Registration Dossier

Administrative data

Description of key information

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

There are three studies according to method OECD Guideline 429 regarding skin sensitisation with C12AS Na (CAS 151-21-3) available. Two of them are deemed to be not reliable. To support this assumption a read-across to a structurally related alkyl sulfate (AS), i.e. C12-13AS Na (CAS 91783-23-2) was performed. The possibility of a read-across to other alkyl sulfates in accordance with Regulation (EC) No 1907/2006 Annex XI 1.5. Grouping of substances and read-across approach was assessed. In Annex XI 1.5 it is given that a read-across approach is possible for substances, whose physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity. The AS reported within the AS category show structural similarity. The most important common structural feature of the category members is the presence of a predominantly linear aliphatic hydrocarbon chain with a polar sulfate group, neutralized with a counter ion. This structural feature confers the surfactant properties of the alkyl sulfates. The surfactant property of the members of the AS category in turn represent the predominant attribute in mediating effects on mammalian health. Therefore, the AS of the AS category have similar physico-chemical, environmental and toxicological properties, validating the read across approach within the category. The approach of grouping different AS for the evaluation of their effects on human health and the environment was also made by the OECD in the SIDS initial assessment profile [1] and by a voluntary industry programme carrying out Human and Environmental Risk Assessments (HERA [2]), further supporting the read across approach between structurally related AS. A detailed justification for grouping of alkyl sulfates into a category is provided separately. Please refer for more details on the read-across also to the document “AS Category Approach Justification” attached in section 13 of IUCLID.


There are three studies with C12AS Na (CAS 151-21-3) available addressing skin sensitisation.

The skin sensitizing potential of C12AS Na (CAS 151-21-3) was assessed in a local lymph node assay similar to OECD guideline 429 (Ikarashi et al., 1993) on 3 mice per dose and experiment. BALB/c mice were treated daily via topical application (25 µL) of 5, 10 and 25% aqueous solution of the test item on 3 consecutive days.

In a second experiment, intradermal injections (50 µL) were performed with test item concentrations of 0.05, 0.5 or 5% in saline. Five days after intradermal injection, mice were challenged daily by dermal application of 25 µL of a 5% solution in vehicle (DMSO 50%) on the ears for 3 consecutive days.

The day after the final exposure, changes in lymph node weight, total cell number in the draining lymph nodes and LNC proliferation for 24 h culture were assessed. The stimulation indices in the first experiment were 0.7, 1.6 and 1.1 at 5, 10 and 25%. After intradermal application of 0.05, 0.5 or 5% test item and subsequent dermal challenge with 5% test item the stimulation indices were 1.6, 1.9 and 1.5.

Next to this negative local lymph node assay also two local lymph node assays with C12AS Na (CAS 151-21-3) resulting in a positive result are provided (Basketter et al., 1994 and Montelius et al., 1994). In both publications 4 female CBA/Ca mice were treated with 25 µl of a 5, 10 or 25% solution in DMSO or DMF on 3 consecutive days on the dorsum of each ear. Even at the lowest concentration the stimulation index (test/control ratios) was above 3 in both publications indicating a skin sensitizing property of C12AS Na. This positive result is however believed to be a testing artefact as irritants can produce false positive reactions in the LLNA.

Montelius et al. used Sodium dodecyl sulphate as irritating substance without known sensitising properties to investigate whether the LLNA is able to differentiate between irritating and sensitising substances. Finally the increased stimulation index was linked to a non-antigen specific proliferative stimulus induced by the irritating effect. Nowadays it is also reported in the OECD Guidance document 429 that the LLNA might result in false positive findings with some surfactant type chemicals due to their irritant activity.

To further underpin that C12AS Na is not sensitising, a read-across from the structurally related C12-13AS Na (CAS 91783-23-2) was performed.
10 Hartley guinea pigs were induced intradermal and epicutaneous with C12-13AS Na (CAS 91783-23-2, analytical purity 27%) in a guinea pig maximisation test performed similar to OECD guideline 406 (Milone, 1984). 48 h after challenge with 3.35% C12-13AS Na (based on a.s.) 2/20 animals were scored positive. 0/20 were scored positive 72 h after challenge. The negative control resulted in 2/10 and 0/10 animals with positive reactions upon challenge with 3.35% C12-13AS Na (based on a.s.). Thus the test substance was not sensitising.


Based on the results of the above mentioned study with C12-13AS Na, C12AS Na (CAS 151-21-3) has no sensitizing properties. In addition sodium lauryl sulphate is also recommended as an agent to induce local irritation in an OECD method to assess skin sensitising properties of chemicals (OECD guideline 406, Guinea Pig Maximisation Test). Therefore, there is a lot of experience with sodium lauryl sulfate in sensitising studies and no evidence occurred that it shows sensitising properties. Thus, skin sensitisation by members of the alkyl sulfates is generally unlikely.

 [1] SIDS initial assessment profile, (2007);

[2] (HERA Draft report, 2002);

Migrated from Short description of key information:
Skin sensitisation (LLNA - OECD 429 and GPMT - OECD 406): not sensitising

Justification for selection of skin sensitisation endpoint:
No study chosen as weight of evidence approach was followed.

Respiratory sensitisation

Endpoint conclusion
Additional information:
Migrated from Short description of key information:
No data available.

Justification for classification or non-classification

The available data on skin sensitisation do not meet the criteria for classification according to Regulation (EC) 1272/2008 or Directive 67/548/EEC, and are therefore conclusive but not sufficient for classification.

No data available for respiratory sensitisation.