This book deals with urgent and timely issues related to radiation health effects and protection that are examined by both young researchers as well as experts. The book is organized into three major sections: biological responses, population monitoring and approaches to protection from radiation exposure. Contributors have provided state of the art research in their respective chapters. Radiation action produces damage to multiple targets in the exposed cells or human body and understanding of molecular mechanisms of the underlying processes becomes central to the monitoring of effects and health consequences of radiation exposure. Many experts have highlighted the outcome of epidemiological studies on human populations in high background radiation areas in different locations around the world as well as consequences and scopes for mitigating radiation health effects after radiation accidents such as Chernobyl in Ukraine and the Fukushima Daiichi Accident in Japan. This book also provides important direction for treatment of radiation for exposed victims. In the concluding chapters, contributors have provided new approaches for protection against ionizing radiation exposure. This book contains rich content on basic aspects of radiation induced cellular response which may give deeper insight to beginners in research, teaching, industry and regulatory authorities for basic understanding of radiobiological processes and molecular mechanisms. The book will prove an authentic reference source for updates in radiation science. It is hoped that students, teachers, experts, safety officers, regulatory officials and policy-makers will find the book handy for gaining a broad view of radiation damage to biological systems, monitoring health consequences and for new approaches in developing effective protection against radiation exposure.