Dichromium trioxalate

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

This article review approximately 700 results reported in the literature with 32 chromium compunds assayed in 130 short-term tests using different targets and/or genetic end-points. Cr (III) compounds are grouped according to their solubility:

• highly soluble Cr (III) compunds including chromic chloride, chromic acetate, chromic nitrate chromic sulfate and chromic potassium sulfate. Chromic chloride induced a variety of genetic effects in acellular or subcellular targets. In contrast all Cr (III) compounds almost consistently failed to induce various genetic effects in bacteria. Weak results were obtained in yeasts, under particular treatment, and in plants. They were generally inactive in cultured mammalian cell systems investigating DNA synthesis, DNA damage, forward mutations and sister-chromatid exchanges. Induction of chromosomal abberations was more frequent than sister-chromatid exchanges although, compared to Cr (VI), much higher Cr (III) concentrations were generally needed. Conflicting results were reported in cell transformation assays. Following in vivo treatment, no DNA fragmentation or induction of micronuclei was detected in rats and in mice, respectively
• Soluble Cr(III) compounds. This group of compounds includes basic chromic sulfate, chromic alum and chromic phosphate. The results reported in the limited number of studies available for these compounds are comparable to those reported for highly soluble Cr (III) compounds.
• Poorly soluble and insoluble Cr (III) compounds. This group of compounds includes chromic hydroxide, chromic oxide, chromite ore and cupric chromite. These compounds were genotoxic in bacteria only when contaminated with Cr (VI). Conflicting results were obtained in cultured mammalian cells, where chromic oxide was found to be taken up by cells and to induce mutation, chromosomal aberrations and sister-chromatid exchanges, although at concentrations 1000-fold higher than for Cr (VI). In addition to the aforementioned compounds, chromium tannins used in the hide and leather industry, most of which are composed of scarecly soluble sulfates, were also tested. None of 17 tannins reverted his- S. typhimurium, whereas 8 out of 13 tannins, 4 of which were contaminated with Cr (VI), increased the frequency of sister-chromatid exhanges in Chinese hamster ovary cells.
• Cr (III) complexes with organic ligands were assayed in both prokaryotic and eukaryotic cell systems. Complexes of chromic chloride with salicylate or citrate were positive in the rec assay with B. subtilis. Out of 17 hexacoordinated Cr (III) complexes, 8 were positive in a differential killing test with E. coli and 4 also reverted his- S. typhimurium. The most active complexes, containing aromatic amine ligands such as 2,2'-bipyridine and 1,10-phenanthroline were confirmed to be mutagenic. On the other hand, complexes of Cr (III) with amino acids did not revert his- S.typhimurium strains. In mammalian cultured cells, chromic glycine complexes did not induce unscheduled DNA synthesis in human skin fibroblasts nor mutation in Chinese hamster V79 cells. However, a chromic phenanthroline complex induced fragmentation and produced a weak DNA fragmentation in the same cells. Cr (acetylacetonate)3 but not Cr maltolate increased the frequency of sister-chromatid exchanges in Chinese Hamster ovary cells.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Performed to GLP and current guidelines.

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Specific details on test material used for the study:

Identification: chromium oxalate
Physical state/Appearance: Dark green powder
Batch: Z-09-2715
Purity: 98% min.
Expiry Date: 17 January 2018
Storage Conditions: Room temperature in the dark

Target gene:

Salmonella typhimurium Strains Genotype Type of mutations indicatedTA1537 his C 3076; rfa-; uvrB-: frame shiftTA98 his D 3052; rfa-; uvrB-;R-factorTA1535 his G 46; rfa-; uvrB-: base-pair substitutionTA100 his G 46; rfa-; uvrB-;R-factorEscherichia coliStrain Genotype Type of mutations indicatedWP2uvrA trp-; uvrA-: base-pair substitution

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Metabolic activation:

with and without

Metabolic activation system:

S9 Microsomal fraction induced with Phenobarbitone/-Naphthoflavone

Test concentrations with justification for top dose:

Eight concentrations of the test item (1.5, 5, 15, 50, 150, 500, 1500 and 5000 ug/plate) were assayed in triplicate against each tester strain, using the direct plate incorporation method in the first test and by pre-incubation in the confirmatoery test; the second test did not include the lower dose concentrations. Top dose recognised maximum for this test method.

Vehicle / solvent:

Suspension in water.
Not sufficiently soluble in acetone, DMSO or other suitable solvents.

Untreated negative controls:

yes

Negative solvent / vehicle controls:

no

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

Details on test system and experimental conditions:

The test item was insoluble in sterile distilled water, dimethyl sulphoxide, 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, therefore, this solvent was selected as the vehicle.

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. Statistical analysis of data as determined by UKEMS (Mahon et al., 1989).5. Fold increase greater than two times the concurrent solvent control for any tester strain (especially if accompanied by an out-of-historical range response (Cariello and Piegorsch, 1996)).

Statistics:

Statistical significance was confirmed by using Dunnetts 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:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no 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:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no 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:

no 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

Remarks:

Slight thinning without S-9

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

The maximum dose level of the test item in the first experiment was selected as the maximum 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 either test.

A test item precipitate (fine and particulate in appearance) was noted at 5000 ug/plate, this observation did not prevent the scoring of revertant colonies.

There were no toxicological 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).

Small, statistically significant increases in TA100 revertant colony frequency were observed at 5000 μg/plate in the first mutation test (absence of S9-mix) and the second mutation test (presence of S9-mix). These increases were considered to be of no biological relevance because there was no evidence of a dose-response relationship or reproducibility. Furthermore, the individual revertant counts at the statistically significant dose levels were within the in-house historical untreated/vehicle control range for the tester strain and the maximum fold increase was only 1.4 times the concurrent vehicle controls.

Conclusions:

Chromium Oxalate Hydroxide was considered to be non-mutagenic under the conditions of this test.

Executive summary:

The maximum dose level of the test item in the first experiment was selected as the maximum 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 either test.

A test item precipitate (fine and particulate in appearance) was noted at 5000 ug/plate, this observation did not prevent the scoring of revertant colonies.

There were no toxicological 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).

Small, statistically significant increases in TA100 revertant colony frequency were observed at 5000 μg/plate in the first mutation test (absence of S9-mix) and the second mutation test (presence of S9-mix). These increases were considered to be of no biological relevance because there was no evidence of a dose-response relationship or reproducibility. Furthermore, the individual revertant counts at the statistically significant dose levels were within the in-house historical untreated/vehicle control range for the tester strain and the maximum fold increase was only 1.4 times the concurrent vehicle controls.

Reference 2

Endpoint:

genetic toxicity in vitro

Type of information:

other: review arrticle

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

GLP compliance:

not specified

Type of assay:

other: Review of endpoints

Conclusions:

Negative based on published review document

Executive summary:

This article review approximately 700 results reported in the literature with 32 chromium compunds assayed in 130 short-term tests using different targets and/or genetic end-points. Cr (III) compounds are grouped according to their solubility:

• highly soluble Cr (III) compunds including chromic chloride, chromic acetate, chromic nitrate chromic sulfate and chromic potassium sulfate. Chromic chloride induced a variety of genetic effects in acellular or subcellular targets. In contrast all Cr (III) compounds almost consistently failed to induce various genetic effects in bacteria. Weak results were obtained in yeasts, under particular treatment, and in plants. They were generally inactive in cultured mammalian cell systems investigating DNA synthesis, DNA damage, forward mutations and sister-chromatid exchanges. Induction of chromosomal abberations was more frequent than sister-chromatid exchanges although, compared to Cr (VI), much higher Cr (III) concentrations were generally needed. Conflicting results were reported in cell transformation assays. Following in vivo treatment, no DNA fragmentation or induction of micronuclei was detected in rats and in mice, respectively
• Soluble Cr(III) compounds. This group of compounds includes basic chromic sulfate, chromic alum and chromic phosphate. The results reported in the limited number of studies available for these compounds are comparable to those reported for highly soluble Cr (III) compounds.
• Poorly soluble and insoluble Cr (III) compounds. This group of compounds includes chromic hydroxide, chromic oxide, chromite ore and cupric chromite. These compounds were genotoxic in bacteria only when contaminated with Cr (VI). Conflicting results were obtained in cultured mammalian cells, where chromic oxide was found to be taken up by cells and to induce mutation, chromosomal aberrations and sister-chromatid exchanges, although at concentrations 1000-fold higher than for Cr (VI). In addition to the aforementioned compounds, chromium tannins used in the hide and leather industry, most of which are composed of scarecly soluble sulfates, were also tested. None of 17 tannins reverted his- S. typhimurium, whereas 8 out of 13 tannins, 4 of which were contaminated with Cr (VI), increased the frequency of sister-chromatid exhanges in Chinese hamster ovary cells.
• Cr (III) complexes with organic ligands were assayed in both prokaryotic and eukaryotic cell systems. Complexes of chromic chloride with salicylate or citrate were positive in the rec assay with B. subtilis. Out of 17 hexacoordinated Cr (III) complexes, 8 were positive in a differential killing test with E. coli and 4 also reverted his- S. typhimurium. The most active complexes, containing aromatic amine ligands such as 2,2'-bipyridine and 1,10-phenanthroline were confirmed to be mutagenic. On the other hand, complexes of Cr (III) with amino acids did not revert his- S.typhimurium strains. In mammalian cultured cells, chromic glycine complexes did not induce unscheduled DNA synthesis in human skin fibroblasts nor mutation in Chinese hamster V79 cells. However, a chromic phenanthroline complex induced fragmentation and produced a weak DNA fragmentation in the same cells. Cr (acetylacetonate)3 but not Cr maltolate increased the frequency of sister-chromatid exchanges in Chinese Hamster ovary cells.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Note that both chromium III and oxalic acid salts are found in food. Chromium III is an essential element and oxalic acid is a product of metabolism that is typically excreted.

In view of high concentrations in the diet and in living tissues, the substance is not considered to be mutagenic.