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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Two Key studies are available according OECD Guideline 301 B and 302 C.
The test item was not readily biodegradable under the conditions of the performed 28 Day CO2 Evolution (Modified Sturm) Test according to the OECD Guideline for Testing of Chemicals, No. 301 B and also not biodegradable according to the OECD guideline for Testing of Chemicals, No. 302 C.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Readily biodegradation

The test item was investigated for its ready biodegradability in a 28‑Day CO2Evolution (Modified Sturm) Test according to the OECD Guideline for Testing of Chemicals, No. 301 B.

The test item was found to be slightly biodegradable by 11.8% under the test conditions within the 28‑day exposure period.

 

However, the pass level for ready biodegradability, i.e. a CO2formation of at least 60% of thein a 10‑day window within the 28‑day period of the test was clearly not reached.

 

In the toxicity control, containing both the test item and the reference item sodium benzoate, no inhibitory effect on the biodegradation of the reference item was determined. Thus, the test item had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 242 mg/L.

 

 

Inherently biodegradation

The test item was investigated for its inherent biodegradability in a manometric respirometry test over 28 days based on the OECD Guideline for Testing of Chemicals No  302 C (1981). The following modifications were made: activated sludge from one source was used, the activated sludge was not fed during the holding period of maximum seven days, the test was run at 22 °C, the test water composition was slightly changed, and only the biological oxygen demand (BOD) was monitored, no test item specific analysis was performed.

 

The oxygen consumption of the test item in the test media was in the normal range of the oxygen consumption in the inoculum controls.

 

Consequently, the test item was not biodegradable under the test conditions within 28 days.

 

In the toxicity control, containing both the test item and the reference item sodium benzoate,
the test item had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 327 mg/L.

 

In the procedure controls, the reference item (sodium benzoate) was degraded by an average of 75% and 86% by Exposure Days 7 and 14, respectively, thus confirming suitability of the activated sludge. At the end of the test (Day 28), the reference item was degraded by an average of 93%.

Conclusion:

The REACH substance has a high molecular weight (98.98% > 1000 Dalton). Under environmental conditions the substance will be oxidized to very big polymeric structures with a very high molecular weight. The bioavailability of the substance is negligible (low potential to cross biological membranes) and no biodegradation could be expected. Therefore additional testing is not justified