Unit«d Stat« Offic* of PwtiodM and Toxic SubMnc«
Environmental Prottction Offic* of Pwtiad* Prognmt (TS-7MC)
Aomcy WMhingtan, DC 20480
540/FS-89-035
• vvEPA 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: l,2^imetlTYl-3,5-cliFtienyl-IH-pyrazolium
Cannon Name: Difenzoquat
Trade and Other Names: AVENGE
EPA Snaughnessy 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
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2. USE PA1TKUNS AND FORMUIATIONS
Application: A 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 Ib 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 - C18H2oN2O4S (Salt)
Melting Point: 155 - 157°C Difenzoquat decomposes above 160°C.
Vapor Pressure: negligible
Density: 41 Ib/cu ft
Solubility in various solvents: 76.5% in water at 23°C. Poorly soluble
in most organic solvents.
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Toxicology Characteristics
Difenzoquat is moderately toxic by the oral route (IT>5o for male rats -
270 mg/kg) and slightly toxic via the dermal route of exposure (LDsg 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
for male rats is greater than 298.2 mg/1 (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). (HOT = 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:HOT) 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 (LC5Q - 90.4 ppm) and Rainbow
Trout (LC50 - 76-99 ppm).
Freshwater invertebrate toxicity: Difenzoquat is moderately toxic to
freshwater invertebrates. Dapnnia
2.6 ppm).
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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.
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5. Summary of Major Data Gaps
Toxicology
Acute Oral Toxicity in one sex (females)
Acute Dermal Toxicity in one sex (females)
Acute Inhalation Toxicity in one sex (females)
Dermal Sensitization
Subchronic Dermal (21-day)
Chronic Toxicity in one species (nonrodent)
Teratogenicity in one species (rat)
Qncogenicity in one species (mouse)
Mutagenicity
(Gene mutation, chromosomal aberration,
and direct DNA damage studies).
Metabolism
Environmental Fate
Hydrolysis
Photodegradation in water and on soil
Aerobic and anaerobic soil metabolism
Leaching and Adsorption/Desorption
Volatility (Lab)
Terrestrial field dissipation (soil)
Accumulation rotational crops (confined)
Fish accumulation
Product Chemistry
Product Identity and Disclosure of Ingredients
Description of Manufacturing Process
Discussion of Formulation and Impurities
Preliminary Analysis of Product Samples
Certification of Ingredient Limits
Analytical Methods to Verify Certified Limits
Physical and Chemical Characteristics
Residue Chemistry; Tolerance Reassessment
Nature of the Residue (Metabolism) in Livestock
Residue Analytical Methods
Storage Stability Data
Magnitude of Residue in Plants, and
Fat/Meat/Meat of Animal Byproducts
Timeframe
for
Submission^/
9 months
9 months
9 months
9 months
9 months
50 months
15 months
50 months
12 months
24 months
9 months
9 months
27 months
12 months
12 months
27 months
39 months
12 months
9 months
9 months
9 months
12 months
12 months
12 months
9 months
18 months
15 months
18 months
18 months
1. Timeframe for submission^Jts-TTlInBer of months from date of issuance of the
registration standard, Dedanber 23, 1988.
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6. CONIACT PERSON AT ERA.
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.
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