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Diss Factsheets

Administrative data

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

No reliable genotoxicity data for palladium monoxide were identified.


Palladium monoxide is a member of the read-across group 'Palladium, Palladium monoxide and Palladium dihyrdroxide'. In a Reverse Mutation Assay ‘Ames Test’ using strains of Salmonella typhimurium and Escherichia coli (OECD TG 471, GLP compliant) Palladium dihydroxide did not induce an increase in the frequency of revertant colonies that met the criteria for a positive result, either with or without metabolic activation (S9-mix). Under the conditions of this test Palladium dihydroxide was considered to be non-mutagenic when tested up to the limit of toxicity.


 


In a limited dominant lethal mutation assay, no evidence of genotoxicity was seen following a single subcutaneous injection of powdered palladium oxide [oxidation state not clear] to male mice prior to mating with untreated females (Arnold et al., 1975).

Link to relevant study records

Referenceopen allclose all

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
23 Sept - 9 Oct 2020
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: ICH S2(R1) guideline adopted June 2012 (ICH S2(R1) Federal Register. Adopted 2012; 77:33748-33749)
Deviations:
no
Qualifier:
according to guideline
Guideline:
JAPAN: Guidelines for Screening Mutagenicity Testing Of Chemicals
Version / remarks:
The Japanese Ministry of Health, Labour and Welfare (MHLW), Ministry of Economy, Trade and Industry (METI), and Ministry of the Environment (MOE) Guidelines of 31 March 2011
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Version / remarks:
30 May 2008
Deviations:
no
Qualifier:
according to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
21 July 1997 as corrected in 2020
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of assay:
bacterial reverse mutation assay
Specific details on test material used for the study:
97.4% Pd(OH)2 (2.6% water)
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Remarks:
The bacteria used in the test were obtained from: • British Industrial Biological Research Association, on a nutrient agar plate, on 17 August 1987 • Trinova Biochem GmbH on 27 June 2017.
Metabolic activation:
with and without
Metabolic activation system:
The Phenobarbitone / β-Naphthoflavone induced S9 Microsomal fractions (Sprague-Dawley) used in this study were purchased from Moltox; Lot No. 4222 and the protein level was adjusted to 20 mg/mL.

The S9-mix was prepared before use using sterilized co-factors and maintained on ice for the duration of the test.
S9 5.0 mL
1.65 M KCl/0.4 M MgCl2 1.0 mL
0.1 M Glucose-6-phosphate 2.5 mL
0.1 M NADP 2.0 mL 0.2 M Sodium phosphate buffer (pH 7.4) 25.0 mL
Sterile distilled water 14.5 mL
A 0.5 mL aliquot of S9-mix and 2 mL of molten, trace histidine or tryptophan supplemented, top agar were overlaid onto a sterile Vogel-Bonner Minimal agar plate in order to assess the sterility of the S9-mix. This procedure was repeated, in triplicate, on the day of each experiment.
Test concentrations with justification for top dose:
Exp1:The maximum concentration was 5000 μg/plate (the OECD TG 471 maximum recommended dose level). Eight concentrations of the test item (1.5, 5, 15, 50, 150, 500, 1500 and 5000 μg/plate) were assayed in triplicate against each tester strain, using the direct plate incorporation method.

Exp2: As the result of Experiment 1 was considered negative, Experiment 2 was performed using the pre-incubation method in the presence and absence of metabolic activation (S9-mix).The dose range used for Experiment 2 was determined by the results of Experiment 1 and was 0.5, 1.5, 5 15, 50, 150, 500 and 1500 μg/plate. Eight test item concentrations were selected in Experiment 2 in order to ensure the study achieved at least four non-toxic dose levels as required by the test guideline, and were selected based on the cytotoxicity noted in Experiment 1 and the potential for a change in the cytotoxicity of the test item following the change in test methodology from plate incorporation to pre-incubation.
Vehicle / solvent:
The test item was insoluble in sterile distilled water at 25 and 50 mg/mL, dimethyl formamide and acetonitrile at 50 mg/mL, acetone at 100 mg/mL and tetrahydrofuran at 200 mg/mL in solubility checks performed in–house. The test item formed the best doseable suspension in sterile distilled water (Baxter, Batch 19F03BA1A) at a maximum concentration of 25 mg/mL, therefore, this solvent was selected as the vehicle.

The test item was accurately weighed and, on the day of each experiment, approximate half-log dilutions prepared in sterile distilled water by mixing on a vortex mixer, sonication for 15 minutes at room temperature and homogenisation for 5 minutes. Formulated concentrations were adjusted to allow for the stated water/impurity content (2.6%) of the test item.

All formulations were used within four hours of preparation and were assumed to be stable for this period. Analysis for concentration, homogeneity and stability of the test item formulations is not a requirement of the test guidelines and was, therefore, not determined.
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
4-nitroquinoline-N-oxide
9-aminoacridine
N-ethyl-N-nitro-N-nitrosoguanidine
benzo(a)pyrene
other:
Remarks:
2-aminoanthracene
Details on test system and experimental conditions:
Top agar was prepared using 0.6% Bacto agar (lot numbers 9105946 expiry date 01/2024 and 9294156 expiry date 08/2024) and 0.5% sodium chloride with 5 mL of 1.0 mM histidine and 1.0 mM biotin or 1.0 mM tryptophan solution added to each 100 mL of top agar. Vogel-Bonner Minimal agar plates were purchased from SGL Ltd (lot number 55979 expiry date 11/2020).

Experiment1
Without Metabolic Activation
A 0.2 mL aliquot of the appropriate concentration of test item or solvent vehicle or 0.1 mL of the appropriate positive control was added together with 0.1 mL of the bacterial strain culture, 0.5 mL of phosphate buffer and 2 mL of molten, trace amino-acid supplemented media. These were then mixed and overlayed onto a Vogel-Bonner agar plate. Negative (untreated) controls were also performed on the same day as the mutation test. Each concentration of the test item, appropriate positive, vehicle and negative controls, and each bacterial strain, was assayed using triplicate plates.
With Metabolic Activation
The procedure was the same as described above except that following the addition of the test item formulation and bacterial culture, 0.5 mL of S9-mix was added to the molten, trace amino-acid supplemented media instead of phosphate buffer.
Incubation and Scoring
All of the plates were incubated at 37 ± 3 °C for between 48 and 72 hours and scored for the presence of revertant colonies using an automated colony counting system. The plates were viewed microscopically for evidence of thinning of the background bacterial lawn (toxicity).

Experiment 2 – Pre-Incubation Method
As the result of Experiment 1 was considered negative, Experiment 2 was performed using the pre-incubation method in the presence and absence of metabolic activation (S9-mix).
Without Metabolic Activation
A 0.1 mL aliquot of the appropriate bacterial strain culture, 0.5 mL of phosphate buffer and 0.2 mL of the appropriate concentration of test item formulation or solvent vehicle or 0.1 mL of appropriate positive control were incubated at 37 ± 3 °C for 20 minutes (with shaking) prior to addition of 2 mL of molten, trace amino-acid supplemented media and subsequent plating onto Vogel-Bonner plates. Negative (untreated) controls were also performed on the same day as the mutation test employing the plate incorporation method. All testing for this experiment was performed in triplicate.
With Metabolic Activation
The procedure was the same as described previously (see 3.3.3.2) except that following the addition of the test item formulation and bacterial strain culture, 0.5 mL of S9-mix was added to the tube instead of phosphate buffer, prior to incubation at 37 ± 3 °C for 20 minutes (with shaking) and addition of molten, trace amino-acid supplemented media. All testing for this experiment was performed in triplicate.
Incubation and Scoring
All of the plates were incubated at 37 ± 3 °C for between 48 and 72 hours and scored for the presence of revertant colonies using an automated colony counting system. The plates were viewed microscopically for evidence of thinning of the background bacterial lawn (toxicity).
Evaluation criteria:
There are several criteria for determining a positive result. Any, one, or all of the following can be used to determine the overall result of the study:
1. A dose-related increase in mutant frequency over the dose range tested (De Serres and Shelby, 1979).
2. A reproducible increase at one or more concentrations.
3. Biological relevance against in-house historical control ranges.
4. A fold increase greater than two times the concurrent solvent control for TA100, TA98 and WP2uvrA or a three-fold increase for TA1535 and TA1537 (especially if accompanied by an out-of-historical range response (Cariello and Piegorsch, 1996)).
5. Statistical analysis of data as determined by UKEMS (Mahon et al., 1989).
A test item is considered non-mutagenic (negative) in the test system if the above criteria are not met.
Statistics:
Statistical significance was confirmed by using Dunnett’s Regression Analysis (* = p < 0.05) for those values that indicate statistically significant increases in the frequency of revertant colonies compared to the concurrent solvent control.
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1537
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
Experiment 1:
There was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix). However, substantial reductions in revertant colony frequency (below the 0.5 threshold when compared to concurrent vehicle controls) were noted in the absence of metabolic activation (S9-mix) from 500 μg/plate (TA1537) and from 1500 μg/plate to the remaining strains. In the presence of metabolic activation (S9-mix), substantial reductions in revertant colony frequency were noted from 1500 μg/plate to all of the bacterial strains.
A test item precipitate (fine, brown and particulate in appearance) was noted at and above 1500 μg/plate in both the presence and absence of metabolic activation (S9-mix). This observation did not prevent the scoring of revertant colonies.
There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix).

Experiment 2:
Based on the results of Experiment 1, the toxic limit of the test item was employed as the maximum concentration in the second mutation test.
Similarly, there was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), however substantial reductions in revertant colony frequency (below the 0.5 threshold when compared to concurrent vehicle controls) were again noted in the absence of metabolic activation (S9-mix) from 500 μg/plate (TA100 and TA1537) and from 1500 μg/plate (TA1535, TA98 and WP2uvrA). In the presence of metabolic activation (S9-mix), substantial reductions in revertant colony frequency were noted from 500 μg/plate (TA1537) and from 1500 μg/plate (TA1535, TA98, TA100 and WP2uvrA).
A test item precipitate (fine, brown and particulate in appearance) was noted at 1500 μg/plate in both the presence and absence of metabolic activation (S9-mix). This observation did not prevent the scoring of revertant colonies.
There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix).
Conclusions:
In a Reverse Mutation Assay ‘Ames Test’ using strains of Salmonella typhimurium and Escherichia coli (OECD TG 471, GLP compliant) the test item Palladium dihydroxide did not induce an increase in the frequency of revertant colonies that met the criteria for a positive result, either with or without metabolic activation (S9-mix). Under the conditions of this test Palladium dihydroxide was considered to be non-mutagenic when tested up to the limit of toxicity.
Executive summary:

Palladium dihydroxide was tested in a GLP-compliant AMES test (acc. to OECD471).


Salmonella typhimurium strains TA1535, TA1537, TA98 and TA100 and Escherichia coli strain WP2uvrA were treated with aqueous suspensions of the test item (based on preliminary solubility checks) using both the Ames plate incorporation and pre-incubation methods at eight dose levels, in triplicate, both with and without the addition of a rat liver homogenate metabolizing system (10% liver S9 in standard co-factors). The dose range for Experiment 1 (plate incorporation) was based on OECD TG 471 and was 1.5 to 5000 μg/plate. The experiment was repeated on a separate day (pre-incubation method) using fresh cultures of the bacterial strains and fresh test item formulations. The dose range was amended following the results of Experiment 1 and was 0.5 to 1500 μg/plate. Eight test item concentrations were selected in Experiment 2 in order to ensure the study achieved at least four non-toxic dose levels as required by the test guideline, and were selected based on the cytotoxicity noted in Experiment 1 and the potential for a change in the cytotoxicity of the test item following the change in test methodology from plate incorporation to pre-incubation. 


The vehicle (sterile distilled water) control plates gave counts of revertant colonies within the normal range. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies, both with and without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.
The maximum dose level of the test item in the first experiment was selected as the OECD TG 471 recommended dose level of 5000 μg/plate. There was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), in the first mutation test (plate incorporation method), however substantial reductions in revertant colony frequency were noted for all of the tester strains, initially from 500 and 1500 μg/plate in the absence and presence of metabolic activation (S9-mix), respectively.
Based on the results of Experiment 1, the toxic limit of the test item (1500 μg/plate) was employed as the maximum concentration in the second mutation test (pre-incubation method). Similarly, there was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), however substantial reductions in revertant colony frequency were again noted for all of the tester strains, initially from 500 μg/plate in the absence and presence of metabolic activation (S9-mix).
A test item precipitate (fine, brown and particulate in appearance) was noted from 1500 μg/plate in both the presence and absence of metabolic activation (S9-mix) in Experiments 1 and 2. This observation did not prevent the scoring of revertant colonies.
There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix) in Experiment 1 (plate incorporation method).
Similarly, no significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix) in Experiment 2 (pre-incubation method).


In this Reverse Mutation Assay ‘Ames Test’ using strains of Salmonella typhimurium and Escherichia coli (OECD TG 471) the test item Palladium dihydroxide did not induce an increase in the frequency of revertant colonies that met the criteria for a positive result, either with or without metabolic activation (S9-mix). Under the conditions of this test Palladium dihydroxide was considered to be non-mutagenic when tested up to the limit of toxicity.

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
23 Sept - 9 Oct 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: ICH S2(R1) guideline adopted June 2012 (ICH S2(R1) Federal Register. Adopted 2012; 77:33748-33749)
Deviations:
no
Qualifier:
according to guideline
Guideline:
JAPAN: Guidelines for Screening Mutagenicity Testing Of Chemicals
Version / remarks:
The Japanese Ministry of Health, Labour and Welfare (MHLW), Ministry of Economy, Trade and Industry (METI), and Ministry of the Environment (MOE) Guidelines of 31 March 2011
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Version / remarks:
30 May 2008
Deviations:
no
Qualifier:
according to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
21 July 1997 as corrected in 2020
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of assay:
bacterial reverse mutation assay
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Remarks:
The bacteria used in the test were obtained from: • British Industrial Biological Research Association, on a nutrient agar plate, on 17 August 1987 • Trinova Biochem GmbH on 27 June 2017.
Metabolic activation:
with and without
Metabolic activation system:
The Phenobarbitone / β-Naphthoflavone induced S9 Microsomal fractions (Sprague-Dawley) used in this study were purchased from Moltox; Lot No. 4222 and the protein level was adjusted to 20 mg/mL.

The S9-mix was prepared before use using sterilized co-factors and maintained on ice for the duration of the test.
S9 5.0 mL
1.65 M KCl/0.4 M MgCl2 1.0 mL
0.1 M Glucose-6-phosphate 2.5 mL
0.1 M NADP 2.0 mL 0.2 M Sodium phosphate buffer (pH 7.4) 25.0 mL
Sterile distilled water 14.5 mL
A 0.5 mL aliquot of S9-mix and 2 mL of molten, trace histidine or tryptophan supplemented, top agar were overlaid onto a sterile Vogel-Bonner Minimal agar plate in order to assess the sterility of the S9-mix. This procedure was repeated, in triplicate, on the day of each experiment.
Test concentrations with justification for top dose:
Exp1:The maximum concentration was 5000 μg/plate (the OECD TG 471 maximum recommended dose level). Eight concentrations of the test item (1.5, 5, 15, 50, 150, 500, 1500 and 5000 μg/plate) were assayed in triplicate against each tester strain, using the direct plate incorporation method.

Exp2: As the result of Experiment 1 was considered negative, Experiment 2 was performed using the pre-incubation method in the presence and absence of metabolic activation (S9-mix).The dose range used for Experiment 2 was determined by the results of Experiment 1 and was 0.5, 1.5, 5 15, 50, 150, 500 and 1500 μg/plate. Eight test item concentrations were selected in Experiment 2 in order to ensure the study achieved at least four non-toxic dose levels as required by the test guideline, and were selected based on the cytotoxicity noted in Experiment 1 and the potential for a change in the cytotoxicity of the test item following the change in test methodology from plate incorporation to pre-incubation.
Vehicle / solvent:
The test item was insoluble in sterile distilled water at 25 and 50 mg/mL, dimethyl formamide and acetonitrile at 50 mg/mL, acetone at 100 mg/mL and tetrahydrofuran at 200 mg/mL in solubility checks performed in–house. The test item formed the best doseable suspension in sterile distilled water (Baxter, Batch 19F03BA1A) at a maximum concentration of 25 mg/mL, therefore, this solvent was selected as the vehicle.

The test item was accurately weighed and, on the day of each experiment, approximate half-log dilutions prepared in sterile distilled water by mixing on a vortex mixer, sonication for 15 minutes at room temperature and homogenisation for 5 minutes. Formulated concentrations were adjusted to allow for the stated water/impurity content (2.6%) of the test item.

All formulations were used within four hours of preparation and were assumed to be stable for this period. Analysis for concentration, homogeneity and stability of the test item formulations is not a requirement of the test guidelines and was, therefore, not determined.
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
4-nitroquinoline-N-oxide
9-aminoacridine
N-ethyl-N-nitro-N-nitrosoguanidine
benzo(a)pyrene
other:
Remarks:
2-aminoanthracene
Details on test system and experimental conditions:
Top agar was prepared using 0.6% Bacto agar (lot numbers 9105946 expiry date 01/2024 and 9294156 expiry date 08/2024) and 0.5% sodium chloride with 5 mL of 1.0 mM histidine and 1.0 mM biotin or 1.0 mM tryptophan solution added to each 100 mL of top agar. Vogel-Bonner Minimal agar plates were purchased from SGL Ltd (lot number 55979 expiry date 11/2020).

Experiment1
Without Metabolic Activation
A 0.2 mL aliquot of the appropriate concentration of test item or solvent vehicle or 0.1 mL of the appropriate positive control was added together with 0.1 mL of the bacterial strain culture, 0.5 mL of phosphate buffer and 2 mL of molten, trace amino-acid supplemented media. These were then mixed and overlayed onto a Vogel-Bonner agar plate. Negative (untreated) controls were also performed on the same day as the mutation test. Each concentration of the test item, appropriate positive, vehicle and negative controls, and each bacterial strain, was assayed using triplicate plates.
With Metabolic Activation
The procedure was the same as described above except that following the addition of the test item formulation and bacterial culture, 0.5 mL of S9-mix was added to the molten, trace amino-acid supplemented media instead of phosphate buffer.
Incubation and Scoring
All of the plates were incubated at 37 ± 3 °C for between 48 and 72 hours and scored for the presence of revertant colonies using an automated colony counting system. The plates were viewed microscopically for evidence of thinning of the background bacterial lawn (toxicity).

Experiment 2 – Pre-Incubation Method
As the result of Experiment 1 was considered negative, Experiment 2 was performed using the pre-incubation method in the presence and absence of metabolic activation (S9-mix).
Without Metabolic Activation
A 0.1 mL aliquot of the appropriate bacterial strain culture, 0.5 mL of phosphate buffer and 0.2 mL of the appropriate concentration of test item formulation or solvent vehicle or 0.1 mL of appropriate positive control were incubated at 37 ± 3 °C for 20 minutes (with shaking) prior to addition of 2 mL of molten, trace amino-acid supplemented media and subsequent plating onto Vogel-Bonner plates. Negative (untreated) controls were also performed on the same day as the mutation test employing the plate incorporation method. All testing for this experiment was performed in triplicate.
With Metabolic Activation
The procedure was the same as described previously (see 3.3.3.2) except that following the addition of the test item formulation and bacterial strain culture, 0.5 mL of S9-mix was added to the tube instead of phosphate buffer, prior to incubation at 37 ± 3 °C for 20 minutes (with shaking) and addition of molten, trace amino-acid supplemented media. All testing for this experiment was performed in triplicate.
Incubation and Scoring
All of the plates were incubated at 37 ± 3 °C for between 48 and 72 hours and scored for the presence of revertant colonies using an automated colony counting system. The plates were viewed microscopically for evidence of thinning of the background bacterial lawn (toxicity).
Evaluation criteria:
There are several criteria for determining a positive result. Any, one, or all of the following can be used to determine the overall result of the study:
1. A dose-related increase in mutant frequency over the dose range tested (De Serres and Shelby, 1979).
2. A reproducible increase at one or more concentrations.
3. Biological relevance against in-house historical control ranges.
4. A fold increase greater than two times the concurrent solvent control for TA100, TA98 and WP2uvrA or a three-fold increase for TA1535 and TA1537 (especially if accompanied by an out-of-historical range response (Cariello and Piegorsch, 1996)).
5. Statistical analysis of data as determined by UKEMS (Mahon et al., 1989).
A test item is considered non-mutagenic (negative) in the test system if the above criteria are not met.
Statistics:
Statistical significance was confirmed by using Dunnett’s Regression Analysis (* = p < 0.05) for those values that indicate statistically significant increases in the frequency of revertant colonies compared to the concurrent solvent control.
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1537
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
Experiment 1:
There was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix). However, substantial reductions in revertant colony frequency (below the 0.5 threshold when compared to concurrent vehicle controls) were noted in the absence of metabolic activation (S9-mix) from 500 μg/plate (TA1537) and from 1500 μg/plate to the remaining strains. In the presence of metabolic activation (S9-mix), substantial reductions in revertant colony frequency were noted from 1500 μg/plate to all of the bacterial strains.
A test item precipitate (fine, brown and particulate in appearance) was noted at and above 1500 μg/plate in both the presence and absence of metabolic activation (S9-mix). This observation did not prevent the scoring of revertant colonies.
There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix).

Experiment 2:
Based on the results of Experiment 1, the toxic limit of the test item was employed as the maximum concentration in the second mutation test.
Similarly, there was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), however substantial reductions in revertant colony frequency (below the 0.5 threshold when compared to concurrent vehicle controls) were again noted in the absence of metabolic activation (S9-mix) from 500 μg/plate (TA100 and TA1537) and from 1500 μg/plate (TA1535, TA98 and WP2uvrA). In the presence of metabolic activation (S9-mix), substantial reductions in revertant colony frequency were noted from 500 μg/plate (TA1537) and from 1500 μg/plate (TA1535, TA98, TA100 and WP2uvrA).
A test item precipitate (fine, brown and particulate in appearance) was noted at 1500 μg/plate in both the presence and absence of metabolic activation (S9-mix). This observation did not prevent the scoring of revertant colonies.
There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix).
Conclusions:
In a Reverse Mutation Assay ‘Ames Test’ using strains of Salmonella typhimurium and Escherichia coli (OECD TG 471, GLP compliant) the test item Palladium dihydroxide did not induce an increase in the frequency of revertant colonies that met the criteria for a positive result, either with or without metabolic activation (S9-mix). Under the conditions of this test Palladium dihydroxide was considered to be non-mutagenic when tested up to the limit of toxicity.
Executive summary:

Palladium dihydroxide was tested in a GLP-compliant AMES test (acc. to OECD471).


Salmonella typhimurium strains TA1535, TA1537, TA98 and TA100 and Escherichia coli strain WP2uvrA were treated with aqueous suspensions of the test item (based on preliminary solubility checks) using both the Ames plate incorporation and pre-incubation methods at eight dose levels, in triplicate, both with and without the addition of a rat liver homogenate metabolizing system (10% liver S9 in standard co-factors). The dose range for Experiment 1 (plate incorporation) was based on OECD TG 471 and was 1.5 to 5000 μg/plate. The experiment was repeated on a separate day (pre-incubation method) using fresh cultures of the bacterial strains and fresh test item formulations. The dose range was amended following the results of Experiment 1 and was 0.5 to 1500 μg/plate. Eight test item concentrations were selected in Experiment 2 in order to ensure the study achieved at least four non-toxic dose levels as required by the test guideline, and were selected based on the cytotoxicity noted in Experiment 1 and the potential for a change in the cytotoxicity of the test item following the change in test methodology from plate incorporation to pre-incubation. 


The vehicle (sterile distilled water) control plates gave counts of revertant colonies within the normal range. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies, both with and without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.
The maximum dose level of the test item in the first experiment was selected as the OECD TG 471 recommended dose level of 5000 μg/plate. There was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), in the first mutation test (plate incorporation method), however substantial reductions in revertant colony frequency were noted for all of the tester strains, initially from 500 and 1500 μg/plate in the absence and presence of metabolic activation (S9-mix), respectively.
Based on the results of Experiment 1, the toxic limit of the test item (1500 μg/plate) was employed as the maximum concentration in the second mutation test (pre-incubation method). Similarly, there was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), however substantial reductions in revertant colony frequency were again noted for all of the tester strains, initially from 500 μg/plate in the absence and presence of metabolic activation (S9-mix).
A test item precipitate (fine, brown and particulate in appearance) was noted from 1500 μg/plate in both the presence and absence of metabolic activation (S9-mix) in Experiments 1 and 2. This observation did not prevent the scoring of revertant colonies.
There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix) in Experiment 1 (plate incorporation method).
Similarly, no significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix) in Experiment 2 (pre-incubation method).


In this Reverse Mutation Assay ‘Ames Test’ using strains of Salmonella typhimurium and Escherichia coli (OECD TG 471) the test item Palladium dihydroxide did not induce an increase in the frequency of revertant colonies that met the criteria for a positive result, either with or without metabolic activation (S9-mix). Under the conditions of this test Palladium dihydroxide was considered to be non-mutagenic when tested up to the limit of toxicity.


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 (negative)

Genetic toxicity in vivo

Description of key information

No in vivo gentoxicity data were identified or are required at this tonnage.

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information


No reliable genotoxicity data for palladium monoxide were identified.


 


In a limited (non-guideline, pre-GLP) study, palladium oxide [oxidation state not clear] was tested for its ability to induce heritable genetic damage (usually indicative of chromosome aberrations) in a dominant lethal mutation assay in albino mice. Single subcutaneous injections of powdered material (100 mg as the metal) in saline (1 ml) were given to 10 males before housing with 3 untreated, virgin females/week for 6 consecutive weeks. The percentage of implants that resulted in early foetal deaths (in utero) did not differ from those measured in saline-treated controls. In conclusion, a mutagenic effect (indicative of chromosome aberrations) was not indicated for palladium oxide under the conditions of this limited dominant lethal mutation assay in mice (Arnold et al., 1975). It is worth noting, that the study has several deviations (e.g. inappropriate route, single dose, no positive control) and does not meet the acceptance criteria listed in the current OECD Test Guideline (478).


 



Palladium monoxide is a member of the read-across group 'Palladium, Palladium monoxide and Palladium dihydroxide'. In a Reverse Mutation Assay ‘Ames Test’ using strains of Salmonella typhimurium and Escherichia coli (OECD TG 471, GLP compliant) Palladium dihydroxide did not induce an increase in the frequency of revertant colonies that met the criteria for a positive result, either with or without metabolic activation (S9-mix). Under the conditions of this test Palladium dihydroxide was considered to be non-mutagenic when tested up to the limit of toxicity.



Justification for classification or non-classification


No evidence of genotoxic activity has been seen with palladium monoxide in a reliable in vitro bacterial mutagenicity assay (via read-across from palladium dihydroxide). In support, no evidence of genotoxicity was seen in a limited dominant lethal mutation assay with palladium monoxide. As such, classification of palladium monoxide for germ cell mutagenicity is not warranted, according to EU CLP criteria (EC 1272/2008).