SUMMARY
Toxicokinetic studies indicate that HFC-23 is readily absorbed by the lungs and that blood concentrations reach a plateau within minutes. HFC-23 is rapidly eliminated from the blood upon termination of exposure.
Table 3-1 summarizes the studies on HFC-23 for cardiac sensitization and Table 3-2 summarizes all the noncancer toxicity studies on HFC-23. The animal toxicity information and human exposure data indicate that HFC-23 has low toxicity. The only significant observations were reduced response to sound in rats exposed at 186,000 ppm and lightheadedness, tingling and numbness of the extremities, and hyperacusis in humans after exposure at 300,000 ppm and above.
Cardiac-sensitization studies conducted in three species indicate that HFC-23 has the potential to cause cardiac sensitization at high concentrations. Evidence of such sensitization was observed in baboons and cats exposed at 700,000 ppm, but no evidence was observed in dogs exposed at concentrations as high as 800,000 ppm.
A developmental toxicity study in rats exposed to HFC-23 at a concentration of 50,000 ppm reported no evidence of maternal or fetal toxicity or teratogenicity.
There is no evidence that HFC-23 is genotoxic.
There are no available long-term toxicity studies or carcinogenicity bioassays of HFC-23.
TABLE 3-1 Summary of Cardiac Sensitization Studies with HFC-23
|
Species |
Concentration, ppm |
Ventricular Arrhythmia |
Reference |
|
Mongrel dogs |
800,000 |
0/5 |
Hopkins and Krantz 1968 |
|
Beagle dogs |
100,000-500,000 |
0/6 |
Hardy and Kieran 1993 |
|
Baboons |
600,000 |
0/8 |
Branch et al. 1994 |
|
Baboons |
700,000 |
1/8 |
Branch et al. 1994 |
|
Cats |
700,000 |
3/5 |
Ewing et al. 1990 |
|
Cats |
700,000 |
3/7 |
Branch et al. 1990 |
TABLE 3-2 Summary of Noncancer Toxicity Information for HFC-23
