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in 1996. EXTOXNET no longer updates this information, but it may be useful
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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Trade names for herbicides containing triclopyr include Access,
Crossbow, ET, Garlon, Grazon, PathFinder, Redeem, Rely, Remedy,
and Turflon. The herbicide may be mixed with picloram or with
2,4-D to extend its utility range.
Some or all applications of the product Access may be classified
as Restricted Use. Restricted Use Pesticides (RUPs) may be
purchased and used only by certified applicators. It is toxicity
class III - slightly toxic, but can cause eye irritation. The
product will either have the Signal Word DANGER or CAUTION on the
label, depending on the specific formulation. Products labeled
DANGER include Garlon 3A, Redeem, and Turflon Amine.
Triclopyr, a pyridine, is a selective systemic herbicide used for
control of woody and broadleaf plants along rights-of-way, in
forests, on industrial lands, and on grasslands and parklands.
Unlike a similar product, 2,4,5-T, which has been banned in the
U.S., dioxin impurities do not occur in triclopyr. Over 70,000
pounds of triclopyr are used annually in the U.S. Triclopyr is
commercially available mainly as a triethylamine salt or
butoxyethyl ester of the parent compound.
Unless otherwise specified, data presented refer to the
technical grade of the parent compound.
is commercially available mainly as a triethylamine salt or
butoxyethyl ester of the parent compound.
- Acute toxicity: The oral LD50 of
triclopyr in rats ranges from 630 to 729 mg/kg [1,6], and
is over 2000 mg/kg for various amine and ester formulated
products . Other oral LD50 values for triclopyr are
550 mg/kg in the rabbit and 310 mg/kg in the guinea pig
[1,6]. The dermal LD50 for the technical material in
rabbits is greater than 2000 mg/kg, and greater than 4000
mg/kg for the formulations [1,6]. Inhalation of triclopyr
did not affect rats, but inhalation of some of the
formulations did cause nasal irritation . A similar
result was seen when rabbit eyes were exposed. The
technical material had only a slight effect on rabbit
eyes, while some formulations caused significant eye
irritation . These data indicate triclopyr is slightly
- Chronic toxicity: Rats fed diets
containing between 3 and 30 mg/kg/day of triclopyr
experienced no ill effects . Male rats fed much higher
doses (100 mg/kg/day) had decreased liver and body weight
and increased kidney weight . Male mice also showed
reduced liver weight but at 60 mg/kg/day . Monkeys fed
smaller doses of triclopyr (20 mg/kg/day) showed no
adverse effects .
- Reproductive effects: Triclopyr fed to
rabbits on days 6 to 18 of gestation at doses of 25, 50,
and 100 mg/kg/day produced no effects on maternal body
weight, litter size, or fetal body weight . A
three-generation study of rats at doses of 3, 10, and 30
mg/kg/day for an 8- to 10-week period prior to breeding
of each generation showed no impact of triclopyr on
fertility rates [6,133]. Triclopyr does not appear to
cause reproductive toxicity.
- Teratogenic effects: Pregnant rats given
moderate to high doses of 50, 100, and 200 mg/kg/day on
days 6 to 15 of gestation had offspring with mild
fetotoxicity, but no birth defects . There were no
teratogenic effects in rabbits treated on days 6 to 18 of
gestation at dose rates of 10 and 25 mg/kg/day. These
data suggest that triclopyr is not teratogenic.
- Mutagenic effects: Triclopyr is
nonmutagenic in bacterial and cytogenetic assay systems
. A mutagenicity study using rats was weakly positive,
but a negative result was found in mice, the more
sensitive species . Based on these data, triclopyr is
unlikely to be mutagenic.
- Carcinogenic effects: Rats and mice fed
oral doses of triclopyr at 3 to 30 mg/kg/day for 2 years
showed no carcinogenic response [6,134]. Even though the
mice did have a high incidence of lymph cancer, this
incidence were apparently characteristic of the
particular strain of mice and did not represent a
dose-related effect [119,134]. Based on these data,
triclopyr is unlikely to be carcinogenic.
- Organ toxicity: Organs affected by
exposure to triclopyr include the kidneys and liver .
- Fate in humans and animals: Data from
animal studies indicate that triclopyr is rapidly
eliminated via the urine as the unchanged parent compound
. At higher oral doses, some triclopyr may be
eliminated through the feces as the absorption capacity
of the intestine is exceeded [6,134]. Reported half-lives
for elimination of triclopyr from mammals are 14 hours
(dog) and <24 hours (monkeys). A human elimination
half-life of approximately 5 hours has been suggested
. Minor metabolites of triclopyr may include
- Effects on birds: Triclopyr is slightly
to practically nontoxic to birds. The LD50 of the parent
compound in the mallard duck is 1698 mg/kg, while the
formulated compounds are of lower toxicity [6,58]. The
LC50 in bobwhite quail and Japanese quail fed triclopyr
for 8 days are 2935 ppm and 3278 ppm, respectively .
- Effects on aquatic organisms: The parent
compound and amine salt are practically nontoxic to fish.
Triclopyr has a LC50 (96-hour) of 117 mg/L in rainbow
trout and 148 mg/L in bluegill sunfish . The compound
is practically nontoxic to the aquatic invertebrate
Daphnia magna, a waterflea, with a reported LC50 for the
amine salt of 1170 mg/L . The ester formulation has
reported 96-hour LC50 values of 0.74 mg/L and 0.87 mg/L
in the rainbow trout and bluegill sunfish, respectively
[6,137]. The compound has little if any potential to
accumulate in aquatic organisms. The bioconcentration
factor for triclopyr in whole bluegill sunfish is only
- Effects on other organisms: The compound
is nontoxic to bees .
- Breakdown in soil and groundwater: In
natural soil and in aquatic environments, the ester and
amine salt formulations rapidly convert to the acid,
which in turn is neutralized to a relatively nontoxic
salt. It is effectively degraded by soil microorganisms
and has a moderate persistence in soil environments .
The half-life in soil ranges from 30 to 90 days,
depending on soil type and environmental conditions, with
an average of about 46 days . The half-life of one
of the breakdown products (trichloropyridinol) in 15
soils ranged from 8 to 279 days, with 12 of the tested
soils having half-lives of less than 90 days. Longer
half-lives may occur in cold or arid conditions.
Triclopyr is not strongly adsorbed to soil particles and
has the potential to be mobile .
- Breakdown in water: Triclopyr is not
readily hydrolyzed at pH 5 to 9. Hydrolysis of the ester
and the amine salt occurs rapidly and results in
formation of triclopyr . Reported half-lives in water
are 2.8 to 14.1 hours, depending on season and depth of
water . The ester formulation half-life is from 12.5
to 83.4 hours . In water, the most important
breakdown process is photolysis .
- Breakdown in vegetation: Triclopyr is
readily translocated throughout a plant after being taken
up by either roots or the foliage. Cowberries contained
residues of 2.4 ppm at 6 days, 0.7 to 1.1 ppm at 30 to 36
days, and 0.2 to 0.3 ppm at 92 to 98 days after
application. The estimated half-life in aboveground
drying foliage as in a forest overstory is 2 to 3 months
- Appearance: Triclopyr is a fluffy,
colorless solid at room temperature and is stable under
normal storage conditions . Values presented below are
for the parent acid.
- Chemical Name:
3,5,6-trichloro-2-pyridyloxyacetic acid 
- CAS Number: 55335-06-3
- Molecular Weight: 256.48
- Water Solubility: 440 mg/L @ 25 C 
- Solubility in Other Solvents: v.s. in
acetone, acetonitrile, xylene, and benzene; s. in hexane
- Melting Point: 148-150 C 
- Vapor Pressure: 0.168 mPa @ 25 C 
- Partition Coefficient: 0.4216 
- Adsorption Coefficient: 20 (amine salt,
estimated ); 780 (ester) 
- ADI: Not Available
- MCL: Not Available
- RfD: 0.025 mg/kg/day 
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
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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