Reaction mass of cobalt olivine and crystalline silicon dioxide

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

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:

2015-09-25 to 2015-11-06

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

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:

yes

Remarks:

Bioaccessibility testing: single loading 2 g/L, measurement after filtration, sampling after 2 and 24 hours agitation (100 rpm) at 37 ± 2 °C, three replicates, two method blanks / artificial media (ALF, GMB, GST)

Principles of method if other than guideline:

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.
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.

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2011-02-07

Specific details on test material used for the study:

Appearance: light violet powder, odourless
Storage conditions: Store in a dry place

Species:

other: in vitro (simulated human body fluids)

Details on exposure:

Test principle in brief:
- three different artificial physiological media,
- single loading of test substance of ~ 2 g/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) of total dissolved cobalt concentrations after filtration
- the study was performed in triplicate

The aim of this test was to assess the dissolution of Olivine, cobalt silicate blue (IPC-2013-006-01) in three artificial physiological media: Artificial lysosomal fluid (ALF, pH= 4.5), Gamble´s solution (GMB, pH= 7.4), Artificial gastric fluid (GST, pH= 1.5). 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 gastro-intestinal tract and by inhalation.

Duration and frequency of treatment / exposure:

Samples were taken after 2h and 24h.

Dose / conc.:

2 other: g of the test item /L artificial physiological 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).

Metal analysis
- Standards: single element standards were used as cobalt standard (Merck Certipur Cobalt ICP standard 1000 mg/L lot no. HC41722713; Darmstadt, Germany; Merck).
- Certified reference materials: quality control standards TM-25.4 (lot no. 0914), TMDA-53.3 (lot no. 0914) and TMDA-54.5 (lot no. 0815) obtained from Environment Canada and multielement standards (CPI 19 Elements, lot no. 15C267, Netherlands; Merck XXI, lot no. HC55190098, Germany) were analysed for total dissolved cobalt by ICP-OES along with the samples to determine the accuracy of the applied analytical method. To meet quality assurance requirements recovery needs to be in the range of ± 15 % of the respective certified value. Furthermore the calibration solutions were measured along with the ICP-OES measurements as recalibration standards.

Instrumental and analytical set-up for the ICP-OES instrument:
- Agilent 720, Agilent Technologies, Waldbronn, Germany
- Nebulizer: Sea spray nebulizer from Agilent
- Spray chamber: Glass cyclonic spray chamber from Agilent
- Carrier gas flow: 0.75 L/min
- RF power: 1200W
- Wavelengths: Co 230.786 nm and 231.406 nm
The applied LOD/LOQ calculations for the Agilent 720 ICP-OES are (according to DIN 32645):
LOD: 3 * standard deviation of calibration blank/slope of the calibration
LOQ: 3 * LOD

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: Co 228.616 nm, 230.786 nm and 231.160 nm

The applied LOD/LOQ calculations for the Thermo IRIS Intrepid 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).

Calibration:
- high calibration: blank, 0.5 mg/L, 1.5 mg/L, 2.5 mg/L, 3.5 mg/L, 4.5 mg/L, 5.5 mg/L, 6.5 mg/L and 7.5 mg/L;
- medium calibration: blank, 100 μg/L, 250 μg/L, 500 μg/L, 750 μg/L, 1000 μg/L, 1250 μg/L, 1500 μg/L, 1750 μg/L and 2000 μg/L
- low calibration: blank, 1 μg/L, 2.5 μg/L, 5 μg/L, 7.5 μg/L, 10 μg/L, 25 μg/L 50 μg/L, 75 μg/L, 100 μg/L, 250 μg/L, 500 μg/L, 750 μg/L and 1000 μg/L

Deviations:
Due to a mistake two vessels of the vessel mass balance for ALF medium were disposed before a sample was taken. According to the results of the vessel mass balance for the media GMB, GST and the remaining ALF medium (one vessel) a total dissolution in aqua regia was measured. After discussion with the study monitor it was decided that the ALF test will not be repeated, because the remaining two vessels are sufficient and this deviation was considered as not critical.

Details on dosing and sampling:

Loading:
The nominal loading in this test was 2 g/L. However, due to weighing uncertainties the actual loadings range from 2.0000 g/L to 2.0016 g/L in the test vessels.

Type:

other: Bioaccessibility

Results:

Highest dissolution of Cobalt (loading: 0.1g/L, after 24h) in GST: 808 ± 32.3 mg/L, GMB: 197 ± 17.2 μg/L, ALF: 529 ± 20.2 mg/L

Method validation summary ICP-OES.

validation parameter	results	Comment
Selectivity	similar data with different wavelengths for ICP-OES method	-
Linearity	applied calibration functions were linear	correlation coefficient at least 0.999648
Limit of detection	Co: 0.48 µg/L (Agilent 720) Co: 0.98 µg/L – 0.07 mg/L (Thermo IRIS Intrepid)
Limit of quantification	Co: 1.45 µg/L (Agilent 720) Co: 3.25 µg/L – 0.23 mg/L (Thermo IRIS Intrepid)
Method blanks	In all samples below LOD	-
Accuracy measurement / Reproducibility GMB medium sample measurements	TM-25.4 (dilution factor 2; 13.8 µg Co/L) Co: 111 ± 2.2 % (n = 6)	Low concentration range (undiluted 27.5 µg Co/L – diluted 13.8 µg Co/L)
Accuracy measurement / Reproducibility ALF method blank sample measurements	TM-25.4 (dilution factor 10; 2.75 µg Co/L) Co: 94.0 ± 3.4 % (n = 7)	Low concentration range (undiluted 27.5 µg Co/L – diluted 2.75 µg Co/L)
Accuracy measurement / Reproducibility ALF method blank sample measurements	TMDA-53.3 (dilution factor 10; 25.1 µg Co/L) Co: 101 ± 3.5 % (n = 7)	Mid concentration range (undiluted 251 µg Co/L – diluted 25.1 µg Co/L)
Accuracy measurement / Reproducibility GMB medium sample measurements	TMDA-53.3 (dilution factor 4; 62.8 µg Co/L) Co: 106 ± 3.9 % (n = 6)	Mid concentration range (undiluted 251 µg Co/L – diluted 62.8 µg Co/L)
Accuracy measurement / Reproducibility ALF sample measurements and GMB mass balance samples (both adapted calibrations)	TMDA-54.5 (318 µg Co/L) Co: 101 ± 1.2 % (n = 18)	Low concentration range
Trueness ALF method blank sample measurements	Quality control standard (Merck XXI 200 µg Co/L Co: 98.2 ± 4.0 % (n = 7)	High concentration range
Trueness ALF sample and GMB mass balance samples (both adapted calibrations) measurements	Quality control standard (CPI 500 µg Co/L) Co: 101 ± 1.8 % (n = 18)	Mid concentration range
Trueness GST medium sample and mass balance sample measurements	Quality control standard (CPI 2.5 mg Co/L) Co: 98.2 ± 0.7 % (n = 6)	High concentration range
Trueness GMB medium sample measurements	Recalibration standard (50 µg Co/L) Co: 98.7 ± 2.6 % (n = 6)	Mid concentration range
Trueness ALF method blank measurements	Recalibration standard (100 µg Co/L) Co: 97.8 ± 2.7 % (n = 7)	Mid concentration range
Trueness GST medium sample and mass balance sample measurements; mass balance vessel samples GMB and ALF samples and mass balance measurements	Recalibration standard (1000 μg Co/L) Co: 102 ± 2.1 % (n = 20)	Low concentration range for GST medium, High concentration range for GMB and ALF samples
Trueness test samples and mass balance	Fortification of samples: Co: 95.9 – 104 %

Solution pH values

After preparation of the artificial physiological media, solution pH was adjusted to their respective target pH. The target pH in all media before addition of test substance was in the nominal range.

During the study, the pH of GST solutions remained mainly stable in the method blank vessels but in the test vessels the pH increased from 1.51 – 1.52 up to 2.31 – 2.52. Therefore, an effect of the test substance cannot be excluded.

The pH of ALF solutions remained mainly stable. In the method blanks the pH was between 4.50 – 4.52 (start of the test to end of the test), a low increase of the pH in test vessel was measurable (4.50 to 4.59). Therefore, as in the GST medium, a low effect of the test substance cannot be excluded.

In GMB medium, the pH in all vessels (including method blanks) increased during the time of the test from 7.40 to 8.88 (test vessels) and 7.4 to 8.69 and 8.76 (method blank vessels). Therefore, an effect of the test substance can be excluded. In fact, the pH of the GMB media does not seem to be stable under the conditions of the test.

Temperature control

The temperature was adjusted to 37.5 in a thermostatically controlled shaking cabinet to reach a temperature of 37 ± 2 °C in the media. The temperature in thermostatically controlled shaking cabinet was confirmed by a certified thermometer and a thermo data logger. In all test vessels, the temperature was constant at 37 ± 2 °C.

Analytical measurements

The nominal loading in this test was 1000 mg/ 500mL. However, due to weighing uncertainties the actual loadings range from 2.0000 g/L to 2.0016 g/L in the 9 test vessels.

Concentration of dissolved cobalt in artificial physiological media.

media and sample	LOD/LOQ of Co measurement series [μg/L] / [mg/L]	total Co ± SD in method blanks [μg/L] / [mg/L]	total Co ± SD in sample vessels [μg/L] / [mg/L]	total Co ± SD in sample vessels [μg/L] / [mg/L] (corrected concentrations, corresponding to a loading of exactly 2 g/L)
GST 2h	LOD: 0.07 mg/L LOQ: 0.23 mg/L	all method blanks below LOD	88.1 ± 39.3 mg/L	88.0 ± 39.3 mg/L
GST 24h	LOD: 0.07 mg/L LOQ: 0.23 mg/L	all method blanks below LOD	808 ± 32.5 mg/L	808 ± 32.3 mg/L
GMB 2h	LOD: 0.98 μg/L LOQ: 3.25 μg/L	all method blanks below LOD	110 ± 37.4 μg/L	110 ± 37.4 μg/L
GMB 24h	LOD: 0.98 μg/L LOQ: 3.25 μg/L	all method blanks below LOD	197 ± 17.2 μg/L	197 ± 17.2 μg/L
ALF 2h	ALF method blanks: LOD: 0.48 μg/L LOQ: 1.45 μg/L ALF test samples LOD: 27.9 μg/L LOQ: 92.8 μg/L	all method blanks below LOD	106 ± 16.5 mg/L	106 ± 16.4 mg/L
ALF 24h	ALF method blanks: LOD: 0.48 μg/L LOQ: 1.45 μg/L ALF test samples LOD: 27.9 μg/L LOQ: 92.8 μg/L	all method blanks below LOD	530 ± 20.3 mg/L	529 ± 20.2 mg/L

Mass balance calculation

The mass balance dissolved cobalt concentrations in vessels and filters as measured by ICP-OES indicate a complete dissolution of IPC-2013-006-01 in the physiological media after addition of aqua regia to the sample vessels. Due to the observations during the mass balance a small amount of particles were still visible which could be a result of insoluble parts of the test item (for example according to CoA 45.2 % SiO2 in test item).

Amount of cobalt in mass balance samples (vessels, filter/syringes and taken samples) for each media

Media	Value for dissolved Co after addition of aqua regia		In samples [mg]	Calculated value Co [mg]*	Nominal amount [mg] #	Recovery [%]
	Vessels [mg/L]	Filters/ syringes [mg]
GST vessel 1	394	0.17	38.4	433	415	104
GST vessel 2	391	0.12	36.4	428	415	103
GST vessel 3	349	0.13	32.8	381	414	92.0
GMB vessel 1	427	0.18	0.01	427	415	103
GMB vessel 2	433	0.28	0.01	433	415	104
GMB vessel 3	442	0.28	0.01	442	415	107
ALF vessel 1	369	1.70	23.9	395	415	95.2
ALF vessel 2	Due to a mistake vessel of mass balance was disposed before sample was taken
ALF vessel 3	369	1.98	26.8	398	415	95.9

* Measured dissolved Co includes the amount of cobalt in test solutions after addition of aqua regia, the amount of cobalt rinsed of used filters and syringe and the amount of cobalt removed with samples during the study.

Example: 394 mg (amount Co in vessels) + 0.17 mg (amount Co in filters/syringes) + 38.4 mg (amount Co in samples) = 433 mg

# nominal amount CoO = 52.70 % in test item (according to CoA) -> 78.6483 % Co in CoO -> 414 mg Co in 1 g test item -> nominal amount 414 mg * initial weight / 1 g

Example: 414 mg Co * 1000.3 mg test item / 1000 mg = 415 mg Co

Conclusions:

The bioaccessibility of Cobalt silicate olivine and silca polymorphs has been investigated experimentally in vitro by simulating dissolution under physiological conditions considered to mimic the most relevant exposure routes (oral and inhalation). At a loading of 2 g test item /L dissolved Co concentrations after 24 h in GST, GMB and ALF were 808 mg/L (88 mg/L after 2 h), 0.197 mg/L and 529 mg/L, respectively, referring to a solubility of ~ 40.4 % (4.41 % after 2h), 0.01 % and ~ 26.45 %, respectively.
The dissolved Co concentrations (according to the CoRC bioaccessibility protocol) were 88 mg/L at a 2 g loading, corresponding to a solubility of 4.41 % in the most effective surrogate physiological medium (GST, 2 hours).

Total Co ± SD in sample vessels (corrected concentrations, corresponding to a loading of exactly 2 g/L)
- GST 2h: 88.0 ± 39.3 mg/L
- GST 24h: 808 ± 32.3 mg/L
- GMB 2h: 110 ± 37.4 μg/L
- GMB 24h: 197 ± 17.2 μg/L
- ALF 2h: 106 ± 16.4 mg/L
- ALF 24h: 529 ± 20.2 mg/L

Reference 2

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:

2010-12-03 to 2010-12-13 and 2011-08-23 to 2013-02-01

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

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:

yes

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 Co concentrations after filtration by ICP-MS.

Principles of method if other than guideline:

Solubility of test item in simulated human fluids. Principle of test is similar to OECD Series on testing and assessment number 29 guidance document on transformation/dissolution of metals and metal compounds in aqueous media (2001; document ENV/JM/MONO(2001)9).

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2009-06-19 and 2012-04-26

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 °C,
- two method blanks per artificial media were tested; measurement (ICP-MS) of dissolved cobalt concentrations after filtration (0.45 µm, Supor membrane)
- the study was performed in triplicates

The aim of this test was to assess the dissolution of olivine, cobalt silicate blue (IPC-2013-006) 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: mg of the test item /L artificial media

Details on study design:

Reagents
Water, HPLC grade obtained from the Laboratory Water Purification System
- Standard solutions at pH 4.00, pH 7.00 and at pH 10.00 (Merck)
- Nitric acid 65 %, Suprapur (Merck)
- Sodium chloride, NaCl (Merck)
- Potassium choride, KCl (Merck)
- Dibasic sodium phosphate, NaH2PO4 (Sigma)
- Dibasic potassium phosphate, KH2PO4 (Merck)
- Urea (Merck)
- Lactic acid (Fluka)
- Ammonia solution 25% (NH4OH) aqueous (Merck)
- Magnesium chloride hexahydrate, MgCl2 x 6H2O (Merck)
- Sodium sulfate, NaSO4 (Merck)
- Calcium chloride dihydrate, CaCl2 x 2H2O (Merck)
- Sodium acetate trihydrate (Sigma)
- Sodium bicarbonate, NaHCO3 (Sigma)
- Sodium citrate dihydrate (SAFC)
- Sodium hydroxide, NaOH (Merck)
- Citric acid (Sigma)
- Calcium chloride, CaCl2 (Merck)
- Sodium phosphate heptahydrate, NaH2PO4 x 7H2O (Sigma)
- Glycerine (Merck)
- Sodium tartrate dehydrate (Sigma)
- Sodium lactate (Sigma)
- Sodium pyruvate (Sigma)
- Formaldehyde (Merck)
- ICP-MS Internal Standard Mix solution 100 mg/L (Li6,Sc,Ge,Rh,In,Tb,Lu,Bi) 10% HNO3, Agilent Technologies.

Reference Material
- Multi-element analytical standard solution at 100 mg/L (ppm) of cobalt (Co) in 5% HNO3, supplied by Ultra Scientific (batch number: L00297, expiry date: 30/04/2013) and Multielement satandard solution at 100 mg/L (ppm) of Cobalt (Co) supplied by Ultra Scientific (batch no. K00285), expiry date: 31/05/2013)

Inductively coupled plasma-mass spectrometer (ICP-MS), Agilent Technologies HP7700
Instrumental conditions
Detector: ICP/MS
Power: 1550 W
Carrier gas: 0.85 L/min
Replicates: 3 times
Sample introduction setting (peristaltic pump)
Pump rate: 0.1 rps
Cobalt (Co): m/z 59 (quantitative)
Germanium (Ge): m/z 72 (used as internal standard correction)
Calibration: 0.1, 1, 2, 5, 10, 20, 50, 100 and 200 µg/L
Quality criteria of the method
Linearity: from 0.1 to 200 µg/L (correlation coefficient > 0.99 for cobalt).
L.O.Q.: 1 µg/L (ppb)
L.O.D.: 0.5 µg/L (ppb)
Precision: +/-10 % in the linearity range

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 99.6 mg/L to 102.32 mg/L in the test vessels.

Type:

other: Bioaccessibility

Results:

Highest dissolution (loading: 0.1g/L, after 24h) in PBS: 694.5 ± 27.7 µg Co/L, GMB: 90.3 ± 23.8 µg Co/L, ASW: 533.2 ± 127.5 µg Co/L, ALF: 25827.2 ± 626.7 µg Co/L, GST: 29321 ± 488 µg Co/L

Analytical method (Inductively-Coupled-Plasma Mass-Spectrometry ICP-MS)

 

Specificity

Cobalt concentrations of blanks from each test medium were analysed. Cobalt concentrations in blanks of all respective media were below the method LOD.

 

Linearity and System Precision

The analysed range of Co concentrations, from 0.1 µg/L to 200 µg/L,was found to be linear (correlation coefficient > 0.99).

Since the fortification levels for the recovery test were 1 µg/L and 10 µg/L, the linear calibration performed for recovery quantification ranged from 0.1 µg/ L to 50 µg/L.

The instrumental limit of detection (I.D.L.) defined as the lowest calibration level, was 0.1 µg/L for cobalt.

The limit of quantification (L.O.Q.) of the method was 1 µg/L for cobalt, defined as the lowest fortification level.

The limit of detection (L.O.D.) of the method, defined as 50 % of the lowest fortification level, was 0.5 µg/L for cobalt.

 

Repeatability (Precision) and Accuracy (Recovery)

For precision, the SANCO/3029/99 rev. 4 guideline requires an RSD to be lower than 20 % for all tested media and fortification levels.

For accuracy, the SANCO/3029/99 rev. 4 guideline requires individual recovery values in the range from 70 to 110 % with a mean between 80 to 100 % for all tested media and fortification levels.

The precision of the analytical method is in accordance with SANCO/3029/99 rev. 4 as RSD values were well below 20 % for all tested media and fortification levels.

For accuracy, the SANCO/3029/99 rev. 4 guideline requires individual recovery values in the range from 70 to 110 % with a mean between 80 to 100 % at each fortification level; therefore the accuracy of the analytical method is not in accordance with the referred guideline for the Co analysis of the following solutions: PBS, artificial sweat and artificial lysosomal fluid.

Considering the low concentrations tested (low fortification level 1 µg/L and high fortification level 10 µg/L), the precision of the analytical method and the complexity of the tested aqueous matrices, the accuracy of the analytical method may be considered acceptable even if specific recovery values are slightly below 80 %.

From the results of the accuracy test it can be concluded that there was not a matrix effect and contamination (e.g. by the filter procedure) did not occur during sample processing.

Recovery (⁵⁹Co)

Test  Medium	Spike add	MeanFound	Test No.	RSD (%)	Mean   Recovery
pH 7.2	1 µg/L 10 µg/L	0.8 µg/L 8.3 µg/L	L (3 det.) H (3 det.)	0.8 % 2.1 %	78.1 %(*) 83.1 %
pH 7.4	1 µg/L 10 µg/L	0.8 µg/L 8.4 µg/L	L (3 det.) H (3 det.)	1.1 % 0.8 %	84.0 % 83.9 %
pH 6.5	1 µg/L 10 µg/L	0.8 µg/L  8.0 µg/L	L (3 det.) H (3 det.)	2.4 % 2.9 %	79.4 %(*) 79.8 %(*)
pH 4.5	1 µg/L 10 µg/L	0.8 µg/L 7.6 µg/L	L (3 det.) H (3 det.)	0.9 % 1.6%	76.6 %(*) 75.8 %(*)
pH 1.5	1 µg/L 10 µg/L	1.1 µg/L 10.2 µg/L	L (3 det.) H (3 det.)	2.2 % 1.2 %	106 % (*) 102 % (*)

(*) Value below or obove the recovery limit of acceptability according to guideline SANCO/3029/99 rev. 4.

⁵⁹Co concentrations of four different artificial body fluids

^59Co  (µg/L)		Phosphate buffered saline (PBS) (pH 7.2)	Artificial interstitial fluid (GMB) (pH 7.4)	Artificial sweat solution (ASW) (pH 6.5)	Artificial lysosomal fluid (ALF) (pH 4.5)	Artificial gastric fluid (GST) (pH 1.5)
T0	Mean	n.d.	n.d.	n.d.	n.d.	n.d.
	S.D.	-	-	-	-	-
	RSD (%)	-	-	-	-	-
T2 h	Mean	365.4	75.8	319.1	3007.9	1297
	S.D.	43.6	7.6	24.3	148.7	767
	RSD (%)	11.9 %	10.1 %	7.6 %	4.9 %	6 %
T24 h	Mean	694.5	90.3	533.2	25827.2	29321
	S.D.	27.7	23.8	127.5	626.7	488
	RSD (%)	4.0 %	26.4 %	23.9 %	2.4 %	2 %

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

Conclusions:

The bioaccessibility of olivine, cobalt silicate blue has been investigated experimentally in vitro by simulating dissolution under physiological conditions considered to mimic the most relevant exposure routes (oral, dermal and inhalation). Dissolved Co concentrations were between 90.3 µg/L to 29.3 mg/L at the loading of 100 mg/L pigment, corresponding to a solubility of less than 30 %. Therefore, olivine, cobalt silicate blue may reasonably be considered poorly bioaccessible.

Executive summary:

The bioaccessibility of olivine, cobalt silicate blue 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:

- 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.

Dissolved Co concentrations were between 90.3 µg/L to 29.3 mg/L at the loading of 100 mg/L pigment, corresponding to a solubility of less than 30 %. Therefore, olivine, cobalt silicate blue may reasonably be considered poorly bioaccessible.

Description of key information

Dissolution of Co was determined in bioaccessibility tests with nominal loadings of 100mg and 2 g pigment sample. A pH-dependent dissolution can be observed.

 

The dissolved Co concentrations (according to the CoRC bioaccessibility protocol) were 88 mg/L at a 2 g loading, corresponding to a solubility of 4.41 % in the most effective surrogate physiological medium (GST, 2 hours). Therefore, the cobalt contained in this pigment can be considered bioaccessible.

Dissolved Co concentrations after 24 h in GST, GMB and ALF were 808 mg/L,197 µg/L and 529 mg/L, respectively, referring to a solubility of ~ 40.4 %, 0.01 % and ~ 26.45 %, respectively.

 

Reaction mass of cobalt olivine and crystalline silicon dioxide an in vitro bioaccessibility in GST (2 hrs) similar to those in the soluble cobalt substances group, i.e. grouping in the highly bioaccessible group appears plausible (CoRC read-across oral systemic). Further details are reported in the read-across report attached to section 13 of the technical dossier.

 

Additional information

The endpoint summary reports the results of in vitro bioaccessibility testing of Reaction mass of cobalt olivine and crystalline silicon dioxide. Further information on the toxicokinetics of the toxic unit "cobalt" is reported in the source endpoint summary of the cobalt category substances.