Inhalation carcinogenesis of N-nitrosomorpholine (NMOR) in rats and hamsters.
N-Nitrosomorpholine (NMOR) is a potent liver carcinogen in rats when administered orally. NMOR was found in the atmosphere at working places in the rubber industry in concentrations up to several hundred micrograms/m3. It can be assumed that NMOR inhalation may play a role in human carcinogenesis. Therefore an inhalation study was carried out to evaluate the carcinogenic potency of NMOR vapors in rats and hamsters. The concentration of volatile NMOR in the inhalation chamber was continuously determined with a Thermal Energy Analyzer. The rats received 29 administrations (4th/day, 5 days/week; mean inhaled daily dose: 130 micrograms/animal; total dose: 15 mg/kg bodyweight). The hamsters inhaled a total of 38 mg/kg of NMOR (21 applications, daily dose 260 micrograms/animal). In rats 4 carcinomas and 5 neoplastic nodules of the liver, 1 neuroblastoma and 1 mucoepidermoidal carcinoma of the nose, and 1 carcinoma of the thyroid gland were induced. In treated hamsters 4 carcinomas of the liver, 2 neurogenic sarcomas of the nasal region, and 5 papillomas of the trachea were found. None of these tumors were observed in control rats and control hamsters.
Klein
R G
RG
German Cancer Research Center, Institute of Toxicology and Chemotherapy, Heidelberg, FRG.
Spiegelhalder
B
B
Preussmann
R
R
D000280:Administration, Inhalation; D000818:Animals; D001273:Atmosphere Exposure Chambers; D002273:Carcinogens / Q000008:administration & dosage; D006224:Cricetinae; D005260:Female; D008297:Male; D008647:Mesocricetus; D009374:Neoplasms, Experimental / Q000139:chemically induced* / Q000473:pathology; D009602:Nitrosamines / Q000008:administration & dosage; D051381:Rats; D011919:Rats, Inbred Strains
D002273:Carcinogens; D009602:Nitrosamines; C002741:N-nitrosomorpholine