United Slates            Office of Pesticides
                   Environmental Proteciion      and Toxic Substances
                   Agency                (H7501C)           540/FS-91-137
S-EPA          Pesticide
                   Fact Sheet
                   Name of Chemical:        uithiopyr
                   Reason for Issuance:       Registration
                   Date Issued:               June is, 1991
                   Fact Sheet Number:        223
          1.   DESCRIPTION OF CHEMICAL

              Generic Name: 3,5-Pyridinedicarbothioic acid,
                           2-(difluoromethyl)-4-(2-methylpropyl)-
                           6-(trifluoromethyl)-S,S-dimethyl ester
              Common Name: MON-72UU, MON-15100 and Dithiopyr
              Trade Names: Dimension" Turf Herbicide
              EPA Shaughnessy  Code: 128994-1
              Chemical Abstracts Service (CAS) Number: 97886-45-8
              Year of Initial  Registration: 1991
              Pesticide Type:  Herbicide
              Chemical Family: Pyridine
              U.S. Producer: Monsanto Company

          2.   USE PATTERNS AND FORMULATIONS

              Application sites:  Terrestrial non-food sites.
                Preemergence  and early postemergence for selective
                control of crabgrass and other susceptible annual
                grasses and broadleaf weeds in established lawns
                and ornamental turf.

              Types of formulations:  The two end-use products
                are liquid emulsified suspensions of the active
                ingredient; with nominal concentrations of 12.7%
                (MON 15151 EC Herbicide) and 13.2% (MON 15104 EC
                Herbicide).  Acute toxicity studies were with
                formulatons containing 12.5%,  and were within the
                limits of variation for these products.

              Amount and Method of Application:   A single application
                of 0.5U Ib. active ingredient per acre per season is
                claimed for both preemergence and postemergence
                selective weed control in the culture of turf.
                Ground spray application of an aqueous suspension
                is the only method of application registered.

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   Carrier:  Water

3.   SCIENCE FINDINGS

    Summary Science Statements:

      Adequate toxicological,  product chemistry,  ecological
      effects, environmental fate and ground water
      data have been submitted and reviewed to support the
      conditional registration of dithiopyr for use as a
      preemergence and postemergence herbicide in the culture
      of ornamental turf grasses.  Technical dithiopyr is class-
      ified as a Toxicity Category IV pesticide and is labeled
      with the signal word "CAUTION", based on a  battery of 6
      acute studies.

      Dithiopyr was non-mutagenic and in developmental
      toxicity studies it did  not appear to be a  potential
      developmental toxicant.   Ecological effects data character-
      ize dithiopyr as practically nontoxic to birds on subacute
      dietary and acute oral bases.  Toxicological data
      demonstrate that it is of low acute toxicity to mammals.
      A subchronic 90-day feeding study in rats indicated
      a no observable effect level (NOEL) of 0.662 mg/kg/day.
      At the 6.62 mg/kg/day there was an increase in organ
      weights and diffused hepatocellular swelling.  It has
      little to no potential for ground water contamination.
      It is stable to hydrolysis in neutral and mildly
      alkaline solutions.  At pH 9 it had a half-life of
      1053 days based on first order kinetics.  Photode-
      gradation in water could contribute significantly
      to the overall degradation of dithiopyr in the
      environment.  Photodegradation of dithiopyr on soil
      is insignificant. Therefore, photodegradation on soil
      will not contribute significantly to its degradation
      in the environment.

 Chemical Characteristics:

       Physical State:          Solid, crystalline
       Color: Chemically Pure:  White
              Technical Grade:  Yellow to Burnt Yellow
       Odor:                    Sulfurous
       Melting Point:           65-67 C
       Density:                 1.413 gm/cm3 at 25 C  (typical)

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       Molecular Weight         401.4
       Solubility        Solvent                  at
       Parts per Million: Water          1.38      20 C

       Grams per 100 ml:  Hexane     <   3.30      25 C
                          Toluene    >  25.00      25 C
                          Acetone    >  33.30      25 C
                          Diethyl
                           ether     >  50.00      25 C
                          Ethanol    >  12.00      25 C
                          Methylene
                           chloride  >  50.00      25 C

      Vapor Pressure:          4.0 x 10~6 mm/Hg at 25C

      Dissociation Constant:   Not required, Dithiopyr is not
                                  an acid

      Octanol/Water Partition Coefficient:  P = 5.625 x 104

      pH: (in non-aqueous solvent):  4.152

      Stability

      Less than 1% change in assay was observed after 14 days
      of exposure to sunlight, 14 days of exposure to Cu, Zn
      and Fe, 14 days of exposure to a temperature of 50 C.
      The formulated end use product (MON-15151 EC Herbicide)
      was stable stored 12 months at 68 and 80F.  Only
      a change of 0.37% in quantity of active ingredient
      occurred.

Toxicology Characteristics:

  Acute Toxicity  ( 90.9%, Technical, MON-7200/MON 15100)

     Acute oral toxicity (rats and mice): LD$Q > 5000 mg/kg,
          Toxicity Category IV.

     Acute dermal toxicity (rat):  LD5Q > 5,000 mg/kg,
          Toxicity Category IV.

     Primary dermal irritation (rabbit): Slight erythema
          but no edema within 0.5 hours.  No effects by 72 hours.
          Toxicity Category IV.

     Primary eye irritation (rabbit): No corneal opacity;
          irritation reversible within 24 hours.
          Toxicity Category IV.

     Acute inhalation toxicity (rat): LCso > 5.89 mg/L for

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        males and females (nose exposure only).
        Toxicity Category IV.

   Dermal sensitization (guinea pig): Not a dermal
        sensitizer by the Buehler method.

Acute Toxicity (12.5% a.i.,  Dimension Turf Herbicide, MON-15151)
   Acute oral toxicity (rats):   L-DSQ = 4100 mg/kg for males
        and 3/000 for females.
        Toxicity Category III.

   Acute dermal toxicity (rats):  No deaths,
        >5000 mg/kg, Category IV.

   Primary dermal irritation (rabbit): Severe dermal
       irritation.  Superficial (epidermis) necrosis,
       clearing within 14 days. Category II.

   Primary eye irritation (rabbit):  Corneal corrosion
        reversible with 21 days, and possibly within 7 days;
        corneal opacity reversible within 7 days.
        Category II.

   Acute inhalation toxicity (rat):  LCso = 11 mg/L                     *
        for males.  LCso = 8-9  mg/L for females.
        Category IV.

   Dermal sensitization (guinea pig):  Positive for dermal
        sensitization by Buehler method.

Acute Toxicity (12.5% a.i., Dimension Turf Herbicide, MON-15104)

   Acute oral toxicity (rat):  LDso > 5000 mg/kg for males
     and females.  Toxicity Category IV.

   Acute dermal toxicity (rabbit):  LD$Q > 5000 for males
     and females.  Toxicity Category IV.

   Primary dermal irritation (rabbit): Very slight or slight
     irritation at 72 hours, clearing within 10 days.
     Toxicity Category IV.

   Primary eye irritation:  (rabbit): No corneal opacity;
     irritation reversible within  24 hours. Toxicity
     Category IV.
   Acute inhalation toxicity (rat):  LCso > 3.4 mg/L for males
     and > 4.5 mg/L for females.  Toxicity Category III.

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Dermal sensitization  (guinea pig):  Not a dermal sensitizer
  by the Buehler method.

Subchronic Toxicity

A 21-day dermal study in rats was conducted using
levels of 0, 50, 500 and 1,000 mg/kg/day.  Limited
to transient mild irritation occurred in all dose
groups.  Incidence was generally dose-related and
higher in females than in males.  The NOEL was
500 mg/kg/day and the LEL was 1000 mg/kg/day.

In a rat developmental toxicity study there were no develop-
mental effects at 1000 mg/kg/day (HDT).  Maternal effect
was decreased food consumption.  The NOEL for this
effect was 300 mg/kg/day and the LEL was 1000 mg/kg/day.

In a rabbit developmental toxicity study there were no develop-
mental effects at 1000 mg/kg/day (HDT).  Maternal effect
was reduced body weight gain.  The NOEL for this
effect was 500 mg/kg/day and the LEL was 1000 mg/kg/day.

In a 90-day subchronic study in rats a NOEL of 0.662
ing/kg/day was indicated based on an LOEL of 6.62 mg/
kg/day in females.  The effect was an increase in
organ weight and diffused hepatocellular swelling.

Mutagenicity

The following mutagenicity studies indicated that
Dithiopyr is not mutagenic at doses tested:

- Ames Assays for mutagenicity with Ames (TA) strains of
  Salmonella typhimurium LT2 were found negative
  for reverse gene mutation (his" to his"*") at limit
  of solubility (3,000" _ug/plate) with or without activation.

- Ames Assays for mutagenicity with Ames (TA) strains of
  Salmonella were found negative for reverse gene mutation
  (his~ to his+) at 5,000 ucf/plate with or without
  activation.

- Gene mutation at the HGPRT locus in Chinese
  hamster ovary cells exposed with or without activation
  up to cytotoxic dose levels: (300 u_g/ml/-S9; 30 \ag/ral/+S9) .

- Structural chromosome aberrations in Chinese hamster
  lung cells exposed to the limit of solubility
  (0.33 and 1.0 mM).

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     - Unscheduled DNA synthesis (UDS)  in primary rat
       hepatocytes (HPC),  as measured by silver grain counts
       indicative of DNA damage/repair.

Mechanism of Pesticidal Action;

     Dithiopyr is a mitotic inhibitor of normal cell
division of susceptible plants.   The formation and
function of microtubulin is inhibited.   Susceptible plant
roots are stunted and fail to function  in the presence
of dithiopyr.   Plants do not grow and develop through
their normal cycle of vegetative growth  followed by
reproduction (flowering and seed setting).  Susceptible
plants react to dithiopyr in such a way  as to be
less competitive.

Environmental  Characteristics:
    Hydrolysis:   Dithiopyr does not hydrolyze in neutral
        solutions and only slowly in alkaline solutions
        (pH 9).  At pH 9 it has a half-life of 1053 days
        based on first order kinetics.  Data indicate
        that ester hydrolysis, which appears to be the
        hydrolysis pathway for dithiopyr/ will not be                 |
        a significant route of degradation of dithiopyr               ^
        in the environment.

    Photodegradation:  The half-life of dithiopyr in
        sunlight was 17.6 and 20.6 days for nonsen-
        sitized and humic acid solutions/ respectively.
        The parent material comprised 24.5% of the
        applied radioactivity.  The half-life of dithiopyr
        in soil was determined to be 444.3 days.  Based
        on the data dithiopyr is classified as photo-
        stable in or on soil.  These findings indicate
        that photodegradation in water could contribute
        significantly to the overall degradation of
        dithiopyr in the environment.  In water dithiopyr
        can be expected to degrade to a mixture of normal
        acid/ reverse acid, and lesser amounts of polar
        compounds upon exposure to sunlight.  Photodegrad-
        ation of dithiopyr on soils is insignificant.
        Therefore/ photodegradation on soil will not
        contribute significantly to its degradation in
        the environment.

    Aerobic Soil Metabolism:  In aerobic soil maintained
        under laboratory conditions/ dithiopyr degraded
        to the normal acid/ reverse acid and diacid.  The
        maximum concentrations of degradates were  reached
        at 6-12 months post-treatment.

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 Anaerobic Soil Metabolism:  An anaerobic aquatic metabolism
     is required and will be submitted as a condition of
     registration.

 Field Dissipation:  Dissipation occurs in the field
     with vegetation coverage with a half-life of between
     17 and 61 days depending on soil composition/
     weather conditions and formulation applied.   Three
     major metabolites of dithiopyr (the normal acid,
     reverse acid and diacid metabolites) are formed
     and dissipated within 365 days.

 Leaching, Adsorption/Desorption:   Vertical mobility
     of dithiopyr and its acid metabolites through
     soil, even in conditions highly susceptible  to
     herbicide leaching, was found not to exceed  24 inches
     and was often not more than 9 to 12 inches.   At
     a use rate of U.5 Ib/A of dithiopyr, metabolites could
     be observed at only barely or nondetectable  levels.
     Residues should not persist beyond the growing season
     and would not be expected to  vertically move to a
     significant extent in soil.

Potential to Contaminate Ground Water:  The low solubility
     in water and its high tendency to bind to soil
     prevents dithiopyr from being carried downward
     through soil.  Dithiopyr has  a low potential for
     leaching into ground water.  Surface water con-
     tamination from soil containing dithiopyr would
     be expected.

Ecological Characteristics

     Avian Studies:  Dithiopyr is  practically non-toxic
             to birds based on the following studies:

     Single Dose Oral Toxicity:
             Mallard duck with 90% Technical:
                       > 2250 mg/kg
     Subacute Dietary Toxicity:
             Mallard duct with 90% Technical:
                  LDso > 5620 ppm
             Bobwhite quail with 90% Technical:
                  LD50 > 5620

     Avian Reproduction:  A study is required as a condition
             of registration.

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   Aquatic Organisms:  The following data indicate that
       dithiopyr is highly toxic to freshwater fish and
       aquatic invertebrates:

   Fish Acute Toxicity:
        Bluegill sunfish,  LCso = 0.47 mg/L
        Rainbow trout, LCso =  0.46 mg/L

   Early Life-stage Toxicity:
        Rainbow trout, NOEC =  0.052 mg/L

   Freshwater Invertebrates:
        A supplemental study indicates that the 48 hour
        LCso based on nominal  concentration is greater
        than 5.6 ug/L.  An acceptable study is required
        as a condition of  registration.

   Endangered Species Hazards:

       Based on available  data,  the conditionally registered
       use-pattern of dithiopyr  is unlikely to pose a hazard to
       endangered aquatic  and  avian species.  There may
       be some hazard to endangered plant species from
       runoff and movement of  the products from treated turf
       areas.

4.  Summary of Regulatory Postion and Rationale

    Available data provide adequate information to support
    the conditional registration of Dimension* Turf
    Herbicide (MON-15151), Dimension* Turf Herbicide
    (MON-15104) and MON-15100, that were first conditionally
    registered June 18, 1991 under Section 3 of the Federal
    Insecticide, Fungicide and Rodenticide Act as amended.

       Use, Formulation, Manufacturing Process or
    Geographic Restrictions:  Aerial applications of
    dithiopyr products are not permitted.  All products
    must bear the precautionary statement: "This pesticide
    is toxic to fish."  End-use  products must bear the
    use precaution: "During mixing and loading wear chemical
    resistant gloves.  Wash non-disposable gloves throughly
    with soap and water before removing".

       Conditional registration will expire on July 31, 1994.

5.  Summary of Data Gaps

   Toxicology Data:
      1.  Dermal Penetration Study  (Guidelines Ref. No. 85-2),
          Data are due July 18,  1992.

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Exposure Data:
   1. Worker Exposure Studies (Upgrade the passive
      dosimetry study and the biological monitoring
      study).   Data are due September 18, 1993.

Ecological Effects Data:
   1.  Acute LCso Freshwater Invertebrate Study,  EPA Ref.
       Guidelines 72-2.   Data are due March 18,  1992.

   2.  Avian Reproduction with a Waterfowl and Bobwhite
       Quail, EPA Ref. Guidelines 71-4.   Data are due
       July 18,  1993.

   3.  Acute LCso Estuarine/Marine Organisms Studies,
       EPA Ref.  Guidelines 72-3, identified as:
        o 96-hour LCso fr an estuarine  marine fish
        o 96-hour LCso for a shrimp species
        o Either a 48-hour embryo larvae study or a
            96-hour shell deposition study with oyster.
        Data are due July 18, 1992.

   4.  Aquatic Invertebrate Life-Cycle Study, EPA Ref.
       Guidelines 72-4.   Data are due September 18, 1992.

   5.  Nontarget Area Phytotoxicity :
       Tier II:   o Seed  germination/seedling emergence,
                   EPA Ref. Guideline 123-1
                 o Vegetative vigor, EPA Ref. Guideline
                   123-1
                 o Aquatic plant growth, EPA Ref. Guide-
                   lines 123-2.

       Tier III: o Terrestrial Field1, EPA Ref.  Guidelines
                   124-1
                 o Aquatic field2, EPA Ref. Guidelines  124-2

                    I/ Required if a 25  percent or greater
                      detrimental effect was found in  1 or more
                      plant species in  corresponding  test  of
                      previous  tier.
                    2/ Required if a 25  percent or greater
                      detrimental effect was found on  any
                      plant species in  the corresponding  test
                      of the previous tier.
       Data are  due March 18, 1992.

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   Environmental Fate and Ground Water Data:

       1.   Anerobic Aquatic Metabolism Study,  EPA Ref.  Guide-
           lines 162-3.  Data are due September 18,  1993.

       2.   Field Dissipation Study, Bare Ground,  EPA Ref.
           Guidelines 164-1.  Data are due September 18, 1993,

6.  Contact Person at EPA

      Joanne I.  Miller
      Product Manager 23
      Fungicide-Herbicide Branch
      Registation Division (H-7505C)
      Office of  Pesticide Programs
      Environmental Protection Agency
      401 M Street SW
      Washington, DC  20460

   Office Location and Telephone Number

      Room 237,  Crystal Mall Building #2
      1921 Jefferson Davis Highway
      Arlington, VA  22202
      (703) 557-1830
   DISCLAIMER:  The information presented in this Pesticide Fact
   Sheet is for informational purposes only and may not be used
   to fulfill data requirements for pesticide registration and
   reregistration.

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