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

Endpoint summary

Additional information

Justification for read-across

There are only limited data available addressing the genetic toxicity of isooctadecanoic acid, 1,1'-(2,2-dimethyl-1,3-propanediyl) ester (CAS 109884-54-0). 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 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 the 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 comparable pattern as a result of structural similarity, the substances heptanoic acid, ester with 2,2-dimethyl-1,3-propanediol (CAS 68855-18-5) and 2,2-dimethyl-1,4-propanediyl dioleate (CAS 42222-50-4) are selected as source substances.

 

In vitro mutagenicity in bacteria

CAS 109884-54-0

A key bacterial gene mutation study (Ames test) performed according to OECD TG 471 and in compliance with GLP with isooctadecanoic acid, 1,1'-(2,2-dimethyl-1,3-propanediyl) ester (CAS 109884-54-0) is available (Verspeek-Rip, 2014). The strains Salmonella typhimurium TA 1535, TA 1537, TA 98, TA 100 and E.coli WP2 uvrA were tested according to the plate incorporation (experiment 1+2) procedure in the absence and presence of a metabolic activation system (Aroclor 1254-induced rat liver S9-mix). Both experiments were conducted in three repetitions with exception of tester strain TA 1537 (-S9-mix, experiment 1) and TA 98 (-/+ S9-mix, experiment 1) with duplicates only at each concentration from 1.7 to 5000 µg/plate or vehicle (ethanol) alone. There was no reduction of the bacterial background lawn and no biologically relevant increase in the number of revertants at any of the concentrations tested in all tester strains in the absence and presence of metabolic activation. No precipitation of the test material was recorded at the start or at the end of the incubation period in any tester strain. Appropriate solvent and positive controls were included into the test and gave the expected results. Hence, the test item was considered to be not mutagenic to bacteria under the conditions of the test.

 

In vitro cytogenicity in mammalian cells

CAS 109884-54-0

A key in vitro chromosome aberration test in human lymphocytes was performed with isooctadecanoic acid, 1,1'-(2,2-dimethyl-1,3-propanediyl) ester (CAS 109884-54-0) according to OECD TG 473 and in compliance with GLP (Buskens, 2014). Human peripheral lymphocytes were cultured and treated with the test material or vehicle (ethanol) in the absence or presence of a metabolic activation system (phenobarbitone/β-naphthoflavone-induced rat liver S9-mix) in duplicates at concentrations of 5.4, 17 and 52 µg/mL for 3 hours (with and without S9-mix, experiment 1) and 17, 164 and 1600 µg/mL for 24 and 48 hours (without S9-mix, experiment 2). Fixation and staining of the cells were either performed 24 hours (experiment 1) or 24 and 48 hours (experiment 2) after start of exposure with the test material. Cytotoxicity was assessed by determination of the mitotic index. Appropriate solvent and positive controls were included in the test and gave the expected results. No cytotoxicity was recorded either in a preliminary toxicity study or in the main cytogenetic assay. Precipitation of the test material was determined at a concentration of 52 µg/mL and above. The test substance did not cause a statistically significant, dose-related increase in chromosome aberrations under the tested conditions. Based on the results of the study the test material is considered not to be clastogenic in this chromosome aberration test in vitro.

 

In vitro mutagenicity in mammalian cells

In summary, two reliable genetic toxicity studies addressing mutagenicity in mammalian cells in vitro are available.

 

CAS 42222-50-4

An in vitro Mammalian Cell Gene Mutation Assay according to OECD guideline 476 and GLP was performed with 2,2-dimethyl-1,3-propanediyldioleate (CAS 42222-50-4) in mouse lymphoma L5178Y cells (Flügge, 2012). The cells were treated for 3 hours with and without S9-mix in the first experiment, for 24 hours without S9-mix in the second experiment and again for 3 hours with S9-mix in the third experiment. The test substance was tested at 312.5, 625, 1250, 2500 and 5000 μg/mL No toxicity was observed and all dose levels were evaluated in the absence and presence of S9-mix. Positive and negative controls were included and gave the expected result. No significant increase in the mutation frequency at the TK locus was observed after treatment with the test substance either in the absence or in the presence of S9-mix. Thus, it was concluded that 2,2-dimethyl-1,3-propanediyldioleate is not mutagenic in the mouse lymphoma L5178Y test system under the experimental conditions described.

 

CAS 68855-18-5

A L5178Y mouse lymphoma assay was conducted according to OECD guideline 476 and under GLP conditions. Two independent experiments were performed (Brown, 2013). In experiment 1, L51787Y TK +/- mouse lymphoma cells (heterozygous at the thymidine kinase locus) were treated with the test item at eight dose levels, in duplicate, together with vehicle (solvent) and positive controls using 4 h exposure groups both in absence and presence of metabolic activation (2% S9-mix). In experiment 2, the cells were treated with the test item at eight dose levels for 4 h in the presence of metabolic activation (1% S9-mix) and for 24 h in the absence of metabolic activation. The dose range of the test substance was selected following the results of a preliminary toxicity test and was determined to be 1.6 to 102.5 µg/mL in both the absence and presence of metabolic activation in experiment 1. In experiment 2 the dose range was 1.6 to 102.5 µg/mL in the absence of metabolic activation, and 3.2 to 205 µg/mL in the presence of metabolic activation. The maximum dose levels used in the test were limited by precipitate and test substance induced toxicity. Precipitation was observed at and above 102.5 µg/mL in the mutagenicity test. The vehicle (solvent) controls had acceptable mutant frequency values that were within the normal range for L5178Y cell line at the TK +/- locus. The positive control items induced marked increases in the mutant frequency indicating the satisfactory performance of the test and of the activity of the metabolising system. The test item did not induce any toxicologically significant dose-related increases in the mutant frequency at any dose level, either with or without metabolic activation.

 

Conclusion for genetic toxicity

There are two studies available addressing the in vitro genetic toxicity of the target substance isooctadecanoic acid, 1,1'-(2,2-dimethyl-1,3-propanediyl) ester, but no information on mutagenicity in mammalian cells is available with the target substance. Therefore read-across using in vitro mammalian mutagenicity studies from two structurally related analogue source substances was applied. The results of the available in vitro studies on source substances did not provide evidence indicative for mutagenic potential. Based on the available data, and following the analogue approach isooctadecanoic acid, 1,1'-(2,2-dimethyl-1,3-propanediyl) ester is not expected to be mutagenic and clastogenic in vitro.

Justification for selection of genetic toxicity endpoint
Hazard assessment is conducted by means of read-across from structural analogues. All available in vitro genetic toxicity studies were negative. All available studies are adequate and reliable based on the identified similarities in structure and intrinsic properties between source and target substances and overall quality assessment (refer to the endpoint discussion for further details).

Short description of key information:
Genetic toxicity in vitro:
Ames test (OECD 471): negative with and without metabolic activation in S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and in E. coli WP2 uvrA
Chromosome aberration (OECD 473): negative in cultured peripheral human lymphocytes with and without metabolic activation
Gene mutation in mammalian cells (OECD 476, WoE): negative in mouse lymphoma L5178Y cells with and without metabolic activation

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

According to Article 13 of Regulation (EC) No. 1907/2006 "General Requirements for Generation of Information on Intrinsic Properties of substances", information on intrinsic properties of substances may be generated by means other than tests e.g. from information from structurally related substances (grouping or read-across), provided that conditions set out in Annex XI are met. Annex XI, "General rules for adaptation of this standard testing regime set out in Annexes VII to X” states that “substances whose physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be considered as a group, or ‘category’ of substances. This avoids the need to test every substance for every endpoint". Since the analogue concept is applied to isooctadecanoic acid, 1,1'-(2,2-dimethyl-1,3-propanediyl) ester, data will be generated from data for reference source substance(s) to avoid unnecessary animal testing. Additionally, once the analogue read-across concept is applied, substances will be classified and labelled on this basis.

Therefore, based on the analogue read-across approach, the available data on genetic toxicity do not meet the classification criteria according to Regulation (EC) 1272/2008, and are therefore conclusive but not sufficient for classification.