Nitrosamines are formed by reaction of secondary or tertiary amines with a nitrosating agent. In foods, the nitrosating agent is usually nitrous anhydride, formed from nitrite in acidic, aqueous solution. Food constituents and the physical make-up of the food can effect nitrosamine formation. Ascorbic acid and sulfur dioxide are used to inhibit nitrosamine formation in foods. Nitrosodimethylamine has been shown to be formed in certain foods as a result of the direct-fire drying process. In this case, oxides of nitrogen in the drying air nitrosate amines in the food being dried. The volatile nitrosamine which occurs most commonly in food is nitrosodimethylamine, and nitrosopyrrolidine occurs to a lesser extent. Due to limitations in analytical methodology, very little information is available on the levels of nonvolatile nitrosamines and other N-nitroso compounds in foods. Foods which have been shown to contain volatile nitrosamines include cured meats, primarily cooked bacon; beer; some cheeses; nonfat dry milk; and sometimes fish. It should be emphasized that not all samples analyzed contain detectable amounts of nitrosamines. When present, the volatile nitrosamines usually occur in the lower microgram/kg range. Estimates by several investigators suggest that the average daily intake of volatile nitrosamines from foods is approximately 1 microgram/person.