Barium 3-hydroxy-4-[(4-methyl-2-sulphonatophenyl)azo]-2-naphthoate

Endpoint summary

Description of key information

Three valid and reliable studies were performed with commercial products of analogue substances. Pigment Red 57:1 (CAS 5281-04-9) did not cause skin sensitization in the Buehler test in guinea pigs (ETAD1995) and in the local lymph node assay in mice (Clariant 2008).

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The substances displayed below are considered read-across analogues based on similar physico-chemical and toxicological properties of the pigments. The substance of this chemical sub-class (monohydrazone pigments, BONA pigment lakes) include an organic part, bearing an aminosulfonic acid coupled onto hydroxy-naphthoic acid, and an inorganic cation represented by an alkaline earth metal such as manganese, strontium or calcium. Thus, the read across is also based on structural similarities as a result of equal manufacturing processes. All BONA Metal Laked Pigments are of low solubility in water and octanol. Dissociation of these metal salt pigments, which is enhanced under a highly acidic condition (such as in the stomach), leads, at least partially, to the release of the metal cation and the organic acid. Therefore, the impact of the metal component and the organic acid is discussed separately. In addition, toxicological information on moieties is available, which provides supporting information regarding the effect of substituents on the toxicological profile. Moreover, reductive cleavage of the azo bond, catalysed by (microbial) azo-reductase or other reductive liver enzymes, may result in the release of these moieties which therefore represent (common) metabolites. Hazard assessment of the metals is assessed by inclusion of information on inorganic soluble salts of the metals.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

Colour index name CAS number EINECS number
Pigment Red 57:1(Ca) 5281-04-9 226-109-5
Pigment Red 57(Sr) 73612-29-0 277-552-6
Pigment Red 57:2 (Ba) 17852-98-1 241-806-4
Pigment Red 48:1(Ba) 7585-41-3 231-494-8
Pigment Red 48:2(Ca) 7023-61-2 230-303-5
Pigment Red 48:3(Sr) 15782-05-5 239-879-2
Pigment Red 48:4(Mn) 5280-66-0 226-102-7
Pigment Red 52(Sr) 67828-72-2 267-291-6
Pigment Red 52:2(Mn) 12238-31-2 241-780-4

Tested products contain at least 80% of the colorant. Purities range from 80% to 90%. Typical impurities are low levels of the starting materials 3-hydroxy-2-naphthoic acid (BONA) and the coupling amine, water of crystallization and free water as depicted in Table 3. Due to the lacking process in synthesis, all substances contain a fraction of the corresponding sodium salt. No impurity was considered to cause any concern regarding human toxicology. Impurities were reported to have no classifications according to information provided by ECHA (https://echa.europa.eu/de/information-on-chemicals/cl-inventory-database).


3. ANALOGUE APPROACH JUSTIFICATION
It is referred to the attached pdf file.

4. DATA MATRIX
It is referred to the attached pdf file.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Species:

mouse

Parameter:

SI

Value:

ca. 2

Test group / Remarks:

all groups

Interpretation of results:

GHS criteria not met

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Reliable experimental data is available for the analogue Calcium complex Pigment Red 57:1. This data is acceptable for read-across because soluble Barium salts do not cause skin sensitization (eg BaCl2, as shown in dissiminated data for CAS 10361-37-2). As Barium salts are generally less soluble than calcium salts, Pigment Red 57:1 is considered to be comparatively better skin permeable. Using data for Pigment Red 57:1 therefore does not underestimate a skin-related hazard.

The first study (ETAD 1995) is a test in guinea pigs (Buehler, 1965, described in OECD testing guideline 406, adopted July 17, 1992) and was performed with a sample of adequate pigment content. Due to the staining properties of the pigment, skin reactions could not be examined visually and were investigated by histopathology (acanthosis, inflammatory cell infiltration, spongiosis) instead. The highest concentration of 60% for both challenge and induction was chosen based on the solubility in the vehicle corn oil. A predominantly slight to minimal inflammatory reaction was recorded in about half of the animals of both control and test groups. Therefore, Pigment Red 57:1 was evaluated as non-sensitizing in the Buehler test.

The second study (Clariant 2008) is a local lymph node assay in mice (OECD 429, adopted in April 24, 2002) and the tested sample was of adequate pigment content. Tested concentrations were 2.5, 6 and 10% using DMSO as vehicle and resulting in stimulation indices of 1.68, 2.06 and 2.00, respectively. The highest concentration was justified by the limit of solubility in DMSO. Higher concentrations could be achieved in DMF, but the sample was demonstrated to be unstable in this solvent. Due to the intense red colour of the test item local irritation reactions such as ear redness could not be evaluated. Based on the stimulation indices, the pigment is considered not to be a skin sensitizer in mice.

 

All studies are adequate to assess the endpoint of skin sensitization.

Commercial products of BONA metal laked pigments differ in their content of additives that are added depending on the intended application. The sensitizing properties of such additives need to be assessed separately. The available data show that the colorant itself does not cause skin sensitization in experimental animals.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Classification, Labeling, and Packaging Regulation (EC) No. 1272/2008

The available experimental test data are reliable and suitable for classification purposes under Regulation 1272/2008. As a result the substance is not considered to be classified as a skin sensitizer under Regulation (EC) No. 1272/2008.

 

Experimental data regarding respiratory sensitization is not available. Considering the absence of a skin sensitizing potential, a hazard of respiratory sensitization is not expected.