Assessing the fate of new and existing chemicals: A five-stage process

A five-stage process is described for obtaining an understanding of the fate of a substance after discharge to the environment and for predicting the concentrations to which organisms in various environmental media will be exposed. These five stages are: classifying the substance as to its chemical type and collecting the appropriate physical, chemical, and reactivity data based on this classification; obtaining information on the substance's past, present, and/or proposed production, use, and discharges and, if appropriate, background concentrations; conducting an evaluative fate assessment with the objective of determining the general features of the substance's behavior; conducting a regional or far-field fate evaluation using regional climatic and geographic conditions, to determine the role of environmental conditions on the substance's behavior and estimate average regional concentrations; and conducting one or more local or near-field evaluations on points of entry and other potentially impacted sites to predict the exposure concentration. With this information on fate, risk can be assessed by comparing predicted environmental concentrations with no-effect concentrations. This paper contains a detailed discussion of stage 1 (classification into one of five categories) and a discussion of how multimedia models can be used to conduct the evaluative (stage 3), regional (stage 4), and near-field (stage 5) assessments.