Toxicology is a branch of science which deals with understanding the effects of poisons on people, animals, wildlife and the environment. Toxicology is as old as humanity. Since antiquity people learned how to use poisons to their advantage.
Toxicologists are professionals who are experts in some aspect of toxicology.
As we know it today, toxicology is the most diversified of all scientific disciplines. Because of this reason, toxicologists usually specialize in some aspect of toxicology. Like the medical professions which are diversified and require specialization, toxicologists also normally specialize in some aspect of this diverse scientific profession. There are several federal and state agencies within the USA which play this regulatory role. Mechanistic Toxicology - deals with understanding mechanisms of how poisons or pollutants cause disease in people, animals, plants, wildlife, etc.