SCIENCE AND JUDGMENT IN RISK ASSESSMENT - A COMMENTARY ON THE NRC REPORT

This article provides a brief overview of the report ''Science and Jud gment in Risk Assessment,'' prepared by a Committee of the National Re search Council/National Academy of Science in response to a U.S. Envir onmental Protection Agency request mandated by the Clean Air Act Amend ments of 1990 (CAAA-1990). The report critiques EPA's current approach es for characterizing human cancer risks from exposure to chemicals an d offers recommendations for the conduct of future cancer risk assessm ents, especially those required in implementing the CAAA-1990 provisio ns which are concerned with hazardous air pollutants. The report offer s specific recommendations that address the role of default options, d ata needs, methods and models, uncertainty, variability, and the aggre gation of data. A cross-cutting theme of the report is the use of an i terative approach in which screening assessments with limited data and , of necessity, default options used in the absence of specific scient ific data may be performed initially followed by subsequent assessment s, as needed, in which increasing amounts of data are developed and in corporated. In some instances, the specific data on a given chemical o r pollutant source will replace conservative default options used in e arlier assignments. The report includes two authored appendices that a ddress issues related to the use of default options and their replacem ent by specific scientific information. One appendix by Finkel advocat es a principle of ''plausible conservatism'' for choosing and altering default options and in making cancer risk estimates. A second appendi x by McClellan and North advocates the full use of scientific informat ion in the risk assessment process. This article gives major attention to the key aspects of the NRC/NAS report, especially those dealing wi th the use and replacement of default options. The default options and the extent to which the options are replaced with specific science ha ve major impact on the final quantitation of cancer risk for exposure to chemicals. (C) 1994 Academic Press, Inc.