Oecd guideline for testing of chemicals

301
Adopted: 17.07.92

OECD GUIDELINE FOR TESTING OF CHEMICALS
Adopted by the Council on 17th July 1992 Ready Biodegradability

INTRODUCTION 1. In this Guideline six methods are described that permit the screening of chemicals for ready biodegradability in an aerobic aqueous medium. They are: 301 A: DOC Die-Away 301 B: CO2 Evolution (Modified Sturm Test) 301 C: MITI (I) (Ministry ofInternational Trade and Industry, Japan) 301 D: Closed Bottle 301 E: Modified OECD Screening 301 F: Manometric Respirometry Method 301 A is similar to the ISO Standard 7827-1984 and replaces the Modified AFNOR method; AFNOR has adopted the ISO standard. Methods 301 B, 301 D and 301 E are modified versions of the earlier OECD Guidelines adopted in 1981. Method 301 C is virtually identical with earlierGuideline 301 C (MITI I). Method 301 F is new; it is similar to 301 C differing mainly in the inocula employed. 2. Much experience has accumulated with the six methods over the years including an OECD inter-laboratory comparison exercise (ring test) in 1988. The accumulated experience, and the ring test, have confirmed that the methods may be used for the assessment of ready biodegradability.However, depending on the physical characteristics of the substance to be tested, a particular method may be preferred. 3. General considerations including those common to all six methods are given hereafter. Details of individual methods are given under separate headings (301 A to F). Throughout the text the reader is referred to the Annexes which contain definitions (Annex I), formulas and usefulguidance material.

GENERAL PRINCIPLE OF THE TESTS 4. A solution, or suspension, of the test substance in a mineral medium is inoculated and incubated under aerobic conditions in the dark or in diffuse light. The amount of DOC in the test solution due to the inoculum should be kept as low as possible compared with the amount of organic carbon due to the test substance. Allowance is made for theendogenous activity of the inoculum by running parallel blanks with inoculum but without test substance, although the endogenous activity of cells in the presence of a chemical will not exactly match that in the endogenous control. A reference compound is run in parallel to check the operation of the procedures.

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OCDE / OECD 5. In general, degradation is followed by the determinationof parameters such as DOC, CO2 production and oxygen uptake and measurements are taken at sufficiently frequent intervals to allow the identification of the beginning and end of biodegradation. With automatic respirometers the measurement is continuous. DOC is sometimes measured in addition to another parameter but this is usually done only at the beginning and end of the test. Specific chemicalanalysis can also be used to assess primary degradation of the test substance and to determine the concentration of any intermediate substances formed. It is obligatory in the MITI method (301 C). 6. Normally, the test lasts for 28 days. Tests however may be ended before 28 days, i.e. as soon as the biodegradation curve has reached a plateau for at least three determinations. Tests may also beprolonged beyond 28 days when the curve shows that biodegradation has started but that the plateau has not been reached by day 28, but in such cases the chemical would not be classed as readily biodegradable.

INFORMATION ON THE TEST SUBSTANCE 7. In order to select the most appropriate method, information on the chemical’s solubility, vapour pressure and adsorption characteristics is essential. Thechemical structure or formula should be known in order to calculate theoretical values and/or check measured values of parameters, e.g. ThOD, ThCO2, DOC, TOC, and COD. Information on the purity or the relative proportions of major components of the test material is required in order to interpret the results obtained, especially when the result lies close to the pass level. 8. Information on the...