Disodium 7-amino-4-hydroxy-3-[[4-[(4-sulphonatophenyl)azo]phenyl]azo]naphthalene-2-sulphonate

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

A reproductive/developmental screening study (OECD 422, GLP compliant) was conducted in rats to investigate the potential adverse effect on reproduction of one analogue substance at doses 0, 30, 150 and 750 mg/ kg bw/day (by gavage). The study covered observation on reproductive performance, including mating, fertility, gestation, parturition data and litter responses. Under the conditions of this study, no test substance-related effects were observed on reproductive performance at any dosage level. Based on these results, 750 mg/kg bw/day was considered to be the NOAEL for reproductive toxicity.

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The target substance CAS 6300-50-1; EC 228-589-1; disodium 7-amino-4-hydroxy-3-[[4-[(4-sulphonatophenyl)azo]phenyl]azo]naphthalene-2-sulphonate is defined as a mono-constituent substance.
 
The available toxicological data on this substance are insufficient to fulfil the data requirements for a REACH Annex VIII dossier.
In order to prevent unnecessary animal testing the occurring data gaps on toxicity studies might be filled by applying read-across from the similar substance with CAS 1325-54-8, a substance of two constituents:
Tetrasodium 5-[[4-[(4-sulfonatophenyl)diazenyl]phenyl]diazenyl]-2-[2-[2-sulfonato-4-[[4-[(4-sulfonatophenyl)diazenyl]phenyl]diazenyl]phenyl]ethenyl]benzenesulfonate (53%) and
Hexasodium 2-((E)-2-sulfonato-4-((E)-(3-sulfonato-4-((E)-2-sulfonato-4-((E)-(4-((E)-(4- sulfonatophenyl)diazenyl)phenyl)diazenyl)styryl)phenyl)diazenyl)styryl)-5-((E)-(4-((E)-(4- sulfona-tophenyl)diazenyl)phenyl)diazenyl)benzenesulfonate (24%)
The read-across is based on the hypothesis that source and target substances have similar toxicological properties because both molecules have the following similarities:
 
a) Structural similarity: sulphonated molecules, aromatic rings, azo bonds.
Both dyes have polyaromatic structures polysulphonated, linked with azo bonds.

b) Both have ionic functional groups (sulphonic, amino, phenol).
The substances in a solid state are sodium salts and in water solution at neutral pH are polyanions solvated with water.
 
c) Both have affinity to the same type of substrates/molecules.
The substances are able to be adsorbed on the same type of substance, e.g. polysaccharides (cellulose), polyphenols (lignine) and proteins.
 
d) Their degradation products belong to the same family (sulphonamines, diamines), of similar size and similar physicochemical properties.
Based on the similarity analysis part of the project “Study of potential toxicity of dyes by read-across approach and QSAR modelling” developed by the Milano Chemometrics and QSAR Research Group, Dept. Earth and Environmental Sciences, University Milano-Bicocca in Italy, both substances are considered analogues on potential main metabolites.
The result of this similarity analysis is that the source and the target substances have two (2) common potential metabolites and each of them a distinct one.
 
 
In summary, it is considered that both substances have the same mode of action with regard to the following endpoints:
 
- repeated dose toxicity and reproductive/developmental toxicity (screening)
- mutagenicity


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

Read across is possible provided that there is no impact of impurities on the toxicological properties of the target and source chemicals. For both, impurities are comparable.

The composition and impurities of the target and source substances are shown in table 1 of the attached document to this record.

3. ANALOGUE APPROACH JUSTIFICATION
Both molecules, source and target are polysulphonates and consequently are polyanions. They are also polyaromatic substances and contain azo bonds. These are important traits of the molecule that determine its physicochemical properties, like solubility and partition coefficient n-octanol/water.
Such properties also play a critical role in determining the environmental fate of substances (including their potential for long-range transport), as well as their toxicity to humans and other life organisms.
Several physical and chemical properties--namely, melting point, water solubility, size, log Kow, Vapour pressure, Henry’s Law constant and acid dissociation constant (pKa)--are important in terms of ecological and human health assessment.
No experimental data on absorption, distribution and excretion is available for the target substances, but a few pieces of information are available for the target substance and the hydrolysis products. Sulphonates display low toxicity in general, but presence of other functional groups may increase its toxicity. Mathematical models were applied to the structures in order to study its toxicokinetics based on physicochemical properties. The bioavailability of both substances has been estimated with Advanced Chemistry Development, Inc. (ACD/Labs). The probability that target compound has % absorption (Oral) > 30% is 0.033; % absorption(Oral) > 70% is 0.008, and the probability that source compound has % absorption (Oral) > 30% is 0.033; % absorption(Oral) > 70% is 0.011(5). Therefore, it has to be expected a similar behaviour in life organisms and environment for both substances. On another hand, being both polyanions, their capability of crossing the life organisms’ membranes will be very limited.
Results from a combined repeated dose toxicity with the reproduction/developmental toxicity screening test (OECD 422) is available for the source substance. Effects at 300 mg/kg bw/day were considered not to represent an adverse effect. Therefore, a ‘No Observed Adverse Effect Level’ (NOAEL) for systemic toxicity was considered to be 300 mg/kg bw/day (target organ: urogenital system, kidney). The predicted health effects using ACD/Labs(6) of the source substances confirms that the target organs will be the kidneys. One could expect that the target substance would behave similarly, with a NOAEL value in the same range. In the same test there were no treatment-related effects detected on the reproductive parameters investigated, therefore the ‘No Observed Effect Level’ (NOEL) for reproductive toxicity was considered to be 750 mg/kg bw/day. In another light, the prediction of the endocrine disrupting properties of both substances was calculated with ACD/Labs(7). The results were as “no binding to Estrogen Receptor alpha (LogRBA<-3)”, and the probability of Estrogen Receptor Binding is LogRBA > -3: 0.01 and LogRBA > 0: 0 for source substance and the probability of Estrogen Receptor Binding is LogRBA > -3: 0.02 and LogRBA > 0: 0 for target substance. Again, one could expect that the target substance would behave similarly, with a NOEL value in the same range.
Other experimental data obtained with the source and target substances indicate that both substances have low oral and dermal acute toxicity (LD50>2000 mg/kg bw). The substances are not irritating to skin and eye, are not sensitising, and are negative in many genotoxicity tests.
The degradation products of both molecules are the same ones or quite similar. p-Phenylendiamine and 4-aminobenzene sulphonic acid are common predicted reductive cleavage products. Each target and source have a distinct degradation product: a substituted naphthalene sulphonate for the target substance and a stilbene disulphonated for the source substance. All these structures are of similar size and similar physicochemical properties.
Generally, the aromatic amines are moderately to highly soluble (6.4–238000 mg/L) in water due to the presence of one or multiple solubilizing functional groups, such as the amino functional group. Most of the aromatic amines are weak bases (pKa values of less than 5.5) that will be protonated at low pH but will be found in their neutral form under environmentally relevant pH (7–9). Given their hydrophilicity and ionic character tend to have low to very low experimental log K and distribution coefficient (log D) values. In our case some of the degradation products have simultaneously the occurrence in the whole structure of amine and sulfonate, which usually favours a diminution of the toxicity in almost all the target organs or aquatic organisms.
Generally stated, genotoxicity is associated with all aromatic amines with benzidine moieties, as well as with some aromatic amines with toluene, aniline and naphthalene moieties. The toxicity of aromatic amines depends strongly on the spatial structure of the molecule or –in other words– the location of the amino-group(s). For instance, whereas there is strong evidence that 2-naphthylamine is a carcinogen, 1-naphthylamine is much less toxic. The toxicity of aromatic amines depends furthermore on the nature and location of other substituents. As an example, the substitution with nitro, methyl or methoxy groups or halogen atoms may increase the toxicity, whereas substitution with carboxyl or sulphonate groups generally lowers the toxicity. As most soluble commercial azo dyestuffs contain one or more sulphonate groups, insight in the potential danger of sulphonated aromatic amines is particularly important. In an extensive review of literature data on genotoxicity and carcinogenicity of sulphonated aromatic amines, it was concluded that sulphonated aromatic amines, in contrast to some of their unsulphonated analogues, have generally no or very low genotoxic and tumorigenic potential(3).
Neither the substances nor the amines that may release by reductive cleavage from both of them, are included in the lists of “Azodyes which can be split into carcinogenic amines pursuant to TRGS 614 (March 2001 edition)” Association TEGEWA e.V. (Germany) (9)(10) or in the “Report on Carcinogens, 14th edition” from the EPA - NTP (National Toxicology Program). 2016.(11) or in the Candidate List of substances of very high concern for Authorisation, published in accordance with Article 59(10) of the REACH Regulation. (12)


4. DATA MATRIX
Two data matrix are included in the attached document to this record: Matrix 1 (Toxicity data on the source and target substance) and Matrix 2 (Main potential metabolites data)

Reason / purpose for cross-reference:

read-across source

Key result

Dose descriptor:

NOEL

Effect level:

750 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reproductive performance

Dose descriptor:

NOEL

Generation:

F1

Effect level:

750 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: offspring development

Key result

Reproductive effects observed:

no

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

750 mg/kg bw/day

Study duration:

subacute

Species:

rat

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Effects on developmental toxicity

Description of key information

A reproductive/developmental screening study (OECD 422, GLP compliant) was conducted in rats to investigate the potential adverse effect on reproduction of one analogue substance at doses 0, 30, 150 and 750 mg/ kg bw/day (by gavage). The study covered observation on reproductive performance, including mating, fertility, gestation, parturition data and litter responses. Under the conditions of this study, no test substance-related effects were observed on reproductive performance at any dosage level. Based on these results, 750 mg/kg bw/day was considered to be the NOAEL for reproductive toxicity.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

750 mg/kg bw/day

Study duration:

subacute

Species:

rat

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Justification for classification or non-classification

A reproductive/developmental screening study (OECD 422, GLP compliant) was conducted in rats to investigate the potential adverse effect on reproduction of one analogue substance. No adverse effects on reproductive/ developmental parameters were noted at doses up to 750 mg/kg bw/day in parental animals. Also, there were no effects on the general physical condition of the offsprings at any dose.

The substance therefore does not qualify for classification for these endpoints according to CLP (Regulation 1272/2008/EC).