Imazapyr

261.28

261.28

617-219-8

DTXSID8034665

Clear, slightly viscous, pale yellow to dark green aqueous liquid|White to tan powder|Crystals from acetone + hexane

2933990090

91.65000

0.51

Off-white crystal

0.34 g/cm³

171 °C

425.1±55.0 °C at 760 mmHg

210.9±31.5 °C

1.632

In water, 1.13X10+4 mg/L at 25 deg C; 9.74 g/L at 15 deg C

0-6°C

1.79X10-11 mm Hg at 25 deg C (est)

LD50 orally in rats: >5000 mg/kg; dermally in rabbits: >2000 mg/kg (Paxman)

Slight ammonical odor

Henry's Law constant = 7.08X10-17 atm-cu m/mol at 25 °C (est)

pKa = 1.81|pKa1 = 1.9; pKa2 = 3.6; pKa3 = 11

157.81 Ų [M+H]+ [CCS Type: DT, Method: stepped-field]|176.07 Ų [M+Na]+ [CCS Type: DT, Method: stepped-field]|164.95 Ų [M-H]- [CCS Type: DT, Method: stepped-field]|164.4 Ų [M-H]-

Stable for at least 2 yrs at 25 °C, 1 year at 37 °C, and 3 months at 45 °C. Stable in aqueous media at pH 5 to pH 9 in the dark... In solution, the acid is decomposed in simulated sunlight|Reacts with acids or bases and strong oxidants|Hydroxyl radical reaction rate constant = 1.38X10-11 cu cm/molec-sec at 25 °C (est)

Corrosive to iron, mild steel, and brass, but not to #304 stainless steel

NONH for all modes of transport

2

36-52/53

26-61

US5682500

Xi

Stable. Incompatible with strong oxidizing agents.

P273-P305 + P351 + P338

H319-H412

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.

USEPA/Office of Pesticide Programs; Reregistration Eligibility Decision Document - Imazapyr, EPA 738-R-06-007 (2006). The RED summarizes the risk assessment conclusions and outlines any risk reduction measures necessary for the pesticide to continue to be registered in the U.S.[Available from, as of May 25, 2011: http://www.epa.gov/pesticides/reregistration/status.htm]|USEPA/Office of Pesticide Programs; Addendum to Reregistration Eligibility Decision Document - Imazapyr (October 23, 2008). The RED summarizes the risk assessment conclusions and outlines any risk reduction measures necessary for the pesticide to continue to be registered in the U.S.[Available from, as of December 23, 2011: http://www.epa.gov/pesticides/reregistration/status.htm]

|Warning|H319: Causes serious eye irritation [Warning Serious eye damage/eye irritation]|P264, P273, P280, P305+P351+P338, P337+P313, and P501|H319 (98.76%): Causes serious eye irritation [Warning Serious eye damage/eye irritation]|P264, P273, P280, P305+P351+P338, P337+P313, P391, and P501|Aggregated GHS information provided by 322 companies from 6 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Chemical-resistant gloves

Fire Extinguishing Media: Water, foam, dry chemical, or CO2. Alcohol foam is the recommended type of foam.

SRP: The scientific literature for the use of contact lenses by industrial workers is inconsistent. The benefits or detrimental effects of wearing contact lenses depend not only upon the substance, but also on factors including the form of the substance, characteristics and duration of the exposure, the uses of other eye protection equipment, and the hygiene of the lenses. However, there may be individual substances whose irritating or corrosive properties are such that the wearing of contact lenses would be harmful to the eye. In those specific cases, contact lenses should not be worn. In any event, the usual eye protection equipment should be worn even when contact lenses are in place.|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/|Chemical-resistant apron when cleaning equipment, mixing, or loading.

Irritating to eyes and skin.

Imazapyr, applied aerially as a liquid at a rate of 2.2 kg active ingredient/ha to two experimental forest plots in Alabama, was detected in the surface water of nearby streams at a concentration of 680 and 130 ug/L(1). The herbicide fell directly into streams during application(1).

Concentrations of imazapyr following forestry application in Georgia were measured at 3 sites at 69, 1 and 30, and 106 days post application(1). Residues on hardwood foliage were <0.5, 4.6 and 1.5, and <0.5 mg/kg; on ground litter: <0.5, 4.1 and 2.1, and <0.5 mg/kg; and on surface soil: <0.5, <0.5 and <0.5, abd <0.5 mg/kg, respectively(1).

LD50 Rat (male & female) oral >5000 mg/kg|LD50 Mouse (female) oral >2000 mg/kg|LD50 Rabbit (male & female) oral 4800 mg/kg|LD50 Rabbit (male & female) percutaneous >2000 mg/kg|For more Non-Human Toxicity Values (Complete) data for IMAZAPYR (7 total), please visit the HSDB record page.

/AQUATIC SPECIES/ A chronic early life stage study conducted on rainbow trout showed a decrease in larval survival at a mean measured concentration of 92.4 mg/L. The NOAEC was 43.1 mg ai/L. The study was originally classified as invalid because survival of control embryos following thinning was below 70%. However, it was upgraded to supplemental because the SEP was met and the data were still considered useful for the purpose of risk assessment. ...A chronic early life stage study conducted on the fathead minnow showed no treatment-related effects at 118 mg ai/L (highest concentration tested). A full life cycle study was also submitted for fathead minnow which showed no treatment-related effects at 120 mg ai/L. This study was classified as supplemental because the F1 generation was maintained for 4 weeks instead of 8 weeks.|/AQUATIC SPECIES/ /In/ ...a 21-day life cycle /test/ on Daphnia magna, the data that were submitted show that imazapyr concentrations up to 97.1 mg/L did not significantly affect survival, reproductive success, or growth of first generation daphnids.|/AQUATIC SPECIES/ The only sublethal effect observed in the acute aquatic animal studies is a decrease in shell deposition in the eastern oyster. The NOAEC/LOAEC for this effect was 109/173 mg/L.|/FIELD STUDIES/ An in situ microcosm study ...was conducted to assess the effects of a single application of imazapyr (stirred into the water column) at the following mean concentrations: 0.19, 2.1 or 19.8 mg/L (equivalent to 1, 10 or 100 times the expected environmental concentration from a normal application rate) on the macroinvertebrate community of a logged pond cypress dome. In situ microcosms were set up in schedule-40 polyvinyl chloride water pipes (diameter 7.62 cm; height 45.7 cm; area 45.6 sq cm) driven approximately 12 cm into the substrate and leaving a mean water column depth of 32.1 cm. The microcosms were immediately dosed with the selected treatments of imazapyr and left undisturbed for two weeks. Forty eight microcosms were set up (3 blocks of 16, each block consisting of 4 replicates of 3 treatment levels and a control). In addition, 12 cypress dome cores, divided equally among the 3 blocks were sampled at the end of the study. These allowed for testing for microcosm influences on the measured parameters. Macroinvertebrates were hand picked from each sample and prepared for identification. Organisms other than chironomids were identified at the family level or to the lowest practical taxonomic level. Chironomids were identified to the genus level. Effects on aquatic plants were not examined. Changes in the macroinvertebrate composition, chironomid biomass and chironomid head-capsule deformities were assessed. A total of 2,904 individuals representing 44 taxa were collected. The following taxa were represented: Caecidotea, Crangonyx, Dipteran, Chironomid, Polypedilum, Chironomus, Ablabesmyia, and Procladius. There were three rain events following treatment. The half-life of imazapyr was calculated to be 3.2, 3.2 and 3.4 days for the 0.19, 2.1 and 19.8 mg/L concentrations, respectively. Imazapyr did not appear to affect any of these parameters at the concentrations tested. However, these results are of limited value because potential effects at the species level were not examined. Individual species could have been affected and the results may not have picked it up because the analysis was conducted at higher taxonomic levels. In addition, effects on aquatic plants were not examined.|For more Ecotoxicity Excerpts (Complete) data for IMAZAPYR (6 total), please visit the HSDB record page.

Imazapyr's production may result in its release to the environment through various waste streams; its use as a herbicide(1) will result in its direct release to the environment(SRC).

TERRESTRIAL FATE: Based on a classification scheme(1), a Koc value of 8.81(2) indicates that imazapyr is expected to have very high mobility in soil(SRC). The pKa2 of imazapyr is 3.6(3), indicating that this compound will exist almost entirely in 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). Imazapyr is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 9.0X10-11 mm Hg(SRC), determined from a fragment constant method(5). Imazapyr is expected to biodegrade based on aerobic soil half-lives of 17.7 to 63.1 days at simulated application rates of 100 to 200 g/ha, incubated for 60 days at 25 °C(6).|TERRESTRIAL FATE: Concentrations of imazapyr following forestry application in Georgia were measured at 3 sites at 69, 1 and 30, and 106 days post application(1). Residues on hardwood foliage were <0.5, 4.6 and 1.5, and <0.5 mg/kg; on ground litter: <0.5, 4.1 and 2.1, and <0.5 mg/kg; and on surface soil: <0.5, <0.5 and <0.5, and <0.5 mg/kg, respectively(1). Imazapyr is subject to photodegradation in air-soil geospheres(2); a half-life of 30 days was reported, encompassing biochemical, chemical, and physical processes(2). Imazapyr had reported half-lives of 67 to 144 days in experiments along a Swedish railway line at application rates of 750 and 1500 g/ha(3). Small amounts of imazapyr were transported deep into the soil and was still detected in groundwater up to 8 years after application(3). Tests run on 28 railroad embankments reported a half-life for imazapyr of 4 months and a 90% loss of 8 months(4). Imazapyr concentration was mainly in the top 30 cm with a trace reported at 70 cm depth(4).|AQUATIC FATE: Based on a classification scheme(1), a Koc value of 8.81(2) indicates that imazapyr is not expected to adsorb to suspended solids and sediment(SRC). A pKa2 of 3.6(3) indicates imazapyr will exist almost entirely 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(4), an estimated BCF of 3(SRC), from its log Kow of 0.22(3) and a regression-derived equation(5), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Imazapyr was transformed using Streptomyces (strain PS1/5), incubated in aqueous culture, indicating biodegradation will occur(6). Exposure to UV light in aqueous solutions caused complete degradation of imazapyr in 48 hrs, with a half-life of 7 hrs reported(7).|AQUATIC FATE: Imazapyr, applied aerially as a liquid at a rate of 2.2 kg active ingredient/ha to two experimental forest plots in Alabama, was detected in the surface water of nearby streams at a concentration of 680 and 130 ug/L(1). The herbicide fell directly into streams during application(1).|ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), imazapyr, which has an estimated vapor pressure of 9.0X10-11 mm Hg at 25 °C(SRC), determined from a fragment constant method(2), is expected to exist solely in the particulate phase in the ambient atmosphere. Particulate-phase imazapyr may be removed from the air by wet and dry deposition(SRC).

Imazapyr is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(1). Exposure to UV light (using sun lamps, wavelengths >290 nm and <620 nm) in aqueous solutions caused complete degradation of imazapyr in 48 hrs, with a half-life of 7 hrs reported(2).

An estimated BCF of 3 was calculated for imazapyr(SRC), using a log Kow of 0.22(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).

100.00 L/kg|Using a clay loam (pH 7.4, OM 3.9%, sat capacity 54.8%, cation exchange capacity 17.4) and a loam (pH 7.75, OM 3.4%, sat capacity 45.8%, cation exchange capacity 19.84), 65 and 80% of the applied imazapyr leached out of the columns, respectively, the difference being attributed to greater clay and organic matter content in the clay loam(1). The Koc of imazapyr was found be 8.81(1). According to a classification scheme(2), this Koc value suggests that imazapyr is expected to have very high mobility in soil. In an adsorption study using 2 humic acids, no measurable adsorption of imazapyr occurred at pH 4.7, while at pH 3.6 and 3.7, the compound did adsorb(3). The pKa2, 3.6, indicates that at the lower pH values, about half of the amount of herbicide would exist in the nonionized form and most of the carboxyl groups of humic acids are combined(3); at pH 4.7, the herbicide is mainly in the ionic form and most of the carboxyl groups of humic acids are also ionized, the carboxyl group remains ionized at higher pHs(3). Using 10 soils, Kd values ranging from no detectable adsorption (pH 7.5, % organic carbon 0.86-1.39) to 3.92 (pH 4.5, % organic carbon 11.66) were obtained(3). A field experiment to determine leach rates in a Templeton silt loam pasture under 2 precipitation volumes, 283 and 208 mm, over a period of four months, resulted in imazapyr leaching below 25 cm in both high and low tests with little loss of compound after 3 months(4). Studies of 8 soil types and varied organic matter and pH levels indicated that imazapyr had high runoff from high pH and low organic matter content(5).

A pKa2 of 3.6(1) indicates imazapyr will exist almost entirely in the anion form at pH values of 5 to 9 and therefore volatilization from water and moist soil surfaces is not expected to be an important fate process(SRC). Imazapyr is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 9.0X10-11 mm Hg(SRC), determined from a fragment constant method(2).

GROUNDWATER: Imazapyr was not detected in 24 samples from two well sites in IA, detection limit 0.02 ug/L, samples were collected June to Oct 1997(1). Imazapyr was not detected in 25 groundwater samples collected in the midwestern United States from May to Aug 1998, method reporting limit of 0.01 ug/L(2).|SURFACE WATER: Imazapyr was reported as not detected to 0.03 ug/L in 38 surface water samples collected June to Oct 1997 from the Tensas, Iowa, Mississippi, Wabash and Illinois rivers(1). Imazapyr was detected in <5% of 129 surface water samples collected from 75 surface water sites from the Upper Mississippi, Missouri, and Ohio River basins in the United States from May to Aug 1998 at median and maximum concentrations of <0.01 and 0.072 ug/L, respectively, method reporting limit of 0.01 ug/L(2).

Occupational exposure to imazapyr may occur through inhalation of particulates and dermal contact with this compound at workplaces where imazapyr is produced or used(SRC). A study conducted in Georgia measuring the breathing zone concentrations of smoke suspended particulate matter, herbicide residues, and carbon monoxide found that no herbicide residues, including imazapyr, were detected in the 140 smoke samples from the 14 fires(1). Sites had been treated with labeled rates of forestry herbicides, including imazapyr and were burned within 30-149 days post application(1).

Pesticides used to destroy unwanted vegetation, especially various types of weeds, grasses (POACEAE), and woody plants. Some plants develop HERBICIDE RESISTANCE. (See all compounds classified as Herbicides.)

In rats, following oral admin, ... 87% of the dose was excreted in the urine and feces within 24 hr. In muscle and fat tissues and blood, residual levels were <0.01 mg/kg at both 24 & 192 hr.|Following foliar application, residues in plants decline rapidly in the first 24 hr. The major residue in plants is the parent compound.|Imazapyr, (unlabeled, 99.5% ai, (14)C-labeled at the 6-carbon on the pyridine ring, 93.4% ai), was administered to Sprague Dawley rats (5/sex/dose) as a single gavage dose of approximately 9.5 mg/kg or 924 mg/kg or as 14-daily doses of unlabeled followed by a single labeled dose of 9.26 mg/kg. Excretion via expired air was examined in a pilot study where two male and two female rats were given a single gavage dose of 10 mg/kg labeled imazapyr. Corn oil was used as the vehicle for all oral treatments. An additional study with five male and five female rats that received 9.94 mg/kg imazapyr by intravenous injection was also done. No sex-related differences in absorption were apparent. Within 48 hours of treatment, > 90% of the administered dose was recovered in the excreta suggesting that elimination of the labeled test material was rapid. No specific sequestering tissues or organs were identified. Seven days after treatment, essentially all the test material had been eliminated. The overall recovery of administered radioactivity for the single low-dose, multiple low-dose, and intravenous dose groups was similar and ranged from 92.1-107.7%, indicating acceptable mass balance. For the oral treatment groups, 68-81% of the administered test material was recovered in the urine and cage wash samples collected within 4 hours of treatment. Essentially all of the remainder was recovered in the feces with <0.2% of the administered dose remaining in the carcass/tissues. Rats that received the test material by intravenous injection excreted 87-95% of the administered dose in the urine and approximately 6% into the feces. This suggests that 15-28% of the administered dose recovered in the feces represents unabsorbed material.

Imazapyr, (unlabeled, 99.5% ai, (14)C-labeled at the 6-carbon on the pyridine ring, 93.4% ai). was administered to Sprague Dawley rats (5/sex/dose) as a single gavage dose of approximately 9.5 mg/kg or 924 mg/kg or as 14-daily doses of unlabeled followed by a single labeled dose of 9.26 mg/kg. Excretion via expired air was examined in a pilot study where two male and two female rats were given a single gavage dose of 10 mg/kg labeled imazapyr. Corn oil was used as the vehicle for all oral treatments. An additional study with five male and five female rats that received 9.94 mg/kg imazapyr by intravenous injection was also done. Metabolite characterization studies show that essentially all of the test material was excreted unchanged. Two minor metabolites CL 252,974 (2-((1-carbamoyl-1,2-dimethylpropyl)- carbamoyl)-nicotinic acid) and CL 60,032 (2-carbamoyl-nicotinic acid) were detected in the urine or feces of treated rats; however, their contribution combined was < 0.5% of the administered dose. Up to 12 additional unidentified metabolites were isolated, but they constituted < 3% of the administered dose. Based on the results, ... what limited metabolism of imazapyr occurs, proceeds through hydrolysis to form the 2-carbonyl derivatives: CL 252,974 and CL 60,032.

A mode or mechanism of action of imazapyr in mammals is currently unknown; however, in plants, imazapyr acts as a meristem inhibitor through inhibition of amino acid branched chain biosynthesis.|Mode of action: Systemic, contact and residual herbicide, absorbed by the foliage and roots, with rapid translocation in the xylem and phloem to the meristematic regions, where it accumulates.|Imazapyr (IMZR), Imazapic (IMZC), Imazethapyr (IMZT), Imazamox (IMZX) and Imazaquin (IMZQ) ... are classified as imidazolinone (IMI) herbicides and their mode of action is to inhibit acetohydroxyacid synthase (AHAS), an enzyme involved in the biosynthesis of the amino acids leucine, isoleucine and valine. ...

Skin decontamination. Skin contamination should be treated promptly by washing with soap and water. Contamination of the eyes should be treated immediately by prolonged flushing of the eyes with large amounts of clean water. If dermal or ocular irritation persists, medical attention should be obtained without delay. /Herbicides/|Gastrointestinal decontamination. Ingestions of these herbicides are likely to be followed by vomiting and diarrhea due to their irritant properties. Management depends on: (1) the best estimate of the quantity ingested, (2) time elapsed since ingestion, and (3) the clinical status of the subject. Activated charcoal is probably effective in limiting irritant effects and reducing absorption of most or all of these herbicides. Aluminum hydroxide antacids may be useful in neutralizing the irritant actions of more acidic agents. Sorbitol should be given to induce catharsis if bowel sounds are present and if spontaneous diarrhea has not already commenced. Dehydration and electrolyte disturbances may be severe enough to require oral or intravenous fluids. ... If large amounts of herbicide have been ingested and the patient is seen within an hour of the ingestion, gastrointestinal decontamination should be considered ... . If the amount of ingested herbicides was small, if effective emesis has already occurred, or if treatment is delayed, administer activated charcoal and sorbitol by mouth. /Herbicides/|Intravenous fluids. If serious dehydration and electrolyte depletion have occurred as a result of vomiting and diarrhea, monitor blood electrolytes and fluid balance and administer intravenous infusions of glucose, normal saline, Ringer's solution, or Ringer's lactate to restore extracellular fluid volume and electrolytes. Follow this with oral nutrients as soon as fluids can be retained. /Herbicides/|Supportive measures are ordinarily sufficient for successful management of excessive exposures to these herbicides ... . If the patient's condition deteriorates in spite of good supportive care, the operation of an alternative or additional toxicant should be suspected. /Herbicides/|For more Antidote and Emergency Treatment (Complete) data for IMAZAPYR (7 total), please visit the HSDB record page.

/CASE REPORTS/ ... Six cases of acute poisoning with Arsenal (imazapyr 23.1%) occurred during the period 1993-1997 in a single hospital. Emergency room records & medical charts were reviewed. ... Of 6 cases, 5 were suicide attempts & 1 was an act of violence inflicted on a child. Three of the 6 patients (50%) presented with severe symptoms, including impairment of consciousness & respiratory distress requiring intubation. Other presentations included metabolic acidosis (2), hypotension (2), leukocytosis (3), fever (2), mild elevation of hepatic transaminase & creatinine (2), unconjugated hyperbilirubinemia (2), oral ulceration (2), pharyngolaryngitis (2), & chemical burns of the cornea (1). All cases had copious vomiting after ingestion of Arsenal. No mortality occurred. ... According to our observations, it appeared the toxic syndrome that results from a large quantity (>100 mL) of Arsenal herbicide ingestion consists of hypotension, pulmonary dysfunction, oral mucosal & gi irritation, & transient liver & renal dysfunction.

2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid

Aqueous liquid with wetting agent|Imazapyr is formulated as a liquid, a wettable powder (in water soluble bags only), and a granular.|Soluble concentrate; granule; emulsifiable concentrate|Mixtures: imazapyr + diuron|For more Formulations/Preparations (Complete) data for IMAZAPYR (34 total), please visit the HSDB record page.

The WHO Recommended Classification of Pesticides by Hazard identifies imazapyr as unlikely to present an acute hazard in normal use; Main Use: herbicide.|Imazapyr technical was first registered in 1985; however, a non-crop end use product had been previously registered in July 1984. The first food use on corn was registered in April 1997. In 2003, the aquatic and grassland uses were registered which resulted in the establishment of additional tolerances.|Synthesis during manufacture results in technical active ingredient with a purity >95%. No additional purification is needed.|(1988) 190 kg active ingredient applied to 300 ha of National Forest lands in the United States, 15% of which were in the southern US.

Two methods are currently listed in the Pesticide Analytical Manual (PAM) Vol. II for enforcing tolerances of imazapyr in or on corn commodities; Method M 2468 is a gas chromatography/mass spectrometry (GC/MS) methods with a limit of quantitation (LOQ) of -0.01 ppm for imazapyr in or on corn grain, forage and fodder, and Method M 2657 is a capillary electrophoresis (CE) method with ultraviolet (UV) detection that has a LOQ of 0.05 ppm for imazapyr in or on corn grain, forage and fodder. CE/UV methods were proposed for determining imazapyr in or on grass forage and hay (M 3023), in livestock tissues (M 3184), in milk and milk fat (M 3075 and M 3223), and in fish and shellfish tissues (M 3066). These methods are similar to the current enforcement method M 2657, and based on the concurrent method recovery data submitted, are adequate for collecting data on residues of imazapyr in grass forage and hay, cattle tissues and milk, and fish and shellfish.|Product by GLC. Residues (1) in raspberries and bilberries, by GLC; (2) in pine branches, leaves and on forest floors, by HPLC; (3) in maize, by GC/MS or capillary electrophoresis with UV ... ; in soil or water, by HPLC.

Agrochemicals -> Herbicides