Pyrethrins and PyrethroidsIn recent years, pyrethrins have become increasingly popular in the production of pesticides. It is now used in numerous commercial products around the world. Many of these products come in the form of sprays and solutions used by many households, pet shampoos, and pesticides. The use of pyrethrins has become even more mainstream since it replaced the use of organophosphates, which have been found to be more toxic to birds and mammals than pyrethrins and pyrethroids. Pyrethrins are considered safer because it is a natural botanical derived from chrysanthemum flowers. Pyrethrins are neurotoxins that can lead to paralysis in insects, followed by death. There are six main components of the chemical that possess pesticidal activity: pyrethrin I, pyrethrin II, cynerin I, cynerin II, jasmolin I, and jasmolin II. (U.S. Department of Health, 2003) Pyrethroids are synthetic products based on the chemical structure of pyrethrins and therefore may function similarly to the natural product found in chrysanthemum flowers. These compounds usually need to be modified to be more stable when exposed to moderate heat. (U.S. Department of Health, 2003) Some of these pyrethroids are shown in Figure 1. Both pyrethrins and pyrethroids are usually sold in combination with synergistic agents such as piperonyl butoxide and MGK-254. These synergists do not have pesticidal properties, but help enhance the effects of neurotoxins by preventing the insect from metabolizing the toxins. (US Department of Health, 2003) Figure 1: Pyrethroids registered for use in the United States The pyrethroids shown here are the compounds permitted for use in the United States of America. Many of the pesticides therefore...... half of the document ......action for the induction of liver tumors by pyrethrins in rats. Toxicology and Applied Pharmacology, 218(2), 186-195.Ray, D. E., & Fry, J. R. (2006). A reevaluation of the neurotoxicity of pyrethroid insecticides.Pharmacology and Therapeutics, 111, 174-193.Soderlund, D., Clark, J., Sheets, L., Mullin, L., Piccirillo, V., Sargent, D., Stevens, J., & Weiner, M. (2002). Mechanisms of pyrethroid neurotoxicity: implications for cumulative risk assessment. Toxicology, 171(1), 3-59. Wolansky, M. J., & Harill, J. A. (2008). Neurobehavioral toxicology of pyrethroid insecticides in adult animals: a critical review. Neurotoxicology and Teratology, 30(2), 55-78. US Department of Health and Human Services, Agency for Toxic Substances and Disease Registry. (2003). Public Health Statement: Pyrethrins and Pyrethroids. Atlanta, Georgia: Agency for Toxic Substances and Disease Registry