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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Ready biodegradation studies according to OECD Guidelines 301B („Ready Biodegradability: CO2Evolution Test”.) and 301F (“Manometric respimetory method") have been conducted with Nonylphenol (NP).

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable, fulfilling specific criteria

Additional information

NP did not pass the 301B test for ready biodegradability (Gledhill et al., 1999), however results show that significant degradation (48%) of NP (CAS No. 84852-15-3; branched Nonylphenol) occurred (as measured by CO2 evolution). NP specific analyses of the water phase confirmed the degradation of the test material (Staples et al., 2001).

In the tests according to OECD Guideline 301F the biodegradability of NP could be confirmed. In the test conducted by Staples et al. (1999) NP (CAS No. 84852-15-3; branched Nonylphenol) met the criteria for ready biodegradability except for the 10-day window. Stasinakis et al. (2008) used 4-n-NP (CAS No. 104-40-5; linear isomer) in OECD 301F, resulting in ready biodegradability for 4-n-NP. The differences in the results of the two tests conducted by Staples et al. (1999) and Stasinakis et al. (2008) is due to structural differences between the isomers. More highly branched molecules may be less biodegradable because of steric hindrance.

It can be concluded that the linear NP isomer is readily biodegradable. In view of the stringent conditions employed in such screening tests, the branched NP isomer cannot be considered persistent. Biodegradation is an important removal process of NP in surface water and treatment plants.