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E X T O X N E T
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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Trade names include Compound 732, DuPont Herbicide 732, Geonter,
and Sinbar. This compound may also be found in mixed formulations
with other herbicides.
Terbacil is registered by the U.S. Environmental Protection
Agency (EPA) as a General Use Pesticide (GUP). The Signal Word
CAUTION is required on containers of formulated terbacil.
Terbacil is in EPA class IV - practically nontoxic.
Terbacil is a selective herbicide used for control of both annual
grasses, broad-leaved weeds, and some perennial weeds in
sugarcane, apples, alfalfa, peaches, pecans, and mints. It is
sprayed on soil surfaces preferably just before, or during, the
period of active weed growth. Terbacil works in plants by
inhibiting photosynthesis. It is a member of the substituted
uracil chemical family. Terbacil is available in wettable powder
formulations. Technical terbacil is 95% pure active material.
is available in wettable powder formulations. Technical terbacil
is 95% pure active material.
- Acute toxicity: Terbacil has low acute
toxicity . Clinical signs of poisoning in rats
include weight loss, pallor, prostration, and rapid
breathing. In dogs, a single dose of 5 mg/kg caused
repeated vomiting . Terbacil may irritate the skin,
eyes, and mucous membranes of the nose and throat. It is
not a skin sensitizer . The oral LD50 of terbacil is
5000 to 7500 mg/kg in rats [1,22]. The dermal LD50 is
greater than 5000 mg/kg (the maximum feasible dose) in
rabbits . These rabbits did not show clinical signs of
toxicity, nor any obvious gross changes caused by
disease. No skin irritation and only mild eye irritation
was seen in rabbits at this dose . Similarly, there
was no skin irritation or sensitization in
terbacil-treated guinea pigs . Dogs given 5000 mg/kg
of terbacil exhibited vomiting and a lack of eye pupil
- Chronic toxicity: No evidence of
toxicity was seen in 2-year studies of rats fed doses as
high as 12.5 mg/kg/day, or in dogs fed doses as high as
6.25 mg/kg/day of terbacil. At 125 to 500 mg/kg/day,
there was a lower rate of weight gain, liver enlargement,
and other liver changes in rats. The highest dose
produced a slight increase in liver weight in dogs .
- Reproductive effects: There were no
adverse effects on lactation, fertility, birth rate, pup
survival, or any other aspect of reproduction in rats fed
2.5 and 12.5 mg/kg/day of terbacil for three generations
. However, the average number of live rat fetuses per
litter and the average final maternal body weight were
significantly lowered in another study in the 103 and 391
mg/kg/day dosage groups . Based on these data,
adverse effects on reproduction in humans are not likely
at expected exposure levels.
- Teratogenic effects: When doses of 30,
200, or 600 mg/kg/day were administered by gavage to
pregnant rabbits on days 7 to 19 of gestation, adverse
effects on the fetuses appeared only at the highest dose
tested. This dose also produced maternal toxicity and
increased maternal mortality. No adverse effects on the
mothers or the pups were observed at lower doses. In
another study, pregnant rats were fed doses of 23, 103,
or 391 mg/kg/day on days 6 to 15 of gestation.
Abnormalities occurred in the renal pelvis, and ureter
dilation was found in pups from all the treatment groups
. Evidence of teratogenicity is inconclusive.
- Mutagenic effects: Terbacil was not
mutagenic in several screening tests .
- Carcinogenic effects: No evidence of
carcinogenicity was found in rats fed 2.5, 12.5, 125, or
500 mg/kg/day of terbacil for 2 years, nor in dogs fed as
much as 12.5 mg/kg/day for 2 years . When mice were
fed dietary doses of 2.5, 62.5, or 250 mg/kg for 2 years,
no increased incidence of cancer was found .
Terbacil does not appear to be carcinogenic.
- Organ toxicity: Liver changes have been
seen in laboratory rats exposed to high doses of terbacil
- Fate in humans and animals: In general,
the uracil herbicides, the chemical class in which
terbacil is included, are rapidly excreted in urine by
mammals. This may account for their reportedly low
toxicity . When given in the feed of lactating cows
at 5 and 30 ppm, terbacil was excreted in the milk at
levels up to 0.03 and 0.08 ppm, respectively. No
herbicide was detected in the cows' urine and feces
- Effects on birds: Terbacil is slightly
toxic to birds . The 8-day dietary LC50 for terbacil
is more than 56,000 ppm in Peking ducklings, and greater
than 31,450 ppm in pheasant chicks . The LD50 for
terbacil in quail is greater than 2250 mg/kg .
- Effects on aquatic organisms: Terbacil
is slightly to practically nontoxic to aquatic organisms.
The 48-hour LC50 of terbacil is 86 mg/L in sunfish .
The LC50 for terbacil is 102.9 mg/L in bluegill sunfish
and 46.2 mg/L in rainbow trout. Terbacil is slightly
toxic to freshwater invertebrates, with an LC50 of 65
mg/L in Daphnia, a small freshwater crustacean. The LC50
for terbacil is greater than 4.9 mg/L in marine oysters
and 49 mg/L in shrimp . Terbacil does not
bioaccumulate in bluegill sunfish . Estuarine and
marine organisms may be exposed to terbacil due to its
use as a sugarcane herbicide . A study on grass
shrimp with an 84.7% formulated terbacil product was
sufficient to characterize the herbicide as slightly
toxic to marine invertebrates. The 48-hour LC50 of
terbacil is 1000 mg/L in fiddler crabs .
- Effects on other organisms: Terbacil is
nontoxic to bees .
- Breakdown in soil and groundwater:
Terbacil is highly persistent in soils . Soil
half-lives of 50 to 180 days have been reported [1,11].
Data from field dissipation studies showed that terbacil
persistence in soil varied with application rate,
rainfall, soil type, and mobility, as well as available
oxygen . In most soil types, terbacil has a
relatively low tendency to be adsorbed. It also is highly
soluble in water. Thus, terbacil is likely to be highly
mobile in soil and potentially pollute groundwater
[11,131]. Because of this, it should not be used on sandy
or gravelly soils that have less than 1% organic matter,
particularly if the water table is near the soil surface
 and when deep tillage is used . Leaching may
be slower in soils that are finer textured and/or have
higher organic matter content . Terbacil was not
detected in a national groundwater survey conducted by
EPA . In moist soils, terbacil is subject to microbial
degradation. However, data suggest that recommended rates
of terbacil use may result in its persistence for more
than one growing season .
- Breakdown in water: Contamination of
surface waters near terbacil-treated areas, and
subsequent exposure of humans and non-target organisms,
is possible due to terbacil's mobility in soil and its
high water solubility . Terbacil is stable in water
and does not readily undergo hydrolysis or
- Breakdown in vegetation: At normal
application rates, terbacil has residual phytotoxicity to
affected species in treated soils for 1 to 2 years .
Terbacil residues were phytotoxic to oats planted 3 years
after a previous application of the herbicide. For
example, in alfalfa, 12% of terbacil plus its metabolites
were still found 6 to 8 months after application .
Terbacil is most readily absorbed through the root system
of plants to which it is applied. Less is absorbed
through the leaves and stems of plants. Studies of
sugarcane plants indicate that terbacil is moved, or
"translocated," upward into the leaves after
absorption by the roots .
- Appearance: Terbacil is a white,
crystalline, odorless solid which is noncorrosive and
- Chemical Name:
- CAS Number: 5902-51-2
- Molecular Weight: 216.70
- Water Solubility: 710 mg/L @ 25 C 
- Solubility in Other Solvents: s.s. in
mineral oils and aliphatic hydrocarbons; v.s. in methyl
isobutyl ketone, butyl acetate, xylene, cyclohexanone,
dimethylformamide, and strong aqueous alkalis 
- Melting Point: 175-177 C 
- Vapor Pressure: 0.0625 mPa @ 30 C 
- Partition Coefficient: 1.8921 
- Adsorption Coefficient: 55 
- ADI: Not Available
- MCL: Not Available
- RfD: 0.013 mg/kg/day 
- PEL: Not Available
- HA: 0.09 mg/L (lifetime) 
- TLV: Not Available
DuPont Agricultural Products
Walker's Mill, Barley Mill Plaza
P.O. Box 8003
Wilmington, DE 19880-0038
- Phone: 800-441-7515
- Emergency: 800-441-3637
References for the information in this PIP can be found in
Reference List Number 10
information in this profile does not in any way replace or
supersede the information on the pesticide product labeling or
other regulatory requirements. Please refer to the pesticide