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in 1996. EXTOXNET no longer updates this information, but it may be useful
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E X T O X N E T
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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Trade names for products containing sulfomturon-methyl include
Oust Weed Killer and DPX 5648.
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.
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).
- 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 . 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 . The technical compound is not a skin
irritant or a skin sensitizer . It has mild eye
irritant properties in rabbits . The acute inhalation
LC50 is above 5.3 mg/L in rats, indicating its slightly
toxic nature by this route .
- 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 .
- Reproductive effects: In a 90-day
reproductive effects study in rats, no reproductive
effects were observed at doses of 300 mg/kg/day .
Another study in rats showed decreased fecundity and body
weight at 300 mg/kg/day . Studies of rabbits showed no
fetotoxic effects at 300 mg/kg/day, the highest dose
tested . 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 . 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 . 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 .
- 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
- 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 . 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 . Fish kills have been
associated with sulfometuron-methyl, but other causes
have not been ruled out . 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 . No bioaccumulation has been
- Effects on other organisms: No data are
- 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 . 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) . Sulfometuron-methyl
does not bind strongly to soil  and is slightly
soluble in water , 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 .
- 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  to 2 months or more
. Photolysis is generally less important than
hydrolysis in its breakdown . Under non-oxygenated
(anaerobic) conditions in water sediments, the compound
had a half-life of several months .
- 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
- Appearance: Sulfometuron-methyl is an
off white or colorless solid compound. The compound is
- Chemical Name:
- CAS Number: 74222-97-2
- Molecular Weight: 364.40
- Water Solubility: 70 mg/L @ 25 C 
- Solubility in Other Solvents: s. in
acetone, acetonitrile, and ethanol; s.s. in xylene; all @
25 C 
- Melting Point: 203-205 C 
- Vapor Pressure: 8 mPa @ 25 C 
- Partition Coefficient: -0.5086 @ pH 7
- Adsorption Coefficient: 78 
- ADI: Not Available
- MCL: Not Available
- RfD: Not Available
- PEL: Not Available
- HA: Not Available
- TLV: 5 mg/m3 (8-hour) 
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 for the information in this PIP can be found in
Reference List Number 9
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