Toxicological profile HFC-32

HFC-32 (difluoromethane)

In animals less than 1% of inhaled difluoromethane is metabolised. The majority of inhaled materials exhaled unchanged. Metabolised, difluoromethane is eliminated as C02 and fluoride. There is no significant formation of carboxyhaemoglobin indicating that carbon monoxide formation is not a significant metabolic pathway.

Acute inhalation toxicity is very low with no mortality seen in the rat after 4 hours exposure to 520,000 ppm. Signs of depression of the central nervous systern were apparent only at concentrations of 86,000 ppm and above. In the dog there was no evidence of cardiac sensitisation in response to exogenous epinephrine challenge at difluoromethane exposure concentrations up to 350,000 ppm, the highest concentration tested.

Inhalation studies in rats with difluoromethane for 4 and 13 weeks at concentrations up to 50,000 ppm produced no toxic effects.

Difluoromethane was not teratogenic to the rat or rabbit. Evidence of minimal foetal and maternal toxicity in the rat, and maternal toxicity in the rabbit was seen at 50,000 ppm.

Difluoromethane was not mutagenic both in in vitro or in vivo studies using bacteria, mammalian cell lines and in the mouse micronucleus assay.

Source: Joint Assessment of Commodity Chemicals No. 32
HFC-32 (difluoromethane)
ECETOC, 1995