Platinum dioxide

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Platinum dioxide,hydrate was tested according to a guideline compliant study (OECD471; Ballantyne (2018)) No compound-related effects were identified, and the study was considered therefore to have provided no evidence of any Platinum dioxide,hydrate mutagenic activity in this assay system.

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 May 2018 - 3 August 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Specific details on test material used for the study:

Purity: 100% PtO2x0.7H2O or 94.5% PtO2 (based on platinum content of 81.17%)

Target gene:

Histidine

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102

Metabolic activation:

with and without

Metabolic activation system:

S-9 derived from Aroclor 1254-treated male Sprague-Dawley rats

Test concentrations with justification for top dose:

Mutation Experiment 1 (with and without S9)
5, 16, 50,160, 500, 1600, 5000 ug/plate

Mutation Experiment 2 (with and without S9)
51.2, 128, 320, 800, 2000, 5000 ug/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Formulations in 1% Methyl Cellulose (1% MC) at concentrations equivalent to at least 100 mg/mL provided stable suspensions, and were used for the formulations and subsequent dilutions of test article in this study. Test article stock formulations were prepared by suspending Platinum dioxide,hydrate under subdued lighting in 1% MC with the aid of Silverson mixing and stirring (where required), to give the maximum required treatment concentration. Subsequent dilutions were made using 1% MC. The test article suspensions were protected from light and used within approximately 5 hours of initial formulation.
- Justification for choice of solvent/vehicle: Preliminary solubility data indicated that Platinum dioxide,hydrate was not soluble in a variety of standard vehicles that are compatible with the assay system for this study, including Water, Ethanol, Acetone, Tetrahydrofuran, Dimethylformamide and NMethyl-2-pyrrolidone. Formulations in 1% Methyl Cellulose (1% MC) at
concentrations equivalent to at least 100 mg/mL provided stable suspensions, and were used for the formulations and subsequent dilutions of test article in this study

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

2-nitrofluorene

sodium azide

benzo(a)pyrene

mitomycin C

other: 2-aminoanthracene

Remarks:

2NF for TA98 (-S9); NaN3 for TA100 and TA1535 (-S9); AAC for TA1537 (-S9); MMC for TA102 (-S9); BaP for TA98 (+S9); AAN for TA100, TA1535, TA1537 and TA102 (+S9)

Details on test system and experimental conditions:

METHOD OF APPLICATION:
- In agar (plate incorporation); preincubation (for experiment 2 in the presence of S9).
- 0.1 mL volume additions of test article suspension were used for all treatments (positive controls were treated using 0.05 mL volume additions)

Triplicate plates for test substance and vehicle&positive controls.

Prepared test suspensions were protected from light and used within approximately 5 hours of initial formulation.

DURATION
As the results of Experiment 1 were equivocal, treatments in the presence of S-9 in Experiment 2 included a pre-incubation step. Quantities of test article, vehicle control
solution (reduced to 0.05 mL) or positive control, bacteria and S-9 mix detailed above, were mixed together and incubated for 20 minutes at 37±1°C, with shaking,
before the addition of 2 mL of supplemented molten agar at 45±1°C. Plating of these treatments then proceeded as for the normal plate-incorporation procedure.

DETERMINATION OF CYTOTOXICITY
The test item was tested for for evidence of toxicity to the background lawn using the 5 tester strains in experiment 1, using triplicate platings.

These platings were achieved by the following sequence of
additions to 2 mL of molten agar at 45±1°C:
• 0.1 mL bacterial culture
• 0.1 mL of testarticle suspension/vehicle control or 0.05 mL of positive control
• 0.5 mL 10% S-9 mix or buffer solution
followed by rapid mixing and pouring on to Vogel-Bonner E agar plates. When set, the plates were inverted and incubated at 37±1°C protected from light for 3 days.
Following incubation, these plates were examined for evidence of toxicity to the background lawn and, where possible, revertant colonies were counted.

Evaluation criteria:

Data were considered acceptable if the vehicle control counts fell within the calculated historical control ranges and the positive control plate counts were comparable with the historical control ranges.

The assay was considered to be valid if all the following criteria were met:
1. The vehicle control counts fell within the laboratory’s historical control ranges
2. The positive control chemicals induced increases in revertant numbers of ≥1.5-fold (in strain TA102), ≥2-fold (in strains TA98 and TA100) or ≥3-fold (in strains TA1535 and TA1537) the concurrent vehicle control confirming discrimination between different strains, and an active S-9 preparation.

For valid data, the test article was considered to be mutagenic if:
1. A concentration related increase in revertant numbers was ≥1.5-fold (in strain TA102), ≥2-fold (in strains TA98 and TA100) or ≥3-fold (in strains TA1535 and TA1537) the concurrent vehicle control values
2. The positive trend/effects described above were reproducible.

The test article was considered positive in this assay if both of the above criteria were met.
The test article was considered negative in this assay if neither of the above criteria were met.

Statistics:

Individual plate counts were recorded separately and the mean and standard deviation of the plate counts for each treatment were determined. Control counts were
compared with the laboratory’s historical control ranges.
The presence or otherwise of a concentration response was checked by non-statistical analysis, up to limiting levels (for example toxicity, precipitation or 5000 μg/plate).
However, adequate interpretation of biological relevance was of critical importance.

Species / strain:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

True negative controls validity:

not examined

Positive controls validity:

valid

Conclusions:

In a guideline Ames test, it was concluded that Platinum dioxide did not induce mutation in five histidine requiring strains (TA98, TA100, TA1535, TA1537 and TA102) of Salmonella typhimurium when tested at concentrations up to 5000 μg/plate for each strain, in the absence and in the presence of a rat liver metabolic activation system (S-9).

Executive summary:

Platinum dioxide ,hydrate was as sayed for mutation in five histidine-requiring strains (TA98, TA100, TA1535, TA1537 and TA102) of Salmonella typhimurium, both in the absence and in the presence of metabolic activation by an Aroclor 1254-induced rat liver post-mitochondrial fraction (S-9), in two separate experiments. As no vehicle could be identified that would dissolve the test article and was compatible with the assay system, all Platinum dioxide,hydrate treatments in this study were performed using suspensions prepared in 1% Methyl Cellulose (1% MC).

The same concentrations were retained for treatments of all the tester strains in Experiment 1 in the absence and in the presence of S-9. Following these treatments, no evidence of toxicity was observed.

Mutation Experiment 1 treatments of all the tester strains were performed in the absence and in the presence of S-9, using final concentrations of Platinum

dioxide,hydrate at 5, 16, 50, 160, 500, 1600 and 5000 μg/plate. Following these treatments, no evidence of toxicity was observed.

Experiment 2 treatments of all the tester strains were performed in the absence and in the presence of S-9. The maximum test concentration of 5000 μg/plate was retained for all strains. Narrowed concentration intervals were employed covering the ranges 51.2 - 5000 μg/plate. In addition, all treatments in the presence of S-9 were further modified by the inclusion of a preincubation step. Following these treatments, no clear evidence of toxicity was observed.

The test article was formulated and treated as a suspension in this study, and therefore any observations of precipitation are not considered relevant and are not reported.

Vehicle and positive control treatments were included for all strains in both experiments. The mean numbers of revertant colonies fell within acceptable ranges for vehicle control treatments, and were elevated by positive control treatments.

Following Platinum dioxide,hydrate treatments of all the tester strains in the absence and presence of S-9, only the Experiment 1 treatments of strains TA98 and TA100 in the presence of S-9 provided any notable increases in revertant numbers. Although these increases approached (in strain TA98) or exceeded (in strain TA100) 2-fold the concurrent vehicle control level, and appeared to provide some evidence of a concentration-relationship as they each occurred at the highest treatment concentration, in both cases the increases were almost entirely attributable to a single elevated replicate plate count. As no comparable increases were observed following either the plate incorporation or pre-incubation methodology treatments of these

strains in the presence of S-9 in Experiment 2, it was considered that the single elevated plate counts with these strain treatments in Experiment 1 were not a true compound-related effect. As no other strain treatments provided any increases in revertant numbers that were ≥1.5-fold (in strain TA102), ≥2-fold (in strains TA98 or TA100) or ≥3-fold (in strains TA1535 or TA1537) the concurrent vehicle control, this study was considered therefore to have provided no evidence of any Platinum dioxide,hydrate mutagenic activity in this assay system.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

No reliable genotoxicity data for platinum dioxide were identified. Platinum oxide [oxidation state not clear] displayed no evidence of genotoxicity in a limited dominant lethal mutation assay in mice (Arnold et al., 1975).

Link to relevant study records

Reference

Endpoint:

in vivo mammalian germ cell study: cytogenicity / chromosome aberration

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Study period:

Not reported

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Brief abstract, basic data only reported, does not meet current guideline methodology

Qualifier:

no guideline followed

Principles of method if other than guideline:

Dominant lethal study in mice to detect mutagenic potential (usually as a result of chromosome aberrations). Treated males were housed with 3 untreated, virgin females/week for 6 consecutive weeks. Mating ability, impregnating ability, viable embryos and percent early deaths (i.e. resorptions) were assessed.

GLP compliance:

not specified

Type of assay:

rodent dominant lethal assay

Species:

mouse

Strain:

other: albino

Sex:

male

Details on test animals or test system and environmental conditions:

No details reported in brief abstract.

Route of administration:

subcutaneous

Vehicle:

Saline (suspension)

Details on exposure:

Single subcutaneous injection of powdered material (100 mg, as the metal) as a suspension in saline (1 ml).

Duration of treatment / exposure:

n/a

Frequency of treatment:

Single dose administered

Post exposure period:

[Presumably] 6 weeks

Remarks:

Doses / Concentrations:
100 mg
Basis:
other: nominal quantity of elemental metal in saline

No. of animals per sex per dose:

10 males

Control animals:

yes, concurrent vehicle

Positive control(s):

no data

Tissues and cell types examined:

Dominant lethal mutations were measured as the percentage of all implants that resulted in early death in utero (i.e. percentage resorptions).

Evaluation criteria:

Early (in utero) deaths as a percentage of all implants were compared in treated and control animals

Statistics:

None reported

Sex:

male

Genotoxicity:

negative

Toxicity:

no effects

Remarks:

Mortality and behavioural assessment only

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

not applicable

Additional information on results:

Numbers of viable embryos: 10.4-11.7 and 10.2-11.5 in control groups; 10.6-12.0 in treated animals.
Percentage early deaths: 3.0-6.7 and 4.8-8.1 in control groups; 5.8-9.3 in treated group

Observations, viable embryo numbers, percentage of early deaths as a proportion of implantations were comparable in treated and control groups.

Conclusions:

Interpretation of results: negative
In a limited dominant lethal mutation assay, no evidence of genotoxicity was seen following a single subcutaneous injection of powdered platinum oxide [oxidation state not clear] to male mice prior to mating with untreated females.

Executive summary:

In a limited non-guideline pre-GLP study, platinum 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 platinum oxide under the conditions of this limited dominant lethal mutation assay in mice.

Its 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).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Mode of Action Analysis / Human Relevance Framework

No data identified.

Additional information

Additional information from genetic toxicity in vivo:

No reliable genotoxicity data for platinum dioxide were identified.

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

 

Several Expert Groups have assessed the toxicity profile of platinum, and various platinum compounds, including CMR properties in their assessment. All reviews have indicated that platinum compounds have been reported to be mutagenic in a range of in vitro studies (DECOS, 2008; EMA, 2008; SCOEL, 2011; WHO, 1991). Cisplatin and related compounds are known DNA-reactive carcinogens and, as these compounds are better investigated due to their pharmaceutical properties, this has been confirmed in vivo. As cisplatin-type substances differ in chemical reactivity (liability of ligands, number of active sites etc.) it is reasonable to expect that not all forms of platinum are carcinogenic (DECOS, 2008). Limited experimental data on reproductive toxicity and carcinogenicity for other platinum compounds give no evidence of activity that would meet classification criteria (DECOS, 2008; SCOEL, 2011).

 

Despite the generally positive in vitro results identified for the platinum compounds in various bacterial/mammalian cell mutagenicity assays (supported by some mammalian cell cytogenicity tests), the in vivo relevance of these in vitro findings remains unclear. Indeed, the available in vivo data returned mostly negative results. However, some of the identified studies might not be considered sufficiently robust (according to ECHA standards) to override the in vitro mutagenicity findings (e.g. a sex-linked recessive lethal test in Drosophila melanogaster (OECD TG 477, performed with dipotassium tetrachloroplatinate) and a liver unscheduled DNA synthesis assay (OECD TG 486, performed with tetraammineplatinum hydrogen carbonate)). Indeed, further in vivo testing of certain platinum compounds has been proposed to further elucidate the in vivo relevance of the in vitro findings.

 

References

DECOS (2008). Dutch Expert Committee on Occupational Standards. Platinum and Platinum Compounds. Health-based recommended occupational exposure limit. Gezondheidsraad, 2008/12OSH. https://www.gezondheidsraad.nl/en/publications/gezonde-arbeidsomstandigheden/platinum-and-platinum-compounds-health-based-recommended

 

EMA (2008). European Medicines Agency. Guideline on the specification limits for residues of metal catalysts or metal reagents. Committee for Medicinal Products for Human Use (CHMP). EMEA/CHMP/SWP/4446/2000. http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2009/09/WC500003586.pdf

 

SCOEL (2011). Recommendation from the Scientific Committee on Occupational Exposure Limits for platinum and platinum compounds. SCOEL/SUM/150. http://ec.europa.eu/social/BlobServlet?docId=7303&langId=en

 

WHO (1991). World Health Organization. Platinum. International Programme on Chemical Safety. Environmental Health Criteria 125. http://www.inchem.org/documents/ehc/ehc/ehc125.htm#SectionNumber:7.4

Justification for selection of genetic toxicity endpoint
The only genetic toxicity study available.

Justification for classification or non-classification

Based on the existing data set, platinum dioxide does not currently meet the criteria for classification as a germ cell mutagen (category 1A or 1B). However, this conclusion should be revisited when the results of the planned in vivo studies (with other Pt compounds than Pt dioxide) are available.