Abstract

This report contains an appraisal of the OECD hierarchy for testing the biodegradability of industrial chemicals. A more pragmatic system is proposed which encompasses (1) selecting both the "soft" and the "hard" chemicals, (2) screening chemicals for potential biodegradability in a specified environmental compartment and (3) simulation methods. Methods of level 91) should be applicable to all chemicals, irrespective of their physico-chemical and biological properties. "Soft" chemicals can be recognized by a positive result in a Ready Biodegradability Test (RBT), wheras a negative result in a so-called Inherent Biodegradability Test (IBT) is an indication for persistence of a compound. Although RBT's have been update in 1990, they still suffer from some shortcomings. In this report simple modifications of existing methods are discussed to overcome these shortcomings together with more satisfactory methods, which have been developed the last decade. The limitations of Inherent Biodegradability Tests are evaluated and alternative techniques are proposed to make IBT's applicable to a wider range of physico-chemical properties. Recently developed useful methods, such as test for sea-water and the anaerobic compartment, proved problematic to place in the current OECD test hierachy but fitt easily in level (2) of the proposed test system.