Palladium

Endpoint summary

Description of key information

In an open epicutaneous test (OET) skin sensitisation study in guinea pigs, conducted according to OECD Test Guideline 406 and to GLP, 24-hr semi-occlusive applications of 0.71 g palladium metal to moistened skin for three days each week for 4 weeks produced no signs of skin irritation (Arcelin, 1992).

Palladium is also considered to fall within the scope of the read-across category of Palladium, Palladium monoxide and Palladium dihydroxide.

In in vitro studies according to OECD431 and OECD439, Palladium dihydroxide was shown to be non corrosive and non-irritant to skin according to UN GHS and EU CLP regulation.

Palladium monoxide was not irritant in a limited (pre-GLP) study, involving 24-hr occluded application to the intact and abraded skin of 6 male rabbits.

No relevant eye or respiratory tract irritation data were identified for palladium. According to an expert review of an unpublished eye irritation study, conducted to US guidelines (CFR 21, part 191 12), a single instillation of palladium monoxide (100 mg) to the eyes of six rabbits produced no signs of irritation.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Reference 1

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

8 Oct 2020-18 Nov 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: MatTek Corporation Protocol: In vitro EpiDermTM Skin Irritation Test (EPI-200-SIT) For use with MatTek Corporation’s Reconstructed Human Epidermal Model EpiDerm (EPI-200-SIT); Version 10 February 2019

Qualifier:

according to guideline

Guideline:

EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)

Version / remarks:

6 July 2012

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test system:

human skin model

Remarks:

The EpiDerm™ tissue consists of normal, human-derived epidermal keratinocytes which have been cultured to form a multilayered, highly differentiated model of the human epidermis.

Source species:

human

Cell type:

other: EpiDerm™ tissue consists of organised basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo.

Vehicle:

unchanged (no vehicle)

Remarks:

The test item was crushed and ground in a mortar and with a pestle to improve the consistency. The test item was tested neat.

Details on test system:

Epi-200-SIT kits and MTT-100 assays are purchased from MatTek Corporation (82105 Bratislava, Slovakia). The EpiDerm™ tissue consists of normal, human-derived epidermal keratinocytes which have been cultured to form a multilayered, highly differentiated model of the human epidermis. It consists of organised basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo. The EpiDerm™ tissues (surface 0.6 cm²) are cultured on specially prepared cell culture inserts (MILLICELL, 10 mm ∅).
EpiDerm™ tissues are shipped with cool packs on medium-supplemented agarose gels in a 24-well plate. Including time in transit, tissues may be stored at 4 °C for up to 6 days prior to use.

Pre-Experiment
Test items which might absorb light in the same range as formazan dye (naturally or after treatment) and test items which might be able to directly reduce the vital dye MTT (to MTT formazan) may interfere with the tissue viability measurements and need the use of additional controls for corrections. Therefore, two pre-experiments were performed to determine the color interference and the MTT interference.

Option for the Main Experiment
Since the test item/ water or test item/ isopropanol solutions changed color significantly in the first pre-experiment and interfered with MTT in the second pre-experiment, the main experiment had to be performed with additional viable, freeze killed and an additional third set of controls in order to avoid double correction. These additional tissues were designated Non-Specific Killed Control (NSKC) and run in duplicates. They are freeze-killed tissues which were treated with the test item but incubated in medium without MTT solution in the MTT assay. At the end Data Correction Procedure III was performed.

Main Experiment
1 Pre-warming of EpiDerm™ Tissues
The plastic bag containing the 24-well plate with epidermal tissues was opened under sterile conditions. Under an airflow using forceps, the gauze was removed, and the inserts were taken out. Any remaining agarose that adheres to the outer sides of the inserts was removed by gentle blotting on the sterile filter paper or gauze and prior to the exposure of the test item and of the controls the EpiDerm™ tissues was inspected for quality:
It was taken care, that
• air bubbles between agarose and insert were not > 30% of the total surface,
• liquid on top of the insert was removed with sterile cotton tips,
• if again moisture was observed on top of the inserts after the pre-incubation or in case of visible defects the respective skin models was discarded.
The inserts with the EpiDerm™ tissues were transferred into 6-well-plates containing 0.9 ml assay medium and incubated for 60 minutes under standard conditions. Afterwards, the medium was changed and a further pre-incubation for 17 - 23 hours at standard incubation conditions follows.

2 Treatment
After pre-warming of the EpiDerm™ tissues was completed, the negative and positive control, and the test item was added atop the tissues. The test item respectively controls were tested in triplicate tissues with an exposure time of 60 minutes. Within this period the 6-well plates were placed in the incubator for 35 minutes at standard incubation conditions. In the remaining period the plates were placed in a sterile bench at room temperature until the end of treatment.
The test item was crushed and ground in a mortar and a pestle to improve the consistency. 25 mg (39.7 mg/cm2 according to guideline) of the test item was applied onto the surface of the tissue. The tissues were wetted with 25 μL DPBS prior to application.
At the end of the treatment interval the tissues were gently rinsed with PBS several times in order to remove any residual test material. Excess PBS was removed by gently shaking the inserts and blotting the bottom with blotting paper. Afterwards, the tissues were incubated in 0.9 mL of fresh assay medium for 24 hours. After this incubation period the medium was changed, and the tissues were incubated for another 18 ± 2 hours at standard incubation conditions. The complete incubation time was about 42 hours.

MTT-Assay
24-well plates were prepared with 300 μl MTT solution per well kept under standard conditions until required.
After the incubation period was completed, the tissues were transferred to the MTT-plates. After a 3 hour ± 5 minutes incubation period under standard conditions the tissues were rinsed with PBS and carefully dried with blotting paper.
The tissues were transferred into new 24-well plates containing 2 mL of extractant solution (isopropanol) in each well ensuring that the tissues were completely covered. The 24-well plates were sealed to minimise isopropanol evaporation. The formazan salt was extracted within 2-4 hours while shaking at room temperature.
At the end of the extraction period the inserts were pierced with an injection needle to allow the extract to run into the well from which the insert was taken, and the insert were discarded.
Per each tissue, 3 × 200 μL aliquots of the formazan solution were transferred into a 96-well, flat bottom, microtiter plate. 200 μL of isopropanol were added to the wells designated as blanks for 96-well plate.

Measurement
The optical density (OD570nm) was determined spectrophotometrically in duplicates by a microplate reader (Versamax® Molecular Devices). The absorbance values were determined using the software SoftMax Pro Enterprise (version 4.7.1).

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

30 μL of positive control or negative control, or25 mg test item were applied on triplicate tissues.

Duration of treatment / exposure:

The test item respectively controls were tested with an exposure time of 60 minutes.

Number of replicates:

The test item respectively controls were tested in triplicate tissues .

Irritation / corrosion parameter:

% tissue viability

Value:

78.94

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Interpretation of results:

GHS criteria not met

Conclusions:

In this study according to OECD439 and under the experimental conditions reported, Palladium dihydroxide is non-irritant to skin according to UN GHS and EU CLP regulation.

Executive summary:

This in vitro study in accordance with OECD439 was performed to assess the irritation potential of Palladium dihydroxide by means of the Human Skin Model Test with EpiDermTM tissue models.
The test item proved to be a MTT reducer in the MTT interference pre-experiment. Also, it dyed deionised water (pre-test for colour interference). Therefore, additional tests with freeze-killed tissues, viable tissues (without MTT addition) and non-specific killed controls (NSKC) had to be performed to determine correction factors for calculating the true viability in the main experiment.
Triplicate tissues of the human skin model EpiDerm™ were treated with the test item, the negative control (DPBS) or the positive control (5% SDS) for 60 minutes.
After treatment with the negative control the absorbance values were well within the required range of the acceptability criterion of mean OD ≥ 0.8 and ≤ 2.8 for the 60 minutes treatment interval, thus assuring the quality of the tissues.
Treatment with the positive control induced a sufficient decrease in the viability as compared to the negative control for the 60 minutes treatment interval, thus assuring the validity of the test system.
After exposure of the tissues to Palladium dihydroxide the mean relative viability value was 78.94% compared to the relative absorbance value of the negative control. This value is above the threshold for irritancy of ≤ 50%. Therefore, the test item is not considered to possess an irritant potential.
In conclusion, it can be stated that in this study and under the experimental conditions reported, Palladium dihydroxide is non-irritant to skin.

Reference 2

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11 Sept 2020-16 Dec 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: MatTek test protocol “In vitro EpiDermTM Skin Corrosion Test (EPI-200-SCT)”, 07 November 2014.

Qualifier:

according to guideline

Guideline:

EU Method B.40 (In Vitro Skin Corrosion: Transcutaneous Electrical Resistance Test (TER))

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 431 (In Vitro Skin Corrosion: Reconstructed Human Epidermis (RHE) Test Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test system:

human skin model

Remarks:

The EpiDerm™ tissue consists of normal, human-derived epidermal keratinocytes which have been cultured to form a multilayered, highly differentiated model of the human epidermis.

Source species:

human

Cell type:

other: The EpiDerm™ tissue consists of organised basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo.

Vehicle:

unchanged (no vehicle)

Remarks:

The test item was crushed and ground in a mortar and with a pestle to improve the consistency. The test item was tested neat.

Details on test system:

Reconstructed Human EpiDerm model purchased from MatTek
Epi-200 SCT kits and MTT-100 assays are purchased from MatTek Corporation (Bratislava, Slovakia). The EpiDerm™ tissue consists of normal, human-derived epidermal keratinocytes which have been cultured to form a multilayered, highly differentiated model of the human epidermis. It consists of organised basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo. The EpiDerm™ tissues (surface 0.6 cm²) are cultured on specially prepared cell culture inserts (MILLICELL, 10 mm ∅).
EpiDerm™ tissues are shipped on cool packs and on medium-supplemented agarose gels in a 24-well plate. Including time in transit, tissues may be stored at a specified storage for up to 6 days prior to use.

Standard Culture Conditions
Each incubation of the tissues was performed at 37 ± 1.5°C and 5 ± 0.5% CO2 in DMEM Medium.

Pre-Experiment
Test items which might absorb light in the same range as formazan dye (naturally or after treatment) and test items which might be able to directly reduce the vital dye MTT (to MTT formazan) may interfere with the tissue viability measurements and need the use of additional controls for corrections. Therefore, two pre-experiments, were performed to determine the color interference and the MTT interference.

Options for the Main Experiment
Since the test item/ water or test item/ isopropanol solutions change color significantly and interferes with MTT in the pre-experiment, the test had to be performed with the controls mentioned in version d of the General Study Plan. The following additional controls were necessary for Data Correction:
• DPBS treated tissues (NC_CC)
• Test item treated tissues (TI_CC)
• DPBS treated freeze-killed tissues (NC_KC)
• Test item treated freeze-killed tissues (TI_KC)
• Test item treated freeze-killed tissues (TI_NSKC)
In this experimental set-up, Data Correction Procedure III had to be performed.

Main Experiment
1 Pre-warming of EpiDerm™ Tissues
The plastic bag containing the 24-well plate with epidermal tissues was opened under sterile conditions. Under an airflow using forceps, the gauze was removed and the inserts were taken out. Any remaining agarose that adheres to the outer sides of the inserts was removed by gentle blotting on the sterile filter paper or gauze and prior to the exposure of the test item and of the controls the EpiDerm™ tissues was inspected for quality:
It was taken care, that
• air bubbles between agarose and insert were not > 30% of the total surface,
• liquid on top of the insert was removed with sterile cotton tips,
• if again moisture was observed on top of the inserts after the pre-incubation or in case of visible defects the respective skin models was discarded.
The inserts with the EpiDerm™ tissues were transferred into 6-well-plates containing 0.9 ml assay medium and incubated for approx. 18 h under standard conditions.

2 Treatment
After the pre-warming of the EpiDermTM tissues is completed, the DMEM-based medium in each well was replaced with 0.9 mL fresh assay medium.
The test item respectively controls were tested in duplicate tissues with exposure times of 3 ± 0.5 minutes and 60 ± 5 minutes. The 6-well plates for the 3 minutes exposure periods were stayed at room temperature in the sterile bench, the 6-well plates for the 60 minutes exposure period were incubated under standard conditions.
The tissues were wetted with 25 μL DPBS prior to application. Approximately 25 mg (39.7 mg/cm2 according to guideline) of the test item were applied onto the surface of the tissue.
At the end of the exposure period the tissues were removed from the 6-well plate and gently rinsed with PBS to remove any residual test material for several times. Excess PBS was removed by gently shaking the tissue insert and blotting the lower surface with blotting paper. The tissues were placed in the prepared holding plate until all tissues have been rinsed.

3 MTT Assay
24-well plates were prepared with 300 μl MTT solution (and only medium for the additional DPBS treated tissues (NC_CC), Test item treated tissues (TI_CC) and NSKC tissues) and kept under standard conditions until required.
Following rinsing, the tissue inserts were transferred from the holding plates to the MTT-plates. After a 3 hour incubation period under standard conditions the tissues were rinsed with PBS and carefully dried with blotting paper.
The tissues were transferred into new 24-well plates containing 2 mL of extractant solution (isopropanol) in each well ensuring that the tissues were completely covered. The 24-well plates were sealed to minimise isopropanol evaporation. The formazan salt was extracted for 4-72 h in the refrigerator at 2-8°C without shaking. At the end of the extraction period the inserts were pierced with an injection needle to allow the extract to run into the well from which the insert was taken, and the inserts were discarded. Subsequently, the plates were shaken for 15 min at room temperature. Additionally, the solution was homogenized by a pipette before transferred into a 96-well plate. Per each tissue, 3 × 200 μL aliquots of the formazan solution were transferred in a flat bottom, microtiter plate. 200 μL of isopropanol were added to the wells designated as blanks for 96-well plate.

Measurement
The optical density (OD570nm) of the formazan extract is determined spectrophotometrically by a microplate reader (Versamax® Molecular Devices). The absorbance values will be determined using the software SoftMax Pro Enterprise (version 4.7.1).

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

50 μL of the controls were applied to each set of duplicate tissues for the 3 min and 1 hour exposure periods.
Approximately 25 mg (39.7 mg/cm2 according to guideline) of the test item were applied onto the surface of the tissue.

Duration of treatment / exposure:

The test item respectively controls were tested with exposure times of 3 ± 0.5 minutes and 60 ± 5 minutes.

Number of replicates:

The test item respectively controls were tested in duplicate tissues.

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

60 min exposure

Value:

100.75

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3 min exposure

Value:

99.59

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Interpretation of results:

GHS criteria not met

Conclusions:

In this study in accordance with OECD431 and under the reported experimental conditions, Palladium dihydroxide is non-corrosive to skin according to EU CLP and UN GHS.

Executive summary:

This in vitro study in accordance with OECD 431 was performed to assess the corrosive potential of Palladium dihydroxide by means of the Human Skin Model Test with EpiDerm™ tissues models.
The test item reduced MTT (pre-test for direct MTT reduction), and it changed colour when mixed with deionised water (pre-test for colour interference). Consequently, additional tests with freeze-killed, viable tissues and Non-Specific Killed Tissues to determine correction factors for calculating the true viability in the main experiment were necessary.
Independent duplicate tissues of EpiDerm™ were exposed to either the test item, the negative control (Dulbecco's Phosphate-Buffered Saline (DPBS)) or the positive control (8.0 N KOH) for 3 minutes and 1 hour, respectively.
After exposure to the negative control the absorbance values met the required acceptability criterion of a mean OD570 ≥ 0.8 and ≤ 2.8 for both treatment intervals thereby confirming the acceptable quality of the tissues.
Exposure to the positive control induced a decrease in the relative absorbance as compared to the negative control, both for the 3 minutes exposure period (8.64%) and for the 1 hour exposure period (2.75%) thus confirming the validity of the test system and the specific batch of tissue models. The CV in the range 20 – 100% viability between the tissue replicates is ≤ 30%, thus the validity of the test system and the specific batch of the tissue models is confirmed.
After exposure of the tissues to the test item the relative absorbance value was 99.59% after 3 minutes exposure. After 1 hour exposure the relative absorbance value was 100.75%. Both values did not reach the threshold for corrosivity which is defined to be < 50% after the 3 minutes exposure or ≥ 50% after 3 minutes exposure and < 15% after the 1 hour exposure. Therefore, the test item is considered to be not corrosive.
In conclusion, it can be stated that in this study and under the reported experimental conditions, the test item Palladium dihydroxide is non-corrosive to skin according to EU CLP and UN GHS.
The required acceptability criteria were met.

Reference 3

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 September - 1 December 1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study (althought not specific to the assessment of dermal irritation, the data appear sufficient and scientifically reliable for this endpoint), to GLP

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 406 (Skin Sensitisation)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EU Method B.6 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Species:

guinea pig

Strain:

Himalayan

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: BRL, Biological Research Laboratories Ltd., Wolferstrasse 4, CH-4414 Fullinsdorf
- Age at study initiation: 7-8 weeks
- Weight at study initiation: 344-475 g
- Housing: Individually in type-3 wire-mesh cages
- Diet (e.g. ad libitum): Pelleted standard Kliba 342, Batches 71/92 and 72/92 guinea pig breeding/maintenance diet ("Kliba", Klingenthalmuhle AG, CH-4303 Kaiseraugst) ad libitum.
- Water (e.g. ad libitum): Community tap water from Fullinsdorf, ad libitum. Once weekly additional supply of ascorbic acid (1 g/L) via the drinking water.
- Acclimation period: One week under test conditions after veterinary examination. Only animals without any visual signs of illness were used for the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/-3
- Humidity (%): 40-70
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 21 September 1992 To: 5 November 1992

Type of coverage:

semiocclusive

Preparation of test site:

other: clipped and shaved

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent no treatment

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.71 g on average (test sites were moistened with bi-distilled water prior to each application)
- Concentration (if solution): No data

Duration of treatment / exposure:

Each application lasted 24 hours (semi-occlusive covering of application site). Applications were performed on 3 days each week for 4 weeks.

Observation period:

24 hours after each application (in the fourth week this was extended to 72 hours after the last removal of the dressings). For the challenge aplication, this was at 24, 48 and 72 hours.

Number of animals:

20

Details on study design:

TEST SITE
- Area of exposure: The test article was settled on a patch of gauze (2 x 2 cm) and applied to the right flanks of the guinea pigs.
- % coverage: No data
- Type of wrap if used: The patches were firmly secured by elastic plaster wound round the trunk and covered with impervious adhesive tape.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): Not conducted
- Time after start of exposure: 24 hours after each exposure the dressings were removed and the application sites were assessed immediately thereafter.

SCORING SYSTEM: 0 = no reaction; 1 = slight erythema (barely perceptible); 2 = well-defined erythema; 3 = strong/severe erythema to slight eschar formation

Irritation parameter:

erythema score

Basis:

mean

Time point:

other: Day 6

Score:

0

Max. score:

3

Reversibility:

other: not applicable

Remarks on result:

other: No evidence of erythema or eschar formation

Irritation parameter:

erythema score

Basis:

mean

Time point:

other: Day 13

Score:

0

Max. score:

3

Reversibility:

other: not applicable

Remarks on result:

other: No evidence of erythema or eschar formation

Irritation parameter:

erythema score

Basis:

mean

Time point:

other: Day 20

Score:

0

Max. score:

3

Reversibility:

other: not applicable

Remarks on result:

other: No evidence of erythema or eschar formation

Irritation parameter:

erythema score

Basis:

mean

Time point:

other: Day 29

Score:

0

Max. score:

3

Reversibility:

other: not applicable

Remarks on result:

other: No evidence of erythema or eschar formation

Irritation parameter:

erythema score

Basis:

mean

Time point:

other: Day 37

Score:

0

Max. score:

3

Reversibility:

other: not applicable

Remarks on result:

other: No evidence of erythema or eschar formation

Irritation parameter:

erythema score

Basis:

mean

Time point:

other: Day 38

Score:

0

Max. score:

3

Reversibility:

other: not applicable

Remarks on result:

other: No evidence of erythema or eschar formation

Irritation parameter:

erythema score

Basis:

mean

Time point:

other: Day 39

Score:

0

Max. score:

3

Reversibility:

other: not applicable

Remarks on result:

other: No evidence of erythema or eschar formation

Irritant / corrosive response data:

No erythema or eschar formation was observed during the four induction weeks in the test group, or in the control and test groups 3 days after the challenge exposure.

Other effects:

One animal died spontaneously on test day 17. Necropsy revealed macroscopic findings in the lungs (many gray-white foci in parenchyma).

Two control animals and five test animals lost weight (6.5-9.2% and 1.2-20.6%, respectively) during the acclimatisation period. One test animal lost weight (up to 2.7%) during the entire study (acclimatisation and treatment period). These bodyweight differences were "considered to be of incidental nature".

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

In an open epicutaneous test (OET) skin sensitisation study in guinea pigs, conducted according to OECD Test Guideline 406 and to GLP, 24-hr semi-occlusive applications of 0.71 g test material to moistened skin for three days each week for 4 weeks produced no signs of skin irritation.

Executive summary:

In a GLP open epicutaneous test (OET) skin sensitisation study in guinea pigs, conducted according to OECD Test Guideline 406, neat palladium (0.71 g) was applied (semi-occluded) to the clipped, shaved skin of twenty female guinea pigs on three days each week for 4 weeks. Patches were removed 24-hr after each application and the skin sites were assessed immediately for erythema (and eschar) formation. These sites were again assessed 24, 48 and 72 hours after a challenge exposure, administered one week after the last reading from the induction exposure period.

No erythema or eschar formation was observed during the 4-week induction period. Residual test material was not washed off the skin during this period. No classification for skin irritancy is required according to EU CLP criteria (EC 1272/2008), based on the results of this OET study (primarily designed to assess skin sensitising potential).

Reference 4

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

8 Oct 2020-18 Nov 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Substance considered to fall within the scope of the read-across category 'Palladium, Palladium monoxide and Palladium dihydroxide'

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

other: MatTek Corporation Protocol: In vitro EpiDermTM Skin Irritation Test (EPI-200-SIT) For use with MatTek Corporation’s Reconstructed Human Epidermal Model EpiDerm (EPI-200-SIT); Version 10 February 2019

Qualifier:

according to guideline

Guideline:

EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)

Version / remarks:

6 July 2012

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test system:

human skin model

Remarks:

The EpiDerm™ tissue consists of normal, human-derived epidermal keratinocytes which have been cultured to form a multilayered, highly differentiated model of the human epidermis.

Source species:

human

Cell type:

other: EpiDerm™ tissue consists of organised basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo.

Vehicle:

unchanged (no vehicle)

Remarks:

The test item was crushed and ground in a mortar and with a pestle to improve the consistency. The test item was tested neat.

Details on test system:

Epi-200-SIT kits and MTT-100 assays are purchased from MatTek Corporation (82105 Bratislava, Slovakia). The EpiDerm™ tissue consists of normal, human-derived epidermal keratinocytes which have been cultured to form a multilayered, highly differentiated model of the human epidermis. It consists of organised basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo. The EpiDerm™ tissues (surface 0.6 cm²) are cultured on specially prepared cell culture inserts (MILLICELL, 10 mm ∅).
EpiDerm™ tissues are shipped with cool packs on medium-supplemented agarose gels in a 24-well plate. Including time in transit, tissues may be stored at 4 °C for up to 6 days prior to use.

Pre-Experiment
Test items which might absorb light in the same range as formazan dye (naturally or after treatment) and test items which might be able to directly reduce the vital dye MTT (to MTT formazan) may interfere with the tissue viability measurements and need the use of additional controls for corrections. Therefore, two pre-experiments were performed to determine the color interference and the MTT interference.

Option for the Main Experiment
Since the test item/ water or test item/ isopropanol solutions changed color significantly in the first pre-experiment and interfered with MTT in the second pre-experiment, the main experiment had to be performed with additional viable, freeze killed and an additional third set of controls in order to avoid double correction. These additional tissues were designated Non-Specific Killed Control (NSKC) and run in duplicates. They are freeze-killed tissues which were treated with the test item but incubated in medium without MTT solution in the MTT assay. At the end Data Correction Procedure III was performed.

Main Experiment
1 Pre-warming of EpiDerm™ Tissues
The plastic bag containing the 24-well plate with epidermal tissues was opened under sterile conditions. Under an airflow using forceps, the gauze was removed, and the inserts were taken out. Any remaining agarose that adheres to the outer sides of the inserts was removed by gentle blotting on the sterile filter paper or gauze and prior to the exposure of the test item and of the controls the EpiDerm™ tissues was inspected for quality:
It was taken care, that
• air bubbles between agarose and insert were not > 30% of the total surface,
• liquid on top of the insert was removed with sterile cotton tips,
• if again moisture was observed on top of the inserts after the pre-incubation or in case of visible defects the respective skin models was discarded.
The inserts with the EpiDerm™ tissues were transferred into 6-well-plates containing 0.9 ml assay medium and incubated for 60 minutes under standard conditions. Afterwards, the medium was changed and a further pre-incubation for 17 - 23 hours at standard incubation conditions follows.

2 Treatment
After pre-warming of the EpiDerm™ tissues was completed, the negative and positive control, and the test item was added atop the tissues. The test item respectively controls were tested in triplicate tissues with an exposure time of 60 minutes. Within this period the 6-well plates were placed in the incubator for 35 minutes at standard incubation conditions. In the remaining period the plates were placed in a sterile bench at room temperature until the end of treatment.
The test item was crushed and ground in a mortar and a pestle to improve the consistency. 25 mg (39.7 mg/cm2 according to guideline) of the test item was applied onto the surface of the tissue. The tissues were wetted with 25 μL DPBS prior to application.
At the end of the treatment interval the tissues were gently rinsed with PBS several times in order to remove any residual test material. Excess PBS was removed by gently shaking the inserts and blotting the bottom with blotting paper. Afterwards, the tissues were incubated in 0.9 mL of fresh assay medium for 24 hours. After this incubation period the medium was changed, and the tissues were incubated for another 18 ± 2 hours at standard incubation conditions. The complete incubation time was about 42 hours.

MTT-Assay
24-well plates were prepared with 300 μl MTT solution per well kept under standard conditions until required.
After the incubation period was completed, the tissues were transferred to the MTT-plates. After a 3 hour ± 5 minutes incubation period under standard conditions the tissues were rinsed with PBS and carefully dried with blotting paper.
The tissues were transferred into new 24-well plates containing 2 mL of extractant solution (isopropanol) in each well ensuring that the tissues were completely covered. The 24-well plates were sealed to minimise isopropanol evaporation. The formazan salt was extracted within 2-4 hours while shaking at room temperature.
At the end of the extraction period the inserts were pierced with an injection needle to allow the extract to run into the well from which the insert was taken, and the insert were discarded.
Per each tissue, 3 × 200 μL aliquots of the formazan solution were transferred into a 96-well, flat bottom, microtiter plate. 200 μL of isopropanol were added to the wells designated as blanks for 96-well plate.

Measurement
The optical density (OD570nm) was determined spectrophotometrically in duplicates by a microplate reader (Versamax® Molecular Devices). The absorbance values were determined using the software SoftMax Pro Enterprise (version 4.7.1).

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

30 μL of positive control or negative control, or25 mg test item were applied on triplicate tissues.

Duration of treatment / exposure:

The test item respectively controls were tested with an exposure time of 60 minutes.

Number of replicates:

The test item respectively controls were tested in triplicate tissues .

Irritation / corrosion parameter:

% tissue viability

Value:

78.94

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Interpretation of results:

GHS criteria not met

Conclusions:

In this study according to OECD439 and under the experimental conditions reported, Palladium dihydroxide is non-irritant to skin according to UN GHS and EU CLP regulation.

Executive summary:

This in vitro study in accordance with OECD439 was performed to assess the irritation potential of Palladium dihydroxide by means of the Human Skin Model Test with EpiDermTM tissue models.
The test item proved to be a MTT reducer in the MTT interference pre-experiment. Also, it dyed deionised water (pre-test for colour interference). Therefore, additional tests with freeze-killed tissues, viable tissues (without MTT addition) and non-specific killed controls (NSKC) had to be performed to determine correction factors for calculating the true viability in the main experiment.
Triplicate tissues of the human skin model EpiDerm™ were treated with the test item, the negative control (DPBS) or the positive control (5% SDS) for 60 minutes.
After treatment with the negative control the absorbance values were well within the required range of the acceptability criterion of mean OD ≥ 0.8 and ≤ 2.8 for the 60 minutes treatment interval, thus assuring the quality of the tissues.
Treatment with the positive control induced a sufficient decrease in the viability as compared to the negative control for the 60 minutes treatment interval, thus assuring the validity of the test system.
After exposure of the tissues to Palladium dihydroxide the mean relative viability value was 78.94% compared to the relative absorbance value of the negative control. This value is above the threshold for irritancy of ≤ 50%. Therefore, the test item is not considered to possess an irritant potential.
In conclusion, it can be stated that in this study and under the experimental conditions reported, Palladium dihydroxide is non-irritant to skin.

The substance is considered to fall within the scope of the read-across category 'Palladium, Palladium monoxide and Palladium dihydroxide'

Reference 5

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

11 Sept 2020-16 Dec 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Substance considered to fall within the scope of the read-across category 'Palladium, Palladium monoxide and Palladium dihydroxide'

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

other: MatTek test protocol “In vitro EpiDermTM Skin Corrosion Test (EPI-200-SCT)”, 07 November 2014.

Qualifier:

according to guideline

Guideline:

EU Method B.40 (In Vitro Skin Corrosion: Transcutaneous Electrical Resistance Test (TER))

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 431 (In Vitro Skin Corrosion: Reconstructed Human Epidermis (RHE) Test Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test system:

human skin model

Remarks:

The EpiDerm™ tissue consists of normal, human-derived epidermal keratinocytes which have been cultured to form a multilayered, highly differentiated model of the human epidermis.

Source species:

human

Cell type:

other: The EpiDerm™ tissue consists of organised basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo.

Vehicle:

unchanged (no vehicle)

Remarks:

The test item was crushed and ground in a mortar and with a pestle to improve the consistency. The test item was tested neat.

Details on test system:

Reconstructed Human EpiDerm model purchased from MatTek
Epi-200 SCT kits and MTT-100 assays are purchased from MatTek Corporation (Bratislava, Slovakia). The EpiDerm™ tissue consists of normal, human-derived epidermal keratinocytes which have been cultured to form a multilayered, highly differentiated model of the human epidermis. It consists of organised basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo. The EpiDerm™ tissues (surface 0.6 cm²) are cultured on specially prepared cell culture inserts (MILLICELL, 10 mm ∅).
EpiDerm™ tissues are shipped on cool packs and on medium-supplemented agarose gels in a 24-well plate. Including time in transit, tissues may be stored at a specified storage for up to 6 days prior to use.

Standard Culture Conditions
Each incubation of the tissues was performed at 37 ± 1.5°C and 5 ± 0.5% CO2 in DMEM Medium.

Pre-Experiment
Test items which might absorb light in the same range as formazan dye (naturally or after treatment) and test items which might be able to directly reduce the vital dye MTT (to MTT formazan) may interfere with the tissue viability measurements and need the use of additional controls for corrections. Therefore, two pre-experiments, were performed to determine the color interference and the MTT interference.

Options for the Main Experiment
Since the test item/ water or test item/ isopropanol solutions change color significantly and interferes with MTT in the pre-experiment, the test had to be performed with the controls mentioned in version d of the General Study Plan. The following additional controls were necessary for Data Correction:
• DPBS treated tissues (NC_CC)
• Test item treated tissues (TI_CC)
• DPBS treated freeze-killed tissues (NC_KC)
• Test item treated freeze-killed tissues (TI_KC)
• Test item treated freeze-killed tissues (TI_NSKC)
In this experimental set-up, Data Correction Procedure III had to be performed.

Main Experiment
1 Pre-warming of EpiDerm™ Tissues
The plastic bag containing the 24-well plate with epidermal tissues was opened under sterile conditions. Under an airflow using forceps, the gauze was removed and the inserts were taken out. Any remaining agarose that adheres to the outer sides of the inserts was removed by gentle blotting on the sterile filter paper or gauze and prior to the exposure of the test item and of the controls the EpiDerm™ tissues was inspected for quality:
It was taken care, that
• air bubbles between agarose and insert were not > 30% of the total surface,
• liquid on top of the insert was removed with sterile cotton tips,
• if again moisture was observed on top of the inserts after the pre-incubation or in case of visible defects the respective skin models was discarded.
The inserts with the EpiDerm™ tissues were transferred into 6-well-plates containing 0.9 ml assay medium and incubated for approx. 18 h under standard conditions.

2 Treatment
After the pre-warming of the EpiDermTM tissues is completed, the DMEM-based medium in each well was replaced with 0.9 mL fresh assay medium.
The test item respectively controls were tested in duplicate tissues with exposure times of 3 ± 0.5 minutes and 60 ± 5 minutes. The 6-well plates for the 3 minutes exposure periods were stayed at room temperature in the sterile bench, the 6-well plates for the 60 minutes exposure period were incubated under standard conditions.
The tissues were wetted with 25 μL DPBS prior to application. Approximately 25 mg (39.7 mg/cm2 according to guideline) of the test item were applied onto the surface of the tissue.
At the end of the exposure period the tissues were removed from the 6-well plate and gently rinsed with PBS to remove any residual test material for several times. Excess PBS was removed by gently shaking the tissue insert and blotting the lower surface with blotting paper. The tissues were placed in the prepared holding plate until all tissues have been rinsed.

3 MTT Assay
24-well plates were prepared with 300 μl MTT solution (and only medium for the additional DPBS treated tissues (NC_CC), Test item treated tissues (TI_CC) and NSKC tissues) and kept under standard conditions until required.
Following rinsing, the tissue inserts were transferred from the holding plates to the MTT-plates. After a 3 hour incubation period under standard conditions the tissues were rinsed with PBS and carefully dried with blotting paper.
The tissues were transferred into new 24-well plates containing 2 mL of extractant solution (isopropanol) in each well ensuring that the tissues were completely covered. The 24-well plates were sealed to minimise isopropanol evaporation. The formazan salt was extracted for 4-72 h in the refrigerator at 2-8°C without shaking. At the end of the extraction period the inserts were pierced with an injection needle to allow the extract to run into the well from which the insert was taken, and the inserts were discarded. Subsequently, the plates were shaken for 15 min at room temperature. Additionally, the solution was homogenized by a pipette before transferred into a 96-well plate. Per each tissue, 3 × 200 μL aliquots of the formazan solution were transferred in a flat bottom, microtiter plate. 200 μL of isopropanol were added to the wells designated as blanks for 96-well plate.

Measurement
The optical density (OD570nm) of the formazan extract is determined spectrophotometrically by a microplate reader (Versamax® Molecular Devices). The absorbance values will be determined using the software SoftMax Pro Enterprise (version 4.7.1).

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

50 μL of the controls were applied to each set of duplicate tissues for the 3 min and 1 hour exposure periods.
Approximately 25 mg (39.7 mg/cm2 according to guideline) of the test item were applied onto the surface of the tissue.

Duration of treatment / exposure:

The test item respectively controls were tested with exposure times of 3 ± 0.5 minutes and 60 ± 5 minutes.

Number of replicates:

The test item respectively controls were tested in duplicate tissues.

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

60 min exposure

Value:

100.75

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3 min exposure

Value:

99.59

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Interpretation of results:

GHS criteria not met

Conclusions:

In this study in accordance with OECD431 and under the reported experimental conditions, Palladium dihydroxide is non-corrosive to skin according to EU CLP and UN GHS.

Executive summary:

This in vitro study in accordance with OECD 431 was performed to assess the corrosive potential of Palladium dihydroxide by means of the Human Skin Model Test with EpiDerm™ tissues models.
The test item reduced MTT (pre-test for direct MTT reduction), and it changed colour when mixed with deionised water (pre-test for colour interference). Consequently, additional tests with freeze-killed, viable tissues and Non-Specific Killed Tissues to determine correction factors for calculating the true viability in the main experiment were necessary.
Independent duplicate tissues of EpiDerm™ were exposed to either the test item, the negative control (Dulbecco's Phosphate-Buffered Saline (DPBS)) or the positive control (8.0 N KOH) for 3 minutes and 1 hour, respectively.
After exposure to the negative control the absorbance values met the required acceptability criterion of a mean OD570 ≥ 0.8 and ≤ 2.8 for both treatment intervals thereby confirming the acceptable quality of the tissues.
Exposure to the positive control induced a decrease in the relative absorbance as compared to the negative control, both for the 3 minutes exposure period (8.64%) and for the 1 hour exposure period (2.75%) thus confirming the validity of the test system and the specific batch of tissue models. The CV in the range 20 – 100% viability between the tissue replicates is ≤ 30%, thus the validity of the test system and the specific batch of the tissue models is confirmed.
After exposure of the tissues to the test item the relative absorbance value was 99.59% after 3 minutes exposure. After 1 hour exposure the relative absorbance value was 100.75%. Both values did not reach the threshold for corrosivity which is defined to be < 50% after the 3 minutes exposure or ≥ 50% after 3 minutes exposure and < 15% after the 1 hour exposure. Therefore, the test item is considered to be not corrosive.
In conclusion, it can be stated that in this study and under the reported experimental conditions, the test item Palladium dihydroxide is non-corrosive to skin according to EU CLP and UN GHS.
The required acceptability criteria were met.

The substance is considered to fall within the scope of the read-across category 'Palladium, Palladium monoxide and Palladium dihydroxide'

Reference 6

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not stated in paper, but submitted for publication in 1974

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Although the study is not conducted to a modern protocol and is somewhat limited, it is nevertheless fairly well documented and scientifically acceptable

Qualifier:

no guideline followed

Principles of method if other than guideline:

Dermal irritancy asessed using male albino rabbits using procedures and evaluation criteria adopted from those in use by the National Institute for Occupational Safety and Health, ... a modification of the official Food and Drug Administration procedure [1973]"

GLP compliance:

no

Remarks:

prior to GLP

Species:

rabbit

Strain:

other: albino

Details on test animals or test system and environmental conditions:

no data

Type of coverage:

occlusive

Preparation of test site:

other: Pairs of test sites, each 2 cm x 2 cm, on the closely clipped dorsolaterals aspects of each animal, one side abraded and the other side intact

Vehicle:

water

Remarks:

0.1 ml

Controls:

yes, concurrent vehicle

Amount / concentration applied:

0.1 g

Duration of treatment / exposure:

24 hours

Observation period:

skin reactions scored immediately on removal of patch and 48 hours later

Number of animals:

Total of 6 rabbits, with up to 7 pairs of test sites each, used to test 14 test substances, some substances tested more than once

Details on study design:

Pairs of test sites, each 2 cm x 2 cm, on the closely clipped dorsolaterals aspects of each animal, one side abraded and the other side intact; Test substances in solid (powder) state were mixed with water (0.1 g quantity mixed with 0.1 ml deionised water) and spread over each site; after application of test substances [several probably tested simultaneously on each animal], test sites occluded; 24 hours later, coverings removed and test sites gently washed with soap, rinsed and dried; skin reactions scored immediately and 48 hours later; evaluation on a grading scale from 0 to 4 [similar to Draize scale]

Irritation parameter:

overall irritation score

Basis:

mean

Remarks:

single test rating or average of two or three

Time point:

other: 24 and 72 hours

Score:

0

Max. score:

4

Remarks on result:

other: Severity rating for both intact and abraded skin sites

Irritant / corrosive response data:

Average skin reaction for 24 and 72 hours after the start of treatment calculated for intact and abraded skin [no individual scores or any further information presented in paper]

Interpretation of results:

GHS criteria not met

Conclusions:

Palladium monoxide was not irritant in a limited (pre-GLP) study, involving 24-hr occluded application to the intact and abraded skin of 6 male rabbits.

Executive summary:

In a pre-GLP study, the dermal irritancy of 14 materials, including palladium monoxide, was assessed in albino rabbits. Test materials, mixed with water, were applied to intact and abraded skin of 6 male albino rabbits as 24-hour occluded patches. Coverings were then removed and sites scored immediately and 48 hours later, using a scale from 0 (non-irritant) to 4 (corrosive).

Palladium monoxide failed to give any indication of irritation (score 0) on both intact and abraded skin (mean of reactions at 24 and 72 hours).

Reference 7

Endpoint:

skin irritation: in vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

not stated in paper, but submitted for publication in 1974

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Although the study is not conducted to a modern protocol and is somewhat limited, it is nevertheless fairly well documented and scientifically acceptable

Justification for type of information:

Substance considered to fall within the scope of the read-across category 'Palladium, Palladium monoxide and Palladium dihydroxide'

Reason / purpose for cross-reference:

read-across source

Qualifier:

no guideline followed

Principles of method if other than guideline:

Dermal irritancy asessed using male albino rabbits using procedures and evaluation criteria adopted from those in use by the National Institute for Occupational Safety and Health, ... a modification of the official Food and Drug Administration procedure [1973]"

GLP compliance:

no

Remarks:

prior to GLP

Species:

rabbit

Strain:

other: albino

Details on test animals or test system and environmental conditions:

no data

Type of coverage:

occlusive

Preparation of test site:

other: Pairs of test sites, each 2 cm x 2 cm, on the closely clipped dorsolaterals aspects of each animal, one side abraded and the other side intact

Vehicle:

water

Remarks:

0.1 ml

Controls:

yes, concurrent vehicle

Amount / concentration applied:

0.1 g

Duration of treatment / exposure:

24 hours

Observation period:

skin reactions scored immediately on removal of patch and 48 hours later

Number of animals:

Total of 6 rabbits, with up to 7 pairs of test sites each, used to test 14 test substances, some substances tested more than once

Details on study design:

Pairs of test sites, each 2 cm x 2 cm, on the closely clipped dorsolaterals aspects of each animal, one side abraded and the other side intact; Test substances in solid (powder) state were mixed with water (0.1 g quantity mixed with 0.1 ml deionised water) and spread over each site; after application of test substances [several probably tested simultaneously on each animal], test sites occluded; 24 hours later, coverings removed and test sites gently washed with soap, rinsed and dried; skin reactions scored immediately and 48 hours later; evaluation on a grading scale from 0 to 4 [similar to Draize scale]

Irritation parameter:

overall irritation score

Basis:

mean

Remarks:

single test rating or average of two or three

Time point:

other: 24 and 72 hours

Score:

0

Max. score:

4

Remarks on result:

other: Severity rating for both intact and abraded skin sites

Irritant / corrosive response data:

Average skin reaction for 24 and 72 hours after the start of treatment calculated for intact and abraded skin [no individual scores or any further information presented in paper]

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: other: evaluation criteria adopted from those in use by the National Institute for Occupational Safety and Health

Conclusions:

Palladium monoxide was not irritant in a limited (pre-GLP) study, involving 24-hr occluded application to the intact and abraded skin of 6 male rabbits.

Executive summary:

In a pre-GLP study, the dermal irritancy of 14 materials, including palladium monoxide, was assessed in albino rabbits. Test materials, mixed with water, were applied to intact and abraded skin of 6 male albino rabbits as 24-hour occluded patches. Coverings were then removed and sites scored immediately and 48 hours later, using a scale from 0 (non-irritant) to 4 (corrosive).

Palladium monoxide failed to give any indication of irritation (score 0) on both intact and abraded skin (mean of reactions at 24 and 72 hours).

The substance is considered to fall within the scope of the read-across category 'Palladium, Palladium monoxide and Palladium dihydroxide'

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Reference 1

Endpoint:

eye irritation: in vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

No data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: US CFR guideline study, pre-GLP, with limited reporting.

Justification for type of information:

Substance considered to fall within the scope of the read-across category 'Palladium, Palladium monoxide and Palladium dihydroxide'

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

other: CFR 21, part 191 12 (revised as of April 1, 1973)

Deviations:

no

GLP compliance:

no

Remarks:

(prior to GLP)

Species:

rabbit

Strain:

not specified

Details on test animals or tissues and environmental conditions:

Albino rabbits with no known ocular abnormalities.

Vehicle:

not specified

Controls:

other: The left eye of each animal served as a control.

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 100 mg (deposited on the eye surface)

Duration of treatment / exposure:

Presumably the observation period

Observation period (in vivo):

3 days

Number of animals or in vitro replicates:

6

Details on study design:

REMOVAL OF TEST SUBSTANCE: Not removed

SCORING SYSTEM: No data

TOOL USED TO ASSESS SCORE: No data

Irritation parameter:

other: Number of animals showing irritant reactions

Basis:

other: Total number of test animals

Time point:

other: 24 hours

Score:

0

Max. score:

6

Reversibility:

other: Not applicable

Irritation parameter:

other: Number of animals showing irritant reactions

Basis:

other: Total number of test animals

Time point:

other: 48 hours

Score:

0

Max. score:

6

Reversibility:

other: Not applicable

Irritation parameter:

other: Number of animals showing irritant reactions

Basis:

other: Total number of test animals

Time point:

other: 72 hours

Score:

0

Max. score:

6

Reversibility:

other: Not applicable

Irritant / corrosive response data:

No corrosive conjunctival lesions or severe inflammation of the cornea and anterior chamber of the eyes

Other effects:

In one animal, the test material was still present in the conjunctival sac at the end of the observation period, but was completely covered with a thick mucous material.

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

According to an expert review of an unpublished eye irritation study, conducted to US guidelines (CFR 21, part 191 12), a single instillation of palladium monoxide (100 mg) to the eyes of six rabbits produced no signs of irritation.

Executive summary:

According to an expert review of an unpublished eye irritation study, conducted to US test guidelines (CFR 21, part 191 12), palladium monoxide (100 mg) was instilled into one eye of each of six rabbits. The other eye remained untreated and acted as the control. The treated eye was then assessed for ocular inflammation 24, 48 and 72 hr after application. No reaction was noted in any of the six animals, indicating that the test material was not irritating.

 Based on the results of this study, palladium monoxide should not be classified for eye irritation according to EU CLP criteria (EC 1272/2008).

The substance is considered to fall within the scope of the read-across category 'Palladium, Palladium monoxide and Palladium dihydroxide'

Reference 2

Endpoint:

eye irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: US CFR guideline study, pre-GLP, with limited reporting.

Qualifier:

according to guideline

Guideline:

other: CFR 21, part 191 12 (revised as of April 1, 1973)

Deviations:

no

GLP compliance:

no

Remarks:

(prior to GLP)

Species:

rabbit

Strain:

not specified

Details on test animals or tissues and environmental conditions:

Albino rabbits with no known ocular abnormalities.

Vehicle:

not specified

Controls:

other: The left eye of each animal served as a control.

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 100 mg (deposited on the eye surface)

Duration of treatment / exposure:

Presumably the observation period

Observation period (in vivo):

3 days

Number of animals or in vitro replicates:

6

Details on study design:

REMOVAL OF TEST SUBSTANCE: Not removed

SCORING SYSTEM: No data

TOOL USED TO ASSESS SCORE: No data

Irritation parameter:

other: Number of animals showing irritant reactions

Basis:

other: Total number of test animals

Time point:

other: 24 hours

Score:

0

Max. score:

6

Reversibility:

other: Not applicable

Irritation parameter:

other: Number of animals showing irritant reactions

Basis:

other: Total number of test animals

Time point:

other: 48 hours

Score:

0

Max. score:

6

Reversibility:

other: Not applicable

Irritation parameter:

other: Number of animals showing irritant reactions

Basis:

other: Total number of test animals

Time point:

other: 72 hours

Score:

0

Max. score:

6

Reversibility:

other: Not applicable

Irritant / corrosive response data:

No corrosive conjunctival lesions or severe inflammation of the cornea and anterior chamber of the eyes

Other effects:

In one animal, the test material was still present in the conjunctival sac at the end of the observation period, but was completely covered with a thick mucous material.

Interpretation of results:

GHS criteria not met

Conclusions:

According to an expert review of an unpublished eye irritation study, conducted to US guidelines (CFR 21, part 191 12), a single instillation of palladium monoxide (100 mg) to the eyes of six rabbits produced no signs of irritation.

Executive summary:

According to an expert review of an unpublished eye irritation study, conducted to US test guidelines (CFR 21, part 191 12), palladium monoxide (100 mg) was instilled into one eye of each of six rabbits. The other eye remained untreated and acted as the control. The treated eye was then assessed for ocular inflammation 24, 48 and 72 hr after application. No reaction was noted in any of the six animals, indicating that the test material was not irritating.

 

Based on the results of this study, palladium monoxide should not be classified for eye irritation according to EU CLP criteria (EC 1272/2008).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

No relevant irritation/corrosion human data were identified for palladium.

 

Reliable in vivo skin study data are available. In a GLP open epicutaneous test (OET) skin sensitisation study in guinea pigs, conducted according to OECD Test Guideline 406, neat palladium (0.71 g) was applied (semi-occluded) to the clipped, shaved skin of 20 female guinea pigs on three days each week for 4 weeks. Patches were removed 24 hr after each application and the skin sites were assessed immediately for erythema (and eschar) formation. These sites were assessed again 24, 48 and 72 hours after a challenge exposure, administered one week after the last reading from the induction exposure period. No erythema or eschar formation was observed during the 4-week induction period. Residual test material was not washed off the skin during this period (Arcelin, 1992). No classification for skin irritancy is required according to EU CLP criteria (EC 1272/2008), based on the results of this guideline OET study (primarily designed to assess skin sensitising potential).

 

No relevant eye irritation data were identified for palladium. 

 

Palladium is considered to be non-bioavailable following dermal exposure, as evidenced by transformation/dissolution (Skaeff 2011 - cf section 4.8)) and bio-elution (Rodrigues 2012 a,b,c,d,e - cf section 7.12)  test data. Although the bio-elution testing does not extend to the use of simulation lachrymal fluid, the available simulation dermal fluid data is nevertheless indicative of negligible bioavailability following exposure via the eyes.

 

Since a chemical is required to be bioavailable in order to induce (non-mechanical) irritation, palladium is considered incapable of inducing eye irritation. Finally, for animal welfare reasons, conducting new in vivo toxicity tests is considered a last resort. Consequently, no testing for eye irritation of palladium is considered justified.

 

No respiratory tract irritation data were identified. A new study was not conducted as it is not a REACH Standard Information Requirement. Further, palladium is not expected to reach the lungs in appreciable quantities (based on respiratory tract deposition modelling data - cf section 4.5). Thus, inhalation will not be a significant route of exposure.

 

Justification for classification or non-classification

Based on the results of the available in vivo skin irritation study with palladium metal and read-across test data from palladium monoxide and palladium dihydroxide, there is no requirement to classify palladium metal for skin irritation according to EU CLP criteria (EC 1272/2008).

 

No eye irritation data are available for palladium. However, such effects are not expected, based on a lack of bioavailability and read-across from palladium monoxide. As such, there is no evidence to classify it for eye irritation according to EU CLP criteria (EC 1272/2008).