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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

under test conditions no biodegradation observed

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The Ready Biodegradability potential of the substance was determined in the DOC Die-Away Test, according to the OECD Guideline 301A. The DOC values at the respective sampling days were compared to the DOC values determined on day 0 at begin of exposure. The following test assays were performed: two blank controls (containing only mineral medium), two test substance assays, one inhibition control assay, one reference substance assay, one assay for control of abiotic elimination and one assay for control of adsorption. The degree of biodegradation of the test substance at the end of exposure, based on the DOC removal, was lower than 10 %, thus the substance resulted as not readily biodegradable. (BASF SE, 2015).

A number of measurements of BOD5 and COD were performed on the substance under registration between 1975 and 1979. All tests resultoutcomes obtained in the key study.

Studies performed on three analogues of the substance under registration CAS 13863-31-5 are also here reported in order to confirm the not readily biodegradation potential and in order to assess the inherent biodegradability: CAS 16324-27-9, the analogous hydroxyethylamino derivative tetrasulphonated sodium salt (similar organic functional groups, higher solubility), CAS 4193-55-9, the analogous dihydroxyethylamino derivative disulphonated sodium salt (same sulphonation level, di-substitution with hydroxyethyl, same metabolic and degradation pathway) and CAS 16470-24-9, the analogue dihydroxyethylamino derivative tetrasulphonated.

For CAS 16324-27-9: a Zahn-Wellens study was performed on the substance to measure the adsorption; the study was not terminated and the adsorption at 24 hours was reported as 37.1 % (Novartis Services AG, 1997). Several screening studies (BOD/COD) are reported to confirm that the substance is not rapidly biodegradable and can be assumed as non readily biodegradable (Various, 2014).

For CAS 4193-55-9: biodegradation was assessed for the substance with a Zahn-Wellens test (Novartis Services AG. 1997), where the substance is demonstrated to adsorb to the sludge from 67 to 84 % in 24h and no biodegradation is observed. As a consequence the substance can be considered ad non readily biodegradable. The result is confirmed by a number of studies with low reliability, summarised in a report (Various 2014) and the provisional calculations based on the chemical structure.

For CAS 16470-24-9: in a ready biodegradability test according to OECD guideline 301A a DOC removal of 1.2 % was observed (Ciba-Geigy Ltd. 1992). Hence, the substance CAS 16470-24-9 is considered not readily biodegradable. Three BOD5 tests, in which no oxygen consumption was measured, confirm the non rapid biodegradability of the test substance. Additional information are given from two Zahn Wellens tests, performed according to the OECD 302B. One of them indicates a biodegradation of 24 % after 28 days (Ciba-Geigy Ltd., 1992): this value is obtained at about the fifth day, afterwards the degradation process seems to stop. The slope of the 28 days curve and the second test of inherent biodegradation (Novartis Services AG., 1997) reported suggest that the 24 % of DOC removal recorded in the first test can still be related to a slow adsorption process more than a biological degradation.

The available studies performed on structural analogous and here report in a weight of evidence approach, about the inherently biodegradation potential, agree to identify the substances as not inherently biodegradable.

In conclusion, the substance can be considered as neither readily nor inherently biodegradable.

[1]Biowin v.4.10 is an application contained in the EpiSuite 4.1, the suite of physical/chemical property and environmental fate estimation programs developed by the EPA’s Office of Pollution Prevention Toxics and Syracuse Research Corporation (SRC).