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Toxicity to microorganisms

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Description of key information

An EC50 of 155 mg/l was determined in a growth inhibition test with Tetrahymena pyriformis.

Key value for chemical safety assessment

EC50 for microorganisms:
155 mg/L

Additional information

Several tests on toxicity towards microorganisms are available.

o-Toluidine was assessed within the scope of the ICCA/HPV-program, and the test procedures described by Bringmann and Kuehn were scored to be reliable for assessment. Bringmann and Kuehn (1979, 1980, 1981) carried out tests on the toxicity of o-toluidine towards other microorganisms following the cell multiplication inhibition test (test described by Bringmann (1978)). The test performed with Uronema parduzci had a duration of 20 hours and an EC5 of 21 mg/l was obtained. The result obtained after 72 hours with Entosiphon sulcatum was an EC5 of 76 mg/l, and with Chilomonas paramaecium after 48 hours an EC5 of 237 mg/l was observed. A test with Pseudomonas putida with duration of 16 hours was performed according to the method designed by Bringmann and Kuehn (1976). Endpoint was inhibition of cell multiplication. An EC3 value (reported as toxicity threshold [TT]) of 16 mg/l was observed. The author reported the results as toxicity threshold (TT). These test are not any longer state-of-the-art, due to deficiencies on documentation, test design and interpretation of test results. Therefore, they are not taken into account for assessment. Nevertheless, even if these values were considered for PNEC-derivation, they would not lead to the most sensitive PNEC-value.

Two Ciliate growth inhibition tests are scored to reliable and are used for assessment.

The toxicity of o-toluidine to Tetrahymena pyriformis was tested in a 40 hours test using the population growth impairment as endpoint. The test was performed according to the method described by Schultz (1997). An EC50 of ca. 155 mg/l was observed (Schultz, 1999). In another test performed with Tetrahymena pyriformis with the cell multiplication inhibition as the endpoint, a 24 h-EC50 of 520 mg/l was obtained (Yoshioka, Ose and Sato, 1985).