Thioacetic acid

Endpoint summary

Description of key information

Thioacetic acid was slightly irritant when applied topically to rabbits and severely irritant when instillated in the eyes of rabbits.

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

Skin irritation

 

The potential of THIOACETIC ACID to induce skin irritation was evaluated in rabbits according to O.E.C.D. (No. 404, 17th July 1992) and E.C. (92/69/E.E.C., B₄, 31 st July 1992) guidelines (Manciaux, 1998). The study was conducted in compliance with the Principles of Good Laboratory Practice Regulations. The test substance was applied in a first assay for periods of 3 minutes and 4 hours to one male New Zealand White rabbit. Since the test substance was not strongly irritant in this first assay, it was applied for 4 hours to two other males in a second assay. A single dose of 0.5 ml of the test substance in its original form was applied to the closely clipped skin of one flank. The test substance was held in contact with the skin by means of a semi-occlusive dressing. Cutaneous reactions were observed approximately 1 hour, 24, 48 and 72 hours after removal of the dressing and the end of the observation period.The mean values of the scores for erythema and oedema were calculated for each animal.After a 3-minute exposure (one animal), no cutaneous reactions were observed during the study. After a 4-hour exposure (three animals), a well-defined erythema was observed in ail animals on day 1; it persisted up to day 11 at the latest.A slight oedema was noted in ail animals from day 1 or 2; it persisted for 24, 48 or 72 hours.Dryness of the skin was recorded in ail animals from day 5 or 6 up to day 12, 13 or 15. A slight yellow colouration of the skin was also observed in ail animals between day 1 and day 4. Mean scores over 24, 48 and 72 hours for each animal were 2.0, 1.7 and 1.7 for erythema and 2.0, 0 and 0 for oedema.

 

Eye irritation

 

The potential of THIOACETIC ACID to induce ocular irritation was evaluatedin rabbits according to OECD (No. 405, 24th February 1987) and EC (92/69/EEC, B.5, 31 st July1992) guidelines (Manciaux, 1999). The study was conducted in compliance with the principles of Good Laboratory Practice Regulations. As possible irritant effects were anticipated, a first assay was conducted in one male New Zealand White rabbit. Since the test substance showed severe irritant properties in this first assay, the study was considered complete and the test substance was not evaluated in other animals. A single dose of 0.1 ml of the undiluted test substance was instilled into the left conjunctival sac. The right eye served as control. The eyes were not rinsed after administration of the test substance. Ocular reactions were observed approximately 1 hour, 24, 48 and 72 hours after the administration. The mean values of the scores for chemosis and corneal opacity were calculated. Slight or moderate conjunctival reactions (slight or moderate chemosis, whitish coloration of the conjunctivae and clear to whitish purulent discharge) were observed between day 1 and day 4. A moderate corneal opacity was recorded between day 1 and day 4; the scoring of iritis was masked by this important corneal opacity. In the view of these ocular reactions, the animal was killed on day 4 for ethical reasons. Mean scores calculated over 24, 48 and 72 hours were 3.0 for chemosis and 3.0 for corneal opacity. Other scores were not calculable. THIOACETIC ACID is severely irritant when administered by ocular route to rabbits.

 

Justification for selection of skin irritation / corrosion endpoint:
Key study

Effects on skin irritation/corrosion: slightly irritating

Effects on eye irritation: highly irritating

Justification for classification or non-classification

Skin irritation:

Mean scores over 24, 48 and 72 hours for each animal were 2.0, 1.7 and 1.7 for erythema and 2.0, 0 and 0 for oedema

in a key study. On this basis and in accordance with Regulation (EC) No 1272/2008 and Annex VI of Commission Directive 2001/59/EC, thioacetic acid was slightly irritant but does not merit classification as a skin irritant.

Eye irritation:

Mean scores calculated over 24, 48 and 72 hours were 3.0 for chemosis and 3.0 for corneal opacity. Other scores were not calculable

. On this basis and in accordance with Regulation (EC) No 1272/2008, thioacetic acid was classified as irritating to eyes 1 (Hazard statement H318: Causes serious eye damage) 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 ‘R41 Risk of serious damage to eyes’.