ASSESSING THE FATE OF NEW AND EXISTING CHEMICALS - A 5-STAGE PROCESS

A five-stage process is described for obtaining an understanding of th e fate of a substance after discharge to the environment and for predi cting the concentrations to which organisms in various environmental m edia will be exposed. These five stages are: classifying the substance as to its chemical type and collecting the appropriate physical, chem ical, and reactivity data based on this classification; obtaining info rmation on the substance's past, present, and/or proposed production, use, and discharges and, if appropriate, background concentrations; co nducting an evaluative fate assessment with the objective of determini ng the general features of the substance's behavior; conducting a regi onal or far-field fate evaluation using regional climatic and geograph ic conditions, to determine the role of environmental conditions on th e substance's behavior and estimate average regional concentrations; a nd conducting one or more local or near-field evaluations on points of entry and other potentially impacted sites to predict the exposure co ncentration. With this information on fate, risk can be assessed by co mparing predicted environmental concentrations with no-effect concentr ations. This paper contains a detailed discussion of stage 1 (classifi cation into one of five categories) and a discussion of how multimedia models can be used to conduct the evaluative (stage 3), regional (sta ge 4), and near-field (stage 5) assessments.