Methyl 12-hydroxyoctadecanoate

Endpoint summary

Description of key information

Conflicting data, but the weight-of-evidence is that the target substance is not a sensitiser

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Remarks:

summary of experimental work

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Justification for type of information:

The analogue approach is used for the hazard assessment of toxicological, eco-toxicological and environmental fate endpoints for the registration of 12-hydroxstearate methyl ester (CAS 141-23- 1). The hypothesis is that data can be read-across between this ester and its structural analogues, based on structural similarity and which cause the same type of effect(s) in physical and biological systems (Scenario 2 of the Read-Across Assessment Framework (RAAF, ECHA, 2015). The primary fatty acids in this read-across are lauric acid (C12) and myristic acid (C14), as these are well studied with high-quality experimental data. Supplemental analogues are used which contribute understanding of the effects of other structural features not contained in the two primary analogues.

There are no GHS classifications for 12-hydroxstearate methyl ester for endpoints which are reliant on read-across. There is a high degree of confidence that hazards for these endpoints are not underestimated, based on a strong weight of evidence from multiple data sources.

Read-across data, all evaluated as reliable according to Klimisch scores of 1 or 2, to estimate the toxicity of the registered substance is used for fulfilling the data requirements of the REACH registration and classifying potential hazards. This read-across approach is adequate for the purposes of risk assessment and classification and labeling.

Reason / purpose for cross-reference:

read-across source

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

GLP compliance:

not specified

Type of study:

mouse local lymph node assay (LLNA)

Specific details on test material used for the study:

Purity 86%

Species:

mouse

Strain:

CBA

Sex:

female

Vehicle:

dimethyl sulphoxide

Concentration:

10, 25, 50%

No. of animals per dose:

5

Details on study design:

Test material in DMSO was applied to the dorsal surface of each ear of the mice, daily for 3 days. On day 5, tritiated thymidine (3HTdR) was administered via the tail vein.

Positive control substance(s):

not specified

Key result

Parameter:

EC3

Value:

16

Remarks on result:

other: positive

Remarks:

Sensitiser. Value is 16% TM in vehicle

None of the animals died, and there were no signs of toxicity. The EC3 value was calculated to be 16% Hydroxystearic acid was considered a sensitiser.

Interpretation of results:

Category 1B (indication of skin sensitising potential) based on GHS criteria

Conclusions:

The test substance (the analogue, 12-HSA) was tested in an LLNA using tritiated thymidine in female CBA mice. The results were positive, and 12-hydroxystearic acid was considered a sensitiser. The EC3 value was calculated to be 16%. This summary data reflects the opinion of the CIR Expert Panel that the data are valid and informative, indicating that the 12-hydroxystearate chain is not sensitising.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

A weight of evidence (WOE) approach is utilised to evaluate the dermal sensitisation potential of the methyl ester of 12-hydroxystearic acid. 

Hypothesis to be evaluated: Is there sufficient evidence to accept the read-across of a lack of skin sensitisation hazard for the methyl ester of 12-hydroxystearate?

Skin sensitisation data for the registered substance, methyl 12-hydroxystearate, were not identified. Animal testing is prohibited for substances used in the cosmetic industry, in which this substance has applications. There are available data from esters of castor oil and fatty acids which may be serve as analogue source data to fill this data gap for REACH data requirements through WOE and Read-across (RA) approaches.

Source chemicals:

For more information and similarity assessment with registered (target) substance, see AARF.

Methyl ricinoleate, CAS 141-24-2

Ethyl ricinoleate, CAS 55066-53-0

12-Hydroxystearic Acid, CAS 106-14-9

 

Evidence Evaluation:

According to the OECD, the aim of evidence evaluation is to determine the inherent quality, usefulness and completeness of the available data. ECHA prioritizes three key terms: relevance, reliability and adequacy. Relevance relates to the appropriateness of the information, and whether it addresses a particular hazard identification or risk characterization.   Reliability allows confidence in the conclusion of the exercise of hypothesis testing and provides strength of inference; it specifically relates to the quality of either the individual test data or to entire data sets being evaluated. ECHA uses Klimisch scoring for evaluating records; SCHEER (2018) uses a similar 4-degree scale. The UK’s Hazardous Substances Advisory Committee (HSAC, 2015) considers the transparency of the aims of a study, or the ability to appropriately test or falsify the hypothesis; it weighs having clear and transparently recorded methodology and identification of known biases.  Adequacy refers to data sufficiency or quantity of lines of evidence, or whether there is enough data to address the problem formulation. This may also include consistency; inconsistent data should be discussed and reasons for divergence proposed; this may be addressed during later discussions of mechanism. 

Evidence Collection: Published literature and STN databases, specifically Medline, Embase, BIOSIS, ToxCenter, Chemical Abstracts, RTECS, and eChem Portal were searched on 11 Jan. 2017. Relevant data were collected.

Evidence Weighting:

Weighing or scoring of evidence in this analysis uses the following scale: The important characteristic is that there is transparency to the weighting. 

 

Characteristics of Evidence leading to Conclusions of the following Ratings for the three Categories:	Relevance	Reliability	Adequacy
NULL	Determined to be not relevant but noted for thoroughness	Determined to be not reliable due to method deficiencies, nature of the report or other valid reason	Determined to be not adequate for hypothesis testing.
LOW	Test material differs to a greater extent from registered substance. Test method or method conditions differ from those required to address the endpoint in question.	Data generated by OECD protocol with deviations or modifications, not always under GLP, Klimisch 2. Summary data or data from reliable texts or handbooks where all methodology and data may not be presented.	The study uses a method recommended by OECD or REACH guidance; it may not address the endpoint. Results may be inconclusive or give rise to questions.
MEDIUM	Test material differs to a lesser extent from registered substance. Test method or method conditions differ to a minor degree from that required to address the endpoint in question.	Data generated by OECD protocol with deviations or modifications, not always under GLP, Klimisch 2. Summary data, peer reviewed by Authoritative body representatives (WHO CICAD, OECD SIAM, CIREP, HSNO).	The study is complete and valid and uses a method designed to address the endpoint, according to OECD methods/REACH methods. There are deviations in the method or results which may cause conclusions to be questionable.
HIGH	Test material differs to a minor degree from registered substance; may have more reactive groups and thus may potentially be “worst case” scenario. Test method or method conditions do not deviate from those required to address the endpoint in question, or any such deviation is determined to be minor and not affecting the validity of the test results.	Data generated by OECD protocol under GLP, Klimisch 1; non-standard data are generated in reputable laboratory and published in a peer-reviewed journal.	The study is complete and valid and uses a method designed to address the endpoint, according to OECD methods/REACH methods. The conclusions are clear to address the hazard and results of study are well discussed.

 

 

 

EVIDENCE REVIEW for Methyl 12-Hydroxystearate

Type of Evidence / Source Name - Reference	Relevance	Reliability	Adequacy
CIT 1999 Manceaux/experimental by GLP/K1. Manceaux, X. 1999. Skin sensitisation test in Guinea Pigs. CIT, Centre International de Toxicologie, BP 563, 27005 Evreux, France. Report No. 18040 TSG. Study owner: Arkema. LOA obtained for use in registration dossier.	HIGH.Test material is methyl ricinoleate, CAS 141-24-2, 88.44% purity. TM is highly relevant as it is an ester of C18 carbon chain with hydroxyl; has C9 double-bond not found in methyl 12-HSA. This TM has more active groups and would be a worst case scenario for prediction of targeted effect.	HIGH. Validated in vivo assay, performed by GLP. Guinea pig maximisation test (GPMT). Very reliable. Standard protocol: Dunkin-Hartley guinea pigs, 20 animals in the experimental group, 10 in the positive control (DCNB) group. Induction with 25% intradermal and 100% epicutaneous; challenge with 100% epicutaneous, occlusive.  Evidence that the ester is less reactive than 12-hydroxystearic acid. Evaluation of skin appearance performed at 24 and 48 hours after challenge and sensitisation reactions were evaluated.	HIGH. The study report was obtained and reviewed, and the data were provided in the i6z endpoint study record. This is an acceptable method for fulfilling the endpoint requirement according to Annex XI and as it was available prior to Commission Regulation (EU)2016/1688.
1995 CIR experimental /K2. Summary data. Cosmetic Ingredient Review, 1996. Final Report on Hydroxystearic Acid, March 17, 1995.	LOW. TM is 12-HSA, CAS 106-14-9, 86% purity. The acid may have a more extreme chemical reactivity than the ester, damaging and entering the skin and forming (false positive) reaction products which could be epitopes for this assay. Esters of large fatty acids are not expected to have significant transdermal penetration.	LOW. LLNA is generally the preferred quantitative assay but shows a high rate of false positives with unsaturated fatty acids. This particular data is of low reliability because it is a secondary source; a summary from the Cosmetic Ingredient Review Expert Committee. This is a valid expert committee to accept data and expert opinion from, as they evaluate risk from chemicals intentionally intended to be placed on the skin, sometimes for long periods of time.	LOW. The study report is not available to the public; only the summary of the data along with the interpretation of the Expert Committee. This is considered adequate as the data have been adopted as valid by authoritative bodies (U.S. FDA).
1995 CIR experimental /K2. Summary data. Cosmetic Ingredient Review, 1996. Final Report on Hydroxystearic Acid, March 17, 1995.	LOW. TM is 12-HSA, CAS 106-14-9. As above, the acid may be more reactive than the ester, damaging and entering the skin and forming (false positive) reaction products. The first trial of this study showed excessive skin irritation with this acid. Esters of large fatty acids are not expected to have significant transdermal penetration.	MEDIUM. LLNA is the preferred quantitative assay. This particular data is of medium reliability because it is a secondary source; a summary from the Cosmetic Ingredient Review Expert Committee.	LOW. The study report is not available to the public; only the summary of the data along with the interpretation of the Expert Committee. This is considered adequate as the data have been adopted as valid by authoritative bodies (U.S. FDA) and are published in a peer reviewed journal (Int. J. Toxicol.).
Bergfeld WF, Belsito DV, Klaassen CD, et al., 2005, Final report of the Cosmetic Ingredient Review Expert Panel on Ricinus communis (castor) seed oil, hydrogenated castor oil, glyceryl ricinoleate, glyceryl ricinoleate SE, ricinoleic acid, potassium ricinoleate, soldium ricinoleate, zinc ricinoleate, cetyl ricinoleate, ethyl ricinoleate, glycol ricinoleate, isopropyl ricinoleate, methyl ricinoleate and octyldodecyl ricinoleate. Int. J. Toxicol. 26 (Suppl 3):31-77.	HIGH. TM is ethyl ricinoleate, CAS 55066-53-0. This TM is also highly relevant as it is an ethyl ester of C18 carbon chain with hydroxyl; has C9 double-bond not found in methyl 12-HSA. This TM has more active groups and would also be a worse case scenario for prediction of targeted effect.	MEDIUM.  The test method (maximisation test in human volunteers) is highly relevant, as it is performed in the target audience (by RIFM, 2000, which always commissions assays by GLP) but human clinical testing is no longer acceptable. This particular data is of medium reliability because it is a secondary source; a summary from the Cosmetic Ingredient Review Expert Committee is available.	LOW. The study report is not available to the public; only the summary of the data along with the interpretation of the Expert Committee. This is considered adequate as the data have been adopted as valid by authoritative bodies (U.S. FDA) and are published in a peer reviewed journal (Int. J. Toxicol.). Minimising the use of animals through read-across methods is proposed through Annex XI and ECHA guidance (RAAF, 2017).
Benton EC, White IR and McFadden JP, 2012. Allergic contact dermatitis to methyl hydroxstearate in a rubber respirator. Contact Dermatitis 67: 238-246.	MEDIUM. TM is methyl hydroxystearate (registered substance). No purity information. Case report in a soldier who had an allergic skin reaction to a military respirator mask. He was subsequently patch-tested with rubber compounds and raw materials used to make the mask. Tested + to methyl hydroxystearates.	LOW. Case reports in human patients are not a reliable method to characterise the hazard of the chemical exposure. We have not found repeated reports of allergy associated with this chemical.	LOW. Case reports in human patients are not an adequate method to characterise the hazard of the chemical exposure; no statistical methods are applied.
1995 CIR experimental /K2. Summary data. Cosmetic Ingredient Review, 1996. Final Report on Hydroxystearic Acid, March 17, 1995.	MEDIUM. TM is 12-hydroxystearic acid. CAS 106-14-9, 86% purity. The acid may damage skin and cause (false positive) reactive sites. Human volunteers were patch tested at 7% semiocclusive; no allergic sequelae were observed, although there were some irritation effects.	MEDIUM.  The test method is highly relevant, as it is performed in the target audience, although human clinical testing is no longer acceptable. This particular data is of medium reliability because it is a secondary source; a summary from the Cosmetic Ingredient Review Expert Committee is available.	LOW. The study report is not available to the public; only the summary of the data along with the interpretation of the Expert Committee. This is considered adequate as the data have been adopted as valid by authoritative bodies (U.S. FDA). The opinion of the dermatologists, toxicologist and regulators on the Panel is that 12-HSA is not a sensitiser.
Shaw DW. 2009. Allergic Contact Dermatitis from 12-Hydroxystearic Acid, the Principal Fatty Acid in Hydrogenated Castor Oil. Dermatitis 20(6):E16-20	MEDIUM. TM is 12-Hydroxystearic acid, CAS 106-14-9, 84% purity. The acid may damage skin and create reactive sites. Additional test compounds include hydrogenated castor oil, castor oil, ricinoleic acid, stearic acid and oleic acid.	MEDIUM. One patient who presented with a cosmetic allergy was patch tested with 10% 12-HSA as well as with other ricinoleates and fatty acids. She showed positive reactions to 12-HSA and ricinoleates but not oleic and stearic acids. Case reports in human patients are not a reliable method to characterise the hazard of the chemical exposure.	LOW. Case reports in human patients are not an adequate method to characterise the hazard of the chemical exposure; no statistical methods can be applied.

 

 

EVIDENCE INTEGRATION:

Evidence is integrated in order to check consistency of lines of evidence, and, in the case of inconsistencies, to understand the discrepancies and reject outliers. This can include examination of plausibility and causality, using the Bradford Hill criteria (1965) for determining confidence in the evidence, which forms the basis for the WHO/IPCS Mode of Action Framework (Meek, et al, 2013).

Type of Evidence	Consistency & Specificity	Likelihood/ Biological Plausibility	Temporality	Confidence / Strength of Evidence	Remaining Uncertainty
Line of Evidence 1: Experimental and clinical data on alkyl ricinoleate esters	One GPMT (Manceaux, 1999) on methyl ricinoleate. Not sensitising. One clinical study with 35 subjects using a standard clinical procedure (Bergfeld, et al., 2007) with ethyl ricinoleate; Not sensitising. Both are consistent in negative effects. One clinical case report, with LOW reliability and LOW accuracy, indicates that it may be possible under extreme conditions to induce an allergic reaction to methyl hydroxystearate; although it is impossible to prove a cause and effect relationship. Based on the HIGH relevance, reliability and adequacy of the 1999 Manceaux study using aggressive procedures, methyl hydroxystearic acid is considered non-sensitising (Read-Across).	Dermal bioavailability of FA esters is lower than that of the corresponding acid (Mack-Correa, et al., 2014). OH group on fatty acid would further lower percutaneous absorption. After esterase cleavage in skin, fatty acid is not expected to be allergenic, as it is identical to endogenously produced fatty acid or fatty acid absorbed through dietary intake. No/few active sites for protein binding (AOP).	The sensitisation AOP provides a temporal sequence of events beginning with delivery of substance through skin, where protein binding takes place (initiating event). The in vivo assays allow time for sensitisation to be induced via protein binding and keratinocyte activation, and then to be elicited via immune recognition upon subsequent exposure to a naïve site on the animal.	High relevance, High reliability, high adequacy that the 1999 Manceaux study characterises the sensitisation potential of the test material. Maximisation protocols include extreme exposures including intradermal with adjuvant, occlusive repeated cutaneous exposures, followed by occlusive challenge exposures; exposures such as these are unlikely to occur in occupational or general population exposures. This study is a Klimisch 1 GLP study with an adequate number of study animals (20 experimental including both sexes); therefore it is robust. Consistent with these results is the human maximisation study on the ethyl ricinoleate ester, showing no allergenicity effects (as presented in the CIR summary).	Low remaining uncertainty that methyl hydroxystearate behaves differently; with one fewer reactive group (double bond in carbon chain), it is expected to be less reactive than a ricinoleate ester. The highly weighted animal study of Manceaux leaves no question that this compound is not sensitising.
Line of Evidence 2: Experimental and clinical data on 12-hydroxystearic acid	An inconsistency is seen with 12-HSA when tested in an LLNA and found to be positive at 16%; it was also tested in a GPMT and was negative, with a repeat of the test needed at lower concentrations, likely due to skin irritation from the acid. These studies carry a MOD to LOW weight as they are less relevant and, while the conclusions from the CIR are trusted, the methods and data are not available for review and so are less reliable and adequate. Shaw, 2009, described a dermatitis patient who reacted to hydroxylated fatty acids including 12-HSA, hydroxylated castor oil, castor oil and ricinoleic acid, but not stearic or oleic acids (non-hydroxylated)	LLNA has been found to be less reliable for unsaturated fatty acids as a chemical group (Kreiling, et al., 2008). Additionally, these have also been found to test positive for protein binding (Yamashita, et al., 2015); thus the GPMT may be the preferred test protocol. Acids may damage the stratum corneum and penetrate into the epidermis, causing disordered tissue and potentially false positive sensitisation reactions (Patzelt, et al, 2012). High irritation is supported by Sato, et al, 1996. The GPMT showed evidence of skin irritation at moderate concentrations of test material and the need for repetition of the study at lower concentrations.	Irritation would be seen prior to signs of redness and edema associated with sensitisation.	Medium relevance and low reliability and adequacy of both the animal and clinical studies. While 12-HSA is saturated, the purity is less than 90% and unsaturated fatty acids may be present to trigger a positive response. The GPMT appears to be a more reliable assay for the fatty acids group.	There is remaining uncertainty after these data are evaluated that hydroxylated fatty acids could be sensitisers. There is an additional body of evidence in the cosmetic industry that castor oil derivatives are not sensitisers and have a long history of safety in use in cosmetics products. As this evaluation should be fit for purpose for hazard identification for the registered substance for worker safety and safety for users down the supply chain, the data on ricinoleate esters is evaluated as adequate to demonstrate lack of sensitisation in a valid animal model.
Conclusion from overall confidence	The WOE prioritises the evaluation of the 1999 Manceaux study of methyl ricinoleate, showing no sensitisation in a test material highly similar to the target substance. The GMPT from 12-HASA supports this finding, although the LLNA from 12-HSA shown the compound to be positive. This could be due to a false positive as other unsaturated fatty acids behave similarly (Kreiling, et al, 2008; Yamashita, et al, 2015), or due to damage from the skin due to acid effects on the skin matrix (Mack-Correa, et al., 2014). Data from a clinical sensitisation study on ethyl ricinoleate also supports a lack of sensitisation in human volunteers. Based on reading-across from compounds of similar structure and similar toxicological behaviour, the registered substance is expected to show sensitisation properties similar to that observed in Manceaux, 1999, and would therefore be considered a non-sensitiser.

 

Through this weight of evidence evaluation, the substance is judged to be non-sensitising. The criteria for classification for dermal sensitisation is not met, and the substance is not classified.