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The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

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E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Bromoxynil

Trade and Other Names: Trade names for commercial products containing bromoxynil include Brominal, Bromotril, Bronate, Buctril, Certrol B, Litarol, M&B 10064, Merit, Pardner, Sabre, and Torch. This compound may also be found in mixed formulations with other herbicides including MCPA, linuron, dicamba, mecoprop, and 2,4-D.

Regulatory Status: Bromoxynil is a Restricted Use Pesticide (RUP), and is not registered for homeowner use. RUPs may be purchased and used only by certified applicators. It is categorized as toxicity class II - moderately toxic. Products containing bromoxynil carry the Signal Word WARNING on their labels.

Chemical Class: nitrile

Introduction: Bromoxynil is a nitrile herbicide that is used for post-emergent control of annual broadleaf 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 target plants. It is available as an emulsifiable concentrate and a suspension concentrate.

Formulation: It is available as an emulsifiable concentrate and a suspension concentrate.

Toxicological Effects:

• Acute toxicity: The bromoxynil product Buctril, has an oral acute LD50 of 779 mg/kg in the rat, and Bronate's LD50 is 691 mg/kg in the rat. Technical bromoxynil has an oral LD50 of 190 mg/kg in rats, an LD50 of 260 mg/kg in rabbits, and an LD50 of 63 mg/kg in guinea pigs, indicating moderate acute toxicity [8,22]. The dermal LD50 of bromoxynil is greater than 2000 mg/kg in rabbits. The compound is a slight eye irritant but it is not a skin irritant in rabbits [1,22]. However, when in contact with abraded skin, bromoxynil may produce a mild irritation [8].
• Chronic toxicity: In one documented case of chronic exposure (about 1 year) of humans to bromoxynil, workers showed symptoms of weight loss, fever, vomiting, headache, and urinary problems [8]. Studies have shown that bromoxynil has no effect on rats given dietary doses of 15 and 50 mg/kg/day for 90 days [8]. Doses up to 5 mg/kg/day for 2 years had no impact on blood chemistry or urine [8].
• Reproductive effects: No changes in reproduction were noted in female rats fed 15 mg/kg/day of bromoxynil over three generations [8]. This suggests that bromoxynil does ot cause reproductive effects.
• Teratogenic effects: Bromoxynil is a suspected teratogen. The compound produced birth defects in rats at oral doses above 35 mg/kg. 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 [8]. In the rabbit, birth defects included changes in bone formation in the skull and hydrocephaly.
• Mutagenic effects: No data are currently available.
• Carcinogenic effects: Rats fed bromoxynil at low levels of 5 mg/kg and below did not develop any cancer related effects [8].
• Organ toxicity: No data were available regarding the target organs affected by bromoxynil.

• Fate in humans and animals: No bromoxynil was present in the milk or feces of cows 9 days after exposure to low doses of the herbicide. Less than 20% of the compound was excreted in urine as the parent compound [8].

Ecological Effects:

• Effects on birds: Bromoxynil is highly toxic to pheasants (LD50 of 50 mg/kg) and is moderately toxic to hens (LD50 of 240 mg/kg), quail (LD50 of 100 mg/kg), and mallard ducks (LD50 of 200 mg/kg) [1].

• Effects on aquatic organisms: Bromoxynil is very highly toxic to moderately toxic to freshwater fish; the potassium salt of bromoxynil has an LC50 of 5.0 mg/L in harlequin fish, 0.46 mg/L in goldfish, and 0.063 mg/L in catfish [1]. Bromoxynil has an LC50 of 0.05 mg/L in rainbow trout [8].
• Effects on other organisms: Bromoxynil is not toxic to bees [8].

Environmental Fate:

• Breakdown in soil and groundwater: Bromoxynil has a low persistence in soil. In sandy soil, the half-life is about 10 days [1]. Degradation in clay was slower, with half of the bromoxynil degraded to its metabolites in about a 2-week period at 25 C [8]. The persistence of the compound is also slightly longer in peat field soils than in the sandy soils [77]. The evidence suggests that, while bromoxynil is broken down by some soil bacteria, it may inhibit the action of other bacteria that promote the formation of nitrite by a process called nitrification [8].
• Breakdown in water: No data are currently available.
• Breakdown in vegetation: The herbicide works by disrupting the plants ability to produce energy for cell-related activities. It is not readily translocated throughout the plant once it has been absorbed [8].

Physical Properties:

• Appearance: Bromoxynil is a colorless crystalline solid at room temperature.
• Chemical Name: 3,5-dibromo-4-hydroxybenzonitrile [1]
• CAS Number: 1689-84-5
• Molecular Weight: 276.93
• Water Solubility: 130 mg/L @ 25 C [1]
• Solubility in Other Solvents: methanol v.s.; ethanol v.s.; acetone v.s.; cyclohexane v.s.; tetrahydrofuran v.s.; all at 25 C [1]
• Melting Point: 194-195 C [1]
• Vapor Pressure: <1 mPa @ 20 C [1]
• Partition Coefficient: Not Available
• Adsorption Coefficient: Not Available

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: 0.02 mg/kg/day [13]
• PEL: Not Available
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

Rhone-Poulenc Ag. Co.
P.O. Box 12014
2 T. W. Alexander Dr.
Research Triangle Park, NC 27709

• Phone: 919-549-2000
• Emergency: 800-334-7577
  

References:

References for the information in this PIP can be found in Reference List Number 10

DISCLAIMER: The 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 product labeling.