Nitrate in drinking water and cancer in northern Jutland,Denmark, with special reference to stomach cancer

Nitrate ingestion has been suggested to be associated with an increased risk of stomach cancer possibly through endogenous nitrosamine formation. The town of Aalborg in the northeast Jutland of Denmark (population approx 100,000) has been known for decades to have an average concentration of approx 30 mg/liter nitrate in its drinking waters. Age-standardized cancer incidence rates for 1943–1972 for various types of cancer were compared between Aalborg, neighboring towns, and all Danish provincial towns. During this 30-year period stomach cancer occurred slightly more frequently in Aalborg than in the town of Aarhus (population approx 200,000), with average standardized incidence ratios of 1.25 among men and 1.20 among women. It is unlikely than the increased incidence of stomach cancer in Aalborg may be explained by diagnostic differences, socioeconomic differences, or differences in dietary or constitutional factors. It is concluded that the results support a possible weak role for nitrate in the etiology of stomach cancer. Decreasing stomach cancer incidence in Aalborg as well as in other towns of Denmark indicate that nitrate may be only one of several factors influencing stomach cancer development.