[The problem of carcinogenic N-nitroso compounds--30 years old].

For 30 years a correlation between N-nitroso compounds and cancer in man has been suspected. Investigations of nitrate and nitrite in food and human gastric cancer were performed all over the world. Literature on nitrosamines and nitrosamides is abundant, but it is impossible to make a realistic assessment of the danger of N-nitroso compounds and their precursors for man. Restriction of unnecessary intake of nitrate through drinking water and food is in any case an important task of hygiene.