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A large number of tests on biodegradability are available for o-toluidine. In the following the tests that were conducted according to standard methods are presented. Several experimental data prove that o-toluidine is readily biodegradable.

The biodegradability of o-toluidine under the conditions described by the OECD TG 301 A and E was tested by 6 different laboratories. All the laboratories followed the same procedure. Based on DOC measurement the following results were obtained after 28 days: with the method OECD TG 301 E, five laboratories obtained > 90 % biodegradation, the other one reported a 67 % value. The results obtained with the method OECD TG 301 A showed biodegradation between 88 and 90 % after 28 days. In all cases the 10 d-window criterion was fulfilled.

According to the national Japanese standard method comparable to the OECD TG 301 C guideline an aerobic ready test was performed. Related to BOD after a period of 28 days 65.4 % biodegradation was observed. No information is given in relation to the 10 d-window.

Results on the inherent biodegradability of o-toluidine are also available.

A test on inherent biodegradability was conducted. The test design is comparable to the Zahn-Wellens-Test (OECD TG 302 B). The test substance o-toluidine in a concentration of 200 mg/L COD was the sole source of carbon. Activated sludge from a sewage treatment plant adapted for 20 days to o-toluidine was used as inoculum in a concentration of 100 mg/L dry matter.

Based on COD measurement, a removal of 97.7 % within 5 days was obtained.

With adapted activated sludge from an industrial sewage treatment plant a test on inherent biodegradation was conducted. The procedure followed the OECD guideline 302 B. After 11 days (4 days adaptation) 96 % of the initial concentration were removed.

Biodegradation in river water was investigated in a simulation experiment. Test filter experiments were carried out in darkness under stable aerobic conditions by circulating water through a glass column filled with pumice. Based on the degradation parameters determined, o-toluidine was classified as biodegradable under the given conditions. Further, in mineral salts medium with and without (NH4)2SO4, complete removal of o-toluidine was achieved after 2 days and after 4 days, respectively. A Gram-positive bacterium (Rhodococcus rhodochrous) with the ability to utilize o-toluidine as sole source of carbon and nitrogen was isolated from soil.

Under anaerobic conditions o-toluidine could not be removed after a period of 10 month in an aquifer slurry. o-Toluidine revealed no biotic transformation, neither under sulfate reducing nor under methanogenic conditions.

In a further test o-toluidine could not be removed after 150 days in a landfill environment under anaerobic conditions. The test was not performed according to current standard methods but indicates that the substance is stable under anaerobic terms.