2-[[4-[ethyl(2-hydroxyethyl)amino]phenyl]azo]-6-methoxy-3-methylbenzothiazolium methyl sulphate

Endpoint summary

Description of key information

The potential of the source substance (90% purity) to cause skin sensitisation reactions was assessed in a dermal sensitization study using the modified Buehler test (OECD 406). Based on the results obtained from this test, the source substance can be considered to be a non-sensitizer.

Furthermore, the substance was assessed in two Human Repeated Insult Patch Tests (Shelanski, 1971 and Shelanski, 1973, see IUCLID section 7.10.4) with 200 volunteers each. Both studies had negative outcome showing no visible skin changes in any subjects, except one volunteer having a severe reaction (Shelanski, 1973).

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

50 % in bi-distilled water

No. with + reactions:

2

Total no. in group:

20

Clinical observations:

2 animals with slight confluent erythema

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

50 % in bi-distilled water

No. with + reactions:

2

Total no. in group:

20

Clinical observations:

2 animals with slight patchy erythema

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no effects

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no effects

Remarks on result:

no indication of skin sensitisation

Group:

positive control

Remarks on result:

not measured/tested

Table 1: Results of the induction screening

Irritancy results
	24 hours reading Concentrations (%) of the test substance				24 hours reading Concentrations (%) of the test substance
Response grade (erythema)	50	25	15	10	50	25	15	10
0	4*	4	4	4	4	4	4	4
±	0	0	0	0	0	0	0	0
1	0	0	0	0	0	0	0	0
2	0	0	0	0	0	0	0	0
3	0	0	0	0	0	0	0	0

 * = number of animals showing response

Grade 0 and ± are considered to be representative of insignificant response, whereas those of one or greater are considered to be significant. The results of the 24- and 48 hours reading were taken into consideration and in this case the test article at 50, 25, 15, and 10 % resulted in 4 scores of 0. Therefore the most representative concentration to stimulate a state of immune hypersensitivity is 50% in bi-distilled water.

Table 2 : Results of the challenge screening

	24 hours reading Concentrations (%) of the test substance				24 hours reading Concentrations (%) of the test substance
Response grade (erythema)	50	25	15	10	50	25	15	10
0	0*	0	0	0	0	0	0	0
±	0	0	0	0	0	0	0	0
1	0	0	0	0	0	0	0	0
2	0	0	0	0	0	0	0	0
3	0	0	0	0	0	0	0	0

 * = number of animals showing response

The highest non-irritating concentration is determined as the concentration which induces responses in the four guinea pigs no more severe than two grades of +/-and two of 0. In this case, all concentrations resulted in 4 scores of 0. Therefore, the highest non-irritating concentration for the challenge was determined as the concentration of 50% in bi-distilled water

 

Table 3: Primary Sensitization Results (Incidence Tables)

Erythema score	Test group 20 animals		Control group 10 animals
	24 hrs	48 hrs	24 hrs	48 hrs
0	18	18	10	10
±	0	2	0	0
1	2	0	0	0
2	0	0	0	0
3	0	0	0	0
No. with grades ≥ 1	2	0	0	0
No. Tested	20	20	20	20
Total**	2		0

** The Total is the number of animals showing a grade ≥ 1 at either 24 or 48 hours.

10% of the animals of the test group were observed with positive reactions (grade 0 and ± are considered to be non-significant responses, whereas those of 1 and greater are considered to be significant) after challenge performed with the highest non-irritating concentration of the test item at 50% in bi-distilled water. No reactions were observed in the control group treated in the same conditions during the challenge phase. Significant responses in at least 15 % of the test group is considered positive and would be warrant for classification. Therefore the test item tested as described, is considered to be a non-sensitizer.

Mortality:

As there were no deaths during the course of the treatment period no necropsies were performed.

Clinical Signs:

Neither local nor systemic symptoms were observed during the study.

Skin Effect in the Challenge:

Two animals of the test group were observed with defined erythema at the 24-hours reading when treated with the highest non-irritating test article concentration of 50% in bi-distilled water. The same reaction was seen at the 48-hour reading with less severity.

Body weight:

One out of 10 animals of the control group, four out of 20 animals of the test group and 3 out of 4 animals of the irritation screen for challenge lost weight during their acclimatization period. Three out of 4 animals of the irritation screen for induction lost weight during their treatment period. No loss of weight was observed during the treatment phase of the control -, test - and irritation screen for challenge group.

Interpretation of results:

GHS criteria not met

Conclusions:

In conclusion, based on the results obtained from a dermal skin sensitisation test, the test item can be considered to be a non-sensitizer.

Executive summary:

In a dermal sensitization study with the test substance (90% purity) in bi-distilled water (50% w/w), young, male Himalayan guinea pigs (20 animals/test group & 10 animals/control) were tested using the modified Buehler test (OECD 406). Twenty male guinea pigs were treated topically with the test article 50% in bi-distilled water once a week for a three week induction phase. Two weeks after the final induction the animals were challenged with the same test substance used for induction at 50% in bi-distilled water. The animals of the control group were not treated during induction, but were treated once at challenge.  Only two animals of the test group showed a slight confluent erythema at the first (24 h) and a slight, patchy erythema at the second reading (48 h). These findings were considered to be not significant. Therefore, based on the results obtained, the test item can be considered to be a non-sensitizer.

This information is used in a read-across approach in the assessment of the target substance.

For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

No data is available for the target substance. Thus, available data from a structural analogue (chloride salt) of the target substance was used in a read-across approach. Details on the read-across rational are provided in section 13.

In a dermal sensitization study with the source substance (90% purity) in bi-distilled water (50% w/w), young, male Himalayan guinea pigs (20 animals/test group & 10 animals/control) were tested using the modified Buehler test (OECD 406). Twenty male guinea pigs were treated topically with the test article 50% in bi-distilled water once a week for a three week induction phase. Two weeks after the final induction the animals were challenged with the same test substance used for induction at 50% in bi-distilled water. The animals of the control group were not treated during induction, but were treated once at challenge.  Only two animals of the test group showed a slight confluent erythema at the first (24 h) and a slight, patchy erythema at the second reading (48 h). These findings were considered to be not significant. Therefore, based on the results obtained, the source substance can be considered to be a non-sensitizer.

Furthermore, the the source substance was assessed in two Human Repeated Insult Patch Tests (Shelanski, 1971 and Shelanski, 1973, see IUCLID section 7.10.4) with 200 volunteers each. Both studies had negative outcome showing no visible skin changes in any subjects, except one volunteer having a severe reaction (Shelanski, 1973).

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

In a dermal sensitization study conducted according to OECD 406, male guinea pigs were tested negative for the source substance. Based on the results from the read-across partner, classification of the target substance is not warranted.