Cobalt chromite blue green spinel

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

In conclusion, since the dissolved Co, Al and Cr concentrations from this pigment (cobalt chromite blue green spinel) under simulated physiological conditions were below 9.89 µg/L, 23.5 µg/L and 1.11 µg/L respectively, even at the highest loading of 0.1g/L, referring to a solubility of 0.01 %, 0.024 and 0.001 %, the pigment is considered biologically inert.

Additional information

The chemical and physiological properties of the pigment cobalt chromite blue green spinel are characterised by inertness because of the specific synthetic process (calcination at high temperatures, approximately1000°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 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, pH7.4) which mimics the interstitial fluid within the deep lung under normal health conditions,

2.) phosphate-buffered saline (PBS, pH7.2), 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, pH4.5), which simulates intracellular conditions in lung cells occurring in conjunction with phagocytosis and represents relatively harsh conditions and

5.) artificial gastric fluid (GST, pH1.5), which mimics the very harsh digestion milieu of high acidity in the stomach.

 

 

The dissolution of Co of the test item is between 0.39 µg/L /0.37 µg/L (GMB) and 6.45 µg/L/ 9.89 µg/L (ALF) at a loading of 0.1g/L after 2 and 24 hours.

                                             

The dissolution of Al of the test item is between <LoD (ASW) and 5.43 µg/L/ 23.5 µg/L (ALF) at a loading of 0.1g/L after 2 and 24 hours.

 

The dissolution of Cr of the test item is between 0.03 µg/L /0.18 µg/L (PBS) and 1.11 µg/L/ 0.99 µg/L (ALF) at a loading of 0.1g/L after 2 and 24 hours.

 

A pHdependent dissolution can be observed.In conclusion, since the dissolvedCo, Al and Cr concentrations were below 23.5 µg/L respectively, even at the highest loading of 0.1g/L, referring to a solubility of 0.024 %, this pigment may reasonably be considered biologically inert.

Justification for classification or non-classification

The chemical and physiological properties of the pigment cobalt chromite blue green spinel 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. Bioavailability which is the basis for the oral, dermal or inhalation exposure route is not given. In consequence, this substance may reasonably be considered inert in all media relevant for uptake into the body and also the compartment relevant for distribute within body tissues. Hence, no genetic toxicity effects are expected and no further testing is considered to be required. No classification for genetic toxicity according to EC Regulation No. 1272/2008 is anticipated.