E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension Offices of
Cornell University, Michigan State University, Oregon State University, and
University of California at Davis. Major support and funding was provided
by the USDA/Extension Service/National Agricultural Pesticide Impact
Publication Date: 9/93
TRADE OR OTHER NAMES
The trade names for herbicides containing this product are Garlon,
Turflon, Access, Redeem, Crossbow, Grazon and ET. The herbicide may be mixed
with picloram or with 2,4-D to extend its utility range (8).
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 (7). Unlike a similar product 2,4,5-T, which has been
banned in the United States, there is no possibility of dioxin impurities
occurring in triclopyr.
Some or all applications of the product Access may be classified as
Restricted Use Pesticides (RUP). Restricted Use Pesticides may be purchased
and used only by certified applicators.
(NOTE: Unless otherwise specified, triclopyr will be assumed to be the
technical material for this document.)
The product will either have a DANGER or CAUTION signal word on the label
depending on the specific formulation. Products marked DANGER include Garlon
3A, Redeem, Turflon Amine.
The oral LD50 of triclopyr in rats ranges from 630 to 729 mg/kg and from
2,000 to 3,000 mg/kg for various formulated products. Similar differences
were noted for skin toxicity in the rabbit The LD50 for the technical
material was greater than 2,000 mg/kg and greater than 4,000 mg/kg for the
formulations. Inhalation of triclopyr (technical) did not affect rats but
inhalation of some of the formulations did cause nasal irritations. A similar
result was seen when rabbit eyes were exposed. The technical material had only
a slight effect on rabbit eyes and the undiluted formulated material caused
significant eye irritation. Other oral LD50 values for triclopyr are 550
mg/kg in the rabbit and 310 mg/kg in the guinea pig.
Rats fed diets containing between 3 and 30 mg/kg/day of triclopyr
experienced no ill effects. Males fed much higher doses (100 mg/kg) had
decreased liver and body weight and increased kidney weight. The male mice
were also sensitive at moderate doses. They had reduced liver weight at 60
mg/kg/day (4). Monkeys fed small amounts of triclopyr (30 mg/kg/day) had no
Triclopyr fed to rabbits daily at low to moderate doses (25 to 100 mg/kg)
caused some maternal toxicity and death but not fetal toxicity or birth
defects. The maternal mortality was inconsistent with other studies. There
is not enough date to draw any conclusion about the reproductive hazards of
triclopyr due to chronic exposure in humans.
Pregnant rats given moderate doses (up to 200 mg/kg/day) on days 6-15 of
gestation had offspring with mild fetotoxicity, but no birth defects (9).
There were no teratogenic effects in rabbits treated in a similar manner at 10
or 20 mg/kg/day. The evidence suggests that the human risk of birth defects
is fairly low due to chronic exposure to triclopyr.
Both bacteria and isolated cells did not mutate in response to the
presence of triclopyr. Another mutagen study using rats was weakly positive,
but negative in mice, the more sensitive species. There were no chromosome
changes noted in rat bone marrow. Triclopyr is not considered to be mutagenic.
Rats and mice fed low levels (3 to 30 mg/kg/day) of triclopyr for two
years showed no carcinogenic response. 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 (1).
Garlon 3A, the triethylamine salt of triclopyr, can cause considerable
eye and skin irritation. Prolonged skin contact will cause flaking but a
different formulation, Garlon 4, is not as severe a skin and eye irritant (4).
Fate in Humans and Animals
When rats were intravenously dosed at 5 mg/kg, most of the dose was
excreted in urine. At 100 mg/kg urinary excretion still predominated. At
higher doses, an increasing amount was in the feces. In dogs, 0.5 mg/kg of
triclopyr had a half-life of 14 hours for clearance from blood plasma, and a
dose of 20 mg/kg had a half-life of 95 hours reflecting the unique capacity
for excretion of organic acids by the dog. Excreted triclopyr is mostly the
parent compound but small quantities of breakdown products are also present.
Triclopyr was found in greater quantities in the liver and fatty tissue
of the rat when compared to the blood plasma. The dog had higher levels in
the kidney than in the blood plasma, and in monkeys, residues in all tissues
were the same as in blood plasma (4). The compound is not expected to
concentrate to any significant degree in the tissues of animals.
Triclopyr is slightly toxic to mallard ducks. When fed the compound, the
LD50 was 1698 mg/kg. Bobwhite quail and Japanese quail fed for eight days had
LC50's of 2,935 ppm and 3,278 ppm, respectively.
The compound is practically non-toxic to fish. Triclopyr has a LC50 of
117 ppm for rainbow trout and a 96-hour LC50 of 148 ppm for bluegill sunfish.
The compound is practically non-toxic to the aquatic invertebrate Daphnia
magna, a water flea (LC50 for the triclopyr salt of 1170 ppm) (10). The
compound is non-toxic to bees (7).
In natural soil and in aquatic environments, the two of the formulations
rapidly convert to the acid which in turn is neutralized to a salt. Triclopyr
is not strongly adsorbed to soil particles, has the potential to be mobile,
and is fairly rapidly degraded by soil microorganisms. Concentrations of 500
ppm had no apparent effects on the growth of common soil microorganisms.
Triclopyr was tested but not found in a host of groundwater sites throughout
the country (11).
The half-life in soil is 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 (trichloro-pyridinol) in 15 soils ranged from 8-
279 days with 12 of the tested soils having half-lives of less than 90 days.
Longer half-lives occur in cold or arid conditions.
Breakdown by the action of sunlight is the major means of triclopyr
degradation in water. The half-life is 10 hours at 25 degrees C. The major
metabolite is trichloropyridinol.
Triclopyr is readily translocated throughout a plant after being taken up
by either roots or the foliage. Cowberries with residues of 2.4 ppm at six
days had 0.7-1.1 ppm at 30-36 days, and 0.2-0.3 ppm in 92-98 days. The
estimated half-life in aboveground drying foliage as in a forest overstory is
two to three months.
PHYSICAL PROPERTIES AND GUIDELINES
|NOEL (dog): ||2.5 mg/kg/day
|RfD: ||0.025 mg/kg/day (OPP)
|CAS #: ||55335-06-3
|Chemical name: ||[(3,5,6-trichloro-2-pyridinyl) Oxy]acetic acid
|Chemical class/use: ||triethylamino acid herbicide
|Solubility in water: ||amine salt: 2,100,000 mg/l; ester: 23 mg/l
|Solubility in other solvents: ||acetone 98.9 g/100 g; benzene 2.73 g/100 g; acetonitrile 12.6 g/100 g
|Melting Point: ||148-150 degrees C
|Vapor Pressure: ||1.26 x 10 to the minus 6 mm Hg at 25 degrees C
9002 Purdue Rd.
Review by Basic Manufacturer:
Comments solicited: November, 1992
Comments received: December, 1992
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