Teflubenzuron

Endpoint summary

Description of key information

GPMT: not sensitizing

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

The skin senitizing properties of the test substance were evaluated in a guinea pig maximization test according to OECD guideline 406 and GLP.

The animals (10 control and 20 test substance group animals, each groups contained 50% males and females each) were treated by intradermal induction with either 2.5% test substance in polypropylene glycol and physiological saline (1:1) or vehicle only, with and without Freud's adjuvant. Seven days after intradermal induction, the animals were subjected to epicutaneous induction. A 4 x 4 cm patch of filter paper was saturated with test article (25% in polypropylene glycol and physiological saline (1:1)) and placed over the injection sites of the test animal. Control animals were treated with vehicle only. The patch was covered by aluminum foil and occlusive dressing and kept in place for approx. 48 hours.

Two weeks following the topical induction, the animals were challenged on a different skin area. A 2 x 2 cm patch of filter paper was again saturated with either test substance (25% in vehicle) or vehicle only, which was applied under occlusive dressing for 24 hours. Following the first challenge, approx. 30% of the control animals and 25% of the test substance treated animals showed skin reactions at 24 hours after removal of the patch. At 48 hours after removal of the patch, no skin findings were made in the control group, while 1/20 test substance exposed animals still showed skin reactions.

Therefore, a re-challenge was conducted one week after the first challenge. The procedure was the same as for the first challenge. At 24 and 48 hours after removal of the patches, none of the animals (control or test substance treated) showed skin reactions.

Overall, no significant difference was found between the results of the animals of the test article treated and vehicle control group.

 

The skin reactions observed in the first challenge experiment can be explained by the vehicle.

Because of the solubility properties of the test article, polypropylene glycol and saline in a 1:1 mixture were used as the vehicle. Positive results noted in the vehicle control group may be related to an allergenic response to polypropylene glycol, therefore the possibility that the positive results noted in the test group may be related to the vehicle rather than the test article.

The positive results observed in the vehicle control group are well known for this vehicle and are described by Th. Maurer et al.; Predictive evaluation in animals of the contact allergenic potential of medically important substances. II. Comparison of different methods of cutaneous sensitization with “weak” allergens. Contact Dermatitis 1979: 5: 1-10.

Importantly, no skin findings were made at 24 or 48 hours following re-challenge, whereas in the case of a sensitization event, a finding of at least equal severity to the first challenge would have been expected.

 

Therefore, the test substance is considered not sensitizing in the guinea pig maximization test.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the data available and applying the criteria laid down in Regulation (EC) 1272/2008 (CLP), no classification for sensitization is warranted.