EPA
       United States
       Environmental Protection
       Agency
            Prevention, Pesticides
            and Toxic Substances
            (7508C)
EPA 738-R-01 -008
March 2O02
Interim Reregistration
Eligibility  Decision  for
Methidathion

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                   United States
                   Environmental Protection
                   Agency
Prevention, Pesticides
and Toxic Substances
(7508C)
EPA 738-F-01-007
March 2002
>EPA   Methidathion   Facts
             EPA has assessed the risks of methidathion and reached an Interim Reregistration Eligibility
      Decision (interim RED) for this organophosphate (OP) pesticide. Provided that risk mitigation measures
      are adopted, methidathion fits into its own "risk cup" - its individual, aggregate.risks are within acceptable
      levels.  Methidathion is also eligible for reregistration, pending a full reassessment of the cumulative risk
      fromallOPs.                                                          ,
             Used on a variety of agricultural crops,
      predominantly alfalfa, citrus and cotton,
      methidathion residues in food and drinking water
      do not pose risk concerns. Methidathion has no .
      residential uses. EPA considered the mitigation
      proposal submitted by the technical registrant, as
      well as comments and mitigation ideas from
      other interested parties, and has decided on a
      number of label amendments (restrictions) to
      mitigate risks of concern posed by the uses of
      methidathion. With the implementation of these
      mitigation measures, methidathion's worker and
      ecological risks also will be below levels of
      concern for reregistration.

              EPA's next step under the Food Quality
      Protection Act (FQPA) is to consider available
      information on the basis of cumulative risk
      encompassing all of the OP pesticides, sharing a
      common mechanism of toxicity.  The final
      tolerance  reassessment decision for methidathion
       cannot be considered final until the cumulative
      risks for all of the OPs is considered. The
       Agency may need to pursue further risk
       management measures at that time.

              EPA is reviewing the OP pesticides to determine whether they meet current health and safety
       standards. Older OPs need decisions about their eligibility for reregistration under FIFRA. OPs with
       residues in food, drinking water and other non-occupational exposures also must be reassessed to make
       sure they meet the new FQPA safely standard.
       The OP Pilot Public Participation Process

           The organophosphates are a group of
    related pesticides that affect the functioning of the
    nervous system. They are among EPA's highest
    priority for review under the Food Quality
    Protection Act.
           EPA is encouraging the public to
    participate in the review of the OP pesticides.
    Through a six-phased pilot public participation
    process, the Agency is releasing for review and
    comment its preliminary and revised scientific risk
    assessments for individual OPs. Please contact
    the OP Docket, telephone (703) 305-5805, or see
    EPA's web site, www.eDa.gov/oesticidles/OD.
            EPA is exchanging information with
    stakeholders and the public about the OPs, their
    uses, and risks through Technical Briefings,
    stakeholder meetings, and other forums. USDA is
    coordinating input from growers and other OP
     pesticide users.
            Based on current information from
     interested stakeholders and the public, EPA is
     making interim risk management decisions for
     individual OP pesticides,  and will make final
     decisions through a cumulative OP assessment.

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        The methidathion interim decision was made through the OP pilot public participation process,
 which increases transparency and maximizes stakeholder involvement in EPA's development of risk
 assessments and risk management decisions. EPA has worked extensively with affected parties to reach
 the decisions presented in this interim RED document, which concludes the OP pilot process for
 methidathion.
 Uses
        An insecticide and acaricide, methidathion is used to control a broad spectrum of agricultural insect
        and mite pests on a variety of nut, citrus and stone and pome fruit tree crops, artichokes, olives,
        cotton, alfalfa (grown for seed), safflower and ornamentals.   .

        Methidathion is a Restricted Use Pesticide applied aerially and by ground methods. There are no
        residential uses for methidathion.

        Annual domestic use in the U.S. is low — approximately 241,000 pounds of active ingredient is
        used per year.
 Health Effects
        Methidathion can cause cholinesterase inhibition in humans; that is, it can overstimulate the
        nervous system causing nausea, dizziness, confusion and at very high exposures (e.g., accidents or
        major spills), respiratory paralysis and death.
Risks
        Based on the data currently available, residues of only methidathion in food do not pose risk
concerns. Dietary exposures from eating food crops treated with methidathion are well below the level of
concern for the entire U.S. population, including infants and children. Similarly, drinking water is not a
significant source of exposure.

        EPA has risk concerns for workers who mix, load and/or apply methidathion to agricultural sites;
        and reentry into treated areas by workers.  While data are insufficient to assess the risks associated
        with pesticide handlers, the Agency has determined that there is considerable potential for post-
        application occupational exposure to methidathion residues.

•       Acute and chronic risks are of concern to birds, mammals and aquatic species. Methidathion may
        pose risks to beneficial insects that may be present at the treated area on an acute contact basis.

Risk Mitigation

        In order to support a reregistration eligibility decision for methidathion, the following risk
mitigation measures are necessary:

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To mitigate risks to agricultural workers:
       Limit the use of water-soluble package formulation (WSP) to non-aerial applications.  The WSP
       formulation will be available to air blast or groundboom applications.
•      To mitigate the concern of air blast applications in citrus groves, the registrant has agreed to require
       a minimum of 500 gallons of water per acre to dilute methidathion products.
       For groundboom application, add chemical-resistant gloves, a chemical-resistant apron and an
       organic vapor-removing respirator for mixers and/or loaders; add personal protective equipment or
       use of closed systems for commercial applicators.
       The Restricted Entry Interval (REI) for methidathion will be established at 3 days for all crops.
       This is based on the day on which MOEs are greater than 100 for activities other than harvesting.
       The Agency believes that an REI of 3 days will sufficiently protect workers.

To mitigate ecological risks:
•      The Agency is proposing buffer zones, improved labeling to limit spray drift and a surface water
       advisory statement on the label.
•      To reduce avian risk, the additional dilution of methidathion products (with a minimum of 500
       gallons of water per acre) is. intended to reduce exposure to workers and may also reduce exposure
       to birds.
•      Methidathion's use could present both acute and chronic risk to birds since applications to citrus
       coincide with the breeding period of many bird species and because citrus orchards are attractive to
       birds. To address this risk, the registrant has agreed to precautionary labeling.
       Labels should be amended to include a surface water advisory statement that will encourage users
       to apply methidathion in a way that will minimize exposure to freshwater fish and invertebrates.
       To reduce the likelihood for significant mortality to bees from exposure to foliage treated with
       methidathion, precautionary labeling is required to mitigate these risks.

 Next Steps

 •       The interim RED for methidathion includes guidance and time frames for complying with any
        necessary label changes for products containing methidathion. The registrants will submit the label
        amendments.

        When the cumulative risks for all OPs is considered, EPA will issue its final tolerance
        reassessment decision for methidathion and may request further risk management measures.

        Numerous opportunities for public comment were offered, through the OP public participation
        process, as this interim decision was being developed. The methidathion interim RED therefore is
        issued in final without a formal public comment period. The docket remains open, however, and
        any comments submitted in the future will be placed in the public docket.

        A Notice of Availability for this interim RED for methidathion is being published in the Federal
        Register. Copies of this interim RED and all supporting documents are available on the Agency's
        website at htto://www.ep(Lsov/pesticides/ov.

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         \
                  UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                                  WASHINGTON, D.C.  20460-0001
                                                                           OFFICE OF
                                                                      PREVENTION, PESTICIDES
                                                                      AND TOXIC SUBSTANCES
CERTIFIED MAIL
Dear Registrant:
APR 0 9 2002
     This is to inform you that the U.S. Environmental Protection Agency (hereafter referred to"
as EPA or the "Agency") has completed its review of the available data and public comments
received related to the preliminary and revised risk assessments for the organophosphate
pesticide methidathion. The public comment period on the revised risk assessment phase of the
reregistration process is closed. Based on comments received during the public comment period
and additional data received from the registrant, the Agency revised the human health and
environmental effects risk assessments and made them available to the public on December 8,
 1999.  Additionally, the Agency held a Technical Briefing on December 8,1999 where the
results of the revised human health and environmental effects risk assessments were presented to
the general public. This Technical Briefing concluded Phase 4 of the OP Public Participation
 Pilot Process developed by .the Tolerance Reassessment Advisory Committee and initiated Phase
 5 of that process. During Phase 5, all interested parties were invited to participate and provide
 comments and suggestions on ways the Agency might mitigate the estimated risks presented in
 the revised risk assessments. This public participation and comment period commenced on
 December 8,1999 and closed on February 7,2000.

      Based on its review, EPA has identified risk mitigation measures that the Agency believes
 are necessary to address the human health and environmental risks associated with the current
 use of methidathiori. The EPA is now publishing its interim decision on the reregistration
 eligibility and risk management decision for the current uses of methidathion and its associated
 human health and environmental risks. The reregistration eligibility and tolerance reassessment
 decisions for methidathion will be finalized once the cumulative risks for all of the
 organophosphate pesticides are considered. The enclosed "Interim Reregistration Eligibility
 Decision for Methidathion," which was approved and signed on September 28,2001, contains
 the Agency's decision on the individual chemical methidathion.

       A Notice of Availability for this Interim Reregistration Eligibility .Decision (interim RED)
  for methidathion is being published in the Federal Register. To obtain a copy of the interim
  RED document, please contact the OPP Public Regulatory Docket (7502C), USEPA, Ariol Rios
  Building, 1200 Pennsylvania NW, Washington, D.C. 20460-0001, telephone (703) 305-5805.
  Electronic  copies of the interim RED and all supporting documents are available on the
          wshsite at http://WM>w.eva.eov/pesticides/ot>.

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      The interim RED is based on the updated technical information found in the methidathion
 public docket. The docket not only includes background information and comments on the
 Agency's preliminary risk assessments, it also now includes the Agency's revised risk
 assessments for methidathion (drinking water assessment revised as of March 22, 2001 and
 dietary assessment revised as of April 27,2001) and a document summarizing the Agency's
 Response to Comments. The Response to Comments document addresses corrections to the
 preliminary risk assessments submitted by chemical registrants, as well as responds to comments
 submitted by the general public and stakeholders during the comment period on the risk
 assessment. The docket will also include comments on the revised risk assessment and any risk
 mitigation proposals submitted during Phase 5. For methidathion, a proposal was submitted by
 Gowan Company, the technical registrant, to mitigate the risks to workers associated with air
 blast application.

      This document and the process used to develop it are the result of a pilot process to
 facilitate greater public involvement and participation in the reregistration and/or tolerance
 reassessment decisions for these pesticides. As part of the Agency's effort to  involve the public
 in the implementation of the Food Quality Protection Act of 1996 (FQPA), the Agency is
 undertaking a special effort to maintain open Public Dockets on the organophosphate pesticides
 and to engage the public hi the reregistration and tolerance reassessment processes for these
 chemicals. This open process follows the guidance developed by the Tolerance Reassessment
 Advisory Committee (TRAC), a large multistakeholder advisory body that advised the Agency
 on implementing the new provisions of the FQPA.  The reregistration and tolerance
 reassessment reviews for the organophosphate pesticides are following this new process.

      Please note that the methidathion risk assessment and the attached interim RED concern
 only this particular organophosphate.  This interim RED presents the Agency's conclusions on
 the dietary risks posed by exposure to  methidathion alone.  The Agency has also concluded its
 assessment of the ecological and worker risks associated with the use of methidathion. Because
 the FQPA directs the Agency to consider available information on the basis of cumulative risk
 from substances sharing a common mechanism of toxicity, such as the toxicity expressed by the
 organophosphates through a common biochemical interaction with a cholinesterase enzyme, the
 Agency will evaluate the cumulative risk posed by the entire organophosphate class of chemicals
 after completing the risk assessments for the individual organophosphates. The Agency is
 working toward completion of a methodology to assess cumulative risk and the individual risk
 assessments for each organophosphate are likely to be necessary elements of any cumulative
 assessment  The Agency has decided to move forward with individual assessments and to  '
 identify mitigation measures necessary to address those human health and environmental risks
 associated with the current uses of methidathion. The Agency will issue the final tolerance
 reassessment decision for methidathion once cumulative risk for all of the organophophates is
 considered.

     This document contains a generic and a product-specific Data Call-In (DCI) that outlines
 further data requirements for this chemical. Note that registrants of products containing
methidathion must respond to DCIs issued by the Agency within 90 days of receipt of this letter.

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     In this interim RED, the Agency has determined that methidathion will be eligible for
reregistration provided that all the conditions identified in this document are satisfied, including
implementation of the risk mitigation measures outlined in Section IV of the document. The
Agency believes that the current uses of methidathion may pose unreasonable adverse effects to
human health and the environment and that such effects can be reduced by the risk mitigation
measures identified in this interim RED. Accordingly, the Agency recommends that registrants
implement these risk mitigation measures immediately.  Section IV and V of this interim RED
describe labeling amendments for end-use products and data requirements necessary to
implement these mitigation measures. Instructions for registrants on submitting revised labeling
can be found in the set of instructions for product-specific data that accompanies this interim
RED.

     Should a registrant fail to implement any of the risk mitigation measures outlined in this
document, the Agency will continue to have concerns about the risks posed by methidathion.
Where the Agency has identified any unreasonable adverse effect to human health and the
environment, the Agency may at any time initiate appropriate regulatory action to address this
concern. At that time, any affected person(s) may challenge the Agency's action.

     If you have questions on this document or the label changes necessary for reregistration,
please contact the Special Review and Reregistration Division representative Carmen Rodia at
(703) 306-0327. For questions about product reregistration and/or the Product DCI that '
accompany this document, please contact Jane Mitchell at (703) 308-8061 .

                                             Lois A. Rossi, Director
                                             Special Review and
                                              Reregistration Division
 Attachment

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Interim Reregistration Eligibility Decision
                    for
               Methidathion
                   List A
                  Case 0034

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                                Table of Contents

Glossary of Terms and Abbreviations	........ i

Executive Summary			Y.

Methidathion Interim Reregistration Eligibility Decision Team	 vm

I.    Introduction	1

II    Chemical Overview  	•	• • •	1
     A.   Regulatory History	3
     B.   Chemical Identification		3
     C.   Use Profile	-	4
     D.   Estimated Usage of Pesticide	 - S

III.  Summary of Methidathion Risk Assessments	6
     A.   Human Health Risk Assessment	.6
          1.   Dietary Risk from Food	6
               a.   Toxicity	6
               b.   FQPA Safety Factor	,		8
               c.   Population Adjusted Dose (PAD)		9.
               d.   Exposure Assumptions	9
               e.   Food Risk Characterization	9
          2.   Dietary Risk from Drinking Water	1Q
               a.   Surface Water	•	 H
               b.   Ground Water	11
               c.   Monitoring Data	• •	11
               d.   Drinking Water Levels of Comparison  .	•.	12
          3.   Aggregate Risk	•	• • 11
          4.   Occupational Risk	11
               a.   Toxicity	11
               b.   Exposure	11
               c.    Occupational Handler Risk Summary	•ซ..-	16
                          1)    Agricultural Handler Risk	17
                          2)    Post-Application Occupational Risk	19
               d.    Human Incident Data	 21
     B.  Environmental Risk Assessment	22
          1.   Environmental Fate and Transport	23
          2.   Risk to Birds and Mammals	21
          3.   Risk to Aquatic Species	,	27
          4.   Risk to Nontarget Insects	11
          5.   Endangered Species	11
          6.   Incident Reports	 32

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 IV.   Interim Risk Management and Reregistration Decision		32
      A.   Determination of Interim Reregistration Eligibility	32
      B.   Summary of Phase 5 Comments and Responses	34
      C.   Regulatory Position 	;	35
           1.    FQPA Assessment	35
                a.    "Risk Cup" Determination	35
                b.    Tolerance Summary	..	.. 35
           2.    Endocrine Disrupter Effects	 39
           3.    Benefits and Alternatives	39
      D.   Regulatory Rationale	40
           i.    Human Health Risk Mitigation	40
                a.    Dietary Mitigation	 .40
                b.    Occupational Risk Mitigation	44
                          1)    Agricultural Uses	4\_
                          2)    Post-Application Risk	42
           2.    Environmental Risk Mitigation			42
                a.    Avian Species Mitigation  		43
                b.    Aquatic Species Mitigation	 43
                c.    Nontarget Insect Mitigation	 44
      E.    Other Labeling			44
           1.    Endangered Species Statement	 44
           2.    Spray Drift Management	     45

V.    What Registrants Need to Do	 46
      A.    Manufacturing Use Products  	,	.4.........         .... 47
           1.    Additional Generic Data Requirements	47
           2.    Labeling for Manufacturing Use Products  	49
      B.    End-Use Products	49
           1.    Additional Product-Specific Data Requirements  	.49
           2.    Labeling for End-Use Products	   .49
      C.    Existing Stocks	          49
      D.    Labeling Changes Summary Table	sj

VI.   Related Documents and How to Access Them	59

VII.   Appendices	          61
          Appendix A	      ... 63
          Appendix B	..73
          Appendix C	79
          Appendix D	,			gj[
          Appendix E	
          Appendix F	
          Appendix G	_
          Appendix H	
          Appendix I	_       135

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                 GLOSSARY OF TERMS AND ABBREVIATIONS
 AE          Acid Equivalent
• a.i.          Active Ingredient
 AGDCI      Agricultural Data Call-In
 aPAD       Acute Population Adjusted Dose
 AR          Anticipated Residue
 ARC        Anticipated Residue Contribution
 BCF        Bioconcentration Factor
 CAS        Chemical Abstracts Service
 CI          Cation                                                                   .
 CNS        Central Nervous System   •
 cPAD       Chronic Population Adjusted Dose
 CSF        Confidential Statement of Formula
 CFR        Code of Federal Regulations
 CSFII       USDA Continuing Surveys for Food Intake by Individuals
 DCI        Data Call-In
 DEEM      Dietary Exposure Evaluation Model
 DFR        Dislodgeable Foliar Residue
 ORES       Dietary Risk Evaluation System
 DWEL      Drinking Water Equivalent Level (DWEL) The DWEL represents a medium-specific (i.e., drinking
             water) lifetime exposure at which adverse, noncarcinogenic health effects are not anticipated.
 DWLOC    Drinking Water Level of Comparison.
 EC         Emulsifiable Concentrate Formulation
 EEC        Estimated Environmental Concentration.  The estimated pesticide concentration in an environment,
             such as a terrestrial ecosystem.
 EP         End-Use Product
 EPA        U.S. Environmental Protection Agency
 FAO       Food and Agriculture Organization
 FDA        Food and Drug Administration
 FIFRA       Federal Insecticide, Fungicide, and Rodenticide Act
 FFDCA      Federal Food, Drug, and Cosmetic Act        .
 FQPA       Food Quality Protection Act
 FOB        Functional Observation Battery
 G           Granular Formulation
 GENEEC    Tier I Surface Water Computer Model
 GLC        Gas Liquid Chromatography
 GLN        Guideline Number
 GM         Geometric Mean
 GRAS       Generally Recognized as Safe as Designated by FDA
 HA         Health Advisory (HA). The HA values are used as informal guidance to municipalities and other
              organizations when emergency spills or contamination situations occur.
 HAFT       Highest Average Field Trial                                 •
 HDT        Highest Dose Tested
 IR          Index Reservoir
 LC50        Median Lethal Concentration. A statistically derived concentration of a substance that can be
              expected to cause death in 50% of test animals. It is usually expressed as the weight of substance
              per weight or volume of water, air or feed, e.g., mg/1, mg/kg or ppm.
  LD50        Median Lethal Dose. A statistically derived single dose that can be expected to cause death in 50%
              of the test animals when administered by the route indicated (oral, dermal, inhalation). It is
              expressed as a weight of substance per unit weight of an animal, e;g., mg/kg.

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LEL         Lowest Effect Level
LOG         Level of Concern
LOD         Limit of Detection
LOAEL      Lowest Observed Adverse Effect Level
MATC       Maximum Acceptable Toxicant Concentration
MCLG       Maximum Contaminant Level Goal (MCLG)  The MCLG is used by the Agency to regulate
             contaminants in drinking water under the Safe Drinking Water Act.
mg/kg/day    Milligram Per Kilogram Per Day
mg/L         Milligrams Per Liter
MOE        Margin of Exposure
MP          Manufacturing-Use Product
MPI         Maximum Permissible Intake
MRID       Master Record Identification (number). EPA's system of recording and tracking studies submitted.
NA          Not Applicable
N/A         Not Applicable
NAWQA     USGS National Water Quality Assessment
NOEC       No Observable Effect Concentration
NOEL       No Observed Effect Level
NOAEL      No Observed Adverse Effect Level
NPDES      National Pollutant Discharge Elimination System
NR          Not Required
OP          Organophosphate
OPP         EPA Office of Pesticide Programs
OPPTS       EPA Office of Prevention, Pesticides and Toxic Substances
Pa       '    pascal, the pressure exerted by a force of one newton -acting on an area of one square meter.
PAD         Population Adjusted Dose
PADI        Provisional Acceptable Daily Intake
PAG         Pesticide Assessment Guideline
PAM         Pesticide Analytical Method
PCA         Percent Crop Area
PDF         USDA Pesticide Data Program
PHED       Pesticide Handler's Exposure Data
PHI         Preharvest Interval
ppb          Parts Per Billion
PPE         Personal Protective Equipment
ppm         Parts Per Million
PRN         Pesticide Registration Notice
PRZM/
EXAMS      Tier II Surface Water Computer Model
Qi*          The Carcinogenic Potential of a Compound, Quantified by the EPA's Cancer Risk Model
RAC         Raw Agriculture Commodity
RBC         RedBloodCell
RED         Reregistration Eligibility Decision
REI          Restricted Entry Interval
RED         Reference Dose
RQ          Risk Quotient
RS           Registration Standard
RUP         Restricted Use Pesticide
SAP         Science Advisory Panel
SCI-GROW   Tier I Ground Water Computer Model
SF           Safety Factor                                                              .
SLC         Single Layer Clothing

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SLN         Special Local Need  (Registrations Under Section 24(c) of FIFRA)
TC          Toxic Concentration. The concentration at which a substance produces a toxic effect.
TD          Toxic Dose. The dose at which a substance produces a toxic effect.
TEP         Typical End-Use Product
TGAI        Technical Grade Active Ingredient
TLC         Thin Layer Chromatography
TMRC       Theoretical Maximum Residue Contribution
torr          A unit of pressure needed to support a column of mercury 1 mm high under standard conditions.
TRR         Total Radioactive Residue
UF          Uncertainty Factor                                    .             (           •
             Micrograms Per Gram
             Micrograms Per Liter
USDA       United States Department of Agriculture
USGS       United States Geological Survey
UV          Ultraviolet                                                                     .
WHO        World Health Organization
WP          Wettable Powder
WPS         Worker Protection Standard
                                                  in

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IV

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Executive Summary

     The U.S. Environmental Protection Agency (hereafter referred to as EPA or the
"Agency") has completed its review of public comments on the revised risk assessments and is
issuing its risk management decision for methidathion. The decisions outlined in this document
do not include the final tolerance reassessment decision for methidathion; however, some
tolerance actions will be undertaken prior to completion of the final tolerance reassessment.
These are examples of actions to be taken now: five tolerances are being revoked because they
are covered by another tolerance; all of the meat, milk and egg tolerances are being revoked
because of use deletions for livestock food items; one tolerance will be modified and several
other commodity definitions will be corrected. The final tolerance reassessment decision for this
chemical will be issued once cumulative risk for all of the organophosphates is considered. The
Agency may need to pursue further risk management measures for methidathion once
cumulative risk is finalized.

     The revised risk assessments are based on review of the required database supporting the
use patterns of currently registered products and new information received. The Agency invited
stakeholders to provide proposals,  ideas or suggestions on appropriate mitigation measures
before the Agency issued its risk mitigation decision on methidathion. EPA developed its risk
management decision for uses of methidathion that pose risks of concern after considering the
revised risk estimates, mitigation measures proposed by Gowan Company (the technical
registrant of methidathion) and comments and mitigation suggestions from other interested
parties. This decision is fully discussed in this document.

      Methidathion is a non-systemic, organophosphate insecticide/acaricide that was first
registered in 1972 to control a broad spectrum of agricultural insect and mite pests on various
crops, predominantly alfalfa, citrus and cotton. Use data from 1987 to 1997 indicate an average
domestic use of approximately 241,000 pounds of active ingredient per year.

Overall Risk Summary

      EPA's human health risk assessment for methidathion indicates some risk of concerns.
Food risk, both acute and chronic,  is well below the Agency's level of concern.  Similarly,
drinking water estimates based on  screening models,, from both ground and surface water for
acute and chronic exposure, is not  of concern. There are, however, some concerns for workers
who mix, load and apply methidathion to agricultural sites.  Also, EPA has identified acute and
chronic risk to birds, mammals and aquatic species that are of concern.

      To mitigate risks of concern posed by the uses of methidathion, EPA considered the
mitigation proposal submitted by the technical registrant, as well as comments and mitigation
ideas from other interested parties, and has decided on a number of label amendments to address
the worker and ecological concerns.  Results of the risk assessments, and the necessary label
amendments to mitigate those risks, are presented in this Interim Reregistration Eligibility
Decision (interim RED).

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Dietary Risk

      Acute and chronic dietary risk assessments for food and drinking water do not exceed the
Agency's level of concern; therefore, no mitigation is warranted at this time for dietary exposure
to methidathion.

Residential Risk

      There are no concerns because methidathion does not have any residential uses.

Occupational Risk

      Of the 18 agricultural scenarios, five exceed the Agency's level of concern (i.e., Margins
of Exposure or MOEs are less than 100). For these 5 scenarios, one has an MOE of 98 when
workers use an organic vapor-removing respirator. Of the final four scenarios, two MOEs are
85 and 87 (mixing/loading the liquid formulation and applying with aircraft, respectively) using
engineering controls and two others are 27 and 39 for mixing/loading the WSP for aerial
application. EPA believes these risks can be mitigated with the following label restrictions: limit
the use of water-soluble package formulation (WSP) to nonaerial applications, addition of
personal protective equipment; use of closed systems and the application of a minimum of 500
gallons of water per acre to dilute methidathion products. Although these measures will riot
result in MOEs above 100 hi all cases, the Agency believes that the remaining risks are
reasonable given protective assumptions in the risk assessment and considering the benefits of
methidathion use.-

      The risk to workers reentering treated fields is not of concern, provided the restricted entry
intervals recommended in this document are established. Therefore, with the addition of the
label restrictions and amendments detailed in this document, the Agency has determined that
until the cumulative risks for all of the organophosphates have been considered, all  currently
registered uses of methidathion may continue.

Ecological Risk

      Ecological risks are also of concern to the Agency. The environmental risk assessment
suggests that exposure to methidathion could result in both acute and chronic risks of concern
for terrestrial and aquatic organisms. In addition, methidathion may pose risks to beneficial
insects that may be present at the treated area.

      The Agency's risk assessment for avian species exceeds the level of concern for both acute
and chronic exposure, though aspects of the use practices are expected to somewhat limit this
exposure.  Since many methidathion applications occur prebloom or to dormant trees when birds
are not breeding, the Agency is less concerned about chronic effects to birds. Sprays to citrus,
however, do coincide with the breeding period of many species of birds.  Because citrus
                                           VI

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orchards are attractive to birds, methidathion's use could present both acute and chronic risk. To
address risk to birds, the registrant has agreed to precautionary labeling.

      The Agency's risk assessment suggests a concern for both estuarine and freshwater aquatic
organisms. Methidathion's  present use in California suggests that its adverse impact on
estuarine organisms is likely to be limited because very little methidathion is used near estuaries.
Methidathion may, however, have an impact on freshwater organisms. To mitigate these risks,
the Agency is proposing buffer zones, improved labeling to limit spray drift and a surface water
advisory statement on the label.

      The Agency is also  concerned about bees that may be exposed to treated foliage. The
Agency believes that additional precautionary labeling will mitigate these risks.

      For the uses of methidathion, the Agency has determined that with the adoption of all of
the label amendments noted in this document, these uses may continue until the outcome of
cumulative risks of all of the organophosphates has been decided.

      The Agency is issuing this interim RED document for methidathion, as announced in a
Notice of Availability published in the Federal Register. This interim RED includes guidance
and time frames for complying with any necessary label changes for products containing
methidathion. Note that there is no comment period for this document. As part of the process
discussed by the TRAC, which sought to open up the process to interested parties, the Agency's
risk assessments for methidathion have already been subject to numerous public comment
periods and a further comment period for methidathion was deemed unnecessary.  With regard
to complying with the risk mitigation measures outlined in this document, the Agency has
shortened this time period so that the risks identified herein are mitigated as quickly as possible.
Neither the tolerance reassessment nor the reregistration eligibility decision for methidathion can
be considered final, however, until the cumulative risks for all organophosphate pesticides is
considered. The cumulative assessment may result in further risk mitigation measures for
methidathion.
                                            Vll

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         Methidathion Interim Reregistration Eligibility Decision Team
Office of Pesticide Programs:

Biological and Economic Analysis Assessment
Donald Atwood
Timothy Kiely
Rafael Prieto
Herbicide & Insecticide Branch
Economic Analysis Branch
Scientific Information & Analysis Branch
Environmental Fate and Effects Risk Assessment
Henry Craven
John Jordan
Jim Lin

Health Effects Risk Assessment

Jose Morales
Robert Tfavaglini
Susan Makris
William Smith
Gary Bangs

Registration Support

Rita Kumar

Risk Management

Michael Goodis
Susan Jennings
Jackie Mosby
Carmen Rodia
Environmental Risk Branch III
Environmental Risk Branch III
Environmental Risk Branch III
Reregistration Branch III
Reregistration Branch III
Toxicology Branch
Chemistry and Exposure Branch
Reregistration Branch III
Insecticide/Rodenticide Branch
Reregistration Branch III
Reregistration Branch III
Reregistration Branch II
Reregistration Branch II
                                         via

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I.    Introduction

     The Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) was amended in 1988 to
accelerate the reregistration of products with active ingredients registered prior to November 1,
1984. The amended Act calls for the development and submission of data to support the
reregistration of an active ingredient, as well as a review of all submitted data by the Agency.
Reregistration involves a thorough review of the scientific database underlying a pesticide's
registration. The purpose of the Agency's review is to reassess the potential hazards arising
from the currently registered uses of the pesticide; to determine the need for additional data on
health and environmental effects and to determine whether the pesticide meets the "no
unreasonable adverse effects" criteria of FIFRA.

     On August 3, 1996, the Food Quality Protection Act of 1996 (FQPA) was signed into law.
This Act amends FIFRA to require tolerance reassessment of all existing tolerances. The
Agency has decided that, for those chemicals that have tolerances and are undergoing
reregistration, the tolerance reassessment will be initiated through this reregistration process.  It
also requires that by 2006, EPA must review all tolerances in effect on the day before the date of
the enactment of the FQPA, which was August 3,1996. FQPA also amends the FFDCA to
require a safety finding in tolerance reassessment based on factors including an assessment of
cumulative effects of chemicals with a common mechanism of toxicity. Methidathion belongs to
a group of pesticides called organophosphates, which share a common mechanism of toxicity -
they all affect the nervous system by inhibiting cholinesterase. Although FQPA significantly
affects the Agency's reregistration process, it does not amend any of the existing reregistration
deadlines. Therefore, the Agency is continuing its reregistration program while it resolves the
remaining issues associated with the implementation of FQPA.

      This document presents the Agency's revised human health and ecological risk
assessments, its progress toward tolerance reassessment and the interim decision on the
reregistration eligibility of metbidathion. It is intended to be only the first step in the
reregistration process for methidathion. The Agency will eventually proceed with its assessment
of the cumulative risk of the OP pesticides and issue a final reregistration eligibility decision for
methidathion.

       The implementation of FQPA has required the Agency to revisit some of its existing
policies relating to the determination and regulation of dietary risk and has also raised a number
of new issues for which policies need to be created.  These issues were refined and developed
through collaboration between the Agency and the Tolerance Reassessment Advisory Committee
(TRAC),  which was composed of representatives from industry, environmental groups and other
interested parties.  The TRAC identified  the following science policy issues it believed were key
to the implementation of FQPA and tolerance reassessment:

      Applying the FQPA 10-Fold Safety Factor
•     Whether and How to Use "Monte Carlo" Analyses in Dietary Exposure Assessments

                                            1

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 •     How to Interpret "No Detectable Residues" in Dietary Exposure Assessments
 •     Refining Dietary (Food) Exposure Estimates
 •     Refining Dietary (Drinking Water) Exposure Estimates
 •     Assessing Residential Exposure
 •     Aggregating Exposure from all Non-Occupational Sources
       How to Conduct a Cumulative Risk Assessment for Organophosphate or Other Pesticides
       with a Common Mechanism of Toxicity
       Selection of Appropriate Toxicity Endpoints for Risk Assessments of Organophosphates
 •     Whether and How to Use Data Derived from Human Studies

       The process developed by the TRAC calls for EPA to provide one or more documents for
 public comment on each of the policy issues described above. Each of these issues is evolving
 and in a different stage of refinement. Some issue papers have already been published for
 comment in the Federal Register and others will be published shortly.

       In addition to the policy issues that resulted from the TRAC process, the Agency issued,
 on September 29,2000 a Pesticide Registration Notice (PR 2000-9) that presents EPA's
 approach for managing risks from organophosphate pesticides to occupational users. The
 Worker PR Notice describes the Agency's baseline approach to managing risks to handlers and
 workers who may be exposed to organophosphate pesticides, and the Agency expects that other
 types of chemicals will be handled similarly. Generally, basic protective measures such as
 closed mixing and loading systems, enclosed cab equipment or protective clothing, as well as
 increased reentry intervals will be necessary for most uses where current risk assessments
 indicate a risk and such protective measures are feasible. The policy also states that the Agency
 will assess each pesticide individually, and based upon the risk assessment, determine the need
 for specific measures tailored to the potential risks of the chemical. The measures included in
 this interim RED are consistent with that Worker Pesticide Registration Notice.

      This document consists of seven sections. Section I contains the regulatory framework for
 reregistration/tolerance reassessment, as well as descriptions of the process developed by  TRAC
 for public comment on science policy issues for the organophosphate pesticides and the worker
 risk management PR notice. Section II provides a profile of the use and usage of the chemical.
.Section HI gives an overview of the revised human health and environmental effects risk
 assessments resulting from public comments and other information. Section IV presents the
 Agency's interim decision on reregistration eligibility and risk management decisions. Section V
 summarizes the label changes necessary to implement the risk mitigation measures outlined in
 Section IV. Section VI provides information on how to access related documents. Finally,
 Section VII lists all Appendices related to the Data Call-in (DCI) information. The revised risk
assessments and other related documents are available on the Agency's website at
http://www. eya. sov/pesticides/op. and in the public docket.

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II   Chemical Overview
     A.    Regulatory History

     Methidathion was first registered in the United States in 1972 to control a broad spectrum
of agricultural insect and mite pests on various crops, predominantly alfalfa, citrus and cotton.
A Registration Standard was issued in 1983. In 1988, the Registration Standard was revised and
reissued based on data submitted since 1983.

     B.    Chemical Identification

     Methidathion:
                                     O
                                                 s
                                                 II
                                                ,p.
                                      -N
                                                OGH3
                                                   OCH
                               H3CO
      •   Common name:

      •   Chemical name:


      •   Chemical family:

      •   Case number:

      •   CAS registry number:

      •   OPP chemical code:

      •   Empirical formula:

      •   Molecular weight:

      •   Trade and other names:

      •  Basic manufacturer:
Methidathion

S-[(5-methoxy-2-oxo-l,3,4-thiadiazole-3-(2H)-yl)
methyl] O,O-dimethyl-phosphorodithioate

Organophosphate

0034

950-37-8

100301

C6HnN204PS3

302.3 g/mole

Supracideฎ

Gowan Company
       Methidathion is a colorless-to-white crystalline solid with an organophosphate odor and a
 melting point of 39ฐ - 40ฐ C. Methidathion is slightly soluble in water at 240 ppm (20ฐ C) and
 is soluble in benzene, acetone, methanol and xylene at >60 g/100 mL (25ฐ C). Methidathion is

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only moderately soluble in chloroform and dichloromethane. The vapor pressure of
methidathion is 2.5 X 10'4 Pa at 20 ฐ C.

      C.   Use Profile

      The following information is based on the currently registered uses of methidathion:

           Type of Pesticide:     Insecticide/Acaricide

           Summary of Use Sites:

           Food Crops: Almonds, apples, apricots, artichokes, carambola, cherries, cotton,
           grapefruit, kiwifruit, lemons, longan, mandarin, mango, nectarines, olives, oranges,
           peaches, pears, pecans, plums and prunes, safflower, sugar apple, sunflower and
           walnuts

           Other Agricultural Sites:  Alfalfa (grown for seed), clover (grown for seed), grass
           hay and timothy

           Residential: None

           Public Health: None

           Other Nonfood: Tobacco, commercial applications to nursery stock, ornamental
           plants and shrubs

           Target Pests: Peach twig borer, scale insects, artichoke plume moth, leafminers,
           spider mites, boll weevils, bollworms, lygus bug, whitefly, aphid, pear psylla,
           mealybugs, thrips, sunflower stern weevil, sunflower moth, sunflower seed weevil,
           sunflower midge, Banks grass mite, flea beetle, hornworm, tobacco budworm,
           codling moth and hickory shuckworm

           Formulation Types Registered: Wettable powder in water-soluble bags (25%
           active Ingredient) and emulsifiable concentrate (22% - 24% active ingredient)

           Method and Rates of Application:

           Equipment: Fixed wing aircraft, groundboom, air blast, low-pressure handwand or
           backpack sprayer

           Method and Rate: Foliar treatment, 0.25 to 5.0 Ibs active ingredient/acre

           Timing: During dormant, delayed-dormant or postbloom phases, depending on the

                                          4

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           crop

           Use Classification: Restricted Use Pesticide due to high acute oral toxicity

      D.   Estimated Usage of Pesticide

      This section summarizes the best estimates available for many of the pesticide uses of
.methidathion, based on available pesticide usage information for 1987 to 1997. A full listing of
 all uses of methidathion, with the corresponding use and usage data for each site, has been
 completed and is in the "Quantitative Use Assessment" document, which is available in the   .
 public docket. The data, reported on an aggregate and site (crop) basis, reflect annual
 fluctuations in use patterns as well as the variability in using data from various  information
 sources. Approximately 241,000 Ibs a.i. of methidathion are used annually, according to
 Agency and registrant estimates.
 Table 1.    Methidathion Estimated Usage1 for Representative Sites2
,." ' - ""({""h^^Crop ' •:' '-.', V';'"
Alfalfa (grown for seed)
Almonds
Apples
Apricot
Artichokes
Cherries
Cotton
Grapefruit
Hay
Kiwifruit
Lemon
Nectarine
Olive
Oranges
Peaches
Pears
Pecans
Plums and Prunes
Safflower
Walnuts
'•-•.' ' "-" '•?"•""• ""f'L''"1
", IAs. Active Ingrediejrt ,
Applied (Wt. Ayglf ,;'
1,000
44,000
8,000
. 2,000
16,000
2,000
16,000
1,000
4,000
<500
1,000
4,000
2,000
42,000 .
25,000
2,000
2,000
35,000
1,000
31,000
'.'•'I'-f-'-^V,^1'*" V;-.,'
Percent Crojj'Treated
(Likely Maximum)
<0.5
9
3
8
63
3
<0.5
1
<0.5
8
2
11
5
3
11
' 5
<0.5
21
9
11
Percent Crop Treated
, ;{Wt.Avg.)
<0.5
6
1
. 5
50
1
<0.5
1
<0.5
7
1
5
2
2
6
1
<0.5
11
1
9

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 1 Usage data primarily covers 1987 to 1997. Calculations of the above numbers are displayed as rounded.
 2 Where usage and percent-crop-treated data are not listed (carambola, clover [grown for seed], longan and mango),
 either no usage is observed or that information on the site is not available or insufficient.
 3 Weighted Average based on data for 11 years; most recent and more reliable data weighted more heavily.

 Sources:                                                                               .
 EPA data (Doane Marketing Research, Maritz Marketing Research, Mike Buckley and Associates).
 California Department of Pesticide Regulation.
 USDA, National Agricultural Statistics Service, Agricultural Chemical Usage: Fruits Summary (1991, 1993, 1995,
 1997) and Field Crop Summary (1990-1997).
Ill   Summary of Methidathion Risk Assessments

      Following is a summary of EPA's revised human health and ecological risk findings and
conclusions for the organophosphate pesticide methidathion, as fully presented in the documents
"Human'Health Risk Assessment Methidathion," dated August 9,2000 and "Methidathion -
Environmental Fate and Effects Chapter," dated November 30,1999, (including drinking water
assessment addenda, dated March 22,2001  and dietary exposure assessment addenda dated,
April 27,2001). The purpose of this summary is to assist the reader by identifying the key
features and findings of these risk assessments and to better understand the conclusions reached
in the assessments.

      These risk assessments for methidathion was presented at a December 8,1999 Technical
Briefing, which was followed by an opportunity for public comment on risk management for
this pesticide. This technical briefing was held in Sacramento, California.  The risk assessments
presented here form the basis of the Agency's risk management decision for methidathion only;
the Agency must consider cumulative risks  of all the organophosphate pesticides before any final
decisions can be made.

      A.   Human Health Risk Assessment

      EPA issued its preliminary risk assessments for methidathion in Phase 3 of the TRAC
process. In response to comments and studies submitted during Phase 3, the risk assessments
were updated and refined. Major revisions to the human health risk assessment include:
reconsideration of the dermal toxicity endpoint selection; inclusion of new data from the
Agricultural Reentry Task Force (ARTF) and recalculation of the restricted entry intervals for
workers; combining dermal and inhalation MOEs in the worker assessment and refinements to
the dietary risk assessment.

           1.    Dietary Risk from Food

                 a.    Toxicity

      The Agency has reviewed all toxicity studies submitted and has determined that the

                                            6

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toxicity database is complete and that it supports an interim reregistration eligibility
determination for all currently registered uses. Further details on the toxicity of methidathion
can be found in the "Human Health Risk Assessment Methidathion," dated August 9, 2000.  A
brief overview of the studies used for the dietary risk assessment is outlined in Table 2 in this
document.

      The toxicology database provides evidence that cholinesterase inhibition (ChEI) is the
most sensitive toxicological observation from exposure to methidathion in laboratory animals.
In an acute neurotoxicity study in rats following a single oral dose, methidathion was associated
with neurotoxicity in both sexes, as evidenced by decreases in maze activity and alterations in
functional observation parameters at the highest dose tested (HDT). In addition, there were
statistically-significant decreases in plasma, red blood cell (RBC) and brain cholinesterase
activity at all dose levels.     ,

      In a subchronic neurotoxicity study in rats, following dietary administration, methidathion
caused significant decreases in plasma, RBC and brain cholinesterase activity in both sexes.
Following  repeated dermal applications to rabbits, ChEFs (plasma, RBC and brain
cholinesterase activity in males and RBC and brain cholinesterase activity in females) was seen
under occlusive conditions, but no biologically or statistically-significant ChEI was seen under
nonocclusive conditions.  Chronic dietary exposures to dogs resulted in inhibition of RBC and -
brain cholinesterase activity, as well as elevation of hepatic enzymes, gross hepatic lesions and
microscopic presence of bile plugs, distended bile canaliculi and chronic hepatitis.

       No evidence of carcinogenicity was seen in male or female rats; however, there was
evidence of carcinogenicity in male mice at the highest level tested (benign and malignant liver
tumors were seen). The Agency has classified methidathion as a Group C, possible human
carcinogen and did not recommend a quantitative risk assessment for human risk   .
characterization. The Agency deemed that a quantitative cancer risk assessment was
unnecessary because the evidence as a whole (i.e., one sex, one species, common tumor type, no
increase in proportion of malignant tumors or apparent shortening of time to tumor) was not
considered strong enough to warrant a quantitative estimation of human risk. This was
 supported  by the lack of evidence of mutagenicity under both in vivo and in vitro conditions.

       There was no evidence of increased susceptibility following in utero exposures to rats and
 rabbits as well as pre/post-natal exposure to rats. Additionally, there was no evidence of
 abnormalities in the development of the fetal nervous system hi these studies.

       An acute neurotoxicity study is available, but was not used to select an endpoint for the
 acute dietary risk assessment, since a No Observable Adverse Effect Level (NOAEL) was not
 identified.  The NOAEL (0.2 mg/kg/day) and endpoint (cholinesterase inhibition), which were
 selected for use in the acute dietary risk assessment, were derived from the subchronic
 neurotoxicity study.  The results of these two studies support one another because the effects and
 levels at which they are observed are similar.

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                 b.    FQPA Safety Factor
      The FQPA Safety Factor for the protection of infants and children was removed (i.e.,
reduced to Ix) for methidathion since: (1) the toxicology data base is complete; (2) there was no
evidence of increased susceptibility seen following in utero exposure to rats and rabbits; (3)
there was no evidence of increased susceptibility in the offspring in the two-generation
reproduction study in rats; (4) there was no evidence of abnormalities in the development of the
fetal nervous system in the offspring; (5) there was no evidence for requiring a developmental
neurotoxicity study; (6) adequate actual data, surrogate data, and/or modeling outputs are
available to satisfactorily assess dietary exposure and to provide a screening level drinking water
exposure assessment; and (7) there are no registered residential (home owner) use.

      Acute and chronic dietary exposure risk assessments were conducted for the U.S.
population and various population subgroups including infants and children.  Aggregate acute
and chronic risk assessments addressed the potential dietary exposure to methidathion residues
from food and drinking water. Because there are no registered uses of methidathion in
residential settings, the aggregate assessment for the general population and specific subgroups
includes only food and water exposures.  Risk assessments were also conducted for dermal and
inhalation exposures to occupational pesticide handlers (mixers/loaders/applicator) as well as for
workers during postapplication activities.

      For acute dietary risk assessment, aNOAEL of 0.2 mg/kg/day established in the
subchronic neurotoxicity study in rats was selected. The NOAEL was based on significant
plasma, RBC and brain ChEI seen at 0.6 mg/kg/day (LOAEL). An Uncertainty Factor (UF) of
100 was applied to the NOAELs to account for intraspecies extrapolation (lOx), interspecies
variation (lOx) and the FQPA safety factor (Ix).  The acute Reference Dose (RfD) was 0.002
mg/kg/day.

      For chronic dietary risk assessment, aNOAEL of 0.15 mg/kg/day, established in the
chronic toxicity study hi dogs, was selected.  The NOAEL was based on significant RBC, and
brain ChEI seen at 1.33 mg/kg/day (LOAEL). A UF of 100 was applied to the NOAELs to
account for intraspecies extrapolation (lOx), interspecies variation (lOx), and FQPA safety factor
(Ix).  The chronic RfD was 0.0015 mg/kg/day.

Table 2.   Summary of Toxicological Endpoints and Other Factors Used in the Human
           Dietary Risk Assessment of Methidathion
Assessment
Acute Dietary
Dose
NOAEL
(mg/kg/day)
0.20
Endpoint
Plasma, red blood cell and
brain ChEI at a LOAEL of
0.6 mg/kg/day
.Study
Subchronic
neurotoxicity in
rats
UF
100
JPQPA
Safety
Factor
1
PAD
(mg/kg/day)
0.0020

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Assessment
Chronic
Dietary
Dose " "
NOAEL ;
(mg/kg/day) *
0.15

il " i- <"
Endpoint " " ,
** /-
s
RBC ChEI and liver toxicity
ataLOAELof 1.33
mg/kg/day

Study
Chronic toxicity
in dogs

TJF
100

FQPA
Safely
Factor
1

PAD
(mg/kg/day)
0.0015

                c.    Population Adjusted Dose (PAD)

     The PAD is a term that characterizes the dietary risk of a chemical and reflects the RfD,
either acute or chronic, that has been adjusted to account for the FQPA safety factor.
Accordingly, since the FQPA safety factor for methidathion is Ix, the RfD is numerically equal
to the PAD.  Risk estimate that are less than 100% of the acute or chronic PAD does not exceed
the Agency's risk concern.

                d.    Exposure Assumptions

     Methidathion residues are generally not expected to occur on any food commodities
except citrus. Methidathion is non-systemic and is applied to plants or trees before the edible
portion of the plant has formed (i.e., dormant  treatments).  Foliar treatments of citrus
commodities while the fruits are on the tree do result in residues; however, these residues are
limited almost entirely to the peel. Processing of these fruit results in very low residues in
peeled fruit and juice.

     A revised acute dietary risk analysis for methidathion was conducted with the Dietary
Exposure Evaluation Model (DEEM™). DEEM incorporates consumption data generated in
USDA's Continuing  Surveys of Food Intakes by Individuals (CSFII), 1989-91.  The highly
refined acute dietary  analysis used percent-crop treated data and residue distributions based on
field trial or USDA Pesticide Data Program (PDP) monitoring data which reflect actual uses. In
addition, zero residues were assumed for apples and stone fruits since: no residues were detected
hi field trials, PDP or FDA  monitoring data; the timing of application is unlikely to leave
residues in the edible crop and, environmental fate data show that methidathion dissipates
rapidly.

      The chronic dietary risk assessment for methidathion was conducted using the Dietary
Risk Estimate System (DRES) analysis. This analysis incorporates percent-crop treated data and
some anticipated residue data.

                  e.     Food Risk Characterization

      The acute dietary risk assessment, based on probabilistic exposure analysis (Monte Carlo),
indicates that methidathion residues in the diet do not  exceed the Agency's level of concern for
any of the population subgroups examined. The highly refined assessment, based on an acute

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PAD of 0.0020 mg/kg and conducted at the 99.9th percentile of exposure, revealed that the
percentages of the acute PAD occupied ranged from 14% for females (13+, nursing) to 64% for
children (less than one year of age). Percent crop treated data, USDA Pesticide Data Program
(PDF) monitoring data, and field trial data were used in this assessment.  The acute dietary
exposure to methidathion from its pesticidal use does not exceed the Agency's level of concern.

      The chronic dietary risk assessment was partially refined, using both percent crop treated
data and anticipated residues. The percent of the chronic PAD occupied from dietary exposure
to residues of methidathion ranged from 3% for females (13+, nursing) to 23% for children (one
to six years).  This assessment was based on a chronic PAD of 0.0015 mg/kg/day. The chronic
dietary exposure to methidathion from its pesticidal use does not exceed Agency's level of
concern.

           2.   Dietary Risk from Drinking Water

      Drinking water exposure to pesticides can occur through ground water and surface water
contamination. EPA considers both acute (one day) and chronic (lifetime) drinking water risks
and uses either modeling or actual monitoring data, if available, to estimate those risks.
Modeling is considered to be an unrefined assessment.  Some ground water and surface water
monitoring data were available for methidathion, but were not considered appropriate for
estimating drinking water exposure; therefore, modeling was used to estimate drinking water
risks from'these sources.

      Estimated environment concentrations (EECs) were obtained for ground and surface water
by Tier I, SCI-GROW model for ground water and Tier II, PRZM-EXAMS model for surface
water. The EECs were 0.4 ppb in ground water, and 5.6 ppb and 0.6 ppb, respectively, for the
acute (peak) and average (56-day) in surface water. These concentrations are supported by
limited California surface and ground water monitoring data. Because dietary risk assessments
based on exposures solely from food do not exceed levels of concern, both acute and chronic
drinking water levels of comparison (DWLOCs) were calculated and compared to EPA model
estimates and monitoring results. For the most sensitive subgroup (children <1 year), the acute
(7.2 ppb) and the chronic (13 ppb) DWLOCs do not indicate a risk concern from potential
exposure to methidathion residues in drinking water.                                    •

      For methidathion, the aggregate risks are limited to food and water exposure, as there are
no residential uses. Both the acute and the chronic dietary (food) risk estimates, risk estimates
for methidathion exposure, were less than 100% of the acute and chronic PAD's.  Additionally
surface and ground water acute and chronic EECs did not exceed the DWLOC. Therefore,
aggregate acute and chronic dietary risk estimates associated with consumption of methidathion
in food and water do not exceed the Agency's level of concern.
                                          10

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           a.    Surface Water

      A Tier II, PRZM-EXAMS screening model is used to estimate the upper-bound
concentrations of methidathion in drinking water derived from surface water. This model is
based on more refined, less conservative assumptions than the Tier I, GENEEC screening model.
The index reservoir represents a watershed that is more vulnerable than most that are sources of
drinking water. It was developed from a real watershed in western Illinois and takes into
account various soils, weather and cropping practices.

      Based on rainfall records and crop production practices, citrus was chosen to represent the
methidathion site with the highest run-off potential.  Modeling results are based on citrus use  in
California, with a typical application rate of 3.0 Ibs. a.i./A and a maximum application rate of
5.0 Ibs. a.i./A. The Agency estimates drinking water concentrations from surface water of 17.1
and 1.8 ppb, respectively, for peak value and annual average value at the 3.0 Ibs. rate and 28.5
and 3.01 at the 5.0 Ibs. rate.

           b.    Ground Water

      A Tier I, SCI-GROW screening model was used to estimate drinking water concentrations
of methidathion derived from ground water.  Tier I, SCI-GROW is an empirical screening model
based on actual ground water monitoring data collected from small-scale prospective ground
water monitoring studies for the registration of a number of pesticides that serve as benchmarks
for the model. The current version of SCI-GROW provides realistic estimates of pesticide
concentrations in shallow, highly vulnerable ground water (i.e., sites with sandy soils and depth
to ground water of 10 to 20 feet). Because of the conservative nature of the monitoring data on
which the model is based, Tier I, SCI-GROW provides an upper bound estimate of pesticide
residues in ground water.  The Agency estimates 0.2 ppb as the upper bound estimate of
methidathion in ground water.

           c.    Monitoring Data

      The Agency considered monitoring data from several sources for its drinking water
assessment. None of these monitoring data were used for the drinking water assessment because
samples could not be linked to drinking water sources in methidathion use areas because of other
uncertainties associated with the data.  For example, EPA's STORET database contains a total of
274 well samples in  California from 1984 to 1987, however, no detection limit was reported. A
second source of monitoring data is the Department of Health Services, California Public
Drinking Water Sources. The methidathion database included a total of 265 drinking water
samples (259 from ground water sources and 6 from surface water sources).  The results
indicated no positive detections.
                                          11

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           d.    Drinking Water Levels of Comparison

      To determine the maximum allowable contribution of water-containing pesticide residues
permitted in the diet, EPA first looks at how much of the overall allowable risk is contributed by
food (and if appropriate, residential uses) and then determines a "drinking water level of
comparison" (DWLOC) to determine whether modeled or monitoring levels exceed this level.
The Agency uses the DWLOC as a surrogate to capture risk associated with exposure from
pesticides in drinking water.  The DWLOC is the maximum concentration in drinking water
which, when considered together with dietary exposure, does not exceed a level of concern.

      For acute risk, the potential drinking water exposure derived from either ground or surface
water was modeled using both the typical application rate for citrus of 3.0 Ibs. a.i./A and the
maximum application rate of 5.0 Ibs. a.i./A. At the typical rate, the acute risk is not of concern
for all populations because the peak methidathion Estimated Environmental Concentrations
(EECs) of 17.1 ppb for surface water and 0.1 ppb for ground water are less than the  acute
DWLOC. At the maximum rate, acute risk to infants, the most sensitive subgroup, is of concern
for those whose drinking water is derived from surface water because the DWLOC of 19 is less
than the surface water EEC of 28.5. As stated earlier, modeling with the index reservoir and the
Percent Crop Area is intended for use as a screen. Actual concentrations of methidathion in
surface water and finished drinking water are likely to be less.  Furthermore, the 5 Ibs. a.i./A rate
is used only intermittently. The table below presents the calculations for the acute drinking
water assessment.

Table 3.   Summary of DWLOC Calculations for Acute Risk

Population
Subgroup

U S
Population
Adult Females
Infants <1 yr.
Children 1-6

Acute PAD
(mg/kg/day)


0.0020
0.0020
0.0020
0.0020

Acute Food
Exposure
(mg/kg/day)


0.000318
0.000233
0.001280
0.000558

Allowable
Water
Exposure
(ing/kg/day)


0.001682
0.001767
0.00072
0.001442
K
Ground
Water Peak
EEC (ppb)


0.2
0.2
0.2
0.2
Surface
Water
Acute
EEC1 :
X
(PPb)

28.5
28.5
28.5
28.5
'Surface
Water
Acute
EEC1
(PPb)

17.1
17.1
17.1
17.0

DWLOC
(PPb)


59
53
7
22
 EEC based on 5.0 Ibs. a.i./A, which is the maximum rate used infrequently on citrus only
2 EEC based on 3.0 Ibs. a.i./A use, which is the typical rate for citrus and the maximum rate for all other crops

      For chronic risk, potential exposures to drinking water derived from either ground or
surface water is not of concern for any population because the EECs in ground and surface water
are less than the chronic DWLOC at both the 3.0 Ibs. a.i./A and the 5.0 Ibs. a.i./A rates. The
table below presents the calculations for the chronic drinking water assessment.
                                           12

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Table 4.   Summary of DWLOC Calculations for Chronic Risk
Population
Subgroup
U.S.
Population
Adult Females
Infants <1 yr.
Children 1-6
Chronic PAD "
(mg/kg/day)
0.0015
0.0015
0.0015
0.0015
Chronic Food
Exposure ',,
(mg/kg?day)
0.000137
0.000040
0.000179
0.000338
Allowable
Water
Exposure
(mgTkg/day)
0.001363
0.001460
0.001321
0.001162
Ground
Water
Peak EEC
(Ppb)
0.1
0.1
0.1
0.1
Surface J
Water
Chronic ,
.EEC1
(ppto) *
3.0
3.0
3.0
3.0
Surface
•Water*
" Chronic
"EEC2
. (ppb):
1.8
1.8
1.8
1.8
DWLOC
(ppb);*
48
44
13
17
1 EEC based on 5.0 Ibs. a.i./A, which is the maximum rate used infrequently on citrus only
2 EEC based on 3.0 Ibs. a.i./A use, which is the typical rate for citrus and the maximum rate for all other crops

           3.    Aggregate Risk

      An aggregate risk assessment looks at the combined risk from dietary exposure (food and
drinking water routes) and residential risk, when appropriate.  Because methidathion has no
residential uses, the risk from food and drinking water sources alone serves as the aggregate risk
assessment. As discussed in the drinking water section above, the only scenario potentially of
concern is the risk to infants from the use of the maximum rate on citrus.

           4.    Occupational Risk

      Occupational workers can be exposed to methidathion through mixing, loading and/or
applying a pesticide or re-entering treated sites. Occupational handlers of methidathion include
individual farmers or growers who mix, load and/or apply pesticides and professional or custom
agricultural applicators. Risk for all of these potentially exposed populations is measured by a
Margin of Exposure (MOE) which determine how close the occupational or residential exposure
comes to a No Observed Adverse Effect Level (NOAEL). Generally, MOEs greater than 100 do
not exceed the Agency's risk concern.

            a.    Toxicity

      The toxicity of methidathion is integral to assessing the occupational risk. All risk
calculations are based on the most current toxicity information available for methidathion,
including a 21-day dermal toxicity study.  The toxicological endpoints and other factors used in
the occupational risk assessments for methidathion are listed below.
                                             13

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 Table 5.   Summary of Toxicological Endpoints and Other Factors Used in the Human
           Occupational Risk Assessment for Methidathion
Assessment
Short-term dermal
Intermediate-term dermal
Short-term inhalation
Intermediate-term inhalation
Dose
NOAEL
(mg/kg/day)
NOAEL = 20
mg/kg/day
NOAEL = 0.2
mg/kg/day
NOAEL = 0.2
mg/kg/day
NOAEL = 0.2
mg/kg/day
Endpoint '
LOAEL not established
Plasma, red blood cell and
brain cholinesterase inhibition
at the LOAEL of 0.6
mg/kg/day
Plasma, red blood cell and
brain cholinesterase inhibition
at the LOAEL of 0.6
mg/kg/day
Plasma, red blood cell and
brain cholinesterase inhibition
at the LOAEL of 0.6
mg/kg/day
; Study
21 -day dermal
toxicity in rabbits
90-day subchronic
neurotoxicity in
rats
90-day subchronic
neurotoxicity in
rats
90-day subchronic
neurotoxicity in
rats
Dermal
Absorption
Factor *
Not
Applicable
30%
100%
100%
      The short-term dermal endpoint is based on a NOAEL of 20 mg/kg/day established in the
21-day dermal toxicity study in rabbits.  Generally, dermal toxicity studies with thio-
organophosphates such as methidathion tend to underestimate the toxicity of these chemicals
because rabbits possess high concentrations of plasma carboxyl esterases, which deactivate the
chemical before it is converted into the active oxon. However, in the case of methidathion, the
weight of evidence from the oral and dermal toxicity data in rats and rabbits indicates that the
dose used in risk assessment would not underestimate any potential dermal risk from
methidathion exposure.

      For assessments that rely on an oral study to approximate dermal toxicity, the Agency
applies a dermal absorption factor to the data derived from the oral study to estimate the amount
of methidathion that may be absorbed through the skin. The Agency believes that the ratio of
the NOAELs of 6 mg/kg/day in the oral developmental toxicity study in rabbits and the NOAEL
of 20 mg/kg/day in the 21-day dermal toxicity study in rabbits yield a 30% dermal absorption
factor. Although 30% may overestimate dermal absorption for the technical product, its
physical/chemical properties (i.e., low melting point and good water solubility) support a
moderate dermal absorption.
Table 6. Acute Toxicity Profile for Occupational Exposure to Methidathion
Route of Exposure
Dermal
Inhalation
Eye Irritation
Dermal Irritation
MRIDNo.
00139326
00011449
00159199
00159200
Toxicity Category ,
.11
III
III
IV
                                          14

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•Route.of Exposure
Dermal Sensitizer
MRIDNo.
00252433
", Toxicity Category
Not Applicable
     The toxicology database is complete and provides evidence that cholinesterase inhibition
(ChEI) is the most sensitive toxicological observation in laboratory animals. Technical
methidathion has high acute oral toxicity (Toxicity Category I) and moderate acute dermal and
inhalation toxicity (Toxicity Categories II and III, respectively). Methidathion is a mild eye
irritant (Toxicity Category III), is not a skin irritant (Toxicity Category IV) and is not a dermal
sensitizer. Methidathion did not induce organophosphate induced delayed neuropathy (OPIDN)
in the hen.  In an acute neurotoxicity study in rats, following a single oral dose, methidathion
was associated with neurotoxicity in both sexes as evidenced by decreases in maze activity and
alterations in functional observation parameters at the highest dose tested (HDT). In addition,
there were statistically-significant decreases in plasma, red blood cell (RBC) and brain
cholinesterase activity at all dose levels. (MRIDs 00139328, 00139326, 00011449, 00159199,
00159200,-00252433, 00011704,43145903 and 43590304)

            b.    Exposure

      Chemical-specific exposure data were not available for methidathion, so risks to pesticide
handlers were satisfied using data from the Pesticide Handlers Exposure Database (PHED),
Version 1.1 The quality of the data and exposure factors represents the best sources of data
currently available to the Agency for completing these kinds of assessments; the application
rates are derived directly from methidathion product labels.  The exposure factors (e.g., body
weight, amount treated per day, protection factors, etc.) are all standard values that have been
used by the Agency over several years, and the PHED unit exposure values are the best available
estimates of exposure. Some PHED unit exposure values are high quality while others are of
lower quality, but are the best available data. The quality of the data used for each scenario
assessed is discussed in the "Human Health Risk Assessment Methidathion," dated August 9,
2000, which is available in the public docket.

      Anticipated use patterns and application methods, range of application rates and daily  .
amount treated were derived from current labeling. Application rates specified on methidathion
labels range from 0.5 to 5.0 pounds of active ingredient per acre in agricultural settings. The
Agency typically uses acres treated per day values that are thought to represent eight solid hours
of application work for specific types of application equipment.                      .

      Occupational handler exposure assessments are conducted by the Agency using different
levels of personal protection. The  Agency typically evaluates all exposures with minimal
protection and then adds additional protective measures using a tiered approach to obtain an
appropriate MOE (i.e., going from minimal to maximum levels of protection).  The lowest suite
of PPE is baseline PPE.  If required (i.e., MOEs are less than 100), increasing levels of risk
mitigation (personal protective equipment (PPE) are applied. If MOEs are still less than 100,
                                            15

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engineering controls (ECs) are applied. In some cases, EPA will conduct an assessment using
PPE or ECs taken from a current label. The levels of protection that formed the basis for
calculations of exposure from methidathion activities include:
     Baseline:
     Wettable Powder Label:
     Emulsifiable Concentrate Label:
     Minimum PPE:
     Maximum PPE:
     Engineering controls:
                                       Long-sleeved shirt and long pants, shoes and socks.
                                       Baseline + chemical-resistant gloves.
                                       Baseline + chemical-resistant gloves and a respirator.
                                       Baseline + chemical-resistant gloves and a respirator.
                                       Coveralls over long-sleeved shirt and long pants,
                                       chemical resistant gloves, chemical footwear plus
                                       socks, chemical resistant headgear for overhead
                                       exposures, and a respirator if risk is driven by
                                       inhalation.
                                       Engineering controls such as a closed cab tractor for
                                       application scenarios, or a closed mixing/loading
                                       system such as a farm closed mechanical transfer
                                       system for liquids or a packaged-based system (e.g.,
                                       Lock-JV-Load for granulars or water soluble
                                       packaging for wettable powders). Some engineering
                                       controls are not applicable for certain scenarios (e.g.,
                                       for handheld application methods, there are no known
                                       devices that can be used to routinely lower the
                                       exposures).

           c.    Occupational Handler Risk Summary

      Occupational exposure risk assessments for handlers (mixer/loaders/applicators) were
based on the Pesticide Handler's Exposure Database (PHED); and MOEs were calculated for
dermal and inhalation exposures. An MOE of 100 or greater does not exceed EPA's level of
concern. For methidathion, the Agency has identified 12 major exposure scenarios for handlers
mixing, loading and applying products containing methidathion to agricultural crops.  Of the 12
scenarios, 11  have MOEs greater than 100 with minimum personal protective equipment (PPE)
[with water soluble packets (WSP), single layer clothing (SLC) which includes long sleeve shirt,
long pants, shoes and socks and gloves], or with additional PPEs,  [that include WSP, coverall
over SLC (i.e., double layer clothing (DLC)], gloves and dust/mist respirator] or with
engineering controls [WSP, SLC, gloves and closed cabs].  For one remaining scenario
(mixing/loading in support of aerial application), risk estimates are of concern since even with
engineering controls, the MOEs for dermal (MOE = 91) and inhalation (MOE = 95) are below
the required MOE of 100 (EPA's level of concern).

     Because the dermal and inhalation NOAELs are based on different toxicological endpoints
(i.e., lack of systemic toxicity via the dermal route and ChEI via the oral route), it is
inappropriate to combine the exposures for these pathways. Therefore, only route-specific
                                          16

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MOEs are appropriate for evaluation. However, since ChEI is the principal toxicological
endpoint of concern for OP's via the dermal and inhalation routes, an analysis of the total MOEs
was conducted for risk characterization purpose only. The combined exposure (dermal+
inhalation), resulted in MOEs that were less than 100 for two additional exposure scenarios for
which the route-specific MOEs were greater than 100: mixing/loading WSP in support of aerial
application (Dermal MOE = 140, Inhalation MOE = 170, Total MOE = 77) and liquid aerial
application with a fixed-wing aircraft (Dermal MOE = 150, Inhalation MOE = 120, Total MOE
= 67). The 12 major handler exposure scenarios identified for methidathion include the
following; they are summarized in Table 7 below.

Table?.   Summary of Occupational Exposure Scenarios
Scenario No.
la, Ib, 2aand2b
Ib and 2b
Ic and 2c
3
4
5
6
7
8
Description
Mixer/Loader
Mixer/Loader
Mixer/Loader
Applicator
Applicator
Applicator
M/L/A
M/L/A .
Flagger
Product
Form - '
WSP/EC
WSP/EC
WSP/EC
Liquid
Liquid
Liquid
Liquid
Liquid
Liquid
' Application
•" Method
Aerial
Groundboom
Air Blast
Aerial
Groundboom
Air Blast
Low-Pressure
Hand Wand
Backpack Sprayer
Aerial
Crops
Citrus/Cotton
Cotton/Artichoke
Citrus/Apples
Citrus/Cotton
Citrus/Cotton
. Citrus/Apples
Nursery Stock
Nursery Stock
Citrus
Acres Treated
350
80
40
350
80
40
10 gal"
40gala
350
 M/L/A = Mixer/Loader/Applicator
 WSP - Water Soluble Packets
 EC = Emulsifiable Concentrate •  .                 ..-.,-••
 "0.5 Ib. a.i./100 gallons of water

                       1)    Agricultural Handler Risk

      Typically, the Agency combines the exposure from both dermal and inhalation pathways
 when the toxicity endpoints are the same. In the case of methidathion, the 21-day dermal study
 which serves as the basis for the dermal assessment of methidathion, did not identify a LOAEL
 (or endpoint) and the highest dose tested was selected as the NOAEL. The inhalation endpoint
 for methidathion is based on cholinesterase inhibition (see Table 5).  Because methidathion is an
 organophosphate, it is reasonable to assume that cholinesterase inhibition would also occur via
 the dermal route. Thus, it is appropriate to combine exposures from both pathways in assessing
 me risk to workers from using methidathion, as reflected in this document.

      Current methidathion Water-Soluble Package (WSP) product labels require long-sleeved
 shirt, long pants, waterproof gloves and shoes plus socks. In addition to this PPE, current EC
 (liquid) products require a respirator. Four of the eighteen exposure scenarios result in MOEs
 that do not exceed the Agency's level of concern (i.e., MOEs are greater than 100) when workers
                                            17

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wear minimum PPE (single layer of clothing and gloves). Of the remaining fourteen scenarios,
one has an MOE of 98 and two others have MOEs greater than 100, when workers use an organic
vapor-removing respirator. Of the remaining eleven scenarios, seven are not of concern if a
closed system is used. For the final four scenarios, two MOEs are 85 and 87 (mixing/loading the
liquid formulation and applying with aircraft, respectively) using engineering controls and two
others are 27 and 39 for mixing/loading the WSP for aerial application.  There are no data for the
two aerial scenarios with the open cockpit applications, therefore, only closed cockpit risk
estimates are provided.

Table 8.    MOEs for Methidathion Mixers, Loaders and Applicators
Scenario
Mixing/Loading Water-
Soluble Pkg. (WSP) Aerial
(la&lb)
Mixing/Loading WSP -
Groundboom (Ic & Id)
Mixing/Loading WSP - Air
blast (le)
Mixing/Loading Liquids -
Aerial (2a & 2b)
Mixing/Loading Liquids-
Groundboom (2c & 2d)
Mixing/Loading Liquids - Air
blast (2e)
Applying with Aircraft
(3a&3b)
Applying with Groundboom
(4a&4b)
Applying with Air blast
Sprayer (5)
Mixing/Loading/Applying
with Low-Pressure Handwand
(6)
Acres
350
1200
80
200
20
350
1200
80
200
20
20
350
1200
80
200
20
20
N/A •
Rate
(Ib a.Uday>
1750
1200
80
200
100
1750
1200
80
200
56
100
1750
1200
80
200
56
100
0.05
Min.
PPE1
Max. PPE*
See engineering
controls
6
8
122
49
175
98
28
40

200
(respirator
only)


See engineering
controls
199
80
30
17
8163

327
(respirator
only)
95
53

s Engineering Controls3
Dermal
"•MOE
140
200
1780
714
1430
93
136




360
530


>1000
737

Inhalation
MOE
33
49
730
290
580
964
1410




118
170


555 •
311

Combined
MOE
27
39
520
207
410
85
124




87
129


i 391
219

                                           18

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; " Scenario •* *' • „
'* ฅ
Mixing/Loading/Applying
with Backpack Sprayer (7)
Flaggers - liquid application
(8)
Acres
N/A
350
Rate
(Iba.L/day)
0.2
1750
Min.
PPE1
1300
1.7
t,
Max." PPE2
f
^ * -i

59
'C Engineering Controls3
Dermal
JMOE

3600
Inhalation
MOE
.. x.. -.

1100
Combined
MOE

870
1 Long pants, long-sleeve shirt, shoes, socks and chemical-resistant gloves (same as current label for WSP formulation).
2 Minimum PPE, plus coveralls and organic vapor-removing respirator.
3 Engineering controls refer to: water-soluble packages (scenarios la, Ib, Ic, Id and le); closed systems (scenarios 2a and
2b); closed cockpit (3a, 3b and 5); flagger in enclosed cab vehicle (8). For mixing/loading WSPs (scenarios la through
le), MOEs only provided for engineering control because wettable powder products are formulated as WSPs. PPE to be
used with engineering controls include long pants, long-sleeve shirt, shoes, socks, chemical-resistant gloves and apron
based on the Worker Protection Standard and methidathion's toxicity.

                       2)   Post-Application Occupational Risk

      The postapplication occupational risk assessment considered exposures to workers entering
treated sites in agriculture. All of the postapplication risk calculations for handlers completed in
this assessment are included in the "Human Health Risk Assessment Methidathion," dated August
9,2000.

      The Agency has determined that there is considerable potential for postapplication
occupational exposure to methidathion residues. The results of the Dislodgeable Foliar Residue
(DFR) studies conducted with methidathion on cotton and citrus crops indicate that workers (i.e.,
scouts, pickers) require entry restrictions or restricted entry intervals (REIs) before engaging in
postapplication activities.  Postapplication risks were estimated using crop-specific DFR data for
citrus and cotton. The citrus data were also translated to minor tree  crops and kiwis. The
combined results of citrus DFR studies conducted in California and  Florida were used for
safflower scouting and irrigation, as well as for artichoke cultivation and harvesting. An MOE of
100 or greater does not exceed the Agency's level of concern.

      For cotton scouting in North Carolina and Texas, the REIs are one day after treatment
(DAT) for early scouts, and for late scouts the REIs are at six days after treatment and seven days
after treatment in North Carolina and Texas, respectively.

      Based on a DFR study in citrus,  adjusted .for average application rate, a MOE of 100 is
achieved for citrus hand pruning and harvesting 9 days after treatment. A MOE of 100 is
achieved 5 days after treatment for lower-contact activities such as propping and worker scouting.
For other tree crops including mango, carambola,  longan and sugar apple, the DFR data were
translated from the citrus studies and adjusted for  label application rate. The MOEs exceeded
 100 for  hand harvesting these tree crops at 8 days  after treatment. Other lower-contact activities,
such as  scouting or propping, achieve an MOE of 100 three days after spraying.
                                               19

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      Translating the dissipation rate from the submitted citrus and cotton DFR studies data, a
REI of 2 days was obtained for workers scouting and irrigating safflower, while a REI of 15 days
is required for cultivating/harvesting/packing artichokes. Because methidathion is applied pre-
bulb formation, and the bulb requires 3 weeks to mature, it is not anticipated to present an
exposure risk for artichoke harvesters.

      It was determined from labeling that methidathion is applied prior to foliation or at budding
to all other tree crops (stone and pome fruit, nuts and olive trees) and kiwifruit vines.  Therefore,
there should be no foliar residue present, per se, during harvesting. Based on these agricultural
practices, the Agency has concluded that there should be negligible postapplication methidathion
chemical exposure to workers from major tree or vine crops other than citrus.

      There are no registered uses of methidathion at the present time that could result in
residential exposures. .The Agency recognizes that there are  many issues related to the use of
agricultural chemicals in the general population, i.e., spray drift exposures and exposures to farm
worker children and farm residents.  The Agency is in the process of developing guidance and
procedures for characterizing these kinds of exposures.  An assessment of the potential exposure
and risk from these kinds of exposures associated with the agricultural use of methidathion are
not addressed hi this document. Table 9 below shows the MOEs for various crops and activities.

Table 9.   Agricultural Post-Application MOEs
Crop
Artichokes
Citrus
Cotton
Tree crops (longan, sugar apple,
carambola)
Activity
Scouting, hoeing, irrigating
Hand cultivating/harvesting
Scouting, irrigating, weeding
Pruning and propping
Harvesting
Scouting (late season) in NC
Scouting (late season) in TX
Scouting (late season) in CA
Scouting, irrigating, weeding
Pruning and propping
Harvesting
MOE
155
88
110
150
98
120
89
110
98
130
90
115
94
130
210
87
110
78
98
120
Days after Treatment
0
18
19
0
3
4
7
8
2
. 3
2
3
1
•2
0
1
2
5
6
7
                                            20

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Crop
Dormant Trees (stone and pome
fruit, nuts and olive trees)
Safflower, timothy, alfalfa and.
clover
Tobacco
,- - Activity >
MOE
Days after Treatment .
See tree crops
See cotton
Harvesting/bundling
100
3
           d.    Human Incident Data

     In assessing the incidents for methidathion, the Agency consulted four sources: the national
Poison Control Centers, California Department of Food and Agriculture (replaced by the
Department of Pesticide Regulation in 1991), the National Pesticide Information Center (NPIC)
and the Office of Pesticide Programs Incident Data System.

     In the Poison Control Center (PCC) database, there were a total of 46 methidathion cases.
Of these, 21 cases were occupational exposure; 15 (72%) involved exposure to methidathion
alone and 6 (28%) involved exposure to multiple chemicals, including methidathion.

     The incidence of systemic poisoning cases in agricultural workers reported to California
was compared to the number of applications of methidathion. Between 1982 and  1989, there
were 31 worker incidents where methidathion was the primary pesticide and 39 where
methidathion was part of multiple pesticide exposure. When used alone, methidathion ranked
number 3 (in comparison to the other 28 chemicals) in the ratio of poisonings per  1,000
applications in field workers.  Only methamidophos and azinphos-methyl ranked higher.

      The Agency also considered the number of methidathion poisonings when compared to the
quantity used.  According to both California and Poison Control Center data for handlers and
workers, when used alone, methidathion. ranked third highest in number of poisoning incidents
and health care referrals per 1,000 applications. However, this determination included fourteen
grape pickers who were  exposed when methidathion was applied to a nearby field. Considering
this event as a single exposure incident, the number of methidathion exposure incidents per 1,000
applications is comparable to the median handler and field worker exposure incidents per 1,000
applications of 29 pesticides.

      Detailed descriptions of 59 cases submitted to the California Pesticide Illness Surveillance
Program were reviewed. In these incidents, methidathion was either used alone or with one other
chemical (dicofol, dimethoate or xylene), but methidathion was judged to be responsible for the
health effects. Accidents, such as hoses breaking or pressure building up hi cans were responsible
for 5 exposures. Two reports noted that workers were not wearing personal protective
equipment.

      As of March 23, 1996, there were 3 reports in the Office of Pesticide Programs Incident
Data System of adverse effects to workers attributable to methidathion. In two reports, the same
                                            21

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 person mixed Supracideฎ with fertilizer and then spread the mixture on the ground on two
 separate occasions. He developed systemic signs of illness (dizziness, .nausea, sore throat and
 shortness of breath) on both occasions. In the other incident, a mixer/loader in California spilled
 Supracideฎ on his coveralls, but continued to work before changing clothes. Two days later, he
 developed ataxia, dizziness and vomiting and was treated for organophosphate poisoning. This
 incident occurred in 1995 and is not included with the analysis of the California data discussed
 above.

      The number of poisoning cases due to methidathion exposure reported to the Poison
 Control Center and the California Pesticide Illness Surveillance Program is small in relation to
 the numbers of poisoning cases associated with other OP and carbamate pesticides. Methidathion
 was not on the list of top 20 chemicals for which the National Pesticide Information Center
 (NPIC) received calls from 1984 through 1991, inclusive.

      B.    Environmental Risk Assessment

      A summary of the Agency's environmental risk assessment is presented below. For
 detailed discussions of all aspects of the environmental risk assessment, see the Environmental
 Fate and Effects Division chapter, dated November 30, 1999, and its addendum, dated April 4,
 2001, available in the public docket. Several revisions have been made since the preliminary risk
 assessment was completed and include the following: determining that the environmental fate
 database is adequate for the reregistration action; revising the assessment to use a foliar
 dissipation half-life of 6.6 days based on open literature, which did.not significantly change the
 Agency's overall risk conclusions; correcting an error in the toxicity value used to calculate the
 chronic risk quotients for freshwater invertebrates, which significantly lowered the risk estimates
 for these organisms.

      The Agency's risk assessment is based principally on methidathion's use on cotton, citrus,
 stone fruits, nut crops, and artichokes.  Methidathion is registered for single as well as multiple
 applications (up to 8 per season for artichokes), but is typically applied only 1-2 times per
 season. A further refinement of methidathion's potential for ecological risk is possible due to its
 predominant use in California. The majority of methidathion is used on citrus as a foliar spray.
 Methidathion is also used on other orchard crops as a nonfoliar dormant spray from mid
 November through February and on cotton as an early season foliar spray.

      The Agency's assessment suggests that the use of methidathion can result in adverse acute
 and chronic effects to terrestrial and aquatic organisms. The methidathion ecological risk
 assessment integrates the results of the exposure and ecotoxicity data to evaluate the potential for
 adverse ecological effects. The method divides exposure estimates by ecotoxicity data to derive
risk quotients (RQs) for acute and chronic effects. RQs are then compared to levels of concern
(LOCs), which are criteria used to indicate potential effects to nontarget organisms.  The criteria
indicate that a pesticide used as directed has the potential to cause adverse effects on nontarget
organisms. An acute RQ equal to or greater than 0.5 and/or a  chronic RQ equal to or greater than

                                           22

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1.0 results in some concern to the Agency, while RQs as low as 0.05 may be of concern under
special circumstances (e.g., for endangered aquatic species).

     Based on estimated environmental concentrations (EECs) from modeling and toxicity data
for aquatic organisms, the Agency's levels of concern are exceeded for acute and chronic effects
to fish and invertebrates. On avian and mammalian food items, methidathion's calculated foliar
dissipation rate of 6.6 days combined with its toxicity result in levels of concern for potential
chronic effects to birds which are exceeded for several weeks following application.

           1.    Environmental Fate and Transport

     Methidathion is relatively nonpersistent in soil with aerobic and anaerobic soil half-lives of
11 and 10 days, respectively. Dissipation half-lives of 5 to 30 days were reported in the top six
inches of soil in supplemental field studies.  Methidathion is moderately mobile with soil-water
partitioning coefficients (Kads) of 2 to 15 mL/g.  It is unlikely to persist in soil long enough to
result in significant contamination of ground water. Methidathion may enter surface water via
spray drift, in solution in runoff water and as residues adsorbed to eroding soil particles.  With an
aerobic soil half-life of 11 days and an anaerobic half-life of 10 days, methidathion is unlikely to
persist in water long enough to be a serious  ground water or drinking water problem.

      The relatively low octanol/water partition coefficient for methidathion of 295 suggests that
it will only moderately partition into the waxy component of leaves.  At the time of foliar
application, substantial amounts of applied methidathion could reach exposed soil and (to a lesser
extent) penetrate the canopy to reach canopy shielded soil.  It can also reach soil via washoff
during post-application rainfall events.

      The relatively low to moderate soil/water partitioning of methidathion (MRID 00158529)
indicates that the methidathion reaching soil may have limited to moderate potentials for leaching
and uptake by plants, and moderate to substantial potentials for runoff depending upon the soil
and other conditions.  However, the calculated overall half-lives of methidathion are 11.3 and 3
days from aerobic soil metabolism studies (MRIDs 44545101  and 42262501) and 10 days in an
anaerobic soil metabolism study (MRID 42262501). Therefore, substantial fractions of the
methidathion reaching soil may degrade and no longer be available for such physical removal
processes within 1-3 weeks after reaching the soil.

      None of the known degradates of methidathion are of toxicological concern. Therefore,
these degradates are not included in this assessment.

            2.    Risk to Birds and Mammals

      A study conducted using the mallard duck showed that methidathion was highly toxic to
 avian species on an acute oral basis. Two subacute dietary studies on the mallard duck (a
                                             23

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 waterfowl) and bobwhite quail (an upland gamebird) showed that methidathion was moderately
 to highly toxic on a subacute basis. (MRIDs 00157347, 00159201 and 42081701)

 Table 10.   Toxicity Endpoints to Assess Risk to Terrestrial Organisms from Methidathion
Species
Bobwhite quail
Mallard duck
Laboratory rat
Laboratory rat
Laboratory rat
Honey bee
Honey bee
Test Type
sub acute dietary
reproduction
acute oral
acute dietary
2-generation reproduction
acute contact
acute foliar residue
; Results
LC50 = 224 ppm
NOAEC = 1 ppm
LOAEC =10 ppm (increased cracked eggs)
LD50 = 12 mg/kg
1-day LC50 = 12 to 400 ppm1
NOAEL = 5 ppm
LOAEL = 25 ppm (lower mating index/pup
weight)
LD50 = 0.236 ug/bee
RT25 > 3 days at 5.0 Ib a.i./A2
Source of Data
(MRID)
42081701
44381602
00012714
N/A
40079812
40079813
00036935
42081708
 1-day LCJO = LD50 (mg/kg) / proportion of body weight consumed. The mammalian LD50 of 12 mg/kg was used to
estimate 1-day LCJ0s ranging from 12 ppm for a 15-gram herbivore (consumes 95%) to 400 ppm for a 1,000 gram
granivore (consumes 3%)
2 RT;,j (residual time) time required to reduce mortality of caged bees to field weathered spray deposits

      The following table shows predicted residues on terrestrial food items that result from
single and multiple applications of methidathion calculated from Hoerger and Kenaga (1972) as
modified by Fletcher et al. (1994):

Table 11.  Estimated Environmental Concentrations on Avian and Mammalian Food
           Items (ppm) Following a Single Application at 1.0 Ib. a.L/A
Food Items
Short grass
Tall grass
Forage and small insects
Fruits, pods, seeds and large insects
EEC (ppm)
Predicted Maximum Residue
240
110
135
15
EEC (ppm)
Predicted Mean Residue
85
36
45
7
      These residues served as the initial concentrations from which first-order residue declines
were calculated. When considering repeat applications, degradation over time is simulated from
the first application to a period following the last application. The time period modeled varies,
depending on the number of applications, the interval between applications and the length of time
the residues were expected to exceed the chronic risk LOG. The program generates a peak value
as well as a time-weighted average value for the time period modeled. The Fletcher peak
maximum value for the food item was compared to the acute toxicity value to produce the acute
RQ.  For chronic exposure, the Fletcher mean value was used as the initial input. Both the peak
mean and time-weighted average mean EECs were used to compute chronic RQs.
                                           24

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      The Agency's assessment suggests the potential for .acute effects to nontarget terrestrial
organisms from all single and multiple applications at or above 0.5 Ib a.i./A for all contaminated
food items except seeds. Though the RQ at 0.5 Ib. a.i./A from ingesting contaminated seeds
exceeds the endangered species LOG for granivores, the Agency is more concerned about risk to
nontarget animals that ingest contaminated vegetation. The avian acute RQs range from less than
0.1 on contaminated seeds (single application at 0.5 Ib. a.i./A) to 5.5 on short grass (3
applications with 7 day intervals at 3.0 Ibs. a.i./A). For the same use patterns/food items,
mammalian acute RQs range from less than 0.1 to 97. The following table illustrates that for
typical application rates, with only one or two applications per year, acute LOCs (0.5) for birds
are slightly exceeded, but small mammal LOCs are exceeded by a substantial margin.

Table 12.   Avian/Mammalian Acute Risk Quotients1 for Single Application of
            Methidathion
Site
App. Rate
(Lbs. a.i./A)
•.Food Items '
^ ^ ^'
."Peak Maximum1 EEC
rs 'f-%?m) "
Avian Acute LC50 = 224 ppm (Bobwhite Quail)
Almonds, walnuts, stone
fruits
Citrus
Artichoke
Cotton
1.5
(1 application)
2
(1 application)
1
(2 applications, 14
days apart)
0.5
(2 applications, 5 days
apart)
Short grass
Forage
Short grass
Forage
Short grass
Forage
Short grass
Forage
360
270
480
270 .
295
166
191
107
Mammalian (Herbivore/Insectivore) Acute LCg, = 12 to 80 ppm *
Citrus
Almonds, walnuts, stone
fruits
Artichokes
Cotton
2
(1 application) .
1.5
, (1 application)
1
(2 applications, 14
days apart)
0.5
(2 applications, 5 days
apart)
Short grass
Forage
Short grass
Forage '
Short grass
Forage
Short grass
Forage
480
270
360
202
295
166
191
107
Acute RQ
(EEC/
LC50)

2
1.2
2
1.2
1.3
0.7
0.8
0.5

6-38
2-21
4-28
2-16
166
2-13
2-15
1-8
 1A foliar dissipation half-life 6.6 days (Willis et al. 1987) was assumed.
 2 One-day LC50 = LD50 (mg/kg) / proportion of body weight consumed. The mammalian LD50 of 12 mg/kg was used to
 estimate 1-day LCSOs ranging from 12 ppm for a 15-gram herbivore (consumes 95%) to 400 ppm for a 1000 gram
 granivore (consumes 3%).
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      When the NOAECs from reproduction studies are compared to estimated exposure levels,
 the avion chronic RQs range from 1.0 (the 30-day time-weighted mean on seeds for a single
 application at 0.5 Ibs. a.i./A) to 436.0 (the peak mean on short grass for 3 applications at with 7
 day intervals at 3.0 Ibs. a.i./A). When the NOAEL in the 2-generation rat study is used as an
 endpoint, the chronic RQs range from less than 1 to 87.  For both birds and mammals, most of the
 RQs are well above the Agency's level of concern.  The  following table illustrates that for typical
 application rates, with only one or two applications per year, chronic LOCs are exceeded by a
 substantial margin and may last for several weeks. In most cases, the time weighted average
' mean as well as the peak mean and estimated exposure levels exceed the test levels at which
 effects were observed (LOAECs).

 Table 13.   Avian/Mammalian Chronic Risk Quotients1 for Methidathion
Site
Application
(lba.L/A)
Food Items
Peak Mean i _ _
EEC (ppm) j Q
:
TimeWgtAvg.j
Mean EEC j RQ
(ppm) '. |
# Days Peak
Mean>LOC
Avian Chronic NOAEL = 1 ppm, LOAEL = 10 ppm
Almonds
Walnuts Stone
Fruits
Artichoke
Cotton
1.5 lbs./A
(1 application)
1.0 lb./A
2 apps /14 days
0.5 lb./A
2 apps/5 days
Short grass
Forage
Short grass
Forage
Short grass
Forage
128 J128
68 J68
104 j 104
55 J55
68 |68
36 |36
40 J40
21 J21
50 150
27 |27
27 127
14 |14
>30
>30
>30
Mammal Chronic NOAEL = 5 ppm, LOAEC = 25 ppm
Almonds
Walnuts Stone
Fruits
Artichoke
Cotton
1.5 lb./A
lapp
1.0 Ib/A
2 apps/14 days
, 0.5 Ib/A
2 apps/5 days
Short grass
Forage
Short grass
Forage
Short grass
Forage
128 i25
68 |13 '
104 |21
55 111
68 |14
36 |7
40 i8
21 J4 •
50 j 10
27 |5
27 |5
14 |3
>30
25
>30
>30
24
1 A foliar dissipation half-life 6.6 days was assumed, FATE model run was for 30 days.
      The acute and chronic RQs are based solely on dietary exposure via contaminated food
sources. Other routes of exposure, including dermal, inhalation and drinking from contaminated
puddles might also be important (Driver et al 1991) and could increase acute risks if methods
were available to include them in the risk assessment.  Other factors contributing to uncertainty
(especially for chronic effects) include the point during the reproductive cycle that exposure
occurs and the duration of exposure required to cause physiological or sublethal effects to adults
that may impact breeding and nurturing behavior.
                                           26

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           3.    Risk to Aquatic Species

     Although Tier II PRAM EXAM modeling with Index Reservoir and Percent Crop Area
input was used to refine the Drinking Water Assessment, those EECs were not used for an
Ecological Aquatic Risk Assessment.  Whereas, EECs for a Drinking Water Assessment are to
reflect concentrations found in reservoirs providing drinking water to a community, the EECs for
an ecological assessment reflect what non target, non human organisms would be exposed to in a
shallow pond adjacent to an area treated with a pesticide. Tier II modeling for only the typical
use on three crops - apples (surrogate for nut and stone fruits), citrus and cotton — concentrations
of methidathion in surface water, when combined with toxicity values, exceed LOCs for acute
and chronic effects to fish and invertebrates. The risk would be higher for the present maximum
labeled rates for the same uses. In, California where the majority of methidathion is used, mostly
as a dormant spray, aquatic organisms are likely to be exposed through runoff during the winter
rainy season. During the remainder of the year, surface water contamination would be primarily
through drift The following table contains the toxicity values used in the risk assessment.

Table 14.  Toxicity Endpoints to Assess Risk of Aquatic Organisms from Methidathion
Species |
^ * ฃV !
Test Type
""f yf Results (ppb of a.i.)
***** ^ *•
'Source of Data
(MRID)
Freshwater Species
Bhiegill
Fathead minnow
Water flea (Daphnia magna)1
Water flea
Acute
Early Life Stage
Acute
Life Cycle
LC50 = 2.2
NOAEC = 6.1
LOAEC = 12.0 (reduced post hatch survival
and growth)
LC50 = 3.0
NOAEC = 0.66
LOAEC =1.13 (reduced young per female
per day)
00011841
00015735
42081704
42081707
Marine Species
Sheepshead minnow
Eastern oyster larvae
Mysid1
Mysid
Acute
Acute
Acute
Life Cycle
LC50 = 7.8
EC50 = 7.9
EC50 = 0.59
NOAEC = 0.022
LOAEC = 0.061 (reduced adult survival)
00157350
40079815
42207902
00157351
 1 Study conducted on 2E (25.5% a.i.).

      Freshwater Species

      For freshwater fish, the acute RQs based on Tier II modeled EECs range from 0.4 (2 aerial
 applications of 0.5 Ib a.i./A to cotton in California ) to 4.0 (1 air blast application of 2.0 Ibs a.i./A
 to citrus in Florida).  The acute risk LOG is exceeded by multiple applications at rates greater
 than or equal to 0.5 Ib a.i./A, and single applications at rates greater than or equal to 1.5 Ibs
 a.i./A. For freshwater fish, the chronic RQs for the same scenarios ranged from 0.19 (2 aerial
                                           27

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 applications of 0.5 Ib a.i./A to cotton in California) tol .88 (1 air blast application of 2.0 Ibs a.i./A
 to citrus in Florida). Multiple applications of methidathion at 0.5 Ib a.i./A and greater, and single
 applications of 2 Ibs a.i./A and greater resulted in exceedance of the chronic LOG.

      For freshwater invertebrates, the acute RQs based on Tier II modeled EECs range from 0.9
 (2 aerial applications of 0.5 Ib a.i./A to cotton in California ) to 8.9 (1 air blast application of 2.0
 Ibs a.i./A to citrus in Florida). The acute risk LOG is exceeded by multiple applications at rates
 greater than or equal to 0.5 Ib a.i./A, and single applications at rates greater than or equal to 1.5
 Ibs a.i./A.  Chronic RQs for the same scenarios ranged from 2.8 (2 aerial applications of 0.5 Ib
 a.i./A to cotton in California ) to 28.5  (1 air blast application of 2.0 Ibs a.i./A to citrus in Florida).
 All application rates exceed the chronic LOG.

      The monitoring data mentioned by the registrant is not sufficiently robust enough for use in
 an ecological risk assessment. As stated in the USGS NAWQA report - "Pesticide data for
 surface water are insufficient to calculate loads or yearly trends, but can be used to assess
 geographic and seasonal occurrence of select pesticides and to relate their agricultural use in the
 study unit." The monitoring results thus can only be used as an indication of seasonal occurrence
 and not for quantitative aquatic exposure purpose. NAWQA data are usually not targeted
 specifically to methidathion and its use and therefore have limited utility in an ecological
 assessment. There is a lack of correlation between  sampling dates and the use patterns of the
 pesticide within the study's drainage basin. Due to different analytical detection limits, no
 specified detection limits, or high detection limits, a detailed interpretation of the monitoring data
 is not always possible.  Even based on the limited monitoring data, the methidathion
 concentration has been detected as high as 15.1 ug/L. (the more typical range is 0.07 - 2.25
 ug/L) in the Sacramento-San Joaquin drainage system. The monitoring data are comparable with
 the peak concentrations of the modeling results for the typical California citrus (5.65 ug/L) and
 California cotton (2.69 ug/L) scenarios, even though the modeling simulates standing water
 environment (e.g., a farm pond), where the monitoring focuses on moving water (e.g., creek,
 stream or river).

      The primary area of uncertainty associated with the  freshwater aquatic risk assessment is
 for chronic risk due to the use of the fathead minnow Fish Early Life Stage  test. The NOAEC of
 6.1 ppb is virtually the same as the LC50s of several other test species including: rainbow trout
 ranging from 6.6 ppb (MRID 420081703) to 14 ppb (MRID 40098001); bluegill ranging from
 2.2 ppb (MRID 00011841) to 9 ppb (MRID 40098001) and gold fish at 6.8  ppb  (MRID
 00011841). In the absence of a fathead minnow LC50 and application factor cannot be calculated
 to estimate chronic values for these other fresh water fish.  However, a preliminary interpretation
 of the existing data suggests that if any of these other species were tested, the NOAEC would be
 lower. Therefore, unless there was a further refinement of methidathion residues in water, the
potential for chronic risk to fish will be greater than the current estimate.
                                            28

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      Estuarine Species                                     -:.-!.

      For estuarine fish, the acute RQs based on Tier II modeled EECs range from 0.34 (2 aerial
applications of 0.5 Ib a.i./A to cotton in California ) to 3.4 (1 air blast application of 2.0 Ibs a.i./A
to citrus in Florida). The acute risk LOG is exceeded by applications of 0.5 Ib a.i./A and greater.
Chronic risk to marine/estuarine fish from methidathion cannot be assessed at this time due to a
lack of acceptable early life-stage or life-cycle data.  Since the acute toxicity of methidathion to
freshwater fish (2.2 to 14 ppb) is similar to the toxicity to marine/estuarine fish (7.8 ppb), it is
likely that the chronic toxicity would also be similar. Comparable or greater risk should be
assumed for marine/estuarine species until acceptable data are received and a complete risk
assessment can be performed. In light of the earlier discussion that  the freshwater fish chronic
NOAEC is probably less than 6.1 ppb, there is uncertainty as to the potential risk to estuarine
fish.

      For estuarine invertebrates, the acute RQs based on Tier II modeled EECs range from 0.3
for oysters and 3.84 for mysids (2 aerial applications of 0.5 Ib a.i./A to cotton in California ) to
38 for mysids (1 air blast application of 2.0 Ibs a.i./A to citrus in Florida).  Mysid chronic RQs
range from 92 to 944 for these same use patterns. Except for acute risk to oysters, acute and
chronic LOCs are exceeded for estuarine invertebrates at all application rates; suggesting that part
of this group of organisms may be negatively effected at least temporarily. Methidathion's use in
areas near estuaries could potentially impact invertebrates, including shrimp and oyster
operations.  Effects on invertebrate numbers and/or diversity could also affect commercial and  .
recreational fisheries, since aquatic invertebrates are the basis of the food supply for many fish
species.

      Currently the predominant usage area for methidathion is California. One of the estuaries
that has been surveyed for pesticide contamination is Monterey Bay. While it is difficult to
determine the actual ecological impacts of agricultural pesticides on the Monterey Bay, nearly
twenty years of monitoring data demonstrate that a host of agricultural pesticides flushing from
adjacent agricultural land are bioaccumulating in the Region's fish and shellfish. Monitoring data
collected by the California State Water Resources Control Board and the California Department
of Fish and Game through their State Mussel Watch Program (SMWP) provide information on
agricultural chemical contamination in the Monterey Bay Area.1 These data are based on
sampling from 41 sites flowing into the Monterey Bay from Santa Cruz to Carmel. The SMWP
provides a uniform statewide approach to the detection and evaluation of the occurrence of toxic
substances in the waters of the California's bays, harbors and estuaries through the analysis of
mussels and clams. Similar findings of pesticide residues in fish in the drainages to Monterey
 1 State Mussel Watch Program, 11987-93 Data Report, 94-1WQ, State Water Resources Control Board, Cal-EPA, March,
 1995.

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 Bay by the State Board's Toxic Substances Monitoring Program2 support these SMWP findings.
 While most of the data collection has occurred in inland drainages without the benefit of seawater
 dilution, data from more limited points in harbors and coastal locations indicate that pesticides
 may be accumulating in the biota of the Bay itself. Residues found in mussels (estuarine and
 fresh water) and relocated fresh water clams indicate that-pesticides are entering into Monterey
 Bay. According to Victor De Vlaming of the California State Water Resources Control Board,
 neither of these two monitoring programs analyze for methidathion.  However, two other
 organophosphate pesticides used as dormant sprays in orchards, diazinon and chlorpyrifos, are
 found in tissues of sentinel organisms.

      Methidathion's present use in California suggests that its adverse impact on estuarine
 organisms is likely to be limited because very little methidathion is used near estuaries.
 Artichokes, principally in Monterey county, are grown along the Salinas and Pajaro Rivers within
 a quarter mile of Pajaro lagoon in Monterey Bay. However methidathion is applied to artichokes
 during June and July (USDA Crop Profiles) when there is little or no rainfall resulting in runoff.
 Therefore, a quarter of a mile may provide a sufficient buffer for spray drift contamination.  All
 other California uses of methidathion (e.g., cotton, orchards ) are either in noncoastal counties or
 in coastal counties where the treated acreage is extremely low and some distance from estuaries.
 Along with dilution and mixing by salt water, methidathion residues may be below levels of
 concern for estuarine organisms including invertebrates.

      The Agency acknowledges that there is uncertainty associated with extrapolating EECs
 from its freshwater aquatic scenario to estuarine and marine environments. In the absence of
 relevant data, it is not possible to determine whether the modeled exposure is higher, lower or
 comparable to residue values that would be monitored in estuaries. EPA recognizes that the
 field-edge pond  is not an estuarine habitat, yet at the same time, the assessment must
 accommodate edge of field estuaries that are relatively slow moving backwater areas with
 minimal exchange and minimal freshwater flow-through. Many estuaries are not fast moving,
 fast exchanging bodies of water that are diluted and replenished regularly. Some backwater areas
 simply rise and fall with tidal action, and only are exchanged over days, as water passes through
 narrow channels to the larger saltwater habitat or as runoff events cause freshwater recharge.
 Irrespective of uncertainties in the exposure estimates used for estuaries, methidathion's impact to
 non-target estuarine organisms is likely to be limited because most current uses of this insecticide
 are not in close proximity to estuaries. However, should the future use of methidathion expand to
 include treated areas adjacent to estuaries there is the potential for adverse effects to fish and
 invertebrates which could result in damage to ecological and commercial resources.
2 Toxic Substances Monitoring Program, 1991 Data Report, 93-1WQ, State Water Resources Control Board, Cal-EPA
June, 1993.

                                           30

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           4.    Risk to Nontarget Insects

      Methidathion is classified as very highly toxic to bees on an acute contact basis. The
results of the residual toxicity study indicate that not only will bees be at acute risk when sprayed
directly, but also from exposure to foliage as long as 3 days after treatment at 5.0 Ibs. a.i./A. The
maximum and typical single application rates for Supracideฎ 25WP are 3.0 and 2.0 Ibs. a.i./A
respectively. Therefore, the available residual study does indicate how long bees would be at risk
from these lower rates.  According to the reference Pollinator Protection. A Bee and Pesticide
Handbook. C.A. Johansen and D.F. Mayer (pg 179), the honey bee RT25 is 1- 3 days at 1 Ib.
a.i./A for methidathion.  To reduce the likelihood for significant mortality to bees precautionary
labeling must be followed.

      Additionally, quoting directly or paraphrasing, Johansen et. al reports; The time of day  an
insecticide is applied directly impacts its risk to foraging bees (pg 71).  Bee kills are often 2-4
times greater when applications are made in early morning as when they are made in late
evenings (pg 73). Methidathion should not be applied to crops in bloom and when adjacent
crops, interplants and weeds in orchard cover crops or field edges are flowering (pg  128). To
reduce the risk to bees, flowering weeds should be eliminated from orchard cover crops or field
edges (pg 129).  This is especially important when there is a dearth of pollen and nectar plants in
the area and bees may fly for several miles in search of flowers (pg 129).  The potential risk to
bees is greatest from aerial applications (pg  82). Spray drift off the target areas causes most bee
kills (pg 82). Small pesticide particles in the air blown into blooming crops or weeds are a major
factor in bee poisoning (pg 82-83). Ground sprays are generally considered safer than aerial
applications because there will be less drift and smaller areas are treated at one time (pg 129).
Johansen also recommends that during aerial applications, the aircraft should not be turned, nor
the materials transported back and forth across blossoming fields (pg 128).

            5.    Endangered Species

      All uses of methidathion exceed the endangered species LOG for all forms of endangered
animal species:  avian acute and chronic, mammalian acute and chronic, freshwater  fish acute and
chronic, freshwater invertebrate acute and chronic, marine/estuarine fish acute and chronic.
Although the endangered species LOCs for  esruarine invertebrates.have been exceeded, there  are
no listed species. The Agency has developed the Endangered Species Protection Program to
identify pesticides whose use may cause adverse impacts on endangered and threatened species,
and to implement mitigation measures that will eliminate the adverse impacts. At present, the
program is being implemented on an interim basis as described in a Federal Register notice (54
FR 27984-28008, July 3,1989), and is providing information to pesticide users to help them
protect these species on a voluntary basis. As currently planned, but subject to change as the
final program is developed, the final program will call for label modifications referring to
required limitations on pesticide uses, typically as depicted in county-specific bulletins or by
 other site-specific mechanisms as specified by state partners. A final program, which may be
 altered from the interim program, will be described in a future Federal Register notice. The

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 Agency is not imposing label modifications at this time through the interim RED. Rather, any
 requirements for product use modifications will occur in the future under the Endangered Species
 Protection Program.                                                                  .

            6.    Incident Reports

      In spite of methidathion's high acute toxicity to all classes to organisms, the Agency has
 received documented field kills only for birds.  California  monitors the impact of dormant sprays
 on raptors wintering in the central valley. The Agency received 5 reports from the California
 Department of Fish and Game. Four red-tailed hawks (Buteo jamaicensis) and one northern
 harrier (Circus cyaneus), sent to the Pesticide Investigation Unit from January 1994 through
 December 1997 contained residues of methidathion.  Four of the five birds were found in or
 adjacent to orchards.

      All birds were subjected to foot washing to analyze for organophosphate residues;
 methidathion residues ranged from 2.7 ppb to 12 ppm.  The presence of residues on the feet
 indicates the birds perched in treated trees within 72 hours of the time the foot wash was
 performed. In addition to dermal absorption through the feet, the raptors could have been
 exposed through ingestion of contaminated prey (the stomach contents of the harrier contained 15
 ppm of methidathion) or while preening (the feathers of one red-tail contained 0.09 ppm) after
 being sprayed directly or from drifting aerosols. When exposed to drift or direct spray the birds
 would acquire additional residues via inhalation. Three of the birds showed brain cholinesterase
 levels less than 50% of normal.  Such findings indicated that death, or severe impairment that
 would have lead to death, was the result of exposure to one or more cholinesterase inhibiting
 agents. The two remaining birds, one of which survived and was released, had their blood plasma
 analyzed for cholinesterase and acetylcholinesterase levels. The level in the surviving bird was
 below the normal range whereas the level of the euthanized bird were at the lower range of
 normal levels.

      In light of mortality to raptors, the Agency has concern for small birds and mammals.
 Carcasses of small birds and mammals are extremely difficult to find or the incidents are not
 reported unless kills are extensive.  Because other birds and small mammals are exposed to
 similar routes of exposure (inhalation, dermal, drinking water, dietary consumption) as raptors
 the Agency presumes they too are at risk from methidathion.
IV.   Interim Risk Management and Reregistration Decision

      A.   Determination of Interim Reregistration Eligibility

      Section 4(g)(2)(A) of FIFRA calls for the Agency to determine, after submissions of
relevant data concerning an active ingredient, whether products containing the active ingredient is
eligible for reregistration. The Agency has previously identified and required the submission of

                                           32

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the generic (i.e., active ingredient specific) data required to support reregistration of products
containing methidathion active ingredients.

     The Agency has completed its assessment of the occupational and ecological risks
associated with the use of pesticides containing the active ingredient methidathion, as well as a
methidathion-specific dietary risk assessment that has not considered the cumulative effects of
organophosphates as a class. Based on a review of these data and public comments on the
Agency's assessments for the active ingredient methidathion, EPA has sufficient information on
the human health and ecological effects of methidathion to make interim decisions as part of the
tolerance reassessment process under FFDCA and reregistration under FIFRA, as amended by
FQPA. The Agency has determined that methidathion is eligible for reregistration provided that:
(i) current data gaps and additional data needs are addressed; (ii) the risk mitigation measures"
outlined in this document are adopted and label amendments are made to reflect these measures;
and (iii) cumulative risks considered for the organophosphates support a final reregistration
eligibility decision. Label changes are described in Section V. Appendix B identifies the generic
data requirements that the Agency reviewed as part of its interim determination of reregistration
eligibility of methidathion and lists the submitted studies that the Agency found acceptable.

      Although the Agency has not yet considered its cumulative risks for the organophosphates,
the Agency is issuing this interim assessment now in order to identify risk reduction measures
that are necessary to support the continued use of methidathion. Based on its current evaluation
of methidathion alone, the Agency has determined that methidathion products, unless labeled and
used as specified in this document, would present risks inconsistent with FIFRA. Accordingly,
should a registrant fail to implement any of the risk mitigation measures identified in this
document, the Agency may take regulatory action to address the risk concerns from use of
methidathion.

       At the time that a cumulative assessment is conducted, the Agency will address any
 outstanding risk concerns.  For methidathion, if all changes outlined in this document are
 incorporated into the labels, then all current risks will be mitigated. But, because this is an
 interim RED, the Agency may take further actions, if warranted, to finalize the reregistration
 eligibility decision for methidathion after assessing the cumulative risk of the organophosphate
 class.  Such an incremental approach to the reregistration process  is consistent with the Agency's
 goal of improving the transparency of the reregistration and tolerance reassessment processes. By
 evaluating each organophosphate in turn and identifying appropriate risk reduction measures, the
 Agency is addressing the risks from the organophosphates in as timely a manner as possible.

       Because the Agency has not yet considered the cumulative risks for the organophosphates,
 this interim RED does not fully satisfy the reassessment of the existing methidathion food residue
 tolerances as  called for by the Food Quality Protection Act (FQPA).  When the Agency has
 considered cumulative risks, methidathion tolerances will be reassessed in that light. At that
 time, the Agency will reassess methidathion along with the other  organophosphate pesticides to
 complete the FQPA requirements and make a final reregistration eligibility determination. By

                                            33

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 publishing this interim decision on reregistration eligibility and requesting mitigation measures
 now for the individual chemical methidathion, the Agency is not deferring or postponing FQPA
 requirements; rather, EPA is taking steps to assure that uses which exceed FIFRA's unreasonable
 risk standard do not remain on the label indefinitely, pending completion of the assessment
 required under the FQPA. This decision does not preclude the Agency from making further
 FQPA determinations and tolerance-related rulemakings that may be required on this pesticide or
 any other in the future.

      If the Agency determines, before finalization of the RED, that any of the determinations
 described in this interim RED are no longer appropriate, the Agency will pursue appropriate
 action, including, but not limited to, reconsideration of any portion of this interim RED.

      B.   Summary of Phase 5 Comments and Responses

      When making its interim reregistration decision, the Agency took into account all
 comments received during Phase 5 of the OP Pilot Public Participation Process. Eleven
 comments were received .during the open public comment period. These comments in their
 entirety are available in the public docket.  A brief summary of the comments and the Agency
 response is noted here.

      Of the eleven comments, ten were received from growers or grower groups and one
 comment was received from the registrant (Gowan Company).  The comment from the registrant
 challenged many of the data and assumptions contained in the Agency risk assessment. Grower
 and grower groups who submitted comments include: Ed Chambers Farm  Management; LoBue
 Brothers, Inc.; California Citrus Mutual; Claussen Family Partnership; AgriCare Production
 Specialists; Sun World International, Inc.; Associated Citrus Packers, Inc.; Almond Hullers &
 Processors Association; Mulholland Citrus Trees and Sea Mist Farms.  Many of the comments
 from grower and grower groups expressed the need for continued use of methidathion on
 artichokes and other crops.  Commentors emphasized that methidathion is  an important tool for
 Integrated Pest Management and without it, resistance would develop quickly because of limited
 effective alternatives.  Comments were also received on the safety of methidathion products to
 field workers. Since they are sold in water-soluble bags, used in a closed system and because of
 the extensive training provided to mixers, loaders and applicators, worker exposure problems
 have not been experienced and are not expected.

     The Agency also took into account three other comments that were received after the
 formal comment period had closed.  Dr. Robert I. Krieger, an extension toxicologist with the
University of California,  Riverside, submitted comments about the lack of an EPA policy
concerning off-site pesticide exposures. California Citrus Mutual submitted additional
information about harvesting activities and a description and data about the differences between
growing practices in California and Florida. Anne Katten of the California Rural Legal
Assistance Foundation submitted comments supporting the 30-day REI established by the State of
                                          34

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California for citrus groves and challenged the Agency's policy of relying on data that has been
generated by the registrants to establish REIs.

      C.   Regulatory Position

           1.    FQPA Assessment

           a.    "Risk Cup" Determination

      As part of the FQPA tolerance reassessment process, EPA assessed the risks associated
with methidathion. The assessment was for this individual organophosphate and does not attempt
to fully reassess these tolerances as required under FQPA.  FQPA requires the Agency to evaluate
food tolerances on the basis of cumulative risk from substances sharing a common mechanism of
toxicity, such as the toxicity expressed by the organophosphates through a common biochemical
interaction with the cholinesterase enzyme. The Agency will consider the cumulative risk posed
by the entire class of organophosphates, once the methodology is developed and the policy
concerning cumulative assessments is resolved.

      EPA has determined that risk from exposure to methidathion is within its own "risk cup."
In other words, if methidathion did not share a common mechanism of toxicity with other
chemicals, EPA would be able to conclude today that the tolerances for methidathion meet the
FQPA safety standards. In reaching this determination, EPA has considered the available
information on the special sensitivity of infants and children, as well as the  chronic and acute
food exposure. An aggregate assessment was conducted for exposures through food, residential
uses and drinking water.  Results of this aggregate assessment indicate that  the human health risks
from these combined exposures are considered to be within acceptable levels; that is, combined
risks from all exposures to methidathion "fit" within the individual risk cup. Therefore, the
methidathion tolerances remain in effect and unchanged until a full reassessment of the
cumulative risk from all organophosphates is considered.

            b.    Tolerance Summary

       The tolerances listed in 40 CFR ง180.298(a and c) are expressed in terms of methidathion
 (S-[(5-methoxy-2-oxo-l ,3a4-thiadiazole-3-(2H)-yl) methyl] O,O-dimethyl-phosphorodithioate)
per se and its metabolites; i.e., its oxygen analog (S-[(5-methoxy-2-oxo-l,3,4-thiadiazole-3-(2H)-
 yl)methyl] O,O-dimethyl-phosphorothioate), its sulfoxide metabolite  (2-methoxy-4-
 (methylsulfinylmethyl)-l,3,4-thiadiazole-5-one) and its sulfone metabolite  (2-methoxy-4-
 (methylsulfonylmethyl)-1,3,4-thiadiazole-5-one).

 Tolerances Listed Under 40 CFR S180.298(a)

       Methidathion residues are generally not expected to occur in any food commodities except
 citrus. Methidathion is nonsystemic and is applied to pome fruits, stone fruits, tree nuts and some

                                            35

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' other crops before the edible portion of the plant has formed.  Foliar treatments of citrus
 commodities while the fruit are on the tree do result in residues; however, these residues are
 almost entirely limited to the peel. Processing of these fruits result in some residues in fruit and
 juice at very low levels. USDA PDF data are available for apples, apple juice, oranges, grape
 fruit, peaches and canned pears.

      Adequate data are available to support the established tolerances for methidathion residues
 in/on the commodities listed in Table 15. The established tolerance for residues in/on citrus fruit
 should be increased from 2 ppm to 4 ppm, as residues of 3.4 and 3.5 ppm have been observed
 following registered use. The group commodity definitions "Almonds, hulls" and "Artichokes"
 should be revised to "Almond, hulls" and "Artichoke, globe," respectively. The group
 commodity definitions "Citrus Fruits (except mandarins)" and "Citrus Oil" should be revised to
 "Fruit, citrus, except mandarin" and "Citrus, oil," respectively. The group commodity definitions
 "Cottonseed" and "Cotton gin byproducts" should be revised to "Cotton, undelinted seed" and
 "Cotton, gin byproducts," respectively. The group commodity definitions "Fruits, pome" and
 "Fruits, stone" should be revised to "Fruit, pome, group" and "Fruit, stone, group," respectively.
 The tolerance for peaches is not necessary as peaches are covered by the tolerance for residues
 in/on "Fruits, stone;" therefore, EPA recommends reassignment of the tolerance for peaches to
 the Fruit, stone, group designation.  The group commodity definition for "Kiwi Fruit" should be
 amended to reflect the correct crop group designation "Kiwifruit."  The group commodity
 definitions "Mandarins" and "Mangos" should be revised to "Tangerine" and "Mango,"
 respectively.  The group commodity definition for "Nuts" should be amended to reflect the
 correct crop group designation "Nut, tree, group," and the tolerances for pecans and walnuts,
 which are covered by the Nut, tree, group designation, should be reassigned.  The group
 commodity definitions "Olives" and "Safflower seeds" should be revised to "Olive" and
 "Safflower seed," respectively.  The group commodity definitions "Sorghum, fodder," "Sorghum,
 forage" and "Sorghum, grain" should be revised to "Sorghum, grain, stover," "Sorghum, grain,
 forage" and "Sorghum, grain, grain," respectively.  The group commodity definition for
 "Sunflower seeds" should be amended to reflect the correct crop group designation "Sunflower,
 seed."

 Tolerances Needed Under 40 CFR ง180.298ra>

      Field residue data are required to determine a tolerance level on methidathion hi the plant
 byproducts from ginning cotton, consisting of burrs, leaves, stems, lint and immature seeds.
 Cotton must be harvested by commercial equipment (stripper and mechanical picker) to provide
 an adequate representation of plant residue for the ginning process.  At least three field trials for
 each type of harvesting (stripper and mechanical picker) are needed, for a total of six field trials.
 The need for additional tolerances and revisions to the exposure/risk assessments will be made
 upon receipt and evaluation of required, data. When adequate field residue data have been
 submitted, a tolerance must be proposed for this commodity.
                                            36

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Tolerances Listed Under 40 CFR ง180.298(1x>

      On August 2, 1999 (64 FR 41933), the Agency published its determination that there is no
reasonable expectation of finite residues in or on meat, milk, poultry and egg commodities
associated with methidathion, and some other specific pesticides, based on exaggerated feeding
studies (lOx the dietary burden) which did not show measurable residues.  On October 5, 2001
(66 FR 50829), the Agency revoked methidathion tolerances in the animal commodities [40 CFR
ง180.298(b)] effective January 3, 2002 for cattle, fat; cattle, mbyp; cattle, meat; eggs; goat, fat;
goat mbyp; goat, meat; hog, fat; hog, mbyp; hog, meat; horse, fat; horse, mbyp; horse, meat;
milk;  poultry, fat; poultry, mbyp; poultry, meat; sheep> fat; sheep, mbyp; and sheep, meat.
Pursuant to 40 CFR ง180.6(a)(3), the Agency revoked those tolerances because they are no
longer needed to cover residues of methidathion and its metabolites; i.e., its oxygen analog, the
sulfoxide metabolite and the sulfone metabolite on those commodities.

Tolerances (with regional registration') Listed Under 40 CFR ง180.298^

      Adequate data are available to support the established tolerances for methidathion residues
in/on  carambola, kiwifruit, longan and sugar apple. The Special Local Need (SLN) label
language for use on clover grown for seed contains restrictions to prevent food or feed use of
treated plant parts.

      The registrant has requested to maintain a regional SLN registration for the use of   .
methidathion on alfalfa, timothy hay and timothy-alfalfa mixes (primarily timothy) in Kittitas
County, WA only.  Approximately 85% of this crop is exported to Japan and Taiwan. There are
no other registered or potential alternatives for methidathion to control grass scale, thrips and
mites on these crops. Most of the hay that is not exported is consumed by horses, not by dairy or
beef cattle; therefore, the potential for dietary intake of methidathion .via meat and milk
consumption is negligible.

      In conclusion, the tolerances on alfalfa and alfalfa hay should be lowered to 5 ppm and
reassigned to tolerances with regional registration under 40 CFR ง180.298(c). The tolerances on
grass  and grass hay (currently under 40 CFR ง180.298(a)) should be reassigned to tolerances with
regional registration under 40 CFR ง180.298(c) for timothy and timothy hay and should also be
lowered to 5 ppm. A summary of the methidathion tolerance reassessment and recommended
modifications in commodity definitions are presented below in Table 15.
                                           37

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Table IS. Tolerance Reassessment Summary for Methidathion.
Commodity
Current Tolerance
(ppm)
Tolerance ป
Reassessment
(ppm)~ " •
'- ~ Comment m
{Correct Commodity Definition]
Tolerances Listed Under 40 CFR ง180.298(a)
Alfalfa
Alfalfa, hay
Almonds, hulls
Artichokes
Citrus Fruits
(except mandarins)
Citrus oil
Cottonseed
Cotton gin byproducts
Fruits, pome
Fruits, stone
Grass
Grass, hay
Mandarins
Mangos
Nuts
Olives
Peaches
Pecans
Safflower seeds
Sorghum, fodder
Sorghum, forage
Sorghum, grain
Sunflower seeds
Walnuts
12.0
12.0
6.0
0.05
2.0
None
0.2
None
0.05
0.05
12.0
12.0
6.0
0.05
0.05
0.05
0.05
0.05
0.5
2.0
2.0
0.2
0.5
0.05
Reassign
6.0
0.05
4.0
420
0.2
To be determined
0.05
0.05
Reassign '
6.0
0.05
0.05
0.05
Reassign
Reassign
0.5
2.0
2.0
0.2
0.5
Reassign
Establish regional tolerances under 40
CFR ง180.298(c)
[Almond, hulls]
[Artichoke, globe]
[Fruit, citrus, except mandarin] •
Increased residues observed in field trials
[Citrus, oil] Residues concentrate an
average of 1 1 8x in oil processed from
methidathion-treated oranges.
[Cotton, undelinted seed]
[Cotton, gin byproducts] Residue data
are required to determine the appropriate
tolerance level.
[Fruit, pome, group]
[Fruit, stone, group]
Establish regional tolerances under 40
CFRง180.298(c)
[Tangerine]
[Mango]
[Nut, tree, group]
[Olive]
Covered by Fruit, stone, group
Covered by Nut, tree, group
/ Safflower seed]
[Sorghum, grain, stover J
[Sorghum, grain, forage J
[Sorghum, grain, grain]
[Sunflower seed}
Covered by Nut, tree, group
Tolerances Listed Under 40 CFR ง180.298(c)
Alfalfa
Alfalfa, hay
Carambola
Kiwi Fruit
Longan
Sugar Apple
12.0
12.0
0.1
0.1
0.1
• 0.2
5.0
5.0
0.1
0.1
0.1
0.2
Restricted to Kirtitas County, WA; other
sites are restricted to seed production.

[Kiwifruit]


                                      38

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Commodity
Timothy
Timothy, hay
/ <
Current Tolerance'
, (ppm/, /
12.0.
12.0
'- -Tolerance
Reassessment
* (ppm)
5.0
5.0
Comment •
[Correct Commodity Definition] f
Restricted to Kittitas County, WA. Other
sites are restricted to seed production.
Covered by Grass.
Restricted to Kittitas County, WA. Other
sites are restricted to seed production.
Covered by Grass, hay.
     The Agency will commence proceedings to revoke, modify (lower) the existing tolerances
and correct commodity definitions. The establishment of a new tolerance or raising tolerances
will be deferred, pending the outcome of cumulative risks.

           2.   Endocrine Disrupter Effects

     EPA is required under the FFDCA, as amended by FQPA, to develop a screening program
to determine whether certain substances (including all pesticide active and other ingredients)
"may have an effect in humans that is similar to an effect produced by a naturally occurring
estrogen, or other such endocrine effects as the Administrator may designate." Following the
recommendations of its Endocrine Disrupter Screening and Testing Advisory Committee
(EDSTAC), EPA determined that there were scientific bases for including as part of the program,
the androgen and thyroid hormone systems, in addition to the estrogen hormone system. EPA  .
also adopted EDSTAC's recommendation that the Program include evaluations of potential
effects in wildlife.  For pesticide chemicals, EPA will use FIFRA and, to the extent that effects in
wildlife may help determine whether a substance may have an effect in humans, FFDCA
authority to require the wildlife evaluations. As the science develops and resources allow,
screening of additional hormone systems may be added to the Endocrine Disrupter Screening
Program (EDSP).

      When the appropriate screening and/or testing protocols being considered under the
Agency's EDSP have been developed, methidathion may be subjected to additional screening
and/or testing to better characterize effects related to endocrine disruption.

           3.    Benefits and Alternatives

      In considering benefits and alternatives, EPA has focused on the dormant sprays on orchard
crops which pose risk to birds and air blast applications to citrus at the maximum rate of 5 Ibs
a.i./A which would pose risk to applicators. Other risks discussed in this section can be mitigated
to acceptable levels with standard mitigation measures; benefits have not been considered for
those uses.
                                           39

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Dormant Sprays to Orchard Crops

      Methidathion is used primarily to control San Jose scale in apples, peaches, pears and nuts
and to control peach twig borer in peaches, nectarines and apricots.  If heavy infestations of San
Jose scale are left unchecked, trees may be seriously damaged, resulting in reduced vigor, thin
foliage, cracked or dying branches and the eventual death of the tree. Young trees may be killed
before fruiting. Due to the damage potential of this pest, annual dormant sprays are
recommended in most areas. Some alternatives to methidathion exist, but are also
organophosphates, e.g., chlorpyrifos and diazinon.

      Peach twig borer damages crops in two ways. Larvae burrow down tender shoots and kill
the tip, which causes problems in training young trees. They also feed on fruit, primarily at the
stem end. Either feeding damage or the presence of larvae will cause fruit to be off grade and
results in decreased revenue for growers.  Dormant sprays are used in orchards with a history of
infestation; monitoring and postbloom sprays can be used  in orchards without a history of peach
twig borer damage. Alternatives to methidathion include diazinon and pyrethroids.

Air Blast Application  to Citrus at Maximum Rate

      Methidathion is used to control numerous types of scale on citrus in Arizona, Florida,
California and Texas.  Labeled application rates range from 0.25 to 5 Ibs a.i./A. Usage data
available to EPA Indicate that actual use rates range from 1 to just over 4 Ibs a.i./A, with an
average of 3 Ibs a.i./A. There are registered, efficacious alternatives to methidathion on citrus.
However, the most efficacious alternatives are other organophosphates (i.e., chlorpyrifos and
ethion). It should be noted that as a result of reregistration review, ethion is being phased out.
Based on the usage information available, it is reasonable to conclude that severe infestations
requiring treatment at the maximum rate of 5 Ibs a.i./A are sporadic.
D.
Regulatory Rationale
      The following is a summary of the rationale for managing risks associated with the current
use of methidathion.  Where labeling revisions are warranted, specific language is set forth in the
summary tables of Section V of this document.

           1.    Human Health Risk Mitigation

           a.    Dietary Mitigation

      The Agency has no risk concerns for any dietary (food and drinking water) exposure to
methidathion (acute or chronic) when it is applied at 3.0 Ibs a.i./A, which is the typical rate on
citrus and the maximum rate on all other crops. Therefore, no risk mitigation is necessary when
methidathion is applied at this rate.
                                            40

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      When methidathion is applied at the maximum rate on citrus of 5.0 Ibs a.i./A, the expected
concentration in surface water is 28.5 ppb, which is above the DWLOC of 19.1 for infants.
However, when methidathion is not applied within 50 feet of surface water, the expected
concentration drops to 10.8 ppb, which is no longer of concern. Therefore, the use of
methidathion at rates greater than 3.0 Ibs a.i./A is eligible for reregistration, provided this buffer
zone is included on the labels as specified in Table 17.

                 b.    Occupational Risk Mitigation

                      1)    Agricultural Uses

      The Agency has concerns about workers using methidathion in several different scenarios.
Each is discussed below.

Mixing/Loading Water Soluble Packs for Aerial Application

      The MOEs for workers mixing/loading the water-soluble package (WSP) formulation for
aerial application are 27 and 39, depending on the application rate that the worker uses.and the
acreage to be treated.  The Agency has proposed, and the registrant has agreed, to limit the use
WSP formulation to nonaerial applications. Under this proposal, the WSP formulation will only
be available for air blast or groundboom applications.

      EPA acknowledges the uncertainties associated with the risk assessment for mixing and
loading WSP for aerial application. Because current WSP data in PHED are of lower quality, the
Agency is investigating the possibility of requiring additional inhalation and passive dosimetry
studies for workers using the WSP. Should the Agency call in this data, it would levy the
requirement on all chemicals with this use pattern so that the cost of conducting the studies could
be shared across the industry. This additional data would lessen the uncertainties involved in
estimating the risks of exposure to workers using the WSP.

Air Blast Application to  Citrus

      To mitigate the concern for air blast applicators in citrus groves, the registrant has agreed to
require a minimum of 500 gallons of water per acre be used to dilute methidathion products.
This change is expected to limit the exposure to applicators as well as ensure that the
methidathion covers the  area more uniformly. At the typical application rate, the MOEs for
mixers/loaders and applicators are all above  100. However, at the highest application rate, the
MOEs for the mixers/loaders and applicators using methidathion on citrus are 85 for
mixers/loaders and 53 for applicators. The Agency is not proposing  that enclosed cabs be
required for this use pattern because usage data indicate that the 5-lb rate is only occasionally
necessary to control heavy infestations and that the acreage typically treated with methidathion is
 approximately one-half of the maximum assumed in the Agency risk assessment.
                                             41

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      The following table summarizes the engineering controls and additional PPE that is needed
 on the label for the different agricultural use scenarios.

 Table 16.  PPE Summary for all Agricultural Scenarios
Scenario
Mixing/Loading Wettable Powders -
Groundboom (Ic & Id)
Mixing/Loading WSP - Air blast ( 1 e)
Mixing/Loading Liquids - Aerial
(2a&2b)
Mixing/Loading Liquids - Groundboom
(2c & 2d)
Mixing/Loading Liquids-Air blast (2e)
Applying with Aircraft (3a & 3b)
Applying with Groundboom
(4a&4b)
Applying with Air blast Sprayer (5)
Mixing/Loading/Applying with Low-
pressure Handwand (6)
Mixing/Loading/Applying with Backpack
Sprayer (7)
Flaggers - liquid application (8)
PPE (in addition to long sleeved shirt,
• long pants, socks and shoes)
Chemical-resistant gloves and chemical-resistant apron
Chemical-resistant gloves and chemical-resistant apron
Chemical-resistant gloves and chemical-resistant apron
Chemical-resistant gloves, chemical-resistant apron and an
organic vapor-removing respirator
Chemical-resistant gloves, chemical-resistant apron
None
Chemical-resistant gloves and an organic vapor-removing
respirator
Double-layer clothing, chemical-resistant gloves, chemical-
resistant apron and an organic vapor-removing respirator
None
None
Not applicable
Engineering
'Controls
WSP
WSP
Closed system
None
None
Closed cockpit
None
Slone
None
Sfone
Human flaggers
are prohibited
                       2)   Post-Application Risk

      Based on data summarized in Section III.A, the REI for methidathion will be established at
3 days for all crops. This is based on the day at which MOEs are greater than 100 for activities
other than harvesting. For tree crops and artichokes, the REI is being established on non-
harvesting activities, as the label prohibits harvesting before the preharvest interval has expired.
For tree crops, the preharvest interval of at least 14 days is substantially longer than 8 days,
which is the day at which the harvesting activity is greater than 100.  For artichokes,
methidathion cannot be applied after the bud is formed,  which will yield a harvest of substantially
longer than  19 days, which, again is the-day at which the harvesting activity is greater than 100.
Therefore, the Agency believes  that an REI of 3 days will sufficiently protect workers.

            2.    Environmental Risk Mitigation

      The environmental risk assessment suggests that exposure to methidathion could result in
both acute and chronic risks of concern for terrestrial and aquatic organisms.
                                            42

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                 a.    Avian Species Mitigation

      The Agency's risk assessment for avian species exceeds the level of concern for both acute
and chronic exposure. However, based on communications with the California Department of
Fish and Game, the Agency believes that these risks may not be unreasonable. Two of the major
uses in California, dormant spray to orchards and foliar spray to cotton, would result in little or
no exposure to breeding birds. One rare exception could occur among mourning doves in
orchards if there had been limited rain fall and warm weather. Mourning doves produce multiple
clutches and, like most other birds, do not breed during the dormant spray period, but rather from
April through June. Foliar sprays to cotton and citrus coincide with the breeding period of many
species of birds. Although cotton fields provide little suitable habitat for breeding birds, citrus
orchards are attractive to birds, therefore methidathion's use should present both acute and
chronic risk. The Agency assumes a similar degree of risk to breeding birds in other states.

      To address avian risk, the Agency believes that the additional dilution of methidathion
products (a rninimum of 500 gallons of water per acre) intended to reduce exposure to workers
may also reduce exposure to birds by eliminating concentrations of pesticide and by reducing the
amount of pesticide on food items.  The registrant has also agreed to additional precautionary
labeling to protect avian species.

                  b.    Aquatic Species Mitigation

      Methidathion's  present use in California suggests that its adverse impact on estuarine
organisms is likely to be limited because very little methidathion is used near estuaries.
Artichokes (principally in Monterey county) are grown along the Salinas and Pajaro Rivers,
within a quarter mile of Pajaro lagoon in Monterey Bay. However, methidathion is applied to
artichokes during June and July when there is little or no rainfall resulting in runoff. Most other
California uses of methidathion (e.g., cotton, orchards) are in non coastal counties.  The
remainder are in coastal counties where the treated acreage is extremely low and some distance
from estuaries, methidathion is conveyed by streams and rivers to coastal areas and diluted with
 salt water, residues may be below levels of concern for estuarine .organisms including
 invertebrates.  Methidathion may, however, have an impact on freshwater organisms. The
 following measures are expected to mitigate these risks.

       For all applications applied at rates greater than 3.0 Ibs a.i./A:
       —    Do not apply within 50 feet of lakes, reservoirs, rivers, permanent streams, natural
            ponds, marshes or estuaries

       For all applications applied at rates of 3.0 Ibs a.i./A or less:
       -     Do not apply within 25 feet of lakes, reservoirs, rivers, permanent streams, natural
             ponds, marshes or estuaries
                                             43

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      For ground applications:
      -    Shut off sprayer when turning at end rows
      -    Do not apply when gusts or sustained winds exceed 12 mph

      For air blast application:
      -    Adjust deflectors and aiming devices so that spray is only directed into the canopy
      —    Block off upward pointed nozzles when there is no overhanging canopy
      -    Use only enough air volume to penetrate the canopy and provide good coverage
      -    Do not allow spray to go beyond the edge of the cultivated area. Spray the outside
            row only from outside the planting

      For aerial application:                                                      .
      -    Do not apply within 150 feet of water
      -    Do not apply when gusts or sustained winds exceed 8 mph

      The Agency believes labels should be amended to include a surface water advisory
 statement, which is outlined in the Environmental Hazards portion of Table 17 in Section V.
 This statement will encourage users to apply methidathion in a way that will minimize exposure
 to freshwater fish and invertebrates.

                 c.    Nontarget Insect Mitigation

      The Agency is concerned about the risk to beneficial insects from the use of methidathion.
 To reduce the likelihood for significant mortality to bees, precautionary labeling is required.

      E.    Other Labeling

            1.    Endangered Species Statement

      The Agency has developed the Endangered Species Protection Program to identify
 pesticides whose use may cause adverse impacts on endangered and threatened species, and to
 implement mitigation measures that address these impacts. The Endangered Species Act requires
 federal agencies to ensure that their actions are not likely to jeopardize listed species or adversely
 modify designated critical habitat. To analyze the potential of registered pesticide uses to affect
 any particular species, EPA puts basic toxicity and exposure data developed for interim REDs
 into  context for individual listed species and their locations by evaluating important ecological
parameters, pesticide use information, the geographic relationship between specific pesticides
uses and species locations and biological requirements and behavioral aspects of the particular
species. This analysis will include consideration of the regulatory changes recommended in this
interim RED. A determination that there is a likelihood of potential impact to a listed species
may result in limitations on use of the pesticide, other measures to mitigate any potential impact
or consultations with the Fish and Wildlife Service and/or the National Marine Fisheries Service
as necessary.

                                           44

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      The Endangered Species Protection Program as described in a Federal Register notice (54
FR 27984-28008, July 3, 1989) is currently being implemented on an interim basis.  As part of
the interim program, the Agency has developed County Specific Pamphlets that articulate many
of the specific measures outlined in the Biological Opinions issued to date. The pamphlets are
available for voluntary use by pesticide applicators on EPA's website at http.VAvww.epa.eov/esyp.
A final Endangered Species Protection Program, which may be altered from the interim program,
is scheduled to be proposed for public comment in the Federal Register before the end of 2001.

           2.    Spray Drift Management

      The Agency is in the process of developing more appropriate label statements for spray and
dust drift control to ensure that public health and the environment is protected from unreasonable
adverse effects.  In August 2001, EPA published draft guidance for label statements in a pesticide
registration (PR) notice ("Draft PR Notice 2001-X" http://www.eva. eov/PR Notices/#2001\ A
Federal Register notice was published on August 22, 2001 (http://w\vw.epa.sov/fedrsstr)
announcing the availability of this draft guidance for a 90-day public comment period. After
receipt and review of the comments, the Agency will publish final guidance in a PR notice for
registrants to use when labeling their products.

       Until EPA decides upon and publishes the final label guidance  for spray and dust drift,
registrants (and applicants) may choose to use the statements proposed in the draft PR notice.
Registrants should refer to, and read the draft PR notice to obtain a full understanding of the
proposed guidance and its intended applicability, exemptions for certain products and the
Agency's willingness to consider other versions of the statements.

        For purposes of complying with the deadlines for label submission outlined in this
document, registrants (and applicants) may elect to  adopt the appropriate sections of the proposed
language below, or a version that is equally protective, for their end-use product labeling.

        For products applied outdoors as liquids (except mosquito adulticides):

        "Do not allow spray to drift from the application site and contact people, structures
        people occupy at any time and the associated property, parks and recreation areas,
        nontarget crops, aquatic and wetland areas, woodlands, pastures, rangelands or animals."

        Alternatively, registrants may elect to use the following language, which is the current
 Agency policy on drift labeling:

        For products that are applied outdoors in liquid sprays (except  mosquito adulticidesX
        regardless of application method, the following must be added to the labels:

        "Do not allow this product to drift."
                                            45

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       The Agency recognizes that the above option does not address other application types.
Registrants may therefore wish to adapt some variation of the old, and proposed new language for
their particular products, depending on their application methods.
V.     What Registrants Need to Do
                 be eligible for reregistration, registrants need to implement the risk mitigation
                 in Section IV and V, which include, among other things, submission of the
       In order to
measures outlined
following:

       A.    For methidathion technical grade active ingredient products, registrants need
to submit the following items.

             Within 90 days from receipt of the generic data call-in (DCI):

             (1)    Completed response forms to the generic DCI (i.e., DCI response form and
                    requirements status and registrant's response form); and

             (2)    Submit any time extension and/or waiver requests with a full written
                    justification.

             Within the time limit specified in the generic DCI:

             (1)    Cite any existing generic data which address data requirements or submit
                    new generic data responding to the DCI.

       Please contact Carmen Rodia at (703) 306-0327 with questions regarding generic
reregistration and/or the DCI. All materials submitted in response to the generic DCI should be
addressed:
Bv US mail:
Document Processing Desk (DCI/SRRD)
ATTN: Mr. Carmen Rodia
US EPA (7504C)
1200 Pennsylvania Ave., NW
Washington, DC 20460-0001
                                              Bv express or courier service:
                                              Document Processing Desk (DCI/SRRD)
                                              ATTN: Mr. Carmen Rodia
                                              Office of Pesticide Programs (7504C)
                                              Room 266A, Crystal Mall 2
                                              1921 Jefferson Davis Highway
                                              Arlington, VA 22202-4501
       B.    For products containing the active ingredient methidathion. registrants need to
submit the following items for each product.
                                          46

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       Within 90 days from the receipt of the product-specific data call-in (PDCI):

       .(!•)  Completed response forms to the PDCI (i.e., PDCI response form and
            requirements status and registrant's response form);  and

       (2)  Submit any time extension or waiver requests with a full written justification.

       Within eight months from the receipt of the PDCI:

       (1)  Two copies of the confidential statement of formula (EPA Form 8570-4);

       (2)  A completed original application for reregistration (EPA Form 8570-1).  Indicate
            on the form that it is an "application for reregistration";

       (3)  Five copies of the draft label incorporating all label amendments outlined in Table
             17 of this document;

        (4)  A completed form certifying compliance with data compensation requirements
            (EPA Form 8570-34);

        (5)  If applicable, a completed form certifying compliance with cost share offer
            requirements (EPA Form 8570-32); and

        (6)   The product-specific data responding to the PDCI.

       Please contact Jane Mitchell at (703) 308-8061 with questions regarding product
reregistration and/or the PDCI. All materials submitted in response to the PDCI should be
addressed:
Bv US mail:
Document Processing Desk (PDCI/PRB)
ATTN: Ms. Jane Mitchell
US EPA (7504C)
1200 Pennsylvania Ave., NW
Washington, DC 20460-0001
       A. Manufacturing Use Products
By express or courier service only:
Document Processing Desk (PDCI/PRB)
ATTN: Ms. Jane Mitchell
Office of Pesticide Programs (7504C)
Room 266A, Crystal Mall 2
1921 Jefferson Davis Highway
Arlington, VA 22202-4501
         1. Additional Generic Data Requirements

       The data base supporting the reregistration of methidathion for the above eligible uses has
been reviewed and determined to be substantially complete.  The following data gaps remain:

                                       .   47

-------
       860.1500 (171-4K)
       201-4-SS

       850.1400 (72-4A)
       72-4-SS
Field Trial Data on Cotton Gin Byproducts3
Background for Pesticide Aerial Drift Evaluation4

Fish Early Life Stage Freshwater Fish: Note that the
current study on Fathead minnow is supplemental
due to the absence of raw data necessary to
corroborate the reported results.  Even if the raw
data was provided, the Agency still has concern that
reported results suggest fathead minnow are not as
sensitive as other freshwater fish. If an LC50 study
was conducted by the same laboratory around the
time of the test in question, then an Application
Factor could be computed and chronic values for the
other fish tested could be computed. If no such LC50
study exists, than there is high value in conducting
another PEL study (and an accompanying LC50
study) on the fathead minnow. Preferably, the study .
would be conducted on the rainbow trout. The value
added for this study is high in order to better assess
the chronic risk of methidathion to fresh water fish.

Fish Early Life Stage Estuarine Fish: Note that there
is no study to address this requirement. The label
permits methidathion to be used on at least two
crops, citrus and cotton, that the Agency uses to
trigger the requirement.  Although methidathion's
current usage appears to be of relatively low volume
and, in California where the degree of estuarine
contamination may be low, the present chronic risk
assessment for estuarine fish is still highly uncertain
.This is especially true in light of the discussion in
the preceding comment for Guideline 72-4A. The
value added for this study is high.
       3 Data depicting the magnitude of methidathion residues of concern in/on cotton gin byproducts following
applications) of a representative formulation according to the maximum registered use patterns are required. Cotton
must be harvested by commercial equipment (stripper and mechanical picker) to provide an adequate representation of
plant residue for the ginning process. At least three field trials for each type of harvesting (stripper and mechanical
picker) are needed, for a total of six field trials.  The need for additional tolerances and revisions to the exposure/risk
assessments will be made upon receipt and evaluation of required data.

       4 Guideline 201-4-SS may be satisfied by participating in the Spray Drift Taskforce.

                                              48

-------
       Additionally, a Data Call-In Notice (DCI) was sent to registrants of organophosphate
pesticides, including methidathion, currently registered under FIFRA (August 6, 1999
64FR42945-42947, August 18 64FR44922-44923). DCI requirements included acute, subchronic
and developmental neurotoxicity studies.

        2. Labeling for Manufacturing Use Products

       To remain in compliance with FIFRA, manufacturing use product (MUP) labeling should
be revised to comply with all current EPA regulations, PR Notices and applicable policies. The
MP labeling should bear the labeling contained in Table 17 at the end of this section.

       B. End-Use Products

         1. Additional Product-Specific Data Requirements

       Section 4(g)(2)(B) of FIFRA calls for the Agency to obtain any needed product-specific
data regarding the pesticide after a determination of eligibility has been made.  Registrants must
review previous data submissions to ensure that they meet current EPA acceptance criteria and if
not, commit to conduct new studies. If a registrant believes that previously submitted data meet
current testing standards, then the study MRID numbers should be cited according to the
instructions in the Requirement Status and Registrants Response Form provided for each product.

       A product-specific data call-in, outlining specific data requirements, accompanies this
interim RED.

         2. Labeling for End-Use Products

       Labeling changes are necessary to implement the mitigation measures outlined in'Section
IV above.  Specific language to incorporate these changes is specified in the Table 17 at the end
of this section.

       C.  Existing Stocks

       Registrants may generally distribute and sell products bearing old labels/labeling for 24
months from the date of the issuance of this interim RED.  Persons other than the registrant may
 generally distribute or sell such products for 50 months from'the date of the issuance of this
interim RED. However, existing stocks time frames will be established case-by-case, depending
 on the number of products involved, the number of label changes and other factors. Refer to
 "Existing Stocks of Pesticide Products; Statement of Policy"; Federal Register, Volume 56, No.
 123, June 26, 1991.
                                           49

-------
       The Agency has determined that registrant may distribute and sell methidathion products
bearing old labels/labeling for 24 months from the date of issuance of this interim RED.  Persons
other than the registrant may distribute or sell such products for 50 months from the date of the
issuance of this interim RED. Registrants and persons other than the registrant remain obligated
to meet pre-existing label requirements and existing stocks requirements applicable to products
they sell or distribute.                                                 .
                                           50

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not apply this product or allow it to drift to blooming crops or we
This chemical has properties and characteristics associated with c
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in ground water contamination.
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VL Related Documents and How to Access Them

       This interim Registration Eligibility Document is supported ^
presently maintained in the OPP docket The OPP docket is located m Room 119 Crystal Mall
#2,1921 Jefferson Davis Highway, Arlington, VA. It is open Monday through Friday,
excluding legal holidays from 8:30 A.M. to 4:00 P.M..

       The docket initially contained preliminary risk assessments and related documents as of
Decembers 1999. Sixty days later the first public comment period closed. The EPA then
considered comments, revised the risk assessment and added the formal "Response to
Comments" document and the revised risk assessment to the docket.

        All documents, in hard copy form, may be viewed in the OPP docket room or
 downloaded or viewed via the Internet at the following site: frgr/fru™ epn rov/petticides/op.
                                            59

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60

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VII. APPENDICES
        61

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72

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Appendix B. Data Supporting Guideline Requirements for the Reregistration of
             Methidathion

GUIDE TO APPENDIX B

Appendix B contains a listing of data requirements which support the reregistration for active
ingredients within the chemical case covered by this interim RED. It contains generic data
requirements that apply in all products, including data requirements for which a "typical
formulation" is the test substance.

The data table is organized in the following formats:

 1      Data Requirement (Columns 1, 2 & 3).  The data requirements are listed in the order of
       New Guideline Number and appear in 40 CFR ง 158. The reference numbers
       accompanying each test refer to the test protocols set in the Pesticide Assessment
       Guidance, which are available .from the National Technical Information Service, 5285
       Port Royal Road, Springfield, VA 22161-0002, (703) 487-4650.

 2     Use Pattern (Column 4). This column indicates the use patterns for which the data
       requirements apply. The following letter designations are used for the given use patterns.

       A.    Terrestrial food
       B.    Terrestrial feed
        C.    Terrestrial nonfood
        D.    Aquatic food    .                                                       .
        E.    Aquatic nonfood outdoor
        F.    Aquatic nonfood industrial
        G.    Aquatic nonfood residential
        H.    Greenhouse food
        I.     Greenhouse nonfood
        J.    Forestry
        K.    Residential
        L.    Indoor food
        M.    Indoor nonfood
        N.     Indoor medical               .
        O.     Indoor residential

  3.     Bibliographical Citation (Column 5)'. If the Agency has acceptable data in its files, this
        column lists the identification number of each of the studies. Normally, this is the
        Master Record Identification (MRID) Number, but may be a "GS" number if no MRID
        number has been assigned. Refer to the Bibliography (Appendix D) for a complete
         citation of the study.
                                            73

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Appendix B. Data Supporting Guideline Requirements for the Reregistration of
            Methidathion
New
Guideline
Number

830.1550
830.1600
830.1670
830.1700
830.1750
830.1800
830.6302
830.6303
830.6304
830.7200
830.7300
830.7840
830.7860
830.7950
830.7370
830.7550
830.7000
830.6313
830.6314
830.6315
830.6316
830.6317
830.7100
8306319
Old
Guideline
• Number

61-1
61-2A
61-2B
62-1
62-2
62-3
63-2
63-3
63-4
63-5
63-7
63-8
63-9
63-10
63-11
63-12
63-13
63-14
63-15
63-16
63-17
63-18
63-19
Requirement
Use
pattern
ซ Bibliographical Citation(s)
' ' ' \ \ JV • '""" * " ""
PRODUCT USE CHEMISTRY
Product Identity and Composition
Starting Materials and Manufacturing
Process
Discussion of Impurities
Preliminary Analysis
Certification of Limits
Enforcement Analytical Method
Color
Physical State
Odor
Melting Point/Melting Range
Density
Solubility
Vapor Pressure
Dissociation Constant in Water
Octanol/Water Partition Coefficient
pH of Water Solutions or Suspensions
Stability
Oxidizing/Reducing Action
Flammability
Explodability
Storage Stability
Viscosity
Miscibility
All
All
AH
All .
All
All
A,B, C
A,B,C
A, B, C
A,B,C
All
All
All
AH
All
All
All
All
All
All
AH
All
AH
41863501, 41863504, 42789701
42789701
42789701
42789701
00131026, 00142590, 40079802,
41863502, 41863505, 42789702
00131026, 40079802, 41863502,
41863505, 42789702, 43733304
0001 1347, 0013 1026, 40079802,
41863503i 41863506, 42789703
00131026, 40079802, 41863503,
41863506,42789703
00011347, 00131026, 41863503,
41863506,42789703
00011347, 41863503, 42789703
41863503,42789701
00011347, 00131026, 41863503,
42789703
41863503,42789701
41863503,42789701
41863503,42789703
41863503, 42789701
41863503, 42789701
42789701
00131026, 41863506, 42789703
00131026, 41863506, 42789703,
43733305
00131026, 41863506, 42789703
00131026,41863506
00131026. 41863506, 43733305
                                        74

-------
| New '
Guideline
Number
830.6320
Old
Guideline
63-20
Requirement
Corrosion Characteristics
Use
Pattern
All
, Bibliographical Citation(s)
00131026, 41863506, 42789703,
43733305
ECOLOGICAL EFFECTS
850.2200
850.2200







850.1025
850.1035


850.1950
850.1950

850-3030







	 T
71-2A
71-2B
71-4B




72-2A

72-3B
72-3C


72-7A
72-7B

141-2


81-2
81-3


81-6
Avian Subacute Dietary Toxicity -
Avian Subacute Dietary Toxicity -






Estuarine/Marine Fish Acute Toxicity
Estuarine/Marine Mollusk Acute
Estuarine/Marine Invertebrate Acute


Simulated Field Testing for Aquatic
Actual Field Testing for Aquatic

Honey Bee Toxicity of Residues on
Foliage
TOXICOLOGY
30-Day Acute Oral Toxicity - Rat
Acute Dermal Toxicity - Rabbit/Rat

Primary Eye Irritation - Rabbit


A,B,C
A,B, C
A,B,C
A,B,C
A,B,C
A,B,C
A,B,C
A,B,C
A,B, C
A,B,C
A,B, C
A,B, C
A,B,C
A,B, C
A,B,C
A,B,C
A,B,C

A,B,-C
A,B,C
A,B,C
A,B,C
A,B, C
A.B.C
42081701,44806601
00157347, 00159201, 42081701,
44381602
44381602
Reserved
Reserved
42081702
42081703
42081704
42081705, 43738501
42185201-02, 42181705
42081706,42207902
Data Gap
42081707
Reserved
Reserved
00036935
42081708

00139328, 44434501
00139326
00011449
00159199
00159200
00252433
75

-------
New
Guideline
Number
870.6100
870.6200
870.3100
870.3200
870.6100
870.4100
870.4100
870.4200
870.4200
870.3700
870.3700
870.3800
870.5140
870.5375
870.5500
870.7485

875.2100
875.1100
875.1300

835.2120
835.2240
835.2410
835.2370
835.4100
835.1410
835 8100
Old
Guideline
Number
81-7
81-8
82-1A
82-2
82-5B
83-1A
83-1B
83-2A
83-2B
83-3A
83-3B
83-4
84-2A
84-2B
84-4
85-1
Requirement
Acute Delayed Neurotoxicity - Hen
Acute Neurotoxicity Screening Battery
90-Day Subchronic Feeding - Rodent
21 -Day Dermal - Rabbit/Rat
90-Day Neurotoxicity, Mammal
Chronic Feeding Toxicity - Rodent
Chronic Feeding Toxicity - Nonrodent
Chronic Carcinogenicity (Feeding) - Rat
Chronic Carcinogenicity (Feeding) -
Mouse
Prenatal Developmental Toxicity - Rat
Prenatal Developmental Toxicity -
Rabbit
2-Generation Reproduction - Rat
Gene Mutation (Ames Test)
Structural Chromosomal Aberration
Other Genotoxic Effects
General Metabolism
Use
Pattern
A,B,C
A
A,B,C
A,B,C
A
A,B, C
A,B,C
A,B,C
A,B,C
A,B,C
A,B,C
A,B, C
A,B,C
A,B, C
A,B,C
A, B, C
J Bibliographical Citation(s)
j '
00011704
43145903-04
43582501
40079806
43582501
00160260
41945001
00160260
00157457
00139326, 40079807
40079809-10
40079811-12
00070213, 00078329-30, 00070832,
00084010
00078335
00078334
40127818
OCCUPATIONAL/RESIDENTIAL EXPOSURE
132-1A
231
232 •

161-1
161-2
161-3
161-4
162-1
163-2
• 163-3
Foliar Residue Dissipation
Estimation of Dermal Exposure at
Outdoor Sites
Estimation of Inhalation Exposure at
Outdoor Sites
AB,C
A,B,C
A,B,C
44680501-02
Reserved
Reserved
ENVIRONMENTAL FATE
Hydrolysis
Photodegradation - Water
Photodegradation - Soil
Photodegradation - Air
Aerobic Soil Metabolism
Laboratory Volatilization from Soil
Field Volatility from Soil
A,B,C
A,B,C
A,B,C
A,B,C
A,B,C
A,B
A,B
42037701, 44545101
42081709
42081710
42647301
42262501, 42647301, 42799601,
44545101
42098801, 42647301
Reserved
76

-------
j New'
Guideline
Number
835.6500
835.1850
835.1900
1 835.1950

860.1300
860.1300
860.1340
860.1480
860.1500
860.1500
1 860.1500
I 860.1500
860.1500
860.1500
860.1500
1 860.1500
860.1500
860.1500

72-4-SS
81-8-SS
201-4-SS
Old
Guideline
Number
164-5
165-1
165-2
165-4

, "Requirement
Long-term Terrestrial Field Dissipation
Confined Accumulation in Rotational
Field Accumulation in Rotational Crops
Bioaccumulation in Fish
Use"
Pattern
A,B,C
A,B,C
A,B,C
A,B,C
Bibliographical Citation(s)
s ^r N **
Reserved .
41902201
Reserved
Reserved
RESIDUE CHEMISTRY ^ 	 1
171-4A 1 Nature of the Residue - Plants
171-4B 1 Nature of the Residue - Livestock
	 1
171-4D
171-4J
171-4K
171-4K
171-4K
171-4K
171-4K
171-4K
171-4K
171-4K
171-4K
171-4K

None
None
None
Residue Analytical Method - Animals
Magnitude of Residues in Meat, Milk,
Poultry and Eggs
Crop Field Trials (Cereal Grains Group)
Crop Field Trials (Cotton Gin
Byproducts)
Crop Field Trials (Citrus Foods Group)
Crop Field Trials (Grass Forage and Hay
Crop Field Trials (Miscellaneous
Commodities Group)
Crop Field Trials (Nongrass Animal
Feeds Group)
Crop Field Trials (Pome Fruits Group)
Crop Field Trials (Root and Tuber
Vegetables Group)
Crop Field Trials (Stone Fruits Group)
Crop Field Trials (Tree Nuts Group)
A,B,C
A,B,C
B,C
A,B,C
A, B, C
A,B
A,B,C
A, B, C
A,B,C
A,B, C
A,B,C
A,B,C
A,B,C
A,B,C
42708901-03,43399701 |
43170001-05,43399702
43296401-02
Waived
„
Reserved 1
Data Gap
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
OTHER
Early Life Stage Estuarine Fish
Acute Neurotoxicity - Rats
Background for Pesticide Aerial Drift
(Evaluation)
A,B, C
A,B
A,B,C
Data Gap 	
43145901-04
Data Gap
77

-------
78

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Appendix C.  Technical Support Documents

      Additional documentation in support of this interim RED is maintained in the OPP
docket; located in Room 119, Crystal Mall #2,1921 Jefferson Davis Highway, Arlington, VA.
It is open Monday through Friday, excluding legal holidays, from 8:30 A.M. to 4 P.M..

      The docket initially contained preliminary risk assessments and related documents as of
August 10,1998. Sixty days later the first public comment period closed. The EPA then
considered comments, revised the risk assessment and added the formal "Response to
Comments" document and the revised risk assessment to the docket on June 16,1999.

       All documents, in hard copy form, may be viewed in the OPP docket room or
downloaded or viewed via the Agency's website at http://www.epa.mv/pesticides/op.

These documents include:

HED Documents:

 1.     Human Health Risk Assessment Methidathion, dated August 9, 2000.

 EFED Documents:

 1     Methidathion - Environmental Fate and Effects Chapter, dated November 30,1999 and
       its addendum, dated April 4, 2001, (including drinking water assessment addenda, dated
       March 22, 2001 and dietary exposure assessment addenda, dated April 27,2001).
                                           79

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80

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Appendix D. Citations Considered to Be Part of the Data Base Supporting the Interim
             Reregistration Eligibility Decision (Bibliography)

GUIDE TO APPENDIX D ' .

1      CONTENTS OF BIBLIOGRAPHY.  This bibliography contains citations of all studies
       considered relevant by EPA in arriving at the positions and conclusions stated elsewhere
       in the Interim Reregistration Eligibility Document. Primary sources for studies in this
       bibliography have been the body of data submitted to EPA and its predecessor agencies
       in support of past regulatory decisions.  Selections from other sources including the
       published literature, in those instances where they have been considered, are included.

2.     UNITS OF ENTRY.  The unit of entry in this bibliography is called a "study." In the
       case of published materials, this corresponds closely to an article. In the case of
       unpublished materials submitted to the Agency, the Agency has sought to identify
       documents at a level parallel to the published article from within the typically larger
       volumes in which they were submitted. The resulting "studies" generally have a distinct
       title (or at least a single subject), can stand alone for purposes of review and can be
       described with a conventional bibliographic citation. The Agency has also attempted to
       unite basic documents and commentaries upon them, treating them as a single study.

 3     IDENTIFICATION OF ENTRIES. The entries in this bibliography are sorted
       numerically by Master Record Identifier, or "MRID" number.  This number is unique to
       the citation, and should be used whenever a specific reference is required. It is not
       related to the six-digit "Accession Number" which has been used to identify volumes of
        submitted studies (see paragraph 4(d)(4) below for further explanation).  In a few cases,
        entries added to the bibliography late in the review may be preceded by a nine character
        temporary identifier. These entries are listed after all MRID entries.  This temporary
        identifying number is also to be used whenever specific reference is needed.     •

 4.     FORM OF ENTRY. In addition to the Master Record Identifier (MRID), each entry
        consists of a citation containing standard elements followed, in the case of material
        submitted to EPA, by a description of the earliest known submission. Bibliographic
        conventions used reflect the standard of the American National Standards Institute
        (ANSI), expanded to provide for certain special needs.

        a      Author. Whenever the author could confidently be identified, the Agency has
               chosen to show ^personal author. When no individual was identified, the
               Agency has shown an identifiable laboratory or testing facility as the author.
               When no author or laboratory could be identified, the Agency has shown the first
                submitter as the author.
                                            81

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b.     Document date. The date of the study is taken directly from the document.
       When the date is followed by a question mark, the bibliographer has deduced the
       date from the evidence contained in the document.  When the date appears as
       (1999), the Agency was unable to determine or estimate the date of the document.

c.     Title. In some cases, it has been necessary for the Agency bibliographers to
       create or enhance a document title.  Any such editorial insertions are contained
       between square brackets.

d.     Trailing parentheses. For studies submitted to the Agency in the past, the trailing
       parentheses include (in addition to any self-explanatory text) the following
       elements describing the earliest known submission:

  (1)  Submission date.  The date of the earliest known submission appears immediately
       following the word "received."

  (2)  Administrative number. The next element immediately following the word
       "under" is the registration number, experimental use permit number, petition
       number or other administrative number associated with the earliest known
       submission.

  (3)  Submitter.  The third element is the submitter.  When authorship is defaulted to
       the submitter, this element is omitted.

  (4)  Volume Identification (Accession Numbers). The final element in the trailing
       parentheses identifies the EPA accession number of the volume in which the
       original submission of the study appears. The six-digit accession number follows
       the symbol "CDL," which stands for "Company Data Library." This accession
       number is in turn followed by an alphabetic suffix which shows.the relative
       position of the study within the volume.
                                     82

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BIBLIOGRAPHY

MRID#     CITATION
00011283    Polan, C.E.; Chandler, P.T. (19??) Metabolism of 14C-Carbonyl labeled
             Supracide by lactating cows. Journal of Dairy Science 54(6):847-853.  (Also In
             unpublished submission received Dec 17,1973 under 4F1450; submitted by
             Ciba-Geigy Corp., Greensboro, N.C.; CDL:093863-B)

00011303    Tweedy, B.; Kahrs, R. (1974) Summary: Methidathion (GS-13005)-Sorghum:.
             Results of Tests on the Amount of Residue Remaining, Including a Description of
             the Analytical Methods Used: Report No. GAAC-74025.  Summary of studies
             094012-B through 094012-K. (Unpublished study received Jun 4,1974 under
             4F1512; submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:094012-A)

 00011304    Dupre, G.D. (1974) Summary of Residue Analyses: Test No. AG-A 2186; Project
             No. 303016. (Unpublished study received Jun 4,1974 under 4F1512;  prepared in
             cooperation with Bio/dynamics,  Inc., submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL-.094012-B)
                                                                          *
 00011305    Turner, WJB. (1972) Residue Report: AG-A No. 2439; Project No. 303016.
              (Unpublished study received Jun 4,1974 under 4F1512; submitted by Ciba-Geigy
              Corp., Greensboro, N.C.; CDL: 094012-C)

 00011314    Kahrs, R.A.; Mattson, A.M. (1969) Residues Found in Eggs and Tissues of
              Chickens Fed Three Levels of GS-13005 in Their Diet for Four Weeks: Report
              No. GAAC-69036.  (Unpublished study including letter dated Feb 2,1968 from
              K. Morgareidge to Jack R. Forsythe, received May 7,1970 under OF0892;
              prepared in cooperation with Food and Drug Research Laboratories, Inc.,
              submitted by Geigy Chemical Corp., Ardsley, N.Y.; CDL:091539-D)

 00011317    Dupuis, G.; Esser, H.O.; Mucke, W. (1969) The Metabolic Behavior of the
              Insecticide GS13005: GAAC-69023. (Unpublished study received May 5,1970
              under OF0892; submitted by Geigy Chemical Corp., Ardsley, N.Y.;
              CDL:091538-B)

  00011318    Mattson, A.M.; Kahrs, R.A. (1969) Determination of GS-13005 Residues in Field
              Treated Forage: Report No.: GAAC-69042. (Unpublished study received May 5,
               1970 under OF0892; submitted by Geigy Chemical Corp., Ardsley, N.Y.;
               CDL:091538-G)
                                           83

-------
BIBLIOGRAPHY
MRID#
CITATION
00011319    Mattson, A.M.; Kahrs, R.A. (1969) Residues of GS-13005 and GS-13007 in
            Alfalfa Arising from Application of GS-13005 by Aircraft: GAAC-69027.
            (Unpublished study received May 5,1970 under OF0892; submitted by Geigy
            Chemical Corp., Ardsley, N.Y.; CDL: 091538-J)

00011320    Kahrs, R.A.; Kanuk,,M.J. (1969) Determination of Residues of GS-13005 in
            Alfalfa by Gas Chromatography Employing Flame Photometric Detection.
            Method no. AG-105 dated Jun 20,1969. (Unpublished study received May 5,
            1970 under OF0892; submitted by Geigy Chemical Corp., Ardsley, N.Y.;
            CDL:091538-K)

00011321    Mattson, A.M.; Kahrs, R.A. (1969) Dissipation of Residues of GS-13005 in
            Forage Grasses: GAAC-69026. (Unpublished study received May 5,1970 under
            OF0892; submitted by Geigy Chemical Corp., Ardsley, N.Y.; CDL:091538-M)

00011323  ' Mattson, A.M.; Kahrs, R.A. (1969) Residues of GS-13005 and Its Oxygen
            Analog in Citrus Fruit and Citrus Fractions: GAAC-69028. (Unpublished study
            received May 5,1970 under OF0892; submitted by Geigy Chemical Corp.,
            Ardsley, N.Y.; CDL:091538-O)

00011324    Kahrs, R.A.; Kanuk, M.J. (1969) Determination of Residues of GS-13005 in
            Citrus by Gas Chromatography Employing Flame Photometric Detection.
            Method No. AG-106 dated Jun 23,1969.  (Unpublished study received May 5,
            1970 under OF0892; submitted by Geigy Chemical Corp., Ardsley, N.Y.;
            CDL:091538-Q)

00011325    Mattson, A.M.; Kahrs, R.A. (1969) Residues of GS-13005 in Cottonseed and
            Cottonseed Fractions: Report No: GAAC-69034. (Unpublished study including
            addendum,  received May 5,1970 under OF0892; submitted by Geigy Chemical
            Corp., Ardsley, N.Y.; CDL:091538-R)

00011326   • Kahrs, R.A.; Kanuk, M.J. (1969) Determination of Residues of GS-13005 in
            Cotton Seed and Cotton Seed Fractions by Gas Chromatography.  Method no.
            AG-107 dated Jun 27,1969. (Unpublished study received May 5,1970 under
            OF0892; submitted by Geigy Chemical Corp., Ardsley, N.Y.; CDL:091538-T)
                                        84

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BIBLIOGRAPHY

MRID #      CITATION
0001 1334    Kanuk, M.J.; Kahrs, R.A. (1969)                           R28
             Metabolites in Milk by Gas Chromatography.  Method-No. AG-98 dated Mar 28,
             1969  (Unpublished study received May 7, 1970 under OF0892; submitted by
             Geigy Chemical Corp., Ardsley, N.Y.; CDL:091540-F)

 00011335    Wood, N.F. (1969) Isolation and Confirmation of the Identity of
             2-Memoxy-4-methylsulfonylmethyl-l;3,4-thiadiazol-5(4H)-one As a Metabolite
             in Milk of aCowFedGS-13005: GAAC-69025. (Unpublished study received
             May 7, 1970 under OF0892; submitted by Geigy Chemical Corp., Ardsley, N.Y.;
             CDL:091540-G)

 0001 1336    Cassidy, I.E.; Wood, N.F.; Lasker, K. (1969) Methods for the Isolation and
             Determination of 14C in Natural Products in Milk-Glycerol, Lactose, and
             Casein. Method no. AG-103 dated Jun 5, 1969. (Unpublished study received
             May 7,  1970 under OF0892; submitted by Geigy Chemical Corp., Ardsley, N.Y.;
              CDL:091540-H)

 00011337    Kahrs, R.A.; Kanuk, MJ. (1969) Determination of GS-13007 in Cow Milk by
              Thin Layer Chromatography. Method no. AG-104 dated Jun 23, 1969.
              (Unpublished study received May 7, 1970 under OF0892; submitted by Geigy
              Chemical Corp., Ardsley, N.Y.; CDL:091540-K)

  0001 1340    Polan, C.E. (1968) Degradation of Supracide in Hay, Silage and the Rumen.
              (Unpublished study received May 7, 1970 under OF0892; prepared by Virginia
              Polytechnic Institute and State Univ., Dept. of Dairy Science, submitted by Geigy
              Chemical Corp., Ardsley, N.Y.; CDL:091540-N)

  0001 1347    Ciba-Geigy Corporation (1977) Chemical Data Section for Methidathion
              (Unpublished study received Jun 28, 1977 under 100-530; CDL:230756-A)

  0001 1350    Vilkas, A.G. (1976) Acute Toxicity of Supracide Technical to the Water
               Flea-Daphnia magna-Straus: AES Proj. #7614-500. (Unpublished study
               received May 17, 1977 under 100-501; prepared by Union Carbide Corp.,
               submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:096136-A)
                                           85

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BIBLIOGRAPHY
MRID#
CITATION
00011373     Rolla, H.M.; Kahrs, R.A. (1972) Determination of Residues of GS-13005 in
             Potatoes and Tomatoes by Gas Chromatography Employing Flame Photometric
             Detection. Method no. AG-199 dated Jun 14, 1972. (Unpublished study received
             Nov 10,1972 under 3F1323; submitted by Ciba-Geigy Corp., Ardsley, N.Y.;
             CDL:092270-F)

00011425     Ragsdale, D. (1974) Residue Report: AG-ANo. 3118 A; Project No. 303035.
             (Unpublished study received Sep 27,1974 under 5F1555; submitted by
             Ciba-Geigy Corp., Greensboro, N.C.; CDL:094463-D)

00011426     Taylor, J.B. (1974) Residue Report: AG-A No. 3161; Project No. 303035.
             (Unpublished study received Sep 27,1974 under 5F1555; submitted by
             Ciba-Geigy Corp., Greensboro, N.C.; CDL-.094463-E)

00011449     Mastri, C. (1969) Report to Geigy Agricultural Chemicals, Division of Geigy
             Chemical Corporation: Acute Toxicity Studies on GS-13005 2E (GA-4-129): IBT
             No. A7199. (Unpublished study received Oct 1, 1969 under OF0892; prepared by
             Industrial Bio-Test Laboratories, Inc., submitted by Geigy Chemical Corp.,
             Ardsley, N.Y.;CDL:091535-AL)

00011456     Houseworth, L.D. (1977) Residues of Methidathion in or on Olives Resulting
             from Single Applications of Methidathion with or without Nonphytotoxic Oils:
             Report No. ABR-77013. (Unpublished study received Jul 19,1977 under
             100-501; submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:096256-A)

00011473     IR-4 Project at Rutgers, the State University (1976) Methidathion Residue
             Tolerance Petition—Mangoes.  Summary of study 098200-B. (Unpublished study
             received Mar 3,1979 under 9E2194; CDL:098200-A)

00011474    Thompson, N.P.; Witkonton, S.; Certain, D. (1976) Mangoes: Methidathion and
             Its Toxic Metabolite GS 13007. Undated method. (Unpublished study received
             Mar 3,1979 under 9E2194; prepared by Univ. of Florida, Institute of Food and
             Agricultural Science, Pesticide Research Laboratory, submitted by Interregional
             Research Project No. 4, New Brunswick, N.J.; CDL:098200-B)
                                         86

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BIBLIOGRAPHY

MRID#      CITATION
00011640    Tweedy, E.G. (1974) Summary: Methidathion (GS-13005): Peaches, Pecans and
             Walnuts: Results of Tests on the Amount of Residue Remaining, Including a
             Description of the Analytical Methods Used: Report No: GAAC-74028.
             Summary of studies 094033-B through 094033-K. (Unpublished study received
             on unknown date under 4F1522; submitted by Ciba-Geigy Corp., Greensboro,
             N.C.; CDL:094033-A)

00011641    Dupre, G.D.; Hiddleson, L. (1974) Summary of Residue Analyses: Bio/dynamics,
             Inc. No. 73033.  (Unpublished study received on unknown date under 4F1522;
             prepared in cooperation with Bio/dynamics, Inc.,  submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:094033-B)

00011642    Dupre, G.D.; Christensen, M.D. (1974) Summary of Residue Analyses:
             Bio/dynamics, Inc. No. 73033.  (Unpublished study received on unknown date
             under 4F1522; prepared hi cooperation with Bio/dynamics, Inc., submitted by
             Ciba-Geigy Corp., Greensboro, N.C.; CDL:094033-C)

 00011704    Sachsse, K.; Ullmann, L. (1977) Acute Oral Toxicity and Neurotoxicity Study of
             Technical GS-13005 in the Domestic Fowl (Gallus domesticus): Project No. Siss
             5927.  (Unpublished study received Jul 25,1978  under 100-501; submitted by
             Ciba-Geigy Corp., Greensboro, N.C.; CDL:097230-A)

 00011722    Fox, R.W. (1975) Residue Report: AG-A No. 3625; Project No. 303901.
              (Unpublished study received Jul 13,1977 under  100-501; submitted by
              Ciba-Geigy Corp., Greensboro, N.C.; CDL:096250-Q)

 00011764     Tweedy, E.G. (1977) SupracideA(R> 2E--Artichokes: Residues Observed
              Including the Analytical Methods Used from California Field Trials: Report No.:
              ABR-77026. Summary of studies 096253-B through 096253-D. (Unpublished
              study received Jul 19,1977 under 100-501; submitted by Ciba-Geigy Corp.,
              Greensboro, N.C.; CDL:096253-A)

 00011769    Kahrs, R.A. (1977) Methidathion--Walnuts: Residues Resulting from a Dormant
              or Delayed Dormant Plus Two Foliar Applications of SupracideA(R> 2E:
              Summary of Residue Data: Report No.: ABR-77019. Summary of studies
              230873-B through 230873-E. (Unpublished study received Jul 20,1977 under
              100-501; submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:230873-A)
                                          87

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00011786     House-worth, L.D. (1977) SupracideA(R> 2E~Cotton; Residues Observed in
             Cottonseed from Multiple Applications: Report No.: ABR-77062. Summary of
             studies 231269-B through 231269-H. (Unpublished study received Aug 15, 1977
             under 100-501; submitted by Ciba-Geigy Corp., Greensboro, N.C.;
             CDL:231269-A)

00011841     Beliles, R.P.; Scott, W.; Knott, W. (1965) GS-13005: Safety Evaluation on Fish
             and Wildlife (Mallard Ducks, Bobwhite Quail, Rainbow Trout, Sunfish and
             Goldfish).  (Unpublished study received Sep 13,1965 under 8F0648; prepared by
             Woodard Research Corp., submitted by Geigy Chemical Corp., Ardsley, N.Y.;
             CDL:096000-A)

00011843     Mattson, A.; Kahrs, R. (1966) The Determination of GS-13005 in Plant Materials
             by Gas Chromatography. Method dated Dec 15,1966. (Unpublished study
             received Aug 5,1967 under 8F0648; submitted by Geigy Chemical Corp.,
             Ardsley, N.Y.;CDL:091126-B)

00011844-     Insler, M.; Mattson, A. (1966) Determination of GS-13007 in Forage Crops by
             Thin Layer Chromatography. Method dated Dec 15,1966.  (Unpublished study
             received Aug 5,1967 under 8F0648; submitted by Geigy Chemical Corp.,
             Ardsley, N.Y.; CDL:091126-C)

00011846     Murphy, R.T.; Kahrs, R.A.; Mattson, A.M. (1966) Gas Chromatographic Method
             for the Detection of Residues in the Milk of a Cow Fed Radioactive GS-13005.
             Method dated Dec 15,1966. (Unpublished study received Aug 5,1967 under
             8F0648; submitted by Geigy Chemical Corp., Ardsley, N.Y.; CDL:091126-F)

00011848     Geigy Chemical Corporation (1967) Determination of GS-13005 in Tissues of a
             Steer Fed 30 PPM GS-13005 for 55 Days. (Unpublished study received Aug 5,
             1967 under 8F0648; prepared in cooperation with Virginia Polytechnic Institute
             and State Univ., Dept of Dairy Science; CDL:091126-1)

00011852     Kahrs, R.A.; Mattson, A.M. (1967) Analytical Method for the Detection of
             Residues of GS-13005 in Cotton Seed and Cotton Seed Fractions. Method dated
             Jun 30,1967. (Unpublished study received Aug 5,1967 under 8F0648;
             submitted by Geigy Chemical Corp., Ardsley, N.Y.; CDL:091126-M)
                                         88

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00011856    Ciba-Geigy Corporation (1970) SupracideA(R> 2E Tobacco Residue Summary.
             Summary of studies 101092-B through 101092-F. (Unpublished study received
             Dec 21,1971 under 100-501; CDL:101092-A)

00011921    Dupre, G.D.; Davidson, W.E. (1974) Summary of Residue Analyses:
             Bio/dynamics, Inc. No. 73033. (Unpublished study received on unknown date
             under 4F1522; prepared in cooperation with Bio/dynamics, Inc., submitted by
            " Ciba-Geigy Corp., Greensboro, N.C.; CDL:094033-D)

00011936    Cassidy, J.E.; Murphy, R.; Mattson, A.M. (1967) The Metabolic Fate of
             5-Carbonyl-14C GS-13005 When Given to a Cow: (Unpublished study received
             Aug 5,1967  under 8F0648; submitted by Geigy Chemical Corp., Ardsley, N.Y.;
             CDL:091126-E)

00012575    Tweedy, B.G.; Kahrs, R.A. (1977) Supracide(R) 2E-Alfalfa Residues Observed
             and Metabolism Data Including the Analytical Methods Used: Report No.:
             ABR-77023. (Unpublished study received Jul 13, 1977 under 100-501; submitted
             by Ciba-Geigy Corp., Greensboro, N.C.; CDL:096248-A)

 00012593    Ross, J.A.; Kahrs, R.A. (1977) Residues of Methidathionm or on Deciduous
             Fruit Resulting from Dormant or Delayed Dormant Applications with or  without
             Oil: Report No.: ABR-77008. Summary of studies 227647-B through 227647-M.
             (Unpublished study received Jan 25,1977 under 100-501; submitted by
             Ciba-Geigy  Corp., Greensboro, N.C.; CDL:227647-A)

 00012594    Christensen, M.DT (1977) Residue Report: AG-A No. 4224; 2nd Report; Project
             No. 303060. (Unpublished study received Jan 25, 1977 under 100-501; prepared
             in cooperation with Bio/dynamics, Inc., submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:227647-B)

 00012595    Maggiore, F.; Christensen, M.D. (1977) Residue Report: AG-A No. 4225; 2nd
             Report; Project No. 303060. (Unpublished study received Jan 25,1977 under
              100-501; prepared in cooperation with Bio/dynamics, Inc., submitted by
              Ciba-Geigy Corp., Greensboro, N.C.; CDL:227647-C)
                                          89

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00012596    Zaccaria, J.J. (1977) Residue Report: AG-A No. 4234; 2nd Report; Project No.
             303060. (Unpublished study received Jan 25,1977 under 100-501; prepared in
             cooperation with Bio/dynamics, Inc., submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:227647-D)

00012597    Zaccaria, J.J. (1977) Residue Report: AG-A No. 4235; 2nd Report; Project No.
             303060. (Unpublished study received Jan 25,1977 under 100-501; prepared in
             cooperation with Bio/dynamics, Inc., submitted by Ciba-Geigy Corp.,  ,
             Greensboro, N.C.; CDL:227647-E)

00012598    Trammel, K.; Higgins, E.R. (1977) Residue Report: AG-A No. 4294; 2nd Report;
             Project No. 303060.  (Unpublished study received Jan 25,1977 under 100-501;
             prepared in cooperation with Bio/dynamics, Inc., submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:227647-F)

00012599    Trammel, K.; Higgins, E.R. (1977) Residue Report: AG-A No. 4295; 2nd Report;
             Project No. 303060.  (Unpublished study received Jan 25,1977 under 100-501;
             prepared hi cooperation with Bio/dynamics, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:227647-G)

00012600    Zaccaria, J.J. (1977) Residue Report: AG-A No. 4321; 2nd Report; Project No.
             303060. (Unpublished study received Jan 25,1977 under 100-501; prepared in
             cooperation with Bio/dynamics, Inc., submitted by Ciba-Geigy Corp.,
            . Greensboro, N.C.; CDL:227647-H)

 00012601    Zaccaria, J.J. (1977) Residue Report: AG-A No. 4322; 2nd Report; Project No.
              303060. (Unpublished study received Jan 25,1977 under 100-501; prepared in
              cooperation with Bio/dynamics, Inc., submitted by Ciba-Geigy Corp.,
              Greensboro, N.C.; CDL:227647-I)

 00012603     Christensen, M.D. (1977) Residue Report: AG-A No. 4367; 2nd Report; Project
             No. 303060.  (Unpublished study received Jan 25,1977 under 100-501; prepared
              in cooperation with Bio/dynamics, Inc., submitted by Ciba-Geigy Corp.,
              Greensboro, N.C.; CDL:227647-K)
                                          90

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MRID#      CITATION
00012604    Christensen, M.D. (1977) Residue Report: AG-A No. 4368; 2nd Report; Project
             No. 303060.  (Unpublished study received Jan 25, 1977 under 100-501; prepared
             in cooperation with Agricultural Advisors, Inc. and Bio/dynamics, Inc., submitted
             by Ciba-Geigy Corp., Greensboro, N.C.; CDL:227647-L)

00014382    Dupre, G.D. (1974) Summary of Residue Analyses: Test No. AG-A 26041, II, III
             (3-IR-1-72); Project No. 303016. (Unpublished study received Jun 4,1974 under
             4F1512; prepared in cooperation with Bio/dynamics, Inc., submitted by
             Ciba-Geigy Corp., Greensboro, N.C.; CDL-.094012-D)

 00014383    Dupre, G.D.  (1974) Summary of Residue Analyses: Test No. AG-A 2646 I, II, III
             (MW-IR-4-72) Second Report; Project No. 303016.  (Unpublished study received
             Jun 4,1974 under 4F1512; prepared in cooperation with Bio/dynamics, Inc.,
             submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:094012-E)

 000143 84    Dupre, G.D. (1974) Summary of Residue Analyses: Test No. AG-A 2689
             (4-IR-l 1-72); Project No. 303016.  (Unpublished study received Jun 4,1974
             under 4F1512; prepared in cooperation with Bio/dynamics, Inc., submitted by
             Ciba-Geigy Corp., Greensboro, N.C.; CDL-.094012-G)

 00014404    Mattson, A.M. (1972) Summary: GS-13005~Tomatoes and Potatoes: Results of
             Tests on the Amount of Residue Remaining, Including a Description of the
             Analytical Methods Used: Report No. GAAC-72105A. Summary of studies
              092270-C through 092270-F,  092270-H through 092270-P, 092270-U and
              092270-Y. (Unpublished study received Nov 10,1972 under 3F1323; submitted
              by Ciba-Geigy Corp., Ardsley, N.Y.; CDL:092270-T)

 00015735     Luke, J., (1978) Metolachlor (Dual (R)8E):  AG-A No. 47371, II.  (Unpublished
              study received May 11,1978 under 100-583; submitted by Ciba-Geigy Corp.,
              Greensboro, N.C.; CDL:097135-T)

 00020944    Kahrs, R.A. (1979) Determination of Residues of Methidathion and Its
              Metabolites GS-13007, GS-28369, and GS-28370 in Animal Tissue by Gas
               Chromatography Employing Flame Photometric Detection.  Method No. AG-334
               dated Jan 9,1979.  (Unpublished study received Aug 21,1979 under 100-501;
               submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:098923-M)
                                          91

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MRID#
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00020945    Kahrs, R. A. (1979) Determination of Methidathion and Some of Its Metabolites
             in Milk by Gas Chromatography. Method no. AG-335 dated Jan 9,1979.
             (Unpublished study received Aug 21,1979 under 100-501; submitted by
             Ciba-Geigy Corp., Greensboro, N.C.; CDL:098923-N)

00020946    Kahrs, R. A. (1979) Residues of Methidathion in or on Deciduous Fruit and Nuts:
             Report No. ABR-79048. (Unpublished study received Aug 21,1979 under
             100-501; submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:098925-A)

00020947    Ross, R.H. (1979) Methidathion (SupracideA(R> 2E: Project No. 303089.
             (Unpublished study received Aug 21,19?9 under 100-501; prepared in
             cooperation with Michigan State Univ., Horticulture Research Station and En-Cas
             Laboratories, submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:098925-B)

00020948    Saario, C.A.; Kapreilian, H. (1979) Methidathion (Supracide 2E): Project No.
             303089. (Unpublished study received Aug 21,  1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098925-C)

00020949    Saario, C.A.; Kapreilian, H. (1979) Methidathion (Supracide 2E): Project No.
             303089. (Unpublished study received Aug 21,1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098925-D)

00020950    Luke, J.E. (1979) Methidathion (Supracide 2E): Project No. 303089.
             (Unpublished study received Aug 21,1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098925-E)

00020951    Christensen, M.D.; Wineinger, H.  (1979) Methidathion (Supracide 2E): Project
             No. 303089. (Unpublished study received Aug 21,1979 under 100-501; prepared
             hi cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098925-F)

 00020952    Christensen, M.D.; Lagorio, A. (1979) Methidathion (Supracide 2E): Project No.
             303089. (Unpublished study received Aug 21, 1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
              Greensboro, N.C.; CDL:098925-G)

                                          92

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MRID #     CITATION
00020953    Wittie, R.L. (1979) Methidathion (Supracide 2E): Project No. 303089.
             (Unpublished study received Aug 21,1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098925-H)

00020954    Zaccaria, JJ. (1979) Methidathion (Supracide 2E): Project No. 303089.
             (Unpublished study received Aug 21,1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098925-I)

00020955    Zaccaria, JJ. (1979) Methidathion (Supracide 2E): Project No. 303089.
             (Unpublished study received Aug 21,1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL-.098925-J)

 00020956    Zaccaria, JJ. (1979) Methidathion (Supracide 2E): Project No. 303089.
             (Unpublished study received Aug 21,1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098925-K)

 00020957    Zaccaria, J J. (1979) Methidathion (Supracide 2E): Project No. 303089.
              (Unpublished study received Aug 21,1979 under 100-501 ^prepared hi
              cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
              Greensboro, N.C.; CDL:098925-L)

 00020958     Schnappinger, M.G.; Drake, C. (1979) Methidathion (Supracide (R) 2E): Project
              No. 303089. (Unpublished study received Aug 21, 1979 under 100-501; prepared
              in cooperation with Virginia Polytechnic Institute and State Univ. and En-Cas
              Laboratories, submitted by Ciba-Geigy Corp., Greensboro, N.C.;
              CDL:098925-M)

 00020959    Wittie, R.L. (1979) Methidathion (Supracide 2E): Project No. 303089.
              (Unpublished study received Aug 21,1979 under 100-501; prepared  in
              cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
              Greensboro, N.C.; CDL:098925-N)
                                          93

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CITATION
00020962    Zaccaria, JJ. (1979) Methidathion (Supracide 2E): Project No. 303089.
             (Unpublished study received Aug 21, 1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.;CDL:098925-Q)

00020965    Higgins, E.R.; Trammel, K. (1979) Methidathion (Supracide 2E): Project No.
             303089. (Unpublished study received Aug 21,1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098925-T)

00020967    Wittie, R.L. (1979) Methidathion (SupracideA(R> 2E): Project No. 303060.
             (Unpublished study received Aug 21,1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098925-V)

00020970    Wittie, R.L. (1979) Methidathion (Supracide (R) 2E): Project No. 303060.
             (Unpublished study received Aug 21,1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098925-Y)                      .

 00020971    Christensen, M.D. (1979) Methidathion (Supracide 2E): Project No. 303060.
             (Unpublished study received Aug 21,1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098925-Z)

 00020979    Kanuk, M.J. (1973) Determination of Residues of GS-13005 and Its Metabolites
             GS-13007, GS-28369, and GS-28370 by Gas Chromatography Employing Flame
             Photometric Detection.  Method no. AG-240 dated Feb 23,1973.  (Unpublished
             study received Aug 21,1979 under 100-501; submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL-.098925-AH)

 00022574    Kahrs, R.A. (1979) Residues of Methidathion and Its Oxygen Analog GS-13007
             in Tissues and Milk of Lactating Dairy Cows Resulting from the Feeding of
             Methidathion: Report No.: ABR-79094. Summary of studies 098923-M and
              098923-N. (Unpublished study including ADC project no. 481 and addendum,
              received Aug 21,1979 under 100-501; submitted by Ciba-Geigy Corp.,
              Greensboro, N.C.; CDL:098923-L)
                                          94

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BIBLIOGRAPHY
MRID#
CITATION
00022903     Thomas, R.D.; Cassidy, I.E. (1974) Metabolism of delta-14C-GS-13005 in
             Artichokes: Report No. GAAC-74092. (Unpublished study received Feb 27,
             1975 under 4F1450; submitted by Ciba-Geigy Corp., Greensboro, N.C.;
             CDL:093863-C)

00022905     Thomas, R.D.; Cassidy, J.E. (1974) Comparison of the Polar Metabolites of
             delta-14C-GS-13005 in Artichokes and Tomatoes Treated with This Compound:
             Report No. GAAC-74086. (Unpublished study received on unknown date under
             4F1450; submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:093863-E)

00022907    Cassidy, I.E.; Ryskiewich, D.P.; Murphy, R.T. (1968) Metabolism of
             u~S~[(2-Methoxy-5-oxo-deltaA2=-1,3,4-thiadiazolin-4-yl)
             methyl] n~o~u,|4.~o~|i-dimethyl-phosphorodithioate(Supracide) in Alfalfa:
             Report No. GAAC-68008-A. (Unpublished study received May 5,1970 under
             OF0892; submitted by Geigy Chemical Co., Ardsley, N.Y.; CDL:091538-E)

 00022909    Polan, C.E.; Chandler, P.T. (1969) Metabolism of S
             [(2-Methoxy-5-oxo-deltaA2=-1,3,4-thiadiazolin-4-yl) methyl]o,o-dimethyl
             phosphorodithioate (GS-13005) By [sic] Lactating Cows. (Unpublished study
             received May 7, 1970 under OF0892; submitted by Geigy Chemical Co., Ardsley,
             N.Y.; CDL:091540-Q) .

 00022910    Cassidy, J.E.; Tracey, B.A. (1973) Desmethyl GS-13005 in Tomatoes Treated
             with delta!4C-GS-13005: Report No. GAAC-73049. (Unpublished study
             received Jul 2,1973 under 3F1323; submitted by Ciba-Geigy Corp., Greensboro,
             N.C.; CDL:092270-A)

 00022911     Cassidy, J.E.; Ryskiewich, D.P.; Murphy, R.T. (1968) Metabolism of
              S-[(2-Methoxy-5-oxo-deltaA2=-l ,3,4-thiadiazolin-4-yl)methyl]o,o-dimethyl
              phosphorodithioate (Supracide) in Alfalfa: Report No. GAAC-68008A.
              (Unpublished study received Jul 13, 1977 under 100-501; submitted by
              Ciba-Geigy Corp., Greensboro, N.C.; CDL:096249-A)

 00026090    Esser, H.O.; Muller, P.W. (1966) Metabolism of GS 13005, a new  insecticide.
              Experientia 22(36):l-6. (Also~In~unpublished submission received Aug 5,1967
              under 8F0648; submitted by Geigy Chemical Co., Ardsley, N.Y.;
              CDL:091128-AE)
                                          95

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BIBLIOGRAPHY

MRID #      CITATION
00027999    Holt, B.E. (1978) Methidathion (Supracide 2E + Oil): AG-A 47541, II.
             (Unpublished study received Aug 21,1979 under 100-501; prepared in
             cooperation with En-Cas Laboratories, submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098924-L)

00029221    Holt, B.E. (1978) Methidathion (Supracide 2E + Oil): AG-A 47561-II-III.
             (Unpublished study received Aug 21,1979 under 100-501; prepared by En-Cas
             Laboratories, submitted by Ciba-Geigy Corp., Greensboro, N.C.;
             CDL:098924-H)

 00029227    Gagnon, S.A.; Teuber, A. (1977) Residue Report: AG-A No. 4598. (Unpublished
             study received Aug 21,1979 under 100-501; submitted by Ciba-Geigy Corp.,
             Greensboro, N.C.; CDL:098924-P)

 00029228    Gagnon, S.A. (1978) Methidathion (SupracideA(R> 2E + Oil): AG-A 47211.
             (Unpublished study received Aug 21,1979 under 100-501; prepared by En-Cas
             Laboratories, submitted by Ciba-Geigy Corp., Greensboro, N.C.;
             CDL:098924-Q)

 00029229    Kanuk, M.J.; Gemma, A. (1973) Determination of Residues of GS-13005 and Its
             Metabolite GS-13007 in Sunflower by Gas Chromatography Employing Flame
             Photometric Detection and Thin-Layer Chromatography. Method no. AG-247
             dated May 14,1973.  (Unpublished study received Aug 21,1979 under 100-501;
             submitted by Ciba-Geigy. Corp., Greensboro, N.C.; CDL:098924-T)

 00036935    Atkins, E.L., et. al. (1975) Toxicity of Pesticides and other agricultural
              chemicals to honey bees. Laboratory studies. Univ. of Calif., Div. Agric. Sci
              Leaflet 2287. 3 8pp

 00036942    Mattson, A.M. (1975) Summary: Methidathion (GS-13005) Almonds: Results of
              Tests on the Amount of Residue Remaining, Including a Description of the
              Analytical Method Used: Report No. GAAC-75047.  Summary of studies
              096100-C through 096100-E. (Unpublished study received May 24,1976 under
              100-501; submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:096100-B)
                                          96

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MRID #     CITATION
00038279    Carlson, E.G. (1976) Results of Tests Concerning the Amount of Residues of
             Methidathion Remaining in or on Safflower Seeds, Including a Description of the
             Analytical Method Used. Includes undated method entitled: Total safflower
            . seeds extraction and cleanup for Supracide. (Unpublished study including
             environmental toxicology report nos. 3521, 3522, 3525..., received Aug 12,1977
             under 7E1999; prepared in cooperation with Univ. of California-Davis, Dept. of
             Entomology, submitted by Interregional Research Project No. 4, New Brunswick,
             N.J.; CDL:097443-B)

 00038280    Christensen, M.D.; Carlson, E.G. (1975) (Residue Report: Safflower Seeds:
             Methidathion): AG-A No. 3511 -A. (Unpublished study including submitter
             summary, received Aug 12,1977 under 7E1999; prepared in cooperation with by
             Univ. of California and Geigy Research Laboratories, submitted by Interregional
             Research Project No. 4, New Brunswick, N.J.; CDL:097443-D)

 00060895    Roger, J.C.; Cassidy, J.E. (1972) Metabolism of GS-13005 on Orange Crops:
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 00060902     Mattson, A.M.; Kahrs, R.A. (1967) Analytical Method for the Detection of
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 00070213     Bodden, M.. (1978) Report: WARF No. 8011641. (Unpublished study received
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 00078329    Ami, P. (1980) Salmonella/Mammalian-microsome Mutagenicity Test with GS
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              (Unpublished study received Aug 13,1981 under 7F1983; prepared by
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                                           97

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00078332    Strasser, F.F. (1980) Point Mutation Assay with Mouse Lymphoma Cells:
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00078334    Hool, G.; Langauer, M.; Loos, H.; et al. (1980) Nucleus Anomaly Test in
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00078342    Kahrs, R.A. (1979) Residues of GS-28370 and GS-28369 in Tissues and Milk of
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00084010    Ami, P. (1980) Sahnonella/Mammalian-Microsome Mutagenicity Test with GS
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                                         100

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     05011904    Eberle,D.O.;Hoermann,W.D.<1971)Fateof
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                                                101'
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40094101    Simoneaux, B. (1981) Methidathion: Radio Labeled Rotational Crop Studies:
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40094102    Bade, T. (1987) Residues of Methidathion and GS-13007 in Rotational Crops
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                                          102

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40127802    Bade, T. (1987) Residue Stability of Methidathion and GS-13007 in Corn
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40127804    Bade, T. (1987) Residues of Methidathion and GS-13007 in Cottonseed and
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 40127821     Simoneaux, B. (1987) Metabolism of Carbon 14o (Carbonyl) Labeled
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                                          103

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                                          104

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                                .          105

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                  Analytical Method for the Determination of Residues of Methidathion in Citrus:
                  Lab Project Number: ABR-92077: 217-92: 303138. Unpublished study prepared
                  by Ciba-Geigy Corp. 70 p.

     42789701    Jackson, W. (1993) Technical Methidathion: Supplement to Product Chemistry.
                  Unpublished study prepared by Ciba-Geigy Corp.  17 p.

     42789702    Jackson, W. (1993) Supplement to Product Chemistry: Technical Methidathion.
                  Unpublished study prepared by Ciba-Geigy Corp.  9 p.

     42789703    Jackson, W.  (1993) Supplement to Product Chemistry (Series 63): Technical
                  Methidathion. Unpublished study prepared by Ciba-Geigy Corp. 6 p.

     42799601    Schabacker, D. (1993) Additional Information Pertaining to the Ciba Response to
                  the August, 1992 USEPA Review of Supracide (Methidathion) Environmental
                  Fate Studies: Lab Project Number: ABR-93035: GS-13005. Unpublished study
                  prepared by Ciba-Geigy Corp.  99 p.

      43145901    Leahy, C. (1993) Acute Rangefmding Neurotoxicity Study with Methidathion
                  Technical in Rats: Final Report: Lab Project Number: F-00177.  Unpublished
                  study prepared by Ciba-Geigy Corp. 107 p.

      43145902    Leahy, C. (1994) Amendment 1 to Final Report: Acute Rangefmding
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                   F-00177.  Unpublished study prepared by Ciba-Geigy Corp. 8 p.

      43145903     Chang, J.; Richter, A. (1994) Acute Neurotoxicity with Methidathion Technical
                   in Rats: Final Report: Lab Project Number: F-00178. Unpublished study
                   prepared by Ciba-Geigy Corp. 462 p.

      43145904     Chang, J.; Richter, A. (1994) Amendment 1 to Final Report: Acute Neurotoxicity
                   with Methidathion Technical in Rats: Lab Project Number: F-00178.
                   Unpublished study prepared by Ciba-Geigy Corp. 8 p.

      43170001     Emrani, J. (1992) Metabolism of (2-(carbon 14)) Methidathion after Multiple
                   Oral Administration to Lactating Goats: Supplement: Lab Project Number:
                   ABR/92061: 303989. Unpublished study prepared by  Ciba-Geigy Corp.  122 p.

                                               109
_

-------
BIBLIOGRAPHY

MRH>#     CITATION
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43170003    Hoffmann, K.; Baillie, T. (1988) The Use of Alkoxycarbonyl Derivatives for the
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43170004    Pearson, P.; Threadgill, M.; Howald, W. et al. (1988) Applications of tandem
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43170005 '   Kennedy, E. (1992) Metabolism of (2-(carbon 14)) Methidathion in Laying Hens:
             Supplement: Lab Project Number: ABR/93060: 5-91. Unpublished study
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 43296401    Geluwe, K. (1993) Analytical Method for the Determination of Methidathion,
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 43296402   Wurz, R. (1994) Method Validation Ruggedness Trial for the Determination of
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              ABR/93072.  Unpublished study prepared by Ciba-Geigy Corp. 42 p.

 43308802    Selman, F. (1994) Methidathion: Magnitude of the Residues hi or on Oranges
              Following Applications of Supracide 2E and Supracide 25W: Lab Project
              Number: ABR/93001: 303139: 23/92.  Unpublished study prepared by
              Ciba-Geigy Corp.  146 p.
                                          110

-------
    BIBLIOGRAPHY
    MRID#
CITATION
     43308803    Selman, F. (1994) Methidathion: Magnitude of the Residues in or on Almonds
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     43308804    Selman, F. (1994) Methidathion: Magnitude of the Residues in or on Timothy
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     43399701    Hackett, D. (1994) Methidathion: Review of Metabolism and Residue Data for an
                 Estimation of Total Dietary Exposure of Methidathion and Related Metabolites
                 Which Have Cholinesterase Inhibiting Potential: Lab Project Number:
                 ABR/94024.  Unpublished study prepared by Ciba-Geigy Corp. 137 p.

     43399702     Simoneaux, B. (1987) Characterization of Methidathion Metabolites from
                  Chicken Dosed with [Carbon 14]- Methidathion: Lab Project Number:
                  ABR/86117. Unpublished study prepared by Ciba-Geigy Corp. 26 p.

     43582501     Chow, E.; Turnier, J. (1995) 90-Day Subchronic Neurotoxicity Study With
                  Methidathion Technical in Rats: Final Report: Lab Project Number: F-00179.
                  Unpublished study prepared by Ciba-Geigy Corp.  751 p.

     43733301     Lail, L. (1995) Technical Methidathion Product Chemistry: (Product Identity and
                  Composition): Supplement:  Lab Project Number: PC-95-027:
                  CC-DOC\PRODCHEM\95027.DOC. Unpublished study prepared by Ciba-Geigy
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     43733302    Lail, L. (1995) Methidathion SOS Product Chemistry: (Product Identity and
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     43733304    Lail, L. (1995) Methidathion 508 Product Chemistry: (Analysis and Certification
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                  Z:\CC-DOC\PRODCHEM\M-50S-62.DOC. Unpublished study prepared by
                  Ciba-Geigy Corp. 55 p.
                                              Ill
_

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BIBLIOGRAPHY
MRID#
CITATION
43733305    Lail, L. (1995) Technical Methidathion & Methidathion 508 Product Chemistry:
             (Physical and Chemical Characteristics): Supplement: Lab Project Number:
             PC-95-027: PC-95-028: Z:\CC-DOC\PRODCHEM\95027-C.DOC. Unpublished
             study prepared by Ciba-Geigy Corp.  5 p.

43738501    Ward, G. (1995) Supracide 2E: Acute Toxicity to the Sheepshead Minnow,
             Cyprinodon variegatus, Under Flow-Through Test Conditions: Lab Project
             Number: J9102004H. Unpublished study prepared by Ciba-Geigy Corp. and
             Toxikon Environmental Services. 39 p.

443 81602    Beavers, J.; Fink, R. (1980) One-Generation Reproduction Study-Mallard Duck:
             Methidathion Technical: Final Report: Lab Project Number: 108-172: 4-79:
             WI-588. Unpublished study prepared by Wildlife International Ltd. 60 p.

44434501    Glaza, S. (1994) Acute Oral Toxicity Study of Methidathion Technical in Rats:
             Lab Project Number: HWI6117-235: 222-93: TP3013NE. Unpublished study
             prepared by Hazleton Wisconsin, Inc. 137 p.

44545101    Gohdes, M. (1998) Aerobic Soil Metabolism of (carbon 14)-Methidathion on
             California Sandy Loam: Lab Project Number: COVANCE 6117-367.
             Unpublished study prepared by Covance Laboratories, Inc.  223 p.

44680501    Rosenheck, L. (1998) Dissipation of Dislodgeable Foliar Residues of
             Methidathion Applied to Citrus: Lab Project Number: ABR-98014: 235-97:
             970001. Unpublished study prepared by Novartis Crop Protection, Inc. 227 p.

44680502    Rosenheck, L. (1998) Dissipation of Dislodgeable Foliar Residues of
             Methidathion Applied to Cotton: Lab Project Number: ABR-98086: 236-97:
             970002. Unpublished study prepared by Novartis Crop Protection, Inc. 241 p.

44806601    Brewer, L.; Stafford, J.; Sullivan, J. (1998) An Evaluation of Supracide 2E
             Residues on Potential Avian Food Items Following its Application to Citrus:
             Final Report: Lab Project Number: 079506: 811-95: CYAL METHOD NO. 18.
             Unpublished study prepared by Ecotoxicology and Biosystems Associates, Inc.
              181 p.

 Johansen, C.A., and D.F. Mayer, 1990. Pollinator Protection, A Bee and Pesticide Handbook.
 Wicwas Press.  Cheshire, Connecticut.

                                         112

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Appendix E. Generic Data Call-In

       See the following table for a list of generic data requirements. Note that a complete Data
Call-In (DCI), with all pertinent instructions, is being sent to registrants under separate cover.
                                            113

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114

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Appendix F. Product Specific Data Call-In

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Appendix G.  EPA's Batching of Methidathion Products for Meeting Acute Toxicity Data
              Requirements for Reregistration

       In an effort to reduce the time, resources and number of animals needed to fulfill the
acute toxicity data requirements for reregistration of products containing methidathion as the
active ingredient, the Agency has batched products which can be considered similar for purposes
of acute toxicity.  Factors considered in the sorting process include each product's active and
inert ingredients (e.g., identity, percent composition and biological activity), type of formulation
(e.g., emulsifiable concentrate, aerosol, wettable powder, granular) and labeling (e.g., signal
word, use classification, precautionary labeling). Note that the Agency is not describing batched
products as "substantially similar" since some products  within a batch may not be considered
chemically similar or have identical use patterns.

       Using available information, batching has been accomplished by the process described in
the preceding paragraph. Notwithstanding the batching process, the Agency reserves the right to
require, at any time, acute toxicity data for an individual product should the need arise.

       Registrants of products within a batch may choose to cooperatively generate, submit or
cite a single battery of six acute toxicological studies to represent all the products within that
batch. It is the registrants' option to participate in the process with all other registrants, only
some of the other registrants, only their own products within a batch or to generate all the
required acute toxicological studies for each of their own products. If a registrant chooses to
generate the data for a batch, he/she must use one of the products within the batch as the test
material. If a registrant chooses to rely upon previously submitted acute  toxicity data, he/she
may do so provided that the database is complete and valid by today's standards (see acceptance
 criteria attached), the formulation tested is considered by EPA to be similar for acute toxicity
 and the formulation has not been significantly altered since submission and acceptance of the
 acute toxicity data. Regardless of whether new data is  generated or existing data is referenced,
 registrants must clearly identify the test material by the EPA Registration Number. If more than
 one confidential statement of formula (CSF) exists for a product, the registrant must indicate the
 formulation actually tested by identifying the corresponding CSF.

        In deciding how to meet the product specific data requirements, registrants must follow
 the directions given in the Data Call-In notice (DCI) and  its attachments  appended to the interim
 RED. The DCI notice contains two response forms which are to be completed and submitted to
 the Agency within 90 days of receipt.  The first form, "Data Call-In Response" asks whether the
 registrant will meet the data requirements for each product. The second  form, "Requirements
 Status and Registrant's Response" lists the product specific data required for each product,
 including the standard six acute toxicity tests. A registrant who wishes to participate in a batch
 must decide whether he/she will provide the data or depend on someone else to do so.  If a
 registrant supplies the data to support a batch of products, he/she must select one of the
 following options: Developing Data (Option 1), Submitting an Existing Study (Option 4),
 Upgrading an Existing Study (Option 5) or Citing an Existing Study (Option 6).  If a registrant

                                             129

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depends on another's data, he/she must choose among: Cost Sharing (Option 2), Offers to Cost
Share (Option 3) or Citing an Existing Study (Option 6).  If a registrant does not want to
participate in a batch, the choices are Options 1,  4, 5 or 6. However, a registrant should know
that choosing not to participate in a batch does not preclude other registrants in the batch from
citing his/her studies and offering to cost share (Option 3) those studies.

       Seven products were found which contain methidathion as the active ingredient.  These
products have been placed into three batches and a "No Batch" category in accordance with the
active and inert ingredients and type of formulation.  The following bridging strategies may be
employed:

       • Batch 2 may cite Batch 1 with the exception of eye and skin irritation data
       • Batch 5 may rely on Batch 4 data
       • Batches 6 and 7 may use the policy for granular pesticide products. However,  due to
         the differences in inerts in Batch 6, products within Batch 6 may not share eye irritation
         data.
Batch 1


EPA Reg. No.
100-530
10163-245
* Percent Dimethoate - ซ•
95.0
95.0
Formulation Type
Liquid
Liquid
Batch 2

EPA Reg. No.
10163-237
Percent Dimethoate " \f
50.0
JFormulation Type
Liquid
Batch 3


EPA Reg. No.
. 100-754
10163-244
Percent Dimethoate ," .
25.0
25.0
Formulation Type -
Solid
Solid
No Batch


EPA Reg. No.
10163-236
10163-238
Percent Dimethoate
25.0
25.0
Formulation Type
Liquid
Liquid
                                            130

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Appendix H.  List of Registrants Sent this Data Call-In
                                          131

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Appendix I. List of Available Related Documents and Electronically Available Forms

Pesticide Registration Forms are available via the Agency's website at
http://www. epa. gov/opprdOOl/forms/.

Pesticide Registration Forms (These forms are in PDF format and require the Acrobat reader)

Instructions

1.     Print out and complete the forms. (Note: Form numbers that are bolded can be filled out
       on your computer then printed).

2.     The completed form(s) should be submitted in hard copy in accord with the existing
       policy.

3.     Mail the forms, along with any additional documents necessary to comply with EPA
       regulations covering your request, to the address below for the Document Processing
       Desk.                   .

DO NOT fax or e-mail any form containing 'Confidential Business Information' or 'Sensitive
Information.'

If you have any problems accessing these forms, please contact Nicole Williams at (703)
308-5551 or by e-mail at Williams.Nicoleฎ,epa.sov.

The following Agency Pesticide Registration Forms are currently available via the Internet at the
following locations:
8570-1
8570-4
8570-5
8570-17
8570-25
8570-27
8570-28
8570-30
8570-32
Application for Pesticide Registration/Amendment
Confidential Statement of Formula •
Notice of Supplemental Registration of Distribution
of a Registered Pesticide Product
Application for an Experimental Use Permit
Application for/Notification of State Registration of a
Pesticide To Meet a Special Local Need
Formulator's Exemption Statement
Certification of Compliance with Data Gap
Procedures
Pesticide Registration Maintenance Fee Filing
Certification of Attempt to Enter into an Agreement
with other Registrants for Development of Data
http://www.epa.gov/opprdOO] /forms/8570-1, pdf
http://www.epa.gov/opprdOOJ/forms/8570-4.pdf
http://www.epa.gov/opprdOOJ/forms/8570-5.pdf

http://www.epa, gov/opprdOOJ /forms/85 70-1 7.pdf
http://www.epa.gov/opprdOOJ/forms/8570-25.pdf

http://www.epa.gov/opprdOOJ/forms/8570-27.~pdf

http://www.epa.eov/opprd001/forms/8570-28.pdf

http://www. epa. gov/opprdOOJ /forms/85 70-30. pdf

http://www.epa.gov/opprdOOJ/forms/8570-32.pdf

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8570-34
8570-35
8570-36
8570-37
Certification with Respect to Citations of Data (PR
Notice 98-5) . '
Data Matrix (PR Notice 98-5)
Summary of the Physical/Chemical Properties (PR
Notice 98-1)
Self-Certification Statement for the
Physical/Chemical Properties (PR Notice 98-1)
httpi//www. epa. sov/opDDmsdl/PR Notices/or98-5. vdf

http://ww-w. epa. sov/opppmsdl/PR Notices/pr98-5. vdf
http://www.eDa.sov/ODDDtnsdl/PR Notices/pr98-Lpdf

http://www.epa.sov/opppmsdl/PR Notices/pr98-l.pdf

Pesticide Registration Kit                http://wwv. epa. zov/pesticides/registrationkit/

Dear Registrant:

       For your convenience, we have assembled an online registration kit which contains the
following pertinent forms and information needed to register a pesticide product with the U.S.
Environmental Protection Agency's Office of Pesticide Programs (OPP):

1.     The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Federal Food,
       Drug and Cosmetic Act (FFDCA) as Amended by the Food Quality Protection Act
       (FQPA)ofl996.

2.     Pesticide Registration (PR) Notices

       A.     83-3 Label Improvement Program—Storage and Disposal Statements
       B.     84-1 Clarification of Label Improvement Program
       C.     86-5 Standard Format for Data Submitted under FIFRA
       D.     87-1 Label Improvement Program for Pesticides Applied through Irrigation
              Systems (Chemigation)
       E.     87-6 Inert Ingredients in Pesticide Products Policy Statement
       F.     90-1 Inert Ingredients in Pesticide Products; Revised Policy Statement
       G.     95-2 Notifications, Non-notifications, and Minor Formulation Amendments
       H.     98-1 Self Certification of Product Chemistry Data with Attachments  (This
              document is in PDF format and requires the Acrobat reader.)

Other PR Notices can be found at http://www. epa. eov/opppmsdl/PR Notices.

3.     Pesticide Product Registration Application Forms (These forms are in PDF format and
       will require the Acrobat reader).

       A.     EPA Form No. 8570-1, Application for Pesticide Registration/Amendment
       B.     EPA Form No. 8570-4, Confidential Statement of Formula
       C.     EPA Form No. 8570-27, Formulator's Exemption Statement
       D.     EPA Form No. 8570-34, Certification with Respect to Citations of Data
       E.     EPA Form No. 8570-35, Data Matrix
                                          136

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4.     General Pesticide Information (Some of these forms are in PDF format and will require
       the Acrobat reader).
Registration Division Personnel Contact List
Biopesticides and Pollution Prevention Division (BPPD) Contacts
Antimicrobials Division Organizational Structure/Contact List
53 F.R. 1 5952, Pesticide Registration Procedures; Pesticide Data Requirements
       A
       B'
       C
       D'.
       E      40 CFR^Se, Labeling Requirements for Pesticides and Devices (PDF format)
       F'     40 CFR ง158, Data Requirements for Registration (PDF format) ^
       G.     50 F.R. 48833, Disclosure of Reviews of Pesticide Data (November 2 /, iySD)

 Before submitting your application for registration, you may wish to consult some additional
 sources of information. These include:

 1.     The Office of Pesticide Programs' website.

 2     The booklet "General Information on Applying for Registration of Pesticides in the
       United States," PB92-221 811, available through the National Technical Information
       Service (NTIS) at the following address:

       National Technical Information Service (NTIS)
        5285 Port Royal Road
        Springfield, VA 22161                                                      :

 The telephone number for NTIS is (703) 605-6000.

 3      The National Pesticide Information Retrieval System (NPIRS) of Purdue University's
        Center for Environmental and Regulatory Information Systems. This service does charge
        a fee for subscriptions and custom searches. You can contact NPIRS by telephone at
        (765) 494-6614 or through their website.

 4      The National Pesticide Information Center (NPIC) can provide information on active
        ingredients, uses, toxicology and chemistry of pesticides. You can contact NPIC by
        telephone at (800) 858-7378 or through their website at http://www.ncis.orst.edu.

 The Agency will return a notice  of receipt of an application for registration or amended
 registration, experimental use permit, or amendment to a petition if the applicant or petitioner
 encloses with his submission a stamped, self-addressed postcard. The postcard must contain the
 following entries to be completed by OPP:

  •      Date of receipt;
        EPA identifying number; and
        Product Manager assignment.

  Other identifying information may be included by the applicant to link the acknowledgment of
  receipt to the specific application submitted. EPA will stamp the date of receipt and provide the
                                            137

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EPA identifying file symbol or petition number for the new submission. The identifying number
should be used whenever you contact the Agency concerning an application for registration,
experimental use permit, or tolerance petition.

To assist us hi ensuring that all data you have submitted for the chemical are properly coded and
assigned to your company, please include a list of all synonyms, common and trade names,
company experimental codes, and other names which identify the chemical (including "blind"
codes used when a sample was submitted for testing by commercial or academic facilities).
Please provide a chemical abstract system (CAS) number if one has been assigned.

Documents Associated with this interim RED

The following documents are part of the Administrative Record for this interim RED document
and may be included hi the EPA's Office of Pesticide Programs public  docket.  Copies of these
documents are not available electronically, but may be obtained by contacting the person listed
on the respective Chemical Status Sheet.

1.     Health Effects Division and Environmental Fate and Effects Division Science Chapters,
       which include the complete risk'assessments and supporting documents.

2.     Detailed Label Usage Information System (LUIS) Report
                                          138

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