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Ecotoxicological information

Toxicity to soil microorganisms

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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 toxicity to soil microorganisms.

Key value for chemical safety assessment

Additional information

Experimental data on the toxicity of Fatty acids, C16-18 and C18-unsatd., hexaesters with dipentaerythritol (CAS 68604-38-6) to soil microorganisms are not available. In accordance with Regulation (EC) No. 1907/2006, Annex IX, column 2, 9.4 studies on terrestrial organisms do not need to be conducted when there is no risk indicated by the chemical safety assessment.
Based on the available experimental toxicity data the substance is expected to be not toxic to soil organisms. A study on the chronic toxicity of the substance to Eisenia fetida according to OECD 222 determined no acute or chronic toxicity (NOEC reproduction (56 d) ≥ 1000 mg/kg soil dw). The substance is expected to be largely physically removed in sewage treatment plants and thus a transfer to the terrestrial environment is not likely. If transferred to the soil an adsorption to soil particles is probable as indicated by the high log Koc (C16 FA component: 2.27, C18 unsat. FA component: 46.87, C18 FA component: 48.16; KOWWIN v1.68; Blum, 2011).
A toxicity control in the biodegradation study with the test substance shows no inhibition to aquatic microorganisms resulting in a NOEC (14 d) ≥ 20 mg/L (based on test material). The applied test concentration is in the range of concentrations that can be expected in the influent of a sewage treatment plant, as the substance is characterised by poor water solubility (< 0.15 mg/L). The ECHA Guidance Document R.7c (ECHA, 2012) states that a test on soil microbial activity will only be additionally necessary for a valid PNEC derivation if inhibition of sewage sludge microbial activity has occurred.
In the absence of a clear indication of selective toxicity, an invertebrate (earthworm or collembolan) test is preferred, as outlined in ECHA Guidance Document R.7c, section R.7.11.5.3 (ECHA, 2012). A study on the chronic toxicity of the substance to earthworms determined no acute or chronic toxicity (see above).
In addition, the long-term toxicity of the substance to Daphnia magna was tested in a guideline study following OECD 211 (Caduff, 2013). An effect on survival or reproduction rate of Daphnia was not observed within the limit of water solubility (NOEC (21 d) ≥ 100 mg/L).
When ingested by aquatic organisms, a relevant uptake is not expected for the substance since it will be presumably metabolised and excreted. Bioaccumulation is therefore not anticipated.
In conclusion, the substance is unlikely to pose a risk for terrestrial microorganisms based on a) the lack of exposure and b) the low toxicity as expected for this substance for the terrestrial compartment based on the available experimental data, metabolism considerations and the lack of adverse effects in aquatic ecotoxicity tests.
In accordance with Regulation (EC) No. 1907/2006, Annex X, Column 2, 9.4 further studies on the effects on terrestrial organisms do not have to be conducted since the chemical safety assessment indicates that toxicity to soil microorganisms is not expected to be of concern.

 

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