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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: 60-63 % based on parallel A in two independent experiments (CO2 evolution) in 28 days 

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

A GLP study with Multi constituent ester of pentaerythritol 2-ethylhexanoate was conducted under aerobic conditions according to OECD guideline 301B using non-adapted, domestic activated sludge as inoculum (Desmares-Koopmans, 2013). The Total Organic Carbon (TOC) content of the substance was determined to be 69%. The test substance was tested in duplicate at approximately 18 mg/l, corresponding to 12 mg TOC/l.

Based on the TOC content the ThCO2 of the substance was calculated to be 2.54 mg CO2/mg.

Since in first experiment the difference in percentage of biodegradation between the two test bottles was more than 20%, a second experiment was performed. The findings of the first experiment were confirmed by the second experiment.

In both experiments weighed amounts were added to the 2-litres test bottles containing medium with microbial organisms and mineral components. To this end, 10-20 ml of Milli-RO water was added to each weighing bottle containing the test substance. After vigorous mixing (vortex) the resulting suspension was added quantitatively to the test medium. The test solutions were continuously stirred during the test, to ensure optimal contact between the test substance and the test organisms. Test duration was 28 days (last CO2-measurement on the 29th day).

In the 1st experiment the relative biodegradation values calculated from the measurements performed during the test period revealed 63% and 35% biodegradation of Multi constituent ester of pentaerythritol 2-ethylhexanoate, for test bottle A and B, respectively. 

In the 2nd experiment the relative biodegradation values calculated from the measurements performed during the test period revealed 60% and 24% biodegradation of Multi constituent ester of pentaerythritol 2-ethylhexanoate for test bottle A and B, respectively. 

Since, the batch of Multi constituent ester of pentaerythritol 2-ethylhexanoate consisted of a mixture of structurally similar chemicals, it was anticipated that a sequential biodegradation of the individual structures took place. Therefore, the 10-day window was not applied to interpret the results of the test and the criterion for ready biodegradability was met in test bottle A of both experiments.

Percentage biodegradation in the toxicity controls on Day 14 was 39% and 14% in experiment 1 and 2, respectively, thus only in experiment 1 the 25% threshold for inhibition was met. However, one of the test bottles reached 60% biodegradation, which indicated that the test substance did not inhibit microbial activity. Therefore it was concluded, that Multi constituent ester of pentaerythritol 2-ethylhexanoate was found not to inhibit microbial activity.

Except that the acceptability criteria adressing a maximum variation of 20% between test bottles in an experiment was not met in both experiments, which was considered to have no adverse effect on the test, all criteria for acceptability of the test were met. Therefore, this study was considered to be valid.

 

In conclusion, Multi constituent ester of pentaerythritol 2-ethylhexanoate was designated as readily biodegradable.