A respirometric method for the assessment of ready biodegradability: results of a ring test.

A collaborative exercise involving twelve laboratories was organized for the European Economic Community to check the validity of an enclosed respirometric method for assessing the ready biodegradability of test chemicals, including insoluble substances. The method, based partly on the OECD-Japanese Ministry of International Trade and Industry (MITI) I method (301C) and partly on the U.K. method, allowed the use of a less restrictive, natural inoculum and a wider variety of respirometers than the original MITI I method. Eight compounds of a wide range of degradative behavior were tested over an incubation period of 28 days. The agreement between participating laboratories in the lag period before biodegradation started and in the proportions of theoretical oxygen uptake achieved was at least as good as in other ring tests; it is proposed that the method be accepted. Differences in behavior of pentaerythritol reported here and in the literature are examined and suggestions for future study are discussed.