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: 5/94
TRADE OR OTHER NAMES
Trade names for commercial products containing bromoxynil include
Brominal, Bromotril, Buctril, Bronate, Certrol B, Litarol, M&B 10064,
Merit, Pardner, and Sabre. Discontinued products include Chipco,
Buctril, Harness and Torch. This compound may also be found in mixed
formulations with a wide variety of other herbicides including MCPA,
linuron, dicamba, mecoprop, and 2,4-D.
Bromoxynil is a nitrile herbicide that is used for post-emergent
control of annual broadleaved weeds. It is especially effective in the
control of weeds in cereal, corn, sorghum, onions, flax, mint, turf, and
on non-cropland. The compound works by inhibiting photosynthesis in the
Bromoxynil is a Restricted Use Pesticide (RUP), and is not
registered for homeowner use. RUPs may be purchased and used only by
Bromoxynil is a moderately toxic compound and carries the signal
word WARNING on the label.
The compound has an oral acute LD50 of 779 mg/kg in the rat
(specifically for the product Buctril) and a LD50 of 691 mg/kg in the
rat for Bronate. The technical material has an acute oral LD50 of 190
mg/kg in rats (1), an LD50 of 260 mg/kg in rabbits, and an LD50 of 63
mg/kg in guinea pigs (4). Dermal acute toxicity of bromoxynil is
greater than 2,000 mg/kg for rabbits. The compound is a slight eye
irritant (1) and it is not a skin irritant in rabbits (2). However,
when in contact with abraded skin, bromoxynil may produce a mild
Dogs fed bromoxynil for 90 days at low doses showed unspecified
adverse effects at and above 5 mg/kg. In the same type of test, the
compound had no observable effect on rats at or below a 16.6 mg/kg/day
dose (1). In another study at low doses (up to 50 mg/kg), rats
developed no significant abnormalities (3). In other tests with rats
administered low doses (up to 5 mg/kg) for up to two years, there were
no significant changes in blood chemistry or in urine (3).
In one documented case of chronic exposure of humans, workers
showed symptoms of weight loss, fever, vomiting, headache and urinary
problems (3). Chronic exposure for these four individuals had lasted
for about one year.
No changes in reproduction were noted in female rats fed low
amounts of bromoxynil (15 mg/kg/day) over three generations of litters
Bromoxynil is a suspected teratogen. The compound produced birth
defects in rats at low oral doses (above 35 mg/kg). The compound was
toxic to the mother and to the fetus at these low doses as well. Toxic
effects included abnormal rib formation, and reduced fetal weight.
Newborn rabbits had birth defects when bromoxynil was administered to
pregnant mothers at doses above 30 mg/kg (3). In the rabbit, birth
defects included changes in bone formation in the skull and
hydrocephaly. The available evidence indicates that bromoxynil may pose
a teratogenic risk to humans.
No information is currently available.
Rats fed bromoxynil in their diets at low levels of 5 mg/kg and
below did not develop any cancer related effects (3).
No information is currently available.
Fate in Animals and Humans
No bromoxynil was present in the milk or feces of cows nine days
after exposure to low doses of the herbicide. Less than twenty percent
of the compound was excreted in urine as the parent compound (3). No
other information on the breakdown of bromoxynil in humans or animals is
Bromoxynil is highly toxic to pheasants (LC50 of 50 mg/kg) and is
moderately toxic to hens (LC50 of 240 mg/kg), quail (LC50 of 100 mg/kg),
and mallard ducks (LC50 of 200 mg/kg) (2). The compound is very highly
toxic to moderately toxic to freshwater fish. The toxicity level is
dependent on the species tested. Bromoxynil has an LC50 of 5.0 mg/l in
harlequin fish (potassium salt), 0.15 mg/l in rainbow trout (octanoate),
0.46 in goldfish, and 0.063 in catfish (1).
Bromoxynil is not toxic to bees (2).
In sandy soil, the half-life of bromoxynil is about ten days (2).
During that time bromoxynil is broken down to less toxic compounds.
Degradation in clay was slower, with half of the bromoxynil degraded to
its metabolites in about a two week period at 25 degrees C (3). The
persistence of the compound is also a bit longer in peat field soils
than in the sandy soils (5). The evidence suggests that, while
bromoxynil is broken down by some soil bacteria, it may inhibit the
action of other bacteria. More specifically, it inhibits the bacteria
that promote the formation of nitrite (NO3), by a process called
In plants, the herbicide works by disrupting the plants ability to
produce energy for cell related activities. The herbicide is not
readily translocated throughout the plant once it has been absorbed (3).
Information about the movement of bromoxynil or its presence or
absence in water and groundwater is currently unavailable.
|NOEL: ||5 mg/kg (dog); 16.6 mg/kg (rat)
|ADI: ||not available
|RfD: ||0.02 mg/kg/day (3)
|CAS #: ||1689-84-5
|Chemical name: ||3,5-dibomo-4-hydroxybenzonitrile
|Chemical class/use: ||nitrile herbicide
|Solubility in water: ||130 mg/l at 25 degrees C
|Solubility in other solvents: ||90 g/l methanol; 70 g/l ethanol; 170 g/l acetone; 170 g/l cyclohexane; 410 g/l tetrahydofuran, all at 25 degrees C.
|Melting Point: ||194-195 degrees C
|Vapor pressure: ||less than 1 mPa at 20 degrees C
P.O. Box 12014
2 T.W. Alexander Drive
Research Triangle Park, N.C. 27709
Review by Basic Manufacturer:
Comments solicited: November, 1991
Worthing, Charles R. 1991. The Pesticide Manual: A World
Compendium. Ninth Edition. The British Crop Protection Council.
The Agrochemicals Handbook. 1991. The Royal Society of Chemistry.
Hazardous Substance Data Base. 1992. National Library of
Medicine. Toxnet. Bromoxynil.
Registry of Toxic Effects of Chemicals. 1981-1982. pg. 639.
Smith, Allan. E. 1980. An Analytical Procedure for Bromoxynil and
its Octanoate in Soils; Persistence Studies with Bromoxynil Octanoate in
Combination with Other Herbicides in Soil. Pesticide Science. 11, 341-346.