Deltamethrin is a pyrethroid ester insecticide. Usage Deltamethrin products are among some of the most popular and widely used insecticides in the world and have become very popular with pest control operators and individuals in the United States in the past five years. This material is a member of one of the safest classes of pesticides: synthetic pyrethroids. While mammalian exposure to deltamethrin is classified as safe, this pesticide is highly toxic to aquatic life, particularly fish, and… (More on Deltamethrin)