Aminopyralid

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal and plant life; and conformance with environmental and public health regulations.

For several good reasons, .... herbicides ... should be handled and applied only with full attention to safety measures that minimize personal contact. Many formulations contain adjuvants (stabilizers, penetrants, surfactants) that may have significant irritating and toxic effects. A number of premixed formulations contain two or more active ingredients; the companion pesticides may be more toxic than the principal herbicide. Good hygienic practice should not be disregarded just because a pesticide is reported to have a high LD50 in laboratory rodents. /Herbicides/

Tolerances are established for residues of the herbicide aminopyralid, 4-amino-3,6-dichloro-2-pyridinecarboxylic acid, including its metabolites and degradates, in or on the commodities in the table below. Compliance with the tolerance levels specified below is to be determined by measuring only free and conjugated aminopyralid. [Table#7800]

Tolerances are established for residues of the herbicide aminopyralid, 4-amino-3,6-dichloro-2-pyridinecarboxylic acid, including its metabolites and degradates, in or on the commodities in the table below. Compliance with the tolerance levels specified below is to be determined by measuring only aminopyralid. [Table#7801]

LC50; Species: Oncorhynchus mykiss (Rainbow trout); Conditions: freshwater, static; Concentration: >100 mg/L for 96 hr /94.5% technical/

LC50; Species: Lepomis macrochirus (Bluegill sunfish); Conditions: freshwater, static; Concentration: >100 mg/L for 96 hr /94.5% technical/

LC50; Species: Rana pipiens (Northern leopard frog); Conditions: freshwater, static; Concentration: >95.2 mg/L for 96 hr /94.5% technical/

LC50; Species: Cyprinodon variegatus (Sheepshead minnow); Conditions: saltwater, static; Concentration: >120 mg/L for 96 hr /94.5% technical/

For more Ecotoxicity Values (Complete) data for Aminopyralid (15 total), please visit the HSDB record page.

TERRESTRIAL FATE: Based on a classification scheme(1), a Koc range of 1.05 to 24.3(2), indicates that aminopyralid is expected to have very high mobility in soil(SRC). The pKa of aminopyralid is 2.56(2), indicating that this compound will partially exist in the anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(3). Volatilization of aminopyralid from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 1.7X10-12 atm-cu m/mole(SRC), using a fragment constant estimation method(3). Aminopyralid is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 1.92X10-10 mm Hg at 25 °C(2). Biodegradation half-lives in soil ranging from 31.5 to 533.2 days(4) suggest that biodegradation is not an important environmental fate process in soil(SRC).

AQUATIC FATE: Based on a classification scheme(1), a Koc range of 1.05 to 24.3(2) indicates that aminopyralid is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(3) based upon an estimated Henry's Law constant of 1.7X10-12 atm-cu m/mole(SRC), developed using a fragment constant estimation method(4). A pKa of 2.56(2) indicates aminopyralid will exist partially in the anion form at pH values of 5 to 9 and therefore volatilization from water surfaces is not expected to be an important fate process(SRC). According to a classification scheme(5), an estimated BCF of 3(SRC), from its log Kow of 0.201(2) and a regression-derived equation(6), suggests the potential for bioconcentration in aquatic organisms is low(SRC). The compound readily photolyzed in water with a half-life of 0.6 days(7). In sediment-water systems, the biodegradation half-life range was 462 to 990 days(2), suggesting that biodegradation is not an important environmental fate process in water(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), aminopyralid, which has a vapor pressure of 1.92X10-10 mm Hg at 25 °C(2), is expected to exist solely in the particulate phase in the ambient atmosphere. Particulate-phase aminopyralid may be removed from the air by wet or dry deposition(SRC). The compound readily photolyzed in water with a half-life of 0.6 days and weakly photolyzed on soil, with a half-life of 72 days reported(1); this suggests that the compound may be susceptible to direct photolysis in sunlight(SRC).

/BIRDS and MAMMALS/ /In an/ acute oral toxicity study conducted with northern bobwhite quail, ...the LD50 was greater than the highest dose tested , i.e., LD50 >292 mg a.e./kg bw. Clinical signs of toxicity (ruffled appearance, loss of coordination, lethargy, neck curl, prostrate posture, and/or lower limb weakness) were observed in oral treatments of 23 through 292 mg a.e./kg bw; therefore, the acute oral no-observed effect level is 14 mg a.e./kg bw. These effects were transitory, with time affected increasing with concentration. No treatment-related effects on body weight changes or feed consumption were observed.

/AQUATIC SPECIES/ Acute toxicity testing of estuarine/marine invertebrates was conducted using the mysid shrimp (Americamysis bahia) and Eastern oyster (Crassostrea virginica). In a 96-hr acute toxicity study of mysid shrimp, no mortality or sub-lethal effects were observed for aminopyralid-treated groups at up to the limit concentration of 100 mg a.e./L. The 96-hr LC50 value exceeds 100 mg a.e./L, and aminopyralid is classified as practically non-toxic to the estuarine/marine mysids on an acute exposure basis.

/AQUATIC SPECIES/ In the 96-hr acute shell deposition toxicity study of Eastern oysters, the EC50 value exceeds 89 mg a.e./L, and no mortality or sub-lethal effects were observed. Aminopyralid is classified as slightly toxic to the estuarine/marine mollusk on an acute exposure basis.

/AQUATIC SPECIES/ In the rainbow trout /96-hour acute/ test, partial loss of equilibrium was observed in 7% of the fish in the treatment group. In the test with bluegill sunfish, no mortality or sublethal effects were observed in the treatment group. For both species, the LC50 values are higher than 100 mg a.e./L, and aminopyralid is classified as practically non-toxic to freshwater fish on an acute exposure basis.

For more Ecotoxicity Excerpts (Complete) data for Aminopyralid (7 total), please visit the HSDB record page.

The Koc of aminopyralid ranges from 1.05 to 24.3 mL/g(1). A Koc range of 0.0 to 38.9 mL/g (mean 10.8 mL/g) has also been reported(3). According to a classification scheme(3), this Koc range suggests that aminopyralid is expected to have very high mobility in soil. The pKa of aminopyralid is 2.56(3), indicating that this compound will partially exist in the anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(4). Kd values ranging from 0.03 to 0.72 have been reported for aminopyralid(1).

AEROBIC: Aminopyralid biodegrades slowly in soil as indicated by half-lives ranging from 31.5 to 533.2 days; CO2 accounted for 66 to 73% of applied compound. In sediment-water systems, the half-life was 462 to 990 days(1). Laboratory studies using soil incubated at 20 °C resulted in a half-life range of 18 to 143 days (mean of 67 days)(2).

An estimated BCF of 3 was calculated in fish for aminopyralid(SRC), using a log Kow of 0.201(1) and a regression-derived equation(2). According to a classification scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC).

The Henry's Law constant for aminopyralid is estimated as 1.7X10-12 atm-cu m/mole(SRC) using a fragment constant estimation method(1). This Henry's Law constant indicates that aminopyralid is expected to be essentially nonvolatile from water and moist soil surfaces(2). Aminopyralid is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 1.92X10-10 mm Hg(3).

/LABORATORY ANIMALS: Acute Exposure/ Groups of five overnight-fasted male and female Fischer 344 rats received aminopyralid (purity: 94.5%) at a dose of 5000 mg/kg bw by gavage as two doses at 2500 mg/kg administered with an interval of 1 hr, as a 50% mixture in 0.5% aqueous methylcellulose. The rats were observed for mortality, clinical signs and body-weight development during the 14 days after dosing and were then necropsied. One male rat died on test day 3, its appearance before death being consistent with a moribund condition. Clinical observations in the surviving rats revealed a high incidence of various combinations of perineal, perioral and perinasal soiling, watery faeces and a lower incidence of periocular soiling, decreases in muscle tone, resistance to removal, extensor-thrust, and reactivity to handling were observed. All surviving animals recovered completely by the time of study termination. Four rats had transient body-weight loss during the first week of the study, but all rats gained weight over the duration of the study. On necropsy, the male that died had treatment-related gross findings consisting of haemolysis, gas in the gastrointestinal tract and perineal soiling. Surviving animals had no treatment-related gross pathological changes

/LABORATORY ANIMALS: Acute Exposure/ Groups of five overnight fasted male and female Fischer 344 rats received a single dose of undiluted GF-871 (41.9% aminopyralid TIPA) at a dose of 5000 mg/kg bw (equivalent to a dose of aminopyralid of 1085 mg/kg bw) by gavage. The rats were observed for mortality, clinical signs and body-weight development during the next 14 days and were then necropsied. The study complied with GLP. All animals survived the 14-day observation period and gained weight. Clinical observations consisted of bilateral cloudy eyes in all animals on day 1, lacrimation, watery or soft feces and soiling of the periocular and/or perineal regions. All clinical signs resolved by test day 4. No treatment-related pathological changes were observed. /Aminopyralid TIPA/

/LABORATORY ANIMALS: Acute Exposure/ Five male and five female Fischer 344 rats were treated by dermal patch application for 24 hr with aminopyralid (purity, 94.5%) at a dose of 5000 mg/kg bw, moistened with 0.5 mL of 0.5% aqueous methylcellulose. The rats were observed for mortality, clinical signs and body-weight development during the next 14 days and were then necropsied. The study complied with GLP. All animals survived the 14-day observation period. Clinical observations consisted of perioral soiling in one male and two females on test day 1 or 2 and periocular soiling in one male on test day 1. All animals lost weight by test day 2, but gained weight over the remainder of the study. There were no gross pathological observations.

/LABORATORY ANIMALS: Acute Exposure/ Five male and five female Fischer 344 rats were treated by dermal patch application for 24 hr with GF-871 (41.9% aminopyralid TIPA) at a dose of 5000 mg/kg bw (equivalent to aminopyralid at a dose of 1085 mg/kg bw). The rats were observed for mortality, clinical signs and body-weight development during the next 14 days and were then necropsied. The study complied with GLP. All animals survived the 14-day observation period. After a body-weight loss on test day 2 in all animals, all animals gained weight over the remainder of the study. Clinical observations consisted of perineal soiling in one male and reddening of the skin on the test site in two males. There were no gross pathological observations. /Aminopyralid TIPA/

Aminopyralid is stable to hydrolysis in the environment(1); the compound was stable at pH 5, 7 and 9 and 20 °C for 31 days(2). The compound readily photolyzed in water with a half-life of 0.6 days and weakly photolyzed on soil, with a half-life of 72 days reported(1).

Aminopyralid's production may result in its release to the environment through various waste streams; its use as a herbicide will result in its direct release to the environment. If released to air, a vapor pressure of 1.92X10-10 mm Hg at 25 °C indicates aminopyralid will exist solely in the particulate phase in the atmosphere. Particulate-phase aminopyralid will be removed from the atmosphere by wet or dry deposition. A photodegradation half-life of 0.6 days in water and 72 days on soil suggests that the compound may be susceptible to direct photolysis in sunlight. If released to soil, aminopyralid is expected to have very high mobility based upon a Koc range of 1.04 to 24.3. The pKa of aminopyralid is 2.56, indicating that this compound will exist partially in the anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts. Volatilization from moist soil surfaces is not expected to be an important fate process based upon an estimated Henry's Law constant of 1.7X10-12 atm-cu m/mole. Aminopyralid may not volatilize from dry soil surfaces based upon its vapor pressure. Biodegradation half-lives in soil ranging from 31.5 to 533.2 days suggest that biodegradation is not an important environmental fate process in soil. If released into water, aminopyralid is not expected to adsorb to suspended solids and sediment based upon the Koc. In sediment-water systems, a biodegradation half-life range of 462 to 990 days suggests that biodegradation is not an important environmental fate process in water. Volatilization from water surfaces is not expected to be an important fate process based upon this compound's estimated Henry's Law constant. The pKa indicates aminopyralid will exist partially in the anion form at pH values of 5 to 9 and therefore volatilization from water surfaces is not expected to be an important fate process. An estimated BCF of 3 suggests the potential for bioconcentration in aquatic organisms is low. Aminopyralid is stable to hydrolysis in the environment. Occupational exposure to aminopyralid may occur through inhalation and dermal contact with this compound at workplaces where aminopyralid is produced or used. (SRC)

Tolerances are established for residues of the herbicide aminopyralid, 4-amino-3,6-dichloro-2-pyridinecarboxylic acid, including its metabolites and degradates, in or on the commodities in the table below. Compliance with the tolerance levels specified below is to be determined by measuring only free and conjugated aminopyralid. [Table#7802]

Tolerances are established for residues of the herbicide aminopyralid, 4-amino-3,6-dichloro-2-pyridinecarboxylic acid, including its metabolites and degradates, in or on the commodities in the table below. Compliance with the tolerance levels specified below is to be determined by measuring only aminopyralid. [Table#7803]

For aminopyralid (USEPA/OPP Pesticide Code: 005100) ACTIVE products with label matches. /SRP: Registered for use in the U.S. but approved pesticide uses may change periodically and so federal, state and local authorities must be consulted for currently approved uses./

Herbicide

For industrial vegetation, rangeland, and pastures

Emulsion, water in oil

Premix Partners: Fluroxypyr; Metsulfuron-methyl

Aminopyralid Technical (Dow Agrosciences LLC) Aminopyralid 95.3%

Cleanwave (Dow Agrosciences LLC) Aminopyralid 1.92%, Fluroxypyr meptyl 20.22%

Grazonnext HL (Dow Agrosciences LLC) Aminopyralid 8.24%, Dimethylamine 2,4-dichlorophenoxyacetate 41.26%