Carcinogenicity of butyraldehyde in rats by a two-year inhalation study.

We conducted a two-year inhalation study of butyraldehyde using F344/DuCrlCrlj rats. The rats were exposed to 0, 300, 1,000 and 3,000 ppm (v/v) for 6 hr/day, 5 days/ week for 104 weeks using whole-body inhalation chambers. The incidence of squamous cell carcinoma of the nasal cavity was increased in the 3,000 ppm groups of both male and female rats, with Fisher's exact test and the Peto test indicating that the incidence was significant. In addition to squamous cell carcinoma in the nasal cavity, in the 3,000 ppm groups one male had an adenosquamous carcinoma, one male had a carcinosarcoma, one male had a sarcoma NOS (Not Otherwise Specified), and one female had a squamous cell papilloma in the nasal cavity. The combined incidence of squamous cell carcinoma, adenosquamous carcinoma and carcinosarcoma was significantly increased in male rats and the combined incidence of squamous cell papilloma and carcinoma was significantly increased in female. Based on these results, we conclude that there is clear evidence of butyraldehyde carcinogenicity in male and female rats.