---

The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

---

E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Triclopyr

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.

Regulatory Status: 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.

Chemical Class: pyridine compound

Introduction: 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.

Formulation: Triclopyr is commercially available mainly as a triethylamine salt or butoxyethyl ester of the parent compound.

Toxicological Effects:

• 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 [8]. 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 [6]. 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 [6]. These data indicate triclopyr is slightly toxic.
• Chronic toxicity: Rats fed diets containing between 3 and 30 mg/kg/day of triclopyr experienced no ill effects [6]. Male rats fed much higher doses (100 mg/kg/day) had decreased liver and body weight and increased kidney weight [6]. Male mice also showed reduced liver weight but at 60 mg/kg/day [6]. Monkeys fed smaller doses of triclopyr (20 mg/kg/day) showed no adverse effects [6].
• 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 [6]. 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 [133]. 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 [6]. A mutagenicity study using rats was weakly positive, but a negative result was found in mice, the more sensitive species [6]. 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 [6].

• Fate in humans and animals: Data from animal studies indicate that triclopyr is rapidly eliminated via the urine as the unchanged parent compound [6]. 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 [135]. Minor metabolites of triclopyr may include trichloropyridinal [6].

Ecological Effects:

• 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 [6].
• 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 [6]. 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 [136]. 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 1.08.
• Effects on other organisms: The compound is nontoxic to bees [1].

Environmental Fate:

• 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 [6]. 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 [137]. 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 [6].
• 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 [6]. Reported half-lives in water are 2.8 to 14.1 hours, depending on season and depth of water [137]. The ester formulation half-life is from 12.5 to 83.4 hours [137]. In water, the most important breakdown process is photolysis [137].
• 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 [6].

Physical Properties:

• Appearance: Triclopyr is a fluffy, colorless solid at room temperature and is stable under normal storage conditions [1]. Values presented below are for the parent acid.
• Chemical Name: 3,5,6-trichloro-2-pyridyloxyacetic acid [1]
• CAS Number: 55335-06-3
• Molecular Weight: 256.48
• Water Solubility: 440 mg/L @ 25 C [1]
• Solubility in Other Solvents: v.s. in acetone, acetonitrile, xylene, and benzene; s. in hexane [1]
• Melting Point: 148-150 C [1]
• Vapor Pressure: 0.168 mPa @ 25 C [1]
• Partition Coefficient: 0.4216 [58]
• Adsorption Coefficient: 20 (amine salt, estimated ); 780 (ester) [11]

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: 0.025 mg/kg/day [13]
• PEL: Not Available
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

DowElanco
9330 Zionsville Road
Indianapolis, IN 46268-1054

• Phone: 317-337-7352
• Emergency: 800-258-3033
  

References:

References for the information in this PIP can be found in Reference List Number 10

DISCLAIMER: The 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 product labeling.