Flumioxazin

Tolerances are established for residues of flumioxazin, 2-(7-fluoro-3,4-dihydro-3-oxo-4-(2-propynyl)-2H-1,4-benzoxazin-6-yl)-4,5,6,7-tet rahydro-1H-isoindole-1,3(2H)-dione, in or on the following raw agricultural commodities: peanuts: 0.02 ppm; and soybean seed: 0.02 ppm.

TERRESTRIAL FATE: Based on column leaching studies and the short aerobic soil half-life, the potential for flumioxazin to leach in field agricultural soil is low(1). In soils that have been treated with flumioxazin, it is generally not found below 3 inches in depth(2). Volatilization losses from soil surfaces are negligible(1). Flumioxazin degrades rapidly in soil water via hydrolysis with half-lives of 3.4 to 5.1 days at pH 5.0, 21.4-24.6 hours at pH 7.0, and 14.6-22.0 minutes at pH 9.0(1); therefore, aqueous hydrolysis in moist soils will be an important fate process(SRC). Microbial degradation in soil is also an important fate process(1); the half-life for aerobic soil metabolism is 11.9 to 17.5 days, with an average of 14.7 days(1,2). The photolysis half-life on soil is 3.2 to 8.4 days (average 5.8 days)(2). The rapid soil dissipation rate indicates flumioxazin is not persistent in soil(1).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 13000(SRC), determined from a structure estimation method(2), indicates that flumioxazin is expected to adsorb to suspended solids and sediment(SRC). The hydrolytic degradation half-life of flumioxazin in soil water is 3.4 to 5.1 days at pH 5.0, 21.4-24.6 hours at pH 7.0, and 14.6-22.0 minutes at pH 9.0(3); therefore, hydrolysis will be the major degradation process in water(SRC). An anaerobic aquatic metabolism half-life of 0.2 days has been reported(4). The photolysis half-life in water at pH 5 is 1 day(4). Volatilization from water surfaces is expected to be slow(5) based upon an estimated Henry's Law constant of 6.28X10-7 atm-cu m/mole(SRC), derived from its vapor pressure, 2.41X10-6 mm Hg(6), and water solubility, 1.79 mg/l(4). Using this estimated Henry's Law constant and an estimation method(5), volatilization half-lives for a model river and model lake are 1,765 hours and 809 days, respectively(SRC). According to a classification scheme(7), an estimated BCF of 18(SRC), from a log Kow of 2.55(4) suggests the potential for bioconcentration in aquatic organisms is low(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), flumioxazin, which has a vapor pressure of 2.41X10-6 mm Hg at 25 °C (2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase flumioxazin 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 6.8 hours(SRC), calculated from its rate constant of 5.68X10-11 cu cm/molecule-sec at 25 °C(SRC) (that was derived using a structure estimation method(3). Particulate-phase flumioxazin may be removed from the air by wet and dry deposition(SRC).

Using a structure estimation method based on molecular connectivity indices(1), the Koc for flumioxazin can be estimated to be 13000(SRC). The Koc can also be estimated as 581 and 2000(SRC), using a log Kow of 2.55(3) and a water solubility of 1.79 mg/l at 25 °C(3) and regression-derived equations(2). According to a classification scheme(3), these estimated Koc values suggests that flumioxazin is expected to have low to no mobility in soil.

The mobility (unaged leaching) of flumioxazin is reported as moderately mobile(1); fluxioxazin is generally not found below 3 inches of soil depth(1). Available data indicate flumioxazin is relatively unstable and its potential to leach to groundwater is low(1); however, the potential for degradation products to leach to groundwater is high(1).

An estimated BCF of 18 was calculated for flumioxazin(SRC), using an experimental log Kow of 2.55(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 flumioxazin is estimated as 6.28X10-7 atm-cu m/mole(SRC) derived from its vapor pressure, 2.41X10-6 mm Hg(1), and water solubility, 1.79 mg/l at 25 °C(1). This estimated Henry's Law constant indicates that flumioxazin is expected to be volatilize slowly from water surfaces(2). Based on this estimated Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec)(2) is estimated as 1765 hours(SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(2) is estimated as 809 days(SRC). Flumioxazin is reported to have negligible volatilization losses from soil(3).

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

An N-phenylimide herbicide, S-53482, inhibits protoporphyrinogen oxidase, an enzyme common to chlorophyll & heme biosynthesis, & produces embryolethality, teratogenicity [mainly ventricular septal defects (VSD) & wavy ribs], & growth retardation in rats. In order to elucidate the mechanism of the developmental toxicity, in particular VSD, effects of the herbicide on rat embryonic blood cells were investigated histologically at the light & electron microscopic levels at 6, 12, 24, 36, & 48 hr after oral admin of the chemical to pregnant rats on day 12 of gestation, the most sensitive day for toxicity. Electron & light microscopy demonstrated mitochondrial lesions, including abnormal iron deposits that were probably due to inhibition of heme biosynthesis, in erythroblasts derived from the yolk sac. Subsequently, degeneration of these erythroblasts occurred followed by erythrophagocytosis. Histologically hearts from exposed embryos had a thin ventricular wall, which may reflect a compensatory reaction to a loss of embryonic blood cells.

Pregnant females were admin 400 mg/kg by gavage on gestation day 11 or 12 or 13 or 14 or 15. Day 12 admin showed: largest incidence of embryonic death, lowest fetal body weights & greatest incidence of ventricular spetal defects.

Mode of action: Herbicide, absorbed by foliage & germinating seedlings. Acts, in the presence of light & oxygen, by inducing massive accumulation of porphyrins, & enhancing peroxidation of membrane lipids, which leads to irreversible damage of the membrane function & structure of susceptible plants.

The hydrolytic degradation half-life of flumioxazin in soil water is 3.4 to 5.1 days at pH 5.0, 21.4-24.6 hours at pH 7.0, and 14.6-22.0 minutes at pH 9.0(1). Similar chemical hydrolysis half-lives of 4.2 days (pH 5), 1 day (pH 7), and 0.01 days (pH 9) are also reported(2). The photolysis half-life in water at pH 5 is 1 day(2). The photolysis half-life on soil is 3.2 to 8.4 days (average 5.8 days)(1).

The rate constant for the vapor-phase reaction of flumioxazin with photochemically-produced hydroxyl radicals has been estimated as 5.68X10-11 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 6.8 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1).

Flumioxazin's production may result in its release to the environment through various waste streams; it's use as a herbicide will result in its direct release to the environment. If released to air, a vapor pressure of 2.41X10-6 mm Hg at 20 °C indicates flumioxazin will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase flumioxazin 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 6.8 hours. Particulate-phase flumioxazin will be removed from the atmosphere by wet and dry deposition. If released to soil, flumioxazin is expected to have a low potential to leach based on column leaching studies and a fast degradation rate. Volatilization from moist soil surfaces is negligible. Flumioxazin degrades rapidly in soil water via hydrolysis with half-lives of 3.4 to 5.1 days at pH 5.0, 21.4-24.6 hours at pH 7.0, and 14.6-22.0 minutes at pH 9.0; therefore, aqueous chemical hydrolysis in moist soils will be an important fate process. Microbial degradation in soil is also an important fate process; the half-life for aerobic soil metabolism is 11.9 to 17.5 days, with an average of 14.7 days. The photolysis half-life on soil is 3.2 to 8.4 days (average 5.8 days). The rapid soil dissipation rate indicates flumioxazin is not persistent in soil. If released into water, chemical hydrolysis will be a major degradation process. Flumioxazin has an anaerobic aquatic metabolism half-life of 0.2 days. Volatilization from water surfaces is not expected to be an important fate process based upon this compound's estimated Henry's Law constant. An estimated BCF of 18 suggests the potential for bioconcentration in aquatic organisms is low. Photodegradation in shallow water can occur (surface half-life of about 1 day at pH 5). Occupational exposure to flumioxazin may occur through short and intermediate-term dermal and inhalation exposure during mixing, loadin

Hazard Traits - Reproductive Toxicity；Authoritative List - EC Annex VI CMRs - Cat. 1B；Report - if used as a fragrance or flavor ingredient

Regulation (EC) No 1107/2009 (amended)

Flumioxazin is listed in the dataset of EPA Human Health Benchmarks for Pesticides under the Safe Drinking Water Act (40 eCFR 141)

02/81/EC, 2010/77/EU, Reg. (EU) 2015/1885, Reg. (EU) 2016/549, Reg. (EU) 2017/841, Reg. (EU) 2019/707, Reg. (EU) 2020/869, Reg. (EU) 2021/745, Reg. (EU) 2022/43, Reg. (EU) No 540/2011, Reg. (EU)2018/917

Flumioxazin: Does not have an individual approval but may be used under an appropriate group standard

Tolerances are established for residues of flumioxazin, 2-(7-fluoro-3,4-dihydro-3-oxo-4-(2-propynyl)-2H-1,4-benzoxazin-6-yl)-4,5,6,7-tet rahydro-1H-isoindole-1,3(2H)-dione, in or on the following raw agricultural commodities: peanuts; and soybean seed.