Effects of formaldehyde in the rat and dog following oral exposure

Formaldehyde was administered orally (p.o.) to groups of rats and dogs at dosages up to 150 and 100 mg/kg/day, respectively, for 91 consecutive days. Significant body weight changes were observed at the higher dosages tested in both species. Decreased water consumption was observed in a dose-related pattern in all treated groups of rats. Food consumption and feed efficiency were decreased at higher dosage levels in dogs. Results of other clinical studies and microscopic pathology revealed no specific, treatment-related effects on any organ or tissue examined. These findings suggest that formaldehyde possesses little subacute toxicity following oral exposure.