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Description of key information

Chronic exposure of sediment organisms is unlikely. Furthermore, the substance is not toxic to aquatic organisms up to the limit of water solubility. In addition, available data indicate, that the substance is not bioaccumulative. Based on the available information, toxicity to sediment organisms is not expected to be of concern.

Key value for chemical safety assessment

Additional information

No experimental data evaluating the toxicity to sediment organisms are available for Octadecanoic acid, ester with 2,2'-[oxybis(methylene)]bis[2-(hydroxymethyl)-1,3-propanediol] (CAS 70969-57-2). Only negligible releases into surface waters from sewage treatment plants are expected to take place due to the high adsorption potential of this substance, resulting in an effective removal in sewage treatment plants. Therefore, chronic exposure of sediment organisms is unlikely. Furthermore, the substance is not toxic to aquatic organisms up to the limit of water solubility. In addition, available data indicate, that the substance is not bioaccumulative. Based on the available information, toxicity to sediment organisms is not expected to be of concern.

Intrinsic properties and fate

Octadecanoic acid, ester with 2,2'-[oxybis(methylene)]bis[2-(hydroxymethyl)-1,3-propanediol] (CAS 70969-57-2) is not readily biodegradable (7.6% (ThCO2) after 28 d). 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 > 5 and poor water solubility indicate that the substance will adsorb to solids and suspended material. The Guidance on information requirements and chemical safety assessment, Chapter R7b (ECHA, 2017) 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.7a, (ECHA, 2017). Thus, discharged concentrations of these substances into the aqueous/sediment compartment are likely to be negligible.

Considering this one can assume that the availability of Octadecanoic acid, ester with 2,2'-[oxybis(methylene)]bis[2- (hydroxymethyl)-1,3-propanediol] in the sediment environment is very low, which reduces the probability of chronic exposure of sediment organisms in general.

 Aquatic ecotoxicity data

Available acute data with fish as well as chronic aquatic toxicity test with aquatic invertebrates and toxicity to microorganisms showed that no adverse effects occurred in the range of the water solubility (< 1.7E-4 mg/L). The acute toxicity of a source 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 reproduction of the test animals and determined no toxic effects up to the limit of water solubility (NOEC (21 d) ≥ 100 mg/L). Also the toxicity to microorganisms test which based on the NOEC determined in the toxicity control reported in the study on ready biodegradability shows no effects up to the highest tested concentration of 20 mg/L. Hence, the substance is not toxic to aquatic microorganisms in the toxicity control and the test item concentration of 20 mg/L can be used as NOEC (14 d). There are no toxicity studies with aquatic algae available as there are mitigating factors indicating that aquatic toxicity is unlikely to occur for instance if the substance is highly insoluble in water or the substance is unlikely to cross biological membranes.

The results obtained indicate that the substance is likely to show no toxicity to sediment organisms as well. It is not expected that results from additional studies with sediment organisms would lie out of the overall ecotoxicological profile of the substance.

Bioaccumulation

Octadecanoic acid, ester with 2,2'-[oxybis(methylene)]bis[2-(hydroxymethyl)-1,3-propanediol] characterized by a low water solubility (< 1.7E-4 mg/L), high log Kow (> 10) and high molecular weight (1853.05 g/mol). Based on the physico/chemical properties such as low water solubility and high potential for adsorption a reduced availability in water is expected. The high molecular weight of the substance significantly reduces the absorption due to steric hindrance to cross biological membranes. It can be concluded that the bioaccumulation potential of Octadecanoic acid, ester with 2,2'-[oxybis(methylene)]bis[2- (hydroxymethyl)-1,3-propanediol] is low. For a detailed overview on bioaccumulation please refer to IUCLID section 5.3.1.

Conclusion

Due to its high potential for adsorption to sewage sludge in conventional STPs will take place and only low concentrations are expected to be released (if at all) into the environment. Once present in the aquatic compartment the substance will mainly partition to the sediment particles due to the low water solubility and high adsorption potential. Thus, the substance will be bioavailable to sediment organisms mainly via feed and contact with suspended organic particles. Moreover, the high molecular weight of the substance significantly reduces the absorption due to steric hindrance to cross biological membranes. Furthermore, all available aquatic toxicity data show that no effects occur up to the limit of water solubility. Therefore, Octadecanoic acid, ester with 2,2'-[oxybis(methylene)]bis[2- (hydroxymethyl)-1,3-propanediol] is unlikely to pose a risk for sediment organisms and testing is thus omitted.

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