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in vitro gene mutation in bacteria

HFC 125 gave negative results when tested up to 100% in the atmosphere in a reverse mutation assay study was performed with five histidine-dependent strains of Salmonella typhimurium and one tryptophan-dependent strain of Escherichia coli with and without metabolic activation (May and Watson, 1992).

in vitro cytogenicity in mammalian cells

A cytogenetic assay for the study of chromosomal aberrations was carried out in Chinese hamster ovary cells exposed to concentrations up to 700,000 ppm (3436000 mg/m3) for 4 hours and up to 600000 ppm (2945000 mg/m3) for 24 and 48 hours, with and without metabolic activation. Positive results were observed only after 48 hours of exposure to 600000 ppm HFC 125 in the absence of metabolic activation.  However, the increased incidence of chromosomal aberration, observed under this experimental condition was concurrent with clear evidence of cytotoxicity (Dance, 1992).

A further chromosomal aberration test was carried out in human lymphocytes exposed up to 700000 ppm (3436000 mg/m3) HFC 125 for 3, 24 and 48 hours, with and without metabolic activation. This study gave clearly negative results (Dance, 1992).

In vitro gene mutation in mammalian cells

No information are available for HFC 125. However, reliable information were retrieved for the structural analogues 1,1,1,2 -tetrafluoroethane (HFC 134a) and 1,1,1,2,3,3,3 -heptafluoropropane (HFC 227ea).

The use of analogue approach for hydrofluorocarbons is justified and documented in the position paper "Use of read across in the human hazard assessment of hydrofluorocarbons (HFCs)", attached in the endpoint summary in Section 7 of the Technical Dossier (Toxicological Infromation)

Both HFC 134a (Alexander and Libretto, 1995) and HFC 227ea (Genesys Research, 1995) resulted not mutagenic to mouse lymphoma L51787 cells with or without metabolic activation.

In vivo cytogenicity

Finally, An erythrocyte micronucleus test was performed by exposing groups of 5 male and 5 female mice up to 600000 ppm (2945000 mg/m3) HFC 125 in atmosphere for 6 hours. Mice were killed 24, 48 and 72 hours after exposure. The highest tested concentration produced clinical signs of toxicity (hunched posture, tremors, slow respiration), but no statistically-significant increased frequency of micronucleated erythrocytes was observed at any tested concentration, in comparison with control.  No significant changes were observed in the ratio of polychromated to mature cells among the control group and the groups treated with HFC 125 (Edwards, 1992).


Short description of key information:
in vitro and in vivo genotoxicity tests

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

HFC-125 was not shown to be genotoxic in vitro and in vivo studies. No Classification is deemed necessary