Earlier this year, the Office of Environmental Health Hazard Assessment (OEHHA) finalized revisions to the Technical Support Document for Exposure Assessment and Stochastic Analysis.  The TSD lays out the methodology and parametric values to be used in California's Toxic Hot Spots risk assessments.  In addition, most California Air Districts refer to the Hot Spots Risk Assessment Guidelines for the methodology used to assess air toxics in their New Source Review programs.  Finally, many other states base their evaluation of toxic impacts from new and existing sources on the Hot Spots guidance documents.

Steve Hill of Sierra Research will describe the changes in official risk calculations and help you understand the effect that they will have on the results.  Prior to joining Sierra Research, Steve was the Manager of Toxics Evaluation for the Bay Area Air Quality Management District, and was part of the team that drafted the original Hot Spots guidelines.