United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508W)
EPA-738JK97-011
January 1998
R.E.D. FACTS
Terbacil
Pesticide
Reregistration
Use Profile
All pesticides sold or distributed in the United States must be regis-
tered by EPA, based on scientific studies showing that they can be used
without posing unreasonable risks to people or the environment. Because
of advances in scientific knowledge, the law requires that pesticides which
were first registered before November 1,1984, be reregistered to ensure
that they meet today's more stringent standards.
In evaluating pesticides for reregistration, EPA obtains and reviews a
complete set of studies from pesticide producers, describing the human
health and environmental effects of each pesticide. To implement provi-
sions of the Food Quality Protection Act of 1996, EPA considers the special
sensitivity of infants and children to pesticides, as well as aggregate expo-
sure of the public to pesticide residues from all sources, and the cumulative
effects of pesticides and other compounds with common mechanisms of
toxicity. The Agency develops any mitigation measures or regulatory
controls needed to effectively reduce each pesticide's risks. EPA then
reregisters pesticides that meet the safety standard of the FQPA and can be
used without posing unreasonable risks to human health or the environ-
ment.
When a pesticide is eligible for reregistration, EPA explains the basis
for its decision in a Reregistration Eligibility Decision (RED) document.
This fact sheet summarizes the information in the RED document for
reregistration case 0039, Terbacil.
Terbacil is a selective herbicide used to control broadleaf weeds on
terrestrial food/feed crops (e.g., apples, mint/peppermint/spearmint,
sugarcane, and ornamentals), forestry [e.g., cottonwood
(fbrest/shelterbelt)], terrestrial food (e.g., asparagus, blackberry, boysen-
beny, dewberry, loganberry, peach, raspberry, youngberry and straw-
berry), and terrestrial feed (e.g., alfalfa, sainfoin (hay and fodder), and
forage).
Formulations include a wettable powder and products are applied by
aircraft or ground equipment including boom sprayers.
Use practice limitations include prohibition of applications through
any type of irrigation system. They also prohibit grazing treated crops or
allowing hay, seeds or seed screening from treated crops to be used for food
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Regulatory
History
Human Health
Assessment
or feed. Grazing or feeding forage or hay from treated areas to livestock is
prohibited.
Terbacil was first registered for use as a herbicide in the U.S. in
1966. EPA issued a Registration Standard for terbacil in May 1982. In
August 1989 a Registration Standard (Second Round Review) was issue for
terbacil. This document reviewed data submitted in response to the 1982
Registration Standard, updated the Agency's assessment of the terbacil data
base, and included a tolerance reassessment. The Second Round Review
required additional data in the area of toxicology, environmental fate,
ecological effects, and residue chemistry. On August 3, 1996, the Food
Quality Protection Act of 1996 (FQPA) was signed into law. FQPA amends
both the Federal Food, Drug, and Cosmetic Act (FFDCA), and the Federal
Insecticide, Fungicide, and Rodenticide Act (FIFRA). The FQPA amend-
ments went into effect immediately and were considered during this
reregistration decision. Currently, there are 5 active terbacil products
registered.
Toxicity
In studies using laboratory animals, terbacil is slightly toxic by the
oral and dermal routes and has been placed in Toxicity Category IV (the
lowest of four categories) for these effects. For the inhalation route, the
Toxicity Category is III. Terbacil per se is mildly irritating to the eyes
(Toxicity Category III).
In a chronic feeding study using beagle dogs, terbacil caused increased
thyroid to body weight ratios, slight increase in liver weights, and elevated
alkaline phosphatase levels.
Terbacil has been evaluated for potential carcinogenic activity in mice
and rats. Terbacil did not induce any increase in tumor incidence in the
treated animals. Terbacil is classified in Group E (no evidence of carcino-
genicity in animals studies) with respect to its cancer potential.
Terbacil demonstrates some evidence of causing developmental
toxicity effects in rats and rabbits. These effects are likely due to maternal
toxicity from exposure to bromacil rather than from specific developmental
toxicity of terbacil. Therefore, the Agency does not consider terbacil a
developmental toxicant.
Dietary Exposure
People may be exposed to residues of terbacil through the diet.
Generally, acute dietary margins of exposure greater than 100 tend to cause
no dietary concern. Because the endpoint of concern was a developmental
effect, the only sub-population of concern is females of child bearing age
(i.e., females, 13+years old). Presently registered commodities result hi an
MOE for females (13+ years) of 3125, which demonstrates that there is no
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cause for concern regarding acute dietary exposure from terbacil for both
existing and proposed uses.
In assessing chronic dietary risk from food, EPA estimates that
terbacil residues in food account for 12.2% of the RfD, based on existing
tolerances and assuming 100% of the crop treated. Incorporating the results
of the Agency's reregistration review (i.e., recommendationns to revoke
tolerances for citrus fruits and pears, and to raise tolerances on caneberries,
blueberries, peaches, apples, and sugarcane), 4.5% of the RfD is utilized.
No Codex Maximum Residue Limits (MRLs) have been established
for terbacil for any agricultural commodity. Therefore, no compatibility
questions exist with respect to U.S. tolerances.
Occupational Exposure
An occupational exposure assessment is required for an active ingredi-
ent if (1) certain lexicological criteria are triggered and (2) there is potential
exposure to handlers (mixers, loaders, applicators, etc.) during use or to
persons entering treated sites after application is complete. The Toxicity
Endpoint Selection Committee found that neither dermal nor inhalation
toxicity criteria were triggered for terbacil. Therefore, no assessments are
needed for occupational exposure/risk at this time.
Human Risk Assessment
EPA conducted additional risk analyses using available data in re-
sponse to the new FQPA requirements. Based on current data require-
ments, terbacil has a complete database for developmental and reproductive
toxicity. Because the developmental NOELs were the same as those for
maternal toxicity, and the NOEL for systemic (parental) toxicity was higher
than the NOEL for reproductive toxicity, these data do not suggest increased
pre- or post-natal sensitivity of children and infants to terbacil exposure.
Therefore, EPA concludes that the available toxicology data do not support
an uncertainty factor of 1000 as specified in FQPA and that the present
uncertainty factor of 100 is adequate to ensure the protection of infants and
children from exposure to terbacil. EPA estimates that terbacil residues in
the diet of infants and children account for 12.8% of the RfD and residues
in drinking water account for 81 % of the RfD. Therefore, the Agency
concludes that aggregate risks for infants and children resulting from
terbacil uses are not of concern.
In assessing aggregate risk dietary, exposure from food and drinking
water were considered. Aggregate acute dietary risk for females of child-
bearing age was calculated and the MOE=1563. Acute dietary risk from
food alone was calculated for females of child-bearing age and the
MOE=4166 (based on tolerance levels reassessed in this RED and 100%
crop treated). In assessing aggregate chronic dietary risk, exposures from
food and drinking water were considered. The aggregate exposures account
for 27.6% of the RfD. Aggregate exposure/risk values are all below the
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Environmental
Assessment
Risk Mitigation
level of Agency concern. This includes the acute exposure of females of
child-bearing age.
In evaluating the potential for cumulative effects, EPA compared
terbacil with other structurally similar substituted uracil compounds, such as
bromacil and lentacil, and then with other compounds producing similar
effects. A comparison of the available lexicological database for terbacil
and bromacil revealed no clear common mode of toxicity for the chemicals.
The toxicology database for lentacil was not considered because there are
currently no registered uses of lentacil. Based on the available data, the
Agency has determined that there is no clear common mode of toxicity
between terbacil and bromacil.
Ecological Effects Risk Assessment
Minimal adverse acute effects are expected for avian, mammalian, and
aquatic species from labeled uses of terbacil. Chronic effects for avian and
aquatic species cannot be evaluated at this tune because of insufficient data.
However, chronic risk quotients (RQs) for mammals indicate that adverse
effects are possible from labeled uses of terbacil. There is some uncer-
tainty in assessing adverse chronic mammalian effects because the NOEL is
greater than the maximum concentration tested in rat reproduction study
design. Therefore, the highest concentration is a default toxicity endpoint
which is a conservative estimate of risk. Since terbacil is a persistent and
mobile herbicide, non-target terrestrial plants are expected to be adversely
affected from runoff and spray drift. Minimal adverse effects, however,
are expected for non-target aquatic plants. Because terbacil is used exclu-
sively on minor crops, terbacil exposure is expected to be very localized and
dependent on site specific conditions. The localized nature of terbacil use
areas is expected to limit human and ecological exposure.
To lessen the risks posed by terbacil, EPA is requiring the following
risk mitigation measures.
o Maximum label application rates should be reduced to be
representative of typical application rates.
o The Agency recommends a surface water label advisory on terbacil
because it has characteristics (persistent and very mobile) of pesticides
found in surface waters. Surface water modeling for a
Louisiana sugarcane scenario indicates terbacil may accumulate at
concentrations greater than 1 mg/L. Since terbacil is used on
vulnerable soils for surface water contamination such as the Louisiana
production area, a surface water label advisory is recommended. The
label advisory should state: "Terbacil has properties that may result in
surface water contamination via dissolved runoff and runoff erosion.
Practices should be followed to minimize the potential for dissolved
runoff and runoff and/or runoff erosion."
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Additional Data
Required
° Terbacil is more mobile and persistent than a number of herbicides
which have been found to contaminate ground water. EPA has
recommended a ground water label advisory since 1989, and continues
to recommend this. The following label language is appropriate:
"This chemical has properties and characteristics associated with chemicals
detected in ground water. The use of this chemical in areas where soils are
permeable, particularly where the water table is shallow, may result in
ground water contamination."
EPA is requiring the following additional generic studies for terbacil
to confirm its regulatory assessments and conclusions:
• Avian Reproduction Quail [71-4(a>]
• Avian Reproduction Duck [71-4(b)]
• Early Life-Stage Fish [72-4(a>]
• Life-Cycle Aquatic Invertebrate [72-4(b)]
• Aerobic Aquatic Metabolism [162-4]
The Agency also is requiring product-specific data including product
chemistry and acute toxicity studies, revised Confidential Statements of
Formula (CSFs), and revised labeling for reregistration.
Product Labeling All terbacil end-use products must comply with EPA's current pesti-
Changes Required cide product labeling requirements and with the following. For a compre-
hensive list of labeling requirements, please see the terbacil RED document.
PPE/Engineering Control Requirements for Pesticide Handlers
For sole-active-ingredient end-use products that contain terbacil, the
product labeling must be revised to adopt the handler personal protective
equipment requirements set forth in this section. Any conflicting PPE
requirements on the current labeling must be removed.
For multiple-active-ingredient end-use products that contain terbacil,
the handler personal protective equipment requirements set forth in this
section must be compared to the requirements on the current labeling and
the more protective must be retained. For guidance on which requirements
are considered more protective, see PR Notice 93-7.
Minimum PPE/Engineering Control Requirements
EPA is not establishing active ingredient-specific PPE or engineering
control requirements for terbacil end-use products.
Actual end-use product PPE requirements
Any necessary PPE for each terbacil occupational end-use product will
be established on the basis of the end-use product's acute toxicity category.
Placement in labeling
The personal protective equipment must be placed on the end-use
product labeling in the location specified in PR Notice 93-7 and the format
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and language of the PPE requirements must be the same as is specified in
PR Notice 93-7.
Entry Restrictions
For sole-active-ingredient end-use products that contain terbacil the
product labeling must be revised to adopt the entry restrictions set forth in
this section. Any conflicting entry restrictions on the current labeling must
be removed.
For multiple-active-ingredient end-use products that contain terbacil
the entry restrictions set forth in this section must be compared to the entry
restrictions on the current labeling and the more protective must be retained.
A specific time-period in hours or days is considered more protective than
"sprays have dried" or "dusts have settled."
Restricted-entry interval
A 12-hour restricted-entry interval (REI) is required for uses within
the scope of the WPS on all terbacil end-use products.
PPE/Engineering Control Requirements for Pesticide Handlers
For sole-active-ingredient end-use products that contain terbacil, the
product labeling must be revised to adopt the handler personal protective
equipment requirements set forth in this section. Any conflicting PPE
requirements on the current labeling must be removed.
For multiple-active-ingredient end-use products that contain terbacil,
the handler personal protective equipment requirements set forth in this
section must be compared to the requirements on the current labeling and
the more protective must be retained. For guidance on which requirements
are considered more protective, see PR Notice 93-7.
Minimum PPE/Engineering Control Requirements
EPA is not establishing active ingredient-specific PPE or engineering
control requirements for terbacil end-use products.
Actual end-use product PPE requirements
Any necessary PPE for each terbacil occupational end-use product will
be established on the basis of the end-use product's acute toxicity category.
Placement in labeling
The personal protective equipment must be placed on the end-use
product labeling hi the location specified hi PR Notice 93-7 and the format
and language of the PPE requirements must be the same as is specified hi
PR Notice 93-7.
Entry Restrictions
For sole-active-ingredient end-use products that contain terbacil the
product labeling must be revised to adopt the entry restrictions set forth in
this section. Any conflicting entry restrictions on the current labeling must
be removed.
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Regulatory
Conclusion
For More
Information
For multiple-active-ingredient end-use products that contain terbacil
the entry restrictions set forth in this section must be compared to the entry
restrictions on the current labeling and the more protective must be retained.
A specific time-period in hours or days is considered more protective than
"sprays have dried" or "dusts have settled."
Restricted-entry interval
A 12-hour restricted-entry interval (REI) is required for uses within
the scope of the WPS on all terbacil end-use products.
The use of currently registered products containing terbacil in accor-
dance with approved labeling will not pose unreasonable risks or adverse
effects to humans or the environment. Therefore, all uses of these products
are eligible for reregistration.
Terbacil products will be reregistered once the required product-
specific data, revised Confidential Statements of Formula, and revised
labeling are received and accepted by EPA.
EPA is requesting public comments on the Reregistration Eligibility
Decision (RED) document for terbacil during a 60-day time period, as
announced in a Notice of Availability published in the Federal Register. To
obtain a copy of the RED document or to submit written comments, please
contact the Pesticide Docket, Public Information and Records Integrity
Branch, Information Resources and Services (7502C), Office of Pesticide
Programs (OPP), US EPA, Washington, DC 20460, telephone
703-305-5805.
Electronic copies of the RED and this feet sheet are available on the
Internet. See http://www.epa.gov/REDs.
Printed copies of the RED and feet sheet can be obtained from EPA's
National Center for Environmental Publications and Information
(EPA/NCEPI), PO Box 42419, Cincinnati, OH 45242-2419, telephone 1-
800-490-9198; fax 513-489-8695.
Following the comment period, the terbacil RED document also will
be available from the National Technical Information Service (NTIS), 5285
Port Royal Road, Springfield, VA 22161, telephone 703-487-4650.
For more information about EPA's pesticide reregistration program,
the terbacil RED, or reregistration of individual products containing
terbacil, please contact the Special Review and Reregistration Division
(7508W), OPP, US EPA, Washington, DC 20460, telephone 703-308-8000.
For information about the health effects of pesticides, or for assistance
in recognizing and managing pesticide poisoning symptoms, please contact
the National Pesticides Telecommunications Network (NPTN). Call toll-
free 1-800-858-7378, from 6:30 am to 4:30 pm Pacific Time, or 9:30 am to
7:30 pm Eastern Standard Time, seven days a week.
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