ABSTRACT
Chapters 2-5 introduced the science involved in tracking toxic chemicals and evaluating whether they are capable of producing adverse effects at the concentrations humans and other species are likely to encounter in their environments. Chemical partitioning, advective transport, and bioaccumulation are some of the conceptual tools for charting pathways of exposure, and the mass-balance concept offers a framework for organizing information about exposure pathways into a working model of environmental fate and transport (Chapter 2). The key to understanding toxic chemical risk is the dose-effect phenomenon, a form of the law of mass action, which makes it possible to characterize and quantify the relationship between chemical dose and toxic effect under controlled laboratory conditions (Chapter 3). The ability of toxic chemicals to harm human health and the environment can be investigated prospectively through toxicity testing in laboratory animals (Chapter 5). Human health impacts can be investigated retrospectively through epidemiological studies of chemicals possessing toxicities that may have eluded the regulatory process (Chapter 4).
