Chromium iron oxide

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-11-10 to 2010-02-10

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study with limitations which do not impair the overall conclusion from the data

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Objective of study:

other: Bioaccessibility

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Solubility of test item in simulated human fluids. Principle of test is similar to Transformation/Dissolution testing according to OECD Series 29 (2001)

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2009-06-19

Test material

Test material information

Constituent 1

Reference substance name:

Chromium iron oxide

EC Number:

235-790-8

EC Name:

Chromium iron oxide

Cas Number:

12737-27-8

Molecular formula:

(Fe, Cr)2O3

IUPAC Name:

chromium(3+) iron(3+) trioxidandiide

Test material form:

solid: particulate/powder

Details on test material:

- Name of test material (as cited in study report): Chromium iron oxide
- Substance type: Inorganic pigment
- Physical state: Black powder, Hematite- corundum
- Storage condition of test material: Keep the container always tightly closed and in an adequately ventilated storage.

Test animals

Species:

other: in vitro (simulated human body fluids)

Details on test animals or test system and environmental conditions:

The test media
Five artificial physiological media (phosphate-buffered saline (pH 7.2), Gamble’s solution (pH 7.4), artificial lysosomal fluid (pH 4.5), artificial gastric fluid (pH 1.5) and artificial sweat solution (pH 6.5)), 5 L each one, were were used.
The pH value of each artificial physiological media was measured using a pH meter, previously calibrated with the pH standard solutions.
The saturation in air of each artificial physiological media was measured using a dissolved oxygen meter and corrected for 30 minutes under air flow in order to obtain a value above 70% as dissolved oxygen concentration.

Administration / exposure

Route of administration:

other: in vitro (simulated human body fluids)

Details on study design:

The dissolved amount of the test item was quantified by the mass concentration of the metals (chromium and iron) in five artificial physiological media (phosphate-buffered saline (pH 7.2), Gamble’s solution (pH 7.4), artificial lysosomal fluid (pH 4.5), artificial gastric fluid (pH 1.5) and artificial sweat solution (pH 6.5)) selected by the Sponsor to simulate relevant human-chemical interactions.
Triplicate samples were prepared for exposure in different test media, each for two different time periods. In addition, one blank sample (without addition of any test item) containing only the test solution was incubated together with triplicate samples for each time period.

Details on dosing and sampling:

Description of the extraction method

Three solutions, 300 mL each one from each test media, were transferred into the 2L plastic containers. The solutions were agitated at 100r.p.m in the mechanical shaker at room temperature for 30minutes. The pH, the temperature and the dissolved oxygen were measured.
In order to measure the blank value two 50 mL blank aliquots were taken from each container, filtered using 0.45µm syringe filters and acidified with 100µL of pure nitric acid before the ICP-MS analysis. These blank samples were stored at 4°C into the refrigerator, until the date of the analysis.

Three 25mg aliquots of the test article were weighted and added to each container solution, labelled A, B and C, preparing a test article solutions with each test media at a solid to liquid ratio of 0.1g/L (example: 25mg in 250mL in order to have a representative weight, using the analytical balance).

Test Media Test vessel Weight [mg]
Phosphate buffered saline (PBS) A 25.4
B 25.1
C 25.0
Artificial sweat solution A 24.9
B 25.4
C 25.6
Artificial interstitial fluid A 25.1
B 25.8
C 25.0
Artificial lysosomal fluid A 25.8
B 25.3
C 25.1
Artificial gastric fluid A 25.1
B 25.9
C 25.3

The solutions were agitated at 100r.p.m in the mechanical shaker at room temperature and at the two sampling times indicated by the Sponsor (2 hours and 24 hours) the pH, the temperature and the dissolved oxygen were measured.

Two 50 mL aliquots from each solution were taken at each sampling time, filtered using 0.45 µm syringe filters, and acidified with 100 µL of pure nitric acid before the ICP-MS analysis. These aliquots were stored at 4°C into the refrigerator, until the date of the analysis.

The dissolved iron and chromium metal ions concentration was measured using the ICP-MS technique.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Toxicokinetic parameters

Toxicokinetic parameters:

other: bioaccessibility

Remarks:

Dissolution of Cr in artifical gastric fluid (pH1.5): 1.2µg/L after 24. Dissolution of Fe 17.5 µg/L (pH1.5) after 24 hours.

Any other information on results incl. tables

^52Cr(µg/L)		Artificial gastric fluid (pH 1.5)	Artificial lysosomal fluid (pH 4.5)	Artificial sweat solution (pH 6.5)	Phosphate buffered saline (PBS) (pH 7.2)	Artificial interstitial fluid (pH 7.4)
Blank	Mean	n.d.	2.7	n.d.	n.d.	n.d.
	S.D.	-	0.1	-	-	-
	CV (%)	-	5.1%	-	-	-
T2h	Mean	<1	n.d.	<1	<1	n.d.
	S.D.	-	-	-	-	-
	CV (%)	-	-	-	-	-
T24h	Mean	1.2	<1	<1	<1	n.d.
	S.D.	0.04	-	-	-	-
	CV (%)	3.4%	-	-	-	-

^56Fe(µg/L)		Artificial gastric fluid (pH 1.5)	Artificial lysosomal fluid (pH 4.5)	Artificial sweat solution (pH 6.5)	Phosphate buffered saline (PBS) (pH 7.2)	Artificial interstitial fluid (pH 7.4)
Blank	Mean	<1	18.4	n.d.	2.0	2.7
	S.D.	-	0.8	-	0.1	0.1
	CV (%)	-	4.3%	-	5.7%	4.0%
T2h	Mean	7.5	1.4	1.5	<1	<1
	S.D.	0.4	0.1	0.3	-	-
	CV (%)	4.8%	5.1%	17.7%	-	-
T24h	Mean	17.5	7.9	<1	<1	n.d.
	S.D.	0.4	0.4	-	-	-
	CV (%)	2.2%	4.5%	-	-	-

n.d.: lower than the method Limit of Detection (L.O.D.) (0.5µg/L for Cr and Fe)

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): other: biologically inert
The dissolution of chromium of the test item Chromium iron oxide is in most cases <1µg/L or below the L.O.D at a loading of 0.1g/L after 2 and 24 hours. Only in artifical gastric fluid (pH1.5) a low concentration of Cr (1.2µg/L) after 24 hours is dissolved.
The dissolution of iron of the test item Chromium iron oxide is in a range of below the L.O.D. (pH 7.4) and 17.5 µg/L (pH1.5) at a loading of 0.1g/L after 2 and 24 hours. A pH dependent dissolution can be observed.
As dissolved Cr and Fe concentrations were below 18 µg/L even at the highest loading of 0.1g/L, referring to a solubility of < 0.018 %, the pigment is considered biologically inert.