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The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

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E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Sulfometuron-methyl

Trade and Other Names: Trade names for products containing sulfomturon-methyl include Oust Weed Killer and DPX 5648.

Regulatory Status: Sulfometuron-methyl is a General Use Pesticide (GUP). It is EPA toxicity class III - slightly toxic. Products containing this compound require the Signal Word CAUTION on their labels.

Chemical Class: sulfonylurea

Introduction: Sulfometuron-methyl is a broad-spectrum sulfonylurea herbicide. It is used for the control of annual and perennial grasses and broad leaved weeds in non-crop land. It also has forestry applications where it is used to control woody tree species. It is applied either post-emergent or pre-emergent. It works by blocking cell division in the active growing regions of stem and root tips (meristematic tissue).

Formulation: Not Available

Toxicological Effects:

• Acute toxicity: Sulfometuron-methyl's acute oral toxicity is very low. The LD50 of sulfometuron methyl in rats is greater than 5000 mg/kg [4,8]. One study showed an LD50 greater than 17,000 mg/kg [8]. The acute dermal toxicity of the compound is also low. The LD50 values for exposure through the skin ranges from over 2000 mg/kg in female rabbits to over 8000 mg/kg in male rabbits [21]. The technical compound is not a skin irritant or a skin sensitizer [21]. It has mild eye irritant properties in rabbits [3]. The acute inhalation LC50 is above 5.3 mg/L in rats, indicating its slightly toxic nature by this route [4].
• Chronic toxicity: Several toxic effects have been seen with chronic exposure to sulfometuron-methyl in test animals. At doses of 25 mg/kg/day, dogs experienced reduced red-blood cell counts and increased liver weight [4,21]. In this study, dogs were fed the compound in their food for a year. In two other studies conducted over 90 days, rats had increased white-blood cell counts (leukocytes) and anemia only at the highest dose tested (375 mg/kg/day) [4,21]. In a 2-year feeding study, no effects were noted below 7.5 mg/kg/day in rats [21].
• Reproductive effects: In a 90-day reproductive effects study in rats, no reproductive effects were observed at doses of 300 mg/kg/day [21]. Another study in rats showed decreased fecundity and body weight at 300 mg/kg/day [4]. Studies of rabbits showed no fetotoxic effects at 300 mg/kg/day, the highest dose tested [21]. Reproductive effects due to sulfometuron-methyl are not likely.
• Teratogenic effects: No tetatogenic effects were observed in studies of rats and rabbits at doses of 300 mg/kg/day [21]. It is unlikely that sulfometuron-methyl is teratogenic.
• Mutagenic effects: The compound was not mutagenic in a variety of assays conducted on Salmonella cells and Chinese hamster ovary cells [21]. It is unlikely that the compound poses a mutagenic risk.
• Carcinogenic effects: No carcinogenic effects have been detected in either rats or mice exposed to sulfometuron-methyl [4,21].
• Organ toxicity: As was noted above, increased liver weight may result from chronic exposure. Damage to blood forming agents may also occur [4,21].

• Fate in humans and animals: Sulfometuron-methyl is readily absorbed through the gastrointestinal tract and is rapidly broken down and removed from the organism. Half-lives of the compound in rats ranged from 28 to 40 hours, depending on the dose (16 mg/kg and 3000 mg/kg, respectively). The compound did not accumulate in rats [22].

Ecological Effects:

• Effects on birds: Sulfometuron-methyl is practically nontoxic to birds. The acute oral LD50 in mallards is greater than 5000 mg/kg [4,8]. An 8-day dietary study with mallard ducks and bobwhite quail also showed an LC50 greater than 5000 ppm for both species [4].

• Effects on aquatic organisms: The compound is slightly toxic to freshwater fish. Its LC50 in rainbow trout and in bluegill sunfish is greater than 12.5 mg/L [23]. While the compound may not present a significant threat to adult aquatic organisms, the embryo hatch stage of fathead minnow may be at particular risk from the presence of the compound [23]. Fish kills have been associated with sulfometuron-methyl, but other causes have not been ruled out [24]. Sulfometuron-methyl is practically nontoxic to the water flea, Daphnia magna. Its LC50 in the water flea is greater than 125 mg/L for the technical material and greater than 1000 mg/L for dispersible granules [23]. No bioaccumulation has been detected [21].
• Effects on other organisms: No data are currently available.

Environmental Fate:

• Breakdown in soil and groundwater: Sulfometuron-methyl is of low to moderate persistence in the soil environment. It is broken down in soil by the action of microorganisms, by the chemical action of water (hydrolysis), and through the action of sunlight (photodegradation) [4,24]. Reported field half-lives of sulfometuron-methyl range from 20 to 28 days [19]. In several field dissipation studies, half of the initial applied amount of the compound remained for 1 to 3 weeks, depending on soil type, vegetation cover, and pH [24,26,27]. Under anaerobic soil conditions, the compound persists slightly longer, though the half-life is still rather short (up to 8 weeks) [24]. Sulfometuron-methyl does not bind strongly to soil [19] and is slightly soluble in water [19], but is rapidly degraded and does not appear to pose a threat to groundwater. Field study data indicated a majority of the parent compound stays within the top 3 inches of soil [23].
• Breakdown in water: In well aerated acidic water, the compound is broken down quickly. Reported field half-lives for sulfometuron-methyl in water vary from 1 to 3 days [23] to 2 months or more [24]. Photolysis is generally less important than hydrolysis in its breakdown [24]. Under non-oxygenated (anaerobic) conditions in water sediments, the compound had a half-life of several months [24].
• Breakdown in vegetation: Because sulfometuron-methyl is toxic to a number of plants and is non-selective, the use of the compound on non-croplands, including rights of way and along ditch banks, may endanger both terrestrial and aquatic plant species [4,24].

Physical Properties:

• Appearance: Sulfometuron-methyl is an off white or colorless solid compound. The compound is odorless [7].
• Chemical Name: 2-(4,6-dimethylpyrimidin-2-ylcarbamoylsulfamoyl)benzoic acid [7]
• CAS Number: 74222-97-2
• Molecular Weight: 364.40
• Water Solubility: 70 mg/L @ 25 C [7]
• Solubility in Other Solvents: s. in acetone, acetonitrile, and ethanol; s.s. in xylene; all @ 25 C [7]
• Melting Point: 203-205 C [7]
• Vapor Pressure: 8 mPa @ 25 C [7]
• Partition Coefficient: -0.5086 @ pH 7 [7]
• Adsorption Coefficient: 78 [19]

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: Not Available
• PEL: Not Available
• HA: Not Available
• TLV: 5 mg/m3 (8-hour) [8]

Basic Manufacturer:

DuPont Agricultural Products
Walker's Mill, Barley Mill Plaza
P.O. Box 80038
Wilmington, DE 19880-0038

• Phone: 800-441-7515
• Emergency: 800-441-3637
  

References:

References for the information in this PIP can be found in Reference List Number 9

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.