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in 1996. EXTOXNET no longer updates this information, but it may be useful
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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Trade names of commercial herbicides containing alachlor include
Alanex, Bronco, Cannon, Crop Star, Lariat, Lasso, and Partner. It
mixes well with other herbicides such as Bullet, Freedom, and
Rasta, and is found in mixed formulations with atrazine,
glyphosate, trifluralin, and imazaquin.
Alachlor is a Restricted Use Pesticide (RUP). RUPs may be
purchased and used only by certified applicators. The EPA
categorizes it as toxicity class III - slightly toxic. However,
alachlor products bear the Signal Word DANGER on their labels
because of their potential to cause cancer in laboratory animals.
Chemical Class: aniline
Alachlor is an aniline herbicide used to control annual grasses
and broadleaf weeds in field corn, soybeans, and peanuts. It is a
selective systemic herbicide, absorbed by germinating shoots and
by roots. It works by interfering with a plant's ability to
produce protein and by interfering with root elongation.
This compound is one of the most highly used herbicides in the
U.S. Over 50 million pounds were applied annually in 1990. It is
available as granules or emulsifiable concentrate.
Formulation: It is
available as granules or emulsifiable concentrate.
- Acute toxicity: Alachlor is a slightly
toxic herbicide. The LD50 of alachlor in rats is between
930 mg/kg and 1350 mg/kg. In the mouse, the LD50 is
between 1910 and 2310 mg/kg . The dermal LD50 in
rabbits is 13,300 mg/kg, but some of the formulated
materials can be more toxic, with dermal LD50 values
ranging from 7800 to 16,000 mg/kg . Skin irritation
is slight to moderate. The inhalation LC50 in rats is
reportedly greater than 23.4 mg/L for 6 hours of exposure
- Chronic toxicity: A 90-day study on rats
and dogs given diets containing low to moderate amounts
of alachlor (1 to 100 mg/kg/day) showed no adverse
effects . However, a 6-month dog study showed liver
toxicity at all doses above 5 mg/kg/day, and a 1-year
study established that above 1 mg/kg/day, alachlor causes
effects in the liver, spleen, and kidney. In 2-year rat
studies, doses above 2.5 mg/kg/day caused irreversible
degeneration of the iris and related eye structures .
- Reproductive effects: High oral doses
(150 or 400 mg/kg/day) fed to rats during gestation
resulted in maternal and fetal toxicity, but there was no
indication that reproduction was affected [60,61].
Alachlor does not appear to cause reproductive effects.
- Teratogenic effects: Doses of up to 150
mg/kg/day fed to rabbits on days 7 through 19 of
pregnancy did not result in any birth defects .
Similar studies in rats at doses up to 400 mg/kg/day did
not result in birth defects, but toxic effects in the
mothers and offspring were seen at the highest dose.
These data indicate that alachlor is not likely to cause
- Mutagenic effects: Alachlor does not
appear to be mutagenic. Mutagenicity assays with a
variety of microbial strains at numerous concentrations
of alachlor were all negative [60,61].
- Carcinogenic effects: Rats given high
doses of alachlor developed stomach, thyroid, and nasal
turbinate tumors . An 18-month mouse study with doses
from 26 to 260 mg/kg/day showed an increase of lung
tumors at the highest dose for females but not males
. Because of inconsistencies in these studies, the
oncogenic potential of alachlor is uncertain .
- Organ toxicity: Long-term studies in
rats and dogs showed effects on the liver, spleen, and
kidneys. The iris and lung have also been affected.
- Fate in humans and animals: Rats given a
single low dose of alachlor (14 mg/kg) eliminated most of
it within the first 48 hours . Nearly all of the
compound was eliminated in 10 days; a third to a half of
the alachlor and its breakdown products were excreted in
urine and nearly a half in feces. Rats absorbed close to
75% of a single low dose (14 mg/kg) through skin while
only 8 to 10% was absorbed through the skin in monkeys
- Effects on birds: Alachlor is slightly
to practically nontoxic to wildfowl. Alachlor has a 5-day
dietary LC50 of greater than 5000 ppm in young mallard
ducks and bobwhite quail . The LD50 of alachlor in
other mallard ducks was greater than 2000 mg/kg . The
LC50 of alachlor in pheasants is greater than 10,000 ppm
- Effects on aquatic organisms: Alachlor
is moderately toxic to fish. The LC50 (96-hour) for
alachlor is 2.4 mg/L in rainbow trout, 4.3 mg/L in
bluegill sunfish, 6.5 mg/L in catfish, and 4.6 mg/L in
carp [1,8]. It is only slightly toxic to crayfish, with a
LC50 (96-hour) of 19.5 mg/L [8,37]. The bioaccumulation
factor in the channel catfish is 5.8 times the ambient
water concentration, indicating that alachlor is not
expected to accumulate appreciably in aquatic organisms
- Effects on other organisms: Alachlor is
not toxic to bees. It is practically nontoxic to
- Breakdown in soil and groundwater:
Alachlor has a low persistence in soil, with a half-life
of about 8 days [1,8]. The main means of degradation is
by soil microbes . It has moderate mobility in sandy
and silty soils, and thus can migrate to groundwater
. The largest groundwater testing program for a
pesticide, the National Alachlor Well Water Survey, was
conducted throughout the last half of the 1980s. Over 6
million private and domestic wells were tested for the
presence of alachlor. Less than 1% of all of the wells
had detectable levels of alachlor . In the wells
where the compound was detected, concentrations ranged
from 0.1 to 1.0 ug/L, with the majority having
concentrations around 0.2 ug/L .
- Breakdown in water: Alachlor breaks down
rapidly in natural water, primarily due to the action of
microorganisms. The breakdown rate is much slower in
water with no oxygen .
- Breakdown in vegetation: Absorption is
primarily by germinating shoots and it is readily
translocated throughout the plant . Higher
concentrations appear in the vegetative parts than in the
reproductive parts of the plant. Alachlor is rapidly
metabolized to water-soluble products in plants . It
is almost completely metabolized within 10 days .
- Appearance: Alachlor is a colorless to
yellow crystal compound .
- Chemical Name:
2-chloro-2',6'-diethyl-N-(methoxymethyl) acetanilide 
- CAS Number: 15972-60-8
- Molecular Weight: 269.77
- Water Solubility: 242 mg/L @ 25 C 
- Solubility in Other Solvents: s. in most
organic solvents 
- Melting Point: 40 C 
- Vapor Pressure: 2.9 mPa @ 25 C 
- Partition Coefficient: 2.8998 
- Adsorption Coefficient: 170 
- ADI: 0.0025 mg/kg/day 
- MCL: 0.002 mg/L 
- RfD: 0.01 mg/kg day 
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
800 N. Lindbergh Blvd.
St. Louis, MO 63167
- Phone: 314-694-6640
- Emergency: 314-694-4000
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