Thioacetic acid

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

The potential of THIOACETIC ACID, to induce delayed contact hypersensitivity following intradermal injection and cutaneous application was evaluated in guinea-pigs according to the maximization method of Magnusson and Kligman and O.E.C.D. (No. 406, 12th May 1981) (Clouzeau, 1994). The study was conducted in compliance with the Principles of Good Laboratory Practice Regulations.

Thirty guinea-pigs (15 males and 15 females) were allocated to 2 groups: a control group 1 (5 males and 5 females) and a treated group 2 (10 males and 10 females).

The sensitization potential of the test substance was evaluated after a 10-day induction periodduring which time the animals were treated with the vehicle (control group) or the test substance(treated group). On day 1, in presence of Freund's complete adjuvant, 0.1 ml of the test substance at a concentration of 1% in the vehicle was administered by intradermal route. On day 8, 0.5 ml of the test substance at a concentration of 10% in the vehicle was applied by cutaneous route during 48 hours by means of an occlusive dressing. After a period of 12 days without treatment, a challenge cutaneous application of 0.5 ml of the vehicle (left flank) and 0.5 ml of the test substance at a concentration of 10% in the vehicle (right flank) were admi­nistered to ail animals.

The test substance and the vehicle were prepared on a dry compress then were applied to the skin and held in place for 24 hours by means of an occlusive dressing. Cutaneous reactions on the challenge application sites were then evaluated 24 and 48 hours after removal of the dressing.

After the final scoring period, the animals were sacrificed and cutaneous samples were taken from the challenge application sites from ail the animals. No histological examination was per­formed on the cutaneous samples.

The sensitivity of the guinea-pigs in the laboratory experimental conditions were checked in a recent study with a positive sensitizer: Dinitro 2.4 Chlorobenzene. During induction period the test substance was applied at 0.05% (day 1) and 0.5% (day 8) concentrations. At cutaneous challenge application, 0.1% and 0.5% were tested on both flanks.

No clinical signs and no deaths were noted during the study.

Sensitization skin reactions characterised by a well-defined and a moderate to severe erythema were observed after 24 hours on the right flank of 14/20 treated animals. No oedema was observed.

Inconclusive evidence of sensitization skin reactions (very slight erythema, score of 1) were noted in 6/20 treated animals.

After 48 hours, intensity of erythema reversed slightly.

A dryness of the skin was noted after 48 hours in 19/20 treated animals.No oedema was observed.

The guinea-pigs which were used showed a satisfactory sensitization response in 100% animals using a positive sensitizer.

THIOACETIC ACID, induced positive skin sensitization cutaneous reactions in 14/20 (60%) guinea-pigs.

Migrated from Short description of key information:
THIOACETIC ACID induced delayed contact hypersensitivity in guinea-pigs.

Justification for selection of skin sensitisation endpoint:
Key study

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Skin sensitization:

In a GPMT assay, thioacetic acid induced skin sensitiziation in 60% of the guinea pigs with an induction concentration of 1%. On the basis of this study and in accordance with Regulation (EC) No 1272/2008, thioacetic acid was classified as skin sensitizer category 1A (Hazard statement H317; May cause an allergic skin reaction) and in accordance with Annex VI of Commission Directive 2001/59/EC, thioacetic acid was classified as irritant with the symbol Xi and the phrase R43 ‘May cause sensitisation by skin contact’.