Parathion is one of the most toxic pesticides that has ever been synthesized. Because of this, Parathion has been classified as a Restricted Use Pesticide (RUP) by the Environmental Protection Agency (EPA), and may be purchased only by certified applicators. Use of Parathion on fruit, nut, and vegetable crops has been banned by the EPA, and the insecticide is now only allowed to be used on alfalfa, barley, corn, cotton, sorghum, soybeans, sunflowers, and wheat.