Sodium fluoroacetate, also known by its trade name as a mammal poison compound 1080, is an organofluorine chemical compound with the chemical formula FCH2CO2Na. It is the sodium salt of fluoroacetic acid, and contains sodium cations Na+ and fluoroacetate anions FCH2CO−2. A colourless salt with a taste similar to table salt (sodium chloride), it is used under the name "1080" to kill small and medium mammals, including rodents. New Zealand has no endemic ground-based mammals and is the world's biggest user of 1080, particularly to kill introduced brushtail possums, often with aerial distribution of bait pellets.
Natural occurrence Fluoroacetate occurs naturally in at least 40 plants in Australia, Brazil, and Africa. It is one of about twenty organofluorine-containing natural products.
Fluoroacetate occurrence in Gastrolobium species Gastrolobium is a genus of flowering plants in the family Fabaceae. This genus consists of over 100 species, and all but two are native to the southwest region of Western Australia, where they are known as "poison peas". Gastrolobium growing in southwestern Australia concentrate fluoroacetate from low-fluoride soils. The brushtail possums, bush rats, and western grey kangaroos native to this region are capable of safely eating plants containing fluoroacetate, but livestock and introduced species from elsewhere in Australia, and even the eastern populations of the brushtail possum and bush rat, are highly susceptible to the poison, as are species introduced from outside Australia, such as the red fox. The fact that many Gastrolobium species also have high secondary toxicity to non-native carnivores is thought to have limited the ability of cats to establish populations in locations where the plants form a major part of the understorey vegetation. The presence of Gastrolobium species in Western Australia has often forced farmers to 'scalp' their land, that is, remove the top soil and any poison pea seed which it may contain, and replace it with a new poison pea-free top soil sourced from elsewhere in which to sow crops. Similarly, after bushfires in north-western Queensland, cattlemen have to move livestock before the poisonous Gastrolobium grandiflorum emerges from the ashes.
The related compound potassium fluoroacetate occurs naturally as a defensive compound in at least 40 plant species in Australia, New Zealand, Brazil, and Africa. It was first identified in Dichapetalum cymosum, commonly known as gifblaar or poison leaf, by Marais in 1944. As early as 1904, colonists in Sierra Leone used extracts of Chailletia toxicaria, which also contains fluoroacetic acid or its salts, to poison rats. Several native Australian plant genera contain the toxin, including Gastrolobium, Gompholobium, Oxylobium, Nemcia, and Acacia. New Zealand's native Puha contains 1080 in very low concentrations.
Structure and synthesis
X-ray crystallography confirms that solid sodium fluoroacetate is a salt with intact fluoroacetate anions interacting with Na+ via a network of Na-O bonds. Sodium fluoroacetate can be produced by the reaction of fluoroacetic acid and a basic sodium salt, such as sodium carbonate and sodium hydroxide. However, it is industrially produced by treating sodium chloroacetate with potassium fluoride.
Toxicology Sodium fluoroacetate is toxic to most obligate aerobic organisms, and highly toxic to mammals and insects. The oral dose of sodium fluoroacetate sufficient to be lethal in humans is 2–10 mg/kg. The toxicity varies with species. The New Zealand Food Safety Authority established lethal doses for a number of species. Dogs, cats, and pigs appear to be most susceptible to poisoning. The enzyme fluoroacetate dehalogenase has been discovered in a soil bacterium, which can detoxify fluoroacetate in the surrounding medium.
Mechanism of action Fluoroacetate is structurally similar to acetate, which has a pivotal role in cellular metabolism. This similarity is the basis of the toxicity of fluoroacetate. Two related mechanisms for its toxicity have been discussed, with both beginning with the conversion of fluoroacetate to 2-fluorocitrate. 2-Fluorocitrate arises by condensation with oxaloacetate with fluoroacetyl coenzyme A, catalyzed by citrate synthase. Fluorocitrate binds very tightly to aconitase, thereby halting the citric acid cycle. This inhibition results in an accumulation of citrate in the blood. Citrate and fluorocitrate are allosteric inhibitors of phosphofructokinase-1 (PFK-1), a key enzyme in glycolysis. When PFK-1 is inhibited, cells are no longer able to metabolize carbohydrates, depriving them of energy. Alternatively, fluorocitrate interferes with citrate transport in the mitochondria.
Symptoms In humans, the symptoms of poisoning normally appear between 30 minutes and three hours after exposure. Initial symptoms typically include nausea, vomiting, and abdominal pain; sweating, confusion, and agitation follow. In significant poisoning, cardiac abnormalities including tachycardia or bradycardia, hypotension, and ECG changes develop. Neurological effects include muscle twitching and seizures; consciousness becomes progressively impaired after a few hours leading to coma. Death is normally due to ventricular arrhythmias, progressive hypotension unresponsive to treatment, and aspiration pneumonia. Symptoms in domestic animals vary: dogs tend to show nervous system signs such as convulsions, vocalization, and uncontrollable running, while large herbivores such as cattle and sheep more predominantly show cardiac signs. Sub-lethal doses of sodium fluoroacetate may cause damage to tissues with high energy needs, especially the brain, gonads, heart, lungs. Fetuses are also highly susceptible. Sub-lethal doses are typically completely metabolised and excreted within four days.
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