Florasulam

LD50; Species: Coturnix japonica (Japanese quail, age 8 wk) oral 1047 mg/kg bw

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

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

EC50; Species: Daphnia magna (Water flea); Conditions: static; Concentration: >292 mg/L for 48 hr; Effect: immobilization

For more Ecotoxicity Values (Complete) data for Florasulam (10 total), please visit the HSDB record page.

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 160(SRC), determined from a structure estimation method(2), indicates that florasulam is expected to have moderate mobility in soil(SRC). The pKa of florasulam is 4.54(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). Volatilization of florasulam from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 5.7X10-12 atm-cu m/mole(SRC), based upon its vapor pressure, 7.5X10-8 mm Hg(3), and water solubility, 6.36X10+3 mg/L(3). Based on experiments using moist and air dried soil exposed to light and dark the estimated photodegradation half-life on soil in summer at 40 deg N latitude was 14 days(5). Florasulam is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(3). An average biodegradation half-life of 2.4 days with ultimate mineralization to CO2 and non-extractable residues(6) indicates that biodegradation may be an important environmental fate process in soil(SRC).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 160(SRC), determined from a structure estimation method(2), indicates that florasulam 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 5.7X10-12 atm-cu m/mole for the neutral species(SRC), derived from its vapor pressure, 7.5X10-8 mm Hg(4), and water solubility, 6.36X10+3 mg/L(3). A pKa of 4.54(4) indicates florasulam 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). The measured photodegradation half-life in water at 51.5 deg N was 3.3 days(5). According to a classification scheme(6), an estimated BCF of 3(SRC), from its log Kow of -1.22(4) and a regression-derived equation(7), suggests the potential for bioconcentration in aquatic organisms is low(SRC). An average biodegradation half-life of 2.4 days with ultimate mineralization to CO2 and non-extractable residues(8) indicates that biodegradation may be 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), florasulam, which has a vapor pressure of 7.5X10-8 mm Hg at 25 °C(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase florasulam is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 20 hours(SRC), calculated from its rate constant of 6.3X10-12 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). Particulate-phase florasulam may be removed from the air by wet or dry deposition(SRC). Florasulam does not absorb light at wavelengths >300 nm(4), therefore it is not expected to be susceptible to direct photolysis by sunlight(SRC).

/BIRDS and MAMMALS/ The acute oral toxicity of florasulam to 8-week-old Japanese quail (Coturnix japonica) was assessed over 14 days. Florasulam was administered to the birds by gavage in corn oil as a single oral dose at nominal concentrations of 0 (control), 175, 292, 486, 810, 1350 and 2250 mg ai/kg-bw. Toxic sublethal effects (lower limb weakness, wing droop, reduced reaction to sound and movement) were observed at 292 mg a.i./kg-bw and above, and were more severe at 2250 mg a.i./kg-bw. Mortality was 40, 60, and 100% in the 810, 1350, and 2250 mg ai/kg treatments, respectively. The NOAEL (based on sublethal effects) and LD50 were 175 and 1047 mg ai/kg-bw, respectively. Florasulam is classified as slightly toxic to Japanese quail on an acute oral exposure basis.

/BIRDS and MAMMALS/ The subacute dietary toxicity of florasulam to 11 -day-old Japanese quail and mallard duck (Anas platyrhynchos) was assessed over 8 days. Florasulam was administered to the birds in the diet at nominal levels of 0 (control), 312, 625, 1250, 2500 and 5000 mg ai/kg diet. There were no compound-related toxic effects. The NOAEC and LC50 were 5000 and >5000 mg ai/kg diet, respectively. Florasulam is classified as practically non-toxic to Japanese quail and mallard duck on a subacute dietary exposure basis.

/BIRDS and MAMMALS/ The chronic toxicity of florasulam to 20-week-old bobwhite quail (Colinus virginianus) and 28-week-old mallard duck were assessed over 21 and 23 weeks, respectively. The adult bobwhite quail and mallard duck were fed diets containing florasulam at nominal concentrations of 0 (control), 240, 600 and 1500 mg aikg diet prepared with the aid of acetone and corn oil. There were no compound-related toxic effects at any of the concentrations tested. The NOAEC for chronic toxicity to birds is 1500 mg ai/kg diet.

/AQUATIC SPECIES/ In 96-hour acute static toxicity studies, rainbow trout (Oncorhynchus mykiss) and bluegill sunfish (Lepomis macrochirus) were exposed to florasulam at a concentration of 100 mg ai/L. No mortality or other adverse effects were observed. The 96-hr LC50 and NOAEC values, based on mortality and non-lethal adverse effects, were >I00 and 100 mg ai/L, respectively. Florasulam is classified as practically non-toxic to freshwater fish on an acute exposure basis.

For more Ecotoxicity Excerpts (Complete) data for Florasulam (6 total), please visit the HSDB record page.

Using a structure estimation method based on molecular connectivity indices(1), the Koc of florasulam can be estimated to be 160(SRC). According to a classification scheme(2), this estimated Koc value suggests that florasulam is expected to have moderate mobility in soil. The pKa of florasulam is 4.54(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). Florasulam, applied at a rate of 25.6 ng/g to Marcham (England; pH 7.7; sandy clay loam) and Naicam-Hoodoo (Canada; pH 7.5; clay loam) soils, exhibited apparent non-equilibrium sorption coefficients at 0 days after treatment of 0.1-0.5 L/kg and increased linearly with time to levels as high as 19-23 L/kg(5).

AEROBIC: Florasulam is not persistent in aerobic soil(1) and temperature was shown to influence the rate of biodegradation(2). The degradation half-life in soil incubated at 20-25 °C ranged from 1 to 8.5 days and 6.4 to 85 days at 5 °C; the half-life of its major product, 5-hydroxy florasulam, ranged from 8 to 36 days at 20-25 °C, and from 43 to 78 days at 5 °C(2). Florasulam incubated in 6 soils at 20 to 25 °C degraded as follows: Speyer 2.2 loamy sand (Germany; 76.3% sand, 15.5% silt, 8.2% clay, 3.9% organic Carbon, 8.7 mEq/100g cation exchange capacity, pH 7.3, 25.6% moisture) 1.7 days; Marcham sandy clay loam (UK; 48.2% sand, 23.0% silt, 26.8% clay, 2.0% organic Carbon, 9.0 mEq/100g cation exchange capacity, pH 7.7, 21.8% moisture) 4.5 days; Kenslow humus silt loam (UK; 13.5% sand, 62.4% silt, 24.1% clay, 6.8% organic Carbon, 16.0 mEq/100g cation exchange capacity, pH 5.6, 38.0% moisture) 0.7 days; Andover silt loam (UK; 18.5% sand, 59.2% silt, 22.3% clay, 3.1% organic Carbon, 12.0 mEq/100g cation exchange capacity, pH 7.6, 25.7% moisture) 1.5 days; Hanford sandy loam (US; 60.0% sand, 31.2% silt, 8.8% clay, 1.0% organic Carbon, 5.2 mEq/100g cation exchange capacity, pH 7.4, 8.5% moisture) 2.5 days; Catlin clay loam (US; 10.8% sand, 62.0% silt, 27.2% clay, 2.2% organic Carbon, 15.3 mEq/100g cation exchange capacity, pH 7.0, 25.4% moisture) 3.3 days. The average half-life was 2.4 days (range 0.7 to 4.5 days). Biodegradation proceeded initially with the conversion of the methoxy group on the triazolopyrimidine ring to a hydroxy group, ultimately being mineralized to CO2 and non-extractable residues(3).

AEROBIC: Florasulam biodegradation on soil(1). [Table#7811]

An estimated BCF of 3 was calculated in fish for florasulam(SRC), using a log Kow of -1.22(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).

The Henry's Law constant for florasulam is estimated as 5.7X10-12 atm-cu m/mole(SRC) derived from its vapor pressure, 7.5X10-8 mm Hg(1), and water solubility, 6.36X10+3 mg/L(1). This Henry's Law constant indicates that florasulam is expected to be essentially nonvolatile from water and moist soil surfaces(3). Florasulam is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(1).

/LABORATORY ANIMALS: Subchronic or Prechronic Exposure/ In a repeated-dose dermal toxicity study, XDE-570 (Florasulam; 99.3% ai) in aqueous 0.5% Methocel was applied to the shaved skin of 5 Fischer 344 rats/sex/dose at dose levels of 0, 100, 500, or 1000 mg/kg/day, 6 hours/day for 7 days/week during a 28-day period. No compound related effects in mortality, clinical signs, body weight, body weight gain, food consumption, hematology, clinical chemistry, urinalysis, organ weights, and gross or microscopic pathology parameters were observed in either sex. At 1000 mg/kg/day, very slight (grade 1) edema and erythema at the treatment site were noted in 4/5 males beginning on Day 23. Dermal irritation was resolved by Day 28 . The systemic LOAEL is not determined and the systemic NOAEL is 1000 mg/kg/day. The dermal LOAEL is 1000 mg/kg/day, based on edema and erythema observed at the treatment site in males (4/5). The dermal NOAEL is 500 mg/kg/day.

/LABORATORY ANIMALS: Subchronic or Prechronic Exposure/ In a 90-day oral toxicity study, XDE-570 (Florasulam; 99.3% ai) was administered to 4 Beagle dogs/sex/dose ad libitum in the diet at dose levels of 0, 5, 50, or 100 mg/kg/day (time-weighted average test substance intake was 0/0, 6/6, 56/55, and 104/94 mg/kg/day (M/F)) for 13 weeks. There were no compound-related effects on mortality, clinical signs, body weight, body weight gain, food consumption, ophthalmoscopy, hematology, urinalysis, or gross pathology observed at any dose. The target organ appeared to be the liver. At 50 mg/kg, alkaline phosphatase activity was increased (p<0.05) by 59-112% in the males and 91-127% in the females on Days 45 and 91, and there was a slight increase in the incidence of hepatic vacuolation (3/4 treated (very slight to slight severity) vs. 1/4 control (moderate severity) females). At 100 mg/kg, the following liver effects were noted: (i) alkaline phosphatase activity was increased (p<0.05) by 213-451% in both sexes on Days 45 and 91; (ii) increased incidence of very slight to slight hepatic vacuolation (4/4 treated vs. 3/4 control males and 3/4 treated vs. 1/4 control females); and (iii) increased (p<0.05) absolute (incr. 22-29%) and relative (to body; incr. 26-27%) liver weight in both sexes. The LOAEL is 50 mg/kg/day, based on increased alkaline phosphatase (59-127%) activity and increased incidence/severity of hepatic vacuolation in both sexes. The NOAEL is 5 mg/kg/day.

/LABORATORY ANIMALS: Subchronic or Prechronic Exposure/ In a subchronic oral toxicity study, XDE-570 (Florasulam; 99.2% ai) was administered in the diet to ten B6C3F1 mice/sex/dose at dose levels of 0, 20, 100, 500, or 1000 mg/kg/day (time-weighted intake was 0/0, 22/20, 110/101, 549/503, and 1125/1007 mg/kg/day (males/females)) for 13 weeks. No adverse treatment-related effects were observed on mortality, clinical signs, body weights, body weight gains, food consumption, food efficiency, ophthalmoscopic examination, hematology, clinical chemistry, organ weights, or gross or microscopic pathology. Very slight multi-focal bilateral hypertrophy was observed in the collecting ducts of the kidney in 10/10 males at 500 and 1000 mg/kg/day and in 8/10 females at 1000 mg/kg/day. There were no significant clinical chemistry or histopathological findings to corroborate the observed kidney effects.

The rate constant for the vapor-phase reaction of florasulam with photochemically-produced hydroxyl radicals has been estimated as 6.3X10-12 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 20 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). Florasulam is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(2). Florasulam does not absorb light at wavelengths >310 nm(3,4) however it may be susceptible to direct photolysis by sunlight(SRC). The estimated photodegradation half-life in summer at 40 deg N latitude was 14 days on soil. The measured photodegradation half-life in water at 51.5 deg N was 3.3 days(4). Aquatic photodegradation is proposed to proceed via two routes. One is the formation of 5-hydroxy florasulam by oxidation of the methoxy group on the triazolopyrimidine ring to the hydroxyl group. An alternative route is through the loss of the difluorophenyl moiety by cleavage of the phenyl carbon-nitrogen bond, followed by the conversion of the methoxy group(5).

Florasulam'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 7.5X10-8 mm Hg at 25 °C indicates florasulam will exist in both the vapor and particulate phases in the atmosphere. Vapor-phase florasulam will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 20 hours. Particulate-phase florasulam will be removed from the atmosphere by wet or dry deposition. Florasulam does not absorb light at wavelengths >300 nm, therefore it is not expected to be susceptible to direct photolysis by sunlight. If released to soil, florasulam is expected to have moderate mobility based upon an estimated Koc of 160. The pKa of florasulam is 4.54, 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 5.7X10-12 atm-cu m/mole. Florasulam may not volatilize from dry soil surfaces based upon its vapor pressure. Based on experiments using moist and dry soil exposed to light and dark the estimated photodegradation half-life in summer at 40 deg N latitude was 14 days on soil. An average biodegradation half-life of 2.4 days with ultimate mineralization to CO2 and non-extractable residues indicates that biodegradation may be an important environmental fate process in soil and water. If released into water, florasulam is not expected to adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization of the neutral species 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 florasulam 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. Hydrolysis is not expected to be an important environmental fate process since this compound lacks functional groups that hydrolyze under environmental conditions. The measured photodegradation half-life in water at 51.5 deg N was 3.3 days. Occupational exposure to florasulam may occur through inhalation and dermal contact with this compound at workplaces where florasulam is produced or used. (SRC)

For florasulam (USEPA/OPP Pesticide Code: 129108) 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./

Florasulam is a triazolopyrimidine sulfonanilide post-emergent herbicide...

Suspension concentrate

Premix Partners: Clodinafop-propargyl; Fluroxypyr; MCPA; Pinoxaden; Pyroxsulam

Orion Herbicide (Syngenta Crop Protection, LLC) MCPA, 2-ethylhexyl ester 42.25%, Primus 0.39%

Axial TBC Herbicide (Syngenta Crop Protection, LLC) Primus 0.75%, Pinoxaden 9%

For more Formulations/Preparations (Complete) data for Florasulam (13 total), please visit the HSDB record page.

Herbicides

Environmental transformation -> Pesticides (parent, predecessor)