Environmental toxicology is the scientific study of the health effects associated with exposure to toxic chemicals occurring in the natural, work, and living environments. The term also describes the management of environmental toxins and toxicity, and the development of protections for humans and the environment. In toxicology, we study both the adverse effects of chemicals on health and the conditions under which those effects occur. A natural outgrowth of biology and chemistry, toxicology began to assume a well-defined shape in just the past five to six decades. Newer still, environmental toxicology is concerned with the effects of chemical contaminants on various ecological systems, both large and small.