Zinc iron chromite brown spinel

Endpoint summary

Description of key information

Short description of key information on bioaccumulation potential result: 
As dissolved Cr, Ni, Zn and Fe concentrations (GST, ALF) were below 5.8 µg/L, 6.03 µg/L, 62 µg/L and 43 µg/L respectively, even at the highest loading of 0.1g/L, referring to a solubility of 0.006%, 0,006%, 0,06 and 0,04 %, the pigment is considered biologically inert.

Additional information

The chemical and physiological properties of the pigment zinc iron chromite brown 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 Cr of the test item is between below LoD (0.05 µg/L) /0.31 µg/L (PBS) and 2.11 µg/L/ 5.81 µg/L (ALF) at a loading of 0.1g/L after 2 and 24 hours.

The dissolution of Ni of the test item is in a range of below LoD (0.19 µg/L)/ below LoQ (0.56 µg/L, GMB) and 2.42 µg/L 6.03 µg/L (ALF) at a loading of 0.1g/L after 2 and 24 hours.

The dissolution of Zn of the test item is in a range of below LoD (1.02 µg/L, GMB) and 51.1 µg/L/ 61.8 µg/L (GST) at a loading of 0.1g/L after 2 and 24 hours.

The dissolution of Fe of the test item is in a range of below LoQ (9.43 µg/L)/ 11.8 µg/L (GMB) and 15.8 µg/L/ 42.7 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 dissolvedCr, Ni, Zn and Fe concentrations were below 62 µg/L even at the highest loading of 0.1g/L, referring to a solubility of 0.062 %, this pigment may reasonably be considered biologically inert.

 

Discussion on bioaccumulation potential result:

The chemical and physiological properties of the pigment zinc iron chromite brown spinel are dominated by inertness due to the characteristics of the production process (calcination at high temperatures, approximately1000°C), rendering the substance to be of a unique, stable crystalline structure. This fundamental process leads to a very low bioaccessibility for the elements contained in the pigment. By simulating the typical physiological conditions of the presumed exposure routes (oral, dermal and inhalation) with

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, pH6.5) 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.

An oral, dermal or inhalative uptake of the substance for humans exposed to the pigment is negligible.

The dissolution of Cr of the test item is between below LoD (0.05 µg/L) /0.31 µg/L (PBS) and 2.11 µg/L/ 5.81 µg/L (ALF) at a loading of 0.1g/L after 2 and 24 hours.

The dissolution of Ni of the test item is in a range of below LoD (0.19 µg/L)/ below LoQ (0.56 µg/L, GMB) and 2.42 µg/L 6.03 µg/L (ALF) at a loading of 0.1g/L after 2 and 24 hours.

The dissolution of Zn of the test item is in a range of below LoD (1.02 µg/L, GMB) and 51.1 µg/L/ 61.8 µg/L (GST) at a loading of 0.1g/L after 2 and 24 hours.

The dissolution of Fe of the test item is in a range of below LoQ (9.43 µg/L)/ 11.8 µg/L (GMB) and 15.8 µg/L/ 42.7 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 dissolvedCr, Ni, Zn and Fe concentrations were below 62 µg/L even at the highest loading of 0.1g/L, referring to a solubility of 0.062 %, this pigment may reasonably be considered biologically inert.