Tebuthiuron (ISO)

SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a POTW is acceptable only after review by the governing authority. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal. If it is not practicable to manage the chemical in this fashion, it must meet Hazardous Material Criteria for disposal.

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational exposure 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, aquatic, and plant life; and conformance with environmental and public health regulations.

In case of spills, collect, cover or incorporate granules/pellets spilled on the soil surfaces to prevent contamination to water.

Do not apply to water, or to areas where surface water is present or to intertidal areas below the mean high water mark. Do not contaminate water when disposing of equipment washwaters or rinsate.

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.

Keep away from children. Do not reuse empty container.

Harmful if swallowed. Avoid contact with skin, eyes, or clothing.In case of contact, flush with water. Avoid breathing mist or dust. Do not apply, drain, or flush equipment on or near desirable trees or other plants, or on areas to which their roots extend. Do not contaminate any body of water.

Tolerances are established for the combined residues of the herbicide tebuthiuron (N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N,N'-dimethylurea) and its metabolites N-(5-(2-hydroxy-1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N,N'-dimethylurea, N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N-methylurea, and N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N'-hydroxymethyl-N-methylurea in or on the following raw agricultural commodities: [Table#6372]

Tolerances are established for the combined residues of the herbicide tebuthiuron (N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N,N'-dimethylurea) and its metabolites N-(5-(2-hydroxy-1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N,N'-dimethylurea, N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N-methylurea, and N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N'-hydroxymethyl-N-methylurea in or on the following raw agricultural commodities: [Table#6373]

A tolerance is established for the combined residues of the herbicide tebuthiuron (N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N,N'-dimethylurea) and its metabolites N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N-methylurea, N-(5-(2-hydroxy-1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N-methylurea, N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)urea, N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N'-hydroxymethyl-N-methylurea, and N-(5-(2-hydroxy-1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N'-hydroxymethyl-N-methylurea in or on the following raw agricultural commodity: milk, 0.8 ppm.

Excerpt from ERG Guide 171 [Substances (Low to Moderate Hazard)]:

The following PPE is the minimum PPE required for all persons handling products containing tebuthiuron: long sleeved shirt, long pants, shoes and socks. In additions, if the tebuthiuron end-use products are in Toxicity Category I, II, or III for acute dermal toxicity or skin irritation potential, chemical-resistant or waterproof gloves (whichever is appropriate) are required.

Long-sleeved shirt and long pants. Protective eyewear. Waterproof gloves. Waterproof boots.

LC50; Species: Anas platyrhynchos (Mallard duck, age 7 days) dietary >2500 ppm for 8 days

LC50; Species: Anas platyrhynchos (Mallard duck, age 4 days) dietary >5093 ppm for 8 days

LD50; Species: Anas platyrhynchos (Mallard duck, age 9 months) oral via capsule >2000 mg/kg

LD50; Species: Anas platyrhynchos (Mallard duck, age 12 months) oral via capsule >500 mg/kg

For more Ecotoxicity Values (Complete) data for TEBUTHIURON (18 total), please visit the HSDB record page.

TERRESTRIAL FATE: Based on a classification scheme(1), Koc values of 130(2), 2.70 to 84.1(3), and 80(4) indicate that tebuthiuron is expected to have very high to high mobility in soil(SRC). Volatilization of tebuthiuron from moist soil surfaces is not expected to be an important fate process(SRC) given a Henry's Law constant of 1.2X10-10 atm-cu m/mole(5). Tebuthiuron is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 3.0X10-7 mm Hg at 25 °C(6). A half-life of 35.4 months in a sandy loam soil at 75% field moisture capacity(7) suggests that biodegradation is not an important environmental fate process in soil(SRC).

TERRESTRIAL FATE: In field experiments in Arizona in which tebuthiuron (0.84 kg/ha) was applied to a rangeland watershed (slope 3%, soil OC about 1.05%, precipitation 586 mm) in February, 1981, 0.42% and 0.047% was removed in runoff water and suspended sediment in 1981 and 1982, respectively(1). The low removal rate in runoff is believed to be due to the timing of the application relative to rain events. Tebuthiuron moved to a depth of 15 cm in 8 months with 326 mm of precipitation and remained at that depth despite additional precipitation(1). The total amount of tebuthiuron remaining in the test plots after 21 months was 38% of that applied(1). Accordingly, it would take 2.9 to 7.2 years for the tebuthiuron level to fall below the detection limit. The herbicide retained its activity after 21 months. Another investigator found that tebuthiuron moved to 61 cm after 6 months in Houston black clay, soil typical of the Blackland Prairie and that the herbicide was still active after 2.5 years(1). In studies in which tebuthiuron was applied to field plots in central Utah as 40% (206 mg) pellets at 0.6 or 1.1 kg/ha, it was found that tebuthiuron moved downward and outward from the point of placement of the pellet(2). Dissipation from the upper 3 cm of soil within 2 cm of the pellet was best explained by a nonlinear expression with the time after placement as the independent variable; after 180, 365, and 730 days the concn in the soil was 53.0, 10.6, and 2.20 ppm, respectively(2). Based on a review of the literature, tebuthiuron exhibits a field half-life of 360 days(3).

TERRESTRIAL FATE: Tebuthiuron has a half life in soil of 12 to 15 months in areas receiving 40 to 60 inches of annual rainfall. The half life is considerably greater in low rainfall areas and in muck and other high organic soils, regardless of rainfall. In field studies, tebuthiuron and its transformation products have seldom been detected below the top 12 inches of soil. Little or no lateral movement has been observed.

TERRESTRIAL FATE: The dissipation and leaching characteristics of the herbicide tebuthiuron, ... were examined in this field study conducted at sites near Live Oak, Florida; Davenport, California; and Mead, Nebraska. The rise and decline of tebuthiuron's major soil metabolite was also followed. The tebuthiuron dissipation half-lives were 383, 806, and 575 days for the Florida, California, and Nebraska sites, respectively. At the California and Nebraska sites, tebuthiuron reached a maximum depth of approximately 69 and 84 cm, respectively. In the sand soil at the Florida site, tebuthiuron leached past the maximum sampling depth of 183 cm. The major soil metabolite reached a concentration of 23% of applied and leached to a maximum depth of approximately 38 cm at the California site. At the other sites, the metabolite did not exceed 9% of applied and leached no deeper than approximately 23 cm.

For more Environmental Fate (Complete) data for TEBUTHIURON (6 total), please visit the HSDB record page.

The concn of tebuthiuron in the coastal bermuda grass after application of the herbicide at 2.24 kg/ha as broadcast spray and pellets was 23.5 and 0.82 ppm, respectively 1 mo after application, 1.40 and 0.57 ppm, respectively 3 mo after application and 0.14 and 0.17 ppm, respectively 6 mo after application(1).

The highest concn of tebuthiuron in runoff water ranged from 40 to 91 ug/L in the first significant rain event after tebuthiuron application to a rangeland watershed in Arizona. Concns in runoff after subsequent rain events were much lower(1). On Texas blacklands prairie, tebuthiuron in surface runoff following spray and pellet application could be as high as 12 and 3 ppm, respectively if heavy rainfall occurred immediately after application(2). However, if rainfall occurred 2 mo after application, <1 ppm tebuthiuron occurred in runoff. The concn of tebuthiuron in runoff 3 mo after application was usually <0.05 ppm(2).

Tebuthiuron

7 x 10 ^-2 mg/kg-day

Tebuthiuron has a half life in soil of 12 to 15 months in areas receiving 40 to 60 inches annual rainfall. The half life is considerably greater in low rainfall areas and in muck and other high organic soils regardless of rainfall. In field studies, tebuthiuron and its transformation products have seldom been detected below the top 12 inches of soil. Little or no lateral movement has been observed .

For tebuthiuron, Koc values of 130(1), 2.70 to 84.1(6), and 80(2) have been reported. According to a suggested classification scheme(3), these Koc values suggest that tebuthiuron has high to very high mobility in soil(SRC). The principal route of dissipation in the environment is mobility in soil(4). The soil/water distribution constant of tebuthiuron in Eufaula sand (% OC not reported) was 0.2(5). Adsorption of tebuthiuron to soil increases with the organic carbon and clay content of the soil. Sorption Kd values for tebuthiuron on six acid, low base saturated sands as a function of depth ranged from 0.002 to 3.6 L/kg with the greatest sorption on soils from the surface 0-5 cm depth and the least on soils from depths >65 cm; sorption was shown to correlate to soil organic carbon(6). A mean Kd value of 1.63 based on 9 samples has been also reported(7).

In field studies conducted at five sites in north-central Arizona, tebuthiuron was primarily found in the upper 30 cm of soil during the first five years after application(1). After 9 years, 55-73% of the tebuthiuron was at depths between 30 and 90 cm(1). Small amounts of tebuthiuron were found as deep as 105 cm 6 to 9 years after application and small amounts were found in the upper 7 cm 10 years after application(1). Long-term leaching was not affected by application rate and leaching was not appreciably different in clay or loam soils(1). Lysimeter experiments were performed with intact soil columns from several upper Great Lakes sites (acidic, sandy soil) in which 440 mm of water was applied over a 130-day study period(2). Tebuthiuron leached to the 150-cm level in two lysimeters after 66 days and was detected at that level in 12 of 36 treated lysimeters. No tebuthiuron reached the 150-cm level in soils from two of the six sites where the pH of the surface 40 cm of soil was 4.7 and the base saturation averaged 22%; small amounts of tebuthiuron were recovered from four more acidic sites where the pH averaged 4.3 and the base saturation was <6%. Concns of tebuthiuron in the surface layers of soil were nearly five times that at the 150 cm level indicating that most of the herbicide remains in the upper profiles after the first growing season. In cited studies(2), the distribution of tebuthiuron applied at 8.8 kg/ha to a boreal podzol was distributed, 310 days post treatment, 98.6% in the surface 8 cm and 1.4% in upper B horizon; in a semi-arid rangeland site, for the first five years post-treatment most of the tebuthiuron remained in the surface 60 cm of soil, mainly in the 7-30 cm zone, and from 9-11 years it was mainly in the 60-90 cm zone(2).

AEROBIC: Tebuthiuron is resistant to biological degradation(1). In a 9-month study, thiadiazole-labled 14C tebuthiuron at a concentration of 6 ppm incubated in a sandy loam soil at 24 °C and 75% field moisture capacity exhibited a half-life of 35.4 months(1). In a 160-day study of the effect of moisture on the disappearance kinetics of tebuthiuron from an alfisol (pH 8.3, 0.640% organic matter, 21.6 meq/100 g CEC) and vertisol (pH 8.4, 1.015% organic matter, 46.9 meq/100 g CEC) soil, it was found that the amount of extractable tebuthiuron decreased rapidly for 40-80 days and then more gradually. The kinetics were consistent with a model in which the tebuthiuron distributes into two compartments, bound and labile, in which the labile pool is degradable and the bound pool is unavailable but may reenter the labile pool after a long time. The disappearance curve was resolved into two first order rates, the faster representing the loss of chemical into the bound pool which is not involved in the degradative process and the slower representing disappearance through degradation. The degradation rates in vertisol at saturation, field capacity, and 50% field capacity were 0.00499, 0.00254, and 0.00251/day (half-lives 139, 276, and 276 days), respectively. The degradation rates in alfisol at saturation, field capacity, and 50% field capacity were 0.00833, 0.00763, and 0.00701/day (half-lives 83, 91, and 99 days), respectively. The binding half-lives at saturation, field capacity, and 50% field capacity were 87, 37, and 30 days, respectively, for the vertisol and 19, 14, and 18 days, respectively, for the alfisol(2). The slow binding rates and the inability to extract the bound tebuthiuron suggests that chemical bond formation may be occurring(SRC). The rate of disappearance from the labile pool was greater at higher moisture levels. The rate of entry into the bound pool and degradation were higher for the soil with higher organic matter and clay content(2).

AEROBIC: Thiadiazole ring labeled (14)C-tebuthiuron in loam soil degraded from 8 ppm immediately post treatment to 5.7 ppm at 273 days post treatment indicating a half-life of greater than 273 days.

ANAEROBIC: (14)C-Tebuthiuron at 1.0 ppm degraded with a half-life of greater than 48 wk in a loam soil maintained under anaerobic conditions in the dark at 23 °C. N-[5-(1,1-Dimethylethyl)-1,3,4-thiadiazol-2-yl]-N-methyl urea was the major degradate.

SOIL: The amount of tebuthiuron, applied at 2.24 kg/ha as broadcast spray and pellets in the upper 15 cm of Texas Blacklands Prairie was 0.30 kg/ha and not detectable, 0.22 and 0.09 kg/ha and 0.120 and 0.56 kg/ha, 1 mo, 3 mo and 6 mo after application, respectively(1).

An estimated BCF of 7 was calculated in fish for tebuthiuron(SRC), using a log Kow of 1.79(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 tebuthiuron is 1.2X10-10 atm-cu m/mole(1). This Henry's Law constant indicates that tebuthiuron is expected to be essentially nonvolatile from water surfaces(2). Tebuthiuron is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 3.0X10-7 mm Hg(3).

Tests indicate that loss due to photodecomposition and volatilization is negligible.

Tolerances are established for the combined residues of the herbicide tebuthiuron (N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N,N'-dimethylurea) and its metabolites N-(5-(2-hydroxy-1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N,N'-dimethylurea, N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N-methylurea, and N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N'-hydroxymethyl-N-methylurea in or on the following raw agricultural commodities: [Table#6374]

Tolerances are established for the combined residues of the herbicide tebuthiuron (N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N,N'-dimethylurea) and its metabolites N-(5-(2-hydroxy-1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N,N'-dimethylurea, N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N-methylurea, and N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N'-hydroxymethyl-N-methylurea in or on the following raw agricultural commodities: [Table#6375]

A tolerance is established for the combined residues of the herbicide tebuthiuron (N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N,N'-dimethylurea) and its metabolites N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N-methylurea, N-(5-(2-hydroxy-1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N-methylurea, N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)urea, N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N'-hydroxymethyl-N-methylurea, and N-(5-(2-hydroxy-1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl)-N'-hydroxymethyl-N-methylurea in or on the following raw agricultural commodity: milk, 0.8 ppm.

A reregistration eligibility decision (RED) for Tebuthiuron, was completed in April 1994, prior to FQPA enactment. Therefore, it needed to be updated to reassess the tolerances under the FQPA standard. The Agency has evaluated the dietary risk associated with Tebuthiuron and has determined that there is a reasonable certainty that no harm to any population subgroup will result from exposure to Tebuthiuron when considering dietary exposure and all other nonoccupational sources of pesticide exposure for which there is reliable information. Therefore, no mitigation measures are needed, and the tolerances established for residues of Tebuthiuron in/on raw agricultural commodities are now considered reassessed as safe under section 408(q) of the FFDCA.

For more FIFRA Requirements (Complete) data for TEBUTHIURON (6 total), please visit the HSDB record page.

(AZ) ARIZONA 35 ug/l

(FL) FLORIDA 490 ug/L

Used as a broad-spectrum herbicide in non-farm areas; [EXTOXNET]

Farming (Pesticides) [Category: Industry]

For tebuthiuron (USEPA/OPP Pesticide Code: 105501) 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

Broad-spectrum herbicide for control of herbaceous and woody plants ... annual weeds ..., many perennial grass and broad-leaved weeds

Sugarcane, rangeland, noncropland, rights-of-way and industrial sites.

Tebuthiuron is produced by reaction of 5-tert-butyl-2-N-methyl isocyanate-1,3,4-thiadiazole with methylamine.

Preparation: GB 1266172 (1972 to Air Products and Chemicals, Inc.); E.V.P. Tao, BE 799575; idem, US 3803164 (1973, 1974 both to Lily)

Single active ingredient: 3.0 and 5.0% granular; 20.0 and 40.0% pelleted/tableted; 80.0% wettable powder; 85.0% water dispersible granules (dry flowable); and 95.0% technical grade/solid.

Multiple active ingredient: 1.0% granular (tebuthiuron plus one other active ingredient); 2.0% granular (tebuthiuron plus one other active ingredient); 2.0% granular (tebuthiuron plus another active ingredient).

Mixtures include: terbuthiuron + 2,4-D + picloram

Pellets, wettable powder, concentrate suspension.

For more Formulations/Preparations (Complete) data for TEBUTHIURON (14 total), please visit the HSDB record page.

The WHO Recommended Classification of Pesticides by Hazard identifies Tebuthiuron (technical grade) as Class III: slightly hazardous; Main Use: Herbicide.

Brush Bullet, Graslan, Perflan are discontinued names.