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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: 68% and 87% in 28 days (OECD 301D and F, respectively, based on read-across)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Since no study assessing the ready biodegradability of Glycerides, C16-18 mono-, di- and tri-, hydrogenated, citrates is available, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 Grouping of substances, read-across to source substances Glycerides, C16-18 mono-, di- and tri-, hydrogenated, citrates, potassium salts (CAS 91744-38-6) and Glycerides, C16-18 mono-, di- and tri-, hydrogenated, citrates, sodium salts (CAS 91744-39-7) is performed in a weight-of-evidence approach. This read-across is justified because both, target and source substances, are structurally identical except for the fact that source substances are either the potassium salt (CAS 91744-38-6) or sodium salt (CAS 91744-39-7) of the target substance. The potassium and sodium ions are not considered to alter environmental fate and ecotoxicity of the source substance in comparison to the target substance. Thus, functional groups, mode of action, biotransformation, environmental behavior and ecotoxicity profile can with very high certainty assumed to be identical.

 

First, read-across source Glycerides, C16-18 mono-, di- and tri-, hydrogenated, citrates, potassium salts (CAS 91744-38-6,) was tested for ready biodegradability according to OECD Guideline 301D (Closed Bottle Test) under GLP following the O2 consumption over a period of 28 days (Sasol, 2001). The substance was tested at an initial concentration of >4 - < 5 mg/L COD. Effluent of a domestic sewage plant was used as inoculum and benzoic acid, sodium salt served as reference substance. Oxygen measurements were performed at Days 0, 7, 14, 21, and 28. Benzoic acid, sodium salt was degraded to 76% after 28 d whereas 68% degradation could be observed for the test substance.

 

Furthermore, the biodegradation potential of source substance (CAS 91744-39-7) in water was determined in a screening study according to OECD TG 301F (Manometric Respirometry) and in compliance with GLP criteria (Evonik, 2010). In this study 100 mg/L test substance was inoculated with activated sludge from a municipal wastewater treatment plant for 28 days under aerobic conditions in the dark. During the incubation period the biological oxygen demand (BOD, measured as pressure decrease) was measured by a Digital Respirometer System. Biodegradation was expressed as percentage of the chemical oxygen demand (the chemical oxygen demand of the test substance was measured in a separate study). After the 28-day incubation period 87% of the substance was biodegraded.

 

In both studies the 10-day-window criterion was not met. However, since the test substances are a mixture of structure similar compounds the criterion of the ten days window was not applied. Such test substances are multi-component substrates and are typically characterized by different kinetic degradation steps. This evaluation is in accordance with the OECD Guidelines for the testing of chemicals, laid down in the revised introduction to the OECD Guidelines for testing of chemicals, section 3; Part 1, Principles and strategies related to the testing of degradation of organic compounds, adopted 23 March 2006. Both source substances are readily biodegradable. Therefore, the target substance Glycerides, C16-18 mono-, di- and tri-, hydrogenated, citrates is also assessed to be readily biodegradable.