title: Characterization of risks posed by combustor emissions.
abstract: Risk characterization is the final step of the risk assessment process as practiced in the U.S. EPA. In risk characterization, the major scientific evidence and "bottom-line" results from the other components of the risk assessment process, hazard identification, dose-response assessment, and exposure assessment, are evaluated and integrated into an overall conclusion about the risks posed by a given situation. Risk characterization is also an iterative process; the results of a specific step may require re-evaluation or additional information to finalize the risk assessment process. Risks posed by atmospheric emissions are an example of an involuntary human health risk which typically receives a great deal of public attention. Characterization of the risks posed by atmospheric emissions typically requires the use of mathematical models to evaluate: 1) the environmental fate of emitted pollutants, 2) exposures to these pollutants, and 3) human dose-response. Integration of these models results in quantitative risk estimates. The confidence in a quantitative risk estimate is examined by evaluating uncertainty and variability within individual risk assessment components. Variability arises from the true heterogeneity in characteristics within a population or an event; on the other hand, uncertainty represents lack of knowledge about the true value used in a risk estimate. U.S. EPA's 1997 Mercury Study will illustrate some aspects of the risk characterization process as well as the uncertainty and variability encountered in the risk assessment process.
authors: U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Cincinnati, OH 45268, USA.
authors: G
authors: G
authors: Rice
authors: J
authors: J
authors: Swartout
authors: E
authors: E
authors: Brady-Roberts
authors: D
authors: D
authors: Reisman
authors: K
authors: K
authors: Mahaffey
authors: B
authors: B
authors: Lyon
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D000818:Animals; D006801:Humans; D007220:Industrial Waste / Q000009:adverse effects; D008767:Methylmercury Compounds / Q000633:toxicity; D008956:Models, Chemical; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D014116:Toxicology / Q000379:methods*; D014481:United States; D014484:United States Environmental Protection Agency; D001335:Vehicle Emissions / Q000009:adverse effects
chemical_list: D000393:Air Pollutants; D007220:Industrial Waste; D008767:Methylmercury Compounds; D001335:Vehicle Emissions