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 ------- —2- 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. ------- —3— 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% ------- -4- 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. ------- —5- 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 ------- -6- 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. ------- |