This introductory textbook provides the background to understand quantitative risk assessment for radiation dangers to human health. It focuses on health physics, which is the part of environmental health engineering that is used to protect the population against radiations harmful effects. Youll find sections on physical principles, atomic and nuclear structure, radioactivity, biological effects of radiation, radiation safety, instrumentation, and principles of radiation protection. It addresses radiation safety and the philosophy of environmental health to reinforce the International Commission on Radiological Protections (ICRP) recommended safety standards for pregnant and other radiation workers, members of the general public, and patients undergoing diagnostic and therapeutic procedures. Practice problems are included at the end of every chapter.