© 1975 Oxford University Press
research-article |
Epidemiology of Stomach Cancer in Chile—The Role of Nitrogen Fertilizers
1 2 Division of Epidemiology, School of Public Health, University of California Los Angeles, Los Angeles, California 90024, U.S.A.
Reprint requests should be addressed to Dr. R. Armijo
Chile ranks second in the world regarding age-adjusted mortality rates from stomach cancer. Analysis of death rates along its 25 provinces for a 15-year period (1957–1971) shows a peculiar geographic pattern of high and low-risk areas. Three agricultural provinces (Maule, Linares and Ñuble, located south of Santiago), population 460,000, show a median rate of 50.1 per 100,000. In contrast, both extremes of the country, distant some 3,000 miles from one another, carry less than one-half the risk. The three northerly provinces (Tarapacá, Antofagasta and Atacama), population 652,500, show a median rate of 21.6, whereas Aysén and Magallanes in the extreme south, population 161,600, share a figure of 22.8 per 100,000.
Data showing the use of nitrates throughout the country were collected for the period 1945–1972. A high correlation has been found between death rates and cumulative per capita exposure to nitrogen fertilizers. Controlling for confounding socio-economic variables, estimated by housing and infant mortality rates, the correlation holds at a significant level. A negative correlation between stomach cancer and infant mortality rates, low correlation with housing rating, and a negative correlation with lung and cervical cancer deaths were also found. The latter reinforces the lack of association with socio-economic conditions. Other major sites show a completely different pattern.
The epidemiological evidence presented agrees with biochemical findings on the synthesis of nitrosamlnes.
Received 9 June 1975