As society's awareness of environmental effects on public health has grown, scientists (especially epidemiologists) have been increasingly drawn into the public arena. The design of studies, the manipulation of statistics, and additional risk factors influence the acceptance of "hazards" as clearly causing certain diseases. In addition, the often major economic effects of reducing these health hazards make formulation of public policy concerning their control a fractious business. Environmental scientists, the media, lawyers, and politicians have difficulty dealing with multifactoral disease, and are still learning how the questions should be framed for an informed public debate on the issues raised. Environmental Health Risks and Public Policy compares decision making in Canada, Britain, and the United States, and the impact of different political traditions on the process. The place and limitations of formal risk assessment are discussed.