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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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bioaccumulation in aquatic species: fish
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Key value for chemical safety assessment

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Experimental data on bioaccumulation of (Z)-N-Octadec-9-enylhexadecan-1-amide (CAS No. 16260-09-6) is not available. The evaluation of the bioaccumulation potential of the substance is therefore based on all available related data. This is in accordance to the REACh Regulation (EC) No 1907/2006, Annex XI General rules for adaptation of the standard testing regime set out in Annexes VII to X, 1.2, to cover the data requirements of Regulation (EC) No. 1907/2007 Annex IX and X (Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance, R., page 123 ff (ECHA, 2012)).

The bioaccumulation potential of a substance is driven by the physic-chemical properties of the substance triggering the bioavailability as well as by metabolism and excretion. As the test substance is highly insoluble in water (< 0.01 mg/L) the bioavailability of the substance in water is negligible. Though the substance has a high partition coefficient (log Kow of > 5.7) indicating the potential to bioaccumulate a significant accumulation is not expected based on the environmental fate and on BCF/BAF calculation.

The log Koc values of > 5 indicates that the substance will adsorb to suspended organic particles, dissolved organic matter and to some degree biota in the aquatic environment. If available, a potential uptake of the substance by organisms of the pelagic zone is expected to occur mainly via food ingestion since the substance may adsorb to solid particles.

Despite that the substance is not readily biodegradable elimination in sewage treatment plants is expected due to the high adsorption potential and the very low water solubility. Insoluble substances are largely removed in the primary settling tank and fat trap during the clarification and sedimentation process of waste water treatment (according to the Guidance on information requirements and chemical safety assessment, Chapter R7. b (ECHA, 2012)). Only small amounts of the substance may enter the secondary treatment and thus get in contact with activated sludge. Due to the high log Koc calculated for the substance components an extensive adsorption to sewage sludge is expected. Thus the substances is expected to be removed from the water column to a significant degree (Guidance on information requirements and chemical safety assessment, Chapter R.7a (ECHA, 2012)). Thus a significant uptake of the substance by aquatic organisms through the water phase is not expected. Considering this, one can assume that the availability of the substance in the aquatic environment is generally very low, which reduces the probability of uptake by aquatic organisms

This assumption is supported by QSAR calculations using BCFBAF v3.01. BCF/BAF values calculated for the substance exhibit a low bioaccumulation potential (Knoell Consult GmbH, 2012). A calculated BCF/BAF of 0.89 L/kg (SRC BCFBAF v3.01 Arnot Gobas, upper trophic level) indicates that the substance has a low bioaccumulation potential.

But it supports the tendency that substances with high log Kow values have a lower potential for bioconcentration as summarized in the ECHA Guidance R.11 (ECHA, 2012) and they are not expected to meet the B/vB criterion, which is also in accordance with Annex IX of Regulation (EC) No 1907/2006.

The substance is characterised by a low water solubility and high log Koc leading to a low bioavailability. Due to its higher molecular weight, no extensive metabolism of the substance is expected but rather direct elimination. In conclusion, a bioaccumulation or biomagnification through the food chain of the substance is not expected. It can hence be concluded that the high log Kow, which indicates a potential for bioaccumulation, overestimates the bioaccumulation potential of the substance.