The concept of stability fields and hot spots in ranking of environmental chemicals.

In contrast to conventional multi-criteria decision aids, such as the well known PROMETHEE approach, AHP or the different versions of ELECTRE, we support the basic assumption of environmetrics: let first the data speak, and then let us include subjective preferences in order to get a unique decision. In the present paper we introduce and discuss the decision support system METEOR (Method of Evaluation by Order Theory). The basis of the method is a data matrix. The rows are defined by the objects which are to be evaluated; the columns are defined by the attributes, which characterize the objects with respect to the evaluation problem. By means of the attributes a partial order is derived. In subsequent steps attributes are aggregated by a weighting procedure, allowing a high degree of participation of stakeholders and other participants of the planning process. The aim is to enrich the partial order stepwise, until the objects of interest can be compared. The software WHASSE written in Delphi is available for scientific purposes from the first author. As an example we evaluate 12 high production volume chemicals (HPVC) which have been detected in the environment by four attributes and discuss the enriched partial order after introducing some weights. It turns out that in some cases the weights have almost no influence concerning the evaluation result, whereas in some other cases slight variations of weights drastically change the evaluation result. Therefore, the metric space spanned by weights can be partitioned in so-called “stability fields” where the evaluation result is invariant and in so-called “hot spots”, where the evaluation is strongly changing. This characterisation of the space of weights is helpful for stakeholders to express their preferences