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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The Reaction Mass of a,a,a’,a’-Tetramethyl-m-xylene-a,a’-diol and a, a, a’, a’ -Tetramethyl-p-xylene-a, a’-diol (m/p DIOL), was not readily biodegradable under the conditions of the test OECD 301B.  A mean total of 2.0% degradation was achieved by Day 28.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The ready biodegradability of the Reaction Mass of a,a,a’,a’-Tetramethyl-m-xylene-a,a’-diol and a,a,a’,a’ -Tetramethyl-p-xylene-a,a’-diol: (m/p DIOL) was assessed over a 28 day period by the CO2Evolution (Modified Sturm) Test. The study was conducted in accordance with procedures outlined in OECD Guideline 301B (1992).

 

The results of the test were as follows (28 day percent biodegradation values):

 

% Biodegradation

m/p DIOL
(Mean)

Sodium Benzoate

 Toxicity Control*

A

B

2.0

93.5

95.8

48.2

 

*The cumulative biodegradation determined in the Toxicity Control bioreactor is expressed in terms of the total organic carbon content resulting from the reference item only (A) and for the total organic carbon resulting from the reference and test item (B).

 

The test item (The Reaction Mass of a,a,a’,a’-Tetramethyl-m-xylene-a,a’-diol anda,a,a’,a’ -Tetramethyl-p-xylene-a,a’-diol: (m/p DIOL) was not readily biodegradable under the conditions of the test as it failed to achieve a transition from 10% to 60% degradation in a 10 day window during the 28 day test. The test item was not considered to be inhibitory to the microbial inoculum since the biodegradation observed in the toxicity control bioreactor was similar to that expected from the individual test and reference bioreactors.

 

The test failed to meet the validity criterion with respect to the differences in extremes of percent biodegradation in the test bioreactors. However, this was judged to be due to very low biodegradation values observed (1.8 and 2.2% for Test Bioreactors 1 and 2 respectively) and the possible influx of atmospheric CO2 into the final trap on Day 29. The test is therefore considered valid.