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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: 77% after 30 days based on DOC removal (OECD 301 D).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Since no reliable biodegradation tests are available for 16-18 and C18–unsatd. AS Na (CAS 1394155-71-5), 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 available for C16-18AS Na (CAS 68955-20-4) were used. Biodegradation will be similar for alkyl sulfates representing the same carbon chain length and presence of the unsaturated bonds will not influence the biodegradation rate.

Several studies proving ready biodegradation of C16-18AS Na (CAS 68955-20-4) are available. In the non-GLP key study according to OECD 301 D guideline (Richterich 2001) 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 test substance can therefore be considered as readily biodegradable.

Supporting studies confirm the above result. The publication of Steber (1988) includes several biodegradability tests with C16-18AS Na (CAS 68955-20-4). The OECD screening test, conf. to Directive 73/405/EEC (MBAS removal) was performed with effluent of a sewage treatment plant (predominantly domestic) and initial concentration of the test substance was 5 mg/L. After 19 days 99% of the test substance was biodegraded (measured as MBAS removal). Another available test was performed according to EU Method C.4-E. Again, effluent of a predominantly domestic sewage treatment plant was used as inoculum and the initial concentration of the test substance was 5 mg/L. Based on O2 consumption biodegradation reached 77% after 28 days. 52% of the substance was biodegraded after 5 days. Moreover, an OECD 301 E guideline study is available. An effluent of a predominantly domestic sewage treatment plant served as inoculum and the initial concentration of the test substance was 10 mg/L. Biodegradation measured as TOC removal reached 85-88% after 28 days. Finally, the OECD confirmatory test - coupled units test is available. Activated domestic sludge was used as inoculum and the initial concentration of the test substance was 20 mg/L as DOC. Biodegradation of 96% was measured based on DOC removal after 3 hours.

Due to structural and property similarities with the tested category member, it can be concluded that 16-18 and C18–unsatd. AS Na (CAS 1394155-71-5) is readily biodegradable according to OECD criteria.