Occupational exposure limits exemplify the practical application of moral values in medical science. But are they really effective in protecting workers from chemical hazards? In order to answer this question on the basis of sound empirical evidence, this book presents an unusually detailed and comprehensive analysis of three lists of exposure limits from the United States, Germany and Sweden. Hansson analyzes the nature of toxicological knowledge and discusses how the standards of proof required in a regulatory context differ from those appropriate in pure science. In his view, decision-makers must deal not only with the known risks but also with the uncertainties that arise as a consequence of the incompleteness of toxicological information. With this in mind, he proposes new ways to organize exposure limits and to evaluate toxicological data for regulatory purposes. Setting the Limit is a thorough, detailed study of the application of ethical principles in an important area of public health practice. It is intended for occupational health professionals and risk analysts, as well as philosophers and sociologists of science.