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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Carboxylic acids, di-, C4-6 is readily biodegradable as well as inherently biodegradable.

Key value for chemical safety assessment

Additional information

Several screening tests on biodegradation in water are available resulting in ready biodegradability of the substance. The test were carried out with the mixture and the single acids.

There is one test available carried out to assess the ready biodegradability of the multi constituent substance “dicarboxylic acids”. The test substance was a residue from adipic acid manufacturing containing the following composition: 60 % adipic acid, 14 % glutaric acid, 6 % succinic acid, 10 % carbon, 6.5 % vanadium pentoxide, 3 % copper nitrate and 5 % copper (Bayer, 1988c). Using this mixture, a Closed Bottle Test was performed resulting in 56 % degradation after 28 days of exposure. It is discussed in the ICCA OECD/HPV-program, that it is not clear how the compounds other than the dicarboxylic acids affect the biodegradation. Therefore, the study should not be used for assessment.

In a test on ready biodegradability of adipic acid conducted according to the OECD guideline 301 D (Determination of the Ready biodegradability: Closed Bottle Test) 83 % degradation was observed after 30 days (Gerike, 1979). Although, no information on the 10-day window criterion is given, and more than 70% of the test substance has been degraded indicating a potential for complete ultimate biodegradation, it is considered that the criteria for ready biodegradability are fulfilled.

Regarding the ready biodegradability of succinic acid, an aerobic ready test, performed according to the national Japanese standard method comparable to the OECD TG 301 C guideline. After a period of 2 weeks more than 90% biodegradation of succinic acid was observed (MITI, 2002).

Concerning ready biodegradability of glutaric acid, 100 % of the test substance had been degraded after 14 days in a Modified OECD Screening Test. (EU Method C.4-B (Determination of the "Ready" Biodegradability - Modified OECD Screening Test)) (Bayer AG, 1993).

Based on this result the substance should be classified as readily biodegradable.

With regard to dicarboxylic acids, only one test for inherent biodegradation of dicarboxylic acids in water exists. The test was performed according to OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test). The biodegradation rate was 99 % after 7 d (BASF, 1988).

Based on these results the subtsance is considered to be inherently biodegradable.