Cryolite, tripotassium

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Based on available information, it is concluded that potassium cryolite does not exhibit any potential for mutagenicity.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

No in vivo data on potassium cryolite are available; however, two negative in vivo bone marrow chromosome aberrations assays are available on a structural analogue of potassium cryolite, sodium cryolite (trisodium hexafluoroaluminate). Taking into account the structural similarity of two substances and their comparable toxicological profiles, it is considered acceptable to derive information on in vivo genotoxicity of potassium cryolite by read-across from sodium cryolite. Consequently, it is concluded that potassium cryolite is not genotoxic in vivo.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

In vitro gene mutation study in bacteria

Potassium cryolite was examined for mutagenic activity in the Ames test (OECD guideline 471 and GLP compliant) using Salmonella typhimurium strains TA 1535, TA 1537, TA 98, TA 100 and the tryptophan-requiring Escherichia coli strain WP2 uvrA, in the absence and presence of metabolic activation (CiTox, 2017). The test item concentrations in the Initial Mutation Test and in the Confirmatory Mutation Test (5 strains) were 5000, 1581, 500, 158.1, 50, 15.81 and 5 (Confirmatory only) μg/plate. The mean values of revertant colonies of the solvent control plates were within the historical control range, the reference mutagens showed the expected increase in the number of revertant colonies, the viability of the bacterial cells was checked by a plating experiment in each test. At least five analyzable concentrations were presented in all strains of the main tests. The tests were considered to be valid. Potassium cryolite did not induce a dose-related increase in the number of revertant (His+) colonies in each of the four tester strains (TA 1535, TA1537, TA98 and TA100) and in the number of revertant (Trp+) colonies in tester strain WP2uvrA both in the absence and presence of S9-metabolic activation. Based on the results of this study it is concluded that Potassium cryolite is not mutagenic in the Salmonella typhimurium and in the Escherichia coli reverse mutation assay.

In vitro gene mutation study in mammalian cells

Since no in vitro gene mutation study in mammalian cells is available for potassum cryolite, the results from the structural analogue multiconstituent aluminium potassium fluoride are used instead (for details see Read-across justification as attached in section 13).

In a study according to OECD guideline 476 and in compliance with GLP, multiconstituent aluminium potassium fluoride was examined for its potential to induce gene mutations at the TK-locus of cultured mouse lymphoma L5178Y cells (TNO, 2010a). One assay was conducted in which 7 duplicate cultures were treated for 24 hours and 4 hours in the absence and presence of S9-mix, respectively. The test substance was suspended in dimethyl sulfoxide (DMSO) prior to testing. Treatment with the positive controls yielded the expected significant increases in mutant frequency compared to the negative control.

The highest concentration of aluminium potassium fluoride tested and evaluated for mutagenicity was 10 mmol/L in both the absence and presence of S9-mix. Aluminium potassium fluoride was cytotoxic in both the absence and presence of S9-mix. In the absence of S9-mix cytotoxicity resulted in a reduction in initial cell yield and suspension growth at and above 1.2 mmol/L. The relative total growth (RTG) value at the highest concentration tested and evaluated for mutagenicity (10 mmol/L) was 29% (mean of duplicate cultures). In the presence of S9-mix, cytotoxicity was observed at and above 2.5 mmol/L; the RTG at the highest concentration tested and evaluated for mutagenicity (10 mmol/L) was 61% (mean of duplicate cultures).In both the absence and presence of S9 -mix no increase in mutant frequency was observed at any test substance concentration evaluated.

In vitro and in vivo chromosome aberration test

For potassium cryolite, no information is available on the potential to induce chromosome aberrations (clastogenicity). Therefore the results from the structural analogues multiconstituent aluminiumpotassium fluoride (in vitro) and sodium cryolite (in vitro and in vivo) are used instead (for details see Read-across justification as attached in section 13).

In a chromosome aberration test with human lymophocytes according to OECD Guideline 487, multiconstituent aluminium potassium fluoride did not induce an increase in the number of micronuclei in human lymphocytes at dose levels up to 1500 µg/ml using pulse treatment with 4 hr exposure duration (with and without S9 mix). However, in a continuous treatment experiment using longer exposure duration times of 20 hr, aluminium potassium fluoride was found to induce a statistically significant increase in the number of micronuclei at concentrations 200 µg/ml and above. In vivo mutagenicity data on multiconstituent aluminium potassium fluoride are not available.

Sodium cryolite did not induce unscheduled DNA synthesis in rat hepatocytes at dose levels up to 50 µg/ml or increases in chromosome aberration frequencies in human lymphocytes up to 1000 µg/ml (with and without metabolic activation, exposure duration 3-4 hours).

Two in vivo cytogenicity tests are available for sodium cryolite. One bone marrow chromosome aberration test, in which male Crl:CD BR Sprague-Dawley rats were exposed by inhalation to 4.6 mg/m3 cryolite for 13 weeks, was run within the 13-week study on repeated dose toxicity (Bayer AG, 1997a). Increased inorganic fluoride concentrations in urine, bones, and teeth were evident, indicating that the test substance has reached the bone marrow. No effect on mitotic activity was observed. Furthermore, no evidence of clastogenicity was observed in the other in vivo bone marrow chromosomal aberration test, in which male and female Crl:CD BR Sprague-Dawley rats were exposed by snout-only inhalation to 2130 mg/m3 cryolite for 6 hours (Huntingdon Life Sciences Ltd., 1997 / Bayer AG, 1997b). Bone marrow cells were sampled after recovery periods of 16, 24 and 48 hours. No clinical signs or mortalities were induced. All experimental parts were run in compliance with GLP and according to OECD guideline 475. In summary, the available data provide conclusive evidence that sodium cryolite does not induce chromosome aberrations in vivo.

Justification for classification or non-classification

Based on the available data and in accordance with EU Classification, Labeling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008, classification is not necessary for mutagenicity.