QUANTITATIVE RISK ASSESSMENT OF STACK EMISSIONS FROM MUNICIPAL WASTE COMBUSTORS

Multi-pathway risk assessment (MRA) is a tool for evaluating the possi bility of adverse effects to human health that may result from contami nant releases from municipal solid waste combustors (MWCs) and other s ources of air pollution. An MRA attempts to model the movement of poll utants within the environment to various points at which they may be c ontacted by people, beginning with inhalation of contaminated air and continuing with indirect pathways such as food chain exposures that en tail contaminant transfer and accumulation through several media. MRAs of MWCs date back to the mid-1980s, and are rooted in methods develop ed to assess the consequences of radionuclide releases from nuclear po wer generation. A detailed example of a typical MRA is presented that follows the classic four-stage risk assessment paradigm (Valberg et al ., 1995). MRA methods, however, continue to be enhanced and refined by recent research. A number of current risk assessment topics are explo red that are new to traditional MRAs and may serve to re-focus our col lective efforts. The purpose of and demands on MRAs must be considered . A philosophical shift toward placing greater realism in MRAs undersc ores the importance of uncertainties inherent to risk estimates. Tools such as probabilistic risk assessment techniques must be developed an d endorsed so that decision-makers may intelligently utilize the infor mation provided by MRAs.