Fuzzy Expert Systems can be applied to study the evolution of an idea, process or methodology from a position of full acceptance and widespread use to one of total rejection and disuse. This paper describes the application of such methods to assess bioaccumulation risk from mercury used in gold mining regions around the World. HgEx is a heuristic expert system which accommodates imprecise data for pH, Eh, water conductivity, biomass productivity, water transparency and degree of contamination. Inaccurate or vague data can be input to describe background and sediment assays, or alternatively, measurements are,transformed into linguistic expressions with respective Degrees of Belief to feed heuristic models based on neural network equations. The paper presents this fuzzy adaptive method and shows its potential for modeling cases such as AIDS research, technological innovation and other risk-assessment problems.