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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable according to OECD criteria: 92% after 30 days based on O2 demand (OECD 301 D).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Since no reliable biodegradability tests are available for C8-10AS Na (CAS 85338-42-7), 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 the following category members were used: C10AS Na (CAS 142-87-0) and C8AS Na (CAS 142-31-4).

The key, non-GLP study assessing biodegradation of C10AS Na (CAS 142-87-0) was performed according to OECD guideline 301 D (Richterich 2001). 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. Based on these results it can be concluded that C10AS Na (CAS 142-87-0) is readily biodegradable. This outcome was confirmed by a supporting non-GLP study performed according to OECD 301 E guideline (Sanchez Leal et al. 1991). Biodegradation reached ca. 90% after 8 days of testing.

Four studies on biodegradation in water are available for C8AS Na (CAS 142-31-4). A GLP test was performed according to OECD guideline 301 B (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 supporting GLP study was performed according to 301 D guideline (Marks 1991). Non-adapted effluent of a SCAS unit was used as inoculum and the initial concentrations of the test substance were 2 and 5 mg/L. Biodegradation measured as O2 consumption reached 98% after 28 days at the concentration 2 mg/L and above 72% at the concentration of 5 mg/L. The 10-day window was passed (more than 68% biodegradation after day 5). Another, non-GLP supporting study was performed according to OECD 301 D guideline (Richterich and Mühlberg 2001). Effluent of a municipal sewage treatment plant was used as inoculum and the initial concentrations of the test substance were 2 and 5 mg/L. Biodegradation measured as O2 consumption reached 91% and 94% after 28 days, respectively. The 10-day window was passed in both cases (more than 80% biodegradation at day 10). The last non-GLP study (Sanchez Leal 1991) was performed according to OECD 301 E guideline. Biodegradation reached ca. 100% after 8 days. It can be concluded that C8AS Na (CAS 142-31-4) is readily biodegradable according to OECD criteria.

Due to structural and property similarities with the tested category members it can be concluded that C8-10AS Na (CAS 85338-42-7) is readily biodegradable according to OECD criteria.