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TERRESTRIAL FATE: Based on a classification scheme(1), Koc values ranging from 5 to 143(2) indicate that imazamox is expected to have very high mobility in soil(SRC). The pKa values of imazamox have been reported as 2.3, 3.3 and 10.8(3), indicating that this compound will exist entirely in anion form in the environment and anions generally do not adsorb as strongly to soils containing organic carbon and clay as their neutral counterparts(4). Volatilization of imazamox is not expected to be an important fate process(SRC) because this chemical expected to exist as an anion in the environment and anions do not volatilize. Imazamox is primarily degraded by microbes in soil under aerobic conditions(2,3); essentially no degradation occurs under anaerobic conditions(2). Imazamox is considered moderately persistent with half-lives ranging between 15 to 142 days(2,3); its limited persistence will restrict leaching of imazamox into groundwater(2).

TERRESTRIAL FATE: In a field study with 5 soils, terrestrial dissipation half-lives ranged between 15 and 130 days(1). Leaching was found to be very limited in field studies(2).

AQUATIC FATE: Based on a classification scheme(1), Koc values ranging from 5 to 143(2) indicate that imazamox is not expected to adsorb to suspended solids and sediment(SRC). The pKa values of imazamox have been reported as 2.3, 3.3 and 10.8(3) indicating imazamox will exist 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 3.2(SRC), from its log Kow of 0.73(5) and a regression-derived equation(6), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Photodegradation can be rapid with a half-life of 6.8 hours observed in laboratory studies(2,3); this rate is only applicable at the surface of the water with rates decreasing with water depth. Imazamox is stable to hydrolysis at pH 5, 7 and 9(2). Imazamox is considered moderately persistent in soil with half-lives ranging between 15 to 142 days(2,3).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), imazamox, which has an estimated vapor pressure of 1.26X10-11 mm Hg at 25 °C determined from a fragment constant method(2), is expected to exist solely in the particulate phase in the ambient atmosphere. Particulate-phase imazamox may be removed from the air by wet and dry deposition(SRC). Imazamox photolytically decays with reported half-lives of 6.8 hours (or 0.3 days)(5,6) and 78 minutes (or 3 days)(7) for primary degradation in aqueous media. Direct aqueous photolysis results in several stable degradates(7). Photolysis in soil is a slower process with a half-life of 65 days(6). The rate of photodegradation decreases in the presence of Cu(II) and Ca(II) salts which form stable complexes with imazamox(7).

In FDA total diet studies analyzing foods as part of the pesticide monitoring program during the fiscal year 2014, imazamox was detected in 3% of food items examined at concentrations of 0.0001-0.005 ppm, in FY2013 imazamox was detected in 2% (0.0001-0.0007 ppm)(1). For fiscal years 2009 through 2012 imazamox was not listed in the reports(1). Imazamox was not listed in the FDA total diet study Market Baskets 2004 to 2005(2).

IDENTIFICATION AND USE: Imazamox is off-white powdered solid. It is a herbicide applied post-emergence in soybean. HUMAN STUDIES: In an in vitro study, human embryonic stem cells were treated with imazamox at a concentration of 0, 1, 10 or 100 umol/L, incubation did not induce cytotoxicity. ANIMAL STUDIES: In the acute toxicity studies, the substance has low acute toxicity when administered orally, dermally or by inhalation to rats. It is not a significant skin or eye irritant or a skin sensitizer. Imazamox showed no short-term and long-term toxicity after oral exposure to rats, mice and dogs up to the limit top dose level tested in each study. Based on available genotoxicity studies imazamox is unlikely to be genotoxic. The substance showed no carcinogenic potential in both species. In the multigeneration toxicity study, fertility and overall reproductive performance was not impaired. In developmental toxicity studies maternal toxicity in rats and in rabbits was observed. No developmental toxicity was observed in rats whereas agenesis of the intermediate lobe of lung and cervical hemivertebra was observed in rabbits. ECOTOXICITY STUDIES: Imazamox is practically nontoxic to avian species, finfish, aquatic invertebrates, and honeybees following acute exposure.

/AQUATIC SPECIES/ The highest concentrations of herbicides measured in flowing surface waters are often only present for short periods of time. These herbicide pulses can reach concentrations that would affect aquatic plants if present over a long time. The aim of this study was to assess the effect of a 3-hr herbicide pulse relative to the effects of long-term (4 and 7 days) exposure of six herbicides with different sites of action and different K(ow) on the growth of the floating macrophyte Lemna minor. The herbicides were the two photosynthetic inhibitors: diquat and terbuthylazine, the inhibitors of acetolactate syntase (ALS), imazamox and metsulfuron-methyl and the microtubule assembly inhibitors propyzamide and pendimethalin. The log K(ow) ranged from -4.6 to 5.2. For imazamox, metsulfuron-methyl, propyzamide and pendimethalin a 3-hr pulse induced the effect on area-specific growth as did a 4-day exposure at an approximate 10-fold higher concentration.

/PLANTS/ Alterations on growth, amino acids metabolism and some antioxidant enzyme activities as result of imazamox treatment were examined in determinate and indeterminate nodules, formed by Phaseolus vulgaris and Vicia sativa, respectively. Young seedlings of both legumes were inoculated with their respective microsymbionts and grown under controlled conditions. At vegetative growth, plants were treated with imazamox (250 uM) in the nutrient solution and harvested 7 days after. Imazamox was mainly accumulated in V. sativa where concentrations were more than six fold higher than those detected in P. vulgaris. Nodule dry weight and total nitrogen content were reduced by the herbicide treatment: the highest decrease of nodule biomass (50%) and nitrogen content (40%) were registered in V. sativa and P. vulgaris, respectively. The concentration of branched-chain amino acids (BCAA) did not change in neither determinate nor indeterminate nodules even though the acetohydroxyacid synthase activity decreased in root and nodules of both symbioses with the herbicide application. Based on this last result and taking into account that total free amino acids increased in roots but not in nodules of common vetch, a possible BCAA translocation from root to nodule could occur. Our results suggest that the maintenance of BCAA balance in nodule become a priority for the plant in such conditions. The involvement of activities glutathione-S-transferase, guaiacol peroxidase and superoxide dismutase in the response of the symbioses to imazamox are also discussed.

/OTHER TOXICITY INFORMATION/ ...Imazamox is practically nontoxic to avian species, finfish, aquatic invertebrates, and honeybees following acute exposure.

EPA has released the Interactive Chemical Safety for Sustainability (iCSS) Dashboard. The iCSS Dashboard provides an interactive tool to explore rapid, automated (or in vitro high-throughput) chemical screening data generated by the Toxicity Forecaster (ToxCast) project and the federal Toxicity Testing in the 21st century (Tox21) collaboration. /The title compound was tested by ToxCast and/or Tox21 assays/[USEPA; ICSS Dashboard Application; Available from, as of July 27, 2017: http://actor.epa.gov/dashboard/]

The experimental Koc of imazamox ranges from 5 to 143, tested in soils with 0.29 to 2.59% organic carbon(1). According to a classification scheme(2), these Koc values suggest that imazamox is expected to have very high mobility in soil. The pKa values of imazamox have been reported as 2.3, 3.3 and 10.8(3), indicating that this compound will exist entirely in anion form in the environment and anions generally do not adsorb as strongly to soils containing organic carbon and clay than their neutral counterparts(4). While imazamox is considered very mobile, the terminal soil metabolite is moderately mobile to immobile, with Koc values ranging between 331 to 1924(5). Leaching of imazamox in field studies was very limited(5). Imazamox is generally weakly bound to soil, but adsorption increases as organic matter and clay content increase and decreasing pH can increase binding due to ionization(3). Adsorption is irreversible and increases with time and as soil becomes drier(3). Imazamox remains in the top 30 cm (12 inches) of soil and field studies suggest little potential for movement with surface water(3).

/PREGNANCY AND HUMAN REPRODUCTION/ In an in vitro study, human embryonic stem cells (WA09) were treated with imazamox at a concentration of 0, 1, 10 or 100 umol/L. Metabolomic changes were assessed by liquid chromatographic-mass spectrometric analysis. According to the authors, incubation did not induce cytotoxicity. Data were analysed with models to predict developmental toxicity, which were set up with data from (1) pharmaceutical agents or (2) selected pesticides from the USEPA's Toxicity Reference Database (ToxRefDB). ...

Imazamox's production may result in its release to the environment through various waste streams; its use as a broad-spectrum herbicide for post-emergence control of broadleaf weeds and grass (1,2) will result in its direct release to the environment(SRC).

AEROBIC: Imazamox decays with half-lives of 25 and 142 days in soil and water-sediment, respectively(1,2). Imazamox is considered moderately persistent in soil, undergoing aerobic degradation in sandy loam soil (half-life = 27 days) to immobile-moderately mobile, inactive (non-herbicidal) metabolites(2). The range of dissipation half-lives is 15 to 130 days with the most representative half-lives appearing to be 35 to 50 days(2); limited persistence will restrict much of imazamox from reaching groundwater(2). Typical field half-lives of 20-30 days have also been reported(3).

ANAEROBIC: Imazamox is not susceptible to anaerobic biodegradation in water and soil(1).

Imazamox concentrations in whole and edible bluegill fish tissue were below the quantification limit, and the BCF for inedible tissue was less than 1X the concentration tested(1). An estimated BCF of 3.2 was calculated in fish for imazamox(SRC), using a log Kow of 0.73(2) and a regression-derived equation(3). According to a classification scheme(4), this BCF data suggests the potential for bioconcentration in aquatic organisms is low(SRC).

The herbicide imazamox, (+-) 2, -[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-(methoxymethyl)-3-pyridinecarboxylic acid, is exempt from the requirement of a tolerance on all food commodities when applied as a herbicide in accordance with good agricultural practices.

Pesticide Fact Sheet: Name of Chemical: Imazamox (Raptor Herbicide); Reason for Issuance: Conditional Registration; Date Issued: May 22, 1997.

Used as broad spectrum post-emergence herbicide for soybeans; [HSDB]

Farming (Pesticides) [Category: Industry]

For imazamox (USEPA/OPP Pesticide Code: 129171) 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

This is a man-made compound that is used as a pesticide.

Imazamox is produced by reaction of 2,3-dicarboxymethyl-5-methoxymethylpyridine with 2-aminoamide-3-methylbutane in the presence of two equivalents of potassium tert-butoxide.

Preparation: R. F. Doehner, Jr., European Patent Office patent 254951; idem et al., United States of America patent 5334576 (1988, 1994 both to American Cyanamid).

5-Hydroxymethyl-2,3-pyridinedicarboxylic acid undergoes dehydration (to form the anhydride), a condensation reaction, and hydrolysis, followed by cyclization to form the imidazolinone ring, and precipitation as the mfg use product.

Raptor Herbicide Technical (BASF Corporation): Active ingredient: imazamox 97.4%.

Raptor Herbicide (BASF Corporation): Active ingredient: imazamox 12.1%.

Raptor DG Herbicide (BASF Corporation): Active ingredient: imazamox 70%.

Clearcast Herbicide (BASF Corporation): Active ingredient: imazamox 12.1%.

For more Formulations/Preparations (Complete) data for Imazamox (10 total), please visit the HSDB record page.

Imazamox is a selective broad-spectrum herbicide with contact and residual activities, used post-emergence for the control of broadleaf and grass weeds in soya beans and other vegetables grown in rotation with sugar beet and other crops. It inhibits acetolactate synthase.