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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:
The trade names and synonyms for chloramben are Ambiben, Amiben,
Amiben DS, Chlorambene, Ornamental Weeder, and Vegiben.
Chloramben is classified as a General Use Pesticide (GUP) by the
U.S. Environmental Protection Agency. A toxicity class IV
pesticide, chloramben is practically nontoxic. Chloramben
products bear the Signal Word CAUTION. It is no longer produced
or sold in the U.S.
Chemical Class: benzoic
Chloramben is a selective, preemergence benzoic acid herbicide
that is primarily soil-applied to control annual grass and
broadleaved weed seedlings. It is mostly used for soybeans, but
it is also used for dry beans, peanuts, sunflowers, peppers,
cotton, sweet potatoes, squash, hardwood trees, shrubs, and some
conifers. Chloramben inhibits seedling root development and
causes plants to bend and die as they emerge from the soil.
- Acute toxicity: The oral LD50 for
chloramben in rats is 3500 mg/kg [5,7] and in mice is
3725 mg/kg. Chloramben irritates the throat, lungs, skin,
and the eyes. However, chloramben is not known to move
through the skin. On rats, a low dose skin application
caused mild irritation that subsided within 24 hours .
The dermal LD50 for rabbits is 3136 mg/kg [6,7]; and for
albino rats, it is greater than 3160 mg/kg. This
indicates that chloramben has about the same toxicity
when applied to the skin as when ingested. The major
health concern for humans is dermatitis resulting from
skin exposure to chloramben.
- Chronic toxicity: In long-term tests on
rats, mice, and dogs, no chloramben-related effects on
body weight, body function, and organs were observed,
even at very high concentrations [7,10].
- Reproductive effects: No effects on
fertility, survival of the fetus, or on nursing ability
were found in a long-term study of rats fed large daily
doses of chloramben . These data suggest that
chloramben does not cause reproductive toxicity.
- Teratogenic effects: When pregnant
rabbits were given high doses of chloramben during the
sensitive period of gestation, no developmental defects
were seen in the fetuses. Pregnant rats fed lower doses
of chloramben during the sensitive period of gestation
were not affected, but fetal deaths increased and fetal
skeletal development was not complete. At even lower
doses, no increase in fetal deaths was seen, but the
bones were not fully developed. No changes were seen at
the lowest doses . This evidence indicates that
chloramben is unlikely to cause teratogenic effects at
expected exposure levels.
- Mutagenic effects: Most bacterial and
mammalian cell assays of chloramben indicate that it is
not toxic to genetic material. However, mutagenicity was
seen in one test using Chinese hamster ovary cells .
These data suggest chloramben shows slight or no
- Carcinogenic effects: Rats given high
daily doses of chloramben for 80 weeks did not show
carcinogenicity. But mice given similar doses (up to 300
mg/kg) each day for 80 weeks developed cancerous tumors
. Thus, the carcinogenic status of chloramben is not
- Organ toxicity: Long-term animal studies
did not show evidence of chronic injury to the organs
- Fate in humans and animals: Several
animal studies have shown that once ingested, chloramben
is rapidly excreted in the urine and feces, with no
residues found in tissues. Very small amounts of
chloramben fed daily to lactating cows left the body via
urine (88%) and the feces (5%) within 4 days. No residues
were found in the milk . Similarly, dogs fed very
small amounts showed rapid chloramben excretion, with no
residues found in the tissues . Chloramben is quickly
absorbed from the gastrointestinal tract of female rats.
About 97% of an oral dose is absorbed and then excreted
through the urine and expired air. In rats fed a single
dose, 70% of that recovered 24 hours later from the urine
was the original compound. Only 0.6% of the dose remained
in the body after 3 to 4 days .
- Effects on birds: The LC50 of chloramben
is 4640 mg/l in mallard ducks, indicating that the
compound is practically nontoxic to this species .
- Effects on aquatic organisms: Chloramben
is not toxic to fish .
- Effects on other organisms: Chloramben
is not toxic to bees [6,7].
- Breakdown in soil and groundwater:
Chloramben is active in the soil. It is moderately
persistent. The wetter the soil, the greater the toxicity
of this compound to target plants. Rainfall or irrigation
within 10 to 14 days of application is needed for
chloramben to be effective against weeds. In a soil
solution, chloramben formulations readily break down into
forms which are quite mobile in the soil . Thus, much
of it is lost from the soil due to leaching, although
some loss is due to breakdown by soil microorganisms.
Leaching is greatest in sandy soil . As the organic
matter content of the soil increases, binding of
chloramben also increases, and leaching decreases. Like
most preemergence herbicides, the activity is nearly the
same on muck soils as on mineral soils. In general,
chloramben activity lasts for about 6 to 8 weeks in soil
[6,21]. The compound does not evaporate appreciably. Of
188 groundwater samples tested, chloramben was found in
only one, at a concentration of 0.0017 mg/L .
- Breakdown in water: Chloramben readily
degrades in water exposed to sunlight .
- Breakdown in vegetation: Chloramben
reacts with plant constituents to form a stable and
nontoxic product in both susceptible and tolerant plants.
The ease of formation of this metabolite seems to be the
reason the herbicide is not totally degraded within the
plant . When soil-applied, plant roots are the primary
site of absorption and chloramben action. Roots of
resistant species, like soybeans, can absorb large
amounts of the compound, but translocate very little of
it to the above-ground portions of the plant. In
contrast, the susceptible barley plant translocates a
significant amount into its leaves, and thus dies .
- Appearance: Chloramben is a colorless
and odorless crystalline solid .
- Chemical Name:
3-amino-2,5-dichlorobenzoic acid 
- CAS Number: 133-90-4
- Molecular Weight: 206.03
- Water Solubility: 700 mg/L @ 25 C 
- Solubility in Other Solvents: alcohol
v.s.; ether s.; acetone v.s.; ethanol v.s. 
- Melting Point: 200-201 C 
- Vapor Pressure: 930 mPa @ 100 C 
- Partition Coefficient: Not Available
- Adsorption Coefficient: 15 (estimated)
(salts at pH < 5) 
- ADI: Not Available
- MCL: Not Available
- RfD: 0.015 mg/kg/day 
- PEL: Not Available
- HA: 0.1 mg/L (lifetime) 
- TLV: Not Available
Chloramben is no longer produced or sold in the U. S.
- Phone: Not Available
- Emergency: Not Available
References for the information in this PIP can be found in
Reference List Number 7
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