Chlorfenvinphos is the common name of an organophosphorus compound that was widely used as an insecticide and an acaricide. The molecule itself can be described as an enol ester derived from dichloroacetophenone and diethylphosphonic acid. Chlorfenvinphos has been included in many products since its first use in 1963. However, because of its toxic effect as a cholinesterase inhibitor it has been banned in several countries, including the United States and the European Union. Its use in the United States was cancelled in 1991. The pure chemical is a colorless solid, but for commercial purposes, it is often marketed as an amber liquid. The insecticides, mostly used in liquid form, contain between 50% and 90% chlorfenvinphos. The substance easily mixes with acetone, ethanol, and propylene glycol. Furthermore, chlorfenvinphos is corrosive to metal and hydrolyzes in the environment. 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. Pesticide use History Dermaton was the first registered product containing chlorfenvinphos. It was introduced in the United States in 1963 and was used as an insecticide and acaricide for controlling fleas and ticks on domestic pets and other animals. Between 1963 and 1970, additional uses were registered, including the use as fly spray, surface spray and larvicide. Because of these effects, chlorfenvinphos was often used on farms to control adult flies in dairy barns, milk rooms, poultry houses and yards, and in other animal buildings. Furthermore, it was used to control larval flies in manure storage pits and piles and other refuse accumulation areas around dairies and feedlots. In the early 1980s, chlorfenvinphos was registered for additional uses in a dust formulation for use in dog kennels and in dog collars for the control of fleas and ticks. Outside the United States, chlorfenvinphos, registered under the trade names Birlane, C8949, CGA 26351, Sapecron, Steladone and Supona, was used as a soil insecticide for controlling root maggots, root worms and cutworms. Chlorfenvinphos was also used against Colorado beetles on potatoes and scale insects and mite eggs on citrus. Furthermore, the compound had the same uses as in the United States. There is no quantitative information on the total volume of chlorfenvinphos really used as a pesticide in the