Iron titanium pseudobrookite

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics, other

Remarks:

Bioaccessibility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-01-13 to 2016-03-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Bioaccessibility testing: loading of 100 mg/L; five artificial physiological media (GST, GMB, ALF, ASW, PBS) agitated at 100 rpm, at 37°C ± 2°C; sampling after 2h and 24h; determination of Cr, Co and Zn concentrations after filtration by ICP-OES and ICP-MS.

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, at 37°C; sampling after 2h and 24h; determination of Fe, Ti and Al concentrations after filtration by ICP-MS.

Qualifier:

according to guideline

Guideline:

other: EEC guideline SANCO/3029/99 rev. 4 dated 11/07/00: Working document “Guidance for generating and reporting methods of analysis in support of residue data requirements for Annex II (part A, Section 4) and Annex III (part A, Section 5)

Deviations:

not specified

Principles of method if other than guideline:

The dissolved amount of the test item (single loading of 100 mg/L) was quantified by the mass concentration (IPC-MS) of iron, titanium and aluminium in five artificial physiological test media (phosphate-buffered saline (PBS) (pH 7.2), artificial interstitial fluid or Gamble’s solution (pH 7.4), artificial sweat solution (pH 6.5), artificial lysosomal fluid (pH 4.5)) and artificial gastric fluid (pH 1.5), which were selected to simulate relevant human-chemical interactions. Three replicates vessels and one control vessel of each medium were sampled twice after 2h and 24h agitation (100 rpm) at 37 °C. Blanks (replicates and control) were sampled twice after 30 min.
Repeatability and recovery tests were performed by spiking each test medium with known amounts of iron, titanium and aluminium at two levels (1 µg/L for low level and 10 µg/L for the high level). Three Control, three Spike Low and three Spike High samples were shaken at 37°C for 24 hours at 100 r.p.m for each medium and tested twice by ICP-MS for dissolved iron, titanium and aluminium concentrations.

The study was performed in compliance with following method: Stopford W, Turner J, Cappelini D, Brock T 2004. Bioaccessibility testing of Cobalt compounds. Journal of Environmental Monitoring 5:675-680.

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2014-10-22

Species:

other: in vitro (simulated human body fluids)

Details on test animals or test system and environmental conditions:

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,
- three replicates and one control per artificial media were tested twice; two additional blank samples were taken from the replicates and control of each medium; measurement (by IPC-MS) of dissolved iron, titanium and aluminium concentrations after filtration
- Repeatability and recovery tests were performed by spiking each test medium with known amounts of iron, titanium and aluminium at two levels (1 µg/L for low level and 10 µg/L for the high level)

The aim of this test was to assess the dissolution of IPC-2018-007 (pseudobrookite) in five artificial physiological media: Artificial lysosomal fluid (ALF, pH = 4.5), Artificial sweat solution (ASW, pH = 6.5), artificial interstitial fluid or Gamble´s solution (GMB, pH = 7.4), Artificial gastric fluid (GST, pH = 1.5), Phosphate buffered saline (PBS, pH = 7.2). 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.:

0.1 other: g of the test item /L artifical media

Details on study design:

EQUIPMENT
- Inductively coupled plasma-mass spectrometer (ICP-MS), Agilent Technologies HP7700
- Analytical balance, Mettler AG204
- Mechanical shaker, IKA KS 4000 I control
- pH meter VWR pH 1000 L
- Dissolved oxygen meter, WTW OXY 315.
- Chronometer Hanhart Profil 1
- Syringe filter PTFE 0.45 µm, diameter 25 mm
- Data logger, Testo 174-T
- Digital thermometer and probe
- Laboratory Water Purification Systems, Sartorius Arium® 611
- Refrigerator, Fiocchetti Scientific ECT-F Control

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)
- Ammonia solution 25 %, NH4OH aqueous (Merck)
- Hydrochloric acid, ≥ HCl 30 % TraceSELECT, for trace analysis (Fluka)
- Nitric acid ≥ 69 %, Trace SELECT,for trace analysis (Fluka)
- ICP-MS Internal Standard Mix solution 100 mg/L (Li6, Sc, Ge, Rh, In, Tb, Lu, Bi) 10 % HNO3, Agilent Technologies.

Certified Reference Material
- IQC-026: Multi-element analytical standard solution at about 100 µg/mL of iron (Fe), titanium (Ti) and aluminium (Al), supplied by Ultra Scientific:
Batch number: CL-4020
Expiration date: 30/11/2017
Certified value: Iron: 100.0 ± 0.5 µg/mL, Titanium: 100.1 ± 0.5 µg/mL, Aluminium: 100.2 ± 0.5 µg/mL
- TM-25.4: A trace element fortified sample (filtered and diluted Lake Ontario water preserved with in 0.2 % nitric acid), supplied by Environment Canada.
Batch no.: 0815
Expiry date: october 2017
Certified value: Iron: 31.0 ± 5.7 µg/L, Titanium: 25.2 ± 1.9 µg/L, Aluminium: 30.0 ± 3.5 µg/L

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
- Iron (Fe): m/z 56 (quantitative)
- Titanium (Ti): m/z 47(quantitative)
- Aluminium (Al): m/z 27 (quantitative)
- Scandium (Sc): m/z 45 (used as internal standard correction for Al and Ti)
- Germanium (Ge): m/z 72 (used as internal standard correction for Fe)

Quality criteria of the method
Linearity: from 0.5 to 200.20 µg/L (correlation coefficient > 0.99 for Iron, Titanium and Aluminium).
L.O.Q.: 1 µg/L (ppb) defined as the lowest fortification level
L.O.D.: 0.5 µg/L (ppb) defined as 50 % of the lowest fortification level
I.D.L.: 0.5 µg/L (ppb) defined as the lowest calibration level
Precision: +/- 10 % in the linearity range
Calibration: nominal concentrations 0.50, 1.00, 2.00, 5.00, 10.00, 20.00, 50.00, 100.00 and 200.00 µg/L (ppb) of iron, titanium and aluminium.

Toxicokinetic parameters:

other: bioaccessibility

Remarks:

Dissolution of Fe at a loading of 0.1 g/L: GST 2h: 25.45 ± 1.9 µg/L; dissolution of Ti at a loading of 0.1 g/L: GST 2h 15.68 ± 1.66 µg/L; dissolution of Al at a loading of 0.1 g/L: GST 2h: 57.85 ± 2.77 µg/L.

Bioaccessibility (or Bioavailability) testing results:

IRON concentrations in five different artificial body fluids (loading of 100 mg test item/L medium)
Phosphate buffered saline (PBS) (pH 7.2): < 1 (Control); n.d. (2 h*, 24 h*)
Artificial interstitial fluid (pH 7.4): n.d. (Control,2 h*, 24 h*)
Artificial sweat solution (pH 6.5): n.d. (Control, 2 h*, 24 h*)
Artificial lysosomal fluid (pH 4.5): n.d. (Control, 2 h*, 24 h*)
Artificial gastric fluid (pH 1.5): 4.39 µg/L ± 0.38 µg/L (Control); 25.45 ± 1.9 µg/L (2 h*); 177.81 ± 2.55 µg/L (24 h*)
n.d.: lower than the Limit of Detection (L.O.D. = 0.5 µg/L for Fe)
< 1: lower than the method Limit of Quantification (L.O.Q. = 1 µg/L for Fe) but higher than the Limit of Detection (L.O.D. = 0.5 µg/L for Fe).
*: This value was calculated subtracting the relevant Control sample value, in order to consider the contribution of the test medium.
The between-vessel variation was less than 20 % in accordance with OECD Series No. 29.

TITANIUM concentrations in five different artificial body fluids (loading of 100 mg test item/L medium)
Phosphate buffered saline (PBS) (pH 7.2): n.d. (Control, 2 h*, 24 h*)
Artificial interstitial fluid (pH 7.4): n.d. (Control, 2 h*, 24 h*)
Artificial sweat solution (pH 6.5): n.d. (Control, 2 h*, 24 h*)
Artificial lysosomal fluid (pH 4.5): n.d. (Control, 2 h*, 24 h*)
Artificial gastric fluid (pH 1.5): n.d. (Control); 15.68 ± 1.66 µg/L (2 h*); 105.76 ± 2.61 µg/L (24 h*)
n.d.: lower than the Limit of Detection (L.O.D. = 0.5 µg/L for Ti)
*: This value was calculated subtracting the relevant Control sample value, in order to consider the contribution of the test medium.
The between-vessel variation was less than 20 % in accordance with OECD Series No. 29.

ALUMINIUM concentrations in five different artificial body fluids (loading of 100 mg test item/L medium)
Phosphate buffered saline (PBS) (pH 7.2): 3.27 ± 0.20 µg/L (Control); n.d. (2 h*); 3.76 ± 0.23 µg/L (24 h*)
Artificial interstitial fluid (pH 7.4): 1.48 ± 0.00 µg/L (Control); 2.03 ± 0.06 µg/L (2 h*); 7.50 ± 0.13 µg/L (24 h*)
Artificial sweat solution (pH 6.5): 1.40 ± 0.12 µg/L (Control); 1.45 ± 0.04 µg/L (2 h*); 1.69 ± 0.07 µg/L (24 h*)
Artificial lysosomal fluid (pH 4.5): n.d. (Control, 2 h*, 24 h*)
Artificial gastric fluid (pH 1.5): 5.24 ± 0.30 µg/L (Control); 57.85 ± 2.77 µg/L (2 h*); 138.36 ± 3.83 µg/L (24 h*)
n.d.: lower than the Limit of Detection (L.O.D. = 0.5 µg/L for Al)
*: This value was calculated subtracting the relevant Control sample value, in order to consider the contribution of the test medium.
The between-vessel variation was less than 20 % in accordance with OECD Series No. 29.

Linearity

The nominal range of iron, titanium and aluminium concentrations, from 0.50 µg/L to 200.00 µg/L, was found to be linear (correlation coefficient > 0.99).

The instrumental limit of detection (I.D.L.) defined as the lowest calibration level, was 0.5 µg/L for iron, titanium and aluminium.

The limit of quantification (L.O.Q.) of the method was fixed at 1 µg/L, 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.

Iron, titanium and aluminium concentrations lower than the L.O.D. were classified as not detected (n.d.), concentrations higher than the L.O.D. but lower than the L.O.Q. were designated as <1 µg/L.

Repeatability (Precision) and Accuracy (Recovery)

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 0.50 µg/L to 200.20 µg/L.

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.

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.

From data obtained, these criteria were fulfilled and therefore precision and accuracy of the analytical method is acceptable.

Mean recovery of fortified samples in five different artificial body fluids

	Phosphate buffered saline (PBS) (pH 7.2)	Artificial sweat solution (pH 6.5)	Artificial interstitial fluid (pH 7.4)	Artificial lysosomal fluid (pH 4.5)	Artificial gastric fluid (pH 1.5)
Fe spiked low (1 µg/L)	89.93 % ± 8.59 %	82.74 % ± 0.98 %	82.58 % ± 0.38 %	82.74 % ± 0.67 %	83.63 % ± 0.86 %
Fe spiked high (10 µg/L)	89.67 % ± 1.64 %	94.68 % ± 0.91 %	98.41 % ± 0.93 %	90.04 % ± 0.73 %	88.55 % ± 0.09 %
Ti spiked low (1 µg/L)	86.38 % ± 1.23 %	91.09 % ± 1.10 %	87.03 % ± 0.36 %	83.11 % ± 0.57 %	86.15 % ± 1.17 %
Ti spiked high (10 µg/L)	96.20 % ± 0.50 %	99.71 % ± 0.13 %	94.42 % ± 0.27 %	95.80 % ± 1.29 %	97.90 % ± 0.78 %
Al spiked low (1 µg/L)	84.52 % ± 1.44 %	82.39 % ± 0.38 %	83.00 % ± 0.08 %	82.89 % ± 0.20 %	83.47 % ± 0.23 %
Al spiked high (10 µg/L)	86.54 % ± 1.31 %	91.23 % ± 1.19 %	93.23 % ± 0.83 %	93.82 % ± 0.66 %	87.77 % ± 0.34 %

Tempearture, pH and dissolved oxygen after 24 h in five different artificial body fluids

Media	Temperature	pH	Dissolved oxygen
Phosphate buffered saline (PBS) (pH 7.2)	36.98 °C ± 0.08 °C	7.217 ± 0.046	88.3 % ± 3.1 %
Artificial interstitial fluid (pH 7.4)	37.01 °C ± 0.04 °C	7.400 ± 0.012	83.9 % ± 5.4 %
Artificial sweat solution (pH 6.5)	36.84 °C ± 0.07 °C	6.519 ± 0.024	85.4 % ± 3.1 %
Artificial lysosomal fluid (pH 4.5)	37.01 °C ± 0.05 °C	4.847 ± 0.028	86.0 % ± 4.5 %
Artificial gastric fluid (pH 1.5)	36.89 °C ± 0.04 °C	1.491 ± 0.010	89.1 % ± 6.4 %

Conclusions:

IRON concentrations in five different artificial body fluids (loading of 100 mg test item/L medium)
Phosphate buffered saline (PBS) (pH 7.2): < 1 (Control); n.d. (2 h*, 24 h*)
Artificial interstitial fluid (pH 7.4): n.d. (Control,2 h*, 24 h*)
Artificial sweat solution (pH 6.5): n.d. (Control, 2 h*, 24 h*)
Artificial lysosomal fluid (pH 4.5): n.d. (Control, 2 h*, 24 h*)
Artificial gastric fluid (pH 1.5): 4.39 µg/L ± 0.38 µg/L (Control); 25.45 ± 1.9 µg/L (2 h*); 177.81 ± 2.55 µg/L (24 h*)
n.d.: lower than the Limit of Detection (L.O.D. = 0.5 µg/L for Fe)
< 1: lower than the method Limit of Quantification (L.O.Q. = 1 µg/L for Fe) but higher than the Limit of Detection (L.O.D. = 0.5 µg/L for Fe).
*: This value was calculated subtracting the relevant Control sample value, in order to consider the contribution of the test medium.
The between-vessel variation was less than 20 % in accordance with OECD Series No. 29.

TITANIUM concentrations in five different artificial body fluids (loading of 100 mg test item/L medium)
Phosphate buffered saline (PBS) (pH 7.2): n.d. (Control, 2 h*, 24 h*)
Artificial interstitial fluid (pH 7.4): n.d. (Control, 2 h*, 24 h*)
Artificial sweat solution (pH 6.5): n.d. (Control, 2 h*, 24 h*)
Artificial lysosomal fluid (pH 4.5): n.d. (Control, 2 h*, 24 h*)
Artificial gastric fluid (pH 1.5): n.d. (Control); 15.68 ± 1.66 µg/L (2 h*); 105.76 ± 2.61 µg/L (24 h*)
n.d.: lower than the Limit of Detection (L.O.D. = 0.5 µg/L for Ti)
*: This value was calculated subtracting the relevant Control sample value, in order to consider the contribution of the test medium.
The between-vessel variation was less than 20 % in accordance with OECD Series No. 29.

ALUMINIUM concentrations in five different artificial body fluids (loading of 100 mg test item/L medium)
Phosphate buffered saline (PBS) (pH 7.2): 3.27 ± 0.20 µg/L (Control); n.d. (2 h*); 3.76 ± 0.23 µg/L (24 h*)
Artificial interstitial fluid (pH 7.4): 1.48 ± 0.00 µg/L (Control); 2.03 ± 0.06 µg/L (2 h*); 7.50 ± 0.13 µg/L (24 h*)
Artificial sweat solution (pH 6.5): 1.40 ± 0.12 µg/L (Control); 1.45 ± 0.04 µg/L (2 h*); 1.69 ± 0.07 µg/L (24 h*)
Artificial lysosomal fluid (pH 4.5): n.d. (Control, 2 h*, 24 h*)
Artificial gastric fluid (pH 1.5): 5.24 ± 0.30 µg/L (Control); 57.85 ± 2.77 µg/L (2 h*); 138.36 ± 3.83 µg/L (24 h*)
n.d.: lower than the Limit of Detection (L.O.D. = 0.5 µg/L for Al)
*: This value was calculated subtracting the relevant Control sample value, in order to consider the contribution of the test medium.
The between-vessel variation was less than 20 % in accordance with OECD Series No. 29.

Description of key information

In conclusion, since the dissolved Fe, Ti and Al and concentrations from this pigment under simulated physiological conditions were below 178 µg/L, 106 µg/L and 139 µg/L (GST) , respectively even at the highest loading of 0.1g/L, corresponding to a solubility of less than 0.4 % after 24 hours, this pigment may reasonably be considered biologically inert.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

The chemical and physiological properties of the pigment Pseudobrookite 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. 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, pH 7.4) which mimics the interstitial fluid within the deep lung under normal health conditions,

2.) phosphate-buffered saline (PBS, pH 7.2), 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, pH 4.5), which simulates intracellular conditions in lung cells occurring in conjunction with phagocytosis and represents relatively harsh conditions and

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

 

Solubility of Fe from the pigment Pseudobrookite in physiological media was in a range of below LOD and 25.5 µg/L (GST) after 2 hours. After 24 hours a dissolution range from below LOD - 178 µg/L (GST) was measured.

 

Solubility of Ti from the pigment Pseudobrookite in physiological media was in a range of below LOD and 15.7 µg/L (GST) after 2 hours. After 24 hours a dissolution range from below LOD – 105.8 µg/L (GST) was measured.

 

Solubility of Al from the pigment Pseudobrookite in physiological media was in a range of below LOD and 57.9 µg/L (GST) after 2 hours. After 24 hours a dissolution range from below LOD – 138.4 µg/L (GST) was determined.

 

In conclusion, since the dissolved Fe, Ti and Al and concentrations from this pigment under simulated physiological conditions were below 178 µg/L, 106 µg/L and 139 µg/L (GST) , respectively even at the highest loading of 0.1g/L, corresponding to a solubility of less than 0.4 % after 24 hours, this pigment may reasonably be considered biologically inert.