Benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs., para-, sodium salts

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

In a key study the dermal sensitisation of the low TBN substance (Benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs., para-, sodium salts, TBN = 3) was evaluated in guinea pigs (Smedley, 2015a). The animals were treated topically with a 75% concentration of the test substance in mineral oil once per week during the three week induction phase. Following a two week rest period, the animals were topically challenged with a 35% concentration of the test substance in mineral oil. After approximately one week the animals were rechallenged with a 15% concentration of the test substance in mineral oil. At the respective 24 hour and 48 hour challenge and rechallenge readings, dermal scores of 2 were noted in 18/20 and 16/20 at the 35% challenge and 14/20 and 14/20 at the 15% rechallenge. The 24/48 hour Draize scores in the 35% challenge group were 1.9/1.8 compared to 0.6/0.6 in the challenge controls. The mean 24/48 hour Draize scores in the 15% rechallenge group were 1.7/1.7 compared to 0.7/0.8 in the rechallenge controls. Based on these results the test substance was determined to be a sensitiser.

 

In another key study the dermal sensitisation of the high TBN substance (Benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs., para-, sodium salts; TBN = 448) was evaluated in guinea pigs (Smedley, 2015b). The animals were treated topically with a 100% concentration of the test substance in mineral oil once per week during the three week induction phase. Following a two week rest period, the animals were topically challenged with a 75% concentration of the test substance in mineral oil. After approximately one week the animals were rechallenged with a 50% concentration of the test substance in mineral oil. Following a one week rest period the animal received a second rechallenge at 25% of the substance in mineral oil. At the respective 24 hour and 48 hour challenge, rechallenge, and second rechallenge readings, dermal scores of 1 were noted in 3/20 and 6/20 at the 75% challenge; dermal scores of 1 or 2 were noted in 13/20 and 13/20 at the 50% rechallenge; and dermal scores of 1 were noted in 10/20 and 12/20 at the 25% second rechallenge. The 24/48 hour Draize scores in the 75% challenge group were 0.2/0.3 compared to 0.3/0.5 in the challenge controls. The mean 24/48 hour Draize scores in the 50% rechallenge group were 1.2/1.2 compared to 0.9/0.3 in the rechallenge controls. The mean 24/48 hour Draize scores in the 25% second rechallenge group were 0.6/0.7 compared to 0.5/0.7 in the rechallenge controls. Based on the weight-of-evidence of these results the test substance was determined not to be a sensitiser.

Migrated from Short description of key information:
Studies in guinea pigs show that low TBN Benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs., para-, sodium salts (TBN = 3) is a skin sensitiser (Smedley, 2015a) while Benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs., para-, sodium salts (TBN = 448) is not a skin sensitiser (Smedley, 2015b). The study results provide additional weight-of-evidence indicating that low TBN sodium and calcium sulfonates (TBN < 300) are skin sensitisers with a specific concentration limit (SCL) of 10% and that high TBN sodium and calcium sulfonates (TBN ≥ 300) are not skin sensitisers (for more details, please refer to the classification and labelling summary for skin sensitisation).

Justification for selection of skin sensitisation endpoint:
No study is selected since the test substance was tested in two forms (as TBN = 3 and as TBN = 448) resulting in two different skin sensitisation responses.

Justification for classification or non-classification

The classification and labelling for Benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs., para-, sodium salts (generic name: C20-24 sodium sulfonate) is based on the results of two recent skin sensitisation studies according to Modified Buehler design and on the results of numerous skin sensitisation animal studies with low and high TBN calcium sulfonates. Results of Human Repeat Insult Test (HRIPT) with low and high TBN calcium sulfonates have also been taken into account (please see attached file or refer to the respective section of the CSR).

In accordance with EU CLP Regulation (EC) No. 1272/2008, classification is required for low TBN sodium sulfonates (TBN < 300) with a specific concentration limit of 10% and classification is not required for high TBN sodium sulfonates (TBN ≥ 300).