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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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and the Institute for Environmental Toxicology, Michigan State
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USDA/Extension Service/National Agricultural Pesticide Impact
EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Trade names include AC 92553, Accotab, Go-Go-San, Herbadox,
Penoxalin, Prowl, Sipaxol, Sovereign, Stomp and Way-Up.
Pendimethalin is a slightly toxic compound in EPA toxicity class
III. Products containing pendimethalin must bear the Signal Word
CAUTION or WARNING, depending on the formulation. Pendimethalin
is a General Use Pesticide (GUP).
Chemical Class: Not
Pendimethalin is a selective herbicide used to control most
annual grasses and certain broadleaf weeds in field corn,
potatoes, rice, cotton, soybeans, tobacco, peanuts, and
sunflowers. It is used both pre-emergence, that is before weed
seeds have sprouted, and early post-emergence. Incorporation into
the soil by cultivation or irrigation is recommended within 7
days following application. Pendimethalin is available in
emulsifiable concentrate, wettable powder, or dispersible granule
Pendimethalin is available in emulsifiable concentrate, wettable
powder, or dispersible granule formulations.
- Acute toxicity: Pendimethalin is
slightly to practically nontoxic by ingestion, with
reported oral LD50 values of 1050 mg/kg to greater than
5000 mg/kg in rats [1,58]. It is slightly to practically
nontoxic by skin exposure, with reported dermal LD50
values of greater than 2000 mg/kg [1,58]. It is not a
skin irritant or sensitizer in rabbits or guinea pigs,
but it causes mild eye irritation in rabbits . The
inhalation 4-hour LC50 for technical pendimethalin in
rats is 320 mg/L, indicating practically no toxicity via
this route . Some formulated products (e.g., Prowl)
may show slight toxicity by inhalation, and may have a
greater capacity to cause skin irritation .
Inhalation of dusts or fumes may be mildly to moderately
irritating to the linings of the mouth, nose, throat, and
- Chronic toxicity: Increases in alkaline
phosphatase level and liver weight were produced in dogs
fed 50 mg/kg/day for 2 years, but not at a dose of 12.5
mg/kg/day [58,116]. In a 90-day feeding study of rats, no
effects were observed at doses of 40 mg/kg/day .
- Reproductive effects: In a
three-generation reproductive study of rats tested at
levels up to 250 mg/kg/day, there were slightly fewer
offspring and they showed decreased weight gain from
weaning to maturity . No effects were observed at 30
mg/kg/day [58,116]. This evidence suggests that
pendimethalin is unlikely to cause reproductive effects
in humans under normal circumstances.
- Teratogenic effects: No birth defects
and no toxic effects on fetuses occurred when pregnant
rats were given 500 mg/kg/day, the highest dose tested.
No fetotoxic or teratogenic effects were seen at the
highest dose tested (60 mg/kg/day) in a teratology study
with rabbits, although maternal toxicity was seen at 30
mg/kg/day . It does not appear that pendimethalin is
- Mutagenic effects: Several mutagenicity
studies, including tests on live animals and mammalian
and bacterial cell cultures, have all indicated that
pendimethalin has no mutagenic activity .
- Carcinogenic effects: Pendimethalin did
not increase tumor formation in mice given dietary doses
of 75 mg/kg/day over an 18-month period . This
evidence suggests that pendimethalin is not carcinogenic.
- Organ toxicity: Chronic exposure to
pendimethalin has resulted in increased liver weights in
- Fate in humans and animals:
Pendimethalin is largely unabsorbed from the
gastrointestinal tract, and excreted unchanged in the
feces . Pendimethalin, which does become absorbed
into the bloodstream from the gastrointestinal tract, is
rapidly metabolized in the kidneys and liver and is then
excreted as metabolites via urine . One day after
administration to rats, 90% of a 37 mg/kg dose was
recovered in feces and urine. After 4 days this figure
was 96% . Lower doses resulted in almost 100%
excretion within 4 days. Tissue burdens of the compound
were on the order of 0.3 mg/kg, with slightly higher
concentrations in the body fat .
- Effects on birds: Pendimethalin is
slightly toxic to birds, with an acute oral LD50 of 1421
mg/kg in mallard duck and 8-day dietary LC50 values of
greater than 3149 mg/kg in bobwhite quail, and greater
than 10,900 mg/kg in mallard duck [58,115].
- Effects on aquatic organisms:
Pendimethalin is highly toxic to fish and aquatic
invertebrates. The reported 96-hour LC50 for
pendimethalin in bluegill sunfish is 199 ug/L, in rainbow
trout is 138 ug/L, and in channel catfish is 420 ug/L
. The 48-hour LC50 in Daphnia magna, a small
freshwater crustacean, is 280 ug/L [58,115]. The
bioconcentration factor for this compound in whole fish
is 5100, indicating a moderate potential to acumulate in
aquatic organisms .
- Effects on other organisms:
Pendimethalin is nontoxic to bees .
- Breakdown in soil and groundwater:
Pendimethalin is moderately persistent, with a field
half-life of approximately 40 days [11,58]. It does not
undergo rapid microbial degradation except under
anaerobic conditions . Slight losses of pendimethalin
can result from photodecomposition and volatilization.
Pendimethalin is strongly adsorbed by most soils [58,11].
Increasing soil organic matter and clay is associated
with increased soil binding capacity. It is practically
insoluble in water, and thus will not leach appreciably
in most soils, and should present a minimal risk of
groundwater contamination [11,58].
- Breakdown in water: Pendimethalin is
stable to hydrolysis, but may be degraded by sunlight in
aquatic systems . Pendimethalin may also be removed
from the water column by binding to suspended sediment
and organic matter [11,58]. It is rapidly degraded under
anaerobic conditions once precipitated to sediment .
- Breakdown in vegetation: Pendimethalin
is absorbed by plant roots and shoots, and inhibits cell
division and cell elongation . Once absorbed into
plant tissues, translocation is limited and pendimethalin
breaks down via oxidation . Pendimethalin is not
absorbed by the leaves of grasses, and only very small
amounts are taken up by plants from the soil. Residues on
crops at harvest are usually below detectable levels
(0.05 ppm) .
- Appearance: Pendimethalin is an
orange-yellow crystalline solid with a faint nutty or
fruit-like odor .
- Chemical Name:
- CAS Number: 40487-42-1
- Molecular Weight: 281.31
- Water Solubility: 0.3 mg/L @ 20 C 
- Solubility in Other Solvents: v.s. in
most organic solvents such as acetone and xylene; s. in
corn oil, isopropanol, heptane, benzene, toluene,
chloroform, and dichloromethane; s.s. in petroleum ether
and petrol 
- Melting Point: 54-58 C 
- Vapor Pressure: 4 mPa @ 25 C 
- Partition Coefficient: 5.1818 
- Adsorption Coefficient: 5000 
- ADI: Not Available
- MCL: Not Available
- RfD: 0.04 mg/kg/day 
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
One Cyanamid Plaza
Wayne, NJ 07470-8426
- Phone: 201-831-2000
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