Isooctadecanoic acid, 1,1'-(2,2-dimethyl-1,3-propanediyl) ester

Endpoint summary

Additional information

The dataset investigating the aquatic toxicity ofIsooctadecanoic acid, 1,1'-(2,2-dimethyl-1,3-propanediyl) ester (CAS 109884-54-0) is not complete.In order to fulfil the standard information requirements, in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006, read-across from structurally related source substances was conducted.

In accordance with Article 13 (1) of Regulation (EC) No 1907/2006, "information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI are met.” In particular for aquatic toxicity, information shall be generated whenever possible by means other than vertebrate animal tests, which includes the use of information from structurally related substances (grouping or read-across).

Having regard to the general rules for grouping of substances and read-across approach laid down in Annex XI, Item 1.5, of Regulation (EC) No 1907/2006 whereby substances may be predicted as similar provided that their physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity. The source substancesneopentylglycol dioleate (CAS 42222-50-4) and Heptanoic acid, ester with 2,2-dimethyl-1,3-propanediol (CAS 68855-18-5)are considered to be similar on the basis of the structural similar properties and activities. The available endpoint information on the source substances is used to predict the aquatic toxicity of the target substanceIsooctadecanoic acid, 1,1'-(2,2-dimethyl-1,3-propanediyl) ester.

The target substance is characterized as a diester of neopentylglycol and mainly C18 isostearic acid with a minor amount of monoesters of neopentylglycol with C18 isostearic acid. The source substance neopentyl glycol dioleate (CAS 42222-50-4) is mainly defined as a diester of C18 and C18 unsaturated linear fatty acids and neopentylglycol whereas Heptanoic acid, ester with 2,2-dimethyl-1,3-propanediol (CAS 68855-18-5) is a diester of linear C7 fatty acids and neopentylglycol.All selected source substances are representative for the target substance. They only differ slightly in their specification. However, none of the selected source substances contains any functional group which might change the overall mode of action and toxicity. A detailed analogue approach justification is provided in the technical dossier (see IUCLID Section 13).

All available experimental data on the target and source substances performed according to internationally accepted guidelines indicate no evidence of acute and chronic toxicity to aquatic organisms. Data for all three trophic levels are available. No toxicity was observed up to the limit of water solubility in all available experimental studies. The water solubility of the target substance was determined to be <8 µg/L at 19.9 °C, pH = 6.9.
The short-term toxicity to fish was determined in standard OECD 203 study for the target substance. No mortality was observed after 96 h resulting in LC50 > the limit test concentration (i.e. above the water solubility limit). The same was recorded for the toxicity to aquatic algae and the short-term toxicity to aquatic invertebrates. No inhibition of growth of aquatic algae and no immobilization of daphnids was observed in experimental studies for the target substance up to the limit of water solubility. Due to the low water solubility, long-term testing to aquatic invertebrates was considered to be necessary to assess the aquatic toxicity. The available study performed with a suitable source substance resulted in a NOELR (21 d) ≥ 1 mg/L (nominal) indicating no effects on reproduction up to the limit of water solubility. Long-term toxicity testing to fish was not considered to be necessary since there was no evidence from the available data that fish are more sensitive compared to aquatic invertebrates. No toxicity to fish was observed in the available acute tests. Thus, in order to avoid unnecessary vertebrate testing, no long-term testing with fish was proposed.
The degradation process in commercial sewage treatment plants is not suspected to be inhibited by the target substance. One available study from a suitable source substance performed with activated sludge from a sewage treatment plant did not indicate a risk since respiration of activated sludge microorganisms was not inhibited. 

Based on the result from the target substance and structurally related read-across substances (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) it can be concluded that Isooctadecanoic acid, 1,1'-(2,2-dimethyl-1,3-propanediyl) ester exhibits no toxic effects on freshwater organisms up to the limit of the water solubility. As it can be seen in the data matrix of the analogue justification in IUCLID Section 13, all reliable data from the target and the source substances support the read-across by showing a consistent pattern of results.