Fatty acids, C18-unsatd., dimers, di-Me esters, hydrogenated

Endpoint summary

Additional information

One study is available on the long-term toxicity to aquatic invertebrates of Fatty acids, C18-unsatd., dimers, di-Me esters, hydrogenated (CAS 147853-32-5). Beyond that, there are no other data available on the aquatic toxicity of the substance. In order to fulfil the standard information requirements set out in Annexes VII-IX, in accordance with Annex XI, Section 1.5 of Regulation (EC) No 1907/2006, read-across from structurally similar substances is 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 human and environmental 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 physico-chemical, toxicological and ecotoxicological properties may be predicted from data for reference substance(s) by interpolation to other substances on the basis of structural similarity, Fatty acids, C18-unsatd., dimers (CAS 61788-89-4), Fatty acids, C18-unsatd., dimers, hydrogenated (CAS 68783-41-5) and Fatty acids, C18-unsatd., trimers (CAS 68937-90-6) are selected as read-across substances for assessment of aquatic toxicity. The read-across is based on structural similarity as a result of common origin and production process line.

The analogue approach covers C16-C18 unsaturated fatty acids-derived dimers and trimers, as well as their hydrogenated products in different proportions and in accordance with their corresponding production and purification processes. The source and target substances are all UVCB substances derived from natural sources, and are structurally similar in the sense that they are all essentially a complex mixture of C16-C18 unsaturated and saturated, branched and linear alkyl chains, their dimers and trimers with varying structural geometric isomers. The source and target substances are all originally derived from the catalytically driven dimerisation or in some cases isomerisation of C16-18 unsaturated fatty acids or other C18 unsaturated fatty acids.

The target substance is produced by esterification of the source substance Fatty acids, C18-unsaturated, dimers (CAS 61788-89-4) with methanol, followed by hydrogenation, yielding the corresponding saturated dimer alcohols (dimerdiols) and methanol. The net reaction at the carbonyl functional group is the reduction of the carboxylic acid to alcohol.

The catalytic dimerisation of unsaturated fatty acids (predominantly C16-C18 acids) from natural sources results in a reaction product denominated crude dimer, containing a mixture of monomeric, dimeric and trimeric fatty acids. Fractional distillation of the crude dimer yields a monomer fraction and a dimer fraction, the latter containing predominantly dimeric but also and trimeric fatty acids and corresponding to the substance Fatty acids, C18-unsaturated, dimers (CAS 61788-89-4). Hydrogenation of this fraction results in the substance Fatty acids, C18-unsaturated, dimers, hydrogenated (CAS 68783-41-5). The trimer fraction contained in the dimer fraction (Fatty acids, C18-unsaturated, trimers (CAS 68937-90-6)) is obtained by a further distillation step. As described above, the target substance is obtained by hydrogenation of an intermediate methylester of Fatty acids, C18-unsaturated, dimers.

The hypothesis of the analogue approach is that read-across from the source substances to the target substance can be performed on the basis of similarities in molecular structure and/or composition arising from their common origin and manufacturing process, resulting in similar physicochemical, toxicological, ecotoxicological and environmental fate properties. The main assumption is that differences in molecular structural features between the target substance (dimers of saturated fatty alcohols) and the source substances (dimers and trimers of unsaturated and saturated fatty acids) are not significant in respect to all the properties under consideration. Furthermore, in regard to toxicological endpoints, the source substances are considered suitable for read-across in view of the fact that the metabolism of fatty alcohols involves their enzymatic oxidation to the corresponding fatty acids. Thus, the biological activity is anticipated to be similar. Therefore, human health effects and environmental effects or environmental fate can be directly read-across from the source substances to the target substance.

A detailed analogue approach justification is provided within the Technical dossier (see IUCLID Section 13).

Table: Aquatic toxicity of target and source substances

Endpoint	Fatty acids, C18-unsatd., dimers, di-Me esters, hydrogenated (a)	Fatty acids, C18-unsatd., dimers(b)	Fatty acids, C18-unsatd., trimers	Fatty acids, C18-unsatd., dimers, hydrogenated
CAS No.	147853-32-5	61788-89-4	68937-90-6	68783-41-5
Short term toxicity to fish	RA CAS 61788-89-4	Experimental result: LC50 (96h) > 350 mg/L	--	--
Long term toxicity to fish	RA CAS 68783-41-5	--	--	Experimental result: NOEC (28d) ≥ 850 µg/L
Short term toxicity to aquatic invertebrates	RA CAS 61788-89-4 RA CAS 68937-90-6	Experimental result: EL50 (48h) > 1000 mg/L	Experimental result: LL50 (48h) > 1000 mg/L	--
Long term toxicity to invertebrates	Experimental result: NOELR (21d) = 100 mg/L	--	--	--
Toxicity to aquatic algae	RA CAS 61788-89-4 RA CAS 68937-90-6	Experimental result: EL50 (72h) > 1000 mg/L NOELR (72h) > 1000 mg/L	Experimental result: EL50 (72h) > 1000 mg/L NOELR (72h) ≥ 1000 mg/L	--
Toxicity to microorganisms	RA CAS 61788-89-4 Experimental result : NOEC (14d) = 12.4 mg/L	Experimental result: NOELR (16h) ≥ 10000 mg/L	--	--

(a) The substance subject to the REACh Phase-in registration deadline of 31 May 2013 is indicated in bold font. Only for this substance a full set of experimental results and/or read-across is given.

(b) Reference (read-across) substances are indicated in normal font. Lack of data for a given endpoint is indicated by “--“.

Further justification is given within the analogue justification attached in IUCLID Section 13.

Short-term aquatic toxicity studies with analogue substances are available for three trophic levels (fish, aquatic invertebrates and algae). No mortality occurred up to the limit of water solubility of the test substances for any of the test organisms. The long-term aquatic toxicity of analogue substances was tested on fish and algae, whereas a chronic study on aquatic invertebrates is available for the target substance Fatty acids, C18-unsatd., dimers, di-Me esters, hydrogenated (CAS 147853-32-5). For all organisms no effects were observed up to the limit of water solubility of the test substances.

In conclusion, based on the data available for the target substance and its structural analogues, Fatty acids, C18-unsatd., dimers, di-Me esters, hydrogenated (CAS 147853 -32 -5) is not expected to result in acute or chronic effects on aquatic organisms.