potassium ferrite

Endpoint summary

Additional information

In vitro:

Ames test (Huntingdon, 1997):

In a GLP-compliant Ames test, performed according to OECD guidelines Nos. 471 and 472, 4 Salmonella typhimurium strains (TA 1535, TA 1537, TA 98, and TA 100) and one Escherichia coli strain (CM 891) were used to investigate the mutagenic potential of the test substance potassium ferrite (concentrations: 50; 150; 500; 1,500 and 5,000 µg per plate), both with and without metabolic activation (S9-mix from aroclor-1254 induced rat livers) (Huntingdon Life Sciences, 1997). The number of revertant colonies compared to solvent controls (solvent: purified water) was not increased in any of the bacterial strains following exposure to Potassium ferrite at any concentration tested, neither in the presence nor in the absence of S9-mix. In conclusion, potassium ferrite shows no mutagenic effect in bacteria.

 

Chromosome aberration test (Huntingdon, 1997):

In a GLP-compliant chromosome aberration test according to OECD guideline No. 473, human peripheral blood lymphocytes were exposed to the test substance, potassium ferrite, with and without metabolic activation with S9-mix from aroclor-1254 induced rat livers (Huntingdon Life Sciences, 1997). Different exposure times (without S9-mix, cells were exposed continuously for 21 or 45 h, with S9-mix exposure was limited to 3 h and cells were harvested 18 or 42 h later) and doses (up to 5,000 µg/mL) were tested in this study. In the absence of metabolic activation the frequency of metaphases with aberrant chromosomes was increased compared to vehicle control values at all concentrations tested. However, in the presence of S9-mix, treatment with Potassium ferrite did not increase the frequency of metaphases with aberrant chromosomes compared to vehicle control values (p>0.05), including and excluding gap-type aberrations. The number of polyploidy cells was within the normal range. Endoreduplication was observed in one single cell. Based on the results obtained, potassium ferrite was considered to be clastogenic in this chromosomal aberration test in the absence of metabolic activation.

 

Chromosome aberration test (Safepharm, 2005):

In a GLP-compliant chromosome aberration study according to OECD guideline No. 473, Potassium ferrite was tested in human peripheral blood lymphocytes at concentrations of 0; 312.5; 625; 1,250; 2,500; 3,750 and 5,000 µg/ml during a 4 h exposure time with and without metabolic activation (Experiment 1); and 0; 39; 78.1; 156.25; 312.5; 625; 1,250; 2,500; 5,000 µg/ml (Experiment 2) with (4 h exposure) and without metabolic activation (24 h continuous exposure) with S9-mix from aroclor-1254 induced rat livers (Safepharm laboratories, 2005).

In Experiment 1, a dose-related inhibition of the mitotic index was observed and 32% mitotic inhibition was achieved at a concentration of 5,000 µg/ml in the absence of S9-mix. In the presence of S9-mix there was no evidence of a dose-related inhibition of the mitotic index. The maximum dose level selected for metaphase analysis was the maximum recommended dose level (5,000 µg/ml). The test material induced a small but statistically significant increase in the frequency of cells with aberrations in the absence of metabolic activation in the upper two dose levels (2,500 and 5,000 µg/ml). However, in both instances the response did not include chromatid exchange aberrations, was within the historical range for the vehicle control, and was comparable to a low concurrent vehicle control value. Therefore, the response was considered to have no toxicological significance. No increases in the frequency of cells with aberrations were observed in the presence of metabolic activation.

In Experiment 2, no marked dose-related inhibition of the mitotic index was observed in the presence of S9-mix and 20% mitotic inhibition was achieved at 5,000 g/ml. In the absence of S9-mix, a clear dose-related inhibition of the mitotic index was observed, with 53% mitotic inhibition being achieved at 2,500 µg/ml. The maximum dose level selected for metaphase analysis was 5,000 µg/ml in the presence of S9-mix and was limited by toxicity in the absence of S9-mix to 2,500 µg/ml. The test material did not induce any statistically significant increases in the frequency of cells with chromosome aberrations in either the absence or presence of metabolic activation. This result confirmed that the weak response seen in Experiment 1 in the absence of metabolic activation was of no toxicological significance.

In conclusion, Potassium ferrite did not induce any toxicologically significant increases in the frequency of cells with chromosome aberrations in either the absence or presence of a liver-enzyme metabolizing system in either of two separate experiments. Potassium ferrite is therefore considered to be non-clastogenic to human lymphocytes under the experimental conditions.

 

V79/HPRT test (Bayer HealthCare, 2008):

In a GLP compliant study on gene mutation in mammalian cells (HPRT test; OECD guideline No. 476) with Fe3O4 (concentrations: 6, 9, 12, 18, 24 and 36 µg/ml) without and with S9 mix there was no biologically relevant increase in mutant frequency above that of the negative controls. Read across to iron oxide is justified, as the ferric ion is considered to be the main toxophore of Potassium ferrite concerning mutagenicity. Both iron oxide and Potassium ferrite are hardly soluble in water. Therefore, it is expected that the substance will not be absorbed easily. However, if there was any absorption present, exposure to the substance is expected to lead to formation of the ionic forms of iron in the gastro-intestinal tract, mainly in the ferric (Fe3+) and a small fraction in the ferrous (Fe2+) state. The same is expected for Fe3O4.

 

 

In vivo:

Micronucleus assay (Huntingdon, 1997):

In a GLP-compliant erythrocyte micronucleus test, tested according to OECD guideline No. 474, Swiss CD mice were treated with a single intraperitoneal (i.p.) injection of Potassium ferrite in 1% aqueous methylcellulose as vehicle at dose levels of 126, 252 and 504 mg/kg bodyweight (Huntingdon 1997). This dose-range was based on the results of a preliminary test. The purpose of this preliminary test was to determine the maximum tolerated dose and thereby derive a suitable dose level for the micronucleus test. Therefore, the animals were treated with potassium ferrite by intraperitoneal injection once. Following dosing (dose range: 250 – 2,000 mg/kg bw) the animals were observed for a 48h period. During the main test, the negative control group received the vehicle, aqueous 1% methylcellulose, intraperitoneally. A positive control group was dosed orally, by intragastric gavage, with mitomycin C at 12 mg/kg bw. Bone marrow smears were obtained from five male and five female animals of the negative control groups, each of the test substance groups and the positive control group at 24 h after dosing. In addition, bone marrow smears were obtained from five male and five female animals of the negative control group and the high dose treatment groups 48 h after dosing. One bone marrow smear from each animal was examined for the presence of micronuclei in 2,000 immature erythrocytes. The proportion of immature erythrocytes was assessed by examination of at least 1,000 erythrocytes from each animal. The incidence of micronucleated immature erythrocytes was also analyzed. No mortalities were observed during the test. Mice treated with the test substance did not show any significant increase in the frequency of micronucleated immature erythrocytes at either sampling time and at any concentration tested. A slight, but statistically significant decrease in the proportion of immature erythrocytes was obtained 48 h after treatment of the animals with potassium ferrite. This decrease could be indicative of slight bone marrow depression but, due to the fact that the decrease was marginal, it was more likely to be a result of chance variation. The positive control compound, mitomycin C, produced expected large, highly significant increases in the frequency of micronucleated immature erythrocytes. In conclusion, potassium ferrite is not genotoxic/clastogenic in vivo.

Short description of key information:
In summary, Potassium ferrite was not mutagenic in bacteria, but showed ambiguous results in two in vitro chromosomal aberration tests (1 positive without metabolic activation/1 negative with and without metabolic activation). A HPRT assay with the read-across substance Fe3O4 as a representative for iron oxides showed no mutagenic potential of the test substance.
However, although potassium ferrite was administered by intraperitoneal injection, no clastogenic potential could be determined in an in vivo micronucleus assay.

Experimental data on the hydrolysis of Potassium ferrite revealed that hydrolysis proceeds to a minor degree and results in small amounts of potassium hydroxide (a 10 % w/v solution of Potassium ferrite revealed a pH of 12.9; for details please refer to IUCLID chapter 7.2.3) and the remaining insoluble iron oxides (confirmed by a water solubility test where the mean measured water solubility in the form of iron was <1.0 mg/L). Therefore, potassium hydroxide as well as the remaining iron oxides can be investigated separately for their toxic properties.
An in vitro test for Potassium hydroxide revealed no evidence for a mutagenic activity. In addition, no mutagenic activity was found for the related substances NaOH (in vitro as well as in vivo) nor KCl and K2CO3 (in vitro; OECD SIDS for KOH; see IUCLID chapter 13).
As iron oxides are hardly soluble in water, bioavailability is expected to be very low. Iron dichloride, an iron salt which is soluble in water, revealed no mutagenic properties, both in vitro and in vivo (OECD SIDS for Iron dichloride; see chapter 13).

As a result of all the information available, it is concluded that potassium ferrite has no genotoxic potential.

Endpoint Conclusion:

Justification for classification or non-classification

Based on the available genotoxicity tests, the test substance does not need to be classified for genotoxicity according to the Directive 67/548/EEC and according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.