Agency! I fngtan. DC KMflO
&EPA Pesticide
Fact Sheet
Name Of Chemical: imazaquin (Scepter)
Reason for Issuance: New chemical
Date Issued: March 20, 1986
Fact Sheet Number: 83
1 . DESCRIPTION OF CHEMICAL
Generic Name: 2-[4,5-dihydro-4-methyl-4-(l-methylethyl)-5-oxo-
1jI-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
U.S. and Foreign Producers: American Cyanamid
2. USE PATTERNS AND FORMULATIONS
Application site: Soybeans
Method 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 treat-
ment followed by a postemergence treatment.
Application rates: Ground or aerial application rates are
2 oz active ingredient per acre (a.i./A). Ground appli-
cations 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 Ib/a.i./A per season may be applied.
Type of formulation: 95% technical grade and 17.3% active
ingredient liquid concentrate end-use product.
Usual carrier: Water
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3. SCIENCE FINDINGS
Summary science statement: Scepter has been found to be
acceptable for the proposed use. It is relatively non-
toxic by the oral, dermal and inhalation routes, non-
irritating to slightly irritating to the eye and skin;
it is not a dermal sensitizer. Hazard to nontarget
organisms is considered to be minimal.
Chemical characteristics:
Physical state : Solid
Color : Light tan
Odor : None
Melting Point : 219-224°C
Solubility : 60 ppm at 25°C
Octanol/water partition
coefficient : 2.2
pH : 3.81/
Toxicology characteristics:
Acute effects. Imazaquin is relatively nontoxic by
oral, derinal and inhalation routes, nonirritating
to slightly irritating to the eye and skin and not
a dermal sensitizer. Acute test results indicate
Toxicity Categories III and 1V 2 / as follow:
Acute oral toxicity (rat): Greater than 5,000 mg/kg bwt
Toxicity Category IV
Acute inhalation (rat) : Greater than 5.7 mg/L
Toxicity Category III
Acute dermal (rabbit) : Greater than 2,000 mg/kg bwt
Toxicity Category III
Acute dermal sensitiza-
tion (guinea pigs) : Not a sensitizer
!1 Slurried into 100 nil of de-ionized water at 23°C; pH is
for this slurry at 23°C.
2/ Toxicity Category III Harmful if swallowed, inhaled or absorbed
through the skin. Contact with skin, eyes or clothing requires
immediate first aid and may require medical attention.
Toxicity Category IV No precautions are required.
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Primary dermal irritation: Mildly irritating
(rabbit) Toxicity Category IV
Primary eye irritation : Nonirritating
(rabbit) 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 bwt/day (HDT)
90-day feeding study : NOEL greater than 10,000
(rats) ppm or 800 mg/kg bwt/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 : NOEL = 1,000 ppm; Lowest-
study (beagle dogs) observed-effect level
(LOEL) 5,000 PPM
2-year oral dietary (rat): NOEL = 10,000 ppm (HDT)
or 500 mg/kg bwt/day
18-month oncogenicity : NOEL 1,000 ppm (150
(mouse) mg/kg bwt); Lowest effect
level (LEL) 4,000 ppm
Three-generation repro- : NOEL 10,000 ppm (1,000
duction (rat) mg/kg bwt) (HDT)
Teratology (rabbits) : Teratogenic NOEL = 500
mg/kg/day; ernbryotoxic
NOEL 500 mg/kg/day;
maternal NOEL 250
mg/kg/day; maternal LEL
500 mg/kg/day
Teratology (rats) : Teratogenic: NOEL greater
than 2,000 mg/kg bwt/day;
fetotoxic: NOEL 500
mg/kg bwt/day, and LOEL
= 2,000 mg/kg/day maternal
toxicity: NOEL = 500 mg/kg
bwt/day, and LOEL =
2,000 mg/kg bwt/day
Single low-dose metab- : Almost entirely excreted
olism study (rats) in 48 hours; urine - 94%;
feces - 4%
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Mutagenicity - Ames test : Negative
Dominant lethal test (rats): Negative
In vitro cytogenetics (CHO): Negative
Unscheduled DNA synthesis : Negative
(rat hepatocytes)
CHO/}IGPRT point mutation : Negative
Major route of exposure: Dermal, inhalation
Physiological and biochemical behavorial characteristics:
Foliar absorption: Absorption occurs through both the foliage
and root8.
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 @ 25° 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
C0 2 , as well as degraded to the major metabolite CL
266,066 and at least 6 minor nietabolites.
Loss from photodecomposition and/or volatilization: Volatili-
zation does not occur.
Resultant average persistence: Imazaquin should not persist
beyond 4 to 6 months.
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Ecological characteristics: The following test results indicate
that irnazaquin is practically nontoxic to avian species,
finfish, aquatic invertebrates, and honeybees:
Avian acute oral toxicity
(mallard duck and bobwhite quail) : Greater than 2,150 ppm
Avian dietary toxicity
(mallard duck and bobwhite quail) : Greater than 5,000 ppm
Fish acute toxicity-- rainbow trout : Greater than 280 ppm
bluegill sunfish: Greater than 420 ppm
channel catfish : Greater than 320 ppm
Aquatic invertebrate toxicity
( Daphnia inagna ) : Greater than 280 ppm
Honeybee : Non-toxic at 100 ug/bee
Tolerance Assessment:
List of crops and tolerances (40 CFR 180.426):
Commodity Part per million
Soybeans 0.05
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 bwt/day) and using a 100-fold
safety factor, is calculated to be 0.25 mg/kg bwt/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
percent of the ADI (0.25 mg/kg bwt/day).
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
Position: The Agency has conditionally accepted the use of thi8
chemical on soybeans.
Rationale: 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
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5. SUIIMARY 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. Environmental Protection Agency (TS-767C)
401 M Street SW.
Washington, DC 20460
(703) 557-1800
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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