Science and Education Publishing Applied Ecology and Environmental Sciences 1 1 2013 05 22 Synthetic Pyrethroids: Toxicity and Biodegradation 33 36 EN A.J. Thatheyus Postgraduate and Research Department of Zoology, The American College, Madurai A.Deborah Gnana Selvam AEES2013132 10.12691/aees-1-3-2 2013 01 09 2013 -1 21 2013 05 22 Synthetic pyrethroids are pesticides derived from naturally occurring pyrethrins, taken from pyrethrum of dried Chrysanthemum flowers. They are chemically designed to be more toxic with lower break down times and are formulated with synergists increasing potency and compromising the body¡¯s ability to detoxify the pesticide. Though claimed to be selectively toxic to insects, synthetic pyrethroids are extremely toxic to aquatic organisms, including fish in concentrations similar to those used for controlling mosquito, black fly and tsetse fly larvae, which are the actual targets of pyrethroids. Many pyrethroids have been linked to the disruption of the endocrine system, reproduction and sexual development, interference with the immune system and the induction of breast cancer. The widespread use of pyrethroids is a major problem as they pollute the agricultural lands and water resources and affect non-target organisms and humans. Recent studies show that some microbes are able to degrade synthetic pyrethroids by esterase production and this application is proposed as an inexpensive and simple method. In the present work, the aspects related to the toxicity and biodegradation of synthetic pyrethroids are discussed.