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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Ready biodegradable according to OECD criteria (weight of evidence)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Since no reliable biodegradability tests are available for C8-18AS Mg & TEA (CAS 85586-38-5), in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read-across to another structurally related category members was conducted. Read-across data from C8AS Na (CAS 142-31-4), C10AS Na (CAS 142-87-0), C12AS Na (CAS 151-21-3), C14AS Na (CAS 1191-50-0), C16-18AS Na (CAS 68995-20-4), C18AS Na (CAS 68140-10-3) and C12-18AS Na (CAS 68955-19-1) were used.

The study with C8AS Na (CAS 142-31-4) was performed according to OECD guideline 301 B and is GLP compliant (Neven 1994). Activated, domestic, non-adapted sludge from predominantly municipal STP was used as inoculum. The initial concentration was 10 mg C/L expressed as DOC. CO2 evolution was measured for 29 days. Biodegradation reached 93.5% after 29 days and 80% after 10 days passing the 10-day window.

The non-GLP study assessing biodegradation of C10AS Na (CAS 142-87-0) was performed according to OECD guideline 301 D (Richterich 2001a). Effluent of the sewage treatment plant handling predominantly domestic sewage was used as inoculum. The initial concentrations of the test substance were 2 mg/L and 5 mg/L. Biodegradation of 98% measured as oxygen demand was observed after 30 days at the initial concentration of 2 mg/L and 92% at the concentration of 5 mg/L. The test substance was biodegraded by more than 60% in both cases within five days.

For the C12AS Na homologue (CAS 151-21-3), a GLP-guideline study according to OECD guideline 301 B is available (Brunswik-Titze 2005).  In this study, activated, non-adapted domestic sludge was used as inoculum and the initial concentration of the test substance was 20 mg/L as DOC. Based on the CO2 evolution measurements, the biodegradation reached 95% after 28 days and the 10-day window was passed.

One GLP study showing ready biodegradation of C14AS Na (CAS 1191-50-0) is available (Hansmann 1995). This study was performed according to OECD 301 B guideline using activated, domestic, non-adapted sludge as inoculum and the initial concentration of the test substance 11 mg/L as TOC. Biodegradation measured as CO2 evolution was greater than 60% after 10 days. The final level of biodegradation after 28 days was 79.8%.

In the non-GLP study with C16-18AS Na (CAS 68955-20-4) according to OECD guideline 301 D (Richterich 2001b) effluent of a municipal sewage treatment plant was used as inoculum. The initial concentration of the test substance was 5 mg/L as DOC. Biodegradation based on DOC removal reached 59% after 5 days and 77% after 30 days.

The inherent biodegradability of C18AS Na (CAS 68140-10-3) was determined in a GLP compliant test performed according to OECD guideline 302 A. Predominantly domestic, non-adapted sewage was used as inoculum and the initial concentration of the test substance were 29 mg a.i./L, equal to 19.5 mg/L of DOC. Biodegradation measured as DOC removal reached 99.2% on day 21.

The biodegradability of C12-18AS Na (CAS 68955-19-1) was investigated in a GLP guideline study according to EU method C4 (Diefenbach 1997). Activated, non-adapted sludge coming from a communal sewage treatment plant was used as inoculum. The initial concentration of the test substance was ca. 45 mg a.i./L, equal to ca. 16.5 mg/L of DOC. Biodegradation measured after 28 days as CO2 evolution reached 93%.

Due to structural and property similarities with the tested category members it can be concluded that the above results apply also to C8-18AS Mg & TEA (CAS 85586-38-5). The substance can be considered as readily biodegradable according to OECD criteria.