Sodium 2-stearoyllactate

Endpoint summary

Description of key information

Information obtained with esterification product of C16-C18 even numbered, saturated fatty acids and lactic acid, sodium salt (SSL, sodium stearoyl lactylate, CAS No. 25383-99-7, EC No. 246-929-7):

In vitro cytotoxicity test on reconstructed human epidermis (RHE): sensitising

Mathematical prediction models: D-optimal design and k-Nearest Neighbour classification (kNN) method along with Genetic Algorithms (GA-kNN Classification) (not reported as endpoint study record): weak/non-sensitizer

Information obtained with sodium lauroyl lactylate (SLL, CAS No. 13557-75-0, EC No. 236-942-6):

Local Lymph Node Assay (LLNA, OECD 429): weak sensitizer

Guinea Pig Maximisation Test (GPMT, OECD 406): weak sensitizer

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vitro

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

A cytotoxicity test was conducted on reconstructed human epidermis (RhE) tissues. The test substance was topically applied to the RhE tissues and the tissues were incubated at 37 °C, in the presence of 5% CO2 and 95% humidity, for 72 h. Following exposure to the test substance, the RhE growth medium was screened for the primary inflammation marker Interleukin-1α (IL-1α) and the delayed inflammation marker Interleukin-8 (IL-8).

GLP compliance:

no

Remarks:

Investigation reported in a scientific publication

Type of study:

other: detection of the inflammation markers Interleukin IL-1α and IL-8

Details on the study design:

A cytotoxicity test was conducted on reconstructed human epidermis (RhE) tissues. Upon delivery, RhE devices were transferred into 3 mL of RhE aqueous growth medium, free from antibiotics and hydrocortisone, and treated immediately.Three reconstructed human epidermis (RhE) tissues were treated with 10 µL of an emulsion containing the test substance at a concentration of 3%. The test substance emulsion was topically applied at the center of the RhE surface. Four untreated RhE tissues were used as controls. Each sample (test substance and control) was placed in 3 mL of aqueous growth medium and incubated at 37 °C, in the presence of 5% CO2 and 95% humidity, for 72 h.

After the incubation period, the RhE growth medium was screened for the primary inflammation marker Interleukin-1α (IL-1α) and the delayed inflammation marker Interleukin-8 (IL-8). The collected RhE growth medium was labeled using the Fluorokine MAP Human Base Kit A and analysed by flow cytometry using the Bioplex-200 instrument (Bio-Rad, Marnes-la-Coquette, France), a device relying on a Luminex Multi-Analyte Profiling technology.

Substances are considered to induce skin sensitisation when the extracellular IL-8 > 1L-1α, and irritants when extracellular IL-8 < IL-1α.

Run / experiment:

other: 72 h

Parameter:

other: Release of Interleukin-1a (IL-1α)

Value:

0.582 %

Vehicle controls validity:

not applicable

Negative controls validity:

not applicable

Positive controls validity:

not applicable

Run / experiment:

other: 72 h

Parameter:

other: Release of Interleukin-8 (IL-8)

Value:

3.407 %

Vehicle controls validity:

not applicable

Negative controls validity:

not applicable

Positive controls validity:

not applicable

Other effects / acceptance of results:

Sodium stearoyl lactylate caused a significant release of IL-8 and no significant IL-1α release. The IL-8/IL-1α ratio was 5.85 (i.e. > 1). The value for release of IL-8 (3.407) was above the threshold of 3, whereas the value for the release of IL-1α (0.582) was not.

Substances applied to the skin can be considered allergens when the extracellular IL-8 > 1L-1α, and as irritants when extracellular IL-8 < IL-1α. Sodium stearoyl lactylate was predicted to be an allergen.

Interpretation of results:

other: Sodium stearoyl lactylate was predicted to be an allergen.

Reference 2

Endpoint:

skin sensitisation, other

Remarks:

LLNA and GPMT

Type of information:

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

Remarks:

Summary of available data used for the endpoint assessment of the target substance.

Adequacy of study:

weight of evidence

Justification for type of information:

Refer to the justification provided in the sensitisation endpoint summary.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Parameter:

EC3

Value:

15

Remarks on result:

other: Source: Basketter et al., 2007, LLNA

Parameter:

SI

Test group / Remarks:

2.5%

Remarks on result:

other: Individual SI values are not reported in the publication. Source: Basketter et al., 2007, LLNA

Parameter:

SI

Test group / Remarks:

5%

Remarks on result:

other: Individual SI values are not reported in the publication. Source: Basketter et al., 2007, LLNA

Parameter:

SI

Test group / Remarks:

10%

Remarks on result:

other: Individual SI values are not reported in the publication. Source: Basketter et al., 2007, LLNA

Parameter:

SI

Test group / Remarks:

25%

Remarks on result:

other: Individual SI values are not reported in the publication. Source: Basketter et al., 2007, LLNA

Parameter:

SI

Test group / Remarks:

50%

Remarks on result:

other: Individual SI values are not reported in the publication. Source: Basketter et al., 2007, LLNA

The results of the Guinea Pig Maximisation Test (GPMT) reported in Basketter et al., 2007, GPMT, are also considered in the WoE approach. The test substance sodium lauroyl lactylate (SLL, CAS No. 13557-75-0, EC No. 236-942-6) was determined to be a weak sensitizer.

Interpretation of results:

other: Skin Sens. 1B, H317. Classification according to Regulation (EC) No. 1272/2008 (CLP/EU GHS).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

The skin sensitisation potential of esterification product of C16-C18 even numbered, saturated fatty acids and lactic acid, sodium salt (SSL, sodium stearoyl lactylate, CAS No. 25383-99-7, EC No. 246-929-7) is assessed by means of a Weight-of-Evidence (WoE) approach according to Annex XI, Section 1.2, of the REACH Regulation (EC) No. 1907/2006. The WoE assessment is based on several independent sources of information obtained with SSL and with the analogue substance sodium lauroyl lactylate (SLL, CAS No. 13557-75-0, EC No. 236-942-6). While the information from each single source alone is regarded insufficient to cover the standard information requirement for skin sensitisation according to REACH Annex VII, Section 8.3, the individual results taken together allow for a robust hazard assessment and to conclude on the classification and labelling of SSL.

 

Data obtained with sodium stearoyl lactylate (SSL)

An in vitro assay was used to assess skin toxicity by means of detection of the inflammation markers Interleukin IL-1α and IL-8 following application of SSL on reconstructed human epidermis (RhE) tissues (Lemery et al., 2015). It was noted that inflammation markers have been released in the growth medium of RhE as a consequence of the immune response to the presence of the test substance. A value for Interleukin release of > 1 corresponds to production of IL-1α or IL-8 induced by the presence of the test substance. IL-1α is expressed as an intracellular protein; it accumulates in keratinocytes and is released by injured cells or after membrane alteration. IL-8 is a secondary inflammatory cytokine, secreted in response to IL-1α release during inflammation. The relative inflammation potency was evaluated by measuring release of the Interleukins by flow cytometry. The threshold for IL-1α and IL-8 release was defined as 3 times that of the control (untreated RhE).

SSL caused a significant release of IL-8 (3.4 times larger than the untreated RHE) and no IL-1α release. IL-8/IL-1α ratio was 5.85 (i.e., > 1). The value for release of IL-8 (3.407) was above the threshold of 3, whereas the value for the release of IL-1α (0.582) was not. Substances applied to the skin can be considered allergens, i.e. causing skin sensitisation, when the extracellular IL-8 > 1L-1α, and as irritants when extracellular IL-8 < IL-1α. SSL was predicted to be a skin sensitizer.

 

In addition to the experimental investigation, skin sensitisation data on a number of very diverse substances, including data on SSL, was calculated to develop multiple predictive classification models (Gunturi, S.B. et al., 2010, Prediction of skin sensitization potential using D-optimal design and GA-kNN classification methods, SAR and QSAR in Environmental Research, 21:3-4, 305-335). The publication is not reported as endpoint study record as the focus of the publication is on the development of the mathematical models and less on the toxicological aspects of the results. Therefore, only very limited relevant information that could be entered in an endpoint study record are reported in the paper. The study is considered useful in the WoE approach to assess the skin sensitisation potential of SSL as it supports the findings of the experimental studies also taken into consideration. Two automated procedures were used to select significant and independent descriptors in order to build the models: 1) D-optimal design to select optimal members of the training and test sets and 2) k-Nearest Neighbour classification (kNN) method along with Genetic Algorithms (GA-kNN Classification). The EC3 values (from a number of LLNA studies) of the substances were ranked quantitatively according to their potencies. Class 1 signified extreme/strong/moderate sensitizers (EC3 < 10%) and Class 2 signified weak/non-sensitizers (EC3 ≥ 10%). Of the five models developed, four placed SSL in Class 2 (weak/non-sensitizer) and only one placed the substance in Class 1 (extreme/strong/moderate sensitizer). Thus, the consensus prediction based on all models was Class 2.

 

Data obtained with sodium lauroyl lactylate (SLL)

In addition to the data obtained with sodium stearoyl lactylate (SSL, esterification product of C16-C18 even numbered, saturated fatty acids and lactic acid, sodium salt, CAS No. 25383-99-7, EC No. 246-929-7) studies performed with sodium lauroyl lactylate (SLL, CAS No. 13557-75-0, EC No. 236-942-6) are considered. This formally constitutes an analogue read-across approach according to REACH Annex XI, Section 1.5, and the adequacy of this approach needs to be demonstrated based on the scientific principles laid down in the Read-Across Assessment Framework (RAAF; Read-Across Assessment Framework (RAAF), ISBN 978-92-9495-758-0, European Chemicals Agency, 2017, and Read-Across Assessment Framework (RAAF), ISBN 978-92-9495-811-2, Considerations on multi-constituent substances and UVCBs, European Chemicals Agency, 2017). The main principle in the RAAF is the demonstration of structural similarity between target and source substances. In order to decide on the structural similarity, detailed information on the qualitative (which compounds are present) and quantitative (concentration of each compound present) composition is needed. The similarities and differences in the composition of target and source substances must be considered and the 'compounds test organisms are exposed to' need to be discussed. It must be established to what extent the prediction of toxicological properties of the target substance (here SSL) is affected by compounds present in the source substance (here SLL) but not in the target substance. Similarly it must be clear how compounds present in the target but not in the source substance have an effect on the prediction. In conclusion, the exact composition of target and source substances is a prerequisite for a robust analogue read-across approach. This conclusion is all the more important as the target and source substances are of UVCB nature (Unknown or Variable composition, Complex reaction products or Biological materials).

It must be noted that the investigations of the skin sensitising potential of sodium lauroyl lactylate (SLL) are reported in a scientific publication. No detailed compositional information in terms of the qualitative and quantitative composition of the tested SLL material is provided in the paper. A detailed discussion of the similarities and differences in composition and their potential implications for the prediction and of the 'compounds test organisms are exposed to' is, therefore, not possible. However, in this particular case the lack of compositional information is not considered to affect the prediction of the skin sensitising properties of SSL because based on the information obtained with SLL, SSL is predicted to be a skin sensitiser in a worst-case approach. The analogue read-across is based on the structural similarity that can be derived from the general chemical characterisation of SLL given in the publication.

The main structural feature of both the target and source substances is the lactylate (lactyl lactate) moiety. Since lactyl lactate contains a hydroxyl (OH) group, esterification with acidic compounds is possible. While the most prominent acid moiety in the source substance (sodium lauroyl lactylate, SLL) is lauric acid (the C12 carboxylic acid), it is a combination of stearic (C18 carboxylic acid) and palmitic acid (C16 carboxylic acid) in the target substance (sodium stearoyl lactylate, SSL). In addition to C12 in the source and C16 and C18 in the target substance, it is expected that further carboxylic acids are present to a lesser extent. However, the presence of additional alkanoyl lactylates in the source and target substances is not expected to affect the worst-case prediction of the skin sensitisation properties of SSL.

In conclusion, it is considered appropriate to use skin sensitisation data with SLL to predict the skin sensitisation properties of SSL in a worst-case approach. Although no detailed composition of the source substance SLL is provided and, hence, no detailed assessment of the similarities and differences in the composition of target and source substances can be made, SLL and SSL are considered to be similar enough to apply a worst-case approach to make a prediction.

 

The potential to induce skin sensitisation of sodium lauroyl lactylate (SLL, CAS No. 13557-75-0, EC No. 236-942-6) was assessed in a Local Lymph Node Assay (LLNA) according to OECD guideline 429 (Basketter et al., 2007, LLNA). Groups of 4 CBA/Ca female mice (7 - 12 weeks of age) were treated topically on the dorsum of both ears with 25 μL of 2.5%, 5%, 10%, 25%, and 50% SLL in AOO vehicle (Acetone:Olive Oil, 4:1, v/v) or equal volumes of the vehicle alone. Treatment was performed daily for three consecutive days. Five days after the initiation of exposure, all mice were injected via the tail vein with 250 µL of phosphate buffered saline (PBS) containing 20 mCi of tritiated thymidine. Mice were sacrificed 5 h later and the draining lymph nodes excised and pooled for each experimental group. The lymph node cell suspension was washed twice in an excess of PBS and then precipitated with 5% trichloroacetic acid (TCA) at 4 °C for 18 h. Pellets were re-suspended in TCA and the incorporation of tritiated thymidine measured by ß-scintillation counting. The test substance concentration required to produce a stimulation of proliferation of at least 3-fold greater when compared to controls (i.e. EC3 value) was calculated to provide a measure of relative skin sensitising potential. The EC3 value was calculated by interpolating between 2 points on the stimulation index (SI) axis, one immediately above, and one immediately below, the SI value of 3. A positive control using hexyl cinnamic aldehyde was performed by the laboratory at routine intervals to ensure test method sensitivity. An EC3 value of 15% was established, classifying SLL as a weak sensitizer.

 

15 Albino Dunkin-Hartley guinea pigs (10 treated, 5 controls, weighing approx. 350 g) were used in a Guinea Pig Maximisation Test (GPMT, OECD guideline 406) to investigate the skin sensitisation potential of Sodium Lauroyl Lactylate (Basketter et al., 2007, GPMT). Preliminary irritation tests were carried out to determine the concentration of the test substance suitable for the induction and challenge phases. For the topical challenge application, the preliminary irritation study used 4 guinea pigs, each treated with a range of concentrations applied under occlusion using 8-mm Finn chambers. Skin reactions were scored 24 h and 48 h after patch removal. The maximum concentration producing no reaction was selected as suitable for challenge. The injection and dermal doses chosen based on the preliminary tests are not reported. The challenge concentration was 0.5%. SLL was identified as a weak sensitizer.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

The available data on skin sensitisation with esterification product of C16-C18 even numbered, saturated fatty acids and lactic acid, sodium salt (sodium stearoyl lactylate, SSL, CAS No. 25383-99-7, EC No. 246-929-7) and with the analogue substance sodium lauroyl lactylate (SLL, CAS No. 13557-75-0, EC No. 236-942-6), assessed in a worst-case Weight-of-Evidence approach, indicate a weak to moderate sensitising potential. It is, therefore, concluded that SSL meets the criteria for classification as Skin Sens. 1B (H317) according to Regulation (EC) No. 1272/2008 (CLP).