Carcinoma of the nasal and paranasal regions in rats fed Cantonese salted marine fish.

Cantonese salted fish is suspected on epidemiological grounds to be an etiological factor in human NPC. To determine whether this food contains a carcinogen which acts on the upper respiratory epithelial lining, WA albino rats and Syrian golden hamsters were given Cantonese salted fish in their diet for one to two years from the age of one month and examined for tumours in that area. Three of 20 treated rats, but no control rats and no treated or control hamsters, developed carcinomas (two adenocarcinomas and one undifferentiated) in the nasal or paranasal sinus cavities after 12 to 24 months' treatment. NDEA was given orally to a similar group of animals as a positive control, and NDMA, the only volatile nitrosamine detected in salted fish, was added to the drinking-water of a third group. Three of 14 NDEA-treated rats developed adenocarcinomas in the nasal cavities, but none of the other animals developed nasal or paranasal tumours. These findings lead us to suspect that salted fish may contain a carcinogen or procarcinogen that can act systematically on the epithelial cells of the nasal and paranasal cavities.