Cobalt zinc silicate blue phenacite

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

The chemical and physiological properties of pigments in general are characterised by inertness because of the specific synthetic process (calcination at high temperatures, approximately 1000°C), rendering the substance to be of a unique, stable crystalline structure in which all atoms are tightly bound and not prone to dissolution in environmental and physiological media. This manufacturing process leads to a very low bioaccessibility of the elements contained in the pigment. This has been investigated for this pigment experimentally in vitro by simulating dissolution under physiological conditions considered to mimic the most relevant exposure routes (oral, dermal and inhalation), as follows:

 

1.) Gamble’s solution (GMB, pH 7.4) which mimics the interstitial fluid within the deep lung under normal health conditions,

2.) phosphate-buffered saline (PBS, pH 7.2), which is a standard physiological solution that mimics the ionic strength of human blood serum,

3.) artificial sweat (ASW, pH 6.5) which simulates the hypoosmolar fluid, linked to hyponatraemia (loss of Na+ from blood), which is excreted from the body upon sweating,

4.) artificial lysosomal fluid (ALF, pH 4.5), which simulates intracellular conditions in lung cells occurring in conjunction with phagocytosis and represents relatively harsh conditions and

5.) artificial gastric fluid (GST, pH 1.5), which mimics the very harsh digestion milieu of high acidity in the stomach.

 

The dissolution of cobalt from the test item Cobalt zinc silicate blue phenacite at a loading of 0.1g/L after 2 hours was between 29.9µg/L (GMB) and 17.39 mg/L (GST) and between 34.6 µg/L (GMB) and 25.1 mg/L (ALF) after 24 hours. Further, the dissolution of zinc from the test item Cobalt zinc silicate blue phenacite was in a range of 21.7 µg/L (GMB) and 24.5 mg/L (GST) at a loading of 0.1g/L after 2 hours and between below LOD (GMB) and 34.8 mg/L (ALF) after 24 hours.

 

In conclusion, the dissolved Co concentrations from this pigment under simulated physiological conditions were below 17.4 mg/L even at the highest loading of 0.1g/L after 2 hours, corresponding to a solubility of less than 18 %. Dissolved Zn concentrations were below 25 mg/L after 2 hours, corresponding to a solubility of less than 25 %.

Justification for classification or non-classification

The chemical and physiological properties of the pigment Cobalt zinc silicate blue phenacite indicate a low bioaccessibility of the element Co from the crystalline structure. Thus, the bioavailability via oral, dermal or inhalation exposure routes can be considered as significantly reduced in all media relevant for uptake into the body and also the compartment relevant for distribute within body tissues.

No classification for genetictoxicity according to Directive 67/548/EEC and EC Regulation No. 1272/2008 is anticipated.