373 Common Themes at the Workshop on Uncertainty in the Risk Assessment of Environmental and Occupational Hazards JOHN C. BAILAR III a AND A. JOHN BAILER b,c a Department of Health Studies and Harris School of Public Policy, University of Chicago, 5841 South Maryland Avenue, MC 2007, Chicago, Illinois 60637, USA b Department of Mathematics and Statistics, Miami University, Oxford, Ohio 45056, USA c National Institute for Occupational Safety and Health, Education and Information Division, Risk Evaluation Branch, 4676 Columbia Parkway, Cincinnati, Ohio 45226, USA The workshop entitled “Uncertainty in the Risk Assessment of Environmental and Occupational Hazards”, which was held during September 21–26, 1998 in Bologna, Italy in the historic council chamber of the Bologna Town Hall, was a collaborative effort of the European Ramazzini Foundation and the International Statistical Insti- tute. The workshop had three objectives: (1) to improve understanding of the sources and magnitude of uncertainty in the risk assessment process; (2) to discuss and dis- seminate means for reducing such uncertainty; and (3) to describe, characterize, and express uncertainty in risk assessment, with a particular view towards its implica- tions on policy. The workshop sessions revolved around the themes of uncertainty and variability in the four components of a common model of the risk assessment process. The presentations were grouped into sessions that considered uncertainty in hazard identification, exposure assessment, exposure-response modeling, and risk characterization. The workshop was designed to be highly practical. The uncertain- ties associated with the assessment of health risks of electromagnetic fields and of dioxin were the focus of more than one presentation. The perspectives of partici- pants from academia, industry, and government enriched discussions about the eval- uation and communication of uncertainty and variability throughout the risk assessment process. The municipal council chamber in Bologna played host to a three-day workshop devoted to uncertainty in the risk assessment of environmental and occupational hazards. The sessions were organized into four components reflecting hazard identi- fication, exposure assessment, concentration-response modeling and risk character- ization. These four sessions were based on a common risk assessment paradigm suggested by the National Academy of Sciences in 1983. 1 After three days of delib- erations, we noted ten general issues that appeared in more than one presentation and discussion. Here is what we heard and saw, or thought we did. Addresses for correspondence: a John C. Bailar, 773-834-1242 (voice); 773-702-1979 (fax). e-mail: jcbailar@midway.uchicago.edu b John Bailer, 513-529-3538 (voice); 513-529-1493 (fax). e-mail: ajbailer@muohio.edu