The public has become increasingly aware of the presence of chemicals in the water supply. In addition, research has provided growing evidence that many chemicals and mixtures of chemicals potentially present in our environment may act to inhibit, mimic, or accelerate the functions of the endocrine system in humans and animals. Disturbing statistics and images of deformed wildlife have generated concern in the general public. The sources of these contaminants are varied: wastewater treatment plant discharge, manufacturing plant wastewater, and chemical spills are a few examples. What course of action to take is one of the most difficult issues faced by regulators and scientists in the 21st century.