PAFT Programme for Alternative Fluorocarbon Toxicity Testing

HFC-125 is one of a series of fluorocarbon alternatives being tested by the Programme for Alternative Fluorocarbon Toxicity Testing (PAFT). HFC-125 is considered primarily as an alternative for refrigeration systems.

Summary of Testing Results HFC-125 has very low acute and subchronic inhalation toxicity. HFC-125 is not a developmental toxicant. HFC-125 is not genotoxic.

HFC-125 has very low acute toxicity by inhalation. The lowest concentration that causes mortality in experimental animals -- the approximate lethal concentration (ALC) -- for a 4-hour exposure is greater than 800,000 ppm (80%) with added oxygen. Even at these high inhalation concentrations, no clinical signs of toxicity are evident.

As with many other halocarbons and hydrocarbons, inhalation of HFC-125, followed by intravenous injection of epinephrine, which simulates human stress reactions, results in a cardiac sensitization response in experimental screening studies with dogs. This cardiac sensitization response is observed at approximately 100,000 ppm of HFC-125, a level well above expected exposures. By comparison, a cardiac sensitization response is observed with CFC-11 at approximately 5,000 ppm.

In repeated inhalation exposure studies, the low toxicity of HFC-125 continued to be evident. No adverse effects were observed in rats exposed by inhalation at concentrations of up to 50,000 ppm for up to 90 days.

Inhalation developmental toxicity studies with rats and rabbits have been completed. The results indicate that HFC-125 is not teratogenic and does not cause fetal effects at inhalation concentra- tions up to 50,000 ppm.

In genetic toxicity testing, HFC-125 was not mutagenic in an Ames assay, Chinese Hamster Ovary assay, or chromosomal aberration study with human lymphocytes. These studies were in vitro assays. Also, HFC-125 was not active in an in vivo mouse micronucleus study.

Metabolism studies with HFC-125 have not detected any metabolism.

The testing of HFC-125 under PAFT III is now complete. The results are summarized in the sidebar above.

An exposure limit for HFC-125 of 1,000 ppm (8-hour time-weighted average) has been recommended by the American Industrial Hygiene Association, Workplace Environmental Exposure Limit (WEEL) Committee.

As for all chemicals, PAFT recommends that exposures be kept to a practicable minimum.

September 1995

Last updated October 11, 1996