Palladium monoxide

Additional toxicological data

Administrative data

Endpoint:

additional toxicological information

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: study performed according to OECD Principles of Good Laboratory Practice, follows a standard operating procedure (Eurometaux (2016), available as an unpublished report, reliable without restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: SOP prepared by Eurometaux (2016); Standard Operating Procedure (SOP) for Bioelution Testing of Metals, Inorganic Metal Compounds, and Metal-Containing Complex Materials: Simulated Gastric Fluid (Eurometaux Brussels, July 2016).

Principles of method if other than guideline:

Bio-elution refers to the in vitro extraction methods used to measure the degree to which a substance (e.g., metal or mineral ion) is dissolved in artificial biological fluids. Simulated biological fluids represent relevant exposure routes. The resulting value is the “bio-accessibility”, and is defined as the “fraction of a substance that is soluble under physiological conditions and therefore potentially available for absorption into systemic circulation”.
The objective of this study was to obtain knowledge about the bio-elution characteristics of the test item in simulated gastric fluid.
This study has been conducted according to the recommended Standard Operating Procedure (SOP) for Bioelution Testing of Metals, Inorganic Metal Compounds, and Metal-Containing Complex Materials: Simulated Gastric Fluid (Eurometaux, February 2018) which is based on ASTM D5517-07: Standard Test method for determining the extractability of metals from art materials - ASTM, 2007 (American Society for Testing and Materials). The extent of dissolution of the test item was tested in a simulated gastric fluid at 37 °C and pH 1.5 for 2 hours (0.2 g/L loading) at an agitation speed of 100 revolutions per minute (rpm) for 1 hour followed by 1 hour of settling (without shaking). The bio-elution endpoints were based on the dissolved elemental concentrations obtained after 2 hours of extraction.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Palladium monoxide

EC Number:

215-218-3

EC Name:

Palladium monoxide

Cas Number:

1314-08-5

Molecular formula:

OPd

IUPAC Name:

palladium monoxide

Test material form:

not specified

Details on test material:

- Name of test material (as cited in study report): PdO
- Substance type: No data
- Physical state: No data
- Analytical purity: No data
- Impurities (identity and concentrations): No data
- Composition of test material, percentage of components: No data
- Isomers composition: No data
- Purity test date: No data
- Lot/batch No.: No data
- Expiration date of the lot/batch: No data
- Stability under test conditions: No data
- Storage condition of test material: No data

Specific details on test material used for the study:

purity: 88.31% Pd content
d10 2.03 µm, d50 6.5 µm, d90 119.7 µm
Approximately 85 % of the particles had a diameter <100 μm
SSA (N-BET): 0.8 m²/g
d = 8.3 g/cm³

Results and discussion

Any other information on results incl. tables

The particle size of the test item exceeded the <100 μm requirement as mentioned in the test guidance (d10: 8.45 μm / d50: 124 μm / d90: 473 μm). However, no further preparation of the test item was performed to test the natural state of the test item.

The temperature of the test solutions at the sampling point was between 36.9 °C and 37.0 °C, which was in line with the test conditions of 37 °C ± 1 °C.

The measured pH of the test medium at the start of the test was 1.50, i.e. within the specifications of pH 1.5 ± 0.1. The pH measured in the additional test item vessel at the start of the test was 1.50 for both loadings i.e. within the specifications of pH 1.5 ± 0.1. At the 2 hours sampling point of the test, the pH in the blank control vessels and the test vessels was between 1.50 and 1.52.

The data of the dissolved palladium concentrations in the test samples, are presented below:

palladium monoxide, 0.2 g/L (=0.16 m²/L surface loading), 2h gastric, pH 1.5
Palladium	x(avg) +/- s(between)	CV
dissolution	<0.5 µg/L	-
absolute Rh release	<0.0025 mg/g	-
% of total available Rh eluted	<0.00028%
Rh release/surface	<0.0031 mg/m²

palladium monoxide, 2 g/L (=1.6 m²/L surface loading), 2h gastric, pH 1.5
Palladium	x(avg) +/- s(between)	CV
dissolution	<0.5 µg/L	-
absolute Rh release	<0.00025 mg/g	-
% of total available Rh eluted	<0.000028%
Rh release/surface	<0.0031 mg/m²

The blank control vessels during the test showed no concentrations of palladium above the limit of quantification (i.e. reporting limit) (i.e. 0.5 μg/L Pd).

The following observations could be made in the test vessels with a loading of 0.2 g/L palladium monoxide:

 Remaining test item (dark grey particles) could be observed on the filter and in the Erlenmeyer flasks at the end of the experiment.

 An average dissolved palladium concentration of <0.5 μg/L Pd (or <0.0025 mg/g test item) was measured after 2 hours of exposure to the simulated gastric fluid (pH 1.5).

The following observations could be made in the test vessels with a loading of 2 g/L palladium monoxide:

 Remaining test item (dark grey particles) could be observed on the filter and in the Erlenmeyer flasks at the end of the experiment.

 An average dissolved palladium concentration of <0.5 μg/L Pd (or <0.00025 mg/g test item) was measured after 2 hours of exposure to the simulated gastric fluid (pH 1.5).

Based on the specific surface area of palladium monoxide (0.8 m²/g test item) a palladium release per surface of <0.0031 mg/m² (0.2 g/L loading) and <0.00031 mg/m² (2 g/L loading) was calculated.

Based on the palladium content of the test item (i.e. 88.31 %) and the average dissolved palladium concentration, a palladium release of <0.00028 % (0.2 g/L loading) and <0.000028 % (2 g/L loading) could be calculated at the 2 hours endpoint.

The following deviations from the SOP were made:

1/ The particle size exceeded the <100 μm requirement as mentioned in the test guidance. No further preparation of the test item was performed to test the natural state of the test item.

2/ The samples were preserved by adding 0.12 mL concentrated HNO3 per 12 mL instead of no preservation in the SOP.

Applicant's summary and conclusion

Conclusions:

During this study on palladium monoxide at a loading of 0.2 g/L and 2 g/L in simulated gastric fluid (pH 1.5), it was shown that for palladium an average value of <0.5 μg/L Pd was found after 2 hours of extraction, corresponding with a palladium release of <0.00028 % (0.2 g/L loading) or <0.000028 % (2 g/L loading).
The results can be assumed reliable since the test conditions stayed constant during the experiment.

Executive summary:

A study to estimate bioelution characteristics has been conducted according to the recommended Standard Operating Procedure (SOP) for Bioelution Testing of Metals, Inorganic Metal Compounds, and Metal-Containing Complex Materials: Simulated Gastric Fluid (Eurometaux, February 2018) which is based on ASTM D5517-07: Standard Test method for determining the extractability of metals from art materials - ASTM, 2007 (American Society for Testing and Materials). Bio-elution refers to the in vitro extraction methods used to measure the degree to which a substance (e.g., metal or mineral ion) is dissolved in artificial biological fluids. Simulated biological fluids represent relevant exposure routes. The resulting value is the “bio-accessibility”, and is defined as the “fraction of a substance that is soluble under physiological conditions and therefore potentially available for absorption into systemic circulation”.

The extent of dissolution of palladium monoxide was tested in a simulated gastric fluid at 37 °C and pH 1.5 for 2 hours (0.2 g/L and 2 g/L loading) at an agitation speed of 100 revolutions per minute (rpm) for 1 hour followed by 1 hour of settling (without shaking). The bio-elution endpoints were based on the dissolved palladium (Pd) concentrations obtained after 2 hours of extraction.

In the blank corrected test item vessels, the following average dissolved palladium concentration was measured after 2 hours of exposure to the simulated gastric fluid (pH 1.5) for both loadings:

<0.5 μg/L Pd.

Based on the specific surface area of palladium monoxide (i.e. 0.8 m²/g), this corresponds with a palladium release per surface of <0.0031 mg/m² Pd (0.2 g/L loading) and <0.00031 mg/m² (2 g/L loading).

Based on the palladium content (i.e. 88.31 %) in the test item and the average dissolved palladium concentrations in the test solutions, a palladium release of <0.00028 % (0.2 g/L loading) and <0.000028 % (2 g/L loading) could be calculated at the 2 hours endpoint.