Public concern regarding environmental pollution and chemicals present in foods, consumer products, and the work place are at an all time high. Whilst there is widespread awareness, confusion still reigns, aggravated by conflicting reports concerning carcinogens in food and drinking water, or about chemicals present in medicines and household products that may cause birth defects. The effort to understand how these pollutants and chemical products may harm human health is led by scientists in the disciplines of toxicology, epidemiology and risk assessment. The central purpose of this book is to describe how scientists come to understand the toxic properties of such chemicals and the health risks they may pose. Rather than attempting to expose governmental and corporate ignorance, negligence or corruption, this book explores the underlying scientific issues. It presents a practical and balanced clarification of the scientific basis for our concerns and uncertainties. It should serve to refocus the debate.