Cobalt chromite blue green spinel

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Data waiving:

other justification

Justification for data waiving:

other:

Justification for type of information:

A 90-day inhalation toxicity study is ongoing with the analogue substance cobalt zinc aluminate blue spinel. An analogue read-across to the substance cobalt zinc aluminate blue spinel has been proposed.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
According to the ECHA Guidance Read-Across Assessment Framework (RAAF, March 2017), the read-across hypothesis for systemic effects is based on the assumption that different compounds give rise to the same common moieties (“(Bio)transformation to common compound(s)”) to which the organisms are exposed.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The target substance Cobalt chromite blue green spinel is a complex inorganic colored pigment (CICP) and and for the time being considered to be a mono-constituent substance under REACH. Following the sector specific guidance for complex inorganic colored pigments (Eurocolour, 2017) Cobalt chromite blue green spinel will be considered as an UVCB and will be renamed to cobalt chromium aluminium zinc spinel. Cobalt and chromium expressed as the respective oxides are the main contributing elements. It is noted, that during the manufacture of CICPs chemical bonds of the raw materials are broken, and atoms are homogeneously and ionically interdiffused to form a specific crystalline matrix. Therefore, metals and oxygen atoms occupy specific places within the crystalline lattice, and individual oxides do not exist.
A detailed characterisation of the target substance is given in the attached justification document, Table 1..
The source substance Cobalt zinc aluminate blue spinel is also a complex inorganic colored pigment (CICP) and for the time being considered to be a mono-constituent substance under REACH. Following the sector specific guidance for complex inorganic colored pigments (Eurocolour, 2017) Cobalt zinc aluminate blue spinel will be considered as an UVCB and will be renamed to Cobalt zinc aluminate spinel. It consists of almost the same contributing elements (Cobalt, zinc and aluminium expressed, as oxides are the main constituent). It is noted, that during the manufacture of CICPs chemical bonds of the raw materials are broken, and atoms are homogeneously and ionically interdiffused to form a specific crystalline matrix. Therefore, metals and oxygen atoms occupy specific places within the crystalline lattice, and individual oxides do not exist.
A detailed characterisation of the sourcesubstance is given in the attached justification document, Table 2.
The common characteristic of the target substance and the source substance is that both substances crystallise in the spinel structure, which forms a strong and inert crystal lattice. Both substances consist of almost the same chemical constituents. Furthermore, both show a similar, very low solubility in different artificial and aqueous media which is used for (eco)toxicological predictions.

3. ANALOGUE APPROACH JUSTIFICATION
Upon uptake of the target substance, the toxicological units will be liberated in the ionic form similar to the source substance, which also liberates the toxicological units, cobalt, aluminium and zinc, respectively. Upon solvation in body-fluids such as gastric juice, the toxic units become indistinguishable. The sole relevant modifier of systemic toxicity is the “solubility” of the cations in the respective body-fluid. The target substance also releases trivalent chromium ions which are not known to show signs of systemic toxicity (EFSA, 2014).
The target as well as the source substance show a very low solubility in different artificial and aqueous media demonstrating the inertness of the substances. The source substance shows slightly higher bioaccessibility without showing any signs of systemic or local toxicity in various studies (acute inhalation, sub-acute oral toxicity, skin/eye irritation and sensitisation). The target substance shows no systemic or local toxicity in an acute inhalation, skin/eye irritation or sensitisation study.
Particle size information of the substance influences the deposition behaviour in the respiratory tract and potential toxic effects. Based on particle size distribution data, trends in deposition and potency of effects can be assessed for locally acting substances.
When comparing the particle size and the MMAD obtained in the acute inhalation toxicity studies of the two substances one can assume that the deposition behaviour of both pigments is comparable. This is further emphasised by the results of the MPPD model, where about 1.5 % or less of inhaled material is predicted to be deposited in the pulmonary region (PU) for both pigments. Most of the material of both pigments deposited in the tracheobronchial (TB) and the extrathoracic region (Head) and may be assumed to be cleared to the GI tract (i. e., by mucociliary escalation and subsequent swallowing). Furthermore, taking into account that the source substance shows slightly higher bioaccessibility in artificial lung fluids (ALF and GMB) read-across can be considered to be conservative.

4. DATA MATRIX
A data matrix is presented in Appendix 1 of the attached justification document.

A detailed read-across justification is provided in the attached document.

Results and discussion

Target system / organ toxicity

Critical effects observed:

not specified