difenzoquat (Avenge) Herbicide Profile 12/88
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-
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.
- 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
-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
- Mutagenicity: Insufficient data available to evaluate the
- Difenzoquat is tightly bound to soil particles and does not readily
- 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).
- 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
4 SUMMARY OF REGULATORY POSITIONS
Based on available information, the Agency has made the following
- 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
- 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
5. SUMMARY OF MAJOR DATA GAPS
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
(Gene mutation, chromosomal aberration,
and direct DNA damage studies). 12 months
Metabolism 24 months
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 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
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
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