Carbofuran is one of the most toxic carbamatepesticides. It is marketed under the trade names Furadan, by FMC Corporation and Curater, among several others. It is used to control insects in a wide variety of field crops, including potatoes, corn and soybeans. It is a systemic insecticide, which means that the plant absorbs it through the roots, and from here the plant distributes it throughout its organs where insecticidal concentrations are attained. Carbofuran also has contact activity against pests.
Carbofuran usage has increased in recent years because it is one of the few insecticides effective on soybean aphids, which have expanded their range since 2002 to include most soybean-growing regions of the U.S. The main global producer is the FMC Corporation.
The technical or chemical name of carbofuran is 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate and its CAS number is 1563-66-2. It is manufactured by the reaction of methyl isocyanate with 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran.
In 2008, the United States Environmental Protection Agency (EPA) announced that it intends to ban carbofuran. In December of that year, FMC Corp., the sole US manufacturer of carbofuran, announced that it had voluntarily requested that the United States Environmental Protection Agency cancel all but six of the previously allowed uses of that chemical as a pesticide. With this change, carbofuran usage in the US would be allowed only on maize, potatoes, pumpkins, sunflowers, pine seedlings and spinach grown for seed. However, in May 2009 EPA cancelled all food tolerances, an action which amounts to a de facto ban on its use on all crops grown for human consumption.
Carbofuran is highly toxic to vertebrates with an oral LD50 of 8–14 mg/kg in rats and 19 mg/kg in dogs.
Carbofuran is known to be particularly toxic to birds. In its granular form, a single grain will kill a bird. Birds often eat numerous grains of the pesticide, mistaking them for seeds, and then die shortly thereafter. Before the granular form was banned by U.S. Environmental Protection Agency in 1991, it was blamed for millions of bird deaths per year. The liquid version of the pesticide is less hazardous to birds since they are not as likely to ingest it directly, but it is still very hazardous.
Carbofuran has been illegally used to intentionally poison wildlife in the US, Canada and Great Britain; poisoned wildlife have included coyotes, kites, golden eagles and buzzards. Secondary fatal poisoning of domestic and wild animals has been documented, specifically, raptors (bald eagles and golden eagles), domestic dogs, raccoons, vultures and other scavengers. In Kenya, farmers are using carbofuran to kill lions and other predators.
In a number of publicized incidents worldwide, carbofuran has also been used to poison domestic pets.
Carbofuran is an endocrine disruptor and a probable reproduction/development intoxicant. At low-level exposures carbofuran may cause transient alterations in the concentration of hormones. These alterations may consequently lead to serious reproductive problems following repeated exposure. When exposed in utero or during lactation, a decrease in sperm motility, sperm count along with increase in percent abnormal sperm was observed in rats at 0.4 mg/kg dose level. In one study, the exposure of rats to sublethal amounts of carbofuran decreased testosterone by 88%, while the levels of progesterone, cortisol, and estradiol were significantly increased (1279%, 202%, and 150%, respectively).
Carbofuran has one of the highest acute toxicities to humans of any insecticide widely used on field crops (only aldicarb and parathion are more toxic). A quarter teaspoon (1 mL) can be fatal. Most carbofuran is applied by commercial applicators using closed systems with engineered controls so there is no exposure to it in preparation. Since its toxic effects are due to its activity as a cholinesterase inhibitor it is considered a neurotoxic pesticide.
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