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Administrative data

Link to relevant study record(s)

Description of key information

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

HFC-125 was assessed for the potential to be metabolised to trifluoroacetic acid in liver, in comparison with other halogenated-ethanes.  Male Fisher rats were exposed to halothane, HCFC-124, HFC-125, HCFC-123 and HFC-134a.  At the end of the exposure, animals were placed in metabolism cages and urinary trifluoroacetic acid excretion was measured. The presence of trifluoroacetylated-hepatic protein was assessed by means of SDS-PAGE and immunoblotted with anti-TFA-protein serum. The potential to form trifluoroacetylated-hepatic protein has the following decreasing order:  Halothane >= HCFC-123 >> HCFC-124 > HFC-125.  TFA-proteins were not detected in samples from rats exposed to HFC-134a.  19F-NMR analysis of urinary TFA excretion confirmed the previous order of reactivity.  The increased fluorination on the dihalomethyl group (-CX2H) decreases the metabolism of these compounds in vivo.  HFC-125 showed a lower potential to form TFA in liver when compared to other halogenated ethanes.

Sprague Dawley rats were exposed to 1,000, 5,000 and 50,000 ppm (4,900, 24,500 and 245,000 mg/m3) HFC-125 for 6 hours in individual inhalation chambers (Anders, 1993). Absorption was calculated by measuring the decrease of HFC-125 concentration in atmosphere within the period of exposure. Results indicated a slight uptake at the end of the exposure period.  Due to the low absorption of HFC-125, kinetic constants of uptake and metabolism were not calculated.

Conclusion

HFC-125 is very poorly absorbed via inhalation. Compared with other hydrofluorocarbons or hydrochlorofluorocarbons, HFC-125 is less likely to be metabolised to TFA in the liver or will be metabolized at a slower rate.