Nitrate nitrogen levels in drinking water of urban areas with high- and low-risk populations for stomach cancer: an environmental epidemiology study

Abstract

A correlation study between mean nitrate nitrogen levels (ppm) in drinking water samples (N = 1389) of Chilean urban areas and age-adjusted death rates per 100 000 population from stomach cancer, by province or region and sex, was made. Drinking water samples from all provinces (N = 25) had a weighed mean of 1.446 ppm (S.E.M. 0.068) with a range of 0.00--30.00 ppm. Nitrate nigrogen levels showed a positive but not significant association with male death rates. The correlation coefficient was +0.0335. Similarly, such levels did exhibit a positive but not significant correlation with female death rates (r = +0.0486). When NO3-N levels and male (r = +0.1367) or female (r = +0.1143) death rates were studied, by region, positive but insignificant correlations were detected. Using Cochran's approximation, mean nitrate nitrogen levels in drinking water samples from six provinces with 50% of the Chilean population (period 1953--55 versus 1973--75), showed a decrease from 1.835 to 1.291 ppm, but there was no significant difference (t = 1.32) between the two values, except in samples from Santiago Province (t = 2.11, P less than 0.05). Provinces (south central area) showing the highest gastric cancer mortality rates in the world for females (up to 40.8/100,000), and ranking second for males (up to 84.1/100,000), exhibited a very low mean level (0.825 ppm).

Contaminated drinking water as a potential cause of cancer in humans

“…Eleven ecological studies (46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56) on the association between nitrate-rich drinking water and gastric cancer incidence or mortality have been reported (Table II) Data on nitrate concentrations in the various water sources supplying a town were often routinely available and the relative contribution of each source was taken into account (53,54,56). In some studies, samples were taken from wells (47,48) or taps in individual homes (51).…”

“…Application of methods for weighted regression to these data did not change the conclusions. For the remaining five studies (49)(50)(51)54,55) it cannot be ruled out that social class differences between the populations compared have affected the (lack of) association observed.…”

“…performed a case-control study to estimate the relative risk of gastric cancer in each population.Of the eleven studies reported, five(46,48,52,53,55) shewed evidence for a positive association between nitrate levels in the drinking water and the occurrence of gastric cancer, five(47,(49)(50)(51)54) did not show any relationship and one (56) showed a negative relationship.Interpretation of findingsTwo studies (49,56) which did not show a positive association could perhaps be explained by the low levels of exposure observed. The studies carried out in Hungary(50), France(54), and Illinois(47), however, involved high levels of exposure but did not show an association.…”

N-Nitroso Compounds: Diet and Cancer Trends

“…Also, there was a vari able intake of fresh fruits and vegetables, namely, a seasonal low consumption of such foods during winter and spring. The geo chemistry often involved elevated soil nitrate and, thus, foods and water rich in nitrate (45,46,47).…”