annually—nearly 50,000 pounds per person. One recent EPA survey found that more than 40 million people live within four miles and about 4 million within one mile of a Superfund site. Residential proximity itself, however, does not mean that exposures and health risks are occurring, only that the potential for exposure is increased.

At the request of the Agency for Toxic Substances and Disease Registry (ATSDR), the National Research Council (NRC) convened the Committee on Environmental Epidemiology to review current knowledge of the human health effects caused by exposure to substances emanating from hazardous-waste sites and to clarify and suggest how to improve the scientific bases for evaluating the effects of environmental pollution on public health, including specifically the conduct of health assessments at hazardous-waste sites. With additional support from the Environmental Protection Agency, the committee is preparing a second volume that will examine relevant information from state health departments, and selected unpublished studies from other sources that are relevant to this field.

This first report of the committee reviews and assesses the published scientific literature on health effects that could be linked with exposure to substances from hazardous-waste disposal sites and makes recommendations about major data gaps that need to be filled as scientists go on to answer important questions in the field. A second volume will review state-generated reports and studies emerging from other countries and will recommend research opportunities for the field of environmental epidemiology.

This report is organized into two broad sections; it contains eight chapters overall. The first section— Chapter 1, Chapter 2, and Chapter 3 —introduces the study of the public health impact of exposure to hazardous-waste sites; discusses the role of state, local, and federal regulations in shaping the development of studies in this area; and sets forth the complexity of assessing exposures to hazardous materials.

The introductory chapter defines environmental epidemiology and discusses conventional views of statistical significance and guidelines for inferring causation based on epidemiologic evidence. After that, the principles of statistical inference are evaluated in the context of constraints associated with the litigious and controversial world of hazardous-waste sites and toxic torts. Toxic torts is a rapidly growing field of litigation that involves legal claims of injuries allegedly caused by exposure to toxic chemicals. The relatively small number