Respiratory retention and acute toxicity of furan.

The respiratory tract retention of furan has been studied in dogs as part of a broad investigation of compounds found in the vapor phase of cigarette smoke. The LD50 of furan has also been determined in mice and rats and the LC50 in mice. Respiratory uptake of furan was between 90 and 95%, varying inversely with the ventilatory rate. Retention was not affected by tidal volume changes but was directly related to concentration inhaled. Intraperitoneal LD50 values were 5.2 mg/kg for rats and 7.0 mg/kg for mice. The LC50 for mice was 0.12 microgram/mL. These results indicate the high toxicity of furan and that it is readily absorbed by the inhalation route.