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imazaquin (Scepter) Herbicide Profile 3/86

                        CHEMICAL FACT SHEET FOR:
                                IMAZAQUIN
FACT SHEET NUMBER: 83
DATE ISSUED: MARCH 20, 1986
                       1. DESCRIPTION OF CHEMICAL
- Generic Name:  2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-
  imidazol-2-yl]-3-quinoline carboxylic acid
- Common Name:  imazaquin
- Trade Name:  Scepter
- EPA Shaughnessy Code:  128821
- Chemical Abstracts Service (CAS) Number:  None
- Year of Initial Registration:  1986
- Pesticide Type:  Herbicide
- Chemical Family:
- U.S. and Foreign Producers:  American Cyanamid
                   2.  USE PATTERNS AND FORMULATIONS
- Application sites:  Soybeans
- Methods of application:  Scepter may be applied preplant incorporated,
  preemergence, or postemergence.  In southern locations only,
  two applications are possible:  an initial preplant incorporated or
  preemergence treatment followed by a postemergence treatment.
- Application rates:  Ground or aerial application rates are 2 oz.
  a.i./A.  Ground applications are in 10 or more gallons of water
  per acre, and aerial applications are in 5 or more gallons of
  water per acre.  Where two applications are permitted, no more
  than 0.25 lb. a.i./A per season may be applied.
- Types of formulations:  95% technical grade and 17.3% active
  ingredient liquid concentrate end-use product.
- Usual carriers:  Water
                       3.  SCIENCE FINDINGS
Chemical Characteristics
- Physical state:  solid
- Color:  light tan
- Odor:  none
- Melting point:  219-224 degrees C
- Solubility:  60 ppm at 25 degrees C
- Octanol/water partition coefficient:  2.2
- pH:  3.8 (slurried into 100 ml of de-ionized water at 23 degrees C)
Toxicological Characteristics
- Acute effects:  Imazaquin is relatively nontoxic by oral, dermal,
  and inhalation routes, non-irritating to slightly irritating to
  the eye and skin, and not a dermal sensitizer.  Acute test results
  indicate Toxicity Categories III and IV as follows:
  - Acute oral toxicity (rat):  Greater than 5,000 mg/kg, Toxicity
    Category IV
  - Acute inhalation (rat):  Greater than 5.7 mg/L, Toxicity Category
    III
  - Acute dermal (rabbit):  Greater than 2,000 mg/kg, Toxicity
    Category III
  - Acute dermal sensitization (guinea pig):  Not a sensitizer
  - Primary dermal irritation (rabbit):  Mildly irritating, Toxicity
    Category IV
  - Primary eye irritation (rabbit):  Non-irritating, Toxicity
    Category IV
- Subchronic effects:  Tests indicate no systemic toxicity at the
  highest dose tested (HDT).
  - 21-day dermal (rabbit):  No-Observed-Effect-Level (NOEL) = 1,000
    mg/kg/day (HDI)
  - 90-day feeding study (rats):  NOEL greater than 10,000 ppm or
    800 mg/kg/day
- Chronic effects:  Tests indicate no oncogenic or teratogenic
  potential and no reproductive toxicity at HDT, and negative
  activity in five mutagenicity studies.
  - 1-year dietary toxicity study (beagle dogs):  NOEL = 1,000 ppm.
    Lowest-Observed-Effect-Level (LOEL) = 5,000 ppm
  - 2-year oral dietary (rat):  NOEL = 10,000 ppm (HDT) or 500
    mg/kg/day
  - 18-month oncogenicity (mouse):  NOEL = 1,000 ppm (150 mg/kg).
    Lowest Effect Level (LEL) = 4,000 ppm
  - 3-generation reproduction (rat):  NOEL = 10,000 ppm (1,000
    mg/kg) (HDT)
  - Teratology (rabbits):  Teratogenic NOEL = 500 mg/kg/day.
    Embryotoxic NOEL = 500 mg/kg/day.  Maternal NOEL = 250 mg/kg/day.
    Maternal LEL = 500 mg/kg/day
  - Teratology (rats):  Teratogenic - NOEL > 2,000 mg/kg/day.
    Fetotoxic - NOEL = 500 mg/kg/day, LOEL = 2,000 mg/kg/day.
    Maternal toxicity - NOEL = 500 mg/kg/day, LOEL = 2,000 mg/kg/day.
  - Single low dose metabolism study (rats):  Almost entirely
    excreted in 48 hours, urine 94% and feces 4%.
  - Mutagenicity (Ames test):  negative
  - Dominant lethal test (rats):  negative
  - In vitro cytogenetics (CHO):  negative
  - Unscheduled DNA synthesis (rat hepatocytes):  negative
  - CHO/HGPRT point mutation:  negative
- Major routes of exposure:  Dermal and inhalation.
Physiological and Biochemical Behavioral Characteristics
- Foliar absorption:  Absorption occurs through both the foliage
  and roots.
- Mechanism of pesticidal action:  When applied to soil,
  susceptible weeds emerge, growth stops, and the weeds either die
  or are not competitive with the crop.  When applied postemergence,
  adsorption occurs through both the foliage and roots, growth
  stops, and the weeds either die or are not competitive with the
  crop.  When applied preemergence, rainfall or irrigation is necessary
  to activate imazaquin.
- Metabolism in plants and animals:  The nature of the residue in
  plants and animals is adequately understood for the use of
  imazaquin on soybeans.  The parent compound is the residue
  compound of concern.  The residue analytical method is adequate
  for the determination of residues in soybeans and for enforcement 
purposes.
Environmental Characteristics
- Imazaquin is stable to hydrolysis at pH 3 and 5, and has an
  aqueous hydrolytic half-life of 5.5 months at pH 9.  It is slightly
  soluble in distilled water, 60 ppm at 25 degrees C.
- Absorption and leaching:  Additional field dissipation studies
  must be submitted to further define the leaching potential of
  imazaquin.
- Microbial breakdown:  Imazaquin is decarboxylated slowly to CO2,
  as well as degraded to the major metabolite CL 266,066 and at
  least 6 minor metabolites.
- Loss from photodecomposition and/or volatilization:  Volatilization
  does not occur.
- Resultant average persistence:  Imazaquin should not persist
  beyond 4 to 6 months.
Ecological Characteristics
- The following test results indicate that imazaquin is practically
  nontoxic to avian species, finfish, aquatic invertebrates, and
  honeybees.
- Avian acute oral toxicity (mallard duck and bobwhite quail):
  > 2,150 ppm
- Avian dietary toxicity (mallard duck and bobwhite quail):  > 5,000
  ppm
- Fish acute toxicity:  rainbow trout, > 280 ppm; bluegill sunfish,
  > 420 ppm; and channel catfish, > 320 ppm.
- Aquatic invertebrate toxicity (Daphnia magna):  > 280 ppm
- Honeybee:  Nontoxic at 100 ug/bee
Tolerance Assessment
- List of crops and tolerances (40 CFR 180.426):  Soybeans at 0.05
  parts per million.
- Results of tolerance assessment:  The Accepted Daily Intake (ADI),
  based on the 1-year dog feeding study (NOEL of 1,000 ppm or 25
  mg/kg/day) and using a 100-fold safety factor, is calculated to be
  0.25 mg/kg/day.  The Maximum Permissible Intake (MPI) for a 60-kg
  person is calculated to be 15 mg/day.  The Theoretical Maximum
  Residue Contribution (TMRC) for use on soybeans is calculated to
  be 0.0007 mg/day, which accounts for 0.00 % of the ADI (0.25 mg/
  kg/day).
Summary Science Statement
  Scepter has been found to be acceptable for the proposed use.  It
  is relatively nontoxic by the oral, dermal, and inhalation routes,
  non-irritating to slightly irritating to the eye and skin, and it
  is not a dermal sensitizer.  Hazard to nontarget organisms is
  considered to be minimal.
           4. SUMMARY OF REGULATORY POSITION AND RATIONALE
- The Agency has conditionally accepted the use of this chemical on
  soybeans.
- The Agency has reviewed the data submitted and, with the exception
  of field dissipation studies, found these data to be adequate for
  the proposed use of this chemical.  The proposed use of this
  chemical, prior to completion of repeated field studies, is not
  expected to result in any adverse effects to humans or the environment
  and will fill a need for a herbicide to control weeds in soybeans.
- Use restrictions:  none
- Unique label statements:  none
                 5.  SUMMARY OF MAJOR DATA GAPS
164-1 Field Dissipation Studies (Soil). due March, 1988.
                  6.  CONTACT PERSON AT EPA
Robert J. Taylor (PM-25)
U.S. EPA (TS-767C)
401 M Street S.W.
Washington, DC  20460
703/557-1800
DISCLAIMER:  THE INFORMATION PRESENTED IN THIS CHEMICAL INFORMATION FACT 
SHEET IS FOR INFORMATIONAL PURPOSES ONLY AND NOT TD BE USED TO FULFILL 
DATA REQUIREMENTS FOR PESTICIDE REGISTRATION AND REREGISTRATION.