An assessment in practice of theoretical and practical aspects of the formulation of an environmental quality index
Theoretische en praktische aspecten van de formulering van een milieukwaliteitsindex in de praktijk getoetst
RIVM Report 482516007
This report describes methods that aim to summarize a particular aspect of environmental quality (like heavy metals in the soil, pesticides in soil water) in a single number. All methods have in common that they result in a number between 0 (worst possible outcome) and 100 (the environmental situation is equal to or better than the standard). The methods differ in the weights they assign to exceedances of environmental standards and in statistical treatment of the data. The various methods are compared by applying them to a number of actual data sets. It is concluded that the differences between the methods are relatively small, despite different theoretical foundations. From this it is concluded that practical considerations rather than theory should guide the choice for a particular method. The methods are subsequently judged on a number of practical criteria: simplicity, sensitivity and consistency. This comparison considerably reduces the number of candidate methods. The consequences of the results for the formulation of an environmental quality index at a higher level of aggregation than discussed in the present report (for example: a national aggregation of environmental themes) is discussed. As long as different environmental variables show similar trends, the question of weighing in the aggregation of indices does not play a major role. A national aggregation of environmental indices requires a system that collects, retrieves and manipulates the required environmental data. If such a system becomes available, the definition of environmental quality indices at different levels of aggregation appears to be straightforward. A straightforward method to assess the variability of such a system is to calculate the required index for a number of years.