Some regulatory definitions of risk: interaction of scientific and legal principles

This paper discusses definitions of risk evolved to accommodate legal principles and scientific development in a time of rapid advances in science. The legal principles that underlie the interrelated definitions of "safe," "significant risk," and "acceptable risk" are examined in light of the major court decisions on benzene and vinyl chloride. The separate origins and development of concepts of de minimis risk and "negligible risk" are examined. The legal definitions are consistent with a judgmental weight-of-the-evidence evaluation of the statutory criteria, the available scientific information, and the risks acceptable in the world in which we live. The legal principles are dynamic, encourage scientific risk assessment based on case-by-case evaluation of the magnitude and character of human risks, and encourage incorporation of new scientific developments in the evaluation to improve the science base for regulatory decisions.