Furadan, Curater, Furacarb
3D model (JSmol)
|Molar mass||g·mol−1 221.256|
|Appearance||White, crystalline solid|
|Melting point||151 °C (304 °F; 424 K)|
|Boiling point||313.3 °C (595.9 °F; 586.5 K)|
|Solubility||Highly soluble in N-methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, acetone, acetonitrile, methylene chloride, cyclohexanone, benzene, and xylene|
|log P||2.32 (octanol/water)|
|Flash point||143.3 °C (289.9 °F; 416.4 K)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|8–14 mg/kg (oral, rat)|
19 mg/kg (oral, dog)
|US health exposure limits (NIOSH):|
|TWA 0.1 mg/m3|
IDLH (Immediate danger)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Carbofuran is one of the most toxic carbamate pesticides. 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.
Carbofuran exhibits toxicity mediated by the same mechanism as that of the notorious V-series nerve agents and presents a risk to human health. It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.
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 corn, 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.
Toxicity to vertebrates
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 not only 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.
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).
Toxicity to humans
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). Most carbofuran is applied by commercial applicators using closed systems with engineered controls so there is no exposure to it in preparation. However in developing countries, occupational exposure to the Carbofuran and resultant carbofuran-serum protein labeling has been reported that impacts human health and well-being. Since its toxic effects are due to its activity as a cholinesterase inhibitor it is considered a neurotoxic pesticide. A recent study reports that carbofuran is a structural mimic of the neurohormone melatonin and could directly bind to MT2 melatonin receptor (Ki = 1.7 uM). Disruption of melatonin signaling could impact the circadian rhythm balance and is linked to elevated risk of developing diabetes.
Health scare in Thailand
Due to nonregistration of 4 carcinogenic chemicals used on crops not listed in the Dangerous Substances Act of Thailand, vegetables with residues of methomyl, carbofuran, dicrotophos, and EPN were taken off supermarket shelves in July 2012.
Death of Lions in Kenya
In 2009, the CBS television news magazine 60 Minutes ran an exposé discussing the use of Furadan as a poison used by Kenyan farmers to kill African lions. The piece suggested that Furadan was a serious threat to the future of the lion population in Africa. FMC has commented extensively on this issue through the media and their websites including furadanfacts.com. They actively engaged with government officials, NGOs and others to try and resolve the illegal use of pesticides to kill wildlife. The company took action to stop the sale of this product and instituted a buy-back program in East Africa when it was determined that the illegal and intentional misuse of chemicals against wildlife could not be controlled by education or stewardship programs alone.
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- Rehman, Tanzila; Khan, Mohd M.; Shad, Muhammad A.; Hussain, Mazhar; Oyler, Benjamin L.; Shad, Muhammad A.; Goo, Young Ah.; Goodlett, David R. (2016-09-22). "Detection of Carbofuran-Protein Adducts in Serum of Occupationally Exposed Pesticide Factory Workers in Pakistan". Chemical Research in Toxicology. 29 (10): 1720–1728. doi:10.1021/acs.chemrestox.6b00222. ISSN 0893-228X. PMID 27657490.
- Popovska-Gorevski, Marina; Dubocovich, Margarita L.; Rajnarayanan, Rajendram V. (2017-02-20). "Carbamate Insecticides Target Human Melatonin Receptors". Chemical Research in Toxicology. 30 (2): 574–582. doi:10.1021/acs.chemrestox.6b00301. ISSN 0893-228X. PMC 5318275. PMID 28027439.
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