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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 include Command, Commence, Gamit, Magister, and
Clomazone is a General Use Pesticide (GUP). It is classified
toxicity class III - slightly toxic. Products containing
clomazone bear the Signal Word CAUTION on the labels.
Chemical Class: Not
Clomazone is a broad-spectrum herbicide used for control of
annual grasses and broadleaf weeds in cotton, peas, pumpkins,
soybeans, sweet potatoes, tobacco, winter squash, and fallow
wheat fields. It can be applied early preplant, pre-emergent or
preplant-incorporated, depending on the crop, geographical area,
- Acute toxicity: Clomazone is a slightly
toxic material by ingestion, inhalation, and dermal
exposure. The oral LD50 for technical clomazone is 1369
mg/kg in female rats and 2077 mg/kg in male rats [8,58].
The oral LD50 for Command 4EC is slightly higher: 1406
mg/kg in female rats and 2343 in male rats . The
dermal LD50 in rabbits is greater than 2000 mg/kg .
The inhalation LC50 for technical clomazone is 4.23 mg/L
in female rats and 6.52 mg/L in male rats . The
inhalation LC50 for Command 4EC in rats is 4.5 to 4.7
- Chronic toxicity: In 2-year feeding
studies with rats and mice, and a 1-year feeding study
with dogs, no long-term adverse effects from Command
. In a 1-year feeding study with dogs, increased
liver weight occurred at the 2.5 mg/kg/day dose . In
2-year feeding studies, rats fed more than 4.3 mg/kg/day
exhibited elevated cholesterol levels, increased liver
weights, and enlarged liver cells. Mice given doses above
15 mg/kg/day had elevated white blood cell counts .
- Reproductive effects: In a
two-generation study with rats, each generation was fed
clomazone at 5, 50, 100, or 200 mg/kg/day for 11 weeks in
between weaning and mating. There was no effect on
reproductive performance . These data suggest that it
does not cause reproductive effects.
- Teratogenic effects: Clomazone does not
appear to be teratogenic . No birth defects were seen
in the offspring of rats given 600 mg/kg/day, the highest
dose tested, nor in the offspring of rabbits given 700
- Mutagenic effects: Clomazone is not
mutagenic. The results of several tests, including a DNA
synthesis test, reverse mutation tests, and a chromosomal
aberration test, were all negative .
- Carcinogenic effects: Clomazone does not
appear to be carcinogenic . No tumor formation
occurred in mice or rats given dietary doses as high as
100 mg/kg for 2 years [58,78].
- Organ toxicity: Animal studies have
shown that clomazone affects the liver.
- Fate in humans and animals: Metabolism
studies show that 90 to 99% of the product Command
administered to rats was excreted within 72 hours and
there was no significant retention of the herbicide in
rat tissues .
- Effects on birds: Clomazone is
practically nontoxic to birds. The oral LD50 for
technical clomazone in bobwhite quail and mallard ducks
is greater than 2510 mg/kg. The 8-day dietary LC50 in
bobwhites and mallards is 5620 ppm .
- Effects on aquatic organisms: Clomazone
is moderately toxic to fish and aquatic invertebrates.
The LC50 (96-hour) for technical clomazone is 19 mg/L in
rainbow trout, 34 mg/L in bluegill sunfish, 6.26 mg/L in
Atlantic silversides, 40.6 mg/L in sheepshead minnows,
0.566 mg/L in mysid shrimp, 5.3 mg/L in eastern oysters,
and 5.2 mg/L in Daphnia magna . The bioconcentration
factor in bluegill sunfish is 40, indicating that there
is only a small potential for this compound to accumulate
in aquatic organisms .
- Effects on other organisms: No data are
- Breakdown in soil and groundwater:
Clomazone is moderately persistent in soil. Microbial
degradation of Command is promoted by high soil moisture,
warm temperature, and by increasing the pH to 6.5.
Degradation was faster in a sandy loam than in silt or
clay loams. In field studies, the half-life of clomazone
was 28 to 84 days, depending on soil type and the organic
matter content . Clomazone is highly soluble in
water, but it has a moderate tendency to adsorb to soil
particles. It therefore has a low to moderate potential
to contaminate groundwater . The product Command has
low mobility in sandy loam, silt loam, and clay loam
soils. It is moderately mobile in fine sand .
- Breakdown in water: Under laboratory
conditions, clomazone was not readily hydrolyzed in
sterile water . However, clomazone is subject to
photodegradation in water with a half life of 1.5 to 7
days reported for clomazone in solutions containing
acetone, a photochemical sensitizer .
- Breakdown in vegetation: Clomazone
inhibits synthesis of chlorophyll and carotenoids in
plants. It is absorbed by plants through the roots from
the soil and by shoots. It is then translocated in the
xylem and diffuses within leaves. It does not move
downward in plants or from leaf to leaf. There is no
foliar absorption of clomazone. Clomazone is metabolized
by plants .
- Appearance: Clomazone is a colorless to
light brown, viscous liquid above room temperature. When
cooled, it forms a white crystalline solid .
- Chemical Name:
- CAS Number: 81777-89-1
- Molecular Weight: 239.70
- Water Solubility: 1100 mg/L 
- Solubility in Other Solvents: acetone
v.s.; chloroform v.s.; cyclohexanone and methanol v.s.;
toluene s. 
- Melting Point: 25 C 
- Vapor Pressure: 19.2 mPa @ 25 C 
- Partition Coefficient: 2.5441 
- Adsorption Coefficient: 300 
- ADI: Not Available
- MCL: Not Available
- RfD: Not Available
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
Agricultural Chemicals Group
1735 Market Street
Philadelphia, PA 19103
- Phone: 215-299-6661
- Emergency: 800-331-3148
References for the information in this PIP can be found in
Reference List Number 10
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