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Biodegradation in water: screening tests

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Description of key information

Within a 47 d degradation study according to the OECD Guideline 301F, 61 % of

the test substance (sulfonic acids, C14 -17 alkane, Ph esters) were degraded based on the oxygen consumption (Bayer Industry Services, 2004).

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

The lowest degradation was observed in the study Mitsubishi (2003) with 23 % degradation after 28 days. Despite that study showed the lowest degradation it was not chosen as key study.

According to the OECD Guideline No 301, the activity of the used sludge should be proved by the means of a reference substance showing a degradation of at least 40 % and 65 % after 7 d and 14 d, respectively. As aniline, chosen as reference substance, was degraded about 54 % (7 d) and 63 % (14 d), the validity criteria set out by the guideline are not completely fulfilled by Mitsubishi (2003). The degradation power of the sludge slowed down after seven days (as can be seen at the degradation of the reference substance). The degradation of sulfonic acid, C14-17-alkane, Ph esters starts after a lag phase of approximately 7 days. Thus, the low degradation might be the result of the low activity of the sludge rather than of the non-degradability of the test item.

Therefore, the study of Bayer Industry Services (2004) was chosen as key study, as it was a GLP Guideline study fulfilling the validity criteria. Furthermore, the test was prolonged to 47 days as the plateau was not reached after 28 days.

Additionally, one study with hexadecane sulfonic acid phenyl ester was conducted (Bayer AG, 2003). That substance was chosen as representative for the UVBC substance sulfonic acids, C14-17-alkane, Ph esters as the aliphatic part of the UVCB substance mainly consists of linear C14 to C17 chains. The degradation of the test item was delayed as well just starting after day 8 of the degradation study. The degradation curve showed that the plateau was not reached yet after 28 days with still ongoing degradation.

As sulfonic acids, C14-17-alkane, Ph esters did not reach the pass level after 28 days, it cannot be classified as readily biodegradable. But there is evidence, supported by the degradation of the hexadecane sulfonic acid phenyl ester, that degradation takes place just starting after a lag phase of approximately one week. Therefore, the substance can be scored as almost biodegradable.