Environmental Toxicology is the study of effects of natural and synthetic pollutants in the environment. Analytical Toxicology deals with the determination of the levels of exposure to potential toxicants via air, water, or food. Environmental toxicology, also called as entox, is a multidisciplinary field of science concerned with the study of the harmful effects of various chemical, biological and physical agents on living organisms. Ecotoxicology is a sub discipline of environmental toxicology concerned with studying the harmful effects of toxicants at the population and ecosystem levels. Harmful effects of chemical and biological agents can include toxicants from pollutants, insecticides, pesticides, and fertilizers all of which can impact an organism and its community through shifts in species diversity and abundance. Resulting changes in population dynamics impact the ecosystem by altering its productivity and stability. Contamination is defined as the introduction of pollutants into the natural environment that causes adverse reactions. Toxicology is concerned with the study of different adverse effects which are caused by the contaminants that are present in the environment.