reasonableness of the tiered approach for determining anticipated residues for use in chronic dietary exposure analysis for pesticides in foods.

The Panel finds that the tiered approach for determining anticipated residues for use in chronic dietary exposure analysis for pesticides in foods is both reasonable and scientifically valid.

The Panel suggests in one instance the inclusion of another tier in which simple calculations show that no residues above the LOQ can be present. The Agency has such a policy to be used on a case-by-case basis, but the Panel suggests that it be developed and explained in this document.

The Panel recommends that one of the existing tiers be folded into another. Tier 2 and Tier 3 individually are based upon data that are available or have been submitted by the registrants. Tier 2 has a correction for the percentage of crop treated. Tier 3 uses data provided by the registrant in support of a registration. Since all the information is available, it is suggested, perhaps, that the Agency consider combining these tiers.

The Panel urges EPA to utilize the best possible and most current food consumption data available. The Agency indicated that it primarily uses data collected in 1977-78 as the basis for food consumption calculations today. The Panel pointed out that the food consumption patterns today are, in all likelihood, dramatically different than they were in 1978.

In the Tier 3 calculation of anticipated residues, the Agency uses mean values to represent several data sets: the mean residue level from each field trial (e.g., from triplicate measurements in an Arizona field trial); the mean of the mean values from all field trials; and, the mean value from multiple concentration/reduction factors. These mean values are used as point estimates and multiplied to produce an estimate of the anticipated residue. The Panel recognizes that the use of means simplifies the calculations, and that in many cases the quality of existing data does not allow distributional analysis. Thus, this approach may be the most efficient use of Agency resources at present. The Agency should strongly consider, however, that such an approach does not capture the variability inherent in these data sets, and the final anticipated residue value has no estimate of variance. As the Agency moves towards the use of distributional analyses in lieu of such point estimates, it will be important to more fully evaluate these procedures and their application in risk assessment.

The Panel supports the use of an adjustment factor for percent of crop treated in Tier 2 and in subsequent tiers, but notes that in some cases compounds with common toxic mechanisms may be used across a crop type. Thus, in the consumption of a particular crop the consumer may be exposed to more than one compound of concern. In the case where some percent of a crop has been treated with the compound under review, and some percent has been treated with a compound with a common mechanism of toxicity, how will the Agency combine these exposures? The Panel recognizes that this issue is newly emerging, and encourages the Agency continue to develop a strategy to address this and similar issues of common mechanisms and exposure aggregation.

2. Does the Panel see any areas where the Policy needs further development, considering availability of data?

The Panel suggests two areas for further development: 1) Use of models to predict residues present on crops. For example IR-4 has done many field trials and residue analyses for malathion on many crops in response to FIFRA re-registration requirements. Some efforts should go to developing a modeling approach to predict residues with time and storage conditions. The industry, IR-4, USDA, and the Agency could work together to develop such a modeling concept. 2) Use of all available data sources to predict residues. The Panel encourages EPA to utilize all possible sources of information on residues on raw agricultural crops, processed products, etc. Sources of information could include state and federal enforcement data, data submitted in support of registration, the food industry (crop producers and food processors), etc.

The Agency is encouraged to continue efforts for international harmonization of methodologies in the development of these policies and data requirements.

3. What types of data should the Agency be looking for in the future to augment the available databases?

The Panel strongly recommends collaboration between relevant federal agencies, affected industry and other stakeholders to develop anticipated residues of pesticides in foods which addresses the limitations of current methodology. Moving in the direction of computer simulation modeling of food consumption would expose weaknesses and gaps in these data. The results of such an exercise could allow for the design of a food consumption survey which would enhance the Agency's risk assessment capabilities.


Certified as an accurate report of findings:

Larry C. Dorsey
Designated Federal Official
FIFRA/Scientific Advisory Panel

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