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A Set of Scientific Issues Being Considered by the Agency in Connection with EPA's Ecological Risk Assessment of Carbofuran Flowable Products.

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A Meeting of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) completed review of a set of scientific issues regarding the Agency's Ecological Risk Assessment of Carbofuran Flowable Products. The review was conducted in an open meeting held in Arlington, Virginia, on May 29-31, 1996. The meeting was chaired by Dr. Ernest E. McConnell. In addition, Mr. James Fairchild (National Biological Service, Columbia, Missouri), Dr. Elwood Hill (Gardnersville, Nevada, NBS-Retired), Ms. Jane Hughes (Carolina Ecotox, Inc., Durham, N.C.), Dr. Christopher Ingersoll (NBS, Columbia, MO), Dr. Ronald Kendall (Clemson University, S.C.) recused himself from the proceedings on carbofuran, Dr. Donald Munson (Washington College, Chestertown, MD), Dr. Barry Wilson (University of California, Davis, CA) served as Ad Hoc experts to the FIFRA SAP.

Public notice of the meeting was published in the Federal Register on May 1, 1996.

Oral statements were received from:

Written statements were provided by:


The Panel addressed the specific questions raised by the Agency and, where necessary, offers additional recommendations for improvement. In consideration of all matters brought out during the meeting and careful review of all documents presented by the Agency, the Panel unanimously submits the following report.


(Agency presentation to SAP by Daniel Balluff)

Carbofuran Report


In this report the Panel focused its attention on the methodology used to assess the risk of the flowable formulation of carbofuran. The Panel saw little difference between the carbofuran assessment and the series of evaluations performed by the Agency on the four "Corn Cluster" chemicals. Therefore, the Panel notes that most of the specific comments made for one of these topics also applies to the other.

The Panel wishes to commend the Agency and the registrant on their efforts to mitigate the effects of the granular formulation of carbofuran to reduce its recognized effects upon wildlife, especially birds and fish. We generally approve of the approach taken by the Agency and we hope it is the beginning of similar industry/Agency efforts on different formulations and that it will be a model for the risk assessment and mitigation of other chemicals based on their unique characteristics and uses.

While generally approving of the approach, the Panel had several questions pertaining to the methodology. Although some of these questions have been raised in the Section 850 part of the report, those pertinent to this section will be mentioned here too.

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General Recommendations

Field Studies

The Panel recommends that field studies to generate site specific data on a case by case basis be conducted without negating the importance of using other more cost effective Predictors where appropriate. Work is needed to clarify exposure, validate field toxicities and establish data for species critical to the regulatory process. Therefore, the Panel strongly urges the Agency to reinstate critical field testing of chemicals, both to monitor chemical use, to validate assessment paradigms and model algorithms and to obtain baseline data on the interactions between chemicals, physiological stressors and habitats to birds and other wildlife. Although some of this needed field research can be done by the private sector, Agency scientists need to take the lead to establish the risks of chemicals in the environment.

The Panel places much importance on a comparison of granular and flowable formulations of the chemical as a model of how other chemicals could be studied. The Panel expects that the most up-to-date science will be used in establishing the data and assessing its importance. The Panel recognizes the severe budgetary constraints under which the Agency has been operating and commends them for their efforts. We strongly urge the Agency be given the resources to keep its scientists and its data as up to date as possible in the rapidly evolving field of Ecotoxicology.

Other Species

The Panel is concerned that the Agency is focusing on avian effects at the expense of a balanced presentation of data for other animals, especially aquatic and mammalian species. Given the approach taken by the Agency, perhaps it would have been more accurate to title the carbofuran review, "Hazard Review Based on Incident Data: Flowable Carbofuran, a Case Study," and presented as an alternative to empirical testing.

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Specific Concerns

Setting aside specific regulatory matters, the Panel has specific questions and comments about the justifications of the paradigms used in the Risk Assessment of the chemical:

  1. Formulations

    The Panel recognizes that the two formulations of the chemical discussed are highly toxic to a spectra of wildlife species.

    1. The Panel recommends that the Agency devote more attention to the relative toxicity of different formulations and uses of the chemicals they regulate.

    2. The Panel recommends the Agency require baseline laboratory toxicity data on relevant formulations of chemicals of interest, and specific information on uses of different formulations. This information will be used to determine additional relevant studies to be conducted (e.g., field work). In this case, there is much less information available on flowable compared to granular formulations of carbofuran, but it is reported that carbofuran emulsifiable concentrate is nearly 4 times as toxic as its granular counterpart. More emphasis should be given to the dose/response slopes in characterizing the hazard between chemicals and between formulations. In addition, dose-response slopes may be important in interpreting relative toxicities of different routes and regimens (e.g., feeding vs. controlled dosing).

  2. Field Tests

    The Panel endorses experimental field studies to validate the use of bird kill incidents in the study of pesticides. (An example is the study of carbofuran presented at this May 28-31, 1996 meeting.) The use of field studies to infer population impacts from widespread and repeated mortality reports has been reviewed, discussed and reported in the Avian Effects Dialogue Series.

  3. Species to Study

    The Panel recommends comprehensive ecological risk assessment trials on appropriate wildlife species.

  4. Dose-Response

    Dose-response data are needed to assess chemical/formulation hazards associated with reduced application rates. (Also see #2 above). Different formulations, chemicals and study designs require specific analyses of dose-response slopes. It is also important to beware of placing undue reliance on extrapolated response levels. ( For example, the use of values outside the linear portion of the dose-response-curve is highly questionable.) Special studies should be designed. Often, in such cases, biochemical/physiological variables will be better end points than lethality. Although few animals die at these points, other debilities may occur.

  5. Nestlings and Protected Species

    The Panel is concerned that the current Risk Assessment Guidelines of the EPA do not adequately protect nestlings, particularly the young of altricial species and threatened and/or endangered species. Precocial young are mobile; they can move from a contaminated site, altricial species cannot. Specific parental success (e.g., foraging/feeding, protection, defense, etc.) is probably much more important to altricial than precocial young.

  6. Criteria for Field Reports

    The criteria for inclusion of field findings should be made clearer. Are the field findings only for the chemical and/or formulation tested? How useful is the information obtained?" on page 22 the statement that the results are 'inadequate to refute a presumption of risk to wildlife..." but that they do "contain information 99 casts some doubt on the Agency interpretation of the usefulness of the data. The Panel does not at this time view incident reports as useful for quantitative comparisons in a weight of evidence approach.

  7. Incident Reports and Monitoring

    The Agency needs to formally address the reliability of incident reports, especially since the report (page 26) notes the lack of a systematic mechanism for monitoring. The Panel suggests that a distinction be made between monitoring as part of a planned study design and opportunistic reports from field scientists, growers and the public.

  8. EEC

    One parameter that is critical to the Risk Assessment approach proposed by the Agency is the EEC. But the Panel finds exposures have been estimated from models that may lack solid evidence for validation. The Panel requests that more information be obtained or generated to establish this important numerator in the Risk Assessment process. Further, what is the best indicator of EEC? Lethality? What about other factors such as reproductive impairment?

  9. Risk Quotient

    The Panel still considers that the Risk Quotient is a qualitative parameter and not necessarily a highly quantitative measure of ecological risk, particularly since exposure and environmental fate are not determined. The Agency report qualifies the usefulness of the risk quotients as providing "relative rankings". The Panel would like to see further discussion on the relative merits of the several risk indices (e.g., LD50/sq ft, LD50/Day the EEC/LC50). Also, the Panel questions a continued focus on lethality as the primary reference. Many chemicals evoke toxicity through interference with the physiological state of the animal including behaviors important to continued reproduction and survival. Each chemical may have certain unique qualities that may influence their potential hazard to wildlife.

  10. Closing

    The Panel finds that carbofuran is such an acutely toxic chemical that its usefulness as a model for the New Paradigm is questionable. It does not provide the well-planned, carefully executed and cost/effective field studies necessary for a model compound. The Panel urges that some form of field study be reinstated for carbofuran. At a minimum, the type of review provided for the chemicals compared in the "Corn Cluster" review should be undertaken.

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Specific Panel Recommendations

The specific data needed for valid risk comparisons are highly complex and dependent both on toxic mechanisms, the likelihood of exposures and coincidence of exposure and critical timing of physiological events, especially those pertaining to reproduction and migration. Experimental field studies involving different formulations may be essential. Other factors ignored in the present risk assessment include: systemic availability in forage plants and animals, and the potential for adsorption of the chemical in the mucosal layer of tolerant aquatic organisms (fish, tadpoles, etc.).

Field study data and incident reports can be used across the boundaries of crops and species, provided the comparisons are based on common circumstances (e.g., time and rate of exposure in relation to migration, reproductive cycle, availability of chemical substance, etc.) . One should not ignore pertinent data because the exact circumstances are not represented. Fair and reasonable extrapolation of well understood data sets is a prudent approach. Experience is needed to understand the difference between reasonable cause - effect relationships and generally improbable scenarios is critical.

The use of field studies in determining population effects is dependent on the selection of the specific populations at risk. (See the Avian Effects Dialogue Series and reports at other recent symposiums for detailed discussions on this topic) . However, it is essential to consider that pesticide use is only part of the potential success/failure of a population, but it is a controllable part. It is not likely that any single "contemporary" chemical will exhibit the specific species effects seen in the "chlorinated hydrocarbon era," but any chemical use clearly causing repeated insult to large numbers of nontarget animals should be carefully reviewed and controlled. We simply do not know which of many potential environmental perturbations (chemical use patterns and contamination, air pollution, habitat destruction, climatic patterns, etc.) alone or in combination, may affect the dynamics of different populations. It is important to evaluate the effects of interactions between controllable (e.g., pesticide use) and uncontrollable (e.g., climate, food and water availability) physiological stressors.

See comment 4 above for discussion of dose-response relationships. Many discussions on appropriate and inappropriate use of dose-response curves have been published. In general, it is not appropriate to extrapolate outside the linear portion of the curve (i.e., + 1 S.D. of the estimated median response level) . Special studies, perhaps more focused on physiological changes, might be appropriate. It is known that the dose-response-curve for a given chemical may be different for different variables (e.g., lethality vs. enzymatic or hormonal changes; acute vs. chronic exposure, etc.).

Different chemical formulations are designed for reasons of efficacy and safety. Therefore, one expects to find differences in chemical release, availability, and potential rate of absorption among formulations. Such formulations should be tested against a few prototypical nontarget life forms to increase the power of the risk assessment.

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