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Biodegradation in water: screening tests

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Description of key information

P-toluenesulfonamide (PTSA): readily biodegradable - 83% biodegradation (based on O2 consumption) in 28 days (OECD 301D)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

As PTSI is extremely water-reactive, no biodegradation test could be performed with this substance. A ready biodegradability test according to OECD 301D, carried out under GLP, is available for the decomposition product of PTSI, p-toluenesulfonamide (PTSA). In this test nominal concentrations of 2 and 4 mg/l were tested. Blanks, a positive control and a toxicity control were included in the test set-up. The biodegradation values calculated from the O2 measurements performed during the test period of 28 days revealed a biodegradation of 86% and 45% of ThOD (mean values) of PTSA for the lowest (2 mg/l) and highest (4 mg/l) concentration, respectively. The toxicity control showed that PTSA did not inhibit microbial activity at 2 mg/l. In the highest concentration (4 mg/l) the onset of the observed oxygen consumption was delayed (longer lag phase); this explains the lower biodegradation level of 45 % reached after 28 days. This may be related to the higher substrate/inoculum ratio. In view of the low toxicity of PTSA to fish, invertebrates and algae, toxic effects on the inoculum are not expected to be the cause of the lower end result for 4 mg/l.

All validity criteria for the test were met.

Based on the results of this test, it can be concluded that PTSA is readily biodegradable, meeting the 10 -d window.