Evaluating environmental persistence
1998
Webster, E. | Mackay, D. | Wania, F.
Environmental persistence is an important consideration when assigning priorities to chemical contaminants. It has been proposed that pass/fail half-life criteria be established for the media of air, water, soil, and sediment. The feasibility of applying such criteria is discussed. It is shown that there are severe problems in estimating these half-lives. Additionally, it is shown that the overall environmental half-life or persistence in a multimedia environment is also a function of the mode of entry of the chemical and its partitioning properties. Examples of potential misclassification are presented. An alternative two-tiered procedure is suggested in which the first tier considers only media half-lives and the second tier considers the overall half-life as deduced by mass-balance models. Furthermore, the overall persistence calculated in the second tier should be given as a distribution rather than a single value. This procedure enables chemicals to be compared, avoids undue reliance on relatively unimportant half-lives, and is regarded as a truer depiction of actual chemical persistence in the environment.
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