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Biodegradation in water: screening tests

Description of key information

Not readily biodegradable: 52% in 28 days (OECD 301B) 

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Additional information

The ready biodegradability of Amides, C18, branched and linear was investigated in a GLP study following OECD Guideline 301B (Roulstone, 2015). The inoculum, predominantly domestic non-adapted sewage, was exposed to a substance concentration of 10 mg carbon/L for 28 days. The biodegradation rate was determined by measuring the CO2 produced by degradation. A degradation rate of 52% was determined at test termination. The toxicity control showed no inhibitory effect of the test substance. A degradation rate of 63% was determined after 14 days and 67% biodegradation after 28 days of incubation. Thus, the test item is considered not inhibitory to activated sludge microorganisms. Amides, C18, branched and linear is an UVCB substance consisting mainly of two components with different degradation rates. QSAR calculations give opposite results for the substance components (BIOWIN v4.10, VEGA 1.1.0). Both estimation programmes predict ready biodegradability for the C18 linear component, whereas the prediction for the C18 iso component is not readily biodegradable. The biodegradation rate of the whole substance might thus be related to a delayed degradation of the C18 iso component. Though the results demonstrated no ready biodegradability a high persistency of the substance in the environment is not expected. This assumption is supported by data on the structural analogue substance erucamide (CAS 112-84-5). The substance was degraded by 64% after 28 days in a study, following OECD 301B, (Mead, 2000). Though the substance failed the 10-days window criterion it was considered readily biodegradable. The available data illustrate that testing the ready biodegradability of fatty amides produces varying results. The difficulties in testing the biodegradability result most likely from the low water solubility of the substances. Similar findings are reported in a hazard characterisation for fatty nitrogen derived amides by the U.S. EPA (2010). The report comes to the conclusions that fatty amides possess low persistence in the environment.
Thus, based on the experimental results Amides, C18, branched and linear has to be considered potentially persistent. However, a low potential to persist in the environment is anticipated for the substance.

A detailed analogue approach justification is provided in the technical dossier (see IUCLID Section 13).

References:

US EPA, 2010: Screening-level hazard characterisation. Fatty Nitrogen Derived (FND) Amides Category