Sodium dodecyl sulphate

Endpoint summary

Description of key information

skin irritation (OECD 404): irritating
eye irritation (OECD 405): highly irritating/corrosive
SCLs according to GHS:
>=10% - <20% Eye Irrit. Cat.2
<10% No Classification

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

There are data regarding skin and eye irritation/corrosion with C12AS Na (CAS 151-21-3) available. Additionally a read across to structurally related AS, i.e. C10-16AS Na (CAS 68585-47-7) and C12-13AS K (CAS 91783-22-1) for eye irritation 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.

Skin irritation

There is one key study for the read-across substance C12AS Na (CAS 151-21-3) available addressing skin irritation.

The key study conducted with C12AS Na (CAS 151-21-3, analytical purity 100%) was performed similar to OECD Guideline 404 under occlusive conditions (Esposito, 1976). Each of six New Zealand White rabbits was exposed for 24 h to 0.5 mL of the unchanged test item and was observed for a period of 72 h for erythema and edema. No scoring was done 48 h after application. The mean erythema and edema score after 24 and 72 h were 2.2 and 1.7. Both were not reversible within 72 h. When using the higher value of the 24 and 72 h reading time point as value for the 48 h value (per animal) the mean erythema and edema score of all animals were 2.4 and 2.2, respectively.

A supporting study conducted with C12AS Na (CAS 151-21-3, analytical purity 25%) was performed similar to OECD Guideline 404 under occlusive conditions (Kästner, 1987). Each of five Kleinrusse White rabbits was exposed for 4 h to 0.5 mL of the unchanged test item and was observed for a period of 21 d for erythema and edema. Skin reactions were scored 24, 48 and 72 h after termination of treatment. The mean erythema and edema score after 24, 48 and 72 h were 4 and 3.7. A clear decrease in skin reactions during the observation period was observed. After 21 d only 1/5 animals showed edema (score 1) and 2/5 animals showed erythema (both scored 1).

The skin irritating potential of C12AS Na (CAS 151-21-3) was further examined in rabbits at concentrations of 2, 10 and 20% under occlusive conditions for 24 haccording to the method of Draize (Ciuchta et al., 1978). Scoring was done 24 and 72 h after removal of the patch. The primary irritation score was 5.2, 6 and 6 at 2, 10 and 20%, respectively. However based on the primary irritation score no conclusion regarding classification for skin irritation according the current regulations could be made.

Next to the animal studies also human data are available. C12AS Na (CAS 151-21-3, analytical purity 97.1%) was applied as a 20% solution to human skin in an Acute Irritation Patch Test for 2 h (P&G, 1998). 21 volunteers were patched daily under occlusive conditions for four consecutive days for 2 h until the patch site exhibits a positive reaction. Any volunteer with a positive reaction was not further exposed. A positive skin reaction was observed latest after 3 days. Thus the test substance was irritating within this study.

There are 3 publications available where 20% C12AS Na (CAS 151-21-3) was applied to the intact skin of human volunteers for 4 h under occlusive conditions (Basketter et al., 2004; Griffiths et al., 1997 and Robinson et al., 1998). Robinson et al. also applied 1 and 10% C12AS Na (CAS 151-21-3) solutions. Consistently C12AS Na at 20% induced skin reactions in human volunteers in all publications. Application of 1 and 10% C12AS Na resulted in skin irritation in some but not in all volunteers. Thus C12AS Na (CAS 151-21-3) is moderately irritating in humans at a concentration of 20 %, supporting the classification of C12S Na as irritating but not corrosive.

Consequently, the test substance was classified as skin irritating Category 2 according to Regulation 1272/2008/EC and R38 according to Directive 67/548/EEC.

Eye irritation

There is one key study available addressing eye irritation for C12AS Na (CAS 151-21-3).

In an OECD guideline 405 study (Kästner, 1987) 0.1 mL of C12AS Na (CAS 151-21-3, analytical purity 25%) was applied to one eye of each of four rabbits (strain: Kleinrusse Chbb:HM). Eye reactions were scored 1, 6, 24, 48 and 72 h and 7, 10, 14, 17 and 21 days after application. The mean (24, 48 and 72 h reading) cornea, iris, conjunctivae and chemosis scores were 1, 0, 2.6 and 1.1. The corneal and the conjunctival findings did not revers fully until days 21. Thus the test item produced irreversible effects on the eye at a concentration of 25 %.

As corrosion and irritation depends on the concentration of the substance in a solvent, further studies with lower concentrations of the test substance were also considered to assess whether specific concentration limits can be set. For this purpose, one study with C12-13AS K (CAS 91783-22-1) and two studies with C10-16AS Na (CAS 68585-47-7) with a concentration range of 10 to 22% were evaluated.

In the study with C12-13AS K (CAS 91783-22-1, analytical purity 44%) 0.1 mL of the diluted test item (1:1 mixture with water) was applied to one eye of each of three New Zealand White rabbits according to OECD guideline 405 (Braun, 1978) without rinsing. In a second experiment with additional 3 rabbits the procedure was repeated but the treated eye was rinsed with 20 mL of lukewarm tap water 4 seconds after application of the test item. The eye reactions were recorded 1, 24, 48, 72 h and 4, 7, 14, 21 and 28 days in both experiments. The mean (24, 48 and 72 h reading) cornea, iris, conjunctivae and chemosis scores of experiment 1 were 2, 0.8, 2.1 and 1.7. The findings reversed in 2/3 animals within 14 days while 1/3 animals showed signs of irritation after 21 days. However, the signs of irritation show a clear tendency to decrease with time. No reading on day 28 was possible. Findings in the experiment with rinsing of the eye were less pronounced but irritating properties were also observed. As the ocular findings clearly reversed within 21 days the result of the study indicate the concentration of 22% to be the turning point between classification as severe damage to the eye and eye damaging.

The first study with 0.1 mL undiluted C10-16AS Na (CAS 68585-47-7, analytical purity 10%) was performed similar to OECD guideline 405 (Kukulinski, 1980) on three New Zealand White rabbits with an observation period of 7 days. The mean (24, 48 and 72 h reading) cornea, iris, conjunctivae and chemosis scores over all animals were 1.4, 0.7, 2 and 1.6. Corneal opacity was still observed in 1/3 animals (scored 1) and conjunctival redness was still present in 2/3 animals (both scored 1) upon reading at day 7. Depending on the classification requirements the test substance is not or only moderate irritating to the eye at a concentration of 10%.

The second study with C10-16AS Na (CAS 68585-47-7, analytical purity 10%) was performed similar to OECD guideline 405 (Kukulinski, 1980). 0.1 mL of the undiluted test item was instilled into one eye of each of three New Zealand White rabbits. Eye reactions were scored at least 24, 48 and 72 h and 14 days after application of the test item. The mean (24, 48 and 72 h reading) cornea, iris, conjunctivae and chemosis scores were 0.9, 0.7, 1.9 and 1.6. All findings were fully reversible within the observation period. Thus, the test substance showed no eye irritating properties at a concentration of 10%.

Based on the above mentioned results with different concentrations of structurally related alkyl sulfates a cut of value for classification as severe irritating to eyes is set at a concentration of 20% and for classification as irritating at a concentration of 10%.

Respiratory inhalation

No data on respiratory irritation are available. AS is mainly used in liquid media and due to its very low vapour pressure [2] inhalation is not viewed as a significant route of exposure. Inhalation of AS may occur by inhalation of aerosols generated by spray cleaners or by inhalation of detergent dusts (e.g. washing powder). In both cases the substance will be used in low concentrations. However in case the substance is available as neat powder the substance will also be classified as STOT Single exp. Cat 3 according to CLP and according to DSD as Xi, R37 irritating to the respiratory system.

 

[1] SIDS initial assessment profile, (2007);
http://www.aciscience.org/docs/Alkyl_Sulfates_Final_SIAP.pdf

[2] (HERA Draft report, 2002);
http://www.heraproject.com/files/3-HH-04-%20HERA%20AS%20HH%20web%20wd.pdf

Justification for selection of skin irritation / corrosion endpoint:
Reliable OECD guideline study

Justification for selection of eye irritation endpoint:
Reliable OECD guideline study

Effects on skin irritation/corrosion: irritating

Effects on eye irritation: corrosive

Justification for classification or non-classification

According to the classification criteria of Directive 67/548/EEC and Regulation (EC) No 1272/2008 the test substance needs to be classified with Xi, R38/R41 and Skin Irrit. 2, H315 and Eye Dam.1, H318, respectively.

It could be shown with experimental data on eye irritation that above 10 to 20% active substance only the classification Eye Irritating Category 2 according to Regulation (EC) No 1272/2008 and according to Directive 67/548/EEC only the classification R36 remains. At and below 10% active substance no classification at all is necessary. Hence, the Generic Concentration Limits (GCLs) can be substituted by the mentioned specific ones (SCLs). As the neat substance has to be classified as skin irritating, the substance will also be classified as “may cause respiratory irritation” (STOT SE3, H335 and R37, respectively) in case the substance is available as neat powder.