This course provides an introduction to health hazards caused by substances that are used at work. Basic toxicological terms and concepts (among others: dose response curves, toxicity testing), and types of health effects are explained. The biology and physiology of the most important human target organs and the possible routes and kinetics for toxic substances are clarified. A large variety of toxic substances is described, what their health effects can be, and where these hazardous substances are commonly used in industry. Some regulatory considerations are given and fundamental epidemiological knowledge is refreshed. Biological hazards are clarified in a separate chapter.