Lanthanum fluoride

Endpoint summary

Additional information

In vitro data

Bacterial reverse mutation

The potential of the test material to cause mutagenic effects in bacteria was assessed in a GLP study which was conducted in accordance with the standardised guidelines OECD 471 and EU Method B.13/14. Furthermore, the test method was designed to be compatible with the guidelines for bacterial mutagenicity testing published by the major Japanese Regulatory Authorities including METI, MHLW and MAFF and the USA, EPA (TSCA) OPPTS harmonised guidelines.

Salmonella typhimurium strains TA1535, TA1537, TA98, TA100 and Escherichia coli strain WP2uvrA were treated with the test material, using the plate incorporation and pre-incubation methods, at five dose levels, both with and without metabolic activation. The dose levels assessed were 50, 150, 500, 1500 and 5000 µg/plate.

The test material caused no visible reduction in the growth of the bacterial background lawn at any dose level and was, therefore, tested up to the maximum recommended dose level of 5000 μg/plate. A test material film (creamy in appearance) was noted at 5000 μg/plate, though this observation did not prevent the scoring of revertant colonies.

No toxicologically significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains. 

The vehicle controls gave revertant colony counts within the normal range. The positive controls gave the expected increases in revertants, validating the sensitivity of the assay and the efficacy of the S9-mix.

The test material was considered to be non-mutagenic under the conditions of this test.

 

Chromosome aberration

The potential of the test material to induce structural chromosomal aberrations was determined in a GLP study which was conducted in accordance with standardised guidelines OECD 473 and EU Method B.10. Duplicate cultures of human lymphocytes, treated with the test material, were evaluated for chromosome aberrations at up to three dose levels; negative and positive controls were run concurrently. Four treatment conditions were used for the study. In Experiment 1, cultures were exposed for 4 hours with a 20 hour expression time, both in the presence and absence of metabolic activation (an induced rat liver homogenate at a final concentration of 2 %). In Experiment 2, the 4 hour exposure period was repeated with metabolic activation (1 % final S9 concentration); whilst in the absence of metabolic activation cells were assayed with a continuous 24 hour exposure time. The frequencies of chromosome aberrations in both vehicle and positive controls were within the expected range and verified the sensitivity of the assay and the efficacy of the S9-mix.

Under the conditions of the test, exposure to the test material did not induce a dose-response reduction in mitotic indexes, or statistically significant increases in the frequency of structural chromosome aberrations, both in the presence and absence of metabolic activation. Furthermore, no polyploidy cells were recorded in any of the exposed cultures. In conclusion the test material was considered to be non-cytotoxic and non-clastogenic.

 

Gene mutation in mammalian cells

A study was conducted to assess the potential mutagenicity of the test material on the hypoxanthine-guanine phosphoribosyl transferase (HPRT) locus of Chinese hamster ovary (CHO) cells in vitro in accordance with the standardised guidelines OECD 476, EU Method B.17, the United Kingdom Environmental Mutagen Society (Cole et al, 1990) and the EPA OPPTS 870.5300.

CHO cells were treated with the test material at six dose levels, in duplicate, together with vehicle and positive controls. The technique used is a plate assay using tissue culture flasks and 6-thioguanine (6-TG) as the selective agent.

Two treatment conditions were used for the test. In Experiment 1, a 4 hour exposure in the presence of 2 % S9 and in the absence of metabolic activation. In Experiment 2, the 4 hour exposure was repeated using a 1 % final S9 concentration, whilst in the absence of metabolic activation the 4 -hour exposure was repeated with to verify a possible response seen in Experiment 1.

The vehicle (Ham's F12 culture medium) controls gave mutant frequencies within the range expected for CHO cells at the HPRT locus. The positive control treatments, both in the presence and absence of metabolic activation, gave significant increases in the mutant frequency indicating the satisfactory performance of the test and of the metabolising system.

An increase in mutant frequency of greater than 20 x 10^-6was seen in the 4-hour exposure group in the absence of S9 in Experiment 1 at the maximum dose tested (1959 μg/mL). However, this response was considered to be related to the toxicity seen at the maximum dose level in this experiment and since it did not reproduce in Experiment 2 it was considered to be of no toxicological significance. The test material did not induce any significant or dose-related increases in mutant frequency per survivor in the presence of metabolic activation in either of the two experiments.

Under the conditions of this study, the test material is considered to be non-mutagenic to CHO cells at the HPRT locus.

 

Justification for selection of genetic toxicity endpoint
Multiple studies have been provided to address the different endpoint of genetic toxicity, each addressing different types of genetic toxicity. Since the studies are not comparable, a single study could not be selected as key over the others.

Short description of key information:
In vitro Gene Mutation Study in Bacteria:
Ames: Harlan (2013), OECD 471 and EU Method B.13/14; Negative (with and without metabolic activation).

In vitro Mammalian Cell Cytogenicity:
Chromosome Aberration: Harlan (2013), OECD 473, EU Method B.10; Negative (with and without metabolic activation).

In vitro Gene Mutation Study in Mammalian Cells:
Chinese hamster Ovary (CHO): Harlan (2013), OECD 476, EU Method B.17, and EPA OPPTS 870.5300; Negative (with and without metabolic activation).

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

In accordance with criteria for classification as defined in Annex I, Regulation 1272/2008, the test material does not require classification for genetic toxicity based on the overall negative response noted in the available genetic toxicity studies.