This book is about the legal, economical, and practical assessment and management of risky activities arising from routine, catastrophic environmental and occupational exposures to hazardous agents. It begins where emission and exposure analysis ends by providing estimates or predictions of deleterious exposures. The book covers the essential aspects of environmental and health law, environmental economics, applied statistical and probabilistic methods, fundamental notions of applied epidemiology and toxicology, as well as decision analysis, to provide an integrated overview of how risk assessment and management combine to produce sound societal outcomes. Risk-based methods play a pivotal role in identifying and ranking alternative, sustainable choices, while accounting for uncertainty and variability. Specifically, most reductions in risks require a balancing of the costs and benefits associated with the action to reduce exposure to a hazard and thus risk. This balancing necessarily involves linking exposure and response through causation. Fundamentally, in risk assessment and management, science and law intersect through legal and scientific causation to the point that the failure to provide a sound causal argument can make an otherwise beneficial law or regulation invalid.