Vanadium zirconium yellow baddeleyite

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics in vitro / ex vivo

Remarks:

Bioaccessibility - transformation/dissolution in artificial physiological media

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-09-11 to 2012-12-19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Objective of study:

bioaccessibility (or bioavailability)

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

Deviations:

no

Remarks:

Bioaccessibility testing: loading of 100 mg/L; five artificial physiological media agitated at 100 rpm, at 37°C ± 2°C; sampling after 2h and 24h; determination of Zr and V concentrations after filtration by ICP-OES and ICP-MS.

Principles of method if other than guideline:

An internationally agreed guideline does not exist for this test (e.g. OECD). However, similar tests have been conducted with several metal compounds, including steels, in previous risk assessments (completed under Regulation (EEC) No 793/93) and in recent preparation for REACH regulation (EC) No 1907/2006.
The test was performed on the basis of the guidance for OECD-Series on testing and assessment Number 29 and according to the bioaccessibility test protocol provided by the study monitor.

GLP compliance:

yes (incl. QA statement)

Remarks:

signed, 2011-02-07

Species:

other: in vitro (simulated human body fluids)

Details on exposure:

Test principle in brief:
- five different artificial physiological media,
- single loading of test substance of 100 mg/L,
- samples taken after 2 and 24 hours agitation (100 rpm) at 37 ± 2 °C,
- two method blanks per artificial media were tested; measurement (by ICP-OES and ICP-MS) of dissolved vanadium and zirconium concentrations after filtration
- the study was performed in duplicates

The aim of this test was to assess the dissolution of IPC-2013-014 (Vanadium zirconium yellow baddeleyite) in five artificial physiological media: Artificial lysosomal fluid (ALF, pH = 4.5), Artificial sweat solution (ASW, pH = 6.5), Gamble´s solution (GMB, pH = 7.4), Artificial gastric fluid (GST, pH = 1.5), Phosphate buffered saline (PBS, pH = 7.4). The test media were selected to simulate relevant human-chemical interactions (as far as practical), i.e. a substance entering the human body by ingestion into the gastrointestinal tract and by inhalation.

Duration and frequency of treatment / exposure:

Samples were taken after 2 h and 24h.

Dose / conc.:

100 other: g of the test item /L artificial media

Details on study design:

Reagents
The water (resistivity >18 MΩ·cm.) used for this test was purified with a Pure Lab Ultra water purification system from ELGA LabWater, Celle, Germany.
- Nitric acid - “Supra” quality (ROTIPURAN® supplied by Roth, Karlsruhe, Germany).
- Hydrochloric acid – “instra-analyzed plus” quality (J.T. Baker, Griesheim, Germany).

- Standards: Multielement standards: Merck XXI lot no. HC075495, Darmstadt, Germany; Merck Certipur Vanadium lot no. HC241278; Fluka Zirconium standard TraceCERT lot no. BCBD9418, Schnelldorf, Germany.
- Certified reference material: TMDA-70 (lot no. 0310), TM-DWS.2 (lot no. 1010) and TM15.2 (lot no. 1011) obtained from Environment Canada; and multielement standard (CPI, Amsterdam, The Netherlands, lot no. 12A089)
- Zirconium single element standard (CPI Zr standard, Amsterdam, The Netherlands, lot no. ZR9301)

Instrumental and analytical set-up for the ICP-OES instrument:
Thermo IRIS Intrepid II from Thermo Electron Corporation, Germany
Nebulizer: Concentric glass nebulizer, from Thermo
Spray chamber: Glass cyclonic spray chamber, from Thermo
Nebulizer gas flow: 0.68 L/min
Make-up gas flow: 0.5 L/min
RF power: 1150 W
Wavelengths: V: 290.882 nm, 292.402 nm and 292.464 nm
Calibration: blank, 1, 5, 10, 25, 50, 75, 100, 200, 250, 300 and 400 µg/L
Correlation coefficients (r): att least 0.9998

Two measurements were performed for the determination of vanadium concentrations in mass balance samples and filter samples.
The applied LOD/LOQ calculations for the IRIS Intrepid ICP-OES are:
LOD: 3 * method standard deviation from calibration line;
LOQ: 10 * method standard deviation from calibration line.
These data were read directly from the Thermo IRIS Intrepid II ICP-OES instrument output (data calculated by internal algorithms of the instrument software).

Instrumental and analytical set-up for the ICP-MS instrument:
Agilent 7700 ICP-MS, Agilent Technologies, Waldbronn, Germany
Nebulizer: Concentric glass nebulizer, from GlassExpansion
Spray chamber: Scott Type spray chamber, from Agilent
Carrier gas flow: 0.91 L/min
Dilution/Make-up gas flow: 0.13 L/min
RF power: 1500 W
Isotopes: 51V, 90Zr, 91Zr, 103Rh (internal standard)
calibrations: blank, 0.1, 0.25, 0.5, 0.75, 1.0, 2.5, 5.0, 7.5, 10.0, 25.0, 50.0, 75.0, 100, 250 and 500 µg/L
Correlation factors (r): at least 0.9974

In sum, five series of measurements were performed for the determination of total dissolved vanadium and zirconium concentrations in samples including the test vessels as well as blanks to determine background levels of elements and fortified samples.
The LOD and LOQ for vanadium and zirconium were calculated using the internal instrument algorithm. This calculation is according to DIN 32645. For this the standard deviation of calibration blanks is multiplied by 3 and divided by the slope of the calibration line.

Determination of mass balance
To the residual, undissolved test item in the vessels, 120 mL aqua regia (3:1 mixture of concentrated hydrochloric and nitric acid) were added after the test. Solutions were sampled after 24h, vanadium concentrations were measured by ICP-OES, and the mass balance was calculated. The filters used for sampling were extensively rinsed with aqua regia, and the vanadium concentrations in the filtrate were also determined.

Details on dosing and sampling:

Loading:
The nominal loading in this test was 100 mg/L. However, due to weighing uncertainties the actual loadings range from 100.308 mg/L to 101.706 mg/L in the test vessels.

Type:

other: Bioaccessibility

Results:

Higest dissolution at a loading of 0.1g/L after 24h for Zirconium are in ALF: 38.2 ± 2.29 µg Zr/L and in GST: 13.1 ± 10.6 µg Zr/L; for Vanadium in GST: 212 ± 14.9 µg V/L, in ASW: 146 ± 2.65 µg V/L and in PBS: 145 ± 1.80 µg V/L.

Method validation summary ICP-OES for the mass balance

validation parameter	results	comment
Selectivity	similar data with two different wavelengths for ICP-OES method	No interference observed
Linearity	applied calibration functions were linear	correlation coefficient at least 0.9998
Limit of detection	V: 2.07 - 3.67 µg/L
Limit of quantification	V: 6.90 - 12.2 µg/L
Accuracy mass balance	mean recovery for CRM TMDA-70: V: 101 ± 3.6 % (n = 4)	High concentration range (312 µg V/L)
Accuracy mass balance	mean recovery for CRM TMDWS.2: V: 105 ± 2.1 % (n = 3)	low concentration range (44.5 µg V/L)
Trueness mass balance samples	mean recovery for recalibration standard : V: 102 ± 1.5 % (n = 4)	low concentration range (50 µg/L)
Trueness mass balance samples	mean recovery for recalibration standard : V: 96.6 ± 1.4 % (n = 3)	high concentration range (250 µg/L)
Reproducibility mass balance	mean recovery for CRM TMDA-70: V: 101 ± 3.6 % (n = 4)	High concentration range (312 µg V/L)
Reproducibility mass balance	mean recovery for CRM TMDWS.2: V: 105 ± 2.1 % (n = 3)	low concentration range (44.5 µg V/L)

 

Concentration of V and Zr method blanks in artificial media (ICP-MS measurement series).

Artificial media	Element
	V	Zr
GST	<LOD	Method blanks above LOQ but at least 7.59 fold lower than concentrations in samples
GMB	<LOD	<LOQ
ALF	<LOD	Method blanks above LOQ but at least 96.3 fold lower than concentrations in samples
ASW	<LOD	Method blanks 2h above LOQ, method blanks 24h three below LOQ one above LOQ but at least 10.1 fold lower than concentrations in samples
PBS	<LOD	<LOD

Method validation summary (ICP-MS)

validation parameter	results	Comment
Selectivity ICP-MS	V: similar in Helium and HiHelium mode Zr: similar in Helium and HiHelium mode, similar on different isotopes	appropriate Isotope and gas mode were selected for interference free measurements
Linearity ICP-MS	applied calibration functions were linear	correlation coefficients ≥0.9974
Limit of detection ICP-MS	V: 0.01 – 0.31 µg/L Zr: 0.02 – 0.22 µg/L
Limit of quantification ICP-MS	V: 0.02 – 0.94 µg/L Zr: 0.06 – 0.67 µg/L
Method blanks	Summary see Table above (Concentration of V and Zr method blanks in artificial media(ICP-MS measurement series).)	Elevated concentrations of Zr in method blanks origin from the applied chemicals for preparation of different media
Accuracy V	mean recovery for CRM TMDA-70: V: 107 ± 9.3 % (n = 18)	high concentration range (312 µg V/L)
Accuracy V	mean recovery for CRM TM15.2: V: 102 ± 6.8 % (n = 16)	low concentration range (13.1 µg V/L)
Trueness V	mean recovery for recalibration standard: V: 101 ± 9.7 % (n = 18)	mid concentration range (50 µg/L)
Trueness Zr	mean recovery for recalibration standard: Zr: 106 ± 9.8 % (n = 15)	low concentration range (1 µg/L)
Trueness Zr	mean recovery for recalibration standard: Zr: 100 ± 8.5 % (n = 12)	high concentration range (50 µg/L)
Trueness V and Zr	Fortification of samples: V: 90.9– 104 % Zr: 91.3 – 109 %
Reproducibility V	mean recovery for CRM TMDA-70: V: 107 ± 9.3 % (n = 18)	high concentration range (312 µg V/L)
Reproducibility V	mean recovery for CRM TM15.2: V: 102 ± 6.8 % (n = 16)	low concentration range (13.1 µg V/L)
Reproducibility Zr	mean recovery for recalibration standard: Zr: 106 ± 9.8 % (n = 15)	low concentration range (1 µg/L)
Reproducibility Zr	mean recovery for recalibration standard: Zr: 100 ± 8.5 % (n = 12)	high concentration range (50 µg/L)

Concentration of vanadium in artificial media, calculated nominal vanadium concentration and dissolved amount of vanadium.

media and sample	total V ± SD in method blanks [µg/L]	total V ±SD in sample vessels [µg/L]	V ± SD in sample vessels with blank subtraction [µg/L]	calculated nominal V concentration in [µg/L]#	dissolved amount V in artificial media [%] normalized for measured background in method blank
ALF 2h	<LOD	108 ± 6.44	108 ± 6.44	393	27.5 ± 1.64
ALF 24h	<LOD	114 ± 0.06	114 ± 0.06	393	28.9 ± 0.01
ASW 2h	<LOD	81.0 ± 5.77	81.0 ± 5.77	393	20.6 ± 1.47
ASW 24h	<LOD	146 ± 2.65	146 ± 2.65	393	37.1 ± 0.67
GMB 2h	<LOD	111 ± 9.22	111 ± 9.22	392	28.4 ± 2.35
GMB 24h	<LOD	135 ± 3.08	135 ± 3.08	392	34.5 ± 0.78
GST 2h	<LOD	113 ± 1.46	113 ± 1.46	394	28.6± 0.37
GST 24h	<LOD	212 ± 14.9	212 ± 14.9	394	53.8 ± 3.78
PBS 2h	<LOD	109 ± 2.44	109 ± 2.44	394	27.6± 0.62
PBS 24h	<LOD	145 ± 1.80	145 ± 1.80	394	36.8 ± 0.46

# (initial weight (e.g. 50mg) * 0.39§ (percentage vanadium in test item)/ 100) * 2 (multiplication to calculate vanadium amount in one litre -> 100 mg/L) = nominal vanadium concentration in [mg/L]/1000 = nominal vanadium concentration in [µg/L]

§according to CoA 0.69 % V as V₂O₅ => 56.02 % vanadium in V₂O₅ => (0.69 % * 56.02 %) / 100 % = 0.39 % V in test item

In five different artificial physiological media, between 20.6 and 53.8 % of vanadium was dissolved from the test item IPC-2013-014 vanadium zirconium yellow baddeleyite depending on solution parameters and test duration.

Concentration of zirconium in artificial media, calculated nominal zirconium concentration and dissolved amount of zirconium

media and sample	total Zr ± SD in method blanks [µg/L]	total Zr ±SD in sample vessels [µg/L]	Zr ± SD in sample vessels with blank subtraction [µg/L]	calculated nominal Zr concentration in [µg/L]#	dissolved amount Zr in artificial media [%] normalized for measured background in method blank
ALF 2h	0.33 ± 0.03	31.9 ± 0.03	31.6 ± 0.03	71926	0.04 ± <0.01
ALF 24h	0.26 ± 0.05	38.4 ± 2.29	38.2 ± 2.29	71926	0.05 ± <0.01
ASW 2h	0.08 ± 0.01	0.79 ± 0.12	0.71 ± 0.12	71852	0.001 ± <0.01
ASW 24h	0.06	2.93 ± 1.29	2.87 ± 1.29	71852	0.004 ± 0.0021
GMB 2h	<LOQ	1.74 ± 0.20	1.74 ± 0.20	71738	0.002 ± <0.01
GMB 24h	<LOQ	0.50 ± 0.09	0.50 ± 0.09	71783	0.001 ± <0.01
GST 2h	0.08 ± <0.01	0.62 ± 0.11	0.54 ± 0.11	72013	0.001 ± <0.001
GST 24h	0.07 ± <0.02	13.1 ± 10.6	13.1 ± 10.6	72013	0.02 ± 0.01
PBS 2h	<LOD	<LOD	<LOD	71954	-
PBS 24h	<LOD	<LOD	<LOD	71954	-

# (initial weight (e.g. 50 mg) * 71.29 § (percentage zirconium in test item) / 100) * 2 (multiplication to calculate zirconium amount in one litre -> 100 mg/L) = nominal zirconium concentration in [mg/L]/1000 = nominal zirconium concentration in [µg/L]

§ according to CoA 96.30 % Zr as ZrO₂ => 74.03 % zirconium in ZrO₂ => (96.30 % * 74.03 %) / 100 % = 71.29 % Zr in test item

In five different artificial physiological media, between 0.001 and 0.05% of zirconium was dissolved from the test item IPC-2013-014 vanadium zirconium yellow baddeleyite depending on solution parameters and test duration.

Mass balance calculation

Total dissolved vanadium concentrations in vessels, filters and syringes measured by ICP-OES indicate an incomplete dissolution of vanadium zirconium yellow baddeleyite in all physiological media after addition ofaqua regiato the sample vessels.

Calculation of vanadium mass balance

media	value for dissolved V after addition ofaqua regia [mg]	nominal concentration [mg] #	recovery [%]
ALF 24h A	0.07	0.20	34.8
ALF 24h B	0.07	0.19	38.5
ASW 24h A	0.07	0.19	36.7
ASW 24h B	0.08	0.19	39.7
GMB 24h A	0.08	0.19	40.9
GMB 24h B	0.08	0.20	43.4
GST 24 A	0.08	0.19	43.3
GST 24h B	0.09	0.20	44.8
PBS 24h A	0.08	0.19	39.4
PBS 24h B	0.08	0.20	41.5

# nominal concentration V = 0.69 % as V₂O₅ in test item = 56.0 % V in V₂O₅ => 0.1933 mg Mn in 50 mg test item => 0.1933 * initial weight / 50 mg

Conclusions:

The bioaccessibility of vanadium zirconium yellow baddeleyite 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 dissolved Zr and V concentrations were below 38.2 µg/L and 212 µg/L respectively, even at the highest loading of 0.1 g/L, referring to a solubility of 0.04 % and 0.2 %, respectively, the pigment is considered biologically inert.

Executive summary:

The bioaccessibility of vanadium zirconium yellow baddeleyite has been investigated experimentally in vitro by simulating dissolution under physiological conditions considered to mimic the most relevant exposure routes (oral, dermal and inhalation).

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

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

- 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,

- 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

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

In five different artificial physiological media dissolved vanadium concentrations were between 20.6 % and 53.8 % and dissolved zirconium concentrations were between 0.001 and 0.05 % a, based on contained elements.

As dissolved Zr and V concentrations were below 38.2 µg/L and 212 µg/L respectively, even at the highest loading of 0.1 g/L, referring to a solubility of 0.04 % and 0.2 %, respectively, the pigment vanadium zirconium yellow baddeleyite is considered biologically inert.

Description of key information

As dissolved Zr and V concentrations were below 38.2 µg/L and 212 µg/L respectively, even at the highest loading of 0.1 g/L, referring to a solubility of 0.04 % and 0.2 %, respectively, the pigment is considered biologically inert.

Additional information

Discussion on bioaccumulation potential result:

The chemical and physiological properties of the pigmentvanadium zirconium yellow baddeleyiteare dominated by inertness due to the characteristics of the production process (calcination at high temperatures, approximately 1000 °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

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

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

- 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,

- 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

- Artificial gastric fluid (GST, pH 1.5), 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 Zr of the test item is between below LoD / LoD (PBS) and 31.6 µg/L/ 38.2 µg/L (ALF) at a loading of 0.1g/L after 2 and 24 hours.

The dissolution of V of the test item is in a range of 78.9 µg/L / 137 µg/L, (ASW) and 113 µg/L/ 212 µg/L (GST) at a loading of 0.1 g/L after 2 and 24 hours.

A pH dependent dissolution can be observed. In conclusion, since the dissolved Zr and V concentrations were below 38.2 µg/L and 212 µg/L respectively, even at the highest loading of 0.1 g/L, referring to a solubility of 0.04 % and 0.2 %, respectively, the pigment is considered biologically inert.