E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension Offices of
Cornell University, Michigan State University, Oregon State University, and
University of California at Davis. Major support and funding was provided
by the USDA/Extension Service/National Agricultural Pesticide Impact
Publication Date: 9/93
TRADE OR OTHER NAMES
The trade names and synonyms for chloramben are Ambiben, Amiben,
Amiben DS, Chlorambene, Ornamental Weeder, and Vegiben. The compound
may be used in combination with a wide range of other pesticides.
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
Chloramben's use is not restricted by the United States
Environmental Protection Agency.
Moderately toxic, chloramben is labeled with a CAUTION signal word.
The major health concern for humans is dermatitis resulting from skin
exposure to the pesticide.
The oral LD50 for rats is 3,500 mg/kg (1, 5) and 3,725 mg/kg for
mice. This suggests it would be fatal to humans only if ingested in
very large amounts.
The dermal LD50 for rabbits is 3,136 mg/kg (5) for albino rats, it
is greater than 3,160 mg/kg. This indicates that chloramben has about
the same toxicity when applied to the skin as when ingested.
Chloramben has not been shown to affect reproduction, but it does
affect the development of the fetus in some animals. Studies indicate
that chloramben is not a mutagen. This chemical's carcinogenic status
has not been determined. Chloramben exposure can be irritating to
mammals, but it is not known to be toxic to any organs. Animals rapidly
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
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 were seen, but the bones were
not fully developed. No changes were seen at the lowest doses (4).
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 (4).
The carcinogenic status of chloramben has not been established by
the Environmental Protection Agency (3).
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 (2, 3).
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
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 (1, 4, 6).
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. For instance, very small amounts of chloramben fed daily to
lactating cows left the body via urine (88%) and the feces (5%) within
four days. No residues were found in the milk (2). Similarly, dogs fed
very small amounts showed rapid chloramben excretion, with no residues
found in the tissues (2).
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 three to four days (4).
Chloramben has a low toxicity to wildlife, including wild birds and
both cold-water and warm-water fish. For example the LC50 of chloramben
is 4,640 in mallard ducks indicating that the compound is practically
non-toxic to this species (8). Chloramben is also not toxic to bees (8,
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
In plants, chloramben quickly changes from its free, unstable form
into a more stable compound which accumulates in both susceptible and
tolerant plants. Chloramben reacts with plant constituents to form a
stable and non-toxic product. The ease of formation of this metabolite
seems to be the reason the herbicide is not totally degraded within the
Chloramben is active in the soil. 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 less attracted to soil and are thus quite mobile in the
soil (7). 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 (2). 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 six to eight weeks in soil (8). Chloramben readily
degrades in water exposed to sunlight (4). Of 188 groundwater samples,
chloramben was found in only one, at a maximum concentration of 1.7 ug/l
(ppb) (4). The compound does not evaporate appreciably.
PHYSICAL PROPERTIES AND GUIDELINES
Chloramben is a 2,3,5-substituted (with chlorine atoms) benzoic
acid. It is a colorless and odorless crystalline solid.
|NOEL: ||1.75 mg/L(4)
|ADI: ||0.25 mg/kg/day(4)
|Drinking water |
|Drinking Water Equivalent Level (DWEL): 0.525 mg/L(4)
|CAS #: ||133-90-4
|Solubility in water: ||799 mg/L at 25 degrees C (6)
|Solubility in solvents: ||soluble in alcohol, alkali, ether, acetone (23.27g/100g at 29 degrees C (1), and ethanol 17.3g/100ml at 25 degrees C.
|Melting point: ||200-201 degrees C.
|Vapor pressure: ||0.007 torr at 100 degrees C (6)
P.O. Box 12014
2 T.W. Alexander Dr.
Research Triangle Park, NC 27709
*Chloramben is no longer produced or sold by Rhone Poulenc (or by anyone
else) in the United States.
Review by Basic Manufacturer:
Comments solicited: October, 1992
Herbicide Handbook. 4th ed. 1979. p. 99. Weed Science Society
National Library of Medicine. (1992) Hazardous Substances
Occupational Health Services. Material Safety Data Sheet on
Chloramben. 4/2/87. NY.
U.S. Environmental Protection Agency. Office of Drinking Water.
"Chloramben Health Advisory." Draft Report. August 1987.
Windholz, M., et al., eds. 1983. The Merck Index. 10th ed. Merck
& Co, Inc, Rahway, NJ.
Worthing, C.R., and Walker, S.B., eds. 1987. "Chloramben." The
Pesticide Manual. 8th ed. p. 142. The British Crop Protection Council.
Johnson, W.W., and Finley, M.T. 1980. Handbook of Acute Toxicity
of Chemicals to Fish and Wildlife. NPMP(DOI/FW) Resource Publication
The Agrochemicals Handbook. The Royal Society of
Chemistry. Cambridge, England.
The Farm Chemicals Handbook. (1992). Meister Publishing.