Bromoxynil is a chemical compound of cyanide that is used as a herbicide. It is not permitted for homeowner use and is used for mainly 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. It works by inhibiting photosynthesis. (4)
Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (3)
Metabolism
Organic nitriles are converted into cyanide ions through the action of cytochrome P450 enzymes in the liver. Cyanide is rapidly absorbed and distributed throughout the body. Cyanide is mainly metabolized into thiocyanate by either rhodanese or 3-mercaptopyruvate sulfur transferase. Cyanide metabolites are excreted in the urine. (2)
No indication of carcinogenicity to humans (not listed by IARC).
Uses/Sources
Bromoxynil is used as a herbicide. It is not permitted for homeowner use and is used for mainly 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. (4)
Minimum Risk Level
Not Available
Health Effects
Exposure to high levels of cyanide for a short time harms the brain and heart and can even cause coma, seizures, apnea, cardiac arrest and death. Chronic inhalation of cyanide causes breathing difficulties, chest pain, vomiting, blood changes, headaches, and enlargement of the thyroid gland. Skin contact with cyanide salts can irritate and produce sores. Bromine vapour causes irritation and direct damage to the mucous membranes. Elemental bromine also burns the skin. The bromide ion is a central nervous system depressant and chronic exposure produces neuronal effects. This is called bromism and can result in central reactions reaching from somnolence to coma, cachexia, exicosis, loss of reflexes or pathologic reflexes, clonic seizures, tremor, ataxia, loss of neural sensitivity, paresis, papillar edema of the eyes, abnormal speech, cerebral edema, delirium, aggressiveness, and psychoses. (5, 6, 7, 2, 3)
Symptoms
Cyanide poisoning is identified by rapid, deep breathing and shortness of breath, general weakness, giddiness, headaches, vertigo, confusion, convulsions/seizures and eventually loss of consciousness. Bromine vapour causes irritation and direct damage to the mucous membranes. Symptoms include lacrimation, rhinorrhoea, eye irritation with mucous secretions from the oropharyngeal and upper airways, coughing, dyspnoea, choking, wheezing, epistaxis, and headache. The bromide ion is a central nervous system depressant producing ataxia, slurred speech, tremor, nausea, vomiting, lethargy, dizziness, visual disturbances, unsteadiness, headaches, impaired memory and concentration, disorientation and hallucinations. This is called bromism. (6, 7, 2, 3)
Treatment
EYES: irrigate opened eyes for several minutes under running water.
INGESTION: do not induce vomiting. Rinse mouth with water (never give anything by mouth to an unconscious person). Seek immediate medical advice.
SKIN: should be treated immediately by rinsing the affected parts in cold running water for at least 15 minutes, followed by thorough washing with soap and water. If necessary, the person should shower and change contaminated clothing and shoes, and then must seek medical attention.
INHALATION: supply fresh air. If required provide artificial respiration.
