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Sediment toxicity

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Description of key information

The chemical safety assessment according to Annex I of Regulation (EC) No. 1907/2006 does not indicate the need to investigate further the effects on sediment organisms.

Key value for chemical safety assessment

Additional information

The chemical safety assessment according to Annex I of Regulation (EC) No. 1907/2006 does not indicate the need to investigate further the effects on sediment organisms. Experimental data on the toxicity of Fatty acids, C16-18 and C18-unsatd., hexaesters with dipentaerythritol (CAS 68604-38-6) to sediment organisms are not available. Acute and chronic toxicity test on aquatic organisms show that the substance is not toxic to aquatic organisms up to the limit of water solubility. Thus, toxicity to sediment organisms is not expected to be of concern.

Distribution to the environmental compartments, intrinsic properties and fate

Fatty acids, C16-18 and C18-unsatd., hexaesters with dipentaerythritol (CAS 68604-38-6) is not readily biodegradable (7.6% (ThCO2) after 28 d (OECD 301 B). Thus the substance will not be degraded in sewage treatment plants. Nevertheless an extensive physical elimination of the substance in STPs is expected. Due to the high log Koc of 7.6 - 30.72 (KOCWIN v2.00; Hopp, 2011) and poor water solubility <0.15 mg/L; Frischmann, 2012) indicate that the substance will adsorb to solids and suspended material. The Guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA, 2012) states that once insoluble chemicals enter a standard STP, they will be extensively removed in the primary settling tank and fat trap and thus, only limited amounts will get in contact with activated sludge organisms. Nevertheless, once this contact takes place, these substances are expected to be removed from the water column to a significant degree by adsorption to sewage sludge (Guidance on information requirements and chemical safety assessment, Chapter R.7b, (ECHA, 2012)). Thus, only limited concentrations of the substance will presumably be discharged to the aqueous/sediment compartment. Thus, due to the low expected environmental concentrations of the substance a chronic exposure of sediment organisms is unlikely.

If the substance is present in the aquatic environment it will presumably adsorb to solid particles and suspended matter due to the low water solubility (< 0.15 mg/L) and high log Koc (7.6 – 30.72). Thus sediment organisms may ingest the substance via food uptake. When ingested, the substance might be hydrolysed and the cleavage products can be further metabolized. However, a bioaccumulation of the substance is unlikely due to the high molecular weight (MW: 1684 – 1853 g/mol) and structural complexity of the substance. A low potential to bioaccumulate is also indicated by the low calculated BCF values of 0.89 L/kg ww (BCFBAF v3.01, Arnot-Gobas, including biotransformation, upper trophic; Blum, 2011).

Aquatic ecotoxicity data
Available acute and chronic aquatic toxicity tests on fish and aquatic invertebrates determined no adverse effects in the range of the water solubility of the substance (WS < 0.15 mg/L; Frischmann, 2012). The acute toxicity of the substance was tested in a short-term study on Zebra fish (Danio rerio). Mortality or symptoms of intoxication were not observed up to the highest tested loading rate resulting in a LL50 (96 h) >100 mg/L. A comparable result was reported by a chronic toxicity test on Daphnia magna. The study focused on the mortality and reproduction of the test animals and determined no toxic effects up to the limit of water solubility (NOEC (21 d) ≥ 100 mg/L).

Metabolisms/Bioaccumulation
Enzymatic breakdown will initially lead to the fatty acid and the corresponding alcohol (Fukami & Yokoi, 2012). The log Kow calculated for the substance components ranges from 42.27 for the C16 FA component to 48.16 for the C18 FA component (KOWWIN v1.68; Blum, 2011) indicating a potential for bioaccumulation. Due to its high molecular weight, absorption of Fatty acids, C16-18 and C18-unsatd., hexaesters with dipentaerythritol is not likely and thus, no extensive metabolism in aquatic organisms is expected but rather direct elimination. In addition, the substance exhibits a low water solubility. Therefore, a relevant uptake and bioaccumulation in aquatic organisms is not expected for Fatty acids, C16-18 and C18-unsatd., hexaesters with dipentaerythritol. 
A low potential to bioaccumulate is also indicated by the low calculated BCF value of 0.89 L/kg ww (BCFBAF v3.01, Arnot-Gobas, including biotransformation, upper trophic; Blum, 2011). Please refer to IUCLID Section 5.3 for a detailed overview on bioaccumulation of the substance.

Conclusion
The substance will be physically removed in sewage treatment plants due to the low water solubility and high adsorption potential. An extensive discharge via a STP effluent is unlikely. However, when discharged an adsorption of the substance to sediment particles is possible. Sediment organisms may take the substance up by ingestion of food particles. When ingested by organisms the substance will be metabolised via enzymatic hydrolysis in fatty acids and the corresponding alcohol. Due to the high molecular weight and metabolism of the substance bioaccumulation is not likely. Furthermore BCF/BAF values calculated for the single components of the substance indicate a low bioaccumulation potential (BCF/BAF = 0.89 L/kg; BCFBAF v3.01 Arnot Gobas, upper trophic level; Blum, 2011). According to aquatic toxicity studies the substance is neither acutely nor chronically toxic to aquatic organisms up to the limit of water solubility (WS < 0.15 mg/L). Thus, Fatty acids, C16-18 and C18-unsatd., hexaesters with dipentaerythritol (CAS 68604-38-6) is unlikely to pose a risk for sediment organisms in general and testing is thus omitted.

 

A detailed reference list is provided in the technical dossier (see IUCLID, section 13) and within CSR.