Standardised OECD tests

Classification categorises substances by their inherent properties to cause harm to man or the environment, based on the results of standardised laboratory tests. Presently such classifications are used only in the EU, although their wider use via the Organisation for Economic Co-operation and Development (OECD) may be a future development. The classifications lend themselves as criteria for selection of solvents, which will be of value both within and outside Europe. 

OECD. 2003h. Detailed background review of the uterotrophic assay. Summary of the available literature in support of the project of the OECD taskforce on endocrine disrupters testing and assessment (EDTA) to standardise and validate the uterotrophic assay. OECD Series on Testing and Assessment No. 38. Environment Directorate, Joint Meeting of the Chemicals Committee and the Working Party on Chemicals, Pesticides and Biotechnology. ENV/JM/MONO(2003)1. Paris OECD. 

In recommending assays, the existence of an internationally standardised protocol is an important factor for the credibility of a given test. Coupled to this, however, is the recognition that there can be a considerable time delay before standardisation is attained and in any case current standard tests have not been fully developed for contaminated soil assessment. Even when tests become standardised, developments do not cease and methods can change on the basis of improved knowledge. For example, a revision of the OECD terrestrial plant growth test (OECD, 2000) first published in 1984 (OECD, 1984) has been... 

The standardised methods OECD 201 [52] and DIN 38412 L33 [54] could both be applied for aqueous samples and for elutriates from compost and soil. Generally, the liquid sample is inoculated with a defined algal species in a specified concentration (e.g., 10 cells/cm final volume) and a mixture of essential mineral nutrients is added from a concentrated stock solution. Growth of the algae is determined periodically over 72 h. The growth curve is integrated and the relative numbers are compared between the samples and a control. A reference, in most cases potassium dichromate, is used to validate the test. 

The freshwater micro-crustacean Daphnia magna is the most often used organism for the standardised methods OECD 202 [45] and DIN 38412-30 [50]. For a short-term test, five animals of a defined physiological state are added to about 25 cm of an aqueous sample or its dilutions. The survival of the Daphnia is observed over a period of 48 hours and compared with the survivors of the control test. For a long-term test the same set up is used but the animals are fed with algae and exposed over a period of up to four weeks. The number of young Daphnia (due to reproduction) is counted and compared with those of the control test. Defined concentrations of potassium chromate are used as a positive reference to validate the required sensitivity of the animals. 

One of the pioneer organisations, which made serious efforts towards standardisation of biodegradation, is the The Organisation for Economic Co-operation and Development (OECD) which published a first series of standardised tests in 1981 with the OECD Guidelines for the Testing of Chemicals [3]. Besides biodegradation tests, these guidelines include various other test procedures such as physico-chemical properties, effects on biotic systems, bioaccumulation and health effects. 

This test is also known under its more popular name of Sturm test after the scientist who developed this test and wrote the first publication on it [6]. The test later became standardised at the OECD level (OECD 301B) [7] and ISO level (ISO 9439) [8]. Yet, these two test procedures were written for low-molecular-weight compounds to be tested at low concentrations and were less suitable for biodegradable polymers with a high molecular weight. 

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