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difenzoquat (Avenge) Herbicide Profile 12/88

EPA Pesticide
Fact Sheet
Name of Chemical:  DIFENZOQUAT
Reason for Issuance:  REGISTRATION STANDARD
Date Issued:  December 1988
Fact Sheet Number:  194
                    1. DESCRIPTION OF CHEMICAL
Generic Name:  1, 2-dimethyl-3,-3,5-diphenyl-1H-pyrazolium
Common Name:  Difenzoquat
Trade and Other Names:  AVENGE
EPA Shaughnessy Codes:  106401 (Salt)
Chemical Abstracts Service (CAS) Number:  43222-48-6 (Salt)
Year of Initial Registration:  1974
Pesticide Type:  Herbicide
Chemical Family:  Pyrazolium
U.S. and Foreign Producers:  American Cyanamid Company
                 2. USE PATTERNS AND FORMULATIONS
- Application:  postemergence herbicide to control wild oats in alfalfa
  (seed crop in CA only), wheat and barley.
- Types and Methods of Application:  Applied as a postemergence
  broadcast treatment by aerial and ground equipment.
- Application Rates:  0.6 - 1.0 lb cation/A
- Types of Formulations:
  - Single active ingredient formulations:
    - 31.2% SC/L, 31.8% SC/L, and 62.5% SC/S
  - Difenzoquat  can be tank mixed with bromoxymil, metsulfuron methyl,
    chlorsulfuron, 2,4-D (2,4-dichlorophenoxyacetic acid) and MCPA (2-
    methyl-4-chlorophenoxyacetic acid).
                          3. SCIENCE FINDINGS
Summary Science Statement
- Chemical Characteristics of the Technical Material
  - Physical State:  Solid
  - Color:  White to off-white
  - Odor:  Odorless
  - Molecular Weight and Formula: 360.4 - Cl8H20N2O4S (Salt)
  - Melting Point: 155 - 157 degrees C  Difenzoquat decomposes above
    160 degrees C.
  - Vapor Pressure:  negligible
  - Density:  41 lb/cu ft
  - Solubility in various solvents:  76.5% in water at 23 degrees C.
    Poorly soluble in most organic solvents.
Toxicology Characteristics
- Difenzoquat is moderately toxic by the oral route (LD50 for male rats
  - 270 mg/kg) and slightly toxic via the dermal route of exposure (LD50
  for male rabbits - 3540 mg/kg). Difenzoquat was found to be slightly
  irritating to the eyes and moderately irritating to abraded skin and
  non-irritating to intact skin.  The inhalation route of exposure does
  not indicate any toxicity problems [LC50 for male rats is greater than
  298.2 mg/l (1 hr. exposure)].
Major routes of exposure: Dermal and inhalation.
- Subchronic toxicity:  No compound related effects were observed in
  90-Day Feeding Study. Systemic NOEL was 2500 ppm (62.5 mg/kg:HDT).
  (HDT = Highest Dose Tested).
- Oncogenicity:  Difenzoquat was negative for oncogenicity at the 5000
  ppm (250 mg/kg:HDT) level in rats.
- Teratogenicity:  Difenzoquat was negative for teratogenicity,
  fetotoxicity and maternal toxicity in rats at the 2500 ppm (125
  mg/kg:HDT) level.
 -Reproduction:  A 3-generation rat reproduction study found the
  parental NOEL was equal to or greater than 2500 ppm (125 mg/kg:HDT)
  and reproductive/developmental NOEL was 500 ppm (25 mg/kg). The
  only maternal effect observed in all three generations was a
  decreased body weight gain in the high dose group during the
  premating period.
- Mutagenicity:  Insufficient data available to evaluate the
  mutagenicity potential.
Environmental Characteristics
- Difenzoquat is tightly bound to soil particles and does not readily
  leach.
Ecological Characteristics
- Avian acute toxicity:  Difenzoquat is slightly toxic to birds. Mallard
  ducks (LC50 - 10,388 ppm) and bobwhite quail (LC50 - 4640 ppm).
- Freshwater fish acute toxicity:  Difenzoquat is slightly toxic to
  fish:  Bluegill (LC50 - 90.4 ppm) and Rainbow
         Trout (LC50 - 76-99 ppm).
- Freshwater invertebrate toxicity:  Difenzoquat is moderately toxic to
  freshwater invertebrates. Daphnia (LC50 - 2.6 ppm).
TOLERANCE ASSESSMENT
- Tolerances have been established for residues of difenzoquat in a
  variety of raw agricultural commodities (40 CFR 180.369).
- The current U.S. tolerances for difenzoquat range from 0.05 ppm in
  fat, meat, meat byproducts and wheat grain, 0.2 ppm for barley grain,
  and 20 ppm for wheat and barley straw. A Canadian maximum residue
  level of 0.1 ppm (negligible residue) has been established for wheat
  and barley grain. There are no Mexican Tolerances or CODEX MRLs for
  difenzoquat.
                    4 SUMMARY OF REGULATORY POSITIONS
Based on available information, the Agency has made the following
determinations:
- Difenzoquat does not exceed any risk criteria for Special Review.
- Difenzoquat does not meet the criteria for restricted use.
- The Agency is not imposing any special labeling for endangered or
  threatened species because of its use patterns of single application
  postemergence to wheat and barley, and because of low toxicity to fish
  and birds.
- Based on available toxicology data the Agency has no concerns with
  human exposure which would require special protective clothing.
- No groundwater advisory labeling is required because difenzoquat does
  not readily leach.
- No tolerances for feed items treated with difenzoquat will be issued
  until data gaps for animal metabolism and magnitude of residue have
  been fulfilled.
                   5. SUMMARY OF MAJOR DATA GAPS
                                                Timeframe for
     Toxicology                                 Submission(1)
____________________________________________________________________
Acute Oral Toxicity in one sex (females)          9 months
Acute Dermal Toxicity in one sex (females)        9 months
Acute Inhalation Toxicity in one sex (females)    9 months
Dermal Sensitization                              9 months
Subchronic Dermal (21-day)                        9 months
Chronic Toxicity in one species (nonrodent)      50 months
Teratogenicity in one species (rat)              15 months
Oncogenicity in one species (mouse)              50 months
Mutagenicity
  (Gene mutation, chromosomal aberration,
   and direct DNA damage studies).               12 months
Metabolism                                       24 months
Environmental Fate
Hydrolysis                                        9 months
Photodegradation in water and on soil             9 months
Aerobic and anaerobic soil metabolism            27 months
Leaching and Adsorption/Desorption               12 months
Volatility (Lab)                                 12 months
Terrestrial field dissipation (soil)             27 months
Accumulation rotational crops (confined)         39 months
Fish accumulation                                12 months
Product Chemistry
Product Identity and Disclosure of Ingredients    9 months
Description of Manufacturing Process              9 months
Discussion of Formulation and Impurities          9 months
Preliminary Analysis of Product Samples          12 months
Certification of Ingredient Limits               12 months
Analytical Methods to Verify Certified Limits    12 months
Physical and Chemical Characteristics             9 months
Residue Chemistry: Tolerance Reassessment
Nature of the Residue (Metabolism) in Livestock  18 months
Residue Analytical Methods                       15 months
Storage Stability Data                           18 months
Magnitude of Residue in Plants, and
  Fat/Meat/Meat of Animal Byproducts             18 months
1. Timeframe for submission is number of months from date of issuance of
   the registration standard, December 23, 1988.
                    6.   CONTACT PERSON AT EPA
Richard F. Mountfort
Product Manager 23
Fungicide/Herbicide Branch
Registration Division (TS-767C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street, S. W.
Washington, D. C.  20460
Office location and telephone number:
Room 237, Crystal Mall #2
1921 Jefferson Davis Highway
Arlington, VA  22202
(703) 557-1830
DISCLAIMER:  THE INFORMATION IN THIS PESTICIDE FACT SHEET IS A SUMMARY 
ONLY AND IS NOT TO BE USED TO SATISFY DATA REQUIREMENTS FOR PESTICIDE 
REGISTRATION AND REREGISTRATION. THE COMPLETE REGISTRATION STANDARD FOR 
THE PESTICIDE MAY BE OBTAINED FROM THE NATIONAL TECHNICAL INFORMATION 
SERVICE. CONTACT THE PRODUCT MANAGER LISTED ABOVE FOR FURTHER 
INFORMATION.