This document provides an overview of toxicology and its branches. It defines key terms like toxin, toxicant, and toxicity. Toxicology is described as the study of how natural and man-made poisons cause adverse effects in living organisms. Several general types of toxicology are outlined, including analytical, applied, clinical, veterinary, forensic, environmental, and industrial toxicology. Environmental toxicology or ecotoxicology is the field that studies the ecological and toxicological effects of chemical pollutants on populations, ecosystems, and the fate of pollutants in the environment. The document discusses factors like dose, duration and route of exposure that determine a substance's toxicity. Common routes of exposure include skin, lungs, ingestion