Sulfentrazone

Time-limited tolerances are established for residues of the herbicide N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazo l-1-yl)phenyl)methanesulfonamide and its metabolites 3-hydroxymethyl sulfentrazone and 3-desmethyl sulfentrazone, in connection with use of the pesticide under section 18 emergency exemptions granted by EPA. ... bean, succulent seed without pod (lima beans and cowpeas): 0.1 ppm, expiration/revocation date 12/31/02; chickpea, seed: 0.10 ppm, expiration/revocaion date 12/31/04; horseradish, roots: 0.1 ppm, expiration/revocation date 12/31/02; pea, dry, seed: 0.10 ppm, expiration/revocation date 12/31/04; strawberry: 0.60 ppm, expiration/revocation date 12/31/04; sugarcane: 0.05 ppm, expiration/revocation date 12/31/02; and sunflower: 0.1 ppm, expiration/revocation date 12/31/02.

A tolerance is established for combined residues of the herbicide sulfentrazone N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazo l-1-yl)phenyl)methanesulfonamide and its major metabolite 3-hydroxymethyl sulfentrazone N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-3-hydroxymethyl-5-oxo-1H-1,2,4 -triazol-1-yl)phenyl)methanesulfonamide in or on the following raw agricultural commodity: soybean, seed: 0.05 ppm.

Tolerances are established for inadvertent and indirect combined residues of the herbicide sulfentrazone N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazo l-1-yl)phenyl)methanesulfonamide and its metabolites 3-hydroxymethyl sulfentrazone N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-3-hydroxymethyl-5-oxo-1H-1,2,4 -triazol-1-yl)phenyl)methanesulfonamide and 3-desmethyl sulfentrazone N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-5-oxo-1H-1,2,4-triazol-1-yl)ph enyl)methanesulfonamide) in or on the following raw agricultural commodities when present therein as a result of the application of sulfentrazone to growing crops: cereal grains (excluding sweet corn), bran: 0.15 ppm; cereal grains (excluding sweet corn), forage: 0.2 ppm; cereal grains (excluding sweet corn), grain: 0.1 ppm; cereal grains (excluding sweet corn), hay: 0.2 ppm; cereal grains (excluding sweet corn), hulls: 0.30 ppm; cereal grains (excluding sweet corn), stover: 0.1 ppm; and cereal grains (excluding sweet corn), straw: 0.6 ppm.

TERRESTRIAL FATE: Sulfentrazone has high mobility in soil based on an average Koc of 43 (and Kd < 1) with a strong potential to leach into groundwater and move offsite to surface water(1). A groundwater monitoring study in North Carolina determined sulfentrazone leaches substantially to groundwater in areas with sandy soil(1). Volatilization losses from soil are negligible(2). Direct photolysis of sulfentrazone in aqueous solutions is rapid (half-life of 1 to 12 hours)(3), therefore, photodecomposition on soil surfaces exposed to sunlight may be possible. Based on laboratory tests, loss of sulfentrazone in soil appears to be primarily by microbial degradation(2). An aerobic half-life of 1.5 years and anaerobic half-life of 9 years has been reported(1). The field dissipation half-life is reported to range from 110 to 280 days(2).

AQUATIC FATE: Based on an average Koc of 43 (and Kd < 1), sulfentrazone is not expected to adsorb to suspended solids and sediment(1). Volatilization from water surfaces is not expected(2) based upon an estimated Henry's Law constant of 6.37X10-13 atm-cu m/mole(SRC), derived from its vapor pressure, 9.75X10-10 mm Hg(3), and water solubility, 780 mg/l(3). According to a classification scheme(4), an estimated BCF of 3.1(SRC), from an experimental log Kow(1) and a regression-derived equation(5), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Direct photolysis of buffered aqueous solutions exposed to simulated sunlight occurs rapidly with half-lives of about 1 hour at pH 6 and pH 7, and 12 hours at pH 5(6). Sulfentrazone is stable to hydrolysis and biodegradation(1).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), sulfentrazone, which has a vapor pressure of 9.75X10-10 mm Hg at 25 °C(2), is expected to exist solely in the particulate phase in the ambient atmosphere. Particulate-phase sulfentrazone may be removed from the air by wet and dry deposition(SRC).

Reproductive Toxin - A chemical that is toxic to the reproductive system, including defects in the progeny and injury to male or female reproductive function. Reproductive toxicity includes developmental effects. See Guidelines for Reproductive Toxicity Risk Assessment.

Sulfentrazone has a reported average Koc of 43 (and Kd < 1) and a high mobility in soil(1). Sulfentrazone has also been reported to be moderately mobile in soil with a mobility greater than alachlor, but less than metribuzin(2). The compound showed a strong potential to leach into groundwater and move offsite to surface water; a groundwater monitoring study in North Carolina determined sulfentrazone leaches substantially to groundwater in areas with sandy soil(1).

Based on laboratory tests, loss of sulfentrazone in soil appears to be primarily by microbial degradation(1). An aerobic half-life of 1.5 years and anaerobic half-life of 9 years has been reported(2). The field dissipation half-life is reported to range from 110 to 280 days(1).

An estimated BCF of 3.1 was calculated for sulfentrazone(SRC), using an experimental log Kow of 0.99 at pH 7(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 sulfentrazone is estimated as 6.37X10-13 atm-cu m/mole(SRC) derived from its vapor pressure, 9.75X10-10 mm Hg(1), and water solubility, 780 mg/l(1). This Henry's Law constant indicates that sulfentrazone is expected to be essentially nonvolatile from water surfaces(2). Sulfentrazone is reported to have negligible volatilization losses from soil(3).

Non-irritating to skin; mild eye irritant (rabbits). Non-sensitizing to skin (guinea pigs).

A 1-yr feeding oral study was performed on dogs. The induction of normochromic microcytosis in animals fed diets containing 1800 ppm test material, although compensated by increased red cell production, reflects an adverse treatment-related effect. The microcytosis may have arisen from the inhibition of heme synthesis as indicated by the presence of brown to yellow/brown pigmentation in hepatocytes & reticuloendothelial cells of the liver. The microcytosis induced by sulfentrazone justifies an oral LOEL of 61.2 mg/kg/day for males & 61.9 mg/kg/day for females. The NOEL is 24.9 mg/kg/day for males & 29.6 mg/kg/day for females.

A developmental toxicity study in rats resulted in a maternal (systemic) LOEL of 50.0 mg/kg/day based upon increased relative spleen weight & splenic extramedullary hematopoiesis. The maternal (systemic) NOEL is 25.00 mg/kg/day. The developmental (fetal) LOEL is 25.0 mg/kg/day based upon 1) decreased mean fetal weight & 2) retardation in skeletal development as evidenced by an increased number of litters with any variation & by decreased numbers of caudal vertebral & metacarpal ossification sites. The developmental (fetal) NOEL is 10.0 mg/kg/day. Evidence of treatment-related developmental toxicity consisted of decreased fetal viability, decreased fetal body weight, & increased incidence of fetal alterations, comprised, for the most part, of skeletal malformations & variations. A supplementary prenatal oral developmental toxicity study in rats confirmed the maternal & fetal findings of the previously conducted study & did not alter the study conclusions. In a dietary 2-generation reproduction study in rats resulted in the systemic & reproductive/developmental NOEL of 14 mg/kg/day for males & 16 mg/kg/day for females.

The aqueous photolysis of radiolabeled sulfentrazone was studied in sterile pH 5, 7 and 9 buffers(1). Quartz tubes containing the buffers were exposed to continuous illumination from a filtered xenon lamp with output set equivalent to summer irradiation at 40 deg N latitude(1). At pH 7 and 9, sulfentrazone had photolysis half-lives of about 1 hour; photolysis at pH 5 was somewhat slower with a half-life of about 12 hours(1). Whole molecule photolysis involved de-chlorination, and in some cases, replacement of the halogen(s) with hydroxyl groups(1).

The rate constant for the vapor-phase reaction of sulfentrazone with photochemically-produced hydroxyl radicals has been estimated as 2.45X10-11 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 15.7 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). Sulfentrazone is not susceptible to aqueous hydrolysis(2).

Time-limited tolerances are established for residues of the herbicide N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazo l-1-yl)phenyl)methanesulfonamide and its metabolites 3-hydroxymethyl sulfentrazone and 3-desmethyl sulfentrazone, in connection with use of the pesticide under section 18 emergency exemptions granted by EPA. ... bean, succulent seed without pod (lima beans and cowpeas), expiration/revocation date 12/31/02; chickpea, seed, expiration/revocaion date 12/31/04; horseradish, roots, expiration/revocation date 12/31/02; pea, dry, seed, expiration/revocation date 12/31/04; strawberry, expiration/revocation date 12/31/04; sugarcane, expiration/revocation date 12/31/02; and sunflower, expiration/revocation date 12/31/02.

A tolerance is established for combined residues of the herbicide sulfentrazone N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazo l-1-yl)phenyl)methanesulfonamide and its major metabolite 3-hydroxymethyl sulfentrazone N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-3-hydroxymethyl-5-oxo-1H-1,2,4 -triazol-1-yl)phenyl)methanesulfonamide in or on the following raw agricultural commodity: soybean, seed.

Tolerances are established for inadvertent and indirect combined residues of the herbicide sulfentrazone N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazo l-1-yl)phenyl)methanesulfonamide and its metabolites 3-hydroxymethyl sulfentrazone N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-3-hydroxymethyl-5-oxo-1H-1,2,4 -triazol-1-yl)phenyl)methanesulfonamide and 3-desmethyl sulfentrazone N-(2,4-dichloro-5-(4-(difluoromethyl)-4,5-dihydro-5-oxo-1H-1,2,4-triazol-1-yl)ph enyl)methanesulfonamide) in or on the following raw agricultural commodities when present therein as a result of the application of sulfentrazone to growing crops: cereal grains (excluding sweet corn), bran; cereal grains (excluding sweet corn), forage; cereal grains (excluding sweet corn), grain; cereal grains (excluding sweet corn), hay; cereal grains (excluding sweet corn), hulls; cereal grains (excluding sweet corn), stover; and cereal grains (excluding sweet corn), straw.

New Active Ingredients ... includes pesticide active ingredients initially registered after November 1, 1984, that currently have active product registrations. By law, these newer pesticides are not subject to the reregistration program. They must, however, meet the new safety standard of the FQPA, and will be reviewed on a 15-year cycle under the registration review program. ... Active Ingredient Number: 129081; Tpye of Pesticide: conventional-herbicide; Use Site: food use; Year: 1997.