Using Daphnia magna as an assay organism, students determine the LC50 (lethal concentration 50: the percentage of a toxin in solution in which 50% of the assay organisms perish) for a number of environmental pollutants. These may include bleach, detergents, fertilizer, or pesticides. Using the dilution scheme in the instructions, students make stock solutions of varying percentages of their chosen toxin prior to the arrival of Daphnia. Once the organisms arrive, they are placed into the different dilutions of the pollutants, with resulting mortality rates plotted to determine LC50, a parameter that is central to water quality and effluent testing. Kit includes Daphnia culture and all other supplies except the pollutants, which are available locally. With detailed instructions. Note: Kit contains coupon for prepaid delivery of live materials; live materials can be delivered with kit upon request.