Advances in technology have created a multitude of airborne hazards that can affect the health and welfare of the population. Airborne toxic releases occur rapidly and the dispersed hazardous chemicals often present immediate acute health effects. The objective of this research is to develop a practical, workable approach for assessing the population at risk to accidents involving airborne toxic hazards. Methods based on the application of geographic information system (GIS) technology will be developed to achieve this goal. A particular emphasis will be placed on the identification of vulnerable population groups, including institutions (e.g., schools and hospitals) and their relationship to locations of potential hazardous material generation sites. In addition to integrating the key components of hazard analysis, the study will also extend and implement a new approach, known as geographic plume analysis, that accounts for directional biases in the distribution of hazards by using a chemical dispersion model to identify the area that is likely to be exposed to airborne toxic releases. Cedar Rapids, IA, will be used as a test-bed for developing these procedures.