Health effects are often overlooked when planning development projects ranging from new runways at major airport sites to developing water supply systems to improve sanitation. Health Impact Assessment (HIA) is the assessment of the health effects, positive or negative, of a project, programme, or policy. It is therefore concerned with the health of populations and attempts to predict the future consequences for health of decisions which have not yet been implemented. HIA is a new and growing field with numerous schools of thought and areas of controversy. This book is the first to give a comprehensive overview of the concepts, theory, techniques and applications of HIA to aid all those preparing projects or carrying out assessments. It draws on examples and thinking from many different disciplines and many parts of the world. It identifies the areas of agreement and the questions remaining unanswered. It maps a confused field and signposts possible directions for future progress. HIA is intended to help decision makers in all areas foresee the consequences of their decisions, to ensure the consequences are considered and reduce the risk of population health being damaged through some indirect and unintended consequence of a decision. This book is a practical handbook for those preparing the assessments be they epidemiologists, environmentalists, health economists or public health specialists as well as serving as a conceptual guide for policy makers, decision makers and planners at national and international level. This book will serve both as a reference for the established HIA practitioner and as an introduction for the novice.