This report is a review and evaluation of the current knowledge of N-nitrosamines (NA) in the environment as related to possible deleterious effects on human health and welfare. Sources, distribution, measurement, and control technology for NA and their precursors are also considered. NA (characterized by the N-N=O group) are formed by the reaction of amines with nitrous acid. Nearly 70% of all N-nitroso compounds studied have been found to be carcinogenic, with a wide range in potency, in all species of laboratory animals tested via all routes of administration. The experimentally produced carcinogenesis appears to be caused by metabolites rather than by NA themselves. Epidemiological studies to date do not show a direct relationship between exposure to NA and cancer in man. Ambient air concentrations of NA of up to 36 microgram/cu m have been found near an emission source; and of up to 0.2 microgram/cu m in major population centers. The relative contributions of natural and man-made sources are indeterminable at present. Average dietary intake of NA is not likely to exceed a few microgram/day. Intake of NA in municipal drinking water would probably be much less than 1 microgram/day. NA in cigarettes range from 0 to 180 ng/cigarette.

"June 1977." Includes bibliographical references.