The use of ecosystem models in risk assessment

Ecosystem models, when used in conjunction with available environmental effects monitoring data enable informed decisions regarding actions that should be taken to manage ecological risks from areas of localized chemical loadings and accumulation. These models provide quantitative estimates of chemical concentrations in various environmental media. The reliable application of these models as predictive tools for environmental assessment requires a thorough understanding of the theory and mathematical relationships described by the models and demands rigorous validation of input data and model results with field and laboratory data. Food chain model selection should be based on the ability to best simulate the interactions of the food web and processes governing the transfer of chemicals from the dissolved and particulate phase to various trophic levels for the site in question. This requires that the user be familiar with the theories on which these models are based, and be aware of the merits and short comings of each prior to attempting to model food chain accumulation. Questions to be asked include: are all potential exposure pathways addressed? are omitted pathways critical to the risk assessment process? is the model flexible? To answer these questions one must consider the, chemical(s) of concern, site-specific ecosystem characteristics,more » risk assessment receptor (aquatic, wildlife, human) dietary habits, influence of effluent characteristics on food chain dynamics.« less