HFC-32 (difluoromethane) is poorly absorbed in the body of mammalian species. Any absorbed HFC-32 is either exhaled unchanged, or rapidly metabolised and excreted, principally as exhaled carbon dioxide.
HFC-32 is essentially non-toxic to laboratory animals. There were minor effects, such as reduced breathing rate and salivation, during brief exposure to high concentrations of 86,000 ppm (183,000 mg/m3) for 4 hours. Once the exposure stopped, animals behaved normally. HFC-32 up to 350,000 ppm (744,000 mg/m3) did not cause cardiac sensitisation to adrenaline, but there were head and limb tremors (pre-narcosis) at 250,000 ppm (531,000 mg/m3) and above.
Repeated exposure studies in rats up to 50,000 ppm (106,000 mg/m3) for 4 or 13 weeks showed no effects that could be attributed to HFC-32. HFC-32 is not genotoxic in vitro and in vivo. HFC-32 is poorly absorbed and does not form any toxicologically significant metabolites. As a consequence, HFC-32 is unlikely to be carcinogenic
In developmental toxicity studies in rats and rabbits, HFC-32 up to 50,000 ppm (106,000 mg/m3) did not interfere with embryo-foetal toxic development or fertility, but foetotoxicity (in the rat) could not be ruled out completely.
There are no known adverse health effects of HFC-32 on humans.
Joint Assessment of Commodity Chemicals No. 54
ECETOC, June 2008