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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Not readily biodegradable: < 10% - 24% degradation (OECD 301 D, 301 F, DGXI/400/84 EEC 19984, L251, 1984.09.19, Part C, EEC 1984)

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Studies on the ready biodegradability of (Z)-N-octadecyldocos-13-enamide (CAS No. 10094-45-8) are not available. Therefore data of the analogue substanceN-octadecylstearamide (stearyl stearamide, CAS 13276-08-9) were used as read-across.The read-across is justified due to the structural similarity of the analogue substances and similar physico-chemical properties resulting in a similar environmental fate and ecotoxicity profile.This read-across is in accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5 and justified in detail in the overall summary (IUCLID Chapter 6.1) and within the category justification attached in IUCLID Section 13. The ready biodegradability of N-octadecylstearamide (stearyl stearamide, CAS 13276-08-9) was investigated in five tests.

The first study comprises a test according to OECD guideline 301 D and a repetitive die away test following DGXI/400/84, EEC 1984 (Balk, 1989). Both tests were carried out under GLP and have a test duration of 6 weeks. In the OECD closed bottle test 2.04 mg/L of the substance was incubated with domestic activated sludge. The substance reached 8% degradation after 28 days and 9% degradation after 42 days. In the die away test 40 mg/L of the substance was incubated with industrial non-adapted activated sludge as inoculum. Degradation rates were 23% after 28 days and 29% after 42 days. The second study is a closed bottle test equivalent to the guideline L251, 1984.09.19, Part C, EEC 1984 (van Ginkel, 1988). Domestic activated sludge was used as inoculum and incubated with 2 mg/L of the substance. The degradation after 28 days was < 10%. The third study comprises two tests according to OECD guidelines 301 D and 301 F (Kolvenbach, 1989) using effluent from a municipal waste water treatment plant as inoculum. The closed bottle test applying 1.8 ppm of the substance resulted in 20% degradation after 28 days. The CO2 evolution test applying 10 and 20 ppm of the substance resulted in maximum degradation rates of 24% with non-adapted inoculum and 19% with adapted inoculum. Altogether it is stated that the substance can be regarded as not readily biodegradable under OECD criteria.