540/FS-89-065
United States Office of Pesticides and Toxic Substances
Environmental Protection Office of Pesticide Programs (H7508C)
Agency Washington, DC 20460
EPA Pesticide
Fact Sheet
Name of Chemical: TERBACIL
Reason for Issuance: REGISTRATION STANDARD (SRR)
Date Issued: August 1989
Fact Sheet Number: 206
1. DESCRIPTION OF CHEMICAL
Generic Name: 3-tert-butyl-5-chloro-6-methyluracil
Common Name: Terbacil
Trade and Other Names: 5-chloro-3-(l,1-dimethylethyl)-6-
methyl-2,4(lH,3H)-pyrimidinedione,
Sinbar , DuPont Herbicide 732, and
Geonter.
EPA Shaughnessy Codes: 012701
Chemical Abstracts Service (CAS) Number: 5902-51-2
Year of Initial Registration: 1966
Pesticide Type: Herbicide
Chemical Family: Uracils
U.S. Producers: E.I. duPont de Nemours Company, Inc.
2. USE PATTERNS AND FORMULATIONS
Application sites: Terrestrial food crops.
Types and Methods of Application: Tractor mounted spray
boom to soil surfaces and small emerged weeds. Aerial
application.
Application Rates: 0.4 tc 8.0 Ib active ingredient per acre
Annual Usage: 290,000 - 610,000 pouncs
Types of Formulation: Wettable Tr Mvde.:
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3. SCIENCE FINDINGS
Chemical Characteristics of the Technical Matericil
Physical State: Crystalline solid
Color: White
Odor: None
Molecular Weight and Formula: 216.7
Boiling Point: Terbacil is a solid at room temperature
Vapor Pressure: 4.7 x 10"7 mm Hg at 29.5°C
Density: 1.34
Solubility in various solvents: Water, xylene, and
dimethylformamide
Toxicology Characteristics
-Acute Oral: 1082 mg/kg (rat) Toxicity Category III
-Acute Dermal: >5000 mg/kg (rabbit) Toxicity Category III
-Primary Dermal Irritation: No irritation demonstrated
-Primary Eye Irritation: slight eye irritation (conjunctiva)
-Dermal Sensitization: Not a dermal sensitizer
-Acute Inhalation: >4.4 mg/liter/4 hours (Toxicity Category III)
-Subchronic dermal (21-day): > 5000 mg/kg. No toxic signs.
-Subchronic Oral (90-day): No Observed Effect Level (NOEL) of
5 mg/kg/day.
-Chronic Oral dog (2-year): NOEL of 1.25 mg/kg/day.
-Oncogenicity: Data Gap.
-Teratogenicity (rat): Not teratogenic. Maternal NOEL was 62.5
mg/kg/day. Teratogenicity NOEL > 250 mg/kg/day.
-Teratogenicity (rabbit): Not teratogenic. Maternal and embryo-
toxicity NOEL was 200 mg/kg/day. Teratogenicity NOEL was 600
600 mg/kg/day (highest dose tested).
-Reproduction: No observed effects with a NOEL of 62.5 mg/kg/day
(highest dose tested).
-Mutagenicity: Non-mutagenic in assays tested.
-Metabolism: Data Gap.
-Major route of exposure: Dermal
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Physiological and Biochemical Characteristics
-Mechanism of Pesticidal Action: Stops photosynthesis
-Metabolism and Persistence in Plants and Animals: The
available data are not adequate to assess the nature of
terbacil in plants or in animals.
Environmental Characteristics
-Terbacil is stable to hydrolysis and photodegrades slowly in
water.
-It has a potential to contaminate ground water particularly in
areas with sandy soil surfaces.
-It leaches slower in fine textured soils and also in soils
having higher organic contents.
-It does not accumulate to significant levels in bluegill
sunfish.
-Residues resulting from multiple applications of terbacil
persisted for 2 years following the final application.
-Preliminary data indicate that terbacil is extremely persistent
with half-lives of 520 days aerobically and 178 days
anaerobically.
Ecological Characteristics
-Avian acute toxicity:
>2250 mg/kg (Quail). Practically Non-toxic.
-Avian dietary toxicity:
>5000 ppm (Mallard duck,). Practically Non-toxic.
-Freshwater fish acute toxicity:
102.9 ppm (Bluegill sunfish) Practically Non toxic.
46.2 ppm (Rainbow trout) Slightly Toxic
-Marine fish acute toxicity: Data Gap
-Freshwater invertebrate toxicity:
65 ppm (Daphnia). Slightly toxic.
-Marine invertebrate toxicity:
>4.9 ppm (Oyster). Moderately toxic
49 ppm (Shrimp). Slightly toxic
TOLERANCE ASSESSMENT
-Tolerances have been established for residues of Terbacil in a
variety of raw agricultural commodities (Refer to 40 CFR
180.209 for listing of tolerances). Terbacil's tolerances have
been reassessed using the Tolerance Assessment System
(TAS). The TAS chronic exposure analysis estimates average
daily exposure for the overall U.S. population and each of
the 22 populations subgroups and compares these estimates
to the acceptable daily intake (ADI) calculated for
terbacil.
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The Theoretical Maximum Residue Contribution (TMRC) for the
overall U.S. population is estimated to be 0.001594
mg/kg/day, which occupies approximately 12% of the ADI. The
two most highly exposed subgroups are non-nursing infants,
less than 1 year old (TMRC= 0.008122 mg/kg/day or 62% of the
ADI), and children , 1- 6 years of age (TMRC= 0.004361
or 34% of the ADI) .
4. Summary of Regulatory Positions
This review of terbacil is the second intensive evaluation of the
compound. In its original Registration Standard, issued in
1982 , the Agency summarized the available data supporting
the registration of terbacil and concluded that additional
data were needed to fully evaluate the pesticide.
The Agency has since received and reviewed the data and has
revised its scientific and regulatory conclusions relative
to these data.
o Terbacil will not be placed in Special Review at this time.
o The Agency will impose a ground water contamination advisory
statement to reduce point source contamination.
o The Agency is requiring the following testing on all terbacil
end-use products: acute oral, acute dermal, primary eye,
primary skin, dermal sensitization, and acute inhalation if
appropriate.
o The Agency will not establish a reentry interval for terbacil
beyond the minimum reentry interval (sprays have dried,
dusts have settled and vapors have dispersed) .
o The Agency will require updated worker safety and protective
equipment statements for end-use products containing terbacil.
o The Agency is requiring a rotational crop statement on all
terbacil labels which may involve rotation to crops other
than those currently registered (refer to section IV. D for
specific wording) . In addition residue data are required
for representative crops from any crop group which could be
rotated from alfalfa, sainfoin, and mint.
o Existing Tolerances for Terbacil per se should be amended to
include metabolites A,B, and C, as specified in 40 CFR
180.209 (b) .
o The Agency will revoke tolerances associated with the
commodities sainfoin (hay) , sainfoin (forage) , and pears.
o The Agency will revise the tolerance for residues in or on
peaches to 0.2 ppm for combined residues of terbacil and its
metabolites.
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o The Agency will impose a label restrictions against the feeding
and grazing of sugarcane forage and spent hay to livestock
or require the development and submission of data in support
of tolerances for residues in or on sugarcane forage and
spent hay.
o The Agency has determined that grasses grown for seed is a food
use. Therefore, data depicting residues of terbacil in or
on members of the grass forage, fodder and hay group are
required.
o The Agency will not propose group tolerances for terbacil.
o The Agency will not grant any significant new food or feed uses
for terbacil until the required residue chemistry and
toxicology studies have been submitted and reviewed.
o The Agency has identified certain data that will receive
priority review when submitted;
Section 158.340 Toxicology
83-1 Chronic Oral Feeding (Rat)
83-2 Oncogenicity (Rat and Mouse)
Section 158.290 Environmental Fate
162-1 Aerobic Soil Metabolism
162-2 Anaerobic Soil Metabolism
163-1 Leaching Adsorption/Desorption
164-5 Soil, Long Term (field)
Section 158.490 Wildlife and Aquatic Organisms
72-3 Estuarine and Marine Testing (Fish)
122- Tier I Nontarget Area Phytotoxicity
Section 158.240 Residue Chemistry
171-4 Metabolism in Plants & Livestock
Required Unique Labeling
A. Groundwater Advisory Statements
B. Environmental Hazards Statement
D. Reentry Statement
E. Feeding and/or Grazing Restrictions
F. Rotational Crop Statement
Summary of Major Data Gaps
Toxicology
Environmental Fate/Exposure
Ecological Effects
Residue Chemistry
Product Chemistry
Timeframe Ranges
12-48 Months
12-48 Months
24 Months
24-48 Months
12-24 Months
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7. CONTACT PERSONS AT EPA
Product Specific Inquiries:
Robert J. Taylor
Product Manager (25)
Fungicide Herbicide Branch
Registration Division (H-7505C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street, S. W.
Washington, D. C. 20460
Office location and telephone number:
Room 245, Crystal Mall #2
1921 Jefferson Davis Highway
Arlington, VA 22202
(703) 557-1800
Reregistration Document Inquiries;
Donna M. Williams
Review Manager
Reregistration Branch
Special Review and Reregistration Division (H-7508C)
Environmental Protection Agency
401 M Street, S. W.
Washington, D. C. 20460
Office location and telephone number:
Room 1124, Crystal Mall #2
1921 Jefferson Davis Highway
Arlington, VA 22202
(703) 557-0639
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 Review Manager listed above
for further information.
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