Ecotoxicology is a field of science that studies the effects of toxic substances on ecosystems. It analyzes environmental damage from pollution and predicts the consequences of proposed human actions in both the short and long term. With more than 100,000 chemicals in commercial use and thousands more being introduced each year, the scale of the task is daunting. Ecotoxicologists have a variety of methods with which they measure the impact of harmful substances on people, plants, and animals. Toxicity tests measure the response of biological systems to a substance to determine if it is toxic. A test could study, for example, how well fish live, grow, and reproduce in various concentrations of industrial effluent. Another could evaluate the point at which metal contaminants in soil damage plants' ability to convert sunlight into food. Still another could measure how various concentrations of pesticides in agricultural runoff affect sediment and nutrient...